1. Photoelectric effect: This interaction occurs when a gamma ray photon transfers all of its energy to a tightly bound electron, causing the electron to be ejected from the atom. The probability of the photoelectric effect decreases with increasing photon energy and is most significant for low-energy gamma rays and high atomic number materials.
2. Compton scattering: In this interaction, a gamma ray photon collides with a loosely bound electron, transferring some of its energy to the electron and causing it to recoil. The scattered photon continues in a different direction with reduced energy. Compton scattering is the dominant interaction mechanism for gamma rays with intermediate energies.
3. Pair production: This interaction occurs when a high-energy gamma ray photon interacts with the strong electric field near an atomic nucleus, converting into an electron-positron pair. The electron and positron have the same energy as the original photon, minus the rest mass energy of the two particles. Pair production is only possible when the photon energy exceeds twice the rest mass energy of an electron (1.022 MeV).
The relative likelihood of these interactions depends on the energy of the gamma ray photons and the atomic number of the material. At low energies, the photoelectric effect is dominant. As the energy increases, Compton scattering becomes more significant, and pair production becomes important at very high energies.
