Luminescence of uranyl ions in phosphate glass and phosphoric acid, spontaneous reduction to uranium(IV) and new description of the electron transfer bands

The absorption and emission spectra of the uranyl ion in phosphate glass and in 85 percent phosphoric acid are similar to the dilute aqueous solution, but the luminescence yield is far higher and small concentrations of uranium(IV) occur, possibly as a quasistationary equilibrium with free oxygen. The quantum numbers Ω of the excited states are discussed, based on "weak-field" coupling between ²F _{1 2} and ω = 3 2 or 1 2 of π_u. Detailed viriations of band positions are related to UO bond length modification, also in borate and germanate glasses. The excited uranyl ion may perform energy transfer to lanthanides, conceivably applicable to lasers.