Controlled collapse of a Bose-Einstein condensate

The point of instability of a Bose-Einstein condensate (BEC) due to attract ive interactions was studied. Stable Rb-85 BECs were created and then cause d to collapse by slowly changing the atom-atom interaction from repulsive t o attractive using a Feshbach resonance. At a critical value, an abrupt tra nsition was observed in which atoms were ejected from the condensate. By me asuring the onset of this transition as a function of number and attractive interaction strength, we determined the stability condition to be N\a\/a(h o) = 0.459 +/- 0.012 +/- 0.054, slightly lower than the predicted Value of 0.574.