Influence of reactant and product decays on hot velectron transfer kinetics

The effect of intramolecular vibrational relaxation of the reactants and products on the hot charge recombination kinetics of excited donor-acceptor complexes in polar solvents has been investigated within the framework of the stochastic approach. The model considered involves the excited electron-vibrational state formation by the pump pulse and accounts for the reorganization of an intramolecular high-frequency vibrational mode. This leads to a manifold of the product (reactant) states divided by a gap equal to the high-frequency vibrational quantum instead of the single product (reactant) state. For a quantitative description of the influence of vibrational relaxation of reactant and product states on the charge transfer kinetics we use the two-level approximation, considering only two states: the state of the donor-acceptor complex with separate charges produced by the electron transfer from second electronically excited state (reactant), and the first electronically excited state (product), populated due hot transition. An analytical expression for the hot electronic transition probability, considering both the reactant and products decays is received. To find this expression we apply method based on the term linearization in the vicinity of their crossing. The hot electronic transition probability depends on factors that take into account the decay of reactants and products. It is converted to the well-known expression in the limit, when the decay of the reactants and products available. Numerical calculations have shown that at the hot stage the electron transfer reaction can be accelerated and slowed down because of the vibrational relaxation of the reactants and products.