Relationship between Energy Gap Time Correlation and Fluorescence Stokes Shift Correlation Functions in Solvation Dynamics

The relationship between the energy gap time correlation function (EGTCF), measured in optical lineshape experiments, for a charged particle in a polar liquid, and the time correlation function obtained from time-dependent fluorescence Stokes shift measurements is explored. We show that if the distortion of the host solvent by the polar solute molecule is neglected, then both provide the same dynamical information. In the presence of a sizeable solvent distortion, emission and absorption lineshapes and Stokes shift measurements are all influenced differently by the solvent dynamics