Multiple time scales in the nonpolar solvation dynamics of supercooled liquids

Recent experimental and theoretical work on the dynamics of solvation in nonpolar supercooled liquids is reviewed. Transient hole burning experiments have shown that solvation dynamics occur on a wide variety of time scales. A major division into phonon-like and structural relaxation is apparent as the viscosity of the solvent increases in the supercooled region. The structural component is strongly nonexponential and extends over many decades in time. Mode-coupling theory provides a consistent explanation of the structural relaxation behavior versus temperature. A continuum model links nonpolar solvation to shear relaxation of the solvent following a size change of the solute upon electronic excitation. The relationship between phonon-like and structural dynamics is examined within the continuum model which distinguishes them as different dynamical regimes of a single coordinate, and is contrasted with ''spectroscopic'' models, which treat the different dynamics as arising from distinct solvent coordinates.