Absorption spectra of some carbon and tin halides in the vapour state

The absorption spectra of the vapours of SnCl4, SnBr4 and of molecules of the types CX4, CHX3, and CH2X2 (X = Cl, Br, I) are investigated. From the number of maxima and their energy differences, and a comparison of the beginnings of the various absorption regions with thermochemical data, it is concluded that the first process of photodissociation corresponds not to the process MX4 → MX3 + X but to MX4 → MX2(1Σ) + 2X etc.; the further absorption regions are due to one or two excited halogen atoms