Alkali-metal-atom doublet anomalies and the relation between relativistic and nonrelativistic theories

The single-configuration Dirac-Fock treatment of doublet splittings in alkalilike spectra is examined, and it is shown that the nonrelativistic limit is not the nonrelativistic Hartree-Fock, but a multiconfiguration, core-polarization approximation. The latter is the mechanism which has conventionally been invoked to account for the anomalous doublet splittings of nonpenetrating states in alkalilike atomic systems. Both approaches should thus be capable of representing the doublet anomalies