Radiative de-excitation of the 1s 2 2s3 p 3 P 0 level in beryllium-like ions: A competition between an E2 and a two-electron one-photon E1 transition

Abstract

I have performed a complete Multi-Configuration Dirac-Fock calculation of the radiative de-excitation of the 1s22s3p3P0 level in beryllium-like ions. Initial and final wave functions are fully optimized, and include valence and core polarization correlation (Coulomb and Magnetic). Non-orthogonality between initial and final state spin-orbitals is exactly accounted for. I show that the main mode of de-excitation of the 1s22s3p3P0 level at high Z is an E2 transition to the 1s22s2p3P2 and that a two-electron one-photon E1 transition to the 1s22p2 3P1 plays an important role at low Z. The latter transition appears to be the difference of two large matrix elements which cancel almost exactly and thus has a very complicated Z dependence, which is studied in the present paper.