Feshbach resonances in an ultracold Li-7 and Rb-87 mixture

We report on the observation of five Feshbach resonances in collisions between ultracold Li-7 and Rb-87 atoms in the absolute ground-state mixture where both species are in their parallel to f,m(f)>=parallel to 1,1 > hyperfine states. The resonances appear as trap losses for the Li-7 cloud induced by inelastic heteronuclear three-body collisions. The magnetic field values where they occur are important quantities for an accurate determination of the interspecies interaction potentials. Results of coupled channels calculations based on the observed resonances are presented and refined potential parameters are given. A very broad Feshbach resonance centered around 649 G should allow for fine-tuning of the interaction strength in future experiments.