We precisely measured the binding energy (ǫ bind ) of a molecular state near the Feshbach resonance in a 85 Rb Bose-Einstein condensate (BEC). Rapid magnetic field pulses induced coherent atommolecule oscillations in the BEC. We measured the oscillation frequency as a function of B-field and fit the data to a coupled-channels model. Our analysis constrained the Feshbach resonance position [155.041(18) G], width [10.71(2) G], and background scattering length [-443(3) a0] and yielded new values for vDS, vDT , and C6. These results improved our estimate for the stability condition of an attractive BEC. We also found evidence for a mean-field shift to ǫ bind .

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