X-ray emission spectrometry. X-ray fluorescence

Since 1895, when W. Röntgen first discovered X-rays, numerous studies into both their emission and their interaction with matter have led to the development of powerful analysis methods, for use in research or control laboratories, and in some cases in situ.

• By observing interference phenomena (diffraction), X-ray scattering allows us to understand the internal organization of matter, and to study the structure of crystals and molecules. It also enables us to detect and study stresses and defects in many materials.

• As the absorption of X-ray radiation depends not only on the nature and, to a lesser extent, the structure of the materials making up the absorbent, but also on the wavelength of the radiation, spectrometric techniques are profitably used for elemental chemical analysis (X-ray absorption spectrometry analysis) as well as for structural analysis of molecules (Extended X-ray Absorption Fine Structures, or EXAFS and X-ray Absorption Near Edge Structures, or XANES).

• But it is emission spectra that have led to the most effective techniques for the qualitative and quantitative elemental analysis of solid or liquid matter; the corresponding instruments differ according to the spectral excitation process:

  • electron excitation (also known as cathodic excitation) is currently used mainly in electron microprobes and analytical electron microscopes, particularly scanning electron microscopes (see the corresponding articles in this treatise);

  • Excitation using an X-ray tube or radioelements has given rise to a whole constellation of analytical devices, which we will examine in this article. We shall see that these devices, first used mainly in the metallurgical, mining and oil industries, and in cement works, have now become universal;

  • Finally, other excitation processes, requiring heavier equipment [79][80] , are also successfully used for analysis.