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The neutron–proton ratio (N/Z ratio or nuclear ratio) of an atomic nucleus is the ratio of its number of neutrons to its number of protons. Among stable nuclei and naturally occurring nuclei, this ratio generally increases with increasing atomic number. [ 1 ]
The first step of the proton-proton chain is a two-stage process: first, two protons fuse to form a diproton: 1 H + 1 H + 1.25 MeV → 2 He; then the diproton immediately beta-plus decays into deuterium: 2 He → 2 H + e + + ν e + 1.67 MeV; with the overall formula 1 H + 1 H → 2 H + e + + ν e + 0.42 MeV.
The boundaries of the valley of stability, that is, the upper limits of the valley walls, are the neutron drip line on the neutron-rich side, and the proton drip line on the proton-rich side. The nucleon drip lines are at the extremes of the neutron-proton ratio. At neutron–proton ratios beyond the drip lines, no nuclei can exist.
Magic numbers are typically obtained by empirical studies; if the form of the nuclear potential is known, then the Schrödinger equation can be solved for the motion of nucleons and energy levels determined. Nuclear shells are said to occur when the separation between energy levels is significantly greater than the local mean separation.
An example that illustrates nuclear binding energy is the nucleus of 12 C (carbon-12), which contains 6 protons and 6 neutrons. The protons are all positively charged and repel each other, but the nuclear force overcomes the repulsion and causes them to stick together. The nuclear force is a close-range force (it is strongly attractive at a ...
The Evans–Polanyi model is a linear energy relationship that serves as an efficient way to calculate activation energy of many reactions within a distinct family. The activation energy may be used to characterize the kinetic rate parameter of a given reaction through application of the Arrhenius equation .
The boundaries of this valley are the neutron drip line on the neutron-rich side, and the proton drip line on the proton-rich side. [2] These limits exist because of particle decay, whereby an exothermic nuclear transition can occur by the emission of one or more nucleons (not to be confused with particle decay in particle physics).
Diproton fusion into helium-4, lithium-4, helium-3 and a proton, and such could proceed much as regular fusion does. Elements with high masses would be more stable, and low neutron numbers would be favored relative to now, because of the neutron's higher mass.