Influence of Temperature on the Lifetime of Electronically Excited Uranyl Ion: I. Liquid and Supercooled H_(2)SO_(4) Solutions

摘要

The influence of temperature (varied in the range 77-300 K) on the lifetime (τ) of electronically excited uranyl (UO_(2)~(2+)) in 0.2-5.0 M aqueous solutions of H_(2)SO_(4) was studied. The activation parameters of the temperature quenching of the uranyl photoluminescence (PL) were determined. The temperature dependences of the rate constant of (UO_(2)~(2+)) PL decay (k=1/τ) in 0.5 and 5 M H_(2)SO_(4) obey the Arrhenius equation only at T>265 K and T>280 K, respectively. The deviations at low temperatures are probably due to both non-exponential temperature dependence of the viscosity of these solutions and a change in the chemical composition of the solvent (H_(2)SO_(4) dissociation), which affect the uranyl speciation and hence the luminescence parameters.