Gamma Ray
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Gamma Ray
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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.
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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.
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References
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use