The dynamic structure factor is most often denoted , where (sometimes ) is a wave vector (or wave number for isotropic materials), and a frequency (sometimes stated as energy, ). It is defined as:[1]
Here , is called the intermediate scattering function and can be measured by neutron spin echo spectroscopy. The intermediate scattering function is the spatial Fourier transform of the van Hove function:[2][3]
Thus we see that the dynamical structure factor is the spatial and temporal Fourier transform of
van Hove
's time-dependent pair correlation function. It can be shown (see below), that the intermediate scattering function is the correlation function of the Fourier components of the density :
The dynamic structure is exactly what is probed in coherent inelastic neutron scattering. The