Correlation and Relativistic Effects in Spin-Orbit Splitting

A pronounced discrepancy between Dirac-Fock calculations and experiment for the spin-orbit splitting, 2P 1/2 - 2P 3/2, in the ground states of B- and F-like ions is resolved. The discrepancy arises from the spurious terms inherent in the relativistic self-consistent-field (SCF) procedure. Removal of these terms significantly improves the agreement between theory and experiment on spin-orbit splitting. It is emphasized that theoretical transition energies obtained through separate initial- and final-state calculations can suffer from the inherent difficulty of treating the two states in a balanced manner. For fine structures of light atoms, molecules, or ions, this difficulty becomes even more serious since the error introduced is a substantial fraction of the actual level splitting. It is demonstrated by examples that the present method of eliminating spurious level separations provides an easy remedy for spin-orbit splitting calculations involving the relativistic SCF procedure.