Determination of the momentum distribution of scattering particles from high-Q scattering spectra of a resonance detector neutron spectrometer

We have measured high-Q neutron scattering spectra from various crystaline solids using an eV resonance detector spectrometer, and analyzed the different contributions to the line profile, namely the finite time spread of the neutron pulse, the detector resolution, the finite size of the moderator, sample and detector, the scattering function and multiple scattering processes, by first-principle calculations. The calculated spectra agree well with the experiments. The momentum distribution of scattering particles can be determined from the high-Q limit of the scattering function. However, deviations from this asymptotical form are clearly observed even for momentum transfers around 100 Å⁻¹.