Radiative Corrections to One-Photon Decays of Hydrogenic Ions

Radiative corrections to the decay rate of n=2 states of hydrogenic ions are calculated. The transitions considered are the M1 decay of the 2s state to the ground state and the E1(M2) decays of the $2p_{1\mathrm{/}2}$ and $2p_{3\mathrm{/}2}$ states to the ground state. The radiative corrections start in order $\alpha (Z \alpha)^2$,butthemethodusedsumsallordersof$Z\alpha$\mathrm{.}Theleading$\alpha (Z\alpha)^2$ correction for the E1 decays is calculated and compared with the exact result. The extension of the calculational method to parity nonconserving transitions in neutral atoms is discussed.