The g-factor of the bound electron: A test of bound-state QED

The measurement of the electronic g-factor of hydrogenic ions is a sensitive test of bound-state QED (Quantum Electrodynamics). The deviations of the g-factor of the bound electron from the free-electron value are mainly due to i) the relativistic binding energy correction -(Z alpha)(2)/3 and ii) the bound-state radiative correction alpha(Z alpha)(2)/4 pi. In the experiment a single hydrogenic ion is stored in the magnetic field of a Penning trap. The g-factor is measured by inducing spin-flip transitions with a microwave field. The magnetic field is calibrated measuring the cyclotron frequency of the stored ion. In the Penning trap the ion is detected electronically and cooled to 4 degrees K through a superconducting resonance circuit connected to the trap electrodes.