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Ion-ion interaction and energy transfer of 4+ transuranium ions in cerium tetrafluoride

Description: Dynamics of excited 5f electron states of the transuranium ions Cm{sup 4+} and Bk{sup 4+} in CeF{sub 4} are compared. Based on time- and wavelength-resolved laser-induced fluorescence, excitation energy transfer processes have been probed. Depending on concentration and electronic energy level structure of the studied 4+ transuranium ion, the dominant energy transfer mechanisms were identified as cross relaxation, exciton-exciton annihilation, and trapping. Energy transfer rates derived from th… more
Date: January 1, 1990
Creator: Liu, G.K. & Beitz, J.V.
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Partner: UNT Libraries Government Documents Department
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Photofragment imaging: The photo-dissociation of bromomethane, bromoethane, and bromoethanol

Description: Bromomethane, bromoethane and bromoethanol are photolyzed with 205-nm light and the velocity of the bromine atoms is recorded by the technique of photofragment imaging. The velocity distribution of the bromine atoms is a direct reflection of the internal-state distribution of the methyl, ethyl, and hydroxy-ethyl radicals and the orientation of the transition moment in the parent molecule. 8 refs., 2 figs., 1 tab.
Date: September 1, 1990
Creator: Chandler, D.W. (Sandia National Labs., Albuquerque, NM (United States)); Thoman, J.W. Jr. (Williams Coll., Williamstown, MA (United States). Dept. of Chemistry) & Hess, W.P. (Battelle Pacific Northwest Lab., Richland, WA (United States))
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Partner: UNT Libraries Government Documents Department
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Variational transition state theory calculations of tunneling effects on concerted hydrogen motion in water clusters and formaldehyde/water clusters

Description: The direct participation of water molecules in aqueous phase reaction processes has been postulated to occur via both single-step mechanisms as well as concerted hydrogen atom or proton shifts. In the present work, simple prototypes of concerted hydrogen atom transfer processes are examined for small hydrogen-bonded water clusters -- cyclic trimers and tetramers -- and hydrogen-bonded clusters of formaldehyde with one and two water molecules. Rate constants for the rearrangement processes are c… more
Date: August 1, 1990
Creator: Garrett, B.C. (Pacific Northwest Lab., Richland, WA (USA)) & Melius, C.F. (Sandia National Labs., Livermore, CA (USA))
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Partner: UNT Libraries Government Documents Department
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A photoemission investigation of compound semiconductor monodisperse clusters

Description: We have used synchrotron radiation photoemission to probe the valence and core level electronic structure of compound-semiconductor monodisperse clusters (nanocrystals). These clusters exhibited a 10% or less variation relative to the mean diameter and were attached to the metal substrates via alkane chains. Direct evidence of gap broadening due to size variation in CdS clusters was observed. The novel utilization of alkane chain attachment is the key to eliminating the otherwise debilitating p… more
Date: December 7, 1990
Creator: Tobin, J. G. (Lawrence Livermore National Lab., CA (USA)); Colvin, V. L. & Alivisatos, A. P. (California Univ., Berkeley, CA (USA))
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Partner: UNT Libraries Government Documents Department
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Semiclassical calculation of two-photon rates

Description: Two-photon absorption and emission processes make small contributions to the radiative rates in a hot plasma. In this paper these rates are calculated as a test of a new semiclassical method. The results agree closely with quantum calculations. 9 refs., 1 fig., 2 tabs.
Date: January 1, 1990
Creator: More, R. (Lawrence Livermore National Lab., CA (USA)) & Rose, S. (Rutherford Appleton Lab., Chilton (UK))
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Partner: UNT Libraries Government Documents Department
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A study of the optical band gap of lithium tungsten trioxide thin films

Description: The insertion of lithium (lithiation) into tungsten trioxide results in the formation of the tungsten bronze Li{sub x}WO{sub 3}. Polycrystalline, rf sputter deposited thin films of Li{sub x}WO{sub 3} were investigated for their application in Smart Window Devices. The optical band gap studies of these films revealed the narrowing of the intrinsic band gap as a consequence of lithium insertion. The results suggest that the rigid band model, which is generally adopted in interpreting the electron… more
Date: January 1, 1990
Creator: Berera, G.; Goldner, R. B.; Arntz, F. O.; Wong, K. K.; Ciaccia, A.; Welch, M. et al.
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Partner: UNT Libraries Government Documents Department
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The electronic structure of grain boundaries in Nb

Description: We present first-principles calculations of the electronic structure of Nb grain boundaries. These are the first such calculations for a bcc metal using the real-space multiple-scattering theory (RSMST). Local densities of states near a {Sigma}5 twist grain boundary are compared to those for bulk Nb. 5 refs., 1 fig.
Date: November 1, 1990
Creator: Sowa, E.C.; Gonis, A. (Lawrence Livermore National Lab., CA (USA)) & Zhang, X.G. (Lawrence Berkeley Lab., CA (USA))
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Partner: UNT Libraries Government Documents Department
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First-principles study of the contractive reconstruction of gold and silver monolayers on gold, silver and aluminum

Description: Using first-principles calculations in conjunction with modeling techniques, the author has investigated the structures of Au and Ag monolayers on a number of metal surfaces. Au(100) has a c(26 {times} 68) surface unit cell and the reconstruction has been interpreted as the top layer transforming to a contracted hexagonal-close-packed layer, superimposed on the square lattice of the underlying substrate atoms. Similar reconstructions have been observed on the 5d fcc metals Ir and Pt, but not in… more
Date: November 16, 1990
Creator: Takeuchi, Noboru.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Elastic shear modulus: Fits to data and extrapolation to large compressions and negative pressure

Description: An analytic form for the elastic shear modulus is presented and its fit to data at different compressions is demonstrated for copper and tungsten. When only shear modulus at zero pressure and its logarithmic derivative are known, an approximate procedure is used to generate the parameters for an analytic form for the shear modulus. This procedure is demonstrated, and estimates are provided of the shear modulus as a function of compression, for Al, Cu, Fe, Mo, W, Ta, and U. 5 refs., 3 figs., 3 t… more
Date: December 1, 1990
Creator: Straub, G. K.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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A comparative study of short range order in Fe-Cr and Fe-V alloys around equiatomic composition

Description: Configurational energies have been calculated for equiatomic Fe-Cr and Fe-V alloys possessing the high temperature bcc crystalline structure, within a first principles electronic band structure approach. In agreement with experimental facts, a tendency towards order, with a B2 ordered structure of CsCl type, is found for FeV whereas phase separation characterized FeCr. These results suggest that the nature of short range order in the high temperature bcc solid solution is not the primary drivin… more
Date: December 4, 1990
Creator: Turchi, P.E.A.; Sluiter, M. (Lawrence Livermore National Lab., CA (USA)) & Stocks, G.M. (Oak Ridge National Lab., TN (USA))
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Partner: UNT Libraries Government Documents Department
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Strained-layer electronics and optoelectronics

Description: Strained-layer epitaxy involves more than the dislocation-free growth of dissimilar materials: effective strained-layer epitaxy exploits lattice-mismatch-induced strain to fine-tune material properties. This paper describes strained-layer epitaxy and describes its application to electronic and optoelectronic device to improve performance.
Date: January 1, 1990
Creator: Myers, D.R.
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Partner: UNT Libraries Government Documents Department
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Electronic structure and charge density of zirconium diboride

Description: Self-consistent calculations of the electronic band structure of zirconium diboride, ZrB{sub 2}, have been performed. The total and individual band charge densities are analysed in terms of their site (zirconium or boron) symmetry and plotted. The total charge density shows very little charge asymmetry about either site. 6 refs., 6 figs., 37 tabs.
Date: January 1, 1990
Creator: Switendick, A.C.
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Partner: UNT Libraries Government Documents Department
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Theoretical investigation of phase stability in non-magnetic Fe-V substitutional alloys

Description: The assessed phase diagram of Fe-V exhibits a continuous high temperature bcc solid solution intersected at lower temperatures by a complex sigma phase centered around equiatomic composition. Slow kinetics of the bcc to sigma transformation make it possible to retain the bcc solid solution at low temperature. It has been observed that this metastable solid solution has a tendency to order with a CsCl type structure (B2) below 970 K. As a first attempt to describe this behavior from an electroni… more
Date: December 18, 1990
Creator: Sluiter, M. & Turchi, P.E.A.
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Partner: UNT Libraries Government Documents Department
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Theoretical studies on the electronic structure and properties of complex ceramic crystals and glasses

Description: This annual report covers the last year of a three-year project supported by the Department of Energy that was started on July 1, 1986. Within these three years, a phenomenal amount of research results have been obtained. In the following section, Section II, we summarize the research work accomplished since July 1, 1986 as was documented in the renewal proposal. In Section III, we list additional accomplishments since the submission of the renewal proposal. Section IV contains the figures that… more
Date: June 1, 1990
Creator: Ching, Wai-Yim.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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New k-phase materials, k-(ET) sub 2 Cu(N(CN) sub 2 )X: X = Cl, Br and I: The synthesis, structure and superconductivity above 11 K in the Cl ( Tc = 12. 8 K, 0. 3 kbar) and Br( Tc = 11. 6 K) salts

Description: The syntheses, structures, selected physical properties, and band electronic structures of three copper (I) dicyanamide halide salts of bis(ethylenedithio)tetrathiafulvalene ({kappa}-(ET){sub 2}Cu(N(CN){sub 2})X, where X = Cl, Br, and I) are discussed. X-ray crystallographic studies demonstrate that the three derivatives are isostructural. The bromide salt is an ambient pressure superconductor with an inductive onset at 11.6 K and a resistive onset at 12.5 K. {kappa}-(ET){sub 2}Cu(N(CN){sub 2})… more
Date: 1990
Creator: Wang, H. H.; Carlson, K. D.; Geiser, U.; Kini, A. M.; Schultz, A. J.; Williams, J. M. et al.
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Partner: UNT Libraries Government Documents Department
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Newly appreciated roles for electrons in ion-atom collisions

Description: Since the previous Debrecen workshop on High-Energy Ion-Atom Collisions there have been numerous experiments and substantial theoretical developments in the fields of fast ion-atom and ion- solid collisions concerned with explicating the previously largely underappreciated role of electrons as ionizing and exciting agents in such collisions. Examples to be discussed include the double electron ionization problem in He; transfer ionization by protons in He; double excitation in He; backward scat… more
Date: January 1, 1990
Creator: Sellin, I.A. (Tennessee Univ., Knoxville, TN (USA). Dept. of Physics and Astronomy Oak Ridge National Lab., TN (USA))
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Partner: UNT Libraries Government Documents Department
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Synchrotron x-ray sources and new opportunities in the soil and environmental sciences

Description: This report contains the following papers: characteristics of the advanced photon source and comparison with existing synchrotron facilities; x-ray absorption spectroscopy: EXAFS and XANES -- A versatile tool to study the atomic and electronic structure of materials; applications of x-ray spectroscopy and anomalous scattering experiments in the soil and environmental sciences; X-ray fluorescence microprobe and microtomography.
Date: July 1, 1990
Creator: Schulze, D. (Purdue Univ., Lafayette, IN (USA)); Anderson, S. (Michigan State Univ., East Lansing, MI (USA)) & Mattigod, S. (Pacific Northwest Lab., Richland, WA (USA))
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Partner: UNT Libraries Government Documents Department
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Optical properties and electronic structures of d- and f-electron metals and alloys, Ag-In, Ni-Cu, AuGa sub 2 , PtGa sub 2 ,. beta. prime -NiAl,. beta. prime -CoAl, CeSn sub 3 , and LaSn sub 3

Description: Optical properties and electronic structures of disordered Ag{sub 1- x}In{sub x}(x = 0.0, 0.04, 0.08, 0.12) and Ni{sub 1-x}Cu{sub x} (x = 0.0, 0.1, 0.3, 0.4) alloys and ordered AuGa{sub 2}, PtGa{sub 2}, {beta}{prime}-NiAl, {beta}{prime}-CoAl, CeSn{sub 3}, and LaSn{sub 3} have been studied. The complex dielectric functions have been determined for Ag{sub 1-x}In{sub x}, Ni{sub 1-x}Cu{sub x}, AuGa{sub 2}, and PtGa{sub 2} in the 1.2--5.5 eV region and for CeSn{sub 3} and LaSn{sub 3} in the 1.5--4.5… more
Date: October 17, 1990
Creator: Kim, Kwang Joo
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
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High-resolution angle-resolved photoemission studies of high Tc superconductor Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8

Description: An angle-resolved photoemission study of the normal and superconducting states in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} was performed. Measurements in the normal state show bands dispersing through the Fermi level from at least 350 meV below E{sub F}. The Fermi level crossings are consistant with local-density band calculation, including a point calculated to be of Bi-O character. Additional measurements were made where bands crossed the Fermi level between 100 and 250K, along with measurements… more
Date: September 21, 1990
Creator: Liu, Rong
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
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Order-disorder phenomena in complex alloys: The case of A15-based substitutional alloys

Description: We first discuss the applicability of the Generalized Perturbation Method to the study of ordering phenomena in complex alloys for which stability properties are electronically driven. In particular, according to previous work, it is recalled that a 3D-generalized Ising model is appropriate to address the problem of configurational order in A15-based substitutional alloys. A ground state analysis of this model, including 1st, 2nd, and weak 3rd and 7th pair interactions, generates two new ordere… more
Date: August 15, 1990
Creator: Turchi, P.E.A. (Lawrence Livermore National Lab., CA (USA)) & Finel, A. (Office National d'Etudes et de Recherches Aerospatiales (ONERA), 92 - Chatillon (France))
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Partner: UNT Libraries Government Documents Department
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Laser conditioning and electronic defect measurements of HfO sub 2 and SiO sub 2 thin films

Description: Multilayer HfO{sub 2}/SiO{sub 2} high reflectors (HR) and polarizers show a permanent increase in their 1064-nm damage thresholds following laser conditioning at subthreshold fluences. Threshold increases of 2--3x are typical. In an effort to better understand the conditioning effect we have made laser conditioning and electronic property measurements on single layers of these two materials. The laser damage threshold of 1-{mu}m thick e-beam deposited SiO{sub 2} was increased by laser condition… more
Date: December 17, 1990
Creator: Kozlowski, M.R.; Staggs, M.; Rainer, F. (Lawrence Livermore National Lab., CA (USA)) & Stathis, J.H. (International Business Machines Corp., Yorktown Heights, NY (USA). Thomas J. Watson Research Center)
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Partner: UNT Libraries Government Documents Department
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Polarized absorption spectra of flavin mononucleotide in flavodoxin crystals

Description: Although it has long been recognized that protein environments modulate the electronic structure of flavins, the precise nature of the interactions that lead to a specific effect are still poorly understood. Detailed knowledge of flavin environments from high resolution crystal structures of flavoproteins, coupled with spectroscopic measurements and molecular orbital calculations should begin to clarify the relative importance of the various possible interactions in a given system. Changes in o… more
Date: January 1, 1990
Creator: Hanson, L.K. (Brookhaven National Lab., Upton, NY (USA)); Christoph, G.W.; Hofrichter, J. (National Insts. of Health, Bethesda, MD (USA). Lab. of Chemical Physics) & Ludwig, M.L. (Michigan Univ., Ann Arbor, MI (USA). Div. of Biophysics Research)
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Partner: UNT Libraries Government Documents Department
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Superconducting materials

Description: This report discusses the following topics: Fermi liquid nesting in high temperature superconductors; optical properties of high temperature superconductors; Hall effect in superconducting La{sub 2-x}Sr{sub x}CuO{sub 4}; source of high transition temperatures; and prospects for new superconductors.
Date: January 1, 1990
Creator: Ruvalds, J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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