Density Effects on the Dynamic Structure of Liquid Deuterium Oxide

Abstract

The temperature and pressure dependences of the deuteron spin‐lattice relaxation time and of the density and viscosity of liquid deuterium oxide were measured in the range of 10–90°C and 1 bar‐5 kbar. The experimental data enabled us to separate the effects of density and temperature on T₁ and viscosity. We found that at constant density the quantity (ηT₁/T) is independent of temperature within experimental error, while the change in density results in a significant increase in the quantity (ηT₁/T). This experimental finding is qualitatively interpreted in terms of possible changes in the degree of coupling between rotational and translational motions and/or changes in the magnitude of the deuteron quadrupole coupling constant. Within the limited density range studied from 1.106 g/cm³ to 1.230 g/cm³, no extensive disruption of the random hydrogen bond network occurs. The data favor the tentative interpretation that an increase in pressure produces a decrease in the average $\mathrm{O–O}$ distance in the $\mathrm{O–D}\mathrm{···}\mathrm{O}$ hydrogen bonds resulting in a decrease in the magnitude of the deuteron quadrupole coupling constant.