Measuring the Antihydrogen Lamb Shift with a Relativistic Antihydrogen Beam," FNAL-Pub-97/426-E, Phys. Rev. D (in press), available at http://publish.aps.org/eprint/gateway/eplist/aps1997dec17

We propose an experiment to measure the Lamb shift and fine structure ͑the intervals 2s 1/2 Ϫ2 p 1/2 and 2 p 1/2 Ϫ2p 3/2 ) in antihydrogen. A sample of 10 000 antihydrogen atoms at a momentum of 8.85 GeV/c suffices to measure the Lamb shift to 5% and the fine structure to 1%. Atomic collisions excite antihydrogen atoms to states with nϭ2; field ionization in a Lorentz-transformed laboratory magnetic field then prepares a particular nϭ2 state, and is used again to analyze that state after it is allowed to oscillate in a region of zero field. This experiment is feasible at Fermilab. ͓S0556-2821͑98͒04711-0