Browsing by Author "Gerton, J.M."

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    Dipolar relaxation collisions in magnetically trapped 7Li
    (American Physical Society, 1999) Gerton, J.M.; Sackett, C.A.; Frew, B.J.; Hulet, R.G.; Rice Quantum Institute
    We report the measurement of the rate constant for dipolar relaxation from the (F=2, mF=2) hyperfine state of 7Li. The atoms are confined in a permanent magnet trap at a field of 103 G. The measured value of (1.05±0.10)×10−14 cm3/s agrees well with theory. Additionally, we determine an upper bound for the three-body molecular recombination rate constant of 10−27 cm6/s, which is also consistent with predictions.
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    Laser-free slow atom source
    (American Physical Society, 1999) Ghaffari, B.; Gerton, J.M.; McAlexander, W.I.; Strecker, K.E.; Homan, D.M.; Hulet, R.G.; Rice Quantum Institute
    A slow atom source, which does not rely on lasers, has been developed and characterized. The device, acting as an atomic low-pass velocity filter, utilizes permanent magnets to passively select the slow atoms present in a thermal atomic beam. Slow atoms are guided along a curved, conduction-limited tube by an octupole magnetic field, while fast atoms, unable to follow the curved trajectory, strike the tube wall and are removed from the beam. The performance of the device is demonstrated by loading a magneto-optical trap. Approximately 2×108 lithium atoms are loaded with a rate of ∼6×106 atoms/s, while maintaining a background gas pressure of ∼10−11 torr. This loading technique provides an exceptionally simple, economical, and robust alternative to laser cooling methods.
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    Measurements of Collective Collapse in a Bose-Einstein Condensate with Attractive Interactions
    (American Physical Society, 1999) Sackett, C.A.; Gerton, J.M.; Welling, M.; Hulet, R.G.
    The occupation number of a magnetically trapped Bose-Einstein condensate is limited for atoms with attractive interactions. It has been predicted that, as this limit is approached, the condensate will collapse by a collective process. The measured spread in condensate number for samples of Li7 atoms undergoing thermal equilibration is consistent with the occurrence of such collapses.
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    Singlet s-wave scattering lengths of Li6 and Li
    (American Physical Society, 1996) Abraham, E.R.I.; McAlexander, W.I.; Gerton, J.M.; Hulet, R.G.; Côté, R.; Dalgarno, A.; Rice Quantum Institute
    Photoassociation of ultracold lithium atoms into bound vibrational levels of the AΣu+1 excited state is used to probe the XΣg+1 ground-state interaction potential of Li26 and Li27. It had been predicted that the s-wave photoassociation signal strength would pass through a minimum as a function of vibrational level for positive s-wave scattering length. We report the observation of this novel effect, and use the location of the minimum to precisely determine the singlet s-wave scattering length for both isotopes. The sensitivity of this technique is demonstrated by distinguishing the minima for collisions involving Li7 atoms in different hyperfine states.
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    Triplet s-wave resonance in Li6 collisions and scattering lengths of Li6 and Li7
    (American Physical Society, 1997) Abraham, E.R.I.; McAlexander, W.I.; Gerton, J.M.; Hulet, R.G.; Côté, R.; Dalgarno, A.; Rice Quantum Institute
    The triplet s-wave scattering length of Li6 is determined using two-photon photoassociative spectroscopy of the diatomic a3Σ+u state of Li26. The measured binding energy of the highest-lying bound state, combined with knowledge of the potential, determines the s-wave scattering length to be (-2160±250)a0, where a0 is the Bohr radius. This extraordinarily large scattering length signifies a near-threshold resonance. A complete table of singlet and triplet scattering lengths for collisions involving Li6 and Li7 determined from this and our previous spectroscopic investigations is given.