Measurement of the g(j) factor of hydrogenic ions: A sensitive test of bound state QED

The g(j) factor measurement of hydrogenic ions in the 1s ground state is with an expected accuracy of 10(-7) a sensitive test of bound state QED. We expect to determine the deviations from the free electron value, caused by relativistic and radiative corrections, up to the order alpha/4 pi(Z alpha)(2) with an accuracy of 1%. As a first step, light ions like C5+ will be investigated. Later on, heavier hydrogenic ions up to U91+ will be examined using the accelerator facilities at GSI in Darmstadt.