H. KLEINPOPPEN AND J. F. WILLIAMS It has only very recently become possible to study angular correlations and coherence effects in different areas of atomic collision processes: These investigations have provided us with an analysis of experimental data in terms of scattering amplitudes and their phases, of target parameters such as orientation, alignment, and state multipoles, and also of coherence parameters (e. g. , the degree of coherence of excita tion). In this way the analysis of electron-photon, ion-photon, atom-photon, or electron-ion coincidences from electron-atom, ion-atom, or atom-atom collisional excitation has led to a breakthrough such that the above quantities represent most crucial and sensitive tests for theories of atomic collision processes. Similarly, the powerful (e, 2e) experiments (electron-electron coincidences from impact ionization of atoms) have attracted much attention where improved experimental studies and detailed theoretical description provide a wealth of information on either the col lisional ionization process or the atomic structure of the target atom. Interference effects, many-electron correlations, and energy and angular momen tum exchange between electrons in a Coulomb field playa decisive role in the under standing of postcollision interactions. New results on coherence effects and orienta tion and alignment in collisional processes of ions with surfaces and crystal lattices show links to relevant interference phenomena in atomic collisions. In small-angle elastic electron-atom scattering the effect of angular coherence can be studied in a crossed beam experiment.

Advances in Atomic and Molecular Physics

In recent years, the impact of new experimental techniques (e.g., nuclear physics methods, availability of high-intensity light sources) as well as an increasing demand for atomic collision data in other fields of physics (e.g., plasma physics, astrophysics, laser physics, surface physics, etc.) have stimulated a renewed, strong interest in atomic collision research. Due to the explosive development of the various fields, scientists often even have dif ficulty in keeping up with their own area of research; as a result, the overlap between different fields tends to remain rather limited. Instead of having access to the full knowledge accumulated in other fields, one uses only the small fraction which at the moment seems to be of immediate importance to one's own area of interest. Clearly, many fruitful and stimulating ideas are lost in this way, causing progress to be made much more slowly than it could be. Atomic col lision physics is no exception to this rule. Although it is of basic interest to many other areas, it is mostly regarded merely as a (nonetheless important) tool by which to gain additional information.

This volume contains the invited papers delivered at the International Symposium on Correlation and Polarization in Electronic and Atomic Collisions. Experts in the field give the current state and outline future directions of research providing a better fundamental understanding of electron-atom and atom(ion)-atom interactions. Correlation and coherence effects in inelastic collisions as manifested by the observation of photon polarization and photon and particle angular distributions are discussed together with spin dependent effects using spin polarized electron beams.

During the last two decades the experimental investigation of atomic coherence phenomena has made rapid progress. Detailed studies have been performed of angular correlations, spin polarization effects, angular momen tum transfer, and the alignment parameters which characterize the charge cloud of excited atoms. The enormous growth in the number of these investigations was made possible through substantial development and application of new experimental technology, the development of sophisti cated theoretical models and numerical methods, and a fine interplay between theory and experiment. This interplay has resulted in a deeper understanding of the physical mechanisms of atomic collision processes. It is the purpose of the chapters in this book to provide introductions for nonspecialists to the various fields of this area as well as to present new experimental and theoretical results and ideas. The interest in spin-dependent interactions in electron-atom scattering has a long history; it dates back to the early investigations of Mott in 1929. While the more traditional measurements in this field were concerned with the determination of spin polarization and asymmetries, the range of investi gations has been expanded enormously during the last few years and now includes many observables sensitive to one or more of the various spin dependent interactions. The understanding of these effects requires a theoretical description of the orientation and alignment parameters of the target atoms, of the forma tion of resonances, of the influence of electron-exchange processes, and of the relativistic interactions inside the atom and between projectile and target.

CD-ROM contains: articles in PDF format and "charge cloud movies" in Quick Time format.

The Hans Kleinpoppen Symposium on "Complete Scattering Experiments" th was held in honor of Hans Kleinpoppen’s 70 birthday. It took place in Il Ciocco, Italy. The symposium had two purposes: to present the work that Hans Kleinpoppen has done or initiated during his remarkable scientific career, and to bring people from various fields together who perform complete scattering experiments. Hans Kleinpoppen’s work included electron and photon impact experiments which were accompanied by studies of entangled states - a field of high current interest. Representatives from each of these fields gave excellent lectures on their particular subjects, and many discussions that started during the sessions were continued later in the relaxed atmosphere of the Il Ciocco resort. The breathtaking view of the beautiful landscape will be an unforg- table memory to all who participated in this extraordinary scientific event. The coherent and ideal combination of subject, people and location reflected the coherence of Hans Kleinpoppen’s aims and activities in science and life. We offer our grateful thanks to all contributers who made this volume such a worthy tribute to Hans Kleinpoppen. We also like to thank Rainer Hentges for the painstaking work to prepare this volume in its complete ready to print version. We are also grateful to the Royal Society of London and the Max– Planck–Gesellschaft who generous support of the Hans Kleinpoppen sym- sium made this marvelous meeting and this proceedings possible.

This book is a short outline of the present state of the theory of electron collisions with atomic particles - atoms, molecules and ions. It is addressed to those who by nature of their work need detailed information about the cross sections of various processes of electron collisions with atomic particles: experimentalists working in plasma physics, optics, quantum electronics, atmospheric and space physics, 'etc. Some of the cross sections have been measured. But in many important cases the only source of information is theoretical calcu lation. The numerous theoretical papers dealing with electronic collision processes contain various approximations. The inter relation between them and the level of their accuracy is often diffi cult to understand without a systematic study of the theory of atomic collisions, not to mention that theoretical considerations are necessary for the consistent interpretation of experimental results. The main constituents of the book are: 1. General theory with special emphasis on the topics most impor tant for understanding and discussing electron collisions with atomic particles.

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