This important book contains the invited papers (plenary and review lectures, progress and special reports) presented at XX.ICPEAC, the Twentieth International Conference on the Physics of Electronic and Atomic Collisions. It highlights the current status of research in photonic, electronic and atomic collision physics, for which experimental studies increasingly rely on laser and synchrotron radiation and are more and more interrelated with other fields, such as molecular and chemical physics, surface science, quantum optics, and spectroscopy and formation of exotic atoms.

There is something magical about ''round birthdays.'' They make one stop and think about where he is, how he got there, and where he is going. The same is apparently true of conferences, especially those like ICPEAC which represent the periodic coming together of a broad range of scientists in a reasonably well-defined discipline. This Vienna conference is the 20th in the ICPEAC series, and a retro- and pro-spective analysis seems appropriate. At the first ICPEAC in New York (1958), there were about 50 participants. In Vienna (1997), there were more than 800 participants. How do we account for this growth? ICPEAC is one of the most democratic conferences of its size. For example, input from a general committee of 50 representing the many geographic and sub- disciplinary areas gives continuous refreshment of ideas for the invited program. And, as in any democracy, there is a constant state of turmoil and self doubt. After all, atomic collisions is a ''mature'' field, and was a ''mature'' field at the time of the first ICPEAC in 1958, 50 what can one expect in new developments? This self doubt is best expressed in the comment of Ben Bederson (the ''Father of ICPEAC'') following the second in Boulder, Colorado, in 1961: ''This conference is the second in a series of informal meetings organized by a group of workers in the general field of electronic and atomic collisions. The first such meeting was held at New York University in 1958, and we will probably continue to meet at irregular intervals in the future ... '' As part of my ''keynote'' talk at the New York ICPEAC XVI in 1989, I gave a brief history of the conference which we can build on to round things off for our twentieth.

If a heavy particle ion (atom, molecule, muon) collides with another in the gas phase at speeds approaching the speed of light, the time-dependent Dirac equation equation must be used for its description, including quantum electro-dynamic, special relativity and magnetic coupling effects. In this book we study one electron in the variety of rearrangement collisions: radiative and non-radiative capture, ionization, capture by pair (one electron, one positron) production and antihydrogen production. Our relativistic continuum distorted-wave theory accounts extremely well for the simultaneous behaviour of the electron with respect to the nuclear charges of the projectile and the target. This is the first book developed in this subject. Containing many diagrams and tables, and fully referenced, it goes beyond chapters in previous books. The relativistic continuum distorted-wave theory developed by the authors group, is shown to be fully Hermitean. Detailed mathematics are provided in nine appendices.

This book provides and elementary introduction to the field of trapping highly charged ions. The first group of chapters is intended to describe the various sorts of highly charged ion traps: EBIT, EBIS, ECR, Storage Rings and various speciality traps. The authors focus on their own ion trap facilities in order to teach by example. The chapters range in scope from comprehensive reviews to brief introductions. The second group of chapters is intended to give a flavour of the various sorts of scientific research which are presently being carried out with traps for highly charged ions. These chapters not only inform, but also stimulate newcomers to think up fresh ideas. The articles in this second group generally fall into one of three broad categories: atomic structure experiments, ion-surface interactions and precision mass spectrometry. The third group of chapters is intended to deal with theory and spectroscopic analysis. It provides some of the background material necessary to make sense of observed phenomenology, to allow detailed explanation of experimental data, and to sensibly plan further experimentation. An appendix provides a complete keyword-annotated bibliography of pa