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Eu3+-doped transparent nano-glass-ceramics, 32(SiO2)9(AlO1.5)31.5(CdF2)18.5(PbF2)5.5(ZnF2):3.5(EuF3)mol %, have been prepared aiming at the investigation of the site structure of the Eu3+ rare-earth dopant. In this nano-glass-ceramic host, other rare-earth dopants, such as Er3+, Tm3+, Ho3+, and Dy3+, also have served as a dopant; however the Eu3+ ion is a preferably sensitive probe for a rare-earth dopant site structure due to its unique purely magnetic and purely electric dipole moment optical transitions involving the nondegenerate excited 5D0 and ground 7F0 states. The splitting in the respective emission and absorption spectra in the crystalline field of the nano-glass-ceramics and its parent glass has been studied. It has been concluded that the major site of the rare-earth dopant in the nano-glass-ceramics is nearly cubic, with an orthorhombic distortion according to the sequence Oh→D4h→D2h, and the majority of the rare-earth dopants substitute onto the Pb2+ site in the PbF2 nanocrystals embedded in the glass network. A vibronic contribution to the strength of the 5D0→7F2 electric dipole moment transition has been found and the respective dominating contributing vibration mode has been proposed to be and to change as a2u→b1u→au, according to lowering the site symmetry in a sequence Oh→D4h→D2h. [ABSTRACT FROM AUTHOR]

Magnetic circular dichroism (MCD), circular dichroism (CD), and axial absorption spectra of Na3Eu(ODA)3·2NaClO4·6H2O are recorded at 4.2 and 150 K between 4500 and 25 500 cm-1. MCD parameters, rotatory strengths, and intensities are calculated using a parametric model for 4f→ 4f transitions. It is shown that the sign and magnitudes of the MCD parameters are very sensitive to the sign and absolute values of the intensity parameters. [ABSTRACT FROM AUTHOR]

The multipolar character of transitions in lanthanide double nitrates is stressed, thereby demonstrating the effect of small deviations from an icosahedral symmetry on the fluorescence and absorption properties. Polarized absorption spectra of Nd3+ in Nd2Mg3(NO3)12·24H2O have been recorded between 11 600 and 28 900 cm-1 at 77 and at 4.2 K. Supplementary data were obtained by fluorescence measurements. The energy level scheme was obtained by diagonalizing a Hamiltonian describing the free ion parameters including two and three body configuration interactions, as well as the crystal field operator. Calculations were performed using the complete basis of 364|αSLJM> kets of the 4f3 configuration of Nd3+. A set of free ion and crystal field parameters have been calculated with an rms deviation of 35 cm-1 with respect to 41 experimentally determined levels. The composition of the wave functions has further been checked by a calculation of the intensities for both magnetic and induced electric dipole transitions. This last mechanism, described by the Judd–Ofelt theory, introduces a set of phenomenological Bλkq parameters. The calculations of the dipole strength were done in order to underline the multipolar character of the crystal field lines of some 2S+1LJ multiplets in the visible region of the spectrum as was also noticed on the base of the selection rules. This work gives the first intensity calculation on lanthanides in double nitrates. These compounds are involved in many ionophoric complexes of lanthanides [J.-C. G. Bünzli, Handbook Phys. Chem. Rare Earths 9, 321 (1987)]. [ABSTRACT FROM AUTHOR]

Locations and assignments of crystal-field levels in low-temperature spectra are reported for Eu3+ in the europium double nitrate system [Eu2M3(NO3)12·24H2O with M=Mg, Zn]. These energy levels are assigned from the polarized luminescence and the polarized absorption measurements on single crystals at 77 K. The arrangement of the oxygen atoms around the europium ion has approximate icosahedral symmetry and we have tried to find out whether the spectroscopic properties of Eu2M3(NO3)12·24H2O reflects this pseudosymmetry, even though the site symmetry of the europium ion is C3. Quantitative crystal-field calculations have first been performed assuming a C3v symmetry which is close to icosahedral. The levels are analyzed in terms of 20 free-ion and 6 crystal-field parameters. Afterwards it is examined how far the C3v parameters can be used to approximate the C3 symmetry. In this case, three additional imaginary crystal-field parameters are taken into account. [ABSTRACT FROM AUTHOR]

It is shown that the sum of the intensities for magnetic dipole transitions between crystal-field components of two free-ion levels in lanthanide spectra is almost independent of the symmetry of the environment. A mean theoretical sum value of 18×10-7D2, 94×10-7D2, and 9×10-7D2 for, respectively, the 5D1←7F0, 5D0←7F1, and 5D2←7F1 dipole strengths has been found. Experimental values of the dipole strength for Eu3+ in different lattices support within reasonable limits the theoretically derived sum rule. We therefore propose to use these magnetic dipole transitions in the Eu3+ spectrum as standards for further Judd–Ofelt parametrization. [ABSTRACT FROM AUTHOR]

The MCD spectra of the 5D1←7F0 and 5D2←7F0 transitions are analyzed for two complexes of the Eu3+ ion with the F- ligand: the LiYF4/Eu3+ (D2d symmetry) and KY3F10/Eu3+ (C4v symmetry). The sign inversion of the A terms, predicted theoretically in a previous paper, is confirmed experimentally. It is shown how MCD is able to distinguish unambiguously between the C4v and the D2d coordination symmetries. [ABSTRACT FROM AUTHOR]

This paper emphasizes the complementarity between optical and magneto-optical measurements on f elements. The magnetic circular dichroism, circular dichroism, and polarized absorption spectra of Na3Nd(ODA)3·2NaClO4·6H2O (NdODA), have been recorded at 4.2 K between 5000 and 30 000 cm-1. The electric dipole contributions to the f–f transitions are analyzed using a parametric model which contains 12 parameters which are determined by fitting the calculated to the empirical dipole strengths of 50 α and 16 π polarized absorption lines. The reliability of these intensity parameters is tested by simulating the more sensitive magneto-optical (magnetic circular dichroism) and chiroptical (circular dichroism) spectra. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We describe fully relativistic calculations for the actinide tetrahalides UF4, ThF4, UCl4, and ThCl4 using the Dirac–Slater local-density model. We use an extended basis set of numerical atomic functions calculated in a potential well. A multipolar expansion technique is used to represent detailed features of the molecular charge density and the local exchange potential used is the Von Barth–Hedin–Lundqvist potential. By describing the molecules with physically reasonable wave functions and charge densities, we are able to calculate transition-state energies in good agreement with most features of the experimental photoelectron spectra. For the chlorine 3s levels we suggest revised ionization energies in the gas phase. The experimental values in the literature seem to have been incorrectly assigned, probably because they occur near the high energy limit for He(I) radiation. [ABSTRACT FROM AUTHOR]