What occurs during classical scatter when a low-energy photon interacts with an atom?

During classical scatter, also known as coherent scatter, a low-energy photon interacts with an atom without transferring enough energy to ionize it. In this process, the photon causes the atom to become momentarily excited, which leads to a change in the direction of the photon as it passes near the atom, while the energy of the photon remains essentially unchanged.

This is different from other interactions, such as those involving higher energy photons, which may lead to ionization or absorption. The characteristics of classical scatter highlight how low-energy photons interact primarily through simple deflection rather than impactful energy transfer, resulting in a change of direction without affecting the atomic structure. Consequently, this principle is fundamental in understanding how low-energy x-rays behave in biological tissues and their limited impact in certain diagnostic imaging scenarios.