Solvent dynamics derived from optical Kerr effect, dielectric dispersion, and time-resolved Stokes shift measurements: An empirical comparison

Data from the optical Kerr effect, time-resolved Stokes shift, and dielectric dispersion experiments on 21 common room temperature solvents are collected and compared. The correlation functions of the collective variables (polarizability, solvation energy, and dipole moment fluctations) responsible for each observable are first extracted from the experimental data and compared directly. In any given solvent the decay times of these various correlation functions are often vastly different. Such differences mainly result from the fact that intermolecular correlations affect the collective variables sampled by each technique in a different manner. To compare dynamics at a more basic level, power law relations are applied in an attempt to account for these correlations and to examine the extent to which the collective dynamics in these three experiments can be viewed as arising from the same underlying single-particle motions (primarily rotations). The Stokes shift and dielectric correlation functions can be reasonably inter-related in this manner, but the polarizability anisotropy monitored with Kerr experiments cannot be as simply related to the former two dynamics, probably due to the importance of collision-induced effects in the latter case. (C) 1998 Elsevier Science B.V.