Relativistic Z-expansions for excited states of He and Li

Abstract

Calculations of first-order relativistic Z-expansion coefficients are extended to states in the He and Li isoelectronic sequences containing 3p and 4p electrons. It is noted that the Briet interaction contributes only through exchange terms when dealing with the jj-configuration average of two non-equivalent electrons. Second-order coefficients for excited two-electron states are extrapolated from the variational calculations of Accad et al. (1971). Z-expansion predictions of the 1s2np 2P doublet splittings (n=2,3,4) are compared to experimental and to other theoretical results.