We have produced ultracold heteronuclear KRb molecules by the process of photoassociation in a two-species magneto-optical trap. Following decay of the photoassociated KRb*, the molecules are detected using two-photon ionization and time-of-flight mass spectroscopy of KRb+. A portion of the metastable triplet molecules thus formed are magnetically trapped. Photoassociative spectra down to 91 cm(-1) below the K(4s)+Rb(5p(1/2)) asymptote have been obtained. We have made assignments to all eight of the attractive Hund's case (c) KRb* potential curves in this spectral region.
We study the widths of interspecies Feshbach resonances in a mixture of the fermionic quantum gases 6Li and 40K. We develop a model to calculate the width and position of all available Feshbach resonances for a system. Using the model, we select the optimal resonance to study the {6}Li/{40}K mixture. Experimentally, we obtain the asymmetric Fano line shape of the interspecies elastic cross section by measuring the distillation rate of 6Li atoms from a potassium-rich 6Li/{40}K mixture as a function of magnetic field. This provides us with the first experimental determination of the width of a resonance in this mixture, DeltaB=1.5(5) G. Our results offer good perspectives for the observation of universal crossover physics using this mass-imbalanced fermionic mixture.
We demonstrate a novel 2D MOT beam source for cold 6 Li atoms. The source is side-loaded from an oven operated at temperatures in the range 600 T 700 K. The performance is analyzed by loading the atoms into a 3D MOT located 220 mm downstream from the source. The maximum recapture rate of ∼ 10 9 s −1 is obtained for T ≈ 700 K and results in a total of up to 10 10 trapped atoms. The recaptured fraction is estimated to be 30 ± 10% and limited by beam divergence. The most-probable velocity in the beam (αz) is varied from 18 to 70 m/s by increasing the intensity of a push beam. The source is quite monochromatic with a full-width at half maximum velocity spread of 11 m/s at αz = 36 m/s, demonstrating that side-loading completely eliminates beam contamination by hot vapor from the oven. We identify depletion of the low-velocity tail of the oven flux as the limiting loss mechanism. Our approach is suitable for other atomic species.
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