Two-body time correlations in (and the structure of) dense krypton gas

The van Hove scattering function S(q,ω) has been measured at 12 state conditions along the 297-K isotherm of krypton gas between 6 and 14×1027 atoms/m3 and for the magnitude of the scattering vectors (q→) between 0.4 and 3.3 -1. Integration of the data gives the static structure factors which have a major peak at q1.8 -1. These data are compared to Monte Carlo calculations with the use of the pair potential for krypton, and differences due to many-body forces are observed. Then the S(q,ω) functions are compared to hardsphere molecular-dynamics simulations and the predictions of the kinetic theory of gases. Data are presented as a function of q for fixed ω, and for low momentum transfer (q≤1.8 -1) significant differences are observed, while for higher momentum transfer the hard-sphere results are in reasonable agreement with the data. Diffraction maxima are observed for energy transfers up to 3 meV with the peak position moving to higher q as ω is increased.