Investigation of microwave π transitions in cesium beam clocks operated with U-shaped H plane waveguide cavities

In this article, we present the characteristics of the ΔF=±1, ΔmF=±1, π microwave transitions which appear in the response of cesium beam resonators operating with U-shaped waveguide Ramsey cavities bent in the plane of the H field. Such resonances are due to the presence in the cavity of microwave magnetic induction perpendicular to the static field direction. It is shown that the π resonance feature is derived from a pure two-level atomic system interacting with four spatially separated oscillating fields. Good agreement is found between experimental data and theoretical predictions when we take into account the actual transverse microwave field profile in the cavity obtained with tridimensional electromagnetic field computations.