Bose-Einstein condensation in atomic hydrogen

The addition of atomic hydrogen to the set of gases in which Bose-Einstein condensation can be observed expands the range of parameters over which this remarkable phenomenon can be studied. Hydrogen. with the lowest atomic mass, has the highest transition temperature, 50 mu K in our experiments. The very weak interaction between the atoms results in a high ratio of the condensate to normal gas densities, even at modest condensate fractions. Using cryogenic rather than laser precooling generates large condensates. Finally, two-photon spectroscopy is introduced as a versatile probe of the phase transition: condensation in real space is manifested by the appearance of a high-density component in the gas, condensation in momentum space is readily apparent in the momentum distribution, and the phase transition line can be delineated by following the evolution of the density of the normal component. (C) 2000 Elsevier Science B.V. All rights reserved.