FT-Raman Polarization Spectroscopy of Nonmesogenic Guest Molecules Oriented in Nematic Liquid Crystal Solvents

Abstract

The experimental technique for Raman spectroscopic measurements of aligned liquid crystals was adopted for studying the orientation of nonmesogenic guest molecules dissolved in nematic liquid crystal hosts. Polarization FT-Raman spectra of diphenylacetylene (tolane) dissolved in nematic liquid crystals of 4-alkyl-4'-cyanobicyclohexyl type (ZLI-1695) have been recorded. The intensity ratios, R = I_YY/I_ZZ, of the bands polarized perpendicular (I_YY) to the preferred molecular orientation, and parallel (I_ZZ) to it, are rediscussed. A clear polarization equivalent to that of the host was found for the guest molecule tolane. The obtained data serve for determining the symmetry properties of the observed vibrations of the dissolved molecule.