Browsing by Author "Tollett, J.J."

Now showing 1 - 4 of 4
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    Adiabatic cooling of atoms by an intense standing wave
    (American Physical Society, 1992) Chen, Jian; Story, J.G.; Tollett, J.J.; Hulet, Randall G.; Rice Quantum Institute
    Lithium atoms channeled in the nodes of an intense standing-wave radiation field are cooled to near the recoil limit by adibatically reducing the radiation intensity. The final momentum distribution has a narrow component with a root-mean-squared momentum of 2ħk in one dimension, where ħk is the momentum of a radiation-field photon. The data are compared with the results of a Monte Carlo simulation using a two-level atom model. This process may be useful for cooling and increasing the phase-space density of atoms confined in a magnetic trap.
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    Evidence of Bose-Einstein Condensation in an Atomic Gas with Attractive Interactions
    (American Physical Society, 1995) Bradley, C.C.; Sackett, C.A.; Tollett, J.J.; Hulet, R.G.; Rice Quantum Institute
    Evidence for Bose-Einstein condensation of a gas of spin-polarized 7Li atoms is reported. Atoms confined to a permanent-magnet trap are laser cooled to 200 μK and are then evaporatively cooled to lower temperatures. Phase-space densities consistent with quantum degeneracy are measured for temperatures in the range of 100 to 400 nK. At these high phase-space densities, diffraction of a probe laser beam is observed. Modeling shows that this diffraction is a sensitive indicator of the presence of a spatially localized condensate. Although measurements of the number of condensate atoms have not been performed, the measured phase-space densities are consistent with a majority of the atoms being in the condensate, for total trap numbers as high as 2×10˄5 atoms. For 7Li, the spin-triplet s-wave scattering length is known to be negative, corresponding to an attractive interatomic interaction. Previously, Bose-Einstein condensation was predicted not to occur in such a system.
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    Observation of velocity-tuned multiphoton "Doppleron" resonances in laser-cooled atoms
    (American Physical Society, 1990) Tollett, J.J.; Chen, J.; Story, J.G.; Ritchie, N.W.M.; Bradley, C.C.; Hulet, Randall G.; Rice Quantum Institute
    An atomic beam of Li was transversely cooled using an intense standing-wave radiation field. A dramatic change in the transverse velocity distribution was observed. Structure in the resulting velocity distribution was found to be due to velocity-tuned multiphoton ‘‘Doppleron’’ resonances. The force due to seven-photon resonances is clearly resolved in the data. The data are in good agreement with theoretical predictions.
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    Permanent magnet trap for cold atoms
    (American Physical Society, 1995) Tollett, J.J.; Bradley, C.C.; Sackett, C.A.; Hulet, R.G.; Rice Quantum Institute
    We report the trapping of neutral atoms in a permanent magnet trap. Approximately 1×10˄8 ground-state lithium atoms have been confined in a nonzero magnetic-field minimum produced by six permanent magnets in an Ioffe configuration. These atoms have a kinetic temperature of 1.1 mK and a peak density of approximately 3×10˄9 cm˄−3. The trapped-atom lifetime is 240 s, limited by collisions with background gas. This trap provides an environment in which quantum-statistical effects, atomic collisions, and other ultralow-temperature phenomena can be studied.