Browsing by Author "Ritchie, N.W.M."

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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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    Precise atomic radiative lifetime via photoassociative spectroscopy of ultracold lithium
    (American Physical Society, 1995) McAlexander, W.I.; Abraham, E.R.I.; Ritchie, N.W.M.; Williams, C.J.; Stoof, H.T.C.; Hulet, R.G.; Rice Quantum Institute
    We have obtained spectra of the high-lying vibrational levels of the 13Σ+g state of Li26 via photoassociation of ultracold Li6 atoms confined in a magneto-optical trap. The 13Σ+g state of the diatomic molecule correlates to a 2S1/2 state atom plus a 2P1/2 state atom. The long-range part of the molecular interaction potential for this state depends on the 2P atomic radiative lifetime. By calculating the energy eigenvalues of a model potential for the 13Σ+g state and fitting them to the experimentally measured vibrational levels, we have extracted a value for the 2P lifetime of 26.99±0.16 ns. The precision is currently limited by the accuracy of a region of the model potential provided by ab initio calculations.
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    Realization of a measurement of a ‘‘weak value’’
    (American Physical Society, 1991) Ritchie, N.W.M.; Story, J.G.; Hulet, Randall G.; Rice Quantum Institute
    We present the first realization of a measurement of a ‘‘weak value,’’ a concept recently introduced by Aharonov, Albert, and Vaidman (AAV). Our experiment uses a birefringent crystal to separate the two linear-polarization components of a laser beam by a distance small compared to the laser-beam waist. This ‘‘weak measurement’’ is followed by a strong measurement which translates the centroid of the beam by a distance far larger than the birefringence-induced separation. In addition, we present data corresponding to orthogonal initial and final states, for which the weak value is not defined. This interference effect may have application in the amplification and detection of weak effects.
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    Trap-loss collisions of ultracold lithium atoms
    (American Physical Society, 1995) Ritchie, N.W.M.; Abraham, E.R.I.; Xiao, Y.Y.; Bradley, C.C.; Hulet, R.G.; Julienne, P.S.; Rice Quantum Institute
    Accurate measurements are presented of the rate of trap-loss-producing collisions between ultracold magneto-optically trapped Li7 atoms for a range of trap laser intensities and frequencies. Intensities from near the atomic saturation intensity to well above it are investigated. At low intensities, fine-structure-changing collisions cause trap loss with a rate constant of ?10?10 cm3/s. At sufficiently high intensity, the trap can be deep enough to effectively freeze out the dominant fine-structure-changing collisions as a loss mechanism, enabling an accurate comparison of the radiative escape loss rate with theory. At the lowest intensities of this radiative escape regime, the measured loss rates compare favorably with those calculated using an optical Bloch equation theory and a three-dimensional model of trap depth. However, the intensity dependence of the measured rates does not show the saturation predicted by the optical Bloch equation theory. It is shown that reliable knowledge of trap depth is necessary to accurately compare experiment with theory.