Investigations on the spectrum of selenium V-Structure of Se II

Abstract

Besides the very early work summarized in Kayser's 'Handbuch' the first considerable list of lines due to singly ionized selenium was given by L. and E. Bloch in 1930. These authors used an electrodeless discharge through selenium vapour and ascribed the lines to the several stages of ionization of the atom by inserting a variable auxiliary gap in series with the discharge tube. Larcroute also investigated the spectrum from λ 2200 to λ 1200. These measurements, however, were not sufficiently complete, and did not extend far enough into the extreme ultra-violet to enable an analysis of the spectrum of Se II to be under-taken, and up to the present there are no published records of any attempts at such an analysis. The present paper, one of a series, deals with the essential features of the quartet and doublet systems found to be characteristic of the singly ionized atom of Se. More than 200 lines have been classified, comprising a majority of the important lines of the spectrum and several of the faint ones. There are, however, some definite groups of lines which are not accounted for by the set of identified terms; these groups lie chiefly in the extreme quartz and the fluorite regions and it would seem that they probably arise from double electron transitions and combinations with sp 4 terms. When the analysis had been obtained, a very irregular feature was observed regarding the intensity of the fundamental resonance group 4 p 4 S - 5 s 4 P; this is discussed in a later section.