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No abstract available

[en] A shortfall of the scattering intensity from protons has been observed in liquids (water, benzene, etc.) and solids (metal hydrogen systems, organic polymers, etc.) using neutron Compton scattering (NCS). However, the suitability of the conventional NCS data reduction scheme, used to obtain the scattering intensities, based on the convolution approximation (CA) of the nuclear momentum distribution with the instrument resolution function has been questioned. In the present work the commonly used data reduction scheme is compared to a model-free approach [B. Dorner, J. Neutron Res. (to be published)] that is independent of the form of the momentum distribution and the resolution function. Specifically, the ratios of the scattering cross section density of H to C are presented for polyethylene. The model-free approach is shown to lead to the same results as for experimental data published earlier and treated with the CA thus addressing a great part of the previous comments

[en] Claims in a Comment by R. Moreh et al. [Phys. Rev. B 75, 057101 (2007)] that their analysis of the keV neutron scattering data is correct and yields conventional results are shown to be wrong. Here we show that accounting for the neutron attenuation in the relatively thick samples, but neglecting the strong anisotropic distribution of double scattered neutrons from protons, creates an artificial and faulty decrease of about 19% in the theoretically predicted scattering intensity ratio of H₂O relative to that of D₂O

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[en] Scattering of neutrons in the 24-150 keV incident energy range from H₂O relative to that of D₂O and H₂O-D₂O mixtures was reported recently by Moreh et al. This work is related to neutron Compton scattering experiments regarding the 'anomalous' scattering from protons, observed earlier at ISIS by Chatzidimitriou-Dreismann et al in the 5-100 eV range. Here we provide the complete data reduction scheme of time-of-flight integrated intensities measured at keV energy transfers, within the impulse approximation of standard theory and for single scattering events. Current investigations of multiple scattering events and the associated preliminary results are mentioned. Direct application of the theoretical results to the new keV scattering data reveals an anomalous ratio of scattering intensity of H₂O relative to that of D₂O of about 20%, thus being in good agreement with the earlier results of the original experiment at ISIS

[en] We discuss the possibility to characterise nuclear quantum effects on the dynamics of heavy nuclei by means of neutron-resonance capture analysis on the VESUVIO spectrometer at ISIS. VESUVIO is equipped with yttrium-aluminium-perovskite gamma-sensitive detectors that can be used to record the Doppler-broadened line shape from a neutron-induced resonance in the neutron-energy range between 1 and 100 eV. The measurement of nuclear momentum distributions for heavy atoms using deep inelastic neutron scattering, the traditional technique for light-weight nuclei from hydrogen to fluorine, is currently severely limited by the resolution of the instrument. On the other hand, gamma-Dopplerimetry studies as the one presented here on gold allow for exquisite precision and short data-collection measurements, of the order of one hour, for the measurements, rendering the technique ideal for high-throughput investigations. (paper)

[en] This paper describes ongoing efforts to implement the reduction and analysis of neutron Compton scattering data within the MANTID framework. Recently, extensive work has been carried out to integrate the bespoke data reduction and analysis routines written for VESUVIO with the MANTID framework. While the programs described in this document are designed to replicate the functionality of the Fortran and Genie routines already in use, most of them have been written from scratch and are not based on the original code base

[en] We discuss ongoing methodological developments underpinning the determination of nuclear-momentum distributions from mass-resolved neutron Compton data of lightweight materials. To this end, two systems are considered in detail, namely, lithium hydride (including its deuterated counterpart) and squaric acid, an organic antiferroelectric material containing hydrogen, carbon, and oxygen. Beyond the usual case of the proton, our approach enables direct access to detailed line shape information associated with the underlying nuclear-momentum distributions of both deuterium and lithium. For oxygen and carbon, mean kinetic energies can also be obtained directly from the neutron data, as demonstrated by a detailed analysis of mass- resolved data from squaric acid. From an instrumentation point of view, this work provides a suitable platform for a detailed assessment of existing capabilities and future developments in mass-selective neutron spectroscopy on the VESUVIO spectrometer at ISIS

[en] The VESUVIO spectrometer at the ISIS pulsed neutron and muon source is an epithermal and thermal neutron station requiring a software suite able to tackle the analysis of experimental data from several neutron techniques. We present an update on the tools available within the MANTID environment for the treatment of neutron Compton scattering data, and we discuss new strategies for the analysis of neutron Compton profiles and momentum distributions that provide robustness to the scientific studies based on this technique. (paper)