It is perhaps surprising that a process which was one of the first to be studied on an atomic scale, and a process which first received attention over seven decades ago, continues to be the object of diverse and intense research efforts. Such is the case with the (seemingly) conceptually simple and familiar mechanism of electron impact ionization of atoms, molecules, and ions. Not only has the multi-body nature of the collision given ground to theoretical effort only grudgingly, but also the variety and subtlety of processes contributing to ionization have helped insure that progress has come only with commensurate work: no pain - no gain. Modern experimental methods have made it possible to effectively measure and explore threshold laws, differential cross sections, partial cross sections, inner-shell ionization, and the ionization of unstable species such as radicals and ions. In most instances the availability of experimental data has provided impetus and guidance for further theoretical progress."

Our understanding of elementary processes in plasmas has been increasing dramatically over the last few years. The development of various swarm techniques, such as the temperature variable selected ion flow tube or the selected ion flow drift tube, has provided the prerequisite for detailed investigations into ion molecule reactions both in binary and three body collisions, and the mechanisms of many reactions are now understood quite satisfactorily. This information could not have been obtained without a detailed knowledge of the transport phenomena involved. Some of these, such as the internal-energy distribution of drifting ions, have only very recently been tackled both theoretically and experimentally; a consistent model is now being developed. As the interactions between the various branches of swarm research have become more and more intense, the most obvious thing to do was putting together a review on the present state of this subject, which is the aim of this book.