Large ground-state and excited-state crystal field splitting of 8-fold-coordinate Cm3+ in [Y(H2O)(8)]Cl-3 center dot 15-crown-5
Lindqvist-Reis, P; Walther, C; Klenze, R; Eichhofer, A; Fanghanel, T
The optical spectra of Cm3+ incorporated into the crystalline host structure of [Y(H2O)(8)]Cl-3 center dot 15-crown-5 (1) is investigated by using laser spectroscopic methods at temperatures between 20 and 293 K. The coordination geometry of the [Y(H2O)(8)](3+) entity in 1 is a distorted bicapped trigonal prism with confirmed CY. 3+ -Q point symmetry, as by single-crystal X-ray diffraction at 200 K. The crystal-field splitting of the S-8'(7/2) ground state and the 6D'(7/2) and P-6'(5/2) excited states of the hydrated Cm3+ ion are measured by high-resolution fluorescence emission and excitation spectroscopy at various temperatures. The transitions between the ground state and the respective lowest crystal-field levels of the excited states exhibit narrow fluorescence lines, resolving the four crystal-field levels of the ground state as sharp, well-resolved lines at about 0, 10, 19, and 35 cm(-1). The total splittings of the D-6'(7/2) and P-6'(5/2) states are 670 and 170 cm(-1), respectively. Thermal population of the ground-state crystal-field levels is observed and quantified ill the excitation spectra in the temperature range of 20-70 K. All spectroscopic results are consistent with the presence of one unique [Cm(H2O)(8)](3+) site. The ground-state splitting of Cm3+ in 1, 35 cm(-1), is comparable to that of Cm3+ in solid ThO2, 36 cm(-1), which shows the strongest crystal field for Cm3+ reported so far. For this reason the present results are different than the findings for Ln(3+) C, aqua ions, which show rather weak crystal field strengths.
Journal of Physical Chemistry B
2006, Volume: 110, number: 11, pages: 5279-5285
Publisher: AMER CHEMICAL SOC
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