Influence of Temperature on the Lifetime of Electronically Excited Uranyl Ion: II. Frozen Aqueous Solutions of H_(2)SO_(4). Effect of Phase Transitions

摘要

The temperature dependences of the lifetime (τ) of electronically excited uranyl ion (UO_(2)~(2+)), measured both on heating from 77 K and on cooling from 300 to 77 K of UO_(2)SO_(4) solutions in 0.2-5.0 M of H_(2)SO_(4), pass through extrema. The peaks of phase transitions in DTA curve and peaks in the temperature dependence of τ appear at the same temperature. The influence of the phase transitions on the temperature dependence of τ is due not only to a change in the molecular mobility upon a phase transition (this factor causes the temperature quenching) but also to the concentration quenching of excited states of (UO_(2)~(2+)).