Feshbach molecule creation in a Bose-Fermi (40K-87Rb) mixture

In an ultracold atom gas, a sweep of a magnetic field across a Fano-Feshbach resonance can associate pairs of atoms into weakly bound molecules. For an ultracold 40K-87Rb mixture, we observe that this association efficiency (the number of observed molecules divided by the number of possible pairs) for adiabatic sweeps is significantly lower than the prediction of a phenomenological model that was developed in conjunction with single-species experiments [Ref.E.Hodby,et al.(2005).PRL 94 120402]. We will report on investigation of this magneto-association process in the 87Rb-40K gas.