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Search Publications by: Bruce D. Ravel (Fed)

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Displaying 26 - 50 of 53

Abiotic bromination of soil organic matter

October 15, 2015
Author(s)
Bruce D. Ravel, Alessandra C. Leri
Biogeochemical transformations of plant-derived soil organic matter (SOM) involve complex abiotic and microbially mediated reactions. One such reaction is halogenation, which occurs naturally in the soil environment and has been associated with enzymatic

Muffin tin potentials in EXAFS analysis

September 1, 2015
Author(s)
Bruce D. Ravel
Muffin tin potentials are the standard tool for calculating the potential surface of a cluster of atoms for use in the analysis of extended x-ray-absorption fine-structure (EXAFS) data. The set of Cartesian coordinates used to define the positions of atoms

Understanding the blue color in antique mosaic mirrored glass from the Temple of the Emerald Buddha, Thailand

February 4, 2015
Author(s)
Bruce D. Ravel, Wantana Klysubun, Christoph Hauzenberger, Prapong Klysubun, Yuying Huang, Weeraya Wongtepa, Panidtha Sombunchoo
Two samples of the blue glass produced in the middle 19th century from the Temple of the Emerald Buddha in Bangkok, Thailand, were studied in order to understand the origin of its blue color. The oxide components and trace elements are quantitatively

Path degeneracy and EXAFS analysis of disordered materials

October 24, 2014
Author(s)
Bruce D. Ravel
The analysis of EXAFS data measured on a material with a disordered local configuration environment around the absorbing atom can be challenging due to the proliferation of photoelectron scattering paths that must be considered in the analysis. In the case

Bromination of marine particulate organic matter through oxidative mechanisms

September 14, 2014
Author(s)
Bruce D. Ravel, Alessandra C. Leri, Kathleen Thornton, Lawrence M. Mayer
Although bromine is considered conservative in seawater, it exhibits a well established correlation with organic carbon in marine sediments. This carbon-bromine association was recently attributed to covalent bonding, with organobromine in sinking

The red color in 19th century Thai glass studied by X-ray and optical spectroscopy

July 2, 2014
Author(s)
Bruce D. Ravel, Wantana Klysubun, G. Lawrence Carr, Christoph Hauzenberger
The Temple of the Emerald Buddha in Bangkok, Thailand is noted for its glass mosaic decorations on exterior walls and statuary. The original mosaic artwork dates to the early 19th century and is composed of variously-colored, mirrored glass pieces. In this

Diamond Sensors and Polycapillary Lenses for X-ray Absorption Spectroscopy

October 13, 2013
Author(s)
Bruce D. Ravel
Diamond sensors are evaluated as incident beam monitors for X-ray Absorption Spectroscopy experiments. These single crystal devices pose a challenge for an energyscanning experiment using hard X-rays due to the e ect of diffraction from the crystalline

Path aggregation techniques for EXAFS visualization and analysis

April 1, 2013
Author(s)
Bruce D. Ravel
The path expansion model used by feff considers the EXAFS spectrum as the sum of contributions from scattering geometries of two or more atoms in a cluster surrounding the absorbing atom. This model and its representation as a collection of les is the

Towards Data Format Standardization for X-ray Absorption Spectroscopy

November 1, 2012
Author(s)
Bruce D. Ravel, J. R. Hester, V. A. Sole, M. Newville
A working group on data format standardization for X-ray Absorption Spectroscopy has recently formed under the auspices of International X-ray Absorption Society and the XAFS Commission of the IUCr. This group of beamline scientists and XAS ractitioners

Fitting EXAFS data using molecular dynamics outputs and a histogram approach

February 29, 2012
Author(s)
Bruce D. Ravel, Stephen W. Price, Nicholas Zonias, Chris-Kriton Skylaris, Andrea Russell
It has been shown that for highly disordered systems, EXAFS underestimates coordination number and thus particle size when compared with the theoretical coordination number based on size determination from other experimental techniques1-4. Similarly, when

Elucidating the Influence of Local Structure Perturbations on the Metal-Insulator Transitions of V1-x MoxO2 Nanowires: Mechanistic Insights from an X-ray Absorption Spectroscopy Study

January 27, 2012
Author(s)
Bruce D. Ravel, C Patridge, Luisa Whittaker-Brooks, S Banerjee
The substitutional doping of Mo within VO2 substantially alters the electronic and structural phase diagrams of the host lattice, most notably by bringing the technologically relevant metal-insulator phase transition temperature in closer proximity to room

Simultaneous XAFS Measurements of Multiple Samples

May 17, 2010
Author(s)
Bruce D. Ravel, C. Scorzato, D. P. Siddons, S. D. Kelly, S. R. Bare
A four-channel ionization chamber has been designed, constructed and tested. This ionization chamber allows X-ray absorption spectra to be collected in transmission from up to four samples simultaneously. This results in spectra that are free of systematic

EXAFS Studies of Catalytic DNA Sensors for Mercury Contamination of Water

December 11, 2009
Author(s)
Bruce D. Ravel, S.C. Slimmer, X. Meng, G.C.L. Wong, Y. Lu
Monitoring of metallic contaminants in domestic and agricultural water systems systems requires technology that is fast, flexible, sensitive, and selective. Recently, metal sensors based on catalytic DNA have been demonstrated as a practical monitoring

Composing complex EXAFS problems with severe information constraints

November 1, 2009
Author(s)
Bruce D. Ravel
In recent work, a model for the structural environment of Hg bound to a catalytic DNA sensor was proposed on the basis of EXAFS data analysis. Although severely constrained by limited data quality and scant supporting structural data, a compelling

Tomography of Integrated Circuit Interconnects

October 1, 2001
Author(s)
Zachary H. Levine, A R. Kalukin, M Kuhn, S P. Frigo, I McNulty, C C. Retsch, Y Wang, Uwe Arp, Thomas B. Lucatorto, Bruce D. Ravel, Charles S. Tarrio
00 Word summary based on the paper:Z. H. Levine, A. R. Kalukin, M. Kuhn, S. P. Frigo, I. McNulty,>C. C. Retsch, Y. Wang, U. Arp, T. B. Lucatorto, B. D. Ravel, and C. Tarrio,>``Microtomography of Integrated Circuit Interconnect with an> Electromigration

Tomography of Integrated Circuit Interconnect With an Electromigration Void

May 1, 2000
Author(s)
Zachary H. Levine, A R. Kalukin, M Kuhn, S P. Frigo, I McNulty, C C. Retsch, Y Wang, Uwe Arp, Thomas B. Lucatorto, Bruce D. Ravel, Charles S. Tarrio
An integrated circuit interconnect was subject to accelerated-life conditions to induce an electromigration void. The silicon substrate was removed, leaving only the interconnect encased test structure encased in silica. We imaged the sample with 1750 eV

Combined EXAFS and First-Principles Theory Study of Pb 1-x Ge x Te

December 1, 1999
Author(s)
Bruce D. Ravel, Eric J. Cockayne, E Newville, K M. Rabe
The narrow band-gap semiconductor Pb 1-xGe xTe has a low-temperature ferroelectric rhombohedral phase whose average structure is a distorted rocksalt structure. We have measured the Extended X-Ray-Absorption Fine-Structure (EXAFS) spectra of Pb 1-xGe xTe

X-Ray-Absorption Edge Separation Using Diffraction Anomalous Fine-Structure

July 1, 1999
Author(s)
Bruce D. Ravel, Charles E. Bouldin, H Renevier, J -. Hodeau, J -. Berar
When two or more absorption edges in a material are sufficiently close in energy, Extended X-ray-Absorption Fine-Structure (EXAFS) spectroscopy may be of limited utility as the usable data range above the lower energy edge is truncated by the presence of

The Local Structure of Ferroelectric Pb 1-x Ge x Te

May 1, 1999
Author(s)
Bruce D. Ravel, Eric J. Cockayne, K M. Rabe
The narrow band-gap semiconductor Pb_{1-x}Ge_xTe has a low-temperature ferroelectric rhombohedral phase whose average structure is a distorted rock salt structure. We have measured the Extended X-ray-Absorption Fine-Structure spectra of Pb_{1-x}Ge_xTe with