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Aims. We report on experimental studies of hyperfine structure splitting of neutral niobium. Methods. We used high-resolution Fourier transform spectroscopy to record a spectrum of niobium produced with a hollow cathode discharge lamp in the range of wavenumbers from 10 000 cm −1 to 30 000 cm −1 . Results. The magnetic dipole hyperfine structure constants A were determined for the 109 levels of odd parity by analyzing the profiles of 224 spectral lines. The A values of 57 of these level are reported for the first time.

Optogalvanic laser spectroscopy has been applied to measure the hyperfine structure of 12 spectral lines of Mn I in the wavelength regions of 660–645 nm and 933–911 nm. Experimental hyperfine structure constants A and B of the isotope 55Mn have been determined for seven levels of even and seven levels of odd parity. Additionally, a parametric analysis of the fine structure and the magnetic dipole hyperfine structure has been performed for the three even configurations 3d54s2, 3d64s and 3d7. Very large values for the ratio a3d10/a3d01 are found. Theoretical predictions for the magnetic dipole hyperfine structure constants A for all levels of the configurations 3d54s2, 3d64s and 3d7 are given.

In this work a parametric study of the fine and hyperfine structure (hfs) for the even parity configurations of atomic niobium (Nb I) is presented. A large amount of new experimental data, published during the last decade, have been considered for the fine and hfs analysis. A multi-configuration fit of 14 configurations have been performed by taking into account second-order of perturbation theory including the effects of closed shell-open shell excitations. Predicted values of level energies as well as magnetic dipole and electric quadrupole hfs constants of A and B are listed, if no experimental values are available.

Optogalvanic laser spectroscopy has been applied to measure the hyperfine structure of 13 spectral lines of Sc I in the wavelength range from 645 to 780 nm. Experimental magnetic dipole hyperfine structure constants A of the isotope 45 Sc have been determined for three levels of even and ten levels of odd parity. For six of these levels the A constants have been measured for the first time. For two further levels the A constants have already been measured but discrepancies between our values and the previous ones are found and discussed. With the new experimental results a parametric analysis of the magnetic dipole hyperfine structure has been performed for the even configuration 3d 2 4s and a very high value for the contact parameter a 10 3d has been found. Additionally, the experimental results for the other even levels are discussed.