The central Lorentzian in the depolarized Rayleigh spectra of liquid CCl4 and GeCl4

The central Lorentzian peak in the depolarized Rayleigh spectrum of CCl4 and GeCl4 is studied as a function of temperature using a high resolution Fabry–Perot interferometer. The results are shown to be consistent with a recent theory by Madden which attributes the depolarized spectrum to scattering by anisotropic pairs of density fluctuations. It is also shown that the ubiquitous presence of long-lived asymmetric vibrationally excited molecules may give rise to a spectrum whose width is determined by the reorientational relaxation time of the molecules. In the molecules studied here, the two relaxation times are comparable.