Circular dichroism spectra and electronic rotatory strengths of the samarium 4f→ 4ftransitions in Na3[Sm(oxydiacetate)3]·2NaClO4·6H2O

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Abstract
Axial absorption and circular dichroism (CD) spectra are reported for single crystals of Na3[Sm(oxydiacetate)3]·2NaClO4·6H2O over the spectral region 17 600–30 500 cm-1. Within this region, 213 individual (4f → 4f) crystal-field transitions may occur from the ground crystal-field level of Sm3+. Each of these transitions is both electric-dipole and magnetic-dipole allowed in the axial spectra (according to D 3 site-symmetry selection rules), and each is predicted to be optically active (i.e., circular dichroic). Rotatory strengths, determined from low-temperature CD measurements, are reported for 52 of these transitions, and dissymmetry factors are reported for 39 of the transitions. Each of the 52 transitions (for which empirical rotatory strengths are reported) is assigned and characterized with respect to the symmetries of the connecting crystal-field levels and their principal 4f 5 multiplet parentages. Calculations of rotatory strengths, dipole strengths, and dissymmetry factors are reported for transitions spanning the entire 17 600–30 500 cm-1 region. These calculations are based on a general parametric model for 4f N energy levels and lanthanide-ligand-radiation field interactions (within the one-electron/one-photon approximation). This model yields excellent fits between calculated and experimentally observed 4f → 4f transition energies, dipole strengths, rotatory strengths, and dissymmetry factors for Sm3+ in Na3[Sm(oxydiacetate)3]·2NaClO4·6H2O. This is the first study in which lanthanide chiroptical properties have been quantitatively measured, analysed, and characterized over a wide spectral range spanning a large number of 4f → 4f crystal-field transitions.

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