Vibrational relaxation and frequencies of liquid molecules. II. Comparison of theoretical and experimental results

Abstract The Raman isotropic band widths and the peak frequencies of totally symmetric vibrational modes were measured for the CH 3 I, CD 3 I, CH 3 Br, and CHCl 3 molecules in liquid phases at various temperatures. The integrated intensities of the Raman scattering and the infrared absorption of the fundamental and overtone bands were measured to obtain the intensity parameters required for calculating the band widths and the gas-to-liquid shifts of the frequency by the theory reported in part I. The agreement between the calculated and the observed values is reasonably good. The phase modulation was the dominant process both in the band broadening and in the frequency shift. It was pointed out, for the first time, that the cross term between the attractive and the repulsive parts of the mechanical collision potential played an important role in the band broadening. Without the cross term, the calculated band widths of the ν CH and δ HCH modes would be an order of magnitude larger than the observed widths.