Cometary Emission Spectra in the Visual Region.

A list of wave lengths of the emission features occurring in the region X > 4800 has been compiled partly on the basis of previously published data but mainly from measurements of spectrograms of the recent bright comets 1940c and 1942g obtained at the McDonald, the Mount Wilson, and the Dominion Astrophysical observatories. It is indicated that certain of the more prominent features behave, with respect to the comet's heliocentric distance, as emissions from polyatomic molecules would be expected to do. Comparison of the cometary spectrum with that of an oxyammonia flame leads to the suggested identification of a number of the emission features, among them the strong "X 6300 group," as due to a dissociation product of ammonia, probably NH2