title: Measurement of the interaction energy near a Feshbach resonance in a 6Li Fermi gas.
abstract: We investigate the strongly interacting regime in an optically trapped 6Li Fermi mixture near a Feshbach resonance. The resonance is found at 800(40) G in good agreement with theory. Anisotropic expansion of the gas is interpreted by collisional hydrodynamics. We observe an unexpected and large shift (80 G) between the resonance peak and both the maximum of atom loss and the change of sign of the interaction energy.
authors.affiliation: Laboratoire Kastler Brossel, Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris 05, France.
authors.forename: T
authors.initials: T
authors.lastname: Bourdel
authors.forename: J
authors.initials: J
authors.lastname: Cubizolles
authors.forename: L
authors.initials: L
authors.lastname: Khaykovich
authors.forename: K M F
authors.initials: KM
authors.lastname: Magalhães
authors.forename: S J J M F
authors.initials: SJ
authors.lastname: Kokkelmans
authors.forename: G V
authors.initials: GV
authors.lastname: Shlyapnikov
authors.forename: C
authors.initials: C
authors.lastname: Salomon