Modern Trends in Physics Research: 4th International Conference on Modern Trends in Physics Research 9814504882, 9789814504881

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MODERN TRENDS IN PHYSICS RESEARCH 4th International Conference on Modern Trends in Physics Research

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MODERN TRENDS IN PHYSICS RESEARCH 4th International Conference on Modern Trends in Physics Research MTPR- 10 12 – 16 December 2010

Cairo University, Egypt

EDITOR

Lotfia M. El Nadi Cairo University, Egypt

CONFERENCE PROCEEDINGS ■ VOLUME 9910

World Scientific NEW JERSEY

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LONDON

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SINGAPORE

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BEIJING

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SHANGHAI

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HONG KONG

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TA I P E I

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Published by World Scientific Publishing Co. Pte. Ltd. 5 Toh Tuck Link, Singapore 596224 USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601 UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE

British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library.

MODERN TRENDS IN PHYSICS RESEARCH Proceedings of the 4th International Conference on MTPR-10 Copyright © 2013 by World Scientific Publishing Co. Pte. Ltd. All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher.

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ISBN 978-981-4504-88-1 ISBN 981-4504-88-2

Printed in Singapore.

Rhaimie - Modern Trends in Phys - MTPR-10.pmd 1

3/5/2013, 11:43 AM

v

FOREWORD

AHMED H. ZEWAIL NOBEL LAUREATE HONORARY CHAIR MTPR-010

The International Conference of “Modern Trends in Physics Research” MTPR-010 is the Fourth of the Bi-annual Int. Meetings organized in Cairo, Egypt by the Physics Department of the Faculty of Science, Cairo University. It was my honor to agree to be the Honorary Chairman of this Conference in response to Prof. Lotfia El Nadi’s invitation, but due to my obligations I was unable to attend, but would follow up its progress. The conference had participants from around the world and many were from Egypt. The conference had attracted well-known scientists in their fields offering their experience and exchange ideas with researchers from Egypt. The success of this conference is due to Professor Lotfia El Nadi, Program Chair of MTPR-010, efforts, devotion and determination as well as her colleagues who were involved with the organization and logistics. I personally would like to take the opportunity to thank also World Scientific Publishing for publishing this proceedings and I look forward to future MTPR’s. Ahmed H. Zewail Caltech, Pasadena, California, USA Zewail City for Science & Technology, Egypt

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PREFACE

Lotfia M. El Nadi Program Chair MTPR-010

The main objectives of this event are: Innovate knowledge about recent breakthroughs in physics research in fundamentals and technology. Develop greater understanding of physics research to promote new research fields. Elaborate the existing possibilities to perform studies on the vast expanding fields of physics. Activate methods for implementing local, regional and international cooperation in physics research. Lay ways for projects to perform Novel Physics. IDEAL for MODERN TRENDS IN PHYSICS RESEARCH TECHNICAL PROGRAM of MTPR-010 comprised of 12 sessions, each 3.5 hours. Sessions were combined for Keynote, Plenary and Invited Presentations. Parallel sessions for oral presentations were devoted to the three topics given below. Evening sessions were devoted for the posters.

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The topics involved in this conference were: IIIIII-

Atomic & Mole. Spectroscopy, Astrophysics, Condensed Matter & Nanotechnology. High Density Lasers, Lasers and Applications and Advanced Technology. Nuclear, Particle & Radiation Physics and Astronomy.

Some of the international participants, who attended the conference and delivered their prestigious talks, were not able to send their manuscripts. The organizing committee, in recognition for their efforts, under my initiative, for the first time, has included their abstracts in this proceedings. I am grateful to all authors who took the effort to submit their papers in a timely manner, to be peer reviewed and published in this proceedings, in spite of the difficult times associated with 25 January 2011 Egyptian Revolution and its consequences. I wish to express my gratitude to Cairo University and the sponsoring authorities for supporting MTPR-010 that helped greatly in the success of this meeting, which was held at Sharm El Shiekh, Dream City. Utmost thanks to the topic chairs and to my colleagues, Dr. Hussien A. Moniem, Dr. Galila A. Mehena and Dr. Magdy Omer, for their sincere efforts before, during and after the conference. Thanks are also extended to all the members of the Physics Department who had, directly or indirectly, contributed to the success of MTPR-010. To the readers, I hope you will look forward to participate in the postponed MTPR-012 international conference which will be held between 21-24 April 2013 with Professor Mostafa A. El-sayed of Georgia Institute of Technology being the Honorary Chairman and delivering the Honorary Keynote Presentation on Breakthroughs in Nanotechnology after the opening session. It is worthwhile to note the website www.eun.eg/MTPR-012/home.htm is also up. For information and updates, please visit the mentioned website. In conclusion, I will always keep up my efforts and devotion to the spread of knowledge, engage international cooperation and support the upgrading of the important world of physics research, which is the way to promote better life for humanity.

Professor Dr. Lotfia El Nadi, Editor Prof. of Nuclear and Laser Physics, Physics Department, Faculty of Science Vice Director International Center of Scientific & Applied Studies of HDSP Lasers, IC-SAS, NILES, Cairo University, Egypt [email protected] www.lotfianadi.name.eg

Photo courtesy of Mohamed Fadel Fahmy and Samy Tobgy excerpted from Egyptian Freedom Story: 25th of January Revolution — A Photo Documentary, Mediaworx (2011).

Photo courtesy of Mohamed Fadel Fahmy and Samy Tobgy excerpted from Egyptian Freedom Story: 25th of January Revolution — A Photo Documentary, Mediaworx (2011).

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CONTENTS

Foreword ......................................................................................................................................... Ahmed Zewail

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Introduction Lotfia El Nadi ...........................................................................................................................

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Conference Photos ..........................................................................................................................

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OPENING HONORARY KEYNOTE PRESENTATION The Variation of the Solar Diameter and Irradiance: Eclipse Observation of July 11, 2010 ................................................................................................................................... Serge Koutchmy, Cyril Bazin, Jean-Yves Prado, Philippe Lamy and Patrick Rocher

3

I. ATOMIC, MOLECULAR AND CONDENSED MATTER PHYSICS I-1 KEYNOTE AND PLENARY PAPERS Photo-excitation and Photoionization for Plasma Opacities under the Iron Project ....................... Sultana N. Nahar Physics of the Corona and Present and Future Major Solar and Heliospheric Space Missions ................................................................................................................................ Luc Damé

15

29

Solar Activities and Space Weather Hazards .................................................................................. Ahmed A. Hady

30

Electron Beam Ion Trap and Its Applications ................................................................................. Yaming Zou

36

Generation, Design and Applications of High Energy Electron Beam Sources — An Overview ................................................................................................................................... Munawar Iqbal, Gulib Ul Islam, Haris Rashid and Fazal-E-Aleem

37

Fundamental Studies and Applications of Highly Charged Ions .................................................... Reinhold Schuch

41

Classification of Spectral Wavelengths in All Regions for Si XII .................................................. A. I. Refaie

42

Some Historic and Current Aspects of Plasma Diagnostics Using Atomic Spectroscopy.............. Roger Hutton

66

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Novelty Preparation, Characterization and Enhancement of Magnetic Properties of Mn Nanoferrites Using Safety Binder (Egg White) ........................................................................ M. A. Ahmed, N. Okasha and S. I. El-Dek

67

I-2 CONTRIBUTING PAPERS Stark Broadening Calculations of Several Ti Lines ........................................................................ A. I. Refaie and H. Sharkawy

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Nanostructure Iron-Silicon Thin Film Deposition Using Plasma Focus Device ............................ M. Kotb, A. H. Saudy, S. Hassaballa and M. M. El-Okr

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Size Confinement and Magnetization Improvement by La3+ Doping in BIFEO3 Quantum Dots ................................................................................................................... M. Ali Ahmed, S. I. El-Dek and M. S. Ayoub

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Synthesis of Rare Earth Doped and Undoped GaN Nano-Crystallites ........................................... Lotfia El Nadi, S. Ahmed, M. Awaad, Magdy Omar and Y. Badr

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The Formation and Characterization of Nanocrystalline Mn-Ferrite from Magnetite .................... M. A. Ahmed, N. Okasha and D. Nabeel

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The Structural, Spectral and Dielectric Properties of Composite System NZF-BT ........................ O. M. Hemeda, A. Tawfik, M. A. Amer, B. M. Kamal and D. E. El Refaay

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On the Electrical Conductivity of Poly(vinyl Chloride) / Poly(ethylene Oxide) Blends ................ G. M. Nasr, S. M. Abd El-Wahab and A. Abd El-Athem

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Conductivity Enhancement of Mn Zn Ferrite by Gamma Irradiation ............................................. M. A. Ahmed, A. M. Diab and S. F. Mansour

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Effect of Y3+ Cation on the Electrical Properties of Ni-Zn Ferrites ................................................ L. M. Salah

141

Characterization and Dramatic Variations of the Magnetic Properties of Cu-Doped Nanometric Co-Ferrite ................................................................................................... M. A. Ahmed, S. F. Mansour and M. A. Abdo

149

Electronic Structure and Magnetic Properties of the Nd2Fe14B Intermetallic Compound ....................................................................................................................................... Abeer E. Aly

155

The Optical Properties of Poly(vinyl Chloride) / Poly(ethylene Oxide) Blends ............................. G. M. Nasr, S. M. Abd El-Wahab and A. Abd El-Athem Giant Enhancement in the Physical Properties of LaFeO3 by Substitution of Divalent Ions ................................................................................................................................... M. A. Ahmed, S. I. Dek and M. M. Arman

160

168

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II. HIGH DENSITY SHORT PULSE LASERS, LASERS AND APPLICATIONS II-1 KEYNOTE, PLENARY AND INVITED PRESENTATIONS Laser Driven Secondary Sources for Spectroscopy, Plasma Diagnostics and Other Applications .......................................................................................................................... 179 Thomas Kuehl, Bastian Aurand, Vincent Bagnoud, Boris Ecker, Udo Eisenbarth, Daniel Hochhaus, Paul Neumayer, Huanyu Zhao, Bernhard Zielbauer, Daniel Zimmer, Jamil Habib, Sophie Kazamias, Annie Klisnick, David Ros, Josef Seres, Christian Spielmann and Daniel Ursescu Advanced Laboratory for High Density Physics............................................................................. Lotfia El Nadi, A. Naser A. Fettoh, A. Refaie, Galila A. Mehena, Hussien A. Moniem, Hisham Imam, Khaled A. Elsayed, Magdy Omar and Salah H. Naby

182

High Energy Density Physics: The Laser Field of Tomorrow ........................................................ Richard R. Freeman

188

Characterization of DC Glow Discharge Plasma by Hollow Cathode ............................................ K. H. Metwally, A. H. Saudy, M. Farouk and M. M. El-Okr

189

The Texas Petawatt Laser and Technology Development Towards an Exawatt Laser................... Todd Ditmier

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II-2 CONTRIBUTING PAPERS Density Packed 2-D Matrix-Addressable Vertical-Cavity Surface-Emitting Laser Arrays ............ Abdel-Sattar Gadallah and Rainer Michalzik

197

XUV and Soft X-ray Laser Radiation from Ni-like Au .................................................................. Wessameldin S. Abdelaziz and H. M. Hamed

203

Enhanced Type-I Polarization-Entangled Photons Using CW-Diode Laser ................................... Salem Hegazy, Mohy S. Mansour and Lotfia El Nadi

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Effect of Preparation Method on Luminescence Properties and Quantum Efficiency of CdTe QDs ................................................................................................................................... A.M. Saad, M. M. Bakr, M. A. Kana and I. M. Azzouz

221

Novel Process for Laser Stain Removal from Archeological Oil Paintings.................................... Lotfia El Nadi, Osama El-Feky, Galila Abdellatif and Sawsan Darwish

228

Application of Laser Induced Plasma Spectroscopy on Breast Cancer Diagnoses ......................... A. Abd-Alfattah, A. A. Eldakrouri, H. Emam and I. M. Azzouz

233

Ultrafast Process in Condensed Matter Studied with Ultrashort Laser Pulses ................................ Panagnioti A. Loukakous

238

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III. NUCLEAR, PARTICLE PHYSICS AND ASTROPHYSICS III-1 KEYNOTE, PLENARY AND INVITED PAPERS Energy Security of India — Nuclear Energy — An Inevitable Option Present Plans and Future Perspectives ......................................................................................................................... Jai P. Mittal

241

Charge Measurements of Fragmented Nuclei of Si at Different Energies ...................................... M. S. EL-Nagdy, A. Abdelsalam, A. Algaood and M. Ahmed

242

Passive Safety Features in Advanced Nuclear Power Plant Design................................................ M. Tahir, I. R. Chughatai and M. Aslam

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Rsearch Studies Performed Using the Cairo Fourier Diffractometer Facility................................. R. M. A. Maayouf

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K-Surfaces in Schwarzschild Geometry .......................................................................................... Ayub Faridi, Fazal-E-Aleem and Haris Rashid

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X-Rays of Heavy Elements for Nanotechnological Applications: W and Pb Ions ......................... Sultana N. Nahar

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Effects of Radon Inhalation on Some Biophysical Properties of Blood in Rats ............................. M. F. Essa, Fayez M. Shahin, Ashour M. Ahmed and Omar Abdel-Salam

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Injection of Scattered Disc Objects into the Inner Solar System in Response to Shrinkage of the Heliosphere .......................................................................................................... Steven Foster and Shahinaz Yousef

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III-2 CONTRIBUTING PAPERS Transverse Momentum Spectra of Alpha-Particles as Projectile Fragments in Nucleus-Em Interaction at (4.1– 4.5)A GeV/C ............................................................................... S. S. Abd El-Aziz, M. Mohery and M. H. Soleiman Light-Strange Mesons Decays in the Quark Model ........................................................................ A. M. Yasser, E. M. Hassan, M. A. Fawzy and M. A. Allosh

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Surprising Rapid Collapse of Sirius B from Red Giant to White Dwarf Through Mass Transfer to Sirius A ......................................................................................................................... Shahinaz Yousef and Ola Ali

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Evaluation of Radioactivity Concentration in Tilapia Nilotica and Radiation Dose to Egyptian Population ........................................................................................................................ Hannan H. Amer and Enas H. El-Khawas

323

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Solar Forcings on Nile and Earthquakes ........................................................................................ Saad Mohammed Al-Shehri, Ismail Sabbah, Shahinaz Yousef and Magdy Y. Amin

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Author Index ...................................................................................................................................

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OPENING HONORARY KEYNOTE PRESENTATION

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 3

THE VARIATION OF THE SOLAR DIAMETER AND IRRADIANCE: ECLIPSE OBSERVATION OF JULY 11, 2010 SERGE KOUTCHMY Institut d’Astrophysique de Paris, UMR 7095, CNRS and UPMC, 98 Bis Bd Arago, F75014 Paris (France) CYRIL BAZIN, JEAN-YVES PRADO, PHILIPPE LAMY, PATRICK ROCHER Consortium for the observation of the July 11, 2011 Solar total eclipse, Paris IAP and IMCCE (France), Toulouse- CNES(France), Marseille LAM (France), The variation of the solar diameter is the subject of hot debates due to the possible effect on the Earth climate and also due to different interpretations of long period solar variabilities, including the total irradiance. We shortly review the topic and show that rather long term variations, corresponding to a length well over a solar magnetic cycle, are interesting to consider. The very recently launched mission “Picard” is entirely devoted to the topic but will just permit a short term evaluation. At the time of the last solar total eclipse of 11/7/2010, several experiments were prepared to precisely measure the transit time of the Moon related to the precise value of the solar diameter. Preliminary results coming from the use of a specially designed CNES photometer, put on different atolls of the French Polynesia, are presented. In addition the results of new experiments devoted to fast observations of flash spectra, including their precise chrono-dating, are illustrated and discussed. A new definition of the edge of the Sun, free of spurious scattered light effects strongly affecting all out of eclipse evaluations, is emerging from these observations, in agreement with the most advanced attempts of modeling the outer layers of the photosphere. We also argue for a definite answer concerning the solar diameter measurement from eclipses based on a better precision of lunar profiles coming from lunar altimetry space experiments which will be possible in the following decades.

1.

Introduction

impose a more rational pre- monotheistic society, well before the Christian era.

1.1. Some historical background During the last decades, considerable efforts have been devoted to the analysis of possible effects of the rather irregular activity cycles of the Sun, through the solar forcing effects. They are related to the question of the anthropogenic origin of global warming, its amplitude and its consequences for the climate and economic life. These seemingly legitimate studies have an intriguing historical background that can be considered as premises for the still disputed methods of evaluation used in these studies, including the influence of the solar variabilities that we will discuss in this paper. In this context, it is difficult to avoid a critical interpretation of the famous episode of the reign of the Pharaoh Akhenaton (Amenophis IV) in 1350 B.C. as a dramatic example of where an excessive belief can lead. In the ancient Egypt of Akhenaton the Sun has been imposed as a single divinity, see Figure 1, leading to a catastrophic end of the reign of this famous Pharaoh, although considered as the 1st historical attempt to

Figure 1- Akhenaton and family 1350 B.C. (Cairo Museum)

1 CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

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Furthermore, following the teaching of famous antique philosophers like Plato, Aristotle and their followers, the Man and not the Sun has been put at the center of the Word as yet reflected in modern religions (Christianism; Islam…). It roughly means that phenomena influencing our life should rather find their origin and result in the human activity. Unfortunately, the excessive belief in geo-centrism (a cosmogonic model imposed during almost 1.5 millennium) leads to wrong conclusions about the real World. The great discoveries of the 16th century changed the situation. Philosophy and Science slowly became disconnected and more progress has been made possible until today.

energy etc.) that do not produce any greenhouse effect gaz.

1.2. The global warming epoch As regards to the global warming, it is now widely accepted (but not really unanimously so) that a global irreversible effect, see Fig. 2 will “soon” result as a consequence of the well confirmed rising amount of CO2 (and other minor components of the Earth atmosphere like NO+).

Figure 3- The recorded at Mauna Loa (NOAA) increasing amount of CO2. Note the Yearly modulation superposed to the long range increase.

Climato-sceptics however exist and a seemingly reasonable opinion is possibly reflected by the following statement coming from the Policy Report No 321 by Iain Murray and H. Sterling Burnett (USA) from the “National Center for Policy Analysis”, 2009: “Global warming is a reality. But whether emissions of carbon dioxide CO2 and other greenhouse gazes from human fossil fuel use are the principal cause- are uncertain.” However even if it is uncertain it is a source of big concern! 1.3. About the solar forcing and the activity cycles.

Figure 2- The global warming effect illustrated by the risisng average temperature recorded on the Earth.

These gazes produce an increasing greenhouse effect in the Earth atmosphere. CO2 see Fig.3, is mainly produced by the industrial and technological activities based on the use of fossil origin energies (coal, oil, natural gaz, etc.). This is in contrast with the so-called durable and renewable energies (wind and solar energies, both thermal and photo-voltaic, geo-thermal

Figure 4- Sunspot cycles as shown using the sunspot numbers. The

Maunder

minimum

http://www.sidc.oma.be/

epoch

is

well

shown.

See

also

3  5 Indeed there are data suggesting a possible solar effect to explain the long term variations of the climate on the Earth. The most popular example is coming from historical reports showing that an extended period of global cooling was recorded during almost 70 Years in the Western Word. It is also sometimes called the “little Ice Age”, and it coincides with the time of the so-called Maunder minimum [1] see Fig. 4, reflected by the well established series of measurements of the co-called international sunspot number now kept at the Brussels Royal Observatory and also “produced” by several US Agencies. This number usually shows a pronounced 11.3 Years periodicity due to a global dynamo effect producing the solar magnetic activity cycle with the same periodicity. To illustrate this climate abnormal cooling in the North Atlantic regions a famous picture of the frozen Thames by Jan Grifier is often shown and even more details of the sunspot cycle are tentatively interpreted [1], like a longer pseudo- periodicity near 100 Years. It is possible that this episode was over interpreted although some more convincing studies are now supporting the assumption of a significant solar forcing. It is first the dendrochronological data-tree rings results concerning the cosmogonic abundance of C14 extended over a much longer period of time, see Fig. 5.

Figure 5- Ten Years average content of the C14 isotope deduced from the study of tree rings (from Intcal98, Quaterly Isotope Lab.).

Note in particular the time of the Medieval Optimum of warming in the 11- 12th centuries when the famous Vikings populated the Greenland and Iceland and developed farming. Also, as recorded in books from merchants, wines were produced in England, etc. No doubt that an extended period of relative warming existed at least in the Northern parts of the Atlantic Ocean Regions. A more extended study would consider several millennia and this has indeed been done using the analysis of proxies of the solar activity such as the

amount of cosmogenic isotopes C14 and Be10 in natural stratified archives (e.g. tree rings and ice cores) [2] to discuss the influence of the solar activity during the Holocene. We will not go so far as new methods and techniques permit today to re-consider some more trivial aspects of this influence starting with the discussion of the irradiance variabilities, their origin and consequences. 2.

Irradiance variations and heliometry.

The most obvious influence that the solar variabilities can have on the Earth climate is related to the slightly variable amount of thermal energy falling on the Earth. This energy is measured using the so-called Total Solar Irradiance (TSI) measurements leading to the popular “solar constant” determination when the total solar spectrum is taken into account and summed. Note that the Yearly variation should first be removed when discussing the topic. It is easy to make it because this rather large modulation (of order of 7%) is very well reproducible and it depends only of the well established with a high precision orbital motion of the Earth around the Sun. All irradiance measurements are corrected for this geometrical effect and only variations extended well over 1 Year are discussed. An excellent former and rather introductory review to the topic can be found in [3]. The book suggested that the Sun has a changing diameter of large magnitude over the centuries and it has been the basis for proposing a space mission called “Picard” (the name of the 1st scientist who performed at the Paris Observatory a long series of measurements of the diameter of the Sun) to the French Space Agency CNES in order to perform solar diameter measurements free of Earth atmospheric effects (distortions, refraction, image motion due to the turbulence, smearing, scattering etc.). The topic was recently reviewed again e.g. [4]. The dedicated space mission Picard was launched in June 2010. Fortunately, solar eclipses offer another opportunity to perform these measurements free of Earth atmospheric effects. Here we now try to discuss the most recent aspects of the question.

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2.1- About the possible variations of the solar diameter. Some correlated variations of the solar total irradiance S and of the solar diameter (or equivalently, the corresponding solar radius R0) are suggested by a 1st approximation analysis of the variation of the total flux arriving at the Earth orbit or a distance of 1 astronomical units A. Assume the Sun is a perfect spherical constantly emitting body (neglecting the centre limb effect) with a temperature T eff of the photosphere, we use the Stefan- Boltzman constant σ to express the irradiance: S= π R02 σ Teff4 / A2

(1)

A is constant and the relative variations of the irradiance δS/S can then be due to variations of T eff or to R0 or to both: δS/S = 2 δR0/R0 + 4 δTeff / Teff

(2)

The most recent measured TSI variations see Fig. 6, shows a typical 0.1 % maximum amplitude over a full solar sunspot cycle. Assume no variation of T eff we can immediately see from (2) that the maximum possible variation δR0 of the solar radius cannot be more than 0”4 (the average radius of the Sun is approximately 960”) and indeed it is considerably less

Concerning δTeff / Teff , measurements performed during 35 Years at Kitt Peak Observatory using the most powerful methods available today suggest no significant variations of the effective temperature of the photosphere in phase, or not, with the solar sunspot cycle, at the level of a noise which is still not sufficient to completely exclude any influence on the TSI [5]. We are then faced with the question of a possible dominant effect due to solar diameter variations, even if the theoretical aspects of the question seem not to be in favor of such explanation as the central nuclear source of solar energy is not believe to change over the human scales. But little details are known concerning the long processes bringing this energy to the surface of the Sun and possibly interacting with the solar activity cycle. To quantitatively translate solar magnetic modulation into irradiance variations, a clear mechanism-understanding is needed, or, better, evidences from solar “global” data are needed, including the fine analysis of solar radius variations. Note that solar radius measurements (see after) are performed since a long time (in the famous Secchi book of 1872 it was already discussed!) and a canonic value of 959”63 is still today almost universally adopted after the extended 40 Years long series of observations summarized and discussed by Auwers [6] where a correction of -1”55 for the irradiation effects was introduced. Needless to say that this is an arbitrary value coming from the discussion of visual type observations which is difficult to justify with today measurements with the use of CCD or CMos detectors and computer assisted type measurements. Another important aspect of the question is related to the definition to be adopted for the edge of the Sun used to measure the diameter. We will see that it is a difficult and controversial question which needs a special attention [8]. 2.2- Different methods used to measure the solar diameter.

Figure 6- Variations of the TSI as measured during 3 solar cycles using different space-borne experiments.

After the long series of measurements of the 17th and of the 18th centuries using micrometers and transit timing, mainly by the French observers after Picard at the Paris Observatory, even more serious series were performed by British and German observers of the 19 th century, based on the use of a specially designed instrument called the heliometer with an entrance

5  7 aperture which could reach 20 cm. The instrument produced a dual image of the Sun and the solar diameter was deduced from the visual evaluation of their contact by measuring the angle of separation of the optical system. Visual evaluations are subject to the irradiation effect which means that a correction has to be introduced in addition to both instrumental and atmospheric effects [8]. A modern variant of this method has been introduced 30 Years ago based on the use of an adaptation of the Danjon astrolabe that is now called the solar astrolabe. A lot of efforts were made to improve the methods, including the use of computer assisted measurements and the use of a CCD detector but rather contradictory results were published and it is not possible here to discuss the details and make an evaluation of this new results. It is just worth mentioning that these new instruments use a really too small aperture to produce an image of the Sun and, accordingly, they are very sensitive to the Earth turbulence effects. Another method takes advantage of the transit of the planet Mercury and even of Venus over the solar disk [7]. However such transits are rare and they are also subject to spurious effects due to the large amount of scattered light from the bright solar disk. Lately a Mercury transit was observed from Space using several imaging devices in EUV and interesting results were reported concerning the level of scattered light in the instrument. Another possibility to study the solar diameter variations free of atmospheric effects was offered by using the guiding telescope (operated in the visible light) of the rapidly spinning satellite used with the X-rays solar telescope RHESSI always pointed to the Sun. Long range relative variations due to the solar oblateness could be precisely analyzed but spurious effects due to the instrumental scattered light are also present and no solar diameter measurement can reasonably be made. Another method which is worth mentioning is coming from the interpretation of heliosismic data. The frequencies of surface gravity waves, the so called fmodes, are related to the solar diameter and their precise determination could give a value of R0. Unfortunately many different factors should also be taken into account and their influence is disputed [9]. The most precise measurements made until now from space take advantage of the Michelson Doppler Imager (MDI) telescope on board the Mission SoHO of ESA

and NASA operated for more than 15 Years. Although the telescope was not designed for making solar diameter measurements a great number of images of the solar disk were made available permitting a deep analysis of the solar diameter variations. Variations were mainly due to instrumental effects (mainly thermomechanical stresses) and no significant truly solar variations has been found [10] above 0”023 peak to peak. There again the amount of scattered light from the instrument does not permit a precise evaluation of the edge of the Sun due to the large illumination of the telescope by the light coming from the whole solar disk. Even the specially designed SODISM instrument of the Picard mission suffers from the same effect. 2.3- Solar eclipses to measure the solar diameter. Only at the time of a total eclipse of the Sun, the Moon occulting the full disk of the Sun in space (at a 400 000 km distance!), images made at the ground will be free of parasitic light. This occurs just before the full occultation, the true edge of the Sun being seen without the usual spurious amount of scattered light typical of non eclipse observations. Both the Earth atmosphere along the line of sight and the imaging instrument (or the photometer producing a light curve) are in the shadow of the Moon and they will not produce any spurious scattered light. It is one of the fundamental advantage of the eclipse method to measure the solar diameter and see the true edge of the Sun (it is also the reason why the solar corona is suddenly revealed during the total eclipse). Its precise angular value can be

Figure 7- Images taken near the time of the 2d contact of a total eclipse of the Sun. Note the Baily beads due to the details of the Lunar limb.

deduced from the timing of the contacts, see Fig. 7, by comparing the determined value at the eclipse with

8   6

the ephemeride value predicted for the contacts and calculated using a standard value of the solar diameter. The method is specially suitable for looking at long time range possible variations of the diameter of the Sun because the Moon is used as a reference and obviously the Moon diameter does not change in time at human scale. It is also a differential method as the occultation of the Sun occurs with a relative timing which is typically 30 times slower than the transit time of a celestial body in the sky due to the Earth rotation. This method has been used for a long time [7] and even historical eclipses were considered for discussing the possible variations of the solar diameters [11]. Unfortunately, the method is also subject to errors due to effects produced by the changing details of the lunar limb for different libration angles. This effect produces the so called Baily beads, see Fig. 7 and the underestimation of their effect probably explains several claims made in the past decades of a large (typically 0”3 to 0”4) variation of the solar radius. Today much more precise measurements can be done using recent technologies including the timing and the site positioning with a GPS basis, the use of fast and precise photometers with extended dynamics and the use of large CMos imagers operating at a high cadence. Even more important, it is possible to record at the same cadence, flash spectra with an excellent dispersion and free of parasitic scattered light in order to look at the true edge of the Sun. Finally, it is also possible to improve the solar eclipse method by introducing more precise lunar profiles coming from the recently flown lunar altimetry experiments (for ex. the Kaguya space mission) to correct the former Watts profiles of the Moon limbs for different libration angles.

3. The 2010 solar preliminary results.

eclipse

experiments

spectroscopic analysis during the inner contacts and during the totality, see Fig. 9.

Figure 8- Map to show where the total eclipse was observable. Note the motion of the lunar shadow (map provided by IMCCE- Paris).

and Figure 9- Eclipse composite image of the solar corona obtained at 18:43 UT with an EUV solar disk image from AIA (SDO) inserted in

At the time of the last solar total eclipse of July 11, 2010 we prepared a set of experiments in order to perform eclipse measurements of the solar diameter. By chance, the totality occurring above the South Pacific Ocean could also be observed from several well separated atolls of the French Polynesia, see Fig. 8. The program of observations included the study of the solar corona using white-light images and also a

place of the image of the Moon. It is taken also during the total eclipse of the Sun but outside the shadow of the Moon. The corona in white light was observed by Jean Mouette of the Institut d’Astrophysique de Paris, CNRS and UPMC on the atoll of Hao, French Polynesia. At top right, a sample of slitless spectra obtained during the totality by Serguei Kuzin, from FIAN in Moscow (Russia).

7  9 3.1- Eclipse photometers to measure the solar diameter. Special photometers were designed by CNES (France) to make precise measurements of the contacts from several selected sites, including sites at the limit of the totality. This rather large experiment will be described in a forthcoming article and here we just mention some preliminary features. 12 photometers were put on different locations of several Atolls the day before the total eclipse and they were collected the day after. Because each photometer included the use of a GPS component, they could operate autonomously and provide an absolute timing of the contact. Some very small drift effect was however influencing the recordings and the effect is still evaluated. The dynamical range of measurements was large, many decades, as the measurements started just before the 1 st contact and ended just after the 4th contact, more than 3 hours after. Unfortunately, clouds interfered with almost all the measurements but this did not really introduce a great uncertainty in the results concerning the timing of the contacts. The location of each photometer, including the altitude above the sea level, was determined with a great precision thanks to the GPS.

the lunar limb, better defined using the mission Kaguya profiles which are not yet available with an absolute reference frame of the optical lunar limb. It is now the subject of a detailed study that is beyond the scope of this paper. 3.2- Eclipse observations and results from Hao. We now show some preliminary results coming from the main eclipse site on the atoll Hao, see Fig. 10. Our team prepared, beside the eclipse photometers experiment see Fig. 11, several imaging and spectroscopic eclipse experiments.

Figure 11- Sample of results from the recordings performed by the eclipse photometer put at the site Hao.

Figure 10- A map of Atoll Hao to show the locations of the photometers put to observe the contacts at different point of the lunar limbs. Figure 12- Poster made of several flash slitless spectra obtained

To determine the best value of R0 from the comparison of the measured contact time and the ephemerides, the most uncertain factor is the position and the details of

during the 2d contact of the eclipse. The spectral range coverage goes from the deep blue to the green.

108  

Fig. 12 illustrates the result from one of the spectroscopic experiment shooting color flash slitless spectra over a large spectral interval, at a cadence of 2 spectra per sec, in order to cover the very edge of the Sun. After, some longer exposure spectra were made to

of us (Cyril Bazin) developed a special technique for making fast flash slitless spectra during the contact and Fig. 13 illustrates the resolution achieved and shows some identification of the very faint emission lines superposed on the continuum spectrum of the very limb, indeed the true edge of the Sun.

study the coronal lines produced above the solar limb when the chromospheres is fully covered by the Moon disk, see Fig. 9 the image of the corona in white light. Fig. 12 already shows that the very edge of the solar disk, which is almost completely occulted by the irregular edge of the Moon, is indeed difficult to define. Although some continuum radiation with F- lines imprinted (seen in absorption) is still well recorded at a location where a valley of the Moon is showing the very bright edge of the Sun, a myriad of new low excitation emission lines is appearing just during a few seconds superposed to the continuum spectrum. Note that 1 sec of observation approximately corresponds to 300 km on the Sun. Outside an eclipse these lines, not to be confounded with the much more extended towards the corona hotter chromospheric lines, are not seen because the strong effect at the solar limb produced by the parasitic light coming from the bright disk. Indeed one

3.3- Discussion of the main Eclipse observations. Such result as shown on Fig. 12 and 13, coming from fast spectroscopic eclipse observations with the aim of observing the solar extreme-limb and eventually measure a solar diameter was a surprise. It needs a careful evaluation and more importantly, it is shedding some light on the past observations and measurements of the solar diameter because such measurements were never done with a spectral resolution good enough to resolve the faint low excitation lines appearing at the solar limb. Depending of the method used in the past (visual; photographic; CCD or CMos detector with filter or not), the influence of these lines could be different giving different values for the solar diameter, although the irradiation correction artificially introduced to correct the measured values includes a correction for this effect. Such correction is not needed for eclipse observations like the measurements done with the CNES eclipse photometers but the effect of the faint emission lines will have to be considered. However the continuum radiation radial variations supposed to define the limb of the Sun was indeed never correctly measured. It is also pointing to the need to have a better definition of the edge of the Sun, a problem which is now starting to be seriously considered [12] although no account for the formation of the faint emission lines is introduced because the used models are 1D and they make the assumption of hydrostatic equilibrium. The upper layers of the solar atmosphere are clearly dominated by the emergence of the magnetic field and this effect can be taken into account only when using a 3D simulation and a full set of MHD equations.

Figure 13- Sample of spectra obtained by Cyril Bazin using a fast CCD to analyze the flash slitless spectra during the last solar total eclipse. Some identification of the superposed faint emission lines on

4.

Conclusion

the very edge of the solar disk is shown at the bottom after making a linearization of the curved spectrum.

Measurements of the solar diameter present a great interest in the frame of the debate concerning the socalled solar forcing effect on the Earth climate. It is also

  11

9

a fundamental “constant” of astrophysical interest and finally it is related to the knowledge of the solar atmosphere and of magnetic phenomena occurring at the heights corresponding to the very extreme limb. We presented a short review of the past observations and measurements with the feeling that they mainly represent a historical interest but that they cannot be taken seriously at the light of modern researches. Eclipse observations permit to more correctly evaluate the very edge of the Sun, see Fig. 12 and 13, but to provide valuable measurements of the solar diameter we need to know not only the details of the lunar limb but also the position of the lunar limb in an absolute reference optical frame, not just with respect to the centre of gravity of the Moon. This is explained in Fig. 14 using the former Watts lunar profiles where already some good correlations were observed with the observed spectra. New more detailed profiles are now available from the mission Kaguya and they will be used as soon as the profiles will be referenced in an optical system.

Figure 14- Schema to illustrate the method used to measure the solar diameter. The precise timing of the flash spectra should be referred to an optical position of the lunar edge in order to compute the angular diameter of the Sun.

The influence of the faint low excitation emission lines will have to be taken into account, after a consensus will be reached regarding the definition of the solar limb. This is a critical point in case of non eclipse observations when the extreme limb of the Sun is not properly measured because a large amount of scattered light is present. This means that special techniques like performing artificial eclipses in Space, could be used in the future. Natural eclipse observations will be improved in the future to provide measurements at long temporal range. Finally, the atmospheric models used to interpret the solar diameter variations should include the discussion of the influence of the faint emission lines and some additional observational works using modern CCD observations will have to be done to provide an atlas describing this effect. Acknowledgments It is a pleasure to thank Prof. Lotfia Nadi, from the Cairo University, for organizing a very successful high level international MTPR meeting and for inviting me to give an inaugural presentation at the Cairo University. The topic on the “discussion of the solar diameter measurements and the solar variabilities” was chosen after discussing with Prof. Ahmed Hady of the same University and we thank him for his help. Eclipse observations reported here are the result of efforts produced by many people who were involved at different stages of preparation and observations. It is difficult to list everybody but we want to name Jean Mouette, Patrick Martinez, Meleana Adams, Michel Lamiroté and Roland Santalo who directly participated in the observations reported here. Costantino Sigismondi also provided very helpful and valuable discussions during the development of this project.

References 1. 2.

H.I. Abdussamatov, IAU Symp. 223, 541 (2007). I. G. Usoskin, Living Rev. Solar Phys., 5, 3 (2008).

1210   

3.

E. Nisme-Ribes and G. Thuillier, Histoire solaire et climatique, Belin Ed. (1966). 4. J-P. Rozelot, C. Damiani and S. Lefebvre, IAU Symp. 264, 301 (2009). 5. W. Livingston, D. Gray, L. Wallace and O.R. White, in Large scale structures and their role in solar activity, NSO Workshop, ASP Conference Series, Vol. 346, 353 (2004). 6. A. Wittmann, Astron. Astrophys. 61, 255 (1977) 7. R.L. Gilliland, Astrophys.J. 248, 1144 (1981) 8. D. Djafer, G. Thuillier, G. and S. Sofia, Astrophys. J. 676, 651 (2008). 9. P. Chatterjee and H.M. Antia, Astrophys. J. 688, L123 (2008). 10. R.I. Bush, M. Emilio and J.R. Kuhn, Astrophys. J. 716, 2, 1381 (2010). 11. A. Kilcik, C. Sigismondi, J.P. Rozelot and K. Guhl, Solar Phys. 257, 237 (2009). 12. G. Thuillier, J. Claudel, D. Djafer, M. Haberreiter, N. Mein, S.M.L. Melo, W. Schmutz, A. Shapiro, C.I. Short and S. Sofia, Solar Phys. 268, 125 (2011).

I. ATOMIC, MOLECULAR AND CONDENSED MATTER PHYSICS I-1 KEYNOTE AND PLENARY PAPERS

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Photo-excitation and Photoionization for Plasma Opacities under the Iron Project Photo-excitation and Photoionization for Plasma Opacities under the Iron Project

1

Sultana N. Nahar Department of Astronomy, The Ohio State Columbus, OH 43210, USA Sultana N. University, Nahar E-mail: [email protected] Department of Astronomy, The Ohio State University, Columbus, OH 43210, USA E-mail: [email protected] Opacity gives a measure of radiation transport in a medium such that higher or lower opacity indicates more or less attenuation of radiation. As the radiation propagates, opacity is caused by the absorption and emission of radiation by Opacity gives a measure of radiation transport in a medium such that higher or lower opacity indicates more or less the constituent elements in the medium, such as astrophysical plasmas. It is also affected by photon scatterings. Hence attenuation of radiation. As the radiation propagates, opacity is caused by the absorption and emission of radiation by opacity depends mainly on the intrinsic atomic processes, photo-excitation in a bound-bound transition, photoionthe constituent elements in the medium, such as astrophysical plasmas. It is also affected by photon scatterings. Hence ization in a bound-free transition, and photon-electron scattering. Monochromatic opacity at a particular frequency, opacity depends mainly on the intrinsic atomic processes, photo-excitation in a bound-bound transition, photoionκ(ν), is obtained mainly from oscillator strengths (f ) and photoionization cross sections (σP I ). However, the total ization in a bound-free transition, and photon-electron scattering. Monochromatic opacity at a particular frequency, monochromatic opacity is obtained from summed contributions of all possible transitions from all ionization stages of κ(ν), is obtained mainly from oscillator strengths (f ) and photoionization cross sections (σP I ). However, the total all elements in the source. Calculation of accurate parameters for such a large number of transitions has been the main monochromatic opacity is obtained from summed contributions of all possible transitions from all ionization stages of problem for obtaining accurate opacities. The overal mean opacity, such as Rosseland mean opacity (κR ), depends all elements in the source. Calculation of accurate parameters for such a large number of transitions has been the main also on the physical conditions, such as temperature and density, elemental abundances and equation of state such problem for obtaining accurate opacities. The overal mean opacity, such as Rosseland mean opacity (κR ), depends as local thermodynaic equilibrium (LTE) of the plasmas. For plasmas under HED (high energy density) conditions, also on the physical conditions, such as temperature and density, elemental abundances and equation of state such fluid dynamics may be considered for shock waves such as in a supernova explosion. as local thermodynaic equilibrium (LTE) of the plasmas. For plasmas under HED (high energy density) conditions, In this report, I will exemplify the necessity for high precision atomic calculations for the radiative processes of phofluid dynamics may be considered for shock waves such as in a supernova explosion. toexcitation and photoionization in order to resolve some perplexing astrophysical problems relevant to elemental In this report, I will exemplify the necessity for high precision atomic calculations for the radiative processes of phoabundances and hence opacities. In particular I will present results on oscillator strengths of Fe XVIII and photoexcitation and photoionization in order to resolve some perplexing astrophysical problems relevant to elemental toionization cross sections of Fe XVII which are abundant in high temperature plasmas, such as solar corona, and abundances and hence opacities. In particular I will present results on oscillator strengths of Fe XVIII and phophotoionization and recombination of O II which is abundant in low temperature plasmas, such as in a planetary toionization cross sections of Fe XVII which are abundant in high temperature plasmas, such as solar corona, and nebula. Sophisticated atomic calculations under the Iron Project are revealing important and dominant features not photoionization and recombination of O II which is abundant in low temperature plasmas, such as in a planetary included in the current opacities. Opacities with these new results are expected to resolve the longstanding problems nebula. Sophisticated atomic calculations under the Iron Project are revealing important and dominant features not on abundances in the sun, orion nebula etc. included in the current opacities. Opacities with these new results are expected to resolve the longstanding problems on abundances in the sun, orion nebulastrengths; etc. Keywords: Photoionization; Oscillator Opacities; Solar and Nebular abundances Keywords: Photoionization; Oscillator strengths; Opacities; Solar and Nebular abundances

1. Introduction 1. Introduction Opacity is a fundamental quantity for studying various quantities such as elemental abundances, physiOpacity is a fundamental quantity for studying varcal of astrophysical iousconditions, quantities stellar such aspulsations elemental etc abundances, physiand laboratory stellar plasmas. It is used cal conditions, pulsations etc in of astrophysical models to obtain internalItstructure, comand laboratory plasmas. is used inchemical astrophysical position, of states, such as,chemical in local thermodels toevolution obtain internal structure, commodynamic equilibrium (LTE) of the plasmas, etc. position, evolution of states, such as, in local therAs the radiation propagates, it looses energy and modynamic equilibrium (LTE) of the plasmas, etc. slows by absorption and it emission the conAs thedown radiation propagates, looses by energy and stituent elements. The resultant effect is the opacity. slows down by absorption and emission by the conBecause of opacityThe the resultant high energy gamma stituent elements. effect is theradiation opacity. produced by the nuclear fusion in the core of the Because of opacity the high energy gamma radiation sun takes over a million years to travel to the surface produced by the nuclear fusion in the core of the and escapeover as optical or low photons. sun takes a million yearsenergy to travel to theOpacity surface depends on as the atomic of photo-excitations, and escape optical or process low energy photons. Opacity photoionization and photon scattering. depends on the atomic process of photo-excitations, However, calculation of opacity is quite involved photoionization and photon scattering. as described the theory of section. Foristhe photon-ion However,incalculation opacity quite involved interactions, depends the oscillator strengths as described init the theoryon section. For the photon-ion and photoionization crosson sections. Consideration of interactions, it depends the oscillator strengths these processes require large amount of atomic data and photoionization cross sections. Consideration of for all processes possible radiative transitions. these require large amountCurrently of atomicavaildata for all possible radiative transitions. Currently avail-

able atomic data for all ions are not accurate and complete enough opacitiesand for able atomic data to forcompute all ions accurate are not accurate various problems.accurate opacities for completeastrophysical enough to compute various astrophysical problems. 1.1. The Opacity Project and the Iron 1.1. Project The Opacity Project and the Iron Prior Project to the Opacity Project (OP),1,2 there were large between observaPrior discrepancies to the Opacity Projectastrophysical (OP),1,2 there were tions theoreticalbetween predictions obtained using exlarge and discrepancies astrophysical observaisting opacities for plasmas. Theseobtained opacities using were caltions and theoretical predictions exculated mainly by Alamos National Labwere (LANL) isting opacities for Los plasmas. These opacities calusing the atomic from simple culated mainly bydata Los obtained Alamos National Lab approxi(LANL) mations. Los Alamos opacities were incorrect by facusing the atomic data obtained from simple approxitors of 2 Los to 5Alamos resulting in inaccurate stellar models. mations. opacities were incorrect by facThese model the Cepheid stars, important tors ofcould 2 to 5not resulting in inaccurate stellar models. to determine distances in astronomy. In response to These could not model the Cepheid stars, important 3 ato plea for accurate opacity from accurate atomic determine distances in astronomy. In response to parameters Opacity intera plea3 for initiated accurate the opacity fromProject, accurateanatomic national collaboration of Opacity about 25Project, scientists 6 parameters initiated the anfrom intercountries national collaboration of about 25 scientists from 6 Under the OP the first systematic and detailed countries studies were outfirst for systematic the radiative Under thecarried OP the andprocesses detailed of photoexcitation and for processes all astrostudies were carried outphotoionization for the radiative of photoexcitation and photoionization for all astro-

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physically abundant atoms and ions from hydrogen to iron. Computations were carried out in ab initio close coupling approximation and using R-matrix method. Large amount of atomic data for energy levels, oscillator strengths and photoionization cross sections were obtained. The atomic data are available at data base TOPbase4 at CDS. New features in photoionization cross sections were revealed. The data were used to calculate the monochromatic opacities and Rosseland mean opacities. The long standing problem on the pulsation ratios of cepheid variables were solved. These atomic data have continued to solve many astrophysical problems. However, a large part of the data are not precise enough for various diagnostics and astrophysical problems. A follow-up of the OP, the international collaboration of the Iron Project (IP)5 was initiated to focus on both the radiative and collisional processes, but mainly for the astrophysically abundant iron and iron-peak elements. Work under IP emphasises the relativistic effects and achievement of high accuracy. A new project, RMAX, was also initiated under the IP to focus on the X-ray astrophysics. The large amount of atomic data from the IP are available at TIPbase6 at CDS, at Atomic Data and Nuclear Data Tables and at the NORAD-Atomic-Data site.7 The monochromatic opacities and Rosseland mean opacities are available at the OPServer8 at the Ohio Supercomputer Center. The OP team extended the existing R-matrix codes for radiative processes.9 The OP results were obtained in nonrelativistic LS coupling approach. In contrast to the OP, IP includes relativistic fine structure effects and the R-matrix method was extended to Breit-Pauli R-matrix (BPRM) method.10 Considerable progresses in computational capabilities for higher accuracy are being made under the Iron Project. Higher order relativistic corrections have been added to the BPRM method.11 Theoretical spectroscopy has been developed for consideration of large number of fine structure levels for all practical purposes.12,13 This enables calculation of accurate oscillator strengths for larger number of transitions than considered before. We are finding existence of extensive and dominant resonant features in the high energy photoionization cross sections. We have also found important fine structure effects in σP I in low energy region. We will illustrate results from recent calculations showing more com-

Table 1. A mixture of “standard” solar abundances (10% uncertainties14 ).

Element (k) H He C N O Ne Na Mg Al Si S Ar Ca Cr Mn Fe Ni

Log Ak 12.0 11.0 8.55 7.97 8.87 8.07 6.33 7.58 6.47 7.55 7.21 6.52 6.36 5.67 5.39 7.51 6.25

Ak /AH 1.0 1.00(-1) 3.55(-4) 9.33(-5) 7.41(-4) 1.18(-4) 2.14(-6) 3.80(-5) 2.95(-6) 3.55(-5) 1.62(-5) 3.31(-6) 2.29(-6) 4.68(-7) 2.46(-7) 3.24(-5) 1.78(-6)

plete atomic data and new features. These should facilitate the computation of more accurate monochromatic opacities. 2. Accurate Atomic Data Need Although data from the OP and IP continue to solve many problems, there are outstanding problems, especially for very high and very low temperature plasmas as discussed below, that remain to be solved. We illustrate the problems in perspectives of the atomic data. 2.1. High Temperature Plasmas in Solar Corona and Abundances The solar elemental abundances are known as: H 90 % (by number) and 70% (by mass fraction), He 10 % (by number) and 28 % (by mass), and metals (all elements heavier than helium) - 2% (by mass). In the metals, oxygen is the most abundant and the next ones are C, N, Ne, Mg, Si, S, Fe. The solar abundances are expressed as Ak , usually in log scale. Traditionally H abundance is taken as log(AH ) = 12 and the other elements are scaled relative to it as given in Table 1. Using the Opacity Project data and mixture of solar elemental abundances given in Table 1, solar opacity were calculated under the OP as shown in Fig. 1.14 In the figure, there about four bumps or kinks in the curves of various R. They represent

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Solar Opacity

3

2

Log κR (cm /g)

−2

2 −3

1

−4

−5 0 −6 −1 3.5

4

4.5

5

5.5 Log T(K)

6

6.5

Fig. 1. Opacities in temperature-density regimes throughout the solar interior. κ is the Rosseland mean opacity and R = ρ(g/cc)/T63 is the temeprature-density parameter with T6 = 106 K, i.e. T6 = T ∗ 10−6 . For the sun, -6 ≤ R ≤ -1. The four bumps in the curves of various R represent H-, He-, Z-, and inner-shell bumps, that is, higher opacities due to excitation/ionization of the atomic species at those temperatures.14

higher opacities due to excitation/ionization of different atomic species at those temperatures. The first one is the H-bump, the second one is the He-bump, the third one the Z-bump (sum of all elements heavier than H and He) and the fourth one is due to innershell excitation/ionization bump. These are general pattern for opacities and are in agreement with the other opacity by OPAL.15 However, these do not solve problems that require more presice elemental abundances. For example, the recent determination of solar abundances of light elements, from measurements and 3D hydro NLTE models, show 30-40% lower abundances of C, N, O, Ne, Ar than the standard abundances; these contradict the accurate helioseismology data. One major problem is with the observed and predicted boundary between the solar radiative zine and the convection zone, RCZ . Sun’s interior is defined from the - nuclear core to the end of convection zone. At the convection zone plasmas bubble beyond which photons escape. The boundary is known to be accurately measured from helioseismology as 0.713 (relative to the total solar radius, Fig. 2). RCZ can be predicted from opacity through elemental abundances in the solar plasma. The calculated boundary RCZ is 0.726, a much larger value than the measured value. Solar opacity depends on the interior elemental abundances. In the convection zone, the temper-

Fig. 2. Solar interior is defined from the core to the end of the convection zone. At the convection zone plasma bubbles and the radiation escapes.

ature is Te ∼193 eV and the density ne ∼ 1023 /cm3 which is a HED (high energy density) condition. At this HED condition, the abundant elements are O, Ne, especially Fe ions in the ionic states of Fe XVII, Fe XVIII, and Fe XIX. Laboratory set-ups, such as zeta pinch or Zpinch machines at the Sandia National Lab (SNL) and high power lasers, such as, at National Ignition Facility (NIF), can now study radiation transport or opacity in fusion plasmas. The measurements will enable calibration of the theoretical calculations of basic parameters that govern the opacity. Bailey et al16 reported achieving HED plasmas at temperature (T > 106 K) and density (N > 1020 cm−3 ) similar to those at the boundary of the solar convection zone. The Z-pinch set-up is a type of plasma confinement system. The plasma is created with laser heating. About 24 Million Amp current is passed through the coil set-ups to generate a gigantic magnetic field that compresses the plasma. The measurement at SNL Zpinch machine showed that the iron opacity at solar corona is much higher than the prediction obtained using the radiative atomic data, oscillator strengths for photoexcitation and cross sections for photoionization, from the Opacity Project (OP). 2.2. Low Temperature Plasmas and Nebular Abundances Similar to high temperature plasms, longstanding problems on abundance exists for low temperature astrophysical plasmas, such as, in Orion nebula, planetary nebulae (PNe). A planetary nebula is the last stage of a typical star. Fig. 4 shows PNe K 4-

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ancy between abundances of oxygen calculated from collisionally excited lines (CEL) of O III Lines and from the recombination lines (REL) from O III to O II. The former is larger than the latter, that is, Ne N (O III)αR (T ) < Ne N (O III)qEIE (T ) and has been a puzzle for many years. One solution for the problem would be to have predicted recombination rate for O III→O II is higher than that at the present time.

Fig. 3. Magnetically driven z-pinch implosions efficiently convert electrical energy into radiation. Internal shock heating gives out high energy X-rays (1.5 MJ X-rays) with power of aobut ∼200 TW.

3. Photo-excitation, Photoionization and Opacity Opacity κ(ν) depends on oscillator strengths of photoexcitation. Photo-excitation and de-excitation can be described as X +Z + hν  X +Z∗

Fig. 4. Planetary nebula Kohoutek 4-55 or K 4-55 by Hubble Space Telescope. The envelope of thin gas is illuminated by the radiation from the hot central core.

55 nearly 4,600 light-years away in the constellation Cygnus. The condensed central star is at very high temperature of about T∼100,000 K whereas for a typical star T≤ 40,000 K. The envelope of a PNe is thin gas formed by the radiatively ejected gas by the star and is illuminated by the radiation from the central star. The cooler envelope is rich in elements, such as, oxygen, nitrogen, at low ionization stages. Lines of O III and O II are detected indicating low density and low temperature. At very low densities, electrons can populate excited metastable energy levels which on de-excitation gives lines, often fobidden ones. Abundance can be obtained from these lines due to collisional excitation. At low temperature, electrons combine with the ions by giving out photons which form the recombination lines. These lines also give abundance of the element. However, there is a discrep-

where X +Z is the ion with charge Z. The emitted or absorbed photon (hν) is observed as a spectral line. The relevant atomic parameters for the direct and inverse processes are oscillator strength (f ) and radiative decay rate (A-value). fij is related to κ(ν) as πe2 κν (i → j) = Ni fij φν (1) mc Ni is the ion density in state i, φν is a profile factor which can be Gaussian, Lorentzian, or combination of both over a small wavelength range. The other radiative process that determines opacity is photoionization when an electron is ejected with absorption of a photon, X +Z + hν  X +Z+1 +  The inverse process is radiative recombination (RR) when an electron recombines to an ion with emission of a photon. These can occur via an intermediate doubly excited state as:  AI e + X +Z +Z +Z−1 ∗∗  (X )  e+X +Z−1 X + hν DR

A colliding electron excites the target and attaches to form the short-lived doubly excited autoionizing state. The state leads either to autoionization (AI) where the electron goes free and target drops to ground state or to dielectronic recombination (DR) where the electron gets bound by emission of a photon. The autoionizing state manifests as an enhancement or resonance in the process. Photoionization resonances can be seen in absorption spectra while

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recombination resonances can be seen in emission spectra. The atomic parameters for these processes correspond to photoionization cross sections (σP I ) and recombination rates. κ(ν) for photoionization is obtained from σP I as κν = Ni σP I (ν)

(2)

κν depends also on two other processes, inverse Bremsstrahlung or free-free (ff) scattering and photon-electron scattering. Bremsstrahlung refers to the radiation emitted by a charged particle accelerated in an electromagnetic field. The inverse process is where a free electron and an ion can absorb a photon in free-free interaction, that is, hν + [X1+ + e()] → X2+ + e( ),

(3)

Explicit calculations for the free-free scattering cross sections may be done using the elastic scattering matrix elements for electron impact excitation of ions. An approximate expression for the free-free opacity is given by κfν f (1, 2) = 3.7 × 108 Ne Ni gf f

Z2 T 1/2 ν 3

(4)

where gf f is a Gaunt factor. The photon electron scattering can be of two type, Thomson scattering, when the electron is free and Rayleigh scattering when the electron is bound to an atomic or molecular species. κ is related to Thomson scattering cross section σ T h , 8πe = 6.65 × 10−25 cm2 /g, 3m2 c4 (5) To Rayleigh scattering cross section σ R , opacity is related as  4 ν R Th κR = n σ ≈ n f σ (6) i i t ν ν νI κ(sc) = Ne σ T h = Ne

local thermodynamic equilibrium (LTE) Saha equation is the EOS. However, Saha equation is not applicable in non-LTE condition. Some details of the opacity calculations can be found in.17 The average opacity also depends on the physical condition of the plasmas, such as, the density and temperature Rosseland mean opacity κR (T, ρ) is the harmonic mean opacity averaged over the Planck function, g(u), ∞ 1 g(u)du 1 , (7) = 0 ∞κν κR g(u)du 0 where g(u) is given by

15 u4 e−u hν , u= 4π 4 (1 − e−u )2 kT

g(u) =

(8)

g(u), for an astrophysical state is calculated with different chemical compositions H (X), He (Y) and metals (Z), such that X +Y +Z =1

(9)

4. Theoretical Approach 4.1. Breit-Pauli R-matrix Method We use the Breit-Pauli R-matrix (BPRM) method to calculate the oscillator strengths and photoionization cross sections. It uses close coupling approximation for the wave function. The relativistic BreitPauli Hamiltonian is given by H BP = H N R + H mass + H Dar + H so +

4

where ni is the density of the atomic or molecular species, hνI is the binding energy and ft is the total oscillator strength associated with the bound electron, i.e. the sum of all possible transitions, such as the Lyman series of transitions 1s → np in hydrogen. To find the average opacity, such as Rosseland opacity, we need elemental abundances. These are obtained from proper equation of state (EOS) which gives the ionization fractions and level populations of each ion of an element in levels with non-negligible occupation probability. For example, for plasmas in

N

1 [gij (so + so ) + gij (ss ) + gij (css )+ 2 i=j

gij (d) + gij (oo )]. H

NR

(10)

is the nonrelativistic Hamiltonian,   N  N    2Z 2 HNR = −∇2i − +  ri rij  i=1

(11)

j>i

and the one-body relativistic correction terms are mass correction, Darwin and spin-orbit interaction terms respectively,   α2  4 α2  2 Z , pi , H Dar = ∇ H mass = − 4 i 4 i ri H so =



Ze2 2 2m2 c2 r3



(12)

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The spin-orbit interaction H so splits LS energy in to fine structure levels. Rest of the terms are two-body interaction terms where the notation are s for spin and a prime indicates ’other’, o for orbit, c for contraction, and d for Darwin. These terms are much weaker but can become important for weak transitions and when relativistic effects are important. BPRM method5,10 included the three one-body relativistic correction terms in the Hamiltonian: BP NR mass Dar so HN +1 = HN +1 + HN +1 + HN +1 + HN +1 ,

(13)

Inclusion of two-body interaction terms are much for complicated. The first two two-body terms provide the Breit interaction  [gij (so + so ) + gij (ss )] (14) HB = i>j

where

gij (so + so ) = −α2 [(

gij (ss ) = 2α 

2



rij 3 × pi ).(si + 2sj ) + rij rij ( 3 × pj ).(sj + 2si )] (15) rij

(si .rij )(sj .rij ) si .sj −3 3 5 rij rij



(16)

which contributes more relatively to the other terms. In the latest development of the BPRM codes, Breit interaction has been included.11 In close coupling (CC) approximation, the wave function is represented by an expansion where the ion is treated as a system of (N+1) electrons. The core ion, termed as the target, has N electrons and the additional electron is the interacting (N+1)th electron. The total wave function expansion is expressed as: N   χi (ion)θi + cj Φj (e + ion) ΨE (e + ion) = A i

j

(17) where χi is the target ion or core wave function which includes excitations. θi is interacting electron wave function (continuum or bound), and Φj is a correlation function of (e+ion). The complex resonant structures in the atomic processes are included through coupling of bound and continuum channels with core excitations. The target wave functions χi are obtained from atomic structure calculations, e.g. SUPERSTRUCTURE (SS),18,19 Substitution of ΨE (e + ion) in HΨE = EΨE results in a set of coupled equations which are solved

Fig. 5. In R-matrix method, the space is divided into two regions, the inner and the outer regions, of a sphere of radius ra with the ion at the center.

by the R-matrix method. In the R-matrix method (Fig. 5), the space is divided in two regions, the inner and the outer regions, of a sphere of radius ra with the ion at the center. ra , the R-matrix boundary, is chosen large enough for electron-electron interaction potential to be zero outside the boundary. The wave function at r > ra is Coulombic due to perturbation from the long-range multipole potentials. In the inner region, the partial wave function of the interacting electron is expanded in terms of a basis set, called  the R-matrix basis, Fi = ak uk , which satisfy   2  l(l + 1) d ulk + − + V (r) +  λnlk Pnl (r) = 0. lk 2 2 dr r n (18) and are made continuous at the boundary by matching with the Coulomb functions outside the boundary. For negative energy, the solution is a bound (e+ion) states, ΨB and for positive energy, the solution is a continuum state, ΨF . 4.2. Atomic Quantities To calculate oscillator strengths and photoionization cross sections, we obtain the line strength first. It depends on the transitions matrix element for the bound-bound (photoexcitation) and bound-free (photoionization) transitions with a dipole operator. The dipole transition matrix elements for photoexcitation and photoionization are < ΨB ||D||ΨB  >, < ΨB ||D||ΨF > (19)  respectively, where D = i ri is the dipole operator and and the sum is over the number of electrons.

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The reduced tensor ||D|| gives 3-j symbols for angular momenta on simplification. The transition matrix element reduces to generalized line strength as  2  N +1    S =  Ψf rj Ψi  (20)   j=1

This is the quantity of interest for both the processes. The oscillator strength (fij ) and radiative decay rate (Aji ) for the bound-bound transition are obtained as     E3 Eji −1 10 ji fij = S S, Aji (sec ) = 0.8032 × 10 3gi 3gj (21) The photoionization cross section, σP I , is obtained as   4π 1 σP I = ωS, (22) 3c gi

where ω is the incident photon energy in Rydberg unit. With consideration of relativistic fine structure effects, BPRM method enables extensive sets of E1 transitions (∆ j=0,±1, ∆L = 0, ±1, ±2, parity π changes) with same spin-multiplicity (∆S = 0) and intercombination (∆S = 0). On the contrary LS coupling allows only same spin-multiplicity transitions. Large sets of various forbidden transitions are considered in Breit-Pauli approximation using atomic structure calculations. Due to small f -values, typically the radiative decay rates, A−values, are calculated for the forbidden transitions. These transitions are mainly i) electric quadrupole (E2) transitions (∆ J = 0,±1,±2, parity does not change) 3 AE2 ji = 2.6733 × 10

5 Eij S E2 (i, j) s−1 , gj

(23)

ii) magnetic dipole (M1) transitions (∆ J = 0,±1, parity does not change), 1 4 AM ji = 3.5644 × 10

3 Eij S M 1 (i, j) s−1 , gj

(24)

iii) electric octupole (E3) transitions (∆ J= ±2, ±3, parity changes) and −3 AE3 ji = 1.2050 × 10

7 Eij S E3 (i, j) s−1 , gj

(25)

iv) magnetic quadrupole (M2) transitions (∆ J = ±2, parity changes) and −2 −1 s AM2 ji = 2.3727 × 10

5 Eij S M2 (i, j) . gj

(26)

Some details of the forbidden transitions are given in.19,20 These transitions are treated through atomic structure code SUPERSTRUCTURE18 and its later version.19 With the A-values, the lifetime of a level can be obtained easily as, 1 . (27) τk (s) =  −1 ) i Aki (s 5. Results and Discussions

The accuracy and completeness of oscillator strengths for bound-bound transitions and new features in photoionization affecting the plasma opacities are discussed with examples in subsections below. 5.1. Energy Levels and Oscillator Strengths Iron is a dominant metal and astrophysical spectra are rich with its lines. However, due to strong electron-electron correlations, it is a computational challenge to compute accurate atomic data for various ionic states of iron. One objective of the Iron Project is to study systematically the energy levels and lines of various ion ions. A few examples of the iron ions for which accurate and complete data for oscillator strengths are available for all practical needs are Fe XVII,19 Fe XVIII,21 Fe XIX22 which are abundant in solar corona. The large number of energy levels and transitions that BPRM method can compute are identified spectroscopically through a major task of many tests. It is different from atomic structure calculations where identification of an energy level is based on the percentage contributions of the configurations. In BPRM method, such contributions can not be obtained. Identification is carried out with a method developed based on the channel contributions in the outer region of the R-matrix method, quantum defect theory, and algebraic algorithms.12,13 The identified levels match with those from atomic structure calculations for most cases. However, since BPRM considers larger number of configurations causing more mixing coefficients and quantum defects are often too close to differentiate for closely lying levels, identifications may differ. The difference also depends on the set of the configurations selected and the way configurations are optimized.

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8 22   Table 2. Sample set of fine structure energy levels of Fe XVIII.21 The levels are grouped as sets of LS term components. Ct is the core configuration, ν is the effective quantum number. Ct (St Lt πt )

Jt

nl 2J

E(Ry)

ν SLπ

Eqv electron/unidentified levels, parity: o 2s22p5 3 -9.98779E+01 0.00 2P o 2s22p5 1 -9.89033E+01 0.00 2P o Nlv(c)= 2 : set complete Eqv electron/unidentified levels, parity: e 2s22p5 1 -9.00863E+01 0.00 2S e Nlv(c)= 1 : set complete Nlv= 3,

4

Le : P ( 5 3 1 )/2

2s22p4 (3Pe) 2s22p4 (3Pe) 2s22p4 (3Pe)

2 2 0

3s 3s 3s

5 -4.30858E+01 2.74 4P e 3 -4.28383E+01 2.75 4P e 1 -4.23704E+01 2.74 4P e

Nlv(c)= 3 : set complete Nlv= 2,

2

Le : P ( 3 1 )/2

2s22p4 (3Pe) 2s22p4 (3Pe)

1 1

3s 3s

3 -4.21961E+01 2.74 2P e 1 -4.19680E+01 2.75 2P e

Nlv(c)= 2 : set complete Nlv= 2,

2

Le : D ( 5 3 )/2

2s22p4 (1De) 2s22p4 (1De)

2 2

3s 3s

5 -4.14059E+01 2.75 2D e 3 -4.13716E+01 2.75 2D e

Nlv(c)= 2 : set complete Nlv= 8, 2s22p4 2s22p4 2s22p4 2s22p4 2s22p4 2s22p4 2s22p4 2s22p4

4

Table 3. Comparison of calculated BPRM absolute energies, Ec , of Fe XVIII21 with observed values, Eo , compiled by NIST.? IJ is the level index for the calculated energy position in symmetry Jπ. The asterisk next to a J-value indicates that the term has missing fine structure components in the observed set. Level 2s22p5 2s22p5 2s2p6 2s22p4(3P )3s 2s22p4(3P )3s 2s22p4(3P )3s 2s22p4(3P )3s 2s22p4(3P )3s 2s22p4(1D)3s 2s22p4(1D)3s 2s22p4(1S)3s 2s22p4(3P )3d 2s22p4(3P )3d 2s22p4(3P )3d 2s22p4(3P )3d 2s22p4(3P )3d 2s22p4(3P )3d 2s22p4(3P )3d 2s22p4(3P )3d 2s22p4(1D)3d 2s22p4(1D)3d 2s22p4(1D)3d 2s22p4(1D)3d 2s22p4(1D)3d

J : IJ 2

o

P Po 2 S 4 P 4 P 4 P 2 P 2 P 2 D 2 D 2 S 4 P 4 P 4 P 2 F 4 D 4 D 2 P 2 D 2 S 2 P 2 P 2 D 2 D 2

1.5 :1 0.5 :1 0.5 :1 2.5 :1 1.5 :1 0.5 :2 1.5 :2 0.5 :3 2.5 :2 1.5 :3 0.5 :4 2.5 :3 1.5 :4 0.5 :5 2.5*:4 1.5*:5 0.5*:6 1.5*:6 2.5*:6 0.5 :7 1.5 :9 0.5 :8 2.5 :8 1.5 :10

Eo (Ry) 9.98779E+01 9.89033E+01 9.00863E+01 4.30858E+01 4.28383E+01 4.23704E+01 4.21961E+01 4.19680E+01 4.14059E+01 4.13716E+01 3.99754E+01 3.77130E+01 3.76699E+01 3.75811E+01 3.70202E+01 3.70925E+01 3.72334E+01 3.68203E+01 3.65122E+01 3.57466E+01 3.55279E+01 3.51835E+01 3.57466E+01 3.52693E+01

Ec (Ry) 1.00100E+02 9.91652E+01 9.03977E+01 4.34010E+01 4.25270E+01 4.25972E+01 4.31631E+01 4.23020E+01 4.17789E+01 4.17443E+01 4.01833E+01 3.71888E+01 3.74741E+01 3.76035E+01 3.74012E+01 3.70494E+01 3.71934E+01 3.67915E+01 3.67031E+01 3.61810E+01 3.59614E+01 3.56351E+01 3.59395E+01 3.57080E+01

Lo : S ( 3 )/2 P ( 5 3 1 )/2 D ( 7 5 3 1 )/2

(3Pe) (3Pe) (3Pe) (3Pe) (3Pe) (3Pe) (3Pe) (3Pe)

2 2 2 2 2 0 0 0

3p 3p 3p 3p 3p 3p 3p 3p

3 5 1 7 5 1 3 3

-4.08315E+01 -4.07910E+01 -4.05398E+01 -4.04861E+01 -4.04822E+01 -4.00221E+01 -3.98416E+01 -3.96589E+01

2.82 2.82 2.83 2.83 2.83 2.82 2.83 2.83

4SPD o 4PD o 4PD o 4D o 4PD o 4PD o 4SPD o 4SPD o

Nlv(c)= 8 : set complete

For example, for Fe XVIII BPRM method produced 1174 fine structure levels with n≤10 and l ≤921 compared to available observed 66 levels (NIST compiled table23 ). The calculated levels are identified and are checked for completeness as shown for Fe XVIII in the Table 2. The top line for each set of energy levels shows total number of possible levels (Nlv) with LS states and corresponding J values. The last column of the set gives the possible LS state with fixed spin multiplicity and parity. The calculated BPRM energies are of high accuracy agreeing with the most accurate and measured values by a few percent. For Fe XVIII levels, the agreement is within 1% for most levels, the highest discrepancy being 3%. Table 3 shows comparison of Fe XVIII energies with the measured values of Shirai et al? listed in NIST23 compilation. The bound levels of Fe XVIII with n ≤ 10 correspond to 141,869 allowed electric dipole transitions

over a broad energy range. The accuracy of these transitions are made with the limited number of available transitions, particularly with those evaluated and compiled by the NIST. The available values are obtained from atomic structure calculations by various investigators and are in good agreement of the BPRM values in general. It may be noted that the evaluated accuracies by NIST are not necessarily consistent with the agreement between BPRM radiative decay rates and other calculations. Table 4 presents comparison of radiative decay rates (Avalues) and good agreements can be seen between BPRM and other values. A single measurement of lifetime of level 2s2p5 (3 P2o ) is also in good agreement with the BPRM value. The IP considers the forbidden transitions mainly for diagnostics and collisional modeling. Because of weaker in nature forbidden transitions are considered up to n ≤ 5 in general and are obtained through atomic structure calculations. Nahar21 reported forbidden transitions of Fe XVIII of type electric (E2, E3) and magnetic (M1, M2) multipoles up to n=4, that is, up to 4f with a total of 29,682 transitions. They are from 243 fine structure levels of fifteen configurations. Comparison of these levels with the measured values (NIST compilation) shows

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agreement within 1% for most levels. The largest difference is 3.4% for the level 2s2p5 (1 P o )3p2 D. Comparison of forbidden transitions is also made in Table 4 showing good agreement with others.

dicates systematic shift in groups of OP energies.

Table 4. Comparison of present radiative decay rates, A-values, (in units of s−1 ) for Fe XVIII with those from previous calculations. The letter in the second column gives NIST accuracy rating. Notation a + b means a × 10b . λ ˚ A

A:Ac Others

Ci − Cj

A Present

SLπ i-j

g i-j

E1 a

+

2

P o −2 S 4-2 2 o P −2 S 2-2

93.926 9.13+10 :C 7.75+10 2s22p5 − 2s2p6 103.94 3.31+10a :C+ 2.81+10 2s22p5 − 2s2p6 15.766 1.4+12a,b :D 1.16+12 2s2 2p5 − 2s2 2p4 16.026 1.5+12a,b :D 1.34+12 2s2 2p5 − 2s2 2p4 15.847 2.0+11a :E 16.072 9.1+10a :E

1.88+11 2s2 2p5 − 2s2 2p4 8.44+10 2s2 2p5 − 2s2 2p4

3 3 3 3

P 3s P 3s P 3s P 3s

2 2 2 2

15.625 1.1+12a,b :D 9.68+11 2s2 2p5 − 2s2 2p4 15.870 1.3+12a,b :D 1.19+12 2s2 2p5 − 2s2 2p4

1

14.152 4.3+12a,b :E 3.55+12 2s2 2p5 − 2s2 2p4 14.361 1.5+13a,b :E 1.33+13 2s2 2p5 − 2s2 2p4

1

14.203 1.9+13a,b :E 1.83+13 2s2 2p5 − 2s2 2p4 14.418 3.2+12a,b :E 2.61+12 2s2 2p5 − 2s2 2p4

1

2.09+11 2s2 2p5 − 2s2 2p4

1

5.32+10 2s2 2p5 − 2s2 2p4 13.919 9.6+10b :E 13.954 1.1+12a,b :D 9.94+11 2s2 2p5 − 2s2 2p4 14.121 1.5+13a,b :D 1.32+13 2s2 2p5 − 2s2 2p4

1

2

1

2

15.209 2.8+11b :E

1

P o −2 P 4-2 P o −2 P 2-2 P o −4 P 4-2 P o −4 P 4-6

D3s 2 P o −2 D 4-6 D3s 2 P o −2 D 2-4

D3d 2 P o −2 D 4-4 1 D3d 2 P o −2 D 2-4 1

D3d 2 P o −2 P 4-4 D3d 2 P o −2 P 2-4 S3s

S3d S3d 1 S3d

2

P o −2 S 4-2

P o −2 D 4-4 P o −2 D 4-6 2 o P −2 D 2-4

E2,M1 974.86 1.9+00 :D 1.98 2s2 2p5 − 2s2 2p5 : E2 974.86 1.93+04a :C 1.94+04 2s2 2p5 − 2s2 2p5 : M 1 a,b

2 2

P o −2 P o 4-2 P o −2 P o 4-2

Lifetime (10−12 s) λ 93.9

Expt 12.2±0.8c

Present 12.90

Ci − Cj 2s22p5 − 2s2p6

SLπ i-j 2

g i-j

P o −2 S 4-2

a - Cheng et al. 1979, b - Fawcett 1984, c - Buchet et al 1980

The effect of accuracy on opacities was tested for Fe IV by Nahar and Pradhan? with more improved oscillator strengths than that obtained earlier under the OP. The oscillator strengths were processed for fine structure splittings, but with no relativistic corrections. They obtained monochromatic opacities for Fe IV at a temperature logT(K)=4.5 and electron density logNe (cm−3 ) = 17.0, where Fe IV dominates the iron opacity. They found that κν which depends primarily on oscillator strengths, differs considerably from those obtained using earlier oscillator strengths of the OP as shown in Fig. 6. κν varies over orders of magnitude between 500 - 4000 ˚ A. Comparison in-

Fig. 6. Monochromatic opacities (κν ) of Fe IV using atomic transitions from the Opacity Project in TOPbase (lower panel) and using data from later calculations under the Iron Project28 showing considerable differences, especially in region of 500 - 4000 ˚ A

5.2. Photoionization Opacity is caused by photoionization, but mainly through the photon absorption at resonant energies. The resonances are introduced as the core goes through excitations. The OP work computed the resonances in photoionzation of the ground and many excited states of many atomic systems for the first time. However, the work focused only the low energy resonances. It was assumed that low energy resonances due to couplings of channels with the lower excitations of the core ion are more dominant. However, later investigations under the IP revealed that resonances due to excitations of the high lying core states of ions, such as for Fe XXI, could play a very important role for cases, such as Fe XXI29 ). Relativistic fine structure effects at low energy can also reveal structures which are not allowed in LS coupling approximation (e.g. for Fe XXI29 ). These structures, not studied before, can be very important for low temperature plasmas where they will change the current calculated opacities and expect to resolve or reduce large gaps of differences between the observational and calculated values. These new features are illustrated in the following two sections. 5.2.1. High Energy Photoionization High energy photoionization is important for high temperature plasmas where elements can be in highly ionized states. It is usually assumed that high energy photoionization is featureless and decays similar to that of a hydrogenic ion. It is also a computational

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(Et − Ep ) = z 2 /ν 2 where Et is an excited core state or threshold and ν is the effective quantum number of the state. Each excited core state corresponds to a Rydberg series although the resonances may not be prominent for the some states. These resonances are usually narrow and more common. The autoionizing states of n=3 levels do not have much impact, except appearing as some weak resonances, on the ground level σP I as seen in the top panel of Fig. 7. The figure present σP I of the a) ground level 2s2 2p6 (1 S0 ) and b) an excited level 2s2 2p5 3d(3 P0o ) of Fe XVII. In the figure arrows point energy limits of n=2 and 3 core states. While resonances introduced by the core excitations to n=2 levels are important for the ground level, excitations to n=3 levels are more important for the excited level photoionization. The high energy region of σP I of the

Photoionization Cross sections of Fe XVII 102 Fe XVII + hν -> Fe XVIII + e 101

a) Ground state: 2s22p6 1S

100

10-1 n=2

σPI(Mb)

challenge to get cross section over a great energy range. Nonetheless, it is highly crucial to study the high energy photoionization features which can be much more promiment than those of low temperature. We have recently completed the computations for photoionization cross sections (σP I ) for Fe XVII30 using the BPRM method. In addition to solar corona, this ion is abundant in high temperature plasmas of many other astronomical objects. This is the first ion for which high energy photoionization has been studied using the BPRM method. The energy diagram for core excitations of this ion gives an image of typical resonant strucutes in a relatively small energy range beyond the ionization threshold. The core ion, Fe XVIII, has three levels in the n=2 complex beyond which there is a large energy gap of about 47 Ry before the core can be excited to n=3 levels. Our computation included 60 levels of n=2 and n=3 complexes of Fe XVIII. Earlier calculations assumed that the very high lying n=3 levels have small coupling effects on photoinization. It is known that the n=3 excitations do not form any bound state of Fe XVII. The n=3 core levels lie too high above to form any bound level. The recent study30 finds that although n=3 core excitations do not form any bound state, they form autoionizing states and appear as strong resonances in photoionization cross section as shown in Fig. 7. Most of these resonances are Rydberg series autoionizing resonances. They form at energies Ep ,

10

3

102

100

n=3 120

140

160

b) Excited Level: 2s22p53d 3Po0

101 100 10-1 n=3

10-2 n=2 10-3 40

60

80

100

Photon Energy (Ry)

Fig. 7. Photoionization cross section σP I of Fe XVII. For the ground level: n=2 resonances are important and for an excited level: n=3 resonances are important. Arrows point energy limits of n=2 and 3 core states.

excited level is filled with high peak resonances. The wide PEC (photo-excitation-of-core) or Seaton resonances in the high energy region are the other dominant contributors to plasma opacity. These resonances occur when the core goes through a dipole allowed transition while the outer electron remains as a spectator. The state is followed by ionization via the outer electron while the core drops down to the ground state. The ground level of core o Fe XVIII is 2s2 2p5 (2 P3/2 ). Hence a PEC resonance can form when the core goes through the dipole trano ) − 2s2 2p4 3s(2 P3/2 ). PEC resosition, 2s2 2p5 (2 P3/2 nances are manifested at the excited energy threshold that the core was excited to. PEC resonances exist in valence electron excited states only, that is, no PEC resonance for the ground or equivalent electron states. The resonant phenomena was first explained by Seaton in.31 Fig. 8 presents σP I of the excited level, 2s2 2p5 7f (3 D1 ), of Fe XVII. The present calculations includes 29 possible dipole allowed transitions for the core ground level and each corresponds to a Seaton resonance. The overlapping Seaton resonances have been pointed by couple of arrows in the figure. As the figure shows, Seaton resonances are strong which increase the background cross sections by orders of magnitude. The shape and strength of

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11   25 102 101

Fe XVII(2p57f 3D1) + hν -> Fe XVIII + e

102

100

5

10-1 10-2

1

10

1

101

a) 2p 3p( P)

a) PEC (∆n=2-2) 9

10

11

c) 2p53d(1Do)

100

100

12

10-1 10-1 10-2 10-2

57.5

58

58.5

59

σPI(Mb)

5 6 7 8 102 101 100 b) PECs (∆n=3-2) 10-1 10-2 10-3 10-4 10-5 55.5 56 56.5 57 101 100 c) PECs (∆n=3-2) 10-1 10-2 10-3 10-4 10-5 60 62 101 100 10-1 10-2 10-3 d) Total energy range 10-4 10-5 10 20 30

Fe XVII + hν -> Fe XVIII + e

OP

OP

10-3

σPI (Mb)

102 Fe XVII + hν -> Fe XVIII + e

10-3

102

1

10

102

b) 2p53p(1P)

101

Present

d) 2p53d(1Do) Present

100 100 10-1

64

10-1

66

10-2 n=2

10-2

n=2 n=3 40

60

80

100

n=3

10-3 40

60

80

100

Photon Energy (Ry)

40

50

60

70

Photon Energy (Ry)

Fig. 8. Photoionization cross section (σP I ) of excited level 2p3 7f (3 D1 ) over various ranges of energy (a,b,c) while the bottom panel (d) presents the total range. PEC resonances appear, positions pointed by arrows, occur at energies of dipole transitions in the core. They are high-peak, wider and enhance the background σP I by orders of magnitude, and will affect photoionization and recombination rates, especially of high temperature plasmas.

PEC resonances depend on the interference of core excitations and overlapping Rydberg series of resonances. These dominating features, especially those due to ∆n =3-2 core transitions, show large enhancement of photon absorptions related to the opacities. These are non-existent in the available data and thereby grossly underestimating the opacity. Photoionization cross sections of two levels of Fe XVII obtained from BPRM calculations and from the OP are compared in Fig. 9. Panels (a,b) shows σP I of level 2p5 3p1 P and panels (c,d) of level 2p5 3d(1 Do ), respectively. Comparison shows low and smooth background in OP cross sections in panels (a) and (c) while BPRM σP I ? filled with resonant structures. These high peak resonances in BPRM cross section indicate higher probability of photoionization. Without inclusion of n=3 core states, σP I is considerably underestimated. These resonances also indicate higher absorption of photons by orders of magnitude. These will increase opacity which currently include only ∆ n=2-2 core excitation.

Fig. 9. Comparison of photoionization cross section (σP I ) of excited levels 2p3 7f (3 D1 ). PEC resonances appear at energies of core dipole transitions. They are strong & enhance the background σP I by orders of magnitude.Will affect photoionization & recombination rates of high temperature plasmas

5.2.2. Low Energy Photoionization Relativistic effects are not significant for low to medium Z elements for most practical applications. Hence photoioniation cross sections calculated in LS coupling can be of high accuracy to benchmark experimental measurement with very good agreement. However, there are cases when resonant features are formed by the allowed fine structure coupling, but not allowed in LS coupling, in the very low energy region and are of crucial importance. An example of such a case is photoionization of O II. Importance of O II as a diagnostic element is well known for the low temperature plasmas in Orion nebula from where its lines can be observed as mentioned above. The radiative and collisional processes of O II are well studied and accurate parameters for the processes are available. The experimental measurement of the O II photoionization at the high resolution set-up of ALS (Advanced Light Source) in Berkeley32,33 has been benchmarked with theoretical calculations in LS coupling.34 However, determination of its abundance has remained an unsolved problem because of the large discrepancy between the abundances calculated from collisional excitation and from recombination processes. Our latest calculations including relativistic fine

12

26  

102

O II + hν -> O III + e

101 a) Ground State 2s22p3 4So (Total): LS

100 -1

10

102 101 100

b) Ground State (Total): Full Breit-Pauli

10-1 2s22p2 3P0 (partial)

c)

σPI(Mb)

σPI(Mb)

102 101 100 10-1 102

2s22p2 3P1

101

(partial)

d)

100 10-1 102

2

2 3

2s 2p P2

101

e)

(partial)

100 10-1 2.588

2.589

2.59

2.591

Photon Energy (Ry)

Fig. 10. Fine structure effects on ground state photoionization (4 S o ) of O II in low energy region.? a) σP I (LS) is a smooth line,36 b) total σP I in relativistic Breit-Pauli showing resonances not allowed in LS couplling. c,d,e) Partial photoionization cross sections ionizing in to levels 3 P0 , 3 P1 , and 3 P of O III. 2

structure for O II photoionization in the very low energy region near ionization threshold has revealed formation of crucial resonant structures by the fine structure couplings not seen before.? Fig. 10 shows o σP I of 2s2 2p3 (4 S3/2 ) ground state of O II in the low energy region.? The top panel shows σP I in LS coupling which is a smooth line without any feature.36 But panel (b) presents total σP I from relativistic BPRM method where contributions of the full BreitPauli interaction has been included. The figure shows the resonant features as well as background jump at each core ionization threshold 3 P0 , 3 P1 , & 3 P2 of O III. Strong resonant structures below the core threshold 4 P state of 5 S o state of Fe XXI were also found due to relativistic fine structure couplings and were seen in measured recombination spectra.37 These fine structure coupling effects in O II were not detected in the experiment32,33 because of its narrow energy range. However, such near threshold resonances have now been found in a recent ALS measurement of σP I of Se II which has similar electronic configuration as O II.38 Existence of these resonances were not explored also because of σP I in LS

20 15 10 5 0 20 15 10 5 0 20 15 10 5 0 20 15 10 5 0 20 15 10 5 0 20 15 10 5 0 20 15 10 5 0 20 15 10 5 0

a) 4So :LS

O II + hν -> O III + e

b) 4So3/2 :FS

c) 2Do :LS

d) 2Do3/2 :FS

e) 2Do5/2 :FS

f) 2Po :LS

g) 2Po1/2 :FS

h) 2Po3/2 :FS

2.5

3

3.5

4

4.5

Photon Energy (Ry)

Fig. 11. Photoionization cross sections σP I of the levels of o ,2 D 0 o , ar,2 P3/2,1/2 ground configuration of O II, 4 S3/2 5/2,3/2 ranged in LS coupling approximation in the top panel followed below by those in fine structure.

coupling similar to that in fine structure except at thresholds and hence showed good agreement with experiment.32 Fig. 11 shows the cross sections of the three states of the ground configuration of O II, 2s2 2p3 (4 S o ,2 Do ,2 P o ). In the figure, σP I in LS coupling is shown in a panel below which σP I in fine structure are shown. The comparison shows that the difference between LS coupling and fine structure cross sections is only right at the threshold where fine structure introduces resonance not seen in that in LS coupling. The new resonant features at in energy σP I should narrow down the discrepancy of oxygen abundance in low temperature thin plasmas. Fig. 12 shows the recombination cross section from the low energy photoionization cross sections. The resonant structures when integrated over the Maxwellian disctribution will increase the earlier rates at low temperature. This should bring the abundance close to that obtained from collision strength.

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e + O III -> O II a) Ground State: 2s22p5(4So3/2)

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101

σRC(Mb)

100

10-1

103 b) Sum of State: 2s22p5(4So,2Do,2P) 2

10

101

100

10-1 0

.01

.02

.03

.04

Photoelectron Energy (eV)

Fig. 12. Recombination cross section σRC of O II in the low energy region obtained (a) from the ground state and (b) from summed contributions of photoionization. The resonant structures at very low energy region, not found earlier, are due to fine structure couplings.

6. Conclusion Accuracy of plasma opacities rely on the accurate atomic physics. Current opacities are not accurate enough to solve many crucial problems of astronomy, such as, solar elemental abundances are widely discordant. With the recent developments under the Iron Project, new results are indicating prospective solutions to the problems by consideration of accurate radiative transitions, relativistic fine structure effects, and photoionization resonances due to highly excited core states. 7. Acknowledgment Partially supported by DOE-NNSA and NASA. Computations were carried out at the Ohio Supercomputer Center. References 1. M.J. Seaton, J. Phys. B 20, 6363 (1987) 2. The Opacity Project Team.The Opacity Project, Vol 1 (1995), Vol. 2 (1996) (Institute of Physics Publishing)

3. N.R. Simon, ApJ 260, L87 (1982) 4. TOPbase: http://vizier.u-strasbg.fr/topbase/topbase.html 5. D.G. Hummer et al. Astron. Astrophys 279, 298 (1993) 6. TIPbase http://cdsweb.u-strasbg.fr/tipbase/home.html 7. NORAD-Atomic-Data: www.astronomy.ohiostate.edu/∼nahar/nahar radiativeatomicdata/index.html 8. OPServer: http://opacities.osc.edu 9. K.A. Berrington al. J. Phys. B 20, 6379 (1987) 10. K.A. Berrington et al. Comput. Phys. Commun. 92, 290 (1995) 11. W. Eissner and G.X. Chen (in preparation, 2011) 12. S.N. Nahar, A.K. Pradhan, Phys. Scr. 61, 675 (2000) 13. S.N. Nahar, Astron. Astrophys. Suppl. Ser. 127, 253 (2000) 14. M. J. Seaton et al., Mon. Not. R. Astron. Soc. 266, 805 (1994) 15. C.A. Iglesias and F.J. Rogers, ApJ 371 40, 1991 (;) ApJ 464, 943 (1996) 16. J.E. Bailey et al. (22 authors), 51st Annual meeting of the Division of Plasma Physics (DPP) of APS, Atlanta, Georgia, November 2-6, 2009, TOc.010 17. Atomic Astrophysics and Spectroscopy, A.K. Pradhan and S.N. Nahar (Cambridge University Press, 2011) 18. W. Eissner, M, Jones, H. Nussbaumer, Comput. Phys. Commun. 8, 270 (1974) 19. S.N. Nahar, W. Eissner, G.X. Chen, A.K. Pradhan, Astron. and Astrophys. 408, 789 (2003) 20. S.N. Nahar, Astron. Astrophys 448, 779 (2006) 21. S.N. Nahar, Astron. Astrophys. 457, 721 (2006); Note- the published data at CDS were replaced later after a bug in R-matrix code was corrected. 22. S.N. Nahar, At. Data. Nucl. Data. (in press, 2011) 23. National Institute for Standards and Technology (NIST), compiled atomic data are available at physics.nist.gov/P hysRef Data/ASD/index.html 24. T. Shirai et al., J. Phys. Chem. Ref. Data Monograph No.8 (AIP Press), 632 pp. (2000) 25. K.T. Cheng, Y.K. Kim, and J.P. Desclaux, At. Data Nucl. Data Tables 24, 111 (1979) 26. B.C. Fawcett, At. Data Nucl. Data Tables 31, 495 (1984) DD 27. J.P. Buchet et al., Phys.Rev. A 22, 2061 (1980) 28. S.N. Nahar and A.K. Pradhan, Astron. Astrophys 437, 345 (2005) 29. S.N. Nahar, J. Quant. Spec. Rad. Transfer 109, 2417 (2008) 30. S.N. Nahar, A.K. Pradhan, G.X. Chen, W. Eissner, (submitted 2011) 31. Y. Yu and M.J. Seaton, J. Phys. B 20, 6409 (198) 32. A.M. Covington et al., Phys. Rev. Lett 87, 243002-1 (2001) 33. H. Kjeldsen et al., Astrophys. J. Suppl. Ser. 138, 219 (2002) 34. S.N. Nahar, Phys. Rev. A 69, 042714-1 (2004)

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35. S.N. Nahar, M. Montenegro, W. Eissner, A.K. Pradhan, Phys. Rev. A Brief Report 82, 065401 (2010) 36. S.N. Nahar, Phys. Rev. A 58, 3766 (1998) 37. S.N. Nahar, J. Quant. Spec. Rad. Transfer 109, 2731 (2008) 38. N. C. Sterling et al. (14 authors), Publications of the Astron. Soc. Australia 26, 339 (2009)

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PHYSICS OF THE CORONA AND PRESENT AND FUTURE MAJOR SOLAR AND HELIOSPHERIC SPACE MISSIONS LUC DAMÉ LATMOS/IPSL/CNRS/UVSQ, 11 boulevard d'Alembert, 78280 Guyancourt, France [email protected]

Several ground facilities and space missions are currently dedicated to the study of the Sun at high resolution and of the solar corona in particular. However, and despite significant progress with the advent of space missions and UV, EUV and XUV direct observations of the hot chromosphere and million degrees coronal plasma, much is yet to be achieved in the understanding of these high temperatures, fine dissipative structures and of the coronal heating in general. Recent missions, in particular Hinode, have shown the definite role of waves and of the magnetic field deep in the inner corona, at the chromosphere-corona interface, where dramatic changes occur. Observations of multithermal loops and modelling will be presented. The dynamics of the chromosphere and corona is controlled by the emerging magnetic field, guided by the coronal magnetic field. Accordingly, the direct measurement of the chromospheric and coronal magnetic fields is of prime importance. The solar corona consists of many thin loops or threads with the plasmas brightening and fading independently. The dynamics in each thread is believed to be related to the formation of filaments, each one being dynamic, in a non-equilibrium state. The mechanism sustaining that dynamics, oscillations or waves (Alfvén or MHD?), require both very high-cadence, multi-spectral observations, and high resolution. This is foreseen in future Space Missions and in particular HiRISE, the ultimate new generation ultrahigh resolution, interferometric and coronagraphic, Solar Physics Mission, proposed for ESA Cosmic Vision M3 call December 3, 2010 (and pre-selected in 2007). HiRISE (High Resolution Imaging and Spectroscopy Explorer), at the L1 Lagrangian point, provides meter class FUV imaging and spectro-imaging, EUV and XUV imaging and spectroscopy, and ultimate coronagraphy by a remote external occulter (2 satellites in formation flying 280 m apart) allowing to characterize temperature, densities and velocities in the solar upper chromosphere, transition zone and inner corona with, in particular, 2D very high resolution multi-spectral imaging-spectroscopy, direct coronal magnetic field measurement: a unique set of tools to understand the structuration and onset of coronal heating. We give a detail account of this unique mission profile, major scientific objectives and model payload adding duty cycle, high resolution, spatial, spectral and temporal multi-temperature diagnostics and full coronal magnetometry to the plasma limited Solar Probe type missions.

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

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SOLAR ACTIVITIES AND SPACE WEATHER HAZARDS AHMED A. HADY Department of Astronomy & Space and Meteorology Faculty of Sciences Cairo University, Giza, Egypt [email protected]

Geomagnetic storms have a good correlation with solar activity and solar radiation variability. Many proton events and geomagnetic storms have occurred during solar cycles21, 22, and 23. The solar activities during the last three cycles, gave us a good indication of the climatic change and its behavior during the 21st century. High energetic eruptive flares were recorded during the decline phase of the last three solar cycles. The appearances of the second peak on the decline phase of solar cycles have been detected. Halloween storms during Nov. 2003 and its effects on the geomagnetic storms have been studied analytically. The data of amplitude and phase of most common indicators of geomagnetic activities during solar cycle 23 have been analyzed. Keywords: Solar activities – solar cycles; Troposphere Halloween storm; Geomagnetic Activities.

1.

Introduction

One of the most important solar phenomena is the evidence of solar activity, which has been found to be periodic with an around 11year cycle. The occurrence of the cycle is a magnetic phenomenon, related to the dynamo effect, which generates the magnetic field of the sun (Zeldovich, et al 1983). The energetic solar events, which are associated with peak and decline phase of the solar cycles, can affect earth's atmosphere, satellites, and humankind activity. The solar cycle is important because it determines the long term variation of regions such as the earth’s ionosphere, a layer of charged particles between 100 and 600 km above the surface of the earth. This layer is important because of its effect on radio signals, either reflecting high frequency signals or retarding those above this frequency range. The solar cycle also underpins the occurrence of short term disturbances to the earth-sun region. These arise in association with spectacular events on the sun such as solar flares and coronal mass ejections and propagate to the earth as changes in the solar wind, an outflow of charged particles from the sun which envelopes the earth. Disturbances disrupt the ionosphere causing rapid variations in its properties and are most obviously seen in the rapid variations in the magnetic field of the earth, events that are known as "geomagnetic storms". A geomagnetic storm is a temporary disturbance of the Earth's magnetosphere caused by a disturbance in space weather. Associated with solar coronal mass ejections (CME), coronal holes, or solar flares, a geomagnetic storm is caused by a solar wind shock wave that typically strikes the Earth's magnetic field 24 to 36 hours after the event. This only happens if the shock wave travels in a direction toward Earth. The solar wind

pressure on the magnetosphere will increase or decrease depending on the Sun's activity. These solar wind pressure changes modify the electric currents in the ionosphere. Magnetic storms usually last 24 to 48 hours, but some may last for many days. The energetic solar events, especially during the decline of solar cycles, can affect on earth's atmosphere, satellites, and on humankind activity. Recently, observations revealed that the solar energetic particles (SEPs) and coronal mass ejections (CMEs) with different origins, were based on magnetic changes of the active region which produced the SEPs, and on the abundances, ionization states and time production of the particles as well as the longitude distribution associations of the events, see for example: Reames, D.V. (1994) and Reames, D.V. (1995). These events (SEPs and CMEs) led to severe effects on the Earth, such as power blackouts, disruption of communications, and damage of satellites. It is well known that solar activity exhibits an 11-year periodicity, and the more dramatic activities usually occur in the maximum of the cycle. The complicated dynamics of magnetic fields play a key role in the solar activities, see Parker (2001). The peak of the Solar cycle 21 was in 1979 but high energetic Solar flares, or secondary peaks, occurred at the declining phase in 1981, 1982, and 1984 before the solar activity minimum in 1986. Also, the peak of the solar cycle 22 was in 1989 but high energetic solar flares occurred at the declining phase in 1991, 1992, and 1994, before the solar activity minimum in 1996. Then the secondary peaks occurred during 2 to 3 years after the first peak, as deduced from the last five solar cycles. See for example Shaltout (1995), and Hady (2002). If a Coronal

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

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Mass Ejections (CMEs) hit the Earth, it can excite a geomagnetic storm. Large geomagnetic storms, among other things, can cause electrical power, which can damage satellite communications. In space CME typically drive shock waves that produce energetic particles that can damage both electronic equipment and astronauts that are outside the protection of the Earth’s magnetic field. So, the predictions of the high energetic particle events are of vital importance for space navigation and airline safety. Shaltout et al (1996), Shaltout and Hady (2001) studied these severe effects. 2.

Table 1: Eruptive solar proton events, and eruptive Flares affecting the Earth environment, During the Peaks and declining phases of the solar cycles 21, 22 and 23.

Data analysis and discussion

Table (1) show the data of proton flux , x-ray and optical flares , the active regions and its location in the sun disk, for the most eruptive events during the peaks and decline phase of solar cycles 21, 22 and 23. The selected proton flux, that which more than 1000 pfu (particle Flux unit), for x-ray flares the selected one which has class of x1 and more, and for optical flares of class 1f and more. The Proton fluxes are integral 5minute averages for energies > 10 MeV, given in 9 pfu), measured by GOES spacecraft at Geo-synchronous orbit: 1 pfu = 1 p/sq. cm-s-sr. SWO defines the start of a proton event to be the first of 3 consecutive data points with fluxes greater than or equal to 10 pfu. The end of an event is the last time the flux was greater than or equal to 10 pfu. From the table (1), we can note that: 1. Through the decline of the current solar cycle 23, there are sudden rises with the solar activates. During the period from 28 October to 4 November 2003, there was a sudden and high solar activity in the active region Number 10486, and produced one of the most eruptive flare recorded since 1976. 2. During the period from 28 October to 4 November 2003, the proton flux reached 29500 pfu. The x-ray flare to X17, and reached to X28 in 4 November 2003. While optical flares are 4B and reached to 3B at 4 November 2003. The x -ray sensors on-board the GOES spacecraft are not capable of registering x-ray intensities up to level of class. It appears that this x-ray flare peaked somewhere between the X30 and X40 class level. The X-ray classification of solar flares is a most useful measure of the strength of a flare. To classify the most energetic flares since 1976, we will use a usual classification of fares, by descriptive letter M if the X-Ray power output is in the range of 0.01 to 0.1 ergs/square centimeter/second and the letter X if it is above a value of 0.1.

A multiplier number is also attached to the description so that an X5.0 flare has a power of 0.5 ergs/square centimeter/second. Class M flares, particularly the less energetic ones, are likely to cause a fadeout on the lowest frequencies of the High Frequency (HF) radio spectrum. On the other hand X class flares will cause a fadeout for all HF frequencies over the entire day light hemisphere of the earth. Class X flares are also more likely to be associated with a host of interesting effects here on earth and in space. It is the Class X flares which are of greatest interest to those affected by the sun, for more details see Richard Thompson (2004). Table (2), the daily Geomagnetic data of the Most eruptive days during the Peak period and decline period of Solar cycle 23. Fredericksburg, College, and Estimated Planetary A and K Indices, were tabulated. The daily 24-hour A index and eight 3-hourly K indices from the Fredericksburg (middle-latitude) and College (high-latitude) stations monitoring Earth's magnetic field. The estimated planetary 24 hour A index and eight 3-hourly K indices are derived in real time from a network of western hemisphere ground-based magnetometers.

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From this table, geomagnetic data show dramatic increases of recorded values during October – November 2003, compared with data during the period

Table 3: X-ray flux and Magnetic flux during the most eruptive days during Peak and decline phase of the solar cycle 2.

Table 2: Daily Geomagnetic data of most robust eruptive days during the Peak and declining phase of solar cycle 23.

of solar cycle 23. This increase has its peak during 29 November as in proton flounce case. This means those there effects of proton particle and the geomagnetic field. The data given from GOES-11 Space Environment Monitor with daily average of 5-Minots records of x-ray flux for two energy bands 1-8 Ao, 0.5-3 Ao were given and tabulated in table (3). The magnetic flux was tabulated too, where: XL XS Hp He Hn Ht

1-8 Ang X-ray Flux (Watts/Meter2) 0.5-3 Ang X-ray Flux (Watts/Meter2) (parallel) Northward Magnetic Flux (nanotesla) Earthward Magnetic Flux (nanotesla) (normal) Eastward Magnetic Flux (nanotesla) Total Magnetic Flux (nanotesla).

Form this table, the on-board GOES magnetic flux sensors are not capable to register over than 327.11 Nanotesla, and the detectors was saturated. For the 4 types of measurements, during October – November 2003. It appears that this Magnetic flux peaked more than that level. The x-ray flux in the selected two bands recorders as decrease of registrations during October – November 2003. In the other hand from table (1), the proton flux reach to 29500 pfu, The x-ray flare to X17 at 28 October 2003, and reach to X28 in 4 November 2003. This means that the eruptive solar flare during October 2003 did not have any effects in these two bands only. All these eruptive and most robust solar events during solar cycle 23 decline developed and released from to active region10486 and 10488.

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Table 4: The selective data for the most eruptive days during peak and decline phase of solar cycle 23, for the Belt Indices of Relative Intensities of NOAA/POES Energetic Particles.

that recorded on 29 October2003. The sudden increase of all belts Index are due to the eruptive flare in October – November 2003, and its clear the great effects of all events related to the sun at that period of time . 3.

Historical occurrences

From August 28 until September 2, 1859, numerous sunspots and solar flares were observed on the sun, the largest flare occurring on the 1st. A massive CME headed directly at Earth due to the solar flare and made it within eighteen hours—-a trip that normally takes three to four days. On September 1 and 2nd, the largest recorded geomagnetic storm occurred. The horizontal intensity of geomagnetic field was reduced by 1600 nT as recorded by the Colaba observatory near Bombay, India. Telegraph wires in both the United States and Europe shorted out, some even causing fires. Auroras were seen as far south as Hawaii, Mexico, Cuba, and Italy—phenomena that are usually only seen near the poles. This was the 1859 solar super-storm.

The belt indices for selective days during solar cycle 23, which have eruptive events, are given in table (4). The belt indices are a measure of the integrated difference, or departure, of individual sensor responses observed on a given day from the responses of those sensors as averaged over the previous year's observations. Just as each orbital data "point" (2x5 degree box) in the "tiger plot" of Relative Intensities of NOAA/POES Energetic Particles displays a color-coded ratio of the particle count to a one-year average particle count, the belt indices are the ratio of the whole day's summed particle counts to their corresponding one-year summed average. The indices are subdivided by the L-values of the points, resulting in three separate values, corresponding to: inner (L-value < 2.0), slot (2.0 = 2.5), and finally a total index which accounts for all points, without regard to L-value. The data of total belt index in the table have a sudden increase of its records during 29 October 2003, after one day from the eruptive flare release. The outer belt index recorded data on29 more than 50 times as on 28 October 2003, compared with that on 20 October 2003. While in total belt index on 29 October is more than 8 times as on 28 October2003. In solar Belt index have its maximum on 30 October for few hours only, its more than 3 time

On 13 March 1989 a severe geomagnetic storm caused the collapse of the Hydro-Québec power grid in a matter of seconds as equipment protection relays tripped in a cascading sequence of events. Six million people were left without power for nine hours, with significant economic loss. The storm even caused auroras as far south as Texas. The geomagnetic storm causing this event was itself the result of a Coronal Mass Ejection, ejected from the Sun on March 9, 1989. In August 1989, another storm affected microchips, leading to a halt of all trading on Toronto's stock market. Since 1989, power companies in North America, the UK, Northern Europe and elsewhere evaluated the risks of geomagnetically induced currents (GIC) and developed mitigation strategies. Since 1995, geomagnetic storms and solar flares have been monitored from the Solar and Heliospheric Observatory (SOHO) joint-NASA-European Space Agency satellite. On Feb. 26, 2008 the magnetic fields erupted inside the magneto tail, releasing about 1015 Joules of energy. The blast launched two gigantic clouds of protons and electrons, one toward Earth and the other away from Earth. The Earth-directed cloud crashed into the planet below, sparking vivid auroras in Canada and Alaska. Figure1 show the sunspot number and AA geomagnetic index correlations since 1968 until 1992.

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Figure 1: Sunspot number and AA index correlations since 1968 until 1992. We can see a good correlation between them and the appearance of 84-year periodicities overwhelm the 11-year solar cycle. Another geomagnetic index correlation with sunspot number (11-year solar cycle) appeare in the figure (2) the Ap index since 1930 until 2000. From figure (3), of the annual average geomagnetic activity index during the solar cycle10 until solar cycle 22 we can observe that during cycles 21, 22 the solar activity is higher than that the other cycles as shown in the figure (3). From figure (3), we can see that the solar cycle 23 has lower sunspot numbers than as in cycles 21, 22, that means the solar activity during cycle23 the lower than that in solar cycles 21, 22.

Figure 2: The Ap index and sunspot number since 1930 until 2000.

Figure3: Annual average geomagnetic activity Index and geomagnetic index during year's period, 1868-1995.

4.

Interactions with planetary processes

The solar wind also carries with it the solar magnetic field. This field will have either a North or South orientation. If the solar wind has energetic bursts, contracting and expanding the magnetosphere, or if the solar wind takes a southward polarization, geomagnetic storms can follow. The southward field causes magnetic reconnection of the dayside magnetopause, rapidly injecting magnetic and particle energy into the Earth's magnetosphere. During a geomagnetic storm, the ionosphere's F2 layer will become unstable, fragment, and may even disappear. In the Northern and Southern pole regions of the Earth, auroras (aka Northern lights) will be observable in the sky. The Magnetosphere in the nearEarth space environment shown in figure (4).

Figure 4: Magnetosphere in the near-Earth space environment.

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5.

Geomagnetic storm effects

1. Radiation hazards to humans: Intense solar flares release very-high-energy particles that can cause radiation poisoning to humans in the same way as lowenergy radiation from nuclear blasts. Earth's atmosphere and magnetosphere allow adequate protection at ground level, but astronauts in space are subject to potentially lethal doses of radiation. The penetration of high-energy particles into living cells can cause chromosome damage, cancer, and a host of other health problems. Large doses can be fatal immediately. Solar protons with energies greater than 30 MeV are particularly hazardous. There is a growing body of evidence that changes in the geomagnetic field affect biological systems. 2. Disrupted systems: In Communications: Many communication systems use the ionosphere to reflect radio signals over long distances. Ionospheric storms can affect radio communication at all latitudes. Some radio frequencies are absorbed and others are reflected, leading to rapidly fluctuating signals and unexpected propagation paths. In Navigation systems: Systems such as GPS, LORAN, and the now-defunct OMEGA, are adversely affected when solar activity disrupts their signal propagation. The OMEGA system consisted of eight transmitters located throughout the world. Airplanes and ships used the very low frequency signals from these transmitters to determine their positions. During solar events and geomagnetic storms, the system gave navigators information that is inaccurate by as much as several miles. In Satellites: Ggeomagnetic storms and increased solar ultraviolet emission heat Earth's upper atmosphere, causing it to expand. The heated air rises, and the density at the orbit of satellites up to about 1000 km increases significantly. This results in increased drag on satellites in space, causing them to slow and change orbit slightly. Unless Low Earth Orbit satellites are routinely boosted to higher orbits, they slowly fall, and eventually burn up in Earth's atmosphere. 6.

Conclusion

1. Solar particle events (SPEs) with very high fluxes of solar protons have correlation with geomagnetic storms. 2. Geomagnetic Indices (A and K indices) increased with increasing solar activities with time delay of one to two days.

3. Solar activity is a direct result of the solar dynamo sustained by the differential rotation and turbulent convection. 4. Solar activity affects solar irradiance. Solar activity results in coronal holes with open magnetic fields that produce fast solar wind. 5. Closed-field regions produce CMEs and flares that have serious space weather consequences, SEPs and geomagnetic storms. References 1. 2.

3. 4.

5. 6. 7.

8. 9. 10.

11. 12.

13. 14.

15.

Hady A., Planetary and space science 50, 2002, pp89-92, (2002). Hady A., Shaltout M. A., European Geo-sciences Union 2004, General Assembly 2004, Vol. 6, 2004, p00195, (2004). Krivski L., Bolleten of Astronomical Institute of Czechoslovakia, Vol. 26, No. 4, 203, (1975). Michalek G., N. Gopalswamy, A. Lara and P.K. Manoharan, European Geosciences Union 2004, General Assembly 2004, Vol. 6, 02819, (2004). Mininni P.D., Gomez D.O. and Mindline G.B., solar physics Rev. Lett. 85, 5476, (2000). Parker E.N., Chin. J. Astron. Astrophys., 1, 99, http://www.chjaa.org (2001). Pontieri A., F. Lepreti, L. Sorriso-Volvo, A. Vecchio and V. Carbone, Solar physics 213, pp195201, (2003). Reames D.V., Meyer J.P., and von Rosenvinge, T. T., Astrophys. J. Suppl. 90, 1994,649. Reames D.V., Revs. Geophys (Suppl.) 33, p585 (1995). Richard Thompson, Copyright IPS- Radio and Space Services, (2002). http://www.noaa.gov/index.html/ Robert Erdelyi, European Geosciences Union 2004, General Assembly 2004, Vol. 6, p06293 (2004). Shaltout M. S. and Hady Ahmed A, IAGA-IASPEI, Joint scientific Assembly, 19-31 August 2001, Hanoi, Vietnam, (2001). Viereck and Puga, JGR, 104, pp9995-10005, (1999) Viereck and Puga, “The Mg II Index: A proxy for Solar EUV”. GRL, 28, April (2001). 2-001, pp1343-1346, (2001). Zeldovich, Ya. B., Ruzmaikin, A. A., and Sokoloff, D. D. “Magnetic field in astrophysics” Golden and Breach Sciences Publishers, 1983, New York, (1983).

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ELECTRON BEAM ION TRAP AND ITS APPLICATIONS YAMING ZOU The Key Lab of Applied Ion Beam Physics, Educational Ministry, China and Shanghai EBIT Lab., Modern Physics Institute, Fudan University, Shanghai 200433, China

Electron Beam Ion Traps (EBIT), initially developed at LLNL, are sophisticated devices capable of acting both as highly charged ion (HCI) light sources and ion sources. As a HCI light source, they can basically provide light from emission states of any charge state of any element in the periodic table, hence almost unique for spectroscopic research. Furthermore, the emitting ions are almost at rest compared to those produced by heavy ion accelerators or storage rings, much less bothered with Doppler shifts and line broadening. Because of its flexibility in producing various ions, it is very good for studies along iso-electronic sequences, and along iso-nuclear charge sequences to reveal physical properties behind experimental phenomenon. In an EBIT, a thin plasma can be formed with basically any elements, and more important with almost mono-energy electrons. On top of this, the electron energy can be tuned in the range of few hundreds eV to above one hundred keV. This property made it possible to use an EBIT for detail studies of processes in hot plasmas, so as to make disentangling studies of hot plasmas and to assist plasma diagnostics for temperature, density, electromagnetic field, as well as ion moving. To promote the above mentioned studies in China, the Shanghai Electron Beam Ion Trap, Shanghi-EBIT project was launched in January of 2002, under a collaboration between Fudan University and the Shanghai Institute of Applied Physics. The design parameters of the S-EBIT put it well into the class of so-called super-EBITs, i.e. electron beam energies up to 200 keV and a current up to 200-250 milliamps, compressed to a current density of around 5000 A/cm2 by a magnetic field up to 5 Tesla. Results from Shanghai EBIT will be shown and discussed.

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

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GENERATION, DESIGN AND APPLICATIONS OF HIGH ENERGY ELECTRON BEAM SOURCES - AN OVERVIEW MUNAWAR IQBAL, GHALIB UL ISLAM, HARIS RASHID AND FAZAL-E-ALEEM Centre for High Energy Physics, University of the Punjab, Quaid-Azam, Campus, Lahore-Pakistan

Thermionic electron beam is a fundamental part of linear accelerators in the field of Experimental High Energy Physics (EHEP). Thermionic type of beam is very economical and easy to produce as compared to the other electron beam sources. In this work, we give an overview of generation, design and applications of the electron beam with particular reference to e-beam generation at high energy physics linear accelerators. The data, which is available in the literature is presented in tabular form for ready reference. In order to have a feel of the vast applications of e-beam technology, we elaborate an e-beam source developed in our laboratory.

1.

Introduction

Beam of particles is the heartbeat of accelerators used in high energy physics laboratories as well as in other applications. In studying electron-positron physics, ebeam is the necessary ingredient. This is normally achieved through thermionic emission of electrons although several other modes of e-beam generation also exist. In view of its economy and ease of use, lot of work has been carried out in this direction. Electron beam gun is a basic component of linear accelerators (linacs) which has a variety of applications in research (particularly in high energy and medical physics) and industry. In the last fifty years, lot of progress has taken place in this important area [1-13]. Continuing efforts are ongoing for the development of high energy electron gun for next generation linear accelerators. With the rapid pace of development in computers and IT, simulations and modeling is now an essential ingredient of R & D projects. Following the latest trends, widely used software to simulate e-beam parameters is “EGUN” [3]. It helps to simulate beam sources and study optimized characteristic parameters. This also helps in obtaining best output for successful experimentation. In this study, electron beam sources used in some of the leading high energy physics laboratories are briefly described. Except SLAC, all sources under considerations are thermionic in nature. Despite applications in high energy/medical physics

research, e-beam technology has a wide variety of industrial applications. In order to give a feel of the ebeam source, we give some details of the one, developed in our laboratory. 2.

The SLAC Electron Gun

The Stanford Linear Accelerator Centre (SLAC) is a Radio Frequency (RF) linear accelerator. It was the longest linear accelerator of the world having length of about 3.2 kilometers [4, 5] with a capacity to accelerate electrons up to 50 GeV. The electron gun for SLAC is a spherical diode gun having two cylindrical Pierce type electrodes with a 14 mm diameter semiconductor photocathode. It has 0.18 mm thick Molybdenum focusing electrodes. An acceleration potential of 120 kV dc was applied between cathode and anode. By changing the cathode-grid voltage up to 1000 V, beam current was varied from 10-8A to 2A. It consists of a grounded vacuum flange on which anode is mounted and on the right side is a rear deck insulated from vacuum flange by using Alumina insulators which were kept at cathode potential. Corona shields were placed on the anode flange, which prevented the arcing [5]. The electron gun assembly is shown in Fig. 1. Coaxial shaped filament was made from Tantalum and was clamped by using two Tantalum screws. The filament to cathode distance was adjustable due to spacers placed at the back of filament.

CP 9910, Modern Trends in Physics Research 1 Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

38 2   

higher energy (BES III). The BEPC electron gun is a thermionic triode electron gun as shown in Figure 2. Cathode-grid assembly for this gun is EIMAC Y 824, with an acceleration voltage of 150 kV and beam current of 11A. For a normal operation of the gun, power supply of 0-50W heating power, at 6V filament voltage, was used to heat the cathode.

Figure 1. Cross sectional view of SLAC Gun [6]

Specifications of the electron gun are summarized in Table 1 [6]. Table 1: Characteristics of SLAC Electron Gun [6] Parameters Gun Type Cathode

Specifications Spherical diode gun GaAs photo cathode of 14 mm diameter

Figure 2. Schematic of Electron Gun with avalanche pulsar [8].

The BEPCII electron gun was operated at an acceleration potential of 150 kV with 25 Hz of repetition rate [9]. Gun emittance was measured to be 17.6 mm.mrad. Electron gun specifications are shown in Table 2.

Acceleration potential

120 kV

Grid Voltage

0-1000 V

Beam current

8.9 A

Pulse width

2 nsec

Parameters

Characteristics

Repetition rate

120 Hz

Type

Thermionic triode electron gun

Cathode

Y796 (EIMAC) dispenser

Filament heating power

35 W

Maximum beam current

>10 A

Acceleration potential

150-200 kV

Emission current density

10 A/cm2

Beam emittance Perveance Pressure

0.1 µA/V3/2 Torr

3. The BEPC Electron Gun The Beijing Electron-Positron Collider (BEPC) is located in the Institute of High Energy Physics (IHEP), Beijong, China. It has an RF linear accelerator up to 202 meters length. Initially, BEPC accelerated electrons up to 2 GeV (BES II)[7] which was later on enhanced to a

Table 2. Characteristics of BEPC Electron Gun [7, 9]

  39

3

Pulse width Grid voltage

4.

1.5 nsec bias

0-500 V 3/2

Perveance

0.22 µA/V

Emittance

17.6

Repetition rate

25 Hz

mm.mrad

The KEK Electron Gun

High Energy Accelerator Research Organization also known as KEK is a research organization in Tsukuba, Ibaraki, Japan [11]. It has the capacity to accelerate electrons up to 30 GeV. Electron gun for positron generator at KEK is a gridded oxide coated triode electron gun. Its cathode is a Ba-Sr-Ca carbonate coated with 10 mm diameter. The cathode to grid distance was kept 0.18 mm. Due to this small distance, low grid pulse voltage could draw a high current. For filament voltage of 6.3 V, the filament current was 1.3 A. For this gun, the maximum peak current of cathode was 20 A. The gun has a small vacuum flange and is mounted on an assembly stem [10]. The cross section view of the electron gun assembly is shown in Fig. 3.

was 8100C. During the normal operation of the gun, cathode voltage was maintained at 105-110 kV. With a long pulse of 1 µsec at 105 kV cathode voltage and 230 V grid pulse, a peak current of 7A was obtained. While peak current of 9.7 A was measured with a short pulse of 10 nsec at 110 kV cathode voltage. At this short pulse mode an average perveance of 0.263 was obtained. The gun was also tested for 5 nsec pulse and emission current of 7 A was observed. Emission current density was 12 . The gun was operated at pressure of 3 × Torr during the measurements [10]. A brief summary of the main specifications of the gun is summarized in the Table 3. Table 3. Characteristics of KEK Electron Gun [10].

Figure 3. Cross-sectional view of the KEK electron gun [10]

Cathode to anode distance is (24 ± 0.5) mm. Anode hole diameter is 13mm. Gun perveance was . 0.26µA/V3/2 with emittance of 1.65× Maximum field gradient, on the anode aperture, was 88 KV/cm at cathode voltage of 110 kV. The gun worked in space charge limited mode at filament voltage of 6.3 V and the measured temperature

5.

Parameters

Specifications

Gun Type

Thermionic, pulsed, Gridded Oxide triode

Filament Voltage

6.3 V

Filament Temperature

810 0C

Cathode voltage

105-110 kV

Maximum Beam Current

10 A

Emission current density

12

Pulse duration

10 nsec

Beam emittance

1.65×

Perveance

0.263 µA/V3/2

Pressure

3 × 10-9 Torr

Line Source Electron Gun

In order to have a glimpse of the electron beam source, we now present some details our reported work [12,13] Our line source electron gun consists of a line cathode, focus electrodes held at the cathode potential, positioned vertically with respect to cathode and grounded anodes. Anode has an opening of 7.5mm with

40  

4

an acceleration gap between the cathode and the anode of 7.5mm. Cathode is a thermionic source with length of 14cm. The filament/cathode is made of Tungsten wire of 1mm diameter. In order to keep the long filament in its original shape, we introduced the spring action mechanism through the spring assembly. Focusing Electrodes (FE) and anode were made from 1mm Tantalum sheet. Above FE, anode is placed at 6mm away and is grounded with high voltage Alumina insulators. The gun was tested up to 50 kW (5000mA x 10kV) and achieved power density of 33 kW/cm2 at the target. A 2-D diagram of the gun is shown in Figure 4. Figure 4. Line Source Electron Gun [12,13]

Due to proper shielding of the gun components as well as the cap to source assembly; the gun was operated swiftly for several hours continuously. The gun has the capability to operate even for higher acceleration voltage to achieve higher beam current [13]. Main specifications are summarized in Table 4. Table 4: Characteristics of Line Source Electron Gun [12-13] Parameters

Characteristics

Gun Type

Thermionic diode gun

Cathode

Tungsten wire of 140 mm length

Heating power

600 W

Acceleration voltage

10 kV

Beam current

5A

Output power

50 kW

Perveance

5µA/V3/2

Beam diameter

1.25mm

Pressure

5 × 10-5 Torr

NOTE In view of the diversity of subject, many details are not included which are available in books and recent conference proceedings (e.g MTPR-08 proceedings). We apologize to all those whose scholarly work either have been cited partially or could not be included due to representative selection of the literature. References 1. Ryoji Nagai, et al., Rev. Sci. Instrum. 81 (3), 033304 (2010). 2. J.W. Lewellen, Proceedings of LINAC Lübeck, Germany, 842 (2004). 3. W. B. Herrmannsfeldt., EGUN-An electron optics and gun design program, SLAC-r-331, (1988). 4. R. B. Neal, The Stanford two-mile accelerator. Chap. 5, W.A. Benjamin, Inc. New York, 59 (1968). 5.http://www.slac.stanford.edu/vvc/accelerators/electro ngun.html. 6. D. Shultz et. al., The polarized electron source of the Stanford Linear Accelerator Centre, SLAC-PUB6606, (1994). 7. Zhang Chaung, BEPC II: Construction & commissioning, CPC, (HEP & NP), 33(Suppl. II): 60 (2009). 8. Gu Ming-Ping et al., A nanosecond pulsed electron gun system for BEPC, IEEE Transaction on Nuclear Science, NS30 (4), 2962 (1983). 9. LIU Bo GU Meng Ping et al; High Energy Physics & Nuclear Physics, 30(5), 466 (2006). 10. S. Fukuda et al., Electron gun for the positron generator, Part. Accel. 27,145 (1990). 11. http://www.kek.jp/intra-e/about/whatskek.html. 12.Munawar Iqbal et al, , Rev. Sci. Instr. 74 (11), 4616 (2003). 13. Munawar Iqbal & Fazal-e-Aleem, Rev. Sci. Instr. 77, 106101 (2006); MTPR-08, Cairo, Egypt http://www.worldscibooks.com/physics/7841.html; Munawar Iqbal, Development & Applications of high power thermionic electron beam sources; PhD Thesis, CHEP, P.U, Lahore, Pakistan (2007).

41

FUNDAMENTAL STUDIES AND APPLICATIONS OF HIGHLY CHARGED IONS REINHOLD SCHUCH Physics Department, Atomic Physics, Stockholm University Alba Nova, S-10691 Stockholm, Sweden

The talk addresses the novel physics that is done with trapped Highly Charged Ions (HCI). We have built up an Electron Beam Ion Trap (SEBIT) at AlbaNova that is now been upgraded to a super-EBIT version for making HCI up to bare uranium ions at rest. Examples are given where this facility together with novel instrumentation is used in challenging new experiments in atomic and fundamental studies: • •

•

•

Physics of strong electromagnetic fields using highly charged ions. The determination of transition energies provides challenges to atomic theory and non-perturbative QED calculations. Precision mass measurements in a Penning trap using a single but cold HCI are done. The higher the charge, the higher is the achieved mass accuracy. This requires cold HCI, made in a cooler trap, to be transferred into the precision Penning trap. The interaction of HCI with solid surfaces and nano-capillaries offer unique conditions due to the high yields of deposited energy and charge. New types of effects occur such as self-arranged in guiding in nano-tubes and nano-capillaries. Plasma spectroscopy from electron-ion processes is directly accessible through optical and x-ray windows at EBIT. Recombination rates and emission lines are studied, of interest for fusion applications and for astrophysical plasma.

An outlook will be given on the planned storage rings of the new FAIR facility in Darmstadt for unprecedented intensities of cold HCI from rest up to relativistic energies.

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

42

CLASSIFICATION OF SPECTRAL WAVELENGTHS IN ALL REGIONS FOR Si XII A. I. REFAIE Department of Physics, Faculty of Science, Cairo University Giza, Egypt

Fine structure energy levels, wavelengths, log gf and radiative dipole allowed (E1) transitions have been calculated for lithium-like Si XII. Relativistic Hrtree-Fock and configuration interaction effects have been included in the calculations using the electrostatic parameters that have been optimized by a least squares approach, in order to improve the adjustment to the observed energy levels and transition rates. The 69 fine structure energy levels of total angular momenta, 1/2 ≤ J ≤ 9/2 of even and odd parities, total angular momentum 2 ≤ l ≤ 5 for 2 ≤ n ≤ 10. The spectral wavelengths of 627 lines have been calculated in addition to their radiative transition probabilities. The calculated results obtained from Breit –Pauli show a very good agreement in soft X-ray, EUV and far UV regions with almost all observed and calculated values. In the visible and near IR, the present results are in comparable with the measured and calculated ones. An acceptable discrepancy has been shown in the mid IR region in both measured and calculated results. The comprehensive data sets are applicable for various models such as for ionization balance and recombination-cascade for EUV and X-ray lines.

1.

Introduction

For a number of problems in astronomy and physics, a large number of different data is needed, so that the arrangement of such data in databases is obviously of great interest. Problems where such databases are particularly important, are for example modeling of different plasmas, spectra synthesis and radiative transfer calculations. The interest for a very extensive list of atomic, collisional and line broadening data is additionally stimulated by the development of space astronomy where an extensive amount of spectroscopic information over large spectral regions of all kind of celestial objects has been and will be collected. Spectroscopic information with the spacebased observations in soft X-ray and extreme UV (EUV) regions provide valuable diagnostic means for understandings of the astrophysical hot plasma [1-5] and high temperature plasmas [6-8] encountered in fusion energy research. Ab initio calculations including relativistic effects for wavelengths, fine structure energy levels, oscillator strengths and transition probabilities have been calculated for Si XII ion [9-17]. The beam foil spectroscopy technique was used to study the spectrum of silicon in the EUV by Trlabert et al [18] and Mosnier et al [19]. Laser plasmas were used to study multiple-charged ions in the X-ray region by Boiko et al [20]. Lines in the range 3–9 Å for the spectra of Si XII and Si XIII was presented by Trlabert et al [21]. In the present work, fine structure energy levels, wavelengths, log gf and radiative allowed transition probabilities are presented for Si XII.The calculations have been performed by using Breit-Pauli (BP) approximation, for describing the relativistic interaction between electrons, i.e., with relativistic Hartree-Fock (HFR) in LS coupling and the relativistic correction is included also in the calculations. The interpretation of the configuration level structures are made by least-squares fit of the observed levels. The energy levels adjusted by this method are used to optimize the electrostatic parameters by a least-squares fitting procedure which is used again to calculate the transition probabilities. The total number of Si XII levels considered is 69, with 627 E1 transitions. The calculated fine structure energy levels and the allowed electric dipole transition probabilities have been tabulated and compared with the measured and calculated data in literatures. The calculated spectral wavelengths in all regions have been reported, classified and compared with the available observed data.

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

43

2.

Method of calculations

2.1. Atomic Structure Theory In nonrelativistic LS coupling calculations, the normal starting point is Schrödinger’s equation where the Hamiltonian for a multi-electron system, in atomic units is given as [22]

Stationary state of N-electrons is described by a wave function space and spin coordinates of the electron i.

, where qi= (ri, si) represents the

The wave function is assumed continuous with respect to the space variables and is a solution to the wave equation. In the multiconfiguration approximation, the wave functions for a state labeled αJMJ are expanded in terms of configuration state functions

where α represents the configuration and the set of quantum numbers are required to specify the state. 2.2. The Relativistic Effects Breit-Pauli (BP) approximation, for describing the relativistic interaction between electrons in an approximate way is [23]

HNR is the non-relativistic Multi- electron system Hamiltonian. The fine-structure operator HFS is

where HSO is the nuclear spin-orbit term, HSOO is the spin-other-orbit term and HSS is the spin-spin term. The relativistic shift operator HRS is commutes with L and S and can be written

is the mass correction term, and are one and two body Darwin terms, is the orbit –orbit term where and is the spin-spin cotact term. The radial wave functions have been generated using the relativistic Hrtree-Fock (RHF) method introduced, using the computer codes (Cowan ATOMIC STRUCTURE PACKAGE) [24] by Cowan et al [25]. The relativistic corrections included in the differential equations are derived from the Pauli-approximation to the Dirac- Hartree – Fock equations. The mass-velocity and the Darwin operators are included in the calculations. The radial parameters were fitted in a least square optimizing program fitting the eigen values of the Hamiltonian to the available experimental energy levels. These optimized integrals were used to compute the wavelengths and the transition rates.

44

2.3. Electric Dipole Decay Rates The strength of a line is defined as the square of the reduced dipole matrix element [26]

where ψ and ψ` are the wave functions composed of many basis states, the sum runs over all N electrons of the atom (or ion) and ri is the radial position of the ith electron.The transition probability is related to S according to

where u and l represents the upper and lower levels, respectively, gu is the statistical weight of the upper level of the transition, ao is the Bohr radius and ∆ E is the wave number of the spectral line in cm-1. The weighted oscillator strength for the transition between ψ and ψ` is defined as

3.

Results and discussion

The theoretical predictions for the energy levels of the configurations are obtained by diagonalizing the energy matrices with HFR values for the energy parameters. The computer code by Cowan [24] is used to calculate energy levels, wavelength, log gf and electric dipole transition probabilities. The configurations 1s2ns (n = 2-10), 1s2nd (n = 3-10) and 1s2ng (n = 5-10) have been considered for even parity configurations. For the odd parity the configurations 1s2np (n = 2-10) and 1s2nf (n = 4-10) are considered. They correspond to total angular momenta 1/2 ≤ J ≤ 9/2 of even and odd parities with n = 10, 0 ≤ l ≤ 4, total orbital angular momenta 0 ≤ L ≤ 4 and spin multiplicity (2S+1) = 2. The fitting procedure has been applied to the mentioned configurations with the experimental energy levels taken from NIST [27] for Si XII. According to the established semiempirical procedure [24], the average energy (Eav), the electrostatic interaction integrals (FK, GK), the spin-orbit integrals (ζK) and the configuration interaction integrals (RK). Some radial parameters have been considered as free parameters and have been adjusted with a least-squares optimization program to minimize the discrepancies between the calculated energy levels and the experimental values taken from NIST. A total 69 fine structure energy levels for Si XII are listed in table 1, as well as the values from observed by NIST [27] and from calculated by Podobedova et al [13], Nahar [15], Zhang et al [28], TOPbase [29] and Aggarwal et al [30] for compilation and comparison. The calculated fine structure energy levels of the Si XII ion agree with the measured values and the calculated values well within 0.15 % for most levels. However, the fully relativistic calculations based on a Dirac-Fock-Slater central potential method by Zhang et al [28], a. b initio calculations including relativistic effects in the Breit-Pauli R-matrix (BPRM) method by Nahar [15], a multiconfigurational Hrtree-Fock relativistic (HFR) approach by Coutinho et al [16] and the fully relativistic Dirac R-matrix by Aggarwal et al [30] show a good agreement with the present calculations of fine structure energy levels.

45 Table 1. Calculated fine structure energy levels (in cm-1) by using BP for Si XII. Configuration

BP

NIST [27]

BPRM [15, 29]

1s22s 2S1/2

0

0

0

2

2

1920620

1920590

1920622

2

2

2002380

2002060

2002377

2

2

2388872

2388872

2388861

2

2

2441940

2441532

2441941

2

2

1s 2p P1/2 1s 2p P3/2

1s 3s S1/2 1s 3p P1/2 1s 3p P3/2

2444335

2443937

2444322

1s23d 2D3/2

2463791

2463771

2463789

1s23d 2D5/2

2464481

2464521

2464470

2

2

3202101

3202101

3202025

2

2

3223450

3223425

3223446

2

2

3224555

3224438

3224543

2

2

1s 4d D3/2

3232733

3232673

3232642

1s24d 2D5/2

3233089

3232989

3232861

1s 4s S1/2 1s 4p P1/2 1s 4p P3/2

2

2

3239433

3233483

3233662

2

2

3239591

3233641

3233827

2

2

3573450

3573451

3573442

2

2

3584656

3584616

3584646

2

2

1s 4f F5/2 1s 4f F7/2

1s 5s S1/2 1s 5p P3/2 1s 5d D3/2

3588906

3588878

3588849

1s25d 2D5/2

3589068

3589004

3589036

1s25p 2P1/2

3590099

3584099

3584141

2

2

3595165

3589275

3589255

2

2

3595247

3589357

3589354

2

2

3595383

3589318

3589343

2

2

1s 5f F5/2 1s 5f F7/2 1s 5g G7/2

1s 5g G9/2

3595432

3589367

3589409

1s26s 2S1/2

3771342

3771342

3771342

1s26p 2P1/2

3779502

3779471

3779145

2

2

3779801

3779770

3779507

2

2

3782704

3782726

3782173

2

2

3782750

3782820

3782283

2

2

1s 6p P3/2

1s 6d D3/2 1s 6d D5/2 1s 6f F5/2

3788420

3794320

3782426

1s26f 2F7/2

3788467

3794367

3782481

1s26g 2G7/2

3788549

3782481

3782481

2

2

3788577

3782509

3782513

2

2

3891943

3891943

3891943

2

2

3897153

3897133

3896838

2

2

1s 7p P3/2

3897351

3897321

3897068

1s27d 2D3/2

3899149

3899119

3898747

3899158

3899178

3898813

1s 6g G9/2 1s 7s S1/2 1s 7p P1/2

2

2

1s 7d D5/2

46

Configuration

BP

NIST [27]

BPRM [15, 29]

1s27f 2F5/2

3904946

3898946

3898901

2

2

3904975

3898975

3898934

2

2

3905027

3898934

3898934

2

2

3905045

3898952

3898956

2

2

3969857

3969857

3969857

2

2

1s 8d D3/2

3974870

3974842

3974400

1s28d 2D5/2

3974870

3974881

3974444

1s 7f F7/2 1s 7g G7/2 1s 7g G9/2 1s 8s S1/2

2

2

3979347

3973160

3973127

2

2

3979473

3973286

3973281

2

2

3980573

3974543

3974510

2

2

3980593

3974562

3974532

2

2

1s 8g G7/2

3980627

3974530

3974532

1s28g 2G9/2

3980639

3974542

3974543

1s 8p P1/2 1s 8p P3/2 1s 8f F5/2 1s 8f F7/2

2

2

4023079

4023079

4023080

2

2

4026707

4026737

4026295

2

2

4026709

4026709

4026262

2

2

4031561

4025371

4025373

2

2

1s 9p P3/2

4031649

4025459

4025483

1s29f 2F5/2

4032421

4026341

4026339

1s 9s S1/2 1s 9d D5/2 1s 9d D3/2 1s 9p P1/2

2

2

4032435

4026355

4026361

2

2

4032459

4026361

4026361

2

2

4032467

4026369

4026372

2

2

4061048

4061048

4061049

2

2

1s 10d D3/2

4063337

4063363

4063364

1s210d 2D5/2

4063339

4063383

4063386

1s 9f F7/2 1s 9g G7/2 1s 9g G9/2 1s 10s S1/2

2

2

4068879

4062709

4062717

2

2

1s 10p P1/2 1s 10p P3/2

4068944

4062774

4062794

2

2

4069505

4063445

4063419

2

2

4069516

4063455

4063430

2

2

1s 10g G7/2

4069533

4063450

4063430

1s210g 2G9/2

4069539

4063456

4063441

1s 10f F5/2 1s 10f F7/2

47

The spectral wavelengths λ (in units of Å), log gf and the radiative transition probabilities for spontaneous emission (in units of 108 s-1) for 627 electric dipole allowed transitions E1 are obtained from BP calculations. The calculations are presented and compared with that measured by Liang et al [6] and NIST [27] and calculated [15, 28-30] values of wavelengths and allowed transition probabilities. Table 2 shows the comparison of the present work (BP) with the observed [27] and the calculated results [15, 29]. Spectral wavelengths in all regions have been tabulated and compared. The calculated wavelengths in the soft X-ray region in the range 24.57-89.14 Å are less than 0.2% accuracy with the observed [27] and calculated by Zhang et al [28] wavelengths. The line emission for the calculated wavelength of 44.1 Å of the 1s22p 2P3/2 - 1s23d 2D5/2 transition is in a very good agreement with that measured by Liang et al [6] within 0.13% accuracy. In the EUV region 116.11-882.19 Å, the calculated wavelength show a very good agreement within 0.0210.48% with almost all accurate calculated [28] and measured [27] values available. The calculated wavelengths in the far UV region 1084.15-1990.5 Å, the accuracy is well within 0.6 %. In the near ultraviolet region there is no available data for wavelengths in literatures to be compared. The calculated wavelengths in the visible and near infra red ranges 4386.14-5383.57 Å and 8679.2-15830.3 Å, respectively, show a good agreement with that observed [27] within 5% accuracy. In the mid-infrared, the agreement of calculated wavelengths in the range 22188.2- 141332.6 Å show agreement within 5-26% with the observed values [27]. The calculated transition probabilities in the soft X-ray region in the range 24.57-89.14 Å and in the EUV region 116.11-882.19 Å show a good agreement with the measured [27] values within the range 0.06-2.5 %, while the comparison with the results by using the Breit-Pauli R-matrix (BPRM) method [29, 30] shows an agreement in the range 11-50%. In the far UV region 1084.15-1990.5 Å, the transition transition probabilities is in agreement with the observed [27] and the calculated [15, 29, 30] within the range 0-2% and 6-45% accuracy, respectively. The calculated transition probability for the spectral line 1802.992 Å of the transition 1s23s 2S1/2 - 1s23p 2P3/2 has exactly the same value of that measured [27] in the far UV region. In the visible and near infra red ranges 4386.14-5383.57 Å and 8679.2-15830.3 Å, the calculated transition probabilities show a good agreement with that observed [27] and calculated [15, 29, 30] within 4-14% and 2067%accuracy, respectively. The calculated allowed transition probabilities in the mid-infrared region 22188.2- 141332.6 Å show an agreement within 15-46% and 50-68% with measured [27] and the calculated [15, 29, 30] results, respectively. The calculated transition probability of the spectral line 43416.9 Å of the 1s26p 2P3/2 - 1s26d 2D3/2 transition shows 50% discrepancy with the observed results [27] and 57% discrepancy with the theoretical results [15, 29] in the mid-infrared region. Absolute electron impact excitation and ionization rate coefficients have been evaluated for arbitrary excited states at certain electron temperatures kTe and electron densities Ne of the Lithium-like ions Si XII by using these atomic data [31].

48 Table 2. Wavelengths (in Å), Log gf and allowed transition probabilities (in s-1) for Si XII.

λ (BP)

λ(NIST)

24.570

25.658 25.66

26.062

26.134 26.134

26.436 26.456 26.459

26.493 26.493

26.975

27.850 27.854

27.876 27.876 27.882 27.946

3.196E+10

2

2

-2.175

1.813E+10

3.176E+10

2

2

2

2

-2.01

2.583E+10

4.516E+10

2

2

2

2

-2.311

2.582E+10

4.544E+10

2

2

2

2

-1.82

3.850E+10

3.88E+10

6.726E+10

2

2

2

2

3.88E+10

6.771E+10

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

1s 2s S1/2 - 1s 7p P3/2 1s 2s S1/2 - 1s 7p P1/2

-2.121

3.849E+10

2

-2.115

1.921E+10

3.508E+10

2

-3.515

1.530E+09

2.754E+09

2

2

-2.815

3.818E+09

6.915E+09

2

2

-1.861

2.292E+10

4.166E+10

2

-3.215

3.041E+09

5.614E+09

-1.966

2.660E+10

-3.366

2.112E+09

-2.666

5.278E+09

5.26E+09

9.578E+09

-1.711

3.173E+10

3.16E+10

5.770E+10

-3.066

4.197E+09

-1.794

3.843E+10

3.82E+10

7.012E+10

-1.593

6.103E+10

6.15E+10

1.064E+11

-1.894

6.100E+10

6.15E+10

1.072E+11

-3.198

3.030E+09

-1.54

4.582E+10

4.56E+10

8.328E+10

-2.494

7.635E+09

7.59E+09

1.383E+10

-2.897

6.020E+09

-1.594

5.853E+10

-3.001

4.572E+09

-2.294

1.163E+10

1.16E+10

2.106E+10

-1.34

6.977E+10

6.94E+10

1.269E+11

-2.701

9.085E+09

-1.352

9.595E+10

9.55E+10

1.749E+11

-1.311

1.050E+11

1.06E+11

1.828E+11

-1.612

1.050E+11

1.07E+11

1.843E+11

-2.051

1.906E+10

1.90E+10

3.452E+10

-1.097

1.144E+11

1.14E+11

2.078E+11

-2.765

7.370E+09

1.341E+10

-2.465

1.464E+10

2.732E+10

2

1s 2p P1/2 - 1s 9d D3/2

1s 2p P3/2 - 1s 9d D3/2 1s 2p P3/2 - 1s 9d D5/2

1s 2p P1/2 - 1s 8d D3/2 1s 2s S1/2 - 1s 6p P3/2 1s 2s S1/2 - 1s 6p P1/2

1s 2p P3/2 - 1s 8d D5/2 1s 2p P3/2 - 1s 8d D3/2 2

2

1s 2p P1/2 - 1s 7d D3/2 2

1s 2p P1/2 - 1s 7s S1/2

27.035 27.035

27.039 27.813

1.813E+10

2

1s 2p P3/2 - 1s 8s S1/2

26.980

26.998

-2.476

2

1s 2p P1/2 - 1s 8s S1/2

26.484

26.998

2.318E+10

1s 2p P3/2 - 1s 9s S1/2

26.427

26.939

1.321E+10

2

1s 2p P1/2 - 1s 9s S1/2

26.117

26.458

-2.32

2

1s 2p P3/2 - 1s 10s S1/2 26.078

1s 2p P3/2 - 1s 7d D3/2 1s 2p P3/2 - 1s 7d D5/2 2

1s 2p P3/2 - 1s 7s S1/2 27.848 27.895 27.899

27.912 27.912

A (BPRM)

2

1s 2p P3/2 - 1s 10d D5/2

25.862

A (NIST)

2

1s 2p P3/2 - 1s 10d D3/2

25.849

26.457

2

1s 2p P1/2 - 1s 10s S1/2

25.849

26.417

2.331E+10

2

1s 2p P1/2 - 1s 10d D3/2

25.807

26.414

1.321E+10

2

1s 2s S1/2 - 1s 8p P1/2

25.795

26.401

-2.621

2

1s 2s S1/2 - 1s 8p P3/2

25.130

26.099

2

1s 2s S1/2 - 1s 9p P3/2

25.129

26.099

2

1s 2s S1/2 - 1s 9p P1/2

24.804

26.044

Transition

1s 2s S1/2 - 1s 10p P3/2

24.804

25.621

A (BP)

2

1s 2s S1/2 - 1s 10p P1/2

24.576

25.619

Log gf

2

1s 2p P1/2 - 1s 6d D3/2 1s 2s S1/2 - 1s 5p P3/2 1s 2s S1/2 - 1s 5p P1/2

1s 2p P3/2 - 1s 6d D3/2 1s 2p P3/2 - 1s 6d D5/2 1s 2p P1/2 - 1s 6s S1/2 1s 2p P3/2 - 1s 6s S1/2

2.65E+10

4.858E+10 3.806E+09

7.756E+09

5.474E+09

1.115E+10 5.82E+10

1.068E+11 8.289E+09

1.687E+10

49

λ (BP)

λ(NIST)

29.395

29.437

29.464 29.466

29.530 29.601 30.955 30.965 32.834 32.919

32.922 33.168 33.258 40.826 40.867 43.95

44.094 44.108 45.429 45.597

29.507 29.508

29.572 29.643 31.01 31.021 32.885 32.885

32.974 33.219 33.31 40.908 40.948 44.019

44.165 44.178 45.517 45.687

59.701

1.751E+11

1.77E+11

3.188E+11

-0.788

2.087E+11

2.11E+11

3.789E+11

2

2

2

2

-1.742

3.478E+10

3.52E+10

6.296E+10

2

2

2

2

-2.468

1.303E+10

1.30E+10

2.391E+10

2

2

2

2

1s 2p P3/2 - 1s 5d D5/2 1s 2p P3/2 - 1s 5d D3/2

1s 2p P1/2 - 1s 5s S1/2 1s 2p P3/2 - 1s 5s S1/2

-2.168

2.588E+10

2.58E+10

4.873E+10

2

2

2

2

-0.934

2.025E+11

2.03E+11

3.559E+11

2

2

2

2

-1.235

2.023E+11

2.04E+11

3.595E+11

2

2

2

2

-0.61

3.800E+11

3.81E+11

6.911E+11

2

2

2

2

-0.355

4.525E+11

4.56E+11

8.224E+11

2

2

2

2

-1.31

7.540E+10

7.45E+10

1.368E+11

2

2

2

2

-2.058

2.652E+10

2.60E+10

4.900E+10

2

2

2

2

-1.758

5.260E+10

5.24E+10

9.987E+10

2

2

2

2

-0.347

4.505E+11

4.51E+11

8.479E+11

2

2

2

2

-0.648

4.492E+11

4.53E+11

8.600E+11

2

2

2

2

0.131

1.166E+12

1.15E+12

2.132E+12

2

2

2

2

0.385

1.386E+12

1.37E+12

2.544E+12

2

2

2

2

-0.57

2.308E+11

2.28E+11

4.239E+11

2

2

2

2

-1.377

6.775E+10

6.61E+10

1.194E+11

2

2

2

2

1.33E+11

2.437E+11

1s 2s S1/2 - 1s 4p P3/2 1s 2s S1/2 - 1s 4p P1/2 1s 2p P1/2 - 1s 4d D3/2 1s 2p P3/2 - 1s 4d D5/2

1s 2p P3/2 - 1s 4d D3/2 1s 2p P1/2 - 1s 4s S1/2 1s 2p P3/2 - 1s 4s S1/2 1s 2s S1/2 - 1s 3p P3/2 1s 2s S1/2 - 1s 3p P1/2 1s 2p P1/2 - 1s 3d D3/2

1s 2p P3/2 - 1s 3d D5/2 1s 2p P3/2 - 1s 3d D3/2 1s 2p P1/2 - 1s 3s S1/2 1s 2p P3/2 - 1s 3s S1/2

-1.078

1.340E+11

2

2

2

2

-2.051

4.160E+09

7.516E+09

2

2

2

2

-2.352

4.159E+09

7.583E+09

-1.895

5.693E+09

1.029E+10

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

-2.196

5.690E+09

1.038E+10

2

-1.81

6.800E+09

1.255E+10

2

-2.951

9.815E+08

1.670E+09

2

2

-1.555

8.125E+09

1.499E+10

2

2

-2.509

1.354E+09

2.495E+09

2

2

-2.65

1.955E+09

3.395E+09

2

-1.612

6.975E+09

1.286E+10

2

1s 3p P3/2 - 1s 10d D5/2

61.727

1s 3p P3/2 - 1s 10d D3/2

61.799

1s 3p P3/2 - 1s 10s S1/2

62.440

2

2

2

2

2

2

-4.071

3.633E+07

6.476E+07

2

2

2

2

-2.758

4.975E+08

9.132E+08

2

2

2

2

-1.457

7.463E+09

1.374E+10

2

2

2

-3.117

3.265E+08

5.880E+08

2

2

2

2

-1.715

8.088E+09

1.460E+10

2

2

2

2

-2.016

8.085E+09

1.474E+10

2

2

2

2

-1.649

9.403E+09

9.38E+09

1.735E+10

2

2

2

2

-1.394

1.123E+10

1.12E+10

2.072E+10

2

2

2

2

-2.349

1.872E+09

1.87E+09

3.450E+09

1s 3d D3/2 - 1s 10f F5/2

62.462

2

1s 3d D3/2 - 1s 10p P3/2

62.469

1s 3d D5/2 - 1s 10f F5/2

62.469

1s 3d D5/2 - 1s 10f F7/2

62.491

2

1s 3d D5/2 - 1s 10p P3/2

63.070

1s 3s S1/2 - 1s 8p P3/2

63.075

63.174

-1.042

1s 3p P1/2 - 1s 10s S1/2

61.726

1s 3s S1/2 - 1s 8p P1/2 63.101 63.196 63.196

A (BPRM)

2

1s 3p P1/2 - 1s 10d D3/2

61.708

A (NIST)

2

1s 3s S1/2 - 1s 9p P1/2

61.635

A (BP)

2

1s 3s S1/2 - 1s 9p P3/2

61.064

Log gf

2

1s 3s S1/2 - 1s 10p P1/2

61.061

63.173

1s22p 2P1/2 - 1s25d 2D3/2

1s 3s S1/2 - 1s 10p P3/2

59.703

63.078

Transition

1s 3p P1/2 - 1s 9d D3/2 1s 3p P3/2 - 1s 9d D5/2 1s 3p P3/2 - 1s 9d D3/2

50

λ (BP)

λ(NIST)

1s23p 2P1/2 - 1s29s 2S1/2

63.182

2

63.278

65.315

65.238

65.339 65.339

66.292 66.301

68.619 68.732 68.732

75.064

-2.586

7.052E+08

1.295E+09

2

2

2

2

-3.905

5.075E+07

9.061E+07

2

2

2

2

-3.206

5.075E+08

9.360E+08

2

2

2

2

-2.951

4.560E+08

8.227E+08

2

2

2

2

-1.462

1.354E+10

1.36E+10

3.622E+10

2

2

2

2

-1.207

1.617E+10

1.62E+10

2.984E+10

2

2

2

2

-2.161

2.695E+09

2.70E+09

4.968E+09

2

2

2

2

-2.6

1.961E+09

3.356E+09

2

2

2

2

1s 3p P1/2 - 1s 8d D3/2

1s 3p P3/2 - 1s 8d D5/2 1s 3p P3/2 - 1s 8d D3/2

-2.3

3.903E+09

6.823E+09

2

2

2

2

-1.237

1.475E+10

2.720E+10

2

2

2

2

-1.082

1.578E+10

2.905E+10

2

2

2

2

-2.383

1.052E+09

1.931E+09

2

2

2

2

-3.71

7.430E+07

1.326E+08

2

2

2

2

-3.011

7.430E+08

1.370E+09

2

2

2

2

-2.756

6.678E+08

1.205E+09

2

2

2

2

-1.5

1.201E+10

1.21E+10

2.168E+10

2

2

2

2

-1.801

1.201E+10

1.21E+10

2.190E+10

2

2

2

2

-1.237

2.054E+10

2.06E+10

3.789E+10

2

2

2

2

-0.982

2.453E+10

2.46E+10

4.526E+10

2

2

2

2

-1.937

4.088E+09

4.09E+09

7.538E+09

2

2

2

2

-2.373

2.982E+09

5.132E+09

2

2

2

2

1s 3s S1/2 - 1s 7p P3/2 1s 3s S1/2 - 1s 7p P1/2

1s 3p P1/2 - 1s 7d D3/2 1s 3p P3/2 - 1s 7d D5/2 1s 3p P3/2 - 1s 7d D3/2

-2.072

5.935E+09

1.043E+10

2

2

2

2

-0.988

2.360E+10

4.354E+10

2

2

2

2

-0.833

2.525E+10

4.652E+10

2

2

2

2

-2.134

1.683E+09

3.093E+09

2

2

2

2

-3.474

1.153E+08

1.15E+08

2.064E+08

2

2

2

2

-2.775

1.153E+09

1.15E+09

2.132E+09

2

2

2

2

-2.52

1.036E+09

1.03E+09

1.874E+09

2

2

2

2

-1.233

1.888E+10

1.91E+10

3.406E+10

2

2

2

2

-1.534

1.887E+10

1.91E+10

3.444E+10

2

2

2

2

-0.953

3.340E+10

3.35E+10

6.154E+10

2

2

2

2

-0.699

3.987E+10

4.00E+10

7.357E+10

2

2

2

2

-1.653

6.645E+09

6.66E+09

1.226E+10

2

2

2

2

-2.085

4.869E+09

1s 3d D5/2 - 1s 7f F7/2

69.627

74.699

2

1s 3d D3/2 - 1s 7f F5/2

69.626

74.694

1.948E+10

2

1s 3p P3/2 - 1s 7s S1/2

69.591

74.565

1.058E+10

2

1s 3p P1/2 - 1s 7s S1/2

68.977

71.861

-1.285

2

1s 3d D5/2 - 1s 8p P3/2

68.863

71.846

2

1s 3d D3/2 - 1s 8p P1/2

66.192

69.707

1.823E+10

2

1s 3d D3/2 - 1s 8p P3/2

66.165

69.680

9.887E+09

2

1s 3d D5/2 - 1s 8f F5/2

66.159

69.670

-1.44

2

1s 3d D5/2 - 1s 8f F7/2

66.144

68.712

2

1s 3d D3/2 - 1s 8f F5/2

66.143

68.709

4.714E+09

2

1s 3p P3/2 - 1s 8s S1/2

66.111

68.598

2.706E+09

2

1s 3p P1/2 - 1s 8s S1/2

65.475

66.261

-2.488

2

1s 3d D5/2 - 1s 9p P3/2

65.372

66.253

2.318E+09

1s 3d D3/2 - 1s 9p P1/2

63.982

1s 3d D5/2 - 1s 7f F5/2 69.756 69.766 69.79 71.888

71.904 74.579 74.712 74.712

A (BPRM)

1.359E+09

1s 3d D3/2 - 1s 9p P3/2

63.955

A (NIST)

-2.789

1s 3d D5/2 - 1s 9f F5/2

63.952

A (BP)

2

1s 3d D5/2 - 1s 9f F7/2

63.951

Log gf

2

1s 3d D3/2 - 1s 9f F5/2

63.950

65.313

2

1s 3p P3/2 - 1s 9s S1/2

63.920

65.212

Transition

1s 3d D3/2 - 1s 7p P3/2 1s 3d D3/2 - 1s 7p P1/2 1s 3d D5/2 - 1s 7p P3/2 1s 3s S1/2 - 1s 6p P3/2

1s 3s S1/2 - 1s 6p P1/2 1s 3p P1/2 - 1s 6d D3/2 1s 3p P3/2 - 1s 6d D5/2 1s 3p P3/2 - 1s 6d D3/2 1s 3p P1/2 - 1s 6s S1/2

8.442E+09

51

λ (BP)

λ(NIST)

1s23p 2P3/2 - 1s26s 2S1/2

75.200 75.732

75.900 75.926 83.564 83.600

87.137 87.308 87.320 88.331 88.519

75.999 76.021 83.62 83.655

87.18 87.351 87.362 88.37 88.558

88.716

89.075 89.116 89.135

89.21 89.25 89.265

120.467 120.478

4.489E+10

8.273E+10

2

2

2

-1.811

2.992E+09

5.503E+09

2

2

2

2

-3.172

1.947E+08

1.93E+08

3.496E+08

2

2

2

2

-2.474

1.946E+09

1.93E+09

3.611E+09

2

2

2

2

-2.218

1.749E+09

1.73E+09

3.175E+09

2

2

2

2

-0.875

3.185E+10

3.22E+10

5.748E+10

2

2

2

2

-1.176

3.181E+10

3.22E+10

5.823E+10

2

2

2

2

-0.565

5.983E+10

6.01E+10

1.100E+11

2

2

2

2

-0.31

7.137E+10

7.17E+10

1.317E+11

2

2

2

2

-1.265

1.189E+10

1.19E+10

2.196E+10

2

2

2

2

-1.686

8.800E+09

8.71E+09

1.546E+10

2

2

2

2

1.73E+10

3.145E+10

1s 3d D3/2 - 1s 6p P3/2 1s 3d D3/2 - 1s 6p P1/2 1s 3d D5/2 - 1s 6p P3/2 1s 3s S1/2 - 1s 5p P3/2 1s 3s S1/2 - 1s 5p P1/2

1s 3p P1/2 - 1s 5d D3/2 1s 3p P3/2 - 1s 5d D5/2 1s 3p P3/2 - 1s 5d D3/2 1s 3p P1/2 - 1s 5s S1/2 1s 3p P3/2 - 1s 5s S1/2

-1.386

1.750E+10

2

2

2

2

-0.202

8.873E+10

1.638E+11

2

2

2

2

-0.047

9.490E+10

1.751E+11

2

2

2

2

-1.348

6.325E+09

1.165E+10

2

2

2

2

-2.751

3.725E+08

3.70E+08

6.707E+08

2

2

2

2

-2.053

3.720E+09

3.70E+09

6.929E+09

2

2

2

2

-1.797

3.345E+09

3.33E+09

6.090E+09

-1.817

1.884E+09

3.450E+09

-2.118

1.883E+09

3.490E+09

1s 3d D3/2 - 1s 5p P3/2 1s 3d D3/2 - 1s 5p P1/2 1s 3d D5/2 - 1s 5p P3/2 2

2

2

2

2

2

2

2

2

2

2

2

-3.372

3.633E+08

6.690E+08

2

2

2

2

-1.578

3.108E+09

5.759E+09

2

2

2

2

-1.324

3.715E+09

6.898E+09

2

2

2

2

-2.278

6.193E+08

1.150E+09

2

2

2

2

-2.559

6.470E+08

1.244E+09

2

2

2

2

-2.258

1.290E+09

2.524E+09

2

2

2

2

-0.312

5.690E+10

5.75E+10

1.035E+11

2

2

2

2

5.76E+10

1.053E+11

1s 4p P1/2 - 1s 10s S1/2

119.463

120.430

-0.51

2

1s 4p P3/2 - 1s 10d D3/2

119.319

120.394

2

1s 4p P3/2 - 1s 10d D5/2

119.192

120.385

7.742E+10

2

1s 4p P1/2 - 1s 10d D3/2

119.189

120.349

4.195E+10

2

1s 3d D3/2 - 1s 10p P1/2

119.048

120.348

-0.665

2

1s 4s S1/2 - 1s 10p P1/2

116.114

120.303

1.716E+10

1s 4s S1/2 - 1s 10p P3/2

116.114

119.687

9.685E+09

1s 3d D5/2 - 1s 5f F5/2

116.105

119.543

-1.785

1s 3d D5/2 - 1s 5f F7/2

88.775

1s 4p P3/2 - 1s 10s S1/2 119.654 119.812

A (BPRM)

2

1s 3d D3/2 - 1s 5f F5/2

88.768

A (NIST)

2

1s 3d D5/2 - 1s 6f F5/2 75.981

A (BP)

2

1s 3d D5/2 - 1s 6f F7/2

75.775

Log gf

2

1s 3d D3/2 - 1s 6f F5/2

75.772

75.882

Transition

1s 3s S1/2 - 1s 4p P3/2 1s 3s S1/2 - 1s 4p P1/2

-0.613

5.670E+10

2

2

2

2

-1.255

4.270E+09

7.887E+09

2

2

2

2

-1.1

4.570E+09

8.433E+09

2

2

2

2

-2.401

3.047E+08

5.613E+08

2

2

2

2

-3.466

3.933E+07

7.385E+07

2

2

2

2

-2.767

3.931E+08

7.595E+08

2

2

2

2

1s 4d D3/2 - 1s 10f F5/2 1s 4d D5/2 - 1s 10f F7/2 1s 4d D5/2 - 1s 10f F5/2

1s 4d D3/2 - 1s 10p P3/2 1s 4d D3/2 - 1s 10p P1/2 1s 4d D5/2 - 1s 10p P3/2

-2.512

3.535E+08

6.698E+08

2

2

2

2

-1.268

3.100E+09

5.727E+09

2

2

2

2

-4.399

3.058E+06

5.581E+06

1s 4f F5/2 - 1s 10g G7/2 1s 4f F5/2 - 1s 10d D5/2

52

λ (BP)

λ(NIST)

1s24f 2F5/2 - 1s210d 2D3/2

120.481 120.490

124.704 124.708

124.655 124.655

124.958

2

-3.098

6.113E+07

1.123E+08

2

2

2

2

-1.643

2.575E+09

4.709E+09

2

2

2

2

-1.944

2.575E+09

4.766E+09

2

2

2

2

-1.399

4.290E+09

4.30E+09

7.943E+09

2

2

2

2

-1.144

5.128E+09

5.15E+09

9.517E+09

2

2

2

2

8.58E+08

1.587E+09

1s 4p P1/2 - 1s 9d D3/2 1s 4p P3/2 - 1s 9d D5/2 1s 4p P3/2 - 1s 9d D3/2

-2.098

8.548E+08

2

2

2

2

-2.374

9.020E+08

1.733E+09

2

2

2

2

-2.074

1.797E+09

3.515E+09

2

2

2

2

-1.065

6.040E+09

1.116E+10

2

2

2

2

-0.91

6.464E+09

1.194E+10

2

2

2

2

-2.211

4.308E+08

7.946E+08

2

2

2

2

-3.276

5.558E+07

1.044E+08

2

2

2

2

-2.577

5.555E+08

1.074E+09

2

2

2

2

-2.322

4.995E+08

9.469E+08

2

2

2

2

-1.058

4.591E+09

8.486E+09

2

2

2

2

-4.198

4.430E+06

8.095E+06

2

2

2

2

-3.052

9.303E+07

1.722E+08

2

2

2

2

-0.945

4.759E+09

8.788E+09

2

2

2

2

-2.489

1.700E+08

3.132E+08

2

2

2

2

1.628E+08

1s 4f F5/2 - 1s 9d D5/2

126.120

1s 4f F5/2 - 1s 9d D3/2

126.123

1s 4f F7/2 - 1s 9g G9/2

126.124

1s 4f F7/2 - 1s 9g G7/2

126.141

1s 4f F7/2 - 1s 9d D5/2 126.451 126.786 126.834

129.564

-2.897

8.855E+07

2

2

2

2

0.066

1.215E+11

1.22E+11

2.220E+11

2

2

2

2

0.32

1.447E+11

1.45E+11

2.675E+11

2

2

2

2

-0.634

2.408E+10

2.41E+10

4.468E+10

2

2

2

2

-1.435

3.648E+09

6.652E+09

2

2

2

2

-1.736

3.646E+09

6.737E+09

2

2

2

2

0.609

2.687E+11

4.965E+11

2

2

2

2

0.763

2.871E+11

5.311E+11

2

2

2

2

-0.538

1.913E+10

3.539E+10

2

2

2

2

-2.046

8.715E+08

8.61E+08

1.575E+09

2

2

2

2

-1.092

7.820E+09

7.75E+09

1.430E+10

2

2

2

2

1s 3p P1/2 - 1s 4d D3/2 1s 3p P3/2 - 1s 4d D5/2 1s 3p P3/2 - 1s 4d D3/2 1s 4s S1/2 - 1s 8p P3/2

129.585

1s 4s S1/2 - 1s 8p P1/2

129.624

1s 3d D3/2 - 1s 4f F5/2

129.723

1s 3d D5/2 - 1s 4f F7/2

129.750

133.329

5.931E+09

2

1s 4f F5/2 - 1s 9g G7/2

126.116

133.156

3.213E+09

2

1s 4d D5/2 - 1s 9p P3/2

126.099

131.881

-1.155

2

1s 4d D3/2 - 1s 9p P1/2

126.094

131.464

2

1s 4d D3/2 - 1s 9p P3/2

126.058

131.325

2.114E+08

2

1s 4d D5/2 - 1s 9f F5/2

126.044

131.279

1.148E+08

2

1s 4d D5/2 - 1s 9f F7/2

125.971

131.150

-2.699

2

1s 4d D3/2 - 1s 9f F5/2

125.969

126.762

1.187E+08

1s 4p P3/2 - 1s 9s S1/2

125.921

126.712

6.423E+07

1s 4p P1/2 - 1s 9s S1/2

125.116

126.377

-3.252

1s 4s S1/2 - 1s 9p P1/2 124.484

1s 3d D5/2 - 1s 4f F5/2 131.437 131.557

131.628 131.541 131.959 133.084 133.279

A (BPRM)

2

1s 4s S1/2 - 1s 9p P3/2

121.373

A (NIST)

2

1s 4f F7/2 - 1s 10d D5/2

121.360

A (BP)

2

1s 4f F7/2 - 1s 10g G9/2

120.501

Log gf

2

1s 4f F7/2 - 1s 10g G7/2

120.490

124.551

Transition

1s 3d D3/2 - 1s 4p P3/2 1s 3d D5/2 - 1s 4p P3/2

1s 3d D3/2 - 1s 4p P1/2

-1.348

8.680E+09

8.62E+09

1.629E+10

2

2

2

2

-1.018

1.851E+10

1.83E+10

3.299E+10

2

2

2

2

1s 3p P1/2 - 1s 4s S1/2 1s 3p P3/2 - 1s 4s S1/2

-0.718

3.668E+10

3.71E+10

6.723E+10

2

2

2

2

-1.184

6.158E+09

6.19E+09

1.139E+10

2

2

2

2

-0.929

7.360E+09

7.41E+09

1.365E+10

1s 4p P1/2 - 1s 8d D3/2 1s 4p P3/2 - 1s 8d D5/2

53

λ (BP)

133.336

λ(NIST)

133.279

133.822

143.822 143.864 147.984 184.225 148.225

1.661E+10

2

2

-0.679

9.613E+09

1.776E+10

2

2

2

2

-1.98

6.408E+08

1.183E+09

2

2

2

-3.046

8.250E+07

1.551E+08

-0.797

7.308E+09

1.351E+10

2

2

2

2

2

2

2

-2.347

8.245E+08

1.595E+09

2

2

2

2

-3.952

6.815E+06

1.247E+07

2

2

2

2

-0.685

7.573E+09

1.399E+10

2

2

2

2

-2.229

2.705E+08

4.988E+08

2

2

2

2

-2.806

1.431E+08

2.651E+08

2

2

2

2

-2.651

1.362E+08

2.508E+08 1.406E+09

2

2

2

2

-2.091

7.415E+08

2

2

2

2

-1.175

5.388E+09

5.45E+09

9.793E+09

2

2

2

2

-1.477

5.385E+09

5.45E+09

9.928E+09

2

2

2

2

-0.913

9.283E+09

9.32E+09

1.714E+10

2

2

2

2

-0.659

1.109E+10

1.11E+10

2.055E+10

2

2

2

2

1.85E+09

3.428E+09

1s 4s S1/2 - 1s 7p P3/2 1s 4s S1/2 - 1s 7p P1/2 1s 4p P1/2 - 1s 7d D3/2 1s 4p P3/2 - 1s 7d D5/2 1s 4p P3/2 - 1s 7d D3/2

-1.613

1.848E+09

2

2

2

2

-1.869

2.024E+09

3.885E+09

2

2

2

2

1s 4p P3/2 - 1s 7s S1/2

-1.568

4.030E+09

7.882E+09

2

2

2

2

-0.539

1.429E+10

2.643E+10

2

2

2

2

-0.384

1.529E+10

2.828E+10

2

2

2

2

-1.685

1.020E+09

1.883E+09

2

2

2

2

-0.455

1.295E+10

2.396E+10

2

2

2

2

-0.342

1.343E+10

2.482E+10

2

2

2

2

-1.887

4.794E+08

8.848E+08

2

2

2

2

-3.635

1.142E+07

2.087E+07

2

2

2

2

-2.488

2.397E+08

4.438E+08

2

2

2

2

4.198E+08

1s 4d D3/2 - 1s 7f F5/2 1s 4d D5/2 - 1s 7f F7/2

150.070

1s 4d D5/2 - 1s 7f F5/2

150.242

1s 4f F5/2 - 1s 7g G7/2

150.273

1s 4f F7/2 - 1s 7g G9/2

150.277

1s 4f F7/2 - 1s 7g G7/2

150.291

1s 4f F5/2 - 1s 7d D5/2

150.305

1s 4f F5/2 - 1s 7d D3/2

150.327

179.294

8.982E+09

2

1s 4p P1/2 - 1s 7s S1/2

150.063

178.999

-0.834

2

1s 4d D5/2 - 1s 8p P3/2

149.999

173.056

2

1s 4f F7/2 - 1s 8d D5/2

149.544

172.967

5.114E+09

2

1s 4f F5/2 - 1s 8d D3/2

149.318

150.441

4.030E+09

2

1s 4f F7/2 - 1s 8g G7/2

134.974

150.412

-1.568

2

1s 4f F7/2 - 1s 8g G9/2

134.973

150.370

2

1s 4f F5/2 - 1s 8d D5/2

134.951

148.303

2.521E+09

2

1s 4d D3/2 - 1s 8p P1/2

134.946

148.290

1.313E+09

2

2

134.944

148.081

-2.152

2

1s 4f F5/2 - 1s 8g G7/2

134.944

1s 4f F7/2 - 1s 7d D5/2 150.444 150.489

150.512 173.1 173.19 178.811 179.163

2.276E+09

1.226E+09

2

134.939

1.24E+09

-1.884

1s 4d D3/2 - 1s 8p P3/2

134.917

A (BPRM)

2

1s 4d D5/2 - 1s 8f F5/2

134.916

A (NIST)

2

1s 4d D5/2 - 1s 8f F7/2

134.774

A (BP)

2

1s 4d D3/2 - 1s 8f F5/2

134.770

Log gf

2

1s 4p P3/2 - 1s 8s S1/2

134.717

143.790

1s24p 2P3/2 - 1s28d 2D3/2 1s 4p P1/2 - 1s 8s S1/2

134.003

143.751

Transition

-2.334

2.282E+08

2

2

2

2

-2.75

1.310E+08

1.30E+08

2.459E+08

2

2

2

2

-2.052

1.309E+09

1.30E+09

2.529E+09

2

2

2

2

-1.796

1.178E+09

1.17E+09

2.230E+09

2

2

2

2

-0.825

8.340E+09

8.41E+09

1.508E+10

2

2

2

2

-1.126

8.325E+09

8.41E+09

1.531E+10

2

2

2

2

-0.544

1.487E+10

1.50E+10

2.737E+10

2

2

2

2

-0.29

1.775E+10

1.79E+10

3.286E+10

1s 4d D3/2 - 1s 7p P3/2 1s 4d D3/2 - 1s 7p P1/2

1s 4d D5/2 - 1s 7p P3/2 1s 4s S1/2 - 1s 6p P3/2 1s 4s S1/2 - 1s 6p P1/2 1s 4p P1/2 - 1s 6d D3/2 1s 4p P3/2 - 1s 6d D5/2

54

λ (BP)

179.324

λ(NIST)

179.163

181.770

204.171 208.620 208.837 208.846 209.453

209.680 210.571 210.638 210.643 210.807 210.820

210.840 210.840 210.843 210.848 210.849 210.876

210.892 210.911 210.916 210.933 220.968

4.624E+10

2

2

0.026

2.679E+10

4.948E+10

2

2

2

2

-1.275

1.785E+09

3.297E+09

2

2

2

2

-1.475

3.376E+09

6.475E+09

2

2

2

2

0.039

2.753E+10

5.089E+10

2

2

2

2

0.152

2.853E+10

5.272E+10

2

2

2

2

-1.392

1.019E+09

1.880E+09

2

2

2

2

-3.186

2.180E+07

3.955E+07

-1.175

6.715E+09

1.314E+10

-2.04

4.575E+08

8.407E+08 7.953E+08

2

2

2

1s 4p P3/2 - 1s 6s S1/2 2

2

2

2

2

2

2

2

1s 4f F5/2 - 1s 6d D3/2

182.280

204.145

2.503E+10

2

2

182.259

182.745

-0.128

2

1s 4f F5/2 - 1s 6d D5/2

182.239

1s 4f F7/2 - 1s 6d D5/2 182.782 182.882 182.882

5.486E+09

2.958E+09

1s 4f F7/2 - 1s 6g G7/2

182.228

2.97E+09

-1.244

1s 4f F7/2 - 1s 6g G9/2

182.164

A (BPRM)

2

1s 4f F5/2 - 1s 6g G7/2

182.154

A (NIST)

2

1s 4p P1/2 - 1s 6s S1/2

182.111

A (BP)

2

1s 4d D5/2 - 1s 6f F5/2

181.903

Log gf

2

1s 4d D5/2 - 1s 6f F7/2

181.874

182.739

1s24p 2P3/2 - 1s26d 2D3/2 1s 4d D3/2 - 1s 6f F5/2

181.859

182.639

Transition

-1.886

4.355E+08

2

2

2

2

-2.339

2.293E+08

2.28E+08

4.264E+08

2

2

2

2

-1.64

2.289E+09

2.27E+09

4.387E+09

2

2

2

2

2.05E+09

3.867E+09

1s 4d D3/2 - 1s 6p P3/2 1s 4d D3/2 - 1s 6p P1/2 1s 4d D5/2 - 1s 6p P3/2

-1.385

2.060E+09

2

2

2

2

-1.587

1.035E+09

1.873E+09

2

2

2

2

-1.888

1.035E+09

1.898E+09

2

2

2

2

-1.357

1.684E+09

3.110E+09

2

2

2

2

-1.102

2.015E+09

3.734E+09

2

2

2

2

-2.056

3.358E+08

6.230E+08

2

2

2

2

-2.221

4.574E+08

8.794E+08

2

2

2

2

1s 5s S1/2 - 1s 10p P3/2 1s 5s S1/2 - 1s 10p P1/2 1s 5p P1/2 - 1s 10d D3/2 1s 5p P3/2 - 1s 10d D5/2 1s 5p P3/2 - 1s 10d D3/2 1s 5p P1/2 - 1s 10s S1/2

1s 5p P3/2 - 1s 10s S1/2

-1.92

9.120E+08

1.783E+09

2

2

2

2

-0.991

2.562E+09

4.739E+09

2

2

2

2

-0.836

2.743E+09

5.071E+09

2

2

2

2

-2.137

1.828E+08

3.378E+08

2

2

-0.844

2.690E+09

4.975E+09

1s 5d D3/2 - 1s 10f F5/2 1s 5d D5/2 - 1s 10f F7/2 1s 5d D5/2 - 1s 10f F5/2 2

2

1s 5f F5/2 - 1s 10g G7/2 2

2

2

2

1s 5d D3/2 - 1s 10p P3/2

-3.02

3.580E+07

6.660E+07

2

2

2

2

-3.726

4.700E+06

8.587E+06

2

2

2

2

-0.731

2.788E+09

5.154E+09

2

2

2

2

-2.275

9.956E+07

1.838E+08

2

2

2

2

-2.58

9.868E+07

1.823E+08

-2.321

3.579E+08

6.839E+08

-2.425

9.395E+07

1.726E+08

1s 5f F5/2 - 1s 10d D5/2 1s 5f F7/2 - 1s 10g G9/2 1s 5f F7/2 - 1s 10g G7/2 1s 5f F5/2 - 1s 10d D3/2 2

2

2

2

1s 5d D3/2 - 1s 10p P1/2 2

2

2

2

1s 5f F7/2 - 1s 10d D5/2 2

2

2

2

-2.066

3.220E+08

6.042E+08

2

2

2

2

-4.545

5.339E+05

9.749E+05

2

2

2

2

-3.114

1.922E+07

3.534E+07

2

2

2

2

-3.001

1.868E+07

3.426E+07

2

2

-1.383

1.413E+09

2.552E+09

1s 5d D5/2 - 1s 10p P3/2 1s 5g G7/2 -1s 10f F7/2 1s 5g G7/2 -1s 10f F5/2 1s 5g G9/2 -1s 10f F7/2 2

2

1s 5s S1/2 - 1s 9p P3/2

55

λ (BP)

λ(NIST)

1s25s 2S1/2 - 1s29p 2P1/2

221.011 226.127 226.377

226.391

225.963 226.219

226.219

227.473

259.599

8.578E+08

2

-2.001

6.430E+08

1.236E+09

2

2

2

2

-1.7

1.282E+09

2.507E+09

2

2

2

-0.77

3.615E+09

6.688E+09

2

2

2

2

-0.616

3.870E+09

7.158E+09

2

2

2

2

-1.917

2.580E+08

4.769E+08

2

2

2

2

-0.604

3.973E+09

7.348E+09

2

2

2

2

-0.491

4.117E+09

7.613E+09

2

2

2

2

-2.035

1.470E+08

2.716E+08

2

2

2

2

-3.486

6.947E+06

1.269E+07

2

2

2

2

-2.339

1.459E+08

2.695E+08

2

2

2

2

-2.185

1.389E+08

2.551E+08

-4.286

8.245E+05

1.507E+06

-2.793

5.128E+07

9.544E+07

-2.855

2.968E+07

5.463E+07

2

2

2

2

2

2

2

2

2

2

2

2

2

2

-2.742

2.885E+07

5.295E+07

2

2

2

2

-2.094

5.125E+08

9.792E+08

2

2

2

2

-1.839

4.610E+08

8.651E+08

2

2

2

2

-1.128

1.993E+09

3.586E+09

2

2

2

2

-1.429

1.991E+09

3.640E+09

2

2

2

2

-0.885

3.315E+09

3.33E+09

6.103E+09

2

2

2

2

-0.63

3.962E+09

3.99E+09

7.335E+09

2

2

2

2

-1.584

6.603E+08

6.65E+08

1.225E+09

2

2

2

2

-1.721

9.485E+08

1.822E+09

2

2

2

2

2

2

1s 5s S1/2 - 1s 8p P1/2 255.984 256.312 256.312

2.587E+09

2

1s 5s S1/2 - 1s 8p P3/2

249.842

259.582

4.65E+08

2

1s 5d D5/2 - 1s 9p P3/2

249.764

259.554

4.623E+08

2

1s 5d D3/2 - 1s 9p P1/2

228.895

259.527

-1.847

2

1s 5p P3/2 - 1s 9d D3/2

1s 5g G9/2 -1s 9f F7/2

228.857

259.484

5.140E+09

2

1s 5g G7/2 -1s 9f F5/2

228.832

259.476

2.80E+09

2

1s 5d D3/2 - 1s 9p P3/2

228.813

259.429

2.775E+09

2

1s 5g G7/2 -1s 9f F7/2

228.810

259.199

-0.893

2

1s 5p P3/2 - 1s 9d D5/2

1s 5f F7/2 - 1s 9d D5/2

228.806

259.185

4.279E+09

2

1s 5f F5/2 - 1s 9d D3/2

228.775

259.090

2.34E+09

2

1s 5f F5/2 - 1s 9d D5/2

228.747

259.007

2.320E+09

2

1s 5f F7/2 - 1s 9g G7/2

228.733

258.661

-1.148

2

1s 5p P1/2 - 1s 9d D3/2

1s 5f F7/2 - 1s 9g G9/2

228.722

256.525

1.412E+09

1s 5f F5/2 - 1s 9g G7/2

228.717

256.499

-1.684

1s 5d D5/2 - 1s 9f F5/2

228.679

A (BPRM)

2

1s 5d D5/2 - 1s 9f F7/2

228.492

A (NIST)

2

1s 5d D3/2 - 1s 9f F5/2

228.484

A (BP)

2

1s 5p P3/2 - 1s 9s S1/2

228.407

Log gf

2

1s 5p P1/2 - 1s 9s S1/2

227.741

256.185

Transition

1s 5p P1/2 - 1s 8d D3/2 1s 5p P3/2 - 1s 8d D5/2 1s 5p P3/2 - 1s 8d D3/2 1s 5p P1/2 - 1s 8s S1/2

1s 5p P3/2 - 1s 8s S1/2

-1.42

1.890E+09

3.696E+09

2

2

2

2

-0.491

5.350E+09

9.896E+09

2

2

2

2

-0.336

5.726E+09

1.059E+10

2

2

2

2

-1.637

3.817E+08

7.060E+08

2

2

2

2

-0.295

6.285E+09

1.163E+10

2

2

2

2

-0.182

6.514E+09

1.205E+10

2

2

2

2

-1.726

2.326E+08

4.299E+08

2

2

2

2

-3.176

1.101E+07

2.012E+07

2

2

2

2

-2.03

2.312E+08

4.272E+08

2

2

2

2

-1.875

2.202E+08

4.044E+08

2

-3.948

1.396E+06

2.551E+06

1s 5d D3/2 - 1s 8f F5/2 1s 5d D5/2 - 1s 8f F7/2 1s 5d D5/2 - 1s 8f F5/2 1s 5f F5/2 - 1s 8g G7/2 1s 5f F7/2 - 1s 8g G9/2

1s 5f F7/2 - 1s 8g G7/2 1s 5f F5/2 - 1s 8d D5/2 1s 5f F5/2 - 1s 8d D3/2 1s 5f F7/2 - 1s 8d D5/2 2

2

2

1s 5g G7/2 -1s 8f F7/2

56

λ (BP)

λ(NIST)

1s25g 2G7/2 -1s28f 2F5/2

259.612 259.632

274.489

274.611

261.746 273.635 274.348

274.461

280.197

286.829 308.446 308.625 317.813

318.277 318.337 322.228 322.365 322.396 322.724

322.790 322.809 322.953 323.005 323.014

1.445E+08

2

2

-1.803

7.765E+08

1.482E+09

2

2

2

2

-1.548

6.985E+08

1.310E+09

2

2

2

2

-0.269

1.316E+10

1.33E+10

2.347E+10

2

2

2

2

-0.571

1.310E+10

1.32E+10

2.394E+10

2

2

2

2

0.052

2.510E+10

2.53E+10

4.586E+10

2

2

2

2

0.307

2.990E+10

3.01E+10

5.523E+10

2

2

2

2

-0.648

4.975E+09

5.01E+09

9.235E+09

2

2

2

2

0.549

5.017E+10

9.268E+10

2

2

2

2

0.704

5.364E+10

9.924E+10

2

2

2

2

-0.597

3.573E+09

6.619E+09

2

2

2

2

0.907

8.524E+10

1.577E+11

2

2

2

2

1.019

8.832E+10

1.634E+11

2

2

2

2

-0.525

3.153E+09

5.832E+09

2

2

2

2

-2.437

5.132E+07

9.328E+07

2

2

2

2

-1.136

1.025E+09

1.876E+09

2

2

2

2

1.983E+09

1s 4s S1/2 - 1s 5p P3/2 1s 4s S1/2 - 1s 5p P1/2 1s 4p P1/2 - 1s 5d D3/2 1s 4p P3/2 - 1s 5d D5/2

1s 4p P3/2 - 1s 5d D3/2

1s 4f F7/2 - 1s 5d D5/2

281.553

285.998

7.770E+07

2

1s 4f F5/2 - 1s 5d D5/2

281.550

284.232

-2.502

2

1s 4f F7/2 - 1s 5g G7/2

281.425

284.069

8.963E+07

1s 4f F7/2 - 1s 5g G9/2

281.064

283.814

4.883E+07

1s 4f F5/2 - 1s 5g G7/2

281.025

1s 4f F5/2 - 1s 5d D3/2 284.131 284.374

284.535 285.714 286.615 308.737 308.928 317.46

317.965 317.965

9.246E+07

-2.404

1s 4d D5/2 - 1s 5f F5/2

280.939

5.023E+07

2

1s 4d D5/2 - 1s 5f F7/2

280.445

-2.516

2

1s 4d D3/2 - 1s 5f F5/2

280.381

A (BPRM)

2

1s 5d D5/2 - 1s 8p P3/2 261.404

A (NIST)

2

1s 5d D3/2 - 1s 8p P1/2

259.940

273.850

2

A (BP)

2

1s 5d D3/2 - 1s 8p P3/2

259.915

261.477

2

Log gf

2

1s 5g G9/2 -1s 8f F7/2

259.830

261.123

Transition

-1.291

1.076E+09

2

2

2

2

-1.651

4.625E+08

4.59E+08

8.575E+08

2

2

2

2

-0.697

4.153E+09

4.12E+09

7.781E+09

2

2

2

2

-0.953

4.605E+09

4.56E+09

8.834E+09

2

2

2

2

-0.812

6.290E+09

6.23E+09

1.202E+10

2

2

2

2

1s 4d D3/2 - 1s 5p P3/2 1s 4d D5/2 - 1s 5p P3/2

1s 4d D3/2 - 1s 5p P1/2 1s 4p P1/2 - 1s 5s S1/2 1s 4p P3/2 - 1s 5s S1/2

-0.512

1.247E+10

1.23E+10

2.446E+10

2

2

2

2

-0.78

2.905E+09

2.93E+09

5.198E+09

2

2

2

2

-1.082

2.901E+09

2.93E+09

5.286E+09

2

2

2

2

-0.525

4.933E+09

4.96E+09

9.060E+09

2

2

2

2

-0.27

5.893E+09

5.94E+09

1.090E+10

2

2

2

2

-1.224

9.818E+08

9.90E+08

1.821E+09

2

2

2

2

-0.105

8.407E+09

1.555E+10

2

2

2

2

0.05

8.996E+09

1.665E+10

2

2

2

2

-1.251

5.995E+08

1.110E+09

2

2

2

2

0.137

1.099E+10

2.032E+10

2

2

2

2

0.25

1.139E+10

2.106E+10

2

2

2

2

-1.294

4.066E+08

7.517E+08

2

2

2

2

-2.741

1.935E+07

3.533E+07

2

-3.469

2.716E+06

4.967E+06

2

-1.595

4.060E+08

7.501E+08

1s 5s S1/2 - 1s 7p P3/2 1s 5s S1/2 - 1s 7p P1/2 1s 5p P1/2 - 1s 7d D3/2

1s 5p P3/2 - 1s 7d D5/2 1s 5p P3/2 - 1s 7d D3/2 1s 5d D3/2 - 1s 7f F5/2 1s 5d D5/2 - 1s 7f F7/2 1s 5d D5/2 - 1s 7f F5/2 1s 5f F5/2 - 1s 7g G7/2

1s 5f F7/2 - 1s 7g G9/2 1s 5f F7/2 - 1s 7g G7/2 1s 5f F5/2 - 1s 7d D5/2 2

2

2

1s 5g G7/2 -1s 7f F7/2 2

2

2

1s 5f F5/2 - 1s 7d D3/2

57

λ (BP)

λ(NIST)

1s25g 2G7/2 -1s27f 2F5/2

323.036

2

323.038

324.202

324.359 324.412

1.745E+08

2

2

-1.329

1.493E+09

2.865E+09

2

2

2

2

-2.096

1.273E+08

2

2

2

2

-1.029

2.971E+09

2

2

2

2

-1.142

1.144E+09

1.13E+09

2.143E+09

2

2

2

2

-1.398

1.271E+09

1.26E+09

2.426E+09

-1.339

6.408E+08

1.149E+09

1s 5d D3/2 - 1s 7p P3/2

1s 5d D5/2 - 1s 7p P3/2 1s 5d D3/2 - 1s 7p P1/2 2

2

2

2

2

2

2

2

2

2

6.405E+08

1.166E+09

-1.119

1.023E+09

1.882E+09

2

2

2

2

-0.864

1.224E+09

2.264E+09

2

2

2

2

-1.818

2.039E+08

3.780E+08

2

2

2

2

-1.887

3.438E+08

6.568E+08

2

2

2

2

-1.587

6.855E+08

1.331E+09

2

2

2

2

-0.734

1.625E+09

3.006E+09

2

2

2

2

-0.579

2.320E+09

3.219E+09

2

2

2

2

-1.88

1.160E+08

2.146E+08

2

2

2

2

-0.524

1.974E+09

3.652E+09

2

2

2

2

-0.411

2.046E+09

3.785E+09

2

2

2

2

-1.955

7.306E+07

1.351E+08

2

2

2

2

-3.205

5.482E+06

1.003E+07

2

2

2

2

-2.059

1.151E+08

2.127E+08

2

2

2

2

1s 6f F5/2 - 1s 10g G7/2

355.781

1s 6f F7/2 - 1s 10g G9/2

355.788

1s 6f F7/2 - 1s 10g G7/2

355.822

1s 6f F5/2 - 1s 10d D5/2

355.847

1s 6f F5/2 - 1s 10d D3/2

355.882

1s 6f F7/2 - 1s 10d D5/2

355.914

-1.904

1.096E+08

2.015E+08

2

2

2

2

-3.792

1.063E+06

1.946E+06

2

2

2

2

-2.36

3.827E+07

7.049E+07

2

2

2

2

-2.248

3.720E+07

6.835E+07

2

2

2

2

-2.617

3.175E+07

5.884E+07

2

2

2

2

-1.918

3.172E+08

6.026E+08

2

2

2

2

-1.663

2.855E+08

5.331E+08

2

2

2

2

-1.086

8.725E+08

1.559E+09

2

2

2

2

-1.387

8.715E+08

1.584E+09

1s 6g G7/2 -1s 10f F7/2

355.927

1s 6g G7/2 -1s 10f F5/2

355.950

1s 6g G9/2 -1s 10f F7/2

356.075

1s 6d D3/2 - 1s 10p P3/2

356.157

1s 6d D3/2 - 1s 10p P1/2

356.194

1s 6d D5/2 - 1s 10p P3/2

396.096

1s 6s S1/2 - 1s 9p P3/2

396.234

1s 6s S1/2 - 1s 9p P1/2 404.531

405.022 405.022

5.814E+09

-1.641

1s 6d D5/2 - 1s 10f F5/2

355.728

2.364E+08

2

1s 6d D7/2 - 1s 10f F5/2

355.482

1.26E+08

2

1s 6d D3/2 - 1s 10f F5/2

355.470

409.462

9.501E+07

2

1s 6p P3/2 - 1s 10s S1/2

355.364

409.438

-1.925

2

1s 6p P1/2 - 1s 10s S1/2

354.946

409.305

7.102E+08

1s 6p P3/2 - 1s 10d D3/2

354.570

405.633

3.867E+08

2

1s 6p P3/2 - 1s 10d D5/2

352.562

405.587

-1.44

2

2

1s 6p P1/2 - 1s 10d D3/2

352.537

A (BPRM)

1.800E+08

1s 6s S1/2 - 1s 10p P1/2

352.190

A (NIST)

9.775E+07

1s 6s S1/2 - 1s 10p P3/2

345.191

A (BP)

-2.037

1s 5p P3/2 - 1s 7s S1/2

345.115

405.141

2

Log gf

2

1s 5p P1/2 - 1s 7s S1/2

324.108

324.142

2

1s 5g G9/2 -1s 7f F7/2

323.565

324.115

2

1s 5f F7/2 - 1s 7d D5/2

323.057

323.944

Transition

2

2

2

2

1s 6p P1/2 - 1s 9d D3/2

-0.859

1.404E+09

1.41E+09

2.580E+09

2

2

2

2

-0.605

1.680E+09

1.69E+09

3.105E+09

2

2

2

2

2.82E+08

5.187E+08

1s 6p P3/2 - 1s 9d D5/2 1s 6p P3/2 - 1s 9d D3/2

-1.559

2.798E+08

2

2

2

2

-0.463

2.285E+09

4.227E+09

2

2

2

2

-0.308

3.260E+09

4.526E+09

2

2

2

2

-1.609

1.630E+08

3.018E+08

1s 6d D3/2 - 1s 9f F5/2 1s 6d D7/2 - 1s 9f F5/2 1s 6d D5/2 - 1s 9f F5/2

58

λ (BP)

λ(NIST)

1s26p 2P1/2 - 1s29s 2S1/2

409.485 409.770

5.563E+09

2

2

-1.665

1.074E+08

1.986E+08

2

2

2

2

-2.009

8.323E+06

1.522E+07

2

2

2

-1.308

9.760E+08

1.897E+09

2

2

2

2

-1.754

1.747E+08

3.229E+08

2

2

2

2

-1.599

1.664E+08

3.059E+08

2

2

2

2

-3.464

1.704E+06

3.120E+06

2

2

2

2

-2.033

6.133E+07

1.130E+08

2

2

2

2

-1.92

5.963E+07

1.096E+08

2

2

2

2

-2.329

4.635E+07

8.587E+07

2

2

2

2

-1.63

4.629E+08

8.794E+08

2

2

2

2

-1.375

4.165E+08

7.780E+08

2

2

2

2

-0.226

4.230E+09

4.27E+09

7.462E+09

2

2

2

2

-0.528

4.212E+09

4.25E+09

7.620E+09

2

2

2

2

-0.839

9.735E+08

9.60E+08

1.228E+09

2

2

2

2

-0.74

1.218E+09

2.164E+09

2

2

2

2

-1.041

1.215E+09

2.202E+09

2

2

2

2

0.059

7.485E+09

7.59E+09

1.365E+10

2

2

2

2

0.313

8.925E+09

9.04E+09

1.648E+10

2

2

2

2

-0.641

1.486E+09

1.50E+09

2.757E+09

2

2

1s 6d D5/2 - 1s 9p P3/2 484.614

485.319 499.412

1s 5s S1/2 - 1s 6p P3/2

1s 5s S1/2 - 1s 6p P1/2 1s 2s S1/2 - 1s 2p P3/2 1s 6s S1/2 - 1s 8p P3/2

499.595

1s 6s S1/2 - 1s 8p P1/2 503.651 504.923

504.923 512.033 512.821 512.821

515.959

1s 5p P1/2 - 1s 6d D3/2 1s 5p P3/2 - 1s 6d D5/2

1s 5p P3/2 - 1s 6d D3/2 2

2

1s 6p P1/2 - 1s 8d D3/2

-0.504

1.985E+09

2.00E+09

3.637E+09

2

2

2

2

-0.249

2.372E+09

2.40E+09

4.383E+09

2

2

2

2

3.98E+08

7.325E+08

1s 6p P3/2 - 1s 8d D5/2 1s 6p P3/2 - 1s 8d D3/2

-1.204

3.950E+08

2

2

2

2

0.526

1.401E+10

2.590E+10

2

2

2

2

0.68

1.498E+10

2.775E+10

2

2

2

2

-0.621

9.980E+08

1.852E+09

2

2

2

2

0.851

2.214E+10

4.097E+10

2

2

2

2

0.964

2.294E+10

4.248E+10

2

2

2

2

1s 5d D3/2 - 1s 6f F5/2

516.265

1s 5d D5/2 - 1s 6f F7/2

516.390

1s 5d D5/2 - 1s 6f F5/2

517.106

1s 5f F5/2 - 1s 6g G7/2

517.249

1s 5f F7/2 - 1s 6g G9/2

517.325

1s 5f F7/2 - 1s 6g G7/2

517.908

-0.58

8.190E+08

1.517E+09

2

2

2

2

-2.67

6.639E+06

1.214E+07

2

2

2

2

-1.239

2.388E+08

4.399E+08

2

2

2

2

1s 5g G7/2 -1s 6f F7/2

518.035

1s 5g G7/2 -1s 6f F5/2

518.041

1s 5g G9/2 -1s 6f F7/2

518.047

-1.127

2.321E+08

4.265E+08

2

2

2

2

-2.02

3.957E+07

7.217E+07

2

2

2

2

-0.719

7.905E+08

1.451E+09

2

2

2

2

-0.874

8.298E+08

1.532E+09

2

2

2

2

-1.158

8.595E+08

1s 5f F5/2 - 1s 6d D5/2

518.267

1s 5f F7/2 - 1s 6d D5/2

518.298 518.994

3.006E+09

2

1s 6d D3/2 - 1s 9p P1/2

499.281

513.766

-0.121

2

1s 6d D3/2 - 1s 9p P3/2

410.759

513.663

2

1s 6g G9/2 -1s 9f F7/2

410.750

512.978

5.368E+09

2

1s 6g G7/2 -1s 9f F5/2

410.601

506.361

2.900E+09

2

1s 6g G7/2 -1s 9f F7/2

410.075

506.121

-0.234

2

1s 6f F7/2 - 1s 9d D5/2

410.051

505.037

9.359E+08

1s 6f F5/2 - 1s 9d D3/2

410.028

497.942

4.899E+08

1s 6p P3/2 - 1s 9s S1/2

410.021

484.479

-1.609

2

409.988

1s 5f F5/2 - 1s 6d D3/2 520.678

A (BPRM)

2

1s 6f F5/2 - 1s 9d D5/2

409.987

A (NIST)

2

1s 6f F7/2 - 1s 9g G7/2

409.942

A (BP)

2

1s 6f F7/2 - 1s 9g G9/2

409.849

Log gf

2

1s 6f F5/2 - 1s 9g G7/2

409.835

483.779

Transition

1s 2s S1/2 - 1s 2p P1/2

8.41E+08

9.677E+08

59

λ (BP)

λ(NIST)

1s26d 2D3/2 - 1s28f 2F5/2

519.566 519.764

607.136 607.173 607.579 607.667 607.688

607.852 607.926 607.946 607.962 607.984

2

0.168

4.531E+09

8.387E+09

2

2

2

2

0.28

4.697E+09

8.694E+09

2

2

2

2

-1.264

1.678E+08

3.104E+08

2

2

2

2

-2.475

1.375E+07

2.513E+07

2

2

2

2

-3.003

3.053E+06

5.591E+06

2

2

2

2

-1.572

1.099E+08

2.024E+08

2

-1.329

2.885E+08

5.330E+08

2

-1.459

1.068E+08

1.963E+08

2

2

2

2

2

2

2

-1.174

2.747E+08

5.049E+08

2

2

2

2

-1.927

7.220E+07

1.337E+08

2

2

2

2

-0.973

6.490E+08

1.212E+09

2

2

2

2

1.229

7.205E+08

1.370E+09

2

2

2

2

-1.219

7.370E+08

1.409E+09

2

2

2

2

-1.419

2.323E+08

2.30E+08

4.299E+08

2

2

2

2

-0.465

2.085E+09

2.06E+09

3.899E+09

2

2

2

2

-0.918

1.468E+09

2

2

2

2

-0.721

2.312E+09

2

2

2

2

-0.668

2.560E+09

4.911E+09

2

2

2

2

1s 6d D3/2 - 1s 8p P3/2 1s 6d D5/2 - 1s 8p P3/2 1s 6d D3/2 - 1s 8p P1/2

1s 6p P1/2 - 1s 8s S1/2 523.834 524.246

523.821

606.957

4.421E+08

2

1s 6f F7/2 - 1s 8d D5/2

523.002

601.908

2.385E+08

2

2

522.896

601.835

-1.237

2

1s 6g G9/2 -1s 8f F7/2

522.807

601.227

2

2

522.552

589.193

6.628E+09

2

1s 6f F5/2 - 1s 8d D3/2

520.795

588.97

4.772E+09

2

2

520.791

530.312

0.064

2

1s 6g G7/2 -1s 8f F5/2

520.774

528.860

6.187E+09

1s 6g G7/2 -1s 8f F7/2

520.769

523.845

3.345E+09

1s 6f F5/2 - 1s 8d D5/2

520.715

523.470

-0.09

1s 6f F7/2 - 1s 8g G7/2

520.667

1s 5d D3/2 - 1s 6p P3/2 1s 5d D5/2 - 1s 6p P3/2 1s 6p P3/2 - 1s 8s S1/2

524.659

A (BPRM)

2

1s 6f F7/2 - 1s 8g G9/2

520.399

A (NIST)

2

1s 6f F5/2 - 1s 8g G7/2

520.366

A (BP)

2

1s 6d D5/2 - 1s 8f F5/2

520.271

Log gf

2

1s 6d D7/2 - 1s 8f F5/2

519.818

523.026

Transition

1s 5d D3/2 - 1s 6p P1/2 1s 5p P1/2 - 1s 6s S1/2

1s 5p P3/2 - 1s 6s S1/2

2.857E+09 2.29E+09

4.419E+09

-0.368

5.075E+09

9.984E+09

2

2

2

2

-1.048

4.303E+08

7.663E+08

2

2

2

2

1s 7s S1/2 - 1s 10p P3/2 1s 7s S1/2 - 1s 10p P1/2

-1.349

4.298E+08

7.788E+08

2

2

2

2

-0.836

6.728E+08

1.235E+09

2

2

2

2

-0.581

8.048E+08

1.488E+09

2

2

2

2

-1.536

1.341E+08

2.486E+08

2

2

2

2

-0.443

1.089E+09

2.016E+09

2

2

2

2

-0.288

1.166E+09

2.160E+09

2

2

2

2

-1.589

7.772E+07

1.440E+08

2

2

2

2

-0.202

1.420E+09

2.628E+09

2

2

2

2

-0.089

1.472E+09

2.724E+09

2

2

2

2

-1.633

5.255E+07

9.727E+07

2

2

2

2

-2.706

5.917E+06

1.084E+07

2

2

2

2

-1.56

1.242E+08

2.297E+08

2

-3.17

1.526E+06

2.797E+06

2

-1.405

1.183E+08

2.177E+08

2

-1.738

5.493E+07

1.013E+08

1s 7p P1/2 - 1s 10d D3/2 1s 7p P3/2 - 1s 10d D5/2 1s 7p P3/2 - 1s 10d D3/2

1s 7d D3/2 - 1s 10f F5/2 1s 7d D5/2 - 1s 10f F7/2 1s 7d D5/2 - 1s 10f F5/2 1s 7f F5/2 - 1s 10g G7/2 1s 7f F7/2 - 1s 10g G9/2 1s 7f F7/2 - 1s 10g G7/2

1s 7f F5/2 - 1s 10d D5/2 1s 7f F5/2 - 1s 10d D3/2 2

2

2

1s 7g G7/2 -1s 10f F7/2 2

2

2

1s 7f F7/2 - 1s 10d D5/2 2

2

2

1s 7g G7/2 -1s 10f F5/2

60

λ (BP)

λ(NIST)

1s27g 2G9/2 -1s210f 2F7/2

608.013 608.194

775.023

771.9

773.1 773.1

1.054E+09

2

2

-2.198

2.850E+07

5.274E+07

2

2

2

2

-1.244

2.563E+08

4.778E+08

2

2

2

2

-1.499

2.846E+08

5.395E+08

2

2

2

2

-0.703

5.805E+08

1.029E+09

2

2

2

2

1.047E+09

-1.004

5.795E+08

2

2

2

2

-0.483

9.153E+08

9.24E+08

1.676E+09

2

2

2

2

-0.228

1.094E+09

1.11E+09

2.022E+09

2

2

2

2

-1.183

1.823E+08

1.84E+08

3.381E+08

2

2

2

2

-0.077

1.517E+09

2.808E+09

2

2

2

2

0.078

1.624E+09

3.010E+09

2

2

2

2

-1.223

1.082E+08

2.008E+08

2

2

2

2

0.182

2.063E+09

3.819E+09

2

2

2

2

0.295

2.138E+09

3.960E+09

2

2

2

2

-1.249

7.634E+07

1.414E+08

2

2

2

2

1s 7p P1/2 - 1s 9d D3/2

1s 7p P3/2 - 1s 9d D5/2 1s 7p P3/2 - 1s 9d D3/2

1s 7f F5/2 - 1s 9d D5/2

784.884

-2.287

9.312E+06

1.706E+07

2

2

2

2

-2.722

2.569E+06

4.712E+06

2

2

2

2

-1.29

9.247E+07

1.706E+08

2

2

2

2

-1.178

8.989E+07

1.655E+08

-1.141

1.954E+08

3.615E+08

1s 7g G7/2 -1s 9f F7/2

784.970

1s 7g G7/2 -1s 9f F5/2

784.995

1s 7g G9/2 -1s 9f F7/2

785.030

2

2

2

2

2

2

2

2

1s 7f F5/2 - 1s 9d D3/2

785.044

1s 7f F7/2 - 1s 9d D5/2

788.021

-0.986

1.862E+08

3.426E+08

2

2

2

2

-1.799

4.268E+07

7.899E+07

2

2

2

2

-0.845

3.835E+08

7.156E+08

2

2

2

2

-1.1

4.258E+08

8.082E+08

2

2

2

2

-1.13

3.966E+08

7.563E+08

2

2

2

2

-0.829

7.895E+08

1.534E+09

-0.185

1.676E+09

2.940E+09

-0.487

1.669E+09

3.004E+09

1s 7d D3/2 - 1s 9p P3/2

788.386

1s 7d D5/2 - 1s 9p P3/2

788.570

1s 7d D3/2 - 1s 9p P1/2

789.899

1s 7p P1/2 - 1s 9s S1/2

791.074

1s 7p P3/2 - 1s 9s S1/2

805.699

2

2

2

2

2

2

2

2

1s 6s S1/2 - 1s 7p P3/2

806.921

857.793

5.440E+08

2

1s 7f F7/2 - 1s 9g G7/2

784.860

857.578

-1.218

2

1s 7f F7/2 - 1s 9g G9/2

784.412

856.546

2

1s 7f F5/2 - 1s 9g G7/2

784.363

856.328

5.201E+08

2

1s 7d D5/2 - 1s 9f F5/2

784.229

855.860

2.729E+08

2

1s 7d D5/2 - 1s 9f F7/2

783.620

840.702

-1.519

2

1s 7d D3/2 - 1s 9f F5/2

783.534

840.287

9.822E+07

1s 7s S1/2 - 1s 9p P1/2

783.259

838.594

5.340E+07

1s 7s S1/2 - 1s 9p P3/2

755.258

774.857

-1.626

1s 7d D3/2 - 1s 10p P1/2

754.754

1s 6s S1/2 - 1s 7p P1/2 835.77 837.87 837.87

A (BPRM)

2

1s 7d D5/2 - 1s 10p P3/2

609.272

A (NIST)

2

1s 7d D3/2 - 1s 10p P3/2

609.251

A (BP)

2

1s 7p P3/2 - 1s 10s S1/2

609.033

Log gf

2

1s 7p P1/2 - 1s 10s S1/2

608.891

773.894

Transition

2

2

2

2

1s 6p P1/2 - 1s 7d D3/2

0.074

2.810E+09

2.86E+09

5.120E+09

2

2

2

2

0.328

3.353E+09

3.41E+09

6.187E+09

2

2

2

2

5.67E+08

1.036E+09

1s 6p P3/2 - 1s 7d D5/2 1s 6p P3/2 - 1s 7d D3/2

-0.626

5.580E+08

2

2

2

2

0.519

5.017E+09

9.277E+09

2

2

2

2

0.674

7.153E+09

9.945E+09

2

2

2

2

-0.627

3.575E+08

6.639E+08

2

2

2

2

0.822

7.531E+09

1.394E+10

2

2

2

2

0.935

7.805E+09

1.446E+10

1s 6d D3/2 - 1s 7f F5/2 1s 6d D7/2 - 1s 7f F5/2 1s 6d D5/2 - 1s 7f F5/2 1s 6f F5/2 - 1s 7g G7/2 1s 6f F7/2 - 1s 7g G9/2

61

λ (BP)

λ(NIST)

1s26f 2F7/2 - 1s27g 2G7/2

857.925 858.910

868.786

869.500

872.22 872.22

873.74

5.165E+08

-2.242

6.471E+06

1.185E+07

2

2

2

2

-0.698

2.264E+08

4.161E+08

2

2

2

2

-0.811

2.328E+08

4.290E+08

2

2

2

2

-1.771

2.550E+07

4.657E+07

2

2

2

2

-0.47

5.093E+08

9.359E+08

2

2

2

2

9.880E+08

-0.625

5.345E+08

2

2

2

2

-1.257

1.224E+08

1.20E+08

2.264E+08

2

2

2

2

-0.303

1.099E+09

1.08E+09

2.052E+09

2

2

2

2

-0.559

1.219E+09

1.19E+09

2.323E+09

2

2

2

2

-0.559

1.190E+09

2.770E+09

2

2

2

2

1s 6d D3/2 - 1s 7p P3/2 1s 6d D5/2 - 1s 7p P3/2

1s 6d D3/2 - 1s 7p P1/2 1s 6p P1/2 - 1s 7s S1/2

882.185

1s 6p P3/2 - 1s 7s S1/2

1084.154

-0.259

2.361E+09

4.629E+09

2

2

2

2

-0.668

3.045E+08

5.386E+08

2

2

2

2

1s 8s S1/2 - 1s 10p P3/2

1084.911

1s 8s S1/2 - 1s 10p P1/2

1109.973

-0.97

3.039E+08

5.486E+08

2

2

2

2

-0.462

4.673E+08

8.549E+08

2

2

2

2

-0.207

5.587E+08

1.032E+09

2

2

2

2

1s 8p P1/2 - 1s 10d D3/2

1111.278

1s 8p P3/2 - 1s 10d D5/2

1111.525

1s 8p P3/2 - 1s 10d D3/2

1122.794

-1.162

9.305E+07

1.726E+08

2

2

2

2

-0.064

7.617E+08

1.410E+09

2

2

2

2

0.091

8.153E+08

1.511E+09

2

2

2

2

-1.21

5.433E+07

1.009E+08

2

2

2

2

0.193

1.028E+09

1.904E+09

2

2

2

2

0.305

1.066E+09

1.975E+09

2

2

2

2

-1.239

3.805E+07

7.054E+07

2

-2.522

1.979E+06

3.634E+06

2

1s 8d D3/2 - 1s 10f F5/2

1123.161

1s 8d D5/2 - 1s 10f F7/2

1123.289

1s 8d D5/2 - 1s 10f F5/2

1124.091

1s 8f F5/2 - 1s 10g G7/2

1124.269

1s 8f F7/2 - 1s 10g G9/2

1124.343

1s 8f F7/2 - 1s 10g G7/2 2

1125.009

2

2

1s 8g G7/2 -1s 10f F7/2 2

1125.029

2

2

1s 8f F5/2 - 1s 10d D5/2

1125.137

-2.145

6.295E+06

1.155E+07

2

2

2

2

-1.091

7.120E+07

1.315E+08

2

2

2

2

-0.978

6.921E+07

1.276E+08

-0.999

1.321E+08

2.446E+08

1s 8g G7/2 -1s 10f F5/2

1125.163

1s 8g G9/2 -1s 10f F7/2

1125.282

2

2

2

2

2

2

2

2

1s 8f F5/2 - 1s 10d D3/2

1125.282

1s 8f F7/2 - 1s 10d D5/2

1129.919

-0.844

1.258E+08

2.319E+08

2

2

2

2

-1.696

2.630E+07

4.867E+07

2

2

2

2

-0.742

2.363E+08

4.408E+08

2

2

2

2

-0.997

2.624E+08

4.975E+08

2

2

2

2

-1.056

2.283E+08

4.347E+08

2

2

2

2

-0.755

4.545E+08

8.813E+08

2

2

2

2

-0.147

7.670E+08

1.342E+09

2

2

2

2

1.372E+09

1s 8d D3/2 - 1s 10p P3/2

1130.421

1s 8d D5/2 - 1s 10p P3/2

1130.741

1s 8d D3/2 - 1s 10p P1/2

1133.954

1s 8p P1/2 - 1s 10s S1/2

1135.575

1s 8p P3/2 - 1s 10s S1/2

1245.067

1s 7s S1/2 - 1s 8p P3/2

1247.021

1295.667

2.786E+08

1s 6f F5/2 - 1s 7d D3/2

879.864

1293.173

-0.609

1s 6f F7/2 - 1s 7d D5/2

859.629

1s 7s S1/2 - 1s 8p P1/2 1287.83 1291.16

A (BPRM)

2

1s 6f F5/2 - 1s 7d D5/2

859.544

A (NIST)

2

1s 6g G7/2 -1s 7f F5/2

859.195

A (BP)

2

1s 6g G9/2 -1s 7f F7/2

859.130

Log gf

2

1s 6g G7/2 -1s 7f F7/2

859.119

868.080

Transition

-0.449

7.635E+08

2

2

2

2

0.093

1.236E+09

1.26E+09

2.249E+09

2

2

2

2

0.348

1.474E+09

1.50E+09

2.721E+09

1s 7p P1/2 - 1s 8d D3/2 1s 7p P3/2 - 1s 8d D5/2

62

λ (BP)

1296.327

λ(NIST)

1291.16

1318.851

1803.1

1930.681

1930.750 1931.091 1931.835 1932.117 1952.843

2.818E+08

2

2

0.808

3.073E+09

5.691E+09

2

2

2

2

0.921

3.183E+09

5.902E+09

2

2

2

2

-0.623

1.136E+08

2.109E+08

2

2

2

2

-1.985

4.931E+06

9.048E+06

2

2

2

2

-0.441

1.725E+08

3.177E+08

2

2

2

2

-0.553

1.773E+08

3.275E+08

2

2

2

2

-1.596

1.607E+07

2.942E+07

2

2

2

2

-0.295

3.210E+08

5.909E+08

2

2

2

2

-0.45

3.370E+08

6.236E+08

2

2

2

2

-1.134

6.845E+07

1.265E+08

2

2

2

2

-0.18

6.145E+08

1.147E+09

2

2

2

2

-0.435

6.810E+08

1.297E+09

2

2

2

2

-0.47

6.115E+08

1.169E+09

2

2

2

2

2.375E+09

-0.171

1.214E+09

2

2

2

2

-0.613

1.250E+08

2

2

2

2

-0.111

3.900E+08

6.809E+08

2

2

2

2

-0.413

3.880E+08

6.965E+08

2

2

2

2

1s 3s S1/2 - 1s 3p P3/2 1s 8s S1/2 - 1s 9p P3/2

1822.988

1930.228

1.516E+08

2

1s 7p P3/2 - 1s 8s S1/2

1820.056

1928.017

-0.624

2

1s 7p P1/2 - 1s 8s S1/2

1362.303

1927.716

2

1s 7d D3/2 - 1s 8p P1/2

1358.821

1927.276

4.220E+09

2

1s 7d D5/2 - 1s 8p P3/2

1340.521

1925.313

2.275E+09

2

1s 7d D3/2 - 1s 8p P3/2

1339.317

1924.794

0.677

2

1s 7f F5/2 - 1s 8d D3/2

1338.263

1923.859

2

1s 7f F7/2 - 1s 8d D5/2

1324.569

1891.913

3.939E+09

2

1s 7f F5/2 - 1s 8d D5/2

1324.402

1890.929

2.127E+09

2

1s 7g G7/2 -1s 8f F5/2

1323.881

1887.419

0.522

2

1s 7g G9/2 -1s 8f F7/2

1323.709

1s 8s S1/2 - 1s 9p P1/2

1884.3

4.555E+08

2.453E+08

1s 7g G7/2 -1s 8f F7/2

1323.675

2.50E+08

-0.607

1s 7f F7/2 - 1s 8g G7/2

1323.360

A (BPRM)

2

1s 7f F7/2 - 1s 8g G9/2

1321.842

A (NIST)

2

1s 7f F5/2 - 1s 8g G7/2

1321.630

A (BP)

2

1s 7d D5/2 - 1s 8f F5/2

1321.322

Log gf

2

1s 7d D5/2 - 1s 8f F7/2

1319.874

1884.726

1s27p 2P3/2 - 1s28d 2D3/2 1s 7d D3/2 - 1s 8f F5/2

1319.527

1802.992

Transition

1s 3s S1/2 - 1s 3p P1/2

1.25E+08

0.933

1.095E+08

2

2

2

2

0.114

6.085E+08

1.107E+09

2

2

2

2

0.368

7.262E+08

1.340E+09

2

2

2

2

1s 8p P1/2 - 1s 9d D3/2 1s 8p P3/2 - 1s 9d D5/2 1s 8p P3/2 - 1s 9d D3/2

1.10E+08

1.512E+08

1.171E+08

-0.586

1.209E+08

2.245E+08

2

2

2

2

0.53

1.018E+09

1.885E+09

2

2

2

2

0.685

1.090E+09

2.022E+09

2

2

2

2

-0.616

7.258E+07

1.350E+08

2

2

2

2

0.803

1.428E+09

2.645E+09

2

2

2

2

0.916

1.479E+09

2.744E+09

2

2

2

2

1s 8d D3/2 - 1s 9f F5/2 1s 8d D5/2 - 1s 9f F7/2

1s 8d D5/2 - 1s 9f F5/2 1s 8f F5/2 - 1s 9g G7/2 1s 8f F7/2 - 1s 9g G9/2 1s 8f F7/2 - 1s 9g G7/2

-0.628

5.280E+07

9.806E+07

2

2

2

2

-1.802

3.528E+06

6.475E+06

2

2

2

2

-0.258

1.234E+08

2.273E+08

2

2

2

2

1s 8g G7/2 -1s 9f F7/2 1s 8g G9/2 -1s 9f F7/2

1s 8g G7/2 -1s 9f F5/2

-0.371

1.269E+08

2.343E+08

2

2

2

2

-1.463

1.028E+07

1.883E+07

2

2

2

2

-0.162

2.053E+08

3.782E+08

2

2

2

2

-0.317

2.155E+08

3.990E+08

-1.034

4.038E+07

7.464E+07

1s 8f F5/2 - 1s 9d D5/2 1s 8f F7/2 - 1s 9d D5/2 1s 8f F5/2 - 1s 9d D3/2 2

2

2

2

1s 8d D3/2 - 1s 9p P3/2

63

λ (BP)

λ(NIST)

1s28d 2D5/2 - 1s29p 2P3/2

1954.341 1956.218

-0.097

6.735E+08

1.316E+09

2

2

2

2

-0.077

2.148E+08

3.747E+08

2

2

2

2

-0.379

2.137E+08

3.833E+08

2

2

2

2

0.135

3.268E+08

5.944E+08

2

2

2

2

0.39

3.900E+08

7.200E+08

2

2

2

2

-0.565

6.490E+07

1.206E+08

2

2

2

2

0.542

5.347E+08

9.898E+08

2

2

2

2

0.696

5.720E+08

1.062E+09

2

2

2

2

-0.605

3.810E+07

7.092E+07

2

2

2

2

0.804

7.313E+08

1.356E+09

2

2

2

2

0.917

7.578E+08

1.406E+09

2

2

2

2

-0.628

2.705E+07

5.026E+07

2

2

2

2

-1.663

2.490E+06

4.575E+06

2

2

2

2

-0.119

8.710E+07

1.605E+08

2

2

2

2

1s 9g G9/2 -1s 10f F7/2

2699.340

1s 9g G7/2 -1s 10f F5/2

2699.893

-0.231

8.957E+07

1.655E+08

2

2

2

2

-1.355

6.733E+06

1.235E+07

2

2

2

2

-0.054

1.345E+08

2.479E+08

2

2

2

2

1s 9f F5/2 - 1s 10d D5/2

2700.914

1s 9f F7/2 - 1s 10d D5/2

2701.352

1s 9f F5/2 - 1s 10d D3/2

2731.162

-0.209

1.412E+08

2.615E+08

2

2

2

2

-0.952

2.497E+07

4.613E+07

2

2

2

2

0.002

2.242E+08

4.180E+08

2

2

2

2

-0.254

2.484E+08

4.721E+08

2

2

2

2

-0.333

2.004E+08

3.821E+08

2

2

2

2

-0.033

3.977E+08

7.761E+08

2

2

2

2

-0.473

2.918E+07

2.79E+07

7.727E+07

2

2

2

2

-0.794

2.546E+07

2.40E+07

6.315E+07

2

2

2

2

-1.222

4.400E+06

5.00E+06

7.381E+06

2

2

2

2

-1.003

4.127E+06

4.70E+06

5.781E+06

2

2

2

2

-1.974

6.108E+05

7.05E+05

7.816E+05

2

2

2

2

-0.369

9.460E+06

8.70E+06

2.940E+07

2

2

2

2

-0.69

8.240E+06

7.59E+06

2.426E+07

2

2

2

2

-0.968

1.398E+06

1.61E+08

3.630E+06

2

2

2

2

-0.749

1.311E+06

1.47E+06

3.002E+06

2

2

2

2

-1.72

1.941E+05

2.20E+05

4.191E+05

2

2

2

2

-0.287

3.773E+06

1.198E+07

2

2

2

2

-0.608

3.285E+06

9.894E+06

1s 9d D3/2 - 1s 10p P3/2

2733.215

1s 9d D5/2 - 1s 10p P3/2

2735.971

1s 9d D3/2 - 1s 10p P1/2

2779.863

1s 9p P1/2 - 1s 10s S1/2

2786.707

15830.299

2

1s 9g G7/2 -1s 10f F7/2

2699.190

15114.985

6.478E+08

2

1s 9f F7/2 - 1s 10g G7/2

2698.600

12789.932

3.394E+08

2

1s 9f F7/2 - 1s 10g G9/2

2695.516

12293.468

-0.397

2

1s 9f F5/2 - 1s 10g G7/2

2695.091

11323.937

2

1s 9d D5/2 - 1s 10f F5/2

2694.499

9087.357

7.643E+08

2

1s 9d D5/2 - 1s 10f F7/2

2691.891

8679.199

4.018E+08

2

1s 9d D3/2 - 1s 10f F5/2

2691.156

5383.566

-0.336

2

1s 9p P3/2 - 1s 10d D3/2

2689.900

5174.631

6.763E+08

1s 9p P3/2 - 1s 10d D5/2

2646.206

4766.376

3.628E+08

1s 9p P1/2 - 1s 10d D3/2

2644.806

4589.914

-0.081

1s 9s S1/2 - 1s 10p P1/2

2640.034

1s 9p P3/2 - 1s 10s S1/2 4453.1

4682.5 4575.4 4961.4 5137.3 8926 9343

10808 11831 12267

A (BPRM)

2

1s 9s S1/2 - 1s 10p P3/2

2553.092

A (NIST)

2

1s 8p P3/2 - 1s 9s S1/2

2548.904

A (BP)

2

1s 8p P1/2 - 1s 9s S1/2

1990.507

Log gf

2

1s 8d D3/2 - 1s 9p P1/2

1985.533

4386.138

Transition

1s 4s S1/2 - 1s 4p P3/2

1s 4s S1/2 - 1s 4p P1/2 1s 3p P1/2 - 1s 3d D3/2 1s 3p P3/2 - 1s 3d D5/2 1s 3p P3/2 - 1s 3d D3/2 1s 5s S1/2 - 1s 5p P3/2 1s 5s S1/2 - 1s 5p P1/2

1s 4p P1/2 - 1s 4d D3/2 1s 4p P3/2 - 1s 4d D5/2 1s 4p P3/2 - 1s 4d D3/2 1s 6s S1/2 - 1s 6p P3/2 1s 6s S1/2 - 1s 6p P1/2

64

λ (BP)

λ(NIST)

22188.195 24088.254

21050 22730

24125.447

25066.426

23530

31250 34480

34480

66356.957 70929.481

74321.813 91328.289 99171.817 130140.384 141332.570

4.

55560

-0.824

5.078E+05

5.95E+05

1.420E+06

-0.604

4.763E+05

5.67E+05

1.186E+06

-0.218

1.736E+06

2

2

-1.576

7.045E+04

2

2

2

2

-0.539

1.510E+06

4.553E+06

2

2

2

2

-0.158

8.868E+05

2.809E+06

2

2

-0.48

7.710E+05

2.319E+06

2

2

2

2

1s 5p P3/2 - 1s 5d D3/2

2

2

2

2

2

2

1s 6p P1/2 - 1s 6d D3/2

5.110E+06

8.53E+04

1.663E+05

-0.721

2.144E+05

4.00E+05

5.998E+05

2

2

2

2

-0.502

2.010E+05

3.57E+05

5.019E+05

2

2

2

2

5.95E+04

7.036E+04

1s 6p P3/2 - 1s 6d D5/2

1s 6p P3/2 - 1s 6d D3/2

-1.473

2.973E+04

2

2

2

2

-0.106

4.903E+05

1.549E+06

2

2

2

2

1.278E+06

1s 9s S1/2 - 1s 9p P1/2 50000

A (BPRM)

2

1s 9s S1/2 - 1s 9p P3/2

54062.821

A (NIST)

2

1s 5p P3/2 - 1s 5d D5/2

1s 8 S1/2 - 1s 8p P1/2

51598.229

61111.583

2

A (BP)

2

1s 8s S1/2 - 1s 8p P3/2

37864.445

43416.911

2

Log gf

2

1s 7s S1/2 - 1s 7p P1/2

36142.170

41723.150

1s25p 2P1/2 - 1s25d 2D3/2

1s 7s S1/2 - 1s 7p P3/2

25272.309

38429.007

Transition

-0.428

4.263E+05

2

2

2

2

-0.641

1.020E+05

1.85E+05

2.830E+05

2

2

2

2

1.63E+05

2.368E+05

1s 7p P1/2 - 1s 7d D3/2 1s 7p P3/2 - 1s 7d D5/2

-0.422

9.562E+04

2

2

2

2

-0.06

2.888E+05

9.095E+05

2

2

2

2

1s 10s S1/2 -1s 10p P3/2

1s 10s S1/2 -1s 10p P1/2

-0.381

2.510E+05

7.500E+05

2

2

2

2

-0.575

5.323E+04

1.465E+05

2

2

2

2

-0.355

4.988E+04

1.223E+05

2

2

2

2

-0.518

2.988E+04

8.170E+04

2

2

2

2

-0.299

2.798E+04

6.811E+04

1s 8p P1/2 - 1s 8d D3/2 1s 8p P3/2 - 1s 8d D5/2 1s 9p P1/2 - 1s 9d D3/2 1s 9p P3/2 - 1s 9d D5/2

Conclusion

Large-scale calculations have been carried out for fine structure energy levels, wavelengths and allowed transition probabilities in lithium like Si XII by including the relativistic effect using the Breit-Pauli approximation. Fine structure energy levels obtained from Breit-Pauli are assessed to be accurate to better than 0.15% with observed and calculated values. Wavelengths and transition probabilities show a good agreement in soft X-ray, EUV and far UV regions with almost all calculated and measured values available. In the visible and near IR, the present results are in comparable with the measured and calculated ones. An acceptable discrepancy has been shown in the mid IR region in both measured and calculated results. The results from the present work should be useful in the analysis of soft X-ray and E UV spectra in order to improve the adjustment to the observed energy levels, wavelengths and transition rates.

65

References [1] J. S. Kaastra, R. Mewe, D. A. Liedahl, S. Komossa and A. C. Brinkman, Astron. Astrophys. 354, L83 (2000). [2] S. Kaspi, W. N. Brandt, H. Netzer, R. Sambruna, G. Chartas, G. P. garmire and J. Nousek, APJ. 535, L17 (2000). [3] S. Kaspi, W. N. Brandt, H. Netzer, I. M. George, G. Chartas, E. Behar, R. M. Sambruna, G. P. Garmire and J. A. Nousek, APJ. 554, 216 (2001). [4] M. Sako, S. M. Kahn, E. Behar, J. S. Kaastra, A. C. Brinkman, Th Boller, E. M. Puchnarewicz, R. Starling, D. A. Liedehl, J. Clavel and Santos-Lieo, Astron. Astrophys. 365, L168 (2001). [5] R. Mewe, A. J. J. Rassen, J. J. Drake, J. S. Kaastra, R. L. J. Van der Meer and D. Porquet, Astron. Astrophys. 368, 888 (2001). [6] G. Y. Liang, G. Zhao, J. Y. Zhong, Y. T. Li, Y. Q. Liu, Q. L. Dong, X. H. Yuan, Z. Jin, and J. Zhang, The Astrophysical Journal Supplement Series 177, 326 (2008). [7] J. D. Lindl, P. Amendt, R. L. Berger, S. G. Glendinning, S. H. Glenzer, S. W. Hann, R. L. Kauffman, O. L. Landen and L. J. Suter, Phys. Plasmas 11, 339 (2004). [8] A. Kumar, D. Misra, K. V. Thulasiram, L. C. Tribedi and A. K. Pradhan, Nuclear Instrument Method In Physics Research B. 248, 247 (2006). [9] Y. S. Kozhedub, A. V. Volotka, A. N. Artemyev, D. A. Glazov, G. Plunien, V. M. Shabaev, I. I. Tupitsyn and Th Stöhlker, Phys. Rev. A 81, 042513 (2010). [10] Jing Jing Zhu, Bing Cong Gou and Yue Dong Wang, J. Phys. B 41, 065702 (2008). [11] Hu Mu-Hong and Wang Zhi-Wen, Chin. Phys. B 17, 908 (2008). [12] L. Natarajan and Anuradha Natarajan, Phys. Rev. A 75, 062502 (2007). [13] L. I. Podobedova, D. E. Kelleher, J.Reader and W. L. Wiese, J. Phys. Chem. Ref. Data 33, 471(2004). [14] W. C. Martin and Romuald Zalubas, J. Phys. Chem. Ref. Data 12, 323 (1983). [15] S. N. Nahar, Astron. Astrophys.389, 716 (2002). [16] L. H. Coutinho and A. G. Trigueiros, J Quant. Spectrosc. Radiat. Transfer 72, 485 (2002). [17] D. E. Kelleher and L. I. Podobedova, J. Phys. Chem. Ref. Data 37, 1285 (2008). [18] E. TrIabert, P. H. Heckmann, Hv Buttlar and K. Brand, Z Phys A 279, 127 (1976). [19] J. P. Mosnier, R. Barchewitz, M. Cukiers, R. Dei-Cas, C. Senemaud and J. Bruneau, J. Phys. B 19, 2531 (1986). [20] V. A. Boiko, A. Ya Faenov and S. A. Pikuz, J Quant. Spectrosc. Radiat. Transfer 19, 11 (1978). [21] E. TrIabert, I. A. Armour, S. Bashkin, N. A. Jelley, R. O’Brien and J. D. Silver, J. Phys. B 12, 1665 (1979). [22] I. I. Sobel’man, Introduction to the theory of atomic Spectra Vol. 40 International Series of Monographs In Natural Philosophy, Pergamon Press (1979). [23] C. F. Fischer, T. Brage and P. Jönsson, Computational atomic structure Institute of Physics Publishing, Bristol and Philadelphia (2000). [24] R. D. Cowan, The Theory of Atomic Structure and Spectra University of California Press, Berkeley, California (1981). [25] R. D. Cowan and D. C. Griffin, J. Opt. Soc. Am. 66, 1010 (1976). [26] I. I. Sobelman, Atomic spectra and radiative transitions Berlin, Springer (1979). [27] http://physics.nist.gov/PhysRefData/ASD/index.html [28] H. L. Zhang, D. H. Sampson and C. J. Fontes, At. Data Nucl. Data Tables 44, 31 (1990). [29] http://www.pa.uky.edu/~peter/atomic/ [30] K. M. Aggarwal and F. P. Keenan, Phys. Scr. 82, 065302 (2010). [31] A. I. Refaie, American Institute of Physics, Modern trends inPhysics Research (MTPR-06) 888, 69 (2006).

66

SOME HISTORIC AND CURRENT ASPECTS OF PLASMA DIAGNOSTICS USING ATOMIC SPECTROSCOPY ROGER HUTTON Modern Physics Institute, Fudan University, Shanghai, P.R. China

The use of atomic spectroscopy in the diagnostics of hot plasma, whether terrestrial or astrophysical, has a long and distinguished history. Some examples of past highlights will be given, along with a mention of their impact on contemporary thinking. In terms of more current lines of research on atomic spectroscopy relevant to plasma diagnostics, we will discuss more subtle effects concerning the influence of magnetic and nuclear interactions on atomic structure. For example, there are more effects of magnetic fields on atomic structure than the often though about Zeeman splitting of atomic energy levels. As magnetic fields exist in many astrophysical plasmas and also in Tokomak machines, this line of research may be of great importance to these very important branches of physics. Similarly, effects of nuclear-spin, through the hyperfine interaction, can have dramatic effects on the lifetimes of forbidden transitions. Again, important additions to plasma diagnostics are expected through effects caused by the hyperfine interaction. We will also stress the importance of Electron Beam Ion Traps as excellent laboratory light sources to study such potentially very interesting effects.

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

67

NOVELTY PREPARATION, CHARACTERIZATION AND ENHANCEMENT OF MAGNETIC PROPERTIES OF MN NANOFERRITES USING SAFETY BINDER (EGG WHITE) M. A. AHMED† Materials Science Lab. (1), Physics Department, Faculty of Science, Cairo University Giza, Egypt N. OKASHA1 and S. I. EL-DEK2 1

Physics Department, College of Women for Arts, Science and Education, Ain Shams University, Cairo, Egypt 2 Materials Science Lab. (1), Physics Department, Faculty of Science, Cairo University, Giza, Egypt

Nanocrystalline MnFe2O4 ferrite was prepared using natural binder; egg white was used as an aqueous medium to extend nanoparticle preparation better than any other interesting materials. X- ray diffraction (XRD) and transmission electron microscope (TEM) showed also that the investigated samples revealed the nanosized structure with crystallite size of 39nm. The magnetic susceptibility measurements give a Curie temperature TC = 613K with effective magnetic moment 23 B. M. The values of magnetic constants as obtained from hysteresis data are, saturation magnetization Ms = 13.71 emu/g, remanent magnetization Mr = 0.1694 emu/g and coercivity Hc = 25.6 Oe. Keywords: Nanostructured materials; Egg white; X-ray diffraction; TEM; Magnetic properties.

CoFe2O4

1. Introduction

and

NiFe2O4

[15].

Using

neutron

In recent years, worldwide researchers have

diffraction, Yamzim et al. [16] studied the distribution

extensively studied nanosized materials due to their

of manganese among tetrahedral and octahedral sites

interesting physical and chemical properties as

in the sample.

compared to their counterpart bulk material [1].

Several authors [17-21] have reported that, the

Manganese nanoferrite is considered as an important

ferrites nanoparticles have counter parts less than their

magnetic materials due to its use in electronic

corresponding

applications [2, 3], enhanced contrast agents in

contributing

magnetic resonance imaging (MRI) technology,

magnetization. This may be due to random canting of

catalytic use, magnetically guided drug delivery,

spins at the particle surface caused by competing

sensors and pigments devices [4-8]. It is also

antiferromagnetic

established that, the magnetic behavior of MnFe2O4

asymmetry in the environmental of these spins and

ferrites is closed to structural properties [9-11].

results in a decrease of magnetization [18, 21].

Several

studied

the

to

the

There

are

reduction

exchange

some of

factors

nanoparticle

interactions

due

to

magnetic

Various methods were developed to synthesize

behavior of Mn-Zn ferrite as a function of temperature

nanocrystalline MnFe2O4 such as citrate [13], co-

[12] and particle size [13]. The magnetic moment of

precipitation [14], sol gel [15] and solid-state

MnFe2O4 ferrite agrees well with the Neel coupling

technique [16]. Here, we use egg white as a natural

scheme [14] and has a much lower resistivity than

material,

†

researchers

bulk.

which

is

Corresponding author: M. A. Ahmed, E-mail: [email protected]

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

cheaper,

nontoxic,

and

68

environmentally good precursor. Egg white is well

2 h. The mixture was dried at 353K, treated at

known for its gelling, foaming and emulsifying

different temperatures of (500, 600, 800, 950, and

characteristics, high nutrition quality [22-24]. Due to

1050°C) and then cooled to room temperature with the

its solubility in water and its ability to associate with

same rate as that of heating (4°C/min). The schematic

metal ions in solutions, it can be used as a binder gel

diagram in Fig. (1) shows simple the preparation

for shaping material especially bulk and ceramics [25,

method.

26]. The use of egg white simplified the process and

2.2. Characterization

provided another alternative process, which is simple and economical synthesis of nanocrystalline ceramic particles.

The phase structure, crystallite size and lattice parameter were studied using X- ray diffractometer (Proker D8 - USA) using CuKα radiation with

The goal of the present work is to synthesize cubic spinel single phase Mn nanoferrite using natural egg white to study its structure and enhanced physical properties.

wavelength λ = 1.5418°A. The XRD pattern of the nanoparticles was compared with the ICDD card (742403). The broadening of the peak was related to the small crystallite size (L) of the prepared sample according to Scherrer’s formula [27]; L = 0.9 λ / β

2. Experimental techniques

Cos θ where, λ is the wavelength of X-ray, β is the full 2.1. Sample Preparation

width at half-maximum (FWHM) and θ is Bragg’s

Nanocrystalline manganese ferrite (MnFe2O4)

angle. Transmission electron microscopy (TEM) was

was synthesized using Mn(NO3)2. 5H2O, Fe (NO3)3.

performed using JEOL, JEM – 1230 electron

9H2O as raw materials and 50 mg of fresh extracted

microscope. The dc molar magnetic susceptibility (χM)

egg white used as a binder in the presence of distilled

of the investigated samples was measured using

water as an aqueous medium. Mixing the fresh egg

Faraday’s method for the powdered samples at

white in distilled water with continuous stirring at

different magnetic field intensities; 1733, 2160, and

room temperature (300K) until a homogeneous

2577 Oe as a function of temperature ranging between

solution is obtained then slowly adding the metal

300-700K.

nitrate solution with a molar ratio corresponding to the

nanoparticles were performed using a vibrating sample

nominal composition of Mn: Fe ratio of 1:2 with

magnetometer (VSM; 9600 – 1LDJ; USA) at room

vigorous stirring using magnet and without heat for

temperature.

50 mg. freshly egg white + Distilled water

Rapid stirring

Fe (NO3)3. 9H2O+Mn(NO3) . 5H2O

Magnetization

dried at 353K

Puffy powder

Fig. (1) Flow chart of the sample preparation technique.

measurements

of

the

69

MnFe2O4 single-phase cubic spinel structure were

3. Results and discussion Figure (2a) shows X-Ray diffraction (XRD)

obtained with no extra peaks for any impurities. This

pattern of MnFe2O4 ferrite nanoparticles. Seven

result agrees well with the standard data of ICDD

sharp

(card No. 73-2403). The value of the lattice constant

lines

corresponding

to

the

lines

of

reported elsewhere [14]. The average crystallite sizes

(311) using Sherrer’s equation mentioned above. The crystallite size of the obtained nanoferrite

(533)

20

(L) was estimated from the FWHM of the main peak

(422) (333) (440)

40

(220) (311) (222) (400)

Counts

(a) is 0.83152 nm and this value is less than that

was 39 nm and this value is less than that obtained by

0

another authors [16, 28]. Figure (2b) shows the 20

30

40

50

60

70

80

electron diffraction (ED) pattern of nanoparticles, the

ICCD74-2403

figure exhibits spots and rings indicating that the nanoparticles are well crystallized where the diffraction rings are indexed for the manganese ferrite system as compared with the obtained value from

20

30

40

50

60

70

80

XRD values. The micrograph and the particle size

2θ (400) X=0.0

(311) (220)

(111)

100 nm Fig. (2)Fig. : a- The patterns of M patterns nFe 2 O 4 nanoferrite sample. (2)XRD a-The XRD of MnFe 2O4 nanoferrite b- Electron diffraction (ED) of M nFe 2 O 4 ferrite nanoparticles sample. b-Electron diffraction (ED) of MnFe2O4

ferrite nanoparticles.

Fig. (3) Transmission electron microscope (TEM) micrograph of the MnFe2O4 nanoparticles.

70

distribution of MnFe2O4 are shown in transmission

sufficient to overcome the effect of magnetic field,

electron microscope (TEM) Fig. (3).

which aligns the magnetic dipoles in its direction, with

The TEM micrograph shows that, the particles

the

result

of

decreasing

χM

with

increasing

are in an agglomerated state, with average particle size

temperature.

(∼ 44.7 nm). This result is in a good agreement with

(paramagnetic), the thermal energy due to heating

the crystallite size calculated from X-ray diffraction

increases the lattice vibration as well as the disordered

pattern. The variation of the molar magnetic

state of dipoles and consequently overcome the field

susceptibility (χM) with absolute temperature ranging

effect causing the fast decrease in χM up to Curie

from 300-700K as a function of magnetic field

temperature (TC = 613K). Moreover, in terms of the

intensity 1733, 2160, and 2577 Oe is shown in

magnetic field effect and by increasing its value, the

Fig. (4).

magnetic moments tend to align in its direction where

At

high

temperature

region

the parallel configuration leads to a decrease in 1.6

magnetic energy (minimum energy state). Figure (5) shows the plot of magnetization (M)

χ M (e m u / g . m o l . )

1.2

versus magnetic field (H) for the MnFe2O4 sample at

0.8

1733Oe

room temperature (300K) in the field range of ∼ ±

2160Oe

3000 Oe. The hysteresis loop shows a normal (S-

2578Oe

shape) type of ferromagnetic behavior. The size and

0.4

shape of the hysteresis curve for a magnetic material are of considerable practical importance. The relative

0.0 300

400

500

600

700 T(K)

Fig.Fig. (4)(4):Variation ofmagnetic the magnetic susceptibility (χM) Variation of the susceptibility ( χ M ) with with temperature asa afunction function of the field magnetic temperature as of the magnetic intensity. field intensity.

thin and narrow area of the loop is related to the specific behavior for soft ferrite. The saturation magnetization (Ms) value is 13.71emu/g, remanent magnetization (Mr) is 0.1694 emu / g. and the coercive field (Hc) is 25.6 Oe. These values are less than those

The data showed a normal ferrimagnetic

reported in [29] where, this reduction is due to the

behavior at low temperature region. One can predict

weakness of the AB interaction when Mn2+ in

that, the thermal energy given to the sample is not

tetrahedral (A) substitutes Fe3+ sites [28].

71

4. Conclusion

M (e m u / g )

15

Based on the above results, we concluded: 10

• A simple and novel route is presented for producing highly homogeneous nanocrystalline

5

manganese ferrites by using water-soluble egg white as a safety binder.

0 -3000

-2000

-1000

0 -5

1000

2000

3000

H (Oe)

• The results of XRD and TEM revealed good crystallinity with crystallite size of 39 nm.

-10

• The manganese nanoferrite exhibited magnetization (Ms) value of 13.71 emu/g, magnetic remanence

-15

Fig. (5): Magnetization versus magnetic field intensity (H) for Fig. (5) Magnetization versus magnetic field intensity MnFe 2 O 4 nanoparticles at room temperature.

(H) for MnFe2O4 nanoparticles at room temperature.

(Mr) is 0.17 emu/g with coercivity (Hc) of 25.6 Oe. • Finally, the formation of MnFe2O4 spinel ferrite using environmental binder such as egg white is considered cost effective, environmental friendly,

As the particle size decreases, a large

easily controlled and expected to be applicable for

percentage of all the atoms in a nanoparticle become

the preparation of other metal oxides with special

surface atoms, which implies that surface and interface

morphologies.

effects become more important. For example, near surfaces, the magnitude of the magnetic moment per atom in ferromagnetic metals can change drastically as a result of reduced coordination at the surface. However, the orientation of each moment can be altered because of competing exchange interactions in an incomplete coordination shell for surface ions. This can lead to a disordered spin configuration near the surface and a reduced average net moment relative to the bulk material. The disordered cation distribution leads to the formation of a magnetically dead layer on the surface and the occurrence of a glassy state arising from frustration induced by magnetic interactions between randomly distributed particles was proposed to explain the reduced saturation magnetization (Ms) in the investigated sample as compared with their bulk counter part [17, 18].

References 1. J. J. Li, W. Xu, H. M. Yuan, J. S. Chen, Solid State Comun. 131 519 (2004). 2. D. Zhang, X. Zhang, X. Ni, J. Song, H. Zhang, J. Chemical Physics Letters 426 120 (2006). 3. M. Sugimoto, J. Am. Ceram. Soc. 82 269 (1999). 4. R. Vautier and M. Paulus, Landolt-Bornstein Numerical Data and Functional Relationships in Science and Technology, New Series (SpringerVerlag, Berlin, Vol. III/4b (1970). 5. J. Smit and H. P. J. Wijn, Ferrites (Wiley, New York, 1959). 6. V. A. M. Brabers, in Handbook of Magnetic Materials (Elsvier, New York), Vol. 8, p. 189 (1995). 7. M. Sugimoto, J. Am. Ceram. Soc., 82 269 (1999). 8. Safarik, M. Safarikova, Magnetic nanoparticles and Biosciences, in: H. Hofmann, Z. Rahman, U. Schubert (Eds.), Nanostructured Materials, Springer, Vienna, 1-23 (2002). 9. K. E. Sickafus, J. M. Wills, and N. W. Grimes, J. Am. Ceram. Soc., 82 3279 (1999).

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10. G. U. Kulkarni, K. R. Kannan, T. Arunarkavalli, C. N. R. Rao, Phys. Rev. B 49 724 (1994). 11. B. Gillot, M. Laarj, S. Kacim, J. Mater. Chem. 7 827 (1997). 12. K. Latha and D. Revinder, J. Phys. Stat. Sol. (a) 139 109 (1993). 13. N.S. Gajbhiye, I. G. Balaji, Thermochimica Acta 385 143 (2002). 14. S. G. Fritsch, A. Navrotsky, P. Tailhades, H. Coradin, M. Wang, J. Solid State Chemistry 178 106 (2005). 15. S. Prasad, N. S. Gajbhiye, J. Alloys Compd., 265 87 (1998). 16. S. Mishra, T. K. Kundu, K. C. Barick, D. Bahadur, D. Chakravorty, J. Mag. Mag. Mater., 307 222 (2006). 17. J. Giri, P. Pradhan, T. Sriharsha, D. Bahadur, J. Appl. Phys., 97 10 Q 916 (2005). 18. N. S. Gajbhiye, G. Balaji, M. Ghafari, J. Physica Status Solidi (a) 189 357 (2002). 19. E. Everett, J. Charles, G. Vincent, J. Applied Physics 85 5175 (1999).

20. D. Vollath, D. V. Szabu, R. D. Taylor, J. U. Willis, J. Mag. Mag. Mater., 12 2175 (1997). 21. Q. A. Pankhurst, R. J. Polland, Phys. Rev. Lett., 67 248 (1991). 22. D. V. Vadehra, K. R. Nath, CRC Crit. Rev. Food Technol., 4 193 (1973). 23. E. Li-Chen, S. Nakai, CRC Crit. Rev. Poultry Biol. 8 21 (1989). 24. Y. Mine, Trends Food Sci. Technol., 6 225 (1995). 25. S. Dhara, P. Bhargava, J. Am. Ceram. Soc., 84 3045 (2001). 26. S. Dhara, P. Bhargava, J. Am. Ceram. Soc., 86 1645 (2003). 27. B. D. Cullity, S. R. Stock, Elements of X-ray Diffraction, third ed., Prentice- Hall, Englewood Cliffs, NJ, (2001). 28. Z. Bianfang, T. Guide, Y. Zonglin, W. Zhenbiao, Y. Qingfen, C. Jianpo, J. Wuhan University of Technology Materials Science 22 514 (2007). 29. D. Zhang, X. Zhang, X. Ni, J. Song, H. Zheng, J. Chemical Physics Letters 426 120 (2006).

I-2 CONTRIBUTING PAPERS

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75

STARK BROADENING CALCULATIONS OF SEVERAL Ti LINES A. I. REFAIE and H. SHARKAWY Department of Physics, Faculty of Science, Cairo University, Giza, Egypt

This work reports calculated Stark broadening transition of several Ti lines at 1064 nm in a laser-produced plasma (ne = 2.27-1.59 × 1019 cm-3). The method is based on the assumption of homogenous plasma and local thermodynamical equilibrium (LTE). Electron temperatures are in the range of 0.79-0.85 eV. There is no data available to be compared with the present calculated parameters except only one experimental reference has been used to compare only three lines with the present data.

1. Introduction Laser induced breakdown spectroscopy (LIBS) has become a widely used analytical tool for rapid quantitative analyses of various fields of technological applications [1-5] especially in plasma diagnostics. Thus, the plasma spectra have to be simulated and compared to the measured line profiles in order to determine the plasma parameters. Stark broadening of spectral lines due to interaction between emitter and charged particles is of interest in plasma [6-9]. It is important to verify theoretical Stark broadening parameter of atomic emission lines experimentally, since they are necessary for spectroscopic density measurements, opacity codes and other astrophysical observations as well as analytical chemistry [10-13]. In LIBS methods, the analytical signal is calculated by integrating the emission line profile. If the line profile changes with conditions during the experiment, the accuracy of the measurement may deteriorate. This is a serious problem in the application of LIBS technique as no appropriate standardization method is available. The purpose of this experiment is to investigate the line broadening coefficients for titanium plasma by monitoring emission spectra in vacuum (p = 4 × 10-6 mbar). Seven atomic transition lines are investigated in the wavelength range (362.48-350.49 nm). In this experiment, Ti spectral line profiles are obtained by using laserproduced plasma. These plasmas are optically thin to permit direct measurements of the electron temperature from Boltzmann plots under the assumption of LTE. The spectra of Ti II lines 357.37, 358.71, 362.48, 364.13 and 348.36 nm are free from self absorption. These spectral lines are chosen for temperature measurements. One spectral line of Ti II at 350.49 nm has been used for measuring the electron density Ne from Stark broadening effect at different distances from the target. Line width is calculated through Voigt curve fitting of spectral data. The electron temperature and the electron density have been compared with the available data in literatures [1, 14-17]. The stark broadening of the calculated parameters has been compared with the only existing experimental reference [17]. Only three lines are found and compared with the present data the results show a fairly good agreement with the data in literature [17]. 2. Experimental Set Up The present work is performed using the experimental set up shown in Figure 1. A Q-switched Nd-YAG Brilliant laser from Quantel delivering the energy per pulse is 670 mJ in 6 ns FWHM at the fundamental wavelength 1064 nm at a repetition rate of 10 Hz was used. This corresponds to a power density of 5.6 × 1010 W/cm2 for a laser focal spot radius of ~ 0.25 mm. The plasma is generated in vacuum by focusing the laser beam using a quartz lens having a focal length f = 20 cm, perpendicularly onto the target. The measurements are carried out under a pressure of 4 × 10-6 mbar, produced by Leybold turbo molecular pump. The emission spectrum is collected perpendicularly with the aid of a two lens system (focal lengths f2 = 20 cm, f3 = 5 cm), both are mounted with the quartz fiber cable of diameter 25 µm on a x-y translation stage that allows for an easy illustration of the slit of the spectrograph. The emission spectrum was recorded using SE 200 Echelle spectrograph (Catalina Crop.), equipped with ICCD camera

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

76

(Andor model iStar DH734-18F). The gain of the camera was fixed at a value 250 with binning model at 1 × 1. This spectrometer allows for a time resolved spectral acquisition over the whole UV-NIR (200-1000 nm) with a constant spectral resolving power λ/∆λ = 4500 over three points. An Oriel low-pressure Hg lamp is used for wavelength calibration of the Echelle spectrograph. The calibration of the system is checked by experimentally measuring two different known lines for emission from exited states of mercury lamp. The instrumental bandwidth of the system is 0.04 nm measured by low pressure Hg lamp, where the natural width of the mercury spectrum is known. The relative spectral response of the experimental system in the range (360 nm – 520 nm) has been determined by using a calibrated Tungsten lamp with the same experimental conditions that were used in the measurements. This calibrated system facilitates comparison of the emission intensities from different plasma species. The emitted spectrum is recorded in a direction parallel to the target surface.

Target

Plume

Focusing lens Vacuum Chamber

Nd:YAG laser

Lenses

Echelle Spectrograph Optical Fiber

ICCD

C

Figure 1. Schematic diagram of the experimental setup.

77

3. Laser Plasma Density and Temperature The excitation temperature is considered one of the most important parameters that used to characterize the state of the plasma. An accurate temperature values lead to understand the plasma processes occurring, namely vaporization, dissociation, excitation, ionization, combination and collisional radiative parameters. The electron (or plasma) temperature can be determined from the measurement of the intensity of its spectral lines, provided that its transition probability from a given excitation state is known assuming that the population of the energy levels follows the Boltzmann distribution law. For full LTE the intensity of the spectral line is given by [18]

N (T ) λ mn I mn E  = exp m  U (T ) g mn Amn  kT 

(1)

where I mn , g i Amn and Em are the intensity, the statistical weight, the transition probability and the excited energy level, T and k are the temperature and the Boltzmann constant respectively. N (T ) Is the total number density and U (T ) is the partition function. Equation 1 can be applied using the absolute intensity of one spectral line provided accurate values for N (T ) and U (T ) are known. However, for two spectral lines emanating from the same atomic or ionic species, the two line radiance method can be used [6]

I1 Ag λ  E − E1 = 1 1 2 exp  2 I 2 A2 g 2 λ1  kT

  

(2)

A plot of ln(λI/gA) versus E indicates a straight is so called Boltzmann plot and the line having a slope which yields to Te under the assumption in the state of LTE and optically thin for the lines observed. The spectra of five Ti II lines 357.37, 358.71, 362.48, 364.13 and 348.36 nm are recorded from the laser induced plasma and are chosen for temperature measurements. The Boltzmann plots of these transitions which are free from self-absorption are used to obtain the corresponding temperature. The accuracy of the excitation temperature is limited by the uncertainty in the transition probability Amn values of the spectral lines. There are several possible mechanisms of line broadening in plasma: natural, Doppler, Stark, self absorption, Van Der Waals, instrumental broadenings and resonance broadenings from collisions between the same neutral species on a strong resonance line, etc. [6, 19]. In laser plasma where low temperatures and high densities prevail, the contributions by Doppler, Van der Waals, and resonance broadening can be neglected [20]. In the hottest region of the laser plasma, the Stark effect leads to a broadening of the atomic and ionic emission lines as well as to a shift in the line-center wavelength. The FWHM of Stark broadening of a line, ∆λ 1 is related to the electron 2 density N e by [19] ο

2

1

1

∆λ 1 ( A) = 2 w(

Ne Ne 4 3 − Ne ) + 3.5 A( 16 ) [1 − N D 3 ]w( 16 ) 16 4 10 10 10

(3)

where w is the electron impact width parameter or Stark width parameter, A is the ion broadening parameter and ND represents the number of particles in the Debye sphere [19] 3

ND =

1.72 × 10 9 [T e ( ev )] 2 [ N e ( cm

−3

1 )] 2

(4)

In the present study the Ti II spectral line at 350.49 nm used to derive the electron density is checked by the ratio of emission intensities to be free from self-absorption. The Stark width parameter w of this line has been

78

accurately determined experimentally [17]. In the experimental conditions of the present work the main contribution to the line widths arises from Stark effect because of the small contribution of the second term of Eq. 3. The FWHM of the spectral line under investigation ∆λ 1 is determined by a Voigt fitting procedure and corrected by convoluting the instrumental line broadening as given2 in details in reference [21, 6, 22]. The electron density (in cm-3) can be determined from the line width as ∆λ1 Ne = (

2

2w

) ×1016

(5)

Analysis of each line profile proceeded in the following way; the instrumental function is convoluted with a Lorentzian function of variable width and fitted to the experimental profile by a least square fitting procedure.

4. Results and Discussion 4.1. Evaluation of the Stark broadening and plasma parameters The emission spectra of titanium plasma are produced in vacuum (p = 4 × 10-6 mbar). Table 1 presents the selected analyzed spectral lines of Ti with their atomic database taken from NIST [23]. Wavelengths, excitation energies, statistical weights and transition probabilities of the measured Ti lines are listed in the table. Stark broadening parameters of Ti lines are not available in the literature. Hence the present calculated parameters have been compared with the only reference existing in literatures. The Stark width parameter w of the Ti II selected line at 350.49 is experimentally determined accurately by Hermann et al [17]. The calculated Stark broadening parameters w for seven neutral and ionized Ti lines are given in Table 2. The three Ti II spectral lines at 346.15 nm, 348.36 nm and 350.49 nm have well-known Stark broadening parameters [17] and have shown a good agreement with that in the literature.

4.2. Evaluation of the plasma parameters Figure 2 shows the variation of the measured plasma temperature at different distances from the Ti target. The spectral line of Ti II at 350.49 nm is used for measuring Ne at different distances from the target is chosen to measure electron density from Stark broadening effect. The variation of the electron density at different distance from the target in the range of 0.1, 0.6, 2, 3 and 4 mm is shown in Figure 3. The effect of the dependence of the measured emission lines at different distances from the target on the electron temperate and electron density is investigated. A significant fraction of the laser energy is absorbed by the plasma due to the inverse Bremsstrahlung so it should increase the plasma temperature as well as the electron density at early stage of plasma generation. Hence it is increased with the distance from the target until a distance of 0.6 mm. It is then observe a fast decrease of the excitation temperature due to the variation of the laser focal positions away from the Ti surface and the enhancement of the cooling rate in the outer part of the plasma as shown in Figure 2. This may be due to pressure, vaporization and dissociation. It is also observe a decrease of the electron density after 0.6 mm due to the shielding of the target by the plasma, which prevents further interaction of the laser radiation with the target. Moreover, it might be due to the enhancement of the recombination processes.

79

The mean value of the derived electron temperature is 0.85 eV at 0 ns delay time in the present work. Khalil et al [1] determined the electron temperature by using LIBS of titanium plasma using single and double pulsed laser excitation scheme with laser irradiance 1.35 × 1010 W cm-2. The electron temperature of the Ti ionized lines has been found 0.86 eV for single pulse and 0.69 eV for double pulse mode at delay time 0 ns which is in good agreement with our value. Giacomo et al [14-16] has been obtained by using LIBS of titanium target in vacuum at different pressures by using different values of laser fluencies (from 1 to 6 J cm-2), different distances from the targets (from 0.6 to 6 mm) and different delay times. The measured electron temperatures are in good agreement with the present measured Te and the electron density with the same order of magnitude at 0 ns. Hermann et al.[17] deduced an electron temperature of 1.7 ± 0.1 eV by using time-space resolved emission and laser induced fluorescence spectroscopic measurements of plasma formation resulting from excimer laser irradiation of titanium targets in a low pressure nitrogen atmosphere. One spectral line of Ti II at 350.49 nm is used for measuring the electron density Ne. The obtained electron density in vacuum is 1.81 × 1016 cm-3 at 0 ns. For a laser intensity of 500 MW/cm2 deduced by Hermann et al. [17] the total number of ablated Ti atoms was estimated to 1016 and after a delay 100 ns with leading to a density of about 1018 cm-3 which indicates that the plasma is initially completely ionized. The present experimental electron density is in agreement with the density [17] at 0 ns. The discrepancy is probably due to that the experiment has been performed only at a delay of 0 ns with respect to the ablating laser pulse and due to the different conditions of the experiments. Table 1. Transition probabilities of Ti I and Ti II spectral lines. Line

λ (nm)

Em (eV)

En (eV)

gm

gn

Amn (108 s-1)

Acc.

Ti II

364.1339

1.236

4.641

4

2

4.90E-01

D

Ti I

365.3496

1.048

3.441

9

11

7.54E-01

C

Ti II

362.4824

1.221

4.64

2

2

2.90E-01

D

Ti I

363.5463

0

3.409

5

7

8.04E-01

B

Ti II

346.1495

0.135

3.716

8

10

6.27E-02

C

Ti II

348.3629

4.308

7.866

10

8

9.70E-01

D

Ti II

350.4896

1.892

5.428

10

10

8.20E-01

D

Note: B 10%, C 25 % and D 50% in accuracy. Table 2. Stark widths

w

of several neutral and ionized titanium spectral lines.

Line

λ (nm)

T (eV)

no (1016 cm-3)

w

Ti II

364.1339

0.85

1.81

0.897±0.15

Ti I

365.3496

0.85

1.81

0.993±0.17

Ti II

362.4824

0.85

1.81

0.667±0.11

Ref.[17]

Ti I

363.5463

0.85

1.81

0.561±0.09

Ti II

346.1495

0.85

1.81

0.384±0.06

0.6±0.1

Ti II

348.3629

0.85

1.81

0.636±0.11

3.1±0.5

Ti II

350.4896

0.85

1.81

0.550±0.09

0.6±0.1

80 0.85 0.84

T(eV)

0.83 0.82 0.81 0.8 0.79 0

1

2

3

4

5

X (mm)

Figure 2. Variation of measured temperature at different distances from the target.

2.2E+16

-3

Electron density (cm )

2.4E+16

2E+16 1.8E+16 1.6E+16 1.4E+16 1.2E+16 1E+16 1

2

3

4

5

X (mm)

Figure 3. Variation of the electron density as a function of distance from the target.

5. Conclusion In the present study, stark broadening parameters have been evaluated when the Stark coefficient of one of the lines is known. The lines of the calculated Ti spectral lines have been shown a good agreement with the only published reference. The Ti II spectral line at 350.49 nm has been used to derive the electron density which has been checked by the ratio of emission intensities to be free from self-absorption. The effect of the dependence of the measured emission lines at different distances from the target on the electron temperate and electron density is investigated. The temperature is increased with the distance from the target until a distance of 0.6 mm, after that it is decreased. This is due to the enhancement of the cooling rate in the outer part of the plasma and it is also due to pressure, vaporization and dissociation. The decrease of the electron density after 0.6 mm is due to the shielding of the target by the plasma, which prevents further interaction of the laser radiation with the target. Moreover, it might be due to the enhancement of the recombination processes.

81

References 1. A. A. I. Khalil, M. Richardson, L. Johnson, and M. A. Gondal, ISSN 1054_660X, Laser Physics 19, 1981 (2009). 2. N. Kumar, S. Dash, A. K. Tyagi and Baldev Raj, Sādhanā (Indian Academy of Sciences) 35, 493 (2010). 3. L. Burgio, K. Melessanaki, M. Doulgeridis, R.J.H. Clark, and D. Anglos, Spectrochim. Acta 56, 905 (2001). 4. Y. Yoon, T. Kim, M. Yang, K. Lee, and G. Lee, Microchem. J. 68, 251 (2001). 5. V. Detalle, R. He´on, M. Sabsabi, and L. St.-Onge, Spectrochim. Acta B 56, 1011 (2001). 6. H. R. Griem, Spectral line broadening by plasma (Academic, New York, 1974). 7. N. Konjevic, A. Lesage, J.R. Fuhr, W.L. Wiese, J. Phys. Chem. Ref. Data 31, 819 (2002). 8. W. Goldstein, C. Hooper, J. Gauthier, J. Seely, and R. Lee, Radiative Properties of Hot Dense Matter (World Scientific, Singapore, 1991). 9. J. Bengoechea, J. A. Aguilera, C. Aragón, Spectrochim. Acta B, 61, 69 (2006). 10. A. Santagata, R. Teghil, A. De Giacomo, M. Dell’Aglio, G.P. Parisi, A. De Bonis, and A. Galasso, Appl. Surf. Sci. 253, 7792 (2007). 11. J. Hermann, A.-L. Thomann, and C. Boulmer-Leborgne, JOURNAL DE PHYSIQUE IV, Colloque C4, suppltiment au Journal de Physique III, 4 (1994). 12. A. N. Mostovych, L.Y. Chan, K.J. Kearney, D. Garren, C.A. Iglesias, M. Klapisch, and F.J. Rogers, Phys. Rev. Lett. 75, 1530 (1995). 13. C. Colon, G. Hatem, E. Verdugo, P. Ruis, and J. Campos, J. Appl. Phys. 73, 4752 (1993). 14. A. De Giacomo, Spectrochim. Acta B 58, 71 (2003). 15. A. De Giacomo, V. A. Shakhatov, G. S. Senesi and S. Orlando, Spectrochim. Acta B 56, 1459 (2001). 16. A. De Giacomo, V. A. Shakhatov and O. De Pascale, Spectrochim. Acta B 56, 753 (2001). 17. J. Hermann, A. L. Thomann, C. Boulmer-Leborgne, B. Dubreuil, M. L. De giorgi, A. Perrone, A. Luches and I. N. Mihailescu, J. Appl. Phys. 77, 2928 (1995). 18. B. Le Drogoff, J. Margot, M. Chaker, M. Sabsabi, O. Barthélemy, T.W. Johnston, S. Laville, F. Vidal, Y. von Kaenel, Spectrochim. Acta part B 56, 987 (2001). 19. G. Bekefi, Principles of Laser Plasmas (Ed. G. Bekefi, Wiley Interscience, New York, 1976). 20. I. B. Gornushkin, L. A. King, B. W. Smith, N. Omenetto, and J. D. Winefordner, Spectrochimica Acta B 54, 1207 (1999). 21. A. Elhassan, A. Giakoumaki, D. Anglos, G. M. Ingo, L. Robbiola, and M. A. Harith, Spectrochim. Acta part B 63, 504 (2008). 22. M. A. Ismail, H. Imam, A. El hassan, W. T. Youniss, and M. A. Harith, J. Anal. At. Spectrom. 19, 489 (2004). 23. WWW.NIST.gov

82

Nanostructure iron-silicon thin film deposition using plasma focus device M. Kotb, A.H. Saudy, S. Hassaballa, M. M. ElOker Physics Department, Faculty of Science, Al-Azhar University, Nasr city, Cairo, Egypt I.

ABSTRACT:

The presented study in this paper reports the deposition of nano-structure iron-silicon thin film on a glass substrate using 3.3 KJ Mather-type plasma focus device. The iron-silicon powder was put on the top of hollow copper anode electrode. The deposition was done under different experimental conditions such as numbers of electric discharge shots and angular position of substrate. The film samples were exposed to energetic argon ions generated by plasma focus device at different distances from the top of the central electrode. The exposed samples were then analyzed for their structure and optical properties using X-ray diffraction (XRD) and UV -visible spectroscopy. The structure of iron-silicon thin films deposited using plasma focus device depends on the distance from the anode, the number offocus deposition shots and the angular position of the sample

1. Introduction

Nanostructured materials are experiencing a rapid development in recent years due to their potential applications in a wide variety of technological areas such as electronics, catalysis, ceramics, magnetic data storage, structural components etc. To meet the technological demands in these areas, the size of the materials should be reduced to the nanometer scale. Novel fabrication technology of nanoparticles is versatile and includes a wide range of vapor, liquid and solid state processing routes [1]. Nanostructure iron-silicon films, such as (~-FeSiz), attract significant attention as perspective material for silicon planar technology [2]. Moreover, for emerging applications of electronic and optical components in optoelectronic systems, direct tunable band gap materials with high carrier mobility and low fabrication cost are demanded. Crystalline silicon (cSi), the most popular electronic material, has an indirect band gap and, hence, poor optical absorption and emission properties. Thin film solar cells with nc-Si layers incorporated showed high stability against light soaking and conversion efficiencies as high as 8-12% have been reported [3]. Among the various plasma based thin film deposition and processing techniques, the dense plasma focus (DPF) device is a promising candidate for fabrication of various nanocrystalline films and for enhancement of surface properties of various materials. The plasma focus device is mainly used as a source ofX-rays, energetic ions and electrons [4]. It is basically a pulsed coaxial plasma accelerator that makes use of the self-generated magnetic field for compressing the plasma to very high density and high temperature. It has been successfully used in various applications, such as an ion source for processing of materials [5-7] and thin film deposition [8]. Plasma focus has some special features with respect to other deposition methods. These features include high deposition rate, energetic deposition process which assist the film formation and possible film deposition under a reactive background gas pressure. The current sheath dynamics in plasma focus allows the formation of high temperature and

high-density plasma column at the end of radial collapse phase [9]. The plasma column then disintegrated due to plasma instabilities, which generate energetic ions and relativistic electrons. The plasma jet and energetic electrons are responsible for the ablation of the anode material and the ablated material is deposited on the substrate. In this study the deposition of nano-structure iron-silicon thin film on a glass substrate using 3.3 KJ Mather-type plasma focus device has been investigated. The deposition process was performed under different experimental conditions such as the numbers of electric discharge shots and the angular position of substrate. The film samples were exposed to energetic argon ions generated by the plasma focus device at different distances from the top of the central electrode. The exposed samples were then analyzed for their structure and optical properties using X-ray diffraction (XRD) and UVvisible spectroscopy.

2. Experimental set up

A 3.3 kJ Mather-type (DPF) device was used for preparation of the iron silicon thin films, Fig. I (a). The device is characterized by a stored energy capacitor of 30!-lF capacitances and maximum charging potential of 15 kV. The electrode assembly is consisting of a hollow copper anode surrounded by six cylindrical copper cathode rods in a squirrel cage fashion. The conventional hollow copper anode was covered with a copper plate includes the Fe and Si (99.99% purity) powders on its top. The films were deposited on glass substrates (76 x 25 x 0.86 mm) after washing using acetone and alcohol. A specially designed substrate holder, Fig. l(b), was used to mount the glass substrates at different angular positions with respect to the anode axis. These positions are named as center (0°), off-centre (25°, 30°) and outermost (55°, 65°).

CP 9910. Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

83

The focusing condition is characterized by an intense voltage peak and a steep dip in the current signals. The gas pressure was constant during the deposition process. Thin films were deposited at different number of focusing shots. The distance between the substrate holder and the anode top was fixed at 60 mm. In this experiment argon is used as the filling gas for depositions, as being inert it does not react with the glass substrate and the synthesized Fe-Si nanostructure. The DPF device has been adjusted at 12 kV and 0.8 mbar gas pressure (optimum condition). The crystal structures of the deposited films were analyzed using Siemens 05005 X-ray diffractometer. The optical charaCteristics of deposited films were deduced from UV-Visible absorption spectra.

60mm hllllllll

(SvFe f

•Iii

Substrate holder (b) Substrate holder that allows multiple depositions at different angular positions.

3.

Trigger Unit J-n----;:- - Spark gap

.:f:.-, 15 KV

Capacitor I Bank

Results and Discussion

3.1 Plasma diagnostic The operation of the DPF device was carried out for a certain number of shots in argon under pressures of0.8 mbar and voltage of 12 kV. The voltage anm I ~

~ll ~

c

:w ll 111

I

I

I

I

... I

1.1

I

I

I

II

I

'

I

I

I

a u

lim~-~~~

Fig. 7. Transmission spectra for thin films and estimated direct band gap at different distance of exposure and for different angular distributi 3.

Conclusions

FeSi nano-particles have been successfully synthesized using a 3.3 kJ Mather type plasma focus machine. FeSi nano-particles with sizes ranging from 10 to 90 nm have been synthesized using different numbers of focus shots at different angular positions. This size dependence is a direct consequence of the ion emission characteristics of the plasma focus device. The increase in the number of deposition increases the size of nanoparticles. The defects on specimen were also confirmed by the change of direct band gap energy owing to bombardment of ion beam. The absorption edge of exposed specimen shifted towards higher wavelength side.

*

87

SIZE CONFINEMENT AND MAGNETIZATION IMPROVEMENT BY LA3+ DOPING IN BIFEO3 QUANTUM DOTS M. A. AHMED*, S. I. El-DEK and M. S. AYOUB Materials Science Lab (1), Physics Department, Faculty of Science, Cairo University, Giza, Egypt

A series of La3+ doped nanoparticles of BiFeO3 multiferroic samples was prepared using solid state reaction. Structural and magnetic properties were investigated using XRD, TEM, magnetic susceptibility and M-H loop. All samples were antiferromagnetic in character. Maximum coercivity HC = 5265 Oe was obtained at x = 0.25. Improvement of the magnetization of BiFeO3 is achieved by La3+ at different doping levels. Keywords: Nanometric BiFeO3; magnetic quantum dots; multiferroic; magnetization; Neel temperature-G-type antiferromagnetic order.

Introduction

and in addition it exhibits a long-wavelength spiral-spin

Multiferroics [1-3] are materials that simultaneously

structure with a wavelength of about 620 ˚A [7]. The

exhibit more than one type of ordering, including

structure of BFO is characterized by two distorted

magnetic, electric and elastic. Magnetic order is

perovskite unit cells (ar = 3.96 Ao, αr = 0.6°) connected

conventionally driven from exchange interactions

along their body diagonal, denoted by the pseudocubic

between magnetic dipoles, originating from unfilled

, to form a rhombohedral unit cell (Fig. 1.a)

shells of electron orbitals. Electric order is the result of

[8-10]. The ferroelectric state is realized by a large

ordering of local electric dipoles. Elastic order is the

displacement of the Bi ions relative to the FeO6

result of ordering of atomic displacements due to strain.

octahedra. This structure results in two important

The simultaneous occurrence of magnetic and electric

considerations. First, the ferroelectric polarization lies

order is particularly interesting as it combines properties

along the pseudocubic leading to the formation

that

of eight possible polarization variants, corresponding to

could

be

utilized

for

information

storage,

processing and transmission. It allows both magnetic

four

structural

and electric fields to interact with magnetic and electric

antiferromagnetic ordering of BFO is G-type, in which

order.

the Fe magnetic moments are aligned ferromagnetically

Perovskite-structure BiFeO3 is one rare example of a

within

(111)

variants

and

[10-13].

Second,

antiferromagnetically

the

between

both

adjacent (111). Additionally, BFO is known to exhibit

magnetic and ferroelectric ordering above room

a cycloidal spin structure in the bulk [14] and the

temperature. The bulk material becomes ferroelectric

preferred

below TC = 1103 K [4], adopting the R3c structure. The

aligned spins is in the (111), perpendicular to the

magnetic

ferroelectric polarization direction with six equivalent

magnetoelectric

multiferroics

moments

of

the

that

Fe

exhibits

cations

order

antiferromagnetically (G-type) below TN = 643 K [5, 6]

**

orientation

of

the

antiferromagnetically

easy axes within that plane (Fig. 1.a) [10].

C Corresponding author: M. A. Ahmed, E-mail: [email protected] CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

88

the same above rate, regrounded for 1.5 hrs and well sieved. Final firing was carried at 870 °C for another 3 hrs with a heating rate of 4 oC/min in air. The prepared samples were checked by X-ray diffraction using Diano corporation of target CoKα (λ = 1.79026 Å) to assure the complete reaction and the formation of single phase structure. Transmission electron microscope (TEM) images were taken using TEM model (JEOl -1010). The dc magnetic susceptibility measurements were carried out using Faraday's method from room temperature up to about 850 K at three different values of magnetic field intensity ranging from 1990 Oe to 2620 Oe. The hysteresis performed

and using

magnetization vibrating

measurements sample

were

magnetometer

(VSM; 9600-1 LDJ, USA) with a maximum applied Fig. (1.a) Schematic crystal structure of BiFeO3 and the ferroelectric polarization (arrow) and antiferromagnetic plane (shaded planes) [8-10].

field of 15 kOe at room temperature.

Results and discussion The aim of this research work is to improve the room temperature magnetic properties of the nanometric multiferroic BiFeO3 by La3+ substitution with different doping levels. Also, one of our goals is to stretch the range of applications of these compounds at room temperature.

XRD patterns, Fig. (1.b), show the formation of (BLFO) Bi1-xLaxFeO3; 0.10 ≤ x ≤ 0.35 with single phase rhombohedral-hexagonal structure as compared and indexed with ICDD card No 86-1519. It is well known that BiFeO3 crystallized in a rhombohedral structure (R3c) at room temperature [15-20]. By introducing La3+ ions, on the expense of Bi3+, the XRD analysis reveal

Experimental (BLFO)

rhombohedral-hexagonal structure for all samples under

Bi1-xLaxFeO3; 0.05 ≤ x ≤ 0.35 were prepared by the

investigation. Small intensities and broad diffraction

conventional solid-state reaction from analar grade form

lines are observed consistent with small crystallite size

oxides (BDH), including Bi2O3, La2O3 and Fe2O3.

in the range of few nanometers. The significant change

Stoichiometric ratios were good mixed and grounded

with increasing La doping is the increase in the intensity

using agate mortar for 3.5 hrs, sieved, then transferred

of the (110) peak. This indicates that the lanthanum

to agate ball mill for another 3 hrs. The samples were

substitution into bismuth positions improves the crystal

sieved again, then pressed into pellet form using

growth in this orientation.

uniaxial press of pressure 5 × 108 N/m2. Presintering

Figure (1: c, d) represents the TEM micrographs of

was carried out in air at 600 °C for 6 hrs with a heating

the samples with x = 0.15 and 0.35 respectively. The

rate of 4 °C/min and cooled to room temperature with

figure shows a homogenous distribution of crystallites

Samples

having

the

chemical

formula

89 50

Counts

40

30

20

30

40

50

60

70

(134)

(036)

(220)

(214)

(116)

(024)

(202)

0

(012)

10

(110)

20

x=0.10 x=0.15 x=0.20 x=0.25 x=0.30 x=0.35

80

2θ

Fig. (1.b) XRD patterns of the samples Bi1-xLaxFeO3; 0.10≤x≤0.35.

(c) x=0.15

20

number of particles

Data: Data1_C Model: Gauss Equation: y=y0 + (A/(w*sqrt(PI/2)))*exp(-2*((x-xc)/w)^2)

15

x=0.15

Weighting: No weighting

y

= 4.5366 Chi^2/DoF R^2 = 0.94914

10

w

2.0301 ±1.88236 11.39588 ±0.17646 1.13924 ±0.885

A

17.89685 ±7.72257

y0 xc

5

0 9

10

11

12

13

L(nm)

(d) x=0.35 20

number of particles

x=0.35

Data: Data1_B Model: Gauss Equation: y=y0 + (A/(w*sqrt(PI/2)))*exp(-2*((x-xc)/w)^2) Weighting: y No weighting Chi^2/DoF = -R^2 = 0.99532

15

y0 xc w A

2.49952 9.40337 1.49854 27.13849

±-±-±-±--

10

5

0 5

6

7

8

9

10

11

12

L(nm)

Fig. (1:c, d) TEM micrographs and the corresponding distribution of the samples.

13

14

90

with

ultra

No

The data in Fig. (2.e) shows a decrease of t with x due

agglomeration or clusters appear in any part of the

to the smaller ionic radius of La3+, thereby decreasing

sample. The crystallite size for the sample with x = 0.15

the Fe-O-Fe angle.

is around 11 nm with quantum dot size and the

The molar magnetic susceptibility is plotted as a

distribution of crystallites is fitted with a Gaussian

function of the absolute temperature at different

function. Well dispersed crystallites are seen also for

magnetic field intensities for the investigated (BLFO)

x = 0.35 with high homogeneity, distributed and fitted

samples in Fig. (3: a-f). One observed a slight increase

with a Gaussian function around 9.5 nm. These

in χM with temperature reaching a hump at the Néel

nanoparticles of BLFO consisting of magnetic spheres

temperature after which it decreases. After this point,

of quantum dot size of uniform shape could be of

the samples behave as a typical paramagnet. It is well

special interest for spintronic applications in spin valves

known that BiFeO3 is an antiferromagnetic material

as a pining layer due to their enormous coercivity.

with G-type structure [26] ordering with a cycloid

The lattice parameters were computed on the basis of

modulation (62 nm) apparent down to 5 K [7, 27]. Due

hexagonal distortion of the rhombohedral unit cell with

to the long-range spin arrangement one may expect the

space group (R3c) and plotted in Fig. (2: a, b). It is clear

magnetic properties of BiFeO3 to be size-dependent.

that the lattice parameters decrease slightly with

One can anticipate that the decrease in the particle

increasing La

fine

3+

size

and

spherical

shape.

ions obeying the well known Vegard's

size below the periodicity of cycloid modulation will

law [21]. This is due to the difference between the ionic

modify considerably the magnetic properties. The weak

3+

radii of both Bi

o

o

(1.16 A) [22].

ferromagnetic component existing in some orthoferrites

These results are in good accordance with those

as well as BiFeO3 originated from the small canting in

obtained by J. R. Chen et al. [23]. The X-ray density

the Fe3+ moments. In the samples with x = 0.2 and 0.25,

and unit cell volume were calculated and plotted vs La3+

the magnetic susceptibility behavior is nearly the same

content (x) in Fig. (2: c, d). Both quantities decrease

but with different values and peak widths. The peak is

with increasing La

3+

(1.17 A) and La

3+

content. The decrease of Dx and V

very narrow in the sample with x = 0.2, while a

despite their inverse proportion is due to the decrease in

broadening occurs at x ≥ 0.25. For the rest of the

the molecular weight (Bi:208.98, La:138.91) which

samples, χM gives nearly stable values with temperature

can't be compensated by the decrease in the unit cell

for a wide range until falling achieving the Néel

volume. The tolerance factor (t) was calculated from

temperature. S. C. Parida et al. [28] observed an

[24, 25]

anomaly (peak) in the heat capacity measurements for

t = (RA+RO)/(√2(RB+RO))

the LaFeO3. This transition resembles the λ-type

where RA, RB and RO are the A, B and oxygen ions radii

transition and was about 724 K. From research work on

respectively. The A-site cation effective ionic radius is

orthoferrite [28, 29], it has been observed that the phase

computed from

transition is second order in nature and involves AF to

RA(eff) = RBi3+ * (1-x) + RLa3+ * (x)

P state i.e. Néel temperature (TN). In all samples the

91 5.65

a = -0.0748x + 5.5906

(a) o

a ( A)

5.6 5.55 5.5 5.45 0

0.1

0.2

0.3

0.4

12

o

c ( A)

c = -0.4608x + 11.834

(b)

11.75 11.5

11.25 11 0

0.1

0.2

0.3

0.4

0.2

0.3

0.4

3

Dx (gm/cm )

10

(c)

9.5 9 8.5 8 0

0.1

330

V = -18.954x + 319.7

o

V( A)

3

(d) 320

310

300 0

0.1

0.2

0.3

0.4

La content (x)

tolerance factor (t)

Fig. (2:a-d) The dependence of the lattice parameters (a, c), theoretical density Dx, and unit cell volume (V) on the La content respectively.

(e) 0.8868

0.8864

0.8860

0.8856 0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

La content (x)

Fig. (2.e) The dependence of tolerance factor (t) on the La content.

92 0.034

0.025

(a) x = 0.10

(b) x = 0.15 0.026

0.017 0.018

χM( emu/g.mole)

0.009 300

500

700

T (K)

0.035

0.01 300

500

700

T (K)

0.05

(c) x = 0.20

(d) x = 0.25

0.025

0.035

0.015

0.02

0.005

0.005 300

500

700

T (K)

300

500

700

T (K)

0.03 0.035

(e) x=0.30

(f) x = 0.35

0.025 0.02 0.015

0.005

1990 (Oe) 2320 (Oe) 2620 (Oe)

0.01 300

500

700 T (K)

300

500

700

T (K)

Fig. (3:a-f) Dependence of the molar magnetic susceptibility χM on the absolute temperature at different magnetic field intensities for the samples Bi1-xLaxFeO3; 0.10≤x≤0.35.

molar magnetic susceptibility decreases with increasing

temperature is remarked for 300 K ≤ T ≤ 650 K. After

magnetic field intensity due to the saturation of the

reaching the Néel temperature, the magnetization

moments.

decreased and the samples behave as a paramagnet. The

The plot of the magnetization vs T Fig. (4: a, b)

doping of La results in further structural distortion as

enhances our discussion about the antiferromagnetic

reflected in the change of Fe–O–Fe bond angles and

character of such samples where an increase of M with

affects the superexchange of Fe–O–Fe interactions. The

93

structure. Moreover, the deformation which leads to x=0.20 x=0.15 x=0.10

M (emu/g)

0.20

rhombic distortion has no effect on the octahedron while it affects on the R3+ polyhedron. The average interatomic distances Fe-O, O-O are kept

0.15

constant with changing R3+ cation radius in RFeO3 series and the mutual positions of the oxygen octahedral change. This leads to a change in Fe-O-Fe bond angle

0.10

[33]. The variation of TN with the Fe-O-Fe angle is in 300

400

500

600

700

800

0.25

900

accordance with that reported by M. Sivakumar et al. [34]. Figure (5.b) illustrates the variation of χM as a

x=0.35 x=0.30 x=0.25

function of La content (x) at 2320 Oe. The data shows

0.20

an increasing trend with x up to x = 0.3 and then decrease again. This behavior could be explained on the basis of two factors, the first one is the change in the

0.15

canting angle with increasing La content. The second one is the change in the anisotropy which affects on the

0.10 300

400

500

600

700

800

900

magnetization of the samples. Figure (6) illustrates the hysteresis loops of the

T(K)

Fig. (4:a, b) Dependence of the magnetization on the absolute temperature at H=2320 Oe for the samples Bi1-xLaxFeO3; 0.10≤x≤0.35.

samples with 0.15 ≤ x ≤ 0.40. At x = 0.15, an almost linear behavior is obtained with a small coercive field (Hc) and a small loop area. The magnetization loops were not really saturated which points to basic

distortion can suppress the spiral spin structure and

antiferromagnetic nature. The data indicates the

increase the weak ferromagnetism which agrees with

collinear type antiferromagnetism which was clear from

other experimental reports [30, 31].

the small value of the saturation and remanent

The Néel temperature was depicted from the plots of

magnetization. As x increases, the values of saturation

dM/dT versus absolute temperature. The value of TN

magnetization (Ms), remanent magnetization (Mr) and

was found to be larger than that reported for undoped

coercive field (HC) increased. In Fig. (7: a-c), the

3+

maximum saturation and remanent magnetization were

content Fig. (5.a), consistent with the reported trend by

attained at x = 0.3 which agree well with our discussion

J. R. Chen et al. [23] where the exchange interaction is

of the variation of χM vs x. The room temperature

mainly due to the antiferromagnetic coupling between

saturation magnetization for x = 0.3 is 0.51 emu/g at

BiFeO3 [14-17]. It increases exponentially with La

Fe

3+

ions through the oxygen anions [32]. It is worth

1.4 T is doubled that at x = 0.15 and is larger than

noting that, for an ideal perovskite structure t = 1 and

MS = 0.308 emu/g at 5K as reported by Yi. Du et al. [35]

o

Θ =180 giving a cubic structure. In our case as, t < 0.9

and is found to be ten-fold that of the un-doped sample

and XRD give hexagonal distortion of the rhombohedral

(0.053 emu/g) at 5 K. Additionaly, the remanence

94

(a)

T N =a+b exp(x/c)

690

Mr (emu/gm)

TN(K)

700

a=603.35, b=31.88, c=0.33

0.2

680

670

0.0 0.15

660

0.20

0.25

0.30

0.35

0.40

0.20

0.25

0.30

0.35

0.40

0.20

0.25

0.30

0.35

0.40

0.6

(b) 0.10

0.15

0.20

0.25

0.30

0.35

La content (x)

Fig. (5.a) Dependence of the Neel temperature on the La3+ content.

Ms (emu/gm)

650

0.4

0.2

0.0 0.15 6000

Hc (Oe)

(c)

4000

2000

0.02

0 0.15

χ M

(emu/g.mole)

0.03

0.01

La content (x) 0 0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

La content (x)

Fig. (5.b) Dependence of the molar magnetic susceptibility χM on the La3+ content (x) at 420K.

Fig. (7:a-c) Dependence of remanence (Mr), saturation magnetization (Ms) and coercive field (HC) on La content respectively on La content (x). magnetization at x = 0.3 attained 10 fold its value at x = 0.15. An enormous increase in the coercive field

M(emu/g)

0.6

x=0.30 x=0.20 x=0.40 x=0.25

0.3

x=0.15

for the sample x = 0.25 HC = 5265Oe which is about 5 fold its value for x = 0.15 is accomplished for the first time at room temperature. The shift in the hysteresis loops, with asymmetry around the y-axis, was observed for larger La doping and can be called an exchange

0.0

bias [36]. It has been reported by L. Malkinski that the exchange

-0.3

bias

exists

in

nanostructural

systems

originates from exchange interactions among magnetic -0.6 -15000

-10000

-5000

0

5000

10000

15000

H (Oe)

Fig. (6) Hysteresis plots of the samples Bi1-xLaxFeO3 at room temperature.

atoms at the ferromagnetic/antiferromagnetic interfaces [37]. Due to the small radius of the A site ion with respect to its surrounding cage, the FeO6 octahedra tilted

95

and buckled to accommodate the lanthanide ion. This is known as (GdFeO3) rotation [38, 39]. Maximum tilting of the octahedral occurs at x = 0.3 which was expected. Accordingly, the magnetocrystalline anisotropy value will be enlarged, resulting in spin clusters thereby increasing the magnetization. We summarize the enhancement of the magnetization as due to the following reasons: i) An incomplete rotation of the spins along the direction of the wave vector (62 nm modulation length of the cycloid), ii) An increase in the spin canting due to the strain extended by the grain shell (which gives rise to ferromagnetism), iii) The potential magnetization locked in the cycloid spin structure of the pure BiFeO3 is released due to the distortion of the crystal structure by La doping.

Conclusion The substitution of Bi3+ by La3+ ions reveals a hexagonal distortion of the rhombohedral unit cell of BiFeO3. By increasing La3+ content, the unit cell volume decreased. Well dispersed homogenous crystallites of quantum dot size are observed in TEM micrographs with size around 10 nm. La3+ doping improve all magnetic parameters at room temperature such as χM, MS, Mr and HC up to x = 0.3. Best Enhancement of the magnetization was achieved at x = 0.3. One could use the sample with x = 0.25 with Hc = 5265 Oe as pinning layer of antiferromagnetic material, in a spin valve between two ferromagnetic layers. Our future work will be focused on exploring the conduction modulation for the BLFO.

References [1] S. C. Abrahams, Acta Crystallogr. B 57 (2001) 485-490.

[2] B. B. Van Aken, T. T. M. Palstra, A. Filippetti, N. A. Spaldin, Nature Mater. 3 (3), (2004) 164. [3] I. S. Lyubutin, T. V. Dmitrieva, and A. S. Stepin J. Exp. and Theo. Phys, 88, (1999)591. [4] J. R. Teague, R. Gerson, W. J. James, Solid State Commun, 8 (1970) 1073. [5] S. V. Kiselev, R. P. Ozerov, G. S. Zhdanov, Sov Phys Dokl, 7 (1963), 742. [6] P. Fischer, M. Polomska, I. Sosnowska, M. Szyman´ ski, J Phys C 13 (1980)1931–40. [7] I. Sosnowska, T. Peterlin-Neumaier, E. Streichele, J Phys C 15 (1982) 4835. [8] C. Michel, et al., Solid State Commun. 7 (1969) 701. [9] F. Kubel and H. Schmid, Acta Crystallogr., Sect. B: Struct. Sci. B46 (1990), 698. [10] C. Ederer, and N. A. Spaldin, Phys. Rev. B 71 (2005), 060401(R). [11] F. Zavaliche, et al., Appl. Phys. Lett. 87 (2005) 182912. [12] M. Abplanalp, et al., J. Appl. Phys. 91 (2002) 3797. [13] S. K.Streiffer, et al., J. Appl. Phys. 83 (1998), 2742. [14] I. Sosnowska, et al., J. Phys. C 15 (1982) 4835. [15] V. R. Palkar, D. C. Kundaliya, S. K. Malik, and S. Bhattacharya, Phys. Rev. B. 69, (2004) 212 102. [16] L. Mitoseriu , Boletı´n de la Sociedad Espan˜ola de Cera´mica y Vidri, 44 (2005)177. [17] F. Kubel, H. Schmid, Acta Crystallogr. B 46 (1990) 698. [18] A. K. Zvezdin and A. P. Pyatakov, Usp. Fiz. Nauk 174 (2004) 465. [19] A. G. Zhdanov, A. K. Zvezdin, A. P. Pyatakov, et al., Fiz. Tverd. Tela 48(2006) 83 [Phys. Solid State 48 (2006) 88]. [20] A. M. Kadomtseva, A. K. Zvezdin, Yu. F. Popov, et al., Pis’ma Zh. Éksp. Teor. Fiz. 79, (2004) 705 [JETP Lett. 79, (2004) 571]. [21] B. D. Cullity, “Elements of X- ray diffraction”, 2nd edition, Addison-Wesley Pub. Company, (1978). [22] R. D. Shannon, Acta Crystallographica. A32 (1976) 751. [23] J. R. Chen, W. L. Wang, J. B. Li, G. H. Rao, J. Alloys and Compds, 459 (2008) 66-70. [24] M. A. Ahmed and S. I. El-Dek, Materials Science and Engineering B: 128 (2006) 30-33. [25] M. A. Ahmed and S. I. El-Dek, Materials Letters, 60 (2006) 1437-1446. [26] Y. P. Wang, G. L. Yuan, X. Y. Chen, et al., J. Phys. D:Appl. Phys. 39 (2006) 2019. [27] A. Pietraszko, I. Szafraniak-Wiza, B. Hilczer, B. Andrzejewski, Acta Cryst. A64, (2008) C642.

96

[28] S. C. Parida, S. K. Rakshit, Z. Singh, J. Solid State Chemistry 181 (2008) 101–121. [29] S. Stّlen, F. Grّnvold, H. Brinks, T. Atake, H. Mori, J. Chem. Thermodyn. 30 (1998) 365. [30] P. Uniyal, K. L. Yadav, Mater. Lett. 62 (2008) 2858. [31] K. S. Nalwa, A. Garg, J. Appl. Phys. 103 (2008) 044101. [32] M. Eibschutz, S. Shtrikman, and D. Treves, Phys. Rev. 156, (1967) 562. [33] C. Ederer and N. A. Spaldin, Phys. Rev. B 71, (2005) 060401(R). [34] M. Sivakumar, A. Gedanken, D. Bhattacharya, I. Brukental, Y. Yeshurun,W. Zhong, Y. W. Du, I. Felner, and I. Nowik, Chem. Mater. 16 (2004) 3623-3632.

[35] Yi Du, Z. X. Cheng, M. Shahbazi, E. W. Collings, S. X. Dou, X. L. Wang, J. Alloys and Compds, 490, 1-2 (2010) 637-641. [36] N. N. Phuoc, N. P.Thuy, et al.: J. Magn. Magn. Mater. 298, (2006) 43. [37] L. Malkinski, T. O’Keevan, R. E. Camley, et al.: J. Appl. Phys. 93 (2003) 6835. [38] Rodriguez-Carvajal, M. Hennion, F. Moussa, A. H. Moudden, L. Pinsard and A. Revcolevschi., Phys. Rev, B., 57 (1998) R3189. [39] B. B.Van Aken, A. Meetsma and T. T. M. Palstra, Acta Cryst E57 (2001), i38-i40.

97

SYNTHESIS OF RARE-EARTH DOPED AND UNDOPED GaN NANO-CRYSTALLITES LOTFIA EL NADI1,3, SAMAH AHMED1, M. AWAAD2, MAGDY OMAR3 and YEHIA BADR1 1

National Institute of Laser Enhanced Sciences, NILES, Cairo University, Giza, Egypt 2 National Research Center, NRC, Ceramics Division, Tahrir St., Dokki, Giza, Egypt 3 Physics Department, Laser Physics Lab. Faculty of Science, Cairo University, Giza, Egypt

Semiconductor nanostructures doped with rare earth ions is a possible way to overcome the limitation of low luminescence efficiency of rare earth ions, providing that the strong confinement of carriers in dots will enhance their recombination in the vicinity of RE ions. [1] Undoped and Eu3+-doped GaN crystallites have been synthesized by the co-precipitation method followed by nitridation reaction at 1100 oC for 2 h, under a continuous flow of NH3 gas. X-ray diffraction patterns (XRD) revealed that the synthesized undoped and Eu3+-doped GaN crystallites are of a single-phase wurtzite structure. The morphology of the samples was examined by field emission scanning electron microscope (FE-SEM) and high resolution transmission electron microscope (HR-TEM), and it was shown that the micron-sized particles are composed of agglomerated nano-crystallites. Under the above band gap excitation, all samples exhibited roomtemperature photoluminescence with the characteristic GaN band-edge emission peak centered at 363 nm (~3.4 eV, FWHM ~ 10 nm) as well as broad defect-related emission peak centered at about 405 nm. The Eu-doped GaN sample, under below bandgap excitation, exhibited red emission peaks centered at 593 nm and 616 nm corresponding to the 5D0 → 7F1 and 5D0 → 7F2 transitions, respectively, within the 4f shell of Eu3+ ions.

Introduction Rare earth (RE) doping of semiconductors is an interesting topic because it is expected to produce hybrid photonic materials able to exhibit some of the unique optical features of RE ions with the electronic properties of semiconductors. [2, 3] For example, it offers the opportunity of combining the electrical excitation of the host material and the remarkable optical properties of RE ions for optoelectronic applications. [4, 5] The thermal quenching effects, which reduce the luminescent efficiency of RE ions in semiconductors, are found to be inversely proportional to the bandgap of the host, making wide bandgap semiconductors attractive hosts for RE ions. [3, 6] Gallium nitride (GaN) possesses a number of properties that make it a suitable host for visible- and infrared-emitting RE ions, including a wide and direct bandgap (Eg ~ 3.4 eV for wurtzite structures), [7] good chemical and thermal stability, excellent high field transport properties, and ability to incorporate rare-earth ions at relatively high concentrations. [4, 6] In addition, it is transparent to visible RE emissions. [8] GaN is also remarkably insensitive to the presence of relatively high concentrations of defects. [6] In fact, it was shown that defect centers can often play an important role in activating RE emission, and the engineering of defect centers to produce tailored activation channels and emission bands is an important area of research. [6, 9] Thus, RE-doping of GaN represents an alternative to semiconductor alloying (GaN/InN/AlN) for visible and infrared emissions. [10] Recently, among different techniques commonly used to obtain GaN materials such as MBE or MOCVD, methods based on powder technology became alternative, cheap and

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

98

relatively simple synthesis procedures, which give possibility to incorporate rare-earth ions into GaN in an easy way. [7, 11] This study aims to synthesis and characterize undoped and Eu3+-doped GaN by applying the powder technique.

Experimental RE-doped and undoped GaN powders have been prepared by the chemical co-precipitation method [12] followed by a nitridation reaction at high temperatures. Ga2O3 powder (Winlab, 99.9%), Eu2O3 powder (Alpha Asear, 99.9%) were used as starting materials. For the REdoped GaN sample, the amount of reactants was calculated and weighted based on the desired molar composition of: 99% GaN + 1% Eu dopants. About 3 gm of Ga2O3 powder was dissolved in a hot concentrated nitric acid to form gallium nitrate (Ga (NO3)3.xH2O). Separately, the desired amount of the Eu2O3 powder was weighted and dissolved in a hot concentrated nitric acid, and then added to the above solution. Then the solution was heated under continuous stirring and evaporated till almost dryness. About 100 ml distilled water was added to the nitrates under continuous stirring for about 30 min to form a clear solution. Ammonium hydroxide (as a precipitating agent) was dripped slowly at room temperature with stirring till PH = 9. A white gel-like product was obtained. Then was centrifuged and thoroughly washed with distilled water and then with ethanol. The white precipitate was dried at 80 oC overnight. The dried powder was grinded in an agate mortar and calcined at a temperature of 600 oC with a rate of 2 oC / min. The white powder was loaded in a quartz tube and placed in a vertical tube furnace, and was heated gradually at a rate of 10 oC / min to the required temperature of 1100 oC and was held at that temperature for 2 h, under a low flow rate of ammonia gas. Thus, the pale-yellow powder was obtained. Undoped GaN sample was also prepared by the same above procedures. Powder X-ray diffraction (XRD) patterns of all samples have been recorded with X´pert Pro powder X-ray diffractometer. The microstructures of the samples were studied by high resolution transmission electron microscopy (HR-TEM) using a JEM-2100 microscope, and by Filed Emission Scanning Electron Microscopy (FESEM) using a JSEM microscope. Photoluminescence (PL) spectra of the samples were measured at room-temperature with Jasco, FP-6300 spectrofluorometer.

Results and Discussions Figure (1) Shows the XRD patterns of the undoped and 1% Eu-doped GaN powders synthesized by the co-precipitation method followed by nitridation at 1100 oC for 2h. In Figs. (a) and (b), all the diffraction peaks are well matched with those of the wurtzite GaN peaks reported in the PDF index (File no. 01-089-7522) and (File no. 01-070-2546), respectively. The absence of any additional crystalline phases, such as Eu2O3, indicates that the Eu3+ dopants were chemically incorporated in the hexagonal GaN lattice [13] and did not affect the phase purity in this study [14]. The lattice constants have been evaluated from the XRD data to be a = 3.1891 Å and c = 5.1853Å for the synthesized undoped GaN powder. For the Eu-doped GaN powder, a = 3.1900 Å and c = 5.1890 Å, which confirm the incorporation of Eu dopant ions into the hexagonal lattice structure of the GaN. [15]

GaN (102)

150

50

GaN (202)

200

GaN (110)

GaN (100) GaN (002)

250

100 GaN (202)

GaN (112) GaN (201) GaN (004)

100

GaN (200)

GaN (102)

200

GaN (103)

GaN (110)

300

Counts (a.u.)

GaN (100)

300

GaN (002)

Counts (a.u.)

500

400

(b) Eu-doped GaN

350

GaN (200) GaN (112) GaN (201) GaN (004)

400

(a) Undoped GaN

GaN (103)

600

GaN (101)

GaN (101)

99

0

0 10

20

30

40

50

2θ (degree)

60

70

80

10

20

30

40

50

60

70

80

2θ (degree)

Figure (1) XRD patterns of (a) undoped GaN, and (b) I% Eu-doped GaN powder.

By using the Scherrer equation: Particle size (nm) = (0.9 x λ ) / (β x cos θ) (Where λ = 0.154 nm for cupper target, β = FWHM [°2Θ], and θ = diffraction angle), for the (101) diffraction peak [12], the average sizes of the crystallites grains have been evaluated to be 24 nm and 18 nm for the undoped and Eu3+-doped GaN powders, respectively. Figure (2) Shows the FE-SEM images, which examined the surface morphology of the synthesized undoped and Eu3+-doped GaN powders. The spindle-like particles with submicron and micron sizes (0.6 - 1 µm), are very much larger than that evaluated from the XRD data. The particles are seemed to be composed of small particles, which may be responsible of the small size which inferred from the XRD data.

(a)

(b)

Figure (2) FE-SEM images of the (a) undoped, and (b) Eu3+-doped GaN powders.

100

(a)

(b)

(c)

(d)

(e)

(f)

Figure (3) TEM, HRTEM, and SAED pattern images of the (a, b, c) Undoped GaN, and (d, e, f) Eu3+-doped GaN powder, respectively.

TEM and high resolution TEM images of the synthesized undoped and Eu3+-doped GaN powders are shown in Fig. (3). The micron-sized particles are composed of agglomerated nano-crystallites with size range of about 19 - 85 nm. The coalescence of GaN nano-sized grains into micron-sized agglomerations is a well known phenomenon for powder systems and has been reported by Contreras et al. [16] and Kudrawiec et al. [17] In general, it is thought that the morphology of GaN powder depends on the sample preparation and post-growth heat treatment. [16, 17] In addition, in this work we did not use a surfactant to prevent the agglomeration. The d-spacing in the HRTEM images of the undoped and Eu3+-doped GaN powders are ~ 0.29 nm (providing that the resolution limit is 0.014 nm), which corresponding to the plane (100) of the wurtzite GaN. [18] The selected area electron diffraction (SAED) patterns of Figs. (c) and (f), confirm the wurtzite crystalline structure of the synthesized powders. Figure (4) shows the room-temperature photoluminescence spectra of the synthesized undoped and 1% Eu3+-doped GaN samples. Under above bandgap excitation (peak at 325 nm), all samples exhibited the characteristic GaN band-edge emission peak centered at 363 nm (~3.4 eV, FWHM ~ 10 nm), and a broad defect-related emission peak centered at about 405 nm. [19]

101 2.4

(a) Undoped GaN

2.8 2.6

(b) Eu-doped GaN

2.2

PL Intensity (a.u.)

PL Intensity (a.u.)

2.4 2.2 2.0 1.8

2.0

1.8

1.6

1.6 1.4

1.4 350

360

370

380

390

400

410

420

430

440

450

350

360

Wavelength (nm)

370

380

390

400

410

420

430

440

450

Wavelength (nm)

Figure (4) Room temperature PL of (a) undoped, and (b) Eu3+-doped GaN samples, under above bandgap excitation peak at 325 nm.

Under below bandgap excitation (peak at 464 nm), the room-temperature PL spectrum of the 1% Eu3+-doped GaN sample is shown in Fig.(5). The sample exhibited red emission peaks centered at 595 and 616 nm, and could be attributed to the 5D0 → 7F1 and 5D0 → 7F2 transitions, respectively, within the 4f shell of Eu3+ ions. [14, 16, 17] A simplified energy levels diagram of the Eu3+ inner 4f shell, and the possible emission mechanisms are shown in Fig. (6) [20]

1.8

5

D0

7

F2

Eu-doped GaN Excitation = 464 nm

PL Intensity (a.u.)

1.6

1.4

5

D0

7

F1

1.2

1.0

0.8 560

580

600

620

640

660

680

Wavelength (nm)

Figure (5) Room temperature PL of Eu3+-doped GaN sample, under below bandgap excitation peak at 464 nm.

102

3.02 ev

5D

3

2.66 ev

5D

2

2.35 ev

5D

1

2.14 ev

5D

0

Excitation by 464 nm 0.27 ev 0.14 ev 0.07 ev

616 nm

4

593 nm

5D

Energy (ev)

3.41 ev

7F

3

7F

2

7F

1

7F

0

Figure (6) The simplified energy level diagram of the Eu inner 4f shell, and the possible emission mechanisms. [20]

Conclusion Undoped and Eu3+-doped GaN crystallites have been synthesized by the co-precipitation method followed by nitridation at 1100 oC, under a continuous flow of ammonia gas. The XRD data confirmed the single-phase wurtzite structure of the synthesized undoped and Eudoped GaN powders. By using the Scherrer equation, the average sizes of the crystallite grains have been evaluated to be and 24 nm and 18 nm for the undoped and Eu3+-doped GaN powders, respectively. FE-SEM and TEM images showed that the GaN nano-sized grains are coalesced into micron-sized agglomerations. The room-temperature PL spectra of the synthesized powders, exhibited the characteristic GaN band-edge emission at 363 nm (3.4 eV, FWHM ~ 10 nm) as well as broad defect-related emission peak at about 405 nm. With below bandgap excitation, the Eu3+-doped GaN sample exhibited red emissions corresponding to the 5 D0 → 7F1 and 5D0 → 7F2 transitions of Eu3+ ions.

References [1] [2] [3] [4] [5]

Y. Hori, X. Biquard, E. Monroy, D. Jalabert F. Enjalbert, Le Si Dang M. Tanaka, O. Oda, B. Daudin, Applied Physics Letters, Vol. 84 (2), (2004) 206-208. C.T.M. Ribeiro, A.R. Zanatta, Journal of Non-Crystalline Solids 338-340 (2004) 469-472. V. Katchkanov, J.F.W. Mosselmans, K.P. O,Donnell, E. Nogales S. Hernandez, R.W. Martin, A. Steckl, D.S. Lee, Optical Materials 28 (2006) 785–789. J. H. Park, A. J. Steckl, Applied Physics Letters, Vol. 85 (20), (2004) 4588-4590. Andrew J. Steckl, Jeong Ho Park, John M. Zavada, Materials Today, Vol. 10 (7-8), (2007) 20-27.

103

[6] [7] [8] [9] [10]

[11] [12] [13] [14] [15] [16] [17] [18] [19] [20]

A.J. Kenyon, Progress in Quantum Electronics 26 (2002) 225–284. A. Podhorodeckia, M. Nyk, J. Misiewicz, W. Streak, Journal of Luminescence 126 (2007) 219–224. D. S. Lee, J. Heikenfeld, R. Birkhahn, M. Garter, B. K. Lee, and A. J. Steckl, Applied Physics Letters, Vol. 76 (12), (2000)1525-1527. H. Y. Peng, C. W. Lee, H. O. Everitta! D. S. Lee , A. J. Steckl , J. M. Zavada, Applied Physics Letters Vol. 86, 051110 (2005). Andrew J. Steckl, Jason C. Heikenfeld, Dong-Seon Lee, Michael J. Garter, Christopher C. Baker, Yongqiang Wang, and Robert Jones, IEEE Journal of Selected Topics In Quantum Electronics, Vol. 8, No. 4, 2002. R. Kudrawiec, M. Nyk, A. Podhorodecki, J. Misiewicz W. Strek, M. Wołcyrz, Applied Physics Letters 88, 061916 (2006). J. Chandradass, Dong Sik Bae, Ki Hyeon Kim, Advanced Powder Technology, 22 (3), (2011), 370-374. Jung Kyun Kim, Yong Gyu Choi, Thin Solid Films 517 (2009) 5084–5086. Hongbo Xie, Limiao Chen, Younian Liu, Kelong Huang, Solid State Communications 141 (2007) 12–16 Junxia Shi, M.V.S. Chandrashekhar, Jesse Reiherzer, William J. Schaff, Jie Lu, Francis J. Disalvob, Michael G. Spencer, Journal of Crystal Growth 310 (2008) 452–456. O. Contreras, S. Srinivasan, F. A. Ponce, G. A. Hirata, F. Ramos, and J. McKittrick, Appl. Phys. Lett. 81, 1993 (2002). R. Kudrawiec, M. Nyk, A. Podhorodecki, J. Misiewicz, W. Strek and M. Wołcyrz, Appl. Phys. Lett. 88, 061916 (2006). Hailin Qiu, Chuanbao Cao, and Hesun Zhu, Materials Science and Engineering B 136 (2007) 33–36. R. Kudrawiec, M. Nyk, M. Syperek, A. Podhorodecki, J. Misiewicz, and W. Strek, Applied Physics Letters 88, 181916 (2006) 1 – 3. J. Heikenfeld, M. Garter, D. S. Lee, R. Birkhahn, and A. J. Steck, Applied Physics Letters, Volume 75, 1999.

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THE FORMATION AND CHARACTERIZATION OF NANOCRYSTALLINE MN-FERRITE FROM MAGNETITE M. A. AHMED* Materials Science Lab (1), Physics Department, Faculty of Science, Cairo University, Giza, Egypt N. OKASHA Physics Department, College of Women for Arts, Science and Education, Ain Shams University, Cairo, Egypt D. NABEEL Materials Science Lab (1), Physics Department, Faculty of Science, Cairo University, Giza, Egypt

Nanocrystalline manganese ferrite of MnxFe3-xO4 with x = 0, 0.2, 0.4 and 0.6 was prepared by chemical co-precipitation method. The as prepared samples were characterized by XRD and magnetization. X- ray diffraction patterns confirmed the inverse spinel structure of ferrites particles with size ranged from 12 to 30 nm. The Magnetic properties such as typical saturation magnetization (Ms), remanence magnetization (Mr) and coercive field (Hc) measured at room temperature along with doped at different Mn contents show that the maximum Mn ions content doped into ferrite lattices is x = 0.4 which agree well with the magnetic susceptibility (χM) measurements and the high magnetic parameters. Keywords: Mn-ferrites; Nano-crystalline material; Co-precipitation; Magnetic properties; X-ray diffraction.

Introduction The synthesis of magnetic nanocrystalline particles is of fundamental and technological interest [1, 2]. Nano-crystalline materials are polycrystalline solids with grain size of a few nanometers. Because of large volume of fraction of interfaces, the electronic structure of nanocrystalline materials is likely differing from perfect single crystals. Nonstructural materials which exhibit unusual physical and chemical properties are significantly different from those of the conventional bulk materials, due to their extremely small size or large specific surface area [3-5]. Accordingly, their preparation and characterization have attracted an increasing attention in the past decade. These materials are also of great technological importance because of their use in the preparation of magnetic fluid, data storage system, medical diagnostics and targeted drug delivery vectors for gene therapy [6-8]. Also magnetic cell sorting schemes [9], binding of magnetic nano-particles to antibodies to label molecules, in vivo imaging and contrast agnts [10], magneto-crystalline agents for treatment of localized cancerous tumors [11].

*

The structural and magnetic properties of spinel ferrites depend upon the method of preparation, nature of dopant and dopant concentration. Several researchers have studied the magnetic properties of Mn-Zn ferrite as a function of temperature [12-14]. The magnetic moment of Mn ferrite (MnFe2O4) agrees with the Neel coupling scheme [15] and has a much lower resistivity than CoFe2O4 and NiFe2O4 [16]. Usma et al. [17] measured the distribution of manganese among tetrahedral and octahedral sites in Mn1-xFe2-xO4 and found that 30% of the octahedral sites are occupied by Mn3+ with the distribution Mn2+0.9Fe3+0.1 [Mn3+0.6Fe3+1.6Fe2+0.1] O2-4 Using neutron diffraction, where the square brackets represent the octahedral site and those to the left of the brackets represent the tetrahedral site. In addition, Usma [17, 18] studied the analyses of X- ray diffraction on MnZn ferrite prepared by slandered ceramic method. Manganese ferrites MnxFe3-xO4 of spinel structure have been the subject of extensive research because of their potential applications such as cores of intermediate frequency transformers, inductors, loudspeakers and other electromagnetic devices such as magnetic recording media and electronic devices.

Corresponding author: M. A. Ahmed, E-mail: [email protected] CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

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3 0

4 0

5 0

6 0

(533)

(620)

0 2 0 2 0

tsn uo C

x = 0 .6

(440)

(220)

2 0

Due to the dependence of ferrites, properties on the preparation conditions, the wet chemical methods gaining prominence for the preparation of homogeneous and compositionally stoichiometric ferrites [19]. 89.950 (magnetite), 74-2403 and 72-2303) which enhances the crystal growth for all the samples as in Fig. (1.a). In view of this, a wet chemical method is known as the co-precipitation method [20-22] used to prepare the desired samples. Aqueous solutions of MnCl2 and FeCl3 in their respective stoichiometry are good mixed and NaOH was added to the boiling solution and adjusting the pH value to ~12, within 30 sec. under constant stirring. Precipitation and formation of nanoferrites takes place by the conversion of metal salts into ferrites. X-ray diffraction analysis was carried out using Scintag (USA) equipment with CuKα radiation (λ = 1.5418oA) to confirm the presence of single-phase cubic nanostructure ferrite for all prepared samples. The particle size (L) is determined from the measurements of the full width at half maximum (FWHM) and the Scherrer formula: LXR = 0.9 λ / β cos θ [ 23 ]; where β – is the (FWHM) of the line in radian, θ − Bragg angle, λ - radiation wavelength.

(311)

Experimental Techniques

(511)

The structure of the investigated nanoparticles was analyzed using X-ray difrractometer. The data confirms the formation of single phase of the face centered cubic (fcc) spinel structure as identified using (ICDD) card no.

(422)

Results and Discussion

Molar magnetic susceptibility XM of the investigated samples was measured using Faraday's method where a very small quantity of sample was inserted in a Pyrex tube at the point of maximum gradient (maximum force). The measurements were carried out at different temperatures from 300K to 900K and at different magnetic field intensities of (1340, 1660, 1990, and 2320 Oe). The temperature of the samples was measured using T-type thermo-couple with junction near the sample keeping it free to avoid the temperature gradient. The accuracy of magnetic susceptibility measurements was ±1% where the data was reproducible. The room temperature magnetic hysteresis of samples was measured up to a maximum field of 5 k Oe using vibrating sample magnetometer (VSM) model 9600-1 LDJ, USA. (400)

In the present work, it could be describe the preparation and characterization of manganese nanoferrites, MnxFe3-xO4; x = 0, 0.2, 0.4 and 0.6 by co-precipitation method as prepared and studied extends such measurements to well characterized mixed iron manganese oxide spinel. Also one of our aims is to reach the critical concentration of Mn2+ ions at which the physical properties are modified and become more applicable.

7 0

8 0

x = 0 .5

1 0 0 2 0 2 0

3 0

4 0

5 0

6 0

7 0

8 0

x = 0 .4 0 2 0

3 0

4 0

5 0

6 0

7 0

8 0

x = 0 .3

2 0 0 2 0

3 0

4 0

5 0

6 0

7 0

8 0

x = 0 .2

1 0 0 2 0

3 0

4 0

5 0

6 0

7 0

8 0

x = 0 .1

1 0 0 2 0

3 0

4 0

5 0

6 0

7 0

2 0

8 0

x = 0 .0

0 2 0

3 0

4 0

5 0

6 0

7 0

8 0

2 θ

8.43 (b)

a (A) 8.42

8.41

8.4

8.39 0

0.2

0.4

0.6

0.8

Mn content (x)

Fig. (1: a, b): a-XRD patterns for as prepared MnxFe3-xO4 nanoferrite. b-The variation of the lattice parameter (a) with different Mn concentration (x).

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The broadness of the peaks and the decrease of its intensity indicate that the particles are of nanometer dimensions. The increase in the lattice parameter (a) with increasing Mn content was expected (Fig. 1b, Table 1). This behavior attributed to the replacement of Mn3+ with larger ionic radius (0.082 nm) by Fe2+ ions with smaller ionic radius (0.076 nm) on tetrahedral sites.

susceptibility (χM) versus absolute temperature ranging from 300-900K as a function of magnetic field intensity (1340-2320 Oe) is shown in Fig. (2). χM(emu/gr mole K ) 8

Mn=0.2

4

5

x 0 0.1 0.2 0.3 0.4 0.5 0.6

L(nm) Dx g/cm 17.5 12.4 13.3 16.2 24.9 21.2 20.7

3

o

a(A )

5.2488 8.4005 5.16759 8.40845 5.1868 8.41187 5.1409 8.4158 5.18831 8.4196 5.0879 8.3978 5.14101 8.3933

V*10

0

0 300

500

700

This substitution leads to an increase not only in the lattice parameter but also in the unit cell size, this agrees well with the values of particle size (L). After x = 0.4, the decrease in (a) is due to the replacement of Mn2+ (0.046 nm) of Fe3+ (0.064 nm) at octahedral sites due to the superexchange Fe2+ + Mn3+ ↔ Fe3+ + Mn2+ interaction. Moreover, the minimum value of (a) appered at x = 0.4, which means that there is a deviation from the ideal formula of cation distribution due to the presence of some Mn4+ with radius 0.52°A. The value of lattice parameter in our sample (a = 0.8399 nm) is lower than that of bulk sample (a = 0.8543 nm) [24] and almost the same as [25]. The average particle sizes (L) determined from the prominent (311) peak of the diffraction using Schrrer’s equation. Reported in Table (1) confirm that, the particle size depends slightly on the manganese molar ratio where its value increases with increasing Mn content because of the replacement of larger ionic radius on expense of small ionic radius as mentioned before and its values were changed from 12.4 nm to 30.7 nm. The effect of partial substitution of iron by manganese ions on the molar magnetic

500

24

1340 Oe 1660 Oe 1990 Oe 2320 Oe

Fe3O4 200

300

900

300

-22

5.8592 5.9489 5.9246 5.9752 5.9182 6.0326 5.968

1340 Oe 1660 Oe 1990 Oe 2320 Oe

10

2

Table (1): The change of partical size (L), X-ray density (Dx), latticeconstant (a), and the volume (V) with different Mn content (x).

Mn=0.4

15

1340 Oe 1660 Oe 1990 Oe 2320 Oe

6

700 Mn=0.6

1340 Oe 1660 Oe 1990 Oe 2320 Oe

18 12

100

6 0

0 300

900

500

700

T(K)

900

300

500

700

900

Fig. (2): The DC molar magnetic susceptibility (χM) as a function of temperature (TK) for various magnetic field intensity.

From the figure, it is clear that, the ferrimagnetic behavior can be observed for all samples and the value of χM gives a maximum value at Fe3O4 sample which indicates high magnetization to the magnetite metal ions and the magnetization increases with increasing Mn content and at the same time it decreases with increasing the applied magnetic field. This behavior is due to the exchange interaction of Mn2+ ions on the expense of Fe3+ ions in octahedral sites. Figure (3: a, b) and Table (2) show the relation between the magnetic susceptibility (χΜ) versus the magnetic field intensity (H). From the data, it observed that, the magnetic susceptibility (χΜ) decreases with increasing the magnetic field intensity and the highest value is at Fe3O4 sample. and the value of the Curie temperature (TC) increases with increasing Mn content up to x = 0.4 then decreases. Figure (3.b) shows the relation between the values of Curie temperature (TC) versus the particles size (L). The value of L increases with increasing TC up to x = 0.4 after which it decreases. This was ascribed to the redistribution of the iron and manganese cations over the tetrahedral (A) and octahedral sites (B) crystallographic sites of the spinel structure.

107 20 χM

(a)

x=0.2 x=0.4 x=0.6

16

180 140 100

(a)

(c) 40

1300

12

80

M (emu/g)

x=0

1800

x=0.0

35 x= 0.4

15

2300

0 -5100

8

-2100

900

3900

-5

-5000

-40

0

5000

-25

4

-80 0 1600

1900

2200

H (Oe)

(b)

(b)

-5000

-10

20

-20

15

-30

760

780

800

820

840

860

880

TC (A)

Table (2): Values of the effective magnetic moment meff.(B.M), Curie constant C (emu/gr.mol.K), CurieWeiss constant θ(K), and Curie temperature (TC) at different concentration of Mn(x) in MnxFe3-xO4, 0.0 ≤ x ≤ 0.6 ferrite. C θ (Κ)

4.517 0.26 0.53 0.59 0.62 0.45 0.31

740 520 620 670 680 720 740

µeff. 4.063 1.37 1.76 2.03 1.54 1087 1.42

H= 1660 Oe C θ (Κ) 2.06 710 0.23 480 0.37 630 0.51 660 0.29 740 0.44 690 0.25 730

H= 1990 Oe C µeff. 3.67 1.682 1.22 0.18 1.71 0.33 1.96 0.48 1.45 0.26 2.06 0.53 1.41 0.25

θ (Κ)

730 500 630 660 730 660 730

µeff. 3.33 1.16 1.64 1.95 1.41 1.76 1.28

H= 2320 Oe C θ (Κ) TC (K) 1.38 0.17 0.34 0.48 0.25 0.39 0.21

730 500 600 650 730 680 740

5000

-5000

0

5000

-40 -80

900

Fig. (3: a, b): a-The variation of χM with H at different concentration of Mn. b-The relationships between the Curie temperature (TC) and the size of the particles (L).

H= 1430 Oe

x=0.6

0 0

H (Oe)

10

µeff. 6.015 1.44 2.06 2.17 2.23 1.89 1.55

40

x=0.2

0

25

0 0.1 0.2 0.3 0.4 0.5 0.6

80 (d)

20 10

35 L (nm) 30

Mn (x)

-45

30

1300

800 703 743 768.1 756 753 733

Magnetization is performed as a function of magnetic field at room temperature to obtain the hysteresis loop Fig. (4: a-d). The values of saturation magnetization (M s ), remanence magnetization (Mr) and coercive field (Hc) for various Mn- concentrations are reported in Table (3). It reveals that, the coercive field reaches to maximum when the partial substitution of Mn content is minimum and the higher saturation magnetization value of about 58.503 emu/g was obtained for precursor prepared at x = 0. The value was less than the bulk value of 80 emu/g reported for MnFe2O4 [26]. Zheng et al. [27] found the reduction in saturation magnetization also and they explained it based on magnetic

Fig. (4: a-d): Magnetization (M) vs. applied magnetic field MnxFe3-xO4 nanoferrite.

dead layer on the surface of the particle. On the other hand, Misra et al. [28] discussed the lower value of saturation magnetization than their bulk counterparts could result from the existence of spin canting which reported in several nanometer-sized ferrites [29] as due to surface structure disorder. The variation of the magnetic parameters with Mn concentration is shows in Table (3). From the reported data, it is clear that, the variation of the saturation magnetization Ms can be explained on the basis of cation distribution and exchange interaction. The Mn ions substitute Fe3+ as Mn2+ at tetrahedral and as Mn3+at octahedral sites, which decrease the inverse character of the studied ferrite. The reported data shows that, the saturation magnetizations of the samples doped with Mn ions are lower than that of un-doped one and decreased with the Mn-doped contents up to x = 0.4, fter which it increases gin until it becomes larger than the undoped sample. It can be seen that the saturation magnetization values of all the samples decrease with decreasing particles sizes up to near x = 0.4 after which it begins increasing. It deduced that the magnetic domains of the nanoparticles increased with the growth of particle sizes. This change in the magnetic properties is due to the influence of cationic stoichiometry and their occupancy in the specific sites. It is known that [30, 31], in the cubic system of ferrimagnetic spinels, the magnetic

108

order is mainly due to the superexchange interaction mechanism occurring between the metal ions in the tetrahedral sites (A) and the octahedral sites (B) sublattices. The substitution of magnetic materials such as Mn, which has a preferential to A and B sites occupancy. The Mn spinel ferrite is considered as inverted spinel with about 80% tetrahedral sites occupied by manganese- according to the reduction of the superexchange interaction Fe3 + Mn2+ ↔ Fe2+ + Mn3+ between A and B. Another reason for this reduction is the formation of dead layer on the surface as mentioned before, existence of random canting of particle surface spins, Table (3): The magnetic parameters of Mn nanoferrites of MnxFe3-xO4, 0.0 ≤ x ≤ 0.6 ferrite. x 0 0.1 0.2 0.3 0.4 0.5 0.6

Ms(emu/g)

Mr(emu/g)

Hc (Oe)

TC (K)

68.504 48.45 39.91 31.4 24.81 45.8 59.5

41.6 25.8 14.4 7.4 5 32.14 48.39

876.44 646 330 246 187 605 824

801.8 780 771.8 758.9 754.6 768.6 785.9

nonsaturation effects due to random distribution of particle size and deviation from the normal cation distribution. While, at 0.4 ≤ x, a lot of Mn3+ migrate to B sites on the expense of Fe3+ which go to A sites as Fe2+, leads to an increase in the magnetization of B sites as well as increasing the total magnetization. Finally, The hysteresis loop of the considered critical concentration (x = 0.4) shows, ferromagnetic behavior with saturation magnetization (Ms), remanent magnetization (Mr), and coercive (Hc) values of about 24.91 emu/g, 3.14 emu/g and 61.14 Oe, respectively. While, these values are different from those reported for MnFe2O4 nanorods (Ms = 68.02, Mr = 14 emu/g, Hc = 361 Oe) [32] and nanoparticles (Ms = 70, Mr = 17 emu/g, Hc = 200 Oe) [33]. Conclusion Nanocrystalline magnetic particles of MnxFe3-xO4 with x = 0, 0.2, 0.4 and 0.6 were as prepared by co precipitation method. XRD

patterns of all systems showed broad peaks consistent with cubic inverse spinel structure of MnFe2O4. The absence of extra reflection in the diffraction patterns of as prepared materials assures the phase purity. The particle size depends slightly on the stoichiometric with diameter ranging between 30.7 to 13.3 nm. Hence, the co-precipitation method is promising for producing fine- grained ferrites. The magnetic properties measured at room temperature such as saturation magnetization, remanence magnetization and coercivity field indicated that, the maximum value was obtained for magnetite (Fe3O4) while the minimum value of x = 0.4 which was consider the critical one and this results agree well with the results of magnetic susceptibility and the crystal structure of this ferrite. Finally, the preparation process is quite simple, inexpensive, since it does not involve intermediate decomposition and / or calcining steps and it is easy to have control on the stoichiometric. References 1. J. L.Dormann, I. Fiorani (Eds.), Magnetic Properties of Fine Particles, North-Holland, ámsterdam, (1992). 2. G. C. Hadjipanayis, R. W. Siegel (Eds.), Nanophase Materials: Síntesis- PropertiesApplications, Kluwer academia Puplishers, Boston, (1993). 3. N. S. Gajbhiye, G. Balaji, Thermochimica Acta 385 (2002) 143. 4. C. Hayashi, Phys. Today 40 (1987) 44. 5. Dong- Hwang Chen, Xin- Rong He, Materials Research Bulletin 36 (2001) 1369. 6. S. K. Sahoo, V. Labhasetwar, Drug Discov. Today 8 (2003) 1112. 7. P. Gould, Mater. Today 15 (2004) 36. 8. Vectoria L. Calero-DdelC, Carlos Rinaldi, J. Mag. Mag. Mater., 314 (2007) 60. 9. C. N. Ramchand, P. Pande, P. Kopcansky, R. V. Mehta, Indian J. Pure Appl. Phys., 39 (2001)683. 10. E. Blums, A. Cebers, M. M. Maiorov, Magnetic Fluids, Berlin, (1996). 11. M. Chastellain, A. Petri, A. Gupta, K. V. Rao, H. Hofmann, Adv. Eng. Mater., 6 (2004) 235. 12. A. Lakshman, K. H. Rao, R. G. Mendiratta, J. Mag. Mag. Mater., 250 (2002)92. 13. K. Latha and D. Ravinder, Phys. St. Sol. (a) 139 (1993)109. 14. P. J. Van der Zaag, M. Kolenbrander and M. Th. Rekveldt. J. Appl. Phys., 83, 11 (1998) 6870.

109 15. K. Takadate, Y. Yamamoto, A. Makino, T. Yamaguchi and I. Sasada, J. Appl.Phys., 83, 11 (1998)6854. 16. F. K. Lotger, J. Phys. Chem. Solid, 25, 95 (1964) 345. 17. Usma Ghazanfar, S. A. Siddigi, G. Abbas, J. Materials Science and Engineering B, 118 (2005) 84. 18. M. H. Abdullah, S. H. Ahmed, SainsMalaysiana, 22 (1993) 1. 19. A. Goldman in: C. M. Srivastava, M. J. Patni (Eds.), Proceeding of the fifth international conference on Ferrites, Bombay, January, 1989, Oxford, IBH, New Delhi, India (1989) 13. 20. R. Y. Hong, T. T. Pan, Y. P. Han, H. Z. Li, J. Ding, Sijin Han, J. Mag. Mag. Mater.,310(2007) 37. 21. P. Wang, C. Lee, T. Young, J. Poly. Sci. Part A: Polym. Chem. 43 (2005) 1342. 22. A. Bocanegra- Diaz, N. D. S. Mohallem, M. A. Novak, R. D. Sinisterra, J. Mag. Mag. Mater., 2395 (2007) 272.

23. P. Scherrer, Cottinger Nachr. 2 (1918) 98. 24. M. Zheng, X. C. Wa, B. S. Zou, Y. J. Wang, J. Mag. Mag. Mater., 183 (1998)152. 25. Anjali Verma, M. I. Alam, Ratnamala Chatterjee, J. Mag. Mag. Mater., 15 (2005)210. 26. R. Tebble, D. J. Craik, Magnetic Materials, Wiley- Interscience, New York, (1969). 27. M. Zheng, X.C. Wu, B.S. Zou, Y.J. Wang, J. Magn. Magn. Mater. 183 (1998) 152. 28. R.D.K. Misra, S. Gubbala, A. Kale, W.F. Egelhoff Jr., Mater. Sci. Eng. B 111(2004) 164. 29. V.A.M. Brabers, Handbook of Magnetic Materials, vol. 8, Buschow, Amsterdam, (1995) 297. 30. J. Smit and P. J. Wing, “Ferrites” Wiley London p. 140 (1059). 31. J. M. Hastings and L. M. Corliss, Phys. Rev., 104 (2) 328 (1956). 32. J. Wang, Q.W. Chen, B.Y. Hou and Z.M. Peng, Eur. J. Inorg. Chem. 25 (2004) 1165. 33. O. Masala and R. Seshadri, Chem. Phys. Lett. 402 (2005) 160.

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THE STRUCTURAL, SPECTRAL AND DIELECTRIC PROPERTIES OF COMPOSITE SYSTEM NZF-BT O. M. HEMEDA1, A. TAWFIK1, M. A. AMER1, B. M. KAMAL2 and D. E. EL REFAAY2 2

1 Tanta University, Faculty of Science, Physics Department Suez Canal University, Faculty of Science, Physics Department

The Composite material of NiZnFe2O4 and BaTiO3 were prepared by double sintering ceramic technique. X-ray diffraction pattern for composite xBaTiO3 + (1-x) Ni0.8Zn0.2 Fe2O4 where (x = 0%, 20%, 40%, 60%, 80% and 100%) show the presence of diphase and confirms the successful preparation the composite. Some parameters were deduced from the analysis of x-ray like porosity, density, particle size and the lattice constant for both phases were calculated from XRD. SEM shows nearly homogeneous microstructure with good dispersion of BT grains and the presence of some pores. There was an enlargement of BT grain by BT content. IR spectra of composite sample indicate that BT content affect the intermolecular character of the ferrite. A rise in dielectric constant occurs at high temperature due to the effect of space change resulting from the increase of change carriers in paramagnetic region. The dielectric loss (tan δ) decrease by increasing BT content.

1. Introduction A combination of two phases such as a combination of ferrimagnetic and ferroelectric phases or piezomagnetic and piezoelectric phases, produce a new material combining several properties of two phases (1). The deformation of ferrite phase causes polarization of piezoelectric phase in the composites and the electrical polarization of piezoelectric phase causes change in magnetism of ferrite phase due to strong mechanical coupling between the piezomagnetic (ferrite) and piezoelectric (ferroelectric) phases (2). In the last years, the magnetoelectric (ME) materials showing simulations magnetic and ferroelectric order became very important for their fundamental physics, for applications as sensors and transducers in radio and microwave electronics and instrumentation (4, 3). The main advantage to produce sintered ME composites are related to the easy and cheep fabrication and to the possibility to control the molar ratio of phases, grain size of each phase and densification. The main problem to be avoided is related to the possible reactions at the interfaces between the ferroelectric and magnetic phases during sintering, leading poor dielectric properties (1). The ESR is a powerful tool for investigations of various properties of solids. ESR spectroscopy would appear to be an ideal method to study the electronic and magnetic properties of these materials on the microscopic scale. In the present paper we used the ceramic method to obtain the composite (NZF-BaTiO3). 2. Experimental 2.1. Preparation The composite samples xBaTiO3 + (1-x) Ni0.8Zn0.2 Fe2O4 where (x = 0%, 20%, 40%, 60%, 80% and 100%) were prepared by ceramic methods. The BaTiO3 was prepared from BaCO3 and TiO2 starting with grindy BaCO3 and TiO2 in molar ratio for 10 hours and presintered at 1200 °C

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

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for 16 hours. Similarly Ni0.8Zn0.2Fe2O4 was prepared from NiO, ZnO and Fe2O3 with purity 99.99% were mixed in molar ratio for 10 hours. These raw materials were presintered at 950 °C for 16 hours and left to be cooled gradually. These composites were mixed and grinded very well for 12 hours for each composite using agate mortar, and then presintered at 950 °C for four hours. Finally, all samples were ground and pressed at room temperature into a tablet under a pressure of 10 kg/cm2 of diameter 1cm and 0.4 cm thickness and other samples in the form of toroid of external diameter 3cm and internal diameter 2 cm and height 0.5 cm, in stainless steel mould, then finally sintered at 1050 °C for 8 hours. The furnace was left to cool gradually by 2.5 °C/min to room temperature. 2.2. Measurements The samples were examined by X-ray diffraction using a Philips model (PW-1729) diffractometer and the powder specimens were exposed to radiation (λ = 1.541178 Ao). Infrared (IR) spectra for the prepared samples were carried out at room temperature by using a PERKINELMER-1430 recording infrared spectra in the range 200 to 4000 cm-1 (at Tanta University Central lab). The ESR spectra were recorded for the mentioned samples using JSE-Fe 2×G Jeol ESR spectrometer. The samples in the powder form were placed at the maximum magnetic field in the cavity. The ESR spectra were recorded as a first derivative. The RLC Bridge of type BM591 was used for the measurement the dielectric constant (έ) and dielectric loss (tanδ) of the prepared samples at 1 KHz. The temperature of the sample was measured by Ni Cr-Ni thermocouple. 3. Results and Discussions 3.1. X-ray Analysis of the Composite Ni0.8Zn0.2Fe2O4-BaTiO3 The X-ray diffraction pattern for the composite (1-x) (Ni0.8 Zn0.2 Fe2O4) + x (BaTiO3) where x = 0%, 20%, 40%, 60%, 80% and 100% BT content) together with the references samples the BT and NZF pure phases as shown in Fig (1). From the diffraction pattern of all samples, we note the absence of any peak belongs to the raw materials. Which indicate the presence of the two phases only. This confirms the successful preparation the Di-phase composite ceramic. The X-ray diffraction pattern Fig (1), shows that the composite consists of two phases, ferrimagnetic phase (Ni0.8Zn0.2Fe2O4) and ferroelectric phase (BaTiO3). We can express the two phases as pizomagnetic phase (Ni0.8Zn0.2Fe2O4) and piezoelectric phase (perovskite Barium titnate). The diffraction pattern shows the variation of (100%) diffraction peaks for both Ni0.8Zn0.2FeO4 and BaTiO3. The intensity of 100% (311) ferrite peak decreases by increasing BaTiO3 content and the intensity of 100% (101) BaTiO3 peak increase by increasing BaTiO3 content. Also the position of the diffraction peaks for both phases changed with the increase of BaTiO3, which indicate the formation of solid state reaction between the two phases during the sintering process. All peaks were indicated by the system (T) belongs to BaTiO3 phase and that has a symbol (f) belongs to ferrimagnetic phase. The symbol ( τ ) belongs to BaCo3.

112

Fig (1): X-ray diffraction of (1-x) Ni0.8Zn0.2Fe2O4 – (x) BaTiO3 where x = 0%, 20%, 40%, 60%, 80% and 100% BT content. By analysis of X-ray diffraction pattern of all samples, we deduced the lattice constant, the theoretical density, porosity and particle size for the two phases as shown in Table (1). The lattice constant for the ferrimagnetic phase doesn’t vary much by increasing BaTiO3 content it is slightly increase as shown in Fig (2). The lattice constant of tetragonal phase (c) decrease by increase BaTiO3 content where the lattice constant (a) increase. The presence of NZF phase with lager grain size affect the perovskite unit cell for BaTiO3 and change its lattice constant. The lattice parameter a of tetragonal phase increase by decreasing NZF content as shown in Fig (2). The tetragonallity factor c\a decrease by increasing BaTiO3 content as shown in Table (1). The bulk density (D) of the samples was calculated by using the Archemides principle. The theoretical density of both phases was calculated from the following equations (5): DNZF =

8M Na 3

(1)

DBT =

1M NV

(2)

where M: is the sample molecular weigh, N: Avogadro's number, V: The volume of the unit cell and equal to a2c, and a: the lattice constant of the ferromagnetic phase.

113

Table (1): The lattice parameter (a) of ferroelectric and ferromagnetic phases (a,c), the tetragonallity factor c\a, average and bulk densities, porosity, particle size and grain size. X%BT

Lattice parameter NZF BT

c/a

Average Bulk porosity density density

Particle size

Grain size

0% 20%

8.429 0 0 8.423 a=3.904 1.084 b=4.233

5.229 5.623

2.833 2.557

0.458 0.545

28.723 22.587 23.711

NZF BT 4.34 2.96 1.38

40%

8.508 a= 3941 b=4.106 8.514 a=4.014 b=4.032 8.512 a=4.001 b=4.029 0 a=3.984 b=4.022

1.042

5.579

3.854

0.309

24.900 23.195

2.62

1.004

5.517

4.103

0.256

23.968 19.346 2.075 3.189

1.007

5.541

3.502

0.368

27.240 19.194

1.009

6.067

3.981

0.344

60% 80% 100%

NZF

-

BT

19.734

1.93

1.55

3.24

-

3.7

Fig (2): The lattice constant for the ferrimagnetic phase (aNZF) and ferroelectric phase (BT).

114

As given in Table (1), the theoretical density slightly increases by increasing BT content. The increase of the density by increase BT content may be due to the large atomic weight of BaTiO3 content. The porosity of the composite materials with BT content is given in Table (1). It notes that the porosity decrease by increasing BT content. The grains of NZF and BT occupied more space in the unite cell which leads to the increase the theoretical density and decrease of porosity. The particle size of both NZF and BT phase were calculated separately by using Scherrer equation (5).

t=

Kλ h 1 cos θ

(3)

2

where K = 51.57 is the Scherrer constant λ = 1.5404 A◦ is the wavelength, h1/2 ; is the full width at half maximum and θ: is the angle of diffraction For the two phases (NZF) and (BT), the particles size slightly decrease by increasing BT content, as shown in Fig (3). The particle size is inversely proportional to the line width of the different peaks. The average particle size of our composite ranged form 25-30 nm. It has been found that the ferrite usually required upper limit of particle size < 50 nm and the concentration of Fe3+ at least 13% to be spinel. The volume distribution showed that the particle size ranged from 25-30 nm, with an average of 27 nm, which is in the spinel limit.

35

30

25

t nm

20

15

10 tNZF tNZF

5

0 0

20

40

60

80

100

120

x% BT

Fig (3): The particle size of the composite of NZF-BT.

115

Figure (4) shows the SEM micrograph for the composite samples. The values of the average grain size or grain diameter of the piezomagnetic phase (NZF) decrease by increasing BT content. The grain size of BaTio3 was found to increase by increasing BT content. The white grain in Fig belongs to ferroelectric phase, while the dark grain belongs to ferromagnetic phase. The composite of 40% BaTiO3 show that the ferromagnetic phase exhibit spinel cubic structure. The grain diameter of ferromagnetic material is in the range of grain size in literature.

X=0%

X=20%

X=40%

X=60%

X=80%

X=100%

Fig (4): Shows the SEM micrograph for the composite samples (1-x) Ni0.8Zn0.2Fe2O4 – (x) BaTiO3 where x = 0%, 20%, 40%, 60%, 80% and 100% BT content.

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The SEM shows nearly homogenous microstructure with good dispersion of BT pervoskite grains and the presences of some pores (6). The ferrite region is largely percolated by small BT grains. It is practically difficult to obtain dense, homogenous and fine grain composite ceramic by solid state ceramic method because of the large different between their sintering behavior and thermal expansion coefficient. Non uniform microstructure with large and different grains sizes always result instead. It is obvious that the densification of the ceramic composite takes place by increasing BT content. The grain size of both BT and NZF phases are given in Table (1). It was observed that the sample composition has an influence on the grain size. There is an enlargement of BT grain size by increasing BT content.

3.2. IR Spectral Analysis of the Composite Ni0.8Zn0.2Fe2O4-BaTiO3 Figure (5) shows IR spectra of the composite materials (NZF- BT). The presence of IR absorption band ν 1 at nearly 580 cm-1 to 552 cm-1 assigned to the vibration of groups Fe+3-O-2 at tetrahedral site. This indicates the occurrence of the crystallization in accordance with the XRD results. Another absorption band ν 2 which assigned to the vibration of groups Fe+3-O-2 at octahedral site are around 418-433 cm-1 as shown in Table (2). Another weak absorption band appeared near the lower frequency absorption band assigned with ν 3 which results from the vibration of divalent metal ion Me+2-O-2 bond. The difference in ν 1 and ν 2 must be related to the difference in Fe+3-O-2 inter ionic distance at A and B site. It was found that Fe+3-O-2 distance at A site is 0.189 nm and that for B site 0.199 nm (7). The presence of a small band between ν 1 and ν 2 may be attributed to B-O stretching vibration at octahedral site, this band appears at concentration of 40%, and 60% BT content. At higher content of BaTiO3, theν 4 band disappears because the few amount of NZF phase don't permit to change the electric dipole moment of this bond during vibration and results in disappearance of this absorption band. The frequency ν 3 may be due to lattice vibration. The lower and higher frequencies ν 1 andν 2 decrease as BT content increase. The shape and the width of absorption band depended on the cation distribution. The intensity of absorption band ν 1 and ν 2 for tetrahedral and octahedral sites respectively decreases by increasing BT content. This may be due to the decrease of Fe3 at both octahedral and tetrahedral site by increasing BT content. For composite with double phases the absorption bands appears around 1039 cm-1, 970, 913 and 857 cm-1 for the samples with x = 40%, 60% and 80% BT content. These absorption bands are assigned to C─O─C asymmetric stretching mode of vibration, C─H and C ═ C respectively due to the presence of traces BaCO3 (8). This absorption bands are nearly disappeared for the BT phase and appears for the composite samples, which may be due to the influence of the NZF phase on the intermolecular character of the BT phase. This means that the asymmetric pending vibration of this bond becomes symmetric pending vibration and there well be change in the electric dipole moment of this bond resulting in the appearance week absorption band.

117

x=100%

x=80%

x=60% x=40%

x=20% x=0%

Fig (5): Shows IR spectra of the composite samples ((1-x) Ni0.8 Zn0.2Fe2O4- x BaTiO3) where x = 0%, 20%, 40%, 60%, 80% and 100% BT content.

Table (2): The composition and the wave number of IR absorption peak in composite. x% BT

ν1

I1

ν2

I2

ν3

I3

ν4

I4

0

580

23.9

418

33.7

220

17.6

-

-

20

565

3.3

409

3.3

-

-

-

-

40

578

4.3

402

3.3

220

9.8

478

6.9

60

578

4.6

402

3.3

200

22

488

10

80

544

4.6

397

3.3

-

-

-

-

100

552

3.2

433

3.5

-

-

-

-

The brooding of the spectral band is due to the population and distribution of cation at A and B sites. The variation of frequency bands ν 1 and ν 2 for different samples may be due to the change in the lattice constant with increase BT content leading to the change of the bond length and bending force. Since the frequencies is proportional to the force constant as in Table (3) and given by equation (9):

118

F = 4π2c2ν 2 µ

(4)

where c: is the light velocity, ν : is the frequency band and µ: is the reduced mass. The force constant for both tetrahedral and octahedral decrease by increasing BT content due to the decrease of frequencies bands. The decrease in the bond angle Fe-O-Fe results in a weaker overlap of Fe-3d electron and O-2p sub shell and hence small negative charge present on the oxygen atoms, which reduced the oxygen energy level. This means that the electronic distribution of Fe-O bond is greatly affected with BT addition, which affects the ratio dµ/dr (the rate of a change of a dipole moment of the bond Fe-O) (10). In conclusion BT affect the inter molecular character of the ferrite.

Table (3): The force constant, the ratio dµ/dr and the brooding of the spectral bands. x% BT

Ft

Fo

(dµ/dr)A

(dµ/dr)B

ГA

ГB

0

2.47*105

1.28*105

4.704*10-11

5.586*10-11

0.0142

0.0139

20

2.344*105 1.228*105

1.748*10-11

1.748*10-11

0.0128

0.0121

40

2.453*105

1.119*105

1.995*10-11

1.747*10-11

0.0109

0.0137

60

2.453*105

1.186*105

2.064*10-11

1.721*10-11

0.0137

0.0111

80

2.17*105

1.547*105

2.037*10-11

1.009*10-11

0.0066

0.0084

100

2.237*105

1.377*105

1.721*10-11

1.009*10-11

3.3. The Electron Spin Resonance (ESR) Spectra For the Composite (Ni0.8Zn0.2Fe2O4 – BaTiO3) The first derivative ESR spectra of of a given samples (NZF + BT) are shown in Fig (6), as a derivative RF power absorbed by the sample with respect to the static field. The first derivatives dP/dB (rate of absorbed powers for samples 0% and 20% BT content are the same as the spectra of the reference material (DPPH). The spectra are reversed for sample 60% and 80% BT content. The dependence of ESR line shape on the porosity has been studied (11) in that work. The ESR line shape for samples with small porosity observed to fit to lorentzion expression. This has been explained on the basis of the magnetic resonance theory developed by KUPO (12). In the present work ESR spectra of NZF- BT was recorded at room temperature. The porosity of our samples ranged from 34-45%. This suggests that the spectrum of the measured sample doesn’t obey to lorentzat shape.

119

x=80%

x=60%

x=40%

x=20%

x=0%

Fig (6): The Electron Spin Resonance (ESR) Spectra for the Composite ((1-x) Ni0.8Zn0.2Fe2O4- x BaTiO3) where x= 0%, 20%, 40%, 60%, 80% and 100% BT content. The spectra of the sample 40% BT content has two peaks, which suggest the presence of hyperfine interaction between the two phases piezomagnetic and piezoelectric phase. Figure (7) shows the relation between the resonance fields Br as a function of BT content. The value of Br increase by increasing BT content. The factors that affect Br are anisotropy, porosity, homogenous demagnetization, saturation magnetization and internal field (13, 14). The increase of the resonance frequencies may be due to the decrease of the internal field by increasing BT content and also due to the decrease of porosity. The energy between two adjacent degenerate spin energy levels ∆u has been calculated from the equation ∆u = gBµB. The value of ∆Bpp were deduced from the ESR spectra (the peak to peak value), was found to decrease by increasing BT content from 430-250 G, as shown in Table (4). The reduction of ∆B may cause reduction in separate in energy ∆u as given in Table (4).

120 4000

3500

Br (G)

3000

2500

2000

1500

1000 0

20

40

60

x%

80

100

Fig (7): The relation between the resonance fields Br as a function of BT content.

Table (4): Shows the resonance fields Br, g factor, ∆Bpp ∆u and the relaxation time τ. x% BT

Br (G)

g

∆Bpp

τ (sec)

∆u (J)

0

1500

4.473

430

6.603*10-15

6.217*10-24

20

2830

2.371

200

2.678*10-14

6.222*10-24

40

3550

1.890

280

2.4*10-14

6.2221*10-24

60

3820

1.757

350

2.006*10-14

6.22*10-24

80

3830

1.752

250

2.9*10-14

6.21*10-24

The spin lattice relaxation process is characterized by a time constant which is a function of static magnetic field and depends on the rate at which microwave energy can be observed. The spin-spin relaxation time t, which arises from the influence of one magnetic on another limits the broodening of the line width. In our sample spin relaxation time decrease by increasing BT content leading to the change of the ∆Bpp. The relaxation time is given by equation (15):

τ=

2(1.1 × 10 −11 ) g∆β pp 3

(5)

121

The Lande g factor equals 2.0023 for an isolated free electron and has different values in solid environment. The ESR data for our samples have slightly g value smaller than the free electron with g value 1.8 and 1.7 for samples 40%, 60%, 80% BT content and higher value of g factor for 0%, and 20% BT content.

3.4. Dielectric Constant for the Composite (Ni0.8Zn0.2Fe2O4 – BaTiO3) The temperature dependence of dielectric constant for NZF- BT composite is shown in Fig (8). It is observed that the dielectric constant (ε) is independent of temperature up to 600 K for all samples. Above 600 K it rapidly increase with increasing temperature and have a peak nearly at 700 K for the first sample NZF and 20% BT content. The pure piezoelectric phase sample have a maximum at nearly 400 K which is attributed the structure phase transition of BaTiO3 from tetragonal to cubic. The transition temperature for BaTiO3 decrease from 120 °C to 50 °C for the sample contains 20% NZF and disappears completely for other samples which may be shifted below the room temperature. This proves that Ni ferrite can lead to strong shift of the phase transition temperature of BaTiO3. This phenomenon is very important in application of this composite material in capacitance ceramic industry. Similar phenomena in Ni doped SrBNb2O6 have been reported (16). With the increase of ferrite phase concentration the conduction contribution of NZF phase to ε becomes more and more significant. For the samples where the ratio NZF 40%, 60%, 80% and 100%, the peak can hardly be observed and the apparent ε increase sharply with increasing temperature. Since the structure transition temperature of BaTiO3 shifts to low temperature the piezoelectric properties decrease correspondingly. The mechanism of conduction is the same as the polarization mechanism of ceramics. Several works have discussed conduction phenomena in ferrite by using polaron hopping model. There are two types of polarons: large and small polaron. In large polaron model the conductivity decrease with frequency at higher temperature, the conduction is by similarly activated hopping mechanism which leaded to similarly activated dielectric constant. The dielectric constant of the composite samples increases by increasing BaTiO3 content and the value of ε for BT phase have highest value at room temperature as shown in Fig (9). The apparent increase of dielectric constant at higher temperature is due to thermally activation of conductivity mechanisms at this temperature range causing high dielectric loss. There is common behavior found by different authors in similar system and is main problem to be solved to achieve good belong and high ME response (17, 18, 19, 20, 16). The problem is attributed to the space charge effect, Maxwell-Wagner relaxation at the interface of the ferroelectric – magnetic phases or even to other dejects mechanisms. This appears at low frequencies and high temperature. The dielectric constant of material composed of for contributions ionic, electron orientation and space charge polarization. The space charges depend on the impurity and imperfection of the material. The increase of dielectric constant with temperature may be due to space charge polarization from lattice defects. For electronic and ionic polarization the frequency effect is neglicable at frequencies above 1011 MHz where as the effect of temperature on electronic and ionic polarization is considered. At low frequencies as in our case 1 KHz a rise in dielectric constant occurs at high temperature due to the effect of space charge resulting from the increase of charge carrier in the paramagnetic region.

122

30000

14000

x=0% BT

25000

x=20% BT

12000

10000

20000

ε

8000

ε

15000

6000

10000

4000 5000

2000

0 300

0 300

400

500

600

700

800

900

400

500

600

Tk

700

800

900

Tk

18000

10000

16000

x=60% BT

x=40% BT 8000

14000 12000

ε

6000

10000

ε

8000 4000 6000 4000

2000

2000 0

0 300

400

500

600

700

800

900

300

400

500

600

700

800

900

Tk

Tk 6000

1200

x=100% BT

x=80% BT

5000

1000

4000

800

ε

3000

ε

600

2000

400

1000

200 0 300

400

500

600

700

800

900

0 300

350

400

450

500

550

Tk

Tk

Fig (8): The dielectric constant (ε) as a function of temperature for the Composite ((1-x) Ni0.8Zn0.2Fe2O4- x BaTiO3) where x = 0%, 20%, 40%, 60%, 80% and 100% BT content.

220 200 180 160 140

ε

120 100 80 60 40 20 0 0

20

40

60

80

100

120

x%BT

Fig (9): The dielectric constant of the composite (Ni0.8Zn0.2Fe2O4 – BaTiO3) at room temperature.

123

3.5. Dielectric Loss (tanδ) for the Composite (Ni0.8Zn0.2Fe2O4 – BaTiO3) The dielectric loss (tan δ) as a function of temperature at different BT content is shown in Fig (10). This figure show that the dissipation factor decrease by increasing BT content and have a peak around 500-550 K which may be referred to the magnetic order phase transition. Below the peak temperature tan δ increase because the hopping rates of electrons between Fe+3-Fe+2 increase with raising temperature. At the peak value the frequency of hopping is equal to the frequency of Ac field. 250

100

x=0% BT

x=20% BT 200

80 150

100

tan δ

tan δ

60

40

50 20 0

0 300

400

500

600

700

800

300

900

400

500

600

700

800

900

Tk

Tk 80

18

x=40% BT

16

60

x=60% BT

14 12

40

tan δ

tan δ

10 8 6

20

4 2

0

0

300

400

500

600

700

800

300

900

400

500

600

10

700

800

900

Tk

Tk 0.18

x=80% BT

8

x=100% BT

0.16 0.14

6

tan δ

tan δ

0.12

4

2

0.10 0.08 0.06

0

0.04 300

400

500

600

Tk

700

800

900

0.02 300

350

400

450

500

550

Tk

Fig (10): The dielectric loss (tan δ) as a function of temperature for the Composite ((1-x)

Ni0.8Zn0.2Fe2O4- x BaTiO3) where x = 0%, 20%, 40%, 60%, 80% and 100% BT content.

124

References 1. L. Mitoseriu, I. Pallecchi, V. Buscaglia, A. Testino, C. E. Ciomaga, A. Stancu , J. Magnetism and Magnetic Materials. 316 (2007) e603-606. 2. S. A. Lokare, R. S. Deven, D. R. Patil, Y. D. KoleKar, K. K. Patankar, B. K. Chougule, J Mater Sci. 42 (2007) e10250-10253. 3. Shmid, H., Multi-ferroic magnetoelectrics. Ferroelectrics. 162 (1994) e317-338 4 Wood, V.E. and Austin, A. E, In Magnetoelectric interaction phenomena in crystal, ed. A. J. Freeman and H. Schmid. Gorden Breach, 1975. 5. Culity, Element of x-ray of differaction. 2nd edition, Addison Wesley Publishing Co. USA, (1959). P 329. 6. L. Mitoseriu, V. Buscaglia, M. Viviani, M. T. Buscaglia, I. Pallecchi, C. Harnagea, A. Testino. V. Trefiletti, P. Nanni, A. S. Siri, J. of the European Ceramic Society 27 (2007) 4379-4382. 7. D. Rodic, M. Mitiric, R. Tellgren, H. Rundlof, J. Magn. Mag. Mater. 232 (2001) 1-8. 8. C. C. Yang, Y. J. Gung, W. C. Hung, T. H. Ting, K. H. Wub, Composites Science and Technology 70 (2010) 466–471. 9. O. M. Hemda, J. Magn. Mag. Mater. 251(2002) 50-60. 10. J. C. Dwcrus, O. G. Maln and A. W. Thomson, Proc- Roy. Soc. A, (1963) 275,295. 11. A. K. Srivastova, M. J. Patni, J. Appl. Phys. 81 (4) (1997) 1863. 12. R. Kubo, Fluctuation, in Ter Tlaar (Ed.), Relaxation and Resonance in Magnetic Systems, O;ive and Boyed, London, (1992), pp. 23-38. 13. M. Sparks, J. Appl. Phys. 36 (1963) 1570. 14. G. Srivastova, M. Patni, N. J. Nandikar, J. Phys. 38 (1977) 267. 15. J. Blakemore, Solid State Physics, Second Edition, Cambridge University, Cambridge, 1985. 16. Qi, X., Zhou, J., Yue, Z., Gui, Z., Li, L. and Buddhudu, S Adv. Funct. Mater., 9 (2004) 920– 926. 17. Zhu, W.M. andYe, Z.G. Ceram. Int., 30 (2004), 1435–1442. 18. Vanden Boomgaard, J. and Born, R. A. J., O. J. Mater. Sci., 13 (1978), 1538–1548. 19. Lupeiko, T.G., Lisnevskaya, I.V., Chkheidze, M.D. and Zvyagintsev, B.I., Inorg. Mater., 31 (1995), 1139–1142. 20. Yu, Z. and Ang, C., O. J. Appl. Phys., 91 (2002, 794–797.

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ON THE ELECTRICAL CONDUCTIVITY OF POLY(VINYLCHLORIDE) / POLY(ETHYLENE OXIDE) BLENDS G. M. NASR, S. M. ABD EL-WAHAB and A. ABD EL-ATHEM Physics Department, Faculty of Science, Cairo University, Egypt

Physical blending of different polymers is a very popular, simple and economical method of preparing composite with desirable and useful properties. The electrical conductivity of blends of amorphous poly(vinyl chloride) (PVC) with semicrystalline poly(ethylene oxide) (PEO) in the form of thin films has been measured by studying the I-V characteristics at room temperature and temperature dependence of the sample conductivity. The results are presented in the form of I-V characteristics and analysis has been made by interpretation of Poole Frenkel, Fowler-Nordheim and Schottky- Richardson plots. The analysis of these results suggests that Schottky - Richardson mechanism are primarily responsible for the observed conduction. Meanwhile, the percolation concentration of PEO in PVC matrix was found to be round 10%. Furthermore, the mechanism of electrical transport in this system is examined in temperature range 300350K. The temperature dependence of conductivity gives evidence for the charge carriers transport mechanism via the occurred agreement of experimental results with the employed hopping models. Keywords: PVC/PEO blends; Conduction mechanism; dc conductivity; Mott’s 3D-VRH.

1. Introduction In recent decades, a great deal of interest has been focused on studying the electrical conduction of the polymer blends. The importance of a polymeric blend is now well established for both fundamental and practical studies [1–3] since blending has proved to be an important process for developing industrial applications of polymeric materials. Blending semi-crystalline polymer with amorphous polymer seems to be an interesting way of preparing polymeric blends since the compatibility among constituents has remarkable influence on thermal, mechanical, and electrical properties of polymer blends. The intermolecular interaction among the constituents of polymeric molecules regulates the compatibility [4, 5]. The properties of blends also strongly depend on the methods and conditions of their preparation; entanglement, and crystallinity, the specific interactions between macrochains, the sample morphology and the molecular weight and its distribution [6]. Polyethylene oxide (PEO) is semicrystaline polymer having many applications in medical and food industry [7]. Polyvinyl chloride (PVC) is amorphous polymer having many valuable properties like low price, good processability, desirable mechanical strength, transparency, heat resistance [8]. Different blends of PVC [9-11] and PEO [12-14] were extensively studied in the past two decades. The structure of these blends was described on the basis of the results obtained from various experimental techniques such as absorption spectroscopy, microscopy or atomic force microscopy (AFM), and differential scanning calorimetry (DSC) [15]. Recently it was found that PVC is miscible with PEO [16-18]. This miscibility was explained on the basis of specific interactions between the proton- acceptor PEO and proton- donor PVC. It was also proved that PVC does not influence the crystallization rate of PEO [16]. Moreover, Kaczmarek et al [15] found that the PVC/PEO blends have an appreciable resistance to photo-oxidative degradation from that in pure components. Electrical properties constitute one of the most convenient and sensitive methods for studying the polymer structure [19]. The purpose of this work is to study current- voltage characteristic of sample prepared from PVC/PEO blends to identify the nature of conduction behavior (the charge carrier origin). We also studied the PEO content dependence of conductivity at room temperature (percolation theory) and finally measured the conductivitytemperature characteristic to know the electronic transport mechanism (variable range hopping). 2. Experimental 2.1. Sample preparation The films of polymer blend were prepared by the solution-cast technique. The host materials Polyvinylchloride (PVC) was supplied by Fluka, while polyethylene oxide (PEO) was obtained from Sigma-Aldrich. The required amounts of PVC

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

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and PEO were dissolved separately in a mixture of 1,2-dichlorobenzene and tetrahydrofuran (1:1v/v), obtained from Riedel-de Haen, then mixed together and stirred. The solutions thus obtained were cast on a glass plate and allowed to evaporate slowly inside a desiccator. Samples were prepared with concentration 0, 10, 25, 30 and 50 wt % of PEO (CF Table 1). Table 1. Represent the blend composition in weight and volume fraction.

PEO% Content

Concentration(PEO)

Volume Fraction

0

0

0

10

0.1

0.12

25

0.25

0.29

30

0.3

0.35

50

0.5

0.56

2.2. Electric coating The electrode coating on the film of measured thickness was done by using quick drying and highly conducting silver paste. A mask of a circular aperture of 1cm diameter was used while coating, to ensure uniform size of coated silver electrode. 2.3. Electrical measurement The sample film with silver electrodes was arranged in sandwich type configuration (metal-insulator-metal) between two brass electrodes of the sample holder which was placed in the electric oven. The electrical measurements were carried at different temperatures ranging from 300K to 350K. The regulated power supply was used as the voltage source, while the current was recorded using Kiethly electrometer. 3. Results and Discussion 3.1. Current (I)–voltage (V) characteristics Figure 1 shows I versus V plots of PVC/PEO blends at constant temperature 300K. The current increases nonlinearly with the applied voltage for most samples and does not follow a power law, I = KVm where K and m are constants. The possibility of Ohmic conductions as well as space charge limited conduction is ruled out from the observed behavior of I - V characteristics. This is evident from the fact that Ohm’s law follows from the free electron model of a metal. In present case the constituents of blends are itself insulators and blends almost amorphous, giving wide scope for irregularities in the structure and so ruling out Ohmic conduction. In most polymeric materials it is very difficult to observe any electronic conductivity at all and what conductivity there is, usually depends upon movement of adventitious ions. Naturally with so feeble a charge carrier density, space charge limited conduction seems a remote possibility [20].

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Fig. 1. Represents the I-V characteristic curves (log-log scale) of PEO/PVC blends at room temperature.

3.2. Conduction mechanism A complex conduction behavior in organic solid has been explained usually in terms of the electron liberation from traps in the bulk of the material i.e. Poole–Frenkel [22], or possibility of tunneling i.e. Fowler–Nordheim [23] or electron emission from cathode i.e. Schottky–Richardson mechanism [24]. Let us now discuss analytically the probable mechanism of conduction following Deshmukh et al. method [20, 21]. 3.2.1. Poole–Frenkel mechanism The current–voltage relationship for Poole–Frenkel mechanism is expressed as 1   −ϕ + β PT E 2  J = A exp   k BT 

(1)

1

where

2 e  e  β PT =  = constant  k B T  πε ε o d 

where A is a constant, T is ambient temperature in Kelvin, kB is Boltzman’s constant, εo is permittivity of space, ε is the dielectric constant of the sample and e is the electronic charge. The Poole–Frenkel mechanism predicts a field dependent conductivity as β E 2  σ = σ 0 exp  PT  .  2k B T  1

β E 2  ln σ = ln σ 0 +  P F   2 k B T 

(2)

1

or

(3)

The Poole–Frenkel mechanism is characterized by the linearity of ln σ versus E1/2 plots with a positive slope as predicted by Eq. (3).

128

Fig. 2. Represents the Poole–Frenkel plots for all PEO/PVC blended samples.

From the Poole-Frenkle plots in Fig. 2, the mechanism does not contribute significantly to the conduction as lnσ does not show appreciable dependence on E1/2 axis, indicating the absence of Poole–Frenkel mechanism for all blended samples except PVC samples loaded with 50% PEO.

3.2.2. Fowler–Nordheim mechanism The Fowler–Nordheim relation for current density is given as

 −ϕ  J = AV 2 exp   V 

(4)

 J  ϕ  ln  2  = ln A −   V   V

(5)

So that,

The Fowler–Nordheim mechanism is characterized by the linearity of the ln (J/V2) versus 1000/V plot with a negative slope as predicted by Eq. (5).

Fig. 3. Represents the Fowler–Nordheim plots for all PEO/PVC blended samples.

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In the present case, the ln (J/V2) versus 1000/V plots for the sample are presented in Fig. 3, which are nearly straight lines with a positive slope for higher as well as lower values of V, indicating the absence of tunneling current for all samples as suggested by Fowler–Nordheim relation. 3.2.3. Schottky mechanism The Schottky–Richordson current–voltage relationship is given by 1   −ϕ J = AT 2 exp  s + β Rs E 2   k BT 

(6)

βRS being the field lowering constant given by 1

2 e  e  β RS =   k B T  4πε ε o d 

(7)

and hence

ln J = ln A T 2 -

ϕ k BT

1

+ β RS E 2

(8)

and ln J versus E1/2 plots should be a straight line with a positive slope. Schottky plots as shown in Fig. 4, are straight lines with positive slope indicating the applicability of the mechanism for all PVC/PEO blends except PVC sample loaded with 50% PEO.

Fig. 4. Represents the Schottky plots for all PEO/PVC blended samples.

3.3. Electrical conductivity 3.3.1. Concentration dependence Figure 5 shows the dc conductivity (σdc) versus concentration of PEO, at a constant temperature of T = 300 K. The percolation threshold is visible, at a critical concentration Pc where the conductivity beings to increase abruptly [25]. The electrical conductivities are negligible up to critical concentration and are several orders of magnitude larger at higher concentrations, indicating the existence of a percolating path via connecting PEO particles.

130

Fig. 5. Variation of conductivity as a function of PEO content.

To apply the percolation concept to the binary disorder system, Zallen [26] used the notation of the critical volume fraction ϕc such that:

ϕ c = f Pc

(9)

where f is the filling factor (packing fraction) and Pc is the concentration of the conducting element at which σ shows a sharp increase (percolation threshold). In our results the volume fraction of PEO at which σ shows a sharp increase is 0.12 (corresponds to 10%). Moreover, according to Eq. (9), if we use f = 0.64. (spheres, random close packing) [27], this gives Pc ≈ 0.19 while, if we use f = 0.78 (rods, uniaxial simple cubic) [27], this gives Pc ≈ 0.15. On the other hand, the exact Pc which corresponds to 10% as estimated from Table (1) is 0.1. This means that the filling factor of PEO is 0.78. So, PEO particles were arranged in rods, uniaxial simple cubic. Kirkpatrick [28] showed that the scaling law of the percolation clusters is of the form

σ = σ o (p − p c )β

(10)

this law holds true in the range P ≥ Pc, where σ0 is constant, P is the concentration of the PEO, Pc is the percolation threshold and β is the exponent (accounts for the cluster size).The percolation theory shows that β does not exceed 3 [26]. In our case one finds that, there is a steep rise in conductivity as the concentration crosses Pc. Figure 5 shows the enhancement in conductivity above particular value of filler concentration. By fitting Eq. (10) in the experimental data, the percolation threshold (pc) and the critical exponent (β) were obtained as 10% (by weight) and 3, respectively Since the value of β accounts for the size of conductive particle cluster inside the polymer matrix, the size of these clusters (for PEO) is in accordance with the percolation theory β ≤ 3. This may be due to the occluded polymer PVC which act as a part of PEO rather than as a part of matrix [29, 30]. In the light of this result, one can conclude that the percolation concept holds true for PVC/PEO blends and PEO plays a role as conducive particles. However, according to the percolation concepts, the sharp increase in σ above the percolation threshold is mainly due to the formation of extended PEO cluster above the percolation threshold. 3.3.2. Temperature dependence Figure 6(a-d) shows the variation of measured dc conductivity (σdc) as functions of (a) 1000/T, (b) T-1/2, (c) T-1/3 and (d) T-1/4 in the temperature range 300-350K for all PVC/PEO samples. Conductivity was found to decrease with the decrease in the temperature (with different rate according to the PEO content) as it has been observed in many other conjugated polymers [31-33]. It is evident from Fig. 6a that the temperature dependence of σdc for all samples except pure PVC does not follow an Arrhenius- type of behavior. The nonlinear functional dependence indicates that these

131

samples show temperature-dependent activation energy. Two linear regions can be distinguished in this Figure, which separately fit into the Arrhenius equation



Ea   k BT 

σ = σ o exp  −

(11)

where σ is the electrical conductivity, σo is the pre-exponential factor and is the activation energy. By calculating the activation energy for all samples at two regions (low and high temperature) and listed the results in the Table 2. One can notice that the values of activation energy decrease with increasing temperature for most samples and decrease with increasing PEO content at higher temperature up to 30% and begin to increase upon further PEO loading. The dc conductivity data indicates that the charge transport seems to occur by phonon assisted hopping or thermally activated jumps between localized states [34]. The general form of the temperature dependent conductivity in the VRH process is given by

  To  n      T  

σ = σ o exp  − 

(12)

where the exponent n=1/((d+1), where d is the dimensionality. The values of d = 1, 2, 3 signify the one-dimensional, two-dimensional and three-dimensional Mott’s VRH. A plot of log σdc versus (T-1)n should give a straight line for proper value of n. This is shown in Fig. 6(b-d) for T-1/2, T-1/3 and T-1/4 at higher temperature. The Fig. 6(d) demonstrates

Fig. 6. Plots of log σdc as function of (a) 1000/T, (b) T-1/2 , (c) T-1/3, (d) T-1/4.

132 Table 2. Represent the variation of activation energy with different concentration of PEO for high and low temperature regions.

PEO% content

Ea (eV) (low temperature region)

Ea (eV) (high temperature region)

0

1.221

1.221

10

1.978

0.642

25

0.592

0.372

30

2.666

0.025

50

1.892

0.126

that the log σdc versus T-1/4 plot, corresponding to the 3D-VRH transport as suggested by Mott[35], gives most linear behavior according to linearity fit factor (FF) for all samples. Therefore, it is illustrated that the Mott’s 3D-VRH mechanism of T-1/4 type seems to be more appropriate for explaining the mechanism of dc conduction in PVC/PEO blends, accordingly different Mott’s parameters could be evaluated by using the coming equation

To =

λα 3

(13)

k B N ( EF )

and

σ o = e 2 R 2 µ ph N ( EF )

where

 4 9 R=  8πα k BTN ( EF ) 

(14) 1

(15)

Here To is the characteristic temperature, σo is the conductivity at infinite temperature, R is the average hopping distance between the two sites, λ is the dimensionless constant and is assumed to have a value 18.1[31, 36], N(EF) is the density of states at the Fermi level, (α=1/rp) is the coefficient of exponential decay of the localized states involved in the hopping process and µ Ph is the phonon frequency ( 1013Hz). The average hopping energy Whop is given by

Whop =

3 4π R3 N ( EF )

(16)

The values of different Mott’s parameters, such as characteristic temperature (T0), density of states at the Fermi level [N(EF)], average hopping distance R, average hopping energy(Whop) for all sample have been computed o by assuming the electron wave function localization length α-1(rp)=3 A [37] and using Eqs. (13–16) and the results are given in Table 3. Table 3. Represent the Mott’s parameters of different concentration of PEO.

PEO% content 0 10 25 30 50

To(K) 1.63x1011 2.26x1010 2.13x109 3.93x104 3.6x107

N(EF) (cm-3eV-1) 4.79x1016 3.44x1017 3.67x1018 1.98x1023 2.17x1020

R(nm) 17.2 10.5 5.8 0.38 2.1

Whop(eV) 0.985 0.601 0.333 0.022 0.12

αR 57.24 34.96 19.35 1.27 6.98

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From Table 3 the larger To implies larger R (hopping distance) and larger energies for a hop. As PEO content increases To decreases and hopping distance decreases so conductivity increases. These results are consistent with the Mott’s requirement that α R ≫ 1 and Whop ≫ k B T for hopping to occur at distant sites [34]. The values of Mott’s parameters (Table 3) suggest that the Mott’s 3D-VRH mechanism is appropriate in explaining the change transport in PVC/PEO blends.

Conclusion After studying electrical conduction through blends under various existing mechanisms, it is observed that in the present case, the behavior can be described by Schottky–Richardson mechanism for all blends except 50% PEO that described by Poole- Frenkel. Increasing the PEO polymer phase, the electrical conductivity increases appreciably after a percolation threshold of 10% so, PEO enhances the electrical conductivity of the PVC. The temperature dependent conductivity of blends indicated that the main contribution to the conductivity came from the carriers that hop via variable-range hopping. Three-dimensional (3D) VRH was observed in the high temperature for all samples.

Acknowledgments The authors wish to acknowledge Prof. H.M. Osman, Physics department, Cairo University, for the support and encouragement to carry out this research work

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CONDUCTIVITY ENHANCEMENT OF Mn Zn FERRITE BY GAMMA IRRADIATION M. A. AHMED Physics Department, Faculty of Science, Cairo University, Giza, Egypt A. M. DIAB Alshorouk Academy, Physics and Mathematic Department, Alshorouk City, Cairo, Egypt S. F. MANSOUR Materials Science Lab (1), Physics Department, Faculty of Science, Zagazig University, Egypt

A series of the ferrite system Mn1-xZnxFe2O4 (x = 0.0, 0.05, 0.1, 0.15, and 2.0) were prepared by the standard ceramic method. The X-ray diffraction patterns confirmed the formation of single phase cubic structure and shows also that the lattice constant decreases with increasing Zn content. The effect of Zn+2 ion concentration on the structural and the electrical properties of the investigated samples are studied. The most important result of γ-irradiation on the electrical properties is the variation of change ratio Fe2+ ↔ Fe3 +e- on the octahedral site leading to an increase in the conductivity as well as the dielectric constant.

1. Introduction Much attention has been paid to microwave absorbing materials due to their unique absorbing microwave energy and promising applications in the stealth technology of aircraft, television image interference of high-rise buildings, and microwave dark-room and protection [1]. Extensive studies have been carried out to develop new microwave absorbing materials with a high magnetic and electric loss [2–4]. Mn-Zn ferrites consider an important category of ceramic magnetic materials with a wide technological applications, in devices that in the broadest sense can be characterized as transformers, inductors or absorbers [5]. Polycrystalline Mn-Zn ferrites have been used widely in high frequency devices such as transformers and magnetic heads. Recently, the dimensions of the electronic devices have been reduced, and simultaneously the driving frequency of switching power supplies have been raised to IMHz range, in which the power loss drastically increases [6]. The suppression of the power loss is an important problem in the case that the ferrite is utilized for high-frequency devices.

Several investigators have studied the magnetic and electrical properties of Mn-Zn ferrite [7-9]. In the samples under investigation the effect of Gamma radiation (γ) and Zn ions content on densification, lattice constant, magnetization and electrical properties were studied. Gamma radiation, is an electromagnetic radiation of high frequency above 1019 Hz and therefore have energies above100keVand wave length less than 10 picometers, often smaller than that of atom Gamma radioactive decay photons commonly have energies of a few hundred keV, and are almost always less than 10 MeV in energy. Because they are a form of ionizing radiation, gamma rays can cause serious damage when absorbed by living tissue, and are therefore a health hazard. X-rays and gamma rays differ only in their source of origin. X-rays are produced by an X-ray generator and gamma radiation is the product of radioactive atoms. They are both part of the electromagnetic spectrum. 2. Experimental Techniques Polycrystalline ferrites of the formula Mn1xZnxFe2O4 (x = 0.0, 0.05, 0.1, 0.15, and 2.0) were prepared by the standard ceramic

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

136

(311)

to be in good agreement with those obtained by ICDD card No. (74-2403) for MnFe2O4. Figure (1b) shows the variation of the lattice parameter, a, with the zinc content (x). The results show that the lattice parameter decreases with increasing Zn content. The decrease of the lattice parameter can be attributed to the ionic radii of the ions. The value of lattice parameter for MnFe2O4 was found to be 0.848 nm which is in good agreement with that obtained by ICDD card where a = 0.851 nm. The X-ray densities were calculated using relation dx = 8M/Na3

(511)

(400)

(220) (210)

(533)

(440)

Intensity

x=0.2

10

20

30

40

50

60

70

80

2θ

0.8500 5.06

(b)

(c)

0.8496

Dx (g/cm3)

5.04

0.8492

3. Results and Discussion 3.1.

0.8484

Figure (1a) shows the X-ray diffraction patterns for the samples Mn1-xZnxFe2O4 before irradiation. The patterns show single phase of cubic spinel ferrites. The results of crystal structure of the sample with x = 0.0 were found

x=0.1

x=0.15

0.8488

X-ray Diffraction pattern

(a) x=0.0

x=0.05

a (nm)

technique. In this method, highly pure oxides (BDH) were mixed together manually for three hours and then transferred to an electric grinding machine for another four hours. The mixtures were presintered at 800°C for 5 hours in air. Each mixture was ground again for 3 hours more and pressed into pellet shape using uniaxial press. The discs were sintered at 1300°C in air for 5 hours and cooled to room temperature using rate of cooling 4°C/min which is equal to that of heating. A disc from each sample was ground in order to get fine powders for X-ray measurements using difrractometer with radiation source Cu–Kα (λ = 1.5405Å). The dc molar magnetic susceptibility (χM) of the investigated samples was measured using Faraday’s method as a function of temperature and magnetic field intensities of 1340, 1660, and 1990 Oe. The accuracy of measuring temperature in the magnetic susceptibility measurements was ±1°C where the data were reproducible Mn Zn ferrite pellets were exposed to γ -rays at different doses (5Gray and 50kGray) at the Technological Research Center of radiation (Nasr city, Cairo). All measurements were performed before as well as after irradiation. The RLC Bridge (Hioki model 3530 Japan) was used to measure the ac electrical resistivity of the investigated samples. The dielectric constant (ε'), dielectric loss factor (ε'') and, tanδ for the samples were measured from room temperature up to 800 K at different frequencies ranging from 600 kHz to 5000 kHz. The temperature of the sample was measured using copper constantan thermocouple connected to Digi-sense thermometer (USA) with junction in contact with the sample. The accuracy of measuring temperature was also better than ±1°C.

5.02

5.00

4.98

0.00

0.05

0.10

Zncontent

0.15

0.20 0.00

0.05

0.10

0.15

0.20

Zncontent

Fig. (1a-c): (a) X-ray diffraction patterns of Mn1-xZnxFe2O4 for 0.0≤x≤0.2. (b) The relation between the lattice parameter (a) and Zn content(x) (c) The dependence of x-ray density on Zn content(x).

137

for all Zn contents was obtained but with different values of both magnetization ( and the Curie point (TC) accept the sample (x=0.2). The trend of magnetization  vs T gives typical ferromagnetic character where  decreases gradually with a small rate after which a rapid fall is observed just before the Curie temperature for the Zn content of x ≤ 0.15. For higher zinc content x = 0.2 the magnetization falls rapidly. As the zinc content increases, the Curie temperature increases. Verma et al. [10] have found greater number of polarizable Fe2+ ions in ferrites doped with Zn+2, so the ratio Fe2+/Fe3+ increases then the A – B exchange interaction increases as well as Tc as shown in Fig. (2: f).

3.2. Electrical properties

Fig. (2a-e): Dependence of magnetization on absolute temperature. Fig. (2: g): The relation between the Curie temperature (TC) and Zn content(x).

Where M is the molecular weight of the sample, N is the Avogadro’s number and (a) is the lattice constant. It is shown from Fig. (1c) that X-ray density increases with the increase of Zn+2 ion content. This can be ascribed to the atomic weight and density of Zn+2 (65.38, 7.14 gm cm-3) respectively which are higher than that of Mn+2 (54.93, 5.95 gm cm-3). The particle size was estimated from the X-ray diffraction patterns using Scherer’s equation [9]. Figure (2: a-e) illustrates the dependence of the magnetization on the absolute temperature at different magnetic field intensities. Same trend

Figure (3: a-d) correlates mthe variation of the d ielectr ic co nstant ε / with the ab so lute temperature at different applied frequencies of (100 kHz -3 MHz) for the unirradiated and irradiated Mn1-xZnxFe2O4 (x=0.0 and 2.0) with dose of 50 kGry. The figure shows clearly that ε/ is increases with increase temperature up to curie temperature Tc and starts to decrease for unirradiated samples but for irradiated samples ε/ is increased slowly with increasing temperature up to T ≈ 500 K followed by a large increase. This is due to the following: the small thermal energy given to the system is not sufficient enough to free the localized dipoles, in this region, ε// is nearly temperature independent which means that the electronic polarization is the most predominant one. In the second region of temperature ε// is increased for all samples but with different rates depending on Zn concentration. This increase is due to electron hopping between the ferrous and ferric ions on the octahedral sites. This electron hopping causes local displacement in the external field direction, producing change of polarization as well as of ε/ [11]. The sample with x = 0.1 has the largest value of dielectric constant due to the presence of very small percent of Mn3+ ions which may encourage the double exchange interaction and finally may take part in the following reaction

138

Fig. (4a-d): Temperature dependence of dielectric loss for x=0.0 and 0.2.

Fig. (3a-d): Temperature dependence of dielectric constant for x=0.0 and 0.2.

creating Fe2+ ions: Mn3+ + Fe3+ → Fe2+ + Mn4+. The presence of Fe2+ ions gives rise to an increase in the polarization as well as ε/. The decrease in ε// with increasing frequency is due to the fast alternation of the electric field accompanied with the applied frequency, where the alternation of the dipoles increases as well as the friction between them, generating a quantity of heat which increases the randomness of the dipoles. Figure (4: a-d) is a typical curves correlates the dielectric loss factor ε// // and the absolute temperature at different frequencies for (x= 0.0 and x=0.2) before and after gamma irradiation. From the figure it is clear that the dielectric loss factor ε// // has the same trend as dielectric constant ε/. /. However the increase of ε// with temperature is due to friction between the dipoles as mentioned above. Figure ( 5: a-d) shows the

Fig. (5a-d): Frequency dependence of dielectric constant for x=0.0 and 0.2.

frequency dependence of the dielectric constant at different temperatures for (x= 0.0 and x=0.2) for the unirradiated and irradiated samples. The samples revealed dispersion due to Maxwell–Wagner interfacial polarization [12, 13], which is in good agreement with Koops phenomenological theory [14]. The data shows that a dispersion of dielectric constant takes

139

place at lower frequency. A comparison of the dispersion curves for the samples with increasing Zn ion concentration shows that, the change in the dielectric constant at lower frequencies is larger than that at higher ones of the externally applied field. In other words the electronic exchange between ferrous and ferric ions can not follow the alternating field [15] and the orientational polarization stopped, leading to decrease in the dielectric constant ε/ ε approaching a constant value at high frequencies due to the space charge polarization only. Figure (6: a, b) shows the variation of the ac conductivity ln (σ)) and the reciprocal of absolute temperature at different frequencies for x=0.0. Increasing the temperature of the sample will help the trapped charges to be liberated and participate in the conduction process, with the result of increasing the conductivity. This increase could be related to the increase in the drift mobility of the thermally activated electrons according to the hopping conduction mechanism and not to thermally creation of the charge carriers. The valence exchange Fe2+ ↔ Fe3+ + e– is the main source of electron hopping in this process. The ac conductivity after irradiation is higher than the unirradiatied one this due to the following mechanism Fe+3 + γ = Fe+2 +e this interaction will lead to an increase in the ratio Fe3+/Fe2+ and in turn increase the hopping rate after irradiation consequently the electrical conductivity increases as shown in Fig. (6: a, b). At high temperature for irradiated sample (x= 0.0), a strange behaviour (as a metallic behaviour) has been seen at high temperature. According to this behaviour, the Matthiessen,s rule can be applied for the total resistivity (ρT) ( : ρT = ρo + ρp (T) where ρo represents the impurity defects and it is predominant in the low temperature. While ρp(T) represents the resistivity by phonon scattering, the larger the amplitude of vibration at high temperature the, the greater ρp, while ρo can be neglected. Also the observed bend or knee at TC is formed.

The Ac conductivity of the samples at room temperature was found to vary from 6.8×10-5 to 51×0-5 Ω-1m-1 with Zn concentration. The variation of conductivity is explained on the basis of actual location of cations in the spinel structure. Occurrence of ions in more than one valence states is caused by the preparation conditions, especially, the sintering temperature: Fe+2 ions in the lattice are created due to zinc loss during the sintering process. Loss of Zn results in cation vacancies and unsaturated oxygen ions. The excess electrons on oxygen then bond with the neighboring Fe3+ ions in the spinel lattice due to electrostatic interaction giving rise to Fe2+ ions. The overall charge balance is restored by oxygen loss from the sample. Formation of Fe2+ ions leads to deviations from ferrite stoichiometry. The number of Fe2+ ions depends on the amount of zinc lost from the sample on volatilization, which in turn is dependent on the sintering temperature of the ferrite. Higher the sintering temperature, greater is the possibility of Fe+2 formation. Creation of Fe2+ ions gives rise to electron hopping between the Fe2+ and Fe3+ ions.

Fig. (6): The effect of temperature on ac conductivity for x=0.0 for un irradiated and irradiated sample.

4. Composition Dependence The lower value of ε// for unirradiated samples than irradiated ones can be explained by the quantity of heat dissipated in the entire volume

140

of the sample and the aligned dipoles will be disturbed with the result of decreasing ε/. The higher value of dielectric loss factor ε// for irradiated samples is due to the heat accompanied by irradiation. 5. Conclusion Mn1-xZnxFe2O4 was prepared by the standard ceramic method. Structural analysis with XRD indicates the formation Mn Zn ferrite. It is found that as the Zinc concentration of the sample is increased, lattice parameter decrease but X-ray density and Curie temperature increases. The three parameters ε/, ε// and σ increases after irradiation and used for detecting the changes in the behavior of the compositions. References 1. Hong-Mei Xiao, Xian-Ming Liu, Shao-Yun Fu, Composites Science and Technology 66 (2006) 2003. 2. Ruan S, Xu B, Suo H, Wu F, Xiang S, Zhao M, J Magn Magn Mater 212 (2000) 175. 3. Babbar VK, Razdan A, Puri RA, Goel TC, J Appl Phys 87 (2000) 4362.

4. Verma A, Saxena AK, Dube DC, J Magn Magn Mater 263 (2003) 228. 5. V.T. Zaspalis, V. Tsakaloudi, M. Kolenbrander, J Magn Magn Mater 313 (2007) 29. 6. J. Smit and H.P.J. Wijn, Ferrites (Phillips Technical Libra?, Eindhoven. The Netherlands. 1959) 134. 7. Yimin Xuan, Qiang Li and Gang Yang, J Magn Magn Mater 312 issue 2 (2007) 464. 8. C.F. Zhang, X.C. Zhong, H.Y. Yu, Z.W. Liu, D.C. Zeng. Physica B 404 (2009) 2327. 9. I.M. Hamada, J Magn Magn Mater 271 (2004) 318. 10. A. Verma, A.K. Saxena, D.C. Dube, J. Mag. Mag. Mater 263 (2003) 228. 11. P. Vengopal Reddy, T.S. Rao, J Less Common Met 86 (1982) 255. 12. J.C. Maxwell, Electricity and Magnetism, Vol. 1 (1929), Oxford University Press, (Section 328). 13. K.W. Wagner, Ann Phys Leipzig 40 (1913) 817. 14. C.G. Koops, Phys Rev 83 (1951) 121. 15. K. Iwauchi, Jpn J Appl Phys 10 (1971) 1520.

141

EFFECT OF Y3+ CATION ON ELECTRICAL PROPERTIES OF Ni-Zn FERRITES L. M. SALAH† Physics Department, Faculty of Science, Cairo University, Giza, Egypt

Two groups of the ferrite samples of the general formula Ni0.5 Zn0.5YyFe2-iyO4; were prepared by double sintering ceramic method. The first group, i=1, 0.02 ≤ y ≤ 0.12 i.e. the Fe ion was partially substituted the Y ion. The second group; i=0, 0.02 ≤ y ≤ 0.08 i.e. the Y ion was added to the Ni0.5 Zn0.5Fe2O4. The influence of Y3+ ion on the electrical properties of the two groups of the investigated samples is studied. It is noticed that the ac conductivity (lnσ) are nearly constant for all Y3+ion concentration for the two groups. This result confirm the x-ray diffraction data and the calculated values of the cation distribution, where the process of dissolution of any ratio of yttrium in the cubic spinel lattice never occurs but exists outside the grain as aggregation and the non stoichiometeric system can redistribute itself to produce a single phase of cubic spinel under the suitable sintering process. The obtained results indicate that the ac conductivity of the investigated samples is controlled by hopping mechanism. The dielectric constant (ε/) as well as dielectric loss (tanδ ) change. The obtained result is discussed in view of Maxwell–Wagner process.

1. Introduction Many workers [1-4] studied the influence of Fe substitution by rare earth cations into the spinel structure of Ni-Zn ferrite. Their investigations showed an important modification of the basic electrical and magnetic properties. They attributed these modifications to the substitution of rare earth ion instead of iron in spinel structure. The solubility of yttrium ions on Ni-Zn ferrite was examined in a previous work [5]. From X-ray diffraction analysis it was noticed that the lattice parameters of cubic spinel are not functions of Y3+ ions concentration i.e. the process of dissolution of any ratio of yttrium in the lattice never occurs and the Y3+ ions are segregated on the grain boundaries [6]. However, the microstructure plays an important role in realizing many application-oriented ferrite properties [7]. The aim of the present work is the study the effect aggregation of Y3+ ion on the electrical properties of the Ni-Zn ferrite.

2. Experimental Procedure Two groups of Ni-Zn ferrite samples of the general formula; Ni0.5 Zn0.5YyFe2-iyO4, were prepared in polycrystalline form. The two groups were prepared by standard ceramic method using highly pure materials of NiO, ZnO, Fe2O3 and Y2O3.Weighted materials were mixed well in molar ratios and were ground to very fine powder for 4 hours. For each sample, the mixtures were pressed into pellet form. Presintering was carried out at 900 oC in air using Lenton furnace type UAF 16/5 (England) for 10 hours with heating rate of 4oC / min. The pellets are good polished and the two surfaces of each pellet are coated with silver paste and checked for a good conduction. The real part of the dielectric constant έ , dielectric loss (tanδ ) and ac conductivity σ were recorded at different temperatures as a function of frequency using RLC bridge model (HIOKI 3530 Japan). A computer controlled X-ray diffract meter (formally made by Diano USA) was used equipped with filtered Co K∝ radiation (λ=1.79026 Ǻ), for structural investigation and grain size determination. The scanning range was from 10-80° (2θ), step size 2θ = 0.1°, step time 1 sec. Winfit Program was used to fit the peak shape function and to use the refined parameters for the determination of crystallite size and internal residual microstrain by single line method [8]. The scanning electron microscope (JSM-T330) micrographs were taken with a suitable magnification depending on the samples.

†

Corresponding author. E-mail: [email protected], tel. 0020122714317 CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

142

3. Results and Discussion Table 1 shows the calculated crystallite size and microstrain of the two groups of the ferrite samples of the general formula Ni0.5 Zn0.5YyFe2-iyO4; The first group, i=1, 0.02 ≤ y ≤ 0.12 i.e. the Fe ion was partially substituted by the Y ion . This group has been designated as (substitution) sb group. The second group; i=0, 0.02 ≤ y ≤ 0.08 i.e. the Y ion was added to the Ni0.5 Zn0.5Fe2O4 in the ratios y which has been designated as (additive) ad group. Table 1. Calculated crystallite size and microstrain of sb and ad groups with Y3+ concentration. Y3+ concentration 0.02 0.04 0.06 0.08 0.10 0.12

(substitution) sb group crystallite size µm microstrain 1.323 0.00050 1.198 0.00087 0.650 0.00018 0.807 0.00012 0.751 0.00236 1.124 0.00093

(additive) ad group crystallite size µm microstrain 0.460 0.00101 0.751 0.00146 1.124 0.00081 0.612 0.00165

It is clear from Table 1 that the variation of particle size with the two methods or Y+3 ion concentration is random. The scanning electron micrographs of some investigated samples are given in Figure 1(a-d). As can be seen in Figure 1, the microstructure of the investigated samples are non-homogeneous and morphology present irregular grain sizes. So, it is important to exclude the little effect of Y+3 ion concentration on the grain size.

Figure 1. Scanning Electron photomicrographs of some investigated the samples the general formula Ni0.5 Zn0.5YyFe2-iyO4, (a) y=0.02 (ad group), (b) y=0.02 (sb group), (c) y=0.04 (ad group) (d) y=0.04 (sb group), (e) y=0.08 (sb group), (f) y=0.12 (sb group),

143

Figure 2. Behavior of the ac conductivity (ln σ) with the reciprocal of absolute temperature (1000/T) of all investigated samples in frequency range from 10kHz to 5MHz.

Figure 2 illustrates the behavior of the ac conductivity (ln σ) with the reciprocal of absolute temperature of all investigated samples in frequency range from 10kHz to 5MHz. From the figure, it is clear that, σ increases with increasing temperature, which is the normal character of semiconducting ferrite. The changes in the gradient of the straight line take place at the transition temperature( Curie temperature).This anomaly strongly supports the influence of magnetic ordering upon the conductivity process in ferrites [9]. Conduction is due to exchange of the 3d electron, localized at the metal ions, from Fe3+ to Fe2+[10].

Figure 3. Behavior curves correlate the real part of the dielectric constant (ε`) with the absolute temperature of all investigated samples in frequency range from 10kHz to 5MHz.

144

Figure 3 is the typical behavior curves correlate the real part of the dielectric constant (έ ) with the absolute temperature of all investigated samples in frequency range from 10kHz to 5MHz. The general trend of all samples is the increase in (ε`) with increasing temperature up to transition temperature (Curie temperature) and the decrease in έ with increasing frequency except at 100 KHz. It is observed that (έ ) has maximum values for all ranges of temperature at this frequency. This behavior was explained on the basis of the strong correlation between the conduction mechanism and the dielectric behavior for the spinel ferrite as Iwauchi [11] pointed out. The conduction mechanism for Ni-Zn ferrites is the electron hopping between Fe2+ and Fe3+ ions (for n-type) and hole hopping between Ni2+ and Ni3+ (for p-type) on B-site [12]. According to the Rezlescu model [13], local displacement of p- carriers takes part in the polarization in an opposite direction to that of the external field and can promote the so called” abnormal dielectric behavior “resulting in a collective contribution of the two types of carriers to the polarization. The contribution of p- carriers is lower and with an opposite sign to that of the electronic exchange Fe2+ ↔ Fe3+. In addition, since the mobility of p- carriers is lower than that n- carriers. Their contribution to polarization will decrease more rapidly after 100 KHz [14] and the electronic exchange between ferrous and ferric ions cannot follow the alternating field.

Figure 4. Behavior curves correlate the dielectric loss factor (ε``) and absolute temperature, of all investigated samples in frequency range from 10kHz t 5MHz.

Figure 4 is the typical behavior curves correlate the dielectric loss factor (ε``) and absolute temperature of all investigated samples in frequency range from 10kHz to 5MHz. From the figure it is clear that (ε``) increases with increasing temperature at all frequencies, this is attributed to the increase in the energy dissipation. Hudson [15] has shown that, the dielectric losses in ferrite a generally reflected in the conductivity measurements where the materials of high conductivity exhibiting high losses and vice versa. The behavior of increasing of the dielectric loss factor (ε``) at low frequency (10 KHz) can be correlated to resonance arising from domain wall displacements [16].

145

Figure 5(a-b). Compositional dependence of (ln σ) of the ferrite samples of the general formula Ni0.5 Zn0.5YyFe2-iyO4; sb (substitution) group, i=1, 0.02 ≤ y ≤ 0.12 and ad (additive) group, i=0, , 0.02 ≤ y ≤ 0.08 for a and b respectively in frequency range from 10kHz to 5MHz at selected range of temp. (590-600).

Figure 5(a-b), Figure 6(a-b) and Figure 7(a-b) show the compositional dependence of (lnσ)) (έ) and (ε``) respectively of the investigated samples in frequency range from 10kHz to 5MHz. At selected range of temperature (590-600K). The ac conductivity (lnσ) are nearly constant for all Y3+ion concentration for the two groups except for y=0.12. This result suggests that the conduction in these ferrites is due to hopping mechanism of electron exchange between Fe2+ and Fe3+ in the n-type and the hole exchange between Ni3+ and Ni2+ in the p-type which occur among the octahedral B-sites. Since XRD analysis [6] confirmed that the process of dissolution of any ratio of yttrium in the lattice never occurs and the Y3+ ions are segregated on the grain boundaries. i.e yttrium ions do not enter the B-site. Which means that, yttrium ions can be provided as additives on spinel unit cells and the sb groups we deal with, can be considered as a non stoichiomteric system with the cation distribution;

 2+ 3+   Zn0.5 Fe0.5− y   3  IV

 2 + 3+   Ni0.5 Fe1.5 − 2 y  O4  3 VI

(1)

While the ad group is stoichiomteric system with the cation distribution:

( Zn

2+ 0.5

3+ Fe0.5 )IV  Ni0.52+ Fe1.53+ VI O4

(2)

it is convenient to consider that the non stoichiomteric cation distribution of sb group can redistribute itself to produce a single phase of cubic spinel under the suitable sintering process. So, Eq. (1) must be normalized to A1B2O4 and will be slightly modified to

( Zn

2+ 0.5 + δ

3+ 3+  2+  Fe0.5 − δ )IV  Ni0.5 + δ Fe1.5 − δ  VI O4

where

δ=

0.5 y 3− y

(3)

146

It can be easily checked that for maximum δ =0.0208 corresponding to y=0.12 i.e the cation distribution for the two group is nearly the same. The number of Fe3+ and Ni2+ions on octahedral sites is constant .The decrease of the conductivity for y=0.12, can be attributed to the high resistivity of the intergranular layers generated by additives segregation of yttrium oxide YO1.04 [6] to the grain boundary [17]. Another possible cause is that the substitutions impede the motion of Fe2+ in the conduction process, although Fe2+ concentration increases slightly [4]. Then one conclude that the resistivity increases by introducing small amount of foreign atoms with large ionic radius.

Figure 6(a-b). Compositional dependence of (ε`) of the ferrite samples of the general formula Ni0.5 Zn0.5YyFe2-iyO4; sb (substitution) group, i=1, 0.02 ≤ y ≤ 0.12 and ad (additive) group, i=0, 0.02 ≤ y ≤ 0.08 for a and b respectively in frequency range from 10kHz to 5MHz at selected range of temp. (590-600).

Figure 7(a-b). Compositional dependence of (ε``) of the ferrite samples of the general formula Ni0.5 Zn0.5YyFe2-iyO4; sb (substitution) group ,i=1, 0.02 ≤ y ≤ 0.12 and ad (additive) group, i=0, 0.02 ≤ y ≤ 0.08 for a and b respectively in frequency range from 10kHz to 5MHz at selected range of temp. (590-600).

147

As shown from Figure 6(a-b), (ε`) does not reflect the same trend of the conductivity (σ) which does not confirm the assumption that the mechanisms of the conductivity and the dielectric constant are of the same origin. The conductivity (σ) minimum for y=0.12, but (ε`) is maximum. This is indicating that other mechanisms exert more effective influence on (ε`): The secondary phases at grain boundaries can act as shunting capacitors at high frequencies, increasing grain boundary thickness, hence increase (ε`). Another qualitative explanation is the introduction of R ions into the ferrite lattice, which produces disorder in the octahedral or tetrahedral sites, associated with the creation of a small amount of cation or anion vacancies. Those defects can raise the possibility of ion jump polarization. The above microstructural analysis throws insight on the higher (ε`). The conclusion is that the conduction mechanism plays the primary role in the polarization process for homogenize microstructure, whereas Maxwell Wagner polarization [18, 19] plays an important role in increasing the conduction of the samples in the region separating the grains and increases the dielectric constant due to increasing polarizability. Figure 7(a-b) enhances our expectation about the (ε``) decreases with increasing the conductivity. Dielectric loss is an important part of the total core loss [20] in ferrites. Hence for low core losses, low dielectric losses are desirable. Thus the present ferrites with relatively lower losses could be useful at frequencies higher than those of the individual ferrites.

4. Conclusion The results of this study can be summarized as follows: 1- The ac conductivity (ln σ) is nearly constant for all Y3+ion concentration for the two groups. This result confirm the x-ray diffraction data and the calculated values of the cation distribution, where the process of dissolution of any ratio of yttrium in the cubic spinel lattice never occur but exist outside the grain as aggregation and the non stoichiometeric system can redistribute itself to produce a single phase of cubic spinel under the suitable sintering process 2- The resistivity increases by introducing small amount of foreign atoms with large ionic radius. This was attributed to the high resistivity of the intergranular layers generated by additives segregation of yttrium oxide YO1.04 to the grain boundary. 3- The behavior of increasing of the dielectric loss factor (ε``) at low frequency (10 KHz) can be correlated to resonance arising from domain wall displacements. 4- The increase of the dielectric constant (έ) for some investigated samples was attributed to high resistivity of the intergranular layers generated by yttrium segregating to the grain boundary. The increase in έ is due to participation of another type of polarization such as Maxwell Wagner.

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

E. Rezlescu, N. Rezlescu, P.D. Popa, L. Rezlescu and C. Pasncu, Phys. Stat. Sol. (a) 162, 673 (1997). J. Sun, J. Li, G. Sun and X. Yhan, J. Magn. Magn. Mater.. 281, 173-177 (2004). J. Sun, J. Li and G. Sun., J. Magn. Magn. Mater., 250, 20 (2002). S.E. Jacobo, W.G. Fano, A.C. Razzitte, Physica B, 320, 261 (2002). M. Salah, Phys. Stat. Sol. (a) 203, No. 2 (2006). R. Valenzuela, “Magnetic Ceramics”, Cambridge University, 27 (1994). A. Verma, R. Chatterjee, J. Magn. Magn. Mater., 306, 313 (2006). S. Krumn, XIIIth Conference on Clay Mineralogy and Petrology, Praha (1994) Acta Universitatis Carolina Geologica, 38, 253 (1994). L.G. Van Uitert, J. Chem. Phys., 24, 306 (1955). A.J. Bosmann and C.C. Creve, Phys. Rev., 144, 763 (1966). K. Iwauchi, Jpn. J. Appl. Phys., 10, 1520 (1971). L.G. Van Uitert; Proc. I.R.E, 44, 1883 (1956). N. Rezlescu, E. Rezlescu, Phys. Stat Sol. (a) 23, 575 (1974). A. Daias, N. Mohallem, R. Moreira, J. Phys. III France, Vol. 6, 843 (1996).

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15. 16. 17. 18. 19. 20.

A.S. Hudson, Marconi Rev., 37 (1968) 43. J.L. Snock, Physica 14, 207 (1948); Nature 160, 90 (1947). N. Rezlescu, L. Rezlescu, P.D. Popa, E. Rezlescu, J. Magn. Magn. Mater,, 215, 216, 194 (2000). J.C. Maxwell, Electricity and Magnetism, 1, Oxford university press, Section (1873) section 328. K.W. Wagner, Ann. Phys., 40, 817 (1913). J. Zhu, K.J. Tseng, C.F. Foo, IEEE Trans. Magn., 36 (5), 3408 (2000).

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CHARACTERIZATION AND DRAMATIC VARIATIONS OF THE MAGNETIC PROPERTIES OF Cu-DOPED NANOMETRIC CO-FERRITE M. A. AHMED Physics Department, Faculty of Science, Cairo University, Giza, Egypt S. F. MANSOUR Materials Science Lab (1), Physics Department, Faculty of Science, Zagazig University, Egypt M. A. ABDO Physics Department, Faculty of Science, Zagazig University, Egypt Structure and magnetic properties of Co1-xCuxFe2O4 were investigated. Cobalt ferrite has been synthesized by double sintering ceramic technique. X-ray Diffraction (XRD) analysis and Transmission Electron Microscope (TEM) confirmed the formation of single phase cobalt ferrite nanoparticles in the range 38 - 46 ± 3nm which is a good result for this method of preparation. The magnetic susceptibility was studied at different temperature as a function of magnetic field intensities. The room temperature hysteresis loop was performed for the present samples in the field intensity of 108kOe using VSM. The parameters of X-ray density (dx) and apparent density (da) increases with increasing Cu+2 concentrations in the prepared samples.

1.

Introduction

Spinel ferrites have received renewed interest in technologically anchored modern society due to their promising magnetic properties [1, 2]. CoFe2O4 ferrites are widely used in magnetic and magneto optical recording devices [3, 4] because of their high coercive force, hardness and moderate saturation magnetization. Moreover the high complex permeability at a wide frequency range make the material high efficient as magnetic filters in microwave absorber [5]. Also CoFe2O4 find extensive applications in microwave devices, radar, digital recording systems [6, 7], ferrofluids and magnetic refrigeration systems [8-10]. The magnetic character of the particles used for recording media depends crucially on the size, shape and purity of these nanoparticles. These particles should be single domain, of pure phase, having high coercivity and medium magnetization. Among spinel ferrites, cobalt ferrite has attracted considerable attention in recent years due to the unique physical properties such high Curie temperature, large magnetocrystalline anisotropy and mechanical hardness [11, 12]. The octahedral Co2+ (3d7) ions in CoFe2O4 are in the high spin state; also the tetrahedral and the octahedral Fe3+ ions are in the high – spin state with spin directions antiparallel to each other. Additionally, this material exhibits a significant higher magnetostriction than metallic Fe or Ni. As the result of high coercivity and moderate magnetization, cobalt ferrite (CoFe2O4) can be

considered as hard magnetic material with great physical and chemical stability. Hence the need for developing fabrication processes that are relatively simple and yield controlled particle sizes. Many researchers have studied Co ferrite [13-15] and Co – Zn ferrite [16]. No studies available on Co - Cu ferrite. The objective of this work is to examine the effect of copper ion content on the hard character of the Co ferrite. Also one of our goals is to determine the interaction between Co2+ ions, is it of randomly oriented with coherent rotation or of magneto static interaction. Another goal is to find a correlation between the area of the hysteresis loop to find a composition of which the sample become more applicable, and to study the effect of Cu2+ ions in Co ferrite on densification, lattice constant, magnetization and coercivity. 2.

Experimental Techniques

CoCu ferrites with chemical composition Co1xCuxFe2O4, i.e. 0.0 ≤ x ≤ 0.6 was prepared by the double sintering method. Highly pure analar oxides from BDH Company with purity 99.9% were mixed together in stoichiometric ratios and grinded for 4 hours. The mixtures were presintered at 800ºC for 5h with heating rate of 4ºC /min and cooled to room temperature with same rate. After that, the samples were pressed in a disc shape at 5 × 108N/m2 and finally sintered at 1100ºC for 5h in air and then slowly cooled to room temperature with rate of 4ºC /min. A disc from each sample was ground in order to get fine powders for X–ray

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

150

diffraction studies using diffractometer model Proker D8 using radiation source Cu–Kα radiation (λ = 1.5405Å). The shape and morphology of the particles were analyzed using transmission electron microscope (TEM) model (JEOI 1010). Infrared spectra (IR) of the investigated samples were recorded using the infrared spectrometer, model 1430, Perkin Elmer in the range 200 – 1000 cm-1 in the KBr medium. The saturation magnetization and coercive field were measured using vibrating sample magnetometer "VSM EG &G Model No 1551 (USA) with maximum mgnetic field 7000 Oe". The dc magnetic susceptibility (χM) of the investigated samples was measured using Faraday’s method as a function of temperature and applied magnetic field intensities; 790, 1100, and 1300 Oe. The accuracy of measuring temperature in the magnetic susceptibility measurements was ±1ºC where the data were reproducible.

Table 1. The values of X-ray density (dx), apparent density (da), porosity P % and IR absorption bands of Co1xCuxFe2O4 as a function of Cu content (x).

dx [gm/cm3]

da [gm/cm3]

P%

Tetrahedral ν1 [cm-1]

Octahedral ν2 [cm-1]

0.0

5.264

4.029

23.50

395

590

254

219

0.1

5.287

4.123

22.10

392

581

257

219

0.2

5.299

4.213

20.50

392

587

254

222

0.3

5.287

4.350

17.55

370

568

---

213

0.4

5.303

4.591

13.36

386

568

263

213

0.5

5.327

4.682

12.06

386

562

266

222

0.6

5.349

4.823

9.78

389

571

263

219

Results and Discussion

X=0.0 (533)

(440)

(511)

(422)

(400)

(311) (222)

(220)

(111)

The XRD patterns of the Co-ferrite samples are shown in Fig. 1. All of the diffraction peaks confirmed the formation of the samples in pure single spinel phase. The size of the particles was determined by Scherer's formula. The average particles size was (38 – 46 ± 3nm) and the average value of lattice parameter for Co ferrite is aexp = 0.839nm which agrees well with the reported values [17, 18], the XRD patterns were indexed using ICDD card no. (79-1744) for CoFe2O4).

X=0.1 Intensity

X=0.2 X=0.3 X=0.4 X=0.5 X=0.6 20

40

60

80

2θ

Figure 1. The XRD patterns of Co1-xCuXFe2O4 (0.0 ≤ x 0.6).

Lattice vibration ν3 [cm-1]

x

3.

The calculated values of X-ray density dx = 5.26 g/cm3 was in good agreement with the value 5.29 g/cm3 obtained by A. Rafferty et.al. [19]. The values of the X-ray and apparent density for all Cu contents are reported in Table 1. The data in the table show that both densities increase with increasing copper content i.e. the apparent density da reflects the same general behavior of the theoretical density. This can be ascribed to the atomic weight and density of Cu2+ (63.546, 8.96 gm cm-3) which are higher than those of Co2+ (58.933, 8.91 gm cm-3). The percentage of porosity was calculated using the relation P = 100 [1-da/dx] where da is apparent density. The porosity decreases when the density increases as reported in Table 1.

The TEM images of the CoCu ferrite particles are uniform in both morphology and particle size as in Fig. 2. All samples give nearly the same platelet shape. The sample with x = 0.6 shows nanotubes shape. By increasing the focusing the image shows that the platelet shape is clear. In this is sample the crystallites are oriented in a preferred direction. This could be due to the existence of Cu+2 with relative high content which affects on the shape anisotropy. The IR spectra for the samples of Co1-xCuxFe2O4, (where 0.0 ≤ x ≤ 0.6) are shown in Fig. 3, and the absorption bands are reported in table 1. It is obvious from the data that, the frequency bands ν1 (568 – 590 cm-1) and ν2 (370 – 395 cm-1) are attributed to the vibration of iron ions on tetrahedral and octahedral positions respectively. Finally, the third band ν3 (213 – 266 cm-1) is attributed to the lattice vibration frequency

151

[20]. The intensity of ν1 and ν2 decreases while broadening increases with increasing Cu content.This decrease in intensity and increase in broadness is explained on the basis of cation redistribution and also Jahn - Teller effect due to high concentration of copper. X=0.1

X=0.0

X=0.3

X=0.6

Figure 2. TEM of (x = 0.0, 0.1, 0.3 and 0.6).

x=0.0

shoulder

υ3

υ1

υ3

x=0.1 x=0.2

Transmittance

x=0.3 x=0.4 x=0.5 x=0.6 1000

900

800

700

600

500

400

300

-1 Wavenumber(cm ) Figure 3. IR absorption spectra of Co1-xCuXFe2O4 (0.0 ≤ x 0.6).

200

Figure 4(a-c) illustrates the dependence of magnetization on absolute temperature as a function of magnetic field intensity for the samples Co1-xCuxFe2O4; (x = 0.0, 0.3 and 0.6). The magnetization increases slightly reaching a hump at 600 K for the sample with x = 0.0 which varies in position and intensity depending on both the magnetic field intensity and Cu content. This means that the magnetic ordering increases slightly achieving maximum at this hump and then decreases reaching the Curie temperature at about 784K which in good agreement with the previous reported for Co ferrite [22, 23]. After the Curie temperature, the sample behaves as a typical paramagnetic material. The values of M increase with increasing the magnetic field intensity due to the alignment of more dipoles in the field direction until reaching the saturation. The Curie temperature increases with increasing 2+ Cu substitution, up to x = 0.3 and then decreases as in Fig. 4d. The increase in TC with increasing Cu2+ substitution is mainly attributed to the increase in the strength of exchange interaction constant JAB. When Cu2+ content is increased, assuming that Co2+ ions are in high spin state; then the AB interaction as well as Tc increase up to x = 0.3 and decreased for x > 0.3 as a consequence of the migration of some Co2+ ions from the B to the A site. This explains the peculiarity that occurred at x = 0.3 the inset of each figure shows the variation of magnetization with temperature (dM/dT) versus absolute temperature to clarify the variation of TC with Cu content. Form the magnetization data; it is also observed that the magnetization data show the ferromagnetic behavior due to the super-exchange interaction between interstitial sites. The hysteresis loopes for all prepared samples are shown in Fig. 5(a-f).Saturation magnetization (Ms), coercive field (Hc), remenance (Mr) and the squarenes ratio R = (Mr / Ms) are listed in Table 2. The obtained values of Ms are lower as compared to the bulk Ms value of 80 emug-1 [24]. It is known that the dead layer resulting from the small particle size in the nanometer range which leads to a large surface/ volume ratio leading to a decrease in magnetization value. The high value of saturation magnetization for x = 0.5 may be attributed to the disordered crystal site orientation of the ions in the spinel structure and the equal amounts of Cu2+ and Co2+ ions

152 790 Oe 1100 Oe 1300 Oe

(a)

X=0.0

1.8

880

1.6 860

1.4 840

1.0 0.8

Tc(K)

M(emu/g)

1.2

0.02

820

800

0.01 0.00

dM/dT

0.6

780

-0.01 -0.02

0.4

-0.03 -0.04

400

0.2

600

800

760

1000

T(K)

300

400

500

600

700

800

900

740

1000

0.0

0.1

0.2

0.3

T(K) X=0.3

790 Oe 1100 Oe 1300 Oe

(b)

10

0.4

0.5

0.6

X

Figure 4d. The dependence of Curie temperature Tc on Cu content (x).

Furthermore, its remanent magnetization Mr of 1.99 emug-1 is quite low in comparison to that of hard magnetic materials. Figure (5:a-f) shows also that, the ratio R = (Mr / Ms) was reported in Table 2, to determine whether the intergrain exchanges [25] exist or not. It has been reported that R = 0.5 for randomly oriented noninteracting particles that undergoing coherent rotations while R < 0.5 for the particles interacting by magnetostatic interactions [26]. The exchange- coupling exists when R > 0.5. Our results show that the value of (Mr / Ms) of the samples is lower than 0.5. Therefore, the cobalt cupper ferrite particles interact by magnetostaticlly.

6

0.04

4

0.00 dM/dT

M(emu/g)

8

2

-0.04 -0.08 -0.12 200

400

600

800

1000

T(K)

0 200

300

400

500

600

700

800

900

1000

T(K) 50 X=0.6 X=0.6

790 Oe 1100 Oe 1300 Oe

(a)

45 10 40 35 8

M(emu/g)

30 25 6 20 15 4

5 2 0 -5 0 200

dM/dT

10

0.1 0.0 -0.1 -0.2

Table 2, The recorded values of the magnetic parameters: saturation magnetization (Ms), remanent magnetization (Mr), coercive field (Hc) and squarenes ratio R = (Mr / Ms).

-0.3 -0.4 -0.5 400

300

600 800 T(K)

400

1000

500

600

700

800

900

1000

T(K)

Figure 4(a-c). The variation of magnetization as a function of absolute temperature at (H = 790,1100 and 1300 Oe ).

The data in Table 2, demonstrate that, the synthesized ferrite is not hard magnetic material, because of its small coercive field Hc= 50 Oe. .

x

Ms[ emug-1]

Mr[ emug-1]

Hc [Oe]

R=Mr/Ms

0.0

54.53

16.22

284.07

0.297

0.1

48.21

17.09

414.66

0.354

0.2

44.15

8.51

130.12

0.192

0.3

47.2

4.98

130

0.105

0.4

46.73

4.38

94.6

0.093

0.5

54.53

4.05

80

0.074

0.6

44.27

1.99

50

0.045

153

Figure 5(a-d). The magnetic hysteresis loops for Co1-xCuXFe2O4 ( 0.0 ≤ x ≤0.4) at room temperature.

Figure 5(e, f). The magnetic hysteresis loops for Co1-xCuXFe2O4 (x = 0.5 and 0.6) at room temperature.

4.

Conclusion

The standard ceramic method was successful in producing nanoparticles of Cu substituted Co ferrite. The results of XRD analysis and IR showed that the samples were prepared in single phase spinel structure. The calculated lattice parameter revealed stability with increasing Cu content. The Curie temperature Tc increases with copper content up to x = 0.3 after which it decreases. The values of HC and SQR assure the soft character of the ferrite.

The highest saturation magnetization value was obtained amongst all substituted samples is 54.53 emu/g for x = 0.5. References 1. M.R. Deguire, G. Kalonji, R.C. O,Handley, J. Am. Ceram. Soc. 73 (1990) 3202. 2. M.A. Willard, Y. Nakamura, E. David Langhlin, E. Michael Mchenry J. Am. Ceram. Soc. 28 (1999) 3342.

154

3. Y.W. Ju, J. H. Park, H.R. Jurg, S.J .Cho, J. Lee Mat. Sci. Eng. B 147 (2008) 7. 4. I. Zhoozh, Zhang, Y. Lei, F. Cao, J. Solid State Chem. 181 (2008) 245. 5. R.C. Che, C.Y. Zhi, C.Y. Liang, X.G. Zhou, Appl. Phys. Letter 88 (2006) 033 6. V. Pallai and D.O. Shah, J. of Magn. and Magn. Mater. 248, (1996) 163. 7. R.K. Sharma, O. Sualka, N. lakshmi, K. Venugopalan, A. Banerjee, P.A. Joy, J. All Compd. 419 (2006)155. 8. M.P. Horvath, J. Magm. Magn. Mater. 215 (2000) 171. 9. J.D. Adams, L.E. David, G.F. Dionne, E.F. Schloemann, S.N. Stitzer, IEEE Trans. Microave Theory Tech. 50 (2002) 721. 10. Z.H. Zhou, J.M. Xue, J. Wang, J. Appl. Phys. 91 (2002) 6015. 11. P.C. Rajath, R.S. Manna, D. Banerjee, M.R. Varma, K.G. Suresh, A.K. Nigam, J. Alloys Compd. 453 (2008) 298. 12. R Skomski, J. Phys.: Cond. Matt. 15, R1-R56, (2003). 13. Y. Kim II, D. Kim, C. Lee, J. Physica B 337 (2003). 14. Y. Shi, J. Ding, H. Yin, J. Alloys Compd. 308 (2000) 290. X

15. E.J. Choi, Y. Ahn, S. Kim, D.H. An, K. U. Kang, B.G. Lee, K.S. Baek, H.N. Oak, J. Mag. Mag. Mater 262 (2003) 198. 16. M.A. Ahmed and S.T. Bishay, J. of Phys. and Chem. of Solids, 64 (2003) 769. 17. M.A. Ahmed, N. Okasha, S.F. Mansour, S.I. Eldek, J. of Alloys and Comp. 496 (2010) 0345. 18. Ayyappan, John Philip, Baldev Raj, Mater. Chem. and Phys. 115 (2009) 712. 19. A. Rafferty, T. Prescott, D. Brabaon, Ceram. Internat. 34 (2008) 15. 20. M.A. Ahmed, J. Vibrat Spectr, 30 (2002) 69. 21. S.C. Watawe, B.D. Sutar, B.D. Sarwade, B.K. Chougule, International Journal of Inorganic Materials 3 (2001)819. 22. Smit and H.P.J. Wijin, Ferrites, (1959). 23. B.S. Randhawa, H.S. Dosanjh, Manpreet Kaur, Ceramics International 35 (2009) 1045. 24. S. Ayyappan, J. Philip, B. Raj, Mater. Chem. and Phys. 115 (2009) 712. 25. Z, L. Wang, Y. Liu, Z. Zhang, Handbook of Nanophase and Nanostructured Materials. Materials Systems and Applications 1 Vol. 3, Kluwer Academic, Plenum publishers, USA, 2003. 26. E.C. Stoner, E.P. Wohlfarth, Philos. Trans. R. Soc. London A 240 (1948)599.

  155

ELECTRONIC STRUCTURE AND MAGNETIC PROPERTIES OF THE ND2FE14B INTERMETALLIC COMPOUND ABEER E. ALY Computer Science Department, Thebes Higher Institute for Computer and Management Sciences, Cairo, Egypt Corresponding author: [email protected] The calculations on electronic structures of Nd2Fe14B are calculated using first-principles full-potential linearized augmented plane wave (FPLAPW) method. We study the magnetic properties of Nd2Fe14B using the LDA+U and spinorbit coupling methods. Results are presented for total density of states (DOS) as well as the site-projected partial density of states (PDOS) and the spin magnetic moment of Fe at each of the six in-equivalent transition-metal sites. The total spin-magnetic moments and the average Fe moment are in a good agreement with the values deduced from the neutron scattering experiment. The spin-polarized calculations, excluding the Hubbard and SO interaction, resulted in the total spin magnetic moment is 46.6 µB compared to the experimental values 34.63 µB to the value of 39.6 µB we obtained using LDA+U scheme without Spin-Orbit coupling(SO). But using LDA+U +SO the total spin magnetic moment is 37.6 µB.

1.

Introduction

expanded in augmented wave functions. In region I, they are expanded in radial functions times spherical harmonics. In the interstitial region II, plane wave’s expansion is used. Each plane wave is augmented by an atomic-like function inside the atomic sphere and matched at the atomic boundary. However, there is no shape restriction on the density and potential. In this paper, we present the calculations of density of states and spin magnetic moment on Nd2Fe14B using FPLAPW method and different schemes.

Nd2Fe14B has considered a good permanent magnet because it has a large saturation magnetization, larger energy products, coercivity and high Curie temperature [1]. It has great interest for significant technological applications [2]. The fundamental role in the determining the magnetic properties are a good understanding of the electronic structure of these materials. So it is necessary to understand the origin of magnetism in Nd2Fe14B. Nd2Fe14B is the most important alloy in the series in terms of practical applications and is the one most intensively studied [3]. Some empirical and non-self consistent calculations have been reported on the electronic structure of Nd2Fe14B [4-10]. One of these calculations for Inoue and Shimizu [4], Itoh et al.[5], and Szpunar, Wallace, and Szpunar [6] used a semi-empirical tight binding and the recursion method and found that Fe atoms at the j2 site have the largest magnetic moments and were included spin-polarized only. We studied the effect of the spin-orbit coupling on the electronic structure and the density of states (DOS) of Nd2Fe14B using self-consistent Full Potential Linearized Augmented Plane Wave (FPLAPW) method based on Density Functional Theory (DFT) [11]. This method is based on local-density approximation. The potential and the electron density are separated into two regions, i.e. inside the non-overlapping atomic spheres (region I) and the interstitial regions (region II). The wave function solutions of the Kohn-Sham equation are

2.

METHOD OF CALCULATIONS

Nd2Fe14B crystal are tetragonal unit cell with a space group P42/mnm, structure No. 136 has two different R sites Nd(f) and Nd(g), six distinct Fe sites (labeled c, e, j1, j2, k1, and k2, respectively) and one B site for a total of 68 atoms per unit cell [12] . In one unit cell , there are two kinds of 8Nd atoms, labeled as 4Nd(f) and 4Nd(g), respectively, six kinds of 56 Fe atoms, labeled as Fe(c),Fe(e),Fe(j1), Fe(j2), Fe(k1), Fe(k2), respectively, and only one kind of 4B atoms, labeled as B(g). Nearneighbor Fe-Fe distances in the structure are between 2.4 and 2.8 A and the B atoms are known to play an important role in bonding [12]. Since they occupy the centers of the trigonal prisms which are formed by 6 neighbor Fe atoms .One Fe(e) and two Fe(k1) atoms above and one Fe(e) and two Fe(k1) atoms below and three Nd atoms[2Nd(f) and 1Nd(g)] are bonded to each B atom through the three vertical prism faces. It is clear 1

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156   2

from the prisms are strong structural units linking the Fe planes above and below those containing Nd and B. The atomic–structure information was taken from ref [12]. We have used the lattice constants and the fourteen atomic position parameters for Nd2Fe14B at 77K [13].The experimental values used in our calculation are a = 8.802, c= 12.179 A0[7,8]. The Local Density Approximation (LDA+U) of Perdew and Wang [14] and the Generalized Gradient Approximation (GGA) of Perdew, Burke and Ernzerhof [15] were used for correlations and exchange potentials as implemented in the Wien2k code [16]. Self-consistent calculations were performed with 30 k-points in the irreducible Brillouin zone. We used the muffin tin (MT) sphere radii Nd Fe B RMT = 2.5 a.u, RMT = 2.09 a.u, RMT = 1.85 a.u and the cut off energy parameters RKmax and Gmax of 7 and 14 respectively. There are two very important crystallographic planes in tetragonal cell of Nd2Fe14B [ref 7,8]: the basal plane (z=0) which contains the two R, B, and Fe(c) sites, and the (110) plane which is parallel to the c axis and contains Fe(e) and Fe(j1) sites in addition to B and R sites [12]. The near-neighbor distances were used to estimate the Wigner-Seitz radii. 4f states in rare earths are highly localized and are very difficult to include the band-structure calculation. Fortunately, their photoemission spectra are reasonable well understood with transition-state analysis [17,18] and renormalized-atom approach [19]. Because of this and the fact that the non-4f parts of the experimental electronic structure are similar 4f states in Nd2Fe14B were included in the valence and core states. Both core and valence states are the frozen self-consistent atomic states. There are nine valence states per site consisting of s, p and d orbitals. With 68 atoms per unit cell, this leads to 612×612 overlap and Hamiltonian matrices. The self-consistent spin-polarized potential parameters are based on the zero-wave-vector (K~0) electronic structure results. Because of the extremely large size of the unit cell so in our work, the Nd f electrons are considered as valence electrons and are treated selfconsistently. Furthermore, we have used a small FPLAPW basis set for Nd atoms and small k-points for the Brillouin zone integration. 3.

Results and Discussion

To describe the electronic and magnetic properties of Nd2Fe14B, we have used the self-consistent Full Potential Linearized Augmented Plane Wave

(FPLAPW) .Both core and valence states are calculated self-consistently, the core states are treated fully relativistically for the spherical part of the potential, whereas the full potential is used for the valence states. In our work, the Nd f electrons are considered as valence electrons. First, here we performed spinpolarized calculation on Nd2Fe14B after that adding LDA+U with and without spin-orbit coupling. LDA+U method [11] will be useful because the LDA+U, removes the deficiency of LDA by incorporating the Hubbard-like interaction term for 4f electrons. 3.1. SPIN-POLARIZED ONLY We performed spin-polarized calculations on Nd2Fe14B, excluding the Hubbard and SO interaction. We calculated the spin magnetic moment Ms (µB) as shown in table I. The magnetic moments Ms(µB) for the Fe sites are 2.39,2.37,2.36,2.43,2.40,2.38 µB for the k1, k2, j1, j2, e and c sites respectively . These numbers are in a good agreement with the experimental values of 2.60, 2.60, 2.30, 2.85, 2.10, 2.75 µB respectively [20, 21]. The Fe-site moments are in agreement with two reported results of neutron-scattering experiments, one on single crystals [20] and another on powder samples [21] . Szpunar et al [6], Inoue et al and Shimizu et al [4] and Itoh et al [5] used a semi-empirical tight binding and the recursion method and found that Fe atoms at j2 site have the largest magnetic moments. Using the spin-polarized only we found the largest Fe magnetic moment at the j2 site, but the smallest Fe magnetic moment at the j1 site. Figure (1) show the majority density of states (DOS) and the orbital-decomposed (PDOS). The total DOS spin-up for Nd2Fe14B in Fig.(1a) is dominated by the Fe 3dstates as shown in Fig.(1c) . The peaks in Fig.(1c) are located from ~ 0 to ~ -5 eV .The highly localized Nd (4f ,4g) peaks are found to be located clustered around the Ef as shown in Fig.(1b) and the low two peaks located at ~ -9 eV due to B states as shown in Fig.(1d) .The sitedecomposed spin-magnetic moments at different Fe site for Nd2Fe14B are summarized in table I. The significantly different PDOS curves indicate strong local environment differences at different Fe site. The average Fe moment is 2.38 µB compared to the experimental values ~ 2.57µB [21,22]. We calculated the total magnetic moment of ~ 46.62µB using this scheme which is larger than the experimental value of ~35.0 µB/f.u or 37.1 µB /f.u [21,22] and this demonstrates that the spinpolarized scheme is not suitable for handling f-systems.

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3  157 And the density of states (DOS) in Fig.(1c) show that the 3d-state of Fe atoms has the largest peak at the c site instead of the j2 site. So it is the important to include LDA+U without spin-orbit coupling as we will show in the next part. Table (I). The calculated and measured spin magnetic moments at different Fe sites in Nd2Fe14B in units of µB using spin-polarized only.

Sites Fe(k1) Fe(k2) Fe(j1) Fe(j2) Fe(e) Fe(c)

Present calculation 2.39 2.37 2.36 2.43 2.40 2.38

Experiment (ref 20,21 ) 2.60 2.60 2.30 2.85 2.10 2.75

shown in table II. . The magnetic moments Ms(µB) for the Fe sites are 2.25,2.28,2.24,2.58,2.18,2.3 µB for the k1, k2, j1, j2, e and c sites respectively. These numbers are to be compared with experimental values of 2.60, 2.60, 2.30, 2.85, 2.10, 2.75 µB respectively [20,21]. The agreement between the theoretical calculation and experimental values is observed. The largest Fe moment is found at the j2 site as before, but the smallest Fe moment is at the e site. Fig. (2b) show that the localized Nd (4f) (spin-up) peak is found to be shifted above the Ef and splitting above and below Ef using LDA+U without spin-orbit coupling. We also note that Nd (4f ) peak at g site is larger than the Nd (4g) peak at f site as shown in Fig.(2b). Figure (2) show that the majority total density of states (DOS) and the orbital-decomposed (PDOS) . The total DOS spin-up for Nd2Fe14B in Fig.(2a) is dominated by the Fe 3d-states as shown in Fig.(3c). The peaks in Fig.(2c) are located from ~ -1 to ~ -5 eV. The highly localized Nd (4f ,4g) peaks are found to be located above and below the Ef as shown in Fig.(2b) . The low two peaks located at ~ -9 eV due to B states as shown in Fig.(2d) . The site-decomposed spinmagnetic moments at each atomic site for Nd2Fe14B are summarized in table II. The Fe-site moments are in a good agreement with two reported results of neutron scattering experiments. We calculated the total magnetic moment of ~ 39.62µB using LDA+U without spin-orbit coupling which is near agreement with the experimental value of ~35.0 µB /f.u or 37.1 µB /f.u [21,22]. The average Fe moment is 2.31 µB compared to the experimental values ~ 2.53µB [21,22] . The density of states (DOS) in Fig.(4c) show that the 3d-state of Fe atoms has the largest peak at the c and j2 sites . So it is important to include LDA+U plus spin-orbit coupling as we will show in the next part.

Figure 1. Total and PDOS spin-up density of states (DOS) for Nd2Fe14B, (a)Total density of states (DOS)(spin-up) of Nd2Fe14B; (b) density of states (DOS) of 2Nd f state at f and g sites; (c) density of states(DOS) of six types of Fe atoms ;(d) Total density of states (DOS) of B atom .Using spin-polarized only.

3.2. LDA+U WITHOUT SPIN-ORBIT COUPLING Using LDA+U without spin-orbit coupling we calculated the spin magnetic moment Ms(µB) as

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4 4 158   Table II. The calculated and measured spin magnetic B inmagnetic units of moments Fe sites in Nd2Fe14spin Table II. at Thedifferent calculated and measured µmoments LDA+U B using spin-polarized Fe14B inspin-orbit units of at different Feplus sites in Nd2without coupling µ using spin-polarized plus LDA+U without spin-orbit B

coupling

Sites Sites Fe(k1) Fe(k Fe(k21)) Fe(j Fe(k12)) Fe(j Fe(j21)) Fe(e) Fe(j2) Fe(c) Fe(e) Fe(c)

Present calculation Present 2.25 calculation 2.28 2.25 2.24 2.28 2.58 2.24 2.18 2.58 2.30 2.18 2.30

Experiment (ref 20,21 ) Experiment (ref 2.60 20,21 ) 2.60 2.60 2.30 2.60 2.85 2.30 2.10 2.85 2.75 2.10 2.75

FIGURE 2. Total and PDOS spin-up density of states (DOS) for of states (DOS)(spin-up) of Nd2Fe14B; Nd 2Fe14B,2.(a)Total FIGURE Total density and PDOS spin-up density of states (DOS) for (b) states (DOS) f state at f and g sites; (c) density Fe14B, of (a)Total densityofof2Nd states (DOS)(spin-up) of Nd2Fe14B; Nd2density of of six(DOS) types ofof2Nd Fe atoms states (b)states(DOS) density of states f state ;(d) at f Total and g density sites; (c)ofdensity (DOS) of B atom spin-polarized without spinof states(DOS) of .Using six types of Fe atoms plus ;(d) LDA+U Total density of states orbit coupling. (DOS) of B atom .Using spin-polarized plus LDA+U without spinorbit coupling.

3.3. LDA+U PLUS SPIN-ORBIT COUPLING 3.3. (SO) LDA+U PLUS SPIN-ORBIT COUPLING (SO) Using spin-orbit coupling including the Hubbard and Using spin-orbit coupling including the Hubbard and exchange parameters (U, J) we calculated the spin exchange moment parameters J) we calculated the spin ) as shown in table III. We magnetic Ms(µ(U, B in table2.38, III. We magnetic moment values of 2.26, 2.29, obtained Ms(µB),Ms(µ B) as shown ), values of 2.26, 2.38, 2.29, obtained Ms(µ 2.72,2.15,2.44 µB for the k1, k2, j1, j2, e and c sites the k1, between k2, j1, j2,the e and c sites 2.72,2.15,2.44 µB for respectively . The agreement theoretical respectivelyand . The agreement values between the theoretical calculation experimental is observed. The calculation and experimental values is observed. 3dlargest magnetic moment is found at the j2 sites of The 3dlargestofmagnetic is found Fe at moment the j2 sites states Fe atoms,moment but the smallest is atofthe e statesFigure of Fe atoms, but the smallesttotal Fe moment the e site. (3) show majority density isofatstates of states site. Figure (3) orbital-decomposed show majority total density The (DOS) and the (PDOS). total (DOS)spin-up and the (PDOS). The total is dominated by DOS fororbital-decomposed Nd2Fe14B in Fig.(3a) Fe14B in dominated DOSFespin-up for Nd the 3d-states as 2shown in Fig.(3a) Fig.(3c).is The peaks by in the Fe 3d-states as from shown~ -1 in to Fig.(3c). TheThe peaks in Fig.(3c) are located ~ -5 eV. highly Fig.(3c) are from ~ -1are to found ~ -5 eV. highly localized Ndlocated (4f ,4g) peaks to The be located localized (4f the ,4g)Ef peaks are in found to be above and Nd below as shown Fig.(3b) andlocated the B above isand below theeV Ef as as shown shown in in Fig.(3d). Fig.(3b) and B states about ~ -9 Thethe sitestates is about ~ -9 eV as shown in at Fig.(3d). The sitedecomposed spin-magnetic moments each atomic site decomposed moments site are summarized in table at III.each We atomic calculated for Nd2Fe14B spin-magnetic Fe B are summarized in table III. We calculated for Nd using spinthe total magnetic moment of ~ 37.61 µ 2 14 B the total magneticwhich moment ~ 37.61 µB using near spinthe orbit coupling is ofapproximately the orbit coupling which is approximately µB /f.u experimental value of ~35.0 µB /f.u or 37.1near /f.u2.38 or µ37.1 µ /f.u experimental value ofFe~35.0 µB is compared [21,22]. The average moment B B compared [21,22]. The average Fe moment 2.38 µB The DOS to the experimental values ~ 2.53 µisB [21,22]. [21,22]. The DOS to the experimental values ~ 2.53 µ structure by using spin-orbit coupling are in good B structure by using spin-orbit coupling are in good agreement with the DOS structure reported by Szpupar agreement with the structure reported by etSzpupar et al and Wallace et DOS al, Inoue et al and Shimizu al and et al et andalWallace et al,found Inoue the et allargest and Shimizu et al Itoh , that they 3d-state of and Fe Itoh etis al , that the they found the largest 3d-state of Fe atoms through j2 site. atoms is through the j2 site. Table III. The calculated and measured spin magnetic moments different Fe sites in units of µB Table III. atThe calculated andNd2Fe14B measured spin magnetic using spin-orbit coupling moments at different Fe sites Nd2Fe14B in units of µ using spin-orbit coupling

Sites Sites Fe(k1) Fe(k Fe(k21)) Fe(j Fe(k12)) Fe(j Fe(j21)) Fe(e) Fe(j2) Fe(c) Fe(e) Fe(c)

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Present calculation Present 2.26 calculation 2.38 2.26 2.29 2.38 2.72 2.29 2.15 2.72 2.44 2.15 2.44

B

Experiment (ref 20,21 ) Experiment (ref 2.60 20,21 ) 2.60 2.60 2.30 2.60 2.85 2.30 2.10 2.85 2.75 2.10 2.75

6. 6. 7. 7. 8. 8. 9. 9. 10. 11. 10. 11. 12. 12. 13. 13. 14. 14. 15. 15. 16. 16. FIGURE 3. Total and PDOS spin-up density of states (DOS) for Nd2Fe14B, (a)Total density of states (DOS)(spin-up) of Nd2Fe14B; FIGURE 3. Total and PDOS spin-up density of states (DOS) for (b) density of states (DOS) of 2Nd f state at f and g sites; (c) density Nd2Fe14B, (a)Total density of states (DOS)(spin-up) of Nd2Fe14B; of states(DOS) of six types of Fe atoms ;(d) Total density of states (b) density of states (DOS) of 2Nd f state at f and g sites; (c) density (DOS) of B atom .Using spin-orbit coupling. of states(DOS) of six types of Fe atoms ;(d) Total density of states (DOS) of B atom .Using spin-orbit coupling.

4. Conclusions 4. Conclusions We have performed ab initio calculation on the Fe14B calculation intermetalliconalloys electronic Nd2initio We have structure performedof ab the using full potential plane alloys wave B intermetallic electronic structure linearized of Nd2Fe14augmented (FPLAPW) method based on DFT theory and different using full potential linearized augmented plane wave The interaction available in thetheory Wien2k (FPLAPW)schemes method based on DFT andcode. different magnetic is best described the LDAcode. + U plus The interactionmoment schemes available in theinWien2k spin-orbit coupling scheme as shown comparison magnetic moment is best described in theby LDA + U plus with available on spin-orbit couplingcalculations scheme as and shownexperiments by comparison B. The agreement good in that on it Nd with available calculationsis quite and experiments 2Fe14 correctly the largest at j2 site. The that agreement is sites quitearegood in that it Nd2Fe14B.predict correctly predict that the largest sites are at j2 site. References References 1. R. W. Lee, Appl. Phys. Lett. 46 ,790 (1985). 2. R. W. Lee, and46F.,790 E. (1985). Pinkerton, 1. J. R. F. W.Herbst, Lee, Appl. Phys. Lett. Mater. Sci.Lee, 16 ,467 2. Ann. J. F. Rev. Herbst, R. W. and (1986). F. E. Pinkerton, 3. K. V. L. Narashimhan, J. (1986). Appl. Phys. 57 Ann.S.Rev. Mater. Sci. 16 ,467 ,4081 (1985). 3. K. S. V. L. Narashimhan, J. Appl. Phys. 57 4. J. Inoue and M. Shimizu, J. Phys. F 16 ,1051 ,4081 (1985). 4. (1986). J. Inoue and M. Shimizu, J. Phys. F 16 ,1051 5. T. Itoh, K. Hikosaka, H. Takahashi, T. Ukai, (1986). and N. Mori, J. Appl. Phys. 61 ,3430 (1987). 5. T. Itoh, K. Hikosaka, H. Takahashi, T. Ukai, and N. Mori, J. Appl. Phys. 61 ,3430 (1987).

17. 17. 18. 18. 19. 19. 20. 20. 21. 21. 22. 22.

  159 5 5 B. Szpunar, W. E. Wallace, and J. Szpunar, Phys. Rev. B W. 36 ,3782 (1987) and . B. Szpunar, E. Wallace, J. Szpunar, Z. Q. Gu and W. Y. Ching, Phys. Rev. B 36 Phys. Rev. B 36 ,3782 (1987) . ,8530 Z. Q. (1987). Gu and W. Y. Ching, Phys. Rev. B 36 X. F. (1987). Zhong and W. Y. Ching, J. Appl. Phys. ,8530 67 (1990). X. ,4768 F. Zhong and W. Y. Ching, J. Appl. Phys. D. J. Sellmyer, 67 ,4768 (1990).M. A. Engelhardt, S. S. Jaswal, and J. Arko,M.Phys. Rev. Lett.S.60 , 2077 D. J. A. Sellmyer, A. Engelhardt, S. Jaswal, (1988). and A. J. Arko, Phys. Rev. Lett. 60 , 2077 S. S. Jaswal, Phys. Rev. B 41,9697 (1990). (1988). W. and L. J. Sham, Phys. Rev. A1133 S. S.Kohn, Jaswal, Phys. Rev. B 41,9697 (1990). ,140 (1965) W. Kohn, and L. J. Sham, Phys. Rev. A1133 J. F. (1965) Herbst, J. J. Croat, F. E. Pinkerton, and ,140 W. Yelon, J.Phys. Rev. B29 (1984).and J. F.B.Herbst, J. Croat, F. E.,4176 Pinkerton, J. F. Herbst, J. J. Croat, and W. B. Yelon, W. B. Yelon, Phys. Rev. B29 ,4176 (1984). J. Appl. Phys. 57 (1985). J. F. Herbst, J. ,4086 J. Croat, and W. B. Yelon, J. J. P. Perdew, Wang,(1985). Phys. Rev. B45 ,13244 Appl. Phys. 57Y.,4086 (1992). J. P. Perdew, Y. Wang, Phys. Rev. B45 ,13244 J. P. Perdew, K. Burke, M. Ernzerhof, Phys. (1992). Rev. 77 ,3865 (1996)M. . Ernzerhof, Phys. J. P. Lett. Perdew, K. Burke, P. Blaha, K. ,3865 Schwar2, G. .K. H. Madsen, K. Rev. Lett. 77 (1996) Kvasnicka, Luitz, G.Wien2k, Karlheinz P. Blaha, K. J.Schwar2, K. H. Madsen, K. Schwarz, Universitat Austria Kvasnicka,Technische J. Luitz, Wien2k,wien, Karlheinz “an Augmented PlaneUniversitat Wave + Local Schwarz, Technische wien, orbitals Austria program for calculating crystal properties”, “an Augmented Plane Wave + Local orbitals (2001). program for calculating crystal properties”, M.R.Norman, D.D.Koelling, and A.J.Freeman, (2001). Phys.Rev.B31, 6251 (1985) and A.J.Freeman, M.R.Norman, D.D.Koelling, S.S.Jaswal, D.J.Sellmyer, M.Engelhardt, Phys.Rev.B31, 6251 (1985) Z.Zhao, and A.J.Arko, Phys.Rev.B35, 996 S.S.Jaswal, D.J.Sellmyer, M.Engelhardt, (1987) Z.Zhao, and A.J.Arko, Phys.Rev.B35, 996 J.F.Herbst and J.W.Wilkins, in Handbook on (1987) Physics and Chemistry of Rare Earths, edited J.F.Herbst and in Handbook on J.W.Wilkins, by K.A.Gschneider, S.Hufner Physics and ChemistryL.Eyring, of Rare and Earths, edited (Elsvier, New York, 1987), Vol.10, by K.A.Gschneider, L.Eyring, andp.321. S.Hufner D. GivordNew anf York, H. S. Li, J. Appl. Phys. 57 ,4100 (Elsvier, 1987), Vol.10, p.321. (1985). D. Givord anf H. S. Li, J. Appl. Phys. 57 ,4100 J. F. Herbst, J. J. Croat, and W. B. Yelon, J. (1985). Appl. Phys. 57,4086 (1985). J. F. Herbst, J. J. Croat, and W. B. Yelon, J. D. Givord, H. S. (1985). Li, J.Appl.Phys.57,4100 Appl. Phys. 57,4086 (1985). D. Givord, H. S. Li, J.Appl.Phys.57,4100 (1985).

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160

THE OPTICAL PROPERTIES OF POLY (VINYL CHLORIDE) / POLY (ETHYLENE OXIDE) BLENDS G. M. NASR, S. M. ABD EL-WAHAB and A. ABD EL-ATHEM Physics Department, Faculty of Science, Cairo University, Egypt

The miscibility and optical properties of polyvinylchloride (PVC) blends with different concentration of polyethylene oxide (PEO) have been studied. FTIR spectroscopy studies show the presence of interactions between blend constituents. The optical properties in the UV-visible regions are investigated at room temperature. From absorption spectra in UVvisible regions, the dependence of the absorption coefficient on the photon energy suggests the presence of both direct and indirect allowed transitions in k-space. The values of the optical band gap (Eopt) for both transitions have been obtained. The width of the tail of localized states in the band gap (Eu) was evaluated using the Urbach-edges. Both the parameters (Eopt) and (Eu) vary with different PEO content. Keywords: PVC/PEO blends; FTIR; UV-visible.

1. Introduction In recent years, blending of polymers has gained significant interest. It is the cheapest way of producing materials with improved properties without laborious development of new products. This field has become economically very important [1, 2]. Nowadays, Plasticized PVC is widely used in the production of a number of array of medical applications [3] such as intravenous fluid bags and tubing, blood and plasma bags, enteral feeding and dialysis equipment, catheters, and gloves. PVC diversibility is due to its many valuable properties like low price, good processability, desirable mechanical strength and transparency [2]. PEO is the most commonly plasticizer used in the production of espatially blood bags, acts as nontoxic plasticizers to PVC, and blood-compatible surface modifiers [4]. In the present work, the miscibility and optical properties of the PVC/PEO blends are studied. For that purpose, blends of variable compositions were prepared. Their miscibility was investigated by FTIR. The optical properties of these blends were investigated using UV-visible spectroscopy in the wave-length range 200-800nm. As a result of this study we calculated all the optical parameters and energy gap of these samples. 2. Experimental Details 2.1. Sample Preparation The films of polymer blend were prepared by the solution-cast technique. The host materials Polyvinylchloride (PVC) was supplied by Fluka, while polyethylene oxide (PEO) was obtained from Sigma-Aldrich. The required amounts of PVC and PEO were dissolved separately in a mixture of 1,2-dichlorobenzene and tetrahydrofuran (1:1v/v), obtained from Riedel-de Haen, then mixed together and stirred. The solutions thus obtained were cast on a glass plate and allowed to evaporate slowly inside a desiccator. A range of blend composition (100/0, 90/10, 75/25, 70/30, 50/50 and 0/100). 2.2. FTIR Analysis FTIR spectra were measured on JASCO model FTIR-460 plus spectrophotometer in the wave number range (4000400 cm-1). The sharply defined transmission peaks corresponding to various modes of vibration of chemical bonds have been investigated for all samples. 2.3. UV-Visible AnalysisThe spectra in the UV-vis region were ascertained on a UV-3101 PC (Shimadzu) spectrophotometer. The optical absorption data were recorded at room temperature in the wavelength range (200 to 800 nm).The optical absorption coefficient α (for each wavelength) was calculated directly from the absorbance, A, using the following equation.

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

161

α =

I 2.3 2.3 A log o = d I d

where d is the thickness of the investigated sample, while respectively.

(1)

IO and I are the intensity of incident and transmitted light

3. Results and Discussion 3.1. Compatibility Studies Infrared spectroscopy has been proven to be highly effective for investigating various interactions between polymers. FTIR can be used to quantitatively and qualitatively study the mechanism of interpolymer miscibility through hydrogen bonds [5] - their presence is confirmed by characteristic changes of absorption bands of functional groups engaged in formation of hydrogen bonds. Absorption changes cause change of force constants of proton donor groups and proton acceptor groups - frequencies of stretching and deformating vibrations of these groups are changing. Bands originating from stretching vibrations of proton donor groups shift to lower wave numbers with parallel increase of intensity and band broadening; simultaneously, bands from deformating vibrations shift to higher wave numbers. For proton acceptor groups, frequencies of stretching vibrations also decrease, however to a lesser extent than frequencies of proton donor groups vibrations [6]. FTIR spectra were recorded in the transmittance mode, The FTIR spectra for pure PVC and pure PEO are shown in Fig. 1. The band assignments for PVC and PEO have already been observed and compared with the literature and are listed in Tables 1 and 2 respectively.

Fig. 1. FTIR spectra of i) pure PVC and ii) pure PEO.

162

Table1. FTIR spectral assignments and wavenumbers of pure PVC. Peak assignments

Bands observed for pure PVC (cm-1)

Literature (cm-1)

References

C-H stretching

2913

2890-2958

[7]

CH2 deformation

1329

1339

[7, 8]

CH-rocking

1251

1240-1257

[7, 8]

C-C stretching

1097

1095

[9]

trans CH wagging

961

961

[7]

C-Cl stretching

838

844

[10]

cis CH wagging

616

600

[8]

Table 2. FTIR spectral assignments and wavenumbers of pure PEO. Peak assignments

Bands observed for pure PEO (cm-1)

Literature (cm-1)

References

O-H stretching

3563

3000-3700

[6,11]

C-H stretching

2904

2900

[12]

CH2 scissoring

1471

1466

[6]

CH2 wagging

1356

1340

[6,13]

C-O stretching

1122

900-1300

[11]

Figure 2i shows the FTIR spectra of pure PVC, pure PEO and PVC-PEO blends in the wave number range 4000 to 2500 cm-1. One can notice that the doublet peak of pure PVC at 2968 and 2913 cm-1 (stretching mode) has changed in shape to broad peak and shifted to lower wave number as PEO content increases, this might be due to overlapping with the broad peak at 2904 cm-1 originating from PEO. On the other hand, the absorption band at 3563 cm-1 corresponds to the O-H stretching band derived from the end hydroxyl group of PEO vanishes in the presence of PVC. Figure 2ii shows the FTIR spectra of pure PVC, pure PEO and PVC-PEO blends in the wave number range 1600 to 1000 cm-1.The peak at 1429 originating from PVC overlaps with the peak 1451 originating from PEO forming doublet broad peaks for all blended samples. The peak of pure PVC at 1329 cm-1 (deformation mode) has shifted to higher wave number with increasing PEO content and doublet in the sample (PVC:PEO) (50:50) at wave number 1359 and 1342 cm-1 as shown in Fig. 2ii. Besides, the characteristic peak 1097 cm-1 of pure PVC becomes broader as PEO content increases and slightly shifted to higher wave number. This may be due to the overlapping with the peak at 1122 cm-1 originating from PEO. From analysis of the FTIR spectra (the change in shape and position of the peaks), one deduced that there is a specific interaction between the PVC/PEO blends that favors the miscibility of the blends.

163

Fig. 2. The FTIR spectra of PVC: PEO blends in wave number range i) 4000-2500 cm-1 ii) 1600-1000 cm-1. 3.2. UV spectroscopy On the basis of the magnitude of absorption coefficient in the investigated spectral range and its dependence on the incident photon energy, several conclusions about band structure of PVC/PEO blends could be deduced. Figure 3i shows the UV absorbanc spectra at room temperature for PVC/PEO blends which illustrate two strong * UV absorption peaks centered at [270, 278 nm] characterizing π − π absorption band of pure PVC. Absorption in the short wavelength UV region ( λ LaFeO3>LaMnO3, which is the inverse ranking

Orthoferrites of the general formula La1−xCaxFeO3 (0.1 ≤

order of activity observed for methane combustion

(13, 16)

.

x ≤ 0.5) have been assayed as catalysts for methane

Rare earth orthoferrites (AFeO3) with orthorhombic

combustion, and partial substitution of the Ca2+ showed

structure have much attention due to their unique

no

physical and chemical properties

(2, 3)

. Because of their

significant

effect

on

the

intrinsic (11)

of the perovskites for this reaction 4+

catalytic

. Although a

mixed conductivity, they exhibit potential applications

greater Fe

in various fields, such as cathodes in solid oxide fuel

Ca

cells,

environmental

approximately constant, suggesting an increase in the

monitoring films, active materials for chemical sensors

formation of oxygen vacancies to preserve charge

for the detection of humidity, alcohols and gases, and so

neutrality(11).

active

oxidation

catalysts,

content was observed with increasing

substitution,

the

Fe4+/Ca2+

ratio

remained

forth(4–6). Moreover, the remarkable properties of

It is well known that perovskite-like, mixed

orthoferrites, such as high domain-wall velocity and the

oxide substitution of the trivalent A-site metal ion with a

existence of Bloch lines, are significant for applications

bivalent or tetravalent metal cation (A/) is accompanied

in magneto optical current sensors and fast latching

by a modification of the oxidation state of the B-site

(7, 8)

magneto-optical switches

. Perovskite materials with

the general formula La1-xSrxFeO3 (0.0 ≤ x ≤ 1.0)

metal

cation,

thus

modifying

catalytic

activity.

Moreover, modification of the oxidation state of the B

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

169

site metal cation by insertion of A/ may be accompanied

CuKα radiation with wavelength λ = 1.5418Å in the

by the formation of structural defects, thus leading to

range of 20-80°. The crystalline phase was identified

non-stoichiometry. In the Co-containing perovskites,

using the International Centre for Diffraction Data

this usually means oxygen defects. The

parent

work

(1)

aimed

(ICDD) cards. The shape and morphology of the to

perform

a

comparative study on the physical properties of the LaFeO3 substituted by different divalent metal ions 2+

(Ca , Sr obtain

2+

2+

and Ba ) with a constant ratio of 30% to

La0.7M2+0.3FeO3

(M

2+

2+

= None, Ca , Sr

2+

particles was analyzed using transmission electron microscope (TEM) model (JEOl-1010). The

hysteresis

and

magnetization

measurements were performed using vibrating sample

and

magnetometer (VSM; 9600-1 LDJ, USA) with a

Ba ). Also one of the important goals is to improve the

maximum applied field of 15 KOe at room temperature.

magnetic constants as well as the transition temperature

The dc magnetic susceptibility (χM) of the investigated

in order to reach a more applicable sample.

samples was measured using Faraday’s method(15) as a

2+

function of absolute temperature at different magnetic 2. Experimental Techniques

field intensities. The RLC Bridge (Hioki model 3531 Japan) was used to measure the ac electrical resistivity

Orthoferrite samples having the chemical formula (LaFeO3,

La0.7Ca0.3FeO3,

La0.7Sr0.3FeO3

of the prepared samples. The dielectric constant (ε/),

and

La0.7Ca0.3FeO3) were prepared by the double sintering ceramic technique from analar grade from oxides (British Drug House BDH, U.K.) La2O3, CaO, BaO, SrO and Fe2O3. Stoichoimetric ratios were good mixed,

dielectric loss tangent (tanδ) and ac resistance of the samples were measured as a function of absolute temperature at different frequencies ranging from 100 kHz to 5 MHz.

grinded using agate mortar for three hours and then pressed into pellet form using uniaxial press of pressure

3. Results and Discussion

5×108 N/m2. The pellets were presintered in air at 900oC for 6 hours with a heating rate of 4oC/min. The

X-ray diffraction patterns of the samples LaFeO3,

samples were cooled to room temperature with the same

La0.7Ca0.3FeO3,

rate as that of heating, regrinded, sieved and pressed

Fig. (1), reveal strong diffraction peaks at 2θ = 22.7,

again into pellets. The pellets were finally sintered at

32.5, 39.9, 46.6, 57.8 and 68o which assure the

1250oC for 10 hours using the same previous rate and

formation of the samples in single phase orthorhombic

then cooled to room temperature with the same rate as

structure with space group (Pbnm). The lattice

that of heating.

parameters a, b and c were calculated on the basis

The X-ray powder diffraction patterns were carried out using diffractometer (Proker D8 - USA)

La0.7Sr0.3FeO3

and

La0.7Ba0.3FeO3

of the orthorhombic unit cell and reported in Table (1).

170

(002) (020)

(161)

(004)

values in accordance with those reported in the

(420)

(400)

(312)

(222)

(202) (220) (200)

corresponding ICCD cards. The change in theoretical density is attributed to the variation of the unit cell

La0.7Ca0.3FeO3 agreed well with those reported by M. A. Ahmed et al.(15).

ICDD Card: 88-641

IR transmission spectra for the parent, Ca2+,

60

(004) (060) (161)

Sr2+ and Ba2+ substituted samples is illustrated in (133)

(042)

B (040) (141)

volume, molecular weight and the number of molecules per unit cell (Z). The values of a, b and c for the sample

(400)

(321)

(301)

(202)

(220)

ICDD Card: 49-1884

(022)

of the divalent metal ions as it is responsible for the A site cation radius < rA >. The theoretical density gives

C

(002)

The reported data in reveals also that the variation of the lattice parameters depends strongly on the ionic radius

D

40

that the values of the lattice parameters a, b and c increase with increasing the ionic radius of A cation.

ICDD Card: 89-1269

(110) (020)

(020)

(042)

(141)

(040)

ICDD Card: 88-641

(022)

(020)

Intensity 20

From the reported data in Table (1), It is clear

E

2θ

Fig. (2: a, b). The spectrum for the parent LaFeO3 shows an absorption band at 565 cm-1 corresponding to Fe-O 80

Fig. (1). XRD of the samples La1-xMxFeO3, x = 0.0 and x = 0.3, M = Ca2+, Sr2+ and Ba2+.

stretching vibration situated on the octahedral site. There are four transmission bands at 582, 387, 259, 221; 578, 375, 262, 223 and 605, 372, 305 and 227 cm-1 corresponding to La0.7Ca0.3FeO3, La0.7Sr0.3FeO3 and

Table (1). The lattice parameters (a, b and c), unit cell volume, theoretical density of the samples LaFeO3, La0.7Ba0.3FeO3, La0.7Ca0.3FeO3 and La0.7Sr0.3FeO3. a(Å)

LaFeO3

5.56

b(Å)

7.862

c(Å)

5.558

V(Å3)

243.34

Dx (g/cm3) 7.061

ICDD Card

88-641

La0.7Ba0.3FeO3 respectively. A small shoulder at about 600 cm-1 was appeared which is a feature of rare earth orthoferrite(16). The band at about 582 and 578 cm-1 for the Ca2+ and Sr2+ samples is assigned to the stretching mode of vibration of the FeO6 octahedron in LaFeO3. The band around 350 cm-1 is regarded as bending

La0.7Ca0.3 FeO3

5.522

7.732

5.552

237.11

2.984

49-1884

La0.7Sr0.3 FeO3

5.517

5.502

7.836

237.93

6.346

89-1269

La0.7Ba0.3 FeO3

5.553

7.845

5.488

239.13

6.728

88-641

vibration of O-Fe-O(17). TEM micrographs for LaFeO3, Ca2+ and Sr2+ substituted LaFeO3 are illustrated in Fig. (3: a-c). It is clear that at x = 0.0 the particles have nearly homogeneous platelet shape with an average crystal size

171

of 90 nm. Large spherical crystallites with homogeneous shape and well distributed were obtained in case of Ca2+ ion substitution, while large platelets are observed with

T%

non homogeneous distribution in case of Sr2+ ion.

a) LaFeO3

1000 

900

800

700

600



500

400

300

Wave number (cm-1)

Fig. (2.a). IR transmission of the sample LaFeO3.

T%

b) La0.7Ca0.3FeO3

Ba Sr Ca 1000

900

800

700

600

500

400

300

Wave number (cm-1)

c) La0.7Sr0.3FeO3

Fig. (2.b). IR transmission of the samples La0.7Ba0.3FeO3, La0.7Sr0.3FeO3 and La0.7Ca0.3FeO3.

Fig. (3: a-c). TEM for the samples b) La0.7Ca0.3FeO3 and c) La0.7Sr0.3FeO3.

a)

LaFeO3,

172

The relation between molar magnetic susceptibility (χM)

0.0075 a)LaFeO3

and absolute temperature at different magnetic field La0.7Sr0.3FeO3 and La0.7Ba0.3FeO3 is shown in Fig. (4:a-d). χM decreases slowly with increasing the absolute temperature up to the transition at which χM decreases

2620 Oe

0.0055

χ M (emu/g.mole)

intensities for the samples LaFeO3, La0.7Ca0.3FeO3,

3050 Oe 0.0035

0.0015 300

500

700

rapidly. The data shows that the samples are with a slight canting resulting in a weak ferromagnetic

1.2

improvement

of

the

χ M (emu/g.mole)

1.6

The

magnetic

properties is emphasized from the values of χM for the parent compound LaFeO3 which is nearly 0.0055 emu/gm.mole

while

that

for

La0.7Ca0.3FeO3

and/or canting angle as well as buckling of the < FeO6 > octahedron. In the case of Ba2+ ion substitution in

3+

4+

2+

2+

change from Fe to Fe as in case of Ca and Sr ions. From a closer look to the plot of χM vs T for Ba

2+

substitution, one could estimate the magnetic ordering as

0.4

400

500

600

700

c) La0.7Sr 0.3FeO3

2320 Oe 2620 Oe

0.08

3050 Oe

0.04

400

500

600

700

T(K)

0.008

χ M (emu/g.mole)

deficiency and there is a lower probability of valence

3050 Oe

0 300

LaFeO3, there is no large change in the value magnetic susceptibility properties, this may be due to the oxygen

2620 Oe

0.12

χ M (emu/g.mole)

depends on the strength and type of exchange interaction

2320 Oe

T(K)

1.65 emu/gm.mole and that for La0.7Sr0.3FeO3 is 0.006 modulation of the magnetization by divalent substitution

b) La0.7Ca0.3FeO3

0.8

0 300

is

emu/gm.mole. From these data, one could argue that

900

T(K)

antiferromagnetic characterized by the presence of TN component.

2320 Oe

d) La 0.7Ba 0.3FeO3

(2320Oe) (2620Oe)

0.006

(3050Oe) 0.004

0.002

a frustrated spin system with spin glass like behavior as a kink at about 710K. This behavior could be interpreted as a structural distortion originated from the larger

0 350

450

550

650

750

850

T(K)

radius Ba2+ ions as compared with that of La3+ ions. Accordingly, < FeO6> octahedrons are expected to be

Fig. (4: a-d). Dependence of the molar magnetic susceptibility

tilted in such away to change the canting angle, suppress

(χM) on the absolute temperature for the samples (a) LaFeO3,

the magnetic ordering and inhibit the super exchange

(b) La0.7Ca0.3FeO3, (c) La0.7Sr0.3FeO3 and (d) La0.7Ba0.3FeO3 at

interaction.

different magnetic field intensities.

173

magnetic

The evolution of the Néel temperature is a

moment, the Curie constant and the Curie-Weis

direct function of the Fe4+ ratio. This is partly due to

constant were calculated from the plots of χM-1 vs. T in

decreasing the number of unpaired electrons when Fe4+

the paramagnetic region and reported in Table (2).

(3d4) replaced Fe3+ (3d5). Moreover, as predicted by P.

These data confirms the antiferromagnetic behavior

W. Anderson(20), the magnetic coupling Fe3+-O- Fe4+

with negative values of Curie-Weis constant. The

(3d5-3d4)

values of the magnetic moment are larger than

consequence, the antiferromagnetic coupling diminishes

those reported for the Sb3+ substituted LaFeO3

more quickly than expected by 3dn-3dn-1 substitution.(21)

The

values

of

the

effective

samples(18) due to the existence of high spin Fe4+ ions Fe3+

is

essentially

ferromagnetic.

As

a

Figure (5) illustrates the hysteresis loops for the

ions.

samples LaFeO3, La0.7Ca0.3FeO3 and La0.7Sr0.3FeO3. The

between

antiferromagnetic character is common for all samples.

ions. These results

The ferromagnetic component is clear for Ca2+ and Sr2+

are similar to the results were obtained by M. A. Ahmed

samples rather than pure sample. One also observed that

coupled Despite

ferromagnetically the

superexchange

antiferromagnetically coupled Fe (19)

with

interaction 3+

. Depending mainly on the synthesis techniques

the shape of the hysteresis changes with the divalent

and conditions (sintering atmosphere, cooling rate, etc.)

metal ion substitution. A weak saturation is observed in

et al.

(rionic =

Ca2+ and Sr2+ substituted samples while a lack of

1.216 Å ) and Ca2+ ions (rionic = 1.180Å) in 9-fold

saturation is the main character for the pure sample. As

coordination, the substitution of La3+ by M2+ in LaFeO3

for all antiferromagnetics, linear shape with low

has at least two possibilities. First: the system La1x

saturation for the pure sample is obtained. The

M2+xFeO3 consists of two or more phases; iron possesses

ferromagnetic like behavior appear to be correlated with

an intermediate valence state that increases gradually

Ca2+ and Sr2+ substitution. The difference here is due to

from Fe3+ to Fe4+ with increasing x. The second

the radius of the divalent ion which affects directly on

possibility is that the iron keeps its stable trivalent state

the Fe-O-Fe bond angle. Accordingly, the exchange

and the oxygen deficiency appears in the lattice in order

interaction will be altered. Moreover, the divalent

to neutralize the compound electrically(15).

substitution will force some of the existing Fe3+ ions to

and the difference in ionic radii between La

3+

change their valence as La0.7M0.32+Fe0.73+Fe0.34+O3 to maintain charge neutralization. This result agrees well Table (2). The values of the magnetic constants: the effective magnetic moment, the Curie constant and the Curie-Weiss constant of the samples LaFeO3, La0.7Ca0.3FeO3, La0.7Sr0.3FeO3 and La0.7Ba0.3FeO3 at magnetic field intensity of 2620 Oe.

with the data of M. A. Ahmed et al.(15). The number of tetravalent iron ions initiated in the system depends on the concentration of divalent metal ion. In our case, the

θ (K)

µeff (B.M.)

LaFeO3

C (emu/gm.mole).K 3.96

-170

5.60

the only factor affecting on the magnetic properties is

La0.7Ca0.3FeO3

33.30

-72

16.33

the type of the divalent cation itself, its electronic

La0.7Sr0.3FeO3

9.00

-208

8.49

La0.7Ba0.3FeO3

2.48

-35

4.463

Samples

divalent metal ion content is kept constant. Therefore,

configuration

and

ionic

radius.

The

saturation

magnetization for both Ca2+ and Sr2+ substituted

174

samples is increased up to 10 times its values for the parent. Such clear and excellent enhancement of the

and Sr

2+

substituted samples as both of them have large

crystallite size. The saturation magnetization, squareness ratio (Mr/Ms) and the A site cation radius are reported in table (3). The remanence magnetization was also

(a) LaFeO3 M (emu/gm) M (emu/gm)

room temperature magnetization is achieved for Ca

0.135

2+

0.0

-0.135

improved as clarified in Table (3) by divalent substitution specially the Sr2+ samples. Accordingly one

-12000

0.0

could say that the Sr2+ doped sample is of hard type like

12000 H(Oe)

materials. The SQR increased from 0.1 for the parent compound to about 0.5 for the Sr2+ doped sample. The 1.5

coercive field was achieved for the Sr2+ doped sample

interpret this improvement in all magnetic parameters at room temperature as due to several reasons as follows (i) The existence of Fe4+ ions in high spin state (HS)

M (emu/gm)

more than 6 times the parent coercivity. One could

(b) La0.7Ca0.3FeO3

Fe4+ (t2g3 eg1) in a reasonable ratio (30% of the total iron content) in addition to the rest Fe

3+

(HS)

(t2g3

eg2).

0.0

-1.5

(ii) -12000

The change in the A site cation radius induces a

0.0

12000 H(Oe)

variation in the Fe-O-Fe bond angle and distance; though affecting the magnitude of the exchange r

1.65

s

Table (3) The values of magnetic constants and the Néel temperatures for the samples LaFeO3, La0.7Ca0.3FeO3, La0.7Sr0.3FeO3 and La0.7Ba0.3FeO3.

LaFeO3

RA (Å) 1.21

HC (Oe) 1196

Mr (emu/gm) 0.014

Ms (emu/gm) 0.161

SQR= Mr/Ms 0.085

TN(K) 763

La0.7Ca0.3FeO3

1.20

658.7

0.642

2.033

0.316

694

La0.7Sr0.3FeO3

1.24

3321

0.978

2.066

0.473

748

La0.7Ba0.3FeO3

1.29

1072

0.011

0.258

0.043

710

M (emu/gm)

interaction itself.

0.0

(c) La0.7Sr0.3FeO3 1.65



-12000

0.0

12000

H(Oe)

Fig. (5: a-c). The hysteresis loops of the samples: (a) LaFeO3 (b) La0.7Ca0.3FeO3 and (c) La0.7Sr0.3FeO3.

175 6

Figure (6: a-d) shows the dependence of the

100 kHz

(a) LaFeO3

200 kHz

real part of the dielectric constant on absolute

400 kHz

4

ɸͬdžϭϬͲϯ

600 kHz

temperature as a function of frequency for the undoped

800 kHz

samples LaFeO3,

1 MHz 2 MHz

2

La0.7Ca0.3FeO3, La0.7Sr0.3FeO3 and

La0.7Ba0.3FeO3 respectively. It is clear that the values of

3 MHz 4 MHz

ε/ differ from Ca2+ and Sr2+ doping as compared with the

5 MHz

0 300

400

500

600

700

800

parent compound. A hump appears at about 470K for

T(K)

Ca2+ doping clearly and is less pronounced for Sr2+

5 100 kHZ

(b)

200 kHZ

4

La0.7Ca0.3FeO3

doping. ε/ reaches maximum values at about 620K and

600 kHZ

then decreased while it doesn't behave similarly to Ca2+

800 kHZ Ͳϰ ɸͬdžϭϬ x10-4

3

2

1

MHZ

2

MHZ

3

MHZ

4

MHZ

5

MHz

doped sample as well as the undoped one. For the Ca2+ doped sample, ε/ continues to increase at T > 600K.

ɸ džϭϬ

1

From the data in Table (4), one observed that, Ca

0 300

400

500

600

substitution improves the conductivity by more than 18

700

times while the Sr enhances it by 25 times.

T(K)

20 100 kHZ

La0.7Sr0.3FeO3

600 kHZ 800 kHZ

(c)

1 MHZ

12

Table (4) The values of ac conductivity and ε/ at different for the samples LaFeO3, La0.7Ca0.3FeO3, La0.7Sr0.3FeO3 and La0.7Ba0.3FeO3.

ͬ

16

Ͳϯ

200 kHZ

RA(Å)

1.216

La0.7Ca0.3FeO3

1.205

75.9×10-3

46.27×10-3

4013.7

La0.7Sr0.3FeO3

1.244

107.8×10-3

41.18×10-3

402.16

Ͳϯ

ɸ džϭϬ

ͬ

4 MHZ 5 MHz

ε/ at 303K 5MHz 52.12

LaFeO3

3 MHZ

8

σac at 303K 5MHz 5.07×10-3

σac at 443K 5MHz 4.2×10-3

2 MHZ

4 0 350

450

550

650

750

T(K) 16 100 kHZ

14

200 kHZ

12

600 kHZ

400 kHZ

800 kHZ 1 MHZ

A giant remarkable increase about 3 orders of

(d)

magnitude is achieved for the Ba substituted sample at

2 MHZ

8

5MHz and 443K. Ca2+ and Sr2+ ion substitution favors

3 MHZ

ͬ

ɸ džϭϬ

Ͳϰ

10

La0.7Ba0.3FeO3

the formation of Fe4+ with a ratio nearly equal to the

4 MHZ

6

5 MHz

4

divalent substituted sample, one expected oxygen

2

deficiency. The expected tilting of the octahedron

0 300

400

500

600

700

800

T(K)

/

Fig. (6: a-d). Dependence of ε on absolute temperature T (K) for the sample (a)LaFeO3, (b)La0.7Ca0.3FeO3, (c)La0.7Sr0.3FeO3 and (d)La0.7Ba0.3FeO3 as a function of frequency.

in case of Ba2+ may induces a dipole moment which results in an increase in the polarization as well as ε/. Also, a mixed state of ionic-electric conductivity is expected to be predominant here.

176

(8) Y. S. Didosyan, H. Hauser, J. Nicolics, Sensors

4. Conclusion

and Actuators, 81, 263(2000). The samples LaFeO3, La0.7Ca0.3FeO3, La0.7Sr0.3FeO3 and La0.7Ba0.3FeO3 were prepared in single phase. There is an improvement in the magnetization with divalent

(9) A. Evdou, V. Zaspalis, L. Nalbandian, Fuel, 89, 1265–1273(2010). (10) Gang

Deng,

Yungui

Chen,

Mingda

Tao,

substitution ions. This improvement is emphasized

ChaolingWu, Xiangqian Shen, Heng Yang,

from the values of χM for the parent compound LaFeO3

Electrochimica Acta, 54, 3910–3914(2009).

which is nearly 0.0055 emu/gm.mole while that

(11) P. Ciambelli, S. Cimino, L. Lisis, M. Faticanti, G.

for La0.7Ca0.3FeO3 is 1.65 emu/gm.mole and for

Minelli, I. Pettiti, P. Porta, Applied Catalysis B:

La0.7Sr0.3FeO3 is 0.006 emu/gm.mole. The saturation

Environmental, 33, 193(2001).

2+

2+

magnetization for both Ca and Sr substituted samples is increased up to 10 times its values for the parent. Such clear and excellent enhancement of the room temperature magnetization is achieved for Ca

2+

and Sr

2+

substituted samples as both of them have large crystallite size.

(12) D. Fino, N. Russo, G. Saracco, V. Specchia, Journal of Catalysis, 217, 367(2003). (13) G.

Saracco,

F.

Geobaldo,

G.

Baldi,

Applied Catalysis B: Environmental , 20, 277(1999). (14) N. Russo, D. Fino, G. Saracco, V. Specchia, Journal of Catalysis, 229, 459(2005).

References

(15) M. A. Ahmed, S. I. El-Dek, Materials Science and Engineering B, 128, 30–33(2006).

(1) G. Pecchi, P. Reyes, R. Zamora, C. Campos, Luis E. Cadu´s, B. P. Barbero, Catalysis Today 133– 135 2008, 420–427. (2) S. Hui, X. Jiayue, W. Anhua, Journal of Rare Earths, 28, 416(2010). (3) J. G. Li, X. L. Kou, Y. Qin, H Y. He, Appl. Phys., 92(12), 7504(2002). (4) Z. Yang, Y. Huang, B. Dong, H. L. Li, Materials Research Bulletin, 41(2), 274(2006). (5) N. N. Toan, S. Saukko, V. Lantto, B. Physica, 327, 279(2003). (6) X. S. Niu, W. M. Du, W. P. Du, Sens. Actuators B, 99, 399(2004). (7) Y. S. Didosyan, H. Hauser, G. A. Reider, W. J. Toriser, Appl. Phys., 95, 7339(2004).

(16) M. A. Ahmed, R. Seoudi, S. I. El-Dek, Journal |of Molecular Structure, 754, 41–44(2005). (17) K. Li, F. Wu, D. Wang, T. Xie, T. Li, Materials

Chemistry

and

Physics,

71,

34–39(2001). (18) M. A. Ahmed, M. Solyman Seluim, M. M. Arman, Materials Chemistry and Physics, under publication. (19) M. A. Ahmed, S. I. El-Dek, Materials Letters, 60, 1437–1446(2006). (20) P. W. Anderson, Phy. Rev., 79, 350–356 and 705–710(1950). (21) S. Komornicki, L. Fournès, J. Grenier, F. Ménil, M.

Pouchard,

P.

Hagenmuller,

Research Bulletin, 92 (2001).

Materials

II. HIGH DENSITY SHORT PULSE LASERS, LASERS AND APPLICATIONS II-1 KEYNOTE, PLENARY and INVITED PRESENTATIONS

This page intentionally left blank

179

LASER DRIVEN SECONDARY SOURCES FOR SPECTROSCOPY, PLASMA DIAGNOSTICS AND OTHER APPLICATIONS THOMAS KUEHL, BASTIAN AURAND, VINCENT BAGNOUD, BORIS ECKER, UDO EISENBARTH, DANIEL HOCHHAUS, PAUL NEUMAYER, HUANYU ZHAO, BERNHARD ZIELBAUER, DANIEL ZIMMER, JAMIL HABIB, SOPHIE KAZAMIAS, ANNIE KLISNICK, DAVID ROS, JOSEF SERES, CHRISTIAN SPIELMANN and DANIEL URSESCU 1

3

GSI Helmholtz Centre, Darmstadt (Germany), 2Friedrich Schiller University, Jena (Germany) Helm University, Paris-Sud 11, Orsay (France), 4National Institute, Lasers, Plasma and Radiation Physics, Bucharest (Romania)

Ultra-High Intensity lasers in the regime above 100 TW have developed into a well studied tool for the preparation of plasma targets. In addition they can provide unprecedented sources of coherent soft x-rays and incoherent hard x-rays and of proton and light-ion beams. These sources are unique in their intensity and time definition. In the specific case of the laser driven x-ray laser, the coherence and narrow bandwidth of the source holds promises for additional applications. Use of secondary sources for plasma diagnostic has already been reported by several groups but in all cases still source developments are going on. The presentation will report on activities at the PHELIX laser at the GSI Helmholtz Centre, and plans and proposals for the application in combination with heavy-ion beams at GSI and the future FAIR facility.

1. The PHELIX Project at the GSI Helmholtz Centre The PHELIX laser at the GSI Helmholtz Centre in Darmstadt [1] is a high-energy Nd: Glass Laser providing pulse energies of up to 2 kJ. Essential for a wide applicability of this laser system is its versatility in the temporal duration of the laser pulses. PHELIX therefore can be operated with either nanosecond or subpicosecond pulse duration. In the short-pulse mode it reaches pulse intensities of several 100 TW. For the investigation of dense plasmas in the temperature regime of 10 to 100 eV, such a laser can provide novel means of precise measurements of density and temperature as a diagnostic tool. In particular with the combination of high-current heavy-ion beams with intense laser beams, a number of fundamental science issues in the field of high energy density physics will become accessible experimentally for the first time. Over the last years at the GSI accelerator facility the FAIR project [2] was started with the aim to increase the intensity by a factor of 1000 for beams of very heavy ions in the energy range from multi-MeV up to the GeV/u – higher than any other accelerator facility in the world. A strong motivation for this upgrade project evolved from present research on dense plasmas at GSI and was stimulated by the perspectives of the future plasma physics program at the international facility for antiproton and ion research which will be installed at GSI.

As outlined in Fig. 1, the laser is situated in the centre of the present accelerator facility, in between of the target area of the linear accelerator and the high energy hall with the heavy-ion synchrotron and the storage ring.

Fig. 1: Overview of the present accelerator faciltiy at GSI and the future FAIR facility. The location of the PHELIX laser is indicated by the red arrow. 2. Soft X-ray Sources X-rays for the diagnostic of plasma states have the advantage to penetrate through dense material, and to provide superior spatial resolution. In particular x-ray lasers can also be used for interferometric analysis. For this reason, the development of x-ray laser sources was

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

180

one of the first subjects started at PHELIX.: For plasma x-ray laser, this means lasers, where the amplification medium is a highly excited hot plasma, a new pumping scheme was established [3,4], which has several advantages. It is by now also used at the LASERIX x-ray laser facility at the university of Paris sud. In the usual approach a nanosecond pre-pulse under normal incidence provides the optimal plasma preparation, and a picosecond pulse under non-normal incidence performs the final heating and excitation process. In contrast to this, here both pulses are produced in the front-end of the CPA (chirped pulse amplification) pump laser chain by a small Mach-Zehnder type beamsplitter, and delivered onto the target by the same optics. The two pulses are focused onto the target with the same spherical mirror under non-normal geometry, optimized for efficient traveling wave excitation for the main-pulse. For Ni-like palladium (14.7 nm) the pump energy can be less than 500 mJ total pulse energy on the target. This proves that this configuration is at least as efficient as the standard GRIP scheme, providing much simpler and more reliable operation. The experimental set-up is depicted in Fig. 2.

line focus on the Pd slab target has a dimension of 50 mm by 5.5 mm FWHM. Both pulses hit the target at the same grazing incidence angle of 29 degrees, a value determined to be the optimal GRIP configuration in the classical scheme [3]. Thereby the electron density at which the energy is absorbed is matched to the optimum density for x-ray lasing.The fact that in the DGRIP (double pulse single beam grazinng incidence pumping) scheme also the first pulse, which creates the plasma plume, hits the target under the non-normal geometry evidently has no negative effect on the plasma creation. The improved double pulse non-normal incidence pumping scheme provides a simplified and efficient way also to produce XRL output photon energy close to 100 eV, requiring around 50 J of pump energy. Even higher expectations for a highly versatile soft x-ray source are seen in a novel x-ray amplification

Fig. 3: The measured exponential and sin² increase are clear indications for XPA and HHG, respectively.

Fig. 2: Experimental set-up showing the pump laser beam-lines and XRL diagnostics. The insert shows the schematic view of the DGRIP pulse shape. The asymmetric path of the input beam leaves room for a secondary beam for high-harmonics generation. A typical focusing system produces a line focus with an intrinsic travelling wave speed of 1.2 c. The beam from the compressor is deflected by a flat mirror onto a spherical mirror with a focal length of 600 mm which is positioned off the normal incidence. A useful

Fig. 4: The spectral narrowing of the emitted radiation of the 41st harmonic is a further indication of the finite gain bandwidth.

181

scheme similar to the process of high harmonic generation (HHG). This was first demonstrated at PHELIX in 2010. In these experiments a strong increase of the HHG output for a specific range of gas pressure [5,6]. A simple theoretical model can describe this as an induced recombination of the electrons in the gas target leading to an amplification of the HHG radiation. Both plasma x-ray lasers and XPA hold great promise for applications in plasma diagnostics and high resolution, temporally resolved imaging. Narrow band x-rays in the region of 10 keV and higher can be generated by the excitation of e.g. K-alpha transitions by laser accelerated electrons in thin foils.The yield of this excitation process is strongly enhanced by the so-called refluxing of the electrons[7]. Under the influence of the ulra-intense laser pulse the electrons are accelerated strongly enough to leave the foil which in turn is charged up and exerts a strong electrical potential. By this potential the electron are accelerated back onto the surface. This happens several times, thus increasing the effectiveness of x-ray generation. Although this source is not coherent, it is sufficiently narrow-band to use it not only as a backlighter, but also for a plasma diagnostic by analysis of the spectrum of scattered radiation. At PHELIX a possibility was created to transport two separate beams to the 31.5 cm free aperture of the amplifiers. In this way, one beam can be used to create a plasma state, while the other beam serves for the production of hard x-rays. 3. Proton Acceleration With the advent of ultra-high power lasers, laser acceleration of particles [8] has become an acknowledged field of research. In the context of diagnostic methods, in particular protons have the already proven potential to provide high resolution imaging with sub-picosecond time resolution. The standard method of ion-acceleration is the so-called Target-Normal Sheath-Acceleration (TNSA). As in the case of the laser driven K-alpha source, the laser is used to accelerate electrons out of a foil target. This electric field points normal to the target surface. optimized conditions the charge separation leads to a strong acceleration potential between the target surface and the electrons leaving the foil. Field gradients in

excess of 1012 V/m, much higher than possible in conventional particle accelerators. This gives the possibility to built extremely compact sources of energetic particle pulses. Also in contrast to standard accelerators, the pulse duration is of the order of a picosecond. A very attractive application could become the use in nuclear medicine. A major obstacle for the application of such sources is the problem, to combine these with beam forming and beam transporting systems as it is well established in conventional accelerators. Therefore at GSI a new experimental station has been set up, where laser accelerated ions can be directed into a section of the GSI ion accelerator [9].

Fig. 4: View of the laser target station at the linear accelerator. The larger tubes cover the beam from the PHELIX laser. The 100 TW compressor is located in the structure on the left. The ion beam transport componrents are visible in the lower front. References 1. 2. 3. 4. 5. 6. 7.

Bagnoud, V. et al., Appl. Phys. B 100, 137, 2010 FAIR Conceptual Design Report, GSI Zimmer, D. et al., Opt. Exp. 16, 10398-10403 (2008) Kuehl, T. et al., Laser & Part. Beams 25, 93 (2007) Seres, J. et al., Nature Physics 6, 455, 2010 B. Aurand et al., Nucl. Instr. and Methods, Accepted Neumayer P. et al., PHYS. OF PLASMAS 17, Article Number: 103103, 2010 8. Cowan, T et al., Laser & Part. Beams, 17, 773, 1999 9. The LIGHT Project Conceptual Design Report, GSI 2010

182

ADVANCED LABORATORY FOR HIGH DENSITY PHYSICS LOTFIA EL NADI1,2,*, A. NASSER A. FETTOH1, A. REFAIE1, GALLILA A. MEHENA1,2, HUSSEIN A. MONIEM1, HISHAM IMAM2, KHALED A. ELSAYED1, MAGDY OMAR1 and SALAH H. NABY2 2

1 Physics Dept., Faculty of Science, Cairo, Egypt, Giza, Egypt International Center of Scientific and Applied Sciences of High Density Lasers NILES, Cairo University, Giza, Egypt *[email protected]

The objectives of establishing an Advanced Laboratory is meant to: *Create facilities and programs for performing systematic studies at Cairo University, relevant to High Energy Density Physics in general, Energy Production, National Industrialization and other applications. *Establish a laboratory highly equipped with high density ultra short pulse Lasers that do not exist in Egypt up to the moment. *Initiate unprecedented large experiments provided by high technological measuring equipments that are widely used in international laboratories. The potential applications of this research are numerous, not only in physics, but also in new energy resources, chemistry, biology, material science, fast ignition approach to fusion, accelerators for relativistic electrons and for nuclear effects and charged ion acceleration. This presentation is meant to report on the experimental equipments needed to initiate this laboratory as well as to enlighten the relevant studies that could be performed towards new energy resources.

Introduction Large HDS experiments provided by high technological measuring equipments are already in operation at International laboratories, namely VULCAN in UK, HIPER in Europe, QBF in Korea, and NIF in LLNL in USA. Establishing a Laboratory for advanced HDP would be dedicated to the pursuit of research for Inertial Fusion Energy as a sustainable, clean and long term solution to mankind energy needs. It simultaneously provides a unique tool in order to carry out scientific and applied research that has direct impact on innovative industrial materials serving the Egyptian and the International society. Other fields of applications are wide open to make of Cairo University a domain of present and future scientific fields, placing Egypt on the International map of new advanced research devoted to serve and upgrade the capacity and needs of societies. It is important to create new scientific young generation of researchers capable of handling and performing high standard research in order to upgrade conventional ones still going on in several centers. It is worthwhile to mention that in Japan there are over 16 labs, in China 8, in Korea 4 in India 3, in Russia several and in USA there are about 22 like laboratories for high density Laser studies. The study of the interaction of high density laser fields with matter is an important rapidly expanding branch of physics since the last ten years [1-22]. The potential

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

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applications of this research are numerous, not only in physics, but also in new energy resources [12], chemistry [19], biology [9, 10, 22], material science [6, 8, 15, 19], in the fast ignition approach to fusion [15-17], in accelerators [2, 3, 13], for relativistic electrons [4, 5, 7, 21] and for Nuclear effects and charged ion acceleration [11, 22]. The High Density Short Pulse (HDSP) Laser system is the most important experimental component in a high density Physics research lab. The decision to adopt the laser system for Cairo University Project, calls for several factors with the priority of its performance which is balanced between the temporal characteristics as well as the spatial characteristics. The possible interaction processes of high density lasers with solid or gas targets should be speculated in order to decide upon the possible fields of research to be adopted by the advanced laboratory that could solve some of the society needs.

1. The Architecture of the High Density Short Pulse Laser The architecture for getting simultaneously ultra short pulse and high energy is completely known and is illustrated in Fig. 1. The detailed combination of the following modules might well lead to develop a terawatt table top laser that could be upgraded to few petawatt laser power. 1.1 Femtosecond Oscillator It is obvious that the easiest way to get a very short pulse at the output of the laser chain is to use an Ultra Short pulse oscillator as the very first front end. Module oscillator of line width more than 90 nm, with pulse duration around 25 femtosecond could be selected, with output of nano-Joule energy, from different technologies. 1.2 Booster 10 Hz Amplifier The Booster is a direct preamplifier for increasing the energy from the oscillator up to few tens of micro-Joules. The Booster is specially designed to get energy gain of 1000 and preserve the spectral linewidth. 1.3 Passive Pulse Cleaner This system provides temporal contrast of approximately 1010 at full energy. The pulse cleaning approach is based on a combination of techniques involving saturable absorbers, achieving such high temporal contrast, similar to that at the University of Salamanca in Spain. 1.4 Stretcher The stretcher is based on an Offner design, in general made up of one afocal and two diffraction gratings laid out in anti-parallel configuration. The output pulse of the stretcher has a 103-104 times longer than the initial pulse and the temporally ordered spectral components are having the longer wavelengths before the shorter ones meaning chirped pulse. The main stretcher performance are: pulse duration 200-300 ps, bandwidth 110 nm and energy stretcher efficiency ~ > 30 %

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Chirped-Pulse Amplification Compression

D. Strickland and G. Mourou, Opt. Commun. 56, 219 (1985)

Amplification Stretching fs, ps

100s ps, ns

fs, ps

Fig. 1. Simplified representation of pulse shapes of the HDSP Laser, at the output of its main modular components describing the Laser Architecture. The upper part of the figure indicates the development of power to reach TW and higher after the pioneer findings of Chirped Pulse Amplification by Strickland and Mourou. (Private communication with Chang Hee Nam.)

1.5 Regenerative Amplifier This Module is based on two pockel cells with a Z cavity configuration integrated to Ti:Sa crystal providing 0.5 to 1 mJ output of approximately 1000 times amplified energy. 1.6 Pre-Amplifier This is multi-pass Ti: Sapphire crystal pumped by Nd: YAG laser. The output pulse from the Regenerative Amplifier are fed through the crystal (4 up to 8 pass) through a specially designed mount, providing energy gain of up to 30 mJ. 1.7 Main High Energy Amplifier A first Amplifier is pumped by one Nd: YAG laser and the output energy could be raised to app. 600 mJ. Then it could be followed by another Main Amplifier raising the output pulse energy to > 3000 mJ is commercially available to deliver 10 Hz pulses with beam size of diameter Ф 5-6 cm. 1.8 Compressor A dispersive system, symmetrical to the Stretcher formed mainly of optical gratings in special parallel geometry in which the pulses from the main amplifier having the shorter wavelength follow an optical path shorter than the longer wavelength in order to compensate for the relative delays introduced by the stretching. Pulses of time

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duration down to 25 fs could then be realized. The power per pulse could then reach 120 terawatt of brightness (1-4) 1010 watt/cm2. This beam could be focused to 100-20 µm leading to on target brightness of app. (1.2-30) 1018 watt/ cm2.

2. Interaction Processes of HDSP Lasers with Matter The strong objective of this advanced project evolved from the present International research on HDSP laser photons interaction when properly focused on targets. Creation of simultaneous exotic conditions similar to astrophysical processes take place within an extremely short time, which was not achieved before in the laboratories.

Fig. 2. HDSP Laser of energy/pulse 3 J, pulse duration 25 fs, peak power 1.2 1014 Watts. When focused on a target to spot size of 20 µm yield brightness 3 1019 W/cm2 .

Experimentally Plasma produced at the interaction region would likely evaporate all the types of processes indicated in Figure 2, accelerated e-, highly ionized ions, light photons, x-rays as well as gamma rays. [23] The electric field associated with such interaction 2 |E|2 = I {εo/ µo} -1/2 providing Very high electric field E [V/m] of the order of 1011V/m as well as gigantic magnetic fields of the order of 109 gauss and associated pressure of 109 bars creating high electron temperatures of the order of 108 degrees Kelvin. Such exotic conditions would definitely initiate severe nonlinearities. Matter exposed to these extreme conditions behaves in ways that produce new insight to the fundamental phenomena from condensed matter studies to nuclear physics, high energy physics, astrophysics, etc… This means NEW SCIENCE DOMAIN which is called High Density Science (HDS).

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3. Conclusion Wider objectives of the Advanced Laboratory is that it could be considered a facility to study new interdisciplinary fields and applications which are now a days emerging induced by HDSP Lasers; such as emission of nuclei and elementary particles, acceleration of electrons, ions and particles, generation of coherent X-rays etc.…The results obtained now are unprecedented and could have significant impact on the long-term future of some of the well - established fields such as nuclear andhigh energy physic. In this project we shall deal with the breakthroughs achieved by some researchers exploring novel uses of the existing HDSP lasers. We shall also point out the important marks to enhance laser performance even forth.

References [1] D, Strickland, G. Mourou, Compression of amplified chirped optical pulses, Opt. Comm. 56, 21 (1985) [2] T. Katsouleas, Accelerator physics: Electrons hang ten on laser wake, Nature 431,515 (2004) [3] J. Faure, et al., A laser-plasma accelerator producing monoenergetic electron beams, Nature 431, 541 (2004) [4] S. Mangles, et al., Monoenergetic beams of relativistic electrons from intense laser- Plasma interaction, Nature 431,535 (2004) [5] C. Geddes, et al., High-quality electron beams from a laser Wakefield accelerator using plasma-channel guiding, Nature 431, 538 (2004) [6] F.N. Beg, et al., A Study of picosecond laser-solid interaction up to 1019 W/cm2, Phys. Plasma4, 447 (1997) [7] S. P. D. Mangles, et al., on the stability of laser Wakefield electron accelerators in the monoenergetic regime, Phys. Plasma 14,056702 (2007) [8] A. Maksimchuk, et al., Forward ion acceleration in thin film driven by a high intensity laser, Phys. Rev. Lett. 84, 4108 (2000) [9] E.L. Clark, et al., Energetic heavy-ion & proton generation from ultra intense laser- Plasma interactions with solids, Phys. Rev. Lett. 85, 1654 (2000) [10] J.A., Cobble, et al., High resolution laser-driven proton radiography, J. Appl. Phys. 92, 1775 (2002) [11] K. Ledingham, et al., High power laser production of short-lived isotopes for positron emission tomography, J. Phys. D 37, 2341 (2004) [12] R. Kodama, et al., Fast heating of ultrahigh-density plasma as a step towards laser Fusion ignition, Nature 412,798 (2001) [13] Enam A. Chowdhury, et al., Lab. for Adv. Laser Target Interaction, 3rd workshop on Energy diode pumped lasers, Ohio State Univ. (2006) [14] V. Malka, et al., Electron Acceleration by a Wakefield forced by an intense ultrashort laser pulses, Science 298, 1596 (2002)

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[15] A. G. R. Thomas, et al., Effect of laser focusing conditions on propagation and Monoenergetic production electron production…, Phys. Rev. Lett. 98,095004 (2007) [16] A. Pukhov, Three dimensional simulations of ion acceleration from a foil irradiated by short-pulse lasers, Phys. Rev, Lett. 86, 3562 (2001) [17] Z. Najmudin, et al., Self-modulated Wakefield and forced laser Wakefield Acceleration of electrons, Plasma 10, 2071 (2003) [18] K. Krushelnick, et al., Energetic proton production from relativistic laser Interaction with high density plasmas, Laser Phys. 12, 368(2002) [19] S. Wilks, et al., Energetic proton generation in ultra-intense laser-solid interaction, Phys. Plasma 8, 542 (2001) [20] Nasr Hafz, et al., Near –GeV electron beam from a laser Wakefield accelerator in the bubble regime, Nuc. Instr. & Methods, Phys. Research A 554, 49 (2006) [21] B. M. Hegelich, et al., laser acceleration of quasi-monoenergetic MeV ion beams, Nature 439, 441 (2006) [22] J. Schreiber, et al., Pointing of Laser Accelerated proton beams, Phys. Plasma, 13, 033111 (2006) [23] Lotfia El Nadi and Magdy Omar, Proceedings of Third Int. Conference CP MTPR-08, 9908, 156 (2011)

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HIGH ENERGY DENSITY PHYSICS: THE LASER FIELD OF TOMORROW RICHARD R. FREEMAN The Ohio State University, Columbus, Ohio, USA

Ever since its invention, the laser has become an increasingly important tool for physics research. Indeed, the laser has made it possible to not only study many extant physical phenomena, but also to actually produce matter in conditions that don’t exist in nature, or more precisely, don’t exist on the earth. In this lecture, I discuss how the development of lasers that produce ultra-short (~fsec) and ultra-intense (≥1020 W/cm2) laser pulses actually produce plasmas that are at a density and temperature that exist only in stars. In doing so I discuss some of the basics of these extreme pulses interacting with electrons, yielding surprisingly intriguing physical phenomena. Finally, I argue that this field is an essential element in any comprehensive physical research endeavor, explicitly citing its fundamental relationship with the development of clean, unlimited fusion energy power.

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

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            

                                                                                                                                                                                                                                                           

                                                                                                                                                                                                                                                                                                                                                                                                                         





   

   

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

189

CHARACTERIZATION OF DC GLOW DISCHARGE PLASMA BY HOLLOW CATHODE K. H. METWALLY, A. H. SAUDY, M. FAROUK, M. M. EL-OKR AI- Azhar University, Faculty of Science, Department of Physics Cairo, Egypt.

Abstract This is where the abstract should be placed. It should consist of one paragraph giving a concise summary of the material in the article below. Replace the title, authors, and addresses with your own title, authors, and addresses. You may have as many authors and addresses as you like. It is preferable not to use footnotes in the abstract or the title; the acknowledgments of funding bodies etc. are to be placed in a separate section at the end of the text.

Introduction

Experimental Setup

Much study has been made on the Hollow Cathode Discharge (HCD) since it was first reported by Paschen [1] . The widely accepted definition of the Hollow Cathode Effect is the enhanced emission from the negative glow within the cathode cavity as well as the increase in discharge current density, up to several orders of magnitude at constant potential resulting from the cathode geometry [2, 3]. Optimum of Hollow Cathode Effect has been identified on basis of fraction of fast electrons in the glow being at maximum [4]. However, Kirichenko et al. [5] defined an optimum pressure range for fully developed hollow cathode discharge in which cathode fall potential increases with pressure at fixed current. Mechanisms believed to be responsible for the hollow cathode effect are primarily due to its efficient confinement of particles (neutrals, ions, electrons) due its geometry [6-8]. These mechanisms depend on a number of parameters such as gas pressure (p), discharge current (1), voltage (V), hollow cathode geometry and material and type of working gas. The apparatus is used to generate steady and continuous plasma. DC Hollow Cathode Discharge devices have been shown to be excellent high electron density. The density of those electrons is large due to the increased flux of the ion which is incident on the hollow cathode surface. Consequently more electrons are released in the secondary emission processes due to this· ion bombardment and the number of the diffusion of charge carriers to the wall of hollow cathode decrease. Applications of these discharges are numerous and include surface treatment, thin film deposition [910]. In the present work the breakdown potential and the discharge voltage-current characteristics were measured for argon and nitrogen glow discharge.

The system consists of three parts, the Hollow Cathode Discharge tube, Vacuum system and electrical circuit. The discharge geometry consists of a Cylindrical Hollow Cathode at one end and a grid anode (mesh) at the distance 0.4cm from the cathode. The cathode electrode (Cylindrical Hollow Cathode) is made of copper. The length of the cylindrical hollow cathode is 12cm, outer diameter 1.8cm and inner radius is 1.64cm. The grid anode is made from cupper or stainless steel with diameter 2.5cm and it has 60 holes/inch. The electrodes are fixed inside the glass chamber. The (HCD) was placed in a Pyrex glass tube envelope of length 20cm and internal diameter 7.5cm. The rotary pump is used to evacuate the system to approximately 1 x 10·2 torr. The work gas is transmitted to the systems from a cylinder through a needle valve to regulate rate of rate flow of gas. The source pressure is monitored by a thermocouple gauge. Which it can measure gas pressure in the range 0.5torr to I o· 4 torr. DC power supply (2.5 kv, IOOmA) is used for initiating the discharge between the anode and the cathode, whereas the anode is grounded and the Hollow Cathode was negative charged. The discharge current and voltage are measured used a digital multimeters.

Gas lalet

Figure (1): Diagram of Hollow Cathode Discharge System.

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

190 Results and Discussion

1600 1460 1400 1360 1300 1260

The breakdown voltage of nitrogen and argon gases as a function of pd [where p is the gas pressure and d is

1200 1160 1100

the inter electrode space] for steel and copper are shown

1060 -1000

in Figure (2a, 2b).These figures indicate the breakdown

~ ~~ 0

potential Vb decreases with increasing Pd, which can be

:> ;~~

~

Stainless Steel Anode (Grid) Distance between two electrode=0.4cm

860 800 660 600 660 600 460 400 360 300 260 200 0.015 0.016 0.017 0.018 0.019 0.02 0.021 0.022 0.023 0.024 0.025 0.026 0.027 0.028 0.0

explained by at low pressure the collision frequency is low, so that sufficient ionization is maintained only by increasing the probability of ionization at each collision,

+--.--...--.---..-....--.--..---.---..---.---..-....--.---4

consequently the electron velocity and the electric field

Pd (torr.cm)

must be high, hence Vb must decreases as p increases. This result indicates that the discharge is formed on left hand side of Pashen's curve. Also these figures indicate that the values of breakdown voltage for nitrogen are higher than for argon. This related to the fact that, the efficiency of electron emission by the incidence of the gas ions on the cathode increases by decreasing ion mass. [Hagstrom (1956)]. Also it depends on the nature of the gas. The nitrogen gas is molecules while the argon gas is atoms. From these considerations, the values of breakdown voltage for nitrogen gas are higher than for argon gas. Figure (2a, 2b). Indicate that the values of the

Figure (2a): Pasehen's Curve For (Ar) and (N2) Gases at different pressures and distance between two electrode=0.4cm and stainless steel Anode (grid). 1500 1450 . 1400 1350 1300 . 1250 1200 1150 1100 1050 1000 950 .! 900 850 ~ 800 750 " 700 650 600 650 . 600 450 400 350 300 250 200 0.015

>

I

Copper Anode (grid) Distance between two electeode=0.4cm

N2 Gas

~ -0.016

0.017

0.018

... 0.019

0.02

0.021

0.022 .

0.023

Pd (torr.cm)

breakdown voltage are higher for the stainless steel grid than for copper grid at the same pressure. It can be attributed that the photoelectric work functions of material (stainless steel and copper) of the anode grid are 4.4eV and 4.07eV-4.8eV respectively. Also the Thermo-Ionic electron emission for steel is (4.04eV4.77eV) and for copper is (3.85eV-4.38eV).

Figure (2b): Pasehen' s Curve For (Ar) and (N2) Gases at different pressures and distance between two electrode=0.4cm and Copper Anode (grid)

191

Figure (3a to 3b) show the discharge current Id with the applied voltage Vd at different gas pressures for N2 gas and Ar gas with steel grid and copper grid. From these figures . In the abnormal glow discharge the whole sample surface is covered by plasma which produces uniform sample sputtering. During the discharge, energetic electrons move around inside the cathode cavity. In this process the ionization is enhanced by particle collision and plenty of electrons are supplied from the cathode cavity to the bulk of discharge. The increase in the discharge current with increasing the discharge voltage is due to the increasing in the ionization processes. From these figures it can be remarked that when the gas pressure increases the discharge current increases this is due to the decreasing in breakdown potential with increasing the gas pressure. The values of discharge current for Ar discharge are higher than that for N2 discharge in all the same values of applied voltage and gas pressure. This is related to the facts that, the values of breakdown potentials of N2 are higher than that for Ar. The relations between the discharge current and discharge voltage (figure 3a to figure 3d) indicate that the values of discharge current for Copper grid are higher than that for steel grid at the same condition of pressure and discharge voltage. It is found that the thermo-ionic electron emission for steel is (4.04 eV- 4.77 eV) and for copper is (3 .85 eV- 4.38 eV). So the thermo-ionic emission is the dominant processes in the glow discharge.

30 28 26 24 22 20 _18 < 16 .§.14 v -12 10 8 6 4 2

..... P=0.070 torr ..... P=0.055 torr

""*" P=0.045 torr -&- P=0.038 torr

0+-----~~----~------~------~----~ 360 380 400 420 320 340

Vd (Volts)

Figure (3b): Discharge current as a function of applied voltage of (Ar) gas with Steel grid at Different pressure. 30 28 26 24 22

..... P=0.070 torr ..... P=0.065 torr "*" P=0.045 torr -&- P=0.038 torr

20

18

~ 16

.§. 14

~

12 10 6

4 2

o+---r-~--~--~--~--r-~--~--~~

400

410

420

430

440

460

460

470

480

490

500

vd (Volts) 30~-----------------------r~~~~

28 26 24 22 20 -18 ~ 16 -14 ...!'12 10

Figure (3c): Discharge current as a function of applied voltage of(N 2) gas with Copper grid at Different pressure 4-4 42 40 38 36 34 32 30 28

8

~ ~: -22

6 4 2

~

0+-~-r~~--~~~-r~~--~~~-r~

200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350

vd (Volts)

Figure (3a): Discharge current as a function of applied voltage of(Ar) gas with copper grid at Different pressure.

20 18 16 14 12 10 8 6 4 2 0 340

:E!:! ? i / -&- P= 0.038 torr

N2 Gas

350

360

370

380

390

400

v. (Volts) Figure (3d): Discharge current as a function of applied voltage of (N 2) gas with Steel grid at Different pressure.

192

References Conclusions

[I]- F. Paschen, Ann. Phys., 50, 90I (I9I6).

A cylindrical Hollow Cathode Discharges was studied experimentally with Argon and Nitrogen as filling gas in a pressure range (0.055torr to 0.07torr) and discharge current varying from (20mA to 40 rnA). Using a copper grid and steel grid the results indicate that the discharge is formed on left hand side of Pashen's curve. Also these results indicate that the values of breakdown voltage for nitrogen are higher than for argon. It is found that an increase in the discharge current is accompanied by an increase in the discharge voltage, where the characteristics of such discharge

are

characterized

by

abnormal

glow

discharge. It is found that the values of electric discharge

current in the characteristics curves are higher for Ar discharge than for N 2 discharge at the same conditions. This is attributed due to the increasing in the ionization processes. Also the values of breakdown potentials of N 2 are higher than that for Ar.

[2]- P.F. Little and A. von Engel, Proc. Roy.

Soc.

A224, 209 (I954). [3]- D. Ciobotaru, J. Electron. Control, I7, 529 (1964). [4]- V.S. Borodin and Yu.M. Kagan, Sov. Phys. Techn. Phys., II (I), 13I (1966). [5]- V.I. Kirichenko, V.M. Tkachenko and V.B. Tyutyunnik, Sov. Phys. -

Techn. Phys., 2I (9), I 080

(1976). [6]- H. Helm, Z. Naturforsch., 27A, I8I2 (1972). [7]- P. Gill and C.E. Webb, J. Phys. D: Appl. Phys., IO, 299 (I977). [8]- E. von Badareu, I. Popescu and I. Iova, Ann. Phys. -Leipzig, 5, 308 (1960). [9]- S. F. Brunatto, Federal Univ. of Parana - UFPR, Department of Mechanical Engineering, 8I53I-990 Curitiba, PR, Brazil, J. of the Brazil. Soc. ofMech. Sci. & Eng., April-June 2008, Vol. XXX, No.2 I I45. [IO]- F.O. de Araujo, E.O. de Almeida, Labplasma, Departamento

de

Fisica

UFRN,

Campus

Universitario, 59072-970 Natal, RN, Brazil, Surface & Coatings Technology 20I (2006) 2990-2993.

193

THE TEXAS PETAWATT LASER AND TECHNOLOGY DEVELOPMENT TOWARDS AN EXAWATT LASER TODD DITMIRE The Texas Center for High Intensity Laser Science, Physics Department, University of Texas Mail Stop C1600, Austin, Texas, 78712 [email protected]

We have completed the construction of a high peak power, ultrafast laser which delivers peak power in excess of 1 petawatt (1015 W). This laser, the Texas Petawatt Laser, is based on a combination of OPCPA and mixed Nd: glass amplifiers, enabling high energy operation with compressed pulse duration of j i < j i < j

N

  ∑ N Ce + ∑ N Cd i ij i ij e i>j i < j

done to predict the laser gain of Ni-like Au theoretically. In this paper, we

  =  

present the gain predicted for the Nilike Au ion by a steady-state model of Ni-like ions, our model treats the

 + ∑ N A i ij   i>j

kinetic of the Ni-like charge state in

(1)

isolation from other ionization stages.

Where Nj is the the population of level

The present gain calculations included

j, A ji is the spontaneous decay rate

the ground state 1s2 2s2 2p6 3s2 3p63d10

from level j to level i, C eji is the

and 34 fine-structure levels contained in the configurations 1s2 2s2 2p6 3s2 6

9

3p 3d 4l (l = s, p, d) for the nickellike Au ion. The model includes all radiative

transitions

as

well

as

electron-impact transitions between all levels.

electron

excitation

rate

coefficient, and C dji is the electron collisional

de-excitation

rate

coefficient, which is related to electron collisional excitation rate coefficient by [16-17]. C dji = Cije [

2. Computation of Gain Coefficient

collisional

gi ] exp[∆Eji/KTe] gj

(2)

The possibility of laser emission from

Where gi and gj are the statistical

plasma of Au51+ ion via electron

weights of lower and upper levels,

collisional pumping, in the XUV and

respectively.

205

The electron impact excitation rates

where 35 is the number of all the

usually are expressed via the effective

levels of the ion under consideration,

collision strengths γij as

the quantity actually obtained from Eq. (1) is the fractional population

N j / NI .

E ij 8.6287 Χ10−6 γ exp ij g iT e1/ 2 KT e

C ije =

cm3.sec-1

After the calculation of levels (3)

population, the quantities Nu /guand Nl /gl can be calculated.

where the values of γij and Aji are obtained by [11].

the j

level is obtained from the

following identity [10],

N J = N j ×N I Where

NI

electron

the lasant ion plasma will transfer the pumped quanta to other levels, and will

(4)

is the quantity of ions

the upper and lower levels. Once a population inversion has been ensured a positive gain through F>0 [18] is obtained.

given by

NI =fI

of

result in population inversions between

which reach to ionization stage I, is

Ne

application

collisional pumping, the collision in

The actual population density NJ of th

By

F=

Z avg

(5)

where fI is the fractional abundance of

gu Nu Nl − ] [ N u gu g l

Where

(7)

Nu Nl and are the reduced gu gl

the Ni- like ionization stages calculated

populations of the upper level and

by Goldstein et al [10] , Ne is the

lower level respectively. Equation (7)

electron density, and Zavg is the average

has been used to calculate the gain

degree of ionization.

coefficient (α) for Doppler broadening

Since the populations calculated from Eq. (1) are normalized such that,

of the various transitions in the Au51+ ion. 1/ 2

(6)

λ3  M  α = lu   Aul N u F 8π  2π KTi 

(8)

206

The present calculations for the

λℓu

is the

Ti

is the

electron densities are plotted in figures

ion temperature in K and u,l represent

(1 to 3) at three different plasma

the upper and lower transition levels

temperatures (0.5, 1, 1.5 KeV) for

respectively.

Au51+ ion.

Where M is the ion mass,

transition wavelength in cm,

reduced populations as a function of

As seen from Eq. (8), the gain

In the calculation we took into

coefficient is expressed in terms of the

account spontaneous radiative decay

upper state density (Nu). This quantity,

rate and electron collisional processes

Nu depends on how the upper state is

between all levels under study.

populated, as well as on the density of

The atomic structure data and

the initial source state. The source state

effective collision strength data needed

is often the ground state for the

were taken from Ref. [11]. The behavior of level populations

particular ion.

can be explained as follows: in general

3. Result and Discussions

at low electron densities the reduced

3.1 Level Population

population density is proportional to

The reduced population densities are

the electron density, where excitation

calculated for 35 fine structure levels

to

arising from 1s2 2s2 2p6 3s2 3p63d10

immediately by radiative decay, and

and 34 fine-structure levels contained

collisional mixing of excited levels can

in the configurations 1s2 2s2 2p6 3s2

be ignored.

an

excited

state

is

followed

3p63d9 4l (l = s, p, d) configurations

This result is in agreement with

that emit radiation in the XUV and soft

that of Feldman et al. [14-15, 19]. See

X-ray

also the data for nickel-like Sm, W,

spectral

regions.

The

calculations were performed by solving

and

Eu

[20-22].At

the coupled rate Eq. (1) simultaneously

densities (

using MATLAB version 7.8.0 (2009a)

decay to all the levels will be

computer program.

negligible compared to collisional

),

high

electron

the radiative

207

depopulations

and

all

the

level

populations become independent of the electron density (see Figures 1 to 3). The (3d3/2 4d3/2)0 level has higher population

density

from

electron

density 1021 to 1022 cm-3 than the other levels at electron temperature 0.5 KeV,

Fig. (2): Reduced population of Au51+ levels

from electron density 1021 to 2×1022

after electron collisional pumping as a function

cm-3 at electron temperature 1 KeV,

of the electron density at temperature 1.0 KeV.

and from electron density 1021 to 4×1022 cm-3 at electron temperature 1.5 KeV which mean that the population inversion occur in these ranges. The population inversion is largest where the electron collisional deexcitation rate for the upper level is comparable to the radiative decay rate for this level [14, 19].

Fig. (3): Reduced population of Au51+ levels after electron collisional pumping as a function of the electron density at temperature 1.5 KeV.

3.2 Gain Coefficient As a result of population inversion there will be positive gain in laser medium. Eq. (8) has been used to calculate gain coefficient for the Doppler Fig. (1): Reduced population of Au51+ levels

broadening

of

various

transitions in the Au51+ ion. Our results

after electron collisional pumping as a function

for the maximum gain coefficient in

of the electron density at temperature 0.5 KeV.

cm-1 for those transitions having a

208

positive inversion factor F>0 in the

The figures show that the population

case of Au51+, in Figures (4 to 6).

inversions occur for several transitions in the Au51+ ion, however, the largest gain occurs in (3d3/2 4d3/2)0 → (3d5/2 (35→12)

4p3/2)1

transition

at

wavelength 41.4 Å at an electron temperature 0.5 KeV , and in (3d3/2 4d3/2)0

→

(3d3/2

(35→9)

4p1/2)1

transition at wavelength 35.1 Å at an Fig. (4): Gain coefficient of possible laser transitions

against

electron

density

at

temperature 0.5 KeV in Au51+.

electron temperatures 1.0, and 1.5 KeV For Ni-like Au, the population inversion is due to strong monopole excitation from the 3d10 ground state to the 3d94d configuration and also the radiative decay of the 3d94d level to the ground level is forbidden, while the 3d94p level decays very rapidly to the ground level.

Fig. (5): Gain coefficient of possible laser transitions

against

electron

density

at

This

short

transitions

wavelength

laser

produced

using

was

plasmas created by optical lasers as the

temperature 1.0 KeV in Au51+.

lasing medium. For electron densities and electron temperatures

that

laboratory

high-density

sources,

such

as

are

laser

typical

of

plasma produced

plasmas, it is possible to create a quasistationary population inversion Fig. (6): Gain coefficient of possible laser transitions

against

electron

temperature 1.5 KeV in Au51+.

density

at

between the 3d94d and 3d94p in Au51+ ion. Our calculations have shown that under favorable conditions large laser

209

gain for these transitions in the XUV

Table 1. Parameters of the most

and soft X-ray regions of the spectrum

intense laser transitions

can be achieved in the nickel like Au51+ ion. It is obvious that the gain increases with the temperature.

Transition (3d3/24d3/2)0→ (3d3/2 4p1/2)1

Atomic data Wavelength λ (Å) Maximum gain α(cm-1) Electron density Ne(cm-3) Electron temperature Te (KeV)

4. Conclusion The analysis that have been presented

(3d3/24d3/2)0→ (3d5/2 4p3/2)1

in this work shows that electron collisional pumping (ECP) is suitable for attaining population inversion and

(3d3/24d3/2)0→ (3d3/2 4p3/2)1

offering the potential for laser emission in the spectral region between 30 and

Au XXXXXII 35.1

572 6.00E+22 1.5

Wavelength λ (Å) Maximum gain α (cm-1) Electron density Ne (cm-3) Electron temperature Te (KeV)

41.4 442 1.00E+23

Wavelength λ (Å) Maximum gain α (cm-1) Electron density Ne (cm-3) Electron temperature Te (KeV)

51 166 8.00E+22

1.5

1.5

100 Å from Au51+ ion. This class of lasers can be achieved under suitable conditions of pumping power as well as electron density. If the positive gain obtained

previously

for

some

transitions in the ion under studies (Au51+ ion) together with the calculated parameters

could

be

achieved

experimentally, then successful lowcost electron collissional pumping

References 1. Vinogradov, A.V.; Sobelman, I.I. and Yukov, E. A., (1975) Sov. J. Quantum Electron. 5, 59. 2. Norton, B. A. and Peacock, N. J., (1975) J. Phys. B 8, 989. 3. Bhagavatula, V. A., (1976) J. Appl. Phys. 47, 4535.

XUV and soft X-ray lasers can be

4. Monier, P.; Chenais-Popovics, C.;

developed for various applications.

Geindre, J. P. and Gauthier, J. C.,

The parameters of most intense laser

(1988) Phys. Rev. A 38, 2508.

transitions in Ni-like Au ion are

5. Nilsen, J., (1991) Phys. Rev. lett.

summarized in Table 1.

66, 305.

210

6.

Porter, J. L.; Spielman, R. B.;

14. Feldman U., Doschek G. A.,

Matzen, M. K.; McGuire, E. J.;

Seely J. F., and Bhatia A. K.,

Ruggles, L. E.; Vargas, M. F.;

(1985) J. appl. Phys. 58(8),

Apruzese, J.P.; Clark, R. W. and

2909.

Davis, J., (1992) phys. Rev. Lett.

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68, 796.

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Zhang, J. and Fill, E. E., (1992)

Phys. 56(9), 2475-2478.

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Nilsen,

J.;

Beiersdorfer,

P.;

16. Chapline G. and Wood L., (1975) Phys. Today 28, 40.

Elliott, S. R.; Phillips, T. W.;

17. Vinogradov A. V. and Shlyaptsev

Bryunetkin, B. A.; Dyakin, V. M.;

V. N., (1980) Sov. J. Quantum

Pikuz, T. A.; Faenov, A. Ya.;

Electron. 10. 754.

Pikuz, S. A.; von Goeler, S.;

9.

15. Feldman U., Seely J. F., and

18. Sobel'man

I.I.,

(1979)

Bitter, M.; Loboda, P. A.; Lykov,

"Introducrion to the Theory of

V. A.; and Politov, V. Yu., (1994)

Atomic Spectra",

Phys. Rev. A 502143.

Series Of Monographs In Natural

Qi, N. and Krishnan, M., (1987)

Philosophy,

Phys. Rev. Lett. 592051.

Vol. 40.

Internatlonal

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10. Goldstein, W. H.; Oreg, J.; Zigler,

19. Feldman, U.; Seely, J. F. and

A.; Bar-Shalom, A. and Klapisch,

Bhatia, A. K., (1985) J. appl.

M., (1988) Phys. Rev. A 38,

Phys. 58(11), 3954-3958. 20. Abdelaziz W. S. Phys Scr 2009;

1797. 11. Zeng, J.; Zhao, G.; Yuan, J., (2007) At. Data Nucl. Data

Suckewer

21. Abdelaziz W. S. Eur Phys J D 2009; 75: 17-21.

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K.,

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42: 699-702.

Enhanced Type-I Polarization-Entangled Photons Using Enhanced Type-I Polarization-Entangled Photons Using CW-Diode Laser CW-Diode Laser

  211

Salem Hegazya*, Mohy S. Mansourb, and Lotfia El Nadia,c Salem Hegazya*, Mohy S. Mansourb, and Lotfia El Nadia,c

a

National Institute of Laser Enhanced Sciences, NILES, Cairo University, Giza, Egypt a Mechnical Engineering Department, Faculty ofNILES, Engineering, Cairo University, Giza, Egypt National InstitutePower of Laser Enhanced Sciences, Cairo University, Giza, Egypt c b Physics Department, Laser Physics Lab., Faculty of Science, Cairo University, Giza, Egypt Mechnical Engineering Power Department, Faculty of Engineering, Cairo University, Giza, Egypt c * [email protected] Physics Department, Laser Physics Lab., Faculty of Science, Cairo University, Giza, Egypt * [email protected] b

Abstract. We used two type-I BBO crystals pumped by violet cw-diode laser of relatively wide bandwidth to produce entangled We photons purity. by While laser laser servesof the mobility andbandwidth the low-cost of the Abstract. used of twoconsiderable type-I BBO degree crystalsofpumped violetdiode cw-diode relatively wide to produce entangled photons suitable temporal is required in this casethe to recover of the state. entangled photons source, of considerable degree ofcompensation purity. While diode laser serves mobilitythe andpurity the low-cost of We the studied also effect of tiltingsuitable the two-crystal on overlapping of the SPDC cones. entangled photons source, temporalsetcompensation is required in this case to recover the purity of the state. We studied also Enter effect Keywords of tilting the two-crystal set on overlapping of the SPDC cones. Keywords: here. PACS: Replace this text with PACS Keywords: Enter Keywords here. numbers; choose from this list: http://www.aip.org/pacs/index.html PACS: Replace this text with PACS numbers; choose from this list: http://www.aip.org/pacs/index.html

1. INTRODUCTION 1. INTRODUCTION

Entanglement is at the core of quantum information. The importance of quantum entanglement is not only due to its novel applications, butcore also,ofthe experimental resultsThe of quantum entanglement the firmness thedue weird Entanglement is at the quantum information. importance of quantum prove entanglement is notofonly to nonlocal structure of quantum mechanics. These results do not reject only the Local theories; it rejects any theory its novel applications, but also, the experimental results of quantum entanglement prove the firmness of the weird searches for knowledge better than the statistical cover defined quantum mechanics. Quantum entanglement has nonlocal structure of quantum mechanics. These results do not by reject only the Local theories; it rejects any theory made deep difference between principal features of causality and locality. While the former is necessarily searches for knowledge better than the statistical cover defined by quantum mechanics. Quantum entanglement has subluminal proved by relativity theory, features the latterofcancausality be superluminal without contradiction proved made deep as difference between principal and locality. While the formerwith is any necessarily physical theory. Experiments of quantum that there canwithout be "spooky action at with a distance". The subluminal as proved by relativity theory,entanglement the latter canprove be superluminal contradiction any proved relativistic process between two separatedentanglement parties is such process that can transferaction of information between physical theory. Experiments of quantum prove that there can allow be "spooky at a distance". The them. relativistic process between two separated parties is such process that can allow transfer of information between The dependence of quantum communication systems on sources of entangled photons, even when individual them. photons are transferred communicating parties,oncannot be disregarded. the last even decades, there is rapid The dependence of between quantumthe communication systems sources of entangledInphotons, when individual progress in efficiency of the entangled photons sources. Rate of the entangled pairs, purity of the produced entangled photons are transferred between the communicating parties, cannot be disregarded. In the last decades, there is rapid state, andinmobility of the source were the principal elements trends this rapid progress efficiency of the entangled photons sources. Rate to ofcharacterize the entangled pairs,ofpurity of theprogress. produced entangled The distribution of entangled photons over two distant parties, combined with independent state, and mobility of the source were the principal elements to characterize trends of this rapid progress.time varying analyzers (space-likeofseparation [1]), first performed to makewith the locality condition as a The distribution entangledexpressed photons in over twowas distant parties, combined independent time act varying consequence of Einstein causality [2, 3]. As a primary step performed towards practical communication analyzers (space-like separation expressed in [1]), was first to makefree-space the locality condition act using as a entangled photons, there causality were outdoor experiments [4, 5]step demonstrated quantumfree-space entanglement distributionusing over consequence of Einstein [2, 3]. As a primary towards practical communication free-space links. On the other hand, long-distance entanglement distribution is fundamentally significant in more entangled photons, there were outdoor experiments [4, 5] demonstrated quantum entanglement distribution over specific areas likeOn quantum encryption [6] and quantum teleportation [7]. free-space links. the other hand, long-distance entanglement distribution is fundamentally significant in more This work mainly aims to implement and test source of entangled photons suitable for free-space communication. specific areas like quantum encryption [6] and quantum teleportation [7]. OneThis of the main characteristics of free-space system (or anysuitable outdoor is its mobility. The work mainly aims to implement and testcommunication source of entangled photons forsystem) free-space communication. pump source of the nonlinear crystal is the most bulky component of the entangled photons source. Here we The use One of the main characteristics of free-space communication system (or any outdoor system) is its mobility. diode laser volumecrystal and light weight effectively enhance the entangled mobility ofphotons the overall system. the pump sourceofofcompact the nonlinear is the mosttobulky component of the source. HereAlso we use degenerate down-conversion 810 nm from this source lies the of clear transmission window of diode laser of compact volumeemission and lightatweight to effectively enhance thewithin mobility the overall system. Also the atmosphere down-conversion and can be detected using silicon degenerate emission at 810APD nm with fromconsiderable this source efficiency lies within(~50%). the clear transmission window of atmosphere and can be detected using silicon APD with considerable efficiency (~50%).

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

212  

2. EXPERIMENT Kwiat et al., 1999 [8] used adjacent two-crystal geometry to make the first stable hyper-entangled source which is more than ten times brighter, per unit of pump power, than previous sources [9]. Using the same two-crystal geometry, Altepeter et al., 2005 [10] could reach high-rates while maintaining the high fidelity of the produced state. They increased the collected solid angle of the down-conversion and using designed Phase compensator, they could recover the coherence of the collected state. After that, Rangarajan et al., 2009 [11] created ultra-bright, two-crystal source with high fidelity, using low-coherence pumps (ultrafast Ti-Saph Laser and cw-diode laser). In our setup, a 30-mw cw-diode laser emitting 1.5-mm collimated beam at 405 nm (2.6-nm FWHM) is used to pump two 0.8-mm type-I BBO crystals. The pump light is prepared to be polarized on 45-degree using half-wave plate HWP@405nm while relative phase between the orthogonal/coherent pump components is adjusted by a subsequent tiltable quarter wave plate QWP@405nm. Two identical BBO crystals of cut-angle θpm=30o are crossed (rotated 90o) with respect to each other, such that the optic axis of the first crystal (second) lies in vertical (horizontal) plane. In this case, the 45o-polarized pump may down-convert coherently in either crystal. Produced pairs from this source are "hyper-entangled" [8], as they are simultaneously entangled in polarization, momentum, and Energy. In our setup, to reach ~1.7 o half-opening degenerate-cone angle, the two-crystal set is tilted by ~3o in horizontal and vertical directions (by ~4.175 o on 45o direction). Two arc-shaped irises with radial width ~1mm are applied to select spatially photons around the degenerate cone at 810 nm (the near-degenerate cones). Arc irises show better performance over the widely used vertical slits when iris width and cone radius at the iris plane are small.

FIGURE 1. Schematic of the experimental setup showing its detailed dimensions.

  213

The polarization measurements assembly consists of half wave plate HWP@810nm and polarizing beam splitter PBS on each measurement arm. An iris diaphragm is inserted on one down-conversion arm to control the vertical opening of the applied arc iris. Interference filters centered at 810 nm (10-nm FWHM) are applied to reduce the background and select the nearly degenerate photons. The passing photons are focused using collection optics into multi-mode fibers which convey them to apertures of the single photon counting module (PerkinElmer SPCMAQ4C). We used reverse tracing beam to grossly align setup components while fine alignment was performed while the whole system is running. To analyze coincidence photons, we have designed, implemented, and tested four-fold coincidence counting circuit. In the experiment, we have used its reduced two-fold version shown in FIGURE 2 (by gating two inputs of the four-fold circuit [12]).

FIGURE 2. Schematic diagram of Coincidence, pulse extension, and counter/display circuits. Its coincidence window is controllable between 5 – 40 ns via variable resistance R1.

2.1. Entanglement Measurements

FIGURE 3. Measurements of polarization correlation in +/- basis. This plot shows coincidence fringes for state

H H 1

2

 V1V2



2

214  

FIGURE 3 shows coincidence records when polarization analysis angle of the second down-conversion arm is fixed at 45◦ while that of the first arm spans over the 360 degrees. Three runs have been performed at each orientation and the shown data points are their average values. The solid red curve is the best fit for these records with visibility V+/- = 89.5% (accidental counts subtracted). The high visibility of the coincidence fringes in FIGURE 3 corresponds to obvious violation of Bell’s inequality [13]. According to CHSH [14], parameter S ≤ 2 for any local realistic theory where:

S (a, a`, b, b`)  E (a`, b)  E (a`, b`)  E (a, b)  E (a, b`)

(1)

Assuming that the detected pairs are a fair sample of all emitted pairs (fair sampling assumption [15]), correlation coefficient E(a, b) can be calculated as by

E ( a, b) 

N ( a , b )  N ( a  , b  )  N ( a  , b )  N ( a, b  ) N ( a, b)  N ( a  , b  )  N ( a  , b )  N ( a , b  )

(2)

In Table 1, Counts with the same color are combined together, according to Eqn. (2), to yield the correlation factor corresponding to this orientation. Here we apply the additional auxiliary assumption that the source state is independent of the analyzers orientations (locality assumption). The four cells colors represent the four correlation factors included in Bell’s inequality in Eqn. (1). TABLE (1). Average coincidence counts for 16 analyzer settings within 128s. These settings yield the largest conflict between local realistic theories and quantum mechanics (accidental counts subtracted).

b`= -45o

b`┴ = 45o

b= 0o

b┴ = 90o

a`= -22.5o

732

2470

3590

817

a`┴ = 67.5o

3641

823

632

4072

a= 22.5o

4338

624

3861

1111

a┴ = 112.5o

683

3074

402

3229

These counts are averages over three runs performed in each orientation within fixed acquisition window 128s. The true coincidence rates in Table 1 are obtained by subtracting the accidental coincidence rate (about 4.8s-1). Following Aspect et al., 1982 [16], these records can be combined to yield the following correlation factors. TABLE (2). Experimentally determined correlation factors.

(a, b)

Eexp(a, b)

(-22.5o, 0o)

0.6819 ± 0.007662

(-22.5o, -45o)

-0.594 ± 0.009185

(22.5o, 0o)

0.6483±0.008209

(22.5o, -45o)

0.7002±0.007646

Subsequently the value of Bell parameter:

S exp  2.625  0.016

(3)

This experimental record is beyond the limit assigned by Bell’s inequality for any local realistic theory by 39 standard deviations.

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3. EFFECT OF TILTING THE TWO-CRYSTAL SET ON OVERLAPPING OF THE SPDC CONES Because of the symmetry of the two crystals, the SPDC degenerate cones perfectly overlap in case of normal pump incidence. The crystal tilting can be used when we need to modify the half-opening angle of the down-conversion cones. Because optic axes of the two crystals lie in perpendicular H/V planes, tilting the set horizontally or vertically will affect the down conversion in each crystal differently. Therefore, we will mention the two cases separately. Let’s start by defining some parameters:

 pi : Incidence angle of pump beam (crystal tilting angle; for normal incidence,  pi = 0o)  pe : Transmission

angle of extraordinary component of pump beam (this angle is considered positive when

transmitted beam direction shifts further from optic axis direction)

 pm : Angle between optic axis and normal incidence direction (phase matching angle)  d : Half-opening angle of degenerate cone inside the crystal.  do : Angles of the two degenerate down-conversion rays outside the crystal Where subscript 1, 2 will refer to 1st and 2nd down-conversion arms and subscripts A, B will refer to case A and case B. 3.1. Case A: Tilting in the plane of pump beam and optic axis:

FIGURE 4. Top view for crystal tilted in the plane of pump beam and optic axis [17].

Applying Snell's law on entry interface of the two-crystal



sin  pi

   n (   ;  )  e pm peA p  

 peA  sin 1 

(4)

 peA can be obtained by solving Eqn. (4) numerically.  peA = 0 in case of normal incidence (Subscript A refers to case A).

216  

Half-opening angle of the degenerate cone inside the birth crystal in case A of energy and momentum (in perfect phase matching direction) as follows,

 dA can be calculated from conservation

 ne ( pm   peA;  p )    n ( 2  ) o p  

 dA  cos 1 

External degenerate ray emission angles along 1st and 2nd down-conversion arms applying Snell’s law on output interface,

(5)

 doA1 and  doA2 can be obtained by

 sin(dA   peA)    n ( 2  ) o p  

(6)

 sin(dA   peA)    n (2 )  o p  

(7)

doA1  sin 1

doA2  sin 1

3.2. Case B: Tilting in plane normal to plane of pump beam and optic axis:

FIGURE 5. Top view for crystal tilted in a plane normal to the plane of the pump beam and optic axis.

In this case, angles  pm and  peB lie in two perpendicular planes and the applied

phase

matching

angle



can

be

expressed

as,

  cos (cos pm cos peB ) . Applying Snell's law in this case: 1



   n (cos [cos  cos  ];  ) e pm peB p  

(8)

 ne (cos1[cos pm cos peB ];  p )    n ( 2  ) o p  

(9)

 peB  sin 1 

sin  pi

1

And degenerate cone angle inside crystal is

dB  cos1

  217

External degenerate angles can be calculated as:

 sin(dB   peB )    n (2 )  o p  

(10)

 sin( dB   peB )    n ( 2  ) o p  

(11)

doB1  sin 1

 doB2  sin 1

Now by tilting the two-crystal set from normal incidence situation in horizontal or vertical planes, the following two conditions should be simultaneously valid to prove that overlapping can occur between the down-conversion rays in the two cases

 sin( dA   peA)   sin( dB   peB )    sin 1   sin 1   n (2 )   n (2 )  o p o p    

(12a)

 sin( dA   peA)   sin( dB   peB )    sin 1   sin 1   n (2 )   n (2 )  o p o p    

(12b)

Satisfying these two conditions can prove that perfect overlapping of the two cones can be attained. These two conditions can be simplified as follows:

These conditions are valid together iff

 pi equal

dA   peA  dB   peB

(13a)

 dA   peA   dB   peB

(13b)

 dA   dB

and

 peA   peB , which can be attained iff  pe and consequently

zero (in case of normal pump incidence). Hence, it can be concluded that tilting the two-crystal will

generally reduce the overlapping between the two degenerate cones. The following parameter characterize amount of overlapping reduction due to tilting the set by an angle

 pi

X ( pi ) can

from normal incidence direction

in horizontal and vertical axes

X ( pi )   dA   dB   peA   peB

(14)

It was realistic to ignore here the non-overlapping of ordinary and extraordinary pump components inside crystal (because of birefringence and walk-off), since we assume thin crystals. Anyway, there are other factors, which help the overlapping of the two cones such as coherence width of the pump beam and the coexistence of imperfect phase matching directions.

4. CALCULATIONS OF SPECTRAL-TEMPORAL COMPENSATION Because we assume thin crystals, walkoff in transverse plane is very small compared to coherence width of the pump beam. For example, in Kwiat et al., 1999 [8], transverse walkoff (after birth crystal) was about 44 μm, and about 53 μm in our case. However, the longitudinal walkoff is more crucial especially when pump beam of lowcoherence time is used. Spectral decoherence arises when the relative phase φ of the entangled state depends on frequency (spectral profile of pump beam). Alternatively, the same effect can be studied in temporal domain. Temporal decoherence can be considered as a result of non-perfect temporal overlapping between two possible photon pairs generated by pump photon in the first and second crystals. This constructs temporal which-crystal information. Here we follow model mentioned in Rangarajan et al., 2009 [11], where calculations are considered in temporal domain. The relative delay

218  

t s ,i between possible photon pair born in the first crystal and corresponding pair of the second crystal can be expressed as

  1 1  t s ,i  t s2,i  t 1s ,i  d  or  ex  V (w ) V (w )  p g s ,i   g

(15)

where d is the crystal thickness, subscripts " s, i " notify that the equation can be used for signal or idler photons, and superscripts "1,2" refer to 1st and 2nd birth crystals. polarization.

V gex is the group velocity for photon with extraordinary

V gor is the group velocity for photon with ordinary polarization.

Temporal-labeling information can be precompensated by inserting a birefringent element in the path of pump beam, with thickness Lcom p satisfying the following relation

  1 1   t s ,i  ex Lcom p or V  ( ) ( ) w V w gcom p p   gcom p p where

(16)

or ex Vgcom p( w p ) , Vgcom p( w p ) are the group velocities for ordinary and extraordinary pump components and

t s ,i is the relative delay between pairs of the two down-conversion processes.

FIGURE 6. Destruction of "which-crystal" information using the precompensator crystal.

We designed numerical code [12] to calculate parameters of the temporal compensation in our experiment. The following table includes its results Calculated Variable

Value

vg_se

=1.813860828470988e+008 ms-1

vg_po

=1.684803050830690e+008 ms-1

delay

=3.378477780731889e-013 s

vg_pe

=1.723724473489015e+008 ms-1

lc

=0.002520863608919 m

where vg_se is group velocity of extraordinary degenerate ray, vg_po (vg_pe) is group velocity of ordinary (extraordinary) pump light, and lc is the thickness of precompensator element. This means that delay between the two-crystal pairs in our case is 338fs and the required thickness of precompensator made from the same crystal with the same cut angle is 2.5 mm.

  219

5. CALCULATIONS OF SPATIAL PHASE COMPENSATION

FIGURE 7. Ordinary and extraordinary rays inside compensation crystal. Ko (Ke) shows ordinary (extraordinary) wave vector direction while So and Se are the corresponding Poynting vectors.

In the two-crystal setup, collecting entangled pairs behind extended spatial filtration (wide iris) averages the measured state over continuum of states with varying relative phase. This hurts the coherence of the state. To obtain the accurate gradient of the varying relative phase, corrected calculations model for the two-crystal case [18] is applied, while a previous compensation technique [10] is used to design thickness and cut angle of the proposed compensation crystal. As shown in FIGURE 7, the phase accumulated by the passing rays inside the compensation crystal can be expressed as:

o 

e 

2no ( )



*

d cos o

2ne ( , e   pm )



(17a)

*

d cos( e   )

* cos 

 Air  d sin  [tan( e   )  tan  o ] Where

 o (  e ) is the phase accumulated

by ordinary (extraordinary) ray passing through the crystal,

(17b)

(17c)

 Air is the

additional phase acquired by ordinary ray in air. The phase slop calculated for our two-crystal source arrangement is ~ -15.9o (taking into consideration tilting the two-crystal set). This can be effectively compensated using two untilted BBO crystals cut at 29 degrees with thickness 235 µm on each down-conversion arm (phase slop ~ 15.9o). To obtain this positive phase slop, the used compensation crystals should be held as shown in FIGURE 7 (optic axis on the side further from direction of down-conversion rays, not as shown in the origin letter [10]). When temporal and spatial-phase compensations are applied together, the design of the temporal precompensator should include temporal effect of the used spatial phase compensator.

220  

REFERENCES 1.

D. Bohm, Quantum Theory, Prentice-Hall, Englewoods Cliffs (1951). Republished by Dover (1989).

2.

A. Aspect, J. Dalibard and G. Roger, "Experimental Test of Bell’s Inequalities Using Variable Analyzers," Phys. Rev. Lett. 49, 1804 (1982).

3.

Weihs, G., Jennewein, T., Simon, C.,Weinfurter, H. & Zeilinger, "A. Violation of Bell’s inequality under strict Einstein locality conditions, " Phys. Rev. Lett. 81, 5039–5043 (1998).

4.

Aspelmeyer, M. et al. "Long-distance free-space distribution of entangled photons," Science 301, 621–623 (2003).

5.

Resch, K. J. et al. "Distributing entanglement and single photons through an intra-city, free-space quantum channel," Opt. Express 13, 202–209 (2005).

6.

Peng, C.-Z. et al., "Experimental free-space distribution of entangled photon pairs over a noisy ground atmosphere of 13 km," Phys. Rev. Lett. 94, 150501 (2005).

7.

R. Ursin, et al. "Quantum teleportation link across the Danube," Nature 430, 849 (2004).

8.

Paul G. Kwiat, Edo Waks, Andrew G. White, Ian Appelbaum, and Philipe H. Eberhard. "Ultrabright source of polarization-entangled photons," Physical Review A, 60(2):R773-R776 (1999).

9.

P.G. Kwiat, K. Mattle, H. Weinfurter, and A. Zeilinger, "New High-Intensity Source of Polarization-Entangled PhotonPairs," Phys. Rev. Lett. 75, 4337 (1995).

10. J. B. Altepeter, E. R. Jeffrey, and P. G. Kwiat, "Phase-compensated ultra-bright source of entangled photons," Opt. Express 13, 8951-8959 (2005). 11. Radhika Rangarajan, Michael Goggin, and Paul Kwiat, "Optimizing type-I polarization-entangled photons," Opt. Express 17(21), 18920-18933 (Oct 2009). 12. Detailed information about design of the four-fold circuit and the text source of the numerical codes is mentioned in [Salem Hegazy, "Free-Space Communication with Entangled Photons", M.Sc. Thesis, Cairo University, 2010]. 13. J. S. Bell, Physics 1, 195 (1964). 14. J.F. Clauser, M.A. Horne, A. Shimony and R.A. Holt, "Proposed experiment to test local hidden-variable theories", Phys. Rev. Lett. 23, 880 (1969). 15. A. Garuccio and V.A. Rapisarda, Nuovo Cimento 65A, 269 (1981). 16. A. Aspect, P. Grangier and G. Roger, "Experimental Realization of Einstein-Podolsky-Rosen-Bohm Gedankenexperiment: A New Violation of Bell’s Inequalities," Phys. Rev. Lett. 49, 91 (1982). 17. One should note that the extraordinary pump beam inside the crystal does not pass direction shown in the figure. Actually it passes in the Poynting vector direction (direction of energy flow) which is further from optic axis direction by the walkoff angle. But as we are only interested in the rays directions (ignoring variations of the emerging points locations as we are using thin crystal), and because the refraction direction is ruled by phase velocity direction (via Snell’s law), we use phase velocity direction to draw the figure. 18. Salem Hegazy, Mohy S. Mansour, and Lotfia El Nadia, "Spatial decoherence of the two-crystal entangled photons", to be published.

221

EFFECT OF PREPARATION METHOD ON LUMINESCENCE PROPERTIES AND QUANTUM EFFICIENCY OF CdTe QDs A. M. SAAD, M. M. BAKER, M. A. KANA and I. M. AZZOUZ* National Institute of Laser Enhanced Sciences, Cairo University, 12613, Giza, Egypt

The effect of preparation procedure on the optical properties of CdTe semiconductor nanoparticles (NPs) has been investigated. CdTe NPs have been prepared via two different methods, organometallic pyrolysis method and microwave assisted aqueous based method. The nanostructure for the prepared NPs via both methods was confirmed by transmission electron microscopy, absorption and photoluminescence spectroscopy. Comparison between the quantum yield emissions of the as-prepared NPs of both methods is presented. The results shows that CdTe NPs which prepared via microwave assisted aqueous method yielded a much higher quantum efficiency (>41%). Amplified stimulated emission is investigated at room temperature (300K) and at low temperature (10K). Lifetime is also measured.

1.

Introduction

The field of semiconductor nanoparticles (NPs) has experienced an enormous development over the past two decades [1,2]. They show novel optical and electronic properties when they have size comparable to, or smaller than, the dimensions of the exciton within their corresponding bulk material. CdTe is one of the most common materials which have special technological importance because it is the only known II-VI semiconductor that can form conventional p-n junctions [3]. Its NPs have been the subject of many scientific and technological applications including lightemitting diodes (LEDs) [4,5,6], photosensitive films [7], micro-resonators [8], waveguides [9], and sensors [10], in addition to its biological application [11,12]. As a result, many of the literature reports are dealing with synthetic of CdTe NPs of unique properties by engineering the chemical functionality of their surrounding medium [13-24]. In this work, we investigate the effect of preparation method on the optical properties and the quantum yield efficiency of CdTe NPs. Two different preparative approaches have been adopted. The nano structure and size growth was examined with the absorption and photoluminescence spectroscopic techniques. Quantum yield of the as-prepared NPs via both methods is presented. Stimulated emission is measured for CdTe NPs at two different temperatures. In addition, lifetime measurement is also presented.

hot surfactant procedure [13]. The second method is the microwave-assisted aqueous synthesis based method [14]. These two methods will be referred to as method “A” and “B”, respectively. 2.1. Method “A” Te solution was prepared by dissolving 0.2g of Te powder in 5ml of TOP and heated up to 150°C until the color of the solution became greenish yellow. 0.2g of CdO was added to 3ml of oleic acid and heated up to 170ºC till complete disappearance of the red color of CdO. 2g of TOPO and 1.0 g of HDA were added to this reaction mixture and heated at 200°C. The previously prepared Te solution was quickly injected into the hot mixture and the mixture was left to cool down to 140°C to allow for the growth of CdTe NPs. Many aliquots samples were withdrawn at different times during the cooling process. The whole synthesis process was carried out under flow of Ar gas. The separation of NPs was done by mixing them with a mixture of an equal volume of hexane and methanol (1/2, V/V) then shaking vigorously and the precipitated powder was separated centrifugally. Powder drying process was carried out in an inert atmosphere (argon). The final powder product can be re-dissolved in a desired solvent (toluene, chloroform, or hexane) for the required measurements. The complete removal of Cd precursors from the final solution was confirmed by UV-VIS spectroscopy. 2.2. Method “B”

2.

Experimental

CdTe NPs were synthesized using two methods. The first method is the colloidal organometallic pyrolysis in *

0.1g of NaBH4 and 0.1g of Te powder was added to 3mL of deionised water. The mixture was left in dark for ~24h during which hydrogen was released through a

Corresponding author: [email protected] CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

222

small outlet of the flask. White precipitate of sodium tetra-borate was formed then NaHTe solution was separated and added to N2-saturated Cd(NO3)2·4H2O solution of PH 11.4. TGA was used as a capping material. A solution of Cd2+/TGA/HTe of molar ratio 1:1: 0.5 was used to prepare the reaction mixture. Equal volumes of this mixture exposed to microwave of different powers and exposure time yielding TGA-CdTe NPs of different sizes. Finally, CdTe NPs were precipitated by centrifugation process. 2.3. Techniques

power increased. For method “A”, the samples were withdrawn after beginning of heating treatment by 0.5, 6 and 15 minutes. The absorption wavelength maxima “λp” (first excitonic peak) of these samples were found to ranges from 440 nm to 620 nm corresponding to band gaps “Eg” of 2.82eV to 2eV. For method “B”, the samples were obtained after microwave irradiation at 160W for 5 and 15 min and 350 W for 15min. Absorption spectra of these samples are not well defined as those of method “A”. λp was ranges from 500 nm to 570 nm corresponding to Eg of ~2.5eV to ~2.2eV.

The nanostructure of the prepared CdTe were characterised by transmission electron microscopy "TEM" (Philips CM20 microscope) operating at 200 kV. A drop of dilute solution was deposited on an amorphous carbon-copper grid and left to evaporate at room temperature. For absorption measurements, the NPs were dispersed in chloroform and absorption spectra were recorded with a Perkin Elmer Lambda 35 spectrometer. Fluorescence emission and excitation spectra were measured using Perkin Elmer LS55 spectrofluorometer. Stimulated emission has been studied at room temperature and at lower temperature (10K). The photoluminescence has been measured at different excitation power values of Ar laser (488 nm). The laser power was varied from 1mW to 200mW using power density filters. For lifetime measurements, nitrogen laser (laser photonics LN1000) of pulse width 800ps and energy of 0.5 mJ was used as an excitation source. 3.

Results

Investigations of nanostructure formation were carried out first via “TEM” transmission electron microscopy. TEM images are presented in Figures 1a and 1b for method “A” and method “B” NPs, respectively. Obviously the nanostructure of the prepared NPs via both methods is confirmed in these images. Figures 2a and 2b present the absorption spectra of some NPs samples grown at various times via method “A” and at various exposure times and powers for method “B”. Red shift is observed in the position of the absorption peak (and so their band gaps) as the time or

Figure 1. TEM images of CdTe NPs prepared by (a) the organometallic pyrolysis method “A” and (b) the microwave assisted aqueous method “B”.

223

Figure 2. Absorption spectra of the different sizes of CdTe NPs grown at: (a) various times via method “A” and at various exposure times and powers for method “B”.

The effect of microwave exposure time and power on the emission spectra of NPs is presented in Figures 3a and 3b, respectively. Emissions spectra show a red shift either by increasing the microwave exposure interval at constant power (Figure 3a) or by increasing the power at constant exposure time (Figure 3b). This shift indicates the growth of NPs with increasing either the time exposure or the power. Also, it is obvious that the emissions spectra are sufficiently narrow where the FWHM is of the order of 40nm. This is indication for the uniformity of the NPs size distribution.

Figure 3. Effect of microwave exposure: a) time and b) power on the emission spectra of the CdTe NPs prepared by method “B”.

Figures 4a and 4b presents the PL spectrum relative to the absorption of the as-prepared NPs via method “A” and method “B”, respectively. It can be seen that, the two PL bands are located typically close to the absorption thresholds (so-called band-edge or “excitonic” PL). For method “A”, the average stock shift is of the order of 27nm and the emission FWHM ranges between 27 nm to 50nm. For method “B”, the average stock shift was of the order of 70nm with FWHM ranges from 34nm to 70nm.

224

Figure 5 presents a comparison between the emission spectra of similar size NPs which prepared by both methods. It can be seen that, the emission spectrum of method “B” sample shows a much higher intensity with wider FWHM than that prepared by method “A”. The fluorescence quantum yield efficiency Q was estimated by comparing the integrated emission band of NPs to that of rhodamine 6G, as a reference, according to: Qn = Qd (In Od /Id On), where I is the peak intensity of the emission spectra; O is the optical density at the excitation wavelength and the subscripts n and d referred to NPs and dye, respectively. Qd was obtained according to Photochem CAD database package by Jonathan Lindsey.

Figure 5. Comparison between the emission spectra of 3.8nm size CdTe NPs, prepared via method “A” and method “B”. Figure 4. Band-edge absorption and normalized PL spectra for the prepared NPs via: (a) method “A” and (b) method “B”.

In general, the emission spectra of NPs prepared by method “B” are found to be more broadening than those of method “A” and the stock shift is further. These two observations indicate that method “B” produced NPs of less uniform size distribution but more likely to be luminescent NPs, respectively. The size of the prepared NPs via both methods was estimated according to the wavelength of the PL maximum. The radius was found to range between ~2nm (at 500nm of green emission) to ~4nm (at 640 nm of red emission).

The quantum yield of CdTe NPs prepared via methods “A” and “B” was calculated to be 5%, and ~ 41%, respectively. This was unexpected, since NPs of method “B” is capped with the electron donor TGA which supposed to quench the emission not to enhance it. This enhancement may be explained as follows: CdTe NPs was passivated with Cd(OH)2 during synthesis in the alkaline media (pH 11.4) therefore, the excess of Cd ions may react with the OH ions forming a hydroxide layer which converted to CdO upon heating by microwave radiation. Since oxides have higher band gap, this may results in enhancement of the emission.

225

Optical amplification and lasing properties of NPs are mainly depend on the multi-exciton emission and also related to the quantum yield efficiency. Therefore, we investigate the amplified stimulated emission ASE for CdTe NPs which yields higher quantum efficiencies (method “B”). The NPs of size 3.1 nm were excited by 488nm of Ar laser at different powers (from 1mW to 200mW). Measurements of the induced fluorescence were obtained for NPs at room temperature and also at a lower temperature (at 10K to eliminate the thermal and phonon contribution effects). The results are displayed in Figures 6a and 6b, respectively.

Figure 6. Photoluminescence spectra of CdTe NPS at different excitation powers (Pex) of Ar laser at temperatures 300K and 10K.

The emission band amplitude as a function of Ar laser pump power is presented in Figures 7a and 7b, for NPs at temperature 300K and 10K. The figures show that the output PL intensity is linearly increases with the

pump power via two different rates (two different slopes). The slower rate is attributed due to monoexciton emissions. The faster rate was attributed to stimulated emission of multiexciton which induced by the high excitation powers. Multiexciton emission is observed with threshold power of nearly 40mW. The threshold power was found to be depends on the NPs size, quality and on the NPs quantum yield efficiency. Also, the emission spectra at room temperature show a mixing between the monoexciton and the multiexciton emissions. This mixing was attributed to the thermal effect. This is confirmed by the mixing disappearing at 10K when thermal effect is eliminated and e-h recombination is considered as the only source of photon emission. This means that, population inversion in 1Se state can be achieved at 10K with threshold pump power of 40mW.

Figure 7. ASE intensity as a function of pump power at temperatures 300K and 10K.

The detection of the multiexcitonic states is very challenging because of their very short lifetime. It needs either very short laser pulse or low temperature measurement to be detected. Therefore, excitation was

226

carried out using N2 laser of 800ps pulse duration and 0.5mJ energy. Figure 8 shows the decay curve of the exciton emission for CdTe NP at room temperature. The lifetime was estimated using the fitting formulas of Origin Lab vr 8. The best fitting was obtained with the second order exponential decay fitting. The decay times were fitted with 2 nsec lifetime of biexciton and 10 nsec of monoexciton.

Figure 8. Experimental emission decay of CdTe NPs excited by N2 laser of energy 0.5mJ with fitting line.

4.

Conclusion

CdTe NPs have been prepared via two methods, namely, “A” organometallic pyrolysis method and “B” microwave assisted aqueous method. The results show that the method of preparation affecting the optical properties and the quality of the yielded CdTe NPs. The quantum yield of CdTe NPs prepared via microwave method show high values (>40%). The organometallic pyrolysis method NPs of the same size (3.1nm) show a much lower quantum yield values (~5%). The high quantum efficiency values was attributed due to that CdTe NPs may be passivated by Cd(OH)2 as the reaction medium was alkaline (pH=11.4), so the excess of Cd ions react with the OH ions in the solution forming the hydroxide. The hydroxide layer could be converted easily to CdO upon microwave heating (oxides have higher band gap material). The as-prepared microwave CdTe NPs show better amplified stimulated emission at 10K than at room temperature with threshold power of the order 40mW. The emission lifetime was estimated to be 2ns and 10ns for mono- and multiexciton emissions, respectively.

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21. S. Wuister, I. Swart, F. Driel, S. Hickey and C. Donega, Nano Lett., 3, (2003). 22. A. Joly, W. Chen, D. McCready, J. Malm and J. Bovin, Phys. Rev. B 71, 165304 (2005).

23. Y. Yang, H. Wu, K. Williams and Y. Chao, Angew. Chem. Int. Ed 44, 6712 (2005). 24. J. K-Olesiak, V. Kloper, R. Osovsky, A. Sashchiuk and E. Lifshitz, Surf. Sci 601, 2667 (2007).

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1 1

Novel Process for Laser Stain Removal from Archaeological Paintings Novel Process for LaserOil Stain Removal from Archaeological Novel Process for LaserOil Stain Removal from Archaeological Paintings Oil Paintings Lotfia El-Nadi, Osama El-Feky*, Galila Abdellatif, Sawsan Darwish*

Lotfia El-Nadi, Osama El-Feky*, Galila Abdellatif, Sawsan Darwish* Physics Dept., Faculty of Science, Cairo University, Giza-Egypt Lotfia El-Nadi, Osama Dept.,Faculty El-Feky*, Galila Abdellatif, Darwish* *Restoration and Conservation of Archaeology, CairoSawsan University.Giza-Egypt

Physics Dept., Faculty Science, Cairo University, Giza-Egypt E-mailof : [email protected] *Restoration and Conservation Dept.,Faculty of Cairo Archaeology, Cairo University.Giza-Egypt Physics Dept., Faculty of Science, University, Giza-Egypt E-mail : [email protected] *Restoration and Conservation Dept.,Faculty of Archaeology, Cairo University.Giza-Egypt E-mail : [email protected]

Abstract Some samples of oil paintings (5 × 5 cm) were prepared on wooden panel with Abstract four types of fungi commonly encountered oil paintings were on selected for panel this study. Some samples of oil paintings (5 × on 5 cm) were prepared wooden with Abstract

Eachtypes ofSome theoffungi iscommonly associated with different stains. Fungus Alternaria tenuis is four fungi encountered oil paintings were selected for panel this study. samples of oil paintings (5 × on 5 colored cm) were prepared on wooden with associated by a dense black stain, Chetomium globosum by a brownish gray stain, Eachtypes of theoffungi associatedencountered with different stains.were Fungus Alternaria tenuis is four fungiiscommonly oncolored oil paintings selected for this study. Aspergillus flavus by a yellowish stain, and Fusaruim oxysporum by a pinkish stain. associated by a dense black stain, Chetomium globosum by a brownish gray stain, Each of the fungi is associated with different colored stains. Fungus Alternaria tenuis is Fungi growing oil affect the and surface characteristics forming agray variety of Aspergillus flavus by paintings ablack yellowish stain, Fusaruim oxysporum by a pinkish stain. associated by aondense stain, Chetomium globosum by abybrownish stain, colored patches typically composed of many complex chemical substances that are Fungi growing on oil affect the and surface characteristics by forming a variety of Aspergillus flavus by paintings a yellowish stain, Fusaruim oxysporum by a pinkish stain. produced during metabolic processes. These colored stains may be encrusted in spores, colored patches typically composed of many complex chemical substances that are Fungi growing on oil paintings affect the surface characteristics by forming a variety of present inpatches mycelium or secreted to a substance such as oilchemical paintings surfaces. While the produced during metabolic processes. These colored stains may be encrusted inthat spores, colored typically composed of many complex substances are fungal stains canmetabolic sometimes betoextracted appropriate solvents, there While arespores, some present in during mycelium or secreted a substance such as oil paintings surfaces. the produced processes. Thesewith colored stains may be encrusted in stains that resist solvent extraction entirely. Developing new solvent system that might fungal stains can sometimes betoextracted with appropriate solvents, there While are some present in mycelium or secreted a substance such as oil paintings surfaces. the attack the paint structure, and is time consuming and requires a great deal of trial and stains that resist solvent extraction entirely. Developing new solvent system that might fungal stains can sometimes be extracted with appropriate solvents, there are some error. Mechanical stain removal also problematic in that it often produces abrasion of attack the paint and isistime consuming and requires a great deal of trial and stains that resist structure, solvent extraction entirely. Developing new solvent system that might the surface, markedly deteriorating the artwork, and is extra ordinarily fine and tedious. error. Mechanical stain removal alsoconsuming problematicand in that it often produces abrasion of attack the paint structure, and isistime requires a great deal of trial and For these reasons, we decided to examine an alternative physical technique as a new the surface, markedly deteriorating the artwork, and is extra ordinarily fine and tedious. error. Mechanical stain removal is also problematic in that it often produces abrasion of approach deal with stain removal. the stains are due to thetechnique existence of afungi, For these to reasons, wedeteriorating decided to examine an alternative physical new the surface, markedly theSince artwork, and is extra ordinarily fine and as tedious. we thought it a good idea to remove them by singlet oxygen. We applied the photo approach deal with removal. Since the stains are due to thetechnique existence as of afungi, For these to reasons, we stain decided to examine an alternative physical new dynamic process through which the fungi were with organic dye we thought it a good idea to remove them bystains singletare oxygen. We existence applied the photo approach to deal with stain removal. Since the stains duecovered to the of fungi, derivatives in solution under controlled illumination in the lab. The samples were then dynamic process through which the them fungibystains covered with organic dye we thought it a good idea to remove singletwere oxygen. We applied the photo irradiated by low power Laser light from a He-Ne laser, the dye will be photoderivativesprocess in solution underwhich controlled the lab. The samples were then dynamic through the illumination fungi stains inwere covered with organic dye decomposed singlet oxygen. We areport in work thedye results as irradiated by lowproduce power Laser light from He-Ne laser, will obtained be photoderivatives inand solution under controlled illumination in this the lab.the The samples were then airradiated function of: decomposed We areport in this work results as byand lowproduce power singlet Laser oxygen. light from He-Ne laser, thethedye will obtained be photo- The concentration and types of the organic dye in solution, adecomposed function of:and produce singlet oxygen. We report in this work the results obtained as -The presence of certain amounts of liquids the solution, concentration and types of the organicadded dye intosolution, a- The function of: -The scanning speed of the laser beam on the sample surface, of certain amounts of liquids the solution, --The Thepresence concentration and types of the organicadded dye intosolution, -The irradiation time. -The scanning speed of the laser beam on the sample surface, presence of certain amounts of liquids added to the solution, For each case fresh samples werebeam used on andthe photographed before and after the treatment. irradiation time. -The scanning speed of the laser sample surface, The each results obtained will be were speculated and photographed discussed. This procedure wasthe applied to the For case fresh samples used and before and after treatment. -The irradiation time. cleaning of archaeological oil paintings for the first time to our knowledge. The method The each results obtained will be speculated and photographed discussed. This procedure wasthe applied to the For case fresh samples were used and before and after treatment. could well be considered as a new field of combined science and technology applied to cleaning of archaeological oil paintings for the first time to our knowledge. The method The results obtained will be speculated and discussed. This procedure was applied to the laser stain and represents a significant addition the techniques available to could well be considered asoila paintings new field of combined science and technology applied to cleaning of removal archaeological for the first time totoour knowledge. The method art conservation. laser stain and represents a significant addition to the could well removal be considered as a new field of combined science andtechniques technologyavailable applied to art conservation. laser stain removal and represents a significant addition to the techniques available to substances that are associated with the 1. Introduction art conservation. type of fungi formed with during Fungi growing on oil paintings affect substances that areand associated the 1. Introduction metabolic processes [1], [2]. the surface characteristics by secreting a type of fungi and formed during substances that are associated with the Fungi growing on oil paintings affect 1. Introduction variety of colored complex chemical metabolic processes [1], [2]. type of fungi and formed during the surface characteristics by secreting Fungi growing on oil paintings affecta metabolic processes [1], [2]. variety of characteristics colored complex chemicala the surface by secreting CP 9910, Modern Trends in Physics Research variety of colored complex chemical Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

2 These stains may be encrusted in spores, present in mycelium or secreted to a substance such as oil paintings surfaces [3], [4]. While the fungal stains can sometimes be extracted with appropriate solvents, there are few affective solvents that do not damage the painted surfaces and many stains resist solvent extraction entirely. Developing new solvent system is time consuming and requires a great deal of trail and error. Mechanical stain removal is also problematic in that it often produces abrasion of the surface, markedly deteriorating the artwork, and is extra ordinarily tedious [5]. For these reasons, we decided to examine an alternative physical technique that might be more specific and flexible. Lasers, unlike conventional light sources, produce a monochromatic pencil-like beam of intense light and high power that is capable of vaporizing colored materials [6]. If the stain absorbs the laser light more effectively than the substance of the painted surface, it should be possible to vaporize the stain while leaving the substrate undamaged. But this method might produce charring of the painted surface. We decided to test the capability of a low power laser and photo sensitizer dyes to remove stains caused by several common fungi from oil paintings surfaces. This simulates the Photodynamic processes applied in medicine [7]. Our findings suggest that this technique of laser stain removal represents a significant addition to the techniques available for art conservation.

2. Experimental Procedure

2. 1. Sample Preparation Some samples of oil paintings (5 × 5cm) were made on wooden panel; four stains of fungi commonly encountered on oil paintings were selected for the experiment. Each of the fungi is associated with different colored stains.

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Fungus Alternaria tenuis is associated with a dense black stain (no.1), Chetomium globosum with a brownish gray stain (no.2), Aspergillus flavus with a yellowish stain (no.3), and .Fusaruim oxysporum with a pinkish stain (no.4). These fungi were cultured on potato-dextrose agar medium. Samples placed in individual Petri dishes cultivated the fungi and treatment were carried out in an optional environment, at pH of 6 at 24oC and with exposure to the light from a standard fluorescent lamp for 8 hours per day for 21 days [8]. Each stained area were photographed before carrying out the experiment. Examples of the four types of induced stains are shown in figure. 1, prior to treatment. The treated stains were also examined under magnifications of binocular microscope and photo graphed with CCD camera.

Fig. 1 Shows the four samples of oil paintings with four types of fungi.

The laser beam spot as reflected from an inclined mirror forms a cicuilar area that could be directed by the mirror to a specific position on the sample as clear from fig.2.

3

230  

Fig. 2 shows the laser beam spot as reflected from an inclined mirror forms a cicuilar area.

scanner, the beam width was spread and so it formed a wide track on the horizontal surface of the sample. Three parallel tracks were initiated due to the reflection of the incident laser beam from the front and back surfaces of the glass layers of the mirror as well as the scanner surface as shown in fig.4. This geometry allowed the irradiation of particular sites on the sample at the same time using the same conditions.

2. 2. Geometrical Setup The He-Ne laser beam of power 10mw wavelength 632nm was allowed to be reflected from an inclined mirror. Thus falling on the surface of highly reflecting hexa surface scanner. The scanner rotates around a vertical axis covering 1000 rotation per second as shown in fig.3. Fig. 4 shows the incident reflected

beam from the mirror and then the scanner surfaces.

3. Treatment of the sample

Fig. 3 shows the geometrical setup of He-Ne laser beam.

The incident reflected beam from the mirror and then the scanner surfaces, was adjusted to produce circular path on the surface of each sample separately. Due to small vertical vibration of the

3.1. The traditional method The usually used method in stain removal is a mechanical process where stain removal is carried out by fine scalpels or by applying a cotton-wool swab dipped into a solvent then rolled on to the painted picture surface, causing the stains of mold to soften and dissolve. Mechanical stain removal is also problematic in that it often produces abrasion of the surface, markedly deteriorating the artwork, and is extra ordinarily fine and tedious [9],[10]. For these reasons, we decided to examine an alternative physical technique that might be more specific and flexible. A new approach to deal with stain removal was used.

4 3.2. Laser Photo Dynamic Process The laser Photo Dynamic Process PDP could be simply explained according to the following phenomena associated with the decomposition of the photosensitizer dyes under laser beam effect. The hypariene derivatives as well as the methyline blue dyes are known to be photosensitizers that can combine with the active biological cells in the medical Photo Dynamic Therapy PDT treatment. Accordingly, the fungi being biological living cells are apt to combine with the hypariene derivatives or the dye. Irradiation of the photosensitizers loaded fungi leads via the photochemical reactions to the photo excitation of the sensitizer and thus producing singlet oxygen and free radicals. The singlet oxygen being highly active chemically will initiate the death of fungi cells and consequently stain removal. The following procedure was fallowed parts of the surface area of the sample within the scanned beam track were treated with solution of a hypariene derivative or the dye. These surface areas were chosen according to the degree of fungus infection. One of the scanned tracks was allowed to impinge on a sample area without any treatment, while the other tracks fall on a hyparine or methylene dye treated areas in order to compare the beam effect on removal of the fungi infection under the same irradiation conditions. The irradiation times were chosen for 5minutes, 15 minutes, 30 minutes and one hour. Also some samples were wetted by distilled water before applying the hypariene derivatives or the methylene blue dye. Two types of hypariene derivatives were used to identify the suitable type for stain removal, namely porphyrine and hyparine.

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4. Method of Inspection

Imaging technique was used to identify the sample surface before and after treatment for the laser photodynamic method. Continuous observation of the sample surface was recorded using CCD camera. Continuous monitoring could be easily done up to 60 minutes irradiation time.

5. Results

Considering the laser photodynamic treatment, it is clear that only the PDP with hyparine can attack all types of fungal stains in different degrees. The Methylene blue dye did not respond at all. The response to the treatment with clear effect started after 15 minutes of irradiation. Complete removal as shown in fig.5-1 and table 1 is recognized and no further effect was detected for longer irradiation time. Also one should emphasize that when wetting the samples with distilled water the fungi no.1 Alternaria tenuis, fungi no.3 Aspergillus flavus the stain removal was complete. While in case of no.2 Chetomium globosum stain removal was partial. The type Fusaruim oxysporum no. 4 partially responded as well for the photdynamic treatment.

Fig. 3 shows the results of laser photodynamic treatment.

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Table 1 summarizes the obtained results for the different types of fungi. Sample No.

Fungi

Irradiation Time 15 min. dry wet Complete Complete removal removal ≈100% ≈100%

1

Alternaria tenuis

2

Chetomium globosum

No effect 0%

Partial ≈70%

3

Aspergillus flavus

No effect 0%

Complete removal ≈100%

4

Fusaruim oxysporum

No effect 0%

Partial ≈50%

6. Discussion and Conclusion

Laser Photo Dynamic Process PDP is proved to be successful in both type 1 and type 3. It does not leave any mechanical effect or change of the surface morphology, retaining the original color for the oil painted surface. This means that the stain is that of the fungi itself. When it is destroyed by the PDP, the colored stains disappear. The presence of H2O could be a suitable agent to supply oxygen during the decomposition of the hyparine derivative dye under visible laser irradiation. One may conclude that the wetted surfaces enhance the removal of the affected area by ≈ 70% as compared to the dry ones. In the other two samples no.2 and no.4 having partial response, the colored stain is most probably associated with the Fungi and their secretion as well. Even when the fungi were decomposed by the PDP, the stain due to the secretions still persisted. Generally, this process can help to get rid of any type of fungi and bacteria (any biological cells). This method could well be used to sterilize and disinfect the archaeological oil painted surfaces.

7. References

Irradiation Time 30 min. dry wet No No further further effect effect No No further further effect effect No No further further effect effect No Further further ≈70% effect

1. Nicolaus, K., The Restoration of Painting, Konemann, London, 1999, pp. 204-207. 2. Gettens, R. J., and Stout, G. A., Painting materials, Dover Publication Inc., New York, 1966. p. 230. 3. Sharmax, O. P., Text book of fungi, department of college merut, Tata Mcgran- Hill publishing company limited, New Delhi, 2001. p. 181. 4. Florian, M.-L. E., Heritage eaters: Insects & fungi in heritage collections. London, James & James. 2002. 5. Mayer, R., The artist’s hand book of materials and techniques, Third edition, The viking press, New York, 1978. pp. 514-515. 6. Cooper, M.I., Laser Cleaning in Conservation: An Introduction, ButterworthsHeinemann, Oxford, 1998. 7. Dougherty, T. J., Gomer C. J., et al., Photodynamic therapy. J. Natl. Cancer Inst. 90: 889-905., 1998. 8. Szczepanowska, H. M., and Moomaw, W., Laser stain removal of fungus-induced stains from paper, JAIC 1994, Volume 33, Number 1, Article 2. pp. 25-32. 9. Szczepanowska, H., and C. M.Lovett, Jr. Fungal stains on paper: Their removal and prevention. In The conservation of Far Eastem art, ed.J. S.Mills, P.Smith, and K.Yamasaki. London: International Institute for Conservation of Historic and Artistic Works. 1988. 13–14. 10. Dantigne, P., Preservation of books, pictures, fabrics and others from mould spoilage. International preservation news: A newsletter of the IFLA Programme on Preservation and Conservation, 2007, (41), 1921.

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APPLICATION OF LASER INDUCED PLASMA SPECTROSCOPY ON BREAST CANCER DIAGNOSES A. ABD-ALFATTAH1, A. A. ELDAKROURI1,2, H. EMAM1 and I. M. AZZOUZ1,* 2

1 National Institute of Laser Enhanced Sciences, Cairo University, Cairo, Egypt College of Applied Medical Science, King Saud University, Kingdom of Saudi Arabia

Worldwide, millions of breast cancer cases appear each year. It ranked as the first malignant tumors in Egypt. Breast cancer patients are at increased risk of developing malignant melanoma and cancers of the ovary, endometrium, colon, thyroid, and salivary glands because of similar hormonal and genetic factors. Therefore, early diagnosis by a quick and accurate method may have a great affect on healing. In this work, we investigate the feasibility of using LIPS as a simple, technique to diagnose breast cancer by measuring the concentration of trace elements in breast tissues. The accuracy of LIPS measurements was confirmed by carrying out another elemental analysis via atomic absorption spectroscopy (AAS) technique. The results obtained via these two techniques showed that the concentration of Ca, Cu, Fe, Zn and Mn in the malignant tissue cells are significantly enhanced. A voting algorithm was built for instantaneous decision of the diagnostic technique (normal or malignant). This study instigates developing a new diagnostic tool with potential use in vivo.

1.

Introduction

Laser-induced plasma (or breakdown) spectroscopy “LIPS” (or “LIBS”) technique is a laser-based elemental and molecular analysis tool [1-5]. The principle of this technique is based on laser-induced material ablation (vaporization and ionization of a minute amount of specimen materials) then spectral analysis of the plasma emission. Qualitative and quantitative analyses are carried out by monitoring the positions and intensities of the induced plasma emission lines. LIPS technique displays some inherent advantages such as samples nonpreparation, no minimal specimen destructiveness, standoff long-range operation, all-optical excitation, high spatial resolution on the target surface, fast sensitive quantitative detection and analysis of multi-elements. These advantages allow for various applications of LIPS in different fields such as: environmental and space [6-10] military and homeland-security [11-13], pharmaceutical products [14-15] in addition to the biological, forensic and medical fields [16-21]. In this paper, LIPS technique is utilized as a diagnostic tool for breast cancer tissue cells. This was done by carrying out a quantitative analysis for the concentration of some trace elemental constituent’s of breast cells (namely; Ca, Cu, Fe, Zn and Mn). The role of trace elements in cancer has been the subject of many reports [22-26]. *

The discrimination between the elemental concentrations in case of: malignant and normal cells is obtained by LIPS and confirmed by the atomic absorption spectroscopic (AAS) technique. Significant variation is observed between the two cases. A voting algorithm for automatic diagnostic decision (normal or malignant) is presented. 2.

Experiment

The schematic diagram of LIPS technique on tissues is presented in Fig. 1.

Figure 1: Experimental schematic setup for LIPS technique.

A Q-switched Nd:YAG laser (continuum, Surelite II) was used at its fundamental frequency of 1064 nm. Pulses of 10 ns duration were

Corresponding author: [email protected] CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

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produced with maximum pulse energy of 350 mJ. The laser was capable of operation at a 10 Hz repetition frequency but typical experiments utilized a single pulse enough to produce plasma followed by a delay during which the specimen was translated to provide a fresh specimen surface. The energy was adjusted by a suitable combination of beam splitters and Q-switch delay to ensure spatial and temporal beam profile stability. An energy meter (Nova, Ophir Optronics Ltd.) was employed to monitor the shot to shot pulse energy. The plasma was produced by focusing the laser using a quartz plano-convex lens (10 cm focal length) onto the tissue’s surface. The tissue specimens were mounted on a three-axis translator stage for alignment during ablation. Plasma emission was collected via a 1 m quartz optical fiber with an aperture of 200µm. The output end of the fiber was coupled to an echelle spectrometer (SE200PI-HOPrinceton) which provides a constant spectral resolution of 3100 (CSR) over a spectral range 190–1100 nm. The echelle spectrometer was connected to a getable intensified ICCD camera (Princeton, IMAX) for light detection and was controlled by a PC running Grams software version 8 for spectrum analysis. The PC controlled the gating (shuttering) of the ICCD and the operation of the pulsed laser. To avoid the electronic interference and jitters, the intensifier high voltage was triggered optically. To achieve the highest signal-to-noise ratio, optimization was carried out first for the gate delay time (the time between firing of the ablation pulse and electronic activation of the ICCD camera) and the gate width (integration time). The optimal time delay was found to be related to the characteristics of laser and target and also to the surrounding atmosphere. The optimum chosen values for quantitative analysis were 1500 ns and 10000 ns for the delay time and the gate width, respectively. These optimum delay and gate times provide almost continuum-free spectra. Each malignant and normal tissue cell has been measured five times at different fresh spot. These five spectra were accumulated to obtain an average LIPS spectrum. An intensity-concentration calibration curve was developed for each element. These curves were used to calculate the concentration of each element from its corresponding spectrum.

One of the advantages of LIPS, is the ease of collecting the results as a computer data sheets files. Therefore, a voting decision making algorithm has been proposed for a spontaneous decision (normal/malignant) according to LIPS results. The data sheet of each elemental concentration variation is treated by the algorithm to give a voting factor. At the end of the algorithm, the decision is taken according to the majority of all votes factors. 3.

Result and Discussion

The study was carried out on thirty random cases. A pathological report was obtained for each case (this report is essential for the treatment protocol). According to these reports, the specimens were classified as either malignant or normal. A large domain of the spectrum can be investigated simultaneously with echelle spectrometer. The wavelengths of interest in LIPS spectra are: 393.6 nm and 422.6 nm for Ca; 388.6 nm for iron; 324.75 nm for copper; 213 nm for zinc and 259.37 nm for manganese. The intensity of Ca line at 393.36 nm was found to be much higher than other elements lines in each individual case. Therefore, the intensity of Ca line in each spectrum was considered as a reference and the intensity ratio of: Zn/Ca, Mn/Ca, Cu/Ca and Fe/Ca were calculated. This was done to reduce the effect of instrumental signal fluctuation and the matrix interference effects. The intensity of various elements was related to the concentration of trace elements in normal and malignant tissue via calibration curves. The results of Ca concentration for all normal and malignant samples are presented in Figure 2a.

Figure 2: Ca concentrations measured via LIPS in malignant and normal tissue cells.

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All malignant samples show higher concentrations for Ca than the normal ones. The results of the elemental concentration ratios of Zn/Ca, Mn/Ca, Cu/Ca and Fe/Ca in case of malignant and normal tissue cells are displayed in Figures 3. The concentration ratio of the most elements in the malignant samples shows an increase over the normal ones. This trend is inverted for some elemental ratio in a number of samples. These samples are: numbers 15 & 25 for Cu/Ca; number 30 for Mn/Ca; and number 18 for Fe/Ca. For the purpose of confirmation the samples were subjected to another quantitative elemental concentrations analysis using AAS technique. The results obtained via this absorption technique are displayed in Figures 4. Again, an enhancement is observed in the concentration of the five elements for the malignant cases. This confirms the results obtained via LIPS technique.

Figure 3: Concentration ratio of: Zn/Ca, Fe/Ca, Mn/Ca and Cu/Ca measured via LIPS in malignant and normal tissue cells. .

Figure 4: Concentration ratio of Ca and Zn, measured via AAS in malignant and normal tissue cells.

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Figure 5: Elemental average increase ratio (malignant to normal) in all samples via LIPS and AAS techniques.

One of the advantages of LIPS is the ease of collecting results as a computer data sheets files. These data are processed by the voting algorithm for instantaneous diagnostic decision. Figure 6 presented the flowchart of the developed decisionmaking algorithm. A malignant decision was designed to be >50% of all vote factors.

Figure 6: Schematic diagram of the voting algorithm. Figure 4: Continued.

Figure 5 presents the calculated elemental average increase in malignant to normal samples via LIPS and AAS techniques. The figure depicts that the increasing ratios of Mn, Fe and Zn have nearly the same values via both techniques. LIPS yielded higher increasing ratio was calculated for Ca and Cu elements via.

Accurate decision, with respect to the pathological report, is obtained for each case. 100% vote factors are achieved for all samples which have been classified pathologically as grade II and grade III. In case of grade grade I (the early stage of cancer), four cases revealed vote factors less than 100% but this does not affect the overall decision for these cases.

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4.

Conclusions

The concentration of some trace elements of breast tissue cell constituents (namely, Zn, Cu, Fe, Mn and Ca) have been measured for thirty normal and malignant tissue cells via two spectroscopic approaches: absorption and an emission technique. These techniques are: laser induced plasma spectroscopy (LIPS) and the atomic absorption spectroscopy (AAS). LIPS results showed that the concentrations of these elements are significantly increased in malignant cells over the normal ones. These findings are also confirmed by the AAS technique. It is also found that the decision making algorithm was a very helpful tool for simultaneous processing of LIPS results. Although the relevance of elevated concentrations of these elements in malignant cells remains a matter of conjecture, we can conclude the following features for LIPS; – LIPS is a simple and promising technique capable enough to diagnose the malignant cells at atmospheric conditions. – The specimens irradiated by LIPS do not need any preparations or treatments which may reduce the possibility of contamination as well as error. – It is minimally invasive, since a very small amount of specimen gives good results. – It gives on-line quantification for all trace elements in a tissue simultaneously. This study instigates developing a new diagnostic tool with potential use in vivo via extensive studies to obtain quantitative results for various elemental constituents of tissue cells. References 1. Ayman Abd Alfattah, MSc thesis NILES, Cairo Univ., (2009). 2. A. W. Miziolek, V. Palleschi, I. Schechter, “LIBS Fundamentals and Applications” Cambridge Univ. Press, UK (2006). 3. D. A. Cremers, L. J. Radziemski, “Handbook of LIBS”, Wiley & Sons, London: john (2006). 4. C. Pasquini, J. Cortez, L. Silva, F. Gonzaga, J. Braz. Chem. Soc. 18, 463 (2007).

5. W. B. Lee, J. Y. Wu, Y. I. Lee, J. Sneddon, Appl. Spectr. Rev. 39, 27 (2004). 6. D. Mukherjee, A. Rai, M. R. Zachariah, J. Aerosol Sci. 37, 677 (2006). 7. B. C. Windom, P. K. Diwakar, D. W. Hahn, Spectrochim. Acta B61, 788 (2006). 8. M. Bossu, H. Zuo-Qiang, M. Baudelet, Y. Jin, Z. Zhe, Z. J. Chin, Phys. Lett. 24, 3466 (2007). 9. B. Sallé, D. A. Cremers, S. Maurice, R. C. Wiens, Spectrochim. Acta B60, 479 (2005). 10. L. Radziemski, D. Cremers, K. Benelli, C. Khoo, R. D. Harris, Spectrochim. Acta, B60, 237 (2005). 11. M. Baudelet, L. Guyon, J. Yu, J. P. Wolf, T. Amodeo, E. Fréjafon, P. Laloi; Appl. Phys. Lett. 88 (2006) 063901-1 12. F. C. De Lucia, Jr., J. L. Gottfried, C. Munson, A. W. Miziolek; Spectroscopy, 24, 1 (2009). 13. F. C. De Lucia, Jr., J. L. Gottfried, A. W. Miziolek, Opt. Express 17, 419 (2009). 14. L. St-Onge, E. Kwong, M. Sabsabi, E.B. Vadas, J. Pharm.Biomed. Anal. 36, 277 (2004). 15. M. Mowery, R. Sing, J. Krisch, A. Razaghi, S. Béchard, R. Reed, J. Pharm. Biomed. Anal. 28, 935 (2002). 16. A. Kumar, F. Y. Yueh, J. P. Singh, S. Burgess, Appl. Opt. 43, 5399 (2004). 17. X. Fang, S. Ahmad, M. Mayo, S. Iqbal, Laser Med. Sci. 20, 132 (2005). 18. M. D. Adamson, S. J. Rehse, Appl. Opt. 46, 10 (2007). 19. C. A. Munson, J. L. Gottfried, F. C. De Lucia Jr, A. Miziolek, Appl. Opt. 47, G48 (2008). 20. S. Hamzaoui, R. Khleifia, N. Jaïdane, Z. Ben Lakhdar, Lasers Med. Sci. 26, 79 (2011). 21. C. R. Dockery, S. R. Goode, Appl. Opt. 42, 6153 (2003). 22. M. Schwartz, Cancer Research 35, 3481 (1975). 23. E. Braverman and C. Pfeiffer, Orthomolecular Psychiatry 11, 28 (1982). 24. J. G. Liehr, J.S. Jones, Curr. Med. Chem. 8, 839 (2001). 25. B. K. Abraham, C. Justenhoven, B. Pesch, et al., Cancer Epidemiology Biomarkers and Prevention 14, 1102 (2005). 26. S. A. Navarro and T. Rohan, Cancer Causes Control 18, 7 (2007).

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ULTRAFAST PROCESSES IN CONDENSED MATTER STUDIED WITH ULTRASHORT LASER PULSES P. A. LOUKAKUS Iesl, FORTH, GREECE

The high peak power and the short temporal duration of modern solid state laser systems are valuable tools to perform research on the interactions of light with matter in fundamental as well as applied and technological directions. In this talk I will present a few topics of my past research activities as well as my current research projects. In these activities, ultrashort laser pulses have been combined with time-resolved photoemission and optical techniques in order to study aspects of the interaction of ultrashort laser pulses with solid state matter. Time-resolved photoemission spectroscopy is a powerful tool in the study of ultrafast dynamics following excitation by ultrashort and intense laser pulses because it provides direct access to the electronic distribution. This can be used to study a variety of fundamental physical effects such as the energy deposition and dissipation dynamics on metallic surfaces, the ultrafast demagnetization and recovery of the magnetic order on magnetic systems, and the dynamics of the self energy of solids that can help us understand the quasiparticle excitations and their subsequent interactions. With time-resolved optical spectroscopy further than surface properties we can obtain information on the bulk properties of solids like semiconductors, metals and their nanostructures, e.g. the ultrafast carrier mobility and trapping in defects in semiconductors and the qualitative changes introduced by the strong confinement in metallic nanocrystals. Ongoing research activities include application of ultrashort sources in the study of ultrafast electron and lattice dynamics of bulk and nano-structured solids and interaction of intense and ultrashort laser pulses with solid targets at intensities close to and above the processing/ablation threshold. Novel aspects involving temporal pulse shaping methods and the possibility to control ultrafast processes are going to be discussed.

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

III. NUCLEAR, PARTICLE PHYSICS & ASTROPHYSICS III.1 KEYNOTE, PLENARY AND INVITED PAPERS

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ENERGY SECURITY OF INDIA — NUCLEAR ENERGY — AN INEVITABLE OPTION PRESENT PLANS AND FUTURE PERSPECTIVES JAI P. MITTAL Raja Ramanna Fellow, Bhabha Atomic Research Centre, Trombay, Mumbai, India

Recently, during last 5-10 years, India has been witnessing a very healthy economic growth of ~6-8% pa in GDP. Energy, particularly electricity becomes a key input for sustaining such an accelerating growth. An overview will be presented of the present strategy for the growth of electricity generation keeping in mind the issues related to sustainability, abundance of available energy resources, diversity of sources of energy supply & technologies, self-sufficiency & effect on local and global environment. In the optimum mixture of conventional (thermal) and non conventional (wind, solar etc.) Nuclear Energy becomes an inevitable option. A road map for an integrated three stage Nuclear Programme has been drawn. It comprises of: 1.

Natural uranium fuelled Pressurized Heavy Water Reactors (PHWR’s).

2.

Fast Breeder reactors utilizing plutonium based fuels (Ist 500 MW PFBR is to be commissioned soon).

3.

Advanced Nuclear Power Systems for utilization of Thorium; AHWR and ADS etc.

CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

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CHARGE MEASUREMENTS OF FRAGMENTED NUCLEI OF Si AT DIFFERENT ENERGIES M. S. EL-Nagdy1, A. Abdelsalam2, A. Algaood3,* and M. Ahmed1 1

Physics Department, Faculty of Science, Helwan University, Helwan, Egypt 2 Physics Department, Faculty of Science, Cairo University, Giza, Egypt 3 Physics Department, Faculty of Science, Amran University, Amran, Yemen

This experimental research is a preparatory study to reflect the accuracy in identifying heavy fragmented nuclei in nuclear emulsion. The distributions of δ–rays produced by projectile fragments from 3.7A GeV 28Si in NIKFI–BR2 emulsion have been investigated. Such 28Si beam was accelerated at Dubna Synchrophastron. For sake of comparison, another source of data due to 14.6A GeV 28Si from Brookhaven National Laboratory (BNL), using different type of photographic emulsion (Fuji), is introduced. The charges of the produced projectile fragments having 2 ≤ Z ≤ 14 are deduced. This research may be important to carry out any subsequent investigation dealing with the mechanism of Si fragmentation at high energy, on the basis of the present identified charges. Keywords: 28Si Ions; Projectile Fragmentation; Nuclear Charge Identification.

INTRODUCTION The heavy ion collision offers a unique opportunity to study the nuclear fragmentation process. Many experimental and phenomenological efforts have been devoted to the investigation of projectile fragmentation in relativistic heavy ion collisions. Fragmentation in finite nuclei is a fascinating research subject which has attracted continued attention for more than thirty years [1–5]. The projectile fragments, (PFs), are strongly collimated in the forward direction [6] with an angle θlab ≤ 3° at 3.7A GeV. In central events this forward cone is empty from any projectile fragments. This paper is a continuation of our analysis of interaction of silicon beam with emulsion target [7–11]. An important aim of this study is to survey the general properties of fragmentation in silicon interactions at two different energies (3.7 and 14.6A GeV). An attempt is made to compare the data obtained from the two silicon beams. This yields additional information helpful to understanding the fragmentation process. In addition, silicon beam has 28 nucleons which are equivalent to 7 alpha particles so there is a choice to examine the existence of α-clusters inside the beam of silicon.

EXPERIMENTAL DETAILS The present experiment was performed in a stack of NIKFI–BR–2 nuclear emulsion of size 20 cm × 10 cm × 0.06 cm. These stack tangentially exposed to a 28Si beam with energy 3.7A GeV at Dubna Synchrophastron. The exposure was made such that the incident beam was almost parallel to the surface of an emulsion pellicle. The inelastic interactions with nuclear emulsion observed for 28Si was detected using the (along the track) method. A total 1058 events were analyzed where the respective mean free path was found to be (9.12 ± 0.27 cm). *

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Out of the emitted 28Si projectile fragments 351, 377 events were respectively identified as helium (Z = 2 PFs), and Z ≥ 2 PFs. These fragments essentially travel with the same speed as that of the parent beam nucleus, and without change in the ionization along their path where followed up to a distance of at least 2 cm from the interaction centre. The energy of the produced PFs is high enough to distinguish them easily from the target fragments. In each event, the PFs having charges Z ≥ 2 are recorded where their charges are identified by δ–ray density measurements [12]. On the other hand, at each interaction point the PFs with Z = 1 can be well separated by visual inspection of tracks where their ionizations are similar to those of shower (~ 30 grains per 100 micron). Helium PFs can be easily identified by visual inspection, where their ionizations are similar to those of grey tracks. They are chosen as charge references. A δ–ray (low–energy electron) which produces a track containing four or more grains has energy > 15 KeV. The number of these δ–rays (Nδ) ejected by a charged particle of charge Z through its passage through the target material helps to identify the particle producing the track (Nδ α Z2) [13]. At each interaction we measure the δ–ray density of PFs with respect to its primary beam. For this purpose, a calibration line is done by using NIKFI–BR–2 nuclear emulsion irradiated by six primary beams available in our laboratory [*], (4He, 6Li, 12C, 16O, 24 Mg, 28Si, and 32S at 3.7A GeV) from Dubna Synchrophastron. The relationship between the average number of δ–rays per mm for a sample of 40 tracks from each beam and the corresponding charge is shown in Fig. (1). The data are fitted by the linear relation, Nδ = AZ2 + B, where A = 7.49 ± 2.16 and B = 0.50 ± 0.04. 150

Nδ / mm

100

50

0 0

150 Z

300

2

Fig. (1): Calibration line due to counting δ–ray density/mm using NIKFI–BR–2 nuclear emulsion irradiated by six primary beams (4He, 6Li, 12C, 16O, 24Mg, 28Si, and 32S at 3.7A GeV).

RESULTS AND DISCUSSIONS According to criteria for separation and identification of the PFs, we show in Table (1), the topology for all events of the minimum biased sample obtained from the present work in

244

comparison with the corresponding ones, for (14.6A GeV 28Si [10] and 3.7A GeV 28Si). Figure (2) represents the topological diagram for the two silicon beams. It should be noticed that, Fig. (2) includes the results of some channels observed in this work, which are not detected in Ref. [10]. All data are normalized to the same number of events. The topology seen in table1 represents all minimum biased events in which each channel includes the participants and the spectators of the Si beam. The participant part is represented by some or all of the H–fragments, so that the total charge in each channel should be 14. On the other hand, Fig. (2) represents the charge distribution (spectators) of the Si beam with and without He PFs in comparison with the corresponding data of 28 Si(14.6 and 3.7A GeV) taken from [10] and [14], respectively. The similarity of the three distributions obviously indicates that the beam energy is of little importance for the nuclear fragmentation process, except probably for the most peripheral interactions. Evidence for a limiting fragmentation hypothesis is shown which implies that both projectile and target may be fragmented irrespective of each other, and that this fragmentation is independent on the beam energy. 28

Si 14.6A GeV Ref.[10] Si 3.7A GeV This work 28 Si 3.7A GeV Ref.[14] 28

Fraction of events

0.20

0.20

0.15

0.15

0.10

0.10

0.05

0.05

0 0.00

14 13 12 12 11 11 10 10 10 9 2 2 2 2 2 2 2

9 2

9

8 2 2 2

8 2 2

8 2

8

7 2 2 2

7 2 2

7 2

7

6 2 2 2 2

6 2 2 2

6 2 2

6 2

6 5 2 2 2 2

5 5 2 2 2 2 2

5 2

5 4 2 2 2 2 2

4 2 2 2 2

4 4 2 2 2 2 2

4 4 2

3 2 2 2 2 2

3 2 2 2 2

3 2 2 2

3 3 3 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2

2 2 2 2 2

2 2 2 2

2 2 2 0 2 2 2

0.00

Fig. (2): Topological diagram for the total sample of events. The numbers below the X–axis represent the charge distribution of the spectators with and without α-fragments.

Charge identification of relativistic multiply charged fragments has been made by measurements of the total number of δ–rays per mm of the track near the star, and at least one point more than 1cm from the star has been also measured.

Table (1): Topology normalized of the 28Si fragmentation at 14.6 and 3.7A GeV (minimum bias). Nh Energy GeV/A

0–1 14.6

Ref.

[10]

Si Al+H Mg+He Mg+2H Na+He+H Na+3H Ne+2He Ne+He+2H Ne+4H F+2He+H F+He+3H F+5H O+Be+2H O+3He O+2He+2H O+He+4H O+6H N+C N+3He+H N+2He+3H N+He+5H N+7H C+B+He+H C+3He+2H C+2He+4H C+He+6H

40 35 8 26 11 6 8 24 8 8 21 8 – – 6 16 3 – – 16 16 8 3 3 8 –

2–7 3.7

This Work 4 2 5 4 15 4 2 11 18 4 22 11 – – – 36 4 – 2 11 38 5 – – 5 18

14.6 [14]

[10]

28 27 16 29 15 14 8 16 17 7 13 12 – 2 12 18 5 – 1 11 19 4 – 3 18 8

– 16 11 37 8 48 5 32 27 19 50 32 – – 19 19 16 3 5 13 13 8 3 3 8 19

•8 3.7

This Work – 7 – 13 11 16 – 17 16 2 20 15 – 2 6 31 20 2 – 2 8 18 – – 9 15

14.6 [14]

[10]

13 37 4 34 10 24 2 18 27 10 16 29 – 3 7 24 22 – 3 15 17 11 – 3 16 14

– 11 – 13 5 19 – 14 8 – 13 16 3 – 8 8 3 – – 11 13 3 – – 8 –

3.7 This [14] Work – 6 4 6 – 0 4 5 – – 7 17 2 1 6 7 14 – 1 7 10 4 14 – – – 1 2 2 4 10 11 12 – – – 2 4 4 11 9 6 16 – – – 1 4 6 16 13

Total Sample 14.6 3.7 This [10] Work 40 4 62 13 19 5 76 21 24 26 73 27 13 4 70 28 43 41 27 6 84 49 56 30 3 – – 2 33 8 43 71 22 35 3 2 5 2 40 17 42 57 19 29 6 – 6 – 24 18 19 49

[14] 47 70 20 68 25 55 11 40 58 18 39 55 – 6 21 52 39 – 6 30 45 31 – 7 40 35 245

246

C+8H – 2 2 – – B+4He+H 2 – – – – B+3He+3H – – 3 – B+2He+5H 5 4 4 5 11 B+He+7H 3 15 4 3 13 B+9H – – 2 3 7 Be+4He+2H 3 – 1 – – Be+3He+4H 2 2 2 3 – Be+2He+6H 3 5 6 – 2 Be+He+8H – 4 6 – 14 Be+10H – – 3 – 4 Li+5He+H – – – – – Li+4He+3H – – – – – Li+3He+5H – 4 2 – – Li+2He+7H – 2 5 – – Li+He+9H – 4 3 – 4 Li+11H – 2 1 – 2 6He+2H – – 5 3 0 5He+4H 11 – 4 16 0 4He+6H 16 5 11 13 11 3He+8H 21 29 26 48 51 2He+10H 45 53 16 51 84 He+12H 37 36 10 100 68 14H – 18 3 64 66 1 – 7 – 3 18 O All 430 413 422 726 585 1 No fragments of projectile in narrow forward cone (i. e, Q = 0)

12 – 5 11 18 7 – 1 5 8 7 1 – 1 5 6 6 1 6 27 45 59 66 60 1 717

– – – 3 3 – – – – – – – – – – – – – – 5 40 101 165 237 75 785

13 – – – 7 4 – – – 15 5 – – – – 6 – – – 7 38 97 163 295 200 943

8 – – 5 10 9 – 2 3 9 10 0 2 2 6 11 12 – 3 8 51 78 132 227 58 802

– 2 – 13 9 3 3 5 3 – – – – – – – – 3 27 34 109 197 302 301 78 1941

15 – – 15 35 11 – 2 7 33 9 – – 4 2 14 4 – – 23 118 234 267 379 225 1941

22 – 8 20 32 18 1 5 14 23 20 1 2 5 16 20 19 6 13 46 122 153 208 290 59 1941

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Mean value of (δ–ray per mm) readings were taken. In order to measure the charge of each PFs, a calibration curve is constructed by using δ–ray of primary 28Si beams and He PFs, chosen as charge references in addition to that beams charge given in Fig. (3).

Si-Em (14.6A GeV)

28

Si-Em (3.7A GeV)

< Nδ > / mm

30

100

50

15

0

< Nδ > / mm

28

0 0

100 Z2

200 0

100 Z2

200

Fig. (3): The calibration lines for all projectile fragments (Z = 2–14) corresponding to the average values of δ–ray per mm characterizing each fragmented track of charge Z through the interactions of 28Si (3.7 and 14.6A GeV) with emulsion nuclei. According to the proportionality of the number of δ–ray per mm (Nδ) with Z2 of the fragment, N δ forSi Z Si2 i.e. = 2 , one is able to obtain the linear relation expressed by Nδ = A + B Z2. The N δ forHe Z He fitting parameters A and B are given in Table (2) characterizing the δ–rays calibration of PFs due to the interactions of 28Si (3.7 and 14.6A GeV) with emulsion nuclei.

Table (2): The fitting parameters of the calibration curves identifying the PFs due to interactions at 3.7 and 14.6A GeV. Fitting Parameters A B

28

Si (3.7A GeV ) 5.37±0.90 0.47±0.01

28

28

Si (14.6A GeV) –0.15±1.74×10–17 0.16±1.68×10–19

Si–Em

248

The δ–rays frequency distributions (histograms) of relativistic projectile fragments having charge Z = 2–14 emitted from 28Si projectile at 3.7A GeV are given in Fig. (4). The Z = 2 histogram represents the δ–rays measurements for 40 tracks produced in randomly chosen inelastic interactions. On the other hand, the Z = 14 histogram indicate the results of the measurements for a sample of 30 tracks of 28Si beam in addition to the primary projectile tracks having Z = 14. A series of histograms were observed. Each of these histograms can be fitted by a Gaussian distribution with a peak corresponding to a certain value of Z, which can be determined by using the calibration line as illustrated by the associated arrow. For comparison Fig. (5) represents the corresponding results for PFs produced in 14.6A GeV 28Si interaction in nuclear emulsion [10].

Z=2

8

Nδ / mm

20

2 80 Nδ / mm

3 55 N / m m 60 δ

Z = 13 2 85

90 Nδ / mm

5 35

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50

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6

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25

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Frequency

Frequency

Z=6

4

4

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Z=5

10

8

6

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Z=3

Frequency

3

8

Z=4

Frequency

Frequency

3

65 N / m m 70 δ

2

Z = 14 1

100

105

110

Nδ / mm

Fig. (4): The charge distributions of δ–rays density/mm for secondary projectile fragments due to Si (3.7A GeV) interactions with emulsion (histograms) fitted by typical Gaussian (solid curves).

28

249 6

15

0

0

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8

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4

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6

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Z= 9

5

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45

6

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Nδ / mm 12

Z = 13

0 65

70

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75

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6

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80

Nδ / mm

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Nδ / mm

6

Z= 12

Nδ / mm

Z= 11 Frequency

10

Frequency

Frequency

Z= 8

Z=7 Frequency

Frequency

Z=6

Frequency

14

Nδ / mm

85

60

Z = 14

6

0

90

Nδ / mm

95

100

Fig. (5): The charge distributions of δ–rays density/mm for secondary projectile fragments due to Si (14.6A GeV) interactions with emulsion nuclei (histograms) fitted by typical Gaussian (solid curves). 28

The similarity of the two figures [Fig. (4) and Fig. (5)] obviously indicates that the beam energy is of little importance for the nuclear fragmentation process. Table (3) represents the average values of δ–ray per mm characterizing each fragment track of charge Z through the interactions of 3.7A GeV 28Si with emulsion nuclei in comparison with those corresponding to interaction of 28Si at 14.6A GeV [10]. The dispersion Dδ of δ–ray spectrum belonging to each charge is defined as Dδ =

N δ2 − N δ

2

.

250

In Fig. (6) the ratios of Dδ/ versus are displayed for silicon beams at both energies. The data (points) can be fitted by 2nd order exponential decay of from, − N /t − N /t Dδ / N δ = A1e δ 1 + A 2e δ 2 and presented in the figure by the smooth curves. The fitting parameters A1, A2, t1, t2 are shown in Table (4). Table (3): The average values of δ–ray per mm characterizing each fragmented track of charge Z through the interactions of 28Si (3.7 and 14.6A GeV) with emulsion nuclei. 28

Si–Em( 3.7A GeV)

7.66±0.05 10.53±0.22 12.99±0.22 16.88±0.14 23.41±0.11 27.85±0.14 35.68±0.20 42.85±0.15 51.70±0.09 61.29±0.33 72.60±0.77 80.92±0 102.42±0

Charge 2 3 4 5 6 7 8 9 10 11 12 13 14

28

Si–Em( 14.6A GeV)

1.81±1.66 – 9.18±0.43 13.25±0.25 17.78±0.34 22.91±0.15 31.88±0.43 40.12±0.17 48.96±0.31 59.24±0.25 69.58±0.33 81.35±0.26 94.48±0.20

It is shown in Fig. (6) for 28Si (3.7A GeV) that, Dδ/ decreases strongly as increase of at small value of ( ~ 20) corresponding to light PFs (He, Li, Be). At larger values of , corresponding to Z > 4, the ratio tends to saturate linearly. The ratio Dδ/ for Si (14.6A GeV) seems to be gradually decreasing.

Table (4): The fitting parameters of the correlation between Dδ / versus through the interactions of 28Si (3.7 and 14.6A GeV) with emulsion nuclei. Projectile A1 A2 t1 t2

28

Si–Em( 3.7A GeV) –0.65±0.21 0.06±0.02 3.97±12.12 34.39±17.38

28

Si–Em( 14.6A GeV) 1.37±8.78 0.18±0.12 1.56±7.55 27.95±41.60

251

D / < Nδ >

Si-Em (3.7A GeV)

28

Si-Em (14.6A GeV)

0.09

0.3 0.06

D / < Nδ >

28

0.6

0.0 0

50

< Nδ >

100

0

50

100

< Nδ >

Fig. (6): The ratio Dδ/for the interactions of 28Si (3.7 and 14.6A GeV) with emulsion nuclei against the < Nδ > belonging to each charge δ–ray spectrum, fitted by hyperbolic shaped curves. For PFs the behavior of the curves illustrated in Fig. (6) suggests that, there is a positive long range correlation in emitting different charge nuclei from both silicon beams. Now the normalized distribution of δ–ray densities P(Nδ) %, is done in its scaling presentation according to the two used energies (3.7 and 14.6A GeV) of 28Si beam. Hence, Fig. (7), represents a plot of ψ(ξ) = < Nδ>P(Nδ)% as a function of the scaling parameter ξ = Nδ/ for silicon beam at (3.7 and 14.6A GeV). It is note worthy that all the data points for, 28Si (3.7A GeV) and 28 Si(14.6A GeV) [10], lie on a simple universal curve represented by a polynomial scaling law of 3

the form, Ψ (ξ ) = ∑ ai ξ i . The fitting parameter ai is listed in Table (5). Therefore, the i =0

universality in the scaling curve implies anenergy independence in high energy projectile fragmentation, regarded as limiting fragmentation hypothesis. Table (5): The parameters of the scaling law characterizing the energy independence for fragmentation in nuclear emulsion. a0 a1 a2 a3

–51.015±6.987 6.632±0.777 –0.189±0.027 0.002±0

28

Si

252 28 28

< Nδ > P ( Nδ ) %

30

S i-E m (3.7A G eV ) T his W ork S i-E m (14.6A G eV ) [10]

15

0 1

2

Nδ / < Nδ > Fig. (7): The normalized multiplicity distributions of available values of δ–ray densities associated with the charged projectile fragments due to the interactions of 28Si (3.7 and 14.6A GeV) with emulsion, fitted by polynomial shapes. Table (6) presents the salient features of primary peripheral events of 28Si nuclei at 3.7A GeV in comparison with 28Si nuclei 14.6A GeV [10], yielding different hydrogen PFs multiplicities, associated with and without heavy PFs of Z > 2. The data of 14.6A GeV 28Si are placed between semi circular parenthesis in Table (6), while those of 3.7A GeV 28Si placed without parentheses. One can observe from the table that, over all the data for 28Si (3.7A GeV) are in satisfactorily agreement with those of 28Si (14.6A GeV). The number of helium PFs per event produced are 1.81 and 2.17 for 28Si (3.7A GeV) and 28Si (14.6A GeV), respectively. These numbers increase to 2.01 and 2.48 with no associated heavy PFs of charge Z > 2 and decrease to 1.38 and 1.59 in case of events associated with heavy PFs of Z > 2. In all cases both data of silicon strongly reflect the presence of α–clusters inside the silicon beam.

253

Table (6): The normalized multiplicity of α particles, with and without heavy fragments, produced due to the interactions of 28Si (3.7 and 14.6A GeV) with emulsion nuclei. No of Emitted α Particles

Percentage of events associated with α and without heavy fragments

Percentage of events associated with α and heavy fragments

15.34 (15.24) 27.09 (19.79) 20.63 (16.44) 5.5 (6.95) – (6.68) – (0.8)

21.16 (15.78) 8.68 (5.24) 1.59 (2.41) – (1.7) – – – –

1α 2α 3α 4α 5α 6α

CONCLUSION From this investigation we conclude the following: (1) (2)

(3) (4)

(5)

The charge of each produced fragment is easily identified using δ–ray measurements. The yield of multiply charged fragments at 3.7A GeV is nearly as same as at 14.6A GeV. This reflects the fact that the beam energy is of a little importance for nuclear fragmentation process at high energy. There is a positive long range correlation in emitting different charges produced from 28Si beam at 3.7 and 14.6A GeV. The fragmentation of 28Si nuclei in nuclear emulsion exhibit a limiting behavior which is achieved by observed scaling in δ–ray multiplicity at the two incident energies, although the considerable difference between 3.7 and 14.6A GeV. The number of helium fragments per event emitted in silicon beam interactions at the two energies strongly reflects the presence of α–clustering inside silicon nuclei.

ACKNOWLEDGEMENT The authors would like to thank all the staff of (Vekseler and Baldin) High Energy Laboratory at JINR, Dubna, Russia, for providing us the irradiated emulsion plates.

254

REFERENCES [1] A. S. Goldhaber, Phys. Lett. B 53, 306 (1974). [2] D. E. Greiner, P. J. Lindstrom, H. H. Heckman, Bruce Cork, and F. S. Bieser, Phys. Rev. Lett. 35, 152 (1975). [3] W. –C. Hsi, K. Kwiatkowski, G. Wang, D. S. Bracken, E. Cornell, D. S. Ginger, V. E. Viola, and N. R. Yoder, R. G. Korteling, F. Gimeno–Nogures, E. Ramakrishnan, D. Rowland, and S. J. Yennello, M. J. Huang, W. G. Lynch, M. B. Tsang, and H. Xi, Y. Y. Chu, S. Gushue, and L. P. Remsberg, K. B. Morley, H. Breuer, Phys. Rev. Lett. 79, 817 (1997). [4] M. I. Adamovich et al (EMU01 Collaboration), Eur. Phys. J. A 6, 421 (1999). [5] B. M. Badawy, International Journal of Modern Physics E 18, 643 (2009). [6] M. S. EL–Nagdy, Phys. Rev. C 47, 346 (1993). [7] M. S. El–Nagdy, A. Abdelsalam, N. Ali–Mossa, A. M. Abdalla, S. M. Abdal–Halim, Khaled Abdel–Waged, Nucl. Phys. A 730, 419 (2004). [8] M. El–Nadi, M. S. El–Nagdy, N. Ali–Mossa, A. Abdelsalam, A. M. Abdalla, and S. M. Abdel–Halim, J. Phys. G 28, 1251(2002). [9] M. El–Nadi, M.S. El–Nagdy, A. Abdelsalam, E. A. Shaat, N. Ali–Mossa, Z. Abou– Moussa, Kh. Abdel–Waged, A. M–Abdalla, and E. El–Falaky, Eur Phys. J. A 10, 177 (2001). [10] M. El–Nadi, M. S. El–Nagdy, N. Ali–Mossa, A. Abdelsalam, A. M. Abdalla, and A. A. Hamed, J. Phys. G 25, 1169 (1999). [11] M. El–Nadi, M. S. El–Nagdy, A. Abdelsalam, E. A. Shaat, N. Ali–Mossa, Z. Abou–Moussa, Kh. Abdel–Waged, W. Osman, and F. A. Abdel–Wahed, J. Phys. G 24, 2265 (1998). [12] C. F. Powell, F. H. Fowler, and D. H. Perkins, "The Study of Elementary Particles by the Photographic Method", Pergamon Press. London, New York, Paris, Los Angles, 474 (1958). [13] M. S. El–Nagdy, A. Abdelsalam, E. A. Shaat, B. M. Badawy, and E. M. Khashaba, Romanian Journal of Physics 53, 487 (2008). [14] S. A. Krasnov et al, JINR Report (Dubna), P1-88-252 (1988) in Russian.

255

PASSIVE SAFETY FEATURES IN ADVANCED NUCLEAR POWER PLANT DESIGN M. TAHIR1,*, I. R. CHUGHTAI1 and M. ASLAM2 1

Pakistan Institute of Engineering and Applied Sciences, P. O. Nilore, Islamabad, Pakistan 2 Informatics Complex, H-8, Islamabad, Pakistan

For implementation of advance passive safety features in future nuclear power plant design, a passive safety system has been proposed and its response has been observed for Loss of Coolant Accident (LOCA) in the cold leg of a reactor coolant system. In a transient simulation the performance of proposed system is validated against existing safety injection system for a reference power plant of 325 MWe. The existing safety injection system is a huge system and consists of many active components including pumps, valves, piping and Instrumentation and Control (I&C). A good running of the active components of this system is necessary for its functionality as high head safety injection system under design basis accidents. Using reactor simulation technique, the proposed passive safety injection system and existing safety injection system are simulated and tested for their performance under large break LOCA for the same boundary conditions. Critical thermal hydraulic parameters of both the systems are presented graphically and discussed. The results obtained are approximately the same in both the cases. However, the proposed passive safety injection system is a better choice for such type of reactors due to reduction in components with improved safety. Keywords: Safety Injection System; Passive Safety Injection System; Nuclear Power Plant; Loss of Coolant Accident.

*

Corresponding author: [email protected] CP 9910, Modern Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

256

RESEARCH STUDIES PERFORMED USING THE CAIRO FOURIER DIFFRACTOMETER FACILITY R. M. A. MAA YOUF NRC, Atomic Energy Authority Cairo, Egypt

Abstract

This report represents the results of research studies performed using the Cairo Fourier diffractometer facility (CFDF), within 10 years after it was installed and put into operation at the beginning of 1996. The main components of the CFDF were supplied by the IAEA according to the technical assistance project EGY/l/022. Plenty of measurements were performed, since then; yielding sel·eral publications, both in local and international scientific periodicals; and 8 M.Sc. & Ph.D. degrees from Egyptian Universities. Besides, a new approach for the analysis of the neutron spectra measured using the CFDF; applying especially designed interface card, along with its proper software program, instead of the reverse time of flight (RTO.F), Finnish make, analyzer originaJiy attached to the facility. It has been verified that the new approach cnn successfully replace the RTOF analyzer; significantly decreasing the time of measurement; and saving the reactor's operation time. A special fault diagnostic system program was developed and tested for caring and handling the possible failures of the CFDF. Besides the new developments required for the CFDF for industrial applications in wide scale, arc also considered.

INTRODUCTION The properties of l:ondensed matter can be efficiently studied through the scattering of slow neutrons, since both their energy and wavelength match the atomic energies and distances characteristic for condensed matter. The time of flight (TOF) method has been successfully used for such purpose, as it allows studying the sample at exceptional conditions, for example at high pressure or temperature. Correlation TOF methods using either Fourier or pseudo-random beam modulation, have been developed to use the available neutron flux in a way more economic than with the usual rermi chopper systen1s; and without deterioration of the rcso!ution.Thc Fourier approach allows for a duty factor up to 50 % while the Fermi chopper systems make use only of -0.1-0.5% of the available neutrons [1]. The Fourier method has been improved by the reverse time-of-flight (RTOF) concept [2] which is based on the triggering of the TOF analyzer by the detected neutrons instead of the rotor's position.Thc usc of the Fourier RTOF diffractometry as efficient tool for studying condensed matter at the ET-RR- I reactor was first assessed by Maayouf [I], and the preliminary arrangements to be used at such type of reactor were also given by him. Further developments of the suggested arrangement were also represented in various articles by Maayouf [3-9], along with the main components required for the data acquisition. Moreover, the basic stage of the Cairo Fourier Diffractometer Facility (CFDF), based on the RTOF concept, was installed at the beginning of 1996, as IAEA-TC Project EGY/ 1/022, at one of the horizontal channels of the ET-RR-1 reactor. The CFDF is one of the four [9) functioning Fourier ditiractometers.A schematic diagram of the CFDF at the ET-RR-1 reactor is represented in Figure l. Neutrons emitted through an in-pile collimator, from one of the ET-RR-1 reactor horizontal channels, are guided by the main neutron guide (22 m in length) at first, then reach the Fourier chopper. After the Fourier chopper, neutrons pass through an auxiliary neutron guide (3 m long) to the sample. Neutrons scattered from the sample at 90° are detected by the detection system. The detector position in the mode of operation at this stage is at 90° scattering angle. The latter gives the best resolution in space localization of a sample scattering volume and could be cfliciently used for studying the internal stresses in materials including neutron diffraction. The arrangement is also equipped with a Fenni chopper which could be used for spectrum measurements, etc. The Fenni chopper has been described in the IAEA report [9]. Preliminary CP 9910, Modem Trends in Physics Research Fourth International Conference MTPR-10 edited by L. El Nadi Copyright @ 2013 by World Scientific Publishing Co. 978-981-4504-88-1

257

reports on the performance and main characteristic pammcters of the CFUF, measured just af'ler the start of operation, were also made by Maayouf[9-ll]. The main parameters of the CFDF arc given in Table 1. 7m

n.,

16m

I IG~ 111 11111

Ql"onblolnli Noullrhl ·rl •tl

Fig. I. Schematic diagram of tbc CFDF nt the ET-RR-1 rc~tctor.

The neutron beam spectrum measurement was carried out using l·cm1i disk type chopper. The Fermi chopper was rotating at 2840 rpm speed and the used detector was a 6Li-glass scintillator (NE-912) set nt 3.46 m distance from the chopper. The measured spectrum was reported in 19], along with the dcwils of the measurement The values of the integral neutron flux, measured both by calibrated detector and activated gold foils method, are consistent (see Table 1). The neutron losses, within 2!! em distance between the exit of the straight NO and the sample position. arc - 6.3%. As the result or the scattering and absorption out of the beam by air molecules, corresponding losses arc estimated to be - 1.4 %, while the losses due to the beam divergence are - 4.9 %. llle value of the neutron nux (l.OSx I0-6 nlcm1.s) at the sample position is slightly less than the value 1.2xl0-6 nlcm 2.s reported [91 for the FSS facility which is installed at the 5 MW reactor of the GKSS Centre (Germany). Ocsides, the neutron losses due to the bcum divergence in case of

.-----------------. Table J: The values of the neutron flux . Point of meas urement

Flux values u~ln g gold foil nctivntlon

(6.66 ± o.J2) 106 n/cm2.s

At the exit of curved NGT At the exit oft he straight NG1

Flux values Ullin~ cnllbrnted detector

( 1.13 0,02) I06 n/ cm2.s

At the sample position with rotating Fourier chopper

( 1.05±0.05) I06 n/cm2.s

At the sample position with o en Fourier chopper

(2.1 ± 0.01) IO~ n/cm 2 .s

258

the FSS facility are - 36.4%. Moreover, the reflecting surface of the FSS neutron guide is made frum natural Ni.The detection system of the CfDf is designed for detecting neutrons scattered from the sample at an angle 29=90° and consists of four independent scintillation detector elements (see Fig. 3). The detection system aperture is determined by the area of all four elements, their angular positions and their distance frum the sample. Consequently, the detector elements have to be arranged according to the time tocusing geometry, in order to increao;e the luminosity of the diffractometer for the given resolution. Each of the detector elements is made of I mm thick 6Li-glass scintillator (NE-912) whose surface area is 200*200 mm 2 • The actual valut:s uf the CFDF detector elements parameters are represented in Figure 2.

Sample

Neutron beam

Fig. 2: A schematic of the four elements of the detection system . . The time focusing surface is uniquely defined by the constants 1\o, Bo and 90, where the locus of constant time arrival and the angle between the tangent to the locus and the incident beam direction arc given by the formula derived in ref [14]. Thus, the locus of the CFDF detection system, was calculated tor constant scattering angle 29o=90°, '!light path lengths Ao=3.33 m and Bo=l.l4 m. The tangent angl~ calculated for Ao and Bois represented in Fig.[ 3 ].

f t-

26 Fig. 3: The dependency between the tangent angle et and the scattering angle 29. The detection system aperture has been precisely calculated by a special program which analyze the detector element positions needed for the fulfillment of the time focusing condition. Thus, the angular aperture was found [~5] equal to Oo=S .1 X 10'2 steradians. A neutron diffraction measurement was carried out for a standard diamond powder sample with the CFDF. The diamond sample was contained in a cylindrical AI toil (5 mm in diameter and 85 mm in height) and the Fourier chopper was rotating at 8000 rpm. Fig.[ 4 J shows the diffraction pattern of the powdered diamond measured within 30 minutes at room temperature. It is noticeable from Fig.[ 4 ], that good

259

separation between the peaks (i.e., good resolution) and high counting rate could be achieved within short measuring time.The Gaussian fitting model was used to determine the diamond peaks positions and their FWHM (~Dhkr). Fig.[ 5 ] shows an example for one of the peaks, fitted by the Gaussian model. Consequently, it has been concluded that the CFDF with the adopted geometry could be suitable for measurements required for solving condensed matter problems. The ditfraction pattern, which was measured using the CFDF for AI powder sample, is displayed in Fig.[ 6 ], as well as Buras one [ 13] obtained by using a conventional TOF method.It is noticeable from Fig.[ 6] that the quality of the presently measured diffraction pattern, with regard to resolution and intensity, is superior to that one obtained with the conventional method. The diffraction ,pattern which was obtained for the Alz03 powder sample was also compared with that one obtained f~l by an analogous RTOF diffractometer (Mini-Sfinks, Russia), whose detector is set at a backward scattering angle (155°), for crystal structure invcstigations.Nevertheless, the quality of the AbOJ diffraction pattern, measured with the CFDF, whose detector is set at 90", was almost the same as that one obtained by Mini- Sfinks Ll5]. This confirms the possibility of successful use of the present geometrical arrangement of the detection system at the CFDF for crystal structure investigations. The neutron diffraction measurements were performed for powder samples trom aluminum oxide (Ah0 3) and aluminum powder metal and further us\!d for studying the behavior of the CFDF resolution. The behavior, represented in Fig. [ 7 ] and deduced from the FWHM of the observed diffraction peaks, was found to be consistent with that previously deduced from measurements with different powder samples at d spacing values between 0.7 A - 2.1 A and scattering angle 28=90°. This makes it possible to obtain, using the CFDF, diffraction patterns which are useful for studying crystal structure and still preserving a reasonable resolution.

100000 (220)

-E:::J

80000

0

60000

~

40000

0

c

Q)

z

20000 4 0

0

1500

1000

500

Channels Fig. 4: The diffraction pattern obtained for a diamond powder sample.

-

(111)

~

I_

I

~

- .. .. - - -

1111

dllniW

Fig. 5: The diamond (111) peak as fitted by a Gaussian model.

260 100000

220

1.266

600

..

• ll• 400

200

t

2.517

1.8P1

b

...

.,, i

..... ual

'"

_l L ___ _i_l

--------~--------~--------._------~ 2.0 1.0 3.0

Fig. 6: The AJ diffraction patterns

~ 0.7

C' 0

s 06 0C/1

~ 0.5

\

''

------·--

u:.-..._..__._.-..~.._..._...___.___._-'-__,____..__.L-......__,___._...,..,

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dhkl (A) Fig. 7: The CFDF resolution: ----- Present; - - - Previously reported [9). Samples from Germany were analyzed with the CFDFboth for comparison with the HRFD of the JlNR (Dubna) and for evaluation of the adequacy of the CFDF for studying the residual stress after welding. The results of measurements, performed with the CFDF for Nb sample (from Htvp-~~!-~~.f!50!l~P.a_red_ with .. those which were measured before with the HRFD.and it was noticeable : that the results of the CFDF measurements are more accurate than those of the HRFD. Bestdes,-The neutron diffraction spectra, measured when scanning another sample from GKSS (Germany), are represented in Fig. [ 8 ]. The sample itself is two welded bars of Aluminum which could be used in aviation industry. Accordingly, the sample was moved, at

261

the sample position, across the neutron beam of the CFDF The neutron diffraction spectra measured at each position, are shown in Fig. [ 8 ]. Moreover, the sample was inverted and rescanned at the same positions, resulting with another five spectra similar to those obtained during the other scanning. This makes it possible to study the residual stress after welding and to decide about the adequacy of the welding itself.

·--,1 d

!i

; E

I

.,e.

~

!I

Fig. 8: The S(>ectra measured during the scanning of the GKSS sample.

It was concluded that: • The CFDf could be successfully used to perfonn neutron diffraction measurements and for studying residual stress at considerable counting rates of the detection system in a relatively short time, thereby significantly saving the measuring time; • The electrical welding is more adequate (for both steel and copper), than the argon one and the residual strain was found to be smaller in case of electrical welding spectra; • However, more work still need to be performed on the industrially applicable analysis of diffraction spectra which were measured. This will help a lot both in the conclusive evaluation of the CFDF and for the additional components, which will be required for its practical use saving the reactor's operation time.

NEW DEVELOPMENTS OF THE CFDF A new design for the CFDf reverse time of flight analyzer was introduced by Maayouf[16j. The new design applies a data acquisition system, a special interface card, and a software program installed in the computer which operates the CFDF in order to perform the required cross·corrclation functions.

262

The first version of the interface card [16] was designed for the CFDf, as attached to the steady state ET-RR-1 reactor. Accordingly, the neutron diirractiun patlt:m of an iron sample was measured using both the designed interface card and the attached to the CFDF RTOF analyzer (made by VTT in Finland). In comparison with the results of the finnish made analyzer of the CFDF, the obtained spectra wert: Iuund to be the same, except for the substantially higher levt:l of noise and background. It was noticed that the noise level had been increased from about 2500 neutron counts to about 10000 neutron counts, and, consequently, the peak to background ratio of the highest peak had been reduced from about 8 to about 4. Accordingly, in order to overcome the problem of noise and background there was a need to modify the introduced design. Thus, the designed interface card was reconstructed and further developed. Besides, in order to improve the performance of the new design the software program was also further enhanced. The new data acquisition system was first implemented and tested at the high resolution Fourier diffractometer facility (HRFD) installed at the IBR-2 pulsed beam reactor of the JINR (Dubna-Russia), and the software card was also adapted for the simultaneous operation with two separate detection systems. Thus, the new approach was first tested using a Pentium 133 computer installed in paralld with the RTOF analyzer of the HRFD. The two patterns, measured for an iron sample, using the developed new approach and the Finnish made RTOF analyzer of the HRFD, are displayed in Fig.l9 J. IVWOO

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