QED calculations of intra-$L$-shell doubly excited states in Be-like ions

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Main Authors: Malyshev, A. V., Kozhedub, Y. S., Shabaev, V. M., Tupitsyn, I. I.
Format: Preprint
Published: 2025
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author Malyshev, A. V.
Kozhedub, Y. S.
Shabaev, V. M.
Tupitsyn, I. I.
author_facet Malyshev, A. V.
Kozhedub, Y. S.
Shabaev, V. M.
Tupitsyn, I. I.
contents The rigorous QED approach is employed to calculate the energies of the $2p2p\,^3P_{0,1,2}$, $2p2p\,^1D_2$, and $2p2p\,^1S_0$ states of selected Be-like highly charged ions over a wide range of nuclear-charge numbers, $18 \leqslant Z \leqslant 92$. Combined with the previously reported energies of the $2s2p \, ^3P_{0,1,2}$ and $2s2p \, ^1P_1$ states [A. V. Malyshev et al., Phys. Rev. A 110, 062824 (2024)], the obtained results are used to study various intra-$L$-shell transition energies. Strong level mixing, caused by the proximity of states with the same symmetry, is overcome by means of the QED perturbation theory for quasi-degenerate levels. The applied approach merges a rigorous perturbative QED treatment up to the second order with the consideration of electron-electron correlation contributions of the third and higher orders evaluated within the Breit approximation. The higher-order screened QED effects are estimated using the model-QED-operator approach. The nuclear-recoil and nuclear-polarization effects are also taken into account. The obtained predictions represent the most accurate theoretical description of the electronic structure of Be-like ions to date and demonstrate good agreement with available experimental data.
format Preprint
id arxiv_https___arxiv_org_abs_2509_04121
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle QED calculations of intra-$L$-shell doubly excited states in Be-like ions
Malyshev, A. V.
Kozhedub, Y. S.
Shabaev, V. M.
Tupitsyn, I. I.
Atomic Physics
The rigorous QED approach is employed to calculate the energies of the $2p2p\,^3P_{0,1,2}$, $2p2p\,^1D_2$, and $2p2p\,^1S_0$ states of selected Be-like highly charged ions over a wide range of nuclear-charge numbers, $18 \leqslant Z \leqslant 92$. Combined with the previously reported energies of the $2s2p \, ^3P_{0,1,2}$ and $2s2p \, ^1P_1$ states [A. V. Malyshev et al., Phys. Rev. A 110, 062824 (2024)], the obtained results are used to study various intra-$L$-shell transition energies. Strong level mixing, caused by the proximity of states with the same symmetry, is overcome by means of the QED perturbation theory for quasi-degenerate levels. The applied approach merges a rigorous perturbative QED treatment up to the second order with the consideration of electron-electron correlation contributions of the third and higher orders evaluated within the Breit approximation. The higher-order screened QED effects are estimated using the model-QED-operator approach. The nuclear-recoil and nuclear-polarization effects are also taken into account. The obtained predictions represent the most accurate theoretical description of the electronic structure of Be-like ions to date and demonstrate good agreement with available experimental data.
title QED calculations of intra-$L$-shell doubly excited states in Be-like ions
topic Atomic Physics
url https://arxiv.org/abs/2509.04121