Energy levels and hypersensitivity of samarium(III) in the elpasolite Cs(2)NaSmCl(6)

Electronic absorption spectra of neat Cs(2)NaSmCl(6) between 300 and 10 K are reported for the spectral region between 900 and 40 000 cm(-1). Interpretation of the intricate vibronic structure enables 91 conclusive and 45 tentative Kramers doublet and quartet energy levels of the 4f(5) ion Sm(3+) in this system to be assigned. Configuration interaction assisted crystal field calculations employing the diagonalization of the combined 4f(5) and 4f(4)6p(1) matrices fit the energy levels better than the conventional 4f(5) crystal field calculation. The 4f(5) calculation is more accurate, however, than for the Pr(3+) and Nd(3+) elpasolite systems, showing the greater importance of intra- rather than inter-configuration interaction for the more complex electronic structure of Sm(3+). The experimental dataset generally shows agreement with that from two-photon excitation spectroscopy and the differences are highlighted. The intensity of structure at and near the zero phonon line of the hypersensitive infrared [Formula: see text] absorption transition increases relative to the intensity of the vibronic sideband when z is increased in Cs(2)NaSm(Cl(1-z)Br(z))(6). This is attributed to the introduction of electric dipole transition intensity into the pure electronic transition by lowering the site-symmetry of SmCl(6)(3-), or by the presence of SmCl(5)Br(3-).