We have measured the Stokes shift and its dynamics for the probe molecules naphthalene (Delta mu approximate to 0) and quinoxaline (Delta mu approximate to 1.3 D) in n-propanol and other glass-forming solvents. The Stokes shift for naphthalene (approximate to 63 cm(-1)) turns out to be independent of the solvent polarity over a wide range of the static dielectric constants. Its time dependence is governed by the structural (or alpha- or shear stress) relaxation time of n-propanol, without any signature of the strong dielectric relaxation. For this solvent; structural and dipolar contributions can be distinguished because the time scale for dipole reorientation is a factor of 25 slower than the alpha-relaxation time. We conclude that the solvation of naphthalene reflects excitation-induced changes in the van der Waals interactions, which makes it an ideal probe for assessing shear stress or mechanical relaxations on microscopic spatial scales near T-g.