2017A&A...600A.108H

Aims. This work reports new experimental radiative lifetimes and calculated oscillator strengths for transitions from 3d⁸4d levels of astrophysical interest in singly ionized nickel.
Methods. Radiative lifetimes of seven high-lying levels of even parity in NiII (98400-100600cm^–1) have been measured using the time-resolved laser-induced fluorescence method. Two-step photon excitation of ions produced by laser ablation has been utilized to populate the levels. Theoretical calculations of the radiative lifetimes of the measured levels and transition probabilities from these levels are reported. The calculations have been performed using a pseudo-relativistic Hartree-Fock method, taking into account core polarization effects.
Results. A new set of transition probabilities and oscillator strengths has been deduced for 477 NiII transitions of astrophysical interest in the spectral range 194-520nm depopulating even parity 3d⁸4d levels. The new calculated gf-values are, on the average, about 20% higher than a previous calculation and yield lifetimes within 5% of the experimental values.