Quantum electrodynamic corrections to the 23S1→11S0+one photon transition rate in helium and helium-like ions

The order (Zα)5, α (Zα)4, and α (Zα)4 log(Zα) energy denominator and recoil corrections to the leading order (Zα)4 decay amplitude for the 23S1→11S0+one photon transition is considered. It is found that order α (Zα)4 terms arise in the individual diagrams but exactly cancel upon summation. In view of the results of this and other recent theoretical work it is concluded that the rates predicted by pure quantum electrodynamics are known to considerable precision. The recent discrepancy between theory and experiment in the decay rate for several helium-like ions appears to have been resolved by placing the detector farther downstream from the foil where the metastable states are produced. At present, all the experimental values are in good agreement with the theory