Wikipedia says Carbon-14 is formed in the atmosphere by the reaction:

1n + 14N → 14C + 1p

This looks like neutron capture. However, I would expect neutron capture to result in 15N. However, "proton emission" seems to be a rare phenomenon:

15N → 14C + 1p

So, my first question is, does the reaction happen in two stages, or is the proton ejected "immediately"?

Secondly, is this overall type of reaction 1n + → + 1p common? Are there any other examples of such reactions, other than with 14N?

  • $\begingroup$ If you insisted on writing this as a two step process, which may or may not be reasonable, the correct intermediate state would not be $^{15}\mathrm{N}$ (which would imply the system was settled), but $^{15}\mathrm{N}^*$ to make it explicit that the intermediate state is excited. $\endgroup$ Commented Apr 16, 2015 at 0:37

1 Answer 1


It is a prompt (immediate) reaction, and is more usually written something like N14(n,p)C14 to indicate that. It is far from the only such reaction.

EDIT - To quantify my statement that there are many similar reactions, I went to the Evaluated Nuclear Data Files site hosted at Brookhaven (ENDF), entered 'n,p' for the reaction, 'sig' for the desired quantity (sig = sigma = cross-section in barns for the reaction). This returned 308 separate data sets, from He3(n,p)H3 to Bi209(n,p)Pb209. So, indeed, the existence of the N14(n,p)C14 reaction is no great surprise.


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