Small-angle scattering (SAS) is a scattering technique based on the deflection of a beam of particles, or an electromagnetic or acoustic wave, away from the straight trajectory after it interacts with structures that are much larger than the wavelength of the radiation. The deflection is small (0.1-10°) hence the name small-angle. SAS techniques can give information about the size, shape and orientation of structures in a sample. Small-angle scattering (SAS) is a powerful technique for investigating large-scale structures from 10 Ä up to thousands and even several tens of thousands of angstroms. The most important feature of the SAS method is its potential for analyzing the inner structure of disordered systems, and frequently the application of this method is a unique way to obtain direct structural information on systems with random arrangement of density inhomogeneities in such large-scales.
The small-angle scattering studies date from the classical works of Guinier in 1938 (Guinier, 1938). Subsequently, Debye, Porod, Kratky, and others developed the theoretical and experimental fundamentals of the method and they were established until around 1960. Later on, new progress in refining the method began in the 1970s and is continuing today. Currently, the SAS technique, with its well-developed experimental and theoretical procedures and wide range of studied objects, is a self-contained branch of the structural analysis of matter. Reflecting these situations, the international meeting on the small-angle scattering studies have been held in every three years. SAS can refer to: