A type of radioactive decay in which a gamma ray photon is ejected from an excited nucleus. *(only needs $\mathcal{O}(10^{-12} \; {\rm s})$)* Proton emission usually occurs after: - alpha or beta decay - neutron capture, nuclear fission, or nuclear fusion - When high-energy gamma rays, electrons, or protons bombard materials, the excited atoms emit characteristic "secondary" gamma rays, which are products of the creation of excited nuclear states in the bombarded atoms. > [!info] Photoelectric Effect > > The **photoelectric effect** is the emission of electrons when electromagnetic radiation (i.e. photons) interacts with a material. > > A gamma ray emitted from a nucleus may transfer its energy directly to any electrons, causing it to be ejected from that atom. This is also included within the photoelectric effect; however, this is not internal energy conversion process where a photon is not produced. This is two separate processes where the photon is the mediator.