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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 conversion of protons to neutrons is the result of another nuclear force, known as the weak (nuclear) force. The weak force, like the strong force, has a short range, but is much weaker than the strong force. The weak force tries to make the number of neutrons and protons into the most energetically stable configuration.
This energy is stored when the protons and neutrons are bound together by the nuclear force to form a nucleus. The mass of a nucleus is less than the sum total of the individual masses of the protons and neutrons. The difference in masses is known as the mass defect, which can be expressed as an energy equivalent. Energy is released when a ...
It is the reaction which occurs when a neutron enters a nucleus and a proton leaves the nucleus simultaneously. [1] For example, sulfur-32 (32 S) undergoes an (n,p) nuclear reaction when bombarded with neutrons, thus forming phosphorus-32 (32 P). The nuclide nitrogen-14 (14 N) can also undergo an (n,p) nuclear reaction to produce carbon-14 (14 C).
The masses of the proton and neutron are similar: for the proton it is 1.6726 × 10 −27 kg (938.27 MeV/c 2), while for the neutron it is 1.6749 × 10 −27 kg (939.57 MeV/c 2); the neutron is roughly 0.13% heavier. The similarity in mass can be explained roughly by the slight difference in masses of up quarks and down quarks composing the ...
An animation of the strong interaction between a proton and a neutron, mediated by pions. The colored small double circles inside are gluons . In nuclear physics and particle physics , the strong interaction , also called the strong force or strong nuclear force , is a fundamental interaction that confines quarks into protons , neutrons , and ...
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 ).
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.