Yuri Dakhnovskii

NONADIABATIC CHEMICAL REACTIONS IN A STRONG TIME-DEPENDENT ELECTRIC FIELD : AN ELECTRON TRANSFER REACTION IN A POLAR SOLVENT

Nonadiabatic chemical reactions of a charge transfer in a polar solvent are considered in the presence of a strong time‐dependent electric field. The integro‐differential kinetic equation for a transfer probability is obtained in the noninteracting blip approximation for an arbitrary electric field. A kernel of the integral part is expressed through a dielectric loss function of the solvent. In a long time limit a high‐temperature solution is obtained. It is found the the rate constant decreases, increases, or oscillates with respect to the intensity and frequency of the field. When the energy of the photon is comparable to the reorganization energy of the solvent, localization of the charge occurs. The localization field parameters are dependent on the heat of the reaction. A strong enhancement of the rate constant is found for barrierless reactions (as much as 18 orders of magnitude) with respect to the intensity of the field. The estimations show that a probable candidate for an observation of these ef...

Dynamics of inner- and outer-sphere electron transfer in a polar solvent

Abstract In this paper, inner-sphere electron transfer reactions in a solvent are studied in the framework of multidimensional transition state theory. It is demonstrated that the preexponential factor essentially depends upon the interaction with the inner-sphere vibrational mode, increasing the rate of electron transfer as much as one order of magnitude. The prefactor is shown to be strongly dependent on the frequency of this vibration. At high frequencies the rate constant increases with the reorganization energy of this inner-sphere mode while at small frequencies, electron transfer is inhibited. Estimations of inner mode reorganization energies have been performed for system where it is necessary to account nonequilibrium solvent relaxation. Finally it is shown that the equilibrium approximation fails when the reaction is close to an activationless regime.

Adiabatic electron transfer in polar solvents. Crossover from activation transfer to tunneling

An electron transfer reaction in a polar solvent has been considered in the region of the crossover from activation transfer to tunneling. An exact expression for the rate constant for an adiabatic potential surface has been found and has also been expressed in terms of a linear response theory for an arbitrary dielectric loss function of the solvent. The specific cases of electron transfer in water and inner‐sphere electron transfer have been studied. The range for which quantum effects are important, in terms of the splitting between the adiabatic potential surfaces, has been found. The theory provides a simple numerical method for calculating the rate constant in this region using a few experimentally obtainable results. This is in contrast to previous methods where complex potential energy surfaces were required to numerically determine the rate.