The Auger effect is a physical phenomenon that occurs when an atom's inner-shell electron is ejected, typically due to the absorption of energy from X-rays or other high-energy radiation. This process creates a vacancy in the electron shell, which can lead to the emission of energy as another electron is released from a higher energy level to fill the vacancy. In the Auger effect, the energy released during this transition can be transferred to a third electron, causing it to be ejected from the atom. This effect is named after French physicist Pierre Auger, who discovered it in the 1920s. The Auger effect is significant in fields like materials science and surface analysis.