Röntgenkleinwinkelstreuung

Röntgenkleinwinkelstreuung, often abbreviated as RKW or SAXS from the English term Small-Angle X-ray Scattering, is a technique used in materials science and biology to study the structure of matter on a nanometer scale. It probes structures in the size range of approximately 1 to 100 nanometers. The method relies on the elastic scattering of X-rays by inhomogeneities in the electron density of the sample.

When a beam of X-rays interacts with a material, it is scattered in all directions. In RKW, the focus is on the scattering that occurs at very small angles relative to the incident beam. These small-angle scattering patterns are characteristic of the size, shape, and distribution of particles, pores, or other structural features within the material. Larger structures cause scattering at smaller angles, while smaller structures scatter at larger angles.

The scattering intensity is measured as a function of the scattering angle. By analyzing this intensity profile, researchers can deduce valuable information about the sample's microstructure. This can include the average size and shape of particles, their size distribution, the degree of particle aggregation, and the correlation distances between structural elements. RKW is a non-destructive technique, meaning the sample is typically not altered during the measurement.

Applications of RKW are diverse. In materials science, it is used to characterize polymers, colloids, porous materials, and alloys. In biology, it is employed to study the structure of proteins, viruses, cell membranes, and supramolecular assemblies in solution or in solid state. The technique provides complementary information to other methods like transmission electron microscopy, as it often probes larger sample volumes and can be used on samples in their native states.