Which interaction is dominant at low energies and in materials with a high atomic number?

Photoelectric absorption is the dominant interaction at low energies, particularly in materials with high atomic numbers. This interaction occurs when a photon collides with an atom and transfers all its energy to an inner-shell electron, resulting in the ejection of that electron from the atom. The likelihood of this interaction occurring increases significantly with the atomic number of the absorbing material due to the higher probability of absorption by tightly bound inner-shell electrons.

At lower photon energies, this absorption process becomes more favorable compared to other interactions like Compton scattering and pair production. While Compton scattering can also occur at these energy levels, it dominates in materials with lower atomic numbers. Pair production, on the other hand, requires higher photon energies (greater than 1.022 MeV) and is more likely to occur in high atomic number materials but is not pronounced at low energy levels. Radiative decay is not significant in the context of photon interactions with matter as it pertains to different phenomena altogether.

Thus, understanding the conditions under which photoelectric absorption is prevalent highlights its role in radiation safety and the behavior of radiative interactions in various materials.