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.

This volume presents the contributions of participants in the Symposium on Swarm Studies and Inelastic Electron-Molecule Collisions, held on July 19-23, 1985, in Tahoe City, California. This was a joint meeting of the Fourth International Swarm Seminar and the Electron-Molecule Collisions Symposium which have been traditionally separate satellite symposia to the International Conference on the Physics of Electronic and Atomic Collisions (ICPEAC). In the early stages of planning for these two satellite symposia to the XIVth ICPEAC, a group of us recognized the significant scientific merit and advantages of having a joint symposium. This idea was particularly appealing due to a large mutual interest in important advances (theoretical, experimental, and modeling) in both fields, and because it provides a forum to bring together a single-collision point of view with a multiple-collision one. For example, studies of multiple-term solutions to Boltzmann's equation and their application to swarm systems are intrinsically coupled to the availability of both integral and differential cross-sections for electron-molecule collisions. In tum, experimental and theoretical studies of these electron-molecule scattering cross-sections are becoming quite sophisticated, accurate, and comprehensive. Furthermore, in swarm studies, computational and experimental methods have advanced to the point where detailed and meaningful comparison with, and use of, single-collision beam data is now possible. More over, recent experimental advances in the study of single-collision electron at tachment phenomena have provided a significant overlap with swarm data and extension to subthermal energies.