| Bose-Einstein condensation in a dilute vapor of magnetically trapped 87Rb was achieved, and the condensed atoms were used to observe de Broglie-wave interference due to atom tunneling between the barriers of an array of traps. The condensed atoms were loaded into a vertically-oriented one-dimensional optical lattice formed by a retro-reflected laser beam, creating the trap array. In the limit of negligible interactions between atoms, the energy difference between adjacent array sites was determined by the gravitational potential energy shift between the sites. This energy difference initiated an oscillating atom mass current similar to an electric current in the ac Josephson effect for two coupled superconductors. In the optical lattice, de Broglie-wave interference occurred between atoms in localized lattice states, and the interference was observed as a train of falling pulses of atoms.; In a separate experiment, using a dilute vapor of lithium, enhanced loading of a 7Li magneto-optic trap with spectrally-broadened cooling and trapping light was demonstrated. By placing the Li oven nozzle near the trap, the Li atoms could be efficiently captured from an atomic beam without using a pre-cooling stage. The trapped atoms were transferred into a three-dimensional optical lattice, formed by four intersecting and interfering beams of far-off-resonant laser light, and adiabatic cooling and velocity selection in three dimensions was demonstrated. |
