J. Phys. Chem. C 2009, 113, 449–458
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Optical Spectra and Crystal-Field Levels of [Cm(H2O)9]3+ Ions with C3h Symmetry in Isotypic Rare-Earth Triflate and Ethyl Sulfate Salts Patric Lindqvist-Reis,*,† Clemens Walther,† Reinhardt Klenze,† and Norman M. Edelstein‡ Institut fu¨r Nukleare Entsorgung, Forschungszentrum Karlsruhe, P.O. Box 3640, 76021, Karlsruhe, Germany, and Lawrence Berkeley National Laboratory, Berkeley, California 94720-8175 ReceiVed: September 24, 2008; ReVised Manuscript ReceiVed: October 30, 2008
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]Cl3 · 15-crown-5 · H2O (4) salt. Small but significant structural differences in the MO9 polyhedra influence the crystal-field levels of the 8S′7/2 groundstate and the 6D′7/2 excited-state multiplets. Thus, the total 6D′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 6 D′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]Cl3 · 15-crown-5 (35 cm-1). Inhomogeneous line broadening prevents resolving the ground multiplet levels in 4. Vibronic side bands associated with the 8S′7/2-6D′7/2 transition are observed in the low temperature emission and excitation spectra. The intensities of these side bands are 2σ(F2)] ) 0.034, wR(F2) ) 0.077, S ) 0.93. (27) DIAMOND 2.1, Crystal Impact GbR, 2001. (28) Abbasi, A.; Eriksson, L. Acta Crystallogr., Sect. E 2006, 62, i126– i128, and references therein. (29) David, F. H.; Vokhmin, V. New J. Chem. 2003, 27, 1627–1632. (30) Shannon, R. D. Acta Crystallogr. 1976, A32, 751–767. (31) An early luminescence and absorption spectroscopic paper on Cm3+ in LaCl3 at 77 K reports all four crystal-filed levels (A1-A4) of the 6D′7/2 multiplets at 16813, 16866, 16935, 16977 cm-1; see: Gruber, J. B.; Cochran, W. R.; Conway, J. G.; Nicol, A. T. J. Chem. Phys. 1966, 45, 1423–1427. (32) Binnemans, K.; Go¨rller-Walrand, C. Chem. Phys. Lett. 1995, 245, 75–78. (33) Auzel, F.; Malta, O. L. J. Phys. (Paris) 1983, 44, 201–206. (34) This parameter may be used for comparisons of crystal-field strengths of different fN ions in a given crystal host or for a particular fN ion in different hosts, and it is proportional to the total (∆Emax) splitting J levels with small J-mixing; Nv′ is linearly related to Nv (defined in ref 33) according to Nv′ ) Nv/(2π) ) (∑k,q (Bkq)2/(2k + 1))1/2. (35) Hammond, R. M.; Reid, M. F.; Richardson, F. S. J. Less-Common Met. 1989, 148, 311.
Lindqvist-Reis et al. (36) Kimura, T.; Choppin, G. R. J. Alloys Compd. 1994, 213/214, 313– 317. (37) Beitz, J. V. Radiochim. Acta 1991, 52-53, 35–39. (38) An upper limit for kr may be estimated, for example, in 2 where kobs(H2O) ) 15.6 ms-1 and kobs(D2O) ) 0.645 ms-1, and since kr is the same for the hydrated and deuterated compounds, kr < 0.645 ms-1. This value may be compared to that calculated for Cm3+(aq), 0.769 ms-1. (39) Beeby, A.; Clarkson, I. M.; Dickins, R. S.; Faulkner, S.; Parker, D.; Royle, L.; de Sousa, A. S.; Williams, J. A. G.; Woods, M. J. Chem. Soc., Perkin Trans. 2 1999, 493–503. (40) (a) Giuliani, J. F.; Donohue, T. Inorg. Chem. 1978, 17, 1090–1091. (b) Breen, P. J.; Horrochs, W. D. Inorg. Chem. 1983, 22, 536–540. (c) Tanka, F.; Yamashita, S. Inorg. Chem. 1984, 23, 2044–2046. (d) Lis, S.; Choppin, G. R. Mater. Chem. Phys. 1992, 31, 159–161. (e) Nelig, A.; Elhabiri, M.; Billard, I.; Albrecht-Gary, A.-M.; Lu¨tzenkirchen, K. Radiochim. Acta 2003, 91, 37. (f) Kimura, T.; Kato, Y. J. Alloys Compd. 1998, 278, 92–97. (g) Kimura, T.; Kato, Y.; Takeishi, H.; Choppin, G. R. J. Alloys Compd. 1998, 271-273, 719–722. (h) For recent review, see: Billard, I. Lanthanide and Actinide Solution Chemistry Studied by Time-Resolved Emission Spectroscopy. In Handbook on the Physics and Chemistry of Rare Earths; Gschneidner, K. A., Jr., Bu¨nzli, J.-C., Pecharsky, V. K., Eds.; Elsevier: Amsterdam, 2003; Vol. 33, Chapter 216, section 3.3. (41) Carnall, W. T.; Rajnak, K. J. Chem. Phys. 1975, 63, 3510–3514.
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