Pure recoil corrections to the Lamb shift in hydrogenic atoms

Abstract

The recoil corrections of order (Zα${)}^6$ ${\mathit{m}}^2$/M to the hydrogenic Lamb shift are reviewed, and additional terms previously thought to be small are calculated numerically. It is found that significant contributions arise from single-transverse–single-Coulomb interactions in which the bulk of the contribution comes from negative-energy electron intermediate states. This term is found to contain a lnZα dependence, which accounts for its large effect. Other smaller terms are also computed and combined with all previous Lamb-shift contributions. The current status of the Lamb shift in hydrogen is reviewed.