Is there a way to convert a proton in a nucleus to a neutron?

Hyperphysics writes that if a proton was supplied with 1.29 MeV of energy, there would be enough energy to make that conversion.

Has this process ever been observed experimentally, and if so, what was the general experiment?

I understand that there are natural decay processes that do this, such as electron capture. My question pertains to the idea that given any nucleus, is there any way to covert a proton to a neutron?

  • 1
    $\begingroup$ Do you mean to exclude natural decay processes like Electron Capture? en.wikipedia.org/wiki/Electron_capture $\endgroup$
    – Paul Young
    Commented Oct 11, 2019 at 14:00
  • $\begingroup$ @PaulYoung Yes, I mean to exclude natural decay processes. I'll edit the question to correct that. $\endgroup$ Commented Oct 11, 2019 at 14:01

1 Answer 1


Yes, you just have to hit it with an antineutrino of the required energy. It needs more than $1.29$ MeV because to conserve charge the process has to create a positron as well as converting the proton to a neutron. The Feynman diagram for the process is:

enter image description here

This was first observed in the Cowan-Reines experiment, and indeed it was used to confirm the existence of the antineutrino.

  • $\begingroup$ So much for my reading comprehension score. $\endgroup$ Commented Oct 11, 2019 at 14:27
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    $\begingroup$ @JohnRennie I've heard of the Cowan-Reines experiment before, is an antineutrino the only interaction that would cause this to happen? Could any arbitrary particle (such as photon) cause P to N to occur? $\endgroup$ Commented Oct 11, 2019 at 16:23
  • $\begingroup$ @AakashSunkari offhand I can't think of any other reaction, but I wouldn't swear that no other reaction is possible. $\endgroup$ Commented Oct 11, 2019 at 17:25

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