ON THE SOLVENT FREQUENCY-SHIFT

It is pointed out that a well established and often-used theoretical expression for the frequency shift of a vibrating molecule in a liquid environment, which was obtained by quantum mechanical perturbation theory, can be obtained by a classical analysis. The formula can therefore be tested by classical computer simulation. This test is carried out for liquids related to liquid nitrogen. The formula is found to be only qualitatively valid and is, for these examples, in quantitative error by a factor between 1.7 and 4.3. The mean length of the molecule is also only approximately predicted. The reasons for the discrepancies are investigated.