Spectral line classification and hyperfine structure investigation of the element holmium in the visible region

In this study, Fourier Transform spectra of Ho, has been investigated with the focus on atomic and ionic transitions and hyperfine structure of Ho. The holmium plasma was produced in a hollow cathode gas discharge. In the very dense Ho spectrum, in the range from 14280 up to 25000 cm-1 or 400 to 700 nm, more than 4000 Ho lines have been identified. From these lines, 1067 have been classified as atomic or ionic holmium and 3126 lines could be assigned to atomic or ionic Ho. These assignments have been done based on the ratio of signal to noise ratio in two different spectra, measured with either Ar or Ne as a buffer gas. All together 3591 atomic and ionic Ho lines had not been listed in the literature up to now. From 926 lines which have been classified as atomic Ho, 164 spectral lines were investigated by the means of hyperfine structure analysis. Hyperfine structure constants A and B have been determined for 96 levels, 55 of which were measured for the first time.