It has a wide range of applications from studies of polymers and biological molecules to nanoparticles to microemulsions and liposomes used for cosmetics and drug delivery.
Small angle scattering (SAS) is the collective name given to the techniques of small angle neutron (SANS), X-ray (SAXS) and light (SALS, or just LS) scattering. In each of these techniques radiation is elastically scattered by a sample and the resulting scattering pattern is analysed to provide information about the size, shape and orientation of some component of the sample.
The type of sample that can be studied by SAS, the sample environment that can be applied, the actual length scales that can be probed and the information that can ultimately be obtained, all depend on the nature of the radiation employed. For example, LS cannot be used to study optically opaque samples and SAXS cannot (easily) be employed to study thick samples or samples requiring complex containers, whilst SANS (and SAXS) probe quite different length scales to LS. Thus to a large extent these techniques are complementary. They do, however, also share several similarities. Perhaps the most important of these is the fact that, with minor adjustments to account for the different types of radiation, the same basic equations and "laws" (for example, those due to Guinier, Zimm, Kratky and Porod) can be used to analyse data from any of the three techniques. This is a tremendous advantage and one that has certainly eased the transition from one technique to another for thousands of students over the years.