BLOCH OSCILLATIONS OF ATOMS, ADIABATIC RAPID PASSAGE, AND MONOKINETICATOMIC-BEAMS

We study the dynamics of ultracold atoms in a periodic optical potenti al submitted to a constant external force. Bloch oscillations in the f undamental and first excited bands of the potential are observed. In a ddition to a solid-state analysis we give a quantum-optics interpretat ion of this effect in terms of photon exchanges between the atoms and the laser waves. The dynamics of Bloch oscillations are equivalent to a sequence of adiabatic rapid passages between momentum states and can be described using the dressed-atom approach. We demonstrate efficien t and dissipation-free acceleration of atoms by coherent transfer of a large number of photon momenta (approximate to 100). This technique p roduces atomic beams with a very small longitudinal velocity spread th at may find applications in atom optics and precision measurements.