helium-4


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helium-4

[′hē·lē·əm ′fȯr]
(nuclear physics)
The isotope of helium with mass number 4, constituting nearly all naturally occurring helium.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Yet it took more than three decades for experimentalists to discover supersolidity in helium-4, which has two neutrons along with the two protons in its nucleus.
Kilvington, Operation of a superthermal ultracold neutron source and storage of ultracold neutrons in super.uid helium-4, Zeit.
In a recent issue of Science Express, two physicists from Penn State University announced new experimental evidence for the existence of a new phase of matter, a "supersolid" form of helium-4 with the extraordinary frictionless-flow properties of a superfluid.
In 1962 the German-born British physicist Heinz London (1907-1970) used a mixture of the two helium isotopes helium-4 and helium-3 for the purpose.
Physicists have now heard a quantum-mechanical whistle emanating from two reservoirs of liquid helium-4 that were separated by a perforated membrane.
As the scientists continued to lower the temperature, they detected signs that at about 175 millikelvins the solid version of the isotope helium-4 stopped being dragged around because of friction with the disk.
Now, researchers in Canada have evidence for the onset of superfluidity in a droplet containing a mere seven atoms of liquid helium-4. For now, isotopes of helium are the only substances known to exhibit superfluidity, which appears at temperatures just above absolute zero (SN: 9/23/00, p.
147), you make the unsubstantiated and false remark regarding cold fusion and Martin Fleischmann and Stanley Pons: "However, neither the original pair nor anyone else could reproduce those findings, which have largely been discredited as a ease study in mistaken science" The peer-reviewed literature since 1989 does indeed contain such substantial replications, including the accurate correlation of excess heat to helium-4 production.
The ratio of two helium isotopes, helium-3 and helium-4, was higher in these fullerenes than in air.
Only by injecting a neutron beam into a cylindrical chamber filled with superfluid helium-4 chilled almost to absolute zero did he and his colleagues capture a few hundred neutrons.
Now, researchers have shown experimentally that superfluidity can occur in a cluster consisting of as few as 60 helium-4 atoms.