Cage effect dynamics.

The kinetics of recombination/dissociation of photogenerated radical pairs (RPs) is described with a generalized model (GM), which combines exponential models (EMs) and contact models (CMs) of cage effect dynamics. The main assumption of EM is the irreversible dissociation of RP as a first-order reaction. CM takes into account repetitive contacts of radicals in the pair or reversible diffusional separation of radicals. The present GM accounts for both the recombination of RP within the cage of outcome and their diffusional separation in a free space. GM predicts that a short initial time RP decay is described by EM, and RP kinetics at longer times of observation is described by CM. This theory successfully describes available experimental data. Solvent viscosity effect on the cage effect values is also analyzed.