Characteristic X-ray Spectroscopy
When an electron from the inner shell of an atom is lost due to some sort of excitation, it is replaced with an electron from the outer shell; the difference in energy is emitted as an X-ray photon which has a wavelength that is characteristic for the element (there could be several of characteristic wavelengths per element). Analysis of the X-ray emission spectrum produces qualitative results about elemental composition of the specimen. Comparison of spectrum of the specimen with spectra of standards of known composition produces quantitative results (after some mathematical corrections for absorption, fluorescence and atomic number). X-rays can be excited by a high-energy beam of charged particles such as electrons (as in electron microscope) or protons (see PIXE), or a beam of X-rays (see X-ray fluorescence, or XRF). These methods enable elements from the entire periodic table to be analyzed, with the exception of H, He and Li. In electron microscopy electron beam excites X-rays; there are two main techniques for analysis of spectrum of characteristic X-ray radiation: Energy-dispersive X-ray spectroscopy and Wavelength dispersive X-ray spectroscopy.
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