RABI PEDESTAL SHIFTS AS A DIAGNOSTIC-TOOL IN PRIMARY FREQUENCY STANDARDS

Some of the systematic errors in primary, atomic-beam frequency standa rds are much larger for the Rabi pedestal part of the lineshape than f or the Ramsey fringe part. We have used a digital servo system to meas ure the frequency offset between the Rabi pedestal and the Ramsey frin ge for all seven Zeeman components of the cesium hyperfine transition. The dependence of these shifts on magnetic field, modulation amplitud e, and microwave power enables us to separate three distinct causes: R abi pulling, cavity pulling, and magnetic field inhomogeneity. From th e measured pedestal shifts, we infer the corresponding shifts for the clock transition with uncertainties of the order of one part in 10(15) or less.