# Radiative data for highly excited 3d8 4d levels in Ni II from laboratory measurements and atomic calculations

## TL;DR

This study provides new experimental radiative lifetimes and theoretical oscillator strengths for highly excited 3d8 4d levels in Ni II, improving atomic data crucial for astrophysical spectral analysis.

## Contribution

It offers the first combined experimental and theoretical data set for these Ni II levels, with improved accuracy over previous calculations.

## Key findings

- Measured radiative lifetimes of seven high-lying Ni II levels with laser-induced fluorescence.
- Calculated transition probabilities and oscillator strengths for 477 Ni II transitions.
- New gf-values are about 20% higher than previous calculations and match experimental lifetimes within 5%.

## Abstract

This work reports new experimental radiative lifetimes and calculated oscillator strengths for transitions from 3d8 4d levels of astrophysical interest in singly ionized nickel. Radiative lifetimes of seven high-lying levels of even parity in Ni II (98400 -100600 cm-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. A new set of transition probabilities and oscillator strengths has been deduced for 477 Ni II transitions of astrophysical interest in the spectral range 194 - 520 nm depopulating even parity 3d8 4d levels. The new calculated gf-values are, on the average, about 20 % higher than a previous calculation by Kurucz (http://kurucz.harvard.edu) and yield lifetimes within 5 % of the experimental values.