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A gamma ray cross section is a measure of the probability that a gamma ray interacts with matter. The total cross section of gamma ray interactions is composed of several independent processes: photoelectric effect, Compton (incoherent) scattering, electron-positron pair production in the nucleus field and electron-positron pair production in the electron field (triplet production).
Pair production and the Compton effect occur at the level of the electron. [1] When a high frequency photon scatters due to an interaction with a charged particle, there is a decrease in the energy of the photon and thus, an increase in its wavelength. This tradeoff between wavelength and energy in response to the collision is the Compton effect.
Pair production often refers specifically to a photon creating an electron–positron pair near a nucleus. As energy must be conserved, for pair production to occur, the incoming energy of the photon must be above a threshold of at least the total rest mass energy of the two particles created. (As the electron is the lightest, hence, lowest ...
Compton scattering and pair production are examples of two other competing mechanisms. [ citation needed ] Even if the photoelectric effect is the favoured reaction for a particular interaction of a single photon with a bound electron, the result is also subject to quantum statistics and is not guaranteed.
The most important interaction mechanisms are the photoelectric effect, the Compton effect, and pair production. Through these processes, the energy of the gamma ray is absorbed and converted into a voltage signal by detecting the energy difference before and after the interaction [ citation needed ] (or, in a scintillation counter , the ...
Compton scattering (incoherent scattering); photoelectric absorption; pair production, electron-positron production in the fields of the nucleus and atomic electrons. The actual values have been thoroughly examined and are available to the general public through three databases run by National Institute of Standards and Technology (NIST):
For highly energetic photons such as X-rays (0.1 keV < < 100 keV) and γ-rays (> 100 keV), three types of interactions are responsible for the energy conversion process in scintillation: photoelectric absorption, [6] Compton scattering, [7] and pair production, [8] which only occurs when > 1022 keV, i.e. the photon has enough energy to create ...
When an ionizing particle passes into the scintillator material, atoms are excited along a track. For charged particles the track is the path of the particle itself. For gamma rays (uncharged), their energy is converted to an energetic electron via either the photoelectric effect, Compton scattering or pair production.