Bose-Einstein condensation of metastable helium.
We have observed a Bose-Einstein condensate in a dilute gas of 4He in the (3)2S(1) metastable state. We find a critical temperature of (4.7+/-0.5) microK and a typical number of atoms at the threshold of 8 x 10(6). The maximum number of atoms in our condensate is about 5 x 10(5). An approximate value for the scattering length a = (16+/-8) nm is measured. The mean elastic collision rate at threshold is then estimated to be about 2 x 10(4) s(-1), indicating that we are deeply in the hydrodynamic regime. The typical decay time of the condensate is 2 s, which places an upper bound on the rate constants for two-body and three-body inelastic collisions.
Pereira Dos Santos
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F
Collège de France, Laboratoire Kastler Brossel, Département de Physique, Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France.
Léonard
J
J
Wang
J
J
Barrelet
C J
CJ
Perales
F
F
Rasel
E
E
Unnikrishnan
C S
CS
Leduc
M
M
Cohen-Tannoudji
C
C