Neutron-scattering evidence for the coupling of shear and reorientational motions in the viscoelastic liquid quinoline

Abstract

The anomalous behavior of several thermal and dynamical properties of liquid quinoline within the temperature range of 260\ensuremath{\le}T\ensuremath{\le}310 K is investigated. The neutron quasielastic scattering spectra are analyzed using, for the purpose, previous dynamical information available from NMR relaxation and depolarized light scattering. The temperature dependence of the mass-diffusion and reorientational coefficients is derived from the experimental data, evidencing that only the rotational motion shows a clear deviation from Arrhenius behavior. The presence of shear wave excitations which couple to reorientational motions is manifested as a strong inelastic background which shows a marked wave-vector dependence.