Single-photon emission from simultaneous two-electron transitions in He-like ions

The electric and magnetic dipole radiations due to a double-electron jump from the S-1(0) state of He-like ions with an empty K shell are evaluated for 21 ions with 10 <= Z <= 92 using fully relativistic multiconfiguration Dirac-Fock wave functions in the active space approximation with the inclusion of a finite nuclear size, the Breit interaction, self-energy, and vacuum polarization. The contributions from correlation and higher-order corrections to the x-ray energies and rates are discussed in detail. The effects of biorthogonal and partially orthogonal spin orbitals of the initial and final states on the correlation sensitive radiative rates are analyzed. The accuracy of our computed data is judged by the uncertainties in the fine structure energy levels along with the agreement in the length and velocity forms of transition rates. The present results are compared with other available theoretical data.