A comprehensive and up-to-date text in the field of electron scattering and ionization, covering fundamentals, experimental background, quantum scattering theories and applications. Electron impact ionization of atoms and molecules in ground/metastable states is discussed comprehensively. The text covers electron scattering phenomena for diatomic and common molecules, polyatomic molecules and radicals including hydro-carbons, fluoro-carbons and other larger molecules together with relevant radical species in detail. Applications of electron impact ionization and excitation in gaseous or plasma and condensed matter is discussed in a separate chapter. Recent advances in the field of electron molecule scattering and ionization for polyatomic molecules is covered extensively.

There is a unity to physics; it is a discipline which provides the most fundamental understanding of the dynamics of matter and energy. To understand anything about a physical system you have to interact with it and one of the best ways to learn something is to use electrons as probes. This book is the result of a meeting, which took place in Magdalene College Cambridge in December 2001. Atomic, nuclear, cluster, soHd state, chemical and even bio- physicists got together to consider scattering electrons to explore matter in all its forms. Theory and experiment were represented in about equal measure. It was meeting marked by the most lively of discussions and the free exchange of ideas. We all learnt a lot. The Editors are grateful to EPSRC through its Collaborative Computational Project program (CCP2), lOPP, the Division of Atomic, Molecular, Optical and Plasma Physics (DAMOPP) and the Atomic Molecular Interactions group (AMIG) of the Institute of Physics for financial support. The smooth running of the meeting was enormously facilitated by the efficiency and helpfulness of the staff of Magdalene College, for which we are extremely grateful. This meeting marked the end for one of us (CTW) of a ten-year period as a fellow of the College and he would like to take this opportunity to thank the fellows and staff for the privilege of working with them.

The papers collected in this volume have been presented during a workshop on "Electron-Atom and Molecule Collisions" held at the Centre for Interdisciplinary Studies of the University of Bielefeld in May 1980. This workshop, part of a larger program concerned with the "Properties and Reactions of Isolated Molecules and Atoms," focused on the theory and computational techniques for the quanti tative description of electron scattering phenomena. With the advances which have been made in the accurate quantum mechanical characterisation of bound states of atoms and molecules, the more complicated description of the unbound systems and resonances important in electron collision processes has matured too. As expli cated in detail in the articles of this volume, the theory for the quantitative explanation of elastic and inelastic electron molecule collisions, of photo- and multiple photon ionization and even for electron impact ionization is well developed in a form which lends itself to a complete quantitative ab initio interpretation and pre diction of the observable effects. Many of the experiences gained and the techniques which have evolved over the years in the com putational characterization of bound states have become an essential basis for this development. To be sure, much needs to be done before we have a complete and detailed theoretical understanding of the known collisional processes and of the phenomena and effects, which may still be un covered with the continuing refinement of the experimental tech niques.

This volume contains the invited papers and selected contributed papers presented at the International Symposium on 'Electron-Molecule Scattering and Photoionization' held at SERC's Daresbury Laboratory, Cheshire, England from 18th to 19th July, 1987. This Symposium was a Satellite Meeting to the XVth International Conference on the Physics of Electronic and Atomic Collisions (ICPEAC I and follows a tradition of Satellite Meetings i. n related areas of collisions held in association with previous ICPEAC's. In order to make this volume as representative of the Symposium as possible 'Hot Topics' presented orally at the meeting together with a few papers selected by the Programme Committee from the contributed posters are included. The Editors are grateful to the authors for responding rapidly to the invitation to submit their contri butions for inclusion in the volume, as indeed they are grateful to all the authors for the high quality of their contributions. The Symposium brought together over 100 scientists from many countries and from broad interdisciplinary backgrounds to hear about current rapid advances in electron-molecule scatteri. ng and photoioniza tion. These advances have been stimulated on the experimental side by the increasing availability of electron beams with millivolt energy resolution, by synchrotron radiation sources and by intense tunable lasers. On the theoretical side the introduction of new computational methods enables accurate predictions to be made, resulting in a new and deeper understanding of the basic physical processes involved.

Benjamin Bederson contributed to the world of physics in many areas: in atomic physics, where he achieved renown by his scattering and polarizability experiments, as the Editor-in-Chief for the American Physical Society, where he saw the introduction of electronic publishing and a remarkable growth of the APS journals, with ever increasing world-wide contributions to these highly esteemed journals, and as the originator of a number of international physics conferences in the fields of atomic and collision physics, which are continuing to this day. Bederson was also a great teacher and university administrator. The first part of this volume of Advances in Atomic, Molecular, and Optical Physics (AAMOP), entitled Benjamin Bederson: Works, Comments and Legacies, contains articles written from a personal perspective. His days at Los Alamos during World War II, working on the A bomb, are recounted by V. Fitch. H. Walther writes on the time when both were editors of AAMOP. H. Lustig, E. Merzbacher and B. Crasemann, with whom Bederson had a long-term association at the American Physical Society, contribute their experiences, one of them in the style of a poem. C.D. Rice recalls his days when he was Dean of the Faculty of Arts and Science at NYU, and the education in physics that he received from Bederson, then Dean of the Graduate School. The contribution by R. Stuewer is on Bederson as physicist historian (his latest interest). N. Lane draws some parallels between "two civic scientists, Benjamin Bederson and the other Benjamin". The papers are introduced by H.H. Stroke, in an overview of Bederson's career. A biography and bibliography are included. The second part of the volume contains scientific articles on the Casimir effects (L. Spruch), dipole polarizabilities (X. Chu, A. Dalgarno), two-electron molecular bonds revisited (G. Chen, S.A. Chin, Y. Dou, K.T. Kapale, M. Kim, A.A. Svidzinsky, K. Uretkin, H. Xiong, M.O. Scully, and resonance fluorescence of two-level atoms (H. Walther). J. Pinard and H.H. Stroke review spectroscopy with radioactive atoms. T. Miller writes on electron attachment and detachment in gases, and, with H. Gould, on recent developments in the measurement of static electric dipole polarizabilities. R. Celotta and J.A. Stroscio's most recent work on trapping and moving atoms on surfaces is contributed here. C.C. Lin and J.B. Borrard's article is on electron-impact excitation cross sections. The late Edward Pollack wrote his last paper for this volume, Atomic and Ionic Collisions. L. Vuskovic and S. Popovi ́c write on atomic interactions in a weakly ionized gas and ionizing shock waves. The last scientific article is by H. Kleinpoppen, B. Lohmann, A. Grum-Grzhimailo and U. Becker on approaches to perfect/complete scattering in atomic and molecular physics. The book ends with an essay on teaching by R.E. Collins. - Benjamin Bederson - Atomic Physicist, Civil Scientist - The Physical Review and Its Editor - Los Alamos in World War II - View from Below - Physics in Poetry - Casimir Effects - Pedagogical Notes - Atomic Physics in Collisions, Polarizabilities, Gases, Atomic Physics and Radioactive Atoms - Molecular Bond Revisited - Resonance Fluorescence in 2-Level Atoms - Trapping and Moving Atoms on Surfaces

Computational Atomic Physics deals with computational methods for calculating electron (and positron) scattering from atoms and ions, including elastic scattering, excitation, and ionization processes. Each chapter is divided into abstract, theory, computer program with sample input and output, summary, suggested problems, and references. An MS-DOS diskette is included, which holds 11 programs covering the features of each chapter and therefore contributing to a deeper understanding of the field. Thus the book provides a unique practical application of advanced quantum mechanics.

Scattering phenomena play an important role in modern physics. Many significant discoveries have been made through collision experiments. Amongst diverse kinds of collision systems, this book sheds light on the collision of an electron with a molecule. The electron-molecule collision provides a basic scattering problem. It is scattering by a nonspherical, multicentered composite particle with its centers having degrees of freedom of motion. The molecule can even disintegrate, Le., dissociate or ionize into fragments, some or all of which may also be molecules. Although it is a difficult problem, the recent theoretical, experimental, and computational progress has been so significant as to warrant publication of a book that specializes in this field. The progress owes partly to technical develop ments in measurements and computations. No less important has been the great and continuing stimulus from such fields of application as astrophysics, the physics of the earth's upper atmosphere, laser physics, radiation physics, the physics of gas discharges, magnetohydrodynamic power generation, and so on. This book aims at introducing the reader to the problem of electron molecule collisions, elucidating the physics behind the phenomena, and review ing, to some extent, up-to-date important results. This book should be appropri ate for graduate reading in physics and chemistry. We also believe that investi gators in atomic and molecular physics will benefit much from this book.

This monograph was written while the author was a visitor at the Center for Theoretical Studies at the University of Miami, Coral Gables, Florida. The author wishes to thank Professor Behram Kursunoglu for the warm hospitality extended to him at the Center and to acknowledge the many interesting and fruitful discussions which he had with other visitors and with members of staff at the Center. Philip G. Burke v Contents 1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2. Scattering by a Short-Range Potential. . . . . . . . . . . . . . . 5 3. Scattering by a Coulomb Potential. . . . . . . . . . . . . . . . . . 11 4. Scattering by a Spin-Orbit Potential . . . . . . . . . . . . . . " 17 5. Scattering by One-Electron Atoms. . . . . . . . . . . . . . . . . . 23 6. Low-Energy Effective-Range Theory. . . . . . . . . . . . . . . . 39 7. Bound States and Resonances. . . . . . . . . . . . . . . . . . . . . . 55 8. Variational Methods and Bound Principles. . . . . . . . . . 75 9. Integral Equation Methods and the Born Approximation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 10. Semiclassical and Eikonal Methods . . . . . . . . . . . . . . . . . 117 Appendix. The Coupling of Angular Momenta . . . . . . . . . . . 127 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 vii 1 Introduction In this monograph we study the scattering of a particle by a potential field with particular reference to elastic electron scat tering by a neutral atom or by an ion. This subject is clearly of interest in its own right as a branch of quantum mechanical scattering theory. However, it also serves as an introduction to many of the basic theoretical concepts which are used in inelastic electron scattering and ionization. Consequently this mono graph can be viewed as an introduction to texts where these subjects are treated.