Terbium Compounds Research Articles

A simple Derivation of the Tunneling Splitting for Large Quantum Spins

With the help of a perturbation treatment to lowest order, general expressions for the tunneling splitting have been derived for a quantum spin S. This spin is assumed to have a main axial Hamiltonian (without applied longitudinal magnetic field), and to be submitted to perturbations with orthorhombic, tetragonal, trigonal or hexagonal symmetries, or to a transverse field. The formulas obtained are valid for general (not very small) S. They are compared with available results of the literature. Previous observations of tunneling splittings in terbium compounds by EPR are mentioned, with the relevant references.

Studies on rare earth carboxylates. III. X-ray and IR studies on Ln(C6H4OHCOO)3�H2O (Ln = La-Ho or Y)

The rare earth salicylate monohydrates Ln(C6H4OHCOO)3·H2O (Ln=La-Ho or Y) were prepared and subjected to X-ray powder diffractometric and infrared absorption spectroscopic investigations. The salts from lanthanum to gadolinium are found to be isomorphous and are indexed on a monoclinic unit cell with space groupP21/c-C 2h 5 (No. 14). Certain dissimilarities between the powder patterns of isomorphous terbium and dysprosium compounds and those of the lighter rare earths necessitated independent indexing of these two compounds, which are found to be monoclinic with space groupP21/c-C 2h 5 . Holmium and yttrium salts are isomorphous and are monoclinic with space groupP2/m-C 2h 1 (No. 10). The assignments of some of the observed bands to certain characteristic vibrations of various functional groups in the spectra of these salts have been done.

Electronic-vibrational spectra of neodymium activated crystals

17. H. Sobue, T. Uryu, K. Matsuzaki, and J. Tabata, "Stereoregularity of polymethacrylo- nitrile," J. Polym. Sci., l, No. 8, Part B, 409-411 (1963). 18. H. Herma, V. Groebe, and R. Schmolke, "Characterization of copolymers. 2. Composition and sequential length distribution of acrylonitrile--methacrylonitrile copolymers," Faserforsch. Textiltechnik, 117, No. 2, 56-60 (1966). ELECTRONIC-VIBRATIONAL SPECTRA OF NEODYMIUM ACTIVATED CRYSTALS V. F. Zolin, V. M. Markushev, V. I. Tsaryuk, and Ch. M. Briskina UDC 535.34:541.65 Electron vibrational (EV) spectra of neodymium (Nd ~+) compounds [I, 2] are interesting from different points of view. They could be useful in connection with investigations of the structure of luminescence centers [3-5]. The presence of EV bands can restrict the applica- bility of selective laser excitation spectroscopy in studying luminescence centers in dis- ordered media (for example, glasses) [6-8]. EV bands can make a considerable contribution to the overlap integrals of the luminescence spectra of donors and the absorption spectra of ac- ceptors, whose magnitude determines the probability of transferring exGitation energy in the luminescence quenching and sensitization processes, as well as with migration and cross- relaxation [9, 10]. Finally, the probabilities of multiphonon transitions, determining the rate of relaxation of excitation of luminescence centers in crystals and glasses activated by lanthanides, depends on the magnitude of EV interaction and the phonon density of states, which can be estimated from the EV spectra [11-13]. The EV spectra of europium and terbium compounds were studied in [4, 5, 14]. The inter- pretation of these spectra was facilitated by the relative simplicity of the Stark structure of the energy levels of the Eu 3+ ion and the similarity of the spectral properties of Eu ~+ and Tb s+. In this paper we present the results of investigations of EV s~ectra of analogous neodymium compounds, for which the EV interaction is stronger than for Eu + and Tb 3+. The use of laser excitation permitted observing easily the EV bands in the luminescence spectra of neo- dymium. The magnitudes of the EV interaction for the Nd s+ ion were estimated from the ratios of the integral intensities of the single-phonon and phononless bands (Io~/Ioo) [12]. Technique and Objects of Investigation. We investigated the spectra of materials used in laser technology: spectra of neodymium pentaphosphate NdPsO~, neodymium tetraphosphates and tetraphosphates of alkali metals MeNdP~O~ (Me = Na, K, Rh, Cs), binary molybdates with composition Na,La~-mNdm(MoO~)~ (m = l, 0.9, 0.25) and BaNda-mGdm(MoO~)~ (m = O, 1,8), binary tungstates Me~Lao.,Ndo.~(WO~)~ (Me = Na, Cs), calciumtungstates CaWOd, and garnets Y3AI2(A104)3 (YAG), Gd,Gaa(GaO~), (GGG), activated with 1% neodymium. Absorption spectra in the region 24,100-14,200 cm -~ were recorded photographically using an ISP-51 spectrograph with a long focal length UF-90 chamber and photoelectrically usin~ a DFS-12 spectrometer and F~U-79. The luminescence spectra in the region 9600-ii,700 cm , excited with a Rhodamine 6G tunable dye laser, were recorded by an MDR-23 monochromator using F~U-62 and a PAR 160 integrator. It is convenient to observe the single-phonon EV satellites, related to internal vibra- tions of ligands, in the absorption spectra of neodymium between bands of the electronic transitions ~I,/2--~G,/2 and ~I,/2--~G,/a, ~G5/2 and in the luminescence spectra between bands of the electronic transitions ~F,/a--~I,/~ and ~F~/a--~I~/2. EV satellites, generated by the transitions dIg/2--dGT/2~ 2G9/2, 2K~,/, and ~I,/a--~F,/,, ~S,/,, are also clearly evident. To separate the EV satellites and to identify them, we used the following: temperature dependence of the line intensities, comparison of EV spectra of different compounds with one another, as well as comparison with IR spectra and Raman scattering spectra, In a number of cases, it is useful to compare with EV spectra corresponding =o europium and terbium com- pounds. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 38, No. 4, pp. 614-620, April, 1983. Original article submitted February i, 1982. 448 0021-9037/83/3804-0448507.50 9 1983 Plenum Publishing Corporation

Anisotropic magnetoelastic properties of terbium compounds with garnet and zircon structure

Jahn-Teller transitions, noncollinear spin arrangements, magnetostriction and thermal anomalies result from the sensitivity of the structure of the low-lying energy levels of the Tb 3+ ions to various anisotropic influences. The similarity between the observed properties in garnets and in zircons is to be related to the similitude of the two structures.

Internal Vibronics in Terbium Compounds—A Cooperative Phenomenon

The observation of absorption and emission vibronics in Tb3+ compounds is reported. This follows a similar analysis of Gd3+ compounds and a comparison is made between the two cases. A theoretical model based on a cooperative approach to these transitions is developed. This model yields the activity of vibrational modes involved in internal vibronics. It also gives the relative intensity of a vibronic compared to its parent electronic transition as a function of the particular rare-earth (RE) ion and of its physical surroundings.

Nonexponential Decay of Luminescence of Rare-Earth Chelates

Studies were made on the nonexponential decay of luminescence of europium complexes of picrate, dibenzoylmethide (DB), and thenoyltrifluoracetonate (TTA) and the DB and TTA compounds of terbium. Solutions in methylcyclohexane, ethanol, and toluene were studied in the temperature range 77-300 deg K. The terbium compounds and the europium picrate yielded simple exponential decays under all conditions, with decay constants of the order 500 x 10/sup -6/ sec in rigid glasses and 30 x 10/sup -6/ sec in fluids at room temperature. The decays of the luminescences of the DB and TTA compounds of europium were not exponential at low temperatures in rigid media. (P.C.H.)

434. Notes on the preparation of pure europium, gadolinium, and terbium compounds

434. Notes on the preparation of pure europium, gadolinium, and terbium compounds