Controlled collapse of a Bose-Einstein condensate

The point of instability of a Bose-Einstein condensate (BEC) due to attractive interactions was studied. Stable Rb-85 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 function of number and attractive interaction strength, we determined the stability condition to be N\a\/a(ho) = 0.459 +/- 0.012 +/- 0.054, slightly lower than the predicted Value of 0.574.