Gamma radiation High-energy photons emitted

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The fundamental principle behind analysis by activation analysis is activation or excitation of an atomic nucleus by exposure to radiation such as neutrons, protons or high-energy photons with subsequent measurement of emitted sub-atomic particles or radiation. The most common aspect of the technique involves activation with neutrons in a nuclear reactor and measurement of delayed emitted gamma rays, denoted neutron activation analysis, either instrumental neutron activation analysis (INAA) or neutron activation followed by radiochemical separation (RNAA) in which the element of interest is chemically separated from the matrix after irradiation to provide for better, unimpeded counting. 

The gamma ray is a photon of electromagnetic radiation with a very short wavelength and high energy. It is emitted from an unstable atomic nucleus and has high penetrating power. 

The decay of a nucleus with the emission of an electron, ie, is usually called beta emission, and the emitted electron is sometimes labeled ij8. A positron is a particle similar to an electron, having the same mass but a positive charge. A gamma photon is a particle of electromagnetic radiation of short wavelength (about 1 pm, or 10 m) and high energy. 

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