Sensitivity coefficients to $\alpha$-variation for astrophysically relevant transitions in Ni II

TL;DR

This paper calculates how transition frequencies in Ni II depend on the fine-structure constant, providing a sensitive probe for detecting possible variations of fundamental constants over cosmological timescales.

Contribution

It presents the first detailed calculation of $q$-factors for Ni II transitions using a configuration interaction method with Dirac-Coulomb Hamiltonian.

Findings

Ni II has high sensitivity to $eta$-variation.

Calculated $q$-factors enable better constraints on fundamental constant variations.

Ni II lines observed at high redshifts are promising for cosmological studies.

Abstract

We calculated the dependence of the transition frequencies on the fine-structure constant $\alpha$ ($q$-factors) for Ni~II. Nickel is one of the few elements with high sensitivity to $\alpha$-variation, whose lines are observed at high redshifts. This makes it a sensitive probe for $\alpha$-variation on the cosmological timescale. The electronic structure of Ni II ion was treated within the configuration interaction (CI) method using Dirac-Coulomb Hamiltonian.