Effect of an external electric field on the yield of free ions. III. Electron scavenging at small concentrations

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Abstract
The method of prescribed diffusion has been applied to obtain the evolution of the neutralization process of an ion pair in the presence of an external electric field. For relatively small external fields the probability of escape calculated by this method agrees exactly with the Onsager formula. The probability of the existence of the ion pair against neutralization has been evaluated in the long‐time limit and its Laplace transform determined to give the scavenging probability in the presence of an external field E at small concentrations. Analysis of the results shows that, at small concentrations, the yield of the scavenging reaction should vary with scavenger concentration c as (c + c0E2)1/2, where c0 is some constant, rather than simply as c1/2. Replotting of the experimental data of Rzad and Bakale according to the present procedure removes the discrepancy between their extrapolated yield at zero concentration and the results of the Onsager theory. The maximum and minimum scavenger concentrations within which a square root variation of yield with concentration is to be expected are evaluated as functions of the external field.