Theoretical Investigation of Decay Process in a Doubly Excited 2 s 2 1 S 0 State of He-Like Ions

In the framework of multi-configuration Dirac–Fock theory, a detailed calculation is performed for the decay rates and the energies of the doubly excited 2s2 1S0 state of He-like ions, of which atomic number Z ranges from 6 to 92. The 2s2 1S0 – 1s2S1/2 Auger decay is predominant at low Z regime, whereas the 2s2 1S0 – 1s2p 1,3P1 two-electron one-photon transitions become quite important in moderate and high Z regimes. For heavy ions with Z≥72, the contribution of 2s2 1S0 – 1s2s3S1 M1 transition is significant. The Breit interaction considerably enhances the 2s2 1S0 – 1s2S1/2 Auger rate at high Z regime.