Feshbach spectroscopy of a K-Rb atomic mixture

We perform extensive magnetic Feshbach spectroscopy of an ultracold mixture of fermionic {sup 40}K and bosonic {sup 87}Rb atoms. The magnetic-field locations of 13 interspecies resonances are used to construct a quantum collision model able to predict accurate collisional parameters for all K-Rb isotopic pairs. In particular, we determine the interspecies s-wave singlet and triplet scattering lengths for the {sup 40}K-{sup 87}Rb mixture as (-108{+-}3)a{sub 0} and (-205{+-}5)a{sub 0}, respectively. We also predict accurate scattering lengths and the position of Feshbach resonances for the other K-Rb isotopic pairs. We discuss the consequences of our results for current and future experiments with ultracold K-Rb mixtures.