Measurement of inelastic losses in a sample of ultracold Rb85

We report on measurements of inelastic loss processes in ultracold Rb85 |F=2 atoms. Our apparatus creates ultracold Rb85 clouds by sympathetic cooling with a Rb87 reservoir in a quadrupole-Ioffe magnetic trap and subsequently in a weak, large-volume optical dipole trap. We demonstrate strong sympathetic cooling of Rb85 in the magnetic trap, increasing its phase-space density by three orders of magnitude with no detectable loss in number. Ultracold samples created in this way are used to observe the variation of inelastic loss in Rb85 |F=2,mF=-2 clouds as a function of magnetic field near the 155-G Feshbach resonance and to measure the decay due to inelastic losses in all five Zeeman sublevels of the F=2 manifold, finding a particularly high three-body recombination rate in the lowest energy state. We have also observed and characterized a previously unobserved loss feature at 219.9(1) G with a width of 0.28(6) G, which we associate with a narrow Feshbach resonance predicted by theory.