The Spectrum of Triply Ionized Niobium

Abstract

The spectrum of Nb IV was observed with a sliding spark in the region from 430-3000 Å on the 6.5 m normal incidence vacuum spectrograph and the 3.4 m Jarrell-Ash spectrograph at the Zeeman-Laboratorium. About 294 lines were observed. The level system (ground configuration 4d2, isoelectronic with Sr I) was revised and extended to include 4d nl with nl = 4d, 5s, 5p, 5d, 4f, 6s and 6p respectively and 5s5p. Parametric calculations were made for the even and the odd level system taking into account the configuration interaction directly. The ionization energy was estimated to be 37.73 eV, from the position of the 4d5s and 4d6s configurations.