Résumé
X-rays and light are electromagnetic waves. Consider first a solid, with atoms fixed at their equilibrium position. When atoms are irradiated by X-rays or light, the electrons vibrate at the frequency of the incident electric field and emit a spherical wave in phase with it. This so-called elastic scattering is the matter of Sect. 7.1 of this chapter. In addition, the thermal motion of atoms produces an inelastic scattering, in which scattered fields are emitted with a small change in frequency. The intensity of this second mechanism is much weaker than that of elastic scattering. Inelastic scattering and its contribution to the investigation of glass structure are discussed in Sect. 7.2. Diffraction and scattering techniques are available for experimental study of structure; Raman scattering allows in addition non-destructive analysis; Brillouin light scattering of light is a technique for the measurement of elastic moduli. Neutrons in a beam emanated from a reactor are quantum particles; their wave function has a wavelength of the order of 1 Å (0.1 nm). When a neutron beam goes through a sample, neutrons interact with the nucleus of atoms in a way similar to diffraction or scattering of X-rays. The basis of light, X-ray and neutron scattering techniques is the same: they are briefly presented in this chapter, together with examples of applications.