Hyperfine structure of the odd-parity configuration 4f95d in singly ionized terbium

•Hyperfine structure constants for 12 new odd-parity levels in Tb II determined from laser spectroscopic investigations.• Semi-empirical calculations of the fine- and the hyperfine structure for the configuration 4f95d performed.•Fine- and hyperfine structure radial integrals determined, comparable to ab initio values.

Within this work experimental investigations of the hyperfine structure for the odd-parity levels belonging to the configuration 4f95d in Tb II were performed. Out of 15 known electronic levels in this configuration, 12 were examined in this context, 11 of them for the first time. Altogether 25 transitions were studied with the odd-parity levels under investigation involved as the lower levels and another 4 transitions involving the previously known odd-parity levels, belonging to the configuration 4f96s. As a by-product, also the hyperfine structure constants for the upper even-parity levels were determined, which in most cases could be compared to the earlier literature data. Semi-empirical calculations of the fine- and the hyperfine structure were performed in single configuration basis. Also ab initio calculations of the hyperfine structure parameters were carried out. Results of the semi-empirical analysis should be considered preliminary because of the scarcity of the available experimental data, in particular the low number of the known electronic levels in the configuration studied.