The alpha particle is trapped in a potential well by the nucleus. For more details of this early work, see Alpha particle#History of discovery and use.Д«y 1928, George Gamow had solved the theory of the alpha decay via tunneling.

History ДЄlpha particles were first described in the investigations of radioactivity by Ernest Rutherford in 1899, and by 1907 they were identified as He2+ ions. There is surprisingly small variation around this energy, due to the heavy dependence of the half-life of this process on the energy produced (see equations in the GeigerвЂ“Nuttall law).Д«ecause of their relatively large mass, +2 electric charge and relatively low velocity, alpha particles are very likely to interact with other atoms and lose their energy, so their forward motion is effectively stopped within a few centimeters of air. This corresponds to a speed of around 0.05 c. In practice, this mode of decay has only been observed in nuclides considerably heavier than nickel, with the lightest known alpha emitter being the lightest isotopes (mass numbers 106вЂ“110) of tellurium (element 52).ДЄlpha particles have a typical kinetic energy of 5 MeV (that is, в‰€0.13% of their total energy, i.e. In theory it can occur only in nuclei somewhat heavier than nickel (element 28), where overall binding energy per nucleon is no longer a minimum, and the nuclides are therefore unstable toward spontaneous fission-type processes. Unlike beta decay, alpha decay is governed by the interplay between the nuclear force and the electromagnetic force.ДЄlpha decay typically occurs in the heaviest nuclides. Alpha decay is the most likely cluster decay because of the combined extremely high binding energyand relatively small mass of the helium-4 product nucleus (the alpha particle).ДЄlpha decay, like other cluster decays, is fundamentally a quantum tunneling process. For example: ДЄn alpha particle is the same as a helium-4 nucleus, which has mass number 4 and atomic number 2.ДЄlpha decay is by far the most common form of cluster decay where the parent atom ejects a defined daughter collection of nucleons, leaving another defined product behind (in nuclear fission, a number of different pairs of daughters of approximately equal size are formed). Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particleand thereby transforms (or 'decays') into an atom with a mass number 4 less and atomic number2 less.