Raman Scattering and Defects in Liquid Crystals Exhibiting Ferrielectric Phases

Overview & Synopsis

Polarized Raman scattering experiments have been performed on tolane series compounds which exhibit a ferroelectric-ferrielectric antiferroelectric phase sequence. Very strong discontinuities in ratios or absolute values of integrated Raman intensities are observed at each transition including those from or to the smectic C*α phase when it is present. More particularly, drastic steps are obtained in the vicinity of the ferrielectric phase(s). The data can be understood as a superposition of a regular part related to the tilt angle variation and of drops (or enhancements) of the Raman intensity resulting from second order local field effects induced by charged defects such as disclination lines.