Intensities in Raman spectra V. Intensity measurements and normal co-ordinates for some group IV tetrahalides

The calculation of the coefficients ltξ, pσ and l-1pσtξ relating symmetry co-ordinates and normal co-ordinates is reported for the series of molecules CCI4, CBr4, SiCl4, SiBr4, GeCl4, GeBr4, SnCl4 and SnBr4. A potential field suggested by Simanouti has been used and tables of the transformation coefficients are quoted. The preparation and purification of some of these compounds is described. The relative Raman intensities of the degenerate vibrational modes of these molecules have been measured. The intensities of these molecules are discussed in terms of the bond-polarizability theory.