Prediction of Feshbach resonances in collisions of ultracold rubidium atoms

Abstract

The observation of Bose-Einstein condensation ~BEC! in dilute ultracold gas samples of rubidium @1#, lithium @2#, and sodium atoms @3# has made it possible to study this macroscopic quantum phenomenon in its pure form without complicated modifications due to strong interactions. A variety of experiments has been proposed or already carried out, fascinating examples being the observation of collective shape oscillations and the observation of the relative phase of two Bose-Einstein condensates @4,5#. A rich variety of other experiments would come into reach if one could alter arbitrarily, possibly even in real time, the sign and magnitude of the atom-atom scattering length a. The scattering length occurs as the coefficient of the condensate self-interaction term in the condensate wave equation and has a profound effect on the stability and other properties of the condensate. An opportunity to change this parameter would arise if it were possible to tune the scattering length by means of external fields, i.e., either a static magnetic field @6# or a timedependent optical @7# or rf field @8#.