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Theoretical Investigation of Cold Alkali Atom
Theoretical techniques are developed to solve the coupled Schrodinger equations that describe cold magnetically trapped alkali atom dynamics. In particular, a multichannel quantum defect formulation is presented to separate cleanly the atomdependent from the atom-independent contributions to the final scattering matrices. The resulting approach provides a more comprehensive understanding of cold alkali collisions and improves substantially on the efficiency of calculations. Improved Rb two-body interaction potentials are extracted from measured 87Rb inelastic collision rates and from the measured position and width of a 85Rb Feshbach resonance. Using these state-of-the-art potentials, specific atomic hyperfine states have been identified whose collisional properties suggest intriguing possibilities for interesting and novel degenerate gas studies. In addition, a detailed analysis of 39K photoassociation lineshapes has permitted the determination of accurate two-body interaction potentials for this atom as well. Finally, three-body recombination of doubly polarized trapped atoms is investigated. Two qualitatively different mechanisms which control the recombination rate are identified for positive and negative two-body scattering lengths α. Surprisingly, the recombination rate is found to scale approximately as α4 in both cases.