SandPStates of the Helium Isoelectronic Sequence up toZ=10

Calculations have been made of the energy levels and other properties of the states $n{}_{}{}^1{}_{}{}^{}S$, $n{}_{}{}^3{}_{}{}^{}S$, $n{}_{}{}^1{}_{}{}^{}P$, and $n{}_{}{}^3{}_{}{}^{}P$, $n=2\mathrm{} \mathrm{to} 5$, for atoms belonging to the helium isoelectronic sequence up to $Z=10\mathrm{}$, and also for the higher excited $S$ states of helium. The theoretical term values, including the contributions from the mass-polarization correction and the relativistic effects of order ${\alpha }^2$ are listed. A detailed comparison with the experimentally determined energy differences between $S$ and $P$ states for He I up to F VIII shows a satisfactory agreement in almost every case, provided that we include an estimate of the Lamb-shift correction to the $S$-state energy level when considering transitions involving the $1{}_{}{}^1{}_{}{}^{}S$, $2{}_{}{}^1{}_{}{}^{}S$, or $2{}_{}{}^3{}_{}{}^{}S$ states.