Electromagnetic observables of open-shell nuclei from coupled-cluster theory

TL;DR

This paper introduces a novel coupled-cluster based method combining the equation-of-motion approach and Lorentz integral transform to accurately compute electromagnetic observables in open-shell nuclei, extending beyond traditional closed-shell limitations.

Contribution

It develops and validates a new computational framework for electromagnetic properties of open-shell nuclei using coupled-cluster theory and Lorentz integral transform techniques.

Findings

Agreement with experimental data for oxygen isotopes.

Predicted lower dipole polarizability in open-shell calcium isotopes.

Motivates future experimental studies at nuclear drip lines.

Abstract

We develop a new method to describe electromagnetic observables of open-shell nuclei with two nucleons outside a closed shell. This approach combines the equation-of-motion coupled-cluster method for such systems and the Lorentz integral transform technique, expanding the applicability of coupled-cluster theory for these properties beyond closed-shell nuclei. To validate this new approach, we compute the non-energy-weighted dipole sum rule and the dipole polarizability of $^{16,24}$O in both the closed-shell and the new equation-of-motion coupled-cluster frameworks, finding agreement within error bars. We then analyze the evolution of the dipole polarizability along the oxygen and calcium isotopic chains. Our predictions agree well with available experimental data and other available theoretical calculations for the closed-shell $^{16,22}$O and the open-shell $^{18}$O. In the calcium isotopes, we observe that our dipole polarizability predictions for open-shell nuclei are lower than those of closed-shell nuclei. Our predictions for $^{24}$O and $^{54,56}$Ca will motivate future experimental studies at the dripline.