189 Matching Results

Search Results

Advanced search parameters have been applied.

in subjects: "Nuclear Techniques In Condensed Matter Physics"

open access

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

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: Article

Partner: UNT Libraries Government Documents Department

open access

Neutron scattering studies of magnetism in the high-Tc materials

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: Article

Partner: UNT Libraries Government Documents Department

open access

Vacancy related defects in thin film Pb(ZrTi)O{sub 3} materials

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: Report

Partner: UNT Libraries Government Documents Department

open access

Surface structure and analysis with scanning tunneling microscopy and electron tunneling spectroscopy. Progress report, May 1, 1991--April 30, 1992

This report discusses the atomic force microscopy and correlation of charge-density-wave energy gaps and impurity pinning in NbSe{sub 3}. (LSP).

Date: March 1, 1992

Creator: Coleman, R. V.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

An investigation of catalytic active phase-support interactions by IR, NMR and x-ray absorption spectroscopies. Progress report, January 15, 1992--September 15, 1992

Active catalytic phases (metal, mixed metals, oxide or mixed oxides) interacting with oxide support on which the active phase is dispersed can affect the percentage exposed, the morphology of supported particles, the degree of reducibility of cations, etc., in a variety of ways. Our objective is to characterize the physical chemistry of the active phase-oxide support interaction by spectroscopic methods and to correlate this structure with catalytic function. Two catalytic systems and their ass… more

Date: September 1, 1992

Creator: Haller, G. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Photoelectron diffraction and holography: Present status and future prospects

Photoelectron diffraction and photoelectron holography, a newly developed variant of it, can provide a rich range of information concerning surface structure. These methods are sensitive to atomic type, chemical state, and spin state. The theoretical prediction of diffraction patterns is also well developed at both the single scattering and multiple scattering levels, and quantitative fits of experiment to theory can lead to structures with accuracies in the {plus_minus}0.03 {Angstrom} range. D… more

Date: July 1, 1993

Creator: Fadley, C. S.; Thevuthasan, S. & Kaduwela, A. P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

4f heavy fermion photoelectron spectra do not exhibit the Kondo scale

It has been the authors contention for some time that the Single Impurity Anderson Model (SIAM), as extended by Gunnarsson and Schonhammer (GS), or the non-crossing approximation (NCA), does not correctly describe the 4f photoelectron spectra of heavy fermions. Recently, they have concentrated on Yb heavy fermions since in these materials the Kondo resonance (KR) is fully occupied and thus accessible via photoemission. In particular, they have repeatedly pointed out that the width, position, sp… more

Date: February 1, 1994

Creator: Arko, A. J.; Joyce, J. J.; Andrews, A. B.; Blyth, R. I. R.; Bartlett, R. J.; Fisk, Z. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Predoctoral training grant in the area of physical sciences. Final technical report, October 1989--October 1993

This final technical report represents the results of the research in nonlinear optics (optical phase conjugation) obtained by five (5) predoctoral students in the department of physics at Alabama Agricultural and Mechanical University (AAMU).

Date: November 1993

Creator: Venkateswarlu, Putcha

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Resonant holographic measurements of laser ablation plume expansion in vacuum and argon gas backgrounds

This thesis discusses the following on resonant holographic measurements of laser ablation plume expansion: Introduction to laser ablation; applications of laser ablation; The study of plume expansion; holographic interferometry; resonant holographic interferometry; accounting for finite laser bandwidth; The solution for doppler broadening and finite bandwidth; the main optical table; the lumonics laser spot shape; developing and reconstructing the holograms; plume expansion in RF/Plasma Enviro… more

Date: October 1, 1993

Creator: Lindley, R. A.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

Fifth Annual Meeting of the Advanced Light Source User`s Association

This report discusses the following topics: ALS Project Status; Accelerator Commissioning; Experimental Systems: Supersmooth Optics and Ultra-Precise Undulators; Planning for Users and User Services; ALS Scientific Program; High Resolution Core-Level Photoemission; Photoelectron Diffraction and Holography; Soft X-Ray Emission Spectroscopy of Solids at the NSLS and the ALS; Gas-Phase Spectrometry; Spectromicroscopy; X-Ray Dichroism Experiments Using Circular Polarization; Magnetic Circular X-Ray… more

Date: October 1, 1993

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Applications of circularly polarized photons at the ALS with a bend magnet source

The purpose of this workshop is to focus attention on, and to stimulate the scientific exploitation of, the natural polarization properties of bend-magnet synchrotron radiation at the ALS -- for research in biology, materials science, physics, and chemistry. The topics include: The Advanced Light Source; Magnetic Circular Dichroism and Differential Scattering on Biomolecules; Tests of Fundamental Symmetries; High {Tc} Superconductivity; Photoemission from Magnetic and Non-magnetic Solids; Studi… more

Date: February 1, 1992

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

X-ray and {gamma}-ray spectroscopy of solids under pressure. Annual technical progress report, October 1991--October 1992

The effort is divided into the following: high pressure transitions (Fe, RbCl), XAFS studies of perovskites under pressure (ReO{sub 3}, high-{Tc} superconductors), studies of XANES of alkali halides, and Moessbauer studies (iron silicate spinel).

Date: April 30, 1992

Creator: Ingalls, Robert L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Positron annihilation study of P implanted Si

High-energy ion implantation (above 200 keV) is now commonly used in a variety of VLSI processes. The high energy required for these implants is often achieved by implanting multiply charged ions, which inevitably brings in the problem of low-energy ion contamination. The low-energy contamination is difficult to diagnose and detect. Positron annihilation spectroscopy is used to examine the defect distributions in these high energy implants with varying degrees of contamination.

Date: December 1, 1992

Creator: Asoka-Kumar, P.; Au, H. L.; Lynn, K. G. & Sferlazzo, P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Structure and shear response of lipid monolayers. Progress report, July 1, 1989--June 31, 1990

Organic monolayers and multilayers are both scientifically fascinating and technologically promising; they are, however, both complex systems and relatively inaccessible to experimental probes. In this Progress Report, we describe our X-ray diffraction studies, which have given us substantial new information about the structures and phase transitions in monolayers on the surface of water; our use of these monolayers as a unique probe of the dynamics of wetting and spreading; and our studies of … more

Date: February 1, 1990

Creator: Dutta, P. & Ketterson, J. B.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

[Investigation of the structure and phase relations of C-S-H gels]

(C-S-H stands for calcium silicate hydrate.) The following areas of study are reported: solution-derived C-S-H, hydration of alite at constant pH, and hydrothermal synthesis of tobermorite.

Date: May 1, 1994

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Inelastic scattering in condensed matter with high intensity Moessbauer radiation. Final technical report, December 1, 1989--November 30, 1992

The QUEGS facility at MURR has produced a number of new results and demonstrated the range of potential applications of high resolution, high intensity Moessbauer scattering. This work has been carried out by both MU and Purdue researchers and includes published results on Na, W, pentadecane, polydimethylsiloxane and other systems, manuscripts submitted on alkali halides (Phys. Rev. B) and accurate Moessbauer lineshape measurements (Phys. Rev. C), and manuscripts in preparation on glycerol, NiA… more

Date: February 1, 1993

Creator: Yelon, W. B. & Schupp, G.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Rietveld refinement of magnetic structures from pulsed-neutron-source powder-diffraction data

The General Structure Analysis System, GSAS, has recently been modified to include magnetic neutron-scattering cross-sections. Low-temperature diffraction data have been taken on the hexagonal noncollinear antiferromagnet UPdSn on both the HIPD and the NPD powder diffractometers at LANSCE. The low-resolution data reveal that the magnetic structure has orthorhombic symmetry (magnetic space group P{sub c}112{sub 1}) between 25K and 40K, and monoclinic symmetry (magnetic space group P{sub c}l12{su… more

Date: May 1, 1993

Creator: Robinson, R. A.; Lawson, A. C.; Larson, A. C.; Von Dreele, R. B. & Goldstone, J. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

NQR-NMR studies of higher alcohol synthesis Cu-Co catalysts. Quarterly technical progress report, December 15, 1991--March 15, 1992

During this period, we focused our attention in analyzing the magnetic nature of the extensively used trimetallic catalyst system Cu-Co-Cr for the production of higher alcohols. We believe that there could be some correspondence between the catalytic and magnetic behaviors of the transition metal catalyst systems. Both the morphology and metallic charge distribution of the particles are known to govern the catalytic as well as the magnetic properties of the system.

Date: May 4, 1992

Creator: Murty, A. N.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

X-ray and {Gamma}-ray spectroscopy of solids under pressure. Annual technical progress report, November 1993--October 1994

During this period, synchrotron beam time (approx. 2 weeks/year) was obtained from the Stanford Synchrotron Radiation Laboratory. The following areas of study are reported: XAFS studies of polyhedral solids (ReO{sub 3}, perovskites, rubidium tungsten bronze), Moessbauer study of sodium nitroprusside, XAFS studies of phase transition mechanisms (effects of high pressure on metallic Fe), and multiple scattering analysis of XANES.

Date: April 30, 1994

Creator: Ingalls, R. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

[Gamma scattering in condensed matter with high intensity Moessbauer radiation]

This report discusses: quasielastic scattering studies on glycerol; gamma-ray scattering from alkali halides; lattice dynamics in metals; Moessbauer neutron scattering, x-ray diffraction, and macroscopic studies of high {Tc} superconductors containing tungsten; NiAl scattering studies; and atomic interference factors and nuclear Casimir effect.

Date: June 1, 1992

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

NMR imaging of components and materials for DOE application

The suitability for using NMR imaging to characterize liquid, polymeric, and solid materials was reviewed. The most attractive applications for NMR imaging appear to be liquid-filled porous samples, partially cured polymers, adhesives, and potting compounds, and composite polymers/high explosives containing components with widely varying thermal properties. Solid-state NMR line-narrowing and signal-enhancing markedly improve the imaging possibilities of true solid and materials. These technique… more

Date: December 1, 1993

Creator: Richardson, B. R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Applications of photon-in, photon-out spectroscopy with third-generation, synchrotron-radiation sources

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: Article

Partner: UNT Libraries Government Documents Department

open access

Nuclear Bragg scattering studies in {sup 57}Fe with synchrotron radiation

Studies of nuclear Bragg x-ray scattering of synchrotron radiation, using crystals of {alpha}-{sup 57}Fe{sub 2}O{sub 3}, have been carried out at the NSLS at Brookhaven National Laboratory and at the Cornell University CHESS facility. These studies have demonstrated that nuclear resonance states can be used to produce filtered x-ray beams which have extremely narrow bandwidth, small angular divergence and unique polarization and temporal properties. this combination of characteristics, unobtain… more

Date: March 1, 1993

Creator: Haustein, Peter E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Optical pumping and xenon NMR

Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower … more

Date: November 1, 1991

Creator: Raftery, M. D.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department