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

TL;DR

This study uses polarized neutron diffraction to measure incoherent scattering in hydrogen-containing liquids, revealing how the incoherent background varies with chemical environment and neutron wavelength, aiding data analysis.

Contribution

It demonstrates the direct measurement of incoherent scattering intensities in liquids using polarized neutrons and explores their dependence on chemical environment and neutron wavelength.

Findings

Incoherent intensity follows a Gaussian distribution.

Gaussian width depends on neutron wavelength.

Chemical environment does not affect Gaussian width.

Abstract

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 $^1$H/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 \AA ) 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.