title: Feshbach enhanceds-wave scattering of fermions: direct observation with optimized absorption imaging.
abstract: We directly measured the normalizeds-wave scattering cross-section of ultracold40K atoms across a magnetic-field Feshbach resonance by colliding pairs of degenerate Fermi gases (DFGs) and imaging the scattered atoms. We extracted the scattered fraction for a range of bias magnetic fields, and measured the resonance location to beB0= 20.206(15) mT with width Δ = 1.0(5) mT. To optimize the signal-to-noise ratio of atom number in scattering images, we developed techniques to interpret absorption images in a regime where recoil induced detuning corrections are significant. These imaging techniques are generally applicable to experiments with lighter alkalis that would benefit from maximizing signal-to-noise ratio on atom number counting at the expense of spatial imaging resolution.
authors.affiliation: Joint Quantum Institute, National Institute of Standards and Technology, and University of Maryland, Gaithersburg, MD, 20899 USA.
authors.forename: D
authors.initials: D
authors.lastname: Genkina
authors.affiliation: Joint Quantum Institute, National Institute of Standards and Technology, and University of Maryland, Gaithersburg, MD, 20899 USA; Physics Department, Cornell University, Ithaca, NY 14850 USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Aycock
authors.affiliation: Joint Quantum Institute, National Institute of Standards and Technology, and University of Maryland, Gaithersburg, MD, 20899 USA.
authors.forename: B K
authors.initials: BK
authors.lastname: Stuhl
authors.affiliation: Joint Quantum Institute, National Institute of Standards and Technology, and University of Maryland, Gaithersburg, MD, 20899 USA.
authors.forename: H-I
authors.initials: HI
authors.lastname: Lu
authors.affiliation: National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, UK.
authors.forename: R A
authors.initials: RA
authors.lastname: Williams
authors.affiliation: Joint Quantum Institute, National Institute of Standards and Technology, and University of Maryland, Gaithersburg, MD, 20899 USA.
authors.forename: I B
authors.initials: IB
authors.lastname: Spielman
keywords: Atomic physics; Quantum gases