Tracer diffusion of tritiated heavy water (DTO) in heavy water (D2O) under pressure

Abstract

The tracer diffusion coefficient of DTO in D₂O is reported at temperatures between 280 and 328 K for pressures up to about 2.2 kbar. The pressure dependence of the diffusion coefficient is considerably different to that of the spin-lattice relaxation time (T₁). Up to about 313 K the diffusion coefficients show an initial increase with pressure to a broad maximum. The position of the maximum moves to lower pressures as the temperature is increased. At the lowest temperature a maximum increase in the diffusion coefficient of about 17 % was obtained at 1.6 kbar pressure: about double the corresponding increase for H₂O. The viscosity product (Dη/T)_V for D₂O is almost identical with that for H₂O. Activation energies for diffusion of D₂O at constant volume are greater than those for H₂O.