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  2. Helium-4 - Wikipedia

    en.wikipedia.org/wiki/Helium-4

    The stability of helium-4 is the reason that hydrogen is converted to helium-4, and not deuterium (hydrogen-2) or helium-3 or other heavier elements during fusion reactions in the Sun. It is also partly responsible for the alpha particle being by far the most common type of baryonic particle to be ejected from an atomic nucleus; in other words ...

  3. Superfluid helium-4 - Wikipedia

    en.wikipedia.org/wiki/Superfluid_helium-4

    This condensation occurs in liquid helium-4 at a far higher temperature (2.17 K) than it does in helium-3 (2.5 mK) because each atom of helium-4 is a boson particle, by virtue of its zero spin. Helium-3, however, is a fermion particle, which can form bosons only by pairing with itself at much lower temperatures, in a weaker process that is ...

  4. Superfluidity - Wikipedia

    en.wikipedia.org/wiki/Superfluidity

    In liquid helium-4, the superfluidity occurs at far higher temperatures than it does in helium-3. Each atom of helium-4 is a boson particle, by virtue of its integer spin. A helium-3 atom is a fermion particle; it can form bosons only by pairing with another particle like itself, which occurs at much lower temperatures. The discovery of ...

  5. File:Phase diagram of Helium-4-en.svg - Wikipedia

    en.wikipedia.org/wiki/File:Phase_diagram_of...

    Original file (SVG file, nominally 730 × 411 pixels, file size: 4 KB) Render this image in Czech (cs) (default language) . This is a file from the Wikimedia Commons .

  6. Triple-alpha process - Wikipedia

    en.wikipedia.org/wiki/Triple-alpha_process

    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 8.19 × 10 −17 s, unless within that time a third alpha particle fuses with the beryllium-8 nucleus [3] to produce an excited resonance state of carbon-12, [4] called the Hoyle state, which ...

  7. Helion (chemistry) - Wikipedia

    en.wikipedia.org/wiki/Helion_(chemistry)

    The term helion is a portmanteau of helium and ion, and in practice refers specifically to the nucleus of the helium-3 isotope, consisting of two protons and one neutron. The nucleus of the other (and far more common) stable isotope of helium, helium-4, consisting of two protons and two neutrons, is called an alpha particle or an alpha for short.

  8. Roton - Wikipedia

    en.wikipedia.org/wiki/Roton

    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. The dispersion relation of elementary excitations in this superfluid shows a linear increase from the origin, but exhibits first a maximum and ...

  9. Proton–proton chain - Wikipedia

    en.wikipedia.org/wiki/Proton–proton_chain

    Once the helium-3 has been produced, there are four possible paths to generate 4 He. In p–p I, helium-4 is produced by fusing two helium-3 nuclei; the p–p II and p–p III branches fuse 3 He with pre-existing 4 He to form beryllium-7, which undergoes further reactions to produce two helium-4 nuclei. About 99% of the energy output of the sun ...