Annihilation radiation

Annihilation radiation

Annihilation radiation is a term used in Gamma spectroscopy for the gamma radiation produced when a particle and Antiparticle collide. Most commonly, this refers to 511-keV gamma rays produced by a gamma ray undergoing Pair production [Knoll, G: "Radiation Detection and Measurement", page 12. John Wiley & Sons, Inc., 2000] .

Annihilation radiation is not monoenergetic, unlike gamma rays produced by radioactive decay. The production mechanism of annihilation radiation introduces Doppler broadening [Gilmore, G., and Hemmingway, J.: "Practical Gamma Ray Spectrometry", page 13. John Wiley & Sons Ltd., 1995] . The annihilation peak produced in a gamma spectrum by annihilation radiation therefore has a higher full width at half maximum (FWHM) than other gamma rays in spectrum. The difference is more apparent with high resolution detectors, such as Germanium detectors, than with low resolution detectors such as Sodium iodide detectors.

Because of their well-defined energy (511 keV) and characteristic, Doppler-broadened shape, annihilation radiation can often be useful in defining the energy calibration of a gamma ray spectrum.


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  • annihilation radiation — radiation produced by the collision and annihilation of a particle and its antiparticle, especially the two 0.511 MeV gamma ray photons produced by the annihilation of a positron and an electron …   Medical dictionary

  • annihilation radiation — Physics. electromagnetic radiation produced by the coalescence and mutual annihilation of a positron and an electron, each pair forming two photons having a minimum energy of 0.5 million electron volts each. [1960 65] * * * …   Universalium

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  • annihilation — /euh nuy euh lay sheuhn/, n. 1. the act or an instance of annihilating. 2. the state of being annihilated; extinction; destruction. 3. Physics. a. Also called pair annihilation. the process in which a particle and antiparticle unite, annihilate… …   Universalium

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  • annihilation — n. 1 the act or process of annihilating. 2 Physics the conversion of a particle and an antiparticle into radiation. Etymology: F annihilation or LL annihilatio (as ANNIHILATE) …   Useful english dictionary

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