Quasielastic neutron scattering in condensed oxygen

The quasielastic spectra of liquid and plastic-crystalline oxygen are shown to be dominated by the magnetic response. An approximate separation of the nuclear and magnetic responses from the total, unpolarized neutron double differential cross-sections is achieved by means of a subtraction of the structural contributions calculated from a Molecular Dynamics simulation. The magnetic scattering spectra are then shown to reproduce the wavevector dependence of the inelastic intensities associated with the magnetic excitations measured in a previous study, and are analyzed in terms of a model for an exchange-coupled paramagnet. Finally, the close resemblance between the magnetic response of the liquid and of the plastic crystal γ-phase are discussed. (orig.)