231 Matching Results

Search Results

Advanced search parameters have been applied.

Pentamethylcyclopentadienyl Derivatives of the Trivalent Lanthanide Elements (Neodymium, Samarium, and Ytterbium)

Description: The anionic complexes of the type (ML{sub x})(Me{sub 5}C{sub 5}){sub 2}M'Cl{sub 2}, where M is lithium or sodium, L is diethyl ether or N,N,-N{prime},N{prime}-tetramethylethylenediamine, and M{prime} is neodymium, samarium, or ytterbium, have been prepared from the metal trichlorides and the pentamethylcyclopentadienide anion. The neutral species (Me{sub 5}C{sub 5}){sub 2}NdCl(THF), (Me{sub 5}C{sub 5}){sub 2}NdN(SiMe{sub 3}){sub 2}, and (Me{sub 5}C{sub 5}){sub 2}YbCl(THF) have also been prepared. The mono-ring derivatives (Na(OEt{sub 2}){sub 2})((C{sub 5}Me{sub 5})NdCl{sub 3}) and (Me{sub 5}C{sub 5})Nd(N(SiMe{sub 3}){sub 2}){sub 2} are also described.
Date: July 1, 1980
Creator: Tilley, T. Don & Andersen, R .A.
Partner: UNT Libraries Government Documents Department

[(eta5-PentamethylcyclopentadienylYb(III)(5,5'-dimethyl-2,2-bipyridyl)mu-OH)2(mu 2-trifluoromethylsulfanato-O,O')][tetraphenylborate](5,5'-dimethyl-2,2-bipyridyl)

Description: The title compound C{sub 81}H{sub 88}BF{sub 3}N{sub 6}O{sub 5}SYb{sub 2}, crystallizes as a half-sandwich complex with a bridging inner-sphere trifluoro-methane sulfonate as well as two bridging hydroxide groups. there is uncoordinated 5,5{prime}-dimethyl-2,2{prime}-bipyridine in the crystal structure. The bound bipyridine ligands have N-C-C{prime}-n{prime} torsion angles of 12-13{sup o}. The triply bridged Yb centers are 3.5990(4) Angstroms apart. The Yb-N bonds range from 2.389(6)-2.424(5) Angstroms.
Date: January 23, 2008
Creator: Kazhdan, Daniel
Partner: UNT Libraries Government Documents Department

Bis(pentamethylcyclopentadienyl)ytterbium: An investigation of weak interactions in solution using multinuclear NMR spectroscopy

Description: NMR spectroscopy is ideal for studying weak interactions (formation enthalpy {le}20 kcal/mol) in solution. The metallocene bis(pentamethylcyclopentadienyl)ytterbium, Cp*{sub 2}Yb, is ideal for this purpose. cis-P{sub 2}PtH{sub 2}complexes (P = phosphine) were used to produce slow-exchange Cp*{sub 2}YbL adducts for NMR study. Reversible formation of (P{sub 2}PtH){sub 2} complexes from cis-P{sub 2}PtH{sub 2} complexes were also studied, followed by interactions of Cp*{sub 2}Yb with phosphines, R{sub 3}PX complexes. A NMR study was done on the interactions of Cp*{sub 2}Yb with H{sub 2}, CH{sub 4}, Xe, CO, silanes, stannanes, C{sub 6}H{sub 6}, and toluene.
Date: July 1, 1995
Creator: Schwartz, D.J.
Partner: UNT Libraries Government Documents Department


Description: Preparation of the sulfates, carbonates, and fluorides of divalent samarium, europium, and ytterbium is described. Crystallographic data from both x-ray and optical examination of the compounds are presented. Due to the instability of these plus (II) salts, the precision of the measurement is affected, but sufficient for characterization. A simple and convenient electrolytic method was devised to prepare the divalent sulfates. By metathetical reactions, carbonates and fluorides were prepared. The compounds were analyzed by a pyrohydrolytic method. (H.G.G.)
Date: October 31, 1963
Creator: Asprey, L.B.; Ellinger, F.H. & Staritzky, E.
Partner: UNT Libraries Government Documents Department

Nd3+ and Yb3+ doped phosphate glass waveguides fabricated using electric field assisted Ag+ diffusion

Description: Solid-state waveguide lasers offer several attractive features that may make high efficiency and effective thermal management possible. Due to the ability to confine pump light to high intensity over distances much longer than the Rayleigh range, as well as maintaining good overlap between the pump and Iasing modes over the entire guiding region, effcient operation with high slope efficiency should be possible, even for quasi-three level laser systems. Since the waveguide region is typically only a few microns of thickness, heat can be extracted efficiently from the structure. The effects of heating are of less significance than in bulk solid-state lasers because mode confinement is maintained by an index of refraction difference, usually much larger than tnat induced by dn/dT or stress-optic effects. Rare earth doped waveguide laser action has been reported in numerous papers [14]. The processes for fabricating waveguides include film deposition methods such as epitaxial growth, RF sputtering, and most recently, thermal bonding of precision finished crystals [5]. In addition, ion implantation, ion exchange in a molten salt and electric field assisted solid film diffusion [6] have been utilized. The ion exchange method remains the simplest, particularly for many common laser glasses that already have mobile ions, and has received considerable attention in recent years. An excellent review is found in reference [7]. Our work has focused on developing process conditions for the fabrication of waveguides in phosphate laser glasses using solid silver film diffusion. These processes are important in determining the overall structure and properties of the guiding region, such as propagation loss, modal profile, and modal overlap between the pump and laser wavelengths. Phosphate laser glass was chosen as the solid state laser medium due to the useful spectroscopic properties of rare earth ions in these materials, as well as the range of material properties ...
Date: December 17, 1997
Creator: Patel, F.D.; Honea, E.C.; Krol, D.; Payne, S.A. & Hayden, J.S.
Partner: UNT Libraries Government Documents Department

Low temperature magnetism in YbPtBi by {sup 170}Yb Moessbauer spectroscopy

Description: The authors report on {sup 170}Yb Moessbauer spectroscopy data in the cubic fcc alloy YbPtBi, in the temperature range 0.06--30 K. The zero field spectra show a two component structure above 1.5 K, which can be analyzed as due to 85% of Yb{sup 3+} ions at a site with cubic symmetry and 15% at a site with non-cubic symmetry. Below 0.3 K, the spectra are resolved and can also be interpreted in terms of two sites, but with a dominant non-cubic site ({approximately} 60%) with Yb ions bearing small magnetic moments. The spectra with a large applied magnetic field give information on the Yb{sup 3+} C.E.F. level scheme and on the exchange interaction. The relation of the Moessbauer data with the results of {micro}SR measurements is discussed.
Date: May 24, 1994
Creator: Le Bras, G.; Bonville, P.; Hodges, J.A.; Imbert, P. & Canfield, P.C.
Partner: UNT Libraries Government Documents Department

Ytterbium divalency and lattice disorder in near-zero thermalexpansion YbGaGe

Description: While near-zero thermal expansion (NZTE) in YbGaGe is sensitive to stoichiometry and defect concentration, the NZTE mechanism remains elusive. We present x-ray absorption spectra that show unequivocally that Yb is nearly divalent in YbGaGe and the valence does not change with temperature or with 1% B or 5% C impurities, ruling out a valence-fluctuation mechanism. Moreover, substantial changes occur in the local structure around Yb with B and C inclusion. Together with inelastic neutron scattering measurements, these data indicate a strong tendency for the lattice to disorder, providing a possible explanation for NZTE in YbGaGe.
Date: May 8, 2006
Creator: Booth, C.H.; Christianson, A.D.; Lawrence, J.M.; Pham, L.; Lashley, J. & Drymiotis, F.R.
Partner: UNT Libraries Government Documents Department

Characterization of bubble core and cloudiness in Yb3+:Sr5(PO4)3F crystals using Micro-Raman spectroscopy

Description: Ytterbium doped strontium fluoroapatite Yb{sup 3+}:Sr{sub 5}(PO{sub 4}){sub 3}F (Yb: S-FAP) crystals have been used in High Average Power Laser systems as gain medium. Growth induced defects associated with the crystal often affect their performance. In order to improve the crystal quality and its optical applications, it is imperative to understand the nature of these defects. In this study, we utilize Micro-Raman spectroscopy to characterize two common growth-induced defects: bubble core and cloudiness. We find the bubble core consist of voids and microcrystals of Yb: S-FAP. These microcrystals have very different orientation from that of the pure crystal outside the bubble core. In contrast to a previous report, neither Sr{sub 3}(PO{sub 4}){sub 2} nor Yb{sub 2}O{sub 3} are observed in the bubble core regions. On the other hand, the cloudy regions are made up of the host materials blended with a structural deformation along with impurities which include CaCO{sub 3}, YbPO{sub 4}, SrHPO{sub 4} and Sr{sub 2}P{sub 2}O{sub 7}. The impurities are randomly distributed in the cloudy regions. This analysis is necessary for understanding and eliminating these growth defects in Yb:S-FAP crystals.
Date: November 15, 2006
Creator: Cui, Y; Roy, U N; Bai, L; Burger, A; Qiu, S R & Schaffers, K
Partner: UNT Libraries Government Documents Department

The Mercury Project: A High Average Power, Gas-Cooled Laser For Inertial Fusion Energy Development

Description: Hundred-joule, kilowatt-class lasers based on diode-pumped solid-state technologies, are being developed worldwide for laser-plasma interactions and as prototypes for fusion energy drivers. The goal of the Mercury Laser Project is to develop key technologies within an architectural framework that demonstrates basic building blocks for scaling to larger multi-kilojoule systems for inertial fusion energy (IFE) applications. Mercury has requirements that include: scalability to IFE beamlines, 10 Hz repetition rate, high efficiency, and 10{sup 9} shot reliability. The Mercury laser has operated continuously for several hours at 55 J and 10 Hz with fourteen 4 x 6 cm{sup 2} ytterbium doped strontium fluoroapatite (Yb:S-FAP) amplifier slabs pumped by eight 100 kW diode arrays. The 1047 nm fundamental wavelength was converted to 523 nm at 160 W average power with 73% conversion efficiency using yttrium calcium oxy-borate (YCOB).
Date: November 3, 2006
Creator: Bayramian, A; Armstrong, P; Ault, E; Beach, R; Bibeau, C; Caird, J et al.
Partner: UNT Libraries Government Documents Department

Collisional population transfer in yterbium ions

Description: Long-lived metastable states of Yb+ ions are used for atomic frequency standards, precision measurements, and quantum information research. The effect of population trapping and transfer in these states must be well understood. We report here the transfer of Yb+ ions into the long-lived {sup 2}F{sub 7/2} state by means of collisions between He buffer gas and Yb+ ions held in a linear Paul trap. Transfer rates were measured as functions of buffer-gas pressure and repump-laser power, and the collisional population transfer rates were extracted. The measured transfer rate coefficients are 8.32(75)x10-11 and 8.65(33)x10-11 cm3/s for the collisional processes {sup 2}P{sub 1/2}{yields}{sup 2}D{sub 5/2} and {sup 2}D{sub 3/2}{yields}{sup 2}F{sub 7/2}, respectively.
Date: January 1, 2009
Creator: Schauer, Martin Michael; Torgerson, Justin R; Danielson, Jeremy R; Zhao, Xinxin; Nguyen, Ahn - Tuan & Wang, Li - Bang
Partner: UNT Libraries Government Documents Department


Description: The high temperature enthalpies of five rare earths were measured from 0 to 1100 deg C using a Bunsen ice calorimeter. The enthalpy of yttrium metal was studied from 1100 to 1675 deg C using a modified high temperature vacuum Bunsen calorimeter. The data were fitted to empirical equations from which the heat of transition and fusion, the heat capacity, and the related thermodynamic quantities were calculated. These results confirmed indications from other properties that europium and ytterbium metals are primarily in the divalert state. Small anomalies observed in europium and ytterbium were attributed to transitions between electronic states when some trivalent ions occur in these metals. The ertropy of the fcc-bcc transition for ytterbium was found to be approximately two- thirds that of the other rare-earth metals for which a close-packed to bodycertered cubic transformation was observed. (auth)
Date: July 26, 1961
Creator: Berg, J.R.; Spedding, F.H. & Daane, A.H.
Partner: UNT Libraries Government Documents Department

Epitaxial Growth of Yb<sub>2</sub>O<sub>3</sub> Buffer Layers on Biaxially Textured-Ni (100) Substrates by Sol-Gel Process

Description: In order to develop an alternative buffer layer architecture using the sol-gel process to produce YBCO (YBa2Cu307+) coated conductors, Yb203 has been chosen as the candidate material. Buffer layers of fi03 were epitaxkdly grown on biaxially textured-Ni (100) substrates by the sol gel process for the first time. The ~03 precursor solution was prepared from an alkoxide sol-gel route in 2-xnetho~ethanol and was deposited on textured-Ni (100) substrates by either spin coating or dip coating methods. The amorphous film was then processed at 1160oC under flowing (96%)MH2(4%) gas mixture for one hour. The fi03 iihn exhibited a strong c-axis orientation on the Ni (100) substrates. The phi and omega scans indicated good in plane and out of plane orientations. The X-ray (222) pde figure showed a cube-on-cube epitaxy. High current YBCO films were grown on the Y&03 sol-gel buffered-Ni substrates.
Date: April 5, 1999
Creator: Beach, D.B.; Chirayil, T.G.; Christen, D.K.; Feenstra, R.; Goyal, A.; Kroeger, D.M. et al.
Partner: UNT Libraries Government Documents Department

Photoelectron Spectroscopy of YbInCu{sub 4}: Direct Testing of Correlated Electron Models

Description: The electronic properties of single crystal YbInCu{sub 4} have been investigated by means of high resolution photoelectron spectroscopy. A first order, isostructural phase transition for YbInCu{sub 4} at T{sub v}=42 K leads to changes in the Kondo temperature of more than an order of magnitude (27 K vs. 400 K). This phase transition and accompanying Kondo temperature change provide the most direct test of the single impurity model (SIM) to date. Particle hole symmetry allows the SIM to be used for Yb compounds as well as Ce heavy fermions with the great advantage that the predicted Kondo resonance is found on the occupied side of the spectral weight function for Yb materials and is thus directly observable in photoemission. The photoemission results are incongruous with the single impurity model predictions for temperature dependence, binding energy and 4f occupancy, encouraging a reevaluation of the single impurity model. The experiments were conducted using the PGM undulator and 4 meter NIM beamlines at SRC. The spectra were taken at photon energies of 40 eV and 90 eV and the combined energy resolution of the analyzer and monochromator was 45- 85 meV.
Date: December 31, 1997
Creator: Joyce, J.J.; Arko, A.J.; Sarrao, J.L. & Fisk, Z.
Partner: UNT Libraries Government Documents Department

Upconversion-pumped luminescence efficiency of rare-earth-doped hosts sensitized with trivalent ytterbium

Description: We discuss the upconversion luminescence efficiencies of phosphors that generate red, green, and blue light. The phosphors studied are single crystals and powders co-doped with Er{sup 3+} and Yb{sup 3+}, and with Tm{sup 3+} and Yb{sup 3+}. The Yb ions are pumped near 980 nm; transfers of two or three quanta to the co-doped rare earth ion generate visible luminescence. The main contribution embodied in this work is the quantitative measurement of this upconversion efficiency, based on the use of a calibrated integrating sphere, determination of the fraction of pump light absorbed, and careful control of the pump laser beam profile. The green phosphors are the most efficient, yielding efficiency values as high as 4 %, with the red and blue materials giving 1 - 2 %. Saturation was observed in all cases, suggesting that populations of upconversion steps of the ions are maximized at higher power. Quasi-CW modeling of the intensity- dependent upconversion efficiency was attempted; input data included level lifetimes, transition cross sections, and cross-relaxation rate coefficients. The saturation of the Yb,Er:fluoride media is explained as the pumping of Er{sup 3+} ions into a bottleneck (long-lived state)- the {sup 4}I{sub 13/2} metastable level, making them unavailable for further excitation transfer. 32 refs., 5 figs., 3 tabs.
Date: July 26, 1997
Creator: Page, R.H.; Schaffers, K.I.; Waide, P.A.; Tassano, J.B.; Payne, S.A.; Kruplce, W.F. et al.
Partner: UNT Libraries Government Documents Department

Yb:FAP and related materials, laser gain medium comprising same, and laser systems using same

Description: An ytterbium doped laser material remarkably superior to all others, including Yb:YAG, comprises ytterbium doped apatite (Yb:Ca{sub 5}(PO{sub 4}){sub 3}F) or Yb:FAP, or ytterbium doped crystals structurally related to FAP. The new laser material is used in laser systems pumped by diode pump sources having an output near 0.905 microns or 0.98 microns, such as InGaAs and AlInGaAs, or other narrowband pump sources near 0.905 microns or 0.98 microns. The laser systems are operated in either the conventional or ground state depletion mode.
Date: December 31, 1991
Creator: Krupke, W.F.; Payne, S.A.; Chase, L.L. & Smith, L.K.
Partner: UNT Libraries Government Documents Department