The spectral intensity of the collision-induced rotational Raman scattering by gaseous CH4and CH4-inert gas mixtures

The collision-induced light scattering spectrum of gaseous pure CH4 and CH4-Ar and CH4-Xe mixtures was studied at 295 K at densities up to 6 m/l. The shape of the high frequency wing is shown to be very well reproduced in all cases by spectra generated with a theory of collision-induced rotational Raman scattering which is based on a long-range interaction mechanism and involves molecular multipole polarizabilities. There is consistency among the values of the magnitude of the dipole-quadrupole polarizability A of CH4 obtained from the intensities of the pure gas and mixture spectra; |A| is found to be 0·88 ± 0·05 Å4, which agrees with ab initio calculations.