The spark spectrum of thallium, Tl III

Abstract

The term structure of the second spark spectrum of thallium, Tl III, was investigated by Carroll in 1926. He found it to be simple doublet spectrum by the identification of the first member of an S, a P and a D term sequence and of a tentative F and a G first member. Carroll also found analogous features in each of the iso-electronic spectra Hg II and Pb IV and showed that these and TI III were similar in character to that of Au I that had been analysed by Thorsen. The doublet structure of each of those spectra is now known to be built on the 1 S (5 d 10 ) state of the next higher ion. The authors examined the spark spectrum of thallium last spring and assigned a number of wave-lengths to the spectrum, Tl II, of the singly ionised atom. Two wave-lengths, namely, λ 2530·88 A. and λ 2452·00 A., that were shown to belong without doubt to Tl II, had previously been used by Carroll to establish the tentative 2 F term of Tl III mentioned above. The 2 F term therefore was invalidated and with it also the dependent 2 G. A subsequent investigation of Tl III was undertaken by us and has resulted in the identification of the real F and G first members and of members of each of the S, P and D series higher than those already located by Carroll. We also sought at the same time to extend the knowledge of the Hg II spectrum and made some progress in this direction. But the recent extensive analysis of Hg II by Paschen has made it unnecessary for us to continue our examination. Our team scheme for Hg II in so far as it was worked out corresponded to Paschen's.