CNO-I cycle ($4p⟶{}^4\mathrm{He}+2e^{+}+2{\nu }_e$)

The principal CNO cycle follows ${}^{12}\mathrm{C}(p,\gamma ){}^{13}\mathrm{N}$, beta-plus decay to carbon-13, proton capture to nitrogen-14, proton capture to oxygen-15, beta-plus decay to nitrogen-15, and ${}^{15}\mathrm{N}(p,\alpha ){}^{12}\mathrm{C}$. The carbon seed is regenerated. The ordinary bottleneck is ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$, so nitrogen-14 accumulates in cycle equilibrium.