Diffusion-kinetic modelling of the cooperative effect of scavengers on the scavenged yield of the hydroxyl radical

Abstract

The scavenger concentration dependence of the scavenged yield of the hydroxyl radical produced by the high-energy electron radiolysis of deaerated, and of nitrous oxide saturated, aqueous solutions is modelled using deterministic diffusion-kinetic methods. These calculations provide a simple, but valuable, method for estimating the scavenged yield of the hydroxyl radical in a variety of systems containing both hydroxyl radical and hydrated electron scavengers. The scavenging of hydroxyl radicals in an aqueous solution usually can be divided into two components: the yield that would be scavenged by the hydroxyl radical scavengers in the absence of any hydrated electron scavenger and an additional contribution arising from the cooperative effect of the hydrated electron scavenger. Hydrated electron scavengers reduce the amount of intraspur e–aq+ OH reaction and so increase the amount of hydroxyl radical scavenged by a given concentration of hydroxyl radical scavenger. The yield of scavenged hydroxyl radicals in nitrous oxide solution is not well represented by the sum of the yield of oxide radical anions produced by the nitrous oxide scavenging of the hydrated electron and the radiation-induced yield of hydroxyl radicals that would be scavenged if the hydrated electron scavenging reaction did not produced hydroxyl radicals. In nitrous oxide solutions a small modification to reflect the increase in intraspur reactions of hydroxyl radicals is necessary.