title: Observation of heteronuclear Feshbach molecules from a 85Rb-87Rb gas.
abstract: We report on the observation of ultracold heteronuclear Feshbach molecules. Starting with a 87Rb Bose-Einstein condensate and a cold atomic gas of 85Rb, we utilize previously unobserved interspecies Feshbach resonances to create up to 25,000 molecules. Even though the 85Rb gas is nondegenerate, we observe a large molecular conversion efficiency due to the presence of a quantum degenerate 87Rb 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.
authors.affiliation: JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309-0440, USA. papp@jilau1.colorado.edu
authors.forename: S B
authors.initials: SB
authors.lastname: Papp
authors.forename: C E
authors.initials: CE
authors.lastname: Wieman