The simple exponential distribution for initial electron-positive ion separation distances as seen in the γ radiolysis of alkanes

Abstract

A numerical solution of the Smoluchowski equation for diffusion, reaction, and neutralization of ion pairs in a dielectric medium in the presence of a scavenger has been applied for analysis of recent electron scavenging experiments in alkanes. It is shown that these experiments can be quantitatively understood in terms of a simple exponential distribution of initial electron-positive ion separation distances. The credibility of this distribution is considerably enhanced when it is employed, in conjunction with Onsager's solution for diffusion of an ion pair in the presence of an external field, to calculate ion yields as a function of field strength. The agreement with experiment is once again excellent. The attenuation parameter which characterizes our initial exponential distribution is related to the liquid structure factor and gas phase molecular scattering cross sections through the multiple scattering theory of Lax. The wave nature of electron motion is explicitly considered in a discussion of the physical meaning of ionization in liquids.