On the enhancement of impurity collisions in a Bose-Einstein condensate

We present a possible explanation of the discrepancy between theory and experiment (observed by Chikkatur et al.) in the collisional density of impurities in a Bose-Einstein condensate of sodium atoms. The discrepancy is ascribed to the fact that the experiment was carried out in a situation of strong instability, where small variations of the initial number of impurities in the condensate may give rise to a large variation in the number of colliding atoms