Breit and QED effects on the 3d9 2D3/2 - 2D5/2 transition energy in Co-like ions

TL;DR

This study uses multiconfiguration Dirac-Hartree-Fock theory to calculate transition energies in Co-like ions, analyzing various relativistic and QED effects across a wide range of atomic numbers, and compares different QED correction methods.

Contribution

It provides a comprehensive analysis of Breit and QED effects on transition energies in Co-like ions, including comparison of different self-energy correction approaches.

Findings

Frequency-independent Breit contribution dominates across all ions.

Self-energy QED correction becomes significant for Z > 50.

The best agreement with experiments is achieved using the model operator approach.

Abstract

The multiconfiguration Dirac-Hartree-Fock theory is used to calculate the 3d9 2D3/2 - 2D5/2 transition energy for Co-like ions with Z = 28-100. We investigate how electron correlation, frequency-independent and -dependent Breit interactions, as well as QED corrections, vary along the sequence. The well-understood frequency-independent Breit contribution has the largest contribution for all ions. Among the corrections to this, correlation decreases rapidly with Z, the frequency-dependent Breit contribution is important especially for high-Z ions, and the self-energy contribution to the QED becomes the largest correction already for Z>50. We evaluate and compare results for the Self-energy in three different approximations, (i) the approach implemented in the GRASP2K package, (ii) the method based on Welton's concept and (iii) a model operator approach recently developed by Shabaev and coworkers. Through comparison with experimental values, it seems that the third set of results have the best agreement with experiments, but the difference from experiments for high-Z ions, is around 0.03%-0.04%, and therefore our results are outside the error bars of the experiments.