We have classified about 400 new spectral lines of neutral tantalum via laser excitation or observation of laser-induced fluorescence. 37 energy levels with even parity and seven levels with odd parity were found by means of systematic hyperfine structure investigations. For the new levels angular momentum, parity, magnetic hyperfine interaction constant A and electric quadrupole interaction constant B were deduced. In addition, we have classified 230 new lines observed in high resolution Fourier transform spectra by analysing their observed hyperfine structure patterns.

The hyperfine structures of 57 new spectral lines of the tantalum atom were investigated by means of laser excitation. From the hyperfine patterns we have determined the angular momenta J; the magnetic hyperfine interaction constants A and the electric quadrupole interaction constants B of 15 new energy levels of even parity and three new levels of odd parity. The observation of laser-induced fluorescence led to the classification of further 156 spectral lines for the first time. Additionally 92 lines, observed in high resolution Fourier transform spectra, were classified using a combination of their wavenumbers and their characteristic hyperfine patterns.

We report the discovery of 25 previously unknown energy levels of even parity and 3 previously unknown energy levels of odd parity of the tantalum atom, including the last two unknown levels with energy values below 32500 cm-1. Thus, below 32500 cm-1, all levels predicted by theory have now been observed. These results are based on investigations of the hyperfine structure of 126 new spectral lines of the tantalum atom (Ta I) by means of laser spectroscopy. The observation of laser-induced fluorescence further led to the classification of 159 spectral lines. Additionally, 235 lines, observed in high resolution Fourier transform spectra, were classified by their wave numbers and their characteristic hyperfine patterns.

The hyperfine structure of 39 lines of the singly charged tantalum ion was investigated by means of dopplerlimited laser spectroscopy. From the spectra we have deduced the magnetic hyperfine interaction constants A and the electric quadrupole interaction constants B of 22 levels with even parity and 17 levels with odd parity.

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