High-resolution emission spectra of several europium complexes with β-diketones, dipyridyl, and phenanthroline have been examined at 77°K in microcrystals. The Stark splitting of the <sup>7</sup><i>F</i> levels in the ground multiplet and the relative intensities of the individual <sup>5</sup><i>D</i><sub>0</sub>→<sup>7</sup><i>F</i> transitions can be used for theoretical correlation with the ligand field parameters, transition probabilities, molecular structure, and Eu-ligand bonding. The fluorescence spectra of the bis-aqua, tris, tris-aqua, tetrakis, and mixed chelates with the bidentate ligands are discussed in relation to molecular configuration.
Nicolae Filipescu, K. Moorjani, N. McAvoy, S. Bjorklund, C. R. Hurt, and J. Zumoff, "Fluorescence Spectra of Homogeneous and Mixed Europium Complexes," Appl. Spectrosc. 22, 513-519 (1968)