QED calculation of the2p1∕2−2sand2p3∕2−2stransition energies and the ground-state hyperfine splitting in lithiumlike scandium

Abstract

We present the most accurate up-to-date theoretical values of the $2{p}_{1∕2}\text{\ensuremath{-}}2s$ and $2{p}_{3∕2}\text{\ensuremath{-}}2s$ transition energies and the ground-state hyperfine splitting in ${\mathrm{Sc}}^{18+}$. All two- and three-electron contributions to the energy values up to the two-photon level are treated in the framework of bound-state QED without $\ensuremath{\alpha}Z$ expansion. The interelectronic interaction beyond the two-photon level is taken into account by means of the large-scale configuration-interaction Dirac-Fock-Sturm (CI-DFS) method. The relativistic recoil correction is calculated with many-electron wave functions in order to take into account the electron-correlation effect. The accuracy of the transition energy values is improved by a factor of 5 compared to the previous calculations. The CI-DFS calculation of interelectronic-interaction effects and the evaluation of the QED correction in an effective screening potential provide significant improvement for the $2s$ hyperfine splitting. The results obtained are in good agreement with recently published experimental data.