The absorption spectra of the gaseous monoxides of silicon, germanium and tin in the Schumann region

The absorption spectra of the molecules SiO, GeO and SnO have been examined in the region 1250 to 2000Å. A number of new band systems have been found, and vibrational analyses have been carried out. The determination of the dissociation enérgies of these molecules is discussed: the values derived spectroscopically for SiO, GeO and SnO are 185∙0±6∙8, 155∙8±5∙3 and 126∙0±4∙9 kcal (0° K) respectively. The values for GeO and SnO are in satisfactory agreement with the results of thermochemical work, but the result for SiO suggests that the value of the latent heat of sublimation of silicon is higher than has been suggested, and indicates Lsi⋍100 kcal. The correlation between the states of carbon monoxide and of silicon monoxide is briefly considered, and a provisional value for the ionization potential of SiO, 10∙51 eV, is derived.