Vapour phase Raman intensity studies on the group IV tetrachlorides

Abstract

The frequency-corrected molar intensities of the four Raman-active bands of the tetrachlorides of carbon, silicon, germanium, tin and titanium have been measured in the vapour state relative to that of the v₁(a₁) band of methane. The results are compared with earlier intensity data pertaining to the same compounds in cyclohexane solutions. The differential Raman scattering cross sections of the vapour phase bands of the molecules are in broad agreement with those of the corresponding liquid phase bands once an allowance has been made for the internal field effect. Polarisability derivatives, t₂-block F matrix elements, and mean square amplitudes of vibration have been calculated from the vapour phase intensity data. The F matrix elements so calculated are somewhat closer to those based on the Coriolis constant as the additional constraint to the force field, but there remains a substantial difference between the two sets of elements. This is presumed to reflect inadequacies in the Wolkenstein assumptions of treating polarisabilities.