Frequency shifts in NIST Cs primary frequency standards due to transverse RF field gradients
Steven R. Jefferts, Neil Ashby, Stephan E. Barlow, Thomas P. Heavner
A single-particle Green's function (propagator) is introduced to study the deflection of laser-cooled Cesium atoms in an atomic fountain due to RF field gradients in the Ramsey TE011 cavity. The deflection results in a state-dependent loss of atoms at apertures in the physics package, resulting in a frequency bias. A model accounting only for motion in one dimension transverse to the symmetry axis of the fountain is discussed in detail and then generalized to two transverse dimensions. Results for fractional frequency shifts due to transverse field gradients are computed for NIST F-1 and F-2 Cesium fountains. The shifts are found to be negligible except in cases of higher RF power applied to the cavities.