Proton recoil and radiative level shifts

Abstract

Proton mass corrections to the Lamb shift of hydrogen of order α(Zα${)}^5$ ${\mathrm{m}}^2$/M are evaluated. These contributions are expected new terms beyond those given earlier for recoil effects to the self-energy of a bound electron in the external-field approximation. The new contribution of this order is -0.53 kHz, thus making the complete radiative-recoil correction of this order -2.53 kHz.