POLARIZED AND DEPOLARIZED RAMAN-SPECTRA OF LIQUID CARBON-DISULFIDE AT 0-10 KBAR .3. INTERACTION-INDUCED NU-2 AND NU-3 SCATTERING AND THE FLUCTUATION OF THE LOCAL FIELD

The effect of pressure on the interaction-induced Raman scattering of the forbidden ν2 and ν3 vibrations of liquid carbon disulfide has been measured up to 10 kbar at 295 K, and a simple model for the fluctuation of the local field has been used to describe the origin of the spectra. The scattering intensities increase with increasing pressure approximately in proportion to the density of the liquid. This is ascribed to the dominant contribution of the orientational fluctuations of the molecules to the fluctuation of the local field. The width of the ν2 band decreases with increasing pressure, and its high-pressure limit is attributed to nondiffusional broadening. The diffusional line width, which was obtained by subtracting the nondiffusional part from the total line width, provided the diffusional time constant, which is linear in the viscosity of the liquid. A large part of the diffusion broadening is ascribed to the relaxation of the local field caused by rotational diffusion. © 1990 American Chemical Society.