New Energy Levels in Au II, Hg III, Tl IV, Pb V and Bi VI

All the previously unknown 5d¹⁰, 5d⁹6s and 5d⁹6p levels in all the stable members of the platinum-like isoelectronic sequence, and some 5d⁹6d and 5d⁹7s levels, have been identified. Several corrections are made to the literature on Au II, Hg III and Tl IV. The Pb V and Bi VI classifications verify Arvidsson's estimates of the stages of ionization for the individual lines. The 5d⁹6p|₀ levels were found only in consequence of Goble's predictions from his solution of the four-vector problem. The dependence of the energy and intensity values upon the atomic number is very smooth, except for a branching effect explained by Goble. New d⁹s screening numbers and Houston parameters are given. Ionization potentials are estimated, by a comparison method, up to 87.9±{}0.7 volts for Bi VI. Analysis of the one (partly resolved) hyperfine structure pattern attributed to Bi VI yields a splitting factor a(6s)=3.1±0.2 cm^-1.