Dynamics of relaxation processes in liquids: Analysis of oscillation and orientation spectra.

Based on the spectra of molecular (Rayleigh) scattering of light, we investigate relaxation dynamics in the molecules of para-, meta-, and ortho-xylenes which are confined in a container and heated from room through critical temperature T c . We experimentally elucidate the successive transitions from hindered to absolutely-free rotations at temperatures up to a pre-critical temperature T *(< T c ) and then from individual to collective motions (macroscopic vibrations) of the molecules at higher temperatures above T ⁎ up to T c . Close to T c , the inner field anisotropy is the same along three axes of inertia of the ellipsoid, and the depolarization degree is universal and independent of the specific nature of xylene isomers. A marked deviation from the Rayleigh's theory is also found in the spectral intensity of scattering light. [ABSTRACT FROM AUTHOR]