BOSE-EINSTEIN CONDENSATION OF ATOMIC-HYDROGEN

We report observation of Bose-Einstein condensation (BEC) of a trapped , dilute gas of atomic hydrogen. The condensate and normal gas are stu died by two-photon spectroscopy of the 1S-2S transition. Interactions among the atoms produce a shift of the resonance frequency proportiona l to density. The condensate is clearly distinguished by its large fre quency shift. The peak condensate density is 4.8 +/- 1.1 x 10(15) cm(- 3), corresponding to a condensate population of 10(9) atoms. The BEC t ransition occurs at about T = 50 mu K and n = 1.8 x 10(14) cm(-3). [S0 031-9007(98)07617-0].