Editing X-ray fluorescence (section)

===Characteristic radiation===
Each element has electronic orbitals of [[characteristic X-ray|characteristic]] energy. Following removal of an inner electron by an energetic photon provided by a primary radiation source, an electron from an outer shell drops into its place. There are a limited number of ways in which this can happen, as shown in Figure 1. The main transitions are [[Siegbahn notation|given names]]: an L→K transition is traditionally called [[K-alpha|K<sub>α</sub>]], an M→K transition is called K<sub>β</sub>, an M→L transition is called L<sub>α</sub>, and so on. Each of these transitions yields a fluorescent photon with a characteristic energy equal to the difference in energy of the initial and final orbital. The wavelength of this fluorescent radiation can be calculated from [[Planck postulate|Planck's Law]]:

:<math> \lambda = \frac{h c}{E} </math>

The fluorescent radiation can be analysed either by sorting the energies of the photons ([[energy-dispersive X-ray spectroscopy|energy-dispersive]] analysis) or by separating the wavelengths of the radiation ([[wavelength-dispersive X-ray spectroscopy|wavelength-dispersive]] analysis). Once sorted, the intensity of each characteristic radiation is directly related to the amount of each element in the material. This is the basis of a powerful technique in [[analytical chemistry]]. Figure 2 shows the typical form of the sharp fluorescent spectral lines obtained in the wavelength-dispersive method (see [[Moseley's law]]).