Prominent enhancement on the radiative branching ratio of the doubly excited resonant states due to the Breit interaction induced ion-core energy inversion

Abstract The Breit interaction is the relativistic correction to the electron-electron interaction which mainly affects the level energies, and it is minor in general. We present a new manifestation of the Breit interaction effects in the highly charged Li- and B-like ions based on the multi-configuration Dirac-Fock calculations, where the strongly correlated many-body wavefunctions of the doubly excited resonant states [1s2p1/22p3/2]3/2 (or [1s(2s2)2p1/22p3/2]3/2) 4P3/2 and 2D3/2 are drastically influenced by the Breit interaction. The strong variation of wavefunctions results in a prominent enhancement of the radiative branching ratio between the two dominant transitions 2p3/2-1s and 2p1/2-1s of the doubly excited states. We elucidate the intrinsic mechanism of this effect is due to the ion-core energy inversion induced by the Breit interaction, and suggest that the possible experimental measurements can be achieved via the dielectronic recombination processes in an electron beam ion trap facility. Based on this effect, we also propose an alternative experimental determination of the fine structure splitting of [1s2p1/2]0,1 (or [1s(2s2)2p1/2]0,1) in heavy He-like (or Be-like) ions from the branching ratio of the doubly excited Li-like (or B-like) ions, which is sensitive to the fine structure level inversions and can be served as a complementary tool to the available hyperfine quenching experimental method aiming for the absolute value of the splitting.