At high energies and high atomic numbers, which interaction predominates?

At high energies and high atomic numbers, pair production becomes the predominant interaction. This phenomenon occurs when a photon with sufficient energy, typically above 1.022 MeV, interacts with the electric field of a nucleus, leading to the creation of a particle-antiparticle pair—specifically, an electron and a positron.

As the energy of the incoming photon increases, the probability of pair production also rises, particularly in materials with high atomic numbers. This is due to the increased interaction cross-section facilitated by the strong electric fields around heavier nuclei, which are able to provide the necessary energy conversion for the formation of the particle pair.

In contrast, other interactions such as photoelectric absorption and Compton scattering become less significant at higher photon energies. Photoelectric absorption is more probable at lower energies and tends to decrease with increasing photon energy and atomic number, while Compton scattering is prevalent at intermediate energy ranges but also decreases as energy increases, giving way to pair production as the dominant process in high-energy and high-Z scenarios.