Absorption and fluorescence spectra of europium and terbium trichloroacetates

The results of spectroscopic investigations of some europium and terbium trichloroacetates, which are possible laser materials, are reported. Trichloriacetates of europium and terbium were prepared and their single crystals were grown from aqueous solutions. The low temperature absorption and fluorescence spectral studies on these complexes could give information regarding the number of fluorescing energy levels of Eu3+ and particularly the number of transitions observed in Eu, 5D07F1 and Eu, 5D07F2 suggest that the likely symmetry around the rare earth ion in these complexes is C2. Fluorescence and absorption spectral studies on these complexes in different states of hydration showed that they lose water in two stages and there exists a new phase for these complexes with two molecules of water of hydration which has not been reported so far. Solid state absorption and fluorescence spectra which are distinctly different from the spectra of the known anhydrous and trihydrated phases are used to identify this new phase. Thermo-gravimetric traces and infrared spectra give further evidences supporting its existence. The analysis of the spectra of the dihydrated europium trichloroacetate indicated the presence of two structural isomers. In the anhydrous state, on the other hand, they appear to be amorphous solids lacking crystallinity. This is inferred by their broad band, absorption and fluorescence lacking the internal fine structure characteristic of crystalline compounds of rare earths. (author)