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positively charged particle, identical to the nucleus of the helium-4 atom, spontaneously emitted by some radioactive substances, consisting of two protons and two neutrons bound together, thus having a mass of four units and a positive charge of two. Discovered and named (1899) by Ernest Rutherford, alpha particles were used by him and coworkers in experiments to probe the structure of atoms...
...quantum-mechanical units of 0, 1, etc.) that is governed by the Bose-Einstein statistics (q.v.). Bosons include mesons (e.g., pions and kaons), nuclei of even mass number (e.g., helium-4), and the particles required to embody the fields of quantum field theory (e.g., photons and gluons). Bosons differ significantly from a group of subatomic particles known as fermions...
Although there are six known isotopes of helium, only two are stable: helium-3 (symbolized 3He) and helium-4 (symbolized 4He). The four other isotopes are all radioactive, decaying very rapidly into other substances. The helium that is present on Earth is not a primordial component of the Earth but has been generated by radioactive decay. Alpha particles, ejected from the...
in superfluidity: Discovery )The stable isotopes of helium are helium-3 (or 3He), with two protons and one neutron, and helium-4 (or 4He), with two protons and two neutrons. 4He forms the bulk of naturally occurring helium, but the lighter isotope 3He has been formed, since about 1950, in experimentally useful quantities by the decay of tritium produced in nuclear reactors.
The-phase-diagrams-of-helium-3-and-helium-4-showThe phase diagrams of (A) helium-3 and (B) helium-4 show which states of these isotopes are stable …
The-phase-diagram-of-helium-4-shows-which-states-ofThe phase diagram of helium-4 shows which states of this isotope are stable.[Credits : Encyclopædia Britannica, Inc.]
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