Associative and Non‐Associative Ion Pair Formation by Fast Atoms

Abstract

AbstractThis review discusses recent results on collision processes of accelerated atoms which lead to ion production. Five general classes of reactions are described ‐ collision‐induced dissociative ion pair formation (polar dissociation), electron transfer, associative ionization, reactive (rearrangement) ionization, and simple collisional ionization. The review is restricted to ion product reactions that have been studied in molecular beam experiments in which two neutral species collide with relative energies up to 20 eV, and the endoergicity of the reaction is provided by the kinetic energy of one of the partners. The accelerating techniques capable of producing beams of fast atoms and molecules in this important energy region are described.Characteristics of such reactions are the cross sections for the various reaction channels and their dependences on the relative energy (i.e., the excitation functions), the behavior of the cross section near threshold, the relative importance of translational and internal energy in promoting the reaction, and the dynamics of the collisions as revealed by the angular distributions of the products. Illustrative results on these properties are presented. The polar dissociation of the thallium halides by accelerated Xe and Kr atoms, and the dynamics of a number of reactions of fast metal and non‐metal atoms with several molecules are described in detail.