Calculations of the atomic structure for the low-lying states of actinium

TL;DR

This paper combines advanced computational methods to accurately calculate atomic properties of low-lying actinium states, improving energy level identification and aiding nuclear structure analysis.

Contribution

It introduces a hybrid computational approach that enhances the accuracy of atomic structure calculations for actinium, including predictions for missing levels and reclassification of some states.

Findings

Good agreement with experimental energy levels

Predictions for missing levels in actinium

Support for reclassification of some atomic states

Abstract

We employ a technique that combines the configuration interaction method with the singles-doubles coupled-cluster method to perform calculation of the energy levels, transition amplitudes, lifetimes, g-factors, and magnetic dipole and electric quadrupole hyperfine structure constants for many low-lying states of neutral actinium. We find very good agreement with existing experimental energy levels and make accurate predictions for missing levels. It has been noted that some of the levels have been previously misidentified; our analysis supports this claim. If spectroscopy is performed with actinium-225, our calculations will lead to values for nuclear structure constants. The accuracy of this can be constrained by comparing with actinium-227.