Second spectrum of chromium (Cr II), Part III: Radiative lifetimes and transition probabilities from highly excited 3d45s levels

Abstract

In this study we have extended our previous investigations of Cr II spectrum to levels of the 3d 4 5s configuration. Once again an overall good agreement is observed for these levels between experimental oscillator strength values and our calculated data using two different approaches, namely the oscillator strength parameterization and the HFR+CPOL methods. Recurring to the latter model we have computed radiative lifetime values for 20 3d 4 5s levels, confirming the well founded basis of recent experimental data, given in literature. From the use of the former method and with the help of a least squares fitting procedure to available experimental gf-values we have taken advantage of extracting for the first time the transition radial integral value for 3d 4 4p−3d 4 5s, ⟨4p|r 1 |5s⟩ = 1.962±0.005, which is confirmed favorably by ab initio results, obtained by the HFR method scaled by a factor 0.92 or directly by the HFR+CPOL approach. Finally a long list of semi-empirical oscillator strength, transition probability and branching fraction values is generated for around 500 Cr II transitions depopulating the 3d 4 5s levels. Our new gf data are compared successfully with those given by Kurucz.

Branching Fractions and Transition Probabilities for UV Transitions in the Spectrum of Cr ii

“…Recent theoretical calculations of transition probabilities include Raassen & Uylings (1996), Kurucz (2016), Bouazza et al (2018a, 2018b), and Tayal & Zatsarinny (2020. The calculations of Bouazza et al (2018a) focus on highly excited 3d 4 5s levels and those of Bouazza et al (2018b) on low-lying 3d 4 4p levels. Both papers focus on levels with previous experimental lifetime measurements.…”