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Research article2009Peer reviewed

Optical Spectra and Crystal-Field Levels of [Cm(H2O)(9)](3+) Ions with C-3h Symmetry in Isotypic Rare-Earth Triflate and Ethyl Sulfate Salts

Lindqvist-Reis, Patric; Walther, Clemens; Klenze, Reinhardt; Edelstein, Norman M.


Fluorescence emission and excitation spectra of [Cm(H2O)(9)](3+) ions with regular and distorted tricapped trigonal prismatic coordination geometries are reported at temperatures of 293 and 20 K. The Cm3+ impurities are incorporated into the hexagonal crystal lattices of the isotypic [M(H2O)(9)](CF3SO3)(3) (M = La (1), Y (2)), and [Y(H2O)(9)](C2H5SO4)(3) (3) salts, and into the low symmetry [La(H2O)(9)]Cl-3 center dot 15-crown-5 center dot H2O (4) salt. Small but significant structural differences in the MO9 polyhedra influence the crystal-field levels of the S-8'(7/2) ground-state and the D-6'(7/2) excited-state multiplets. Thus, the total D-6'(7/2) splitting is smaller in 1-3 (376-393 cm(-1)) than in 4 (430 cm(-1)), which explains the marked blue shifts of the emission spectra of 1-3 to those of 4 and Cm3+ (aq) at 293 K. The transitions between the ground state and the two lowest crystal-field levels of the D-6'(7/2) MUltiPletS in 1-3 give rise to narrow fluorescence lines at the emitting level at 20 K, resolving the crystal-field levels of the ground state as sharp and narrowly spaced lines. The total ground-state splittings in 1 (8.0 cm(-1)), 2 (6.0 cm(-1)), and 3 (7.5 cm(-1)) are about three to four times larger than those for Cm3+ in LaCl3 (2.0 cm(-1)), but four to six times smaller than those for Cm3+ in [Y(H2O)(8)]Cl-3 center dot 15-crown-5 (35 cm(-1)). Inhomogeneous line broadening prevents resolving the ground multiplet levels in 4. Vibronic side bands associated with the S-8'(7/2)-D-6'(7/2) transition are observed in the low temperature emission and excitation spectra. The intensities of these side bands are < 1% of the parent electronic transition, the stronger ones being located below similar to 400 cm(-1) and correspond to various CmO9 skeletal modes. The luminescence lifetimes in 1-4 are between 63 and 74 mu s.

Published in

Journal of Physical Chemistry C
2009, Volume: 113, number: 1, pages: 449-458

    UKÄ Subject classification

    Inorganic Chemistry

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