Bose-Einstein Condensation in a Gas of Sodium Atoms

TLDR

A novel trap combining magnetic and optical forces confined the sodium atoms. Bose–Einstein condensation of up to 5 × 10⁵ sodium atoms was achieved, with phase‑space density rising six orders of magnitude in seven seconds and a sudden bimodal velocity distribution appearing below ~2 µK at densities exceeding 10¹⁴ cm⁻³.

Abstract

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\ifmmode\times\else\texttimes\fi{}${10}^{5}$ atoms at densities exceeding ${10}^{14}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. The striking signature of Bose condensation was the sudden appearance of a bimodal velocity distribution below the critical temperature of \ensuremath{\sim}2\ensuremath{\mu}K. The distribution consisted of an isotropic thermal distribution and an elliptical core attributed to the expansion of a dense condensate.