Interaction induced phenomena in Raman spectra of mesogens

We present the results of experimental studies of light scattering in the i sotropic phase of two mesogens, p-n-pentyl-p'-cyanobiphenyl (5CB) and p-n-p entyl-(p'-cyanophenyl)-cyclohexane (5PCH) and in their solutions in CCl4, a globular molecules solvent. Integral intensities of various Raman bands an d Rayleigh wing polarized spectra were studied. Dilution experiments have s hown that in mesogen systems, due to molecular interactions, intensity of l ight scattering may be substantially (about 30%) reduced. Isotropic compone nt of the scattered light is influenced by orientation-translational molecu lar correlations, while for anisotropic component pure orientational molecu lar correlations are also important. As a result, depolarization ratio in t he condensed state may be substantially different from that for the isolate d molecule and may vary through the mesomorphic phase transitions. (C) 1998 American Institute of Physics. [S0021-9606(98)50744-1].