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Observation of Fermi Pressure in a Gas of Trapped Atoms by Andrew G. Truscott and others Created 2026-10-18 Updated 2026-11-05
By Andrew G. Truscott, Kevin E. Strecker, William I. McAlexander, Guthrie B. Partridge, Randall G. Hulet. Science 291(5513), 2570–2572, 30 March 2001. IIT Delhi hosts this journal reprint. The 14 April 2008 cover timestamp records a download, not publication.
Institutional full text: web.iitd.ac.in/~sankalpa/Fermi-pressure.pdf
Observation of Fermi pressure in trapped lithium Created 2026-10-18 Updated 2026-10-20
In 2001, Andrew G. Truscott, Randall G. Hulet, and collaborators observed degeneracy pressure in trapped lithium. A Zeeman slower fed a dual magneto-optical trap; optical pumping prepared atoms for a cloverleaf apparatus for magnetic trapping of neutral atoms. Microwave evaporation removed energetic lithium-7 bosons; elastic collisions cooled lithium-6 fermions by sympathetic cooling.[ref]
Observation of Fermi Pressure in a Gas of Trapped Atoms by Andrew G. Truscott and others. Truscott et al., Observation of Fermi Pressure in a Gas of Trapped Atoms (2001), p. 2570, preparation and cooling
Sequential absorption imaging recorded both trapped clouds on a camera. Fits to axial profiles used the boson cloud as a thermometer. At common temperature, the nearly equal magnetic trapping potentials provided a comparison: the clouds had similar sizes near , but the fermion cloud remained broader as cooling reached . Figure 3 compared its radius with ideal Fermi gas and classical predictions.[ref]
Observation of Fermi Pressure in a Gas of Trapped Atoms by Andrew G. Truscott and others. pp. 2570–2572, Figs. 1–3, imaging, thermometry, and radius comparison
Varying the wait before imaging tested thermal equilibrium. Finite imaging resolution restricted the analysis to the axial direction; fits neglected interaction-induced density shifts. Cooling eventually suffered from the dwindling boson heat capacity. The result supports quantum occupation effects, without directly resolving individual occupied states or reaching zero temperature.[ref]
Observation of Fermi Pressure in a Gas of Trapped Atoms by Andrew G. Truscott and others. p. 2571, axial resolution and negligible-interaction approximation; p. 2572, equilibration test and cooling limit
These were neutral alkali atoms in a spatially varying trap. The Fermi energy of a model electron gas instead uses uniform electrons, two equally populated spin states, and the electron mass. The measured trapped-atom radii are not measurements of that electron model's or ; comparing their numerical Fermi energies requires the appropriate particle mass, internal-state populations, and confining potential.
Randall G. Hulet Created 2026-10-18 Updated 2026-11-05
Randall G. Hulet developed experiments with quantum-degenerate atomic gases, including the observation of Fermi pressure in trapped lithium. The comparison of bosonic and fermionic isotopes made their different population statistics experimentally accessible.
A degenerate fermionic cloud remains spread over many occupied one-particle states because of the Pauli exclusion principle. Its size and distribution therefore reflect quantum statistics as well as temperature and confinement. The experiment connected the same pressure mechanism important in dense astrophysical matter to a dilute laboratory gas.[ref]
