Higher-order binding corrections to the Lamb shift

This paper reports the status and progress regarding the evaluation of higher order binding corrections to the Lamb shift in systems with low nuclear charge Z. Recently, the evaluation of all binding corrections to the Lamb shift of nP states in hydrogenlike systems at low Z up to the order of alpha(7) (n = 2,3,4) has been completed [1, 2]. Using an extrapolation of numerical results, it is possible to obtain an approximate value for higher-order corrections to excited S-states also. Moreover, a calculation is in progress whose ultimate goal is to eliminate any error from low-Z type series expansions or extrapolations of numerical data for high Z. This calculation involves the use of convergence acceleration techniques for certain hypergeometric series [3] and takes advantage of the NIST SGI POWER ONYX and IBM SP/2 supercomputing facilities.