arXiv:cond-mat/0208108 · Physical Review Letters

Ionization Rates in a Bose-Einstein Condensate of Metastable Helium

O. Sirjean, Signe Louise Seidelin, José Viana‐Gomes, Denis Boiron, Christoph Ira Westbrook, Alain Aspect, Georgy V. Shlyapnikov

Published Nov 12, 2002• 26 citations

arXiv HTML PDF

Abstract

We have studied ionizing collisions in a BEC of metastable He. Measurements of the ion production rate combined with measurements of the density and number of atoms for the same sample allow us to estimate both the two- and three-body contributions to this rate. A comparison with the decay of the atom number indicates that ionizing collisions are largely or wholly responsible for the loss. Quantum depletion makes a substantial correction to the three-body rate constant.

DOI: 10.1103/physrevlett.89.220406

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arXiv:cond-mat/0208108 · Physical Review Letters

Ionization Rates in a Bose-Einstein Condensate of Metastable Helium

O. Sirjean, Signe Louise Seidelin, José Viana‐Gomes, Denis Boiron, Christoph Ira Westbrook, Alain Aspect, Georgy V. Shlyapnikov

Published Nov 12, 2002• 26 citations

arXiv HTML PDF

Abstract

DOI: 10.1103/physrevlett.89.220406

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We have observed a Bose-Einstein condensate in a dilute gas of

{}^{4}\mathrm{He}

in the

^{3}2S_{1}

metastable state. We find a critical temperature of $(4.7\ifmmode\pm\else\textpm\fi{}0.5)\ensuremath{\mu}\mathrm{K}$ and a typical number of atoms at the threshold of $8\ifmmode\times\else\texttimes\fi{}{10}^{6}$. The maximum number of atoms in our condensate is about $5\ifmmode\times\else\texttimes\fi{}{10}^{5}$. An approximate value for the scattering length $a\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(16\ifmmode\pm\else\textpm\fi{}8)\mathrm{nm}$ is measured. The mean elastic collision rate at threshold is then estimated to be about $2\ifmmode\times\else\texttimes\fi{}{10}^{4}{\mathrm{s}}^{\ensuremath{-}1}$, indicating that we are deeply in the hydrodynamic regime. The typical decay time of the condensate is

2\mathrm{s}

, which places an upper bound on the rate constants for two-body and three-body inelastic collisions.

{}^{87}\mathrm{Rb}

. The ratio of these is

7.4(2.6)

which agrees with the theoretical factor of

3!

and demonstrates that condensate atoms are less bunched than noncondensate atoms.

We present a theoretical and experimental investigation of homonuclear ionizing collisions of laser-cooled metastable

(2\phantom{\rule{0.2em}{0ex}}^{3}S_{1})

helium atoms, considering both the fermionic

^{3}\mathrm{He}

and bosonic

^{4}\mathrm{He}

isotopes. The theoretical description combines quantum threshold behavior, Wigner's spin-conservation rule, and quantum-statistical symmetry requirements in a single-channel model, complementing a more complete close-coupling theory that has been reported for collisions of metastable

^{4}\mathrm{He}

atoms. The model is supported with measurements (in the absence of light fields) of ionization rates in magneto-optically trapped samples that contain about $3\ifmmode\times\else\texttimes\fi{}{10}^{8}$ atoms of a single isotope. The ionization rates are determined from measurements of trap loss due to light-assisted collisions combined with comparative measurements of the ion production rate in the absence and presence of trapping light. Theory and experiment show good agreement.