We have developed large basis-set methods to solve the nonlinear Schroedinger equation for atomic BECs in current experimental traps. Shapes, sizes, lifetimes, and excitation spectra are computed for BECs with up to several million atoms. Unlike 23Na and 87Rb, the interactions between 7Li atoms at low temperature are attractive. It had been predicted theoretically that such a gas could not undergo a Bose-Einstein condensation. We present data in which a condensate in gaseous lithium is observed directly.
Measurements show an abrupt phase transition.