Positron Emission
Radioactive decay in which a proton converts into a neutron, emitting a positron and a neutrino.
Formula / equation
p → n + e⁺ + ν
Unit
MeV
In depth
Also called beta-plus decay, it occurs in proton-rich nuclei and lowers the atomic number by one. The emitted positron travels only a short distance before annihilating with an electron to produce two 511 keV gamma photons in exactly opposite directions.
Examples in the real world
Fluorine-18 used in PET scanning, where the back-to-back annihilation photons locate the emission point.