Fourier analysis of Ramsey fringes observed in a continuous atomic   fountain for in situ magnetometry
  Ramsey fringes observed in an atomic fountain are formed by the superposition of the individual atomic signals. Due to the atomic beam residual temperature, the atoms have slightly different trajectories and thus are exposed to a different average magnetic field, and a velocity dependent Ramsey interaction time. As a consequence, both the velocity distribution and magnetic field profile are imprinted in the Ramsey fringes observed on Zeeman sensitive microwave transitions. In this work, we perform a Fourier analysis of the measured Ramsey signals to retrieve both the time averaged magnetic field associated with different trajectories and the velocity distribution of the atomic beam. We use this information to reconstruct Ramsey fringes and establish an analytical expression for the position of the overall observed Ramsey pattern. 
Gianni Di Domenico, Laurent Devenoges, Andr\'e Stefanov, Alain Joyet,   Pierre Thomann
physics.atom-ph