Observation of Heteronuclear Feshbach Molecules from a ~(85)Rb-~(87)Rb Gas

摘要

We report on the observation of ultracold heteronuclear Feshbach molecules. Starting with a ~(87)Rb Bose-Einstein condensate and a cold atomic gas of ~(85)Rb, we utilize previously unobserved interspecies Feshbach resonances to create up to 25 000 molecules. Even though the ~(85)Rb gas is nondegenerate, we observe a large molecular conversion efficiency due to the presence of a quantum degenerate ~(87)Rb gas; this represents a key feature of our system. We compare the molecule creation at two different Feshbach resonances with different magnetic-field widths. The two Feshbach resonances are located at 265.44 ± 0.15 G and 372.4 ± 1.3 G. We also directly measure the small binding energy of the molecules through resonant magnetic-field association.