Excluded Volume Effects in Photoinduced Electron Transfer and Geminate Recombination: Analytical Theory and Simulations

Abstract

Analytical theory and Monte Carlo (MC) simulations are used to examine the problem of photoinduced electron transfer and geminate recombination in both infinite three-dimensional systems and in restricted geometry systems. As an example of a restricted geometry system, donor and acceptor molecules on the surface of a spherical micelle are considered. The analytical theory is an exact treatment for fixed donors and acceptors when the distance dependence of the transfer rate falls off exponentially and donor-acceptor excluded volume (DA EV) is included. Comparisons to the MC simulations, which include DA EV, show perfect agreement for both the 3D system and the micelle system. However, comparisons of the analytical theory to the simulations show that for sufficiently high acceptor concentration, acceptor-acceptor excluded volume (AA EV) becomes important. With AA EV, the analytical theory is no longer exact. A new approximate method for the inclusion of AA EV in the analytical theory is described. Comparisons with the simulations show that it is accurate up to substantial concentrations, but at sufficiently high acceptor concentrations, significant deviation from the MC simulation results are seen. 53 refs., 8 figs.