What is the filling of the inner-shell electron vacancy in the photoelectric effect referred to as?

In the context of the photoelectric effect, when an inner-shell electron vacancy is created as a result of an incident photon interacting with the atom, the subsequent filling of that vacancy is referred to as the "Auger effect." This process occurs when an outer-shell electron falls into the lower-energy vacancy left by the ejected electron. As the outer-shell electron transitions to fill the inner-shell vacancy, it can release energy in the form of another electron being ejected from the atom, rather than emitting a photon.

The cascade effect describes a series of interactions that might occur as a result of one initial event, which can happen in relation to ionization but does not specifically refer to the filling of an electron vacancy. Ionization generally refers to the process of removing an electron from an atom but does not encompass the mechanism of filling inner-shell vacancies specifically. The photoelectric effect primarily deals with the ejection of electrons from an atom due to electromagnetic radiation, but it does not specifically refer to the processes that occur subsequently within the atom after that ejection.

Understanding these distinctions helps clarify why the Auger effect is the appropriate term for the filling of inner-shell vacancies after an initial electron has been ejected, highlighting the intricate processes that follow photon interactions with matter