Nonequilibrium photoinduced electron transfer

We consider photoinduced electron transfer, which is intrinsically a three-state system consisting of electronic ground, electronic excited (electron donor), and electron acceptor states. It is assumed that the bath consists of a collection of harmonic oscillators. Using an elementary time-dependent perturbation theory, it is found that the nonequilibrium Golden rule formula proposed by Coalson et al. [J. Chem. Phys. 101, 436 (1994)] can be rigorously obtained in a certain limit of our results. Invoking a stationary phase approximation, a simple result analogous to the Marcus expression is obtained, except for the presence of time-dependent reorganization energy. The multidimensional nature of the solvation coordinate system is discussed further. Finally a few numerical calculations are presented.