![]() ![]() Different from standard RIXS measurements, the scattered photons are considered to have the same energy as the incident photons. It is possible to enhance the X-ray scattering yield by matching the energy of X-ray source to a resonant absorption edge in as it is done for resonant inelastic X-ray scattering. The X-ray source can be a laboratory source or synchrotron light which provides a higher X-ray flux. Applications are very broad and include colloids, ,, of all types including interpolyelectrolyte complexes,, , micelles,, ,, , microgels, liposomes,, , polymersomes,, metals, cement, oil, polymers,, ,, plastics, proteins,, foods and pharmaceuticals and can be found in research as well as in quality control. The method is accurate, non-destructive and usually requires only a minimum of sample preparation. Not only particles, but also the structure of ordered systems like lamellae, and fractal-like materials can be studied. The materials can be solid or liquid and they can contain solid, liquid or gaseous domains (so-called particles) of the same or another material in any combination. SAXS is used for the determination of the microscale or nanoscale structure of particle systems in terms of such parameters as averaged particle sizes, shapes, distribution, and surface-to-volume ratio. However, owing to the random orientation of dissolved or partially ordered molecules, the spatial averaging leads to a loss of information in SAXS compared to crystallography. Nuclear magnetic resonance spectroscopy methods encounter problems with macromolecules of higher molecular mass (> 30–40 kDa). Furthermore, the properties of SAXS allow investigation of conformational diversity in these molecules. In the case of biological macromolecules such as proteins, the advantage of SAXS over crystallography is that a crystalline sample is not needed. SAXS and USAXS belong to a family of X-ray scattering techniques that are used in the characterization of materials. USAXS (ultra-small angle X-ray scattering) can resolve even larger dimensions, as the smaller the recorded angle, the larger the object dimensions that are probed. Depending on the angular range in which a clear scattering signal can be recorded, SAXS is capable of delivering structural information of dimensions between 1 and 100 nm, and of repeat distances in partially ordered systems of up to 150 nm. It belongs to the family of small-angle scattering (SAS) techniques along with small-angle neutron scattering, and is typically done using hard X-rays with a wavelength of 0.07 – 0.2 nm. This is achieved by analyzing the elastic scattering behaviour of X-rays when travelling through the material, recording their scattering at small angles (typically 0.1 – 10°, hence the "Small-angle" in its name). This means that it can determine nanoparticle size distributions, resolve the size and shape of (monodisperse) macromolecules, determine pore sizes, characteristic distances of partially ordered materials, and much more. ![]() Small-angle X-ray scattering ( SAXS) is a small-angle scattering technique by which nanoscale density differences in a sample can be quantified. ![]()
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