M. Lemaitre-Blaise

The crystal field strength parameter and the maximum splitting of the 7F1 manifold of the Eu3+ ion in oxides

Departamento de Quimica Geral e Inorĝanica Instituto de Quimica UNESP, Rua Prof. Francisco Degni, S/N, Araraquara, 14800-900 SP

Simulation of the energy level scheme of Nd3+ and Eu3+ ions in rare-earth orthovanadates and phosphates

The absorption spectra of the Nd3+ ion in the tetragonal xenotime-type NdVO4 and in the monoclinic monazite-type LaVO4, LaPO4 and NdPO4 as well as the luminescence of the Eu3+ ion in LaVO4 and LaPO4 were measured and the spectra were analysed according to the appropriate symmetry of the RE site. In addition to pure zero-phonon electronic lines the absorption spectra of the Nd3+ ion showed extensive vibronic side bands which were identified with the aid of the measured Raman scattering spectra of LaVO4:Nd3+ and NdVO4. Based on the energy level schemes derived from the absorption and luminescence spectra the parametrization of the free-ion and crystal-field effects were carried out with good results as indicated by the low RMS deviation values. The parameter sets for Nd3+ and Eu3+ ions in the same matrices are consistent with each other but no correlation was found between sets for matrices of different structures.

Observation and simulation of the energy-level scheme of the Pr3+ ion in REOCI

Absorption spectra of REOCI (RE = La, Pr, Gd and Y) have been measured in the range 435–950 nm at ambient, liquid nitrogen and liquid helium temperatures. Luminescence from the 3P1, 3P0 and 1D2 levels in PrOCI, LaOCI/Pr3+, GdOCI/Pr3+ and YOCI/Pr3+(Pr3+ content 2 mol%) was observed under argon-ion laser excitation in the visible region between 475 and 800 nm. The transitions were assigned and the energy-level scheme derived from absorption and emission spectra and consisted of some 50 levels; i.e. 68 Stark components out of 91 for the 4f2 configuration. This set was fitted to a Hamiltonian of 13 adjustable parameters including free-ion [Racahs (E0–3), Trees (α, β and γ) and spin—orbit coupling constant (ζ) as well as crystal-field (B20, B40, B44, B60 and B64) parameters. Good simulation of the experimental energy-level scheme was achieved with a root mean square deviation equal to 17 cm–1. A comparison with the energy-level parametrization of Nd3+(4f3) in NdOCl, as well as of Eu3+(4f6) and Tb3+(4f8) in GdOCl, shows the consistency of the present results.

Crystal fields in Pr3+ doped rare earth gallium garnets, RE3Ga5O12:Pr3+

The optical absorption, site selective excitation and luminescence spectra of the trivalent praseodymium ion in three rare earth gallium garnet matrices, RE3Ga5O12 (REGG; RE=Y, Gd, and Pr) were detected at 4, 77 and 300 K. The 4f2 energy level schemes comprising 56 to 68 crystal field (CF) sublevels were simulated according to a phenomenological model taking into account both the free ion and CF effects. The model consisting of 17 parameters with 8 free ion and 9 CF parameters appropriate to the D2 point symmetry of the RE3+ site reproduced the experimental energy level schemes in a satisfactory manner with RMS deviations between 17 and 23 cm-1. The CF parameters vary only slightly as a function of the host matrix. The Bqk parameter sets for PrGG and YGG:Pr3+ are consistent with those obtained for the other REGG and YGG:RE3+, respectively.

Spectroscopic properties and simulation of the energy level schemes of Nd3+ and Pr3+ ions in rare earth tellurium oxides

Absorption and emission measurements at liquid-helium temperature, liquid-nitrogen temperature and room temperature have been performed on monoclinic RE2Te4O11 (RE identical to Nd3+, Pr3+), on rare-earth tellurium oxides and on Pt-doped Gd2Te4O11 samples, respectively. The rare earth occupies a single crystallographic position with a low point symmetry C1. The spectra were analysed according to the crystal-field theory. From the experimental data, nearly complete energy level schemes of the Pr3+ and Nd3+, on the 4f2 and 4f3 configurations, were derived. Very good correlation was obtained between the experimental and stimulated energy level schemes, for the approximate C2v and/or Cs site symmetries. The crystal-field parameters vary smoothly with the atomic number of the rare earth, when compared with those determined previously for Eu3+ in the same matrix.

The optical properties of lanthanides in theLn2BaZnO5 area of the mixed oxide systemLnBaZnO

Abstract The absorption spectrum of neodymium is investigated at 4.2 K in the tetragonal phase Ln 4−2x Ba 2+2x Zn 2−x O 10−2x (Ln =La, Nd) (0 ɤ x ɤ 0.25) . There is evidence for a single site for which the 4f 3 energy levels are given. The fluorescence spectra of Eu 3+ is analyzed in the orthorhombic phase Y 2 BaZnO 5 . There are two sites for the europium ions. The energy levels of 4f 6 are given and the crystal field parameters are determined for one of the sites. The fourth-order parameters are large. The absorption spectra of the two neodymium sites in the doped orthorhombic phases along the rare-earth series show a pronounced nephelauxetic effect (shift to the red).

Crystal-field effect in CsCdBr3:Pr3+

Abstract Absorption as well as fluorescence measurements on CsCdBr 3 :Pr 3+ permit us to construct an energy level scheme for the main site occupied by the rare earth corresponding to the [RE 3+ -Vacancy-RE 3+ ] pair entity. A simulation of these levels made on the basis of a C 3v symmetry for the point site gives a low r.m.s. deviation. The crystal field parameters (CFPs) vary smoothly when compared with other rare earths embedded in the same matrix.

Structure and optical properties of KGd(CO3)F2:Eu3+

Abstract The crystal structure of KGd(CO3)F2 is solved from single crystal X-ray diffraction, and the luminescence properties of KGd(CO3)F2 are analysed. KGd(CO)3F2:Eu3+ is orthorhombic, of space group Fddd (No. 70), with a=7.006(2) A, b=11.181(3) A and c=21.865(6) A. The three-dimensional network is built up from infinite sheets of GdO4F4 polyhedra in the (a, b) plane, which are linked by the carbonate groups and K+ ions along c. A single crystallographic site for Eu3+ with C2 symmetry, as predicted by X-ray study, is confirmed from the luminescence spectrum recorded at 77 K. Simulation of the crystal field effects is also carried out.

The aragonite-type neodymium borate NdBO3 : energy levels, crystal field, and paramagnetic susceptibility calculations

Abstract Optical absorption spectra of NdBO3 single crystals were measured between 3900 and 31,700 cm−1 at liquid helium to room temperature. The derived energy level scheme with 119 levels was simulated according to the crystal field theory including free ion effects yielding a rms deviation of 15 cm−1. The 14 free ion and 14 crystal field parameters allowed by the Cs symmetry of the neodymium site were calculated. The derived wavefunctions were used in calculating the paramagnetic susceptibility and its variation with the temperature between 4.2 and 500 K by the van Vleck formula. Experimental and calculated values are in good agreement.

The optical properties of Eu3+ embedded in the rare earth borogermanate matrix: REBGeO5

The luminescent properties of the trivalent europium ion in two borogermanate matrices, LaBGeO5 (trigonal) and GdBGeO5 (monoclinic), have been analysed. The energy level schemes of the 24 and 20 7FJ (J5=0-4) electronic levels are well reproduced with 14 (LaBGeO5) and 9 (GdBGeO5) crystal field parameters (CFPs) according to the local point site symmetry occupied by the rare earth element in the matrix.