Isotope shift calculations in Ti II

TL;DR

This paper introduces an advanced ab initio method for calculating transition energies and isotope shifts in Ti II, crucial for astrophysical studies of the early universe and fundamental constants.

Contribution

It extends previous configuration-interaction and many-body perturbation theory methods by including effective three-body interactions and energy denominator modifications, improving accuracy for Ti II.

Findings

Effective three-body interactions significantly impact isotope shift calculations.

The method enhances the accuracy of transition energy predictions in Ti II.

Results support the use of isotope shifts to study early universe chemistry.

Abstract

We present an accurate ab initio method of calculating transition energies and isotope shifts in the 3d-transition metals. It extends previous work that combines the configuration-interaction calculation with many-body perturbation theory by including the effective three-body interaction and modification of the energy denominator. We show that these effects are of importance in Ti II. The need to develop methods that can accurately calculate isotope shifts in 3d-transition metals comes from studies of quasar absorption spectra that seek to measure possible variation of the fine-structure constant alpha over the lifetime of the Universe. Isotope shift can also be used to measure isotope abundances in gas clouds in the early Universe, which are needed in order to test models of chemical evolution.