Relativistic configuration-interaction calculation of $K\alpha$ transition energies in beryllium-like iron

Abstract

We perform relativistic configuration-interaction calculations of the energy levels of the low-lying and core-excited states of beryllium-like iron, Fe$^{22+}$. The results include the QED contributions calculated by two different methods, the model QED operator approach and the screening-potential approach. The uncertainties of theoretical energies are estimated systematically. The predicted wavelengths of the K\alpha transitions in beryllium-like iron improve previous theoretical results and compare favorably with the experimental data.