Table Of ContentRadiationless Processes
NATO ADVANCED STUDY INSTITUTES SERIES
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Radiationless Processes
Edited by
Baldassare DiBartolo
Department ofP hysics
Boston College
Assistant Editor
Velda Goldberg
Department of Physics
Boston College
PLENUM PRESS • NEW YORK AND LONDON
Published in cooperation with NATO Scientific Affairs Division
Library of Congress Cataloging in Publication Data
Nato Advanced Study Institute on Radiationless Processess, Erice, Italy, 1979.
Radiationless processes.
(Nato advanced study institutes series: series B, Physics; v. 62)
Includes bibliographical references and index.
1. Radiationless transitions-Congresses. 2. Molecular theory-Congresses. I. Di
Bartolo, Baldassare. II. Goldberg, Velda. III. Title. IV. Series.
QC795.8.15N371979 541.2'24 80-21961
ISBN-13: 978-1-4613-3176-6 e-ISBN-13: 978-1-4613-3174-2
DOl: 10.1007/978-1-4613-3174-2
Proceedings of the NATO Advanced Study Institute on Radiationless Processes,
held at the Ettore Majorana Centre for Scientific Culture, Erice, Sicily, Italy,
November 18-December 1, 1979.
© 1980 Plenum Press, New York
A Division of Plenum Publishing Corporation
227 West 17th Street, New York, N.Y. 10011
Softcover reprint of the hardcover 1st edition 1980
All righ ts reserved
No part of this book may be reproduced, stored in a retrieval system, or transmitted,
in any form or by any means, electronic, mechanical, photocopying, microfilming,
recording, or otherwise, without written permission from the Publisher
God loves the search for truth
by means of reason and science
Frederick II (1194-1250)
Holy Roman Emperor
King of Germany and Sicily
PREFACE
This book presents an account of the NATO Advanced Study
Institute on "Radiationless Processes," held in Erice, Italy, from
November 18 to December 1, 1979. This meeting was organized by
the International School of Atomic and Molecular Spectroscopy of
the "Ettore Majorana" Centre for Scientific Culture.
The objective of the Institute was to formulate a comprehensive
treatment of the various processes by which molecules and crystals
in excited electronic levels relax nonradiatively to the ground
level.
A total of 83 participants came from 62 laboratories and 22
nations (Australia, Belgium, Brasil, Canada, Czechoslovakia, France,
F. R. Germany, Greece, Hungary, India, Ireland, Israel, Italy,
Mexico, The Netherlands, Poland, Portugal, Switzerland, Turkey,
United Kingdom, United States, and U.S.S.R.). The secretaries of the
Institute were: Velda Goldberg for the scientific aspects and
Antonino La Francesca for the administrative aspects of the meeting.
Eleven series of lectures for a total of 36 hours were given.
Nine "long" seminars and 7 "short" seminars were also presented. In
addition, two informal seminars and 2 round-table discussions were
held.
After an introductory overview of the theory of radiation1ess
processes, the Institute dealt firstly with the interaction of
electrons with the distribution of vibrational modes in simple
molecules, then with the increasingly complex situation found in
large lsolated molecules, gnd finally with the coupling of excited
electrons with the continuous phonon distribution in insulating
solids.
The theory of nonradiative relaxation was also considered in
two areas of current technological importance, namely that of
vii
viii PREFACE
luminescence of phosphors and that of solid-state lasers. Non
radiative transitions in semiconductors and defect structures in
phosphors produced by radiationless processes were also treated.
Specific aspects of the theory were also presented in seminar
form together with several applications to various areas of current
interest.
I would like to acknowledge the sponsorship of the Institute
by the North Atlantic Treaty Organization and the very valuable
assistance received from Dr. Mario di Lullo, Head of the NATO
Advanced Study Institutes Programme. I wish to acknowledge also
the sponsorship by the Italian Ministry of Public Education, the
Italian Ministry of Scientific and Technological Research, the
Regional Sicilian Government and the Department of Physics of
Boston College.
I would like to thank for their help Prof; A. Zichichi,
Director of the "Ettore Majorana" Centre for Scientific Culture,
Dr. A. Gariele, Ms. P. Savalli, and all the personnel of the
"Ettore Majorana" organization in Erice, Prof. R. L. Carovillano,
chairman of the Department of Physics at Boston College, Prof.
V. Adragna, Dr. G. Denaro and Rag. M. Strazzera.
I would like to thank the members of the organizing committee
of the meeting (Prof. F. Williams and Dr. F. Auzel) and Prof. A.
Scharmann for their valuable help and advice.
I am especially grateful to my friends and collaborators, A.
La Francesca and V. Goldberg, who helped me tremendously with the
various aspects of the meeting. V. Goldberg was the assistant
editor of this book: without her patient and intelligent work,
these proceedings could not have been produced.
It is difficult to describe in words the interest and the
enthusiasm with which everybody participated in the proceedings of
this Institute. I brought with me many fond memories of the two
weeks I spent in Ericedirecting this meeting. I feel richer for
the scientific knowledge I acquired by listening to the lectures
of my learned colleagues. I feel also richer from the human and
spiritual points of view for having shared this experience with so
many fine people. I am sure we shall meet again soon.
Erice, December, 1979 B. Di Bartolo
Editor and Director of the Institute
CONTENTS
PRESENT TRENDS IN THE THEORY OF RADIATIONLESS
PROCESSES ••.•..•••••• 1
F. Williams, D.E. Berry, and J.E. Bernard
Abstract
I. Introduction 1
II. The Born-Oppenheimer Adiabatic Approximation 3
III. The Radiationless Transition ••.•.•.• 5
III.A. Introduction to Radiationless Transitions 5
III.B. Some Types of Radiationless Transitions 6
III.C. Radiationless Transitions Revisited 7
III.D. Radiationless Electronic Transitions 7
III.E. The Problem of Radiationless Decay. 9
IV. Some General Methods in Radiationless Decay
Calculations • • . • . . . . • . . • . 11
IV.A. Introduction .•.••...• 11
IV.B. The Landau-Zener-Rosen Method 11
IV.C. The Density Matrix Method 14
IV.D. Effective Hamiltonian and Correlation
Function Methods • 16
IV.E. Summary . . . • • 17
Appendix A. Glossary of Terms 21
Appendix B. Bibliography • . 27
SPECTROSCOPY AND RADIATIONLESS DEACTIVATION 39
B. Di Bartolo
Abstract •••• 39
I. Introduction. 39
II. Quantum Theory of a Molecular System 40
II.A. The Hamiltonian • . . . . • 40
II.B. The Meaning of the Adiabatic Approximation 42
II.C. The Adiabatic Approximation and the Role
of Symmetry • • • • • • • • • • • 43
ix
x CONTENTS
III. Radiation Field and Radiative Processes 47
III.A. The Radiation Field. Classical
Description . . . • • . • . . • 47
IILB. The Quantum Radiation Field 51
IILC. Interaction of a Radiation Field with
Charged Particles .. . • . • . 51
IILD. Absorption and Emission Processes 52
III.E. Absorption and Emission in the Electric
Dipole Approximation . • . . • • . . • • 55
IV. Interaction of a Radiation Field with a Molecular
System 58
IV.A. The Franck-Condon Principle • • • • • • 58
IV.B. Probability of Radiative Transitions • . 64
IV.C. Integrated Intensity of a Vibronic Band 66
V. Simple Models for Molecular Spectra 68
V.A. Radiative Transitions in Diatomic
Molecules 68
V.B. The Formula of Huang and Rhys 73
VI. Nonradiative Processes 75
VI.A. Deviations from the Adiabatic
Approximation ......• 75
VI.B. Mechanisms for Radiation1ess
Transitions ••. . • . 77
VI.C. Radiation1ess Transition Probability
per Unit Time 78
VII. Multiphonon Relaxation of Ions in Solids 81
VII.A. Introduction • 81
VILB. Generalization of the Franck-Condon
Approximation • . . . • . 84
VILC. Radiationless Transitions 85
References . 87
SPECTROSCOPY AND RADIATIONLESS PROCESSES IN
SIMPLE MOLECULES . . . •. .•.....• 89
D.A. Ramsay
Abstract
I. General Considerations 89
II. Selection Rules 92
II.A. Diatomic Molecules. 92
II.B. Polyatomic Molecules 93
CONTENTS xi
III. Examples
IILA. CN 94
IILB. ~ 95
IILC. C02 97
III. D. .!!2CO 97
IV. Predissociation 98
V. Singlet-Triplet Perturbations in Formaldehyde 98
References 101
ELECTRONIC RELAXATION IN LARGE MOLECULES • 103
J. Jortner
Abstract 103
I. Prologue 104
II. History 107
III. Methodology 112
IV. Basic Molecular Model 119
V. Time Evolution •••• 121
VI. Beyond the Golden Rule 125
VII. Observables 133
VIII. Absorption Lineshapes 134
IX. The Rise and Fall of Excited States of
Large Molecules 140
X. Future Trends 146
References 151
INTERSYSTEM CROSSING IN COMPLEX MOLECULES 157
R.G. Pappalardo
Abstract 157
I. Introduction. 158
II. Relaxation of Complex Molecules in the Gaseous
Phase • • • • • . • • • • . • ••• • 159
