2025/09/04 by Malyshev, A. V., Kozhedub, Y. S., Shabaev, V. M. +1
#Atomic Physics (physics.atom-ph) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2509.04121
The rigorous QED approach is employed to calculate the energies of the 2p2p 3P0,1,2, 2p2p 1D2, and 2p2p 1S0 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 3P0,1,2 and 2s2p 1P1 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.