Structure of Heavy Ice Formed by Rapid Cooling of Heavy Water to a Temperature of 77 or 15 K

Abstract

High-resolution measurements of a cold-neutron total cross-section in heavy ice were carried out by the combined use of a time-of-flight technique with a solid-mesitylene moderator for cold-neutron production. A careful study of several sharp peaks on the cross-section data reveals the presence of a high-degree of structural order in a direction parallel to, say, the c-axis for a hexagonal ice crystal. An attempt is made to estimate coherent elastic structure factors for heavy ice at 77 and 15 K on the basis of the observed cross-section data. It turns out that the structure factors thus obtained consist of a family of sharp peaks having both a monotonous rise with an increasing momentum transfer, and an abrupt fall at a certain value of the momentum transfer. The results of the present study suggest that information about the degree of structural ordering in the heavy ice may be obtained directly from the slope of the cold-neutron total cross-section curve.