Laser cooling and the highest bound states of the Na diatom system

Using a multichannel bound-state method we predict the highest bound states of the 23Na diatom system, which are closely related to the collisional behavior of ultracold atoms. The results agree well with a model where the hyperfine interaction is treated in first-order perturbation theory, except for the triplet level closest to the continuum, which we predict to be very weakly bound. This level is responsible for the large, positive scattering length of the mf=±f states of the lower hyperfine manifold. Its experimental observation would confirm our prediction of a stable Bose condensate.