Recombination and scavenging of a randomly walking excess electron in solution

We consider a geminate reaction between A and B reactants affected by the bulk reaction between B and scavengers C. The exact solution of the problem obtained for randomly walking B reactant (excess electron) and diffusing scavengers C is compared with the superposition approximation commonly used to interpret experimental data. The difference is shown to be great enough to lead to qualitatively incorrect description of the experiment even at small concentration of scavengers. In particular, it is shown that the superposition approximation can decrease essentially the rate and the ultimate probability of geminate recombination in the presence of scavengers.