Beta-plus decay (${}_Z^{A}X⟶{}_{Z-1}^{A}Y+e^{+}+{\nu }_e$)

An energetically allowed weak nuclear transition converts a proton into a neutron, emitting a positron and electron neutrino. Positron annihilation deposits additional electromagnetic energy, while the neutrino can escape. These transitions are steps of the CNO cycle and the pp III branch; an isolated free proton cannot undergo this decay.