Multistability in the laser cooling of atomic beams

Summary We describe the interaction of a beam of two-level atoms with multiple laser beams propagating in the opposite direction. The lasers are frequency-chirped in order to remain close to resonance and they continuously decelerate the atoms by radiation pressure. In a deterministic treatment, the average atomic velocity exhibits multistability cycles as a function of the chirping rate. A statistical (Fokker-Planck) treatment shows the corresponding splitting of the atomic velocity distribution into well-separate, quasi-monokinetic bunches of atoms. In the laboratory reference frame, multistability shows up through the increasingly decelerated motion of these atomic bunches. Analytical results are presented, as well as numerical simulations for a beam of cesium atoms, both in the laboratory frame and in the non-inertial frame. The conditions for the observation of multiple cooling with frequency-chirped lasers are discussed. A comparison with standard chirped cooling is outlined. Possible applications are indicated.