Photophysical studies of uranyl complexes. 4. X-ray photoelectron and luminescence studies of hydrolyzed uranyl salts

The solid-state hydrolysis products of uranyl ion, UO/sub 2//sup 2 +/, have been studied with use of x-ray photoelectron and luminescence spectroscopy. The products, consisting of uranium oxides and various forms of uranyl hydroxide, gave averaged uranium 4f photoelectron binding energies of 381.5-381.8 eV and oxygen 1s binding energies of 530.8-531.9 eV. Evidence for carbon dioxide chemisorption from the atmosphere was observed by monitoring the carbon 1s line for samples that had been exposed to the atmosphere for extended periods of time. The luminescence spectra of all sets of hydrolysis products were essentially identical, consisting of two well-defined, broad peaks at 10 K. The luminescence lifetimes of each pair of bands were found to be identical within experimental error. A lifetime of 100-115 ..mu..s was observed for most samples, yielding a ground-state vibrational energy of 700-730 cm-/sup 1/. For other products, the emission lifetimes were significantly smaller, giving ground-state vibrational energies of less than 700 cm-/sup 1/ and implying that counterion interactions were operable in several of the hydrolysis product mixtures.