In energy-dispersive analysis, dispersion and detection are a single operation, as already mentioned above. Where d is the spacing of atomic layers parallel to the crystal surface.Ī portable XRF analyzer using a silicon drift detector

The wavelength of this fluorescent radiation can be calculated from Planck's Law: 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 main transitions are given names: an L→K transition is traditionally called K α, an M→K transition is called K β, an M→L transition is called L α, and so on. There are a limited number of ways in which this can happen, as shown in Figure 1. 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. The term fluorescence is applied to phenomena in which the absorption of radiation of a specific energy results in the re-emission of radiation of a different energy (generally lower).įigure 3: Spectrum of a rhodium target tube operated at 60 kV, showing continuous spectrum and K lines Characteristic radiation Įach element has electronic orbitals of characteristic energy. Thus, the material emits radiation, which has energy characteristic of the atoms present. In falling, energy is released in the form of a photon, the energy of which is equal to the energy difference of the two orbitals involved. The removal of an electron in this way makes the electronic structure of the atom unstable, and electrons in higher orbitals 'fall' into the lower orbital to fill the hole left behind.

X-rays and gamma rays can be energetic enough to expel tightly held electrons from the inner orbitals of the atom. Ionization consists of the ejection of one or more electrons from the atom, and may occur if the atom is exposed to radiation with an energy greater than its ionization energy. When materials are exposed to short- wavelength X-rays or to gamma rays, ionization of their component atoms may take place. Figure 1: Physics of X-ray fluorescence in a schematic representation.

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