Rayleigh–Brillouin scattering studies of the rotation-translation coupling and bulk viscosity relaxation of liquids composed of anisotropic molecules: p-Anisaldehyde and aniline

Abstract

Articles you may be interested inCoherent Rayleigh-Brillouin scattering measurements of bulk viscosity of polar and nonpolar gases, and kinetic theory J. Chem. Phys. 133, 164315 (2010); 10.1063/1.3491513 Rayleigh-Brillouin scattering studies of liquid and supercooled liquid oterphenyl J. Chem. Phys. 74, 3175 (1981); 10.1063/1.441511 Theory of depolarized Rayleigh-Brillouin spectra and rotation-translation coupling in molecular liquids and solids J. Chem. Phys. 70, 3796 (1979); 10.1063/1.437930 Rayleigh-Brillouin scattering and structural relaxation of a viscoelastic liquid J. Chem. Phys. 70, 681 (1979); 10.1063/1.437495 Rayleigh-Brillouin scattering of gases with internal relaxationThe coupling of reorientational motion to longitudinal acoustic modes was investigated by studying the Rayleigh-Brillouin spectra of aniline and p-anisaldehyde over a wide range of scattering angles. Aniline and p-anisaldehyde were chosen for investigation since their depolarized spectra at the temperature of interest show a pronounced coupling between orientation and shear modes. The experimental results for attenuation and velocity of the longitudinal waves show that there is indeed relaxation in the shear viscosity. However, shear relaxation due to the coupling of the longitudinal acoustic mode to reorientation plays only a minor role in causing the dispersion of the hypersonic longitudinal waves. To account for the large dispersion, it is essential to consider the mechanism associated with the relaxation of the bulk viscosity through the T-V energy transfer.

Shape Persistence in Polymers and Supramolecular Assemblies

“…The observed differentiation can be attributed to non-random spatial orientation correlations due to rotation-translation coupling proposed for small molecules. [52][53][54][55][56] For semi-flexible polymers, however, the effect is strong and the dynamics are slow that renders the finding unique. A further advantage is the observation of the effect at equilibrium without macroscopic flow.…”