Ultra-violet Extensions of the Arc Spectra of the Alkaline Earths: The Absorption Spectrum of Barium Vapour

Abstract

The absorption spectra of the alkaline earth metal vapours have been photographed in the quartz ultra-violet and Schumann regions, by means of a 3 m vacuum spectrograph and large King furnace. Considerable extensions of the are spectra of these elements have resulted, many of the new lines being two-electron transitions. Extreme cases of autoionization and many examples of series perturbations occur. The results are presented for the case of Ba, including assignments for 64 out of about 68 new lines. The presence of a doubly excited level practically coincident with the lowest ionization limit has striking effects on the photoionization cross section and on the intensities of the high members of the singlet principal series of Ba, which is extended to the m=37 member.