Atomic Collisions Involving Low Energy Electrons and Ions

Abstract

This chapter presents a survey that is concerned with recent advances in our knowledge of collisions of low energy electrons and ions with atoms or molecules and with each other. In general, the term “low energy” is intended to include the range from thermal energies, ∼0.03 ev, to a few ev. An independent experimental determination of the e-H scattering was provided by Brackman, Fite, and Neynaber (BFN), who used a modulated atomic beam method, is also illustrated. Using the trapped electron method, Schulz was unable to observe vibrational excitation in hydrogen by incident electrons whose energy lay between threshold value and ∼0.1 ev higher than threshold. Hasted points out that departure from the “adiabatic” energy dependence, yielding substantially larger cross sections at low energies, are sometimes observed, possibly as a result of intrusion of other processes in the experimental measurement. By combining the results of microwave afterglow and mass spectrographic techniques, Biondi and Fox have determined the absolute cross section as a function of electron energy for I− formation.The technique of simultaneous mass analysis of the ions reaching the walls of the microwave afterglow cavity, together with the usual electron density determinations, is just entering into extensive use.