Solvent effects on Raman and infra-red intensities in the “continuous dielectric” model

It is shown that the derivation of equations of Polo and Wilson and of Mallard and Straley for solvent effects in vibrational spectroscopy does not take into account the change of molecular polarizability during vibrations. This change can be accounted for by considering the effective dipole moment and polarizability of solute molecule, as given by Onsager's theory of dielectric polarization, and their derivatives with respect to the normal coordinate. In this way new equations are derived for solvent effects on infra-red and Raman intensities.