Information om | Engelska ordet HELIUM-4

Exempel på hur man kan använda HELIUM-4 i en mening

• An alpha particle is identical to the nucleus of a helium-4 atom, which consists of two protons and two neutrons.
• It was first synthesized in 1950 at Lawrence Berkeley National Laboratory (then the University of California Radiation Laboratory) by bombarding curium with alpha particles (helium-4 ions).
• Superfluid helium-4 (helium II or He-II) is the superfluid form of helium-4, an isotope of the element helium.
• Nuclear fusion reaction of two helium-4 nuclei produces beryllium-8, which is highly unstable, and decays back into smaller nuclei with a half-life of , unless within that time a third alpha particle fuses with the beryllium-8 nucleus to produce an excited resonance state of carbon-12, called the Hoyle state, which nearly always decays back into three alpha particles, but once in about 2421.
• In the case of helium, helium-4 obeys Bose–Einstein statistics, while helium-3 obeys Fermi–Dirac statistics.
• From the perspective of Big Bang nucleosynthesis, a larger amount of ordinary (baryonic) matter implies a denser early universe, more efficient conversion of matter to helium-4, and less unburned deuterium remaining.
• In theoretical physics, a roton is an elementary excitation, or quasiparticle, seen in superfluid helium-4 and Bose–Einstein condensates with long-range dipolar interactions or spin-orbit coupling.
• This is a large amount of energy for a nuclear reaction; the amount is so high because the binding energy per nucleon of the helium-4 nucleus is unusually high because the He-4 nucleus is "doubly magic".
• The known doubly magic isotopes are helium-4, helium-10, oxygen-16, calcium-40, calcium-48, nickel-48, nickel-56, nickel-78, tin-100, tin-132, and lead-208.
• 4% of fissions are ternary fissions, producing a third light nucleus such as helium-4 (90%) or tritium (7%).
• In 1951 Salpeter suggested that stars could burn helium-4 into carbon-12 with the Triple-alpha process not directly, but through an intermediate metastable state of beryllium-8, which helped to explain the carbon production in stars.
• For example, if superfluid helium-4 is placed in an open vessel, a thin Rollin film will climb the sides of the vessel, causing the liquid to escape.
• The preponderance of sulfur-32 is explained by its production from carbon-12 plus successive fusion capture of five helium-4 nuclei, in the so-called alpha process of exploding type II supernovas (see silicon burning).
• Most oxygen-16 is synthesized at the end of the helium fusion process in stars; the triple-alpha process creates carbon-12, which captures an additional helium-4 to make oxygen-16.
• By evaporative cooling of helium-4 (the more common isotope of helium), a 1-K pot liquefies a small amount of helium-3 in a small vessel called a helium-3 pot.
• These thermal neutrons are captured by the injected boron-10, forming excited (boron-11) which breaks down into lithium-7 and a helium-4 alpha particle both of these produce closely spaced ionizing radiation.
• The types R of ionizing radiation most considered in RBE evaluation are X-rays and gamma radiation (both consisting of photons), alpha radiations (helium-4 nuclei), beta radiation (electrons and positrons), neutron radiation, and heavy nuclei, including the fragments of nuclear fission.
• Therefore, the only stable nuclides created by the end of Big Bang nucleosynthesis are protium (single proton/hydrogen nucleus), deuterium, helium-3, helium-4, and lithium-7.
• No observationally stable isobars exist for mass numbers 5 (decays to helium-4 plus a proton or neutron), 8 (decays to two helium-4 nuclei), 147, 151, as well as for 209 and above.
• In 1970, Simpson, William Dietrich, and John David Anglin discovered that some impulsive sun flares produce energetic particles, among which helium-3 (a light non-radioactive isotope of helium with two protons and one neutron) is at least ten times more abundant than helium-4 (another light non-radioactive isotope of helium with two protons and two neutrons).

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