gamma radiation

Electromagnetic radiation produced by a nuclear or particle process. In theory, it can be of any energy and of any wavelength. The radiation is emitted as a photon, the elementary particle that is the quantum of electromagnetic radiation, and this emission is called gamma ray. The highest energy/shortest wavelengths of electromagnetic radiation are the hard X-rays produced only by nuclear processes and emitted as gamma radiation. Gamma radiation is generated by radioactivity, the decay of radioactive (unstable) atoms both in Earth's crust and in the atmosphere, and in reactions caused by cosmic ray collisions with atmospheric constituents, as well as by the decay of elementary particles produced by these collisions.