What is the kinetic temperature required to fuse two protons in a plasma? How much energy does it release? What are the products of the fusion reaction?

  • $\begingroup$ Note that fusing two protons almost always yields a diproton, which is unstable and immediately falls apart. $\endgroup$
    – ProfRob
    Apr 29, 2020 at 8:13
  • $\begingroup$ How often does it fuse into Deuterium? $\endgroup$
    – Cr Ev
    Apr 29, 2020 at 8:47
  • $\begingroup$ I do not know the exact number, but it is a vanishingly small probability that enables the Sun to continue fusing hydrogen for about 12 billion years. $\endgroup$
    – ProfRob
    Apr 29, 2020 at 10:04

1 Answer 1


This is answered in the wikipedia article on proton-proton chain reaction

The first step in all the branches is the fusion of two protons into deuterium (D). As the protons fuse, one of them undergoes beta plus decay, converting into a neutron by emitting a positron and an electron neutrino

$p + p → D + e^+ + ν_e$

The positron will probably annihilate with an electron from the environment into two gamma rays. Including this annihilation the whole reaction has a Q value (released energy) of 1.442 MeV.


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