What characterizes photoelectric absorption?

Photoelectric absorption is characterized by the complete absorption of an x-ray photon by inner shell electrons of an atom. In this process, an incoming x-ray photon interacts with an electron in a tightly bound inner shell (typically K-shell or L-shell), giving all of its energy to the electron. This results in the ejection of the electron from its orbit, thereby ionizing the atom. The energy of the x-ray photon must be greater than the binding energy of the inner shell electron for this process to occur. Following this event, the atom becomes ionized, and to achieve stability, it may undergo a process called electron vacancy filling, where an outer shell electron transitions to fill the inner shell vacancy, often resulting in the emission of characteristic x-rays or Auger electrons.

The correct association of photoelectric absorption with the inner shell electrons highlights its significance in radiation therapy and diagnostic imaging, particularly in enhancing contrast in imaging since lower-energy x-ray photons are more likely to undergo this type of absorption in dense tissues like bone or certain organs.

In contrast, creation of excess heat in tissue is more related to thermal effects from radiation rather than specific interactions like photoelectric absorption. Reflection of x-rays without energy loss does not accurately describe any significant interaction with matter