Effect of Relaxation of Intramolecular High-Frequency Vibrational Mode on Nonthermal Electron Transfer Probability. Stochastic Point-Transition Approach

A nonthermal electron transfer assisted by an intramolecular high-frequency vibrational mode has been investigated. An analytical expression for the nonthermal transition probability in the framework of the stochastic point-transition approach has been derived. The expression explicitly accounts for the decay of the excited vibrational states. For the strong electron transfer, the decay of the product state can vastly enhance the nonthermal transition probability in the whole range of parameters except for the areas where the probability is already close to unity. The exploration of electron transfer in the solvent-controlled regime has uncovered that in the solvents exhibiting two or more relaxation time scales the nonthermal transition probability is always larger than that in the solvents with monoexponential relaxation. What is most unexpected is that the appearance of a fast component in the solvent relaxation function with a small weight can considerably increase the nonthermal transition probability. The underlying physics has been clarified.