PAIR-PRODUCTION

Third principle mechanism of ionization

The third process of ionization is known as pair-production. In this process, the initial photon energy is very high, normally occurring at energies of 1.02 Mev and above. This particular process does not involve orbital electrons, rather the interaction occurs near the nucleus of the atom instead.

As the photon energy approaches the nucleus of the atom, it is changed into an electron -positron pair. The electron and positron move in different paths away from each other. A positron is nuclear in origin, possessing a positive charge, and mass equal to that of an electron. Technically a positron is the sister particle to the electron. Being positively charged, the positron immediately joins with an electron. The result of this process is annihilation of the positron, and the emission of two new photons, each with equal energy, but one half that of the original photons. These two new photons continue to go through ionization, eventually producing the Compton effect, and finally diminishing to the Photoelectric effect and total absorption.

 

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