Deep inelastic neutron scattering from fluid para- and orthohydrogen

New experimental neutron scattering data from fluid and solid molecular hydrogen at high momentum transfer are interpreted by means of a theoretical calculation able to describe the data both for parahydrogen and for an ortho-parahydrogen mixture over a wide momentum transfer range. Our approach, valid for any diatomic molecule, reveals the occurrence of final state effects in the scaling function and their q dependence. It appears that at high momentum transfer the dominant final state effects are those coming from the intramolecular interaction