Читать книгу Patty's Industrial Hygiene, Physical and Biological Agents - Группа авторов - Страница 30

Ionizing photons (X‐rays and gamma rays) interact with absorbing media by several different competing mechanisms, depending on the quantum energy and the atomic number of the absorber. Two of these mechanisms, photoelectric absorption and Compton scattering, involve an interaction between an orbital electron and the photon, which results in the ejection of the electron. For photons whose energy exceeds 1.02 MeV, interaction with the absorber nucleus by the pair production mechanism, which is the direct conversion of energy into mass according to Einstein's theory, results in the transformation of the photon's energy into two particles: a negatively charged electron and a positively charged electron or positron. In each of these types of interactions, high‐speed electrons that carry a part of the photon's energy are produced. These energetic electrons, which are called primary ionizing particles, then transfer their energy by ionizing collisions with the orbital electrons of the absorbing media. The primary ionizing particles are the means by which energy is transferred from photons to the absorbing media.