Uranyl fluoride luminescence in acidic aqueous solutions

Abstract

Luminescence emission spectra and decay rates are reported for uranyl species in acidic aqueous solutions containing HF or added NaF. The longest luminescence lifetime, 0.269 f 0.006 ms, was observed from uranyl in 1 M HF + 1 M HC104 at 296 K and decreased with increasing temperature. Based on a luminescence dynamics model that assumes equilibrium among electronically excited uranyl fluoride species and free fluoride ion, this long lived uranyl luminescence in aqueous solution is attributed primarily to U02F2. Studies on the effect of added LiN03 or Na2W04'2Hz0 showed relatively weak quenching of uranyl fluoride luminescence which suggests that high sensitivity determination of the u F 6 content of w F 6 gas should be feasible via uranyl luminescence analysis of hydrolyzed gas samples of impure w F 6 .

Equilibrium constants in aqueous lanthanide and actinide chemistry from time-resolved fluorescence spectroscopy: The role of ground and excited state reactions

“…For fluoride ions, the situation appears somewhat more controversial. [15] concludes that photochemical processes are very fast and that the values of K * (for the 1 : 1 and 1 : 2 complex) are different from those of the ground state (one being smaller, the other one larger). In contrast, the decay was found to be biexponential when the UO 2 2+ and the 1 : 1 complex are present, while the decay becomes monoexponential when the 1 : 1 and 1 : 2 complex exist in solution [58].…”

“…This facilitates considerably the handling of highly radioactive materials and allows to study speciation under environmental conditions. When applied to radiochemical problems, TRLFS is more or less restricted to solutions of U(VI) [15][16][17][18][19][20][21][22], Cm(III) [23][24][25][26][27][28][29] and various lanthanide(III) elements [30][31][32][33][34][35][36][37][38]. Among these, Eu(III) is the most commonly used one, as it is considered a good homologue of *Author for correspondence (E-mail: isabelle.billard@ires.in2p3.fr).…”

Aqueous Solutions of Uranium(VI) as Studied by Time-Resolved Emission Spectroscopy: A Round-Robin Test

“…The question of the mono-or multi-exponential behaviour of U(VI)/F -aqueous solutions has been long debated in the literature: One publication 26 presented only monoexponential decays, from which the conclusion that photochemical processes were very efficient was derived. In another paper devoted to this system, a bi-exponential decay was observed for UO 2…”

Charge Transfer in Uranyl(VI) Halides [UO2X4]2− (X = F, Cl, Br, and I). A Quantum Chemical Study of the Absorption Spectra

“…3 In particular, uranyl fluoride draws substantial attention in uranium chemistry since it is a product of the reaction of UF 6 with moisture. 4 In the past, optical properties of the uranyl chloride complexes in the solid state have been extensively studied [5][6][7] and thermodynamic data of U(VI) aquo chloro complexes have been reported. 8 However, uranyl bromide and iodide are less stable than the fluoride and chloride complexes, especially in the solid state; for example bromide complexes decompose already at room temperature.…”