Small-Angle Scattering

TL;DR

Small-Angle Scattering (SAS) is a technique used to investigate structures from 0.5 nm to a few hundred nm using x-rays or neutrons, applicable to diverse samples including biological, polymeric, and material systems.

Contribution

This paper provides a comprehensive overview of SAS techniques, instrument setups, data acquisition, and evaluation methods for planning and analyzing SAS experiments.

Findings

SAS effectively investigates a wide range of sample structures.

SAXS and SANS are the primary sources for small-angle scattering.

The paper details procedures for data analysis and experiment planning.

Abstract

Small-Angle Scattering (SAS) investigates structures in samples that generally range from approximately 0.5 nm to a few 100 nm. This can both be done for isotropic samples such as blends and liquids, as well as anisotropic samples such as quasi-crystals. In order to obtain data about that size regime scattered intensity, mostly of x-rays or neutrons, is investigated at angles from close to zero, still in the region of the primary beam up to 10\deg , depending on the wavelength of the incoming radiation. The two primary sources for SAS experiments are x-ray (small-angle x-ray scattering, SAXS) sources and neutron (small-angle neutron scattering, SANS) sources, which shall be the two cases discussed here. Also scattering with electrons or other particle waves is possible, but not the main use case for the purpose of this manuscript. For most small-angle scattering instruments, both SAXS and SANS, the science case covers the investigation of self-assembled polymeric and biological systems, multi-scale systems with large size distribution of the contained particles, solutions of (nano-)particles and soft-matter systems, protein solutions, and material science investigations. In the case of SANS this is augmented by the possibility to also investigate the spin state of the sample and hence perform investigations of the magnetic structure of the sample. In the following sections the general setup of both SAXS and SANS instruments shall be discussed, as well as data acquisition and evaluation and preparation of the sample and the experiment in general. The information contained herein should provide sufficient information for planning and performing a SAS experiment and evaluate the gathered data.