Neutron Brillouin scattering in simple liquids and the description of their collective dynamics

A comparison of models traditionally used to describe the dynamic structure factor S(Q,v) obtained from earlier and more recent inelastic scattering studies is briefly presented. The case of monatomic systems, mostly addressed so far, is extended to the more complex case of molecular liquids. As a significant test case, the results of a recent neutron experiment on liquid methane is discussed. The relevance of neutron investigations on molecular fluids, though at the cost of some extra complication, is confirmed by the available results.