High resolution Feshbach spectroscopy of cesium

We measure high-resolution Feshbach resonance spectra for ultracold cesium atoms colliding in different hyperfine and magnetic sublevels. More than 25 resonances are observed for magnetic fields up to 230 G and their position s are measured with an accuracy down to 0.03 G. From these spectra several ground-state molecular interaction parameters can be extracted with suffici ent accuracy to permit for the first time an unambiguous and accurate deter mination of cesium's ultracold collision properties [P.J. Lee, C.J. William s, and P.S. Julienne, following Letter, Phys. Rev. Lett. 85, 2721(2000)].