Circular dichroism spectra and electronic rotatory strengths of the europium 4f→4f transitions in Na 3[Eu(ODA) 3]·2NaClO 4·6H 2O

Abstract

Axial absorption and circular dichroism (CD) spectra are reported over the 16000–37700 cm −1 spectral region for single crystals of Na 3[Eu(oxydiacetate) 3]·2NaClO 4·6H 2O at room temperature. The transitions observed in these spectra originate from crystal-field levels of the 7F 0, 7F 1, and 7F 2 multiplets of Eu 3+, and they terminate in crystal-field levels spanning excited-state multiplet manifolds. Rotatory strengths for 14 crystal-field transitions are determined from the experimental CD data. Calculations of rotatory strengths, dipole strengths, and dissymmetry factors are reported for transitions spanning the entire 16000–37700 cm −1 spectral region, and these calculated properties are used to simulate CD and absorption spectra. The calculations are based on a parametric model calibrated to yield optimized fits between calculated and experimental energy level data and dipole strength data. Rotatory strengths are somewhat more sensitive to the SLJM J compositions of the 4f N crystal-field state vectors and to the interactions responsible for coupling (or mixing) the 4f N states with electronic states of opposite parity. The calculated and observed CD and absorption spectra exhibit very good agreement in all but a few transition regions, which suggests that the crystal-field energy levels and state vectors of Eu 3+ in Na 3[Eu(ODA) 3]·2NaClO 4·6H 2O are well characterized by the parametric model employed in this study. The most prominent disagreements between calculation and experiment are observed in the 7F 0→ 5D 2 and 7F 0→ 5F 2 transition regions, and possible reasons for these disagreements are discussed.