The neutron cross section of low-temperature heteronuclear diatomic fluids

TL;DR

This paper models the neutron response of heteronuclear diatomic liquids, focusing on hydrogen deuteride, and highlights the need for more experimental data to improve understanding of neutron scattering in such fluids.

Contribution

It provides a formal description of neutron scattering in heteronuclear diatomic liquids and introduces a model for the neutron double differential cross section, using the ideal gas law approximation.

Findings

Preliminary model calculations align with limited total cross section data.

Identifies the need for more precise measurements of total and differential cross sections.

Highlights the importance of simulating translational dynamics in weakly quantum fluids.

Abstract

The present work deals with the formal description of the response to neutrons of heteronuclear diatomic liquids, with special interest in the case of hydrogen deuteride as a possible candidate for the moderation process required in the production of cold neutrons. Preliminary evaluations of the model giving the neutron double differential cross section of a heteronuclear vibrating rotor are performed by using, as a first approximation, the ideal gas law for the centre-of-mass translational dynamics, which is expected to be appropriate at incident neutron energies above the thermal region. The unavailability of double differential cross section experimental data on liquid HD compels to test the model calculations only at an integral level, i.e. against the only measurement carried out on liquid HD for the determination of its neutron total cross section. The present findings indicate the evident need of more accurate measurements of the total cross section, as well as of future work devoted to double differential cross section determinations and appropriate simulations of the translational dynamics of this weakly quantum fluid.