Table Of ContentSpringer Series on 1
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Editors: G. Ecker P. Lambropoulos H. Walther
Volume 1 Polarized Electrons 2nd Edition
By J. Kessler
Volume 2 Multiphoton Processes
Editors: P. Lambropoulos and S. J. Smith
Volume 3 Atomic Many-Body Theory 2nd Edition
By I. Lindgren and J. Morrison
Joachim Kessler
Polarized Electrons
Second Edition
With 157 Figures
Springer-Verlag Berlin Heidelberg GmbH
Professor Dr. Jo achim Kessler
WesWilische Wilhelms-Universitiit Miinster, Physikalisches Institut, DomagkstraBe 75
D-4400 Miinster, Fed. Rep. of Germany
Series Editors:
Professor Dr. Giinter Ecker
Ruhr-Universitiit Bochum, Institut fUr Theoretische Physik, Lehrstuhl 1
U niversitiitsstraBe 150
D-4630 Bochum-Querenburg, Fed. Rep. of Germany
Professor Peter Lambropoulos, Ph. D.
University of Crete, P. O. Box 470, Iraklion, Crete, Greece, and
Department of Physics, University of Southern California, University Park
Los Angeles, CA 90089-0484, USA
Professor Dr. Herbert Walther
Sektion Physik der Universitiit Miinchen, Am Coulombwall 1
D-8046 GarchingjMiinchen, Fed. Rep. of Germany
The first edition was published in 1976 in Texts and Monographs in Physics
Palarized Electrans
ISBN 978-3-642-05734-2 ISBN 978-3-662-02434-8 (eBook)
DOI 10.1007/978-3-662-02434-8
Library of Congress Cataloging in Publication Data. Kessler, Joachim, 1930~. Polarized electrons. (Springer series on atoms
and plasmas; vi). Blbhography: p. Includes mdex. l. Electrons~PolanzatlOn. 1. Title II Senes.
QC793.5.E628K47 1985 539.7'2Jl2 85-14804
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© Springer-Verlag Berhn Heidelberg 1976 und 1985
Originally published by Springer-Verlag Berlin Heidelberg New York Tokyo in 1985
Softcover reprint of the hardcover 2nd edition 1985
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Preface to the Second Edition
The rapid growth of the subject since the first edition ten years ago has made
it necessary to rewrite the greater part of the book. Except for the introductory
portion and the section on Mott scattering, the book has been completely
revised. In Chap. 3, sections on polarization violating reflection symmetry, on
resonance scattering, and on inelastic processes have been added. Chapter 4 has
been rewritten, taking account of the numerous novel results obtained in
exchange scattering. Chapter 5 includes the recent discoveries on photoelectron
polarization produced by unpolarized radiation with unpolarized targets and on
Auger-electron polarization. In Chap. 6, a further discussion of relativistic
polarization phenomena has been added to the book. The immense growth of
polarization studies with solids and surfaces required an extension and new
presentation of Chap. 7. All but one section of Chap. 8 has been rewritten and a
detailed treatment of polarization analysis has been included.
Again, a nearly comprehensive treatment has been attempted. Even so,
substantial selectivity among the wide range of available material has been
essential in order to accomplish a compact presentation. The reference list,
selected along the same lines as in the first edition, is meant to lead the reader
through the literature giving a guide for finding further references.
I want to express my indebtedness to a number of people whose help has been
invaluable. In addition to the persons referred to in the first edition I mention the
coworkers who have joined my group in the meantime. Their enthusiasm and
competence has been crucial to the success of our work. Among the results added
to this edition are those obtained by Drs. O. Berger, K. Franz, R. M611enkamp,
G. SchOnhense, A. Wolcke, and W. Wiibker in their theses. The close
cooperation on the theoretical aspects of polarization phenomena with Dr. K.
Blum and Dr. K. Bartschat was an invaluable asset for our polarized-electron
studies. The time-consuming task of updating my lectures and transforming
them into a book was achieved during a stay at the National Bureau of Standards
(NBS) in Gaithersburg, Maryland. I greatly enjoyed the warm hospitality of the
Electron Physics Group which has played a fundamental role in the rapid
expansion of polarized-electron physics in the past decade. I gratefully
acknowledge helpful comments and many stimulating discussions, both in the
past and present, with members of this group, in particular with the group leader
Dr. R. J. Celotta and with Dr. D. T. Pierce. The manuscript has benefitted again
from constructive suggestions by Dr. M. Reading, who critically, and with great
understanding, read the lectures underlying this book. Warm thanks are due to
VI Preface to the Second Edition
my secretary H. Nicolai, who typed the manuscript with unique reliability and,
despite innumerable changes, never lost her patience. I very much appreciate the
accuracy of the illustrations made by W. David and the photographical work by
K. Brinkmann. I am also grateful to the secretaries at NBS for their assistance in
completing the typescript. The help of M. Chirazi in proofreading is gratefully
acknowledged. Last but not least, I am pleased to acknowledge the constructive
cooperation with Dr. H. Lotsch and R. Michels, Springer-Verlag. The project
has been supported by Sonderforschungsbereich 216 of the Deutsche For
schungsgemeinschaft.
Washington D.C., January 1985 Joachim Kessler
From the Preface to the First Edition
This book deals with the physics of spin-polarized free electrons. Many aspects
of this rapidly expanding field have been treated in review articles, but to date a
self-contained monograph has not been available.
In writing this book, I have tried to oppose the current trend in science that
sees specialists writing primarily for like-minded specialists, and even physicists
in closely related fields understanding each other less than they are inclined to
admit. I have attempted to treat a modern field of physics in a style similar to that
of a textbook.
The presentation should be intelligible to readers at the graduate level, and
while it may demand concentration, I hope it will not require deciphering. If the
reader feels that it occasionally dwells upon rather elementary topics, he should
remember that this pedestrian excursion is meant to be reasonably self
contained. It was, for example, necessary to give a simple introduction to the
Dirac theory in order to have a basis for the discussion ofMott scattering - one of
the most important techniques in polarized-electron studies.
This monograph is intended to be an introduction to the field of polarized
electrons and not a replacement for review articles on the individual topics
discussed. It does not include electron polarization in f3 decay, a field which has
been covered in other books. Areas such as electron spin resonance, in which it is
not the spins of free electrons that are oriented, are beyond the scope of this
book. Well-established areas, like Mott scattering, have naturally been treated in
more detail than areas that are just starting to develop, such as high-energy
electron scattering. Ideas or general results that have not been quantitatively
established, theoretically or experimentally, have not been considered, since
physical results must be put on a quantitative basis.
In keeping with the introductory character of the book, the main purpose of
the reference lists is to aid the reader in completing or supplementing the
information in certain sections. The newcomer to the field should refer to the
review articles wherever they exist. Primary sources have been cited if they are
directly referred to in the text or if they have not yet been listed in review papers
or other references.
It is a pleasure to express my gratitude to the many people who have
contributed to the completion of this project. Several sections have been
considerably influenced by the ideas and achievements of my coworkers -
particularly Drs. G. F. Hanne, U. Heinzmann, and K. Jost - with whom, over
the years, I have studied many of the topics discussed. The generous hospitality
VIII From the Preface to the First Edition
of the Joint Institute for Laboratory Astrophysics gave me the chance to write
this book. The stimulating atmosphere of JILA which I enjoyed during my stay
as a Visiting Fellow provided the ideal setting for this project. I gratefully
acknowledge the excellent work of the JILA editorial office; thanks to the
numerous helpful suggestions from L. Volsky and the typing skill ofO. Romey,
the transformation (in record time) of my stacks of messy, marked-up sheets
into a beautiful manuscript was a joy to behold. I am particularly grateful to
Dr. M. Lambropoulos who was kind enough to read the entire manuscript; her
constructive criticisms have improved it considerably. Discussions with Prof. H.
Merz in Munster and with many colleagues in Boulder have helped to clarify
several passages. I appreciate the application and conscientiousness of H.
Oerberon and B. 06hlsdorf who prepared most of the illustrations. I am also
grateful for the assistance of E. Russel and Dr. C. B. Lucas in translating a
number of my lectures which I used in preparing parts of the manuscript. Finally,
I wish to thank those listeners, at home and abroad, who, by their reactions to my
lectures, have helped to clarify this presentation.
Boulder, Colorado, August, 1975 Joachim Kessler
Contents
1. Introduction . . . . . . . . . . . . 1
1.1 The Concept of Polarized Electrons 1
1.2 Why Conventional Polarization Filters Do Not Work with
Electrons . . . . . . . . . 2
2. Description of Polarized Electrons 7
2.1 A Few Results from Elementary Quantum Mechanics 7
2.2 Pure Spin States . . . . . . . . . . . . . . . . 9
2.3 Statistical Mixtures of Spin States. Description of Electron Polari-
zation by Density Matrices . . . . . . . . . .. . . . . 14
3. Polarization Effects in Electron Scattering Caused by Spin-Orbit
Interaction ..................... 20
3.1 The Dirac Equation and Its Interpretation . . . . . 20
3.2 Calculation of the Differential Scattering Cross Section 31
3.3 The Role of Spin Polarization in Elastic Scattering . 38
3.3.1 Polarization Dependence of the Cross Section. 38
3.3.2 Polarization of an Electron Beam by Scattering 41
3.3.3 Behavior of the Polarization in Scattering . . 42
3.3.4 Double Scattering Experiments . . . . . . . 46
3.4 Simple Physical Description of the Polarization Phenomena 49
3.4.1 Illustration of the Rotation of the Polarization Vector 49
3.4.2 Illustration of the Change in the Magnitude of the Polar
ization Vector . . . . . . . . . . . . . . . . . . . 50
3.4.3 Illustration of the Asymmetry in the Scattering of a Polar-
ized Beam. . . . . . . . . . . . . . . . . . . . . 53
3.4.4 Transversality of the Polarization as a Consequence of
Parity Conservation. Counterexample: Longitudinal Polar-
ization in f3 Decay . . . . . . . . . . . 53
3.4.5 Equality of Polarizing and Analyzing Power . 56
3.5 Polarization Violating Reflection Symmetry 58
3.6 Quantitative Results . . 62
3.6.1 Coulomb Field. . 62
3.6.2 Screened Coulomb Field 64
X Contents
3.7 Experimental Setups . . . . . . . 71
3.7.1 Double Scattering Experiments 71
3.7.2 Triple Scattering Experiments 74
3.8 Resonance Scattering 76
3.9 Inelastic Scattering . . . . . . . . 79
4. Polarization Effects Caused by Exchange Processes in Electron-
Atom Scattering . . . . . . . . . . . . . . . . . . 84
4.1 The Polarization Mechanism in Exchange Scattering. . . 84
4.2 The Composite Spin Space of Electron and Target . . 91
4.3 Cross Section and Polarization in Elastic Exchange Scattering. 97
4.4 Polarization Experiments in Elastic Exchange Scattering. 102
4.5 Inelastic Exchange Processes with One-Electron Atoms . .. 107
4.5.1 Spin-Dependent Electron-Impact Ionization . . . .. 107
4.5.2 Spin-Dependent Effects in Electron-Impact Excitation. 109
4.5.3 Emission of Circularly Polarized Light Induced by Excita-
tion with Polarized Electrons . . . . . . . . . . . . . 117
4.6 General Laws for Polarization of Light Emitted After Excitation
by Polarized Electrons . . . . . . . . . . . . . . 121
4.7 Inelastic Exchange Processes with Two-Electron Atoms 127
4.8 M0ller Scattering . . . . . . . . . . . . . . . . 137
5. Polarized Electrons by Ionization Processes 142
5.1 Photoionization of Polarized Atoms. 142
5.2 The Fano Effect and Its Consequences 144
5.2.1 Theory of the Fano Effect. . . 144
5.2.2 Illustration of the Fano Effect. Experimental Results. 151
5.2.3 Polarized Electrons Ejected from Unpolarized Atoms by
Unpolarized Light . . . . . . . . . . . 156
5.2.4 The "Perfect" Photoionization Experiment 162
5.3 Ionizing Transitions of Excited Atomic States. 165
5.3.1 Autoionizing Transitions 165
5.3.2 Auger Transitions . . . . . . . 170
5.4 Multiphoton Ionization . . . . . . . . 173
5.5 Collisional Ionization of Polarized Atoms 180
5.5.1 Collisional Ionization of Polarized Metastable Deuterium
Atoms 180
5.5.2 Penning Ionization . . . . . . . . . . . . . 182
6. Further Relativistic Processes Involving Polarized Electrons 186
6.1 Bremsstrahlung and Other Relativistic Electron-Photon Processes 186
6.2 Spin-Flip Synchrotron Radiation . . . . . . . . . . . . . . 191
