Isotope shifts and relativistic shifts of Cr II for study of alpha-variation in quasar absorption spectra

TL;DR

This paper employs advanced computational methods to accurately calculate isotope and relativistic shifts in Cr II, aiding the study of potential variations in the fine-structure constant through quasar spectra analysis.

Contribution

It introduces a comprehensive CI+MBPT approach including second-order diagrams for five-valence-electron systems, improving accuracy over previous methods.

Findings

Second-order MBPT diagrams are essential for accurate calculations in Cr II.

Calculated isotope and relativistic shifts for Cr II relevant to astrophysical observations.

Enhanced understanding of electron correlation effects in complex ions.

Abstract

We use the combination of configuration interaction and many-body perturbation theory method (CI+MBPT) to perform ab initio calculations the low-energy spectra of Cr II with high accuracy. It is found that second-order MBPT diagrams should be included in a consistent and complete way for the MBPT to improve the accuracy of calculations in this five-valence-electron system. This contrasts with previous ions with fewer valence electrons where it was found that single-valence-electron diagrams dominate the corrections. Isotope shifts and relativistic shifts (q-values) are calculated for use in astronomical determination of the fine-structure constant in quasar absorption spectra.