1.2 Instrumentation 41.2.1 Nuclear Resonance Beamline ID18 at the ESRF 51.2.2 The UHV System for In Situ Nuclear Resonant Scattering Experimentsat ID18 of the ESRF 61.3 Synchrotron Radia
Trang 3M €OSSBAUER SPECTROSCOPY
Trang 5M €OSSBAUER SPECTROSCOPY
APPLICATIONS IN CHEMISTRY, BIOLOGY, AND NANOTECHNOLOGY
Edited by Virender K Sharma, Ph.D.
Göstar Klingelhöfer Tetsuaki Nishida
Trang 6Copyright Ó 2013 by John Wiley & Sons, Inc All rights reserved.
Published by John Wiley & Sons, Inc., Hoboken, New Jersey.
Published simultaneously in Canada.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken,
NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permission
Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose No warranty may be created or extended by sales representatives or written sales materials The advice and strategies contained herein may not be suitable for your situation You should consult with a professional where appropriate Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.
For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002.
Wiley also publishes its books in a variety of electronic formats Some content that appears in print may not be available in electronic formats For more information about Wiley products, visit our web site at www.wiley.com
Library of Congress Cataloging-in-Publication Data:
M €ossbauer spectroscopy : applications in chemistry, biology, industry, and nanotechnology / [edited by] Virender K Sharma, Ph.D.,
G €ostar Klingelh€ofer, Tetsuaki Nishida.
pages cm
Includes bibliographical references and index.
ISBN 978-1-118-05724-7 (hardback)
1 M €ossbauer spectroscopy I Sharma, Virender K., editor of compilation II Klingelh€ofer, G€ostar, 1956- editor of compilation.
III Nishida, Tetsuaki, 1950- editor of compilation.
QD96.M6M638 2014
Printed in the United States of America
10 9 8 7 6 5 4 3 2 1
Trang 7We dedicate this book to the late Professor Attila Vertez, E€otv€os Lorand University, Budapest, Hungary
Trang 91.2 Instrumentation 41.2.1 Nuclear Resonance Beamline ID18 at the ESRF 51.2.2 The UHV System for In Situ Nuclear Resonant Scattering Experiments
at ID18 of the ESRF 61.3 Synchrotron Radiation-Based M€ossbauer Techniques 101.3.1 Coherent Elastic Nuclear Resonant Scattering 101.3.2 Coherent Quasielastic Nuclear Resonant Scattering 251.3.3 Incoherent Inelastic Nuclear Resonant Scattering 301.4 Conclusions 38
Acknowledgments 39References 39
Chapter 2 | M€ossbauer Spectroscopy in Studying Electronic Spin and Valence
Jung-Fu Lin, Zhu Mao, and Ercan E Alp2.1 Introduction 43
2.2 Synchrotron M€ossbauer Spectroscopy at High Pressures andTemperatures 44
2.3.1 Crystal Field Theory on the 3d Electronic States 462.3.2 Electronic Spin Transition of Fe2þin Ferropericlase 472.3.3 Spin and Valence States of Iron in Silicate Perovskite 492.3.4 Spin and Valence States of Iron in Silicate Postperovskite 522.4 Conclusions 54
Acknowledgments 55References 55
Chapter 3 | In-Beam M €ossbauer Spectroscopy Using a Radioisotope Beam and
Yoshio Kobayashi3.1 Introduction 583.2 57Mn (!57Fe) Implantation M€ossbauer Spectroscopy 613.2.1 In-Beam M€ossbauer Spectrometer 61
3.2.2 Detector for 14.4 keV M€ossbauer g-Rays 623.2.3 Application to Materials Science—Ultratrace of Fe Atoms in Siand Dynamic Jumping 62
vii
Trang 103.2.4 Application to Inorganic Chemistry 633.2.5 Development of M€ossbauer g-Ray Detector 653.3 Neutron In-Beam M€ossbauer Spectroscopy 66
References 67
Chapter 4 | Lanthanides (151Eu and 155Gd) M€ossbauer Spectroscopic Study
of Defect-Fluorite Oxides Coupled with New Defect Crystal
Akio Nakamura, Naoki Igawa, Yoshihiro Okamoto, Yukio Hinatsu, Junhu Wang,Masashi Takahashi, and Masuo Takeda
4.1 Introduction 734.2 Defect Crystal Chemistry (DCC) Lattice Parameter Model 764.3 Lns-M€ossbauer and Lattice Parameter Data of DF Oxides 794.3.1 151Eu-M€ossbauer and Lattice Parameter Data of M-Eus (M4 þ¼ Zr, Hf, Ce, U,and Th) 79
4.3.2 155Gd-M€ossbauer and Lattice Parameter Data of Zr1 yGdyO2 y/2 804.4 DCC Model Lattice Parameter and Lns-M€ossbauer Data Analysis 844.4.1 DCC Model Lattice Parameter Data Analysis of Ce–Eu and Th–Eu 854.4.2 Quantitative BL(Eu3þO)-Composition (y) Curves in Zr–Eu and Hf–Eu 884.4.3 Model Extension Attempt from Macroscopic Lattice Parameter Side 894.5 Conclusions 92
References 93
Tadahiro Nakamoto, Akio Nakamura, and Masuo Takeda5.1 Introduction 95
5.2 237Np M€ossbauer Spectroscopy 965.3 Magnetic Property of Neptunyl Monocation (NpO2 þ) 975.4 M€ossbauer and Magnetic Study of Neptunyl(þ1) Complexes 985.4.1 (NH4)[NpO2(O2CH)2] (1) 98
5.4.2 [NpO2(O2CCH2OH)(H2O)] (2) 1005.4.3 [NpO2(O2CH)(H2O)] (3) 1015.4.4 [(NpO2)2((O2C)2C6H4)(H2O)3]H2O (4) 1045.5 Discussion 106
5.5.1 237Np M€ossbauer Relaxation Spectra 1065.5.2 Magnetic Susceptibility and Saturation Moment: Averaged Powder Magnetizationfor the Ground Jjz¼ 4i Doublet 107
5.6 Conclusion 113Acknowledgment 113References 113
Chapter 6 | M€ossbauer Spectroscopy of 161
Masashi Takahashi, Clive I Wynter, Barbara R Hillery, Virender K Sharma, Duncan Quarless,Leopold May, Toshiyuki Misu, Sabrina G Sobel, Masuo Takeda, and Edward Brown
6.1 Introduction 1166.2 Experimental Methods 1176.3 Results and Discussion 117Acknowledgment 122
References 122
Trang 11Chapter 7 | Study of Exotic Uranium Compounds Using 238U M€ossbauer
Satoshi Tsutsui and Masami Nakada7.1 Introduction 1237.2 Determination of Nuclear g-Factor in the Excited State of238U Nuclei 1257.2.1 Background of238U M€ossbauer Spectroscopy and Its Application
to Magnetism in Uranium Compounds 1257.2.2 238U M€ossbauer and235U NMR Measurements of UO2in theAntiferromagnetic State 125
7.2.3 Determination of the Nuclear g-Factor in the First ExcitedState of238U 127
7.3 Application of238U M€ossbauer Spectroscopy to Heavy FermionSuperconductors 127
7.3.1 Introduction of Uranium-Based Heavy Fermion Superconductors 1277.3.2 Magnetic Ordering and Paramagnetic Relaxation in Heavy FermionSuperconductors 129
7.3.3 Summary of238U M€ossbauer Spectroscopy of Uranium-BasedHeavy Fermion Superconductors 133
7.4 Application to Two-Dimensional (2D) Fermi Surface System of UraniumDipnictides 134
7.4.1 Introduction of Uranium Dipnictides 1347.4.2 Hyperfine Interactions Correlated with the Magnetic Structures in UraniumDipnictides 135
7.4.3 Summary of238U M€ossbauer Spectroscopy of Uranium Dipnictides 137
Acknowledgments 138References 138
Satoru Nakashima8.1 Introduction 1438.2 Three Assembled Structures of Fe(NCX)2(bpa)2(X¼ S, Se) and TheirStructural Change by Desorption of Propanol Molecules [23] 1448.3 Occurrence of Spin-Crossover Phenomenon in Assembled
Complexes Fe(NCX)2(bpa)2(X¼ S, Se, BH3) by EnclathratingGuest Molecules [25–27] 145
8.4 Reversible Structural Change of Host Framework of Fe(NCS)2(bpp)22(Benzene) Triggered by Sorption of Benzene Molecules [29] 1478.5 Reversible Spin-State Switching Involving a Structural Change
of Fe(NCX)2(bpp)22(Benzene) (X ¼ Se, BH3) Triggered by Sorption
of Benzene Molecules [30] 1498.6 Conclusions 150
References 151
Chapter 9 | Spin-Crossover and Related Phenomena Coupled with Spin,
Norimichi Kojima and Akira Sugahara9.1 Introduction 1529.2 Photoinduced Spin-Crossover Phenomena 1539.2.1 LIESST for Fe(II) Complexes 153
Trang 129.2.2 LIESST for Fe(III) Complexes 1579.2.3 Recent Topics of Photoinduced Spin-Crossover Phenomena 1609.3 Charge Transfer Phase Transition 161
9.3.1 Thermally Induced Charge Transfer Phase Transition 1619.3.2 Photoinduced Charge Transfer Phase Transition 1649.4 Spin Equilibrium and Succeeding Phenomena 1689.4.1 Rapid Spin Equilibrium in Solid State 168
9.4.2 Concerted Phenomenon Coupled with Spin Equilibrium and ValenceFluctuation 173
10.3.2 Spin Crossover Between S¼ 3/2 and S ¼ 5/2 19210.4 Spin-Crossover Triangle in Iron(III) Porphyrin Complexes 19510.5 Conclusions 198
Acknowledgments 198References 199
Chapter 11 | Tin(II) Lone Pair Stereoactivity: Influence on Structures and
Georges Denes, Abdualhafed Muntasar, M Cecilia Madamba, and Hocine Merazig11.1 Introduction 202
11.2 Experimental Aspects 20311.2.1 Sample Preparation 20311.3 Crystal Structures 20411.3.1 The Fluorite-Type Structure: A Typically Ionic Structure 20411.3.2 Tin(II) Fluoride: Covalent Bonding and Polymeric Structure 20511.3.3 The a-PbSnF4Structure: The Unexpected Combination of IonicBonding and Covalent Bonding 207
11.3.4 The PbClF-Type Structure: An Ionic Structure and a Tetragonal Distortion
of the Fluorite Type 20711.4 Tin Electronic Structure and M€ossbauer Spectroscopy 20811.4.1 Tin Electronic Structure, Bonding Type, and Coordination 20811.4.2 Using M€ossbauer Spectroscopy to Probe the Tin Electronic Structureand Bonding Mode 211
11.5 Application to the Structural Determination ofa-SnF2 21311.5.1 History 213
11.5.2 Using119Sn M€ossbauer Spectroscopy to Determine that the Tin PositionsUsed by Bergerhoff Were Incorrect 214
11.6 Application to the Structural Determination of the Highly LayeredStructures ofa-PbSnF4and BaSnF4 216
11.6.1 History 21611.6.2 Unit Cell of MSnF4and Relationships with the Fluorite-Type MF2 217
Trang 1311.6.3 M€ossbauer Spectroscopy, Bonding Type, Crystal Symmetry, and PreferredOrientation 220
11.6.4 Combining All the Results: The a-PbSnF4Structural Type 22511.7 Application to the Structural Study of Disordered Phases 22611.7.1 Disordered Fluoride Phases 226
11.7.2 Disordered Chloride Fluoride Phases 23211.8 Lone Pair Stereoactivity and Material Properties 24111.9 Conclusions 242
Acknowledgments 243References 243
Part IV Biological Applications 247
Chapter 12 | Synchrotron Radiation-Based Nuclear Resonant Scattering:
Yisong Guo, Yoshitaka Yoda, Xiaowei Zhang, Yuming Xiao, and Stephen P Cramer12.1 Introduction 249
12.2 Technical Background 25012.2.1 Theoretical Aspects of NFS 25012.2.2 Theoretical Aspects of SRPAC 25212.2.3 Experimental Aspects of NFS and SRPAC 25512.3 Applications in Bioinorganic Chemistry 25812.3.1 Nuclear Forward Scattering 258
12.3.2 SRPAC 26412.4 Summary and Prospects 269Acknowledgments 269
References 269
Alexander A Kamnev, Krisztina Kovacs, Irina V Alenkina, and Michael I Oshtrakh13.1 Introduction 272
13.2 Microorganisms-Related Studies 27313.3 Plants 276
13.4 Enzymes 28013.5 Hemoglobin 28113.6 Ferritin and Hemosiderin 28313.7 Tissues 284
13.8 Pharmaceutical Products 28613.9 Conclusions 286
Acknowledgments 287References 287
Chapter 14 | Controlled Spontaneous Decay of M€ossbauer Nuclei
Vladimir I Vysotskii and Alla A Kornilova14.1 Introduction to the Problem of Controlled Spontaneous Gamma Decay 29214.2 The Theory of Controlled Radiative Gamma Decay 293
14.2.1 General Consideration 29314.3 Controlled Spontaneous Gamma Decay of Excited Nucleus in the System
of Mutually Uncorrelated Modes of Electromagnetic Vacuum 29514.3.1 Spontaneous Gamma Decay in the Case of Free Space 296
14.3.2 Spontaneous Gamma Decay of Excited Nuclei in the Case of ScreenPresence 298
Trang 1414.4 Spontaneous Gamma Decay in the System of SynchronizedModes of Electromagnetic Vacuum 302
14.5 Experimental Study of the Phenomenon of Controlled Gamma Decay
of M€ossbauer Nuclei 30314.5.1 Investigation of the Phenomenon of Controlled Gamma Decay by Analysis ofDeformation of M€ossbauer Gamma Spectrum 303
14.6 Experimental Study of the Phenomenon of Controlled Gamma Decay
by Investigation of Space Anisotropy and Self-Focusing ofM€ossbauer Radiation 309
14.7 Direct Experimental Observation and Study of the Process of ControlledRadioactive and Excited Nuclei Radiative Gamma Decay by the DelayedGamma–Gamma Coincidence Method 311
14.8 Conclusions 314References 314
Chapter 15 | Nature’s Strategy for Oxidizing Tryptophan: EPR and M€ossbauer
Characterization of the Unusual High-Valent Heme Fe Intermediates 315
Kednerlin Dornevil and Aimin Liu15.1 Two Oxidizing Equivalents Stored at a Ferric Heme 31515.2 Oxidation ofL-Tryptophan by Heme-Based Enzymes 31615.3 The Chemical Reaction Catalyzed by MauG 318
15.4 A High-Valent Bis-Fe(IV) Intermediate in MauG 31915.5 A High-Valent Fe Intermediate of Tryptophan 2,3-Dioxygenase 32015.6 Concluding Remarks 321
References 322
Jolanta Gała˛zka-Friedman, Erika R Bauminger, and Andrzej Friedman16.1 Introduction 324
16.2 Neurodegeneration and Oxidative Stress 32416.3 M€ossbauer Studies of Healthy Brain Tissue 32516.4 Properties of Ferritin and Hemosiderin Present in Healthy Brain Tissue 32716.5 Concentration of Iron Present in Healthy and Diseased Brain Tissue:
Labile Iron 32816.6 Asymmetry of the M€ossbauer Spectra of Healthy and DiseasedBrain Tissue 330
16.7 Conclusion: The Possible Role of Iron in Neurodegeneration 331References 331
Chapter 17 | Emission (57Co) M€ossbauer Spectroscopy: Biology-Related Applications,
Alexander A Kamnev17.1 Introduction 33317.2 Methodology 33417.3 Microbiological Applications 33617.4 Enzymological Applications 34017.4.1 Choosing a Test Object 34017.4.2 Prerequisites for Using the 57Co EMS Technique 34217.4.3 Experimental57Co EMS Studies 342
17.4.4 Two-Metal-Ion Catalysis: Competitive Metal Binding at the Active Centers 34417.4.5 Possibilities of 57Co Substitution for Other Cations in Metalloproteins 34517.5 Conclusions and Outlook 345
Acknowledgments 345References 346
Trang 15Part V Iron Oxides 349
Chapter 18 | M€ossbauer Spectroscopy in Study of Nanocrystalline Iron Oxides
Ji9rı Tu9cek, Libor Machala, Ji9rı Frydrych, Ji9rı Pechou9sek, and Radek Zbo9ril18.1 Introduction 351
18.2 Polymorphs of Iron(III) Oxide, Their Crystal Structures, MagneticProperties, and Polymorphous Phase Transformations 35218.2.1 a-Fe2O3 353
18.2.2 b-Fe2O3 35818.2.3 g-Fe2O3 36018.2.4 e-Fe2O3 36418.2.5 Amorphous Fe2O3 36918.3 Use of57Fe M€ossbauer Spectroscopy in Monitoring Solid-StateReaction Mechanisms Toward Iron Oxides 371
18.3.1 Thermal Decomposition of Ammonium Ferrocyanide—A Valence ChangeMechanism 371
18.3.2 Thermal Decomposition of Prussian Blue in Air 37418.3.3 Thermal Conversion of Fe2(SO4)3in Air—Polymorphous Exhibition of Fe2O3 37618.3.4 Nanocrystalline Fe2O3Catalyst from FeC2O42H2O 376
18.4 Various M€ossbauer Spectroscopy Techniques in Study of ApplicationsRelated to Nanocrystalline Iron Oxides 378
18.4.1 57Fe Transmission M€ossbauer Spectroscopy at Various Temperatures 37818.4.2 In-Field57Fe Transmission M€ossbauer Spectroscopy 379
18.4.3 In Situ High-Temperature57Fe Transmission M€ossbauer Spectroscopy 38118.4.4 57Fe Conversion Electron and Conversion X-Ray M€ossbauer Spectroscopy 38318.5 Conclusions 389
Acknowledgments 389References 389
Chapter 19 | Transmission and Emission57Fe M€ossbauer Studies on Perovskites
Zoltan Homonnay and Zoltan Nemeth19.1 Introduction 393
19.2 Study of High-TCSuperconductors 39419.2.1 Study of57Co-Doped YBa2Cu3O7d 39519.2.2 Study of57Co-Doped Y1xPrxBa2Cu3O7d 39719.3 Study of Strontium Ferrate and Its Substituted Analogues 40119.3.1 Study of Sr0.95Ca0.05Co0.5Fe0.5O3dand Sr0.5Ca0.5Co0.5Fe0.5O3d 40119.4 Pursuing Colossal Magnetoresistance in Doped Lanthanum Cobaltates 40719.4.1 Emission M€ossbauer Study of La0.8Sr0.2CoO3 dPerovskites 408
19.4.2 Emission and Transmission M€ossbauer Study of Iron-Doped
La0.8Sr0.2FeyCo1 yO3 dPerovskites 411References 413
Chapter 20 | Enhancing the Possibilities of57Fe M€ossbauer Spectrometry
Karen E Garcıa, Cesar A Barrero, Alvaro L Morales, and Jean-Marc Greneche20.1 Introduction 415
20.2 M€ossbauer Characterization of Some Iron Phases Presented in the RustLayers 416
20.2.1 Akaganeite 416
Trang 1620.2.2 Goethite 41820.2.3 Magnetite/Maghemite 42020.3 Determining Inherent Properties of Rust Layers by M€ossbauerSpectrometry 421
20.3.1 Rust Layers in Steels Submitted to Total Immersion Tests 42120.3.2 Rust Layers in Steels Submitted to Dry–Wet Cycles 42420.3.3 Rust Layers in Steels Submitted to Outdoor Tests 42620.4 Final Remarks 426
Acknowledgments 426References 426
Lakshmi Nambakkat21.1 Introduction 42921.2 Spinel Ferrites 43021.2.1 Microstructure Determination 43021.2.2 Elucidation of Bulk Magnetic Properties in Nanoferrites Using In-Field M€ossbauerSpectroscopy 434
21.2.3 Core–Shell Effect on the Magnetic Properties in SuperparamagneticNanosystems 436
21.3 Nanosized Fe–Al Alloys Synthesized by High-Energy Ball Milling 44121.3.1 Nanosized Al–1 at% Fe 442
21.4 Magnetic Thin Films/Multilayer Systems:57Fe/AI MLS 44621.4.1 Structural Characterization 447
21.4.2 DC Magnetization Studies 44821.4.3 M€ossbauer (CEMS) Study 45121.5 Conclusions 452
Acknowledgments 453References 453
Jose F Marco, Jose Ramon Gancedo, Matteo Monti, and Juan de La Figuera22.1 Introduction 455
22.2 The Physical Basis: How and Why Electrons Appear in M€ossbauerSpectroscopy 456
22.3 Increasing Surface Sensitivity in Electron M€ossbauer Spectroscopy 45822.4 The Practical Way: Experimental Low-Energy Electron M€ossbauerSpectroscopy 460
22.5 M€ossbauer Surface Imaging Techniques 46522.6 Recent Surface M€ossbauer Studies in an “Ancient” Material:
Fe3O4 466Acknowledgment 468References 468
Chapter 23 | 57Fe M€ossbauer Spectroscopy in the Investigation of the
Svetozar Music, Mira Ristic, and Stjepko Krehula23.1 Introduction 470
23.2 Complexation of Iron Ions by Hydrolysis 47023.3 Precipitation of Iron Oxides by Hydrolysis Reactions 47223.4 Precipitation of Iron Oxides from Denseb-FeOOHSuspensions 480
Trang 1723.5 Precipitation and Properties of Some Other Iron Oxides 48323.5.1 Ferrihydrite 483
23.5.2 Lepidocrocite (g-FeOOH) 48523.5.3 Magnetite (Fe3O4) and Maghemite (g-Fe2O3) 48723.6 Influence of Cations on the Precipitation of Iron Oxides 49023.6.1 Goethite 490
23.6.2 Hematite 49523.6.3 Magnetite and Maghemite 496Acknowledgment 496
References 497
Chapter 24 | Ferrates(IV, V, and VI): M€ossbauer Spectroscopy Characterization 505
Virender K Sharma, Yurii D Perfiliev, Radek Zbo9ril, Libor Machala, and Clive I Wynter24.1 Introduction 505
24.2 Spectroscopic Characterization 50624.3 M€ossbauer Spectroscopy Characterization 50824.3.1 Ferryl(IV) Ion 508
24.3.2 Ferrates(IV, V, and VI) 51024.3.3 Case Studies 513
Acknowledgments 517References 517
Chapter 25 | Characterization of Dilute Iron-Doped Yttrium Aluminum
Kiyoshi Nomura and Zoltan Nemeth25.1 Introduction 52125.2 Sample Preparations by the Sol–Gel Method 52325.3 X-Ray Diffraction and EXAFS Analysis 52325.4 Magnetic Properties 525
25.5 M€ossbauer Analysis of YAG Doped with Dilute Iron 52625.6 Microdischarge Treatment of Iron-Doped YAG 52825.7 Conclusions 531
Acknowledgments 532References 532
Part VI Industrial Applications 533
Chapter 26 | Some M €ossbauer Studies of Fe–As-Based
Amar Nath and Airat Khasanov26.1 Introduction 53526.2 Experimental Procedure 53526.3 Where Do the Injected Electrons Go? 53726.4 New Electron-Rich Species in Ni-Doped Single Crystals: Is ItSuperconducting? 538
26.5 Can O2 Play an Important Role? 539Acknowledgment 541
References 541
Tetsuaki Nishida and Shiro Kubuki27.1 Introduction 54227.1.1 Electrically Conductive Oxide Glass 54227.1.2 Cathode Active Material for Lithium-Ion Battery (LIB) 543
Trang 1827.2 Structural Relaxation of Electrically Conductive Vanadate Glass 54427.2.1 Increase in the Electrically Conductivity of Vanadate Glass 544
27.2.2 Cathode Active Material for Li-Ion Battery (LIB) 547
Acknowledgments 551References 551
Chapter 28 | Applications of M€ossbauer Spectroscopy in the Study of Lithium
28.3 Anode Materials for Li-Ion Batteries 55628.3.1 Conversion Oxides 556
28.3.2 Tin Alloys and Intermetallic Compounds 55828.3.3 Antimony Alloys and Intermetallic Compounds 56028.4 Conclusions 561
Acknowledgments 561References 562
Chapter 29 | M€ossbauer Spectroscopic Investigations of Novel Bimetal Catalysts
Wansheng Zhang, Junhu Wang, Kuo Liu, Jie Jin, and Tao Zhang29.1 Introduction 564
29.2 Experimental Section 56429.2.1 Catalyst Preparation 56429.2.2 Catalytic Activity Test 56529.2.3 M€ossbauer Spectra Characterization 56529.3 Results and Discussion 565
29.3.1 PtFe Alloy Nanoparticles Catalyst 56529.3.2 Ir–Fe/SiO2Catalyst 567
29.4 Conclusions 574Acknowledgments 574References 575
Chapter 30 | The Use of M€ossbauer Spectroscopy in Coal Research: Is It Relevant
Frans B Waanders30.1 Introduction 57630.2 Experimental Procedures 57730.2.1 M€ossbauer Spectroscopy 57730.2.2 SEM Analyses 577
30.2.3 XRD Analyses 57730.2.4 Samples and Sample Preparation 57730.3 Results and Discussion 578
30.3.1 M€ossbauer Analyses of the As-Mined Samples 57830.3.2 Weathering of Coal 578
30.3.3 Corrosion of Mild Steel Due to the Presence of Compacted Fine Coal 58330.3.4 Coal Combustion 584
30.3.5 Coal Gasification and Resultant Products 587
Trang 1930.4 Conclusions 590Acknowledgments 591References 591
Part VII Environmental Applications 593
Chapter 31 | Water Purification and Characterization of Recycled
Shiro Kubuki and Tetsuaki Nishida31.1 Introduction 59531.1.1 Water-Purifying Ability of Recycled Iron Silicate Glass 59531.1.2 Iron Silicate Glass Prepared by Recycling Coal Ash 59631.2 Properties and Structure of Recycled Silicate Glasses 59631.2.1 Water-Purifying Ability of Recycled Silicate Glasses 59631.2.2 Electromagnetic Property of Recycled Silicate Glasses 601
31.3.1 Water-Purifying Ability of Recycled Silicate Glasses 60531.3.2 Electromagnetic Property of Recycled Silicate Glasses 606References 606
Chapter 32 | M€ossbauer Spectroscopy in the Study of Laterite Mineral Processing 608
Eamonn Devlin, Michail Samouhos, and Charalabos Zografidis32.1 Introduction 608
32.2 Conventional Processing 60932.3 Microwave Processing 612References 619
Index 621
Trang 21Five decades ago, the M€ossbauer concept was invented Since then the M€ossbauer spectroscopy has been applied in a widerange of fields including physics, chemistry, biology, and nanotechnology The M€ossbauer spectroscopy is still beingapplied vigorously in understanding the hyperfine interactions of electromagnetic nature This is evident from a similarnumber of publications on the M€ossbauer concept (14,000/decade) in the last three decades This book presents thecurrent knowledge on the applications of M€ossbauer spectroscopy With this theme in the minds of editors, manyexperts were invited to contribute to the book on the use of the M€ossbauer effect in a number of subject areas Theeditors also made sure that the contributors were from almost every region of the world (i.e., North America, SouthAmerica, Europe, Africa, and Asia) in order to cover different aspects of the M€ossbauer spectroscopy
In Chapters 1 and 2, an introduction is made to the synchrotron M€ossbauer spectroscopy with examples Examplesinclude the in situ M€ossbauer spectroscopy with synchrotron radiation on thin films and the study of deep-earth minerals.Investigations of in-beam M€ossbauer spectroscopy using a57Mn beam at the RIKEN RIBF is presented in Chapter 3 Thischapter demonstrates innovative experimental setup for online M€ossbauer spectroscopy using the thermal neutroncapture reaction,56Fe (n, g)57Fe The M€ossbauer spectroscopy of radionuclides is described in Chapters 4–7 Chapter 4gives full description of the latest analysis results of lanthanides (151Eu and155Gd) M€ossbauer structure and powder X-raydiffraction (XRD) lattice parameter (a0) data of defect fluorite (DF) oxides with the new defect crystal chemistry (DCC)
a0model Chapter 5 reviews the237Np M€ossbauer and magnetic study of neptunyl(þ1) complexes, while Chapter 6describes the M€ossbauer spectroscopy of organic complexes of europium and dysprosium.238U M€ossbauer spectros-copy is presented in Chapter 7 There are three chapters on spin-state switching/spin-crossover phenomena (Chapter 8–10) Examples in these chapters are mainly on iron compounds, such as iron(III) porphyrins The use of M€ossbauerspectroscopy of physical properties of Sn(II) is discussed in Chapter 11
Chapters 12–17 are devoted to applications of the M€ossbauer spectroscopy to the biological chemistry Chapter 12details the recent progress on the application of57Fe NFS,57Fe SRPAC, and61Ni SRPAC to bioinorganic chemistry Thefuture prospect of these techniques is also given The role of M€ossbauer spectroscopy in biological and biomedicalresearch is described in Chapters 13 and 17 These chapters demonstrate how M€ossbauer spectroscopy can be applied
to study microorganisms, plants, tissues, enzymes, hemoglobin, ferritin, and hemosiderin Chapter 15 deals with theM€ossbauer characterization of high-valent iron intermediates in the oxidation ofL-tryptophan by heme-based enzymes.Chapter 16 is focused on the use of M€ossbauer spectroscopy to study iron in neurodegenerative diseases
Recent advances on studying iron and iron oxides using M€ossbauer spectroscopy are described in Chapters 18–25.Chapter 18 discusses the nanocrystalline iron oxides, while Chapter 19 presents perovskite-related systems whereemission M€ossbauer spectroscopy contributes to exploring the structure and electronic or magnetic behavior of thesematerials The use of57Fe M€ossbauer spectrometry to study iron phases in rust layers is described in Chapter 20 Theprogress made on understanding bulk magnetic properties of nanosized powders of ferrites, mechanically alloyed/milledFe–Cr–Al intermetallics, and a Fe–Al multilayer system is presented in Chapter 21 The application of surface M€ossbauerspectroscopy to study very thin layers (a few atomic layers thick) of iron oxides is discussed in Chapter 22 Chapter 23describes in detail the precipitation of iron oxides from aqueous iron salt solutions using M€ossbauer spectroscopy.Chapter 24 is focused on the spectroscopic characterization of ferrates in high-valent oxidation states (þ4, þ5, and þ6).Chapter 25 deals with dilute iron-doped yttrium aluminum garnets
M€ossbauer spectroscopy of materials of industrial interest is discussed in Chapters 26–30 Chapter 26 deals with Fe–As-based high-temperature superconductors M€ossbauer study of cathode active material for lithium-ion battery (LIB)and electrically conductive vanadate glass is presented in Chapter 27 More details on the applications of M€ossbauerspectroscopy to LIB are given in Chapter 28 Chapter 29 is the example of applying M€ossbauer spectroscopy to developnovel bimetal heterogeneous catalysts for preferential CO oxidation in H2 Chapter 30 shows the successful use ofM€ossbauer spectroscopy to identify and quantify the iron mineral phases of South African coal fractions The last twochapters are mainly on the applications of M€ossbauer spectroscopy to the environmental field, for example, describingthe recycling process of iron-containing “waste” of silicate glasses, which is related to purification of polluted water
xix
Trang 22(Chapter 31) The variables control in the laterite mineral processing using M€ossbauer spectroscopy is another example(Chapter 32).
Finally, the editors of the book would like to acknowledge contributions by late Professor Attila Vertez, E€otv€osLorand University In addition to studying fundamentals of M€ossbauer spectroscopy, Attila applied the M€ossbauer effect
to various fields One of the coeditors, Virender K Sharma, met Attila in fall 2002 when he was visiting Budapest underthe sustainability grant, received by Florida Tech, from the U.S Department of States During the visit, Attila was verykind to accept him in his group Since then Virender had several interactions in Budapest and on one occasion inMelbourne, Florida Because of the admiration for Attila, the M€ossbauer community organized a special symposium titled
“Chemical Applications of M€ossbauer Spectroscopy,” honoring him at the American Chemical Society Spring Meeting atSan Francisco in March 2010 In the summer 2010, Virender traveled to Budapest to present the “Salute of Excellence”from the American Chemical Society It was heartening to see that leading chemists from Hungary, including thepresident of the chemistry division of the Hungarian Academy of Science and president of E€otv€os Lorand University, werepresent at that occasion Attila will always be known as a great scientist with a gentleman touch and we will miss himdearly This book is dedicated to late Professor Attila Vertez for his many accomplishments in M€ossbauer spectroscopy
VIRENDERK SHARMA
G€oSTAR KLINGELH€oFER
TETSUAKINISHIDA
Trang 23Ricardo Alcantara, Laboratorio de Quımica Inorganica, Universidad de Cordoba, Cordoba, Spain
Irina V Alenkina, Faculty of Physical Techniques and Devices for Quality Control, Institute of Physics and Technology,Ural Federal University, Ekaterinburg, Russian Federation
Ercan E Alp, Advanced Photon Source, Argonne National Laboratory, Argonne, IL, USA
Cesar A Barrero, Grupo de Estado Solido, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia,Medellın, Colombia
Erika R Bauminger, Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem, Israel
Edward Brown, Chemistry Department, Nassau Community College, Garden City, NY
Stephen P Cramer, Department of Applied Science, University of California-Davis, Davis, CA, USA
Juan de la Figuera, Instituto de Quımica Fısica “Rocasolano”, CSIC, Madrid, Spain
Georges Denes, Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec, CanadaEamonn Devlin, Institute of Materials Science, N.C.S.R “Demokritos”, Attiki, Athens, Greece
Kednerlin Dornevil, Department of Chemistry, Georgia State University, Atlanta, GA, USA
Andrzej Friedman, Department of Neurology, Faculty of Health Science, Medical University of Warsaw, Warsaw,Poland
Ji9rı Frydrych, Regional Center of Advanced Technologies and Materials, Olomouc, Czech Republic
Jolanta Gała˛zka-Friedman, Faculty of Physics, Warsaw University of Technology, Warsaw, Poland
Jose Ramon Gancedo, Instituto de Quımica Fısica “Rocasolano”, CSIC, Madrid, Spain
Karen E Garcıa, Grupo de Estado Solido, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia,Medellın, Colombia
Jean-Marc Greneche, LUNAM, Universite du Maine, Institut des Molecules et Materiaux du Mans, Le Mans Cedex,France
Yisong Guo, Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, USA
Barbara R Hillery, Chemistry Department, Nassau Community College, Garden City, NY
Yukio Hinatsu, Department of Chemistry, Hokkaido University, Sapporo, Hokkaido, Japan
Zoltan Homonnay, Faculty of Science, Eotvos Lorand University, Budapest, Hungary
Naoki Igawa, Quantum Bean Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki, JapanJie Jin, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
Alexander A Kamnev, Laboratory of Biochemistry, Institute of Biochemistry and Physiology of Plants and organisms, Russian Academy of Sciences, Saratov, Russian Federation
Micro-Airat Khasanov, Department of Chemistry, University of North Carolina at Asheville, Asheville, NC, USAYoshio Kobayashi, Department of Engineering Science, The University of Electro-Communications, Tokyo, Japan
xxi
Trang 24Norimichi Kojima, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo, JapanJozef Korecki, Institute for Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen,Karlsruhe, Germany
Alla A Kornilova, Moscow State University, Moscow, Russia
Krisztina Kovacs, Laboratory of Nuclear Chemistry, Institute of Chemistry, E€otv€os Lorand University, Budapest,Hungary
Stjepko Krehula, Division of Materials Chemistry, Rudjer Bo9skovic Institute, Zagreb, Croatia
Shiro Kubuki, Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University,Hachioji, Japan
Pedro Lavela, Laboratorio de Quımica Inorganica, Universidad de Cordoba, Cordoba, Spain
Jan Ła_zewski, Institute for Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen,Karlsruhe, Germany
Jung-Fu Lin, Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin,Austin, TX, USA
Aimin Liu, Department of Chemistry, Georgia State University, Atlanta, GA, USA
Kuo Liu, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
Libor Machala, Regional Center of Advanced Technologies and Materials, Olomouc, Czech Republic
M Cecilia Madamba, Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec, CanadaZhu Mao, Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin,Austin, TX, USA
Jose F Marco, Instituto de Quımica Fısica “Rocasolano”, CSIC, Madrid, Spain
Leopold May, Chemistry Department, Nassau Community College, Garden City, NY
Hocine Merazig, Laboratoire de Chimie Moleculaire, du Contr^ole de l’Environnement et de Mesures Chimiques, Departement de Chimie, Faculte des Sciences, Universite Mentouri, Constantine, Algeria
Physico-Toshiyuki Misu, Department of Chemistry, Faculty of Science, Toho University, Funabashi, Chiba, Japan
Matteo Monti, Instituto de Quımica Fısica “Rocasolano”, CSIC, Madrid, Spain
Alvaro L Morales, Grupo de Estado Solido, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia,Medellın, Colombia
Abdualhafed Muntasar, Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec,Canada
Svetozar Music, Division of Materials Chemistry, Rugjer Bo9skovic Institute, Zagreb, Croatia
Masami Nakada, Advanced Science Research Center, Japan Atomic Energy Agency, Ibaraki, Japan
Tadahiro Nakamoto, Department of Materials Characterization, Toray Research Center, Inc., Otsu, Shiga, JapanAkio Nakamura, Advanced Science Research Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki,Japan
Mikio Nakamura, Department of Chemistry, Faculty of Science, Toho University, Funabashi, Chiba, Japan
Satoru Nakashima, Natural Science Center for Basic Research and Development, Hiroshima University,Higashi-Hiroshima, Japan
Lakshmi Nambakkat, Department of Physics, University College of Science, Mohanlal Sukhadia University, Udaipur,Rajasthan, India
Trang 25Amar Nath, Department of Chemistry, University of North Carolina at Asheville, Asheville, NC, USA
Zoltan Nemeth, Faculty of Science, Eotvos Lorand University, Budapest, Hungary
Tetsuaki Nishida, Department of Biological and Environmental Chemistry, Faculty of Humanity-Oriented Science andEngineering, Kinki University, Iizuka, Japan
Kiyoshi Nomura, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
Yoshihiro Okamoto, Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Naka-gun,Ibaraki, Japan
Michael I Oshtrakh, Faculty of Physical Techniques and Devices for Quality Control, Institute of Physics andTechnology, Ural Federal University, Ekaterinburg, Russian Federation
Krzysztof Parlinski, Institute for Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), Leopoldshafen, Karlsruhe, Germany
Eggenstein-Ji9rı Pechou9sek, Regional Center of Advanced Technologies and Materials, Olomouc, Czech Republic
Carlos Perez Vicente, Laboratorio de Quımica Inorganica, Universidad de Cordoba, Cordoba, Spain
Yurii D Perfiliev, Chemistry Department, Florida Institute of Technology, Melbourne, FL, USA
Duncan Quarless, Chemistry Department, Nassau Community College, Garden City, NY
Mira Ristic, Division of Materials Chemistry, Rugjer Bo9skovic Institute, Zagreb, Croatia
Ralf R€ohlsberger, Institute for Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), Leopoldshafen, Karlsruhe, Germany
Eggenstein-Michail Samouhos, School of Mining and Metallurgical Engineering, National Technical University of Athens,Athens, Greece
Bogdan Sepiol, Institute for Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen,Karlsruhe, Germany
Virender K Sharma, Chemistry Department, Florida Institute of Technology, Melbourne, Florida, USA
Marcel Sladecek, Institute for Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), Leopoldshafen, Karlsruhe, Germany
Eggenstein-Michał Sle˛zak, Institute for Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen,Karlsruhe, Germany
Tomasz Sle˛zak, Institute for Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen,Karlsruhe, Germany
Sabrina G Sobel, Chemistry Department, Nassau Community College, Garden City, NY
Nika Spiridis, Institute for Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen,Karlsruhe, Germany
Svetoslav Stankov, Institute for Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), Leopoldshafen, Karlsruhe, Germany
Eggenstein-Akira Sugahara, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo, JapanMasashi Takahashi, Department of Chemistry, Faculty of Science, Toho University, Funabashi, Chiba, JapanMasuo Takeda, Department of Chemistry, Faculty of Science, Toho University, Funabashi, Chiba, Japan
Jose L Tirado, Laboratorio de Quımica Inorganica, Universidad de Cordoba, Cordoba, Spain
Satoshi Tsutsui, Research and Utilization Division, SPring-8/JASRI, Sayo-cho, Sayo-gun, Hyogo, Japan; AdvancedScience Research Center, Japan Atomic Energy Agency, Ibaraki, Japan
Trang 26Ji9rı Tu9cek, Regional Center of Advanced Technologies and Materials, Olomouc, Czech Republic
Gero Vogl, Institute for Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen,Karlsruhe, Germany
Vladimir I Vysotskii, Mathematics and Theoretical Radiophysics Department, Kiev National Shevchenko University,Kiev, Ukraine
Frans B Waanders, School of Chemical and Minerals Engineering, North West University, Potchefstroom, SouthAfrica
Junhu Wang, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
Clive I Wynter, Chemistry Department, Nassau Community College, Garden City, NY
Yuming Xiao, HPCAT, Advanced Photon Source, Argonne National Laboratory, Argonne, IL, USA
Yoshitaka Yoda, Research and Utilization Division, SPring-8/JASRI, Kouto, Sayo, Hyogo, Japan
Marcin Zaja˛c, Institute for Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen,Karlsruhe, Germany
Radek Zbo9ril, Regional Center of Advanced Technologies and Materials, Olomouc, Czech Republic; ChemistryDepartment, Florida Institute of Technology, Melbourne, FL, USA
Tao Zhang, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
Wansheng Zhang, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
Xiaowei Zhang, Photon Factory, KEK, 1-1 Oho, Tsukuba, Ibaraki, Japan
Charalabos Zografidis, School of Mining and Metallurgical Engineering, National Technical University of Athens,Athens, Greece
Trang 27P A R T I
INSTRUMENTATION
Trang 29C H A P T E R 1
SPECTROSCOPY WITH SYNCHROTRON RADIATION
ON THIN FILMS
SVETOSLAVSTANKOV, TOMASZSLE ˛ZAK, MARCINZAJA ˛C, MICHAŁSLE ˛ZAK, MARCELSLADECEK,
RALFR€oHLSBERGER, BOGDANSEPIOL, GEROVOGL, NIKASPIRIDIS, JANŁA _ZEWSKI,
KRZYSZTOFPARLI NSKI,ANDJoZEFKORECKI
Institute for Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Karlsruhe, Germany
1.1 INTRODUCTION
Soon after the first observation [1–3] by Rudolf M€ossbauer in 1958 of nuclear resonant recoilless absorption andemission of g-rays from nuclei of191Ir, the M€ossbauer effect became a well-established spectroscopic method for probingthe electronic, magnetic, and dynamic properties of solids, liquids, and even gases [4] The unprecedentedly high intrinsicenergy resolving power on the order of 1013offered by the M€ossbauer effect is determined by the natural linewidth ofthe nuclear resonant exited state The relatively simple and easily accessible experimental setup, and the observation ofthe effect in isotopes of widely spread and technologically relevant elements such as iron and tin and their compoundsstimulated the explosion of applications of the M€ossbauer spectroscopy not only in solid state physics but also infundamental physics [5], chemistry [6], geology [7], biology [8], industry [9], and many other fields
If a photon with an energy equal to the resonant energy impinges on the M€ossbauer nucleus in its ground state, thephoton may, with a probability given by the Lamb–M€ossbauer factor fLM, excite the nuclear resonant level without anenergy loss due to recoil After the mean lifetime of this state, the nucleus returns back into its ground state either byemitting a photon or by ejecting an electron with probabilities 1/(1þ a) and a/(1 þ a), respectively, where a is thecoefficient of total internal conversion For most of the M€ossbauer isotopes, a is significantly greater that 1; therefore,the dominant mechanism for the de-excitation is internal conversion The limited mean-free path of ejected electronsdefines an escape depth of only few nanometers By detecting the conversion electrons (conversion electron M€ossbauerspectroscopy, CEMS), information about the electronic and magnetic properties of the materials’ surface can be derived.The high values of the cross section for nuclear resonant absorption and the small escape depths of the conversionelectrons established CEMS as a standard technique for investigating surface layers of materials [10] Moreover, byanalyzing the energy of the ejected electrons depth-selective information can be retrieved [11,12] This determined thevast range of applications of this technique to surface science and nanotechnology already soon after the first observation
of the M€ossbauer effect
The feasibility for in situ experiments on ultrathin57Fe films consisting of only one atomic layer of iron by the CEMStechnique has been successfully demonstrated [13] in the mid-1980s However, the relatively long data acquisition times
3
M €ossbauer Spectroscopy: Applications in Chemistry, Biology, and Nanotechnology, First Edition.
Edited by Virender K Sharma, G €ostar Klingelh€ofer, and Tetsuaki Nishida.
Ó 2013 John Wiley & Sons, Inc Published 2013 by John Wiley & Sons, Inc.
Trang 30(15 h) needed for accumulating spectra with reasonable statistics by using a conventional radioactive source havelimited further applications.
A new era in the M€ossbauer spectroscopy emerged in the year 1985 from the first observation of coherent elasticnuclear resonant scattering (NRS) of synchrotron radiation by the group of Erich Gerdau in Hamburg [14] Thedemonstration that nuclear resonant experiments are indeed feasible by using synchrotron radiation instead ofradioactive source was a tremendous success However, only the advent of the third-generation synchrotron radiationsources in the middle 1990s along with the rapid development of high-resolution X-ray optics [15–19] and fast avalanchephotodiode detectors (APDs) [20] established M€ossbauer spectroscopy with synchrotron radiation as a standardtechnique for probing electronic, magnetic, and dynamic properties of materials [21] The enormous brilliance of the X-ray beams provided by insertion devices such as wigglers and undulators, which is by more than 10 orders of magnitudelarger in comparison with that of the conventional radioactive sources, allowed for the investigation of samples containingvery small quantities of the resonant isotope This resulted in a significant expansion of applications to layered systems(thin- and ultrathin films, and multilayers), nanostructures (islands, clusters), and samples under extreme conditions, forexample, very high pressures and temperatures [22]
The possibility to finely tune the energy of the photons using high-resolution monochromators (HRMs) has resulted
in a new technique for direct determination of the phonon density of states of the resonant element—the nuclearinelastic scattering (NIS) [23–25] Thus, in the same experimental setup, one is able to probe simultaneously hyperfineinteractions and lattice dynamics of the sample
Investigation of well-defined nanostructures often requires that the preparation, characterization, and maintenance
of the samples during experiments are performed under controlled, in most cases ultrahigh vacuum (UHV), conditions.Corresponding instrumentation [26,27] has been constructed and permanently installed at the nuclear resonancebeamline ID18 [28] of the European Synchrotron Radiation Facility (ESRF) in Grenoble, France This opened up newperspectives for in situ investigations of electronic and magnetic properties, vibrational dynamics, and diffusionphenomena by several nuclear resonant scattering-based techniques such as coherent elastic nuclear resonant scattering,coherent quasielastic nuclear resonant scattering, and incoherent inelastic nuclear resonant scattering/absorption.The aim of this chapter is to report on recent advances in the in situ M€ossbauer spectroscopy with synchrotronradiation on thin films that became possible due to the instrumentation developments at the nuclear resonance beamlineID18 of the ESRF After a detailed description of the beamline and of the UHV system for in situ experiments, a briefintroduction into the basic NRS techniques is given Finally, the application of these techniques to investigate magnetic,diffusion, and lattice dynamics phenomena in ultrathin epitaxial57Fe films deposited on a W(110) substrate is presentedand discussed
1.2 INSTRUMENTATION
The Classical M€ossbauer spectroscopy with a standard radioactive source has been performed in the energy domain,whereas the nuclear resonant scattering using synchrotron radiation measures the time-domain spectra This impliesfundamental differences in the experimental approach and the associated instrumentation The Synchrotron radiation atthird-generation sources is produced by insertion devices (wigglers or undulators) installed in the straight sections of thestorage ring, where relativistic electrons (positrons) circulate the ring [29] One of the prerequisites for performing NRSexperiments is the timing mode of the storage ring operation For nuclear resonant scattering applications, the storagering is filled with equidistant electron (positron) bunches that produce intensive X-ray pulses having a width of about
100 ps Especially suitable for NRS applications at the ESRF is the 16-bunch mode providing a time spacing of 176 nsbetween the bunches
The second condition that has to be fulfilled is the utilization of fast detectors and associated timing electronics.Avalanche photodiodes have been successfully introduced [20] for NRS applications due to their quick time response,high dynamic range, and relatively high quantum efficiency The time resolution ranges from 0.1 to 1.0 ns and the efficiencyfrom several percent to about 50% depending on the energy of the X-rays The timing electronics is based on standardNIM modules, including constant fraction discriminators, gate generators, fast ADCs (analog digital converters), andMCAs (multichannel analyzers) A reference timing signal from the radio frequency system of the storage ring provides asynchronization of the electronics with the photon pulse arrival time
To further improve the performance of the APD detectors for nuclear resonant scattering applications, the degree suppression of the nonresonant radiation is essential This is achieved by using high-resolution monochromators
high-4 1 IN SITU M €OSSBAUER SPECTROSCOPY WITH SYNCHROTRON RADIATION ON THIN FILMS
Trang 31based on asymmetrically cut Si single crystals with high-order reflections [19,30] The role of the HRM in nuclearresonant scattering techniques is twofold: (1) it filters out a significant part of the nonresonant photons, thus preventingthe detector in forward direction from overload during the intense X-ray pulses; and (2) the HRM provides the necessaryinstrumental energy resolution in the range of few millielectron volts to submillielectron volts for the purposes of thenuclear inelastic scattering experiments A separate HRM has to be developed for each M€ossbauer transition in order toprovide the highest energy resolution, flux, and/or degree of polarization Table 1.1 summarizes the isotopes that arecurrently accessible at ID18 of the ESRF for nuclear resonant scattering experiments with the natural lifetime and energy
of the nuclear resonant level and the energy resolution of the corresponding high-resolution monochromator
1.2.1 Nuclear Resonance Beamline ID18 at the ESRF
A layout of the beamline for nuclear resonant scattering experiments ID18 of the ESRF in Grenoble is schematicallyshown in Fig 1.1 It consists of a front end, two optical and three experimental hutches with adjacent control cabins Thefront end accommodates three revolver-type undulators that allow one to switch between magnetic structures with 20
or 27 mm period While the former provides photons with energy 14.413 keV on its fundamental, the latter is optimizedfor M€ossbauer isotopes with lower/higher energies (Table 1.1) The first optics hutch (OH1) accommodates the primaryslit system that shapes the synchrotron beam and defines its size, the high heat load monochromator (HHLM), furthercollimating optics, and beam intensity monitors (not shown in the figure) The HHLM [31] is a fixed exit double-crystal
TABLE 1.1 M€ossbauer Isotopes with the Natural Lifetime and Energy of the Nuclear Resonant Level, and Energy
Resolution Provided by the Corresponding High-Resolution Monochromator at ID18 of the ESRFIsotope Natural Lifetime (ns) Resonant Energy (keV) Energy Resolution (meV)
Trang 32Si(111) monochromator with a bandwidth of few electron volts A cryogenic cooling allows for handling the heat load andensures short- and long-term stability of the crystals positions The second optics hutch (OH2) hosts variousexchangeable high-resolution monochromators For the resonant energy transition of 14.413 keV in 57Fe, severalpossibilities exist offering various energy resolution and beam flux The most suitable one has to be selected according tothe needs of the particular experiment A bending focusing monochromator (FM) for reducing the horizontal beam size
to100 mm is also available in OH2
A standard six-circle diffractometer for diffraction experiments in horizontal and vertical scattering geometries
at ambient conditions is operational in the first experimental hutch (EH1) In addition, it can accommodate a furnace(300–1200 K) and continuous flow cryostat (10–300 K) allowing for NRS experiments in a large temperature range.The second experimental hutch (EH2) is devoted to experiments on samples at extreme conditions It accom-modates the UHV system [26] devoted to in situ experiments on thin films and nanostructures that is described in detail inthe next section A cryomagnet system offers external magnetic fields up to 8 T in horizontal direction, eitherperpendicular or parallel to the X-ray beam and a temperature range between 1.5 and 297 K It is mounted on atwo-circle heavy-duty goniometer used for sample tilting to an angular range of5both parallel and perpendicular to
the direction of propagation of the X-ray beam The setup is particularly suitable for experiments on surfaces, thin films,and multilayers The sample holder is capable of carrying up to six samples
The third experimental hutch (EH3) offers enough space for user equipment, for example, portable vacuum chambers It is also used for setting up a high-resolution backscattering monochromator [32] This type of HRM
ultrahigh-is used for M€ossbauer ultrahigh-isotopes with resonant energies above ca 30 keV, that ultrahigh-is, 125Te (35.493 keV) and 121Sb(37.1298 keV) [33,34]
An interlock system allows for carrying out an experiment in any of the experimental hutches while enabling freeaccess to the others The beam inside these hutches is either transported in shielded vacuum tubes or blocked by theupstream beam shutter By this means, the experiment in one hutch can be performed in parallel with the preparationwork in others Computers and electronics to run the experiment are located in three separated control cabins(CC1–CC3) adjacent to the corresponding experimental hutches
Depending on the X-ray energy used in the experiments, compound refractive lenses (CRL), made of either Be,plastic, or Al [35], are employed for collimating the beam in order to match the beam divergence to the angularacceptance of the monochromators In addition, CRLs serve to focus the beam to approximately 15 250 mm2
for theneeds of particular experiments These comprise, for example, high-pressure applications by using diamond anvil cells, orinvestigations of nanostructured samples deposited on a substrates where grazing incidence geometry has to be utilized.Alternatively, focusing of the X-ray beam down to about 5 10 mm2
is achieved by bending multilayer mirrors arranged
in Kirkpatrick–Baez geometry
1.2.2 The UHV System for In Situ Nuclear Resonant Scattering Experiments at ID18 of the ESRF
The UHV instrument is permanently installed in the second experimental hutch of ID18 of the ESRF, which requiresremote control of the entire system Figure 1.2 presents schematically the instrument, while Fig 1.3 displays a top-viewphotograph The UHV setup with a base pressure of 1 1010mbar consists of a central distribution chamber equippedwith a sample transfer mechanism and peripherally attached chambers as described in detail below
The preparation chamber, number 1 in Figs 1.2 and 1.3, is equipped with two electron beam evaporators and aneffusion cell A four-pocket mini electron beam evaporator serves for deposition of metals from rods and crucibles fromeach pocket separately, as well as for codeposition of different combinations of the evaporants A single-pocket e-beamsource is used for deposition of the M€ossbauer isotope57Fe An effusion cell is available for evaporation of rare-earthmetals A precise calibration of the deposition rate with a thickness reproducibility of 1 A is done by a quartz-balancemonitor The deposited structures can be characterized by low-energy electron diffraction (LEED) and Auger electronspectroscopy (AES) In this chamber, the samples can be cooled down to about 90 K and heated up to 2300 K by amultifunctional manipulator
The chamber for NRS experiments, number 2 in Figs 1.2 and 1.3, is mounted on a two-circle goniometer that serves
to align the sample and perform experiments with the focused synchrotron beam in grazing incidence scatteringgeometry The manipulator provides contacts for temperature measurement, resistive and electron-bombardmentheating, and feedthrough for cooling the sample down to 90 K by flow of liquid nitrogen In addition, the sample holdercan be rotated in the range of180 degrees about an axis perpendicular to the sample surface, allowing for angularresolved studies For the purpose of nuclear inelastic scattering experiments, an avalanche photodiode detector isbrought close to the sample via a tube reaching into the chamber with a Be window at its end, as shown on the
6 1 IN SITU M €OSSBAUER SPECTROSCOPY WITH SYNCHROTRON RADIATION ON THIN FILMS
Trang 33photograph in Fig 1.4 The figure also shows the entrance and exit Be windows for the focused synchrotron radiationbeam that impinges on the sample under grazing angles of few milliradians It further shows the sample mounted on thesample station, and the Z-stage for the APD detector used for nuclear inelastic scattering experiments as well as theAPDs for detecting the nuclear forward scattered radiation.
The distribution chamber, number 3 in Figs 1.2 and 1.3, connects the above-described chambers and serves fortransferring the sample holders between them In addition, a sample storage chamber, number 4 in Figs 1.2 and 1.3, with
FIGURE 1.2
A schematic view of the UHVsystem with the preparation 1,NRS 2, distribution 3, storage 4,and load-lock 5 chambers (forsimplicity all bypasses and evap-oration sources are omitted).Number 6 shows the CF63 portwhere the portable chambers can
be connected to the system.(Reproduced from Ref 26 withpermission of the AmericanInstitute of Physics.)
FIGURE 1.3
A top-side photograph of theUHV system with the preparation
1, NRS 2, distribution 3, storage 4,and load-lock 5 chambers.Chamber 6 shows the portablechamber for XRD, GISAXS, andXPCS experiments connected tothe system (Reproduced fromRef 26 with permission of theAmerican Institute of Physics.)
Trang 34the capacity to store up to six sample holders, is an integrated part of the distribution chamber The lowestposition provides electrical contacts for resistive heating and temperature control allowing for annealing of the sampleholders The load-lock chamber, number 5 in Figs 1.2 and 1.3, serves for introducing the sample holder into the UHVsystem.
Two additional portable chambers are available for transferring samples to other beamlines of the ESRF Theportable chamber for NRS experiments (Fig 1.5) was constructed in order to extend the in situ NRS experiments tothin films and nanostructures of noniron isotopes (Formerly the end-station ID22N of the ESRF was optimized for the
FIGURE 1.4
A site photograph of the sample station in the NRS chamber 2 Shown are the detectors (APD) for the nuclear forwardscattering and the nuclear inelastic scattering experiments, sample, entrance and exit Be windows for the grazingincidence scattering geometry with the focused X-ray beam During the nuclear inelastic scattering experiment, thedistance between the APD (above the sample) and the sample is reduced to about 2 mm
FIGURE 1.5
A schematic view of the portable
UHV chamber for NRS
experi-ments (Reproduced from Ref 26
with permission of the American
Institute of Physics.)
8 1 IN SITU M €OSSBAUER SPECTROSCOPY WITH SYNCHROTRON RADIATION ON THIN FILMS
Trang 35nuclear resonances of149Sm,151Eu, and161Dy) This chamber is based on two crossed CF100 tubes with a samplestation The station provides electrical contacts to the sample holder for temperature control (K- or C-typethermocouples), resistive or electron-bombardment heating, and feedthroughs for sample cooling down to 90 K byflow of liquid nitrogen The sample holder can be rotated in the range of180 degrees around an axis perpendicular
to the surface normal This chamber is pumped by a double-flanged 100 l s1ion getter pump ending with a viewport.Entrance and exit windows for the X-ray beam are made out of a 100 mm thick Be foil diffusion bonded to CF63flanges Additional CF40 flanges are used for a viewport and a vacuum gauge Similarly to the main NRS chamber, aCF63 tube with welded Be window on the bottom is mounted above the sample station on a stage with a lineartransfer in order to reduce the distance between the APD detector and the sample This chamber was employed
to study magnetic properties and lattice dynamics of the extremely reactive Sm and Eu metallic films at the end-stationID22N
A portable chamber for wide-angle XRD, GISAXS, and XPCS experiments, shown in Fig 1.6, is constructed totransfer the already prepared and characterized samples to other beamlines at the ESRF in order to apply thesetechniques in situ The chamber is based on CF100 tubes including three CF40 flanges for a vacuum gauge, a viewport, and
a simple evaporation source, allowing one to perform in situ deposition Two diametrically mounted entrance and exit ray Be windows with thickness of 200 mm are specially polished in order to minimize the small-angle X-ray scatteringfrom the windows, which is an important issue for the XPCS spectroscopy A Be dome for wide-angle X-ray diffraction(XRD) can be mounted on the top CF100 flange By a linear manipulator, the sample holder is vertically transferredbetween the positions for small- and wide-angle X-ray scattering Resistive heating and temperature control of thesample are provided via electrical feedthroughs on the manipulator The chamber is pumped by a 75 l s1ion getter pump
X-By using this chamber, the morphology of ultrathin Fe films on MgO (001) [36,37] was systematically investigatedemploying GISAXS at beamline ID10A of the ESRF
The entire UHV setup is mounted on a support table with horizontal (2 102
steps mm1) and vertical(2 105
steps mm1) motorized movements to allow for precise adjustment of the sample to the synchrotronbeam The chamber for in-situ NRS experiments at grazing incidence geometry and for X-ray reflectivity measure-ments is mounted on a two-circle goniometer (1 105
steps deg1for an angular range of5) The synchrotron
beam can be conditioned to a sample spot size as small as 15 250 mm2
by compound refractive lenses or by
Trang 361.3 SYNCHROTRON RADIATION-BASED M €OSSBAUER TECHNIQUES
In this section, an introduction into the most common synchrotron radiation M€ossbauer techniques is given emphasizing
on the applications to thin films A detailed elaboration of the methods can be found elsewhere [21,22,38]
In the following, atoms of the M€ossbauer isotopes bound in a crystal lattice with single-line resonances (vanishinghyperfine interactions) are considered If a photon with an energy matching that of the nuclear resonant transitionimpinges on a nucleus, the following absorption processes could take place: (i) the photon is resonantly absorbed by thenucleus without energy and momentum exchange with the crystal lattice, that is, elastic absorption The probability for anelastic absorption is given by the Lamb–M€ossbauer factor fLM (ii) The photon is resonantly absorbed by the nucleusinvolving energy and momentum transfers with the crystal lattice, that is, inelastic absorption The probability for thisprocess is defined as 1 fLM After the mean lifetime of the excited state the nucleus returns into the ground state When
a resonant photon is emitted (without energy and momentum exchange with the crystal lattice) and the system returnsinto a state that is indistinguishable from the state before the resonant absorption, this process is coherent scattering Theemission of conversion electrons or the fluorescent radiation leads to incoherent scattering since the system is movedback into a state that differs from the initial state
Each of these processes is considered separately below Selected examples of relevant in situ experiments on thinfilms illustrating the capabilities of the techniques are presented and discussed
1.3.1 Coherent Elastic Nuclear Resonant Scattering
1.3.1.1 Brief Theoretical Background In the case of coherent elastic scattering, a macroscopic ensemble ofscattering atoms can be replaced by a continuous medium characterized by an index of refraction n [39]:
For anisotropic media, the index of refraction depends on the polarization state of light and is represented by a 2 2matrix [40] In that case, the propagation of light in forward direction is described by the propagation matrix: F¼ k0þ f ,with f ¼ ð2p=k0ÞPiriMibeing the forward scattering matrix Then (1.2) can be written in more general form:
From (1.2) and (1.3) directly follows the relation between the index of refraction n and the forward scattering matrix f:
n¼ 1 þ f =k0
The propagation matrix F describes the modification of the wave field A upon propagation from coordinate z tocoordinate zþ dz It is a multidimensional matrix with dimension given by the number of the open scattering channels.This formalism is successfully applied not only to describe the propagation of light in forward direction but also in case ofX-ray diffraction from single crystals, and reflection from surfaces, thin films, and multilayers
While the structural arrangement of the scattering centers determines the dimension and the symmetries of F thatare of importance for calculating the matrix exponential eiFzin (1.3), the interaction of the photons with the atoms is given
by the atomic scattering length M In order to account for its energy dependence and the polarization mixing M(v) isdescribed by 2 2 matrix: M vð Þ ¼ E vð Þ þ N vð Þ E(v) represents the nonresonant contribution of the electronic chargescattering, and N(v) contains the contributions from the resonant nuclear scattering processes The electronic scatteringlength is then given by
Trang 37whereenandemare the polarization vectors, Z is the atomic number, r0is the classical electron radius, and stis the totalabsorption cross section.
For the case of 2L-pole resonance, the resonant scattering length is given by [41]
fast-FLM(v) These functions are the energy-dependent resonant strengths for transitions with a change of M in the magneticquantum number In the general case they are given by [41]
16s that
is essentially prompt In contrast, the width of nuclear resonances is in the range of 106–1012eV; therefore, thescattering proceeds on comparatively long timescales This is essential for separating both contributions one fromanother and for establishing the nuclear resonant scattering of synchrotron radiation as a time-domain spectroscopy.The expression (1.5) for the resonant scattering length can be expanded in powers of the unit vector m that definesthe magnetic quantization axis of the atom in the sample The resonant scattering length for an electric dipole transition(L¼ 1) gets the form [42]
N vð Þ
½ mn¼ 3
16pðem enÞ F½ þ1þ F1 i eð m enÞ m F½ þ1 F1þ eðm mÞ eðn mÞ 2F½ 0 Fþ1 F1: (1.7)For convenience, the subscript L is omitted
For the case of a magnetic dipole transition the role of the electric and magnetic fields of the radiation are interchangedand polarization vectors in Eq (1.7) have to be transformed according to the rulee ! e k0, where k0is a unit vector of thephoton wave vector The three terms in Eq (1.7) represent different polarization dependences The first term is notsensitive to the sample magnetization Its polarization dependence given byðem enÞ is that of nonresonant charge scattering.The second term describes circular dichroism because it depends on the difference between the resonant scatteringamplitudes Fþ1and F1 Since its polarization dependence isðem enÞ, it describes orthogonal scattering, for example,
s ! p and p ! s The third term is proportional to 2F0 Fþ1 F1 and describes linear magnetic dichroism Itspolarization dependence allows for all scattering processes within the given polarization basis
For a linear polarization basis, as it is frequently used in case of scattering experiments with synchrotron radiation,the matrix elements can be explicitly written as
Trang 38wave vector and its polarization state The off-diagonal elements describe the orthogonal scattering that turns incidents-polarization into p- polarization and vice versa Equation (1.8) is often used to describe the polarization effects innuclear resonant scattering experiments with synchrotron radiation.
Figure 1.7 sketches the grazing incidence scattering geometry used for studies of thin films and surfaces The set ofpolarization vectors (s, p), the polar and azimuthal angles (Q, f) describing the relative orientation of the wave vector k0
of the incident photons to the direction of the magnetization vector m of the sample are indicated
1.3.1.2 Time Spectra of the Nuclear Resonant Scattering In the following discussion, the case of the nuclearresonant scattering from the 14.413 keV resonance of57Fe is considered Due to its large absorption cross section, largeLamb–M€ossbauer factor, and its relevance in many fields of natural sciences, this resonance is one of the most widelyapplied M€ossbauer transitions It is a magnetic dipole transition with spins Ig¼ 1=2, Ie¼ 3=2, magnetic moments
mg¼ 0:091mN, me¼ 0:153mN of the ground and excited states, respectively, and a natural lifetime t0¼ 141 ns Inmagnetic materials the spin-polarized 3d electrons create a spin polarization of the s-electrons via the exchangeinteraction that leads to a strong magnetic field at the nucleus with a magnitude of 33.3 T in the case of ferromagnetica-Fe This magnetic field lifts the degeneracy of ground and excited states, resulting in a Zeeman splitting of the nuclearenergy levels According to the dipole selection rule M¼ me mg ¼ 0; 1, six allowed energy transitions, correspond-ing to six separated resonances, are observed, as depicted in Fig 1.8a In the case of a pure magnetic hyperfine interaction,the energetic positions of the resonances are given by
In nonmagnetic materials the degeneracy of the ground and excited states could, in general, be partly lifted as a result
of an electric field gradient (EFG) acting on the nucleus The sources of the EFG are the distributed electric chargesaround the M€ossbauer nuclei These could be either charges of the neighboring ions or ligands surrounding the resonantatom (lattice/ligand contribution), or charges in partially filled valence orbitals of the M€ossbauer atom (valence electroncontribution) The EFG is a second-rank symmetrical tensor and in a coordinate system related to its principal axes VXX,
VYY, and VZZ, selected so that Vj XXj Vj YYj Vj ZZj It is fully determined by the z-component VZZand by the asymmetryparameter h ¼ Vð XX VYYÞ=VZZ From the definition of the asymmetry parameter, and the fact that the Laplaceequation holds, that is, VXXþ VYYþ VZZ ¼ 0 since the sources of the EFG are fully external for the nucleus, for h applies:
0 h 1 Assuming a purely electric quadrupole interaction the energy levels of the excited state splits to two levels,
Trang 39resulting in two resonances (Fig 1.8b) with energy positions given by
E¼ E0eQVZZ
2
ffiffiffiffiffiffiffiffiffiffiffiffiffi
1þh23
r
with Q being the quadrupole moment of the nucleus
For the particular case of nuclear resonant scattering, the functions FMdefined by Eq (1.6) with L¼ 1 are given by thefollowing expression [22,43]:
describe the relative strength of the transitions
Since the nuclear resonant scattering is a coherent elastic process it is impossible to identify the scattering atom inthe sample Instead, for each individual resonant nucleus there is a small probability that this nucleus is excited Thesummation of all these small amplitudes gives the total probability amplitude for a photon to interact resonantly with thenuclei If the incident radiation pulse is short compared to the nuclear lifetimet0, these probability amplitudes exhibit thesame temporal phase As a result, a collectively excited state is created, where a single excitation is coherently distributedover the resonant atoms of the sample [44] The wave function of this collectively excited state is given by a coherent
FIGURE 1.8Energy dependence of the func-tionsFMin the case of nuclearresonant scattering from a mag-netic dipole resonance betweennuclear spinsIg¼ 1/2 and Ie¼ 3/2.(a) Pure magnetic hyperfineinteraction The energetic posi-tions apply to the case of a-57Fewith a magnetic hyperfine field
of 33.3 T The six dipole-allowedtransitions decompose into threedifferent polarization depen-dencies: the functionsF1,F0, and
Fþ1describe the scattering ofright-circular, linear, and left-cir-cular polarization, respectively.(b) Pure electric hyperfine inter-action (Reproduced from Ref 22with permission of Springer.)1.3 SYNCHROTRON RADIATION-BASED M €OSSBAUER TECHNIQUES 13
Trang 40where gj i ej i denotes the state in which the ith resonant atom at the position ri iis in its excited state ej i This collectivelyi
excited state is named nuclear exciton and exhibits remarkable optical properties resulting from the coherentsuperposition of states Below some important implications of the nuclear exciton concept on the time spectrum ofnuclear resonant scattering is given A detailed elaboration of the formalism can be found elsewhere [42,45]
In a nuclear resonant scattering experiment all resonant levels of the M€ossbauer nuclei in the sample aresimultaneously excited by a short pulse of synchrotron radiation, creating the nuclear exciton The time dependence
of the delayed intensity emitted upon de-excitation of the nuclear exciton in forward direction is the time spectrum ofnuclear forward scattering (NFS)
In the absence of magnetic and electric fields in the sample, the M€ossbauer spectrum consists of a single resonant line.The NFS time spectrum in this case is determined by an exponential decay of the nuclear exciton consisting of only oneresonant frequency In a semilogarithmic scale, the decay is a straight line with a slope defined by the lifetime of theexcited state Figure 1.9 illustrates a comparison between the M€ossbauer transmission spectrum (a), NFS spectra inenergy (b) and in time (c) domain, calculated for 0.2 mm thick stainless steel absorber (thin approximation holds, that is,self-absorption and multiple scattering effects are neglected) [46]
If hyperfine fields are acting on the nucleus, the degeneracy of the nuclear levels is lifted, leading to a splitting of thenuclear transition into six (magnetic hyperfine interaction, Fig 1.8a) or two (electric hyperfine interaction, Fig 1.8b)resonances The superposition of wave’s amplitudes with frequency differences corresponding to the various resonanttransitions leads to oscillations of the intensity in the temporal evolution of the exciton decay These oscillations arereferred to as quantum beats that contain information about the magnitude and orientation of the hyperfine fields.Figure 1.10 illustrates a comparison between the M€ossbauer transmission spectrum (a), NFS spectra in energy (b) and intime (c) domain, calculated for the case of electric quadrupole interaction in 0.2 mm thick stainless steel absorber [46].The time spectrum of NFS consists of quantum beats that result from coherent superposition of waves corresponding tothe two possible resonant transitions The quantum beat period is inversely proportional to the energy splitting of theresonant level, implying that small energy differences result in large quantum beat periods
A modulation of the delayed intensity additional to the quantum beats is very often encountered in the time spectra.Contrary to the quantum beats these oscillations, referred to as dynamical beats [46,47], are aperiodic and their periodsincrease with increasing time after excitation and decrease with increasing thickness of the sample Figure 1.9d–fillustrates the influence of the sample thickness on the transmission M€ossbauer spectrum, NFS energy spectrum, and NFStime spectrum, respectively These spectra are calculated for a single-line stainless steel absorber with a thickness of
3 mm [46] From the simulations it is obvious that in comparison to the thin absorber (Fig 1.9a–c), an increase of thesample thickness leads to significant changes in the energy and time-domain NFS spectra, while the change in transmissionM€ossbauer spectrum is a moderate broadening of the absorption line due to resonant self-absorption [48]
FIGURE 1.9
Calculated M€ossbauer
transmis-sion spectra (a), nuclear forward
scattering spectra in energy (b)
and in time (c) domain for the
case of single resonance in a
0.2 mm thick stainless steel foil
100% enriched in57Fe (d), (e),
and (f) are the corresponding
spectra for a 3.0 mm thick
stain-less steel foil 100% enriched in
57Fe (Reproduced from Ref 46
with permission of Kluwer
Aca-demic Publishers.)
14 1 IN SITU M €OSSBAUER SPECTROSCOPY WITH SYNCHROTRON RADIATION ON THIN FILMS