Correlation, Breit, and QED effects in spectra of Mg-like ions

TL;DR

This paper presents highly accurate calculations of spectra for Mg-like ions, emphasizing the importance of Breit and QED effects for ions with higher nuclear charge, using advanced computational methods.

Contribution

The study applies the CI+AO method to Mg-like ions, achieving unprecedented accuracy and analyzing the significance of Breit and QED corrections across the isoelectronic sequence.

Findings

Transition energies accurate to 0.1% or better

Breit and QED effects become significant for Z > 20

Retardation Breit and QED effects for l ≠ 0 are negligible

Abstract

We calculated spectra of the first six members of the Mg-like isoelectronic sequence using different approximations. The most accurate results were obtained with the configuration interaction + all order method (CI+AO), which provided relative accuracy for transition energies on the level of 0.1\%, or better. On this level of accuracy the Breit and QED corrections become important for the systems with nuclear charge $Z\gtrsim 20$. The retardation part of the Breit interaction and QED corrections for the partial waves with $l\ne 0$ are still too small to be important.