Collision-induced ion pair formation of thallium halides: Threshold behavior

Abstract

The threshold laws for direct polar disociation A+BC → A+B++C− and for ion-complex formation A+BC → AB++C− are determined for the collision of Xe and Kr atoms with TlCl, TlBr, and TlI by analysis of the experimental excitation functions presented in the preceding paper. The cross section for direct polar dissociation is parameterized by the expression A(Etot−E0)n/Erel, where Etot and Erel are the total energy and the relative translational energy, respectively, of the reactants, and E0 is the threshold energy. The cross section is averaged over the experimental translational and internal energy distributions, and, for each pair of reactants, E0, n, and A are determined from the best fit to the data. For ion-complex formation, the data are analyzed in terms of a step behavior at the reaction threshold. For the system Xe + TlCl, experimental measurements of the cross section as a function of internal energy are presented, and the relative importance of translational and internal energy in promoting polar dissociation is discussed. It is found that an increment of internal energy is more effective in promoting polar dissociation than an equal increment of translational energy.