Lamb-shift measurement in hydrogen by the anisotropy method

Abstract

A high-precision measurement of the Lamb shift in hydrogen by theanisotropy method is presented. The result of 1057.852(15) MHz isconsistent with theory and other measurements, thereby confirming thatthe anisotropy method and its interpretation are valid at the 15 partsper million level of accuracy. For the case of He + , a discrepancyof 70(12) parts per million between theory (including two-loop bindingcorrections) and experiment remains to be resolved.PACS Nos. 3130J, 3220D