Coupling of orientational and translational motions in viscoelastic fluids. Low frequency depolarized (VH) light scattering

Physical processes in supercooled liquids are discussed and it is explained how elasticity might prevail. Consequently a theory is presented for the VH spectrum of low frequency light scattering from an isotropic solid-like visco-elastic medium containing molecules with orientational degrees of freedom. In contrast with the low frequency VH spectrum from non-elastic fluids the present one contains under specified conditions two central lorentzians instead of only one in addition to two pairs of shifted lorentzians and dispersion curves. The information that can be extracted from comparing this theory to experimental data contains a constant which designates the degree of elasticity and also orientational relaxation times, shear viscosities and coupling constants between the translational and the orientational motions.