Brillouin scattering in a liquid crystal: frequency and temperature dependences

Abstract

Brillouin scattering measurements have been carried out in the liquid crystal mixture Merck ZLI-2861 with a low viscosity and a broad nematic phase. Scattering from longitudinal acoustic phonons with different wave vectors was measured by changing the geometries from backscattreing to nearly forward scattering that cover the frequency range from 10 to 1 GHz. In the nematic phase the dispersion in both the hypersonic attenuation and sound velocity is describing by a single relaxation process with the characteristic frequency 3.2 GHz. Evident anomalies in attenuation and hypersonic velocity were found at lower temperatures in the vicinity of the phase transition from a nematic to, probably, a smectic state.