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Korringa-Kohn-Rostoker electronic structure method for space-filling cell potentials

Description: The multiple scattering theory (MST) method of Korringa, and of Kohn and Rostoker for determining the electronic structure of solids, originally developed in connection with potentials bounded by non-overlapping spheres (muffin-tin (MT) potentials), is generalized to the case of space-filling potential cells of arbitrary shape through the use of a variational formalism. This generalized version of MST retains the separability of structure and potential characteristic of the application of MST t… more
Date: December 31, 1991
Creator: Gonis, A.; Butler, W. H. & Zhang, X.-G.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Neutron scattering studies of magnetism in the high-Tc materials

Description: In this paper, I shall attempt to review what has been learned about magnetism in the high-{Tc} family of compounds using neutron scattering techniques. Whether or not it is true that magnetic effects are involved in an essential way in the mechanism for superconductivity in these materials (a point which has not yet been firmly established), they offer fascinating examples for the study of magnetism for its own sake, being realizations of spin {1/2} 2D quantum antiferromagnets. Further, the ra… more
Date: December 31, 1990
Creator: Sinha, S. K.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Vacancy related defects in thin film Pb(ZrTi)O{sub 3} materials

Description: Positron annihilation techniques have been applied to characterize vacancy-related defects in ferroelectric thin film structures. Variable energy positron beam measurements were carried out on doped and undoped Pb(ZrTi)O{sub 3} (PZT) samples subjected to different post-deposition cool down and anneal conditions. The PZT was deposited by sol-gel with either with platinum or RuO{sub 2} electrodes, or by laser ablation with La{sub 0.5}Sr{sub 0.5}CoO{sub 3} electrodes. The RuO{sub 2} and La{sub 0.5… more
Date: December 31, 1994
Creator: Krishnan, A.; Keeble, D. J.; Ramesh, R.; Warren, W. L.; Tuttle, B. A.; Pfeffer, R. L. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Applications of photon-in, photon-out spectroscopy with third-generation, synchrotron-radiation sources

Description: This report discusses the following topics: Mother nature`s finest test probe; soft x-ray emission spectroscopy with high-brightness synchrotron radiation sources; anisotropy and polarization of x-ray emission from atoms and molecules; valence-hole fluorescence from molecular photoions as a probe of shape-resonance ionization: progress and prospects; structural biophysics on third-generation synchrotron sources; ultra-soft x-ray fluorescence-yield XAFS: an in situ photon-in, photon-out spectros… more
Date: December 31, 1991
Creator: Lindle, D. W. & Perera, R. C. C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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X-ray scattering studies of non-equilibrium ordering processes. Progress report, November 1, 1990--October 31, 1991

Description: We report on the progress of the project entitled ``X-ray Scattering Studies of Non-Equilibrium Ordering Processes.`` The past year has seen continued progress in the study of kinetic effects in metallic binary alloys and polymers. In addition, work has begun on a low dimensional CDW system: blue bronze. A sample chamber has been constructed to perform small angle neutron scattering measurements on a model quantum system with phase separation: solid He3/He4. Work is continuing on magnetic syste… more
Date: December 31, 1991
Creator: Nagler, S. E.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Two dimensional NMR and NMR relaxation studies of coal structure. Progress report, October 1, 1993--December 31, 1993

Description: Four major areas of inquiry are being pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups that determine the reactivity of coals. Special attention is being paid to methods that are compatible with the very high magic angle sample spinning rates needed for operation at the high magnetic field strengths available today. Polarization inversion methods utilizing the difference in heat capacities of small groups of spins… more
Date: December 31, 1993
Creator: Zilm, K. W.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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FEFF5: An ab initio multiple scattering XAFS code

Description: FEFF5 is an efficient automated code which calculates multiple scattering (MS) curved wave XAFS spectra for molecules and solids. The theoretical ingredients and approximations contained in the code are revised, with the aim of describing the how XAFS spectra are efficiently simulated. The FEFF5 code consists of 4 independent modules: a scattering potential and phase shift module, a path finder module, a scattering amplitude module and an XAFS module. Multiple scattering Debye-Waller factors ar… more
Date: December 31, 1992
Creator: Rehr, J. J. & Zabinsky, S. I.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Neutron scatter studies of chromatin structure related to functions. Progress report, July 1, 1988--June 30, 1989

Description: Neutron scatter studies have been performed at LANSCE, LANL and at the Institute Laue Langevin, Grenoble, France. In the previous progress report (April 1, 1988--July 1, 1988) the following objectives were listed: shape of the histone octamer; location of the N-terminal domains of histone in the nucleosome core particle (specific aim 1 of original grant proposal); effect of acetylation on nucleosome structure (specific aim 2); location of the globular domain of histone H1 (specific aim 6); and … more
Date: December 31, 1989
Creator: Bradbury, E. M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Surface electronic structure of GaAs(110) studied by Auger photoelectron coincidence spectroscopy

Description: We have used Auger photoelectron coincidence spectroscopy to study the M{sub 4,5}VV Auger spectra of GaAs(110). Using this technique, the Ga and As spectra can be separated and studied independently. The lineshape of the As-M{sub 4,5}VV measured in coincidence with the As 3d photoemission line differs significantly from the conventional Auger spectrum. We attribute this to the surface electronic properties of the system. In addition, we have found that the ss-component of the As spectrum is mor… more
Date: December 31, 1990
Creator: Bartynski, R. A.; Garrison, K.; Jensen, E.; Hulbert, S. L. & Weinert, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Magnetic effects in anomalous dispersion

Description: Spectacular enhancements of magnetic x-ray scattering have been predicted and observed experimentally. These effects are the result of resonant phenomena closely related to anomalous dispersion, and they are strongest at near-edge resonances. The theory of these resonances will be developed with particular attention to the symmetry properties of the scatterer. While the phenomena to be discussed concern magnetic properties the transitions are electric dipole or electric quadrupole in character … more
Date: December 31, 1992
Creator: Blume, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Suppression of charge scattering in Moessbauer experiments using synchrotron radiation

Description: The extremely small ratio of linewidth to energy combined with the character of recoil free absorption and reemission makes the low lying nuclear resonances a unique spectroscopic tool. Further, considering the simplicity of performing Moessbauer experiments, they have become very useful in a wide range of disciplines. {sup 57}Fe has remained the most widely used isotope despite its low natural abundance (2%) because iron is ubiquitous in nature and shows a strong effect. The energy width of th… more
Date: December 31, 1992
Creator: Bergmann, U.; Siddons, D. P. & Hastings, J. B.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Positron implantation in solids

Description: The Monte Carlo technique for modeling positron prior to annihilation and electron implantation in semi-infinite metals is described. Particle implantation is modelled as a multistep process, a series of collisions with the atoms of the host material. In elastic collisions with neutral atoms there is no transfer of energy. The particle loses energy by several different channels, excitation of the electron gas, ionization of the ion cores, or, at low energies, by phonon excitation. These competi… more
Date: December 31, 1993
Creator: Ghosh, V. J.; Lynn, K. G. & Welch, D. O.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Magnetic resonance as a structural probe of a uranium (VI) sol-gel process

Description: NMR investigations on the ORNL process for sol-gel synthesis of microspherical nuclear fuel (UO{sub 2}), has been useful in sorting out the chemical mechanism in the sol-gel steps. {sup 13}C, {sup 15}N, and {sup 1}H NMR studies on the HMTA gelation agent (Hexamethylene tetramine, C{sub 6}H{sub l2}N{sub 4}) has revealed near quantitative stability of this adamantane-like compound in the sol-Gel process, contrary to its historical role as an ammonia source for gelation from the worldwide technica… more
Date: December 31, 1989
Creator: King, C. M.; Thompson, M. C.; Buchanan, B. R.; King, R. B. & Garber, A. R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Trip report: Marshall Space Center computed tomography

Description: BIR Inc. is a small company out of the Chicago area which sells equipment for producing images by tomography. They have built a relatively large instrument, called ACTIS, for NASA at the Marshall Space Center in Huntsville, Alabama and still gave access to this instrument. BIR has a grant from the Department of Energy (DOE) to determine the utility of computed tomography (CT) for characterization of nuclear and hazardous waste within the DOE complex. As part of this effort, the potential of thi… more
Date: December 31, 1991
Creator: Harbour, J. R. & Andrews, M. K.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Non-linear optical crystal vibration sensing device

Description: The report describes a non-linear optical crystal vibration sensing device including a photorefractive crystal and a laser. The laser produces a coherent light beam which is split by a beam splitter into a first laser beam and a second laser beam. After passing through the crystal the first laser beam is counter-propagated back upon itself by a retro-mirror, creating a third laser beam . The laser beams are modulated, due to the mixing effect within the crystal by vibration of the crystal. In t… more
Date: December 31, 1992
Creator: Kalibjian, R.
Item Type: Refine your search to only Patent
Partner: UNT Libraries Government Documents Department
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NMR measurement of pore structure

Description: An attempt was made to pursue {sup 129}Xe NMR as a pore measurement technique. Samples studied were synthetic imogolite (tubular aluminosilicate with gibbsite structure), sodium Y-zeolite, and an aerogel and a xerogel. Gases used were normal Xe, {sup 13}CO{sub 2}, and {sup 15}N{sub 2}. Although a completely general NMR technique for measuring pore size distributions may not be possible, information about molecular motion and interactions can be obtained, because NMR is sensitive to short range … more
Date: May 31, 1993
Creator: Earl, W. L.; Kim, Yong-Wah & Smith, D. M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Comparison of synchrotron x-ray microanalysis with electron and proton microscopy for individual particle analysis

Description: This paper is concerned with the evaluation of the use of synchrotron/radiation induced x-ray fluorescences ({mu}-SRXRF) as implemented at two existing X-ray microprobes for the analysis of individual particles. As representative environmental particulates, National Institutes of Science and Technology (NIST) K227, K309, K441 and K961 glass microspheres were analyzed using two types of X-ray micro probes: the white light microprobe at beamline X26A of the monochromatic (15 keV) X-ray microprobe… more
Date: December 31, 1991
Creator: Janssens, K. H.; van Langevelde, F.; Adams, F. C.; Vis, R. D.; Sutton, S. R.; Rivers, M. L. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Characterization of defects in Si and SiO{sub 2}-Si using positrons

Description: Positron annihilation spectroscopy of overlayers, interfaces, and buried regions of semiconductors has seen a rapid growth in recent years. The characteristics of the annihilation gamma rays depend strongly on the local environment of the annihilation sites, and can be used to probe defect concentrations in a range inaccessible to conventional defect probes. Some of the recent success of the technique in examining low concentrations of point defects in technologically important Si-based structu… more
Date: December 31, 1993
Creator: Asoka-Kumar, P. & Lynn, K. G.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Amplitude modulation of charge-density-wave domains in 1T-TaS{sub 2} at 300 K

Description: Measurements of the charge-density-wave (CDW) amplitude modulation in 1T-TaS{sub 2} at room temperature have been made using a scanning tunneling microscope (STM) operating in the constant current mode. The amplitude profiles are in good agreement with the profile predicated by the CDW domain model of Nakanishi and Shiba. Interference effects between the atomic and CDW lattices have been analyzed and do not modify these profiles significantly. They represent the true CDW amplitude variation con… more
Date: December 31, 1991
Creator: Coleman, R. V.; McNairy, W. W. & Slough, C. G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Surface structure and spectroscopy of charge-density wave materials using scanning tunneling microscopy

Description: The Scanning tunneling microscope (STM) has been used to study the effects of Fe doping on the charge-density wave (CDW) structure in NbSe{sub 3} and 1T-TaS{sub 2}. In NbSe{sub 3} small amounts of Fe reduce both CDW gaps by 25--30% and change the relative CDW amplitudes of the high and low temperature CDWs. The CDW amplitudes remain strong on all three chains of the surface unit cell with no evident disorder. In 1T-Fe{sub 0.05}Ta{sub 0.95}S{sub 2} the Fe introduces substantial disorder in the C… more
Date: December 31, 1991
Creator: Coleman, R. V.; Dai, Zhenxi; McNairy, W. W.; Slough, C. G. & Wang, Chen
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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[Structure and dynamics of microemulsions in bulk, at interfaces, and in confined geometries]. Progress report

Description: The authors have been constructing a special purpose small angle neutron scattering spectrometer (SAND) in collaboration with IPNS of Argonne National Laboratory and Texaco Research Laboratories in Beacon, New York. The spectrometer, having a moderate neutron flux, will be uniquely suited for detailed studies of complex fluids in their various phases. This spectrometer will be fully available to general users of the small angle scattering community after a year of testing and upon installation … more
Date: December 31, 1993
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Precursor phenomenon of martensitic transformation in Au-49.5at%Cd alloy

Description: Phonon softening was observed in the parent phase of a AuCd alloy which t=forms from the {beta}{sub 2}(B2) parent to {zeta}{sub 2}{prime} (trigonal) martensitic. Since Cd strongly absorbs neutrons, the isotope {sup 114}Cd was used in preparing the single crystal for the measurements. The [{zeta}{zeta}0]TA{sub 2} phonon branch was measured and found to be anomalously low. A minimum is present at {zeta} = 0.35 which softens with decreasing temperature towards Ms. The results are consistent with t… more
Date: December 31, 1994
Creator: Ohba, Takuya; Shapiro, S. M.; Aoki, Shingo & Otsuka, Kazuhiro
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Optical design and performance of the inelastic scattering beamline at the National Synchrotron Light Source

Description: Phase I of the X21 beamline at the National Synchrotron Light Source was commissioned during 1993. The research program at the X21 beamline is focused on the study of electronic excitations in condensed matter with total energy resolution of 0.1 eV to 1.0 eV. The source is a 27 pole hybrid wiggler. A water-cooled horizontal focusing Si(220) monochromator and a spherically bent Si(444) analyzer were installed and commissioned. At 8 keV the energy resolution of the monochromator is about 0.7 eV, … more
Date: December 31, 1994
Creator: Kao, C. C.; Siddons, D. P.; Oversluizen, T.; Hastings, J. B.; Hamalainen, K. & Krisch, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Laser-synchrotron hybrid experiments: ``A photon to tickle, a photon to poke``

Description: In this paper we present the preliminary results from a new experimental technique to synchronize the pulses from a mode-locked NdYAG laser to the light pulses in the VUV storage ring at the National Synchrotron Light Source (NSLS). We describe a method to electronically change the delay time between the laser pulses and the synchrotron pulses. We also illustrate a method to overlap the synchrotron pulses with the laser pulses in space and time. Preliminary results will be presented for two exp… more
Date: December 31, 1991
Creator: Ederer, D. L.; Rubensson, J. E.; Mueller, D. R.; Shuker, R.; O`Brien, W. L.; Jai, J. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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