Determination of Cs-Cs interaction parameters using Feshbach spectroscopy

We measure high-resolution Feshbach resonance spectra for ultracold cesium atoms colliding in different hyperfine and magnetic sublevels. More than 25 Feshbach resonances are observed for magnetic fields below 230 G in the elastic and inelastic ground state collision cross sections, as well as in the cross section for light-assisted collisions. From these spectra a consistent set of ground state molecular interaction parameters for cesium is extracted, including singlet and triplet scattering lengths of A(s) = (280 +/- 10)alpha (0) and A(t) = (2400 +/- 100)alpha (0), a van der Waals coefficient C-6 (6890 +/- 35) a.u., as well as the strength of the indirect spin-spin coupling. This set of parameters allows for the first time a complete characterization of cesium's ultracold-collision properties. (C) 2001 Academie des sciences/Editions scientifiques et medicales Elsevier SAS