Rayleigh scattering: Orientational motion in highly anisotropic liquids

Abstract

Light scattering studies of the depolarized Rayleigh line are reported for liquid benzene over the temperature range +13 to 76°C and for other substituted benzenes. Values of the 〈 P2(o)P2(t)〉 and 〈 Ṗ2(o)Ṗ2(t)〉 correlation functions calculated from these spectra show considerable free rotor behavior (∼ 15° steps) and incomplete loss of memory after collision. Further consideration of the 〈 Ṗ2(o)Ṗ2(t)〉 correlation allows calculation of the angular velocity correlation function. The time between collisions, τBC, is also obtained and found to be in good agreement with a ``moveable wall'' cell model. It is proposed that the ``shoulder'' noted in the wings of many anisotropic liquids is caused by incomplete loss of memory after collision.