Microscopic Structure and Collective Modes in Liquid Hydrogen: a Preliminary Inelastic X-ray Scattering Study

We have performed an inelastic X-ray scattering experiment on normal liquid H2 at a temperature of 31.5 K and a density of 21.5 nm-3 on the ID16 beam line at the European Synchrotron Radiation Facility. We compare three independent methods to determine experimentally its static structure factor S(Q): method (i) is from a diffraction measurement; method (ii) is through an omega integration of the dynamic structure factor S(Q, omega); method (iii) is from a best-fit procedure of the spectral line shape with a viscoelastic model. The measurements have then been compared with both classical and quantum path integral Monte Carlo simulations. The comparison between experimental and computed S(Q) indicates that quantum effects must be explicitly taken into account in the simulation in order to obtain good agreement with the data.