title: Precise characterization of 6Li Feshbach resonances using trap-sideband-resolved RF spectroscopy of weakly bound molecules.
abstract: We perform radio-frequency dissociation spectroscopy of weakly bound 6Li2 Feshbach molecules using low-density samples of about 30 molecules in an optical dipole trap. Combined with a high magnetic field stability, this allows us to resolve the discrete trap levels in the radio-frequency dissociation spectra. This novel technique allows the binding energy of Feshbach molecules to be determined with unprecedented precision. We use these measurements as an input for a fit to the 6Li scattering potential using coupled-channel calculations. From this new potential, we determine the pole positions of the broad 6Li Feshbach resonances with an accuracy better than 7×10(-4) of the resonance widths. This eliminates the dominant uncertainty for current precision measurements of the equation of state of strongly interacting Fermi gases. As an important consequence, our results imply a corrected value for the Bertsch parameter ξ measured by Ku et al. [Science 335, 563 (2012)], which is ξ=0.370(5)(8).
authors.affiliation: Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, 69120 Heidelberg, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Zürn
authors.forename: T
authors.initials: T
authors.lastname: Lompe
authors.forename: A N
authors.initials: AN
authors.lastname: Wenz
authors.forename: S
authors.initials: S
authors.lastname: Jochim
authors.forename: P S
authors.initials: PS
authors.lastname: Julienne
authors.forename: J M
authors.initials: JM
authors.lastname: Hutson