Velocity autocorrelation function of dense hydrogen gas determined by neutron scattering

By means of neutron scattering the Fourier-transformed velocity autocorrelation function z(?) of a simple fluid (hydrogen at 119 K and 768 bar) is determined for practically all frequencies ? [i.e., up to 28 ps-1, where z(?)=z(0)/10]. The result is consistent with the mode-coupling theory for small ?, and with the Enskog theory for large ?. The shape over the entire ? range is similar to the shape of the velocity autocorrelation function as determined from molecular-dynamics simulations.