A viscoelastic continuum model of non-polar solvation. II. Vibrational dephasing in moderate to high-viscosity liquids and glasses

A recent continuum model of non-polar electronic solvation [M. Berg, J. Phys. Chem., A 102 (1998) 17] is extended to treat vibrational dephasing at moderate to high viscosities. Standard theories of vibrational dephasing in low-viscosity liquids predict an unphysical divergence of the linewidth at high viscosity. The current theory corrects this problem by explicitly accounting for the existence of both inertial and diffusive components in the liquid dynamics. At high viscosity or in a glass, the Raman line is predicted to be inhomogeneous and to have a finite width. In contrast to existing theories, this theory predicts that structural dynamics dominate the Raman linewidth. Collision-like processes only contribute weak, broad wings to the line. This theory also predicts quantitative connections between vibrational dephasing and electronic-state solvation. (C) 1998 Elsevier Science B.V. All rights reserved.