On the single-line spectra of magnesium and other metals and their ionising potentials

Abstract

It has been shown by Frank and Hertz that when heated mercury vapour is traversed by electrons possessing kinetic energy slightly above that acquired in a fall of potential of 4·9 volts the vapour is stimulated to the emission of the single spectral line λ = 2636·72 Å. U. It has also been shown by McLennan and Henderson that a spectrum consisting of line single line only can be obtained from mercury vapour when it is bombarded by electrons possessing energy corresponding to any fall of potential within a range beginning at about 5 volts and extending up to slightly over 10 volts. The investigation has also been extended by McLennan and Henderson to include a study of the radiation emitted by zinc and cadmium vapours when traversed by electrons. With these vapours they have found that single-line spectra can be obtained when the electrons traversing these vapours possess kinetic energy lying within a limited and clearly defined range, which has not been fully investigated as yet but which corresponds roughly to potential differences lying between 4 volts and 13·6 volts. With zinc vapour the single-line spectrum consists of light of wave-length λ = 3075·99 Å. U., and with cadmium vapour of light of wave-length λ = 3260·17 Å. U. It should be pointed out here that the lines λ = 2536·72 Å. U., λ = 3075·99 Å. U., and λ = 3260·17 Å. U. are respectively the first members of Paschen's combination series v = 2, p 2 = m , S, for the elements mercury, zinc and cadmium.