title: Interferometric determination of the s and d-wave scattering amplitudes in 87Rb.
abstract: We demonstrate an interference method to determine the low-energy elastic scattering amplitudes of a quantum gas. We linearly accelerate two ultracold atomic clouds up to energies of 1.2 mK and observe the collision halo by direct imaging in free space. From the interference between s- and d- partial waves in the differential scattering pattern we extract the corresponding phase shifts. The method does not require knowledge of the atomic density. This allows us to infer accurate values for the s- and d-wave scattering amplitudes from the zero-energy limit up to the first Ramsauer minimum using only the van der Waals C6 coefficient as theoretical input. For the 87Rb triplet potential, the method reproduces the scattering length with an accuracy of 6%.
authors.affiliation: FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam, The Netherlands.
authors.forename: Ch
authors.initials: Ch
authors.lastname: Buggle
authors.forename: J
authors.initials: J
authors.lastname: Léonard
authors.forename: W
authors.initials: W
authors.lastname: von Klitzing
authors.forename: J T M
authors.initials: JT
authors.lastname: Walraven