Pr Gd Research Articles

Extended Calculations of Energy Levels and Transition Rates for Singly Ionized Lanthanide Elements. I. Pr–Gd

Abstract Lanthanide elements play important roles as an opacity source in the ejected material from neutron star mergers. Accurate and complete atomic data are necessary to evaluate the opacities and to analyze the observed data. In this paper, we perform extended, ab initio atomic calculations from Pr ii (Z = 59) to Gd ii (Z = 64). By using multiconfiguration Dirac–Hartree–Fock and relativistic configuration-interaction methods, implemented in the general-purpose relativistic atomic structure package (GRASP2K), we calculate the energy levels and transition data of electric dipole transitions. These computations are based on strategies (with small variations) of Nd ii published by Gaigalas et al. Accuracy of data is evaluated by comparing computed energy levels with the National Institute of Standards and Technology (NIST) database or other works. For the energy levels, we obtain the average relative accuracy of 8%, 12%, 6%, 8%, and 7% for Pr ii, Pm ii, Sm ii, Eu ii, and Gd ii ions, respectively, as compared with the NIST data. Accuracy of energy transfer to the wavelength is 3%, 14%, and 11% for Pr ii, Eu ii, and Gd ii. Our computed E1 type transition probabilities are in good agreement with experimental values presented by other authors especially for strong transitions.

Temperature dependence of excited-state relaxation processes of Pr3+ in Pr-doped and Pr, Gd-doped CsCdBr3

Abstract The temperature dependence and mechanisms for relaxation of the 1 D 2 and 3 P 1 states of Pr 3+ in symmetrical Pr–Pr and Pr–Gd pairs in 0.12% Pr:CsCdBr 3 and 0.025% Pr:1.5% Gd:CsCdBr 3 , respectively, are presented. Both single-ion and pair relaxation mechanisms are considered. The temperature dependences of the energy-transfer processes in Pr–Pr pairs are all well-explained in terms of resonance considerations for the donor and acceptor zero-phonon crystal-field transitions.

Concentration and distribution of elements in Late Permian coals from western Guizhou Province, China

With the aim of better understanding geochemistry of coal, 71 Late Permian whole-seam coal channel samples from western Guizhou Province, Southwest China were studied and 57 elements in them were determined. The contents of Al, Ca, Co, Cr, Cu, Fe, Ga, Hf, K, Li, Mn, Mo, Nb, Ni, Sn, Ta, Ti, Th, U, V, Zr, and REEs in the Late Permian coals from western Guizhou Province are higher than the arithmetic means for the corresponding elements in the US coals, whereas As, Ba, Br, F, Hg, P, Se, and Tl are lower. Compared to common Chinese coals, the contents of Co, Cr, Cu, Ga, Hf, Li, Mn, Mo, Ni, Sc, Sn, Ti, U, V, Zn, and Zr in western Guizhou coals are higher, and As, F, Hg, Rb, Sb, Tl, and W are lower. Five groups of elements may be classified according to their mode of occurrence in coal: The first two, Group A, Tm–Yb–Lu–Y–Er–Ho–Dy–Tb–Ce–La–Nd–Pr–Gd–Sm, and Group B, As–Sr–K–Rb–Ba–F–Ash–Si–Sn–Ga–Hf–Al–Ta–Zr–Be–Th–Na, have high positive correlation coefficients with ash yield and they show mainly inorganic affinity. Some elements from Group B, such as Ba, Be, Ga, Hf, and Th, are also characterized by significant aluminosilicate affinity. In addition, arsenic also exhibits high sulfide affinity ( r S–Fe>0.5). The elements, which have negative or lower positive correlation coefficients with ash yield (with exceptions of Bi, Cs, Nb, Mn, Se, and Ti), are grouped in other four associations: Group C, Cr–V–Mo–U–Cd–Tl; Group D, Hg–Li–Sc–Ti–Eu–Nb–Cs–W; Group E, Bi–Sb; and Group F, Co–Ni–Cu–Pb–Zn–Mg–Se–Ca–Mn–S–Fe. The correlation coefficients of some elements, including Co, Cr, Cu, Fe, Hg, Li, Mo, Ni, P, S, Sc, U, V, and Zn, with ash yield are below the statistically significant value. Only Cr and Cu are negatively correlated to ash yield (−0.07 and −0.01, respectively), showing intermediate (organic and inorganic) affinity. Manganese and Fe are characterized by carbonate affinity probably due to high content of epigenetic veined ankerite in some coals. Phosphorus has low correlation coefficients with any other elements and is not included in these six associations. There are five possible genetic types of enrichment of elements in coal from western Guizhou Province: source rock, volcanic ash, low-temperature hydrothermal fluid, groundwater, and magmatic hydrothermal inputs.

Structural study in the (La,Nd) 2− xSr xCuO 4 system

The presence of layers of corner-sharing square CuO 4 units is a common structural feature of the superconducting copper oxide ceramics. There are three closely related structure types with stoichiometry (RE) 2CuO 4, each containing isolated sheets of fourfold (T ′ structure), fivefold (T ∗ structure) or sixfold (T structure) Cu-O coordination. For the longest rare earth cation (La), (RE) 2CuO 4 crystallizes in a slightly distorted K 2NiF 4 T structure. Change of the lanthanide ion from La 3+ to Pr 3+ or Nd 3+ leads to the closely related structure called T ′ structure (8). This is due to the intermediate size of the rare earth ion in the range (Pr–Gd). The relative simplicity of these rare earth systems allows us to examine how structure is related to ionic size effects and cation ordering. The study of the solid solubility of La 2CuO 4 (T) and Nd 2CuO 4 (T ′) provides a measure of the relative stabilities of these structural types. This work reports the crystal structure of the La 2− x− y Nd y Sr x CuO 4 ( x=0.1, y=0.1, 0.3), determined by neutron powder diffraction ( T=10 K, RT), with data obtained at Studsvik Neutron Research Laboratory (Sweden). These specimens crystallize in the Cmca space group, showing the T structure and thus the solubility of Nd in this network.

Conversion of VUV to Visible in K5Li2LnF10 Containing Rare‐Earth Ions (Ln: Pr—Gd).

AbstractFor Abstract see ChemInform Abstract in Full Text.

Conversion of VUV to visible in K 5Li 2LnF 10 containing rare-earth ions (Ln=Pr–Gd)

Potential of single crystals of K 5Li 2LnF 10 for application as VUV excited phosphors has been examined. The crystals can be doped by rare-earth ions (Pr–Gd) with concentrations up to 100 at.% keeping a minimal distance between two of the nearest rare-earth ions superior to 6.5 Å. For this reason the efficiency of self-quenching of their luminescence is greatly reduced. Luminescence spectra and excitation spectra in the 50–250 nm spectral region have been recorded at room temperature. Intense visible and UV emission excited in the VUV region has been observed in crystals containing Nd, Eu and Gd. Slightly weaker emission in crystals containing praseodymium and markedly weaker emission in crystals containing samarium has been recorded and attributed to enhanced selfquenching of luminescence. Tentative assignment of spectra has been proposed.

Thermal decomposition behavior of heteronuclear complexes Ln[Fe xCo 1− x(CN) 6]4H 2O (Ln=Pr–Yb)

Heteronuclear complexes Ln[Fe x Co 1− x (CN) 6]4H 2O (Ln=Pr–Yb) were synthesized and the crystal structures of thermally decomposed complexes were investigated. For Ln=Pr–Gd, only perovskite-type oxides (crystal system: orthorhombic) were formed even when the complexes decomposed at 800°C. The lattice constants ( a, b and c) of the oxides increased linearly with increasing Fe/Co ratio. On the other hand, for Ln=Dy–Yb, the Ln 2O 3 phase was obtained as the major product, especially for lower Fe content. The single phase of the perovskite-type oxide could not be obtained even for x=1, although the diffraction peaks due to the perovskite structure gradually increased with increasing Fe content.

Rare earth separation using a chemical vapour transport process mediated by vapour complexes of the LnCl 3AlCl 3 system

Mutual separations of rare earth chlorides in the PrEr, PrSm and PrNd binary systems and the PrGdEr ternary system were performed using chemical vapour transportation of vapour complexes LnAl n Cl 3+3 n , (Ln, rare earths). Heavier rare earth chlorides were more readily transported and concentrated in the deposits in lower temperature zones while lighter ones were selectively deposited in higher temperature zones. Good separation characteristics (efficiency and purity) were observed for the resulting LnCl 3 deposits by optimization of temperature gradients for the selective deposition of LnCl 3 and by repeating the transport reaction. The separation factors, expressed as atomic ratios for the resulting chlorides, Pr:Er and Pr:Sm, were equal to 10.8 and 2.3 respectively.

Growth and magnetooptical properties of thin garnets films in the system (Pr Gd Yb) 3-xBi x(Fe Al) 5O 12

Growth from liquid phase epitaxy and magnetooptical properties of single crystal garnet films in (Pr Gd Yb) 3-xBi x(Fe Al) 5O 12 system are reported. The dependences of the distribution coefficient and the Bi content of the films on the growth temperature are analyzed. The influence of the growth condition on the magnetic and magneto-optical properties of the materials are described and discussed in order to obtain in planemagnetization films having large Faraday rotation (> 1 800 degr./cm) and figure of merit (50 – 80 degr./dB) suitable for integrated magnetooptics application.

Low field magnetic properties of dilute alloys of rare-earths in Pr

Low field magnetic susceptibility and electrical resistivity measurements on dilute (0.5–20%) dhcp Pr—Gd alloys suggest that the magnetic order is not long-range as expected, but of spin glass character. This and other studies on dilute Pr-rare-earth alloys demonstrate that the occurence of long-range (periodic) magnetic ordering in these alloy systems depends on whether the solute is from the light or heavy rare-earth series.

Magnetic and Crystallographic Properties of Pr–Gd Alloys

Various Pr–Gd alloys, covering the whole range of compositions, have been studied by x-ray diffraction and static magnetic measurements. The magnetization measurements were made in fields extending to 26 KOe in the temperature range 2°–500°K. For the Pr–Gd system, we find the following phase diagram with the corresponding magnetic properties: (1) a Pr-rich phase of double hexagonal structure which is paramagnetic down to 2°K and which follows the Curie-Weiss Law; (2) A Gd-rich phase of compact hexagonal structure which is ferromagnetic at low temperature; and (3) A phase based on the composition Pr2Gd5 of super hexagonal structure (analogous to the structure of Sm) which is antiferromagnetic at low temperature. Two alloys having compositions just either side of this superhexagonal phase were studied. Their crystallographic structures could not be determined with precision. Their magnetic behavior corresponds to that observed in ferrimagnets. The ferromagnetic Curie temperatures of these alloys are higher than those observed in Gd93Pr7, situated in the Gd-rich phase.