PURE RECOIL CORRECTIONS TO THE LAMB SHIFT IN HYDROGENIC ATOMS

The recoil corrections of order (Z-alpha)6m2/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 1nZ-alpha 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.