Calculation of QED effects in hydrogen

Atomic mass differences are influenced by QED corrections, and a reliable u nderstanding of these corrections is therefore of importance for the curren t and next generation of high-precision mass determinations based on Pennin g traps. We present a numerical evaluation of the self-energy correction, w hich is the dominant contribution to the Lamb shift, in the region of low n uclear charge. Our calculation is nonperturbative in the binding field and has a numerical uncertainty of 0.8 Hz in atomic hydrogen for the ground sta te and of 1.0 Hz for L-shell states (2S(1/2), 2P(1/2), and 2P(3/2)).