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.