Pump-Probe Spectroscopy and Velocimetry of a Slow Beam of Cold Atoms

We have observed Raman, Rayleigh and recoil induced resonances (RIR) in a continuous beam of slow and cold cesium atoms extracted from a 2D MOT with the moving molasses technique. We use the RIR to measure the velocity distribution, therefore the average speed (0.6-4 m/s) and temperature (50-500 μK) of the atomic beam. Compared to time of flight (TOF), this technique has the advantage of being local, more sensitive in the low-velocity regime (ν< 1 m/s) and it gives access to transverse velocities and temperatures. It may be extended to measure atomic velocities in the 2D MOT source of the atomic beam. It is an additional tool to study and optimize the cooling, the extraction and the (transverse) post-cooling of slow atomic beams.