Expansion of a lithium gas in the BEC-BCS crossover

We report on experiments in 6Li Fermi gases near Feshbach resonances. A broad s‐wave resonance is used to form a Bose‐Einstein condensate of weakly bound 6Li2 molecules in a crossed optical trap. The measured molecule‐molecule scattering length of 170−60+100 nm at 770 G is found in good agreement with theory. The expansion energy of the cloud in the BEC‐BCS crossover region is measured. Finally we discuss the properties of p‐wave Feshbach resonances observed near 200 Gauss and new s‐wave resonances in the heteronuclear 6Li‐ 7Li mixture.