Practical Electron Microscopy and Database

Inelastic scattering, places the atom in an excited (unstable) state. The atom tend to return to a ground (unexcited state). Therefore, at a later time the atoms will relax giving off the excess energy. Three ways of relaxation processes takes place: X-Rays, cathodoluminescence and Auger electrons. The
relaxation energy is the fingerprint (characteristics) of each element.

When the sample is bombarded by the electron beam electron microscopes, electrons are ejected from the atoms in the materials. A resulting electron vacancy is filled by an electron from a higher shell, and an X-ray is emitted to balance the energy difference between the two electrons. The EDS X-ray detector measures the number of emitted x-rays versus their energy. The energy of the x-ray is characteristic of the element from which the x-ray was
emitted. Cathodoluminescence (CL) is the emission of photons of characteristic wavelengths from a material that is under high-energy electron bombardment.
Auger electrons are electrons ejected by radiationless excitation of a target atom by the incident electron beam. Auger electrons are exploited in Auger
Electron Spectroscopy tools (AES)

The volume inside the specimen in which interactions occur while being struck with an electron beam is called specimen interaction volume.