Scattering of Thermal Neutrons by Liquid Solutions of Orthohyphen; and Paradeuterium

摘要

The structures of two samples of liquid deuterium, one enriched in paradeuterium (85percent; parahyphen;D2) and the other enriched in orthodeuterium (the 20deg;K equilibrium concentration 96.9percent; orthohyphen;D2), have been investigated by diffraction of 1hyphen;Aring; neutrons. The scattering data have been interpreted both as an assemblage of atom scatterers and, somewhat more exactly, as molecular scatterers. Fourier inversion of the intermolecular scattering yields a radial distribution interpretable for both samples as exhibiting approximately 10.3 nearesthyphen;neighbor molecules (cf. 12 for close packing of spheres). In the case of the converted sample (96.9percent;Jthinsp;equals;thinsp;0, nonrotating D2) the nearesthyphen;neighbor molecules are at a mean distance of 3.85 Aring; from the reference molecule; in the enriched sample (85percent;Jthinsp;equals;thinsp;1) the nearesthyphen;neighbor distance is 3.72 Aring; corresponding to a smaller molar volume attributable to the angular anisotropy of the intermolecular interactions when the rotations are hindered. Smallhyphen;angle scattering also indicates a higher compressibility for the 96.9percent; parahyphen;D2lpar;Jthinsp;equals;thinsp;0rpar;sample.