Differing applications of Raman scattering to liquid crystals

An overview of the differing possibilities offered by Raman scattering in the study of liquid crystals is given, together with a few experimental examples of the least studied phenomena. Among them, changes in the intrinsic Raman polarizabilities and phonon self-energies as a function of temperature which provide, in principle, an experimental method for the study of coexisting and/or inhomogeneous phases through Raman imaging. We show that the C-H in-plane deformation mode of the phenyl rings is particularly suited to monitor both intrinsic scattering efficiencies and frequency changes. This mode is present in a large family of liquid crystal compounds and we present evidence indicating that the origin of these changes is its electron-phonon coupling to the lowest allowed electronic transition in the ultraviolet.

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