Neutron diffraction of hydrogenous materials: measuring incoherent and coherent intensities separately from liquid water - a 40-year-old puzzle solved

TL;DR

This paper presents the first accurate measurements of coherent and incoherent neutron scattering contributions in hydrogenous materials, overcoming a 40-year-old challenge and enabling better structural analysis of such materials.

Contribution

It introduces polarized neutron diffraction techniques to separately measure coherent and incoherent intensities in hydrogenous liquids, a novel approach in the field.

Findings

First accurate separation of coherent and incoherent structure factors

Measurements over an unprecedented wide momentum transfer range

Potential to revolutionize neutron diffraction studies of hydrogen-rich materials

Abstract

(short version) Accurate determination of the coherent static structure factor of disordered materials containing proton nuclei is prohibitively difficult by neutron diffraction, due to the large incoherent cross section of $^1$H. This notorious problem has set severe obstacles to the structure determination of hydrogenous materials up to now, via introducing large uncertainties into neutron diffraction data processing. Here we present the first accurate separate measurements, using polarized neutron diffraction, of the coherent and incoherent contributions to the total static structure factor of 5 mixtures of light and heavy water, over an unprecedentedly wide momentum transfer range. The structure factors of H$_2$O and D$_2$O mixtures derived in this work may signify the beginning of a new era in the structure determination of hydrogenous materials, using neutron diffraction.