Hyperfine structure investigations for the odd-parity configuration system in atomic holmium

Highlights: • The hyperfine structure for 97 spectral lines recorded by laser spectroscopy in a hollow cathode discharge lamp. • The hyperfine structure constants for 40 new odd-parity levels in the holmium atom determined on the basis of laser spectroscopic investigations, 21 levels remeasured. • The results found generally fairly consistent with the available literature data (experimental and theoretical), although in some cases important differences observed. In this work new experimental results of the hyperfine structure (hfs) in the holmium atom are reported, concerning the odd-parity level system. Investigations were performed by the method of laser induced fluorescence in a hollow cathode discharge lamp on 97 spectral lines in the visible part of the spectrum. Hyperfine structure constants: magnetic dipole - A and electric quadrupole - B for 40 levels were determined for the first time; for another 21 levels the hfs constants available in the literature were remeasured. Results for the A constants can be viewed as fully reliable; for B constants further possibilities of improving the accuracy are considered.