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This work is devoted to investigations of unclassified spectral lines in atomic holmium, aiming at identification of new electronic levels and determination of their hyperfine structure. Altogether 113 unclassified lines were investigated with the method of laser induced fluorescence in a hollow cathode discharge lamp. As a result, 35 odd-parity electronic levels with previously unknown energies were identified; for all of them the hyperfine structure constants A and B were also determined. The data reported greatly facilitated the semi-empirical fit of the fine and hyperfine structure of the odd-parity level system, performed in our group.

In this work the hyperfine structure of some tens of unclassified spectral lines in the holmium atom was investigated with the method of laser induced fluorescence in a hollow cathode discharge lamp. As a result, 21 new electronic odd-parity levels, with previously unknown energies within the range 33000–42000 cm − 1 , were identified and their hyperfine structure constants A and B were determined. The experimental data obtained will facilitate the semi-empirical fit of the fine and hyperfine structure of the odd-parity level system for the atomic holmium, currently in progress in our group.

In the present work measurements of Lande gJ factors for some electronic levels of the europium atom are presented. The measurements were performed with the use of the Zeeman effect of the hyperfine structure, observed with the method of laser spectroscopy in a hollow cathode discharge lamp placed in constant magnetic field, with laser induced fluorescence detection. Investigation of 54 spectral lines of europium in the spectral range 511–662 nm enabled for the first time the determination of gJ factors for 16 levels belonging to the odd-parity configurations of Eu and 4 levels belonging to the even-parity configurations. Moreover, 3 gJ values for levels belonging to the even-parity configurations, previously known from the literature, were corrected.

This work presents the measurements of the hyperfine structure constants A and B, as well as the isotope shifts, for 26 electronic levels belonging to the even-parity configurations at the energy range 28000–40000 cm − 1 in the europium atom. The measurements were performed with the use of laser spectroscopy with a hollow cathode discharge lamp as the source of the atoms and the detection of laser induced fluorescence. Among the results obtained, 10 levels were measured for the first time, in the case of another 3 levels results somewhat more precise than the earlier published ones were obtained. The A and B hyperfine structure constants’ values were determined on the basis of the measurements on 73 spectral lines located in two wavelength ranges: 480–560 nm and 625–680 nm.

In this work laser-spectroscopic investigations of selected electronic levels in the holmium atom are performed in the context of possible second-stage laser cooling transitions which can be considered in a magneto-optical trap. Five transitions were directly recorded by the method of laser induced fluorescence in a hollow cathode discharge. The hyperfine structure constants A and B for the upper even-parity J = 17 / 2 levels, evaluated in earlier works, were generally confirmed, and their accuracy was improved; thus the frequency differences between the hyperfine structure components, relevant for the possibility of application of the hyperfine repumping, could be determined. Investigations of the Zeeman-hyperfine structure of these spectral lines were performed in order to evaluate the Lande gJ factors of the upper levels; these were reported for the first time. Semi-empirical preliminary calculations of the lifetimes of the even-parity levels in question were also carried out, allowing estimation of the expected Doppler limits for the possible narrow-band laser cooling at the respective transitions. The degree of similarity between the gJ factors of the upper levels of the cooling transitions and the ground state is important for the efficiency of the sub-Doppler laser cooling in a magneto-optical trap. The results presented might facilitate the choice of the most favorable option of obtaining narrow-band laser cooling of the holmium atoms.

In this work the hyperfine structure of 43 odd-parity levels of the terbium atom was investigated with the method of laser induced fluorescence in a hollow cathode discharge. Altogether 73 spectral lines were examined, with the odd-parity levels involved as the upper levels. For 41 levels the constants A and B were determined for the first time, and for the remaining two levels improved values could be obtained due to the supplementary measurements performed. As a by-product, also the hyperfine structure constants for two lower even-parity levels could be corrected. The obtained results concerning the odd-parity levels contributed to considerable extension of the available database of the hyperfine structure constants for the atomic terbium; they would be included in the semi-empirical analysis of the fine and the hyperfine structure for the odd-parity configurations system, planned in our research group.