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 die lectric dispersion experiments on 21 common room temperature solvents are collected and compared. The correlation functions of the collectiv e variables (polarizability, solvation energy, and dipole moment fluct ations) responsible for each observable are first extracted from the e xperimental data and compared directly. In any given solvent the decay times of these various correlation functions are often vastly differe nt. Such differences mainly result from the fact that intermolecular c orrelations affect the collective variables sampled by each technique in a different manner. To compare dynamics at a more basic level, powe r law relations are applied in an attempt to account for these correla tions and to examine the extent to which the collective dynamics in th ese three experiments can be viewed as arising from the same underlyin g single-particle motions (primarily rotations). The Stokes shift and dielectric correlation functions can be reasonably inter-related in th is manner, but the polarizability anisotropy monitored with Kerr exper iments cannot be as simply related to the former two dynamics, probabl y due to the importance of collision-induced effects in the latter cas e. (C) 1998 Elsevier Science B.V.