Ultracold gases spin a winding yarn. (General Developments).Experiments on quantum gases continue to yield amazing and counter-intuitive results. In autumn 2001, researchers at NIST (National Institute of Standards & Technology, Washington, DC, www.nist.gov) The standards-defining agency of the U.S. government, formerly the National Bureau of Standards. It is one of three agencies that fall under the Technology Administration (www.technology. found that a non-condensed Bose-Einstein gas could display spatial segregation of internal spin states, even though the thermal energy thermal energy Internal energy of a system in thermodynamic equilibrium (see thermodynamics) by virtue of its temperature. A hot body has more thermal energy than a similar cold body, but a large tub of cold water may have more thermal energy than a cup of boiling in the gas was more than 1000 times greater than the interaction energy of the two states. The effect was seen following the sudden preparation of all atoms in a coherent superposition su·per·po·si·tion n. 1. The act of superposing or the state of being superposed: "Yet another technique in the forensic specialist's repertoire is photo superposition" of two states, after which the populations of the two states separate. This suggests an astonishingly a·ston·ish tr.v. as·ton·ished, as·ton·ish·ing, as·ton·ish·es To fill with sudden wonder or amazement. See Synonyms at surprise. robust effect of quantum coherence in a thermalized gas. A report of this experimental work was published in the February 18, 2002, edition of Physical Review Letters Physical Review Letters is one of the most prestigious journals in physics.[1] Since 1958, it has been published by the American Physical Society as an outgrowth of The Physical Review. . Theorists at NIST began an investigation of this phenomenon and found that it was attributable to the generation of a damped "spin wave" due to quantum interference between direct- and exchange-scattering of atoms in the two spin states. A first-principles kinetic theory kinetic theory n. A theory concerning the thermodynamic behavior of matter, especially the relationships among pressure, volume, and temperature in gases. that used no fitting parameters gave excellent agreement with the experimental data. The theoretical paper describing this work has been accepted for publication in Physical Review Letters. The experimental and theoretical groups have since collaborated on a third paper, which reports the first spatially-resolved images of spin waves in a gas. That paper has been submitted for publication. CONTACT: Charles W. Clark, (301) 975-3709; charles.clark@nist.gov. |
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