The Classification of the First Spark Spectrum of Lead: Pb II

Abstract

The spectrum of Pb II as excited in a Schüler hollow cathode discharge in helium has been photographed in the region from 800A to 10,000A. With these data the classification given by Fraülein H. Gieseler (Zeits. f. Physik 42, 265 (1927)) has been corrected and extended. 247 lines have been classified, which locate 89 levels below the ionization level of the ion. These include the $s$, $p$, $d$, $f$ and $g$ series based on $6s^2$, extending to values of $n$ of from 14 to 19, and all levels of the other configurations which are expected below ionization. The assignment of these levels is checked by series considerations, by Zeeman effect data, by hyperfine structure data, by comparison with the similar spectra Ge II and Sn II, and by the agreement with the regular and irregular doublet laws in the isoelectronic sequence with T1 I and Bi III. The observed anomalous location of a number of the levels is shown to be explained qualitatively by the perturbations expected between the even levels.