Ab initio calculations of the $2p_{3/2} \rightarrow 2s$ transition in He-, Li-, and Be-like uranium

TL;DR

This paper presents high-precision ab initio QED calculations of specific transition energies in highly charged uranium ions, incorporating various nuclear and electron correlation effects, and achieves results consistent with experimental data.

Contribution

It introduces a combined QED and Breit approximation approach for calculating transition energies in uranium ions, including quasidegenerate levels and higher-order effects.

Findings

Transition energies agree with experimental data

Higher-order effects are effectively estimated

Uncertainty analysis enhances result reliability

Abstract

The bound-state QED approach is applied to calculations of the $2p_{3/2} \rightarrow 2s$ transition energies in He-, Li-, and Be-like uranium. For U$^{90+}$ and U$^{89+}$, standard perturbation theory for a single level is employed, while the calculations of U$^{88+}$ have required its counterpart for quasidegenerate levels. The utilized approach merges the rigorous QED treatment up to the second order of perturbation theory with the higher-order electron-correlation contributions evaluated within the Breit approximation. The higher-order screened QED effects are estimated by means of the model-QED operator. The nuclear recoil, nuclear polarization, and nuclear deformation effects are taken into account as well. Along with the transition energies, their pairwise differences are calculated. The comprehensive analysis of the uncertainties due to uncalculated effects is carried out, and the most accurate theoretical predictions, which are in perfect agreement with available experimental data, are obtained.