Single-particle dynamics in fluid hydrogen and deuterium

Single-particle response functions for liquid D2 and H2 , obtained from previous inelastic neutron scattering measurements, are compared with an exact quantum calculation for D2 and a Wentzel-Kramers-Brillouin (WKB) model for D2 and H2 . The exact and WKB calculations both provide satisfactory descriptions of the experimental response function of these fluids over a wide range of momentum and energy transfers, which spans from the roto-vibrational excitations up to the molecular dissociation regime.