RAMAN SPECTROSCOPY OF LOW PRESSURE GASES AND VAPORS

Abstract

Raman spectra of gases and vapors at pressures of a few atmospheres were obtained with a carefully diaphragmed Raman tube of large volume, irradiated by five high intensity mercury lamps with water-cooled electrodes. Frequencies and intensity contours of 32 of the 35 fundamental bands of CH₄, CH₃Cl, CH₂Cl₂, CHCl₃, CCl₄, and CH₃Br were measured. Vibrational assignments, based on the intensity contours of the bands, showed no discrepancies in previous assignments. The integrated intensities of the bands, determined on the same intensity scale for all compounds of the series, show the inadequacy of the bond polarizability theory of Raman intensities. Depolarization factors, calculated from the intensity distribution in totally symmetric bands, are somewhat greater than those measured for the liquid. Asymmetries in the Q branches of some totally symmetric bands are explained quantitatively in terms of anharmonicity and isotope effect.