Origin of depolarized light scattering in supercooled liquids: Orientational fluctuation versus induced scattering mechanisms

Depolarized light scattering spectra of liquid salol that have been analyzed in recent studies of the liquid-glass transition are reexamined in order to determine the relative importance of orientational fluctuations and interaction-induced scattering. First, the spectra of ${\mathrm{CCI}}_4$, ${\mathrm{CHCI}}_3$, ${\mathrm{CH}}_2$ ${\mathrm{CI}}_2$, and ${\mathrm{CS}}_2$ for which all the relevant parameters are known are compared to theoretical predictions in order to verify the experimental procedure. The same procedure is then applied to the molecular glass former salol for which we find that orientational fluctuations dominate at all frequencies up to at least 4000 GHz. We suggest that the previously reported agreement beween depolarized light scattering spectra and predictions of the mode coupling theory for salol and other molecular glass forming materials results from coupling between rotational and translational motions of the molecules. © 1996 The American Physical Society.