Recoil corrections in the hydrogen isoelectronic sequence

Abstract

A version of the Bethe-Salpeter equation appropriate for calculating recoil corrections in highly charged hydrogenlike ions is presented. The nucleus is treated as a scalar particle of charge Z, and the electron treated relativistically. The known recoil corrections of order $m^2/M(Z\alpha {)}^4$ are derived in both this formalism and in NRQED.