Excitation of the uranyl ion in U(IV) oxidation with xenon difluoride in frozen aqueous sulfuric acid solutions: III. Effect of solvent deuteration

Abstract

The effect of the solvent deuteration on the reaction of U(IV) with XeF₂ in solutions of H₂SO₄ in H₂O and D₂SO₄ in D₂O, occurring in the course of heating these solutions after their quick cooling (10–15 K s⁻¹) to 77 K, was examined. The effect is manifested in essentially different temperature dependences of the chemiluminescence accompanying the oxidation of U(IV) with XeF₂. The results obtained are interpreted within the framework of the concept that the low-temperature reaction of U(IV) with XeF₂ is catalyzed by the juvenile surface of crystal hydrates of sulfuric and deuterosulfuric acids, formed in the course of low-temperature phase transitions. The isotope effect is due to different kinetics of the phase transitions in solutions of H₂SO₄ in H₂O and D₂SO₄ in D₂O. In the course of crystallization of supercooled H₂SO₄ solutions, depending on the mode of temperature variation, either one or two eutectics appreciably differing in the physical properties are formed. In the course of crystallization of supercooled solutions of D₂SO₄ in D₂O, one stable eutectic is formed in each sample, and its characteristics depend on the thermal history of the sample. The eutectics melt in the course of heating of the frozen solution at temperatures differing by only 3–4 K.