Feshbach resonances in $\mathsf{^{23}}$ Na- $\mathsf{^{87}}$ Rb

We describe s-wave collisions between ultracold 23Na and 87Rb atoms in the presence of a magnetic field. For any collision input channel knowledge of the singlet and triplet intermolecular potentials [1] enables us to predict the variation in scattering lengths as a function of the magnetic field. We employ the Born-Oppenheimer approximation to predict several Feshbach resonances for 23Na87Rb. We also include a discussion of why these resonances are expected to be narrow as observed in the case of 87Rb2.