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In this work, we report a list of 91 strong Th  ii spectral lines in the visible wavelength region that could be used as cosmochronometers in future investigations to determine stellar ages from thorium radioactive decay. This list was established on the basis of a pseudo-relativistic Hartree–Fock model including core-polarization corrections (HFR+CPOL) allowing us to compute the corresponding radiative decay parameters, the latter being found to be in good overall agreement with the most accurate experimental data when available. Besides this semi-empirical approach, the fully relativistic ab initio multiconfiguration Dirac–Hartree–Fock (MCDHF) method was attempted, showing large discrepancies with both the present HFR+CPOL and the most recent experimental oscillator strengths, although the calculated wavelengths from theoretical energy levels agreed with observed spectral line wavelengths within 2.4  per cent. [ABSTRACT FROM AUTHOR]

The radiative lifetime measurements by the time-resolved laser-induced fluorescence technique are reported for 24 levels of Co I with the energy range of 283 45.86-55 922.3 cm-1, amongst which the lifetimes of 20 levels are reported for the first time. The branching fraction measurements by the emission spectrum of a hollow cathode lamp were performed for 11 levels of them together with other two levels reported in the literature, and branching fractions of 39 transitions were obtained. By combining them with lifetime values, the transition probabilities and absolute oscillator strengths of these lines were determined. [ABSTRACT FROM AUTHOR]

The determination of radiative transition probabilities or oscillator strengths is of common interest in astrophysics. The analysis of the high-resolution stellar spectra is now available in order to estimate the stellar abundances. In this paper, 93 experimentally obtained transition probability values (Aki) for singly ionized krypton spectral lines belonging to the ultraviolet (UV) wavelength region (208-360) nm are presented. These data, expressed in absolute units, were derived from the measurements of relative spectral line intensities and the values of transition probability data taken from the literature. The results obtained extend considerably the transition probability data base. As a light source, a plasma from a low-pressure pulsed arc was used. Its electron density was in the range of (1.5-3.4) × 1022 m-3, while the temperature was between 28 000 and 35 000 K. A detailed analysis of the results is also given. Only a few relative and a few absolute transition probabilities from other authors, for the mentioned spectral region, are available in the literature. [ABSTRACT FROM AUTHOR]