A single anion diffusing near several stationary cations

2 A SINGLE ANION DIFFUSING NEAR SEVERAL STATIONARY CATIONS 

Sano (501] has discussed the probability of escape of an anion (e.g, solvated electron) from several stationary cations which are also sinks. This marks an extension of the Onsager theory of ion-pair recombination [321]. If the N cations are located at p1( p2... pw and all quite close to one another, the potential energy of the anion is 

As usual, the Smoluchowski boundary condition on the density and escape probability adequately described the fact that, once an anion and cation form an encounter pair, the chance of separation is negligible, 

When the electron is far from the cations, it has effectively escaped and so the outer boundary condition is 

That is, the escape probability of an anion from N cations is the product of the escape probability of the anion from each of the cations taken one at a time, but with the same distances of separation between anion and cations. 

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