Accurate Dirac-Coulomb energies for the ground states of helium-like atoms

We present accurate (relative errors ≅ 10-7) eigenvalues for the 1s21S0 eigenstates of the Dirac-Coulomb Hamiltonian for helium-like atoms. A novel non-perturbative method, based upon a sequence of multiconfiguration Dirac-Fock calculations together with an extrapolation procedure, is used to arrive at the numbers given. In conjunction with perturbation theory, the same technique may be extended to calculate higher-order contributions to the energies of two-electron systems to high precision. As an example, we have obtained estimates of the energies of the interelectronic electromagnetic interaction. (author)