Ion-pair production and chemi-ionization in atomic collisions

Molecular-beam studies are described of ion-pair production (IPP) in the atomic systems Na-Cl, Na-Na, Na* (3P)-Na, and He* (2/sup 1,3/S)-Li and of chemi-ionization (CI) in the He (2/sup 1,3/S)-Li system. Reactions of IPP can be represented as A + B → A+ + B- and CI as A* + B → A + B+ + e (Penning ionization, or PI) and A* + B → AB+ + e (associative ionization, or AI), where in this case, A and B are atoms, and A is an electronically excited atom. Absolute and relative cross sections, Q, are measured as a function of the relative kinetic energy, W, of the reactants. The general theory of potential curve crossing is described, and an application of this theory to IPP and the connection of the theory to CI are given