High frequency relaxation in nematic liquid crystal mixtures by brillouin scattering

Brillouin scattering as a function of scattering angles from 180 to similar to 10 degrees has been measured in the nematic phases of two liquid crystal mixtures, E. Merck ZLI-2861 and E7, without any preferred orientation. Such measurements at room temperature cover the frequency range from similar to 10 to similar to 1 GHz. The behavior of both the frequency shifts and linewidths is explained by a single time internal relaxation process with the characteristic frequencies 3.2 (ZLI-2861) and 1.2 (E7) GHz respectively. The behavior of the hypersonic attenuation shows no correlation with the static bulk viscosity in the nematic phase.