Bose-Einstein Condensation in a Gas of Sodium Atoms

We have observed Bose-Einstein condensation of sodium atoms. The atoms were trapped in a novel trap that employed both magnetic and optical forces. Evaporative cooling increased the phase-space density by 6 orders of magnitude within seven seconds. Condensates contained up to 5×10⁵ atoms at densities exceeding 10¹⁴ cm^-3. The striking signature of Bose condensation was the sudden appearance of a bimodal velocity distribution below the critical temperature of ∼2μK. The distribution consisted of an isotropic thermal distribution and an elliptical core attributed to the expansion of a dense condensate.