Electron Transition
A core electron can be removed from its core-level upon absorption of electromagnetic radiation (X-ray) and excited to an empty outer shell or emitted as photoelectron (photoelectric effect). The resulting atom with one of its core-level (a so-called core-hole) empty is in a metastable state and decays within 10−15 s by x-ray fluorescence or by Auger effect.
By detecting the emitted photoelectrons (photoemission spectroscopy), the X-ray photons (XAS and fluorescence spectroscopy) or the Auger electrons (Auger electron spectroscopy) useful information on the electronic and the local lattice structures of a material can be obtained.
The atoms of such techniques results from the fact that since every atom has core-level electrons with well-defined binding energies, it is possible to select the element to probe by tuning the x-ray energy to the appropriate absorption edge. For the same reason the spectra of the radiation emitted (electrons or photons) can be used to determine the elemental composition of a material.
Read more about this topic: Core Electron
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