Deuterium
= Deuterium
{title2=$^2\mathrm H$}
{wiki}
This stable <hydrogen> isotope has one <proton> and one <neutron>. In the <Proton–proton chain> it is produced by the slow weak proton-pair reaction and is rapidly consumed by <proton> capture to make <helium-3>. Its short nuclear lifetime inside a stellar core allows a <deuterium quasi-equilibrium in proton-proton burning> approximation.