Fluorescence Spectra and Lifetimes of the Lanthanide Aquo Ions and their Complexes

Abstract

High resolution fluorescence spectra of the aquo Sm(III), Eu(III), Gd(III), Tb(III) and Dy(III) ions have been investigated in order to establish the energy levels of the ground state multiplets. The energy levels of the aquo Eu(III) ion have been established using both fluorescence and excitation spectra. The effect of coordination of simple inorganic and organic ligands have been investigated using changes in the fluorescence intensities and lifetimes of the aquo ions. The lanthanides-carbonate systems have received special attention due to the important role of carbonates in the geoche-mical process. We have observed strong hypersensitive fluorescence transitions for the ions mentioned above and including Tm(III) in the anionic tetracarbonato complexes. Extreme hypersensitivity was observed for the sDo + 7F2 transition of the Eu allowing us to detect an Eu concentration ~10-7M in solution. The lifetime of the excited states in the tetracarbonato complexes are Sm(4Gs/2) 12, Eu(sDo)465, Gd(6 P7/2)1460, Tb(sD4)1100, Dy(4 F9/2)11 and Tm(lG4) 7 ~sec. Energy transfer from the SD4 level of Tb to the sDo level of Eu in the mixed tetracarbonato system was also observed. It was monitored by measuring the change of lifetimes of Eu and Tb ions ln this mixed system. The exchange time is ~25 ~sec. Mixed fluoro-carbonato complex of Eu(III) was selected as a model system for the geologically occuring bastnasite. Indication of the presence of a mono-fluoro-Eu(III)-carbonato complex was obtained. 451 S. P. Sinha (ed.), Systematics and the Properties of the Lanthanides, 451-500.