Spectra of doubly and trebly ionised thallium

Abstract

CONTINUING our previous work on Tl II and Pb III, the spectra of Tl III and Tl IV have been under examination by us for some time past. A preliminary attempt, by the application of the X-ray doublet-laws, revealed a number of regularities consisting of mainly the regular doublet terms. As a result of further attempts, it has now been possible to identify the inverted 2D term (5d96s2) and the quartet terms of (5d96s6p) and (5d96s6d) configurations. The starting point for the discovery of the inverted 2D term was given by the identification of 76150, 81834, and 100452 as 6s'2D – 7p2P. The super multiplet accompanying the electron transition 6p'6d' contains about forty lines in the ultra-violet. A few combinations due to transitions 6p7s have also been established. The (5d96s2) 2D term interval is found to be 18618. The combinations that could not be identified are either very faint or out of range.