Читать книгу Essentials of Nuclear Medicine Physics, Instrumentation, and Radiation Biology - Rachel A. Powsner - Страница 36

The excited nucleus can transfer its excess energy to an orbital electron (generally an inner‐shell electron) causing the electron to be ejected from the atom. This can only occur if the excess energy is greater than the binding energy of the electron. This electron is called a conversion electron. The resulting inner orbital vacancy is rapidly filled with an outer‐shell electron (as the atom assumes a more stable state, inner orbitals are filled before outer orbitals). The energy released as a result of the “fall” of an outer‐shell electron to an inner shell is emitted as an X‐ray (Figure 1.20a) or as a free electron, an Auger electron (Figure 1.20b). The emitted X‐ray is called a characteristic X‐ray because its energy always equals the difference in binding energies between the electron shells.