The great advantage of coincidence measurements is that by suitable choice of the kinematical and geometrical arrangement one may probe delicate physical effects which would be swamped in less differential experiments. The measurement of the triple dif ferential and higher-order cross sections presents enormous technical difficulties, but refined experiments of this type provide an insight into the subtleties of the scattering process and offer a welcome, if severe, test of the available theoretical models. The last few years have been an exciting time to work in the field and much has been learned. Profound insights have been gleaned into the basic Coulomb few body problem in atomic physics: the experimental study of the fundamental (e,2e) processes on hydrogen and helium targets continues to add to our knowledge and indeed to challenge the best of our theoretical models; significant advances have been made in the understanding of the "double excitation problem," that is the study of ionization processes with two active target electrons: important measurements of (e,3e), (, ), 2e), excitation-ionization and excitation autoionization have been reported and strides have been made in their theoretical description; the longstanding discrepancies between theory and experiment for relativistic (e,2e) processes were resolved, spin dependent effects predicted and ob served and the first successful coincidence experiments on surfaces and thin films were announced. Theory and experiment have advanced in close consort. The papers pre sented here cover the whole gambit of research in the field. Much has been achieved but much remains to be done."

The last few years have seen some remarkable advances in the understanding of atomic phenomena. It is now possible to isolate atomic systems in traps, measure in coincidence the fragments of collision processes, routinely produce, and study multicharged ions. One can look at bulk matter in such a way that the fundamental atomic character is clearly evident and work has begun to tease out the properties of anti matter. The papers in this book reflect many aspects of modem Atomic Physics. They correspond to the invited talks at a conference dedicated to the study of "New Directions in Atomic Physics," which took place in Magdalene College, Cambridge in July of 1998. The meeting was designed as a way of taking stock of what has been achieved and, it was hoped, as a means of stimulating new research in new areas, along new lines. Consequently, an effort was made to touch on as many directions as we could in the four days of the meeting. We included some talks which overviewed whole subfields, as well as quite a large number of research contributions. There is a unity to Physics and we tried to avoid any artificial division between theory and experiment. We had roughly the same number of talks from those who are primarily concerned with making measurements, and from those who spend their lives trying to develop the theory to describe the experiments.

An (e,2e) experiment is the measurement of an electron impact ionization process where both the exiting electrons are detected in coincidence. Such measurements are almost at the limit of what can be known, in quantum mechanical terms, and its description presents a substantial theoretical challenge. There are at least two very good reasons for studying (e,2e) and related processes. In the first place we are now only beginning to understand the dynamics of the collision process. The range and sophistication of present experiments allow us to identify kinematic regimes where delicate and subtle effects can be observed, stretching current theories to their limit. Secondly, the multiple coincident technique offers us the possibility of an analytical tool that could be used to probe the structure of the target, be it atom, molecule, thin film or surface. Measurements are now being performed at threshold on H, on the inner shell levels of Au and Ag using projectiles at relativistic energies, with spin-polarized electrons on Li, on a myriad of molecules in symmetric, noncoplanar kinematics, and on He in a multitude of different geometries. The technique has recently been extended to excitation ionization (e,3e) and (gamma,2e) experiments. Major theoretical advances have also been made, but much still remains to be done. This volume contains the invited papers that were presented at the Workshop on (e,2e) and related processes which took place in September/October 1992 in Cambridge, UK. The three major review papers which it contains together form an excellent introduction to this new and rapidly expanding area of physics and set the scene for the wide range of research contributions, both experimental and theoretical, from the leading scientists in the field.

The last few years have seen some remarkable advances in the understanding of atomic phenomena. It is now possible to isolate atomic systems in traps, measure in coincidence the fragments of collision processes, routinely produce, and study multicharged ions. One can look at bulk matter in such a way that the fundamental atomic character is clearly evident and work has begun to tease out the properties of anti matter. The papers in this book reflect many aspects of modem Atomic Physics. They correspond to the invited talks at a conference dedicated to the study of "New Directions in Atomic Physics," which took place in Magdalene College, Cambridge in July of 1998. The meeting was designed as a way of taking stock of what has been achieved and, it was hoped, as a means of stimulating new research in new areas, along new lines. Consequently, an effort was made to touch on as many directions as we could in the four days of the meeting. We included some talks which overviewed whole subfields, as well as quite a large number of research contributions. There is a unity to Physics and we tried to avoid any artificial division between theory and experiment. We had roughly the same number of talks from those who are primarily concerned with making measurements, and from those who spend their lives trying to develop the theory to describe the experiments."

The great advantage of coincidence measurements is that by suitable choice of the kinematical and geometrical arrangement one may probe delicate physical effects which would be swamped in less differential experiments. The measurement of the triple dif ferential and higher-order cross sections presents enormous technical difficulties, but refined experiments of this type provide an insight into the subtleties of the scattering process and offer a welcome, if severe, test of the available theoretical models. The last few years have been an exciting time to work in the field and much has been learned. Profound insights have been gleaned into the basic Coulomb few body problem in atomic physics: the experimental study of the fundamental (e,2e) processes on hydrogen and helium targets continues to add to our knowledge and indeed to challenge the best of our theoretical models; significant advances have been made in the understanding of the "double excitation problem," that is the study of ionization processes with two active target electrons: important measurements of (e,3e), (, ), 2e), excitation-ionization and excitation autoionization have been reported and strides have been made in their theoretical description; the longstanding discrepancies between theory and experiment for relativistic (e,2e) processes were resolved, spin dependent effects predicted and ob served and the first successful coincidence experiments on surfaces and thin films were announced. Theory and experiment have advanced in close consort. The papers pre sented here cover the whole gambit of research in the field. Much has been achieved but much remains to be done."

An (e,2e) experiment is the measurement of an electron impact ionization process where both the exiting electrons are detected in coincidence. Such measurements are almost at the limit of what can be known, in quantum mechanical terms, and its description presents a substantial theoretical challenge. There are at least two very good reasons for studying (e,2e) and related processes. In the first place we are now only beginning to understand the dynamics of the collision process. The range and sophistication of present experiments allow us to identify kinematic regimes where delicate and subtle effects can be observed, stretching current theories to their limit. Secondly, the multiple coincident technique offers us the possibility of an analytical tool that could be used to probe the structure of the target, be it atom, molecule, thin film or surface. Measurements are now being performed at threshold on H, on the inner shell levels of Au and Ag using projectiles at relativistic energies, with spin-polarized electrons on Li, on a myriad of molecules in symmetric, noncoplanar kinematics, and on He in a multitude of different geometries. The technique has recently been extended to excitation ionization (e,3e) and (gamma,2e) experiments. Major theoretical advances have also been made, but much still remains to be done. This volume contains the invited papers that were presented at the Workshop on (e,2e) and related processes which took place in September/October 1992 in Cambridge, UK. The three major review papers which it contains together form an excellent introduction to this new and rapidly expanding area of physics and set the scene for the wide range of research contributions, both experimental and theoretical, from the leading scientists in the field.