The Third Spectrum of Tantalum (Ta III): Fine and Hyperfine Structure

Abstract

Presented is the first successful analysis of the Ta III spectrum. All the 37 levels of the low lying even configurations 5d3, 5d26s, and 5d6s2, and all the 68 levels of the higher odd configurations 5d26p and 5d6s6p have been established. About 720 spectral lines have been classified in the region of 1000–3950 Å as belonging to the (5d3 + 5d26s + 5d6s2) - (5d26p + 5d6s6p) transition array. The results are mainly based on spectrograms obtained by means of a vacuum sliding spark discharge and a 10.7 m normal incidence spectrograph at the Paris-Meudon Observatory, which provides a unique plate factor of 0.25 Å/mm in the first order. The resulting line list has been completed by partial data taken from earlier lists used for the Ta II and Ta IV studies. The analysis was guided by predicted energy level values and transition probabilities calculated by means of a complete set of orthogonal operators. The program suite IDEN for computer-aided spectra analyses played a crucial role in the study.