Fundamental Physics Cold Atom Paper Displays Quantum Statistics

Rice University Fundamental Physics investigator Randy Hulet announces that his group will publish a paper in Science on March 30. The paper describes the cooling of a mixture of the two isotopes of lithium, lithium-6 and lithium-7, the isotopes differing only in that lithium-7 has one additional neutron in the nucleus. By cooling the mixture to within a microdegree of absolute zero, the investigators were able to graphically show the influence of quantum statistics on the behavior of the two samples. Lithium-6 is a fermion, so the atoms cannot have two particles in the same state, so an effect called the "Fermi pressure" is seen to operate, keeping the particles apart. On the other hand, lithium-7 is a boson, so below some temperature a cloud of lithium-7 atoms condenses into the lowest energy state. This difference in behaviors is displayed graphically in a series of pictures at successively lower temperatures, the lithium-7 cloud shrinking dramatically at the transition, while the lithium-6 cloud remains larger.

Cold Atom Paper Displays