Bethe logarithms for the 1 singlet S, 2 singlet S and 2 triplet S states of helium and helium-like ions

We have computed the Bethe logarithms for the 1 singlet S, 2 singlet S and 2triplet S states of the helium atom to about seven figure-accuracy using ageneralization of a method first developed by Charles Schwartz. We have alsocalculated the Bethe logarithms for the helium-like ions of Li, Be, O and S forall three states to study the 1/Z behavior of the results. The Bethe logarithmof H minus was also calculated with somewhat less accuracy. The use of ourBethe logarithms for the excited states of neutral helium, instead of thosefrom Goldman and Drake's first-order 1/Z-expansion, reduces by several ordersof magnitude the discrepancies between the theoretically calculated andexperimentally measured ionization potentials of these states