Shifting the boundaries: Pulse-shape effects in the atom-optics kicked rotorP. H. Jones, M. Goonasekera, H. E. Saunders-Singer and D. R. Meacher
Department of Physics and Astronomy, University College London Gower Street, London, WC1E 6BT, UK
(Received 22 January 2004; accepted in final form 23 July 2004)
We present the results of experiments performed on cold caesium in a pulsed sinusoidal optical potential created by counter-propagating laser beams having a small frequency difference in the laboratory frame. Since the atoms, which have average velocity close to zero in the laboratory frame, have non-zero average velocity in the co-moving frame of the optical potential, we are able to centre the initial velocity distribution of the cloud at an arbitrary point in phase space. In particular, we demonstrate the use of this technique to place the initial velocity distribution in a region of phase space not accessible to previous experiments, namely beyond the momentum boundaries arising from the finite pulse duration of the potential. We further use the technique to explore the kicked-rotor dynamics starting from a region of phase space where there is a strong velocity dependence of the diffusion constant and quantum break time and demonstrate that this results in a marked asymmetry in the chaotic evolution of the atomic momentum distribution.
32.80.Pj - Optical cooling of atoms; trapping.
05.45.Mt - Quantum chaos; semiclassical methods.
© EDP Sciences 2004