  We have observed 28 heteronuclear Feshbach resonances in 10 spin combinations
of the hyperfine ground states of a 40K 87Rb mixture. The measurements were
performed by observing the loss rates from an atomic mixture at magnetic fields
between 0 and 700 G. This data was used to significantly refine an interatomic
potential derived from molecular spectroscopy, yielding a highly consistent
model of the KRb interaction. Thus, the measured resonances can be assigned to
the corresponding molecular states. In addition, this potential allows for an
accurate calculation of the energy differences between highly excited levels
and the rovibrational ground level. This information is of particular relevance
for the formation of deeply bound heteronuclear molecules. Finally, the model
is used to predict Feshbach resonances in mixtures of 87Rb combined with 39K or
41K.
