Atoms excited states, with inner-shell vacancies

The Auger electrons and characteristic X-rays are emitted from initial states with one inner-shell vacancy or sometimes with several vacancies in inner-and outer-shells, where the initial states are formed by ionization and excitation of inner- and outer-shell electrons. In ionization of the isolated atom, constituents of all the atomic orbitals except for an ionized electron remain unchanged after... 

With AES, the sample is subjected to a high-energy (typically 2-20 KeV) electron beam that can cause ejection of a core electron from an atom to form an atomic inner shell vacancy. An outer-level electron will then fill the inner-level vacancy, which will induce an excited state. One of the ways that the atom can then relax is by emitting another electron to form a doubly ionized species. This electron is the Auger electron (named for Pierre Auger, who recognized the effect... 

The principle of both of these techniques is to excite the atoms of the substance to be analyzed by bombarding the sample with sufficiently energetic X-rays/y-rays or charged particles. The ionization (photoionization for XRF and ionization caused due to Coulomb-interaction in case of PIXE) of inner-shell electrons is produced by the photons and charged particles, respectively. When this interaction removes an electron from a specimen s atom, frequently an electron from an outer shell (or orbital) occupies the vacancy. The distribution of electrons in the ionized atom is then out of equilibrium and within an extremely short time s) returns to the normal state, by transitions... 

---