Exact expressions are derived for the depolarization ratios of Raman scattering by a rotating molecule. Two limiting cases are considered. one describing excitation in a continuum of states, the other describing resonance with a single discrete state. The resulting expressions are directly amenabLe to experimental verificatioo.
Rzunan scattering is increasingly used as a means of determining molecular and vibrational structure. Apart from the scattering frequencies which give information about the energetics of a molecule, measurements of depolarization ratios are valuable as a means of determining the symmetry characteristics of a molecule and its vibrational or electronic states [l]. The commonly employed theory of Raman scattering is only valid when the exciting Light frequency is far removed from any of the transition frequencies of the molecule. Very often today, however, measurements are made on molecules where this condition is not met and it seems of interest to investigate what happens to the depolarization ratio under these circumstances, and whether useful information can still be derived from its measurement. This is the purpose of the present note. To bring the argument into a quantitative form we consider here Raman scatteri% by an .isolated freely rotating molecule.