Bose-Einstein Condensation of Metastable Helium

Original · EN

We have observed a Bose-Einstein Condensate in a dilute gas of ⁴He in the 2³S₁ metastable state. We find a critical temperature of (4.7±0.5) μK and a typical number of atoms at the threshold of 8×10⁶. The maximum number of atoms in our condensate is about 5×10⁵. An approximate value for the scattering length a=(16±8) nm is measured. The elastic collision rate is then estimated to be about 5×10⁴ 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 2-body and 3-body inelastic collisions.