![]() The intensity of the energy measured by these detectors is proportional to the abundance of the element in the sample. X-rays of intermediate wavelength (K spectra produced from Zn to Zr and L spectra from Ba and the rare earth elements) are generally measured by using both detectors in tandem. The scintillation detector is commonly used to analyze shorter wavelengths in the X-ray spectrum (K spectra of element from Nb to I L spectra of Th and U). The flow counter is commonly utilized for measuring long wavelength (>0.15 nm) X-rays that are typical of K spectra from elements lighter than Zn. Various types of detectors (gas flow proportional and scintillation) are used to measure the intensity of the emitted beam. If a sample has many elements present, as is typical for most minerals and rocks, the use of a Wavelength Dispersive Spectrometer much like that in an EPMA allows the separation of a complex emitted X-ray spectrum into characteristic wavelengths for each element present. This energy release is in the form of emission of characteristic X-rays indicating the type of atom present. When this happens, energy is released due to the decreased binding energy of the inner electron orbital compared with an outer one. The ejected electrons are replaced by electrons from an outer, higher energy orbital. How does this happen? The atoms in the sample absorb X-ray energy by ionizing, ejecting electrons from the lower (usually K and L) energy levels. The excited sample in turn emits X-rays along a spectrum of wavelengths characteristic of the types of atoms present in the sample. When this primary X-ray beam illuminates the sample, it is said to be excited. X-Ray Fluorescence (XRF) Instrumentation - How Does It Work?Īn XRF spectrometer, with the sample port on top, and a set of samples in silver metallic holders in the sample changer in front. Because the energy of the emitted photon is characteristic of a transition between specific electron orbitals in a particular element, the resulting fluorescent X-rays can be used to detect the abundances of elements that are present in the sample. The emitted radiation is of lower energy than the primary incident X-rays and is termed fluorescent radiation. If the energy of the radiation is sufficient to dislodge a tightly-held inner electron, the atom becomes unstable and an outer electron replaces the missing inner electron. When materials are excited with high-energy, short wavelength radiation (e.g., X-rays), they can become ionized. The analysis of major and trace elements in geological materials by x-ray fluorescence is made possible by the behavior of atoms when they interact with radiation. ![]() The XRF method depends on fundamental principles that are common to several other instrumental methods involving interactions between electron beams and x-rays with samples, including: X-ray spectroscopy (e.g., SEM - EDS), X-ray diffraction ( XRD), and wavelength dispersive spectroscopy (microprobe WDS).
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