The peak in the GCR spectrum occurs at about 1 GeV
per nucleon, although energies over 10 ^ 21 eV have been measured.
The data can then be used to plot the binding energy
per nucleon graph.
Its nucleus has a total binding energy of about 2.2 MeV, so the average binding energy
per nucleon is about 1.1 MeV.
If two deuterium nuclei merge to become helium, 2.2 MeV + 2.2 MeV of binding energy are replaced by helium - 4's average binding energy of 7.1 MeV
per nucleon, or a total of 4 x 7.1 MeV.
Iron and nickel nuclei have the largest binding energies
per nucleon of all nuclei and therefore are the most stable.