Application of the smoluchowski equation to electron scavenging in dielectric liquids. numerical evaluation of the scavenging probability for a given initial separation of an ion pair

A numerical procedure for the evaluation of the probability for electron scavenging by a solute aL a given concentration in the radiolysis of hydrocarbon solutions is developed. This procedure is based on the use of the Smoluchowski equation to describe the relative motion of the electrons and their positive ion partners. The results of these calculations for different initial ion-pair separation distances show that the observed concentration dependences of the scavenging probability is intimately related to the initial distribution of thermalization distances. It is shown that at a concentration of 10-1 M methyl bromide in cyclohexane essentially no electrons separated from their positive ion partners by 80 Å escape being scavenged. Experimentally it is observed that at this concentration only 50 % of the electrons are scavenged so that an appreciable fraction of the ion pairs must be characterized by smaller separation distances. The selectivity of reaction is indicated by results at 0. 01 M methyl bromide where scavinging occurs for 98 % of the pairs initially separated by 160 Å but only 15 % where the separation distance is 40 Å