**3.1 A Brillouin neutron scattering measurement**

Once the *S Q*ð Þ , *E* surface is measured, different constant *Q* cuts of it are determined by interpolation. As an example of a typical INS measurement outcome, in **Figure 1** we show the spectrum of liquid silver at *<sup>Q</sup>* <sup>¼</sup> <sup>6</sup>*nm*�<sup>1</sup> measured with the Brillouin spectrometer BRISP [15] at the High Flux Reactor of the Institut Laue Langevin (Grenoble, France) [16, 17]. The spectral intensity has the typical shape of the spectrum from a disordered samples, which consists of a central peak broadened around the elastic energy *E* ¼ 0 sided by a pair of inelastic peaks shifted from the elastic energy by an amount of �ℏ*ωs*, which defines the energy of the excitation. The

#### **Figure 1.**

*Dynamic structure factor of liquid silver measured on the Brillouin spectrometer BRISP at a momentum transfer Q = 6 nm*�<sup>1</sup> *and an incident energy E*<sup>0</sup> *= 83.9 meV. The experimental data points are affected by resolution broadening. The dashed dot line is a fit obtained from an oversimplified model: A central Lorentzian line is summed to a damping harmonic oscillators (DHO) function to describe the inelastic excitations [16].*

*Bayesian Inference as a Tool to Optimize Spectral Acquisition in Scattering Experiments DOI: http://dx.doi.org/10.5772/intechopen.103850*

peaks sitting at positive and negative energy are respectively the well-known Stokes and Anti-Stokes lines of a Brillouin spectrum [18].
