Combination Bands in the Infra-Red Spectra of CCl4and SiCl4

It is assumed that the six Raman bands of C${\mathrm{Cl}}_4$ found by Pringsheim and Rosen give the fundamental absorption frequencies. Simple combinations of these frequencies by addition account for all of the absorption bands between 1μ and 16μ, except a few very weak bands. The absorption bands of Si${\mathrm{Cl}}_4$ in the same region are accounted for by similar combinations of six fundamental frequencies, four of which are known either as Raman bands or as resonance frequencies in the dispersion formula. The two systems of fundamental frequencies and their combinations are strikingly similar, as one might expect in consequence of the chemical similarity of the compounds.