The influence of diffusion on photoinduced electron transfer and geminate recombination

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Abstract
The influence of diffusion on photoinduced electron transfer and geminate recombination in solutions of randomly distributed donors and acceptors is explored. The focus is on the effect diffusional motion has on geminate recombination. The reactive state (state following photoinduced electron transfer) probability is calculated as a function of diffusion constant and relative permittivity for three intermolecular potential cases: attractive, repulsive, and no Coulomb potentials. Also calculated are the reactive state yield and reactive state survival fraction. Both forward and back electron-transfer rates are distance dependent (not contact transfer). Any diffusion constant can be investigated, and donor–acceptor and acceptor–acceptor excluded volumes are taken into account. The model developed here is compared with slow and fast diffusion limits as well as with the theories of Smoluchowski, and Collins and Kimball.