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UBC Theses and Dissertations

Progress towards the study of Li+Rb ultra-cold collisions Kong, Tao


The work described in this thesis is related to two projects I worked on towards the ultracold collisions experiment between fermionic lithium and bosonic rubidium atoms in our lab. The first part is about the simulation of sympathetic cooling of Bose-Fermi mixture inside the magnetic trap. An original single species code, which was specially designed for simulating the forced radio-frequency evaporation of ¹³³Cs atoms in the magnetic trap (within harmonic approximation), is developed so that it can simulate the dynamics of a multi-species trap including iriter-atomic collisions and honharmonic trapping potentials, and thus aid in the design of our future degenerate gas experiments. To validate the consistence between our multi-species code and the original single-species code, a comparison was tried using the parameters from Clauz Zimmermann's sympathetic cooling of fermionic Lithium using Rubidium atoms. The result shows a very good consistence between the multi-species and single species codes. Based on the same parameters from Zimmermann's experiment, another comparison is performed to check the influence of different macro-atom distributions on the simulation results when the total number of real atoms is constant, since the number of macro-atoms determines how fast the simulation can run. The result shows that using less number of macro-atoms (2¹¹ vs 2¹³) won't effect the simulation too much and we can use less number of macro-atoms to speed up the simulation. The second part of this thesis is concerned with the design of the experimental apparatus to study hetero-nuclear Feshbach resonances between Lithium and Rubidium. The strategy for this study was discussed in the experimental setup section, in which the required experimental subsystems for the Feshbach resonance studies were discussed, such as the vacuum system, the atomic sources for both species. This work also involved some experiments to calibrate the alkali metal dispensers to be used in this apparatus. A model was created to describe the Rubidium partial pressure in room temperature, parameters required by this model was calibrated by an absorption experiment, in which the Rubidium resonant laser was sent through a vapor cell.

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