PREDICTION OF FESHBACH RESONANCES IN COLLISIONS OF ULTRACOLD RUBIDIUMATOMS

On the basis of recently measured Rb-2 bound-state energies and contin uum properties, we predict magnetically induced Feshbach resonances in collisions of ultracold rubidium atoms. The resonances make it possib le to control the sign and magnitude of the effective particle-particl e interaction in a Rb Bose-Einstein condensate by tuning a bias magnet ic field. For the case of Rb-85 they occur at field values in the rang e where these atoms can be magnetostatically trapped. For Rb-87 they a re predicted to occur at negative field values.