Feshbach resonances in mixtures of ultracold Li 6 and Rb 87 gases

We report on the observation of two Feshbach resonances in collisions between ultracold $^{6}\mathrm{Li}$ and $^{87}\mathrm{Rb}$ atoms in their respective hyperfine ground states $\ensuremath{\mid}F,{m}_{F}⟩=\ensuremath{\mid}1∕2,1∕2⟩$ and \ensuremath{\mid}1,1⟩. The resonances show up as trap losses for the $^{6}\mathrm{Li}$ cloud induced by inelastic Li-Rb-Rb three-body collisions. The magnetic field values where they occur represent important benchmarks for an accurate determination of the interspecies interaction potentials. A broad Feshbach resonance located at $1066.92\phantom{\rule{0.3em}{0ex}}\mathrm{G}$ opens interesting prospects for the creation of ultracold heteronuclear molecules. We furthermore observe a strong enhancement of the narrow $p$-wave Feshbach resonance in collisions of $^{6}\mathrm{Li}$ atoms at $158.55\phantom{\rule{0.3em}{0ex}}\mathrm{G}$ in the presence of a dense $^{87}\mathrm{Rb}$ cloud. The effect of the $^{87}\mathrm{Rb}$ cloud is to introduce Li-Li-Rb three-body collisions occurring at a higher rate than Li-Li-Li collisions.