The configuration interaction theory for charge transfer chemical processes in a polar solvent

Abstract

A semi-microscopic version of the electron transfer theory is presented which combines an explicit quantum-chemical calculation of the free energy functional (playing the role of a potential energy surface) with a phenomenological treatment of the polar medium dynamics in terms of a complex dielectric permittivity function. The self-consistent reaction field technique for calculating equilibrium solvation effects is deduced from the variational principle for thus functional. Using the configuration interaction (CI) expansion of the wavefunction of a chemical subsystem enables to explicitly perform a separation of the total polarization field into inertial and noninertial components. The dynamic equation for the inertial polarization field is reduced to a set of stochastic equations operating with discrete medium variables. The theory is illustrated by its application to the simplest electron transfer process between a pair of atomic centers in two- and three-configuration approximations. The problem how collective medium modes emerge in the general case in terms of the CI treatment is discussed.