CAVITY PHASE-SHIFT ERROR EVALUATION IN A MAGNESIUM ATOMIC-BEAM FREQUENCY STANDARD

In high resolution atomic or molecular beam spectroscopy, where the Ramsey interrogation method is used, one of uncertainty sources in determining the resonance frequency accurately is the phase-shift of the electromagnetic radiation in the cavity. This phenomenon, which depends on losses and asymmetries, is analyzed in a general way for a transverse atomic beam dimension much larger than the transition wavelength, a case which occurs in Mg or Ca beam frequency standards and the effects of different misalignments in collimated or divergent beams are examined. Numerical evaluations have been performed in the special case of an experimental Mg beam frequency standard. Divergence plays an important role in determining the cavity phase shift frequency error which is reduced about 100 times with respect to the case of a collimated beam.