Structural studies of 1H-containing liquids by polarized neutrons: Chemical environment and wavelength dependence of the incoherent background

Following a demonstration of how neutron diffraction with polarization analysis may be applied for the accurate determination of the coherent static structure factor of disordered materials containing substantial amounts of proton nuclei (Temleitner et al., Phys. Rev. B 92, 014201, 2015), we now focus on the incoherent scattering. Incoherent contributions are responsible for the great difficulties while processing standard (non-polarized) neutron diffraction data from hydrogenous materials, hence the importance of the issue. Here we report incoherent scattering intensities for liquid acetone, cyclohexane, methanol and water, as function of the H-1/H ratio. The incoherent intensities are determined directly by polarized neutron diffraction. This way, possible variations of the incoherent background due to the changing chemical environment may be monitored. In addition, for some of the water samples, incoherent intensities as a function of the wavelength of the incident neutron beam (at 0.4, 0.5 and 0.8 angstrom) have also been measured. It is found that in each case, the incoherent intensity can be described by a single Gaussian function, within statistical errors. The (full) width (at half maximum) of the Gaussians clearly depends on the applied wavelength. On the other hand, the different bonding environments of hydrogen atoms do not seem to affect the width of the Gaussian. (C) 2022 The Author(s). Published by Elsevier B.V.

Automated summary

This article demonstrates how neutron diffraction with polarization analysis can be used to accurately determine the coherent static structure factor of disordered materials containing large amounts of proton nuclei. The focus is on incoherent scattering, which poses challenges in processing neutron diffraction data from hydrogenous materials. Incoherent scattering intensities for liquid acetone, cyclohexane, methanol, and water are reported, along with variations due to the changing chemical environment. The study also measures incoherent intensities as a function of the incident neutron beam wavelength for certain water samples. The results show that the incoherent intensity can be described by a single Gaussian function, with the width of the Gaussians depending on the applied wavelength and unaffected by the bonding environments of hydrogen atoms.