The investigation of scattering phenomena is a major theme of modern physics. A scattered particle provides a dynamical probe of the target system. The practical problem of interest here is the scattering of a low energy electron by an N-electron atom. It has been difficult in this area of study to achieve theoretical results that are even qualitatively correct, yet quantitative accuracy is often needed as an adjunct to experiment. The present book describes a quantitative theoretical method, or class of methods, that has been applied effectively to this problem. Quantum mechanical theory relevant to the scattering of an electron by an N-electron atom, which may gain or lose energy in the process, is summarized in Chapter 1. The variational theory itself is presented in Chapter 2, both as currently used and in forms that may facilitate future applications. The theory of multichannel resonance and threshold effects, which provide a rich structure to observed electron-atom scattering data, is presented in Chapter 3. Practical details of the computational implementation of the variational theory are given in Chapter 4. Chapters 5 and 6 summarize recent appli cations of the variational theory to problems of experimental interest, with many examples of the successful interpretation of complex structural fea tures observed in scattering experiments, and of the quantitative prediction of details of electron-atom scattering phenomena.

This book brings together the essential ideas and methods behind applications of variational theory in theoretical physics and chemistry. The emphasis is on understanding physical and computational applications of variational methodology rather than on rigorous mathematical formalism. The text begins with an historical survey of familiar variational principles in classical mechanics and optimization theory, then proceeds to develop the variational principles and formalism behind current computational methodology for bound and continuum quantum states of interacting electrons in atoms, molecules, and condensed matter. It covers multiple-scattering theory, including a detailed presentation of contemporary methodology for electron-impact rotational and vibrational excitation of molecules. The book ends with an introduction to the variational theory of relativistic fields. Ideal for graduate students and researchers in any field that uses variational methodology, this book is particularly suitable as a backup reference for lecture courses in mathematical methods in physics and theoretical chemistry.

On March 26-27, 1980, a symposium organized by one of us (P. P. ) was held at the l79th American Chemical Society National ~1eeting in Houston, Texas, under the sponsorship of the Theoretical Chemistry Subdivision of the Division of Physical Chemistry. The symposium was entitled "The Role of the Electrostatic Potential in Chemistry," and it served as a stimulus for this book. The original scope and coverage have been broadened, however; included here, in addition to contributions from the eleven invited symposium speakers and two of the poster-session participants, are four papers that were specially invited for this book. Furthermore, several authors have taken this opportunity to present at least partial reviews of the areas being discussed. Most of the manuscripts were completed in the late spring and early summer of 1980. We hope that this book will achieve two goals: First, we are trying to provide an overall picture, including recent advances, of current chemical research, both fundamental and applied, involving the electrostatic potential. Second, we want to convey an appreci ation of both the powers and also the limitations of the electro static potential approach. In order to achieve these goals, we have selected contributors whose research areas provide a very broad coverage of the field. Throughout the book, we have used a. u.

The latest volume in the highly acclaimed series addresses atomic collisions, assessing the status of the current knowledge, identifying deficiencies, and exploring ways to improve the quality of cross-section data.Eleven articles, written by foremost experts, focus on cross-section determination by experiment or theory, on needs in selected applications, and on efforts toward the compilation and dissemination of data. This is the first volume edited under the additional direction of Herbert Walther. Presents absolute cross sections for atomic collisions Uses benchmark measurements and benchmark calculations Discusses needs for cross-section data in applications Contains a guide to data resources, bibliographies, and compendia

Professor Philip G. Burke, CBE, FRS formally retired on 30 September 1998. To recognise this occasion some of his colleagues, friends, and former students decided to hold a conference in his honour and to present this volume as a dedication to his enormous contribution to the theoretical atomic physics community. The conference and this volume of the invited talks reflect very closely those areas with which he has mostly been asso- ated and his influence internationally on the development of atomic physics coupled with a parallel growth in supercomputing. Phil’s wide range of interests include electron-atom/molecule collisions, scattering of photons and electrons by molecules adsorbed on surfaces, collisions involving oriented and chiral molecules, and the development of non-perturbative methods for studying multiphoton processes. His devel- ment of the theory associated with such processes has enabled important advances to be made in our understanding of the associated physics, the interpretation of experimental data, has been invaluable in application to fusion processes, and the study of astrophysical plasmas (observed by both ground- and space-based telescopes). We therefore offer this volume as our token of affection and respect to Philip G. Burke, with the hope that it may also fill a gap in the literature in these important fields.

The Advances in Chemical Physics series provides the chemical physics and physical chemistry fields with a forum for critical, authoritative evaluations of advances in every area of the discipline. Filled with cutting-edge research reported in a cohesive manner not found elsewhere in the literature, each volume of the Advances in Chemical Physics series serves as the perfect supplement to any advanced graduate class devoted to the study of chemical physics.

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.

"Proceedings of the Ninth International Conference on Computing Methods in Applied Sciences and Engineering, Paris, France, January 29-February 2, 1990"--T.p. verso.