Anomalies in QED corrections to the 3d states of K-like ions

Higher-order QED corrections to atomic energy levels from electron correlations are typically smaller in magnitudes than the lowest-order radiative corrections. However, such is not the case for the $3d$ states of K-like ions, as screened QED corrections are enhanced by interactions with the $1s-3p$ core electrons which have much larger one-loop self-energy and vacuum polarization corrections than the $3d$ valence electrons. In this work, screened vacuum polarization corrections are found to be almost two orders of magnitudes larger than the lowest-order corrections for the $3d$ ground states of K-like krypton. Similar enhancements should exist in the self-energies of these $3d$ states.