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

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.