When the gamma energy is much lower than the electron binding energy, what is the probable outcome?

When gamma energy is significantly lower than the electron binding energy, the probable outcome is photoelectric absorption. In this interaction, the incoming gamma photon is completely absorbed by an inner-shell electron, which subsequently causes the electron to be ejected from its atom. This process occurs when the photon energy is less than the binding energy of the electron but sufficient to exceed the work function of the atom.

In photoelectric absorption, the photon transfers all of its energy to the electron, leading to the release of the electron from its atomic shell. The absorbed energy also creates vacancy in the electron shell, leading to further interactions, such as the emission of characteristic X-rays as outer-shell electrons fall into lower energy states to fill the vacancy.

The likelihood of photoelectric absorption increases with the decrease in energy of the gamma photon and is also highly dependent on the atomic number of the absorbing material. Materials with higher atomic numbers have a higher probability for this interaction at lower photon energies due to an increased likelihood of interaction with tightly bound electrons.

This mechanism is essential in the context of radiation therapy and diagnostics, making it a fundamental concept in medical dosimetry. In contrast, pair production and Compton scattering occur at higher photon energies, and elastic scattering involves a change in the direction of