Simulation of Geminate Recombination in the Presence of an Absorbing Plane

A theoretical investigation is presented of the competition between recombination of a geminate pair and reaction with an absorbing plane surface. Full random flights simulations are compared with the predictions of the independent pairs approximation for a variety of spatial configurations and, where possible, analytic solutions. Differences resulting from the competition are manifested as an underestimate of the amount of recombination and average hit−hit separation in the independent pairs relative to the random flights. These discrepancies are rationalized in terms of a correlation between the pair separation and the closest distance of the pair to the plane. The exact solution of a related one-dimensional problem is presented in order to give further insight into the correlation effect.