The magnetic moment anomaly of the electron bound in hydrogenic ions

The measurement of the g factor of the electron bound in a hydrogenic ion is a high-accuracy test of the theory of Quantum Electrodynamics (QED) in strong fields. Here we report on the measurement of the g factor of the bound electron in hydrogenic carbon (12C5+). In our experiment a single 12C5+ ion is stored in a Penning trap. The electronic spin state of the ion is monitored via the continuous Stern-Gerlach effect in a quantum non-demolition measurement. Quantum jumps between the two spin states (spin up and spin down) are induced by a microwave field at the spin precession frequency of the bound electron. The g factor of the bound electron is obtained by varying the microwave frequency and counting the number of spin flips. The comparison of our experimental value for the g factor of the bound electron, gexp(12C5+)=2.001041596(5), with the theoretical value of gth=2.001041591(7) shows excellent agreement and confirms the recent non-perturbative calculations by T. Beier et al