Microscopic Structure in Liquid Hydrogen and Deuterium: An X-Ray Scattering Study

The static structure factors S(Q) of liquid normal H2 and D2 have been measured in the wave-vector region 5 nm-1 < Q < 30 nm-1 through X-ray scattering using two independent sets of data. While the first set has been derived using a standard liquid diffraction geometry, the second has been worked out integrating the dynamic structure factors S(Q,omega), measured through inelastic X-ray scattering spectroscopy. In the latter case the first spectral-moment sum rule has been used to obtain directly absolute static structure factor values. A comparison with quantum and classical Monte Carlo simulations shows that a quantitative agreement with the experimental data for both H2 and D2 can be obtained only if quantum effects are properly taken into account.