Simulation of geminate ion recombination kinetics in anisotropic media

A Monte Carlo random flights technique is presented for simulating ion-pair recombination kinetics in systems with diffusional and dielectric anisotropy, and is applied to geminate electron-hole recombination in anthracene and naphthalene. While the importance of the anisotropy is evident in the dependence of the escape probability on the orientation of the initial interion vector, it is found to be more significant in determining the time-scale of the reaction kinetics, which can vary by a factor of up to three in the systems studied. Comparisons for pairs with the same escape probability indicate that reaction in anthracene is likely to be considerably faster than in naphthalene.