Controlled Collapse of a Bose-Einstein Condensate

The point of instability of a Bose-Einstein condensate (BEC) due to attractive interactions was studied. Stable ${}^{85}\mathrm{Rb}$ 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 function of number and attractive interaction strength, we determined the stability condition to be $\frac{N|a|}{a_{\mathrm{ho}}}=0.459\mathrm{}\pm 0.012\pm 0.054$, slightly lower than the predicted value of 0.574.