Can a free proton normally be changed to a free neutron by electron capture?

Oct 7, 2014

No, a free proton cannot normally be changed to a free neutron by electron capture.

The proton and neutron must be part of a larger nucleus.

During electron capture, the nucleus captures one of the inner electrons, usually from the K or L shell.

The capture converts a proton into a neutron and emits an electron neutrino. The net process is

""_-1^0"e" + _1^1"H" → _0^0"n" + ν_e

But it has to happen inside a nucleus. For example,

""_-1^0"e" + _4^7"Be" → _3^7"Li" + ν_e

You can see this happen iin the image below.