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 $\text{A}{}_{\mathrm{<mtext>s</mtext>}}\text{=(280±10)a}{}_0$ and $\text{A}{}_{\mathrm{<mtext>t</mtext>}}\text{=(2400±100)a}{}_0$, a van der Waals coefficient $\text{C}{}_6\text{=(6890±35)}$ 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.