C. I. Westbrook

Specular versus diffuse reflection of atoms from an evanescent-wave mirror

We tested the specularity of the ref lection of slow atoms from an evanescent-wave mirror at normal incidence. In two of the three prisms that we tested the atoms were ref lected diffusely. This nonspecular ref lection appears to be correlated with the rms roughness of the surface supporting the evanescent wave. Only the highest quality surface (rms roughness of the order of 0.1 nm) leads to specular ref lection. This discovery imposes stringent limits on the use of these mirrors in atomic-optics experiments.

Observation of intensity correlations in the fluorescence from laser cooled atoms

Abstract We report the observation of intensity correlations in the fluorescence from a three dimensional Rb optical molasses. This constitutes a new, non-destructive, in situ probe of laser cooled atoms. The power spectrum of the photocurrent displays a 100 kHz wide feature corresponding to the Doppler width of the atomic velocity distribution, and a narrow peak interpreted as being due to the localization of the atoms in wavelength sized potential wells. As the atoms rms velocity decreases, the height of the narrow peak increases while its width decreases to as little as 2 kHz. We discuss the potential for new applications of this method.

Getting the elastic scattering length by observing inelastic collisions in ultracold metastable helium atoms

We report an experiment measuring simultaneously the temperature and the flux of ions produced by a cloud of triplet metastable helium atoms at the Bose-Einstein critical temperature. The onset of condensation is revealed by a sharp increase of the ion flux during evaporative cooling. Combining our measurements with previous measurements of ionization in a pure Bose-Einstein condensate, we extract an improved value of the scattering length a=11.3(+2.5)(-1.0) nm. The analysis includes corrections that take into account the effect of atomic interactions on the critical temperature, and thus an independent measurement of the scattering length would allow a new test of these calculations.

Realizing a stable magnetic double-well potential on an atom chip

Abstract.We discuss design considerations and the realization of a magnetic double-well potential on an atom chip using current-carrying wires. Stability requirements for the trapping potential lead to a typical size of order microns for such a device. We also present experiments using the device to manipulate cold, trapped atoms.

Theory of atomic diffraction from evanescent waves

Abstract.We review recent theoretical models and experiments dealing with the diffraction of neutral atoms by a reflection grating, formed by a standing evanescent wave. We analyze diffraction mechanisms proposed for normal and grazing incidence, point out their scopes and confront the theory with experiment.

Thermalization of magnetically trapped metastable helium

We have observed thermalization by elastic collisions of magnetically trapped metastable helium atoms. Our method directly samples the reconstruction of a thermal energy distribution after the application of a RF knife. The relaxation time of our sample toward equilibrium gives an elastic collision rate constant of

Fast production of Bose-Einstein condensates of metastable helium

\ensuremath{\alpha}\ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9} {\mathrm{cm}}^{3}/\mathrm{s}

Three-dimensional laser cooling at the Doppler limit

at a temperature of 1 mK. This value is close to the unitarity limit.

Resonant focusing in a planar microcavity

We report on the Bose-Einstein condensation of metastable Helium-4 atoms using a hybrid approach , consisting of a magnetic quadrupole and a crossed optical dipole trap. In our setup we cross the phase transition with 2 × 10^6 atoms, and we obtain pure condensates of 5 × 10^5 atoms in the optical trap. This novel approach to cooling Helium-4 provides enhanced cycle stability, large optical access to the atoms and results in production of a condensate every 6 seconds – a factor 3 faster than the state-of-the-art. This speed-up will dramatically reduce the data acquisition time needed for the measurement of many particle correlations, made possible by the ability of metastable Helium to be detected individually.

Quantum reflection: atomic matter-wave optics in an attractive exponential potential

Many predictions of Doppler cooling theory of two-level atoms have never been verified in a three-dimensional geometry, including the celebrated minimum achievable temperature