Velocity-autocorrelation function in liquids, deduced from neutron incoherent scattering results

The Fourier transform p(ω) of the velocity-autocorrelation function is derived from neutron incoherent scattering results, obtained from the two liquids Ar and H₂. The quality and significance of the results are discussed with special emphasis on the long-time t^-3/2 tail, found in computer simulations and recent theories. The available experimental data from Na, Ar, and H₂ close to their normal melting points are consistent with calculations which take into account the contribution to p(ω) from the tail at low frequencies.