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    Dynamics of Bose-Einstein condensation in lithium-7

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    Author
    Sackett, Charles Ackley
    Date
    1999
    Advisor
    Hulet, Randall G.
    Degree
    Doctor of Philosophy
    Abstract
    Bose-Einstein condensation (BEC) of 7Li has been investigated. Because the effective interaction between 7Li atoms is attractive, the condensate occupation number N 0 is limited to ∼ 1250 atoms, and when this limit is exceeded, the condensate becomes unstable with respect to mechanical collapse. The interplay of this limit and the natural growth of the condensate during BEC leads to complicated dynamical behavior, which has been studied both theoretically and experimentally. It has been modeled by solving the quantum Boltzmann equation, in conjunction with results from the nonlinear Schrodinger equation. It is found that N0 oscillates rapidly as the condensate alternately fills and collapses, and that the oscillations can persist for many cycles before the gas comes to equilibrium. Experimental evidence for these oscillations was obtained by repeatedly producing a condensate and measuring N 0. The results were seen to vary randomly from one measurement to the next, which is to be expected as the timing of the oscillations is intrinsically stochastic. The distribution of N0 values occurring was measured, and provides quantitative information on the condensate growth and collapse. The equilibration process itself was also observed, by quenching the gas into degeneracy and observing its relaxation. In order to carry out these experiments, sensitive measurement and analysis techniques were developed which enabled N0 to be determined in situ with an accuracy of +/-20% and a precision of +/-60 atoms. The theoretical tools used to study quantum degenerate gases were also applied to the important experimental technique of evaporative cooling, which led to substantial optimization and improvements. As part of this study, the rate constant for dipolar relaxation was measured to be 1.05 +/- 0.1 x 10-14 cm3/s, in agreement with theoretical predictions.
    Keyword
    Atomic physics
    Citation
    Sackett, Charles Ackley. "Dynamics of Bose-Einstein condensation in lithium-7." (1999) Diss., Rice University. https://hdl.handle.net/1911/19433.
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    Managed by the Digital Scholarship Services at Fondren Library, Rice University
    Physical Address: 6100 Main Street, Houston, Texas 77005
    Mailing Address: MS-44, P.O.BOX 1892, Houston, Texas 77251-1892
    Site Map