Energy levels of core-excited $1s2l2l'$ states in lithium-like ions: argon to uranium

TL;DR

This paper calculates the energy levels of core-excited states in lithium-like ions from argon to uranium using advanced relativistic methods, providing highly accurate data for spectral calibration.

Contribution

It introduces a relativistic configuration-interaction approach that includes QED effects and nuclear recoil, improving the accuracy of energy level predictions for core-excited states.

Findings

Predicted transition energies are more accurate than current experimental data.

The method accounts for relativistic, QED, and recoil effects.

Results can be used for precise X-ray spectral calibration.

Abstract

Energy levels and fine-structure intervals of the $1s2l2l'$ core-excited states are calculated for ions along the Li isoelectronic sequence from argon to uranium. The calculation is performed by the relativistic configuration-interaction method adapted for treatment of autoionizing core-excited states. The calculational approach includes the relativistic treatment of the nuclear recoil effect, the leading QED shifts as delivered by the model QED operator, and the frequency dependence of the Breit interaction. The $1s2l2l'-1s^22l$ transition energies are obtained by combining the present results for the $1s2l2l'$ states with energies of the $1s^22l$ states compiled from previous calculations. All theoretical energies are supplied with uncertainty estimates. Our theoretical predictions for the $1s2l2l'-1s^22l$ transitions are significantly more accurate than the best experimental results available today and can be used for calibrating experimental X-ray spectra.