Question

Is more energy released by positron emission or electron capture? I read online that "electron capture is more economical in energy than positron emission, its competitor. The creation of a positron requires 511 keV, the mass energy of the positron. If the energy released in the decay is smaller than 511 keV, the emission of a positron (beta-plus decay) is not allowed. Below this energy threshold, electron capture becomes the only process available to reduce an excess of protons." Which I believe is saying it requires more energy for positron emission to occur, but doesn't say which releases more.

Answer 1

See during positron decay a proton converts into a neutron and releases a positron and electron neutrino , and during electron capture the electron from innermost shell is captured by nucleus and then a proton converts into neutron and gamma radiation+ Xray radiation + electron neutrino released out by the atom.

The gamma radiation and X ray radiation comes because when the innermost electron is captured there is a vacancy left in the shell so this vacancy is filled by electron present in next upper shell and the energy different comes out to be as x ray and sometimes the nucleus may left in excited states which then comes to ground state by releasing gamma radiation.

So we can say electron capture releases more energy than positron decay as there is no such energetic radiation comes out during positron decay.