A model of photoinduced ultrafast charge separation and ensuing charge recombination into the ground state has been developed. The model includes explicit description of the formation and evolution of nonequilibrium state of both the intramolecular vibrations and the surrounding medium. An effect of the high-frequency intramolecular vibrational mode excitation by a pumping pulse on ultrafast charge separation and charge recombination kinetics has been investigated. Simulations, in accord with experiment, have shown that the effect may be both positive (the vibrational mode excitation increases the charge-transfer rate constant) and negative (opposite trend). The effect on charge separation kinetics is predicted to be bigger than that on the charge recombination rate but nevertheless the last is large enough to be observable. The amplitude of both effects falls with decreasing vibrational relaxation time constant, but the effects are expected to be observable up to the time constants as short as 200 fs. Physical interpretation of the effects has been presented. Comparisons with the experimental data have shown that the simulations, in whole, provide results close to that obtained in the experiment. The reasons of the deviations have been discussed.

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Influence of excitation pulse carrier frequency on photoinduced ultrafast intramolecular charge transfer kinetics is investigated in the framework of a multichannel stochastic point transition model involving an excited state formation. It is supposed that an intramolecular high frequency vibrational mode being active at the excitation stage also accepts the energy at the stage of photoinduced charge transfer. A strong dependence of the photoinduced charge transfer rate constant on excitation pulse carrier frequency is uncovered. Since this dependence is associated with charge separation from different excited states of an intramolecular high frequency vibrational mode, it is named the vibrational spectral effect. The simulations show that the effect may be both positive (the photoinduced charge transfer rate constant increases with increasing the excitation pulse carrier frequency) and negative (opposite trend). In the area of low exergonicity of the photoinduced charge transfer, the effect is mostly positive, while in the field of strong exergonicity, it is mostly negative. The amplitude of the vibrational spectral effect predicted by the model is rather large and can be observed in experiments even if the vibrational relaxation/redistribution time constant is as short as 100 fs.

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