Which scatter type describes low-energy photon interaction without ionization?

Thomson scatter describes the interaction of low-energy photons with matter where the photons collide with electrons, but do not have enough energy to remove them from their atoms. This process is characterized by the elastic scattering of photons, meaning the photon changes direction but retains its energy after the interaction. This is important in the context of radiation and personnel protection as it illustrates a low-energy interaction that does not lead to ionization of the atom.

In contrast, the photoelectric effect involves the complete absorption of a photon, resulting in the ejection of an electron from an atom, which leads to ionization. Compton scatter also involves photon interactions, but typically at higher energy levels where a photon loses energy by ejecting an electron and changing direction, which again results in ionization. Neutron scatter refers to the interaction of neutrons rather than photons, and this scenario is distinctly different from the photon interactions being discussed. Thus, Thomson scatter is correctly identified as the phenomenon that represents low-energy photon interaction without causing ionization.