Controlled Collapse of a Bose-Einstein Condensate

The point of instability of a Bose-Einstein Condensate (BEC) due to attractive interactions was studied. Stable 85-Rb BECs were created and then caused to collapse by slowly changing the atom-atom interaction from repulsive to attractive using a Feshbach resonance. At a critical value, an abrupt transition was observed in which atoms were ejected from the condensate. By measuring the onset of this transition as a funstion of number and attractive interactions strength, we determined the stability condition to be N|a|/(aho)=0.461(12)(54), slightly lower than the predicted value of 0.574.