Rayonnement synchrotron (Fr). Synchrotronstrahlung (Ge). Radiazione di sincrotrone (It). Radiación de sincrotrón (Sp). Синхротронное излучение (Ru).
Electromagnetic energy emitted by charged particles which are accelerated at speeds close to the speed of light in a curved orbit. Instead of using the characteristic X-radiation produced by X-ray tubes or microfocus sources, it is possible to make use of the radiation produced as a by-product of particle acceleration in a synchrotron.
There are several advantages:
· Very high intensity and very low divergence
· Tunable wavelength
· High degree of polarization
Synchrotron sources are widely distributed around the world. They are mostly applied for structure determination of very small crystals and macromolecules (mainly proteins), for high-resolution powder diffraction experiments, and for other special measurements, making use of the highly polarized beam.
An electron diffractometer which uses electrons instead of X-rays has a great advantage even over a synchrotron facility. Smaller crystals can now be analyzed. Normally, and in general, the crystal size of a crystalline substance must be some 5-10 µm in all three dimensions so that even with a synchrotron beam reasonable diffraction patterns can be obtained. Electron Diffraction (ED) experiments have the advantage that they need to be performed in crystals having < 1µm dimensions. In this sense, an electron diffractometer can be seen as a “synchrotron facility in a shoebox”, as previously inaccessible crystalline systems become per se, accessible.
1 W. Massa, “Crystal structure determination”, 3rd Ed., Books on Demand, Norderstedt 2016, 29-30.