Current members:
John Obrecht, Rob Wild ,and Eric Cornell

The hybrid trap BEC machine

We have measured magnetic trap lifetimes of ultra-cold 87Rb atoms at distances of 5-1000 µm from surfaces of conducting metals with varying resistivity. Good agreement is found with a theoretical model for losses arising from near-field magnetic thermal noise, confirming the complications associated with holding trapped atoms close to conducting surfaces. A dielectric surface (silicon) was found in contrast to be so benign that we are able to evaporatively cool atoms to a Bose-Einstein condensate by using the surface to selectively adsorb higher energy atoms.

cond-mat

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We have performed precision microwave spectroscopy on ultra-cold Rb-87 confined in a magnetic trap, both above and below the Bose-condensation transition. The cold collision shifts for both normal and condensed clouds were measured, which allowed the intra- and inter-state density correlations (characterized by sometimes controversial "factors of two") to be determined. Additionally, temporal coherence of the normal cloud was studied, and the importance of mean-field and velocity-changing collisions in preserving coherence is discussed.

Phys. Rev. A 66, 053616 (2002)
Effect of cold collisions on spin coherence and resonance shifts in a magnetically trapped ultra-cold gas (cond-mat)

Proceedings ICAP 2002
The mystery of the Ramsay fringe that didn't chirp (cond-mat)

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We present the first spatially resolved images of spin waves in a gas. The complete longitudinal and transverse spin field as a function of time and space is reconstructed. Frequencies and damping rates for a standing-wave mode are extracted and compared with theory.

Phys. Rev. Lett. 89, 090402 (2002)
cond-mat

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Anomalous spin-state segregation

We observe counterintuitive spin segregation in an inhomogeneous sample of ultracold, noncondensed rubidium atoms in a magnetic trap. We use spatially selective microwave spectroscopy to verify a model that accounts for the differential forces on two internal spin states. In any simple understanding of the cloud dynamics, the forces are far too small to account for the dramatic transient spin polarizations observed.

Phys. Rev. Lett. 88, 070403 (2002)
cond-mat

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We have devised a new, stronlgy simplified BEC apparatus creating large condensates of 87Rb. Atoms are first loaded into a MOT from background vapor. Two quadrupole coils mounted on a mechanical translation state transport the atoms into a glass cell surrounded by two permanent magnets. The permanent magnets form a Ioffe-Pritchard type magnetic trap in which evaporative cooling is carried out.

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