title: Tomographic rf spectroscopy of a trapped Fermi gas at unitarity.
abstract: We present spatially resolved radio-frequency spectroscopy of a trapped Fermi gas with resonant interactions and observe a spectral gap at low temperatures. The spatial distribution of the spectral response of the trapped gas is obtained using in situ phase-contrast imaging and 3D image reconstruction. At the lowest temperature, the homogeneous rf spectrum shows an asymmetric excitation line shape with a peak at 0.48(4)epsilonF with respect to the free atomic line, where epsilonF is the local Fermi energy.
authors.affiliation: Department of Physics, MIT-Harvard Center for Ultracold Atoms, and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA. yishin@mit.edu
authors.forename: Y
authors.initials: Y
authors.lastname: Shin
authors.forename: C H
authors.initials: CH
authors.lastname: Schunck
authors.forename: A
authors.initials: A
authors.lastname: Schirotzek
authors.forename: W
authors.initials: W
authors.lastname: Ketterle