SOLVENT-INDUCED DYNAMIC POLARIZATION AND VIBRATIONAL DEPHASING OF ELECTRONICALLY EXCITED MOLECULES

In order to account for the extra vibrational Raman bandwidths observe d specifically for electronically excited molecules in solution, a new model, the dynamic polarization model, has been introduced. In this m odel, the vibrational frequency of a highly polarizable electronically excited molecule in solution is stochastically modulated by the solve nt-induced polarization. An olefinic C=C double bond is considered as the simplest prototype, for which the carbon-carbon stretch frequency can take values between the unpolarized (C=C) and the completely polar ized (C+-C-) frequencies. The two-frequency exchange model is first in troduced, followed by more general models. A focus is placed on the as ymmetric exchange limit in which the solvent-induced polarization can be treated as a perturbation, so that the effect of the dynamic polari zation manifests as a shift of the peak position and an increase in th e bandwidth of the original unperturbed C=C stretch vibrational band. The experimental results on S-1 trans-stilbene are discussed, based on the formulae derived.