Nonrelativistic-energyZ-expansion coefficients for singly excitedSandPstates of two-electron ions

Coefficients $E_k$ in the $Z$-expansion series for $E\left(Z\right)\mathrm{}$, where $E\left(Z\right)\mathrm{}$ is the nonrelativistic total energy and $Z$ the nuclear charge, are tabulated for singly excited $n\left({}_{}{}^{1,3}{}_{}{}^{}S\right)$ and $n\left({}_{}{}^{1,3}{}_{}{}^{}P\right)$ states of two-electron ions, $n=2-5$. These results were obtained largely from an analysis of variational $E\left(Z\right)\mathrm{}$ values given by Accad, Pekeris, and Schiff but were taken in some cases from variational-perturbation calculations of other authors. The $Z$-expansion estimates of nonrelativistic term values for ions with $Z\ge 11$ have been compared with the corresponding results of Ermolaev and Jones, and agreement within 1 or 2 parts in ${10}^7$ was found for most states.