Parameter Tree:

Gamma Rays (or gamma radiation) is electromagnetic radiation originating from
transitions between energy levels of atomic nuclei.

A nucleus formed as a consequence of beta or alpha emission sometimes exists
briefly in an excited energy level and makes a transition to a lower energy
level accompanied by emission of a gamma ray photon with energy equal to the
difference between the energies of the initial and final levels. Gamma ray
energies from radioactive decay lie in the approximate range 10 keV6 MeV. Gamma
rays are also emitted in nuclear reactions. The boundary between x-rays and
gamma rays is fuzzy, the latter term being most often used for electromagnetic
radiation of nuclear origin.

American Meteorological Society Glossary of Meteorology Online

Boorse, H. A., and L. Motz, 1966: The World of the Atom, Vol. I, 446448.