Nonlocal electrostatic effects on polar solvation dynamics

A phenomenological theory of polar solvation dynamics in electron transfer that accounts for the spatial- and frequency-dependent dielectric function of the solvent is developed and described in a format appropriate to time-dependent fluorescence Stokes shifts. The basic features of the relaxation dynamics are explored by using various analytical expressions for the dielectric function. The presence of spatial correlations persisting to frequencies higher than those corresponding to longitudinal solvent relaxation, τ−1L, yields significant or even substantial decay components with relaxation times shorter than τL. These are associated with motions of individual molecules within the solvent structural network. The implications of these predictions for solvation dynamics in activated charge-transfer processes are noted.