Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I am confused by a simple fact about the $\beta^{-}$ decay of ${}^{60}{\rm Co}$ nucleus. According to Wikipedia, the most likely decay branch is to an excited state of ${}^{60}{\rm Ni}$, see the diagram:

Decay scheme of Co-60

But the energy indicated on the diagram (0.31 MeV) is less than the electron rest mass (0.511 MeV)! How is that possible?

share|cite|improve this question
up vote 4 down vote accepted

When they show a decay with a certian amount of energy, this energy is net of the masses of the particles. So you get Co = $\beta$ + Ni + 0.31 MeV, the energy is attached to the ejected beta particle.

share|cite|improve this answer
Fair enough, thanks. So 0.31 MeV is just the kinectic energy of the electron and the anti-neutrino. – Slaviks Mar 28 '14 at 11:45

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.