Accurate calculations of interstellar lines of Mg⁺ using the coupled cluster approach

Abstract

One of the most successful ab initio, highly correlated all-order many-body methods, the relativistic coupled cluster theory, is employed to calculate excitation energies of the doublet states of Mg⁺ and allowed transitions among them that are of interest in astrophysical problems. We have also calculated oscillator strength for the 3s-4p doublet transitions, which is improved over the existing results. These transition lines have been sought after in astronomical observations because they represent the best column density identifier in the interstellar medium. Our calculated oscillator strength (9.3 × 10^-4) and branching ratio (1.80) of these doublet lines matches well with the recent empirical and semiempirical calculations.