Photons pair production

In addition to Compton scattering, y-rays having energies above 1022 keV interact with matter by a process called pair production, in which the photon is converted into a positron and an electron. The y-ray energy in excess of the 1022 keV needed to create the pair is shared between the two new particles as kinetic energy. Each j3 -particle is then slowed down and annihilated by an electron producing two 511-keV photons. 

Pair Production—An absorption process for x- and gamma radiation in which the incident photon is absorbed in the vicinity of the nucleus of the absorbing atom, with subsequent production of an electron... 

Pair production, in which the photon is annihilated in a nuclear interaction giving rise to an electron-positron pair, which carries the energy of the photon less twice the rest energy of the electron. 

Figure 5 X-ray mass attenuation coefficients for aluminum as a function of photon energy. At low energies, photoelectric absorption predominates. At higher energy, incoherent (Compton) scatter becomes almost the exclusive contributing mode. Eventually, pair production dominates at very high energies (above 10 MeV).

BOSONS. Those elementary particles for which there is symmetry under intra-pair production. They obey Bose-Einstein statistics. Included are photons, pi mesons, and nuclei with an even number of particles. (Those particles for which there is antisymmetry fermions.) See Mesons Particles (Subatomic) and Photon and Photonics. 

Figure 17.14 Summary of the relative importance of the three mechanisms by which photons interact with matter. The curves indicate the locations in the atomic number-photon energy plane at which the cross section for Compton scattering is equal to that for photoelectric absorption, left side, or is equal to that for pair production, right side.

Prove that a photon with Ey > 1.022 MeV cannot undergo pair production in free space. 

Spin and velocity of photons from pair production and bremsstrahlung17 may help decide between emission theories and (Lorentzian or Einsteinian) relativistic theories. 

Figure 1. Phenomenological model of electron-hole pair production and charge trapping following absorption of an energetic photon of energy greater than the band gap.

The interaction of ionizing electromagnetic radiation with matter is different from the processes previously mentioned, and the concept of ranges and specific ionization loss cannot be applied. Only the three most important absorption processes are considered the photoelectric effect, the Compton effect, and the pair-production effect. The corpuscular description of electromagnetic radiation is the most appropriate for these effects, as one photon in a well-collimated beam of photons disappears at each interaction. The attenuation of the photon beam can be described by a simple exponential law... 

With pair production all of the energy of the incident photon (component of which X-rays and y-rays are comprised) is lost in the production of the electron/positron pair. In the interaction of X-rays or y-ray photons with atoms, electrons can therefore be ejected (e.g., via Compton scattering) from irradiated media atoms and carry with them energy transferred to them by the incidence photon. These secondary electrons then interact with the surrounding media producing additional ionizations in the same manner as beta particles. 

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