Nickel-62 is an isotope of nickel having 28 protons and 34 neutrons.
It is a stable isotope, with the highest binding energy per nucleon of any known nuclide (8.7945 MeV).[1][2] It is often stated that 56Fe is the "most stable nucleus", but only because 56Fe has the lowest mass per nucleon (not binding energy per nucleon) of all nuclides. The lower mass per nucleon of 56Fe is possible because 56Fe has 26/56 ≈ 46.43% protons, while 62Ni has only 28/62 ≈ 45.16% protons; and the larger fraction of lighter protons in 56Fe lowers its mean mass-per-nucleon ratio in a way that has no effect on its binding energy.
During nucleosynthesis in stars the competition between photodisintegration and alpha capturing causes more 56Ni to be produced than 62Ni (56Fe is produced later in the star's ejection shell as 56Ni decays). The 56Ni is the natural end product of silicon-burning at the end of a supernova's life and is the product of 14 alpha captures in the alpha process which builds more massive elements in steps of 4 nucleons, from carbon. This alpha process in supernovas burning ends here because of the higher energy of zinc-60, which would be produced in the next step, after addition of another "alpha" (or more properly termed, helium nucleus).
Nonetheless, 28 atoms of nickel-62 fusing into 31 atoms of iron-56 releases 0.011 u of energy; hence the future of an expanding universe without proton decay includes iron stars rather than "nickel stars".
https://en.wikipedia.org/wiki/Nickel-62
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