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of the Binding Energy
Due to Neutron-Proton
Spin Pair Formation
Atomic nuclei are held together largely by the binding energies associated with the spin pair formations of nucleons: proton-proton, neutron-neutron and neutron-proton. The proton-proton and neutron-neutron cases are handled elsewhere. Isolated illustrations of the neutron-proton case have been presented but this material give all of the neutron-proton cases.
The neutron-proton cases are handled in groups of five proton numbers. The proton and neutron numbers are denoted as p and n, repectively.
The results are shown only for even proton numbers. This is to avoid the effect of having the creation of a proton-proton spin pair shown on top of the effect of not having the creation of a neutron-proton spin pair.
Here the Incremental Binding Energies of Neutrons is defined as
What is displayed is the Incremental Binding Energies of Neutrons (IBEn) expressed as a function of the number of excess neutrons (n−p). This is to make comparisons of the results between different proton more convenient.
The results for small proton numbers differ significantly from those for large proton numbers. Results for proton numbers in the 20's will be taken to represent the typical case. They include the results for Ti p=22, Cr p=24, Fe p=26, Ni p=28 and Zn p=30.
The drops in IBEn for an additional neutron are remarkably close.
The average drop in IBEn beyond n=p in the above is 5.3775 MeV.
Here are the results for Mg p=12, Si p=14, S p=16, Ar p=18 and Ca p =20.
The drops in IBEn for an additional neutron beyond n=p are remarkably close.
Here are the results for He p=2, Be p=4, C p=6, O p=8 and Ne p=10.
The drops in IBEn for an additional neutron beyond n=p are not remarkably close.
At the other end of the range of proton numbers the drops in IBEn for an additional neutron beyond n=p are also not remarkably close. Here are the results for Ge p=32, Se p=34, Kr p=36, Sr p=38, and Zr p=40.
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