Dominance of the Breit Interaction in the X-Ray Emission of Highly Charged Ions Following Dielectronic Recombination

The Breit interaction typically appears as a—more or less small—correction to the Coulomb repulsion acting among the electrons. We here propose two x-ray measurements on the angular distribution and linear polarization of the 1s2s²2p_1/2 J=1→1s²2s² J=0 electric-dipole radiation of high-Z, beryllium-like ions, following the resonant electron capture into initially lithium-like ions, for which the Breit interaction strongly dominates the Coulomb repulsion and leads to a qualitative change in the expected x-ray emission pattern. The proposed measurements are feasible with present-day x-ray detectors and may serve a stringent test on relativistic corrections to the electron-electron interaction in the presence of strong fields.