Analysis of hydrogen Bose-Einstein condensate growth data

Abstract

Summary form only given. The atomic hydrogen BEC is of a rather different kind from those prevalent in the now almost ubiquitous alkali-metal vapor condensates. The characteristic features of the hydrogen system are: 1. The condensate fraction is rather low, typically about 5%; 2. The number of atoms in the condensate is nevertheless very large, /spl ap/10/sup 9/, compared to /spl ap/10/sup 6/ for Na condensates and /spl ap/10/sup 5/ for Rb condensates; 3. The hydrogen condensate at MIT is a hot condensate formed with radial and axial trap frequencies; giving a trap aspect ratio of an almost one-dimensional condensate. 4. Because of the rather small scattering length of hydrogen, the condensate density is very much higher than in the alkali-metal condensates, and experimentally is measured spectroscopically using the cold-collision frequency shift for the 1S-2S two-photon transition. 5. The condensate would decay rather rapidly by two body dipolar relaxation processes, but is maintained by being fed from the very large number of noncondensate atoms. The system is thus not in thermodynamic equilibrium.