# Is the beta-plus decay that converts two colliding protons into deuterium more likely (energetically favorable) than beta-plus in a larger nucleus?

In the Sun, two nearby protons have to get extremely lucky and have one (or both?) of the protons convert to a neutron in a positron-emission, or beta-plus decay...

I would think that there is less energy available in a tiny nucleus like 'diprotium' than in a much larger nucleus, but the two protons initially have no neutrons at all to 'separate' them, unlike a larger nucleus...

• If both protons convert to neutrons you have two free neutrons which will decay back to protons quickly. Jan 2 at 16:37
• The diproton to deuteron conversion rate is very low, as I mentioned here. And the probability of a diproton converting to two neutrons would be the square of that, so around $10^{-52}$. Feb 16 at 20:35

## 1 Answer

The decay energy equals to the mass difference of the parent and daughter nucleus.

It seemed that larger atoms often (but not always) has larger energy release than 1.4 MeV in the proton-proton fusion. (But you can check the decay energies here. 'e+b$$^+$$' seems to be the notation for $$\beta^+$$ decay.