Study of the dynamic structure factor of hydrogen fluoride by inelastic X-ray scattering

Abstract

The dynamic structure factor S(Q, ω) of liquid hydrogen fluoride is investigated by inelastic X-ray scattering at T = 239 K in a momentum transfer region between 2 and 31 nm−1. The extracted apparent sound velocity c(Q) shows a transition due to the structural or α relaxation with a relaxation time τα(Q) on the subpicosecond (less than 10−12 s) time scale. Nevertheless, from a comparison with existing molecular dynamics simulations, it arises that a second faster relaxation is present. This allows us to discuss our experimental results in terms of a two-relaxation-process scenario.