Gamma Ray

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Gamma Ray

A quantum of electromagnetic radiation emitted by a nucleus, each such photon being emitted as the result of a quantum transition between two energy levels of the nucleus. Gamma rays have energies usually between 10 thousand electron volts and 10 million electron volts with correspondingly short wavelengths and high frequencies. Also called gamma radiation. </dd>
X-rays occur in the same energy range as gamma rays but are of nonnuclear origin. In atmospheric electricity, gamma rays are of some importance in contributing to atmospheric ionization, along with alpha particles and beta particles. Gamma ray photons have much greater penetration ranges than do alpha and beta particles, often amounting to distances of the order of a hundred meters in air at sea level. These high-energy photons may initiate their ionizing action by ejecting photoelectrons from neutral atoms or molecules of the air, by ejecting electrons by the Compton effect, or (for gamma photons with energies above a few million electron volts) by pair production in which an electron and a positron are created. [[/a>|/a> ]]


This article is based on NASA's Dictionary of Technical Terms for Aerospace Use