Inorganic photophysics in solution. Part 2.—Temperature activation of decay processes in the luminescence of uranyl[UO 2+2] ion

Abstract

The luminescent decay of excited uranyl ion has been studied over a wide temperature range in dilute aqueous acid, concentrated HClO₄, H₂SO₄, H₃PO₄, a borosilicate glass, acetone, CH₃CN, CF₃CO₂H, CH₃OH, CD₃OD and a polymeric film (of cellulose acetate). In those cases where it was possible to work at temperatures as low as 77 K, it proved possible to rationalise the temperature-dependence of the rate in terms of the equation k_(T)=B+A exp (–Delta;E^{[graphic omitted]}/RT).

B, which is similar for all systems studied (within a factor of 3), is taken as reflecting a combination of radiative and non-radiative processes of a physical nature. The second term is characterised by high values of ΔE^≠ and (like the first) the presence of kinetic isotope effects, and is taken to refer to chemical quenching, usually by a process of rapidly reversed hydrogen–atom abstraction, but (when this is impossible) by electron-abstraction.