Hyperfine structure of the $4{f}^{8}5{d}^{2}6s$ configuration in the Tb atom

Abstract

Within this work new experimental results concerning the hyperfine structure (hfs) in the terbium atom are presented. Hfs constants A and B for eight levels belonging to the even-parity configuration were determined, based on the results of measurements performed using the laser-induced fluorescence method in a hollow cathode discharge at 18 spectral lines. The configuration in the terbium atom was hitherto very scarcely investigated; for seven of the levels examined within this work results concerning the hfs were obtained for the first time. As a by-product, hfs constants for 12 odd-parity levels, involved as upper levels in the transitions investigated, were also determined. A preliminary attempt at a semi-empirical analysis of Tb I hfs on a multi-configuration basis, based on the results of this work, yielded a value of the one-electron parameter as well as the respective radial integral , which can be compared with the values along the lanthanide elements series reported in the literature. More conclusive results can certainly be obtained once the experimental database for Tb I becomes more extensive.