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1

Solar X-Ray Spectroscopy And Polarimetry By Instrument Ping-M Onboard Interhelioprobe  

NASA Astrophysics Data System (ADS)

The instrument PING-M for X-ray spectroscopy and polarimetry of solar full disk radiation is described. It will be the part of scientific instrument set for the InterHelioProbe space mission. Instrument consists of three detectors: the Soft X-ray detector (SXRD), the Hard X-ray detector (HXRD) and Hard X-ray polarimeter (PING-P). Spectrometer SXRD is based on a relatively novel type of semiconductor detector SDD (Silicon Drift Detector) that will operate in the energy range 1.5-25 keV, which is similar to GOES X-Ray Sensor (XRS) region. Unlike GOES the SXRD is capable to measure the energy of each photon with high resolution (better 200 eV at 5.9 keV) and operate with high count rate. The X-ray spectra of solar flares obtained by the SXRD should show evidence of Fe and Fe/Ni line emission and multi-thermal plasma. HXRD operates in energy range 15-150 keV. Fast nonorganic scintillator (is based on LaBr3(Ce)) with good energy resolution (?12% at 60keV and ?3.5% at 662keV) is used. Apart from measurement of spectra the value of the break energy point that separates the thermal and non-thermal processes in flare would be revealed. In the talk the results of testing of laboratory models are presented. PING-P Hard X-ray polarimeter consists of active scatterer made of three organic p-terphenyl scintillators and six peripheral scattered radiation detectors made of CsI(Tl) scintillators. Effective area of polarimeter is about 5 cm2 in its energy range. Minimal measurable degree of polarization is 0.9 % for 100 sec exposition and X1 solar flare.

Kotov, Yury; Dergachev, Valentin; Kochemasov, Alexey; Yurov, Vitaly; Tyshkevich, V.; Glyanenko, Alexander; Savchenko, Mikhail; Lazutkov, Vadim; Skorodumov, Dmitry; Trofimov, Yury; Zakharov, Mikhail; Rubtsov, Igor; Kruglov, Evgeniy

2

A laser-based instrument for the study of ultrafast chemical dynamics by soft x-ray-probe photoelectron spectroscopy  

Microsoft Academic Search

A laser-based instrument is described for the study of femtosecond dissociation dynamics of gas phase molecules via time-resolved vacuum ultraviolet and soft x-ray photoelectron spectroscopy. Visible or UV pump pulses are generated with nonlinear crystal techniques on a Ti:sapphire laser output, while soft x-ray probe pulses are created via high-order harmonic generation of the same laser in rare gases. Here

Lora Nugent-Glandorf; Michael Scheer; David A. Samuels; Veronica Bierbaum; Stephen R. Leone

2002-01-01

3

Instrument for single-shot X-Ray emission-spectroscopy experiments  

NASA Astrophysics Data System (ADS)

We present the design and the characteristics of a portable and compact photon spectrometer to be installed in freeelectron- laser (FEL) beamlines for photon in - photon out experiments, in particular single-shot X-ray emission spectroscopy. The instrument is operated in the 30 - 800 eV energy range with two channels and is designed to be initially used in the LDM (Low-Density Matter) and TIMEX (TIme-resolved studies of Matter under EXtreme conditions) beamlines of the FERMI@ELETTRA FEL, covering the whole spectral range of FERMI-1 and FERMI-2 emissions. The design of the instrument is tailored to achieve high spectral resolution in the whole interval of operation, high acceptance angle and high dynamic range. These characteristics are achieved in a compact environment to give a portable instrument that may be easily installed in different experimental chambers. The design consists of an entrance slit, a grazing-incidence diffraction grating and a detector. The number of elements within the optical path is kept to a single component, to minimize the losses due to reflectivity. The grating is spherical with variable line spacing along its surface, to provide an almost flat spectral focal plane that is perpendicular to the direction of the diffracted light. The detector is a back-illuminated CCD. The spectral resolution is better than 0.2% in the 30 - 800 eV region and the acceptance angles are 10 × 17 mrad in the 30-250 eV and 5 × 17 mrad in the at 250-800 eV.

Poletto, Luca; Frassetto, Fabio; Miotti, Paolo; Coreno, Marcello; Di Cicco, Andrea; Stagira, Salvatore

2013-05-01

4

Instrument for x-ray absorption spectroscopy with in situ electrical control characterizations  

SciTech Connect

We report a synchrotron-based setup capable of performing x-ray absorption spectroscopy and x-ray magnetic circular dichroism with simultaneous electrical control characterizations. The setup can enable research concerning electrical transport, element- and orbital-selective magnetization with an in situ fashion. It is a unique approach to the real-time change of spin-polarized electronic state of a material/device exhibiting magneto-electric responses. The performance of the setup was tested by probing the spin-polarized states of cobalt and oxygen of Zn{sub 1-x}Co{sub x}O dilute magnetic semiconductor under applied voltages, both at low (?20 K) and room temperatures, and signal variations upon the change of applied voltage were clearly detected.

Huang, Chun-Chao; Chang, Shu-Jui; Yang, Chao-Yao; Tseng, Yuan-Chieh [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan (China)] [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan (China); Chou, Hsiung [Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan (China)] [Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan (China)

2013-12-15

5

X-ray spectroscopy of low-mass X-ray binaries  

E-print Network

I present high-resolution X-ray grating spectroscopy of neutron stars in low-mass X-ray binaries (LMXBs) using instruments onboard the Chandra X-ray Observatory and the X-ray Multi-Mirror Mission (XMM-Newton). The first ...

Juett, Adrienne Marie, 1976-

2004-01-01

6

X-ray Absorption Spectroscopy  

SciTech Connect

This review gives a brief description of the theory and application of X-ray absorption spectroscopy, both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), especially, pertaining to photosynthesis. The advantages and limitations of the methods are discussed. Recent advances in extended EXAFS and polarized EXAFS using oriented membranes and single crystals are explained. Developments in theory in understanding the XANES spectra are described. The application of X-ray absorption spectroscopy to the study of the Mn4Ca cluster in Photosystem II is presented.

Yano, Junko; Yachandra, Vittal K.

2009-07-09

7

Tokamak x ray diagnostic instrumentation  

SciTech Connect

Three classes of x-ray diagnostic instruments enable measurement of a variety of tokamak physics parameters from different features of the x-ray emission spectrum. (1) The soft x-ray (1 to 50 keV) pulse-height-analysis (PHA) diagnostic measures impurity concentrations from characteristic line intensities and the continuum enhancement, and measures the electron temperature from the continuum slope. (2) The Bragg x-ray crystal spectrometer (XCS) measures the ion temperature and neutral-beam-induced toroidal rotation velocity from the Doppler broadening and wavelength shift, respectively, of spectral lines of medium-Z impurity ions. Impurity charge state distributions, precise wavelengths, and inner-shell excitation and recombination rates can also be studied. X rays are diffracted and focused by a bent crystal onto a position-sensitive detector. The spectral resolving power E/..delta..E is greater than 10/sup 4/ and time resolution is 10 ms. (3) The x-ray imaging system (XIS) measures the spatial structure of rapid fluctuations (0.1 to 100 kHZ) providing information on MHD phenomena, impurity transport rates, toroidal rotation velocity, plasma position, and the electron temperature profile. It uses an array of silicon surface-barrier diodes which view different chords of the plasma through a common slot aperture and operate in current (as opposed to counting) mode. The effectiveness of shields to protect detectors from fusion-neutron radiation effects has been studied both theoretically and experimentally.

Hill, K.W.; Beiersdorfer, P.; Bitter, M.; Fredrickson, E.; Von Goeler, S.; Hsuan, H.; Johnson, L.C.; Liew, S.L.; McGuire, K.; Pare, V.

1987-01-01

8

High resolution spectroscopy of X-ray emission from high mass X-ray binaries  

Microsoft Academic Search

This article briefly reviews first the progress of spectroscopy in X-ray astronomy from proportional counters, a major instrument in early phase of X-ray astronomy, to gas scintillation proportional counters, X-ray CCD cameras, transmission and reflection gratings, and finally to X-ray micro-calorimeters. As a typical example of spectral features observed from high mass X-ray binaries (HMXBs), the spectra observed from Vela

F. Nagase; S. Watanabe

2006-01-01

9

X-ray astronomical spectroscopy  

NASA Technical Reports Server (NTRS)

The current status of the X-ray spectroscopy of celestial X-ray sources, ranging from nearby stars to distant quasars, is reviewed. Particular emphasis is placed on the role of such spectroscopy as a useful and unique tool in the elucidation of the physical parameters of the sources. The spectroscopic analysis of degenerate and nondegenerate stellar systems, galactic clusters and active galactic nuclei, and supernova remnants is discussed.

Holt, S. S.

1980-01-01

10

X-Ray Absorption Spectroscopy of Metallobiomolecules  

E-print Network

9/6/09 1 X-Ray Absorption Spectroscopy of Metallobiomolecules The Outskirts of Structural Biology 6, 09] This is a tutorial about the use of X-ray Absorption Spectroscopy (XAS) in biology, RG; Eisenberger, P; Kincaid, BM "X-ray Absorption Spectroscopy of Biological Molecules" Annu. Rev

Scott, Robert A.

11

X-Ray Absorption Spectroscopy of Metallobiomolecules  

E-print Network

2/9/07 1 X-Ray Absorption Spectroscopy of Metallobiomolecules The Outskirts of Structural Biology 9, 07] This is a tutorial about the use of X-ray Absorption Spectroscopy (XAS) in biology, RG; Eisenberger, P; Kincaid, BM "X-ray Absorption Spectroscopy of Biological Molecules" Annu. Rev

Scott, Robert A.

12

X-ray Spectroscopy of Cool Stars  

E-print Network

High-resolution X-ray spectroscopy has addressed not only various topics in coronal physics of stars, but has also uncovered important features relevant for our understanding of stellar evolution and the stellar environment. I summarize recent progress in coronal X-ray spectroscopy and in particular also discuss new results from studies of X-rays from pre-main sequence stars.

M. Guedel

2006-09-11

13

Complex of instrumentation KORTES for the EUV and x-ray imaging and spectroscopy of the solar corona  

NASA Astrophysics Data System (ADS)

We report on the current status of the KORTES project - the first sun-oriented mission for the International Space Station to be launched in 2016-2017. KORTES will comprise several imaging and spectroscopic instruments that will observe solar corona in a number of wavebands, covering EUV and X-Ray ranges. A brief overview of the instrumentation of KORTES, its' layout, technical parameters and scientific objectives is given. An additional attention is given to the design of multilayer optics and filters to be employed in EUV instruments of KORTES.

Shestov, Sergey V.; Ulyanov, Artem S.; Vishnyakov, Eugene A.; Pertsov, Andrei A.; Kuzin, Sergey V.

2014-07-01

14

X-ray astronomical spectroscopy  

NASA Technical Reports Server (NTRS)

The contributions of the Goddard group to the history of X-ray astronomy are numerous and varied. One role that the group has continued to play involves the pursuit of techniques for the measurement and interpretation of the X-ray spectra of cosmic sources. The latest development is the selection of the X-ray microcalorimeter for the Advanced X-ray Astrophysics Facility (AXAF) study payload. This technology is likely to revolutionize the study of cosmic X-ray spectra.

Holt, Stephen S.

1987-01-01

15

Resonant x-ray emission spectroscopy of liquid water: novel instrumentation, high resolution, and the"map" approach  

SciTech Connect

Techniques to study the electronic structure of liquids are rare. Most recently, resonant x-ray emission spectroscopy (XES) has been shown to be an extremely versatile spectroscopy to study both occupied and unoccupied electronic states for liquids in thermodynamic equilibrium. However, XES requires high-brilliance soft x-ray synchrotron radiation and poses significant technical challenges to maintain a liquid sample in an ultra-high vacuum environment. Our group has therefore developed and constructed a novel experimental setup for the study of liquids, with the long-term goal of investigating the electronic structure of biological systems in aqueous environments. We have developed a flow-through liquid cell in which the liquid is separated from vacuum by a thin Si3N4 or SiC window and which allows a precise control of temperature. This approach has significant advantages compared to static liquids cells used in the past. Furthermore, we have designed a dedicated high-transmission, high-resolution soft x-ray spectrometer. The high transmission makes it possible to measure complete resonant XES"maps" in less than an hour, giving unprecedented detailed insight into the electronic structure of the investigated sample. Using this new equipment we have investigated the electronic structure of liquid water. Furthermore, our XES spectra and maps give information about ultra-fast dissociation on the timescale of the O 1s core hole lifetime, which is strongly affected by the initial state hydrogen bonding configuration.

Weinhardt, L.; Fuchs, O.; Blum, M.; Bär, M.; Weigand, M.; Denlinger, J.D.; Zubavichus, Y.; Zharnikov, M.; Grunze, M.; Heske, C.; Umbach, E.

2008-06-17

16

Current Status of AIST X-ray-Absorption-Spectroscopy (XAFS) Instrument with 100-Pixel Superconducting-Tunnel-Junction Array Detector  

NASA Astrophysics Data System (ADS)

We constructed a fluorescence yield X-ray absorption fine structure (XAFS) apparatus for the measurement of local structure around trace light element impurities in light element matrices. Our XAFS instrument with a 100-pixel STJ detector is now in the stage of routine operation and open to users at a synchrotron radiation facility (KEK PF). The average energy resolution of the 100 pixels is 11.8 0.6 at 400 eV in a sensitive area of 1 mm. As an example of functional materials, we successfully measured nitrogen K-edge XAFS spectra of a compound semiconductor, 4H-SiC, with a nitrogen dopant concentration of 300 ppm. The faint N-K line was clearly separated from the strong C-K line.

Shiki, S.; Ukibe, M.; Matsubayashi, N.; Zen, N.; Koike, M.; Kitajima, Y.; Ohkubo, M.

2014-08-01

17

X-ray spectroscopy of magnetic CVs  

NASA Astrophysics Data System (ADS)

I discuss two topics in X-ray spectroscopy of magnetic CVs: reflection from the white dwarf surface, and opacity effects in the post shock plasma. I also briefly mention future observational perspectives, with particular emphasis on the Constellation X-ray mission.

Matt, Giorgio

18

European XFEL: Soft X-Ray instrumentation  

SciTech Connect

The currently constructed European X-Ray Free Electron Laser (XFEL) will generate new knowledge in almost all the technical and scientific disciplines that are shaping our daily life-including nanotechnology, medicine, pharmaceutics, chemistry, materials science, power engineering and electronics. On 8 January 2009, civil engineering work (tunnels, shafts, halls) has been started at all three construction sites. In this presentation status and parameters of the European XFEL facility and instrumentation as well as planned research applications particularly in the range of soft X-rays are reviewed.

Molodtsov, S. L., E-mail: serguei.molodtsov@xfel.eu [European XFEL GmbH (Germany)

2011-12-15

19

X-ray Spectroscopy of Inorganic Materials  

Microsoft Academic Search

X-ray spectroscopies have been applied on different inorganic materials with a main focus on 3d-metal materials and iron compounds in particular. Different theoretical treatments of x-ray absorption spectroscopy (XAS) are compared with each other and with experimental data. XAS calculations have been performed for iron to study the XAS shapes of different spin states of iron as well as the

P. S. Miedema

2012-01-01

20

Large Area X-Ray Spectroscopy Mission  

NASA Technical Reports Server (NTRS)

The Large Area X-ray Spectroscopy (LAXS) mission concept study continues to evolve strongly following the merging of the LAXS mission with the Next Generation X-ray Observatory (NGXO, PI: Nick White) into the re-named High Throughput X-ray Spectroscopy (HTXS) Mission. HTXS retains key elements of the LAXS proposal, including the use of multiple satellites for risk-reduction and cost savings. A key achievement of the program has been the recommendation by the Structure and Evolution of the Universe (SEUS) (April 1997) for a new start for the HTXS mission in the 2000-2004 timeframe.

Tananbaum, H.

1997-01-01

21

X-ray spectroscopy: Enlightened state  

NASA Astrophysics Data System (ADS)

Determining the sequence of events following photon absorption by a molecule can be a surprisingly challenging task. An innovative use of time-resolved X-ray spectroscopy has revealed an important insight into the ultrafast excited-state dynamics of a well-known inorganic chromophore.

McCusker, James K.

2014-07-01

22

Theoretical standards in x-ray spectroscopies  

SciTech Connect

We propose to extend our state-of-the-art, ab initio XAFS (X-ray absorption fine structure) codes, FEFF. Our current work has been highly successful in achieving accurate, user-friendly XAFS standards, exceeding the performance of both tabulated standards and other codes by a considerable margin. We now propose to add the capability to treat more complex materials. This includes multiple-scattering, polarization dependence, an approximate treatment of XANES (x-ray absorption near edge structure), and other improvements. We also plan to adapt FEFF to other spectroscopies, e.g. photoelectron diffraction (PD) and diffraction anomalous fine structure (DAFS).

Not Available

1992-01-01

23

X-ray spectroscopy of supernova remnants  

NASA Astrophysics Data System (ADS)

The information which can be obtained from X-ray spectroscopy of supernova remnants is considerd. The fitting of X-ray detector counts to models of the incident spectrum is discussed, and the types of thermal emission models generally employed are presented, including the power law, black body, and thermal bremsstrahlung models of the continua and models of the emission of a hot, optically thin plasma in collisional equilibrium. Observations of 12 supernova remnants made with the Solid State Spectrometer on board the Einstein Observatory are reported, and metal abundances inferred from the lines of the eight remnants showing thermal spectra are summarized. Questions raised by the failure to observe the overabundance of Fe predicted by stellar evolution and hydrodynamic modeling are discussed, and the need to develop more detailed models of the conditions in a supernova remnant in order to interpret the X-ray spectra is noted.

Szymkowiak, A. E.

24

A laboratory-based hard x-ray monochromator for high-resolution x-ray emission spectroscopy and x-ray absorption near edge structure measurements.  

PubMed

We report the development of a laboratory-based Rowland-circle monochromator that incorporates a low power x-ray (bremsstrahlung) tube source, a spherically bent crystal analyzer, and an energy-resolving solid-state detector. This relatively inexpensive, introductory level instrument achieves 1-eV energy resolution for photon energies of ?5 keV to ?10 keV while also demonstrating a net efficiency previously seen only in laboratory monochromators having much coarser energy resolution. Despite the use of only a compact, air-cooled 10 W x-ray tube, we find count rates for nonresonant x-ray emission spectroscopy comparable to those achieved at monochromatized spectroscopy beamlines at synchrotron light sources. For x-ray absorption near edge structure, the monochromatized flux is small (due to the use of a low-powered x-ray generator) but still useful for routine transmission-mode studies of concentrated samples. These results indicate that upgrading to a standard commercial high-power line-focused x-ray tube or rotating anode x-ray generator would result in monochromatized fluxes of order 10(6)-10(7) photons/s with no loss in energy resolution. This work establishes core technical capabilities for a rejuvenation of laboratory-based hard x-ray spectroscopies that could have special relevance for contemporary research on catalytic or electrical energy storage systems using transition-metal, lanthanide, or noble-metal active species. PMID:25430123

Seidler, G T; Mortensen, D R; Remesnik, A J; Pacold, J I; Ball, N A; Barry, N; Styczinski, M; Hoidn, O R

2014-11-01

25

A laboratory-based hard x-ray monochromator for high-resolution x-ray emission spectroscopy and x-ray absorption near edge structure measurements  

NASA Astrophysics Data System (ADS)

We report the development of a laboratory-based Rowland-circle monochromator that incorporates a low power x-ray (bremsstrahlung) tube source, a spherically bent crystal analyzer, and an energy-resolving solid-state detector. This relatively inexpensive, introductory level instrument achieves 1-eV energy resolution for photon energies of ˜5 keV to ˜10 keV while also demonstrating a net efficiency previously seen only in laboratory monochromators having much coarser energy resolution. Despite the use of only a compact, air-cooled 10 W x-ray tube, we find count rates for nonresonant x-ray emission spectroscopy comparable to those achieved at monochromatized spectroscopy beamlines at synchrotron light sources. For x-ray absorption near edge structure, the monochromatized flux is small (due to the use of a low-powered x-ray generator) but still useful for routine transmission-mode studies of concentrated samples. These results indicate that upgrading to a standard commercial high-power line-focused x-ray tube or rotating anode x-ray generator would result in monochromatized fluxes of order 106-107 photons/s with no loss in energy resolution. This work establishes core technical capabilities for a rejuvenation of laboratory-based hard x-ray spectroscopies that could have special relevance for contemporary research on catalytic or electrical energy storage systems using transition-metal, lanthanide, or noble-metal active species.

Seidler, G. T.; Mortensen, D. R.; Remesnik, A. J.; Pacold, J. I.; Ball, N. A.; Barry, N.; Styczinski, M.; Hoidn, O. R.

2014-11-01

26

In situ soft X-ray absorption spectroscopy of flames  

NASA Astrophysics Data System (ADS)

The feasibility of in situ soft X-ray absorption spectroscopy for imaging carbonaceous species in hydrocarbon flames is demonstrated using synchrotron radiation. Soft X-rays are absorbed by core level electrons in all carbon atoms regardless of their molecular structure. Core electron spectroscopy affords distinct advantages over valence spectroscopy, which forms the basis of traditional laser diagnostic techniques for combustion. In core level spectroscopy, the transition linewidths are predominantly determined by the instrument response function and the decay time of the core-hole, which is on the order of a femtosecond. As a result, soft X-ray absorption measurements can be performed in flames with negligible Doppler and collisional broadening. Core level spectroscopy has the further advantage of measuring all carbonaceous species regardless of molecular structure in the far-edge region, whereas near-edge features are molecule specific. Interferences from non-carbon flame species are unstructured and can be subtracted. In the present study, absorption measurements in the carbon K-edge region are demonstrated in low-pressure ( P total = 20-30 Torr) methane jet flames. Two-dimensional imaging of the major carbonaceous species, CH4, CO2, and CO, is accomplished by tuning the synchrotron radiation to the respective carbon K-edge, near-edge X-ray absorption fine structure (NEXAFS) transitions and scanning the burner.

Frank, Jonathan H.; Shavorskiy, Andrey; Bluhm, Hendrik; Coriton, Bruno; Huang, Erxiong; Osborn, David L.

2014-10-01

27

Tomographic x-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Hard x-ray absorption spectroscopy is combined with scanning microtomography to reconstruct full near edge spectra of an elemental species at each location on an arbitrary virtual section through a sample. These spectra reveal the local concentrations of different chemical compounds of the absorbing element inside the sample and give insight into the oxidation state, the local atomic structure, and the local projected free density of states. The method is implemented by combining a quick scanning monochromator and data acquisition system with a scanning microprobe setup based on refractive x-ray lenses. The full XANES spectra reconstructed at each point of the tomographic slice allow to detect slight variations in concentrations of chemical compounds, such as metallic and monovalent copper. The method is applied to the analysis of a heterogeneous catalyst.

Schroer, Christian G.; Kuhlmann, Marion; Gunzler, Til Florian; Lengeler, Bruno; Richwin, Matthias; Griesebock, Bernd; Lutzenkirchen-Hecht, Dirk; Frahm, Ronald; Ziegler, Eric; Mashayekhi, Ali; Haeffner, Dean; Grunwaldt, Jan-Dierk; Baiker, Alfons

2004-10-01

28

X-Ray Spectroscopy of Photoionized Plasmas  

NASA Technical Reports Server (NTRS)

Spectroscopy allows study of sources on small spatial scales, and can provide detailed diagnostic information about elemental abundances, temperature, density and gas dynamics. For compact sources such as accreting black holes in active galactic nuclei (AGN) and X-ray binaries X-ray spectra provide truly unique insight. Observations using Chandra and XMM have revealed components of gas in these systems which were previously unknown or poorly studied. Interpretation of these data presents modeling and analysis challenges, and requires an understanding of atomic physics, ionization and spectrum formation in a radiation-dominated environment. In this talk I will discuss examples, and how they have contributed to our understanding of accreting sources and the nearby gas.

Kallman, Tim

2008-01-01

29

Hard X-ray imaging spectroscopy of FOXSI microflares  

NASA Astrophysics Data System (ADS)

The ability to investigate particle acceleration and hot thermal plasma in solar flares relies on hard X-ray imaging spectroscopy using bremsstrahlung emission from high-energy electrons. Direct focusing of hard X-rays (HXRs) offers the ability to perform cleaner imaging spectroscopy of this emission than has previously been possible. Using direct focusing, spectra for different sources within the same field of view can be obtained easily since each detector segment (pixel or strip) measures the energy of each photon interacting within that segment. The Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket payload has successfully completed two flights, observing microflares each time. Flare images demonstrate an instrument imaging dynamic range far superior to the indirect methods of previous instruments like the RHESSI spacecraft.In this work, we present imaging spectroscopy of microflares observed by FOXSI in its two flights. Imaging spectroscopy performed on raw FOXSI images reveals the temperature structure of flaring loops, while more advanced techniques such as deconvolution of the point spread function produce even more detailed images.

Glesener, Lindsay; Krucker, Sam; Christe, Steven; Camilo Buitrago-Casas, Juan; Ishikawa, Shin-nosuke; Foster, Natalie

2015-04-01

30

X-Ray spectroscopy of cooling flows  

NASA Technical Reports Server (NTRS)

Cooling flows in clusters of galaxies occur when the cooling time of the gas is shorter than the age of the cluster; material cools and falls to the center of the cluster potential. Evidence for short X-ray cooling times comes from imaging studies of clusters and X-ray spectroscopy of a few bright clusters. Because the mass accretion rate can be high (a few 100 solar mass units/year) the mass of material accumulated over the lifetime of a cluster can be as high as 10(exp 12) solar mass units. However, there is little evidence for this material at other wavelengths, and the final fate of the accretion material is unknown. X-ray spectra obtained with the Einstein SSS show evidence for absorption; if confirmed this result would imply that the accretion material is in the form of cool dense clouds. However ice on the SSS make these data difficult to interpret. We obtained ASCA spectra of the cooling flow cluster Abell 85. Our primary goals were to search for multi-temperature components that may be indicative of cool gas; search for temperature gradients across the cluster; and look for excess absorption in the cooling region.

Prestwich, Andrea

1996-01-01

31

Miniaturization in x ray and gamma ray spectroscopy  

NASA Technical Reports Server (NTRS)

The paper presents advances in two new sensor technologies and a miniaturized associated electronics technology which, when combined, can allow for very significant miniaturization and for the reduction of weight and power consumption in x-ray and gamma-ray spectroscopy systems: (1) Mercuric iodide (HgI2) x-ray technology, which allows for the first time the construction of truly portable, high-energy resolution, non-cryogenic x-ray fluorescence (XRF) elemental analyzer systems, with parameters approaching those of laboratory quality cryogenic instruments; (2) the silicon avalanche photodiode (APD), which is a solid-state light sensitive device with internal amplification, capable of uniquely replacing the vacuum photomultiplier tube in scintillation gamma-ray spectrometer applications, and offering substantial improvements in size, ruggedness, low power operation and energy resolution; and (3) miniaturized (hybridized) low noise, low power amplification and processing electronics, which take full advantage of the favorable properties of these new sensors and allow for the design and fabrication of advanced, highly miniaturized x-ray and gamma-ray spectroscopy systems. The paper also presents experimental results and examples of spectrometric systems currently under construction. The directions for future developments are discussed.

Iwanczyk, Jan S.; Wang, Yuzhong J.; Bradley, James G.

1993-01-01

32

Constellation-X Spectroscopy X-Ray Telescope Segmented Optic Assembly and Alignment Implementation  

E-print Network

Constellation-X Spectroscopy X-Ray Telescope Segmented Optic Assembly and Alignment Implementation. ABSTRACT The Constellation-X mission will perform X-Ray science with improvements in energy resolution and effective area over its predecessor missions. The primary instrument on each of the four Constellation

33

X-ray microprobe for micro x-ray fluorescence and absorption spectroscopies at GSECARS  

NASA Astrophysics Data System (ADS)

The hard x-ray microprobe for x-ray fluorescence and absorption spectroscopy at GeoSoilEnviroCARS is presented. Using focused synchrotron radiation from an undulator beamline at the Advanced Photon Source at Argonne National Lab, the x-ray microprobe provides bright, monochromatic x-rays with typical spot sizes down to 1x1 ?m for x-ray fluorescence and absorption spectroscopies. Quantitative x-ray fluorescence (XRF) analysis gives precise elemental composition and correlations, while x-ray absorption spectroscopy (XAS) gives the chemical state and local atomic coordination for a selected atomic species. These two techniques can be used in conjunction with one another on a wide range of samples, including minerals, glasses, fluid inclusions, soils, sediments, and plant tissue. This x-ray microprobe is part of the GeoSoilEnviroCARS user facility, available for use in all areas geological, soil, and environmental sciences, and selected examples from these fields will be given.

Newville, M.; Sutton, S.; Rivers, M.

2002-12-01

34

High Resolution Imaging X-ray Spectroscopy of Mars  

Microsoft Academic Search

The first observation of Mars with XMM-Newton, in November 2003, has provided a wealth of novel information about the X-ray properties of our neighbouring planet. High resolution imaging spectroscopy with RGS clearly shows that its X-ray emission is composed of two different components: fluorescent scattering of solar X-rays on neutral molecules in its upper atmosphere, and emission from highly charged

K. Dennerl

2006-01-01

35

The Need for X-Ray Spectroscopy  

NASA Technical Reports Server (NTRS)

For over four decades, X-ray, EUV, and UV spectral observations have been used to measure physical properties of the solar atmosphere. During this time, there has been substantial improvement in the spectral, spatial, and temporal resolution of the observations for the EUV and UV wavelength ranges. At wavelengths below 100 Angstroms, however, observations of the solar corona with simultaneous spatial and spectral resolution are limited, and not since the late 1970's have spatially resolved solar X-ray spectra been measured. The soft-X-ray wavelength range is dominated by emission lines formed at high temperatures and provides diagnostics unavailable in any other wavelength range. In this presentation, we will discuss the important science questions that can be answered using spatially and spectrally resolved X-ray spectra.

Winebarger, Amy R.; Cirtain, Jonathan; Kobayashi, Ken

2011-01-01

36

A high-resolution large-acceptance analyzer for X-ray fluorescence and Raman spectroscopy  

SciTech Connect

A newly designed multi-crystal X-ray spectrometer and its applications in the fields of X-ray fluorescence and X-ray Raman spectroscopy are described. The instrument is based on 8 spherically curved Si crystals, each with a 3.5 inch diameter form bent to a radius of 86 cm. The crystals are individually aligned in the Rowland geometry capturing a total solid angle of 0.07 sr. The array is arranged in a way that energy scans can be performed by moving the whole instrument, rather than scanning each crystal by itself. At angles close to back scattering the energy resolution is between 0.3 and 1 eV depending on the beam dimensions at the sample. The instrument is mainly designed for X-ray absorption and fluorescence spectroscopy of transition metals in dilute systems such as metalloproteins. First results of the Mn K{beta} (3p -> 1s) emission in photosystem II are shown. An independent application of the instrument is the technique of X-ray Raman spectroscopy which can address problems similar to those in traditional soft X-ray absorption spectroscopies, and initial results are presented.

Bergmann, Uwe; Cramer, Stephen P.

2001-08-02

37

Instrument and method for X-ray diffraction, fluorescence, and crystal texture analysis without sample preparation  

NASA Technical Reports Server (NTRS)

An X-ray diffraction and X-ray fluorescence instrument for analyzing samples having no sample preparation includes a X-ray source configured to output a collimated X-ray beam comprising a continuum spectrum of X-rays to a predetermined coordinate and a photon-counting X-ray imaging spectrometer disposed to receive X-rays output from an unprepared sample disposed at the predetermined coordinate upon exposure of the unprepared sample to the collimated X-ray beam. The X-ray source and the photon-counting X-ray imaging spectrometer are arranged in a reflection geometry relative to the predetermined coordinate.

Gendreau, Keith (Inventor); Martins, Jose Vanderlei (Inventor); Arzoumanian, Zaven (Inventor)

2010-01-01

38

Soft X-ray induced damage in PVA-based membranes in water environment monitored by X-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

The effect of synchrotron X-ray flux in a soft X-ray scanning-transmission microspectroscope (STXM) instrument on the chemical structure of air-filled poly(vinyl alcohol) (PVA) based microbubbles and their stabilizing shell has been examined. Prolonged soft X-ray illumination of the particles in aqueous suspension leads to the breaking of the microbubbles' protective polymer shell and substantial chemical changes. The latter were clarified via a micro-spot C K-edge near-edge X-ray absorption fine structure (NEXAFS) spectroscopy with further respect to the absorbed X-ray doses. Our results revealed a continuous degradation of the PVA network associated with formation of carbonyl- and carboxyl-containing species as well as an increased content of unsaturated bonds. The observed effects must be taken into account in studies of micro- and nanostructured polymer materials utilizing X-rays.

Tzvetkov, George; Späth, Andreas; Fink, Rainer H.

2014-10-01

39

Crystals for astronomical X-ray spectroscopy  

NASA Technical Reports Server (NTRS)

Crystal spectrometric properties and the factors that affect their measurement are discussed. Theoretical and experimental results on KAP are summarized and theoretical results based on the dynamical theory of X-ray diffraction are given for the acid phthalates as well as for the commonly used planes of ADP, PET and EDDT. Anomalous dispersion is found to be important for understanding the details of crystal Bragg reflection properties at long X-ray wavelengths and some important effects are pointed out. The theory of anomalous dispersion is applied to explain the anomalous reflectivity exhibited by KAP at 23.3 A.

Burek, A.

1976-01-01

40

The Advanced X-ray Spectroscopy and Imaging Observatory (AXSIO)  

NASA Technical Reports Server (NTRS)

Following recommendations from the 2010 "New Worlds, New Horizons" (NWNH) report, the Advanced X-ray Spectroscopy and Imaging Observatory (AXSIO) concept streamlines the International X-ray Observatory (IXO) mission to concentrate on the science objectives that are enabled by high-resolution spectroscopic capabilities. AXSIO will trace orbits close to the event horizon of black holes, measure black hole spin for tens of supermassive black holes (SMBH), use spectroscopy to characterize outflows and the environment of AGN during their peak activity, observe 5MBH out to redshift z=6, map bulk motions and turbulence in galaxy clusters, find the missing baryons in the cosmic web using background quasars, and observe the process of cosmic feedback where black holes and supernovae inject energy on galactic and intergalactic scales. These measurements are enabled by a 0.9 sq m collecting area at 1.25 keV, a micro calorimeter array providing high-resolution spectroscopic imaging and a deployable high efficiency grating spectrometer. AXSIO delivers a 30-fold increase in effective area for high resolution spectroscopy. The key simplifications are guided by recommendations in the NWNH panel report include a reduction in focal length from 20m to 10m, eliminating the extendable optical bench, and a reduction in the instrument complement from six to two, avoiding a movable instrument platform. A focus on spectroscopic science allows the spatial resolution requirement to be relaxed to 10 arc sec (with a 5 arc sec goal). These simplifications decrease the total mission cost to under the $2B cost to NASA recommended by NWNH. AXSIO will be available to the entire astronomical community with observing allocations based on peer-review.

White, Nicholas E.; Bookbinder, Jay; Petre, Robert; Smith, Randall; Ptak, Andrew; Tananbaum, Harvey; Garcia, Michael

2012-01-01

41

Spectroscopy and X-Ray Astronomy  

NASA Technical Reports Server (NTRS)

The new x-ray astronomical observatories have sufficient spectroscopic capability to allow the determination of plasma conditions in the form of velocities, temperatures, densities, and turbulence parameters at levels that were previously unattainable. The utilization of these diagnostics are possible only if the atomic and plasma physics are well-enough understood to match the observational sensitivity.

Holt, Stephen S.

2000-01-01

42

X-ray spectroscopy of manganese clusters  

SciTech Connect

Much of this thesis represents the groundwork necessary in order to probe Mn clusters more productively than with conventional Mn K-edge XAS and is presented in Part 1. Part 2 contains the application of x-ray techniques to Mn metalloproteins and includes a prognosis at the end of each chapter. Individual Mn oxidation states are more readily distinguishable in Mn L-edge spectra. An empirical mixed valence simulation routine for determining the average Mn oxidation state has been developed. The first Mn L-edge spectra of a metalloprotein were measured and interpreted. The energy of Mn K{beta} emission is strongly correlated with average Mn oxidation state. K{beta} results support oxidation states of Mn(III){sub 2}(IV){sub 2} for the S{sub 1} state of Photosystem II chemical chemically reduced preparations contain predominantly Mn(II). A strength and limitation of XAS is that it probes all of the species of a particular element in a sample. It would often be advantageous to selectively probe different forms of the same element. The first demonstration that chemical shifts in x-ray fluorescence energies can be used to obtain oxidation state-selective x-ray absorption spectra is presented. Spin-dependent spectra can also be used to obtain a more simplified picture of local structure. The first spin-polarized extended x-ray absorption fine structure using Mn K{beta} fluorescence detection is shown.

Grush, M.M. [Univ. of California, Davis, CA (United States). Dept. of Applied Science; [Lawrence Berkeley National Lab., CA (United States). Energy and Environment Div.

1996-06-01

43

X-Ray Spectroscopy of Gold Nanoparticles  

NASA Astrophysics Data System (ADS)

Inner shell transitions, such as 1s-2p, in heavy elements can absorb or produce hard X-rays, and hence are widely used in nanoparticles. Bio-medical research for cancer treatment has been using heavy element nanoparticles, embeded in malignant tumor, for efficient absorption of irradiated X-rays and leading emission of hard X-rays and energetic electrons to kill the surrounding cells. Ejection of a 1s electron during ionization of the element by absorption of a X-ray photon initiates the Auger cascades of emission of photons and electrons. We have investigated gold nanoparticles for the optimal energy range, below the K-edge (1s) ionization threshold, that corresponds to resonant absorption of X-rays with large attenuation coefficients, orders of magnitude higher over the background as well as to that at K-edge threshold. We applied these attenuation coefficients in Monte Carlo simulation to study the intensities of emission of photons and electrons by Auger cascades. The numerical experiments were carried out in a phantom of water cube with a thin layer, 0.1mm/g, of gold nanoparticles 10 cm inside from the surface using the well-known code Geant4. We will present results on photon and electron emission spectra from passing monochromatic X-ray beams at 67 keV, which is the resonant energy for resonant K_{?} lines, at 82 keV, the K-shell ionization threshold, and at 2 MeV where the resonant effect is non-existent. Our findings show a high peak in the gold nanoparticle absorption curve indicating complete absorption of radiation within the gold layer. The photon and electron emission spectra show resonant features. Acknowledgement: Partially supported by a Large Interdisciplinary Grant award of the Ohio State University and NASA APRA program (SNN). The computational work was carried out on the Cray X1 and Itanium 4 cluster at the Ohio Supercomputer Center, Columbus Ohio. "Resonant X-ray Irradiation of High-Z Nanoparticles For Cancer Theranostics" (refereed presentation), A Pradhan, S Nahar, M Montenegro, C Sur, M Mrozik, R Pitzer, E Silver, Y Yu, 50th Annual Meeting of the American Association of Physicists in Medicine in Houston, Texas, July 27 - 31, 2008

Nahar, Sultana N.; Montenegro, M.; Pradhan, A. K.; Pitzer, R.

2009-06-01

44

Temperature dependent soft x-ray absorption spectroscopy of liquids.  

PubMed

A novel sample holder is introduced which allows for temperature dependent soft x-ray absorption spectroscopy of liquids in transmission mode. The setup is based on sample cells with x-ray transmissive silicon nitride windows. A cooling circuit allows for temperature regulation of the sample liquid between -10?°C and +50?°C. The setup enables to record soft x-ray absorption spectra of liquids in transmission mode with a temperature resolution of 0.5?K and better. Reliability and reproducibility of the spectra are demonstrated by investigating the characteristic temperature-induced changes in the oxygen K-edge x-ray absorption spectrum of liquid water. These are compared to the corresponding changes in the oxygen K-edge spectra from x-ray Raman scattering. PMID:25362366

Meibohm, Jan; Schreck, Simon; Wernet, Philippe

2014-10-01

45

Soft X-Ray and Vacuum Ultraviolet Based Spectroscopy of the Actinides  

SciTech Connect

The subjects of discussion included: VUV photoelectron spectroscopy, X-ray photoelectron spectroscopy, Synchrotron-radiation-based photoelectron spectroscopy, Soft x-ray absorption spectroscopy, Soft x-ray emission spectroscopy, Inverse photoelectron spectroscopy, Bremstrahlung Isochromat Spectroscopy, Low energy IPES, Resonant inverse photoelectron spectroscopy.

Tobin, J G

2011-03-17

46

X-Ray Spectroscopy Using Low Temperature Detectors  

NASA Technical Reports Server (NTRS)

After several decades of development, a significant amount of the effort in low temperature detectors (LTDs) is concentrated on deploying real-world experiments. This has resulted from a great deal of basic detector physics performed by several generations of students, post-docs, and researchers. One of the most fruitful applications of LTDs is in non-dispersive x-ray spectroscopy. LTD x-ray spectrometers are broadband, efficient, moderately high-resolution, and can handle moderately high count rates. However, they require significantly more power, mass, and infrastructure compared to traditional solid state x-ray spectrometers, and cannot achieve, at least at low energies, the resolving powers achieved with dispersive spectrometers. In several fields, however, LTDs have or will make a significant contribution. In this review, we will discuss x-ray spectroscopy in general, the fields of science where LTDs are making a significant impact, and some of the current and near-term LTD spectrometers.

Porter, Frederick

2011-01-01

47

Carbon X-ray Raman Spectroscopy of PAHs and Asphaltenes  

Microsoft Academic Search

The application of x-ray Raman spectroscopy (XRRS) to gain information about the local structure of carbonaceous systems including\\u000a complex polycyclic aromatic hydrocarbons (PAHs) and asphaltenes is discussed in this chapter. This novel approach to directly\\u000a probe carbon type in such systems has become practical only recently with the help of intense new synchrotron x-ray sources\\u000a and innovation in spectrograph design.

Uwe Bergmann; Oliver C. Mullins

48

Femtosecond x-ray absorption spectroscopy with hard x-ray free electron laser  

SciTech Connect

We have developed a method of dispersive x-ray absorption spectroscopy with a hard x-ray free electron laser (XFEL), generated by a self-amplified spontaneous emission (SASE) mechanism. A transmission grating was utilized for splitting SASE-XFEL light, which has a relatively large bandwidth (?E/E ? 5 × 10{sup ?3}), into several branches. Two primary split beams were introduced into a dispersive spectrometer for measuring signal and reference spectra simultaneously. After normalization, we obtained a Zn K-edge absorption spectrum with a photon-energy range of 210 eV, which is in excellent agreement with that measured by a conventional wavelength-scanning method. From the analysis of the difference spectra, the noise ratio was evaluated to be ?3 × 10{sup ?3}, which is sufficiently small to trace minute changes in transient spectra induced by an ultrafast optical laser. This scheme enables us to perform single-shot, high-accuracy x-ray absorption spectroscopy with femtosecond time resolution.

Katayama, Tetsuo; Togashi, Tadashi; Tono, Kensuke; Kameshima, Takashi [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan)] [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Inubushi, Yuichi; Sato, Takahiro; Hatsui, Takaki; Yabashi, Makina [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan)] [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Obara, Yuki; Misawa, Kazuhiko [Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan)] [Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan); Bhattacharya, Atanu; Kurahashi, Naoya [Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502 (Japan)] [Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502 (Japan); Ogi, Yoshihiro [Molecular Reaction Dynamics Research Team, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako 351-0198 (Japan)] [Molecular Reaction Dynamics Research Team, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako 351-0198 (Japan); Suzuki, Toshinori [Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502 (Japan) [Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502 (Japan); Molecular Reaction Dynamics Research Team, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako 351-0198 (Japan)

2013-09-23

49

X-ray induced damage in DNA monitored by X-ray photoelectron spectroscopy  

SciTech Connect

In this work, the chemical changes in calf thymus DNA samples were analyzed by X-ray photoelectron spectroscopy (XPS). The DNA samples were irradiated for over 5 h and spectra were taken repeatedly every 30 min. In this approach the X-ray beam both damages and probes the samples. In most cases, XPS spectra have complex shapes due to contributions of C, N, and O atoms bonded at several different sites. We show that from a comparative analysis of the modification in XPS line shapes of the C 1s, O 1s, N 1s, and P 2p peaks, one can gain insight into a number of reaction pathways leading to radiation damage to DNA.

Ptasinska, Sylwia; Stypczynska, Agnieszka; Nixon, Tony; Mason, Nigel J. [Department of Physics and Astronomy, Open University, Walton Hall, Milton Keynes, MK7 6AA (United Kingdom); Klyachko, Dimitri V.; Sanche, Leon [Groupe en Sciences des Radiations, Departement de Medecine Nucleaire et de Radiobiology, Faculte de Medecine, Universite de Sherbrooke, Sherbrooke, J1H 5N4 Quebec (Canada)

2008-08-14

50

X-ray Photoelectron Spectroscopy Database (Version 4.1)  

National Institute of Standards and Technology Data Gateway

SRD 20 X-ray Photoelectron Spectroscopy Database (Version 4.1) (Web, free access)   The NIST XPS Database gives access to energies of many photoelectron and Auger-electron spectral lines. The database contains over 22,000 line positions, chemical shifts, doublet splittings, and energy separations of photoelectron and Auger-electron lines.

51

X-RAY SPECTROSCOPY OF RARE-EARTH ELEMENTS  

Microsoft Academic Search

Four applications of x-ray spectroscopy to rare earth research are ; discussed. A method was developed for the determination of rare earth elements ; in fractions obtained from bastnaesite and euxenite ones. Yttrium, thorium, and ; the fourteen rare earth elements may be analyzed in complex mixtures of various ; concentrations. A rapid method for the qualitative and quantitative analysis

F. W. Lytle; K. R. Stever; H. H. Heady

1958-01-01

52

Transient x-ray absorption spectroscopy of hydrated halogen atom  

E-print Network

Time-resolved x-ray absorption spectroscopy has been used to observe the transient species generated by one-photon detachment of an electron from aqueous bromide. The K-edge spectrum of the short-lived Br(0) atom exhibits a resonant 1s-4p transition...

Elles, Christopher G.; Shkrob, Ilya A.; Crowell, Robert A.; Arms, Dohn A.; Landahl, Eric C.

2008-02-11

53

Local lattice distortions probed by X-ray absorption spectroscopy  

Microsoft Academic Search

In the last decade, we have witnessed a number of cases where a small deviation from crystallographic or average structure strongly modifies electron states, physical and chemical properties and functions. The crucial role of breaking local symmetry, stabilizing a certain electronic (spin-state) configuration, has been recognized recently, by x-ray absorption spectroscopy (XAS). In biological systems such as haeme proteins, having

H. Oyanagi

2001-01-01

54

Improved x-ray spectroscopy with room temperature CZT detectors.  

PubMed

Compact, room temperature x-ray spectroscopy detectors are of interest in many areas including diagnostic x-ray imaging, radiation protection and dosimetry. Room temperature cadmium zinc telluride (CZT) semiconductor detectors are promising candidates for these applications. One of the major problems for CZT detectors is low-energy tailing of the energy spectrum due to hole trapping. Spectral post-correction methods to correct the tailing effect do not work well for a number of reasons; thus it is advisable to eliminate the hole trapping effect in CZT using physical methods rather than correcting an already deteriorated energy spectrum. One method is using a CZT detector with an electrode configuration which modifies the electric field in the CZT volume to decrease low-energy tailing. Another method is to irradiate the CZT surface at a tilted angle, which modifies depth of interaction to decrease low-energy tailing. Neither method alone, however, eliminates the tailing effect. In this work, we have investigated the combination of modified electric field and tilted angle irradiation in a single detector to further decrease spectral tailing. A planar CZT detector with 10 × 10 × 3 mm³ size and CZT detector with 5 × 5 × 5 mm³ size and cap-shaped electrode were used in this study. The cap-shaped electrode (referred to as CAPture technology) modifies the electric field distribution in the CZT volume and decreases the spectral tailing effect. The detectors were investigated at 90° (normal) and 30° (tilted angle) irradiation modes. Two isotope sources with 59.6 and 122 keV photon energies were used for gamma-ray spectroscopy experiments. X-ray spectroscopy was performed using collimated beams at 60, 80 and 120 kVp tube voltages, in both normal and tilted angle irradiation. Measured x-ray spectra were corrected for K x-ray escape fractions that were calculated using Monte Carlo methods. The x-ray spectra measured with tilted angle CAPture detector at 60, 80 and 120 kVp tube voltages were compared to corresponding theoretical spectra. The low-energy tailing was nearly completely eliminated from 59.6 and 122 keV isotope spectra, and 60, 80 and 120 kVp x-ray spectra, when CAPture detector was used with 30° tilted angle irradiation. It is concluded that using a CZT detector with modified electric field in tilted angle configuration resolves problem of the tailing effect in CZT detectors, opening promising possibilities in gamma-ray and x-ray spectroscopy applications. PMID:21841213

Fritz, Shannon G; Shikhaliev, Polad M; Matthews, Kenneth L

2011-09-01

55

Characterization of LCLS X-Ray Pulses Using Atomic Spectroscopy  

NASA Astrophysics Data System (ADS)

The first experiments at the LCLS succeeded in not only revealing the nature of interactions between intense x-rays and atomic or molecular systems, but also properties of the LCLS x-ray pulses. Our spectroscopic measurements of the interaction with neon atoms have revealed information on x-ray photon energy, the pulse duration, and the focal spot size. When analyzed in conjunction with diagnostics of the electron beam, the data yields information on the photon energy bandwidth and shot-to-shot photon energy jitter. The intrinsic bandwidth of the LCLS pulse is strongly dependent on the LINAC tuning, thus high resolution photoelectron spectroscopy is a valuable diagnostic that can be implemented in a pass through configuration.

March, A. M.; Young, L.; Southworth, S. H.; Kanter, E. P.; Krässig, B.; Santra, R.; Li, Y.; Pratt, S. T.; Berrah, N.; Höner, M.; Fang, L.; Cryan, J. P.; Glownia, J. M.; Reis, D. A.; Ghimire, S.; Bucksbaum, P.; Dimauro, L.; Doumy, G.; Roedig, C.; Bozek, J. D.; Bostedt, C.; Messerschmidt, M.

2010-03-01

56

Simultaneous surface plasmon resonance and x-ray absorption spectroscopy  

SciTech Connect

We present an experimental setup for the simultaneous measurement of surface plasmon resonance (SPR) and x-ray absorption spectroscopy (XAS) on metallic thin films at a synchrotron beamline. The system allows measuring in situ and in real time the effect of x-ray irradiation on the SPR curves to explore the interaction of x-rays with matter. It is also possible to record XAS spectra while exciting SPR in order to study changes in the films induced by the excitation of surface plasmons. Combined experiments recording simultaneously SPR and XAS curves while scanning different parameters can be also carried out. The relative variations in the SPR and XAS spectra that can be detected with this setup range from 10{sup -3} to 10{sup -5}, depending on the particular experiment.

Serrano, A. [Instituto de Ceramica y Vidrio (ICV-CSIC), Cantoblanco, 28049 Madrid (Spain); Departamento de Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid (Spain); Rodriguez de la Fuente, O. [Departamento de Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid (Spain); Collado, V.; Rubio-Zuazo, J.; Castro, G. R. [SpLine, Spanish CRG Beamline at the ESRF, F-38043 Grenoble, Cedex 09, France and Instituto de Ciencia de Materiales de Madrid, (ICMM-CSIC), Cantoblanco, 28049 Madrid (Spain); Monton, C. [Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, California 92093 (United States); Garcia, M. A. [Instituto de Ceramica y Vidrio (ICV-CSIC), Cantoblanco, 28049 Madrid (Spain); IMDEA Nanociencia, Cantoblanco, 28049 Madrid (Spain)

2012-08-15

57

An upgraded x-ray spectroscopy diagnostic on MST  

SciTech Connect

An upgraded x-ray spectroscopy diagnostic is used to measure the distribution of fast electrons in MST and to determine Z{sub eff} and the particle diffusion coefficient D{sub r}. A radial array of 12 CdZnTe hard-x-ray detectors measures 10-150 keV Bremsstrahlung from fast electrons, a signature of reduced stochasticity and improved confinement in the plasma. A new Si soft-x-ray detector measures 2-10 keV Bremsstrahlung from thermal and fast electrons. The shaped output pulses from both detector types are digitized and the resulting waveforms are fit with Gaussians to resolve pileup and provide good time and energy resolution. Lead apertures prevent detector saturation and provide a well-known etendue, while lead shielding prevents pickup from stray x-rays. New Be vacuum windows transmit >2 keV x-rays, and additional Al and Be filters are sometimes used to reduce low energy flux for better resolution at higher energies. Measured spectra are compared to those predicted by the Fokker-Planck code CQL3D to deduce Z{sub eff} and D{sub r}.

Clayton, D. J.; Almagri, A. F.; Burke, D. R.; Forest, C. B.; Goetz, J. A.; Kaufman, M. C.; O'Connell, R. [Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

2010-10-15

58

High-resolution X-ray spectroscopy of Theta Car  

E-print Network

Context : The peculiar hot star Theta Car in the open cluster IC2602 is a blue straggler as well as a single-line binary of short period (2.2d). Aims : Its high-energy properties are not well known, though X-rays can provide useful constraints on the energetic processes at work in binaries as well as in peculiar, single objects. Methods : We present the analysis of a 50ks exposure taken with the XMM-Newton observatory. It provides medium as well as high-resolution spectroscopy. Results : Our high-resolution spectroscopy analysis reveals a very soft spectrum with multiple temperature components (1--6MK) and an X-ray flux slightly below the `canonical' value (log[L_X(0.1-10.)/L_{BOL}] ~ -7). The X-ray lines appear surprisingly narrow and unshifted, reminiscent of those of beta Cru and tau Sco. Their relative intensities confirm the anomalous abundances detected in the optical domain (C strongly depleted, N strongly enriched, O slightly depleted). In addition, the X-ray data favor a slight depletion in neon and iron, but they are less conclusive for the magnesium abundance (solar-like?). While no significant changes occur during the XMM-Newton observation, variability in the X-ray domain is detected on the long-term range. The formation radius of the X-ray emission is loosely constrained to <5 R_sol, which allows for a range of models (wind-shock, corona, magnetic confinement,...) though not all of them can be reconciled with the softness of the spectrum and the narrowness of the lines.

Yael Naze; Gregor Rauw

2008-08-25

59

High-Resolution Kaonic-Atom X-ray Spectroscopy with Transition-Edge-Sensor Microcalorimeters  

NASA Astrophysics Data System (ADS)

We are preparing for an ultra-high resolution X-ray spectroscopy of kaonic atoms using an X-ray spectrometer based on an array of superconducting transition-edge-sensor microcalorimeters developed by NIST. The instrument has excellent energy resolutions of 2-3 eV (FWHM) at 6 keV and a large collecting area of about 20 mm. This will open new door to investigate kaon-nucleus strong interaction and provide new accurate charged-kaon mass value.

Okada, S.; Bennett, D. A.; Doriese, W. B.; Fowler, J. W.; Irwin, K. D.; Ishimoto, S.; Sato, M.; Schmidt, D. R.; Swetz, D. S.; Tatsuno, H.; Ullom, J. N.; Yamada, S.

2014-09-01

60

Fast X-Ray Spectroscopy Using Si-Drift Detectors  

Microsoft Academic Search

Fast counting applications with energy discrimination like X-ray absorption spectroscopy require an energy resolution of some hundred eV even at highest count rates and ask for small form factors. The development, fabrication and test of a small number of 7-cell Si-drift detectors have been successfully finished at DESY fitting these claims with a good cost-versus-performance tradeoff. The monolithic 7-cell sensor

Karsten Hansen; Christian Reckleben; Inge Diehl; Helmut Klar; Edmund Welter

2009-01-01

61

X-ray spectroscopy of neutron star low-mass X-ray binaries  

E-print Network

In this thesis, I present work spanning a variety of topics relating to neutron star lowmass X-ray binaries (LMXBs) and utilize spectral information from X-ray observations to further our understanding of these sources. ...

Krauss, Miriam Ilana

2007-01-01

62

Probing deeper by hard x-ray photoelectron spectroscopy  

SciTech Connect

We report an hard x-ray photoelectron spectroscopy method combining high excitation energy (15?keV) and improved modelling of the core-level energy loss features. It provides depth distribution of deeply buried layers with very high sensitivity. We show that a conventional approach relying on intensities of the core-level peaks is unreliable due to intense plasmon losses. We reliably determine the depth distribution of 1 ML La in a high-?/metal gate stack capped with 50?nm a-Si. The method extends the sensitivity of photoelectron spectroscopy to depths beyond 50?nm.

Risterucci, P.; Renault, O., E-mail: olivier.renault@cea.fr; Martinez, E.; Delaye, V. [CEA, LETI, MINATEC Campus, 38054 Grenoble Cedex 09 (France); Detlefs, B. [CEA, LETI, MINATEC Campus, 38054 Grenoble Cedex 09 (France); European Synchrotron Radiation Facility, 6 rue Jules Horowitz, F-38043 Grenoble (France); Zegenhagen, J. [European Synchrotron Radiation Facility, 6 rue Jules Horowitz, F-38043 Grenoble (France); Gaumer, C. [STMicroelectronics, 850 rue Jean Monnet, 38926 Crolles (France); Grenet, G. [Institut des Nanotechnologies de Lyon (INL), UMR CNRS 5270, Ecole Centrale de Lyon, 36, avenue Guy de Collongue 69 134 Ecully Cedex (France); Tougaard, S. [Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, DK-5230 Odense M (Denmark)

2014-02-03

63

Pushing the Boundaries of Suborbital Soft X-ray Spectroscopy  

NASA Astrophysics Data System (ADS)

There are two primary objectives for this investigation. First, we propose to launch a preexisting payload to perform scientific investigations. Second, we propose to build a new payload which will integrate and demonstrate key technologies vital to future X-ray observatories. These efforts will train graduate students and prepare junior researchers to be major contributors to the next suite of NASA missions. We propose to increase the ability of gratings to obtain high resolution at energies below 1 keV. The concept that will be developed in this proposed investigation will be capable of meeting the requirements of future X-ray observatories. In addition, the design could be utilized effectively on smaller, Explorer class missions as pathfinders to the larger observatories while providing important scientific insights along the way. For this investigation, we propose to fly two separate, but related, rocket payloads. The first payload, christened OGRESS, has already been constructed and successfully flown three times. OGRESS is optimized to observe diffuse X-ray sources with a wire-grid collimating optic, parallel groove sinusoidal gratings, and Gaseous Electron Multiplier (GEM) detectors and is capable of attaining high resolution of E/dE ~ 25-80 in the 1/4 keV band. OGRESS will take high resolution spectra of the Vela Supernova Remnant (SNR) in the 1/4 keV band. This flight will provide the highest resolution spectra yet taken of Vela in this band and will produce a PhD thesis. The second payload, OGRE, will demonstrate key technologies necessary for the next X-ray observatory and provide even higher resolution of E/dE ~ 1000-2000 between 0.2 1.0 keV. To improve upon the resolution of OGRESS, OGRE will integrate several key technologies which have already been developed in a laboratory setting, but have not been flight proven. OGRE will use a modified Wolter telescope made from slumped glass to provide a smaller focus and increase throughput. Slumped glass optics are planned for every future large X-ray mission and flight-proving the design is extremely important. The gratings will be radially grooved and blazed to reduce grating aberrations and to focus the spectrum to one side of zero-order. Gratings of this type have been well developed by the IXO Off- Plane X-ray Grating Spectrometer concept study, but have not been flight proven. The spectrum will be focused onto high spatial resolution CCD detectors. OGRE will draw heavily from the heritage gained from OGRESS. OGRE will observe Capella. Due to its high flux and spectral line density, Capella is an ideal target for showcasing the resolution capabilities of our instrument. As an important calibration target, our improved resolution measurements will be extremely helpful for many future X-ray observations. OGRESS has already provided three thesis projects for past graduate students. The upgrades and flights proposed here will produce at least two more PhD theses. This program in hands-on training of young scientists in the techniques of instrumental X-ray astronomy has proven very successful over nearly three decades, leading to high rates of launch, publication, graduation, and flight qualification of instrumental PI's. It will also provide full experiment cycle experience - design, fabrication, tolerancing, assembly, flight-qualification, calibration, integration, launch, and data analysis - with reflection gratings, GEM and CCD detectors, and other technologies suitable for adaptation to NASA's major missions. The University of Iowa and University of Colorado programs in suborbital X-ray astronomy represent an exciting mix of compelling science, cutting- edge technology development, and training of young scientists.

McEntaffer, Randall

64

Operando X-ray absorption and infrared fuel cell spectroscopy  

SciTech Connect

A polymer electrolyte fuel cell enables operando X-ray absorption and infrared spectroscopy of the membrane electrode assembly catalytic layer with flowing fuel and air streams at controlled temperature. Time-dependent X-ray absorption near edge structure spectra of the Pt and Ni edge of Pt based catalysts of an air-breathing cathode show that catalyst restructuring, after a potential step, has time constants from minutes to hours. The infrared Stark tuning plots of CO adsorbed on Pt at 100, 200, 300 and 400 mV vs. hydrogen reference electrode were obtained. The Stark tuning plots of CO adsorbed at 400 mV exhibit a precipitous drop in frequency coincident with the adsorption potential. The turn-down potential decreases relative to the adsorption potential and is approximately constant after 300 mV. These Stark tuning characteristics are attributed to potential dependent adsorption site selection by CO and competitive adsorption processes.

Lewis, Emily A.; Kendrick, Ian; Jia, Qingying; Grice, Corey; Segre, Carlo U.; Smotkin, Eugene S. (NuVant); (IIT); (NEU)

2011-11-17

65

X-ray Absorption Spectroscopy: a powerful tool for the investigation  

E-print Network

X-ray Absorption Spectroscopy: a powerful tool for the investigation of the role of metals is to illustrate the potentialities of X-ray Absorption Spectroscopy (XAS) to investigate structural properties Protein and Zinc ions 2 Introduction to the X-ray Absorption Spec- troscopy XAS uses Synchrotron Radiation

Morante, Silvia

66

X-ray photon correlation spectroscopy under flow.  

PubMed

X-ray photon correlation spectroscopy was used to probe the diffusive dynamics of colloidal particles in a shear flow. Combining X-ray techniques with microfluidics is an experimental strategy that reduces the risk of X-ray-induced beam damage and also allows time-resolved studies of processes taking place in flow cells. The experimental results and theoretical predictions presented here show that in the low shear limit for a ;transverse flow' scattering geometry (scattering wavevector q perpendicular to the direction of flow) the measured relaxation times are independent of the flow rate and determined only by the diffusive motion of the particles. This is not generally valid and, in particular, for a 'longitudinal flow' (q parallel flow) scattering geometry the relaxation times are strongly affected by the flow-induced motion of the particles. The results here show that the Brownian diffusion of colloidal particles can be measured in a flowing sample and that, up to flux limitations, the experimental conditions under which this is possible are easier to achieve at higher values of q. PMID:18552431

Fluerasu, Andrei; Moussaïd, Abdellatif; Falus, Péter; Gleyzolle, Henri; Madsen, Anders

2008-07-01

67

X-ray absorption spectroscopy of liquid surfaces  

NASA Astrophysics Data System (ADS)

By combining synchrotron-based x-ray spectroscopy with liquid microjets, we have developed new techniques for the investigation of the geometric and electronic structure of volatile liquid surfaces. An endstation has been constructed to allow windowless introduction of volatile liquids to the UHV environment of synchrotron soft x-ray beamlines (Advanced Light Source, LBL). The high vacuum (10-5 torr) obtained in the photon-microjet interaction volume, allows the use of standard surface science charged particle detection to analyze the ions and electrons produced via core-level excitation. The difference in escape depths of ions and electrons from condensed phase samples yields convenient surface-bulk contrast via the total ion (TIY) (˜5 A) versus the total electron (TEY) (˜20--50 A) yields. This contrast has been exploited in an effort to understand the surface hydrogen bond structure of liquid water and methanol. The temperature profile of these microjets has been characterized under the high vacuum conditions essential for measuring x-ray absorption "action" spectra. We find only moderate cooling of larger diameter (>10 microns) microjets, while smaller jets undergo rapid evaporation, yielding liquid water temperatures as low as -36°C. Extended x-ray absorption fine structure (EXAFS) is a common technique that is an ideal probe of local "liquid structure" (near neighbor distance, coordination numbers, etc.). Moreover, the EXAFS TIY and TEY "action" spectra allow the direct comparison of surface and bulk liquid properties. In both liquid water and methanol, a sizable surface relaxation of the intermolecular O-O distance is observed. On average water molecules at the liquid surface are ˜6% further apart than their bulk counterparts. Near edge x-ray absorption fine structure (NEXAFS) has been shown to be extremely sensitive to not only to the formation of hydrogen bonds, but more importantly to the detailed nature (acceptor vs. donor) of such bonds. TIY NEXAFS spectra combined with DFT analysis has yielded evidence for at least two different species at the liquid water surface. The sharp spectral structure in the TIY signal provides a clear fingerprint for "acceptor-only" H2O molecules at the liquid water interface. Analysis of mass-selected NEXAFS spectra provide corroborating evidence for surface single donor molecules that have been previously identified by SFG spectroscopy. (Abstract shortened by UMI.)

Wilson, Kevin Roger

68

X-Ray Absorption Spectroscopy of Uranium Dioxide  

SciTech Connect

After the CMMD Seminar by Sung Woo Yu on the subject of the x-ray spectroscopy of UO2, there arose some questions concerning the XAS of UO2. These questions can be distilled down to these three issues: (1) The validity of the data; (2) The monchromator energy calibration; and (3) The validity of XAS component of the figure shown. The following will be shown: (1) The data is valid; (2) It is possible to calibrate the monchromator; and (3) The XAS component of the above picture is correct. The remainder of this document is in three sections, corresponding to these three issues.

Tobin, J G

2010-12-10

69

The Future of X-ray Spectroscopy of Galactic Black Hole Binaries  

E-print Network

There are four major X-ray satellites currently in operation, with two more shortly to follow, and several very ambitious observatories in various stages of planning. This very rich period of X-ray observation is leading to great advances in our understanding of the accretion flow onto the black hole, although we are quickly learning (or perhaps better put, remembering) exactly how complicated this flow can be. This review was meant to assess future prospects for X-ray spectroscopy of black hole binaries; however, I first look backward to the observations and theories that helped us arrive at our current `paradigm'. I then discuss current and near-future spectroscopic studies, which increasingly (and very fruitfully) treat X-ray spectroscopy as part of a larger, intimately connected picture along with radio, optical, and gamma-ray spectroscopy. Equally importantly, and in large part thanks to the success of RXTE, there is now a strong realization that spectral-temporal correlations, even across wavelength bands, are crucial to our understanding of the physics of these systems. Going forward, we are well-poised to continue to advance our knowledge via X-ray spectroscopy, both with existing satellites that have a long lifetime ahead of them, and with the next generation of instruments. If there is any `hole' in this bright future, it is the potential loss of RXTE, with no designated follow-up mission. Studies of multi-wavelength spectral-temporal correlations will become more difficult due to the loss of two important attributes of RXTE: its fast timing capabilities and its extremely flexible scheduling which has made many of these studies possible.

Michael A. Nowak

2003-12-18

70

X-ray absorption spectroscopy: EXAFS (Extended X-ray Absorption Fine Structure) and XANES (X-ray Absorption Near Edge Structure)  

SciTech Connect

The x-ray absorption spectroscopy (XAS) had been an essential tool to gather spectroscopic information about atomic energy level structure in the early decades of this century. It has also played an important role in the discovery and systematization of rare-earth elements. The discovery of synchrotron radiation in 1952, and later the availability of broadly tunable synchrotron based x-ray sources have revitalized this technique since the 1970's. The correct interpretation of the oscillatory structure in the x-ray absorption cross-section above the absorption edge by Sayers et. al. has transformed XAS from a spectroscopic tool to a structural technique. EXAFS (Extended X-ray Absorption Fine Structure) yields information about the interatomic distances, near neighbor coordination numbers, and lattice dynamics. An excellent description of the principles and data analysis techniques of EXAFS is given by Teo. XANES (X-ray Absorption Near Edge Structure), on the other hand, gives information about the valence state, energy bandwidth and bond angles. Today, there are about 50 experimental stations in various synchrotrons around the world dedicated to collecting x-ray absorption data from the bulk and surfaces of solids and liquids. In this chapter, we will give the basic principles of XAS, explain the information content of essentially two different aspects of the absorption process leading to EXAFS and XANES, and discuss the source and samples limitations.

Alp, E.E.; Mini, S.M.; Ramanathan, M.

1990-04-01

71

X-ray-induced photo-chemistry and X-ray absorption spectroscopy of biological samples  

PubMed Central

As synchrotron light sources and optics deliver greater photon flux on samples, X-ray-induced photo-chemistry is increasingly encountered in X-ray absorption spectroscopy (XAS) experiments. The resulting problems are particularly pronounced for biological XAS experiments. This is because biological samples are very often quite dilute and therefore require signal averaging to achieve adequate signal-to-noise ratios, with correspondingly greater exposures to the X-ray beam. This paper reviews the origins of photo-reduction and photo-oxidation, the impact that they can have on active site structure, and the methods that can be used to provide relief from X-ray-induced photo-chemical artifacts. PMID:23093745

George, Graham N.; Pickering, Ingrid J.; Pushie, M. Jake; Nienaber, Kurt; Hackett, Mark J.; Ascone, Isabella; Hedman, Britt; Hodgson, Keith O.; Aitken, Jade B.; Levina, Aviva; Glover, Christopher; Lay, Peter A.

2012-01-01

72

Past, Present and Future Prospects of High Resolution X-ray Spectroscopy of Clusters of Galaxies  

NASA Astrophysics Data System (ADS)

The first high resolution X-ray spectra of clusters of galaxies have revolutionised the study of cooling flows. These excellent data have been obtained with an instrument (the RGS of XMM-Newton) that has not been optimised for spectroscopy of extended sources. I will present a few recent examples of what can be achieved further with the RGS in combination with the imaging EPIC cameras for the study of chemical enrichment of clusters. The new generation of high spectral resolution imaging TES arrays that is currently being studied for a variety of possible future X-ray observatories (such as XEUS, Constellation-X, DIOS, Estremo and NEW) offer exciting new opportunities to study the physics of clusters of galaxies. I will present examples of how these new instruments will achieve this.

Kaastra, J.

2006-08-01

73

Hubbard Model Approach to X-ray Spectroscopy  

NASA Astrophysics Data System (ADS)

We have implemented a Hubbard model based first-principles approach for real-space calculations of x-ray spectroscopy, which allows one to study excited state electronic structure of correlated systems. Theoretical understanding of many electronic features in d and f electron systems remains beyond the scope of conventional density functional theory (DFT). In this work our main effort is to go beyond the local density approximation (LDA) by incorporating the Hubbard model within the real-space multiple-scattering Green's function (RSGF) formalism. Historically, the first theoretical description of correlated systems was published by Sir Neville Mott and others in 1937. They realized that the insulating gap and antiferromagnetism in the transition metal oxides are mainly caused by the strong on-site Coulomb interaction of the localized unfilled 3d orbitals. Even with the recent progress of first principles methods (e.g. DFT) and model Hamiltonian approaches (e.g., Hubbard-Anderson model), the electronic description of many of these systems remains a non-trivial combination of both. X-ray absorption near edge spectra (XANES) and x-ray emission spectra (XES) are very powerful spectroscopic probes for many electronic features near Fermi energy (EF), which are caused by the on-site Coulomb interaction of localized electrons. In this work we focus on three different cases of many-body effects due to the interaction of localized d electrons. Here, for the first time, we have applied the Hubbard model in the real-space multiple scattering (RSGF) formalism for the calculation of x-ray spectra of Mott insulators (e.g., NiO and MnO). Secondly, we have implemented in our RSGF approach a doping dependent self-energy that was constructed from a single-band Hubbard model for the over doped high-T c cuprate La2-xSrxCuO4. Finally our RSGF calculation of XANES is calculated with the spectral function from Lee and Hedin's charge transfer satellite model. For all these cases our calculated x-ray spectra yield reasonable agreement with experiment. The above work has been implemented as an extension into the FEFF9 code, and we have also included notes for the new and modified key features of this development. Aside from the x-ray spectroscopy of correlated systems, we also present our calculation of the ground state local electronic structure of DNA nucleotides on graphene, and the transmission currents through graphene nanopores. Our calculation and analysis provide theoretical guidelines for developing DNA sequencing techniques using scanning tunneling spectroscopy (STS) and nanopore experiment. Evolved as a secondary focus of this thesis, we have added an additional chapter discussing our calculation of DNA-graphene hybrids.

Ahmed, Towfiq

74

CUBIC - A non-dispersive Diffuse X-ray Background spectrometer. [Cosmic Unresolved X-ray Background Instrument  

NASA Technical Reports Server (NTRS)

The Cosmic Unresolved X-ray Background Instrument using CCDs (CUBIC) is designed to obtain spectral observations of the Diffuse X-ray Background (DXRB) with moderate spectral resolution over the energy range 0.2-10 keV, using mechanically-collimated CCDs. At this time, it is the only planned satellite payload devoted to the study of the spectrum of the DXRB. Over the anticipated 3 year lifetime of the satellite, CUBIC will be able to study up to 50 percent of the sky with 5 x 5 deg spatial resolution for the subkilovolt Galactic diffuse background, and with 10 x 10 deg spatial resolution for the extragalactic diffuse background above 2 keV. CUBIC will obtain high quality nondispersive spectra of soft X-ray emission from the interstellar medium, supernova remnants, and some bright sources, and will make a sensitive seach for line emission or other features in the extragalactic cosmic X-ray background from 2-10 keV.

Burrows, David N.; Skinner, Mark A.; Antunes, Alexander J. D.; Catalano, Mark A.; Cocklin, Eric J.; Engel, Leland G.; Entingh, Timothy J.; Garmire, Gordon P.; Green, Roland; Kelly, Douglas A.

1992-01-01

75

X-ray Spectroscopy of O Supergiant Winds: Shock Physics, Clumping, and Mass-Loss Rates  

E-print Network

X-ray Spectroscopy of O Supergiant Winds: Shock Physics, Clumping, and Mass-Loss Rates David Cohen-ray emission: wind shocks 1. X-ray constraints on the shocked wind plasma 2. X-ray absorption as a mass. Adiabatic shocks Open questions: very dense winds (WR stars); low density winds (B stars); magnetic OB stars

Cohen, David

76

Multianode linear SDDs for high-resolution X-ray spectroscopy  

Microsoft Academic Search

Radiation detectors are used in a variety of fields to sense X-rays and y-rays, visible, UV and IR photons, neutrons or charged particles. With their help, advanced medical diagnostics can be performed (e.g. X-ray radiography, computed tomography, fluoroscopy), material research can undergo a rapid development (e.g. X-ray microanalysis, X-ray diffraction, Mauer spectroscopy and element imaging), space and its evolution (astronomy

J. Sonsky

2002-01-01

77

Electronic Structure of In2O3 from Resonant X-ray Emission Spectroscopy  

SciTech Connect

The valence and conduction band structures of In2O3 have been measured using a combination of valence band x-ray photoemission spectroscopy, O K-edge resonant x-ray emission spectroscopy, and O K-edge x-ray absorption spectroscopy. Excellent agreement is noted between the experimental spectra and O 2p partial density of states calculated within hybrid density functional theory. Our data are consistent with a direct band gap for In2O3.

Piper, L.; DeMasi, A; Cho, S; Smith, K; Fuchs, F; Bechstedt, F; Korber, C; Klein, A; Payne, D; Egdell, R

2009-01-01

78

X-Ray Spectroscopy of the Liquid Water Surface  

NASA Astrophysics Data System (ADS)

We have developed a new experiment for probing molecular details of liquid-vapor interfaces of volatile substances and their solutions under equilibrium conditions. Electronic and geometric structures of interfacial molecules are probed by EXAFS and NEXAFS methods in the soft X-ray region, using the Advanced Light Source, Berkeley, CA. Liquids are introduced into a high vacuum environment through the use of liquid microjets, which have been characterized independently by Raman spectroscopy. Detection of ions and electrons produced by the Auger avalanche probe the bulk and surface regions of the microjet, respectively, as a result of their different escape depths. Our first efforts involved a comparative study of the interfaces of water and methanol, wherein we detailed the first observation of surface relaxation for a liquid. Analysis of EXAFS data yielded a 6distance at the water interface, whereas a 5was found for methanol. NEXAFS measurements, interpreted in terms of density functional theory simulations, indicate a large population of interfacial water molecules having two free OH bonds ("acceptor only molecules"). This complements the "single donor" species identified in sum frequency generation experiments. These results are supported by recent theoretical calculations. For methanol and other simple alcohols, the data indicate that free alkyl groups extend into the vapor part of the interface. Preliminary results for aqueous solutions, as well as for other pure liquids, have been obtained and are presently under analysis. REFERENCES 1. K.R. Wilson, R.D. Schaller, B.S. Rude, T. Catalano, D.T. Co, J.D. Bozek, and R.J. Saykally, "Surface relaxation in liquid water and methanol studied by X-ray absorption spectroscopy," J. Chem. Phys 117,7738(2002). 2. K.R. Wilson, M. Cavalleri, B.S. Rude, R.D. Schaller, A. Nilsson, L.G.M. Pettersson, N. Goldman, T. Catalano, J.D. Bozek, and R.J. Saykally, "Characterization of hydrogen bond acceptor molecules at the water surface using near-edge x-ray absorption fine-structure spectroscopy and density functional theory," J. Phys.: Condens. Matter 14, L221-L226 (2002).

Saykally, Richard

2004-03-01

79

Polytetrafluoroethylene transfer film studied with X-ray photoelectron spectroscopy  

NASA Technical Reports Server (NTRS)

Polytetrafluoroethylene (PTFE) was rubbed against nickel in ultrahigh vacuum at loads up to 3.9 N and speeds up to 94 mm/sec. The transfer film formed on the nickel was analyzed using X-ray phototectron spectroscopy. The film was indistinguishable from bulk PTFE except for the possible presence of a small amount of NiF2. The transfer film was found to be about 1 molecule (0.5 nm) thick under all conditions; but at speeds above 10 mm/sec, there was evidence of bulk transfer in the form of fragments as well. The thickness measurements required a choice among conflicting published values of the inelastic mean free path for electrons in polymers. The values chosen gave internally consistent results.

Wheeler, D. R.

1980-01-01

80

Geophysics Studies With High-Resolution X-ray Spectroscopy  

NASA Astrophysics Data System (ADS)

The introduction of high-resolution (about 1 meV) inelastic x-ray scattering techniques to third generation synchrotron radiation facilities around the world has been very successful. New opportunities for the study of vibrational properties of condensed matter have emerged for research areas like biophysics, geophysics, and nanoscience. In particular, the determination of phonon dispersion relations with momentum-resolved inelastic x-ray scattering (IXS), of vibrational density of states with nuclear resonant inelastic x-ray scattering (NRIXS), and of the determination of valences, spin states, and magnetic ordering with synchrotron Mössbauer spectroscopy (SMS), all under extreme conditions, provided novel and often remarkable results in the scientific area of geophysics [1]. In this contribution, the combination of high-resolution spectroscopy with diamond anvil cell technology and its impact on the geoscientific area will be discussed. Nuclear resonant spectroscopy (NRIXS & SMS) under extreme conditions has become a key method to provide sound velocities and elasticity on iron, iron alloys, and iron oxides, to study valence and high-spin to low-spin transitions in lower mantle minerals, and to investigate magnetic ordering transitions of iron-bearing materials. Its sensitivity in combination with isotope selectivity allowed investigations on materials under high pressures using diamond anvil cells and Laser heating. Examples will illustrate the present and potential future use of nuclear resonant spectroscopy in the Earth and planetary sciences. Momentum resolved IXS detects phonon dispersions and has been applied to Earth materials like iron metal and MgO under high pressure in diamond anvil cells. In single crystals, the dispersion of the acoustic phonons at low energies provides sound velocities for various directions and potentially the elastic tensor of the material. The technical requirements for nuclear resonant andmomentum resolved IXS methods have favored the diamond anvil cell for generation of high pressures. The x-ray energies are typically between 10 keV and 30 keV, and the high-pressure device has to accommodate sufficiently low absorption at those energies. In addition, momentum-resolved IXS needs access to a plane with 20-30 degree opening angle. NRIXS experiments require access to a significant solid angle. These conditions have been more readily met by diamond anvil cells. Here we will discuss the possibility of using a multi-anvil device instead and evaluate the conditions for IXS experiments in such apparatus. This work is supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. References [1] W. Sturhahn and J.M. Jackson, in Advances in High-Pressure Mineralogy, E.Ohtani, ed., Special Paper 421, 157-174 (2007)

Sturhahn, W.

2009-05-01

81

The Constellation-X Spectroscopy X-Ray Telescope  

NASA Technical Reports Server (NTRS)

The status of technology development for the Constellation-X Spectroscopy X-ray Telescope (SXT) mirror is presented. The SXT mirror combines a large (1.6 m) aperture with modest (12 arc sec half power diameter) angular resolution and low mass (750 kg). The overall collecting area, larger than 9,600 square cm at 0.25 keV, requires high throughput, and thus nesting of a substantial number of thin reflectors. A phased development program is underway to develop reflectors, mounting and alignment approaches, and metrology techniques for components and the mirror has a whole. The latest results in all these areas are summarized, along with an overview of results of optical testing of reflector performance.

Petre, Robert; Content, David; Lehan, John; O'Dell, Stephen; Owens, Scott; Podgorsky, William; Stewart, Jeff; Zhang, William

2004-01-01

82

Ultrasoft x-ray spectroscopy using multilayer mirrors on TCV  

NASA Astrophysics Data System (ADS)

The TCV tokamak is equipped with a four-channel ultrasoft x-ray monochromator allowing low resolution (lgr/Dgrlgr ~ 30) measurements in the energy range 200-800 eV. Its main purpose is to simultaneously monitor emission from four of the main Kagr resonance lines of highly ionized light impurities such as boron, carbon, nitrogen and oxygen. Wavelength selectivity is achieved using synthetic multilayer mirrors having 30-40 alternate layers with layer periods in the range 3-7 nm, depending on the design wavelength range. Recently the instrument was modified for measuring the radial profiles of Kagr and Lyman-agr lines from He-like and H-like intrinsic carbon impurities to allow estimates of impurity diffusivities by comparisons with simulations using the impurity transport code STRAHL.

Piffl, V.; Weisen, H.; Zabolotsky, A.; TCV Team

2004-11-01

83

Synchrotron Radiation X-Ray Spectroscopy for Investigations of Intracellular Metallointercalators: X-Ray Fluorescence Imaging and X-Ray Absorption Spectroscopy  

NASA Astrophysics Data System (ADS)

In an effort to determine the therapeutic feasibility of DNA metallointercalators as potential anticancer drugs it is important to confirm that they are capable of targeting DNA in cancer cells or tumours - as is the intended purpose of their design. Microprobe synchrotron radiation X-ray fluorescence (micro-SRXRF) spectroscopy is an ideal technique for investigating the cellular uptake and distribution of metallointercalators. The technique is capable of submicron elemental imaging so that samples as small as individual cells (~10 ?m diameter), and the features within them, can be resolved. Consequently, the technique can ascertain whether intracellular metallointercalators colocalise with DNA; namely, in the nucleus during interphase or at the chromosomes during middle prophase to late anaphase. Metals, such as those commonly incorporated into metallointercalators (e.g., Cr, Ni, Co, Pd, Pt, Ru, Rh), are often naturally present in negligible quantities in cancer cells. This fact, together with their higher atomic number, Z, makes them ideal for direct probing using hard X-ray microprobes (as discussed in Sect. 11.2). There is no need for the incorporation of fluorescent tracker dyes or radioactive labels into their chemical structure. This is advantageous since it is unknown whether such chemical modifications alter the uptake kinetics of the metallointercalator [1, 2].

Dillon, Carolyn T.

84

Relation between copper L x-ray fluorescence and 2p x-ray photoelectron spectroscopies  

Microsoft Academic Search

Lalpha1,2,beta1(L3,2-V) x-ray fluorescence spectra (XRF) and 2p1\\/2,3\\/2 x-ray photoelectron spectra (XPS) of various copper compounds are measured. It is found that the intensity of the high-energy hump of the Cu Lalpha XRF has a correlation with that of the high-binding-energy satellite (corresponding to the poorly screened 2p-1 final state) of the Cu 2p3\\/2 XPS. While both the poorly screened peak

Jun Kawai; Kuniko Maeda; Katsumi Nakajima; Yohichi Gohshi

1993-01-01

85

X-Ray diffraction and Fourier transformation infrared spectroscopy studies of copper (II) thiourea chloro and sulphate complexes  

NASA Astrophysics Data System (ADS)

Copper (II) thiourea complexes were synthesized by chemical route method. To analyze the samples, X-Ray diffraction and Fourier transformation infrared spectroscopy method have been used. XRD analysis shows that sample is crystalline in nature and having particle size in the range of nanometres. FTIR spectroscopy shows the organic and inorganic compounds present in the sample. The X-ray diffraction pattern (XRD) using Bruker D-8 advance instrument and Infrared spectra of the complexes were obtained by KBr disc technique by using VERTEX 70 (Bruker).

Mishra, Ashutosh; Dwivedi, Jagrati; Shukla, Kritika; Malviya, Pramod

2014-09-01

86

High-efficiency blazed transmission gratings for high-resolution soft x-ray spectroscopy  

NASA Astrophysics Data System (ADS)

High-resolution spectroscopy of astrophysical sources is the key to gaining a quantitative understanding of the history, dynamics, and current conditions of the cosmos. A large-area (> 1,000 cm2), high resolving power (R = ?/?? > 3,000) soft x-ray spectrometer that covers the lines of C, N, O, Ne and Fe ions is the ideal tool to address a number of high-priority sciences questions from the 2010 Decadal Survey, such as the connection between super-massive black holes and large-scale structure via cosmic feedback, the evolution of large-scale structure, the behavior of matter at high densities, and the conditions close to black holes. Numerous mission concepts that meet these requirements have been studied and proposed over the last few years, including grating instruments for the International X-ray Observatory. Nevertheless, no grating missions are currently approved. To improve the chances for future soft x-ray grating spectroscopy missions, grating technology has to progress and be advanced to higher TRLs. We have developed Critical-Angle Transmission (CAT) gratings that combine the advantages of blazed reflection gratings (high efficiency, use of higher diffraction orders) with those of conventional transmission gratings (low mass, relaxed alignment tolerances and temperature requirements, transparent at higher energies). A CAT grating-based spectrometer can provide performance 1-2 orders of magnitude better than current grating instruments on Chandra and Newton-XMM with minimal resource requirements. We have fabricated large-area free-standing CAT gratings with minimal integrated support structures from silicon-on-insulator wafers using advanced lithography and a combination of deep reactive-ion and wet etching, and will present our latest x-ray test results showing record high diffraction efficiencies in blazed orders.

Heilmann, Ralf K.; Bruccoleri, Alexander R.; Schattenburg, Mark L.

2015-01-01

87

X-ray microprobe system for XRF analysis and spectroscopy at SPring-8 BL39XU.  

PubMed

An X-ray microprobe system for X-ray fluorescence (XRF) analysis and spectroscopy has been developed at SPring-8 BL39XU; it comprises an X-ray focusing or collimation system, energy-dispersive (ED) and wavelength-dispersive (WD) XRF spectrometers, and a sample-scanning system. The conventional ED spectrometer will be utilized for qualitative and quantitative trace-element analysis, and the WD spectrometer will be used both for trace-element analysis and XRF spectroscopy. A combination of monochromated undulator radiation and the WD spectrometer will enable resonant XRF spectroscopy using brilliant hard X-ray undulator radiation. PMID:15263763

Hayakawa, S; Goto, S; Shoji, T; Yamada, E; Gohshi, Y

1998-05-01

88

Application of X-ray synchrotron microscopy instrumentation in biology  

SciTech Connect

X-ray micro-fluorescence imaging technique has been used as a significant tool in order to investigate minerals contents in some kinds of materials. The aim of this study was to evaluate the elemental distribution of calcium and zinc in bone substitute materials (nano-hydroxyapatite spheres) and cortical bones through X-Ray Micro-fluorescence analysis with the increment of Synchrotron Radiation in order to evaluate the characteristics of the newly formed bone and its interface, the preexisting bone and biomaterials by the arrangement of collagen fibers and its birefringence. The elemental mapping was carried out at Brazilian Synchrotron Light Laboratory, Campinas - Sao Paulo, Brazil working at D09-XRF beam line. Based on this study, the results suggest that hydroxyapatite-based biomaterials are biocompatible, promote osteo-conduction and favored bone repair. (authors)

Gasperini, F. M. [Medical Science Program, Fluminense Federal Univ., Niteroi (Brazil); Pereira, G. R. [Dept. of Metallurgical and Materials Engineering, Federal Univ. of Rio de Janeiro (Brazil); Granjeiro, J. M. [Molecular and Cell Biology Dept., Fluminense Federal Univ., Niteroi, Rio de Janeiro (Brazil); Calasans-Maia, M. D. [Oral Surgery Dept., Fluminense Federal Univ., Niteroi, Rio de Janeiro (Brazil); Rossi, A. M. [Biomaterials Laboratory, Brazilian Center of Physics Research, Rio de Janeiro (Brazil); Perez, C. A. [Brazilian Synchrotron Laboratory, Campinas, Sao Paulo (Brazil); Lopes, R. T.; Lima, I. [Nuclear Engineering Laboratory, Federal Univ. of Rio de Janeiro (Brazil)

2011-07-01

89

X-ray Absorption Spectroscopy of Transition Metal-Magnesium Hydride Thin Films  

E-print Network

X-ray Absorption Spectroscopy of Transition Metal-Magnesium Hydride Thin Films T. J. Richardsona and coordination of the magnesium and transition metal atoms during hydrogen absorption were studied using dynamic in situ transmission mode X-ray absorption spectroscopy. Mg K-edge and Ni, Co, and Ti L-edge spectra

90

TES-based microcalorimeter for future X-ray astronomy missions. Software development for instrument calibration  

NASA Astrophysics Data System (ADS)

The XMS (X-ray Microcalorimeter Spectrometer) is an instrument prototype with imaging capability in X-rays and high-spectral resolution. This instrument is a microcalorimeter based on transition edge sensors. As part of the Spanish contribution to the advancement of the XMS, we present the work carried out by the X-ray astronomy group at the Instituto de Física de Cantabria in collaboration with The Netherlands Institute for Space Research. The main work hereby presented includes the development and testing of software for this prototype with the purpose of instrument calibration and characterization, X-ray pulse detection and energy resolution calculations (Bergmann 2004, Tekst. Proefschrift Universiteit Utrecht; Boyce et al. 1999, Proc SPIE 3765; Den Herder et al. 2011, SRON-XMS-RP-2011-033; ATHENA Assessment Study Report, ESA/SRE(2011)17)

Fraga-Encinas, R.; Cobo, B.; Ceballos, M.; Schuurmans, J.; van der Kuur, J.; Carrera, F.; Barcons, X.

2013-05-01

91

X-Ray Line Spectroscopy of Massive X-Ray Binaries  

NASA Technical Reports Server (NTRS)

Spectra from ASCA have provided the most, detailed view to date of the X-ray spectral properties of stellar winds in massive X-ray binaries. Using detailed atomic models that account for recombination cascade kinetics, we have reexamined archival data from Vela X-1 and Cen X-3 in the context of simple models of their wind geometries and velocity distributions. Our approach emphasizes apparent differential emission measure (DEM) distributions, and their dependence on orbital phase and wind parameters. A grid of theoretical DEM distributions is used to generate model spectra, which are compared to the data. We obtain good fits, and derive constraints oil the stellar wind parameters. We provide a summary of the method, and show that, even though the companion stars in Vela X-1 and Cen X-3 have comparable mass-loss rates, the winds in these two systems are dramatically different, in character.

Liedahl, D. A.; Sako, M.; Wojdowski, P. S.; Paerels, F.; Kahn, S. M.

2000-01-01

92

CXO X-ray spectroscopy of comets and abundances of heavy ions in the solar wind  

NASA Astrophysics Data System (ADS)

X-rays from comets originate in charge exchange between heavy ions of the solar wind and cometary species. Spectra of nine comets observed by the Chandra X-ray Observatory (CXO) are analyzed using the time-dependent instrument sensitivity and the energy-dependent spectral resolution. X-ray emissions are extracted from the spectra in the range of 150-1100 eV using the ?2-fitting. Production of X-rays varies in the observed comets by a factor of 500 from 4.4 × 1013 erg s-1 in Comet 73P to 2.2 × 1016 erg s-1 in Comet Ikeya-Zhang. The measured solar wind flow varies within a factor of 20, being the weakest in Comet 73P and the strongest in 9P/Tempel 1. The retrieved X-ray line intensities vary within a factor of 5 × 104. These lines above 300 eV are attributed to emissions of the H- and He-like ions, and laboratory data on the excitation cross sections for these emissions (Greenwood et al. [2000]. Astrophys. J. 533, L175-L178) are used to convert the observed emissions into abundances of heavy ions in the solar wind. Continuity equations for charge exchange in comets are solved analytically and result in relationships between the X-ray emissions and the ion fluxes. The flux of O7+ scaled to 1 AU varies within a factor of 35 with a mean value of 1.6 × 104 cm-2 s-1. The retrieved ratios of O8+/O7+, C6+/C5+, Ne10+/Ne9+, C6+/O7+, N6+/O7+, and Ne9+/O7+ demonstrate significant variations, while their mean values for O, C, and N agree with those recommended by Schwadron and Cravens (Schwadron and Cravens [2000]. Astrophys. J. 544, 558-566) for the slow and fast solar wind. (Data on Ne9+ and Ne10+ are lacking in Scwadron and Cravens (Schwadron and Cravens [2000]. Astrophys. J. 544, 558-566).) The results are compared with the ion ratios from Bodewits et al. (Bodewits et al. [2007]. Astron. Astrophys. 469, 1183-1195) that were obtained from the same CXO spectra of comets, and some significant differences are briefly discussed. CXO X-ray spectroscopy of comets is a diagnostic tool to study the composition of the solar wind and its variations.

Krasnopolsky, Vladimir A.

2015-02-01

93

Electron Spectroscopy: Ultraviolet and X-Ray Excitation.  

ERIC Educational Resources Information Center

Reviews recent growth in electron spectroscopy (54 papers cited). Emphasizes advances in instrumentation and interpretation (52); photoionization, cross-sections and angular distributions (22); studies of atoms and small molecules (35); transition, lanthanide and actinide metal complexes (50); organometallic (12) and inorganic compounds (2);…

Baker, A. D.; And Others

1980-01-01

94

Fast CCD camera for x-ray photon correlation spectroscopy and time-resolved x-ray scattering and imaging  

SciTech Connect

A new, fast x-ray detector system is presented for high-throughput, high-sensitivity, time-resolved, x-ray scattering and imaging experiments, most especially x-ray photon correlation spectroscopy (XPCS). After a review of the architectures of different CCD chips and a critical examination of their suitability for use in a fast x-ray detector, the new detector hardware is described. In brief, its principal component is an inexpensive, commercial camera - the SMD1M60 - originally designed for optical applications, and modified for use as a direct-illumination x-ray detector. The remainder of the system consists of two Coreco Imaging PC-DIG frame grabber boards, located inside a Dell Power-edge 6400 server. Each frame grabber sits on its own PCI bus and handles data from 2 of the CCD's 4 taps. The SMD1M60 is based on a fast, frame-transfer, 4-tap CCD chip, read out at12-bit resolution at frame rates of up to 62 Hz for full frame readout and up to 500 Hz for one-sixteenth frame readout. Experiments to characterize the camera's suitability for XPCS and small-angle x-ray scattering (SAXS) are presented. These experiments show that single photon events are readily identified, and localized to within a pixel index or so. This is a sufficiently fine spatial resolution to maintain the speckle contrast at an acceptable value for XPCS measurements. The detective quantum efficiency of the SMD1M60 is 49% for directly-detected 6.3 keV x rays. The effects of data acquisition strategies that permit near-real-time data compression are also determined and discussed. Overall, the SMD1M60 detector system represents a major improvement in the technology for time-resolved x-ray experiments, that require an area detector with time-resolutions in few-milliseconds-to-few-seconds range, and it should have wide applications, extending beyond XPCS.

Falus, P.; Borthwick, M.A.; Mochrie, S.G.J. [Department of Physics, Yale University, New Haven, Connecticut 06520 and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Departments of Physics and Applied Physics, Yale University, New Haven, Connecticut 06520 (United States)

2004-11-01

95

Development of spatially resolved high resolution x-ray spectroscopy for fusion and light-source research  

NASA Astrophysics Data System (ADS)

One dimensional spatially resolved high resolution x-ray spectroscopy with spherically bent crystals and 2D pixelated detectors is an established technique on magnetic confinement fusion (MCF) experiments world wide for Doppler measurements of spatial profiles of plasma ion temperature and flow velocity. This technique is being further developed for diagnosis of High Energy Density Physics (HEDP) plasmas at laser-plasma facilities and synchrotron/x-ray free electron laser (XFEL) facilities. Useful spatial resolution (micron scale) of such small-scale plasma sources requires magnification, because of the finite pixel size of x-ray CCD detectors (13.5 ?m). A von-Hamos like spectrometer using spherical crystals is capable of magnification, as well as uniform sagittal focusing across the full x-ray spectrum, and is being tested in laboratory experiments using a tungsten-target microfocus (5-10 ?m) x-ray tube and 13-?m pixel x-ray CCD. A spatial resolution better than 10 ?m has been demonstrated. Good spectral resolution is indicated by small differences (0.02 - 0.1 eV) of measured line widths with best available published natural line widths. Progress and status of HEDP measurements and the physics basis for these diagnostics are presented. A new type of x-ray crystal spectrometer with a convex spherically bent crystal is also reported. The status of testing of a 2D imaging microscope using matched pairs of spherical crystals with x rays will also be presented. The use of computational x-ray optics codes in development of these instrumental concepts is addressed.

Lu, J.; Hill, K. W.; Bitter, M.; Delgado-Aparicio, L.; Pablant, N. A.; Efthimion, P.; Beiersdorfer, P.; Chen, H.; Widmann, K.; Sanchez del Rio, M.

2014-09-01

96

A new endstation at the Swiss Light Source for ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy measurements of liquid solutions  

NASA Astrophysics Data System (ADS)

A new liquid microjet endstation designed for ultraviolet (UPS) and X-ray (XPS) photoelectron, and partial electron yield X-ray absorption (XAS) spectroscopies at the Swiss Light Source is presented. The new endstation, which is based on a Scienta HiPP-2 R4000 electron spectrometer, is the first liquid microjet endstation capable of operating in vacuum and in ambient pressures up to the equilibrium vapor pressure of liquid water at room temperature. In addition, the Scienta HiPP-2 R4000 energy analyzer of this new endstation allows for XPS measurements up to 7000 eV electron kinetic energy that will enable electronic structure measurements of bulk solutions and buried interfaces from liquid microjet samples. The endstation is designed to operate at the soft X-ray SIM beamline and at the tender X-ray Phoenix beamline. The endstation can also be operated using a Scienta 5 K ultraviolet helium lamp for dedicated UPS measurements at the vapor-liquid interface using either He I or He II ? lines. The design concept, first results from UPS, soft X-ray XPS, and partial electron yield XAS measurements, and an outlook to the potential of this endstation are presented.

Brown, Matthew A.; Redondo, Amaia Beloqui; Jordan, Inga; Duyckaerts, Nicolas; Lee, Ming-Tao; Ammann, Markus; Nolting, Frithjof; Kleibert, Armin; Huthwelker, Thomas; Mächler, Jean-Pierre; Birrer, Mario; Honegger, Juri; Wetter, Reto; Wörner, Hans Jakob; van Bokhoven, Jeroen A.

2013-07-01

97

A new endstation at the Swiss Light Source for ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy measurements of liquid solutions  

SciTech Connect

A new liquid microjet endstation designed for ultraviolet (UPS) and X-ray (XPS) photoelectron, and partial electron yield X-ray absorption (XAS) spectroscopies at the Swiss Light Source is presented. The new endstation, which is based on a Scienta HiPP-2 R4000 electron spectrometer, is the first liquid microjet endstation capable of operating in vacuum and in ambient pressures up to the equilibrium vapor pressure of liquid water at room temperature. In addition, the Scienta HiPP-2 R4000 energy analyzer of this new endstation allows for XPS measurements up to 7000 eV electron kinetic energy that will enable electronic structure measurements of bulk solutions and buried interfaces from liquid microjet samples. The endstation is designed to operate at the soft X-ray SIM beamline and at the tender X-ray Phoenix beamline. The endstation can also be operated using a Scienta 5 K ultraviolet helium lamp for dedicated UPS measurements at the vapor-liquid interface using either He I or He II ? lines. The design concept, first results from UPS, soft X-ray XPS, and partial electron yield XAS measurements, and an outlook to the potential of this endstation are presented.

Brown, Matthew A.; Redondo, Amaia Beloqui; Duyckaerts, Nicolas; Mächler, Jean-Pierre [Institute for Chemical and Bioengineering, ETH Zürich, CH-8093 Zürich (Switzerland)] [Institute for Chemical and Bioengineering, ETH Zürich, CH-8093 Zürich (Switzerland); Jordan, Inga; Wörner, Hans Jakob [Laboratory of Physical Chemistry, ETH Zürich, CH-8093 Zürich (Switzerland)] [Laboratory of Physical Chemistry, ETH Zürich, CH-8093 Zürich (Switzerland); Lee, Ming-Tao; Ammann, Markus; Nolting, Frithjof; Kleibert, Armin; Huthwelker, Thomas; Birrer, Mario; Honegger, Juri; Wetter, Reto [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland)] [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Bokhoven, Jeroen A. van [Institute for Chemical and Bioengineering, ETH Zürich, CH-8093 Zürich (Switzerland) [Institute for Chemical and Bioengineering, ETH Zürich, CH-8093 Zürich (Switzerland); Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland)

2013-07-15

98

X-ray photoelectron spectroscopy of Ni doped boron carbides  

NASA Astrophysics Data System (ADS)

Ni acts as an n-type dopant for semiconducting boron carbide (BC). A series of samples with increased Ni doping were grown on Si substrates using plasma enhanced chemical vapor deposition (PECVD) and characterized using IV measurements and X-ray photoelectron spectroscopy (XPS). Increased Ni doping leads to a linear increase in Ni concentration as evidenced by the intensity of the Ni 2p photoemission peak relative to that of the B 1s peak; concomitantly, the IV curves indicate that the BC becomes increasingly n doped. B1s peak shapes shows B-C and B-B bonding structure, and the C1s peak shows B11C icosahedra bonds and C-B-C chain bonds in all samples. The overall binding energies for B and C agree with the results from sputter deposited stoichiometric B4C [1]; in these PECVD grown samples, however, the graphite peak commonly seen in the sputter deposited B4C is absent. [1] I. Jimenez, L. J. Terminello, et al. J. Elect. Spec. Relat. Phenom., 101-103, 611-615 (1999).

Hong, Nina; Langell, M. A.; Adenwalla, S.

2009-03-01

99

X-ray absorption spectroscopy of dinuclear metallohydrolases.  

PubMed

In this mini-review, we briefly discuss the physical origin of x-ray absorption spectroscopy (XAS) before illustrating its application using dinuclear metallohydrolases as exemplary systems. The systems we have selected for illustrative purposes present a challenging problem for XAS, one that is ideal to demonstrate the potential of this methodology for structure/function studies of metalloenzymes in general. When the metal ion is redox active, XAS provides a sensitive measure of oxidation-state-dependent differences. When the metal ion is zinc, XAS is the only spectroscopic method that will provide easily accessible structural information in solution. In the case of heterodimetallic sites, XAS has the unique ability to interrogate each metal site independently in the same sample. One of the strongest advantages of XAS is its ability to examine metal ion site structures with crystallographic precision, without the need for a crystal. This is key for studying flexible metal ion sites, such as those described in the selected examples, because it allows one to monitor structural changes that occur during substrate turnover. PMID:25229134

Tierney, David L; Schenk, Gerhard

2014-09-16

100

The BioCAT undulator beamline 18ID: A facility for biological non-crystalline diffraction and x-ray absorption spectroscopy at the APS  

SciTech Connect

The 18ID undulator beamline of the Biophysics Collaborative Access Team at the Advanced Photon Source, Argonne, IL, USA, is a high-performance instrument designed for, and dedicated to, the study of partially ordered and disordered biological materials using the techniques of small-angle X-ray scattering, fiber diffraction, and X-ray absorption spectroscopy. The beamline and associated instrumentation are described in detail and examples of the representative experimental results are presented.

Fischetti, R.; Stepanov, S.; Rosenbaum, G.; Barrea, R.; Black, E.; Gore, D.; Heurich, R.; Kondrashkina, E.; Kropf, A.J.; Wang, S.; Zhang, K.; Irving, T.C.; Bunker, G.B. (IIT); (Georgia)

2008-07-02

101

XMM-Newton spectroscopy of an X-ray selected sample of RL AGNs  

Microsoft Academic Search

This paper presents the X-ray spectroscopy of an X-ray selected sample of 25 radio-loud (RL) AGNs extracted from the XMM-Newton Bright Serendipitous Survey (XBSS). The main goal of the work is to assess and study the origin of the X-ray spectral differences usually observed between radio-loud and radio-quiet (RQ) AGNs. To this end, a comparison sample of 53 RQ AGNs

E. Galbiati; A. Caccianiga; T. Maccacaro; V. Braito; R. Della Ceca; P. Severgnini; H. Brunner; I. Lehmann; M. J. Page

2005-01-01

102

X-Ray Diffraction and Fluorescence Measurements for In Situ Planetary Instruments  

NASA Astrophysics Data System (ADS)

The ESA/NASA ExoMars mission, due for launch in 2018, has a combined X-ray fluorescence/diffraction instrument, Mars-XRD, as part of the onboard analytical laboratory. The results of some XRF (Xray fluorescence) and XRD (X-ray diffraction) tests using a laboratory chamber with representative performance are reported. A range of standard geological reference materials and analogues were used in these tests.

Hansford, G. M.; Hill, K. S.; Talboys, D. L.; Vernon, D.; Ambrosi, R. M.; Bridges, J. C.; Hutchinson, I. B.; Marinangeli, L.

2011-10-01

103

The soft x-ray instrument for materials studies at the linac coherent light source x-ray free-electron laser  

SciTech Connect

The soft x-ray materials science instrument is the second operational beamline at the linac coherent light source x-ray free electron laser. The instrument operates with a photon energy range of 480-2000 eV and features a grating monochromator as well as bendable refocusing mirrors. A broad range of experimental stations may be installed to study diverse scientific topics such as: ultrafast chemistry, surface science, highly correlated electron systems, matter under extreme conditions, and laboratory astrophysics. Preliminary commissioning results are presented including the first soft x-ray single-shot energy spectrum from a free electron laser.

Schlotter, W. F.; Turner, J. J.; Rowen, M.; Holmes, M.; Messerschmidt, M.; Moeller, S.; Krzywinski, J.; Lee, S.; Coffee, R.; Hays, G. [LCLS, SLAC National Accelerator Laboratory, 2575 Sand Hill Rd., Menlo Park, California 94025 (United States); Heimann, P. [LCLS, SLAC National Accelerator Laboratory, 2575 Sand Hill Rd., Menlo Park, California 94025 (United States); Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Krupin, O. [LCLS, SLAC National Accelerator Laboratory, 2575 Sand Hill Rd., Menlo Park, California 94025 (United States); European XFEL GmbH, Albert-Einstein-Ring 19, 22761 Hamburg (Germany); Soufli, R.; Fernandez-Perea, M.; Hau-Riege, S. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States); Kelez, N. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Beye, M.; Gerken, N.; Sorgenfrei, F.; Wurth, W. [Institute for Experimental Physics and CFEL, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); and others

2012-04-15

104

Structure of oxychloride glasses by neutron and x-ray 'difference' and x-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

A previous study of the binary system, [Sb2O3]x-[ZnCl2]1-x (Johnson et al 2003 J. Phys.: Condens. Matter 15 755-64), where nominally x = 0.25, 0.50, 0.75 and 1.00, has been extended to include Sb2O3-PbCl2. Information about the structure has been obtained from a combination of neutron and x-ray diffraction measurements, which were complemented by x-ray photoelectron spectroscopy. The data clearly show preferential bonding of oxygen to antimony and chlorine to zinc or lead in a single-phase glass with minimal change in the polyhedral structure with composition. The structure appears to be controlled by the need to avoid Sb-Cl-Sb links.

Johnson, J. A.; Holland, D.; Urquidi, J.; Gee, I. A.; Benmore, C. J.; Johnson, C. E.

2003-07-01

105

X-ray Photoemission and X-ray Absorption Spectroscopy of Hexagonal Ba3CuSb2O9  

NASA Astrophysics Data System (ADS)

We have investigated the electronic structure of hexagonal Ba3CuSb2O9 [3] by means of X-ray photoemission and X-ray absorption spectroscopy (XPS and XAS). The Cu 2p XPS spectrum exhibits the charge-transfer satellite which allows us to estimate the electronic-structure parameters of the system using the cluster-model calculation. Two parameters of the system, charge-transfer energy ? and (pd?) are estimated as 0.1 eV and -1.65 eV, respectively. The Cu 2p XAS spectrum indicates the small charge-transfer energy as well. Based on the electronic-structure parameters, the magnitude of the Cu-O-O-Cu superexchange interaction J is estimated to be around 20.7 meV using the cell perturbation method.

Sugimoto, Takuya; Mizokawa, Takashi; Wadati, Hiroki; Takubo, Kou; Damascelli, Andrea; Regier, Tom Z.; Sawatzky, George A.; Katayama, Naoyuki; Sawa, Hiroshi; Kimura, Kenta; Nakatsuji, Satoru

106

Instrument for x-ray magnetic circular dichroism measurements at high pressures  

SciTech Connect

An instrument has been developed for x-ray magnetic circular dichroism (XMCD) measurements at high pressures and low temperatures. This instrument couples a nonmagnetic copper-beryllium diamond anvil cell featuring perforated diamonds with a helium flow cryostat and an electromagnet. The applied pressure can be controlled in situ using a gas membrane and calibrated using Cu K-edge x-ray absorption fine structure measurements. The performance of this instrument was tested by measuring the XMCD spectra of the Gd{sub 5}Si{sub 2}Ge{sub 2} giant magnetocaloric material.

Haskel, D.; Tseng, Y. C.; Lang, J. C.; Sinogeikin, S. [Magnetic Materials Group, Advanced Photon Source, Argonne National Laboratory, Argonne, lllinois 60439 (United States); HPCAT, Carnegie Institution of Washington, Advanced Photon Source, Argonne National Laboratory, Argonne, lllinois 60439 (United States)

2007-08-15

107

X-ray spectroscopy in the EC nucleus  

NASA Astrophysics Data System (ADS)

The probabilities PKK of double K-shell vacancy production per K electron capture decay and per K internal conversion of 109Cd and 207Bi have been determined by means of the double- and triple-coincidence experiments using K? X-ray and K internal conversion. For 109Cd we find PKK(EC) = (4.2 ± 0.5) × 10 -5 and PKK(IC) = (4.32 ± 0.46) × 10 -5, and for 207Bi, PKK(EC) = (2.54 ± 0.50) × 10 -5. The observed X-ray energy shifts of the hypersatellite Ag ( K?1H) X-ray and the hypersatellite Pb ( K?1H) X-ray lines are 545±15 eV and 1238±45 eV, respectively.

Ko, Seung Kook; Cho, Hyun Jae; Nha, Sang Kyun

1998-10-01

108

Spectroscopy of six X-ray-selected BL Lacertae candidates  

SciTech Connect

Results of a continuing program aimed at extending the small list of X-ray-selected BL Lac objects are reported. High-quality spectra have been obtained of six faint blue objects that lie within the positional error boxes of X-ray sources discovered serendipitously by the Einstein Observatory. Three of the objects are found to be previously uncataloged low-red-shift quasi-stellar objects, including one formerly suggested as BL Lac candidate. Two are faint galactic stars, while the final object has a featureless spectrum, and thus remains a candidate. Although X-ray selection may ultimately be an effective means of discovering faint BL Lac objects, such sources are evidently rare at the X-ray flux levels attainable by the Einstein Observatory. 15 references.

Margon, B.; Boroson, T.A.; Chanan, G.A.; Thompson, I.B.; Schneider, D.P.

1986-11-01

109

A novel instrument for quantitative nanoanalytics involving complementary X-ray methodologies  

NASA Astrophysics Data System (ADS)

A novel ultra-high vacuum instrument for X-ray reflectometry and spectrometry-related techniques for nanoanalytics by means of synchrotron radiation has been constructed and commissioned. This versatile instrument was developed by the Physikalisch-Technische Bundesanstalt, Germany's national metrology institute, and includes a 9-axis manipulator that allows for an independent alignment of the samples with respect to all degrees of freedom. In addition, a rotational and translational movement of several photodiodes as well as a translational movement of an aperture system in and out of the beam is provided. Thus, the new instrument enables various analytical techniques based on energy dispersive X-ray detectors such as reference-free X-ray fluorescence analysis (XRF), total-reflection XRF, grazing-incidence XRF in addition to optional X-ray reflectometry measurements or polarization-dependent X-ray absorption fine structure analyses. With this instrument samples having a size of up to 100 mm × 100 mm can be analyzed with respect to their mass deposition, elemental or spatial composition, or the species in order to probe surface contamination, layer composition and thickness, the depth profile of matrix elements or implants, the species of nanolayers, nanoparticles or buried interfaces as well as the molecular orientation of bonds. Selected applications of this advanced ultra-high vacuum instrument demonstrate both its flexibility and capability.

Lubeck, J.; Beckhoff, B.; Fliegauf, R.; Holfelder, I.; Hönicke, P.; Müller, M.; Pollakowski, B.; Reinhardt, F.; Weser, J.

2013-04-01

110

X-ray spectroscopy studies of nonradiative energy transfer processes in luminescent lanthanide materials  

NASA Astrophysics Data System (ADS)

Luminescent materials play important roles in energy sciences, through solid state lighting and possible applications in solar energy utilization, and in biomedical research and applications, such as in immunoassays and fluorescence microscopy. The initial excitation of a luminescent material leads to a sequence of transitions between excited states, ideally ending with the emission of one or more optical-wavelength photons. It is essential to understand the microscopic physics of this excited state cascade in order to rationally design materials with high quantum efficiencies or with other fine-tuning of materials response. While optical-wavelength spectroscopies have unraveled many details of the energy transfer pathways in luminescent materials, significant questions remain open for many lanthanide-based luminescent materials. For organometallic dyes in particular, quantum yields remain limited in comparison with inorganic phosphors. This dissertation reports on a research program of synchrotron x-ray studies of the excited state electronic structure and energy-relaxation cascade in trivalent lanthanide phosphors and dyes. To this end, one of the primary results presented here is the first time-resolved x-ray absorption near edge spectroscopy studies of the transient 4f excited states in lanthanide-activated luminescent dyes and phosphors. This is a new application of time-resolved x-ray absorption spectroscopy that makes it possible to directly observe and, to some extent, quantify intramolecular nonradiative energy transfer processes. We find a transient increase in 4f spectral weight associated with an excited state confined to the 4f shell of trivalent Eu. This result implies that it is necessary to revise the current theoretical understanding of 4f excitation in trivalent lanthanide activators: either transient 4f-5d mixing effects are much stronger than previously considered, or else the lanthanide 4f excited state has an unexpectedly large contribution having a strong charge-transfer character. A second primary result comes from an an x-ray excited optical luminescence (XEOL) study that demonstrates, for the first time, that the high flux of modern synchrotron light sources can induce high fractional populations of excited states in trivalent lanthanide phosphors. In this work we have identified the leading-order nonlinear-response mechanism by drawing on strong similarities between XEOL and cathodoluminescence. These results establish the groundwork for studies that would allow deeper inquiry into energy-transfer mechanisms through time-resolved x-ray pump/optical-probe spectroscopies, through time-resolved x-ray emission spectroscopy, or through quantifying of higher-order nonlinear effects at further-enhanced fractional excitation levels. The above scientific results are augmented by a supporting effort in instrumental methodology. This includes the development of high-efficiency x-ray emission spectrometers and their use in collaborations to study pressure-induced changes in f-electron physics and to characterize the intermediate states that occur after photoexcitation of the photosystem-II protein.

Pacold, Joseph I.

111

X-ray spectroscopy of five BL Lacertae objects  

NASA Technical Reports Server (NTRS)

Five X-ray bright BL Lacertae objects were observed in the energy range 0.6-4.5 keV with the solid state spectrometer (SSS) of the Einstein Observatory. The 14 SSS spectra obtained represent most of the X-ray spectra of BL Lac objects with resolution better than approximately 3. These data do not reveal the presence of large amounts of thermal gas, with upper limits for the equivalent width of individual spectral features typically less that about 100 eV. However, the SSS spectra are the first set of X-ray data to indicate low-energy absorption in excess of that caused by the cold interstellar matter in the Galaxy. Comparison with contemporaneous, lower energy X-ray data implies that this absorption does not arise in cold neutral material, but in hotter, highly ionized material, probably intrinsic to the source. All five BL Lac objects have X-ray continua that are well fitted by power-law models, with power-law energy indices usually greater than about 1. In a few cases, a flattening at higher energies is observed; these and other data suggest that two-component X-ray spectra, steep at low energies and flat at high energies, are a common feature of BL Lac objects. Three of the five sources clearly vary between SSS observations, with time scales ranging from days to years. A historical synopsis of the X-ray spectral data confirms the tendency for BL Lacertae objects to be highly variable in the X-ray band but reveals no correlation between spectral and intensity changes.

Urry, C. M.; Mushotzky, R. F.; Holt, S. S.

1986-01-01

112

Multiple Scattering Calculations of Bonding and X-ray Absorption Spectroscopy of Manganese Oxides  

E-print Network

Multiple Scattering Calculations of Bonding and X-ray Absorption Spectroscopy of Manganese Oxides B edge X-ray absorption spectra of manganese oxides at the Mn L2,3, Mn K, and O K edges to investigate The particularly rich redox chemistry of manganese is evident in its oxides, which are of wide contemporary

Haskel, Daniel

113

Field Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-Ray (EDX) Spectroscopy  

E-print Network

system with 30 take-off angle for quantitative analysis, digital imaging, and X-ray mapping. The EDAXField Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-Ray (EDX) Spectroscopy of objective aperture. Dual SE detectors allow versatile imaging. The FE-SEM is equipped with fully digital

Gelfond, Michael

114

A whole-system approach to x-ray spectroscopy in cargo inspection systems  

NASA Astrophysics Data System (ADS)

The bremsstrahlung x-ray spectrum used in high-energy, high-intensity x-ray cargo inspection systems is attenuated and modified by the materials in the cargo in a Z-dependent way. Therefore, spectroscopy of the detected x rays yields information about the Z of the x-rayed cargo material. It has previously been shown that such ZSpectroscopy (Z-SPEC) is possible under certain circumstances. A statistical approach, Z-SCAN (Z-determination by Statistical Count-rate ANalysis), has also been shown to be effective, and it can be used either by itself or in conjunction with Z-SPEC when the x-ray count rate is too high for individual x-ray spectroscopy. Both techniques require fast x-ray detectors and fast digitization electronics. It is desirable (and possible) to combine all techniques, including x-ray imaging of the cargo, in a single detector array, to reduce costs, weight, and overall complexity. In this paper, we take a whole-system approach to x-ray spectroscopy in x-ray cargo inspection systems, and show how the various parts interact with one another. Faster detectors and read-out electronics are beneficial for both techniques. A higher duty-factor x-ray source allows lower instantaneous count rates at the same overall x-ray intensity, improving the range of applicability of Z-SPEC in particular. Using an intensity-modulated advanced x-ray source (IMAXS) allows reducing the x-ray count rate for cargoes with higher transmission, and a stacked-detector approach may help material discrimination for the lowest attenuations. Image processing and segmentation allow derivation of results for entire objects, and subtraction of backgrounds. We discuss R&D performed under a number of different programs, showing progress made in each of the interacting subsystems. We discuss results of studies into faster scintillation detectors, including ZnO, BaF2 and PbWO4, as well as suitable photo-detectors, read-out and digitization electronics. We discuss high-duty-factor linear-accelerator x-ray sources and their associated requirements, and how such sources improve spectroscopic techniques. We further discuss how image processing techniques help in correcting for backgrounds and overlapping materials. In sum, we present an integrated picture of how to optimize a cargo inspection system for x-ray spectroscopy.

Langeveld, Willem G. J.; Gozani, Tsahi; Ryge, Peter; Sinha, Shrabani; Shaw, Tim; Strellis, Dan

2013-04-01

115

Examination of the local structure in composite and lowdimensional semiconductor by X-ray Absorption Spectroscopy  

SciTech Connect

X-ray absorption methods have been successfully used to obtain quantitative information about local atomic composition of two different materials. X-ray Absorption Near Edge Structure analysis and X-Ray Photoelectron Spectroscopy allowed us to determine seven chemical compounds and their concentrations in c-BN composite. Use of Extended X-ray Absorption Fine Structure in combination with Transmission Electron Microscopy enabled us to determine the composition and size of buried Ge quantum dots. It was found that the quantum dots consisted out of pure Ge core covered by 1-2 monolayers of a layer rich in Si.

Lawniczak-Jablonska, K.; Demchenko, I.N.; Piskorska, E.; Wolska,A.; Talik, E.; Zakharov, D.N.; Liliental-Weber, Z.

2006-09-25

116

Novel Approaches to Soft X-ray Spectroscopy: Scanning TransmissionX-ray Microscopy and Ambient Pressure X-Ray PhotoelectronSpectroscopy  

SciTech Connect

This workshop focused on novel spectroscopies at Beamlines 11.0.2, 5.3.2 and 9.3.2 at the ALS. The workshop brought together users from a wide range of fields to highlight recent experimental and technical developments both in scanning transmission X-ray spectroscopy (STXM) and ambient pressure photoelectron spectroscopy (APPES). The morning session featured talks on experiments involving new developments at the STXM, while the afternoon session was devoted to those using APXPS. In the morning session, Tolek Tyliszczak discussed the improved detector developments at the STXM, such as an avalanche photodiode detector and fluorescence and electron detection, as well as the continued development of in situ cells for heating, gas flow, and electrochemical cells. Of these, only the avalanche photodiode in combination with a novel multichannel photon-counting system is in routine use in time-resolved studies. Bartel Van Waeyenberge (Ghent University) presented results of magnetic imaging with a time resolution of 70-100 ps combined with a lateral resolution of 20-40 nm performed with the STXM (Beamline 11.0.2). As a complement to the time-domain ''pump-and-probe'' measurements, they developed a frequency-domain ''sine-excitation'' technique in order to study specific eigenmodes of these ferromagnetic patterns with high spatial resolution. This new approach was used to study the gyrotropic vortex motions in micron-sized ferromagnetic patterns. Adam Hitchcock (McMaster University) presented the development, in collaboration with Daniel Guay (INRS, Varennes) and Sherry Zhang, of the apparatus and techniques for applying STXM to in-situ studies of electrochemistry, in particular electrochromism in polyaniline. In addition, substantial progress was reported on a joint project to develop substrates and methods for chemically selective lithography of multilayer polymer systems. Selective patterns, such as that displayed in the figure, can now be written efficiently with the bend magnet STXM on Beamline 5.3.2. Yves Acremann (SSRL) discussed time and spatially resolved X-ray magnetic circular dichroism (XMCD) experiments on spin transfer devices at the STXM (Beamline 11.0.2). These elegant experiments explore time resolved measurements of the magnetization dynamics within a 100 x 150 nm sample influenced by a spin-polarized current. This experiment shows that the magnetization in these magnetic nanostructures are not uniform, as they are influenced by the Oersted field of the charge current needed to generate the spin current. The implementation of a novel multichannel photon counting system in combination with an avalanche photon detector decreased the data-acquisition time by a factor of 10, owing to its ability to resolve the structure of multi bunch mode. Gordon E. Brown, Jr. (Stanford University and SSRL) described ''Applications of STXM to Microbial Bioweathering and Biomineralization''. In the interaction of bacteria with ferrihydrite nanoparticles, microenvironments that were very different than the bulk material were observed, showing that bulk thermodynamics may not be useful for predicting micro phases. Gordon also presented work showing that iron nanoparticles are attracted to the negatively charged bacteria and form a coating that reduces iron oxide minerals. The afternoon session started with presentations by Simon Mun and Hendrik Bluhm, who discussed the current status and the future plans for the two APPES end-stations at the ALS, which are located at Beamlines 9.3.2 and 11.0.2, respectively. In both end-stations, samples can be measured in gaseous environments at pressures of up to several Torr, which makes possible the investigation of numerous phenomena, in particular in the fields of atmospheric and environmental science as well as heterogeneous catalysis. Specific examples of the application of APPES were shown in the following presentations. John Hemminger (University of California, Irvine) reported on APPES investigations at Beamlines 9.3.2 and 11.0.2 of the interaction of alkali halide surfaces with water. The m

Bluhm, Hendrik; Gilles, Mary K.; Mun, Simon B.; Tyliszczak, Tolek

2006-02-01

117

Selenium speciation in whole sediment using X-ray absorption spectroscopy and micro X-ray fluorescence imaging.  

PubMed

A field survey was conducted in a freshwater lake system in the Athabasca Basin, northern Saskatchewan, Canada that receives treated metal mining and milling process effluent containing elevated levels of selenium. Whole sediment, pore water, surface water, and chironomid larvae were analyzed in an attempt to link whole sediment selenium speciation to various environmental factors, including selenium availability to benthic macro-invertebrates, a trophic level through which selenium can enter the diet of higher trophic level organisms. Speciation was measured using synchrotron-based selenium K-edge X-ray absorption spectroscopy (XAS). All lake averages of sediment samples (reference or exposure sites) contained a significant proportion (approximately 50%) of elemental selenium which is relatively insoluble in water, immobile, and not considered to be bioavailable. The presence of elemental selenium was confirmed by extended X-ray absorption fine structure (EXAFS) analysis of select samples. Inorganic metal selenides were also found in whole sediment samples and confirmed using micro X-ray fluorescence imaging. Dissolved selenium concentrations in pore water were correlated to the amount of selenite in whole sediments provided that the sites were classified according to whole sediment sand content. Sand content itself is likely inversely correlated to sediment organic matter content, adsorption sites, and redox potential. PMID:20575568

Wiramanaden, Cheryl I E; Liber, Karsten; Pickering, Ingrid J

2010-07-15

118

Quick extended x-ray absorption fine structure instrument with millisecond time scale, optimized for in situ applications  

E-print Network

Quick extended x-ray absorption fine structure instrument with millisecond time scale, optimized in situ structural changes in materials at subseconds time scale, we have further refined the techniques of quick extended x-ray absorption fine structure QEXAFS and quick x-ray absorption near edge structure

Sparks, Donald L.

119

New Homogeneous Standards by Atomic Layer Deposition for Synchrotron X-ray Fluorescence and Absorption Spectroscopies.  

SciTech Connect

Quantification of synchrotron XRF analyses is typically done through comparisons with measurements on the NIST SRM 1832/1833 thin film standards. Unfortunately, these standards are inhomogeneous on small scales at the tens of percent level. We are synthesizing new homogeneous multilayer standards using the Atomic Layer Deposition technique and characterizing them using multiple analytical methods, including ellipsometry, Rutherford Back Scattering at Evans Analytical, Synchrotron X-ray Fluorescence (SXRF) at Advanced Photon Source (APS) Beamline 13-ID, Synchrotron X-ray Absorption Spectroscopy (XAS) at Advanced Light Source (ALS) Beamlines 11.0.2 and 5.3.2.1 and by electron microscopy techniques. Our motivation for developing much-needed cross-calibration of synchrotron techniques is borne from coordinated analyses of particles captured in the aerogel of the NASA Stardust Interstellar Dust Collector (SIDC). The Stardust Interstellar Dust Preliminary Examination (ISPE) team have characterized three sub-nanogram, {approx}1{micro}m-sized fragments considered as candidates to be the first contemporary interstellar dust ever collected, based on their chemistries and trajectories. The candidates were analyzed in small wedges of aerogel in which they were extracted from the larger collector, using high sensitivity, high spatial resolution >3 keV synchrotron x-ray fluorescence spectroscopy (SXRF) and <2 keV synchrotron x-ray transmission microscopy (STXM) during Stardust ISPE. The ISPE synchrotron techniques have complementary capabilities. Hard X-ray SXRF is sensitive to sub-fg mass of elements Z {ge} 20 (calcium) and has a spatial resolution as low as 90nm. X-ray Diffraction data were collected simultaneously with SXRF data. Soft X-ray STXM at ALS beamline 11.0.2 can detect fg-mass of most elements, including cosmochemically important oxygen, magnesium, aluminum and silicon, which are invisible to SXRF in this application. ALS beamline 11.0.2 has spatial resolution better than 25 nm. Limiting factors for Stardust STXM analyses were self-imposed limits of photon dose due to radiation damage concerns, and significant attenuation of <1500 eV X-rays by {approx}80{micro}m thick, {approx}25 mg/cm{sup 3} density silica aerogel capture medium. In practice, the ISPE team characterized the major, light elements using STXM (O, Mg, Al, Si) and the heavier minor and trace elements using SXRF. The two data sets overlapped only with minor Fe and Ni ({approx}1% mass abundance), providing few quantitative cross-checks. New improved standards for cross calibration are essential for consortium-based analyses of Stardust interstellar and cometary particles, IDPs. Indeed, they have far reaching application across the whole synchrotron-based analytical community. We have synthesized three ALD multilayers simultaneously on silicon nitride membranes and silicon and characterized them using RBS (on Si), XRF (on Si{sub 3}N{sub 4}) and STXM/XAS (holey Si{sub 3}N{sub 4}). The systems we have started to work with are Al-Zn-Fe and Y-Mg-Er. We have found these ALD multi-layers to be uniform at {micro}m- to nm scales, and have found excellent consistency between four analytical techniques so far. The ALD films can also be used as a standard for e-beam instruments, eg., TEM EELS or EDX. After some early issues with the consistency of coatings to the back-side of the membrane windows, we are confident to be able to show multi-analytical agreement to within 10%. As the precision improves, we can use the new standards to verify or improve the tabulated cross-sections.

Butterworth, A.L.; Becker, N.; Gainsforth, Z.; Lanzirotti, A.; Newville, M.; Proslier, T.; Stodolna, J.; Sutton, S.; Tyliszczak, T.; Westphal, A.J.; Zasadzinski, J. (UCB)

2012-03-13

120

Simulated 'On-Line' Wear Metal Analysis of Lubricating Oils by X-Ray Fluorescence Spectroscopy  

NASA Technical Reports Server (NTRS)

The objective of this project was to assess the sensitivity of X-ray Fluorescence Spectroscopy (XFS) for quantitative evaluation of metal particle content in engine oil suspensions and the feasibility of real-time, dynamic wear metal analysis. The study was focused on iron as the majority wear metal component. Variable parameters were: particle size, particle concentration and oil velocity. A commercial XFS spectrometer equipped with interchangeable static/dynamic (flow cell) sample chambers was used. XFS spectra were recorded for solutions of Fe-organometallic standard and for a series of DTE oil suspensions of high purity spherical iron particles of 2g, 4g, and 8g diameter, at concentrations from 5 ppm to 5,000 ppm. Real contaminated oil samples from Langley Air Force Base aircraft engines and NASA Langley Research Center wind tunnels were also analyzed. The experimental data conform the reliability of XFS as the analytical method of choice for this project. Intrinsic inadequacies of the instrument for precise analytic work at low metal concentrations were identified as being related to the particular x-ray beam definition, system geometry, and flow-cell materials selection. This work supports a proposal for the design, construction and testing of a conceptually new, miniature XFS spectrometer with superior performance, dedicated to on-line, real-time monitoring of lubricating oils in operating engines. Innovative design solutions include focalization of the incident x-ray beam, non-metal sample chamber, and miniaturization of the overall assembly. The instrument would contribute to prevention of catastrophic engine failures. A proposal for two-year funding has been presented to NASA Langley Research Center Internal Operation Group (IOG) Management, to continue the effort begun by this summer's project.

Kelliher, Warren C.; Partos, Richard D.; Nelson, Irina

1996-01-01

121

Electrochemical in-situ reaction cell for X-ray scattering, diffraction and spectroscopy  

SciTech Connect

An electrochemical in-situ reaction cell for hard X-ray experiments with battery electrodes is described. Applications include the small angle scattering, diffraction, and near-edge spectroscopy of lithium manganese oxide electrodes.

Braun, Artur; Granlund, Eric; Cairns, Elton J.

2003-01-27

122

Precision X-ray spectroscopy of 3C 273 jet knots  

E-print Network

We present results from precision X-ray spectroscopy using high-resolution ([delta lambda] = 0.01A) spectra of 3C 273 jet knots extracted from eight observations made using Chandra in conjunction with the HETGS. Using these ...

Avara, Mark J

2008-01-01

123

HIGH-RESOLUTION X-RAY SPECTROSCOPY OF THE MULTIPHASE INTERSTELLAR MEDIUM TOWARD Cyg X-2  

E-print Network

High-resolution X-ray absorption spectroscopy is a powerful diagnostic tool for probing chemical and physical properties of the interstellar medium (ISM) at various phases. We present detections of K transition absorption ...

Schulz, Norbert S.

124

X-ray imaging crystal spectroscopy for use in plasma transport research  

E-print Network

This research describes advancements in the spectral analysis and error propagation techniques associated with x-ray imaging crystal spectroscopy (XICS) that have enabled this diagnostic to be used to accurately constrain ...

Bitter, M.

125

Electronic Structure of KH2PO4 Single Crystal Studied by Soft-X-Ray Spectroscopy  

Microsoft Academic Search

The problem of resolving molecular components of the electronic structure of KH2PO4 single crystal with respect to its chemical and orbital character has been approached by X-ray absorption spectroscopy (XAS) and soft X-ray emission spectroscopy (SXES). XAS around K-absorption edge of O atom was carried out in order to the existence of relation between the electronic structure and ferroelectric phase

Tetsuya Nishina; Tohru Higuchi; Eisuke Magome; Poul Olade Velasco; Jeng Long Chen; Wang Li Yang; Jinghua Guo; Masanori Fukunaga; Masaru Komukae

2011-01-01

126

Characterization of arsenic in lake sediments by X-ray photoelectron spectroscopy  

SciTech Connect

Arsenic in the sediments of Lake Usori (Usori-ko or Osoresan-ko) and Lake Mashu (Mashu-ko) has been characterized by X-ray photoelectron spectroscopy (XPS) and X-ray induced Auger electron spectroscopy and shown to exist as sulfide and arsenite, respectively. In the Lake Mashu sediment, surface concentration of As determined by XPS was significantly higher than the average concentration.

Soma, Mitsuyuki; Tanaka, Atsushi; Seyama, Haruhiko; Satake, Kenichi (National Institute for Environmental Studies, Ibaraki (Japan))

1994-06-01

127

Characterization of arsenic in lake sediments by X-ray photoelectron spectroscopy  

Microsoft Academic Search

Arsenic in the sediments of Lake Usori (Usori-ko or Osoresan-ko) and Lake Mashu (Mashu-ko) has been characterized by X-ray photoelectron spectroscopy (XPS) and X-ray induced Auger electron spectroscopy and shown to exist as sulfide and arsenite, respectively. In the Lake Mashu sediment, surface concentration of As determined by XPS was significantly higher than the average concentration.

Mitsuyuki Soma; Atsushi Tanaka; Haruhiko Seyama; Kenichi Satake

1994-01-01

128

Analysis of chemical structure of wood charcoal by X-ray photoelectron spectroscopy  

Microsoft Academic Search

Wood charcoal carbonized at various temperatures was analyzed by X-ray photoelectron spectroscopy (XPS), Fourier-transform\\u000a infrared spectroscopy (FTIR), and X-ray diffractometry to investigate the changes of chemical structures during the carbonization\\u000a process. From the infrared spectra, the carbon double bonds and aromatic rings were seen to form at a carbonization temperature\\u000a of about 600°C. From the XPS spectra, the ratio of

Koei Nishimiya; Toshimitsu Hata; Yuji Imamura; Shigehisa Ishihara

1998-01-01

129

A robot-based detector manipulator system for a hard x-ray nanoprobe instrument.  

SciTech Connect

This paper presents the design of a robot-based detector manipulator for microdiffraction applications with a hard X-ray nanoprobe instrument system being constructed at the Advanced Photon Source (APS) for the Center for Nanoscale Materials (CNM) being constructed at Argonne National Laboratory (ANL). Applications for detectors weighing from 1.5 to 100 kg were discussed in three configurations.

Shu, D., Maser, J., Holt, M. , Winarski, R., Preissner, C.,Lai, B., Vogt, S., Stephenson, G.B.

2007-11-11

130

Mineralogy by X-ray Diffraction on Mars: The Chemin Instrument on Mars Science Laboratory  

NASA Technical Reports Server (NTRS)

To obtain detailed mineralogy information, the Mars Science Laboratory rover Curiosity carries CheMin, the first X-ray diffraction (XRD) instrument used on a planet other than Earth. CheMin has provided the first in situ XRD analyses of full phase assemblages on another planet.

Vaniman, D. T.; Bristow, T. F.; Bish, D. L.; Ming, D. W.; Blake, D. F.; Morris, R. V.; Rampe, E. B.; Chipera, S. J.; Treiman, A. H.; Morrison, S. M.; Achilles, C. N.; Downs, R. T.; Farmer, J. D.; Crisp, J. A.; Morookian, J. M.; Des Marais, D. J.; Grotzinger, J. P.; Sarrazin, P.; Yen, A. S.

2014-01-01

131

Atomic physics studies of highly charged ions on tokamaks using x-ray spectroscopy  

SciTech Connect

An overview is given of atomic physics issues which have been studied on tokamaks with the help resolution x-ray spectroscopy. The issues include the testing of model calculations predicting the excitation of line radiation, the determination of rate coefficients, and accurate atomic structure measurements. Recent research has focussed primarily on highly charged heliumlike (22 less than or equal to Z less than or equal to 28) and neonlike (34 less than or equal to Z less than or equal to 63) ions, and results are presented from measurements on the PLT and TFTR tokamaks. Many of the measurements have been aided by improved instrumental design and new measuring techniques. Remarkable agreement has been found between measurements and theory in most cases. However, in this review those areas are stressed where agreement is worst and where further investigations are needed. 19 refs., 13 figs., 2 tabs.

Beiersdorfer, P.; von Goeler, S.; Bitter, M.; Hill, K.W.

1989-07-01

132

A novel von Hamos spectrometer for efficient X-ray emission spectroscopy in the laboratory  

SciTech Connect

We present a novel, highly efficient von Hamos spectrometer for X-ray emission spectroscopy (XES) in the laboratory using highly annealed pyrolitic graphite crystals as the dispersive element. The spectrometer covers an energy range from 2.5 keV to 15 keV giving access to chemical speciation and information about the electronic configuration of 3d transition metals by means of the K? multiplet. XES spectra of Ti compounds are presented to demonstrate the speciation capabilities of the instrument. A spectral resolving power of E/?E = 2000 at 8 keV was achieved. Typical acquisition times range from 10?min for bulk material to hours for thin samples below 1??m.

Anklamm, Lars, E-mail: anklamm@physik.tu-berlin.de; Schlesiger, Christopher; Malzer, Wolfgang; Grötzsch, Daniel; Neitzel, Michael; Kanngießer, Birgit [Institute for Optic and Atomic Physics, Technical University Berlin, Hardenbergstr. 36, 10623 Berlin (Germany)

2014-05-15

133

Soft X-ray emission spectroscopy study of the valence electron states of ?-rhombohedral boron  

NASA Astrophysics Data System (ADS)

High energy-resolution boron K-emission spectra of single-crystalline ?-rhombohedral-boron (?-r-B) were measured with a newly developed soft X-ray emission spectroscopy (SXES) instrument attached to a conventional transmission electron microscope. The intensity profiles of the spectra, which correspond to the density of states of the valence bands with p-symmetry, were compared with those of amorphous boron (am-B), single-crystalline ?-rhombohedral-boron (?-r-B) and B4C. A characteristic shoulder structure appears in the spectrum of ?-r-B but not of am-B, ?-r-B or B4C. This structure should be due to the inter-cluster three-center bonding states among B12 clusters in ?-r-B.

Terauchi, Masami; Sato, Yohei; Hyodo, Hiroshi; Kimura, Kaoru

2009-06-01

134

The determination of local structural units in amorphous SiBN 3 C by means of X-ray photoelectron and X-ray absorption spectroscopy  

Microsoft Academic Search

X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) spectroscopy at the K-edge of Si, N, and B are presented as techniques suited to determine structural units in amorphous SiBN3C. The measurements reported give evidence for the presence of tetrahedral (SiN4)- and planar (BN3)-groups. It is concluded that these structural elements dominate the atomic surroundings of B and

R. Franke; St. Bender; I. Arzberger; J. Hormes; M. Jansen; H. Jüngermann; J. Löffelholz

1996-01-01

135

X-ray absorption spectroscopy of chicken sulfite oxidase crystals  

SciTech Connect

Sulfite oxidase catalyzes the physiologically vital oxidation of sulfite to sulfate. Recently, the crystal structure of chicken sulfite oxidase has been reported at 1.9 {angstrom} resolution. In contrast to the information available from previous X-ray absorption spectroscopic studies, the active site indicated by crystallography was a mono-oxo species. Because of this the possibility that the crystals did in fact contain a reduced molybdenum species was considered in the crystallographic work. The authors report herein an X-ray absorption spectroscopic study of polycrystalline sulfite oxidase prepared in the same manner as the previous single-crystal samples, and compare this with data for frozen solutions of oxidized and reduced enzyme.

George, G.N.; Pickering, I.J. [Stanford Univ., CA (United States). Stanford Synchrotron Radiation Lab.] [Stanford Univ., CA (United States). Stanford Synchrotron Radiation Lab.; Kisker, C. [State Univ. of New York, Stony Brook, NY (United States). Dept. of Pharmacological Sciences] [State Univ. of New York, Stony Brook, NY (United States). Dept. of Pharmacological Sciences

1999-05-17

136

X-ray imaging crystal spectroscopy for use in plasma transport research.  

PubMed

This research describes advancements in the spectral analysis and error propagation techniques associated with x-ray imaging crystal spectroscopy (XICS) that have enabled this diagnostic to be used to accurately constrain particle, momentum, and heat transport studies in a tokamak for the first time. Doppler tomography techniques have been extended to include propagation of statistical uncertainty due to photon noise, the effect of non-uniform instrumental broadening as well as flux surface variations in impurity density. These methods have been deployed as a suite of modeling and analysis tools, written in interactive data language (IDL) and designed for general use on tokamaks. Its application to the Alcator C-Mod XICS is discussed, along with novel spectral and spatial calibration techniques. Example ion temperature and radial electric field profiles from recent I-mode plasmas are shown, and the impact of poloidally asymmetric impurity density and natural line broadening is discussed in the context of the planned ITER x-ray crystal spectrometer. PMID:23206059

Reinke, M L; Podpaly, Y A; Bitter, M; Hutchinson, I H; Rice, J E; Delgado-Aparicio, L; Gao, C; Greenwald, M; Hill, K; Howard, N T; Hubbard, A; Hughes, J W; Pablant, N; White, A E; Wolfe, S M

2012-11-01

137

X-ray imaging crystal spectroscopy for use in plasma transport research  

NASA Astrophysics Data System (ADS)

This research describes advancements in the spectral analysis and error propagation techniques associated with x-ray imaging crystal spectroscopy (XICS) that have enabled this diagnostic to be used to accurately constrain particle, momentum, and heat transport studies in a tokamak for the first time. Doppler tomography techniques have been extended to include propagation of statistical uncertainty due to photon noise, the effect of non-uniform instrumental broadening as well as flux surface variations in impurity density. These methods have been deployed as a suite of modeling and analysis tools, written in interactive data language (IDL) and designed for general use on tokamaks. Its application to the Alcator C-Mod XICS is discussed, along with novel spectral and spatial calibration techniques. Example ion temperature and radial electric field profiles from recent I-mode plasmas are shown, and the impact of poloidally asymmetric impurity density and natural line broadening is discussed in the context of the planned ITER x-ray crystal spectrometer.

Reinke, M. L.; Podpaly, Y. A.; Bitter, M.; Hutchinson, I. H.; Rice, J. E.; Delgado-Aparicio, L.; Gao, C.; Greenwald, M.; Hill, K.; Howard, N. T.; Hubbard, A.; Hughes, J. W.; Pablant, N.; White, A. E.; Wolfe, S. M.

2012-11-01

138

X-ray imaging crystal spectroscopy for use in plasma transport research  

SciTech Connect

This research describes advancements in the spectral analysis and error propagation techniques associated with x-ray imaging crystal spectroscopy (XICS) that have enabled this diagnostic to be used to accurately constrain particle, momentum, and heat transport studies in a tokamak for the first time. Doppler tomography techniques have been extended to include propagation of statistical uncertainty due to photon noise, the effect of non-uniform instrumental broadening as well as flux surface variations in impurity density. These methods have been deployed as a suite of modeling and analysis tools, written in interactive data language (IDL) and designed for general use on tokamaks. Its application to the Alcator C-Mod XICS is discussed, along with novel spectral and spatial calibration techniques. Example ion temperature and radial electric field profiles from recent I-mode plasmas are shown, and the impact of poloidally asymmetric impurity density and natural line broadening is discussed in the context of the planned ITER x-ray crystal spectrometer.

Reinke, M. L.; Podpaly, Y. A.; Hutchinson, I. H.; Rice, J. E.; Gao, C.; Greenwald, M.; Howard, N. T.; Hubbard, A.; Hughes, J. W.; White, A. E.; Wolfe, S. M. [MIT-Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Bitter, M.; Delgado-Aparicio, L.; Hill, K.; Pablant, N. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2012-11-15

139

High resolution X-ray spectroscopy of comets  

NASA Astrophysics Data System (ADS)

Remote plasma diagnostics is an important tool for astrophysical studies. In order to fully utilize its power, a detailed knowledge of the properties of the atomic processes which give rise to the observable emission is essential. However, retrieving this information to the necessary accuracy, either by theoretical computation or by laboratory experiments, is often a challenging task. In this context, the X-ray emission of comets provides a welcome opportunity for checking and improving our knowledge of basic atomic quantities. Cometary X-ray emission is the result of charge exchange processes between highly ionized heavy atoms in the solar wind and neutrals in the cometary coma - a textbook example of an interaction between a highly ionized plasma and cold gas far from thermal equilibrium, which takes place in a huge, clean 'laboratory' fairly nearby. Thus, cometary X-ray spectra do not only provide information about the elusive properties of the heavy ion content of the solar wind over the solar cycle and in three dimensions, but are also valuable for plasma diagnostics in general.

Dennerl, K.

2009-09-01

140

High-resolution X-ray Emission Spectroscopy as a Microprobe Imaging Modality  

NASA Astrophysics Data System (ADS)

Hard x-ray microprobe beamlines at third generation light sources have made significant impacts in several fields of science and technology. Such facilities permit rapid 2-dimensional studies of multiphase materials on submicron length scales using a variety of pixel-by-pixel imaging modalities (e.g., x-ray diffraction, x-ray absorption near edge fine structure, or x-ray fluorescence). Here, we aim to expand hard x-ray microprobe imaging modalities to include high-resolution x-ray emission spectroscopy (XES). When performed at 1-eV resolution, such measurements can provide quite direct atomic-level information on ionic valence, spin, and local electronic and chemical environment. Ongoing work in our research group has improved the efficiency of XES via the development of a new type of compact and inexpensive x-ray spectrometer design, the "miniature x-ray spectrometer" or "miniXS" paradigm. We will report preliminary 2-dimensional XES studies of planar multiphase materials, with specific applications to samples of interest for geophysics and catalysis science.

Pacold, Joseph; Seidler, Gerald; Mattern, Brian; Haave, Matthew; Gordon, Robert

2011-03-01

141

Quantitative investigation of two metallohydrolases by X-ray absorption spectroscopy near-edge spectroscopy  

NASA Astrophysics Data System (ADS)

The last several years have witnessed a tremendous increase in biological applications using X-ray absorption spectroscopy (BioXAS), thanks to continuous advancements in synchrotron radiation (SR) sources and detector technology. However, XAS applications in many biological systems have been limited by the intrinsic limitations of the Extended X-ray Absorption Fine Structure (EXAFS) technique e.g., the lack of sensitivity to bond angles. As a consequence, the application of the X-ray absorption near-edge structure (XANES) spectroscopy changed this scenario that is now continuously changing with the introduction of the first quantitative XANES packages such as Minut XANES (MXAN). Here we present and discuss the XANES code MXAN, a novel XANES-fitting package that allows a quantitative analysis of experimental data applied to Zn K-edge spectra of two metalloproteins: Leptospira interrogans Peptide deformylase ( LiPDF) and acutolysin-C, a representative of snake venom metalloproteinases (SVMPs) from Agkistrodon acutus venom. The analysis on these two metallohydrolases reveals that proteolytic activities are correlated to subtle conformation changes around the zinc ion. In particular, this quantitative study clarifies the occurrence of the LiPDF catalytic mechanism via a two-water-molecules model, whereas in the acutolysin-C we have observed a different proteolytic activity correlated to structural changes around the zinc ion induced by pH variations.

Zhao, W.; Chu, W. S.; Yang, F. F.; Yu, M. J.; Chen, D. L.; Guo, X. Y.; Zhou, D. W.; Shi, N.; Marcelli, A.; Niu, L. W.; Teng, M. K.; Gong, W. M.; Benfatto, M.; Wu, Z. Y.

2007-09-01

142

Prototyping a Global Soft X-ray Imaging Instrument for Heliophysics, Planetary Science, and Astrophysics Science  

NASA Technical Reports Server (NTRS)

We describe current progress in the development of a prototype wide field-of-view soft X-ray imager that employs Lobster-eye optics and targets heliophysics, planetary, and astrophysics science. The prototype will provide proof-of-concept for a future flight instrument capable of imaging the entire dayside magnetosheath from outside the magnetosphere. Such an instrument was proposed for the FSA AXIOM mission

Collier, Michael R.; Porter, F. Scott; Sibeck, David G.; Carter, Jenny A.; Chiao, Meng P.; Chornay, Dennis J.; Cravens, Thomas; Galeazzi, Massimiliano; Keller, John W.; Koutroumpa, Dimitra; Kuntz, Kip; Read, Any M.; Robertson, Ina P.; Sembay, Steve; Snowden, Steven; Thomas, Nick

2012-01-01

143

Prototyping a Global Soft X-Ray Imaging Instrument for Heliophysics, Planetary Science, and Astrophysics Science  

NASA Technical Reports Server (NTRS)

We describe current progress in the development of a prototype wide field-of-view soft X-ray imager that employs Lobstereye optics and targets heliophysics, planetary, and astrophysics science. The prototype will provide proof-of-concept for a future flight instrument capable of imaging the entire dayside magnetosheath from outside the magnetosphere. Such an instrument was proposed for the ESA AXIOM mission.

Collier, M. R.; Porter, F. S.; Sibeck, D. G.; Carter, J. A.; Chiao, M. P.; Chornay, D. J.; Cravens, T.; Galeazzi, M.; Keller, J. W.; Koutroumpa, D.; Kuntz, K.; Read, A. M.; Robertson, I. P.; Sembay, S.; Snowden, S.; Thomas, N.

2012-01-01

144

Prototyping a global soft X-ray imaging instrument for heliophysics, planetary science, and astrophysics science  

NASA Astrophysics Data System (ADS)

We describe current progress in the development of a prototype wide field-of-view soft X-ray imager that employs Lobster-eye optics and targets heliophysics, planetary, and astrophysics science. The prototype will provide proof-of-concept for a future flight instrument capable of imaging the entire dayside magnetosheath from outside the magnetosphere. Such an instrument was proposed for the ESA AXIOM mission.

Collier, M. R.; Porter, F. S.; Sibeck, D. G.; Carter, J. A.; Chiao, M. P.; Chornay, D. J.; Cravens, T.; Galeazzi, M.; Keller, J. W.; Koutroumpa, D.; Kuntz, K.; Read, A. M.; Robertson, I. P.; Sembay, S.; Snowden, S.; Thomas, N.

2012-04-01

145

Pixellated Cd(Zn)Te high-energy X-ray instrument  

Microsoft Academic Search

We have developed a pixellated high energy X-ray detector instrument to be used in a variety of imaging applications. The instrument consists of either a Cadmium Zinc Telluride or Cadmium Telluride (Cd(Zn)Te) detector bump-bonded to a large area ASIC and packaged with a high performance data acquisition system. The 80 by 80 pixels each of 250 ?m by 250 ?m

P Seller; S Bell; R J Cernik; C Christodoulou; C K Egan; J A Gaskin; S Jacques; S Pani; B D Ramsey; C Reid; P J Sellin; J W Scuffham; R D Speller; M D Wilson; M C Veale

2011-01-01

146

High Resolution X-Ray Spectroscopy with a Microcalorimeter  

SciTech Connect

Energy-dispersive spectrometry (EDS) is often the preferred choice for X-ray microanalysis, but there are still many disadvantages associated with EDS, the most significant of which is the relatively poor energy resolution, which limits detection sensitivity and the ability to distinguish among closely spaced spectral features, limiting even qualitative analysis. A new type of EDS detector that operates on the principle of microcalorimetry has the potential to eliminate this shortcoming, reaching resolutions an order of magnitude better. The detector consists of an absorber in thermal contact with a transition edge sensor (TES). An X-ray from the specimen hits the absorber and manifests itself as a change in temperature. Because the system is kept at 80 mK, the heat capacity is low and the temperature spike is observable. The TES responds to the increase in temperature by transitioning from its superconducting to its normal conducting state, thus sharply raising the overall resistance of the circuit. The circuit is kept at a constant voltage, so the increase in resistance is manifested as a decrease in current flow. This decrease in current is measured by a superconducting quantum interference device (SQUID), and by integrating the current over time, the energy of the incident X-ray is determined. The prototype microcalorimeter was developed by NIST, and this technology is now available commercially through a partnership between Vericold Technologies and EDAX International. ORNL has received the first of these commercial microcalorimeters in the United States. The absorber in this detector is gold, and the TES consists of a gold-iridium bilayer. It is designed to offer spectral resolution of 10-15 eV at a count rate of ~150 s-1. The goal of this project was to analyze and document the performance of the detector, with particular attention given to the effects of an X-ray optic used to improve collection efficiency, the multiple window system and any other sources of spectral artifacts. It was found that the detector is capable of distinguishing many L? and L? spectral lines, with a resolution between 13 and 17 eV. It was also observed that the background has an unusual shape, and this is largely being attributed to the variable transmission coefficient of the X-ray optic. These preliminary results suggest that the microcalorimeter has a high potential for use in microanalysis, but more work to quantify its capabilities must still be done.

Norrell, J.; Anderson, I.

2005-01-01

147

Thin CdTe detector in diagnostic x-ray spectroscopy.  

PubMed

A CdTe Schottky diode detector of 1 mm thickness was employed in diagnostic x-ray spectroscopy. The detector response to monoenergetic photons was investigated with gamma rays from the calibration sources (241Am and 133Ba). As spectral distortion due to carrier trapping, known as tailing, was small in gamma-ray spectra, the effects of carrier trapping were not taken into account in the calculation of response functions. The distortion due to the transmission of primary x rays and the escape of secondary x rays (K-fluorescent x rays and Compton-scattered x rays) from the crystal was included in the calculated response functions. X-ray spectra corrected using the response functions were in good agreement with the reference spectra obtained with a high-purity germanium detector. The results indicated that correction for the distortion due to carrier trapping is not necessary when using a thin CdTe detector in diagnostic x-ray spectroscopy. PMID:12772983

Miyajima, Satoshi

2003-05-01

148

Hard X-ray imaging spectroscopy of hot coronal sources and active regions with NuSTAR  

NASA Astrophysics Data System (ADS)

We present imaging spectroscopy of the Sun with the NuSTAR hard X-ray (HXR) telescope, searching for high temperature and non-thermal emission in the “non-flaring” Sun. Launched in 2012, NASA's astrophysics mission NuSTAR uses focusing optics to directly image X-rays between ~2-80 keV. In the band below ~50 keV the field of view is 12'x12' and the instrument has an energy resolution of ~0.4 keV. Although not optimized for solar observations, NuSTAR’s high sensitivity can probe previously inaccessible X-ray emission from the Sun. NuSTAR observed the Sun three times during late 2014 and we present these first directly imaged hard X-rays from non-flaring active regions. Using NuSTAR’s imaging spectroscopy capabilities we are able to derive the active region’s multi-thermal characteristics. We will also discuss a hot (>3MK) source that appears to linger high in the corona and could be associated with the occulted active region AR12192.

Hannah, Iain; Marsh, Andrew; Glesener, Lindsay; Smith, David; Grefenstette, Brian; Madsen, Kristin; Krucker, Sam; Hudson, Hugh; White, Stephen; Shih, Albert Y.

2015-04-01

149

Very high resolution UV and X-ray spectroscopy and imagery of solar active regions  

NASA Technical Reports Server (NTRS)

A scientific investigation of the physics of the solar atmosphere, which uses the techniques of high resolution soft X-ray spectroscopy and high resolution UV imagery, is described. The experiments were conducted during a series of three sounding rocket flights. All three flights yielded excellent images in the UV range, showing unprecedented spatial resolution. The second flight recorded the X-ray spectrum of a solar flare, and the third that of an active region. A normal incidence multi-layer mirror was used during the third flight to make the first astronomical X-ray observations using this new technique.

Bruner, M.; Brown, W. A.; Haisch, B. M.

1987-01-01

150

Dose estimation by EPR spectroscopy of tooth enamel in Chinese medical diagnostic X-ray workers.  

PubMed

Individual accumulated doses were determined by electron paramagnetic resonance spectroscopy of tooth enamel in Chinese medical diagnostic X-ray workers. Dose determination was performed using a specially developed automatic spectrum processing procedure. The determined dose values owing to X rays for the three workers with entry year (the year they began their career as medical diagnostic X-ray workers) in the 1950s ranged from 435 to 903 mGy, the converted effective doses ranged from 91 to 190 mSv. PMID:16105893

Weizhang, Wu; Ao, Yu; Wenyi, Zhang; Guangfu, Dai; Liang'an, Zhang

2006-01-01

151

X-ray Raman spectroscopy of carbon in asphaltene: light element characterization with bulk sensitivity.  

PubMed

X-ray Raman spectra of the carbon K-edge have been recorded using 6.461 keV radiation for a petroleum asphaltene. By comparison with coronene, graphite, and paraffin standards, the asphaltene spectrum is seen to be composed of contributions from saturated and aromatic carbon species. The information contained in the carbon K-edge was extracted with bulk (approximately 1 mm) sensitivity, because the Raman method used hard X-rays. This helps alleviate concerns about surface artifacts that frequently occur with soft X-ray spectroscopy of light elements. X-ray Raman spectroscopy shows great potential for characterization of light elements in fuels, catalysts, and other complex materials under chemically relevant conditions. PMID:10857643

Bergmann, U; Mullins, O C; Cramer, S P

2000-06-01

152

Recent Developments of Multilayer Mirror Optics for Laboratory X-ray Instrumentation  

NASA Astrophysics Data System (ADS)

In this paper we review various improvements that we made in the development of multilayer mirror optics for home-lab x-ray analytical equipment in recent years. For the detection of light elements using x-ray fluorescence spectrometry, we developed a number of new multilayers with improved detection limits. In detail, we found that La/B4C multilayers improve the detection limit of boron by 29 % compared to the previous Mo/B4C multilayers. For the detection of carbon, TiO2/C multilayers improve the detection limit also by 29 % compared to the V/C multilayers previously used. For the detection of aluminum, WSi2/Si or Ta/Si multilayers can lead to detection limit improvements over the current W/Si multilayers of up to 60 % for samples on silicon wafers. For the use as beam-conditioning elements in x-ray diffractometry, curved optics coated with laterally d-spacing graded multilayers give rise to major improvements concerning usable x-ray intensity and beam quality. Recent developments lead to a high quality of these multilayer optics concerning beam intensity, divergence, beam uniformity and spectral purity. For example, x-ray reflectometry instruments equipped with such multilayer optics have dynamic ranges previously only available at synchrotron sources. Two-dimensional focusing multilayer optics are shown to become essential optical elements in protein crystallography and structural proteomics.

Michaelsen, Carsten; Wiesmann, Jörg; Hoffmann, C.; Wulf, K.; Brugemann, Lutz; Storm, A.

2002-12-01

153

What Can Be Learned from X-Ray Spectroscopy Concerning Hot Gas in the Local Bubble and Charge Exchange Processes?  

NASA Technical Reports Server (NTRS)

Both solar wind charge exchange emission and diffuse thermal emission from the Local Bubble are strongly dominated in the soft X-ray band by lines from highly ionized elements. While both processes share many of the same lines, the spectra should differ significantly due to the different production mechanisms, abundances, and ionization states. Despite their distinct spectral signatures, current and past observatories have lacked the spectral resolution to adequately distinguish between the two sources. High-resolution X-ray spectroscopy instrumentation proposed for future missions has the potential to answer fundamental questions such as whether there is any hot plasma in the Local Hot Bubble, and if so, what are the abundances of the emitting plasma and whether the plasma is in equilibrium. Such instrumentation will provide dynamic information about the solar wind including data on ion species which are currently difficult to track. It will also make possible remote sensing of the solar wind.

Snowden, S. L.

2008-01-01

154

Gate oxide process control optimization by x-ray photoelectron spectroscopy in a semiconductor fabrication line  

Microsoft Academic Search

X-ray photoelectron spectroscopy is a metrology technique that is used for in-line control of decoupled plasma nitridation processes in the fabrication of logic devices. This article shows XPS results of thickness and composition obtained on two types of gate oxide nitrided by a decoupled plasma nitridation process. Measurements are performed in specific test structures with an x-ray spot which can

A. Le Gouil; N. Cabuil; P. Dupeyrat; B. Dickson; M. Kwan; D. Barge; E. Gurer; O. Doclot; J.-C. Royer

2008-01-01

155

X-ray absorption spectroscopy study of prototype chemical systems: Theory vs. experiment  

Microsoft Academic Search

Understanding the details of the intensities and spectral shapes of x-ray absorption spectra is a long-standing problem in chemistry and physics. Here, I present detailed studies of x-ray absorption for prototypical liquids, solids and gases with the goal of enhancing our general understanding of core-level spectroscopy via comparisons of modern theory and experiment. In Chapter 2, I investigate the importance

Craig Philip Schwartz

2010-01-01

156

Characterization of CdTe Detectors for Quantitative X-ray Spectroscopy  

Microsoft Academic Search

Silicon diodes have traditionally been the detectors of choice for quantitative X-ray spectroscopy. Their response has been very well characterized and existing software algorithms process the spectra for accurate, quantitative analysis. But Si diodes have limited sensitivity at energies above 30 keV, while recent regulations require measurement of heavy metals such as lead and mercury, with K X-ray emissions well

Robert H. Redus; John A. Pantazis; Thanos J. Pantazis; Alan C. Huber; Brian J. Cross

2009-01-01

157

In Situ X-Ray Absorption Spectroscopy Study of the LiNiO2 Electrode  

Microsoft Academic Search

LiNiO2 is one of the most promising active material for the development of novel 4V rechargeable lithium batteries. Recent x-ray diffraction studies showed that the electrochemical reactivity of this electrode is sensitive to the structure of the starting material as well as the charged products. To further examine this material, we have conducted an x-ray absorption spectroscopy (XAS) study to

A. N. Mansour; J. McBreen; C. A. Melendres

1997-01-01

158

An X-ray absorption spectroscopy investigation of speciation and biotransformation of copper in Elsholtzia splendens  

Microsoft Academic Search

Elsholtzia splendens is a Cu-tolerant plant growing in copper mine areas in the south of China. In this study, X-ray absorption spectroscopy (XAS)\\u000a was used to investigate the Cu speciation and biotransformation in E. splendens with 300 ?M Cu treatment from 10 days to 60 days. The results showed that 300 ?M Cu was phytotoxic to E. spendens. The Cu K-edge X-ray absorption near

Jiyan Shi; Bei Wu; Xiaofeng Yuan; Cao YY; Xincai Chen; Yingxu Chen; Tiandou Hu

2008-01-01

159

Many-body Green's function approach to attosecond nonlinear x-ray spectroscopy  

SciTech Connect

Closed expressions are derived for resonant multidimensional x-ray spectroscopy using the quasiparticle nonlinear exciton representation of optical response. This formalism is applied to predict coherent four wave mixing signals which probe single and two-core-hole states. Nonlinear x-ray signals are compactly expressed in terms of one- and two-particle Green's functions which can be obtained from the solution of Hedin-type equations at the GW level.

Harbola, Upendra [Department of Chemistry and Biochemistry, University of California, San Diego, California 92093-0340 (United States); Mukamel, Shaul [Department of Chemistry, University of California, Irvine, California 92697-2025 (United States)

2009-06-15

160

X-ray absorption spectroscopy study of a copper-containing material after thermal treatment  

Microsoft Academic Search

Thermal immobilization of copper contaminant in a copper-containing solid material collected from local copper smelting and foundry area is investigated in the present work. X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) are employed for copper speciation. XAS results indicate that cupric hydroxide is the major copper species in the solid material dried at 105°C. After being subjected to a

Y.-L. Wei; M.-Y. Huang; H.-C. Wang; H.-C. Huang; J.-F. Lee

2006-01-01

161

Watching energy transfer in metalloporphyrin heterodimers using stimulated X-ray Raman spectroscopy  

PubMed Central

Understanding the excitation energy transfer mechanism in multiporphyrin arrays is key for designing artificial light-harvesting devices and other molecular electronics applications. Simulations of the stimulated X-ray Raman spectroscopy signals of a Zn/Ni porphyrin heterodimer induced by attosecond X-ray pulses show that these signals can directly reveal electron–hole pair motions. These dynamics are visualized by a natural orbital decomposition of the valence electron wavepackets. PMID:24019462

Zhang, Yu; Healion, Daniel; Mukamel, Shaul

2013-01-01

162

High resolution X- and gamma-ray spectroscopy of cosmic X-ray sources  

NASA Technical Reports Server (NTRS)

A high resolution X-ray spectrometer and large area phoswich detector were designed and co-aligned in a common elevation mounting in order to measure solar and cosmic X-ray and gamma ray emission in the 13 to 600 KeV energy range from a balloon. The instrument is described and results obtained for the Crab Nebula, the supernova remnant Cas A, and the Sun are discussed and analyzed.

Lin, R. P.

1983-01-01

163

X-ray imaging and spectroscopy using low cost COTS CMOS sensors  

NASA Astrophysics Data System (ADS)

Whilst commercial X-ray sensor arrays are capable of both imaging and spectroscopy they are currently expensive and this can limit their widespread use. This study examines the use of very low cost CMOS sensors for X-ray imaging and spectroscopy based on the commercial off the shelf (COTS) technology used in cellular telephones, PC multimedia and children's toys. Some examples of imaging using a 'webcam' and a modified OmniVision OV7411 sensor are presented, as well as a simple energy dispersive X-ray detector based on an OmniVision OV7221 sensor. In each case X-ray sensitivity was enabled by replacing the sensor's front glass window with a 5 ?m thick aluminium foil, with X-rays detected as an increase in a pixel's dark current due to the generation of additional electron-hole pairs within its active region. The exposure control and data processing requirements for imaging and spectroscopy are discussed. The modified OV7221 sensor was found to have a linear X-ray energy calibration and a resolution of approximately 510 eV.

Lane, David W.

2012-08-01

164

Investigation of surface structure with X-ray absorption and electron emission spectroscopies  

NASA Astrophysics Data System (ADS)

The use of electron spectromicroscopy for the study of the chemical composition and electronic properties of surfaces, overlayers, and interfaces has become widely accepted. Improvements to the optics of instruments such as the X-ray photo electron emission microscope have pushed spectroscopic microscopies into the realm of very high spatial resolution, at and below 1 micrometer [1]. Coupled with the high spectral resolution available from third generation synchrotron sources, this spatial resolution allows the measurement of micro-X-ray absorption near-edge spectra in addition to the more typical electron emission spectra and diffraction patterns. Complementary to the experimental developments is the development of improved theoretical methods for computational modeling of X-ray absorption and emission spectroscopies. In the field of tribochemistry, zinc dialkyl dithiophosphate (ZDDP) has long been a topic of much study. ZDDP is widely used as an anti-wear additive in engine oils and there is interest in determining the decomposition products of ZDDP that provide this protection against friction. An analysis of X-ray absorption near-edge spectra of thermal films from ZDDP samples is presented, including a comparison of the Zinc L-edge spectra with model calculations [2]. It was found essential to carry out self-consistent calculations of the electronic structure for the modeling. For the techniques of electron diffraction, a new method for a full multiple-scattering calculation of diffraction patterns from crystals with two-dimensional periodicity parallel to the surface is presented [3]. The calculation makes use of Helmholtz's reciprocity principle to compute the path-reversed process of the back propagation of a photoelectron from the position of a distant detector to that of the emitting atom. Early application is demonstrated with simulations of 64 eV M2,3VV and 914 eV L 2,3VV Auger electron diffraction from a Cu(001) surface. The functionality of the path-reversed calculation is greatly increased by extension to photoelectron diffraction for crystal surfaces with many atoms per unit cell [4]. The results are essentially indistinguishable from those of a conventional forward-path calculation. Application to photoelectron diffraction for 955 eV O 1s emission from a MgO(001) surface shows good agreement with experiment.

Pauli, Mark Daniel

165

Note: Application of a pixel-array area detector to simultaneous single crystal x-ray diffraction and x-ray absorption spectroscopy measurements  

SciTech Connect

X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) are two main x-ray techniques in synchrotron radiation facilities. In this Note, we present an experimental setup capable of performing simultaneous XRD and XAS measurements by the application of a pixel-array area detector. For XRD, the momentum transfer in specular diffraction was measured by scanning the X-ray energy with fixed incoming and outgoing x-ray angles. By selecting a small fixed region of the detector to collect the XRD signal, the rest of the area was available for collecting the x-ray fluorescence for XAS measurements. The simultaneous measurement of XRD and X-ray absorption near edge structure for Pr{sub 0.67}Sr{sub 0.33}MnO{sub 3} film was demonstrated as a proof of principle for future time-resolved pump-probe measurements. A static sample makes it easy to maintain an accurate overlap of the X-ray spot and laser pump beam.

Sun, Cheng-Jun, E-mail: cjsun@aps.anl.gov; Brewe, Dale L.; Heald, Steve M. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Zhang, Bangmin [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States) [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Department of Materials Science and Engineering, National University of Singapore, 117575 Singapore (Singapore); NUSNNI-Nanocore, National University of Singapore, 117411 Singapore (Singapore); Chen, Jing-Sheng; Chow, G. M. [Department of Materials Science and Engineering, National University of Singapore, 117575 Singapore (Singapore)] [Department of Materials Science and Engineering, National University of Singapore, 117575 Singapore (Singapore); Venkatesan, T. [NUSNNI-Nanocore, National University of Singapore, 117411 Singapore (Singapore) [NUSNNI-Nanocore, National University of Singapore, 117411 Singapore (Singapore); Department of Physics, National University of Singapore, 117542 Singapore (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, 117575 Singapore (Singapore)

2014-04-15

166

X-ray spectroscopy of the SSME plume  

NASA Technical Reports Server (NTRS)

In order to examine the potential of using SSME exhaust plume radiation in the soft X-ray spectrum as an early warning system of imminent engine failure, a low cost, low risk experiment was devised. An approach was established, equipment was leased, the system was installed and checked out, and data were successfully acquired demonstrating the proof-of-concept. One spectrum measurement of the SSME plume was acquired during a 300 second burn on the A-1 Test Stand. This spectrum showed a prominent, line emission feature at about 34.5 KeV, a result which was not expected, nor can it be explained at this time. If X-ray spectra are to be useful as a means of monitoring nominal engine operation, it will be necessary to explore this region of the EM spectrum in greater detail. The presence of structure in the spectrum indicates that this technology may prove to be useful as an engine health monitoring system.

Olive, Dan F.

1988-01-01

167

X-Ray Diffraction and Fluorescence Measurements for In-situ Planetary Instruments  

NASA Astrophysics Data System (ADS)

The X-Ray Diffraction (XRD) instruments are core components of the forthcoming NASA Mars Science Laboratory (MSL) and ESA/NASA EXOMARS missions and will provide the first demonstrations of an XRF/XRD instrument’s capabilities in-situ on an extraterrestrial planetary surface. The University of Leicester team is part of the Italy-UK collaboration that is responsible for building the ExoMars X-Ray Diffraction instrument, Mars XRD. The ExoMars X-ray diffraction instrument incorporates an 55-Fe radioisotope source and three fixed-position CCDs to simultaneously acquire an X-Ray fluorescence spectrum and a diffraction pattern providing a measurement of both elemental and mineralogical composition [1]. The CCDs cover an angular range from 6 to 65-deg enabling the analysis of silicates, from clays, or other phyllosilicates characterised by varying d-spacings, to oxides, and carbonates or evaporites. The identification of hydrous minerals may help identify past Martian hydrothermal systems capable of preserving traces of life. Here we present some initial findings from XRF and XRD tests carried out at the University of Leicester using an 55-Fe source and X-ray sensitive CCD [1]. The XRD/XRD test system consists of a single CCD on a motorised arm, an 55-Fe X-ray source, source collimator and a sample table which approximately replicate the reflection geometry of the XRD instrument. It was used to test geological reference standard materials and Martian analogues. Incidence angle and CCD angles on both the diffraction and fluorescence results were evaluated. A key area of interest is the effect of sample roughness on the XRD/XRF results. We present results from testing pressed powder pellet samples of varying surface roughness, and a comparison with model results [2]. So far we have found that increased roughness causes a reduced intensity at lower take-off angles. Several methods for measuring surface roughness of the samples have been used including an Alicona Infinite Focus microscope. [1] Marinangeli et al. (2007) LPSC #1322 [2] Hansford et al. (2010) EGU General Assembly 2010

Hansford, G.; Hill, K. S.; Vernon, D.; Ambrosi, R. M.; Bridges, J.; Hutchinson, I.

2010-12-01

168

Surface and in depth chemistry of polycrystalline WO3 thin films studied by X-ray and soft X-ray photoemission spectroscopies  

Microsoft Academic Search

The chemical composition of surface and underneath layers of WO3 thin films, deposited by thermal evaporation and annealed in air at different temperatures, has been studied by means of soft X-ray and X-ray photoemission spectroscopies. Both the W 4f and valence band spectra have been analyzed. The analysis has been performed on samples as inserted and after an annealing process

Luca Lozzi; M. Passacantando; Sandro Santucci; S. La Rosa; N. Yu. Svechnikov

2003-01-01

169

X-ray Spectroscopy for Quality Control of Chemotherapy Drugs  

SciTech Connect

We develop a method, employing Compton peak standardization and the use of matrix-matched spiked samples with Total Reflection X-ray Fluorescence (TXRF), for the determination of platinum plasma concentrations of patients undergoing chemotherapy with Pt-bearing drugs. Direct blood plasma analysis attains Pt detection limits of 70 ng/ml. Measurement results of prescribed drug doses are compared to achieved blood Pt concentrations indicating a lack of expected correlations. Direct analysis of Pt-containing infused drugs from a variety of suppliers indicates cases of abnormal concentrations which raises quality control issues. We demonstrate the potential usefulness of the method for pharmacokinetic studies or for routine optimization and quality control of Pt chemotherapy treatments.

Greaves, E. D.; Barros, H.; Bermudez, J.; Sajo-Bohus, L. [Universidad Simon Bolivar, Apartado 89000, Caracas 1080A (Venezuela); Angeli-Greaves, M. [Universidad Central de Venezuela, Apartado 90373 Caracas 1083A (Venezuela)

2007-10-26

170

Bromine in Scleractinian Coral Aragonite: X-Ray Absorption Spectroscopy  

NASA Astrophysics Data System (ADS)

Initial examination of Br K-edge XANES (x-ray absorption near-edge structure) suggests that the bulk of the bromine in these corals is present in the form of sodium bromide. We examined 12 coral specimens, including the taxa Porites lobata, Porites lutea, Pavona clavus, and Pavona gigantea, all collected live in the Pacific from Galapagos, Rarotonga, Fiji, and Gulf of Panama, and Montastrea annularis, collected from the Pleistocene of Marie Galante, Guadeloupe, in the Caribbean. The spectra of seven specimens provided sufficient detail to attempt to match the absorption edge and the first few peaks to those of the sodium bromide reference standard. The identification can be considered positive in the best sample since the match included the full XANES region and the first oscillation in the EXAFS (extended x-ray absorption fine structure) region. The quality of the data on the other 6 samples was sufficient to show consistency with the NaBr reference standard. Superficial sea salts from marine water presumably were lost when the corals were rinsed in tap water subsequent to collection, and when they were slabbed on a diamond-bladed slow-speed saw, using deionized water as a lubricant and coolant. This suggests that the bromine is present as a salt at a more intimate level of the aragonite skeletal structure, perhaps at crystal boundaries or in association with organic matter. Data were collected at the Stanford Synchrotron Radiation Laboratory on beam line 4-3 in fluorescence mode, using a Lytle detector and a Se 6 filter. A sodium bromide foil was run behind the Lytle detector as an internal reference.

Pingitore, N. E.; Cruz-Jimenez, G.; Wellington, G. M.

2002-05-01

171

A stored-ion target for x-ray spectroscopy of multicharged ions  

SciTech Connect

With the evolution of the new third generation synchrotron radiation sources providing intense beams of hard x-rays, it is natural to consider exploiting these to investigate the 3-body Coulomb problem. The atomic physics community could advance this field considerably by developing general techniques to investigate the x-ray spectroscopy of heliumlike ions. To do so, however, requires the development of a target of such ions with sufficient density to permit photoexcitation studies in the hard x-ray regime. A possible scheme to achieve this is described. Such a target system would permit x-ray studies with exotic species such as highly charged atomic ions, size-selected cluster ions, and atomic and molecular negative ions which have hitherto been impractical to study with conventional techniques.

Kanter, E.P.

1996-08-01

172

Ultrafast conversions between hydrogen bonded structures in liquid water observed by femtosecond x-ray spectroscopy  

SciTech Connect

We present the first femtosecond soft x-ray spectroscopy in liquids, enabling the observation of changes in hydrogen bond structures in water via core-hole excitation. The oxygen K-edge of vibrationally excited water is probed with femtosecond soft x-ray pulses, exploiting the relation between different water structures and distinct x-ray spectral features. After excitation of the intramolecular OH stretching vibration, characteristic x-ray absorption changes monitor the conversion of strongly hydrogen-bonded water structures to more disordered structures with weaker hydrogen-bonding described by a single subpicosecond time constant. The latter describes the thermalization time of vibrational excitations and defines the characteristic maximum rate with which nonequilibrium populations of more strongly hydrogen-bonded water structures convert to less-bonded ones. On short time scales, the relaxation of vibrational excitations leads to a transient high-pressure state and a transient absorption spectrum different from that of statically heated water.

Wen, Haidan; Huse, Nils; Schoenlein, Robert W.; Lindenberg, Aaron M.

2010-05-01

173

X-ray photoemission and energy dispersive spectroscopy of hydroxyapatite-coated titanium  

SciTech Connect

The purpose of this study was to determine the chemical composition changes of hydroxyapatite (HA) coated titanium using surface analysis (X-ray photoemission) and bulk analysis (energy dispersive spectroscopy). The specimens examined were controls and specimens aged 30 min and 3 h at room temperature in distilled water and 0.2M sodium phosphate buffer (pH 7.2). Each X-ray photoemission cycle consisted of three scans followed by argon sputtering for 10 min for usually 20 cycles, corresponding to a sampling depth of {approximately}1,500 {angstrom}. The energy dispersive spectroscopy analysis was on a 110 by 90 {micro}m area for 500 s. The X-ray photoemission results indicated the oxidation effect of water on the titanium (as TiO{sub 2}) and the effect of the buffer to increase the surface concentration of phosphorus. No differences in the chemical composition were observed by energy dispersive spectroscopy analysis.

Drummond, J.L.; Steinberg, A.D. [Univ. of Illinois, Chicago, IL (United States). Coll. of Dentistry; Krauss, A.R. [Argonne National Lab., IL (United States)

1997-07-01

174

X-Ray Diffraction Techniques for a Field Instrument: Patterns of Lithologic Provences  

NASA Technical Reports Server (NTRS)

Future exploration of Mars will attempt to shed light on the mineralogy of surface materials. Instruments deployed from remote platforms should have the capability to conduct both intensive analyses as well as rapid, reconnaissance surveys while they function in the martian environment as surrogate geologists. In order to accommodate the reconnaissance mode of analysis and to compensate for analytical limitations imposed by the space-flight conditions, data analysis methods are being developed that will permit interpretation of data by recognition of signatures or "fingerprints". Specifically, we are developing a technique which will allow interpretation of diffraction patterns by recognition of characteristic signatures of different lithologic provences. This technique allows a remote vehicle to function in a rapid-scan mode using the lithologic signature to determine where a more thorough analysis is needed. An x-ray diffraction pattern is characterized by the angular positions of diffracted x-rays, x-ray intensity levels and background radiation levels. These elements may be used to identify a generalized x-ray signature. Lithologic signatures are being developed in two ways. A signature is composed using the ideal powder diffraction indices from the mineral assembledge common to a specific lithologic provence. This is then confirmed using a laboratory diffraction pattern of a whole rock powder. Preliminary results comparing the diffraction signatures of the major mineral assembledges common to basalt, carbonate, and evaporite basin deposits indicate that lithologies are differentiable as a "fingerprint". Statistical analyses are being performed to establish the confidence levels of this technique.

Marshall, J.; Keaten, R.

1999-01-01

175

A Positional X-ray Instrumentation Test Stand For Beam-Line Experiments  

NASA Astrophysics Data System (ADS)

A multi-axis, motion controlled test stand has been built in the PSU 47 m X-ray beam-line for the purpose of testing X-ray instrumentation and mirrors using parallel rays. The test stand is capable of translation along two axes and rotation about two axes with motorized fine position control. The translation stages have a range of motion of 200 mm with a movement accuracy of ± 2.5 microns. Rotation is accomplished with a two-axis gimbal which can rotate 360° about one axis and 240° about another; movement with ± 35 arcsecond accuracy are achieved in both axes. The position and status are monitored using a LabView program. An XCalibr source with multiple target materials is used as an X-ray source and can produce multiple lines between 0.8 and 8 keV. Some sample spectra are shown from a Si-PIN diode detector. This system is well suited for testing X-ray mirror segments which are currently being developed.

Nikoleyczik, Jonathan; Prieskorn, Z.; Burrows, D. N.; Falcone, A.

2014-01-01

176

Instrumental limits to our knowledge of the X-ray sky  

NASA Astrophysics Data System (ADS)

In the last decade, performances of X-ray detectors have improved over all parameter spaces (throughput, energy and spatial resolution, timing). However, the quality of our science is only as good as the quality our instruments' calibration. Measurements of X-ray observables in celestial sources are increasingly limited by systematic rather then by statistical errors. Unfortunately, all attempts at defining X-ray "standard candles" have proven unsuccessful so far. The energy scale can be still absolutely calibrated through emission lines produced by atomic transitions in on-board or astrophysical calibration sources. Likewise, timing accuracy can be estimated using fast rotators such as the Crab pulsar. On the other hand, uncertainties at the level of the order of 10% (and more) affect the absolute flux calibration. These "cross-calibration" uncertainties are energy-dependent, thus implying uncertainties on spectral measurements. I present in this talk the calibration and cross-calibration status of historical and operational X-ray detectors. Efforts to monitor, document and improve the cross-calibration status are carried out primarily by the IACHEC (International Astronomical Consortium for High Energy Calibration: http://web.mit.edu/iachec/). I will also briefly discuss the impact that these uncertainties (may) have on fields as diverse as the measurements of spin in accreting black holes, and the determination of cosmological parameters through surveys of galaxy clusters.

Guainazzi, Matteo

2014-08-01

177

Feasibility of an integrated X-ray instrument for Mars exobiology and geology. [Abstract only  

NASA Technical Reports Server (NTRS)

By employing an integrated X-ray instrument on a future Mars mission, data obtained will greatly augment those returned by Viking; details relevant to the possibility of the origin and evolution of life on Mars will be acquired. An integrated combined X Ray Fluorescence/X Ray Detection (XRF/XRD) instrument has been breadboarded and demonstrated to accommodate important exobiology and geology experiment objectives outlined for Mars Environmental Survey (MESUR) and future Mars missions. Among others, primary objectives for the exploration of Mars include: the intense study of local areas on Mars to 'establish the chemical, mineralogical, and petrological character of different components of the surface material; to determine the distribution, abundance and sources and sinks of volatile materials, including an assessment of the biologic potential, now and during past epochs; and to establish the global chemical and physical characteristics of the Martian surface'. The XRF/XRD breadboard instrument identifies and quantifies soil surface elemental, mineralogical, and petrological characteristics and acquires data necessary to address questions on volatile abundance and distribution. Additionally, the breadboard is able to characterize the biogenic element constituents of soil samples providing information on the biologic potential of the Mars environment.

Fonda, M. L.; Schwartz, D. E.; Koppel, L. N.; Franco, E. D.; Kerner, J. A.

1994-01-01

178

In situ anodization of aluminum surfaces studied by x-ray reflectivity and electrochemical impedance spectroscopy  

SciTech Connect

We present results from the anodization of an aluminum single crystal [Al(111)] and an aluminum alloy [Al 6060] studied by in situ x-ray reflectivity, in situ electrochemical impedance spectroscopy and ex situ scanning electron microscopy. For both samples, a linear increase of oxide film thickness with increasing anodization voltage was found. However, the slope is much higher in the single crystal case, and the break-up of the oxide film grown on the alloy occurs at a lower anodization potential than on the single crystal. The reasons for these observations are discussed as are the measured differences observed for x-ray reflectivity and electrochemical impedance spectroscopy.

Bertram, F., E-mail: florian.bertram@sljus.lu.se; Evertsson, J.; Messing, M. E.; Mikkelsen, A.; Lundgren, E. [Division of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund (Sweden); Zhang, F.; Pan, J. [KTH Royal Institute of Technology, School of Chemical Science and Engineering, Department of Chemistry, Division of Surface and Corrosion Science, Drottning Kristinas väg 51, 10044 Stockholm (Sweden); Carlà, F. [ESRF, B. P. 220, 38043 Grenoble (France); Nilsson, J.-O. [Sapa Technology, Kanalgatan 1, 612 31 Finspång (Sweden)

2014-07-21

179

FORTRAN program for x ray photoelectron spectroscopy data reformatting  

NASA Technical Reports Server (NTRS)

A FORTRAN program has been written for use on an IBM PC/XT or AT or compatible microcomputer (personal computer, PC) that converts a column of ASCII-format numbers into a binary-format file suitable for interactive analysis on a Digital Equipment Corporation (DEC) computer running the VGS-5000 Enhanced Data Processing (EDP) software package. The incompatible floating-point number representations of the two computers were compared, and a subroutine was created to correctly store floating-point numbers on the IBM PC, which can be directly read by the DEC computer. Any file transfer protocol having provision for binary data can be used to transmit the resulting file from the PC to the DEC machine. The data file header required by the EDP programs for an x ray photoelectron spectrum is also written to the file. The user is prompted for the relevant experimental parameters, which are then properly coded into the format used internally by all of the VGS-5000 series EDP packages.

Abel, Phillip B.

1989-01-01

180

X-ray photoelectron spectroscopy and X-ray-excited Auger electron spectroscopy studies of diamondlike carbon films deposited using unbalanced magnetron sputtering  

NASA Astrophysics Data System (ADS)

The electronic structure of diamondlike carbon (DLC) films deposited using unbalanced magnetron sputtering is examined using Electron Energy-Loss, X-ray photoelectron and X-ray-excited Auger spectroscopies. The characteristics of DLC films are discussed as functions of deposition conditions, e.g. argon gas pressure and substrate bias voltage. As the substrate bias voltage is increased, the films show the evidence of graphite and carbide formation as revealed in the C 1s and valance band spectra. However, with increasing argon gas pressure, the electron spectra of the films show diamondlike structure. ^1 Soon-Cheon Seo, David C. Ingram, and Hugh H. Richardson, J. Vac. Sci. Technol. A 13 Nov/Dec (1995).

Seo, Soon-Cheon; Ingram, David C.

1996-03-01

181

X-ray temperature spectroscopy of simulated cooling clusters  

E-print Network

Results from a large sample of hydrodynamical/N-body simulations of galaxy clusters in a LCDM cosmology are used to simulate cluster X-ray observations as expected from Chandra observations. The physical modeling of the gas includes radiative cooling, star formation, energy feedback and metal enrichment. The biasing of spectral temperatures with respect to mass-weighted temperatures is found to be influenced by two independent processes. The first scale dependency is absent in adiabatic runs and is due to cooling, whose efficiency to transform cold gas into stars is higher for cool clusters and this in turn implies a strong dependency of the spectral versus mass-weighted temperature relation on the cluster mass. The second dependency is due to photon emission because of cool gas which is accreted during merging events and biases the spectral fits. These events have been quantified according to the power ratio method and a robust correlation is found to exist between the spectral bias and the amount of cluster substructure. The shape of the simulated temperature profiles is not universal and it is steeper at the cluster center for cool clusters than for the massive ones. The profiles are in good agreement with data in the radial range between $\\sim 0.1 r_{vir}$ and $\\sim 0.4 r_{vir}$; at small radii ($r< 0.1 r_{vir}$) the cooling runs fail to reproduce the shape of the observed profiles. The fit is improved if one considers a hierarchical merging scenario in which cluster cores can accrete cooler gas through merging with cluster subclumps, though the shape of the temperature profiles is modified in a significant way only in the regime where the mass of the substructure is a large fraction of the cluster mass.

R. Valdarnini

2006-08-17

182

Spatially resolved high resolution x-ray spectroscopy for magnetically confined fusion plasmas (invited).  

PubMed

The use of high resolution x-ray crystal spectrometers to diagnose fusion plasmas has been limited by the poor spatial localization associated with chord integrated measurements. Taking advantage of a new x-ray imaging spectrometer concept [M. Bitter et al., Rev. Sci. Instrum. 75, 3660 (2004)], and improvements in x-ray detector technology [Ch. Broennimann et al., J. Synchrotron Radiat. 13, 120 (2006)], a spatially resolving high resolution x-ray spectrometer has been built and installed on the Alcator C-Mod tokamak. This instrument utilizes a spherically bent quartz crystal and a set of two dimensional x-ray detectors arranged in the Johann configuration [H. H. Johann, Z. Phys. 69, 185 (1931)] to image the entire plasma cross section with a spatial resolution of about 1 cm. The spectrometer was designed to measure line emission from H-like and He-like argon in the wavelength range 3.7 and 4.0 A with a resolving power of approximately 10,000 at frame rates up to 200 Hz. Using spectral tomographic techniques [I. Condrea, Phys. Plasmas 11, 2427 (2004)] the line integrated spectra can be inverted to infer profiles of impurity emissivity, velocity, and temperature. From these quantities it is then possible to calculate impurity density and electron temperature profiles. An overview of the instrument, analysis techniques, and example profiles are presented. PMID:19044464

Ince-Cushman, A; Rice, J E; Bitter, M; Reinke, M L; Hill, K W; Gu, M F; Eikenberry, E; Broennimann, Ch; Scott, S; Podpaly, Y; Lee, S G; Marmar, E S

2008-10-01

183

Use of portable X-ray fluorescence instrument for bulk alloy analysis on low corroded indoor bronzes  

NASA Astrophysics Data System (ADS)

One of the most often used non-destructive methods for elemental analysis when performing field measurements on bronze sculptures is X-ray fluorescence (XRF) analysis based on portable instrumentation. However, when performing routine in-situ XRF analysis on corroded objects obtained results are sometimes considerably influenced by the corrosion surface products. In this work the suitability of portable XRF for bulk analysis of low corroded bronzes, which were initially precisely characterized using sophisticated and reliable laboratory methods, was investigated and some improvements in measuring technique and data processing were given. Artificially corroded bronze samples were analyzed by a portable XRF instrument using the same methodology and procedures as when performing in-situ analysis on real objects. The samples were first investigated using sophisticated complementary laboratory techniques: Scanning Electron Microscopy, Proton-Induced X-ray Emission Spectroscopy and Rutherford Backscattering Spectrometry, in order to gain precise information on the formation of the corrosion product layers and in-depth elemental profile of corrosion layers for different aging parameters. It has been shown that for corrosion layers of up to ca. 25 ?m a portable XRF can yield very accurate quantification results.

Šatovi?, D.; Desnica, V.; Fazini?, S.

2013-11-01

184

Visible, EUV, and X-ray Spectroscopy at the NIST EBIT Facility  

E-print Network

After a brief introduction to the NIST EBIT facility, we present the results of three different types of experiments that have been carried out there recently: EUV and visible spectroscopy in support of the microelectronics industry, laboratory astrophysics using an x-ray microcalorimeter, and charge exchange studies using extracted beams of highly charged ions.

J. D. Gillaspy; B. Blagojevic; A. Dalgarno; K. Fahey; V. Kharchenko; J. M. Laming; E. -O. Le Bigot; L. Lugosi; K. Makonyi; L. P. Ratliff; H. W. Schnopper; E. H. Silver; E. Takacs; J. N. Tan; H. Tawara; K. Tokési

2006-03-16

185

X-ray photon correlation spectroscopy using the Mythen 1D detector  

NASA Astrophysics Data System (ADS)

X-ray Photon Correlation Spectroscopy (XPCS) is an experimental technique to measure the dynamics of materials on nano- and microscales. Often, the maximum frame rate of the detector limits which dynamical processes can be investigated. This study examines the applicability of the Mythen 1D detector for coherent scattering applications with special focus on XPCS experiments.

Westermeier, F.; Zozulya, A. V.; Bondarenko, S.; Parenti, A.; Lohmann, M.; Schavkan, A.; Grübel, G.; Sprung, M.

2013-03-01

186

Visible, EUV, and X-ray Spectroscopy at the NIST EBIT Facility  

SciTech Connect

After a brief introduction to the NIST EBIT facility, we present the results of three different types of experiments that have been carried out there recently: EUV and visible spectroscopy in support of the microelectronics industry, laboratory astrophysics using an x-ray microcalorimeter, and charge exchange studies using extracted beams of highly charged ions.

Gillaspy, J.D.; Blagojevic, B.; Le Bigot, E.-O.; Makonyi, K.; Ratliff, L.P.; Tan, J.N. [National Institute of Standards and Technology, Gaithersburg, MD 20899-8421 (United States); Dalgarno, A.; Kharchenko, V.; Schnopper, H.W.; Silver, E.H. [Harvard-Smithonian Center for Astrophysics, 60 Garden St., Cambridge, MA 0213 (United States); Fahey, K. [National Institute of Standards and Technology, Gaithersburg, MD 20899-8421 (United States); University College Dublin, Department of Experimental Physics. Belfield, Dublin 4 (Ireland); Laming, J.M. [E.O. Hurlburt Center for Space Research, Naval Research Lab, Washington, DC 20375 (United States); Lugosi, L.; Tokesi, K. [Institute of Nuclear Research of the Hungarian Academy of Sciences, Debrecen, Bem ter 18/c, H-4026 (Hungary); Takacs, E. [National Institute of Standards and Technology, Gaithersburg, MD 20899-8421 (United States); University of Debrecen, Experimental Physics Department, Debrecen, Bem ter 18/a, H-4026 (Hungary); Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 20375 (United States); Tawara, H. [National Institute of Standards and Technology, Gaithersburg, MD 20899-8421 (United States); The Queen's University, Department of Pure and Applied Physics, Belfast BT7 1NN (United Kingdom)

2004-10-20

187

Passive Spectroscopy Bolometers, Grating- And X-ray Imaging Crystal Spectrometers  

SciTech Connect

This tutorial gives a brief introduction into passive spectroscopy and describes the working principles of bolometers, a high-resolution grating spectrometer, and a novel X-ray imaging crystal spectrometer, which is also of particular interest for profile measurements of the ion temperature and plasma rotation velocity on ITER and future burning plasma experiments.

Bitter, M.; Hill, K. W.; Scott, S.; Paul, S. [Princeton Plasma Physics Laboratory, Princeton, NJ, 08543 (United States); Ince-Cushman, A.; Reinke, M.; Rice, J. E. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Beiersdorfer, P.; Gu, M. F. [Lawrence Livermore national Laboratory, Livermore, CA 94550-9234 (United States); Lee, S. G. [Korea Basic Science Institute, Taejeon 305-333 (Korea, Republic of); Broennimann, Ch.; Eikenberry, E. F. [Paul Scherrer Institut, CH5232 Villigen-PSI (Switzerland)

2008-03-12

188

THE JOURNAL OF CHEMICAL PHYSICS 135, 074505 (2011) X-Ray absorption spectroscopy investigation  

E-print Network

properties of ILs requires a de- tailed understanding of their structural and dynamical fea- tures at atomic used and a deep understanding of their structural properties, such as the nature of the interactionTHE JOURNAL OF CHEMICAL PHYSICS 135, 074505 (2011) X-Ray absorption spectroscopy investigation of 1

Boyer, Edmond

2011-01-01

189

Partial X-ray photoelectron spectroscopy to constructing neural network model of plasma etching surface  

Microsoft Academic Search

A new model to control plasma processes was constructed by combining a backpropagation neural network (BPNN) with X-ray photoelectron spectroscopy (XPS). This technique was evaluated with the data collected during the etching of silicon carbide films at NF3 inductively coupled plasma. The etching characteristics modeled were the etch rate and surface roughness measured by scanning electron microscope and atomic force

Byungwhan Kim; Woo Suk Kim

2007-01-01

190

X-ray Absorption Spectroscopy Study of the Effects of pH and Ionic  

E-print Network

X-ray Absorption Spectroscopy Study of the Effects of pH and Ionic Strength on Pb(II) Sorption SiO2 was studied as a function of pH and ionic strength using XAS to characterize the sorption products formed. Pb sorption increased with increasing pH and decreasing ionic strength. The XAS data

Sparks, Donald L.

191

Quantitative arsenic speciation in mine tailings using X-ray absorption spectroscopy  

Microsoft Academic Search

X-ray absorption fine structure spectroscopy (XAFS) was used to determine arsenic (As) oxidation state, local coordination (to a radius of 7Aaround As), and the relative proportion of different As species in model compounds and three California mine wastes: fully oxidized tailings (Ruth Mine), partially oxidized tailings (Argonaut Mine), and roast- ed sulfide ore (Spenceville Mine). Mineralogy was characterized by Rietveld

ANDREA L. FOSTER; GORDON E. BROWN JR; TRACY N. TINGLE; GEORGE A. PARKS

192

Multi-angular regolith effects on planetary soft X-ray fluorescence spectroscopy  

NASA Astrophysics Data System (ADS)

Fluorescent X-rays from the surfaces of airless planetary bodies in the inner solar system have been measured by instruments on several spacecraft. MESSENGER carries an X-ray spectrometer (XRS) on-board and has already attempted to obtain fluorescent X-rays from the Hermean surface. BepiColombo will later on carry an X-ray telescope (MIXS-T) along with a more conventional collimating detector (MIXS-C) to the Hermean orbit, supported by a next-generation X-ray solar monitor (SIXS). These instruments will provide unprecedented knowledge about the geochemical properties of the Hermean regolith. X-ray emission from planetary surfaces follows photoionisation by incident solar X-rays and charged particles and reveals information about the elemental composition of the surface. Analyses of X-ray spectra, obtained by orbiting spacecraft, use both the relative intensities of elemental emission lines (e.g., Ca/Si, Fe/Si) and absolute abundancies of the elements to determine the geochemistry of the target body. Historically, the analysis of X-ray spectra has largely assumed that surfaces can be considered as homogeneous plane-parallel media. It has been shown, however, that fluorescent line intensities are affected by the physical properties of the target surface (e.g., surface roughness of the regolith) as a function of the viewing and illumination geometry of observations in a way that cannot be explained by the traditional models. We describe experimental investigations where we simulated the effects of regolith properties on the fluorescent lines measured by an orbiting instrument, with a large variety of illumination and viewing angles. The planetary regolith analogue used in these experiments was a terrestrial, olivine rich basalt, which has been used by previous authors as an analogue to the lunar maria. The basalt samples were ground to powder and sieved to discriminate particles in the ranges, <75 micrometers, 75-250 micrometers, and 250-500 micrometers. These separate powders were then pressed into solid pellets. The separation of particles with different sizes allows some determination of the effects due to changes in, e.g., surface roughness. The pellets were imaged with a CT scanner to obtain the physical parameters of the samples. All measurements were made at near-vacuum pressures to prevent absorption of fluorescent X-rays in air. The relative fluorescent line ratios of several major rock-forming elements (e.g., Si, K, Ca, Ti, Fe) were measured. In addition to experimental studies we have simulated the X-ray emission from a regolith using a numerical Monte-Carlo ray-tracing model. This model simulates a regolith of spherical particles, with defined physical properties (particle size distribution, packing density, etc.) and with a realistic macro-scale surface roughness characteristics generated by constraining the surface with a fractional-Brownian-motion surface model. A comparison is made between the modelling and experimental results to validate the modelling. A good agreement between the results is found. We find that both the measured and the simulated spectra become increasingly hard as the phase angle increases (i.e., X-ray lines at higher energies are enhanced relative to those at lower energies). Some hardening of spectra is predicted by the fundamental parameters equation (FPE) of X-ray fluorescence, which assumes a smooth, flat, and homogeneous surface, but we observe further spectral hardening that is in excess to that predicted by the FPE and that this excess hardening is also a function of the surface roughness. We propose to use modelling similar to ours for the data analysis of soft X-ray fluorescence spectra to take the multi-angular effects related to the physical properties of the regolith into account.

Näränen, J.; Parviainen, H.; Carpenter, J.; Muinonen, K.

2009-04-01

193

Set of instruments for solar EUV and soft X-ray monitoring onboard satellite Coronas-Photon  

NASA Astrophysics Data System (ADS)

Coronas-Photon mission is the third satellite of the Russian Coronas program on solar activity observation. The main goal of the "Coronas-Photon" is the study of solar hard electromagnetic radiation in the wide energy range from UV up to high energy gamma-radiation (2000MeV). Scientific payload for solar radiation observation consists of three types of instruments: Monitors (Natalya-2M, Konus-RF, RT-2, Penguin-M, BRM, PHOKA, Sphin-X, SOKOL spectral and timing measurements of full solar disk radiation have timing in flare/burst mode up to one msec. Instruments Natalya-2M, Konus-RF, RT-2 will cover the wide energy range of hard X-rays and soft gamma-rays (15keV to 2000MeV) and will together constitute the largest area detectors ever used for solar observations. Detectors of gamma-ray monitors are based on structured inorganic scintillators. For X-ray and EUV monitors the scintillation phoswich detectors, gas proportional counter, CdZnTe assembly and filter-covered Si-diodes are used. Telescope-spectrometer TESIS for imaging solar spectroscopy in X-rays has angular resolution up to 1arcsec in three spectral lines. Satellite platform and scientific payload is under construction to be launched in autumn 2008. Satellite orbit is circular with initial height 550km and inclination 82.5degrees. Accuracy of the spacecraft orientation to the Sun is better 3arcmin. In the report the capability of PHOKA, SphinX, SOKOL and TESIS as well as the observation program are described and discussed.

Kotov, Yury; Kochemasov, Alexey; Kuzin, Sergey; Kuznetsov, Vladimir; Sylwester, Janusz; Yurov, Vitaly

194

X-Ray Diffraction and Fluorescence Measurements for In Situ Planetary Instruments  

NASA Astrophysics Data System (ADS)

The ESA/NASA ExoMars mission, due for launch in 2018, has a combined X-ray fluorescence/diffraction instrument, Mars-XRD, as part of the onboard analytical laboratory. The results of some XRF (X-ray fluorescence) and XRD (X-ray diffraction) tests using a laboratory chamber with representative performance are reported. A range of standard geological reference materials and analogues were used in these tests. The XRD instruments are core components of the forthcoming NASA Mars Science Laboratory (MSL) and ESA/NASA ExoMars missions and will provide the first demonstrations of the capabilities of combined XRD/XRF instrumentation in situ on an extraterrestrial planetary surface. The University of Leicester team is part of the Italy-UK collaboration that is responsible for building the ExoMars X-ray diffraction instrument, Mars-XRD [1,2]. Mars-XRD incorporates an Fe-55 radioisotope source and three fixed-position charge-coupled devices (CCDs) to simultaneously acquire an X-ray fluorescence spectrum and a diffraction pattern providing a measurement of both elemental and mineralogical composition. The CCDs cover an angular range of 2? = 6° to 73° enabling the analysis of a wide range of geologically important minerals including phyllosilicates, feldspars, oxides, carbonates and evaporites. The identification of hydrous minerals may help identify past Martian hydrothermal systems capable of preserving traces of life. Here we present some initial findings from XRF and XRD tests carried out at the University of Leicester using an Fe-55 source and X-ray sensitive CCD. The XRF/XRD test system consists of a single CCD on a motorised arm, an Fe-55 X-ray source, a collimator and a sample table which approximately replicate the reflection geometry of the Mars-XRD instrument. It was used to test geological reference standard materials and Martian analogues. This work was funded by the Science and Technology Facilities Council, UK. References [1] Marinangeli, L., Hutchinson, I., Baliva, A., Stevoli, A., Ambrosi, R., Critani, F., Delhez, R., Scandelli, L., Holland, A., Nelms, N. & the Mars-XRD Team, Proceedings of the 38th Lunar and Planetary Science Conference, 12 - 16 March 2007, League City, Texas, USA. [2] L. Marinangeli, I. B. Hutchinson, A. Stevoli, G. Adami, R. Ambrosi, R. Amils, V. Assis Fernandes, A. Baliva, A. T. Basilevsky, G. Benedix, P. Bland, A. J. Böttger, J. Bridges, G. Caprarelli, G. Cressey, F. Critani, N. d'Alessandro, R. Delhez, C. Domeneghetti, D. Fernandez-Remolar, R. Filippone, A. M. Fioretti, J. M. Garcia Ruiz, M. Gilmore, G. M. Hansford, G. Iezzi, R. Ingley, M. Ivanov, G. Marseguerra, L. Moroz, C. Pelliciari, P. Petrinca, E. Piluso, L. Pompilio, J. Sykes, F. Westall and the MARS-XRD Team, EPSC-DPS Joint Meeting 2011, 3 - 7 October 2011, La Cité Internationale des Congrès Nantes Métropole, Nantes, France.

Hansford, G.; Hill, K. S.; Talboys, D.; Vernon, D.; Ambrosi, R.; Bridges, J.; Hutchinson, I.; Marinangeli, L.

2011-12-01

195

THE JOURNAL OF CHEMICAL PHYSICS 137, 194306 (2012) Core and valence excitations in resonant X-ray spectroscopy  

E-print Network

stimulated X-ray Raman spectroscopy (SXRS) signals of cysteine at the oxygen, nitrogen, and sulfur K and L2. It was performed in atoms. Impulsive 1D- stimulated X-ray Raman spectroscopy (SXRS)6 and 2D- SXRS signals7 wereTHE JOURNAL OF CHEMICAL PHYSICS 137, 194306 (2012) Core and valence excitations in resonant X

Mukamel, Shaul

196

High-resolution soft X-ray beamline ADRESS at the Swiss Light Source for resonant inelastic X-ray scattering and angle-resolved photoelectron spectroscopies  

PubMed Central

The concepts and technical realisation of the high-resolution soft X-ray beamline ADRESS operating in the energy range from 300 to 1600?eV and intended for resonant inelastic X-ray scattering (RIXS) and angle-resolved photoelectron spectroscopy (ARPES) are described. The photon source is an undulator of novel fixed-gap design where longitudinal movement of permanent magnetic arrays controls not only the light polarization (including circular and 0–180° rotatable linear polarizations) but also the energy without changing the gap. The beamline optics is based on the well established scheme of plane-grating monochromator operating in collimated light. The ultimate resolving power E/?E is above 33000 at 1?keV photon energy. The choice of blazed versus lamellar gratings and optimization of their profile parameters is described. Owing to glancing angles on the mirrors as well as optimized groove densities and profiles of the gratings, the beamline is capable of delivering high photon flux up to 1 × 1013?photons s?1 (0.01% BW)?1 at 1?keV. Ellipsoidal refocusing optics used for the RIXS endstation demagnifies the vertical spot size down to 4?µm, which allows slitless operation and thus maximal transmission of the high-resolution RIXS spectrometer delivering E/?E > 11000 at 1?keV photon energy. Apart from the beamline optics, an overview of the control system is given, the diagnostics and software tools are described, and strategies used for the optical alignment are discussed. An introduction to the concepts and instrumental realisation of the ARPES and RIXS endstations is given. PMID:20724785

Strocov, V. N.; Schmitt, T.; Flechsig, U.; Schmidt, T.; Imhof, A.; Chen, Q.; Raabe, J.; Betemps, R.; Zimoch, D.; Krempasky, J.; Wang, X.; Grioni, M.; Piazzalunga, A.; Patthey, L.

2010-01-01

197

Energy-dispersive X-ray absorption spectroscopy at LNLS: investigation on strongly correlated metal oxides.  

PubMed

An energy-dispersive X-ray absorption spectroscopy beamline mainly dedicated to X-ray magnetic circular dichroism (XMCD) and material science under extreme conditions has been implemented in a bending-magnet port at the Brazilian Synchrotron Light Laboratory. Here the beamline technical characteristics are described, including the most important aspects of the mechanics, optical elements and detection set-up. The beamline performance is then illustrated through two case studies on strongly correlated transition metal oxides: an XMCD insight into the modifications of the magnetic properties of Cr-doped manganites and the structural deformation in nickel perovskites under high applied pressure. PMID:20029117

Cezar, Júlio C; Souza-Neto, Narcizo M; Piamonteze, Cínthia; Tamura, Edilson; Garcia, Flávio; Carvalho, Edson J; Neueschwander, Régis T; Ramos, Aline Y; Tolentino, Hélio C N; Caneiro, Alberto; Massa, Nestor E; Martinez-Lope, Maria Jesus; Alonso, Jose Antonio; Itié, Jean Paul

2010-01-01

198

Two-dimensional stimulated resonance Raman spectroscopy of molecules with broadband x-ray pulses  

SciTech Connect

Expressions for the two-dimensional stimulated x-ray Raman spectroscopy (2D-SXRS) signal obtained using attosecond x-ray pulses are derived. The 1D- and 2D-SXRS signals are calculated for trans-N-methyl acetamide (NMA) with broad bandwidth (181 as, 14.2 eV FWHM) pulses tuned to the oxygen and nitrogen K-edges. Crosspeaks in 2D signals reveal electronic Franck-Condon overlaps between valence orbitals and relaxed orbitals in the presence of the core-hole.

Biggs, Jason D.; Zhang Yu; Healion, Daniel; Mukamel, Shaul [Department of Chemistry, University of California, Irvine, California 92697-2025 (United States)

2012-05-07

199

Two-dimensional stimulated resonance Raman spectroscopy of molecules with broadband x-ray pulses  

PubMed Central

Expressions for the two-dimensional stimulated x-ray Raman spectroscopy (2D-SXRS) signal obtained using attosecond x-ray pulses are derived. The 1D- and 2D-SXRS signals are calculated for trans-N-methyl acetamide (NMA) with broad bandwidth (181 as, 14.2 eV FWHM) pulses tuned to the oxygen and nitrogen K-edges. Crosspeaks in 2D signals reveal electronic Franck-Condon overlaps between valence orbitals and relaxed orbitals in the presence of the core-hole. PMID:22583220

Biggs, Jason D.; Zhang, Yu; Healion, Daniel; Mukamel, Shaul

2012-01-01

200

Theoretical standards in x-ray spectroscopies. Annual progress report, 1991--1992  

SciTech Connect

We propose to extend our state-of-the-art, ab initio XAFS (X-ray absorption fine structure) codes, FEFF. Our current work has been highly successful in achieving accurate, user-friendly XAFS standards, exceeding the performance of both tabulated standards and other codes by a considerable margin. We now propose to add the capability to treat more complex materials. This includes multiple-scattering, polarization dependence, an approximate treatment of XANES (x-ray absorption near edge structure), and other improvements. We also plan to adapt FEFF to other spectroscopies, e.g. photoelectron diffraction (PD) and diffraction anomalous fine structure (DAFS).

Not Available

1992-09-01

201

Transformation of nanodiamond into carbon onions: A comparative study by high-resolution transmission electron microscopy, electron energy-loss spectroscopy, x-ray diffraction, small-angle x-ray scattering, and ultraviolet Raman spectroscopy  

Microsoft Academic Search

The structural properties of both nanodiamond particles synthesized by detonation and the products of their transformation into carbon onions via vacuum annealing at 1000 and 1500 °C have been studied using high-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy, x-ray diffraction (XRD), small-angle x-ray scattering (SAXS), and Raman spectroscopy. The advantages of UV Raman spectroscopy over visible Raman spectroscopy for

Oleksandr O. Mykhaylyk; Yurii M. Solonin; David N. Batchelder; Rik Brydson

2005-01-01

202

Time and space resolved spectroscopy of x-ray laser experiments  

SciTech Connect

We report experimental data from one of the first of this new generation of instruments designed specifically for laboratory x-ray laser diagnosis. Representative TGSS-EM data are presented from three different x-ray laser inversion schemes: collisional excitation of neon-like selenium (lambda approx. = 206, 209A); resonant photoexcitation of hydrogen-like fluorine (lambda = 81A); and recombination of hydrogen-like magnesium (lambda approx. = 130A). The data illustrate the measurement capabilities of the TGSS-EM and provide insight to the dynamics and emission characteristics of this new class of laser produced plasmas.

Ceglio, N.M.

1986-04-01

203

Arsenic Speciation by X-Ray Spectroscopy using Resonant Raman Scattering  

NASA Astrophysics Data System (ADS)

We have shown that X-ray resonant Raman scattering (RRS) spectroscopy can be used to analyze arsenic species. This work is a pioneering work in the area and is important in the interpretation of results in the future. Nevertheless, the behavior of RRS residuals of compounds can be used to identify the oxidation state of the elements under study, offering a new possibility for chemical environment determination using RRS spectroscopy.

Sánchez, H. J.; Leani, J. J.; Pérez, C. A.; Pèrez, R. D.

2014-01-01

204

X-ray excited optical luminescence, photoluminescence, photostimulated luminescence and x-ray photoemission spectroscopy studies on BaFBr:Eu  

NASA Astrophysics Data System (ADS)

The results of x-ray excited optical luminescence (XEOL), photoluminescence (PL), photostimulated luminescence (PSL) and x-ray photoemission spectroscopy (XPS) studies on the x-ray storage phosphor BaFBr:Eu are presented in this paper. Analyses of XEOL, PL and PSL spectra reveal features corresponding to the transitions from 0953-8984/9/22/027/img9 to 0953-8984/9/22/027/img10 configurations in different site symmetries of 0953-8984/9/22/027/img11. Increasing x-ray dose is seen to lead to a red shift in the maximum of the PL excitation spectrum for the 391 nm emission. The XEOL and XPS spectra do not show any signature of 0953-8984/9/22/027/img12 in the samples studied by us, directly raising doubts about the model of Takahashi et al in which 0953-8984/9/22/027/img11 is expected to ionize to 0953-8984/9/22/027/img12 upon x-ray irradiation and remain stable until photostimulation. XEOL and PSL experiments with simultaneous x-ray irradiation and He - Ne laser excitation as well as those with sequential x-ray irradiation and laser stimulation bring out the competition between the F centre population and depopulation rates. A time scale 0953-8984/9/22/027/img15 - 2 s, possibly related to the process of production of the electron/hole traps themselves, during x-ray irradiation, is observed. Relaxation of these traps upon photostimulation is also seen.

Subramanian, N.; Kesavamoorthy, R.; Rajan, K. Govinda; Yousuf, Mohammad; Bera, Santanu; Narasimhan, S. V.

1997-06-01

205

Photon statistics and speckle visibility spectroscopy with partially coherent X-rays.  

PubMed

A new approach is proposed for measuring structural dynamics in materials from multi-speckle scattering patterns obtained with partially coherent X-rays. Coherent X-ray scattering is already widely used at high-brightness synchrotron lightsources to measure dynamics using X-ray photon correlation spectroscopy, but in many situations this experimental approach based on recording long series of images (i.e. movies) is either not adequate or not practical. Following the development of visible-light speckle visibility spectroscopy, the dynamic information is obtained instead by analyzing the photon statistics and calculating the speckle contrast in single scattering patterns. This quantity, also referred to as the speckle visibility, is determined by the properties of the partially coherent beam and other experimental parameters, as well as the internal motions in the sample (dynamics). As a case study, Brownian dynamics in a low-density colloidal suspension is measured and an excellent agreement is found between correlation functions measured by X-ray photon correlation spectroscopy and the decay in speckle visibility with integration time obtained from the analysis presented here. PMID:25343797

Li, Luxi; Kwa?niewski, Pawe?; Orsi, Davide; Wiegart, Lutz; Cristofolini, Luigi; Caronna, Chiara; Fluerasu, Andrei

2014-11-01

206

X-RAY ABSORPTION SPECTROSCOPY OF YB3+-DOPED OPTICAL FIBERS  

SciTech Connect

Optical fibers doped with Ytterbium-3+ have become increasingly common in fiber lasers and amplifiers. Yb-doped fibers provide the capability to produce high power and short pulses at specific wavelengths, resulting in highly effective gain media. However, little is known about the local structure, distribution, and chemical coordination of Yb3+ in the fibers. This information is necessary to improve the manufacturing process and optical qualities of the fibers. Five fibers doped with Yb3+ were studied using Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy and X-ray Absorption Near Edge Spectroscopy (XANES), in addition to Yb3+ mapping. The Yb3+ distribution in each fiber core was mapped with 2D and 1D intensity scans, which measured X-ray fluorescence over the scan areas. Two of the five fibers examined showed highly irregular Yb3+ distributions in the core center. In four of the five fibers Yb3+ was detected outside of the given fiber core dimensions, suggesting possible Yb3+ diffusion from the core, manufacturing error, or both. X-ray absorption spectroscopy (XAS) analysis has so far proven inconclusive, but did show that the fibers had differing EXAFS spectra. The Yb3+ distribution mapping proved highly useful, but additional modeling and examination of fiber preforms must be conducted to improve XAS analysis, which has been shown to have great potential for the study of similar optical fi bers.

Citron, Robert; Kropf, A.J.

2008-01-01

207

Gas cell for in situ soft X-ray transmission-absorption spectroscopy of materials  

NASA Astrophysics Data System (ADS)

A simple gas cell design, constructed primarily from commercially available components, enables in situ soft X-ray transmission-absorption spectroscopy of materials in contact with gas at ambient temperature. The cell has a minimum X-ray path length of 1 mm and can hold gas pressures up to ˜300 Torr, and could support higher pressures with simple modifications. The design enables cycling between vacuum and gas environments without interrupting the X-ray beam, and can be fully sealed to allow for measurements of air-sensitive samples. The cell can attach to the downstream port of any appropriate synchrotron beamline, and offers a robust and versatile method for in situ measurements of certain materials. The construction and operation of the cell are discussed, as well as sample preparation and proper spectral analysis, illustrated by examples of spectral measurements. Potential areas for improvement and modification for specialized applications are also mentioned.

Drisdell, W. S.; Kortright, J. B.

2014-07-01

208

IN SITU STUDIES OF CORROSION USING X-RAY ABSORPTION NEAR SPECTROSCOPY (XANES)  

SciTech Connect

Applications of x-ray absorption near-edge spectroscopy (XANES) and the design of cells for in situ corrosion studies are reviewed. Passive films studies require very thin metal or alloy layers be used having a thickness of the order of the films formed because of penetration of the x-ray beam into the metal substrate. The depth of penetration in water also limits the thickness of solutions that can be used because of water reduces the x-ray intensity. Solution thickness must also be limited in studies of conversion layer formation studies because the masking of the Cr in solution. Illustrative examples are taken from the anodic behavior of Al-Cr alloys, the growth of passive films on Fe and stainless steels, and the formation of chromate conversion layers on Al.

ISAACS, H.S.; SCHMUKI, P.; VIRTANEN, S.

2001-03-25

209

X-ray absorption spectroscopy at the Ni-K edge in Stackhousia tryonii Bailey hyperaccumulator  

SciTech Connect

Young plants of Stackhousia tryonii Bailey were exposed to 34 mM Ni kg-1 in the form of NiSO4- 6H2O solution and grown under controlled glasshouse conditions for a period of 20 days. Fresh leaf, stem and root samples were analysed in vivo by micro x-ray absorption spectroscopy (XAS) at the Ni-K edge.Both x-ray absorption near edge structure and extended x-ray absorption fine structure spectra were analysed, and theresulting spectra were compared with spectra obtained from nine biologically important Ni-containing model compounds. The results revealed that themajority of leaf, stem and root Ni in the hyperaccumulator was chelated by citrate.Our results also suggest that in leavesNi is complexed by phosphate and histidine, and in stems and roots, phytate and histidine. The XAS results provide an important physiological insightinto transport, detoxification and storage of Ni in S. tryonii plants.

Ionescu, Mihail; Bhatia, Naveen P.; Cohen , David D.; Siegele, R.; Marcus, Matthew A.; Fakra, Sirine C.; Foran, G.; Kachenko, A.

2007-10-08

210

Identification of newly discovered radio-emitting X-ray sources: results from spectroscopy  

NASA Astrophysics Data System (ADS)

We present optical identifications for a sample of 20 previously unknown X-ray/radio sources that are present both in the source catalogue of ROSAT PSPC pointed observations (ROSAT SRC) and in the NRAO VLA Sky Survey (NVSS). The optical spectroscopy was carried out with the 2.1-m telescope at San Pedro Martir (Mexico) during 1995 April and September. We have identified 15 active galactic nuclei [including 12 broad-emission-line (FWHM >1000kms^-1) objects, one bona fide BL Lac, one BL Lac candidate and one narrow-line (FWHM < 1000kms^-1) radio galaxy] and five radio galaxies. We derive the X-ray fluxes and luminosities by analysing the PSPC exposures, and show the radio morphology from the NVSS maps. We find that the correlation between the monochromatic X-ray luminosity at 2 keV and the core radio luminosity at 5 GHz for the radio galaxies in our sample follows that found for the 3CR radio galaxies, suggesting a possible nuclear origin for the X-ray emission in these sources. This correlation is weaker in the case of broad-line objects, indicating the presence of another (unbeamed) mechanism for the X-ray emission only weakly related to the radio emission.

Wolter, A.; Ruscica, C.; Caccianiga, A.

1998-10-01

211

Infrared-x-ray pump-probe spectroscopy of the NO molecule  

SciTech Connect

Two color infrared-x-ray pump-probe spectroscopy of the NO molecule is studied theoretically and numerically in order to obtain a deeper insight of the underlying physics and of the potential of this suggested technology. From the theoretical investigation a number of conclusions could be drawn: It is found that the phase of the infrared field strongly influences the trajectory of the nuclear wave packet, and hence, the x-ray spectrum. The trajectory experiences fast oscillations with the vibrational frequency with a modulation due to the anharmonicity of the potential. The dependences of the x-ray spectra on the delay time, the duration, and the shape of the pulses are studied in detail. It is shown that the x-ray spectrum keep memory about the infrared phase after the pump field left the system. This memory effect is sensitive to the time of switching-off the pump field and the Rabi frequency. The phase effect takes maximum value when the duration of the x-ray pulse is one-fourth of the infrared field period, and can be enhanced by a proper control of the duration and intensity of the pump pulse. The manifestation of the phase is different for oriented and disordered molecules and depends strongly on the intensity of the pump radiation.

Guimaraes, F.F.; Felicissimo, V.C. [Theoretical Chemistry, Roslagstullsbacken 15, Royal Institute of Technology, S-106 91 Stockholm (Sweden); Departamento de Quimica, Universidade Federal de Minas Gerais, Avenida Antonio Carlos, 6627, CEP-31270-901, Belo Horizonte, Minas Gerais (Brazil); Kimberg, V.; Gel'mukhanov, F.; Aagren, H. [Theoretical Chemistry, Roslagstullsbacken 15, Royal Institute of Technology, S-106 91 Stockholm (Sweden); Cesar, A. [Departamento de Quimica, Universidade Federal de Minas Gerais, Avenida Antonio Carlos, 6627, CEP-31270-901, Belo Horizonte, Minas Gerais (Brazil)

2005-07-15

212

Probing electronic structure and chemical bonding with x-ray spectroscopy  

NASA Astrophysics Data System (ADS)

The availability of synchrotron sources has expanded significantly the use of x-ray photoelectron (PE) and photoabsorption (PA) spectroscopy to probe the molecular electronic structure and to test the various bonding models the understanding of which is central to all aspects of chemistry. All features observed in x-ray spectra result from electronic transitions within the molecule, which are in turn determined by the molecular electronic structure. For this Ph.D. thesis, x-ray Photoelectron and photoabsorption spectra were measured for a variety of small model molecules. Of particular interest were simple compounds containing nitrogen, oxygen, chlorine and fluorine bound to phosphorus and sulphur wherein these latter elements exist in a highly oxidized valence state, because the state of bonding in these molecules is not well understood. The experiments were conducted at the Canadian Synchrotron Radiation Facility (CSRF) located at the Synchrotron Radiation Center (SRC), University of Wisconsin, Madison, Wisconsin. A synchrotron light source displays several unique features ideal for x-ray spectroscopy. The light produced has a continuous frequency distribution from the ultraviolet to the x-ray region-specific frequencies can be selected with a monochromator, and finally, the light produced is intense, collimated and polarized. An of these properties contribute to the measurement of very high resolution x-ray spectra. The research program involved the collection of experimental spectra of carefully selected compounds in the gas phase, which simplified analysis because all the observed spectral structure results from the electronic structure of the molecule without crystal lattice or intermolecular interaction effects. The experimental spectra were compared with the results of electronic structure calculations done with MS-Xalpha and Gaussian-94 programs. This comparison with experimental results allows the evaluation of the theory and refinement of the bonding model.

Jurgensen, Astrid

1999-11-01

213

Performance and status of beamline BL8 at SLRI for X-ray absorption spectroscopy.  

PubMed

Beamline BL8 of the Synchrotron Light Research Institute (Thailand) is routinely operated for X-ray absorption spectroscopy (XAS) in an intermediate photon energy range (1.25-10 keV). The photon energy is scanned by using a double-crystal monochromator, the crystal pair of which can be interchanged among KTP(011), InSb(111), Si(111) and Ge(220). The experimental set-up conveniently facilitates XAS measurements in transmission and fluorescence-yield modes at several K-edges of elements ranging from magnesium to zinc. Instrumentation and specification of the beamline and the XAS station are described, together with the determination of the available photon flux [0.1-6 × 10(10) photon s(-1) (100 mA)(-1)], energy resolution (1-5 × 10(-4)) and stability of photon energy calibration (0.07 eV), representing the beamline performance. Data quality and accuracy of XANES and EXAFS measured at BL8 are compared with those of other well established beamlines. A noted distinction of BL8 is its relatively high sensitivity for studying phosphorous, sulfur and chlorine in diluted systems and its maximum beam size of 14 mm (width) × 1 mm (height), which is suitable for bulk characterization. PMID:23093751

Klysubun, Wantana; Sombunchoo, Panidtha; Deenan, Weeraya; Kongmark, Chanapa

2012-11-01

214

Improvements in the Reliability of X-ray Photoelectron Spectroscopy for Surface Analysis  

NASA Astrophysics Data System (ADS)

An overview is given of improvements in the reliability of X-ray photoelectron spectroscopy (XPS) measurements over the past three decades. Early inter-laboratory comparisons showed wide variations in measurements of peak energies and relative peak intensities for the same material. Procedures now exist for calibration of instrumental energy and intensity scales. It was generally necessary in early work to assume that the surface was homogeneous over the XPS sampling depth. It is now possible to assess the extent of compositional inhomogeneities in depth with angle-resolved XPS measurements or from analyses of the photoelectron energy distributions in the vicinity of major peaks. The surface sensitivity of XPS was assumed in early work to be given by the so-called "universal curve" for effective attenuation lengths (EALs) as a function of electron energy. Calculations of electron inelastic mean free paths (IMFPs), however, show appreciable material dependencies. In addition, elastic scattering of the signal electrons is often significant. As a result, the EAL can be appreciably different from the corresponding IMFP. Brief mention is also made of the development of NIST data resources for XPS: an XPS database, IMFP and EAL databases, and standard test data for XPS. The standard test data for XPS are a useful teaching tool for estimating uncertainties of peak parameters for overlapping peaks in an XPS or other spectrum.

Powell, Cedric J.

2004-12-01

215

SURFACE SEGREGATION STUDIES OF SOFC CATHODES: COMBINING SOFT X-RAYS AND ELECTROCHEMICAL IMPEDENCE SPECTROSCOPY  

SciTech Connect

A system to grow heteroepitaxial thin-films of solid oxide fuel cell (SOFC) cathodes on single crystal substrates was developed. The cathode composition investigated was 20% strontium-doped lanthanum manganite (LSM) grown by pulsed laser deposition (PLD) on single crystal (111) yttria-stabilized zirconia (YSZ) substrates. By combining electrochemical impedance spectroscopy (EIS) with x-ray photoemission spectroscopy (XPS) and x-ray absorption spectroscopy XAS measurements, we conclude that electrically driven cation migration away from the two-phase gas-cathode interface results in improved electrochemical performance. Our results provide support to the premise that the removal of surface passivating phases containing Sr2+ and Mn2+, which readily form at elevated temperatures even in O2 atmospheric pressures, is responsible for the improved cathodic performance upon application of a bias.

Miara, Lincoln J.; Piper, L.F.J.; Davis, Jacob N.; Saraf, Laxmikant V.; Kaspar, Tiffany C.; Basu, Soumendra; Smith, K. E.; Pal, Uday B.; Gopalan, Srikanth

2010-12-01

216

The GALAXIES beamline at the SOLEIL synchrotron: inelastic X-ray scattering and photoelectron spectroscopy in the hard X-ray range.  

PubMed

The GALAXIES beamline at the SOLEIL synchrotron is dedicated to inelastic X-ray scattering (IXS) and photoelectron spectroscopy (HAXPES) in the 2.3-12 keV hard X-ray range. These two techniques offer powerful complementary methods of characterization of materials with bulk sensitivity, chemical and orbital selectivity, resonant enhancement and high resolving power. After a description of the beamline components and endstations, the beamline capabilities are demonstrated through a selection of recent works both in the solid and gas phases and using either IXS or HAXPES approaches. Prospects for studies on liquids are discussed. PMID:25537606

Rueff, J P; Ablett, J M; Céolin, D; Prieur, D; Moreno, Th; Balédent, V; Lassalle-Kaiser, B; Rault, J E; Simon, M; Shukla, A

2015-01-01

217

Quick extended x-ray absorption fine structure instrument with millisecond time scale, optimized for in situ applications  

SciTech Connect

In order to learn about in situ structural changes in materials at subseconds time scale, we have further refined the techniques of quick extended x-ray absorption fine structure (QEXAFS) and quick x-ray absorption near edge structure (XANES) spectroscopies at beamline X18B at the National Synchrotron Light Source. The channel cut Si (111) monochromator oscillation is driven through a tangential arm at 5 Hz, using a cam, dc motor, pulley, and belt system. The rubber belt between the motor and the cam damps the mechanical noise. EXAFS scan taken in 100 ms is comparable to standard data. The angle and the angular range of the monochromator can be changed to collect a full EXAFS or XANES spectrum in the energy range 4.7-40.0 KeV. The data are recorded in ascending and descending order of energy, on the fly, without any loss of beam time. The QEXAFS mechanical system is outside the vacuum system, and therefore changing the mode of operation from conventional to QEXAFS takes only a few minutes. This instrument allows the acquisition of time resolved data in a variety of systems relevant to electrochemical, photochemical, catalytic, materials, and environmental sciences.

Khalid, S.; Caliebe, W.; Siddons, P.; So, I.; Clay, b.; Hanson, J.; Wang, Q.; Frenkel, A.; Marinkovicl, N.; Hould, N.; ginder-Vogel, M.; Landrot, G.L.; Sparks, D.L.; Ganjoo, A.

2010-01-19

218

Thermal design and performance of the REgolith x-ray imaging spectrometer (REXIS) instrument  

NASA Astrophysics Data System (ADS)

The REgolith X-ray Imaging Spectrometer (REXIS) instrument is a student collaboration instrument on the OSIRIS-REx asteroid sample return mission scheduled for launch in September 2016. The REXIS science mission is to characterize the elemental abundances of the asteroid Bennu on a global scale and to search for regions of enhanced elemental abundance. The thermal design of the REXIS instrument is challenging due to both the science requirements and the thermal environment in which it will operate. The REXIS instrument consists of two assemblies: the spectrometer and the solar X-ray monitor (SXM). The spectrometer houses a 2x2 array of back illuminated CCDs that are protected from the radiation environment by a one-time deployable cover and a collimator assembly with coded aperture mask. Cooling the CCDs during operation is the driving thermal design challenge on the spectrometer. The CCDs operate in the vicinity of the electronics box, but a 130 °C thermal gradient is required between the two components to cool the CCDs to -60 °C in order to reduce noise and obtain science data. This large thermal gradient is achieved passively through the use of a copper thermal strap, a large radiator facing deep space, and a two-stage thermal isolation layer between the electronics box and the DAM. The SXM is mechanically mounted to the sun-facing side of the spacecraft separately from the spectrometer and characterizes the highly variable solar X-ray spectrum to properly interpret the data from the asteroid. The driving thermal design challenge on the SXM is cooling the silicon drift detector (SDD) to below -30 °C when operating. A two-stage thermoelectric cooler (TEC) is located directly beneath the detector to provide active cooling, and spacecraft MLI blankets cover all of the SXM except the detector aperture to radiatively decouple the SXM from the flight thermal environment. This paper describes the REXIS thermal system requirements, thermal design, and analyses, with a focus on the driving thermal design challenges for the instrument. It is shown through both analysis and early testing that the REXIS instrument can perform successfully through all phases of its mission.

Stout, Kevin D.; Masterson, Rebecca A.

2014-08-01

219

Structural investigations of LiFePO 4 electrodes and in situ studies by Fe X-ray absorption spectroscopy  

Microsoft Academic Search

Fe K-edge X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) have been performed on electrodes containing LiFePO4 to determine the local atomic and electronic structure and their stability with electrochemical cycling. A versatile electrochemical in situ cell has been constructed for long-term soft and hard X-ray experiments for the structural investigation on battery electrodes during

Aniruddha Deb; Uwe Bergmann; S. P. Cramer; Elton J. Cairns

2005-01-01

220

Multilayer graphene stacks grown by different methods-thickness measurements by X-ray diffraction, Raman spectroscopy and optical transmission  

SciTech Connect

X-ray diffraction, Raman spectroscopy and Optical absorption estimates of the thickness of graphene multi layer stacks (number of graphene layers) are presented for three different growth techniques. The objective of this work was focused on comparison and reconciliation of the two already widely used methods for thickness estimates (Raman and Absorption) with the calibration of the X-ray method as far as Scherer constant K is concerned and X-ray based Wagner-Aqua extrapolation method.

Tokarczyk, M., E-mail: mateusz.tokarczyk@fuw.edu.pl; Kowalski, G.; K?pa, H.; Grodecki, K.; Drabi?ska, A. [University of Warsaw, Institute of Experimental Physics, Faculty of Physics (Poland); Strupi?ski, W. [Institute of Electronic Materials Technology (Poland)

2013-12-15

221

Characterisation by X-ray absorption spectroscopy of oxide thin films prepared by ion beam-induced CVD  

Microsoft Academic Search

Structural characterisation of amorphous or partially amorphous thin films can be carried out by X-ray absorption spectroscopy in its X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) approaches. The EXAFS spectra have been analysed using the FEFF procedure, while XANES spectra are dealt with on a fingerprint basis. PbTiO3 and CoO\\/Co3O4 thin films prepared by ion

J. P Holgado; A Caballero; J. P Espinós; J Morales; V. M Jiménez; A Justo; A. R González-Elipe

2000-01-01

222

Ni-(In,Ga)As Alloy Formation Investigated by Hard-X-Ray Photoelectron Spectroscopy and X-Ray Absorption Spectroscopy  

NASA Astrophysics Data System (ADS)

The electrical, chemical, and structural interactions between Ni films and In 0.53Ga 0.47A s for source-drain applications in transistor structures have been investigated. It was found that for thick (>10 nm ) Ni films, a steady decrease in sheet resistance occurs with increasing anneal temperatures, however, this trend reverses at 450 °C for 5 nm thick Ni layers, primarily due to the agglomeration or phase separation of the Ni-(In,Ga)As layer. A combined hard-x-ray photoelectron spectroscopy (HAXPES) and x-ray absorption spectroscopy (XAS) analysis of the chemical structure of the Ni-(In,Ga)As alloy system shows: (1) that Ni readily interacts with In 0.53Ga 0.47A s upon deposition at room temperature resulting in significant interdiffusion and the formation of NiIn, NiGa, and NiAs alloys, and (2) the steady diffusion of Ga through the Ni layer with annealing, resulting in the formation of a Ga2O3 film at the surface. The need for the combined application of HAXPES and XAS measurements to fully determine chemical speciation and sample structure is highlighted and this approach is used to develop a structural and chemical compositional model of the Ni-(In,Ga)As system as it evolves over a thermal annealing range of 250 to 500 °C .

Walsh, Lee A.; Hughes, Greg; Weiland, Conan; Woicik, Joseph C.; Lee, Rinus T. P.; Loh, Wei-Yip; Lysaght, Pat; Hobbs, Chris

2014-12-01

223

Characterization and Evolution of the Swift X-ray Telescope Instrumental Background  

NASA Technical Reports Server (NTRS)

The X-ray telescope (XRT) on board the Swift Gamma Ray Burst Explorer has successfully operated since the spacecraft launch on 20 November 2004, automatically locating GRB afterglows, measuring their spectra and lightcurves and performing observations of high-energy sources. In this work we investigate the properties of the instrumental background, focusing on its dynamic behavior on both long and short timescales. The operational temperature of the CCD is the main factor that influences the XRT background level. After the failure of the Swift active on-board temperature control system, the XRT detector now operates at a temperature range between -75C and -45C thanks to a passive cooling Heat Rejection System. We report on the long-term effects on the background caused by radiation, consisting mainly of proton irradiation in Swift's low Earth orbit and on the short-term effects of transits through the South Atlantic Anomaly (SAA), which expose the detector to periods of intense proton flux. We have determined the fraction of the detector background that is due to the internal, instrumental background and the part that is due to unresolved astrophysical sources (the cosmic X-ray background) by investigating the degree of vignetting of the measured background and comparing it to the expected value from calibration data.

Hill, Joanne; Pagani, C.; Morris, D. C.; Racusin, J.; Grupe, D.; Vetere, L.; Stroh, M.; Falcone, A.; Kennea, J.; Burrows, D. N.; Nousek, J. A.; Abbey, A. F.; Angelini, L.; Beardmore, A. P.; Campana, S.; Capalbi, M.; Chincarini, G.; Citterio O.; Cusumano, G.; Giommi, P.; Godet, O.; Hill, J. E.; LaParola, V.; Mangano, V.; Mineo, T.

2007-01-01

224

In Situ Identification of Mineral Resources with an X-Ray-Optical "Hands-Lens" Instrument  

NASA Astrophysics Data System (ADS)

The recognition of material resources on a planetary surface requires exploration strategies not dissimilar to those employed by early field geologists who searched for ore deposits primarily from surface clues. In order to determine the location of mineral ores or other materials, it will be necessary to characterize host terranes at regional or subregional scales. This requires geographically broad surveys in which statistically significant numbers of samples are rapidly scanned from a roving platform. To enable broad-scale, yet power-conservative planetary-surface exploration, we are developing an instrument that combines x-ray diffractometry (XRD), x-ray fluorescence spectrometry (XRF), and optical capabilities; the instrument can be deployed at the end of a rover's robotic arm, without the need for sample capture or preparation. The instrument provides XRD data for identification of mineral species and lithological types; diffractometry of minerals is conducted by ascertaining the characteristic lattice parameters or "d-spacings" of mineral compounds. D-spacings of 1.4 to 25 angstroms can be determined to include the large molecular structures of hydrated minerals such as clays. The XRF data will identify elements ranging from carbon (Atomic Number = 6) to elements as heavy as barium (Atomic Number = 56). While a sample is being x-rayed, the instrument simultaneously acquires an optical image of the sample surface at magnifications from lx to at least 50x (200x being feasible, depending on the sample surface). We believe that imaging the sample is extremely important as corroborative sample-identification data (the need for this capability having been illustrated by the experience of the Pathfinder rover). Very few geologists would rely on instrument data for sample identification without having seen the sample. Visual inspection provides critical recognition data such as texture, crystallinity, granularity, porosity, vesicularity, color, lustre, opacity, and so forth. These data can immediately distinguish sedimentary from igneous rocks, for example, and can thus eliminate geochemical or mineral ambiguities arising, say between arkose and granite. It would be important to know if the clay being analyzed was part of a uniform varve deposit laid down in a quiescent lake, or the matrix of a megabreccia diamictite deposited as a catastrophic impact ejecta blanket. The unique design of the instrument, which combines Debye-Scherrer geometry with elements of standard goniometry, negates the need for sample preparation of any kind, and thus negates the need for power-hungry and mechanically-complex sampling systems that would have to chip, crush, sieve, and mount the sample for x-ray analysis. Instead, the instrument is simply rested on the sample surface of interest (like a hand lens); the device can interrogate rough rock surfaces, coarse granular material, or fine rock flour. A breadboard version of the instrument has been deployed from the robotic arm of the Marsokhod rover in field trials at NASA Ames, where large vesicular boulders were x-rayed to demonstrate the functionality of the instrument design, and the ability of such a device to comply with constraints imposed by a roving platform. Currently under development is a flight prototype concept of this instrument that will weigh 0.3 kg, using about 4500 J of energy per sample analysis. It requires about 5 min. for XRD analysis, and about 30 min. for XRF interrogation. Its small mass and rugged design make it ideal for deployment on small rovers of the type currently envisaged for the exploration of Mars (e.g., Sojourner-scale platforms). The design utilizes a monolithic P-N junction photodiode pixel array for XRD, a Si PIN photodiode/avalanche photodiode system for XRF, and an endoscopic imaging camera system unobtrusively embedded between the detectors and the x-ray source (the endoscope with its board-mounted camera can be adapted for IR light in addition to visible wavelenths. A rugged, miniature (7 cu cm) x-ray source for the instrument has already b

Marshall, J.; Koppel, L.; Bratton, C.; Metzger, E.; Hecht, M.

1999-09-01

225

In Situ Identification of Mineral Resources with an X-Ray-Optical "Hands-Lens" Instrument  

NASA Technical Reports Server (NTRS)

The recognition of material resources on a planetary surface requires exploration strategies not dissimilar to those employed by early field geologists who searched for ore deposits primarily from surface clues. In order to determine the location of mineral ores or other materials, it will be necessary to characterize host terranes at regional or subregional scales. This requires geographically broad surveys in which statistically significant numbers of samples are rapidly scanned from a roving platform. To enable broad-scale, yet power-conservative planetary-surface exploration, we are developing an instrument that combines x-ray diffractometry (XRD), x-ray fluorescence spectrometry (XRF), and optical capabilities; the instrument can be deployed at the end of a rover's robotic arm, without the need for sample capture or preparation. The instrument provides XRD data for identification of mineral species and lithological types; diffractometry of minerals is conducted by ascertaining the characteristic lattice parameters or "d-spacings" of mineral compounds. D-spacings of 1.4 to 25 angstroms can be determined to include the large molecular structures of hydrated minerals such as clays. The XRF data will identify elements ranging from carbon (Atomic Number = 6) to elements as heavy as barium (Atomic Number = 56). While a sample is being x-rayed, the instrument simultaneously acquires an optical image of the sample surface at magnifications from lx to at least 50x (200x being feasible, depending on the sample surface). We believe that imaging the sample is extremely important as corroborative sample-identification data (the need for this capability having been illustrated by the experience of the Pathfinder rover). Very few geologists would rely on instrument data for sample identification without having seen the sample. Visual inspection provides critical recognition data such as texture, crystallinity, granularity, porosity, vesicularity, color, lustre, opacity, and so forth. These data can immediately distinguish sedimentary from igneous rocks, for example, and can thus eliminate geochemical or mineral ambiguities arising, say between arkose and granite. It would be important to know if the clay being analyzed was part of a uniform varve deposit laid down in a quiescent lake, or the matrix of a megabreccia diamictite deposited as a catastrophic impact ejecta blanket. The unique design of the instrument, which combines Debye-Scherrer geometry with elements of standard goniometry, negates the need for sample preparation of any kind, and thus negates the need for power-hungry and mechanically-complex sampling systems that would have to chip, crush, sieve, and mount the sample for x-ray analysis. Instead, the instrument is simply rested on the sample surface of interest (like a hand lens); the device can interrogate rough rock surfaces, coarse granular material, or fine rock flour. A breadboard version of the instrument has been deployed from the robotic arm of the Marsokhod rover in field trials at NASA Ames, where large vesicular boulders were x-rayed to demonstrate the functionality of the instrument design, and the ability of such a device to comply with constraints imposed by a roving platform. Currently under development is a flight prototype concept of this instrument that will weigh 0.3 kg, using about 4500 J of energy per sample analysis. It requires about 5 min. for XRD analysis, and about 30 min. for XRF interrogation. Its small mass and rugged design make it ideal for deployment on small rovers of the type currently envisaged for the exploration of Mars (e.g., Sojourner-scale platforms). The design utilizes a monolithic P-N junction photodiode pixel array for XRD, a Si PIN photodiode/avalanche photodiode system for XRF, and an endoscopic imaging camera system unobtrusively embedded between the detectors and the x-ray source (the endoscope with its board-mounted camera can be adapted for IR light in addition to visible wavelenths. A rugged, miniature (7 cu cm) x-ray source for the instrument has already b

Marshall, J.; Koppel, L.; Bratton, C.; Metzger, E.; Hecht, M.

1999-01-01

226

X-ray photo-emission and energy dispersive spectroscopy of HA coated titanium  

SciTech Connect

The purpose of this study was to determine the chemical composition changes of hydroxyapatite (HA) coated titanium using surface analysis (x-ray photo-emission) and bulk analysis (energy dispersive spectroscopy). The specimens examined were controls, 30 minutes and 3 hours aged specimens in distilled water or 0.2M sodium phosphate buffer (pH 7.2) at room temperature. Each x-ray photo-emission cycle consisted of 3 scans followed by argon sputtering for 10 minutes for a total of usually 20 cycles, corresponding to a sampling depth of {approximately} 1500 {angstrom}. The energy dispersive spectroscopy analysis was on a 110 by 90 {mu}m area for 500 sec. Scanning electron microscopy examination showed crystal formation (3P{sub 2}O{sub 5}*2CAO*?H{sub 2}O by energy dispersive spectroscopy analysis) on the HA coating for the specimens aged in sodium phosphate buffer. The x-ray photo-emission results indicated the oxidation effect of water on the titanium (as TiO{sub 2}) and the effect of the buffer to increase the surface concentration of phosphorous. No differences in the chemical composition were observed by energy dispersive spectroscopy analysis. The crystal growth was only observed for the sodium phosphate buffer specimens and only on the HA surface.

Drummond, J.L.; Steinberg, A.D. [Univ. of Illinois, Chicago, IL (United States); Krauss, A.R. [Argonne National Lab., IL (United States)] [and others

1997-08-01

227

X-ray and photoelectron spectroscopy of the structure, reactivity, and electronic structure of semiconductor nanocrystals  

SciTech Connect

Semiconductor nanocrystals are a system which has been the focus of interest due to their size dependent properties and their possible use in technological applications. Many chemical and physical properties vary systematically with the size of the nanocrystal and thus their study enables the investigation of scaling laws. Due to the increasing surface to volume ratio as size is decreased, the surfaces of nanocrystals are expected to have a large influence on their electronic, thermodynamic, and chemical behavior. In spite of their importance, nanocrystal surfaces are still relatively uncharacterized in terms of their structure, electronic properties, bonding, and reactivity. Investigation of nanocrystal surfaces is currently limited by what techniques to use, and which methods are suitable for nanocrystals is still being determined. This work presents experiments using x-ray and electronic spectroscopies to explore the structure, reactivity, and electronic properties of semiconductor (CdSe, InAs) nanocrystals and how they vary with size. Specifically, x-ray absorption near edge spectroscopy (XANES) in conjunction with multiple scattering simulations affords information about the structural disorder present at the surface of the nanocrystal. X-ray photoelectron spectroscopy (XPS) and ultra-violet photoelectron spectroscopy (UPS) probe the electronic structure in terms of hole screening, and also give information about band lineups when the nanocrystal is placed in electric contact with a substrate. XPS of the core levels of the nanocrystal as a function of photo-oxidation time yields kinetic data on the oxidation reaction occurring at the surface of the nanocrystal.

Hamad, K.S.

2000-05-01

228

ON RELATIVISTIC DISK SPECTROSCOPY IN COMPACT OBJECTS WITH X-RAY CCD CAMERAS  

SciTech Connect

X-ray charge-coupled devices (CCDs) are the workhorse detectors of modern X-ray astronomy. Typically covering the 0.3-10.0 keV energy range, CCDs are able to detect photoelectric absorption edges and K shell lines from most abundant metals. New CCDs also offer resolutions of 30-50 (E/{Delta}E), which is sufficient to detect lines in hot plasmas and to resolve many lines shaped by dynamical processes in accretion flows. The spectral capabilities of X-ray CCDs have been particularly important in detecting relativistic emission lines from the inner disks around accreting neutron stars and black holes. One drawback of X-ray CCDs is that spectra can be distorted by photon 'pile-up', wherein two or more photons may be registered as a single event during one frame time. We have conducted a large number of simulations using a statistical model of photon pile-up to assess its impacts on relativistic disk line and continuum spectra from stellar-mass black holes and neutron stars. The simulations cover the range of current X-ray CCD spectrometers and operational modes typically used to observe neutron stars and black holes in X-ray binaries. Our results suggest that severe photon pile-up acts to falsely narrow emission lines, leading to falsely large disk radii and falsely low spin values. In contrast, our simulations suggest that disk continua affected by severe pile-up are measured to have falsely low flux values, leading to falsely small radii and falsely high spin values. The results of these simulations and existing data appear to suggest that relativistic disk spectroscopy is generally robust against pile-up when this effect is modest.

Miller, J. M.; Cackett, E. M. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); D'Ai, A. [Dipartimento di Scienze Fisiche ed Astronomiche, Universita di Palermo, Palermo (Italy); Bautz, M. W.; Nowak, M. A. [Kavli Institute for Astrophysics and Space Research, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Bhattacharyya, S. [Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Mumbai 400005 (India); Burrows, D. N.; Kennea, J. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, College Park, PA 16802 (United States); Fabian, A. C.; Reis, R. C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 OHA (United Kingdom); Freyberg, M. J.; Haberl, F. [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany); Strohmayer, T. E. [Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Tsujimoto, M., E-mail: jonmm@umich.ed [Japan Aerospace Exploration Agency, Institute of Space and Astronomical Sciences, 3-1-1 Yoshino-dai, Sagamihara, Kanagawa 229-8510 (Japan)

2010-12-01

229

High resolution x-ray fluorescence spectroscopy - a new technique for site- and spin-selectivity  

SciTech Connect

X-ray spectroscopy has long been used to elucidate electronic and structural information of molecules. One of the weaknesses of x-ray absorption is its sensitivity to all of the atoms of a particular element in a sample. Through out this thesis, a new technique for enhancing the site- and spin-selectivity of the x-ray absorption has been developed. By high resolution fluorescence detection, the chemical sensitivity of K emission spectra can be used to identify oxidation and spin states; it can also be used to facilitate site-selective X-ray Absorption Near Edge Structure (XANES) and site-selective Extended X-ray Absorption Fine Structure (EXAFS). The spin polarization in K fluorescence could be used to generate spin selective XANES or spin-polarized EXAFS, which provides a new measure of the spin density, or the nature of magnetic neighboring atoms. Finally, dramatic line-sharpening effects by the combination of absorption and emission processes allow observation of structure that is normally unobservable. All these unique characters can enormously simplify a complex x-ray spectrum. Applications of this novel technique have generated information from various transition-metal model compounds to metalloproteins. The absorption and emission spectra by high resolution fluorescence detection are interdependent. The ligand field multiplet model has been used for the analysis of K{alpha} and K{beta} emission spectra. First demonstration on different chemical states of Fe compounds has shown the applicability of site selectivity and spin polarization. Different interatomic distances of the same element in different chemical forms have been detected using site-selective EXAFS.

Wang, Xin [Univ. of California, Davis, CA (United States). Dept. of Applied Science

1996-12-01

230

Pixellated Cd(Zn)Te high-energy X-ray instrument  

PubMed Central

We have developed a pixellated high energy X-ray detector instrument to be used in a variety of imaging applications. The instrument consists of either a Cadmium Zinc Telluride or Cadmium Telluride (Cd(Zn)Te) detector bump-bonded to a large area ASIC and packaged with a high performance data acquisition system. The 80 by 80 pixels each of 250 ?m by 250 ?m give better than 1 keV FWHM energy resolution at 59.5 keV and 1.5 keV FWHM at 141 keV, at the same time providing a high speed imaging performance. This system uses a relatively simple wire-bonded interconnection scheme but this is being upgraded to allow multiple modules to be used with very small dead space. The readout system and the novel interconnect technology is described and how the system is performing in several target applications. PMID:22737179

Seller, P.; Bell, S.; Cernik, R.J.; Christodoulou, C.; Egan, C.K.; Gaskin, J.A.; Jacques, S.; Pani, S.; Ramsey, B.D.; Reid, C.; Sellin, P.J.; Scuffham, J.W.; Speller, R.D.; Wilson, M.D.; Veale, M.C.

2012-01-01

231

Electrochemical flowcell for in-situ investigations by soft x-ray absorption and emission spectroscopy.  

PubMed

A new liquid flow-cell designed for electronic structure investigations at the liquid-solid interface by soft X-ray absorption and emission spectroscopy is presented. A thin membrane serves simultaneously as a substrate for the working electrode and solid state samples as well as for separating the liquid from the surrounding vacuum conditions. In combination with counter and reference electrodes this approach allows in-situ studies of electrochemical deposition processes and catalytic reactions at the liquid-solid interface in combination with potentiostatic measurements. As model system in-situ monitoring of the deposition process of Co metal from a 10 mM CoCl2 aqueous solution by X-ray absorption and emission spectroscopy is presented. PMID:25362384

Schwanke, C; Golnak, R; Xiao, J; Lange, K M

2014-10-01

232

Technology Development for the Constellation-X Spectroscopy X-Ray Telescope  

NASA Technical Reports Server (NTRS)

The Constellation-X Spectroscopy X-ray Telescope (SXT) is a large diameter, high throughput, grazing incidence imaging mirror system, designed to perform high sensitivity spectroscopy of cosmic X-ray sources in the 0.2-10.0 keV band. The baseline effective area requirement is -3 m# at 1 keV. The system-level angular-resolution requirement is a 15-arcseconds half-power diameter, with a 5-arcsecond goal. The effective area is attained through a modular design, involving the nesting of many confocal, thin-walled Wolter I mirror segments. Considerable progress has been made in developing thin, thermally formed, glass mirror substrates that meet or better the angular-resolution requirement. Several approaches to mounting and aligning reflector segments into a mirror system are under investigation. We report here on the progress of the SXT technology development program toward reaching the performance goals.

Petre, Robert; Lehan, John; O'Dell, Stephen; Owens, Scott; Reid, Paul B.; Saha, Timo; Stewart, Jeff; Jones, William D.; Zhang, William

2005-01-01

233

X-Ray Spectroscopy of the Photosynthetic Oxygen-Evolving Complex  

SciTech Connect

Water oxidation to dioxygen in photosynthesis is catalyzed by a Mn{sub 4}Ca cluster with O bridging in Photosystem II (PS II) of plants, algae and cyanobacteria. A variety of spectroscopic methods have been applied to analyzing the participation of the complex. X-ray spectroscopy is particularly useful because it is element-specific, and because it can reveal important structural features of the complex with high accuracy and identify the participation of Mn in the redox chemistry. Following a brief history of the application of X-ray spectroscopy to PS II, an overview of newer results will be presented and a description of the present state of our knowledge based on this approach.

Sauer, K.; Yano, J.; Yachandra, V.K.

2009-05-27

234

X-ray spectroscopy of the photosynthetic oxygen-evolving complex  

SciTech Connect

Water oxidation to dioxygen in photosynthesis is catalyzed by a Mn4Ca cluster with O bridging in Photosystem II (PS II) of plants, algae and cyanobacteria. A variety of spectroscopic methods have been applied to analyzing the participation of the complex. X-ray spectroscopy is particularly useful because it is element-specific, and because it can reveal important structural features of the complex with high accuracy and identify the participation of Mn in the redox chemistry. Following a brief history of the application of X-ray spectroscopy to PS II, an overview of newer results will be presented and a description of the present state of our knowledge based on this approach.

Sauer, Ken; Yano, Junko; Yachandra, Vittal K

2007-04-05

235

Electrochemical flowcell for in-situ investigations by soft x-ray absorption and emission spectroscopy  

SciTech Connect

A new liquid flow-cell designed for electronic structure investigations at the liquid-solid interface by soft X-ray absorption and emission spectroscopy is presented. A thin membrane serves simultaneously as a substrate for the working electrode and solid state samples as well as for separating the liquid from the surrounding vacuum conditions. In combination with counter and reference electrodes this approach allows in-situ studies of electrochemical deposition processes and catalytic reactions at the liquid-solid interface in combination with potentiostatic measurements. As model system in-situ monitoring of the deposition process of Co metal from a 10 mM CoCl{sub 2} aqueous solution by X-ray absorption and emission spectroscopy is presented.

Schwanke, C.; Lange, K. M., E-mail: Kathrin.lange@helmholtz-berlin.de [Helmholtz-Zentrum Berlin für Materialien und Energie, Institute of Solar Fuels, Albert-Einstein-Straße 15, 12489 Berlin (Germany); Golnak, R.; Xiao, J. [Helmholtz-Zentrum Berlin für Materialien und Energie, Institute of Methods for Material Development, Albert-Einstein-Straße 15, 12489 Berlin (Germany)

2014-10-15

236

X-ray reflectivity and photoelectron spectroscopy study of interdiffusion at the Si /Fe interface  

NASA Astrophysics Data System (ADS)

We have investigated the nature of silicon on iron interface in electron beam deposited Fe /Si bilayers, with various iron and silicon thicknesses. The Fe and Si layer thicknesses are varied from 30to330Å and 20to86Å, respectively. Grazing incidence x-ray reflectivity and photoelectron spectroscopy measurements were carried out on these samples to determine interface characteristics. Si on Fe (Si&barbelow;Fe) interlayer thickness, roughness, and composition do not depend on the thickness of Fe and Si. The thickness of the interlayer is around 13Å. A systematic variation in silicide concentration across this interface is observed by x-ray photoelectron spectroscopy measurement. Change in the density of states in valence band across this interface is also observed by ultraviolet photoelectron measurement.

Naik, S. R.; Rai, S.; Lodha, G. S.; Brajpuriya, R.

2006-07-01

237

Origins of the instrumental background of the x-ray CCD camera in space studied with Monte Carlo simulation  

Microsoft Academic Search

We report on the origin of the instrumental background of the X-ray CCD camera in space obtained from the Monte Carlo simulation with GEANT4. In the space environment, CCD detects many non-X-ray events, which are produced by the interactions of high-energy particles with the materials surrounding CCD. Most of these events are rejected through the analysis of the charge split

Hiroshi Murakami; Masaki Kitsunezuka; Masanobu Ozaki; Tadayasu Dotani; Takayasu Anada

2006-01-01

238

The X-ray microcalorimeter spectrometer (XMS): a reference cryogenic instrument for Constellation-X  

NASA Astrophysics Data System (ADS)

The first two of four observatories in the constellation will be launched together in 2013 and followed a year later by the launch of the remaining pair. The four will independently orbit the Sun-Earth Lagrange point L2. An instrument compliment resides in the focal plane module (FPM) of each observatory 10 m from the optics module and consists of three hard X-ray telescope (HXT) detectors, a reflection grating spectrometer (RGS) focal plane CCD camera (RFC) and an X-ray microcalorimeter spectrometer (XMS). Instrument awards are scheduled for early 2006. The reference detector system for XMS is a 32 × 32 array of microcalorimetric superconducting transition edge sensors (TES) with SQUID based multiplexed readout and amplification. A multi-stage continuous ADR will provide the stable 50 mK desired for the TES array and a stable 1 K for the SQUID amplifiers while also lifting thermal parasitic and inefficiency loads to a 6 K cryocooler interface. The 6 K cryocooler is expected to emerge from the joint-project advanced cryocooler technology development program (ACTDP) in which Constellation-X is an active partner. Project pre-formulation activities are marked by extensive technology development necessitating early, but realistic, thermal and cooling load requirements for ADR and ACTDP-cryocooler design points. Such requirements are driven by the encompassing XMS cryostat and ultimately by the thermal environment imposed by the FPM. It is further desired that the XMS instrument be able to operate horizontally in the laboratory, with a warm vacuum shell, during an extensive calibration regime. It is that highly integrated reference instrument (microcalorimeter, ADR, cryocooler and cryostat) that will be examined here.

Whitehouse, Paul L.; Shirron, Peter J.; Kelley, Richard L.

2004-06-01

239

Toward Femtosecond X-ray Spectroscopy at the Advanced Light Source  

SciTech Connect

The realization of tunable, ultrashort pulse x-ray sources promises to open new venues of science and to shed new light on long-standing problems in condensed matter physics and chemistry. Fundamentally new information can now be accessed. Used in a pump-probe spectroscopy, ultrashort x-ray pulses provide a means to monitor atomic rearrangement and changes in electronic structure in condensed-matter and chemical systems on the physically-limiting time-scales of atomic motion. This opens the way for the study of fast structural dynamics and the role they play in phase transitions, chemical reactions and the emergence of exotic properties in materials with strongly interacting degrees of freedom. The ultrashort pulse x-ray source developed at the Advanced Light Source at the Lawrence Berkeley Laboratory is based on electron slicing in storage rings, and generates {approx}100 femtosecond pulses of synchrotron radiation spanning wavelengths from the far-infrared to the hard x-ray region of the electromagnetic spectrum. The tunability of the source allows for the adaptation of a broad range of static x-ray spectroscopies to useful pump-probe measurements. Initial experiments are attempted on transition metal complexes that exhibit relatively large structural changes upon photo-excitation and which have excited-state evolution determined by strongly interacting structural, electronic and magnetic degrees of freedom. Specifically, iron(II) complexes undergo a spin-crossover transition upon optical irradiation. The dynamics of the transition involve a metal-to-ligand charge transfer, a {Delta}S=2 change in magnetic moment and 10% bond dilation in the first coordination shell of the iron. Studies of the electronic dynamics are studied with time-resolved optical absorption measurements. The current progress of time-resolved structural studies to complete the picture of the spin-crossover transition is presented.

Chong, Henry Herng Wei

2004-04-16

240

X-ray absorption spectroscopy of the cubic and hexagonal polytypes of zinc sulfide B. Gilbert,1,  

E-print Network

X-ray absorption spectroscopy of the cubic and hexagonal polytypes of zinc sulfide B. Gilbert,1 Received 18 June 2002; published 26 December 2002 We investigate the sensitivity of x-ray absorption. Experimental spectra and multiple-scattering calculations are reported at the major absorption edges

Haskel, Daniel

241

Microelemental and mineral compositions of pathogenic biomineral concrements: SRXFA, X-ray powder diffraction and vibrational spectroscopy data  

NASA Astrophysics Data System (ADS)

X-ray fluorescence analysis using synchrotron radiation (SRXRF), X-ray powder diffraction, infrared and Raman spectroscopy had been applied for determination of microelemental and mineral composition of the kidney stones, gallstones and salivalities from natives of Novosibirsk and Novosibirsk region, Russia. The relationship between mineral, organic and microelemental composition of pathogenic calcilus was shown.

Moroz, T. N.; Palchik, N. A.; Dar'in, A. V.

2009-05-01

242

Characterization of alkanethiol/ZnO structures by X-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

1-Propanethiol (CH 3CH 2CH 2SH) was connected with O-polar zinc oxide (ZnO) surfaces toward biofunctional devices. X-ray photoelectron spectroscopy (XPS) measurement revealed that the S sbnd O bonds were formed between 1-propanethiol and ZnO layers. Although the surface coverage of the molecule is less than a few percent, 1-propanethiol/ZnO structures were stable even at thermal treatment of 400 °C.

Ogata, K.; Hama, T.; Hama, K.; Koike, K.; Sasa, S.; Inoue, M.; Yano, M.

2005-02-01

243

Elemental depth profiling of fluoridated hydroxyapatite by X-ray photoelectron spectroscopy  

Microsoft Academic Search

Structural and chemical changes that arise from a fluoridation of synthetic hydroxyapatite in neutral and acidic fluoridation agents are investigated. For synthetic hydroxyapatite (Ca5(PO4)3OH = HAp), the elemental depth profiles were determined by X-ray photoelectron spectroscopy (XPS) to reveal the effect of fluoridation in nearly neutral (pH = 6.2) and acidic agents (pH = 4.2). Due to the high surface

Frank Mueller; Christian Zeitz; Hubert Mantz; Karl-Heinz Ehses; Flavio Soldera; Matthias Hannig; Stefan Huefner; Karin Jacobs

2008-01-01

244

X-ray photoelectron spectroscopy of ultradispersed copper alloy powder surface after processing by fluorinated polyethers  

Microsoft Academic Search

Ultradispersed powders of Cu-Sn alloy were processed by fluorinated polyethers of different compositions. X-ray photoelectron\\u000a spectroscopy was used to show that a polymeric film no thicker than 2 nm was formed on the surface of particles as a result\\u000a of processing. The film formed by fluorinated polyethers with a molecular mass of 3000 prevents the interaction of metal particles\\u000a of

M. V. Kuznetsov; A. Ya. Zapevalov; L. V. Zolotukhina; I. G. Arefiev; B. R. Gelchinsky

2011-01-01

245

Identification of lead chemical form in mine waste materials by X-ray absorption spectroscopy  

Microsoft Academic Search

X-ray absorption spectroscopy (XAS) provides a direct means for measuring lead chemical forms in complex samples. In this study, XAS was used to identify the presence of plumbojarosite (PbFe6(SO4)4(OH)12) by lead L3-edge XANES spectra in mine waste from a small gold mining operation in Fiji. The presence of plumbojarosite in tailings was confirmed by XRD but XANES gave better resolution.

Raijeli L. Taga; Jiajia Zheng; Trang Huynh; Jack Ng; Hugh H. Harris; Barry Noller

2010-01-01

246

Chemical reaction between polyvinyl alcohol and titanate coupling agent with x-ray photoelectron spectroscopy  

Microsoft Academic Search

The chemical reaction between polyvinyl alcohol (PVA) and tri (dioctylpyrophosphoryloxy) isopropyl titanate (NDZ-201) was studied using X-ray photoelectron spectroscopy (XPS). The results show that some C?OH functional groups of PVA react\\u000a with the titanate coupling agent to form CPVA?O?Ti?O?CPVA bond. The cross-linking of the PVA chains occurs through the formation of CPVA?O?Ti?O?CPVA bonds and produces a three dimensional hydrophobic polymer

Li Bei-xing; Zhang Wen-sheng

2003-01-01

247

Atomic structure of machined semiconducting chips: An x-ray absorption spectroscopy study  

SciTech Connect

X-ray absorption spectroscopy (XAS) has been used to examine the atomic structure of chips of germanium that were produced by single point diamond machining. It is demonstrated that although the local (nearest neighbor) atomic structure is experimentally quite similar to that of single crystal specimens information from more distant atoms indicates the presence of considerable stress. An outline of the technique is given and the strength of XAS in studying the machining process is demonstrated.

Paesler, M.; Sayers, D.

1988-12-01

248

X-ray absorption spectroscopy of folded and unfolded copper(I) azurin  

Microsoft Academic Search

The structure of the copper site in folded and unfolded copper(I) azurin has been investigated by X-ray absorption spectroscopy (XAS). Analysis of the Cu K-edge spectra demonstrates that Cu(I) occupies a trigonal coordination site in the unfolded protein; and EXAFS data indicate a structure with 1.5–2 Cu?S(Cl) and 1.5–1 Cu?N(O) bonds. It is likely that the cysteine S and one

Serena DeBeer; Pernilla Wittung-Stafshede; Johan Leckner; Göran Karlsson; Jay R Winkler; Harry B Gray; Bo G Malmström; Edward I Solomon; Britt Hedman; Keith O Hodgson

2000-01-01

249

Valences of iron and copper in coral skeleton: X-ray absorption spectroscopy analysis  

Microsoft Academic Search

Synchrotron-based X-ray absorption spectroscopy (XAS) indicates that both iron and copper are present in their normal fully oxidized states, Fe(III) and Cu(II), in the aragonite (CaCO3, orthorhombic) skeletons of scleractinian reef corals. The Fe(III) may substitute for Ca(II) at its structural sites; alternatively, it may be present in clay or other detritus incorporated in the coral skeleton. The XAS-determined Cu(II)

Nicholas E. Pingitore Jr.; Arturo Iglesias; Allison Bruce; Farrel Lytle; Gerard M. Wellington

2002-01-01

250

Constellation-X Spectroscopy X-ray Telescope Assembly and Alignment  

Microsoft Academic Search

The Constellation-X mission is a follow-on to the current Chandra and XMM missions. It will place in orbit an array of four identical X-ray telescopes that will work in unison, having a substantial increase in effective area, energy resolution, and energy bandpass over current missions. To accomplish these ambitious increases new optics technologies must be exploited. The primary instrument for

William A. Podgorski

251

Constellation-X Spectroscopy X-ray Telescope Assembly and Alignment  

Microsoft Academic Search

The Constellation-X mission is a follow-on to the current Chandra and XMM missions. It will place in orbit an array of four identical X-ray telescopes that will work in unison, having a substantial increase in effective area, energy resolution, and energy bandpass over current missions. To accomplish these ambitious increases new optics technologies must be exploited. The primary instrument for

William A. Podgorski; Paul E. Glenn; Jason H. Hair; Robert Petre; Timo T. Saha; Mark L. Schattenburg; Jeff Stewart; William W. Zhang

2003-01-01

252

The X-ray Microcalorimeter Spectrometer (XMS): A Reference Cryogenic Instrument Design for Constellation-X  

NASA Technical Reports Server (NTRS)

Constellation-X, a mission now belonging to the Beyond Einstein initiative, is being planned to inherit the x-ray sky from Chandra, XMM-Newton and Astro-E. The first two of four observatories in the constellation will be launched together in 2013 and followed a year later by the launch of the remaining two. The four will independently orbit the Sun-Earth Lagrange point L2. An instrument compliment resides in the Focal Plane Module (FPM) of each observatory 10 m from the Optics Module and consists of three Hard X-ray Telescope (HXT) detectors, a Reflection Grating Spectrometer (RGS) focal plane CCD camera and an X-ray Microcalorimeter Spectrometer (XMS). Instrument awards are scheduled for early 2006. The reference detector for XMS is a 32 x 32 array of microcalorimetric superconducting Transition Edge Sensors (TES). Each pixel casts a variable resistance in a SQUID based multiplexed readout circuit which is coupled to series SQUID arrays for amplification and finally read out by external electronics. A multi-stage continuous ADR will provide the stable 50 mK desired for the TES array and a stable 1 K for the series SQUID arrays while also lifting thermal parasitic and inefficiency loads to a 6 K cryocooler interface. The 6 K cryocooler is expected to emerge from the joint-project Advanced Cryocooler Technology Development Program (ACTDP) in which Constellation-X is an active participant. Project Pre-Formulation activities are marked by extensive technology development necessitating early, but realistic, thermal and cooling load requirements for ADR and ACTDP-cryocooler design points. Such requirements are driven by the encompassing XMS cryostat and ultimately by the thermal environment imposed by the FPM. It is further desired that the XMS instrument be able to operate on its side in the laboratory, with a warm vacuum shell, during an extensive calibration regime. It is that reference system design of the XMS instrument (microcalorimeter, ADR, cryocooler and cryostat) which is the subject of this paper.

Whitehouse, Paul L.

2003-01-01

253

Development of Thin-Window Silicon Drift Detector for X-ray Spectroscopy  

SciTech Connect

A new set of thin-window silicon drift detectors composed of an array of hexagonal shaped detectors has been designed, constructed and tested for X-ray spectroscopy. Each individual ThinWinSDD has a thin entrance window on one side and a spiral shaped hexagonal cathode around a center anode on the other side. To produce the thin entrance window a 10 keV implantation of boron through a 500 A silicon dioxide was used. The implantation was followed by an annealing at 700 C for 30 min and a reactive ion etching step to ensure the removal of silicon dioxide from the smallest feature (5 mum). An aluminum layer is coated in the same vacuum system after back-sputtering. This step involves removing the native oxide that has formed on the top of the silicon substrate and then sputtering a 1100 A thick layer of aluminum onto the X-ray entrance window. The aluminum layer must be thick enough to block visible light, but thin enough to be transparent to soft X-rays down to 280 eV. We discuss first test results that include detector leakage current measurements and the response for multiple detectors exposed to the National Synchrotron Light Source's UV beam line U3C located at Brookhaven National Laboratory for X-ray energies as low as 280 eV.

Chen, W.; Carini, G.A.; De Geronimo, G.; Fried, J.; Gaskin, J.A.; Keister, J.W.; Li, Z.; Ramsey, B.D.; Rehak, P.; Siddons, D.P.

2009-10-01

254

Development of Thin-Window Silicon Drift Detector for X-ray Spectroscopy  

SciTech Connect

A new set of Thin-Window Silicon Drift Detectors composed of an array of hexagonal shaped detectors has been designed, constructed and tested for X-ray spectroscopy. Each individual ThinWinSDD has a thin entrance window on one side and a spiral shaped hexagonal cathode around a center anode on the other side. To produce the thin entrance window a 10 keV implantation of boron through a 500 {angstrom} silicon dioxide was used. The implantation was followed by an annealing at 700 C for 30 min and a reactive ion etching step to ensure the removal of silicon dioxide from the smallest feature (5 {micro}m). An aluminum layer is coated in the same vacuum system after back-sputtering. This step involves removing the native oxide that has formed on the top of the silicon substrate and then sputtering a 1100 {angstrom} thick layer of aluminum onto the X-ray entrance window. The aluminum layer must be thick enough to block visible light, but thin enough to be transparent to soft x-rays down to 280 eV. We discuss first test results that include detector leakage current measurements and the response for multiple detectors exposed to the National Synchrotron Light Source's UV beam line U3C located at Brookhaven National Laboratory for X-ray energies as low as 280 eV.

Chen, W.; Carini, G.; De Geronimo, G; Fried, J.; Gaskin, J.A.; Keister, J.W.; Li, Z.; Ramsey, B.D.; Rehak, P.; Siddons, D.P.

2008-01-22

255

A von Hamos x-ray spectrometer based on a segmented-type diffraction crystal for single-shot x-ray emission spectroscopy and time-resolved resonant inelastic x-ray scattering studies  

SciTech Connect

We report on the design and performance of a wavelength-dispersive type spectrometer based on the von Hamos geometry. The spectrometer is equipped with a segmented-type crystal for x-ray diffraction and provides an energy resolution in the order of 0.25 eV and 1 eV over an energy range of 8000 eV-9600 eV. The use of a segmented crystal results in a simple and straightforward crystal preparation that allows to preserve the spectrometer resolution and spectrometer efficiency. Application of the spectrometer for time-resolved resonant inelastic x-ray scattering and single-shot x-ray emission spectroscopy is demonstrated.

Szlachetko, J. [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Institute of Physics, Jan Kochanowski University, 25-406 Kielce (Poland); Nachtegaal, M.; Boni, E. de; Willimann, M.; Safonova, O.; Sa, J.; Smolentsev, G.; Szlachetko, M.; Bergamaschi, A.; Schmitt, B.; David, C.; Luecke, A. [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Bokhoven, J. A. van [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Institute for Chemical and Bioengineering, ETH Zurich, 8093 Zuerich (Switzerland); Dousse, J.-Cl.; Hoszowska, J.; Kayser, Y. [Department of Physics, University of Fribourg, 1700 Fribourg (Switzerland); Jagodzinski, P. [University of Technology, Kielce (Poland)

2012-10-15

256

Oxidation of polycrystalline indium studied by x-ray photoelectron spectroscopy and static secondary ion mass spectroscopy  

Microsoft Academic Search

The chemisorption of oxygen on clean polycrystalline indium surfaces is investigated by the combined techniques of x-ray photoelectron spectroscopy (XPS) and the static mode of secondary ion mass spectroscopy (SIMS). Oxygen uptake is characterized by a moderately rapid formation of In2O3, with no preoxidation adsorbed O2 phase discernable in the XPS spectra. A high binding energy O (1s) peak becomes

R. W. Hewitt; Nicholas Winograd

1980-01-01

257

X-ray spectroscopy of PSR B1951+32 and its pulsar wind nebula  

E-print Network

We present spatially resolved X-ray spectroscopy of PSR B1951+32 and its pulsar wind nebula (PWN) in supernova remnant (SNR) CTB 80 using a {\\sl Chandra} observation. The {\\sl Chandra} X-ray map reveals clearly various components of a ram-pressure confined PWN embedded in the SNR ejecta: a point source representing the pulsar, X-ray emission from the bow shock, a luminous X-ray tail, a 30$\\arcsec$ diameter plateau whose northwestern part is absent, and the outside more diffuse X-ray emission. The plateau is just surrounded by the radio, [O III], [S II], and [N II] shells, and the outside diffuse emission is mostly within the H${\\alpha}$ shells. While the spectra of all the features are well fitted with power law models, a power law plus blackbody model can fit the spectrum of the pulsar significantly better than using a power law model alone. Generally the spectra of these components obey the trend of steepening from the inside to the outside. However, the edge of the plateau probably has a harder spectrum than that of the central region of the plateau. The cause of the apparent hard spectrum of the plateau edge is unclear, and we speculate that it might be due to a shock between the PWN and the SNR ejecta. The possible blackbody radiation component from the pulsar has a temperature of 0.13$\\pm0.02$ keV and an equivalent emitting radius of 2.2$^{+1.4}_{-0.8}$ (d/2 kpc) km, and is thus probably from the hot spots on the pulsar. We also show in this paper that the blackbody temperature of the entire surface of PSR B1951+32 is much lower than those predicted by the standard neutron star cooling models.

X. H. Li; F. J. Lu; T. P. Li

2005-04-13

258

Influence of elastic scattering of photoelectrons on angle-resolved x-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

The validity of the electron effective attenuation length database developed by National Institute of Standards and Technology (NIST) is examined for x-ray photoelectron spectroscopy (XPS) measurement of HfO2 (2.7nm )/SiON (0.8nm)/Si. The angular dependences of photoelectron yields are calculated using the NIST database and composition depth profiles measured by high-resolution Rutherford backscattering spectroscopy. The calculated result reproduces the observed XPS result fairly well even at larger emission angles up to 80°, indicating that the accuracy of XPS depth profiling can be improved using the NIST database.

Kimura, Kenji; Nakajima, Kaoru; Conard, Thierry; Vandervorst, Wilfried

2007-09-01

259

Disentangling atomic-layer-specific x-ray absorption spectra by Auger electron diffraction spectroscopy  

NASA Astrophysics Data System (ADS)

In order to investigate the electronic and magnetic structures of each atomic layer at subsurface, we have proposed a new method, Auger electron diffraction spectroscopy, which is the combination of x-ray absorption spectroscopy (XAS) and Auger electron diffraction (AED) techniques. We have measured a series of Ni LMM AED patterns of the Ni film grown on Cu(001) surface for various thicknesses. Then we deduced a set of atomic-layer-specific AED patterns in a numerical way. Furthermore, we developed an algorithm to disentangle XANES spectra from different atomic layers using these atomic-layer-specific AED patterns. Surface and subsurface core level shift were determined for each atomic layer.

Matsui, Fumihiko; Matsushita, Tomohiro; Kato, Yukako; Hashimoto, Mie; Daimon, Hiroshi

2009-11-01

260

Focal plane instrumentation for the Wide-Field X-ray Telescope  

E-print Network

The three X-ray imaging focal planes of the Wide-Field X-ray Telescope (WFXT) Mission will each have a field of view up to 1 degree square, pixel pitch smaller than 1 arcsec, excellent X-ray detection efficiency and spectral ...

Bautz, Marshall W.

261

Probing Ultrafast Solution-Phase Chemistry in the X-ray Water Window and beyond via Soft X-ray Spectroscopy  

NASA Astrophysics Data System (ADS)

A prerequisite for a microscopic understanding of chemical reactions is knowledge of the ultrafast interplay of valence charge distributions, spin states, and nuclear degrees of freedom. These degrees of freedom are often intricately coupled, leading to very complex dynamics. Femtosecond core-level spectroscopy is very well suited to study such dynamics via x-ray absorption near-edge structure (for information on changes in valence charge distribution / spin-state) and via the extended x-ray absorption fine structure (for information in nuclear arrangements) due to the very localized nature of the initial states of well-defined symmetry and the high chemical specificity of core-level excitations. We have employed femtosecond core-level spectroscopy to study metal-ligand interactions in solvated transition metal complexes as an important class of model systems to demonstrate the feasibility and merit of ultrafast solution-phase soft X-ray spectroscopy.ootnotetextN. Huse, T. K. Kim, L. Jamula, J. K. McCusker, F. M. F. de Groot, R. W. Schoenlein, J. Am. Chem. Soc., 132, 6809.^,ootnotetextH. Wen, N. Huse, R. W. Schoenlein, A. M. Lindenberg, J. Chem. Phys., 131, 234505. Laser-induced charge transfer reactions on sub-100 fs time scales trigger structural dynamics in first-row transition-metal complexes that display multiple spin-state changes within 300 fs upon photo-excitation. The combined analysis of vibrational, optical, and core-level spectroscopy reveals a complex interplay of nuclear, electronic, and spin degrees of freedom in these systems that leads to detailed insights into the underlying reaction mechanisms. These are prototypical in nature for a variety of organometallic systems. The chemical specificity of core-level spectroscopy is exploited by probing metal-centered transitions to elucidate the "metallic view." We have very recently succeeded in also following the "ligand view" via soft X-ray spectroscopy in the X-ray water window. The later experiment has far-reaching consequences as it demonstrates the feasibility of studying ultrafast processes and short-lived species of solvated organic compounds via Nitrogen K-edge spectroscopy to deliver a detailed picture of the evolving valence charge density in chemical reactions.

Huse, Nils

2011-03-01

262

Determination of surface structure and orientation of polymerized tetrafluoroethylene films by near-edge X-ray absorption fine structure, X-ray photoelectron spectroscopy, and static secondary ion mass spectrometry  

Microsoft Academic Search

Films of conventional and radio frequency glow discharge (RFGD) polymerized tetrafluoroethylene (TFE) were examined by ultrasoft X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and static secondary ion mass spectrometry (SIMS). The polarization-dependent intensity changes of transitions to C-C and C-F Ï orbitals in the carbon and fluorine near-edge X-ray absorption fine structure (NEXAFS) spectra revealed different CFâ chain orientations.

David G. Castner; Kenneth B. Lewis; B. D. Ratner; D. A. Fischer; John L. Gland

1993-01-01

263

Phase distinction in semi-insulating polycrystalline silicon by pattern recognition of X-ray photoelectron spectroscopy/X-ray-induced Auger electron spectroscopy data  

NASA Astrophysics Data System (ADS)

X-ray photoelectron spectroscopy (XPS) and X-ray-induced Auger electron spectroscopy (XAES) supported with the lineshape analysis by the pattern recognition (PR) method and the fuzzy k-nearest neighbor rule ( kNN FR) were applied to study semiinsulating polycrystalline silicon layers (SIPOS). The aim of the present work was to obtain the qualitative and quantitative information about the surface region of as-received SIPOS layers. For the purpose of qualitative analysis the binding energies (BE), binding energy shifts (?BE), the half widths (FWHM) and the lineshapes of the Si 2p, O 1s and O KLL lines were analysed. The quantitative analysis was performed on the basis of the XPS using sensitivity factor method, multiline (ML) approach and the kNN FR. The performance of the kNN rule is possible after selecting the proper set of reference standard materials to which the rule refers during identification of an ambiguous chemical state. By selecting the reference samples supplying the information about the chemical state of Si, SiO x and SiO 2, the kNN rule allowed to distinguish qualitatively these three different phases in SIPOS samples. The particular application of the kNN FR makes possible the quantitative analysis by referring the fuzzy probability of classification for the given chemical state to the concentration of particular constituents in the investigated SIPOS. All the methods applied are consistent in revealing the quantitative results and show that SIPOS is a deeply non-homogeneous material, consisting of two phases: silicon and silicon oxide.

Lesiak, Beata; Zemek, Jozef; Jozwik, Adam

1998-09-01

264

A short-pulse X-ray beamline for spectroscopy and scattering.  

PubMed

Experimental facilities for picosecond X-ray spectroscopy and scattering based on RF deflection of stored electron beams face a series of optical design challenges. Beamlines designed around such a source enable time-resolved diffraction, spectroscopy and imaging studies in chemical, condensed matter and nanoscale materials science using few-picosecond-duration pulses possessing the stability, high repetition rate and spectral range of synchrotron light sources. The RF-deflected chirped electron beam produces a vertical fan of undulator radiation with a correlation between angle and time. The duration of the X-ray pulses delivered to experiments is selected by a vertical aperture. In addition to the radiation at the fundamental photon energy in the central cone, the undulator also emits the same photon energy in concentric rings around the central cone, which can potentially compromise the time resolution of experiments. A detailed analysis of this issue is presented for the proposed SPXSS beamline for the Advanced Photon Source. An optical design that minimizes the effects of off-axis radiation in lengthening the duration of pulses and provides variable X-ray pulse duration between 2.4 and 16?ps is presented. PMID:25178012

Reininger, R; Dufresne, E M; Borland, M; Beno, M A; Young, L; Evans, P G

2014-09-01

265

X-ray spectroscopy of the galaxy M87 - Radiative accretion of the hot plasma halo  

NASA Technical Reports Server (NTRS)

Canizares et al. (1979) have reported the detection of the O VIII Lyman-alpha line from the vicinity of the giant elliptical galaxy M87 in the Virgo cluster. The detection is based on high-resolution X-ray spectroscopy studies performed with the Focal Plane Crystal Spectrometer on the Einstein Observatory. The presence of a strong O VIII line indicates the existence of some material which is cooler than the bulk of the X-ray emitting gas surrounding M87. The result is interpreted as favoring models which call for radiative accretion of the hot gas onto M87. The present investigation is concerned with further high-resolution X-ray spectroscopy of M87. Seven additional emission line blends due primarily to ionized iron have been detected. These data make it possible to derive the approximate distribution of the quantity of emitting material over more than a decade in temperature for the central part of the M87 source. The obtained results are in excellent agreement with expectations for radiative, pressure driven accretion.

Canizares, C. R.; Clark, G. W.; Jernigan, J. G.; Markert, T. H.

1982-01-01

266

Surface Arsenic Speciation of a Drinking-Water Treatment Residual Using X-Ray Absorption Spectroscopy  

SciTech Connect

Drinking-water treatment residuals (WTRs) present a low-cost geosorbent for As-contaminated waters and soils. Previous work has demonstrated the high affinity of WTRs for As, but data pertaining to the stability of sorbed As is missing. Sorption/desorption and X-ray absorption spectroscopy (XAS), both XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure) studies, were combined to determine the stability of As sorbed by an Fe-based WTR. Arsenic(V) and As(III) sorption kinetics were biphasic in nature, sorbing <90% of the initial added As (15,000 mg kg{sup -1}) after 48 h of reaction. Subsequent desorption experiments with a high P load (7500 mg kg{sup -1}) showed negligible As desorption for both As species, approximately <3.5% of sorbed As; the small amount of desorbed As was attributed to the abundance of sorption sites. XANES data showed that sorption kinetics for either As(III) or As(V) initially added to solution had no effect on the sorbed As oxidation state. EXAFS spectroscopy suggested that As added either as As(III) or as As(V) formed inner-sphere mononuclear, bidentate complexes, suggesting the stability of the sorbed As, which was further corroborated by the minimum As desorption from the Fe-WTR.

Makris, K.C.; Sarkar, D.; Parsons, J.G.; Datta, R.; Gardea-Torresdey, J.L.

2009-06-03

267

Mineral identification in Colombian coals using Mössbauer spectroscopy and X-ray diffraction  

NASA Astrophysics Data System (ADS)

Minerals were identified in three Colombian coal samples from the Southwest of the country using Mössbauer spectroscopy and X-ray diffraction. Original and sink separated coal fractions of specific gravity 1.40 and 1.60 with particle size less than 600 µm were used in the study. Using Mössbauer spectroscopy, the minerals identified in the original coal samples were pyrite jarosite, ankerite, illite and ferrous sulfate, whereas by means of X-ray diffraction, minerals identified were kaolinite, quartz, pyrite, and jarosite. Differences in mineral composition were found in the original and sink separated fractions using both techniques. Mössbauer spectra show that the mineral phases in low concentrations such as illite, ankerite and ferrous sulfate do not always appear in the spectra of sink coals, despite of those minerals occurring in the original coal, due to the fact that they are associated with the organic matter and not liberated in the grinding process. X-ray results show that the peak intensity grows as the specific gravity is increased indicating that the density separation method could be an effective process to clean coal.

Fajardo, M.; Mojica, J.; Barraza, J.; Pérez Alcázar, G. A.; Tabares, J. A.

1999-11-01

268

Decorated pottery study: Analysis of pigments by x-ray absorbance spectroscopy measurements  

NASA Astrophysics Data System (ADS)

Characterization of pigments on decorated pottery fragments has been fully carried out by nondestructive x-ray absorbance spectroscopy (XAS). The samples were a series of pottery shards excavated from the archeological site of Caltagirone (Sicily, Italy), a well-known ceramic production center. Aesthetical criteria and morphological observations allowed us to attribute the samples to quite different historical periods, starting from the 18th century B.C. up to the 16th century A.D. An extensive time interval led us to suppose that different materials and techniques were used for the production of the ceramic paste and also for the preparation of pigments. XAS measurements were performed at the Cu and Fe K-edges. The analysis was carried out both in the near-edge (x-ray absorption near-edge spectroscopy, XANES) and in the extended (extended x-ray absorption fine structure, EXAFS) region. From the results, we observed Fe oxides as the main pigmenting agents in the most ancient fragment, while in the other ceramic shards, besides Fe oxides, copper oxides were also found. Oxidation states and local environments of the atoms present were characterized.

Barilaro, D.; Crupi, V.; Majolino, D.; Venuti, V.; Barone, G.; D'Acapito, F.; Bardelli, F.; Giannici, F.

2007-03-01

269

THE CHANDRA MULTI-WAVELENGTH PROJECT: OPTICAL SPECTROSCOPY AND THE BROADBAND SPECTRAL ENERGY DISTRIBUTIONS OF X-RAY-SELECTED AGNs  

E-print Network

From optical spectroscopy of X-ray sources observed as part of the Chandra Multi-wavelength Project (ChaMP), we present redshifts and classifications for a total of 1569 Chandra sources from our targeted spectroscopic ...

Trichas, Markos

270

Structural characterization of nickel oxide nanowires by X-ray absorption near-edge structure spectroscopy.  

PubMed

Nickel oxide nanowires modified by poly(vinylpyrrolidone) (PVP) were synthesized via a simple chemical pattern. For the first time NiO nanowires with diameters ranging from 40 to 100 nm with the expected ratio (length vs diameter) ranging from 54 to 90 were grown using a simple solution-phase approach (mild method). These nickel nanowires exhibited unique photoluminescence features and displayed a significant UV luminescence. X-ray absorption near-edge spectroscopy has been used to characterize the local Ni environment and identify the electronic structure. Comparing experimental and theoretical spectra at the Ni and O K edges, we determine the lattice distortion via the analysis of the characteristic preedge features and the multiple-scattering structures detected in the X-ray absorption near-edge structure spectra. The correlation between experimental features and the disordered or distorted local structures is also discussed. PMID:16851250

Wu, Z Y; Liu, C M; Guo, L; Hu, R; Abbas, M I; Hu, T D; Xu, H B

2005-02-24

271

Application of X-ray Fluorescence Spectroscopy in Analysis of Oil Paint Pigments  

NASA Astrophysics Data System (ADS)

X-ray Fluorescence (XRF) spectroscopy is a rapid, noninvasive technique for both detecting and identifying chemical elements within a given sample. At North Georgia College and State University, a sealed tube x-ray source and slightly focusing polycapillary optic are used in nondestructive XRF analysis of oil paint pigments. Oil paints contain both organic and inorganic matter, and the inorganic ingredients such as titanium, vanadium, iron, zinc, and other elements are easily detected by XRF, which can be used to uniquely differentiate between various paint pigments. To calibrate the XRF system for paint color identification, six different colors of oil paint were fluoresced and identified based off of their characteristic spectra. By scanning the paint sample in two dimensions, the characteristic XRF spectra obtained were compiled to produce an XRF replica of the painting.

Major, Cassandra; Formica, Sarah

2011-10-01

272

Note: Sample chamber for in situ x-ray absorption spectroscopy studies of battery materials  

NASA Astrophysics Data System (ADS)

In situ x-ray absorption spectroscopy (XAS) provides element-specific characterization of both crystalline and amorphous phases and enables direct correlations between electrochemical performance and structural characteristics of cathode and anode materials. In situ XAS measurements are very demanding to the design of the experimental setup. We have developed a sample chamber that provides electrical connectivity and inert atmosphere for operating electrochemical cells and also accounts for x-ray interactions with the chamber and cell materials. The design of the sample chamber for in situ measurements is presented along with example XAS spectra from anode materials in operating pouch cells at the Zn and Sn K-edges measured in fluorescence and transmission modes, respectively.

Pelliccione, C. J.; Timofeeva, E. V.; Katsoudas, J. P.; Segre, C. U.

2014-12-01

273

Wiggler-base Hard X-ray Spectroscopy Beamline at CLS  

NASA Astrophysics Data System (ADS)

The CLS 06ID-1 Hard X-ray Micro-Analysis Beamline (HXMA) is a general purpose hard X-ray spectroscopy beamline (5 to 40 keV) designed to serve users in XAFS, diffraction and microprobe communities. The beamline uses the synchrotron radiation from a superconducting wiggler. The primary beamline optics include a 1.2 m water-cooled silicon collimating mirror (separate Rh and Pt coating stripes), a liquid nitrogen cooled double crystal monochromator (Kohzu CMJ-1) housing two crystal pairs (Si 111 and 220), and a 1.15 m long water-cooled silicon toroidal focusing mirror (separate Rh and Pt coating stripes). All mirrors are equipped with dynamical meridian benders. The experimental hutch hosts three experimental setups for XAFS, diffraction and microprobe, respectively. Primary design considerations and some commissioning results are discussed.

Jiang, D. T.; Chen, N.; Sheng, W.

2007-01-01

274

Wiggler-base Hard X-ray Spectroscopy Beamline at CLS  

SciTech Connect

The CLS 06ID-1 Hard X-ray Micro-Analysis Beamline (HXMA) is a general purpose hard X-ray spectroscopy beamline (5 to 40 keV) designed to serve users in XAFS, diffraction and microprobe communities. The beamline uses the synchrotron radiation from a superconducting wiggler. The primary beamline optics include a 1.2 m water-cooled silicon collimating mirror (separate Rh and Pt coating stripes), a liquid nitrogen cooled double crystal monochromator (Kohzu CMJ-1) housing two crystal pairs (Si 111 and 220), and a 1.15 m long water-cooled silicon toroidal focusing mirror (separate Rh and Pt coating stripes). All mirrors are equipped with dynamical meridian benders. The experimental hutch hosts three experimental setups for XAFS, diffraction and microprobe, respectively. Primary design considerations and some commissioning results are discussed.

Jiang, D. T. [Canadian Light Source, University of Saskatchewan, Saskatoon, SK (Canada); Department of Physics, University of Guelph, Guelph ON N1G 2W1 (Canada); Chen, N. [Canadian Light Source, University of Saskatchewan, Saskatoon, SK (Canada); Geological Sciences Department, University of Saskachewan, Saskatoon, SK (Canada); Sheng, W. [Canadian Light Source, University of Saskatchewan, Saskatoon, SK (Canada)

2007-01-19

275

Local Structure of Photo-Induced Phases Probed by X-Ray Absorption Spectroscopy  

NASA Astrophysics Data System (ADS)

We describe X-ray absorption spectroscopy (XAS) technique to probe the local structure of photo-induced phase. Photo-induced melting of chalcogenide glass (amorphous selenium, a-Se) was investigated. A grazing-incidence fluorescence excitation and a high efficiency X-ray detector were used to detect a small change of coordination number due to photo-induced transformation. It was shown that photo-induced three-fold coordinated sites are formed upon light irradiation forming cross-linking between selenium chains (photo-induced melting). A simple model is proposed which describes the reorientation of selenium chain perpendicular to the polarization direction of excitation light leading to photo-induced dichroism (anisotropy). Potential of XAS as a local probe of nanoscale structural modifications induced by photo-excitation is clearly demonstrated.

Oyanagi, H.; Kolobov, A.; Tanaka, K.

276

Bulk-Sensitive X-Ray Absorption Spectroscopy Free of Self-Absorption  

NASA Astrophysics Data System (ADS)

We demonstrate a new method to measure x-ray absorption spectroscopy (XAS) in addition to traditional transmission, total-electron yield (TEY) and total-fluorescence yield (TFY) that is bulk sensitive, like TFY, and is not affected by self-absorption corrections that plague TFY measurements. This measure of XAS is accomplished by measuring the x-ray emission (partial fluorescence yield, PFY) from a different element or excitation than the one probed by the incident photon energy. It is found that the reciprocal of such a PFY spectrum is proportional to the linear attenuation coefficient, offset by an energy independent constant. We demonstrate this technique on Cu L, La M and Nd M edges of the high-TC cuprate La2-x-yNdySrxCuO4 by comparing its TEY, TFY and PFY spectra.

Achkar, Andrew; Regier, Tom; Wadati, Hiroki; Sawatzky, George; Kim, Young-June; Hawthorn, David

2010-03-01

277

Microcalorimeters for High Resolution X-Ray Spectroscopy of Laboratory and Astrophysical Plasmas  

NASA Technical Reports Server (NTRS)

The proposal has three major objectives. The first focuses on advanced neutron-transmutation-doped (NTD)-based microcalorimeter development. Our goal is to develop an array of microcalorimeters with sub- 5 eV energy resolution that can operate with pile-up-free throughput of at least 100 Hz per pixel. The second objective is to establish our microcalorimeter as an essential x-ray diagnostic for laboratory astrophysics studies. We propose to develop a dedicated microcalorimeter spectrometer for the EBIT (electron beam ion trap). This instrument will incorporate the latest detector and cryogenic technology that we have available. The third objective is to investigate innovative ideas related to possible flight opportunities. These include compact, long lived cryo-systems, ultra-low temperature cold stages, low mass and low power electronics, and novel assemblies of thin windows with high x-ray transmission.

Silver, E.; Flowers, Bobby J. (Technical Monitor)

2003-01-01

278

Electronic Properties of Hydrogen Storage Materials with Photon-in/Photon-out Soft-X-Ray Spectroscopy  

SciTech Connect

The applications of resonant soft X-ray emission spectroscopy on a variety of carbon systems have yielded characteristic fingerprints. With high-resolution monochromatized synchrotron radiation excitation, resonant inelastic X-ray scattering has emerged as a new source of information about electronic structure and excitation dynamics. Photon-in/photon-out soft-X-ray spectroscopy is used to study the electronic properties of fundamental materials, nanostructure, and complex hydrides and will offer potential in-depth understanding of chemisorption and/or physisorption mechanisms of hydrogen adsorption/desorption capacity and kinetics.

Guo, Jinghua

2008-09-22

279

Optimization of future high-resolution X-ray instrumentation in astrophysics  

E-print Network

Cadmium Zinc Telluride and Cadmium Telluride are the detector materials of choice for the detection of X-rays in the X-ray energy band E >= 5keV with excellent spatial and spectral resolution and without cryogenic cooling. Owing to recent breakthroughs in grazing incidence mirror technology, next-generation hard X-ray telescopes will achieve angular resolution between 5 and 10 arc seconds - about an order of magnitude better than that of the NuSTAR hard X-ray telescope. As a consequence, the next generation of X-ray telescopes will require pixelated X-ray detectors with pixels on a grid with a lattice constant of science drivers for a high angular-resolution X-ray mission include studies and measurements of black hole spins, the cosmic evolution of super-massive black holes, active galactic nuclei feedback, and the behaviour of matter at very high densities. In this...

Zajczyk, Anna; Dowkontt, Paul; Guo, Qingzhen; Kislat, Fabian; Krawczynski, Henric; De Geronimo, Gianluigi; Li, Shaorui; Beilicke, Matthias

2015-01-01

280

Imaging x-ray sources at a finite distance in coded-mask instruments  

SciTech Connect

We present a method for the correction of beam divergence in finite distance sources imaging through coded-mask instruments. We discuss the defocusing artifacts induced by the finite distance showing two different approaches to remove such spurious effects. We applied our method to one-dimensional (1D) coded-mask systems, although it is also applicable in two-dimensional systems. We provide a detailed mathematical description of the adopted method and of the systematics introduced in the reconstructed image (e.g., the fraction of source flux collected in the reconstructed peak counts). The accuracy of this method was tested by simulating pointlike and extended sources at a finite distance with the instrumental setup of the SuperAGILE experiment, the 1D coded-mask x-ray imager onboard the AGILE (Astro-rivelatore Gamma a Immagini Leggero) mission. We obtained reconstructed images of good quality and high source location accuracy. Finally we show the results obtained by applying this method to real data collected during the calibration campaign of SuperAGILE. Our method was demonstrated to be a powerful tool to investigate the imaging response of the experiment, particularly the absorption due to the materials intercepting the line of sight of the instrument and the conversion between detector pixel and sky direction.

Donnarumma, Immacolata; Pacciani, Luigi; Lapshov, Igor; Evangelista, Yuri

2008-07-01

281

GEOC Thursday, March 25, 2010 192 -In situ characterization of environmental redox reactions using quick-scanning X-ray absorption spectroscopy  

E-print Network

quick-scanning X-ray absorption spectroscopy (Q-XAS) Donald L Sparks, Dr. Matthew Ginder-Vogel, Dr. In this presentation, we will describe the use of quick X-ray absorption spectroscopy (Q-XAS), at a subsecond time by calculated rate constants that do not change with concentration. In addition to using X-ray absorption near

Sparks, Donald L.

282

Excited-state molecular structures captured by x-ray transient absorption spectroscopy : a decade and beyond.  

SciTech Connect

Transient molecular structures along chemical reaction pathways are important for predicting molecular reactivity, understanding reaction mechanisms, as well as controlling reaction pathways. During the past decade, X-ray transient absorption spectroscopy (XTA, or LITR-XAS, laser-initiated X-ray absorption spectroscopy), analogous to the commonly used optical transient absorption spectroscopy, has been developed. XTA uses a laser pulse to trigger a fundamental chemical process, and an X-ray pulse(s) to probe transient structures as a function of the time delay between the pump and probe pulses. Using X-ray pulses with high photon flux from synchrotron sources, transient electronic and molecular structures of metal complexes have been studied in disordered media from homogeneous solutions to heterogeneous solution-solid interfaces. Several examples from the studies at the Advanced Photon Source in Argonne National Laboratory are summarized, including excited-state metalloporphyrins, metal-to-ligand charge transfer (MLCT) states of transition metal complexes, and charge transfer states of metal complexes at the interface with semiconductor nanoparticles. Recent developments of the method are briefly described followed by a future prospective of XTA. It is envisioned that concurrent developments in X-ray free-electron lasers and synchrotron X-ray facilities as well as other table-top laser-driven femtosecond X-ray sources will make many breakthroughs and realise dreams of visualizing molecular movies and snapshots, which ultimately enable chemical reaction pathways to be controlled.

Chen, L. X.; Zhang, X.; Lockard, J. V.; Stickrath, A. B.; Attenkofer, K.; Jennings, G.; Liu, D.-J.; Northwestern Univ.

2010-03-02

283

Three-Dimensional Electron Realm in VSe2 by Soft-X-Ray Photoelectron Spectroscopy: Origin of Charge-Density Waves  

NASA Astrophysics Data System (ADS)

The resolution of angle-resolved photoelectron spectroscopy (ARPES) in three-dimensional (3D) momentum k is fundamentally limited by ill defined surface-perpendicular wave vector k? associated with the finite photoelectron mean free path. Pushing ARPES into the soft-x-ray energy region sharpens the k? definition, allowing accurate electronic structure investigations in 3D materials. We apply soft-x-ray ARPES to explore the 3D electron realm in a paradigm transition metal dichalcogenide VSe2. Essential to break through the dramatic loss of the valence band photoexcitation cross section at soft-x-ray energies is the advanced photon flux performance of our synchrotron instrumentation. By virtue of the sharp 3D momentum definition, the soft-x-ray ARPES experimental band structure and Fermi surface of VSe2 show a textbook clarity. We identify pronounced 3D warping of the Fermi surface and show that its concomitant nesting acts as the precursor for the exotic 3D charge-density waves in VSe2. Our results demonstrate the immense potential of soft-x-ray ARPES to explore details of 3D electronic structure.

Strocov, Vladimir N.; Shi, Ming; Kobayashi, Masaki; Monney, Claude; Wang, Xiaoqiang; Krempasky, Juraj; Schmitt, Thorsten; Patthey, Luc; Berger, Helmuth; Blaha, Peter

2012-08-01

284

X-ray spectroscopy for chemical and energy sciences: the case of heterogeneous catalysis.  

PubMed

Heterogeneous catalysis is the enabling technology for much of the current and future processes relevant for energy conversion and chemicals synthesis. The development of new materials and processes is greatly helped by the understanding of the catalytic process at the molecular level on the macro/micro-kinetic time scale and on that of the actual bond breaking and bond making. The performance of heterogeneous catalysts is inherently the average over the ensemble of active sites. Much development aims at unravelling the structure of the active site; however, in general, these methods yield the ensemble-average structure. A benefit of X-ray-based methods is the large penetration depth of the X-rays, enabling in situ and operando measurements. The potential of X-ray absorption and emission spectroscopy methods (XANES, EXAFS, HERFD, RIXS and HEROS) to directly measure the structure of the catalytically active site at the single nanoparticle level using nanometer beams at diffraction-limited storage ring sources is highlighted. The use of pump-probe schemes coupled with single-shot experiments will extend the time range from the micro/macro-kinetic time domain to the time scale of bond breaking and making. PMID:25177997

Frenkel, Anatoly I; van Bokhoven, Jeroen A

2014-09-01

285

X-ray Intensity Fluctuation Spectroscopy Studies of Near-Atomic-Scale Disorder  

NASA Astrophysics Data System (ADS)

The technique of x-ray intensity fluctuation spectroscopy (XIFS) has been developed and used to make the first observations of the dynamics of critical fluctuations in a binary alloy at equilibrium.( S. Brauer, G.B. Stephenson, M. Sutton, R. Brüning, E. Dufresne, S.G.J. Mochrie, G. Grübel, J. Als-Nielsen, D.L. Abernathy, Phys. Rev. Lett. 74), 2010 (1995). A coherent beam of hard x-rays with 6 × 10^7 photons/second has been formed using a 4 ? m diameter pinhole aperture and a Si(111) crystal monochromator, at undulator beamline 9 (Troika) of the European Synchrotron Radiation Facility. The coherent x-ray beam was used to perform scattering measurements from a single crystal of Fe_3Al near the B2/DO3 order-disorder phase transition (T_c=824.1 K). Below T_c, static speckle patterns were observed near the (1/2 1/2 1/2) superlattice reflection, arising from antiphase domains in the ordered phase. Above Tc however, the scattered intensity was not constant but fluctuated in time. From the intensity time-correlation functions we deduce short-range order correlation times in the range 500-1600 seconds for temperatures 0.15-0.55 K above T_c. These results point the way to future studies of equilibrium dynamics using XIFS techniques.

Brauer, Stephan F.

1996-03-01

286

The amorphous Zn biomineralization at Naracauli stream, Sardinia: electron microscopy and X-ray absorption spectroscopy.  

PubMed

An amorphous Zn biomineralization ("white mud"), occurring at Naracauli stream, Sardinia, in association with cyanobacteria Leptolyngbya frigida and diatoms, was investigated by electron microscopy and X-ray absorption spectroscopy. Preliminary diffraction analysis shows that the precipitate sampled on Naracauli stream bed is mainly amorphous, with some peaks ascribable to quartz and phyllosilicates, plus few minor unattributed peaks. Scanning electron microscopy analysis shows that the white mud, precipitated in association with a seasonal biofilm, is made of sheaths rich in Zn, Si, and O, plus filaments likely made of organic matter. Transmission electron microscopy analysis shows that the sheaths are made of smaller units having a size in the range between 100 and 200 nm. X-ray absorption near-edge structure and extended X-ray absorption fine structure data collected at the Zn K-edge indicate that the biomineral has a local structure similar to hemimorphite, a zinc sorosilicate. The differences of this biomineral with respect to the hydrozincite biomineralization documented about 3 km upstream in the same Naracauli stream may be related to either variations in the physicochemical parameters and/or different metabolic behavior of the involved biota. PMID:23832800

Medas, D; Lattanzi, P; Podda, F; Meneghini, C; Trapananti, A; Sprocati, A; Casu, M A; Musu, E; De Giudici, G

2014-06-01

287

Elastic photoelectron-scattering effects in quantitative X-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

We present improved formulae for the correction parameters Qx and ?eff that are used to account for elastic scattering of photoelectrons in quantitative X-ray photoelectron spectroscopy (XPS). The new formulae are based on new Monte Carlo simulations for 584 photoelectrons in 39 elemental solids that could be excited by Mg K? and Al K? X-rays in 315 different XPS configurations. The new simulations differed from similar earlier calculations in that differential elastic-scattering cross sections calculated from the Dirac-Hartree-Fock potential were utilized rather than those from the Thomas-Fermi-Dirac potential, a smaller analyzer acceptance angle was chosen, and the number of trajectories in each simulation was an order of magnitude larger. New values of Qx and ?eff were obtained for each photoelectron line, each X-ray source, and each XPS configuration. These Qx and ?eff values could be fitted to simple two-parameter expressions, each a function of the single-scattering albedo and the photoelectron emission angle. Values of Qx from the new predictive formula differed from the previous expression by less than 1%. Larger deviations in the values of ?eff, up to 2.5%, were found from the new fit to the ?eff parameter. The new expressions for Qx and ?eff provide a convenient means for correction of elastic-scattering effects in XPS.

Jablonski, A.; Powell, C. J.

2012-03-01

288

In Situ X-Ray Absorption Spectroscopy Study of the LiNiO2 Electrode  

NASA Astrophysics Data System (ADS)

LiNiO2 is one of the most promising active material for the development of novel 4V rechargeable lithium batteries. Recent x-ray diffraction studies showed that the electrochemical reactivity of this electrode is sensitive to the structure of the starting material as well as the charged products. To further examine this material, we have conducted an x-ray absorption spectroscopy (XAS) study to determine the structure of this electrode as a function of its charge state. Specifically, the x-ray absorption Ni K-edge energy, the pre-edge structure, and local structure parameters such as bond lengths, coordination numbers and disorders were investigated at various states of charge corresponding to Li_(1-x)NiO2 for x values of 0.0, 0.11, 0.23, 0.34, 0.45, 0.82, and 0.99. The charging which proceeds via lithium de-intercalation was conducted using constant current anodization at 0.5 mA in a non aqueous electrolyte consisting of 1M LiPF6 in 1:1:3 propylene ! carbonate, ethylene carbonate and dimethyl carbonate. The XAS results for this electrode will be compared with those of ?-NiOOH and KNiIO_6, the latter being used as a reference for quadrivalent nickel.

Mansour, A. N.; McBreen, J.; Melendres, C. A.

1997-03-01

289

The Constellation-X Spectroscopy X-ray Telescope: Recent Technology Development  

NASA Technical Reports Server (NTRS)

We describe recent progress in the technology development program for the mirror system for the Constellation-X Spectroscopy X-ray Telescope (SXT). Development of this mirror represents a significant technology challenge, as it must provide a combination of large effective area (3 sq. m) and modest angular resolution (15 arc second half power diameter requirement; 5 arc second goal) with a limited mass allocation. The baseline design incorporates over 200 nested Wolter 1 mirrors. Each of these in turn is segmented in order to simplify handling of the mirrors and facilitate mass production. The X-ray reflecting surfaces are fabricated from thin, thermally formed glass sheets. Production improvements have yielded mirror segments that approach the performance requirement without the need for epoxy replication. A mounting and alignment approach incorporating piezoelectric actuators has been shown to manipulate mirror segments with the required precision without introducing significant distortion. Substantial improvements in metrology methodology have provided insights into the mirror segment forming and alignment processes. An X-ray demonstration of a mirror segment pair is planned for early 2006.

Petre, Robert; Lehan, John L.; Owens, Scott; Saha, Timo; Stewart, Jeff; Zhang, William W.; O'Dell, Stephen L.; Jones, Wiliam D.; Reid, Paul B.

2006-01-01

290

ODS steel raw material local structure analysis using X-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Oxide dispersion strengthened (ODS) steels are promising materials for fusion power reactors, concentrated solar power plants, jet engines, chemical reactors as well as for hydrogen production from thermolysis of water. In this study we used X-ray absorption spectroscopy at the Fe and Cr K-edges as a tool to get insight into the local structure of ferritic and austenitic ODS steels around Fe and Cr atoms and its transformation during mechanical alloying process. Using the analysis of X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) we found that for austenitic samples a transformation of ferritic steel to austenitic steel is detectable after 10 hours of milling and proceeds till 40 hours of milling; only small amount of a-phase remains after 80 hours of milling. We found that the Cr K-edge EXAFS can be used to observe distortions inside the material and to get an impression on the formation of chromium clusters. In-situ EXAFS experiments offer a reliable method to investigate the ferritic to austenitic transformation.

Cintins, A.; Anspoks, A.; Purans, J.; Kuzmin, A.; Timoshenko, J.; Vladimirov, P.; Gräning, T.; Hoffmann, J.

2015-03-01

291

Diamond sensors and polycapillary lenses for X-ray absorption spectroscopy  

SciTech Connect

Diamond sensors are evaluated as incident beam monitors for X-ray absorption spectroscopy experiments. These single crystal devices pose a challenge for an energy-scanning experiment using hard X-rays due to the effect of diffraction from the crystalline sensor at energies which meet the Bragg condition. This problem is eliminated by combination with polycapillary lenses. The convergence angle of the beam exiting the lens is large compared to rocking curve widths of the diamond. A ray exiting one capillary from the lens meets the Bragg condition for any reflection at a different energy from the rays exiting adjacent capillaries. This serves to broaden each diffraction peak over a wide energy range, allowing linear measurement of incident intensity over the range of the energy scan. Extended X-ray absorption fine structure data are measured with a combination of a polycapillary lens and a diamond incident beam monitor. These data are of comparable quality to data measured without a lens and with an ionization chamber monitoring the incident beam intensity.

Ravel, B. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)] [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Attenkofer, K. [Photon Sciences Division, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States)] [Photon Sciences Division, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States); Bohon, J. [Center for Synchrotron Biosciences, Case Western Reserve University, Cleveland, Ohio 44106 (United States)] [Center for Synchrotron Biosciences, Case Western Reserve University, Cleveland, Ohio 44106 (United States); Muller, E. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11974-3800 (United States)] [Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11974-3800 (United States); Smedley, J. [Instrumentation Division, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States)] [Instrumentation Division, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States)

2013-10-15

292

Bulk sensitive x-ray absorption spectroscopy free of self-absorption effects  

NASA Astrophysics Data System (ADS)

We demonstrate a method of x-ray absorption spectroscopy (XAS) that is bulk sensitive, like traditional fluorescence yield measurements, but is not affected by self-absorption or saturation effects. This measure of XAS is achieved by scanning the incident photon energy through an absorption edge and using an energy-sensitive photon detector to measure the partial fluorescence yield (PFY). The x-ray emission from any element or core-hole excitation that is not resonant with the absorption edge under investigation is selected from the PFY. It is found that the inverse of this PFY spectrum, which we term inverse partial fluorescence yield (IPFY), is linearly proportional to the x-ray absorption cross-section without any corrections due to saturation or self-absorption effects. We demonstrate this technique on the Cu L2,3 and Nd M4,5 absorption edges of the high-Tc cuprate La1.475Nd0.4Sr0.125CuO4 by measuring the O K? PFY and comparing the total electron yield, total fluorescence yield, and IPFY spectra.

Achkar, A. J.; Regier, T. Z.; Wadati, H.; Kim, Y.-J.; Zhang, H.; Hawthorn, D. G.

2011-02-01

293

Investigating the speciation of copper in secondary fly ash by X-ray absorption spectroscopy.  

PubMed

Although some researchers have reported that chlorides may play an important part in the evaporation of copper during heat treatment of municipal solid waste incinerators (MSWI) fly ash (1, 2) , details on the copper speciation in volatile matters (secondary fly ash, SFA) are still lacking. In this work, we used in situ X-ray absorption spectroscopy (XAS) experiments involving three types of SFA, which was collected from a high-temperature tubular electric furnace by thermal treatment of municipal solid waste incinerator (MSWI) fly ash at 1000, 1150, and 1250 degrees C. The results obtained by a linear combination fit (LCF) of X-ray absorption near edge structure (XANES) spectra revealed that in MSWI fly ash copper mainly exists as CuO and CuSO(4).5H(2)O while chloride almost dominated all the content of the SFA conformation, which was more than 80%. Extended X-ray absorption fine structure (EXAFS) data analysis indicated the presence of both Cu-O and Cu-Cl bonds in the first coordination shell of Cu ions in all SFA, while only Cu-O bonds occur in the MSWI fly ash. Consequently, in the MSWI fly ash during heat treatment copper evaporated as chloride, and the latter plays an important role in the formation of copper chloride. PMID:19928760

Tian, Shulei; Yu, Meijuan; Wang, Wei; Wang, Qi; Wu, Ziyu

2009-12-15

294

The focusing optics x-ray solar imager (FOXSI): instrument and first flight  

NASA Astrophysics Data System (ADS)

Solar flares accelerate particles up to high energies (MeV and GeV scales for electrons and ions, respectively) through efficient acceleration processes that are not currently understood. Hard X-rays (HXRs) are the most direct diagnostic of flare-accelerated electrons. However, past and current solar HXR observers lack the necessary sensitivity and imaging dynamic range to make detailed studies of faint HXR sources in the solar corona (where particle acceleration is thought to occur); these limitations are mainly due to the indirect Fourier imaging techniques used by these observers. With greater sensitivity and dynamic range, electron acceleration sites could be systematically studied in detail. Both these capabilities can be advanced by the use of direct focusing optics. The recently own Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket payload demonstrates the unique diagnostic power of focusing optics for observations of solar HXRs. FOXSI features grazing-incidence replicated nickel optics with 5 arcsecond resolution and fine-pitch silicon strip detectors with a 7.7 arcsecond strip pitch. FOXSI flew successfully on 2012 November 2, producing images and spectra of a microflare and performing a search for non-thermal emission (4{15 keV) from nanoflares occurring outside active regions in the quiet Sun. A future spacecraft version of FOXSI, featuring similar optics and detectors, could make detailed observations of HXRs from flare-accelerated electrons, identifying and characterizing particle acceleration sites and mapping out paths of energetic electrons as they leave these sites and propagate throughout the solar corona. This paper will describe the FOXSI instrument and present images from the first flight.

Krucker, Säm.; Christe, Steven; Glesener, Lindsay; Ishikawa, Shinnosuke; Ramsey, Brian; Gubarev, Mikhail; Saito, Shinya; Takahashi, Tadayuki; Watanabe, Shin; Tajima, Hiroyasu; Tanaka, Takaaki; Turin, Paul; Glaser, David; Fermin, Jose; Lin, Robert P.

2013-09-01

295

Scanning transmission X-ray microscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry study on the enhanced visible photocatalytic mechanism of carbon-TiO2 nanohybrids  

NASA Astrophysics Data System (ADS)

Carbon-TiO2 nanohybrids (CTs, 5-10 nm TiO2 nanocrystals evenly dispersed on carbon film) have been successfully prepared via a mild, one-step hydrothermal approach. The interactions and electronic structures of carbon and TiO2 nanoparticles and the enhanced visible photocatalytic mechanism were investigated by scanning transmission X-ray microscopy, X-ray photoelectron spectroscopy and cyclic voltammetry in detail. Meanwhile, it was demonstrated that the as-obtained CTs had a large BET specific surface area of 304.6 m2/g and showed excellent photocatalytic abilities towards organic (Rhodamine B, benzene) and inorganic pollutant (K2Cr2O7) degradation in visible light. This work provided a new approach for the high performance catalyst design towards new energy sources and environmental issues.

Ming, Hai; Zhang, Hengchao; Ma, Zheng; Huang, Hui; Lian, Suoyuan; Wei, Ying; Liu, Yang; Kang, Zhenhui

2012-02-01

296

Investigation by laser induced breakdown spectroscopy, X-ray fluorescence and X-ray powder diffraction of the chemical composition of white clay ceramic tiles from Veliki Preslav  

NASA Astrophysics Data System (ADS)

The paper presents the results of the application of laser induced breakdown spectroscopy, X-ray fluorescence spectrometry, and X-ray powder diffraction in assessing the chemical and phase composition of white clay decorative ceramic tiles from the medieval archaeological site of Veliki Preslav, a Bulgarian capital in the period 893-972 AC, well-known for its original ceramic production. Numerous white clay ceramic tiles with highly varied decoration, produced for wall decoration of city's churches and palaces, were found during the archaeological excavations in the old capital. The examination of fourteen ceramic tiles discovered in one of the city's monasteries is aimed at characterization of the chemical profile of the white-clay decorative ceramics produced in Veliki Preslav. Combining different methods and comparing the obtained results provides complementary information regarding the white-clay ceramic production in Veliki Preslav and complete chemical characterization of the examined artefacts.

Blagoev, K.; Grozeva, M.; Malcheva, G.; Neykova, S.

2013-01-01

297

Ultra-Small-Angle X-ray Scattering – X-ray Photon Correlation Spectroscopy Studies of Incipient Structural Changes in Amorphous Calcium Phosphate Based Dental Composites  

PubMed Central

The local structural changes in amorphous calcium phosphate (ACP) based dental composites were studied under isothermal conditions using both static, bulk measurement techniques and a recently developed methodology based on combined ultra-small angle X-ray scattering – X-ray photon correlation spectroscopy (USAXS-XPCS), which permits a dynamic approach. While results from conventional bulk measurements do not show clear signs of structural change, USAXS-XPCS results reveal unambiguous evidence for local structural variations on a similar time scale to that of water loss in the ACP fillers. A thermal-expansion based simulation indicates that thermal behavior alone does not account for the observed dynamics. Together, these results suggest that changes in the water content of ACP affect the composite morphology due to changes in ACP structure that occur without an amorphous-to-crystalline conversion. It is also noted that biomedical materials research could benefit greatly from USAXS-XPCS, a dynamic approach. PMID:22374649

Zhang, F.; Allen, A.J.; Levine, L.E.; Espinal, L.; Antonucci, J.M.; Skrtic, D.; O’Donnell, J.N.R.; Ilavsky, J.

2012-01-01

298

Investigation of magnetic field manipulated electrons produced from laser-driven ultrafast x-ray sources using x-ray emission spectroscopy  

NASA Astrophysics Data System (ADS)

We used x-ray emission spectroscopy to study energetic electrons (10–100?keV) generated at the laser focus of an intense ultrafast laser interacting with a primary thin film tape target. The electrons penetrated the tape and reached a secondary target of thin metal foils as the probe. The trajectories of these electrons were manipulated with an external magnetic field generated from a home-made Halbach magnet. The interaction of these energetic electrons with the probe produced characteristic x-rays, which were used to infer the flux and temperature of the electrons emitted from the laser focus at the primary tape target. A potential application using these energetic electrons is discussed.

Lee, Changju; Davidson, R. Andrew; Guo, Ting

2015-03-01

299

Measurement of c-axis angular orientation in calcite (CaCO3) nanocrystals using X-ray absorption spectroscopy  

PubMed Central

We demonstrate that the ability to manipulate the polarization of synchrotron radiation can be exploited to enhance the capabilities of X-ray absorption near-edge structure (XANES) spectroscopy, to include linear dichroism effects. By acquiring spectra at the same photon energies but different polarizations, and using a photoelectron emission spectromicroscope (PEEM), one can quantitatively determine the angular orientation of micro- and nanocrystals with a spatial resolution down to 10 nm. XANES-PEEM instruments are already present at most synchrotrons, hence these methods are readily available. The methods are demonstrated here on geologic calcite (CaCO3) and used to investigate the prismatic layer of a mollusk shell, Pinctada fucata. These XANES-PEEM data reveal multiply oriented nanocrystals within calcite prisms, previously thought to be monocrystalline. The subdivision into multiply oriented nanocrystals, spread by more than 50°, may explain the excellent mechanical properties of the prismatic layer, known for decades but never explained. PMID:21693647

Gilbert, P. U. P. A.; Young, Anthony; Coppersmith, Susan N.

2011-01-01

300

Synchrotron soft X-ray absorption spectroscopy study of carbon and silicon nanostructures for energy applications.  

PubMed

Carbon and silicon materials are two of the most important materials involved in the history of the science and technology development. In the last two decades, C and Si nanoscale materials, e.g., carbon nanotubes, graphene, and silicon nanowires, and quantum dots, have also emerged as the most interesting nanomaterials in nanoscience and nanotechnology for their myriad promising applications such as for electronics, sensors, biotechnology, etc. In particular, carbon and silicon nanostructures are being utilized in energy-related applications such as catalysis, batteries, solar cells, etc., with significant advances. Understanding of the nature of surface and electronic structures of nanostructures plays a key role in the development and improvement of energy conversion and storage nanosystems. Synchrotron soft X-ray absorption spectroscopy (XAS) and related techniques, such as X-ray emission spectroscopy (XES) and scanning transmission X-ray microscopy (STXM), show unique capability in revealing the surface and electronic structures of C and Si nanomaterials. In this review, XAS is demonstrated as a powerful technique for probing chemical bonding, the electronic structure, and the surface chemistry of carbon and silicon nanomaterials, which can greatly enhance the fundamental understanding and also applicability of these nanomaterials in energy applications. The focus is on the unique advantages of XAS as a complementary tool to conventional microscopy and spectroscopy for effectively providing chemical and structural information about carbon and silicon nanostructures. The employment of XAS for in situ, real-time study of property evolution of C and Si nanostructures to elucidate the mechanisms in energy conversion or storage processes is also discussed. PMID:25204894

Zhong, Jun; Zhang, Hui; Sun, Xuhui; Lee, Shuit-Tong

2014-12-10

301

X-ray Spectroscopy of K- and L-shell Z-pinch and Astrophysical Plasmas  

SciTech Connect

In recent years, there have been significant advances in instrumental capabilities for making X-ray spectroscopic measurements of astrophysical plasmas. There have been corresponding improvements in X-ray diagnostics for advanced multi-mega-ampere pulse power machines that produce increasingly large radiative yields from gas-puff and wire array Z pinch plasmas. Analysis used for Z pinches can be used to study ICF and also astrophysical plasmas where laboratory measurements and simulations are the only means to interpret observed data. The astrophysical data for Fe, the most cosmically abundant high Z element, can provide a wealth of information about cosmic plasmas. Fe is also the key element in stainless steel (SS) wire arrays that are investigated as an intense X-ray radiation source at the Z machine at Sandia National Laboratories. The implosion dynamics of an array of wires on the Z and/or refurbished Z accelerator produces an abundance of radiation from the K- and L-shell ionization stages. These dynamic plasmas are inherently non-LTE, with opacity and other factors influencing the X-ray output. As the plasma assembles on axis, a number of time resolved snapshots provide temperature and density profiles and map the emitting region. We will analyze the ionization dynamics and generate K- and L-shell spectra using the conditions generated in the Z and/or refurbished Z accelerator, described by a 1-D non-LTE radiation-hydrodynamics model. Diagnostics based on spectral shape of L-shell emissions are inherently more difficult than those based on K-shell emissions because of more complex multiplet structures and line overlaps. The non-LTE populations are obtained by using detailed atomic models that include all important excitation, ionization, and recombination processes. We will highlight the connection between laboratory Z-pinch plasma simulations and astrophysical plasmas.

Dasgupta, A.; Davis, J.; Giuliani, J. G. [Plasma Physics Division, Naval Research Laboratory, Washington DC 20375 (United States); Clark, R. W. [Berkeley Research Associates, Beltsville, Maryland 20705 (United States)

2009-09-10

302

Black hole accretion rings revealed by future X-ray spectroscopy  

NASA Astrophysics Data System (ADS)

Spectral features can arise by reflection of coronal X-rays on a black hole accretion disc. The resulting profile bears various imprints of a strong gravitational field acting on the light-emitting gas. The observed shape of the reflection line is formed by integrating contributions over a range of radii across the accretion disc plane, where the individual photons experience a different level of energy shifts, boosting and amplification by relativistic effects. These have to be convolved with the intrinsic emissivity of the line, which is a function of radius and the emission angle in the local frame. We study if the currently discussed instruments on-board X-ray satellites will be able to reveal the departure of the line radial emissivity from a simple smooth power-law function, which is often assumed in data fitting and its interpretation. Such a departure can be a result of excess emission occurring at a certain distance. This could be used to study variations with a radius of the line production or to constrain the position of the inner edge of the accretion disc. By simulating artificial data from a bright active galactic nucleus of a type 1 Seyfert galaxy (inclination ?30°, X-ray flux ?1-2 mCrab in a keV energy band) we show that the required sensitivity and energy resolution could be reached with a large area detector of the proposed Large Observatory for X-ray Timing mission. Galactic black holes will provide another category of potentially suitable targets if the relativistic spectral features are indeed produced by reflection from their accretion discs.

Sochora, V.; Karas, V.; Svoboda, J.; Dov?iak, M.

2011-11-01

303

WR 138: new results from X-ray and optical spectroscopy  

NASA Astrophysics Data System (ADS)

Context. Massive-binary evolution models predict that some systems will go through an evolutionary phase where the original primary has become a supernova and left a compact object behind that then orbits a Wolf-Rayet (WR) star. WR 138 is an X-ray bright WR star that has been described as a triple system, including a compact companion in a short-period orbit. Aims: Our goal is to search for spectroscopic evidence of a compact companion around WR 138. Methods: We used optical and X-ray spectra to search for signatures of a compact companion, which can be revealed by systematic variations in WR optical spectral lines induced by orbital motion of the compact companion or by hard, luminous X-rays from accretion onto this companion. Results: The optical spectra display emission-line profile variations that are most probably caused by clumps inside the stellar winds. The radial velocities do not vary on a short time-scale compatible with the suggested orbital period of a putative compact companion. The X-ray spectra are found to be normal for a WN5-6+OB system with no indication of accretion by a compact companion. Conclusions: There is no evidence for the presence of a compact companion, and we therefore conclude that WR 138 is a normal long-period (P ~ 1521 d) eccentric WR+OB system. Based on observations collected at the Observatoire de Haute-Provence (France), the San Pedro Mártir observatory (Mexico), and with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and the USA (NASA).Tables 2-5 are available in electronic form at http://www.aanda.org

Palate, M.; Rauw, G.; De Becker, M.; Nazé, Y.; Eenens, P.

2013-12-01

304

Modular instrument mounting system for variable environment in operando X-ray experiments  

NASA Astrophysics Data System (ADS)

In the growing field of in operando and in situ X-ray experiments, there exists a large disparity in the types of environments and equipment to control them. This situation makes it challenging to conduct multiple experiments with a single mechanical interface to the diffractometer. Here, we describe the design and implementation of a modular instrument mounting system that can be installed on a standard six-circle diffractometer (e.g., 5021 Huber GmbH). This new system allows for the rapid changeover of different chambers and sample heaters and permits accurate sample positioning (x, y, z, and azimuthal rotation) without rigid coupling to the chamber body. Isolation of the sample motion from the chamber enclosure is accomplished through a combination of custom rotary seals and bellows. Control of the pressure and temperature has been demonstrated in the ranges of 10-6-103 Torr and 25°C-900°C, respectively. We have utilized the system with several different modular instruments. As an example, we provide in situ sputtering results, where the growth dynamics of epitaxial LaGaO3 thin films on (001) SrTiO3 substrates were investigated.

Folkman, C. M.; Highland, M. J.; Perret, E.; Kim, S. K.; Fister, T. T.; Zhou, H.; Baldo, P. M.; Seifert, S.; Eastman, J. A.; Fuoss, P. H.; Fong, D. D.

2013-02-01

305

Modular instrument mounting system for variable environment in operando X-ray experiments  

SciTech Connect

In the growing field of in operando and in situ X-ray experiments, there exists a large disparity in the types of environments and equipment to control them. This situation makes it challenging to conduct multiple experiments with a single mechanical interface to the diffractometer. Here, we describe the design and implementation of a modular instrument mounting system that can be installed on a standard six-circle diffractometer (e.g., 5021 Huber GmbH). This new system allows for the rapid changeover of different chambers and sample heaters and permits accurate sample positioning (x, y, z, and azimuthal rotation) without rigid coupling to the chamber body. Isolation of the sample motion from the chamber enclosure is accomplished through a combination of custom rotary seals and bellows. Control of the pressure and temperature has been demonstrated in the ranges of 10{sup -6}-10{sup 3} Torr and 25 Degree-Sign C-900 Degree-Sign C, respectively. We have utilized the system with several different modular instruments. As an example, we provide in situ sputtering results, where the growth dynamics of epitaxial LaGaO{sub 3} thin films on (001) SrTiO{sub 3} substrates were investigated.

Folkman, C. M.; Highland, M. J.; Perret, E.; Kim, S. K.; Baldo, P. M.; Eastman, J. A.; Fuoss, P. H.; Fong, D. D. [Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Fister, T. T. [Chemical Sciences and Engineering, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Zhou, H.; Seifert, S. [X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)

2013-02-15

306

Atmospheric Electron-induced X-Ray Spectrometer (AEXS) Instrument Development  

NASA Technical Reports Server (NTRS)

Introduction: This paper describes the progress in data acquisition and establishing the observational capability of the AEXS instrument. The AEXS is a miniature instrument[1-4] based on the excitation of characteristic X-Ray Fluorescence (XRF) and luminescence spectra using a focused electron beam which enables nondestructive evaluation of sample surfaces in planetary ambient atmospheres. In situ operation is obtained through the use of a thin electron transmissive membrane to isolate the vacuum of the AEXS source from the outside ambient atmosphere. Thus eliminating the need for a vacuum pumped sample chamber as is common in all laboratory SEM s. The transmitted electrons impinge on the sample exciting XRF spectra from the irradiated spot on in-situ or collected samples with sub-mm to cm-scale spatial resolution at Mars atmospheric pressure. The AEXS system (Fig 1) consists of a high-energy (>10keV) electron gun encapsulated by the isolation membrane, an XRF detection and analyzer system, and a high voltage power supply. The XRF data are analyzed to determine the elemental abundance for the irradiated spots. The approach to demonstrating a proof of concept of the AEXS has been through 1) demonstrating the viability of microfabricated membranes, 2) assembling AEXS setups with increasingly integrated functional components, and 3) simulating the AEXS observational capabilities. The development of the instrument is described in detail in the poster paper[4] at this conference. This paper focuses on describing the progress of the AEXS instrument to acquire XRF data and using commercially available software to analyze the data streams and determine the accuracy, precision and resolution of the analysis compared to the certified elemental abundance.

Urgiles, E.; Wilcox, J. Z.; Toda, R.; Crisp, J.; George, T.

2005-01-01

307

Oxidation of stepped Pt(111) studied by x-ray photoelectron spectroscopy and density functional theory  

SciTech Connect

In this comparative density functional theory and x-ray photoelectron spectroscopy study on the interaction of oxygen with stepped Pt(111) surfaces, we show that both the initial adsorption and oxidation occur at the steps rather than terraces. An equivalent behavior was observed for the oxide formation at higher chemical potentials, where, after the formation of a one-dimensional PtO{sub 2}-type oxide at the steps, similar oxide chains form on the (111) terraces, indicating the initial stages of bulk oxide formation.

Bandlow, Jochen; Kaghazchi, Payam; Jacob, Timo [Institut fuer Elektrochemie, Universitaet Ulm, Albert-Einstein-Allee 47, D-89069 Ulm (Germany); Papp, C.; Traenkenschuh, B.; Streber, R.; Lorenz, M. P. A.; Fuhrmann, T.; Steinrueck, H.-P. [Lehrstuhl fuer Physikalische Chemie II, Universitaet Erlangen-Nuernberg, Egerlandstr. 3, D-91058 Erlangen (Germany); Denecke, R. [Wilhelm-Ostwald-Institut fuer Physikalische und Theoretische Chemie, Universitaet Leipzig, Linnestr. 2, D-04103 Leipzig (Germany)

2011-05-01

308

Contact-free pyroelectric measurements using x-ray photoelectron spectroscopy  

SciTech Connect

Non-contact pyroelectricity measurements based on x-ray photoelectron spectroscopy (XPS) are presented. Applied to Lithium Tantalate crystals, we demonstrate how the XPS-derived surface potential provides a simple probe of the desired property, free of all top-contact related difficulties. In particular, the increase in Lithium Tantalate spontaneous polarization under cooling, an experimentally challenging feature, is evaluated. We further inspect the roll of surface contaminants and the control over trapped surface charge in the XPS vacuum environment. Our approach can be extended to other non-contact probes, as well as to measuring additional electrical properties, such as piezoelectricity and ferroelectricity.

Ehre, D. [Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100 (Israel)] [Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100 (Israel); Cohen, H. [Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100 (Israel)] [Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100 (Israel)

2013-07-29

309

Iron location in O-carboxymethyl chitosans determined by X-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Chitosans represent a class of functional natural polymers. Their unique attribute is the capability to bind metal ions into their structure. This property can be exploited in many biomedical applications, but before that, some questions about metal binding mechanism must be answered. O-carboxymethyl chitosans with accumulated Fe atoms were studied by X-ray absorption spectroscopy. It was shown that iron bonding depends on the technological processes used in chitosan production. The applied technology allows for the selective introduction of either oxygen alone or of nitrogen and oxygen into the nearest neighbourhood of Fe. Therefore, it is possible to control the surroundings of a metal atom depending on requirements.

Klepka, Marcin T.; Lawniczak-Jablonska, Krystyna; Wolska, Anna; Slawska-Waniewska, Anna; Rodrigues, Clóvis A.; Lorini, Josiane; Cruz, Karianne Araujo da

2011-01-01

310

X-ray Spectroscopy of E2 and M3 Transitions in Ni-like W  

SciTech Connect

The electric quadrupole (E2) and magnetic octupole (M3) ground state transitions in Ni-like W{sup 46+} have been measured using high-resolution crystal spectroscopy at the Livermore electron beam ion trap facility. The lines fall in the soft x-ray region near 7.93 {angstrom} and were originally observed as an unresolved feature in tokamak plasmas. Using flat ADP and quartz crystals the wavelengths, intensities, and polarizations of the two lines have been measured for various electron beam energies and compared to intensity and polarization calculations performed using the Flexible Atomic Code (FAC).

Clementson, J; Beiersdorfer, P; Gu, M F

2009-11-09

311

Slow dynamics of nanocomposite polymer aerogels as revealed by X-ray photocorrelation spectroscopy (XPCS)  

NASA Astrophysics Data System (ADS)

We report on a novel slow dynamics of polymer xerogels, aerogels, and nanocomposite aerogels with iron oxide nanoparticles, as revealed by X-ray photon correlation spectroscopy. The polymer aerogel and its nanocomposite aerogels, which are porous in nature, exhibit hyper-diffusive dynamics at room temperature. In contrast, non-porous polymer xerogels exhibit an absence of this peculiar dynamics. This slow dynamical process has been assigned to a relaxation of the characteristic porous structure of these materials and not to the presence of nanoparticles.

Hernández, Rebeca; Nogales, Aurora; Sprung, Michael; Mijangos, Carmen; Ezquerra, Tiberio A.

2014-01-01

312

The Chemical Forms of Mercury in Human Hair: A Study using X-ray Absorption Spectroscopy  

PubMed Central

Human hair is frequently used as a bio-indicator of mercury exposure. We have used X-ray absorption spectroscopy to examine the chemical forms of mercury in human hair samples taken from individuals with high fish consumption and concomitant exposure to methylmercury. The mercury is found to be predominantly methylmercury cysteine or closely related species, comprising approximately 80% of the total mercury with the remainder an inorganic thiolate-coordinated mercuric species. No appreciable role was found for selenium in coordinating mercury in hair. PMID:20225071

George, Graham N.; Singh, Satya P.; Myers, Gary J.; Watson, Gene E.; Pickering, Ingrid J.

2013-01-01

313

FPGA-based compression of streaming x-ray photon correlation spectroscopy data  

SciTech Connect

A data acquisition system to perform real-time background subtraction and lower-level-discrimination-based compression of streaming x-ray photon correlation spectroscopy (XPCS) data from a fast charge-coupled device (CCD) area detector has been built and put into service at the Advanced Photon source (APS) at Argonne National Laboratory. A commercial frame grabber with on-board field-programmable gate array (FPGA) was used in the design, and continuously processes 60 frames per second each consisting of 1,024 x 1,024 pixels with up to 64512 photon hits per frame.

Madden, Timothy; Jemian, Peter; Narayanan, Surcsh; Sandy, Alec; Sikorski, Marcin; Sprung, Michael; Weizeorick, John

2011-08-09

314

Damage profile of ion-implanted GaAs by x-ray photoelectron spectroscopy  

SciTech Connect

We report on the use of x-ray photoelectron spectroscopy for the investigation of radiation damage in GaAs. The technique has been used to profile the damage induced by 7 MeV Si{sup +} ions. Arsenic displaced by the ions is found in an interstitial elementary state. Using chemical etching, we are able to trace the distribution of As displacement. The results are in good agreement with trim calculations of radiation damage. The potential applications of this technique to the study of the nature and distribution of radiation damage are discussed.

Lu, Z.H.; Azelmad, A.; Trudeau, Y.; Yelon, A. (Groupe des Couches Minces and Departement de Genie Physique, Ecole Polytechnique de Montreal, Case postale 6079, Succursale A, Montreal H3C 3A7, Canada (CA))

1989-08-28

315

Contact-free pyroelectric measurements using x-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

Non-contact pyroelectricity measurements based on x-ray photoelectron spectroscopy (XPS) are presented. Applied to Lithium Tantalate crystals, we demonstrate how the XPS-derived surface potential provides a simple probe of the desired property, free of all top-contact related difficulties. In particular, the increase in Lithium Tantalate spontaneous polarization under cooling, an experimentally challenging feature, is evaluated. We further inspect the roll of surface contaminants and the control over trapped surface charge in the XPS vacuum environment. Our approach can be extended to other non-contact probes, as well as to measuring additional electrical properties, such as piezoelectricity and ferroelectricity.

Ehre, D.; Cohen, H.

2013-07-01

316

Quantitative analysis of annealed scanning probe tips using energy dispersive x-ray spectroscopy  

SciTech Connect

A quantitative method to measure the reduction in oxide species on the surface of electrochemically etched tungsten tips during direct current annealing is developed using energy dispersive x-ray spectroscopy. Oxide species are found to decrease with annealing current, with the trend repeatable over many tips and along the length of the tip apex. A linear resistivity approximation finds significant oxide sublimation occurs at 1714 K, but surface melting and tip broadening at 2215 K. This method can be applied to calibrate any similar annealing stage, and to identify the tradeoff regime between required morphological and chemical properties.

Cobley, R. J.; Brown, R. A.; Barnett, C. J.; Maffeis, T. G. G.; Penny, M. W. [Multidisciplinary Nanotechnology Centre, College of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP (United Kingdom)] [Multidisciplinary Nanotechnology Centre, College of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP (United Kingdom)

2013-01-14

317

Slow dynamics of nanocomposite polymer aerogels as revealed by X-ray photocorrelation spectroscopy (XPCS).  

PubMed

We report on a novel slow dynamics of polymer xerogels, aerogels, and nanocomposite aerogels with iron oxide nanoparticles, as revealed by X-ray photon correlation spectroscopy. The polymer aerogel and its nanocomposite aerogels, which are porous in nature, exhibit hyper-diffusive dynamics at room temperature. In contrast, non-porous polymer xerogels exhibit an absence of this peculiar dynamics. This slow dynamical process has been assigned to a relaxation of the characteristic porous structure of these materials and not to the presence of nanoparticles. PMID:24437913

Hernández, Rebeca; Nogales, Aurora; Sprung, Michael; Mijangos, Carmen; Ezquerra, Tiberio A

2014-01-14

318

Slow dynamics of nanocomposite polymer aerogels as revealed by X-ray photocorrelation spectroscopy (XPCS)  

SciTech Connect

We report on a novel slow dynamics of polymer xerogels, aerogels, and nanocomposite aerogels with iron oxide nanoparticles, as revealed by X-ray photon correlation spectroscopy. The polymer aerogel and its nanocomposite aerogels, which are porous in nature, exhibit hyper-diffusive dynamics at room temperature. In contrast, non-porous polymer xerogels exhibit an absence of this peculiar dynamics. This slow dynamical process has been assigned to a relaxation of the characteristic porous structure of these materials and not to the presence of nanoparticles.

Hernández, Rebeca, E-mail: rhernandez@ictp.csic.es, E-mail: aurora.nogales@csic.es; Mijangos, Carmen [Instituto de Ciencia y Tecnología de Polímeros, ICTP-CSIC, Juan de la Cierva, 3, 28006 Madrid (Spain)] [Instituto de Ciencia y Tecnología de Polímeros, ICTP-CSIC, Juan de la Cierva, 3, 28006 Madrid (Spain); Nogales, Aurora, E-mail: rhernandez@ictp.csic.es, E-mail: aurora.nogales@csic.es; Ezquerra, Tiberio A. [Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121, 28006 Madrid (Spain)] [Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121, 28006 Madrid (Spain); Sprung, Michael [Petra III at DESY, Notkestr. 85, 22607 Hamburg (Germany)] [Petra III at DESY, Notkestr. 85, 22607 Hamburg (Germany)

2014-01-14

319

X-Ray Absorption Spectroscopy of Cuprous-Thiolate Clusters in Saccharomyces Cerevisiae Metallothionein  

SciTech Connect

Copper (Cu) metallothioneins are cuprous-thiolate proteins that contain multimetallic clusters, and are thought to have dual functions of Cu storage and Cu detoxification. We have used a combination of X-ray absorption spectroscopy (XAS) and density-functional theory (DFT) to investigate the nature of Cu binding to Saccharomyces cerevisiae metallothionein. We found that the XAS of metallothionein prepared, containing a full complement of Cu, was quantitatively consistent with the crystal structure, and that reconstitution of the apo-metallothionein with stoichiometric Cu results in the formation of a tetracopper cluster, indicating cooperative binding of the Cu ions by the metallothionein.

Zhang, L.; Pickering, I.J.; Winge, D.R.; George, G.N.

2009-05-28

320

X-ray absorption spectroscopy of cuprous-thiolate clusters in Saccharomyces cerevisiae metallothionein.  

PubMed

Copper (Cu) metallothioneins are cuprous-thiolate proteins that contain multimetallic clusters, and are thought to have dual functions of Cu storage and Cu detoxification. We have used a combination of X-ray absorption spectroscopy (XAS) and density-functional theory (DFT) to investigate the nature of Cu binding to Saccharomyces cerevisiae metallothionein. We found that the XAS of metallothionein prepared, containing a full complement of Cu, was quantitatively consistent with the crystal structure, and that reconstitution of the apo-metallothionein with stoichiometric Cu results in the formation of a tetracopper cluster, indicating cooperative binding of the Cu ions by the metallothionein. PMID:18972536

Zhang, Limei; Pickering, Ingrid J; Winge, Dennis R; George, Graham N

2008-10-01

321

Localized high spin states in transition-metal dimers: X-ray absorption spectroscopy study  

NASA Astrophysics Data System (ADS)

X-ray absorption spectroscopy provides direct evidence for localized valence electrons in Cr2+ , Mn2+ , and CrMn+ dimer cations. Bonding in these transition-metal molecules is predominantly mediated by 4s electrons. This behavior is markedly different from other 3d transition-metal dimers with open 3d subshells and can be ascribed to the highly stable 3d5(S6) configuration of the 3d subshell in chromium and manganese atoms and ions. In Cr2+ , Mn2+ , and CrMn+ , 3d electron localization indicates local high spin states.

Lau, J. T.; Hirsch, K.; Langenberg, A.; Probst, J.; Richter, R.; Rittmann, J.; Vogel, M.; Zamudio-Bayer, V.; Möller, T.; von Issendorff, B.

2009-06-01

322

Calorimetric Low-Temperature Detectors for X-Ray Spectroscopy on Trapped Highly-Charged Heavy Ions  

NASA Technical Reports Server (NTRS)

The application of Calorimetric Low-Temperature Detectors (CLTDs) has been proposed at the Heavy-Ion TRAP facility HITRAP which is currently being installed at the Helmholtz Research Center for Heavy Ion Research GSI. This cold ion trap setup will allow the investigation of X-rays from ions practically at rest, for which the excellent energy resolution of CLTDs can be used to its full advantage. However, the relatively low intensities at HITRAP demand larger solid angles and an optimized cryogenic setup. The influence of external magnetic fields has to be taken into account. CLTDs will also be a substantial part of the instrumental equipment at the future Facility for Antiproton and Heavy Ion Research (FAIR), for which a wide variety of high-precision X-ray spectroscopy experiments has been proposed. This contribution will give an overview on the chances and challenges for the application of CLTDs at HITRAP as well as perspectives for future experiments at the FAIR facility.

Kilbourne, Caroline; Kraft-Bermuth, S.; Andrianov, V.; Bleile, A.; Echler, A.; Egelhof, P.; Ilieva, S.; Kilbourne, C.; McCammon, D.

2012-01-01

323

Where Water Is Oxidized to Dioxygen: Structure of the Photosynthetic Mn(4)Ca Cluster From X-Ray Spectroscopy  

SciTech Connect

Light-driven oxidation of water to dioxygen in plants, algae, and cyanobacteria is catalyzed within photosystem II (PS II) by a Mn{sub 4}Ca cluster. Although the cluster has been studied by many different methods, its structure and mechanism have remained elusive. X-ray absorption and emission spectroscopy and extended X-ray absorption fine structure studies have been particularly useful in probing the electronic and geometric structures and the mechanism of the water oxidation reaction. Recent progress, reviewed here, includes polarized X-ray absorption spectroscopy measurements of PS II single crystals. Analysis of those results has constrained the Mn{sub 4}Ca cluster geometry to a set of three similar high-resolution structures. The structure of the cluster from the present study is unlike either the 3.0- or 3.5-{angstrom}-resolution X-ray structures or other previously proposed models. The differences between the models derived from X-ray spectroscopy and crystallography are predominantly because of damage to the Mn{sub 4}Ca cluster by X-rays under conditions used for the structure determination by X-ray crystallography. X-ray spectroscopy studies are also used for studying the changes in the structure of the Mn{sub 4}Ca catalytic center as it cycles through the five intermediate states known as the S{sub i} states (i = 0--4). The electronic structure of the Mn{sub 4}Ca cluster has been studied more recently using resonant inelastic X-ray scattering spectroscopy (RIXS), in addition to the earlier X-ray absorption and emission spectroscopy methods. These studies are revealing that the assignment of formal oxidation states is overly simplistic. A more accurate description should consider the charge density on the Mn atoms, which includes the covalency of the bonds and delocalization of the charge over the cluster. The geometric and electronic structures of the Mn{sub 4}Ca cluster in the S states derived from X-ray spectroscopy are leading to a detailed understanding of the mechanism of O-O bond formation during the photosynthetic water-splitting process.

Yano, J.; Yachandra, V.K.

2009-05-28

324

The design and application of an in-laboratory diffraction-enhanced x-ray imaging instrument  

SciTech Connect

We describe the design and application of a new in-laboratory diffraction-enhanced x-ray imaging (DEXI) instrument that uses a nonsynchrotron, conventional x-ray source to image the internal structure of an object. In the work presented here, a human cadaveric thumb is used as a test-sample to demonstrate the imaging capability of our instrument. A 22 keV monochromatic x-ray beam is prepared using a mismatched, two-crystal monochromator; a silicon analyzer crystal is placed in a parallel crystal geometry with the monochromator allowing both diffraction-enhanced imaging and multiple-imaging radiography to be performed. The DEXI instrument was found to have an experimentally determined spatial resolution of 160{+-}7 {mu}m in the horizontal direction and 153{+-}7 {mu}m in the vertical direction. As applied to biomedical imaging, the DEXI instrument can detect soft tissues, such as tendons and other connective tissues, that are normally difficult or impossible to image via conventional x-ray techniques.

Nesch, Ivan; Fogarty, Daniel P.; Tzvetkov, Tochko; Reinhart, Benjamin; Walus, A. Charles [Nesch, LLC 9800 Connecticut Drive, Crown Point, Indiana 46307 (United States); Khelashvili, Gocha [Nesch, LLC 9800 Connecticut Drive, Crown Point, Indiana 46307 (United States); Department of Radiation Oncology, Rush University Medical Center, 500 S. Paulina St., Chicago, Illinois 60612 (United States); Muehleman, Carol [Department of Biochemistry, Rush Medical College, 1735 W. Harrison St., Chicago, Illinois 60612 (United States); Chapman, Dean [Department of Anatomy and Cell Biology, College of Medicine, B331 Life Sciences Building, 107 Wiggins Road, Saskatoon, Saskatchewan S7N5E5 (Canada)

2009-09-15

325

Core and Valence Excitations in Resonant X-ray Spectroscopy using Restricted Excitation Window Time-dependent Density Functional Theory  

SciTech Connect

We report simulations of X-ray absorption near edge structure (XANES), resonant inelastic X-ray scattering (RIXS) and 1D stimulated X-ray Raman spectroscopy (SXRS) signals of cysteine at the oxygen, nitrogen and sulfur K and L2,3 edges. The simulated XANES signals from the restricted window time-dependent density functional theory (REW-TDDFT) and the static exchange (STEX) method are compared with experiments, showing that REW-TDDFT is more accurate and computationally less expensive than STEX. Simulated RIXS and 1D SXRS signals from REW-TDDFT give some insights on the correlation of different excitations in the molecule.

Zhang, Yu; Biggs, Jason D.; Healion, Daniel; Govind, Niranjan; Mukamel, Shaul

2012-11-21

326

Core and valence excitations in resonant X-ray spectroscopy using restricted excitation window time-dependent density functional theory  

PubMed Central

We report simulations of X-ray absorption near edge structure (XANES), resonant inelastic X-ray scattering (RIXS) and 1D stimulated X-ray Raman spectroscopy (SXRS) signals of cysteine at the oxygen, nitrogen, and sulfur K and \\documentclass[12pt]{minimal}\\begin{document}$\\textrm {L}_{2,3}$\\end{document}L2,3 edges. Comparison of the simulated XANES signals with experiment shows that the restricted window time-dependent density functional theory is more accurate and computationally less expensive than the static exchange method. Simulated RIXS and 1D SXRS signals give some insights into the correlation of different excitations in the molecule. PMID:23181305

Zhang, Yu; Biggs, Jason D.; Healion, Daniel; Govind, Niranjan; Mukamel, Shaul

2012-01-01

327

Soft X-ray spectroscopy and quantum chemistry characterization of defects in onion-like carbon produced by nanodiamond annealing  

Microsoft Academic Search

The electronic structure of onion-like carbon (OLC) consisted of quasi-spherical and polyhedral nanoparticles and produced as a result of nanodiamond annealing at 1800 K and 2140 K has been probed by soft X-ray emission and X-ray absorption spectroscopy. The enhanced density of states in the vicinity of the Fermi level was revealed for OLC prepared at moderate temperature. Ab initio calculation on

L. G. Bulusheva; A. V. Okotrub; V. L. Kuznetsov; D. V. Vyalikh

2007-01-01

328

The photochemical formation of a Titan haze analog. Structural analysis by X-ray photoelectron and infrared spectroscopy  

E-print Network

The photochemical formation of a Titan haze analog. Structural analysis by X-ray photoelectron their mixing ratios on Titan (N2, CH4, H2, C2H2, C2H4, and HC3N) (0.98, 0.018, 0.002, 3.5 10 4 , 3 10 4 , 1 a Titan haze analog as a solid product. X-ray photoelectron spectroscopy (XPS) gave a composition of 93

Ferris, James P.

329

X-ray photoelectron spectroscopy characterization of the {omega} phase in water quenched Ti-5553 alloy  

SciTech Connect

X-ray photoelectron spectroscopy was used to investigate the {omega} phase in water quenched Ti-5553 alloy with a nominal composition of Ti-5Al-5V-5Mo-3Cr (wt.%), and the {omega} and the {beta} phase were distinguished by deconvoluting the XPS spectra of Al2p, V2p and Cr2p core level regions. In addition, it is found that the binding energy of core level electron of alloying elements shifts comparing with that of pure metals, and the fact was interpreted by charge redistribution model. X-ray photoelectron spectroscopy technique could be used to characterize the nano-scale {omega} phase in {beta} alloys. - Highlights: Black-Right-Pointing-Pointer We characterize the {omega} phase in Ti-5553 alloy by XPS. Black-Right-Pointing-Pointer Binding energy of Al2p, V2p and Cr2p electron are different in the {omega} and {beta} phase. Black-Right-Pointing-Pointer Structural difference leads to the binding energy gap.

Qin, Dongyang, E-mail: qindongyang19831205@126.com [State Key Laboratory for Mechanical Behavior of Materials, Xian Jiaotong University, Xi'an 710049 (China) [State Key Laboratory for Mechanical Behavior of Materials, Xian Jiaotong University, Xi'an 710049 (China); Northwest Institute for Non-ferrous Metal Research, Xi'an 710016 (China); Lu, Yafeng [Northwest Institute for Non-ferrous Metal Research, Xi'an 710016 (China)] [Northwest Institute for Non-ferrous Metal Research, Xi'an 710016 (China); Zhang, Kong; Liu, Qian [The State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)] [The State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Zhou, Lian [Northwest Institute for Non-ferrous Metal Research, Xi'an 710016 (China)] [Northwest Institute for Non-ferrous Metal Research, Xi'an 710016 (China)

2012-11-15

330

XPS: A multi-channel preamplifier shaper IC for X-ray spectroscopy  

SciTech Connect

An integrated circuit featuring 48 channels of charge-sensitive preamplifiers followed by variable-gain pulse shaping amplifiers is being developed as part of an x-ray spectrometer with a highly segmented detector to handle high fluxes in synchrotron experiments. Such detector systems can provide excellent energy resolution combined with one-dimensional spatial information. The IC combines many basic spectroscopy amplifier functions with a low-noise preamplifier section to produce a unique circuit capable of driving conventional ADC modules directly. An important feature of the design is the novel CR-RC{sup 2} pulse shaper. In this section, high-linearity transconductor circuits are required in order to provide a broad range of continuously variable peaking times while still maintaining the linearity and noise performance necessary for x-ray spectroscopy. Reported here are first measurements made on the performance of a 16-channel prototype integrated circuit. At present, the preamplifier-shaper circuit achieves an equivalent input noise of 26 electrons rms at 2 {micro}s peaking time with a 0.2 pF external capacitor, which is similar to the capacitance of a single detector element. The design was fabricated in standard 1.2 {micro}m CMOS technology.

Krieger, B.; Kipnis, I.; Ludewigt, B.A.

1997-11-01

331

XPS: A multi-channel preamplifier-shaper IC for X-ray spectroscopy  

SciTech Connect

An integrated circuit featuring 48 channels of charge-sensitive preamplifiers followed by variable-gain pulse shaping amplifiers is being developed as part of an x-ray spectrometer with a highly segmented detector to handle high fluxes in synchrotron experiments. Such detector systems can provide excellent energy resolution combined with one-dimensional spatial information. The IC combines many basic spectroscopy amplifier functions with a low-noise preamplifier section to produce a unique circuit capable of driving conventional ADC modules directly. An important feature of the design is the novel CR-RC{sup 2} pulse shaper. In this section, high-linearity transconductor circuits are required in order to provide a broad range of continuously variable peaking times while still maintaining the linearity and noise performance necessary for x-ray spectroscopy. Reported here are first measurements made on the performance of a 16-channel prototype integrated circuit. At present, the preamplifier-shaper circuit achieves an equivalent input noise of 26 electrons rms at 2 {micro}s peaking time with a 0.2 pF external capacitor, which is similar to the capacitance of a single detector element. The design was fabricated in standard 1.2 {micro}m CMOS technology.

Krieger, B.; Ludewigt, B.A. [Lawrence Berkeley National Lab., CA (United States)] [Lawrence Berkeley National Lab., CA (United States); Kipnis, I. [Hewlett-Packard Co., Newark, CA (United States)] [Hewlett-Packard Co., Newark, CA (United States)

1998-06-01

332

X-ray emission and photoluminescence spectroscopy of nanostructured silica with implanted copper ions  

NASA Astrophysics Data System (ADS)

Quartz glass samples and compacted SiO2 nanopowders have been studied by x-ray emission (Cu L 2, 3 transition 3 d4 s ? 2 p 1/2, 3/2) and photoluminescence spectroscopy following pulsed Cu+ ion implantation (energy, 30 keV; pulse current up to 0.5 A; pulse duration, 400 ?s; irradiation doses, 1015, 1016, and 2 × 1017 cm-2). It has been established that ion irradiation gives rise to the formation of glassy and compacted SiO2 samples of nanosized metallic and oxide phases in the structure. An analysis of Cu L x-ray emission spectra has shown that copper nanoparticles are thermodynamically metastable and chemically active because ion beam bombardment transfers them readily to the oxide form. This results from the radiation-stimulated fracture of regular Si-O-Si bonds in amorphous SiO2 and the formation of defective Si-Si bonds, followed by capture of oxygen by copper atoms. The enhanced degree of oxidation of copper ions in SiO2 nanostructured pellets can be reduced by coimplantation and thermal annealing. Optical spectroscopy studies suggest that, in glasses and SiO2 nanostructured pellets, there exist metallic Cu{/n 0} nanoclusters, which at low temperatures exhibit quantum-confined photoluminescence with a characteristic stepped excitation spectrum.

Zatsepin, D. A.; Kortov, V. S.; Kurmaev, É. Z.; Gavrilov, N. V.; Wilks, R. G.; Moewes, A.

2008-12-01

333

Near-Edge X-ray Absorption Fine Structure Spectroscopy of Diamondoid Thiol Monolayers on Gold  

SciTech Connect

Diamondoids, hydrocarbon molecules with cubic-diamond-cage structures, have unique properties with potential value for nanotechnology. The availability and ability to selectively functionalize this special class of nanodiamond materials opens new possibilities for surface-modification, for high-efficiency field emitters in molecular electronics, as seed crystals for diamond growth, or as robust mechanical coatings. The properties of self-assembled monolayers (SAMs) of diamondoids are thus of fundamental interest for a variety of emerging applications. This paper presents the effects of thiol substitution position and polymantane order on diamondoid SAMs on gold using near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and X-ray photoelectron spectroscopy (XPS). A framework to determine both molecular tilt and twist through NEXAFS is presented and reveals highly ordered diamondoid SAMs, with the molecular orientation controlled by the thiol location. C 1s and S 2p binding energies are lower in adamantane thiol than alkane thiols on gold by 0.67 {+-} 0.05 eV and 0.16 {+-} 0.04 eV respectively. These binding energies vary with diamondoid monolayer structure and thiol substitution position, consistent with different amounts of steric strain and electronic interaction with the substrate. This work demonstrates control over the assembly, in particular the orientational and electronic structure, providing a flexible design of surface properties with this exciting new class of diamond clusters.

Willey, T M; Fabbri, J; Lee, J I; Schreiner, P; Fokin, A A; Tkachenko, B A; Fokina, N A; Dahl, J; Carlson, B; Vance, A L; Yang, W; Terminello, L J; van Buuren, T; Melosh, N

2007-11-27

334

X-ray absorption spectroscopy (XAS) of toxic metal mineral transformations by fungi.  

PubMed

Fungi can be highly efficient biogeochemical agents and accumulators of soluble and particulate forms of metals. This work aims to understand some of the physico-chemical mechanisms involved in toxic metal transformations focusing on the speciation of metals accumulated by fungi and mycorrhizal associations. The amorphous state or poor crystallinity of metal complexes within biomass and relatively low metal concentrations make the determination of metal speciation in biological systems a challenging problem but this can be overcome by using synchrotron-based element-specific X-ray absorption spectroscopy (XAS) techniques. In this research, we have exposed fungi and ectomycorrhizas to a variety of copper-, zinc- and lead-containing minerals. X-ray absorption spectroscopy studies revealed that oxygen ligands (phosphate, carboxylate) played a major role in toxic metal coordination within the fungal and ectomycorrhizal biomass during the accumulation of mobilized toxic metals. Coordination of toxic metals within biomass depended on the fungal species, initial mineral composition, the nitrogen source, and the physiological state/age of the fungal mycelium. PMID:17222130

Fomina, Marina; Charnock, John; Bowen, Andrew D; Gadd, Geoffrey M

2007-02-01

335

Reflection electron-energy-loss spectroscopy, x-ray-absorption spectroscopy, and x-ray photoelectron spectroscopy studies of a new type of layer compound CrPS4  

NASA Astrophysics Data System (ADS)

A new type of layer compound, CrPS4, has been investigated by means of reflection electron-energy-loss spectroscopy (REELS), x-ray-absorption spectroscopy (XAS), and x-ray photoelectron spectroscopy (XPS). Information on the bonding states of the compositional atoms and the occupied energy states has been deduced from the core- and valence-electron XPS results. The binding energies and the multiplet structures of core levels have been discussed in detail. Information on the unoccupied energy states has been deduced from the XAS results. On the basis of the REELS results, energy positions and the joint density of states have been discussed. The optical properties have been investigated through the Kramers-Kronig analysis of the REELS spectrum. We have made an attempt to derive the depth profile of the localized energy states from the incident-energy dependence. A schematic energy-band model has been proposed.

Ohno, Youichi; Mineo, Ayako; Matsubara, Ichiro

1989-11-01

336

The experiment with the fast X-ray monitor (BRM) instrument onboard the CORONAS-PHOTON satellite  

NASA Astrophysics Data System (ADS)

The "Fast X-ray Monitor" (BRM) instrument operated in the complex of the scientific instruments onboard the CORONAS-PHOTON satellite from February 19, 2009, until December 1, 2009. The instrument is intended for the registration of the hard X-ray radiation of solar flares in the 20-600 keV energy range in six differential energy channels (20-30, 30-40, 40-50, 50-70, 70-130, and 130-600 keV) with temporal resolution to 1 ms. In the instrument, a detector based on the YAP: Ce scintillator is used; this detector is 70 mm in diameter and 10 mm thick (the decay time is about 28 ns). For the decrease of the back-ground charge of the detector, the collimator limiting the angle of view of the instrument of value 12° is mounted over the scintillator. The effective area of the detector amounts to 27.7 cm2 (at the X-ray radiation energy 80 keV), and the dead time of the detector is 1 ?s. Over the operation onboard the CORONAS-PHOTON satellite, the BRM instrument has registered gamma ray burst series and, perhaps, one solar flare of the class C1.3 on October 26, 2009.

Trofimov, Yu. A.; Yurov, V. N.; Kotov, Yu. D.; Zhuchkova, E. A.

2011-04-01

337

X-ray spectrum of CT system acquired by Compton spectroscopy using high resolution Schottky CdTe detector  

NASA Astrophysics Data System (ADS)

Recently, x-ray computed tomography (CT) systems were developed dramatically; e.g. a multi-detector-row CT or a 4-dimensional CT, but it has been expressed anxiety that a patient dose is increased. Analysis of x-ray spectrum is important for quality assurance and quality control of radiographic systems to estimate a quality of an imaging system and to decrease a patient dose. The aim of this study is to measure the x-ray spectra of CT system under clinical conditions using a high resolution Schottky CdTe detector. When measuring diagnostic x-ray spectra, the long distance from the x-ray source to the detector is requested for reducing a number of photons detected per unit time to prevent pile-up of the detector. However, that is very difficult to set up the long source-to-detector distance in a gantry of a CT unit. For resolving this problem, the Compton spectroscopy is very suitable. Using this method, a number of photons detected per unit time can be reduced by detecting the scattered x-ray photons. If the 90° scattered photons can be detected, the energy correction and reconstruction of spectra can be calculated easily by use of the Klein-Nishina formula. So we attempt to acquire the primary x-ray spectra in the gantry of the CT unit by using Compton spectroscopy under a clinical (tube-rotating) condition. Moreover, to estimate the variation of x-ray spectra owe to changing position in the gantry, we measured the x-ray spectra and exposure doses at various points in the gantry.

Maeda, Koji; Matsumoto, Masao

2005-04-01

338

Advances in Time Resolved X-ray Excited Optical Luminescence Instrumentation at the Canadian Light Source  

SciTech Connect

Measurement of the optical emission properties of samples excited by x-rays can be used to study defect states in crystals and the optical properties of nanostructured materials. Changes in the intensities, wavelengths and lifetimes of the optical emission can occur when specific core level electrons are excited using tuneable light from a synchrotron light source. At the Canadian Light Source (CLS), collaboration between the user community, the experimental facilities group and the accelerator division has resulted in improved capabilities in the acquisition of Time Resolved XEOL (TRXEOL) data. Using a streak camera, the optical luminescence decay curves from samples excited with 35 ps long synchrotron pulses have been obtained. The streak tube is operated in single sweep mode and is triggered by the 500 MHz RF signal, which has been resynchronized to the orbit clock frequency giving a highly stable trigger pulse. A transverse kicker system is used to improve bunch purity from 10{sup 2} to 10{sup 6}. The decay curves of the XEOL of nanostructured ZnO and a high pressure form of SiO{sub 2} have been measured and demonstrate the unique capabilities of this instrumentation.

Regier, T. Z.; Vogt, J. M. [Canadian Light Source, Inc., 101 Perimeter Road, Saskatoon, Saskatchewan (Canada); Sammynaiken, R. [Sasakatchewan Structural Science Centre, 110 Science Place, Saskatoon, Saskatchewan (Canada); Sham, T. K. [Department of Chemistry, The University of Western Ontario, 1151 Richmond Street, London, Ontario (Canada)

2010-06-23

339

An XPS /ESCA/ study of lunar surface alteration profiles. [X ray Photoemission Spectroscopy  

NASA Technical Reports Server (NTRS)

We describe several important potential applications of surface analyses in planetology, and discuss some fundamental questions pertinent to the use of X-ray photoemission spectroscopy XPS or Auger electron spectroscopy AES to study complex powder samples. It appears that in addition to specific studies of surface chemistry, XPS may be able to provide useful major element analyses for all elements except hydrogen and perhaps helium and lithium. We provide data on the chemical changes associated with sputtering of a synthetic lunar glass. The surface is depleted in Si and enriched in Ca and Ti with Fe remaining nearly constant in parallel with changes observed during thermal volatilization. No Fe reduction was observed. Composition profiles obtained by sputtering 15301 fines suggest that surface alterations and reduced Fe are confined largely to depths of a few 100 A.

Housley, R. M.; Grant, R. W.

1977-01-01

340

Energy Dispersive X-Ray and Electrochemical Impedance Spectroscopies for Performance and Corrosion Analysis of PEMWEs  

NASA Astrophysics Data System (ADS)

Proton exchange membrane water electrolyzers (PEMWEs) are a promising energy storage technology due to their high efficiency, compact design, and ability to be used in a renewable energy system. Before they are able to make a large commercial impact, there are several hurdles facing the technology today. Two powerful techniques for both in-situ and ex- situ characterizations to improve upon their performance and better understand their corrosion are electrochemical impedance spectroscopy and energy dispersive x-ray spectroscopy, respectively. In this paper, the authors use both methods in order to characterize the anode gas diffusion layer (GDL) in a PEMWE cell and better understand the corrosion that occurs in the oxygen electrode during electrolysis.

Steen, S. M., Iii; Zhang, F.-Y.

2014-11-01

341

A miniature metal-ceramic x-ray source for spacecraft instrumentation.  

PubMed

Definitive mineralogical identification of materials with x-ray diffraction and fluorescence on remote planetary probes requires the development of a rugged miniature x-ray source that complies with the mass, power, thermal, and electrical management constraints imposed by space missions. Conventional x-ray tubes are generally fragile, glass-envelope designs with heat-sensitive seals. They are too brittle and bulky for planetary missions, and usually require cumbersome and power-consuming cooling systems. Here we describe the development of a novel, rugged miniature x-ray source employing a ceramic BeO substrate upon which a metal target material is deposited. Conventional thermionic emission and high-voltage acceleration of electrons to strike the metal target material produce an x-ray yield comparable to conventional x-ray tubes. Thermal management of the x-ray source is achieved with the excellent heat transport properties of the BeO target substrate coupled with a passive heatpipe. PMID:11542818

Koppel, L N; Marshall, J R

1998-04-01

342

Probing local structure of pyrochlore lead zinc niobate with synchrotron x-ray absorption spectroscopy technique  

NASA Astrophysics Data System (ADS)

Local structure of lead zinc niobate (PZN) ceramic, synthesized via B-site oxide precursor route in atmospheric pressure, was investigated using synchrotron x-ray absorption spectroscopy (XAS) technique. The x-ray absorption near-edge structure (XANES) simulation was first carried out. The XANES simulation results indicate that the PZN ceramic is in pyrochlore phase having Zn2+ substituted on Nb5+ site. Afterwards, the extended x-ray absorption fine structure (EXAFS) analysis was performed to extract the bond length information between Zn2+ and its neighboring atoms. From the EXAFS fitting, the bond length between Zn2+ and Pb2+ in the pyrochlore phase was found to be longer than the previously reported bond length in the perovskite phase. Further, with the radial distribution information of Zn2+'s neighboring atoms, the formation energies along the precursor-to-pyrochlore and precursor-to-perovskite reaction paths were calculated using the density functional theory (DFT). The calculated results show that the formation energy of the perovskite phase is noticeably higher than that of the pyrochlore phase, which is influenced by the presence of energetic Pb2+ lone pair, as the perovskite phase has shorter Zn2+ to Pb2+ bonding. This therefore suggests the steric hindrance of Pb2+ lone pair and the mutual interactions between Pb2+ lone pair and Zn2+ are main causes of the instability of lead zinc niobate in the perovskite structure and confirm the efficacy of XAS and DFT analysis in revealing local structural details of complex pyrochlore materials.

Kanchiang, Kanokwan; Pramchu, Sittichain; Yimnirun, Rattikorn; Pakawanit, Phakkhananan; Ananta, Supon; Laosiritaworn, Yongyut

2013-08-01

343

Atomic data needs for X-ray spectroscopy of photo-ionised plasmas  

SciTech Connect

High-resolution X-ray spectroscopy of Active Galactic Nuclei has become possible thanks to the launch of XMM-Newton and Chandra with their grating spectrometers, and will be explored further after the expected launch of ASTRO-E2 with its XRS detector. In several AGN the X-ray spectra show the signatures of on outflowing, photo-ionised wind. Also several X-ray binaries show a similar imprint of a photo-ionised gas. The clearest signatures are formed by the broad range of absorption lines, mostly from the ground states of a wide range of ionisation states of the abundant elements. In addition to absorption lines due to the valence electrons, the spectra show many inner-shell absorption lines. Examples are the K-shell transitions of the most abundant metal, oxygen, in the 19-23 A band, and 2p-3d transitions of lowly ionised iron in the 15-17 A region. These transitions have an extremely important diagnostic value, as other transitions of the same ions frequently occur in the unobservable extreme ultraviolet. Several of these inner-shell transitions, however, lack accurate experimental or theoretical wavelengths, which makes the spectral analysis complicated and ambiguous. This is even more the case for transitions from metastable levels, which can be used as density diagnostics. Finally, attention is paid to the role of atomic data in the photo-ionisation equilibrium calculations. Uncertainties in for example dielectronic recombination rates cause large uncertainties in the predicted absorption line strengths.

Kaastra, Jelle S. [SRON, Sorbonnelaan 2, 3584 CA Utrecht (Netherlands)

2005-05-27

344

Characterization of metalloproteins by high-throughput X-ray absorption spectroscopy  

PubMed Central

High-throughput X-ray absorption spectroscopy was used to measure transition metal content based on quantitative detection of X-ray fluorescence signals for 3879 purified proteins from several hundred different protein families generated by the New York SGX Research Center for Structural Genomics. Approximately 9% of the proteins analyzed showed the presence of transition metal atoms (Zn, Cu, Ni, Co, Fe, or Mn) in stoichiometric amounts. The method is highly automated and highly reliable based on comparison of the results to crystal structure data derived from the same protein set. To leverage the experimental metalloprotein annotations, we used a sequence-based de novo prediction method, MetalDetector, to identify Cys and His residues that bind to transition metals for the redundancy reduced subset of 2411 sequences sharing <70% sequence identity and having at least one His or Cys. As the HT-XAS identifies metal type and protein binding, while the bioinformatics analysis identifies metal- binding residues, the results were combined to identify putative metal-binding sites in the proteins and their associated families. We explored the combination of this data with homology models to generate detailed structure models of metal-binding sites for representative proteins. Finally, we used extended X-ray absorption fine structure data from two of the purified Zn metalloproteins to validate predicted metalloprotein binding site structures. This combination of experimental and bioinformatics approaches provides comprehensive active site analysis on the genome scale for metalloproteins as a class, revealing new insights into metalloprotein structure and function. PMID:21482623

Shi, Wuxian; Punta, Marco; Bohon, Jen; Sauder, J. Michael; D'Mello, Rhijuta; Sullivan, Mike; Toomey, John; Abel, Don; Lippi, Marco; Passerini, Andrea; Frasconi, Paolo; Burley, Stephen K.; Rost, Burkhard; Chance, Mark R.

2011-01-01

345

Characterization of Metalloproteins by High-throughput X-ray Absorption Spectroscopy  

SciTech Connect

High-throughput X-ray absorption spectroscopy was used to measure transition metal content based on quantitative detection of X-ray fluorescence signals for 3879 purified proteins from several hundred different protein families generated by the New York SGX Research Center for Structural Genomics. Approximately 9% of the proteins analyzed showed the presence of transition metal atoms (Zn, Cu, Ni, Co, Fe, or Mn) in stoichiometric amounts. The method is highly automated and highly reliable based on comparison of the results to crystal structure data derived from the same protein set. To leverage the experimental metalloprotein annotations, we used a sequence-based de novo prediction method, MetalDetector, to identify Cys and His residues that bind to transition metals for the redundancy reduced subset of 2411 sequences sharing <70% sequence identity and having at least one His or Cys. As the HT-XAS identifies metal type and protein binding, while the bioinformatics analysis identifies metal-binding residues, the results were combined to identify putative metal-binding sites in the proteins and their associated families. We explored the combination of this data with homology models to generate detailed structure models of metal-binding sites for representative proteins. Finally, we used extended X-ray absorption fine structure data from two of the purified Zn metalloproteins to validate predicted metalloprotein binding site structures. This combination of experimental and bioinformatics approaches provides comprehensive active site analysis on the genome scale for metalloproteins as a class, revealing new insights into metalloprotein structure and function.

W Shi; M Punta; J Bohon; J Sauder; R DMello; M Sullivan; J Toomey; D Abel; M Lippi; et al.

2011-12-31

346

Characterization and speciation of mercury-bearing mine wastes using X-ray absorption spectroscopy  

USGS Publications Warehouse

Mining of mercury deposits located in the California Coast Range has resulted in the release of mercury to the local environment and water supplies. The solubility, transport, and potential bioavailability of mercury are controlled by its chemical speciation, which can be directly determined for samples with total mercury concentrations greater than 100 mg kg-1 (ppm) using X-ray absorption spectroscopy (XAS). This technique has the additional benefits of being non-destructive to the sample, element-specific, relatively sensitive at low concentrations, and requiring minimal sample preparation. In this study, Hg L(III)-edge extended X-ray absorption fine structure (EXAFS) spectra were collected for several mercury mine tailings (calcines) in the California Coast Range. Total mercury concentrations of samples analyzed ranged from 230 to 1060 ppm. Speciation data (mercury phases present and relative abundances) were obtained by comparing the spectra from heterogeneous, roasted (calcined) mine tailings samples with a spectral database of mercury minerals and sorbed mercury complexes. Speciation analyses were also conducted on known mixtures of pure mercury minerals in order to assess the quantitative accuracy of the technique. While some calcine samples were found to consist exclusively of mercuric sulfide, others contain additional, more soluble mercury phases, indicating a greater potential for the release of mercury into solution. Also, a correlation was observed between samples from hot-spring mercury deposits, in which chloride levels are elevated, and the presence of mercury-chloride species as detected by the speciation analysis. The speciation results demonstrate the ability of XAS to identify multiple mercury phases in a heterogeneous sample, with a quantitative accuracy of ??25% for the mercury-containing phases considered. Use of this technique, in conjunction with standard microanalytical techniques such as X-ray diffraction and electron probe microanalysis, is beneficial in the prioritization and remediation of mercury-contaminated mine sites. (C) 2000 Elsevier Science B.V.

Kim, C.S.; Brown, G.E., Jr.; Rytuba, J.J.

2000-01-01

347

Atomic data needs for X-ray spectroscopy of photo-ionised plasmas  

NASA Astrophysics Data System (ADS)

High-resolution X-ray spectroscopy of Active Galactic Nuclei has become possible thanks to the launch of XMM-Newton and Chandra with their grating spectrometers, and will be explored further after the expected launch of ASTRO-E2 with its XRS detector. In several AGN the X-ray spectra show the signatures of on outflowing, photo-ionised wind. Also several X-ray binaries show a similar imprint of a photo-ionised gas. The clearest signatures are formed by the broad range of absorption lines, mostly from the ground states of a wide range of ionisation states of the abundant elements. In addition to absorption lines due to the valence electrons, the spectra show many inner-shell absorption lines. Examples are the K-shell transitions of the most abundant metal, oxygen, in the 19-23 Å band, and 2p-3d transitions of lowly ionised iron in the 15-17 Å region. These transitions have an extremely important diagnostic value, as other transitions of the same ions frequently occur in the unobservable extreme ultraviolet. Several of these inner-shell transitions, however, lack accurate experimental or theoretical wavelengths, which makes the spectral analysis complicated and ambiguous. This is even more the case for transitions from metastable levels, which can be used as density diagnostics. Finally, attention is payed to the role of atomic data in the photo-ionisation equilibrium calculations. Uncertainties in for example dielectronic recombination rates cause large uncertainties in the predicted absorption line strengths.

Kaastra, Jelle S.

2005-05-01

348

A fluorescence XAFS measurement instrument in the soft x-ray region toward observation under operando conditions  

NASA Astrophysics Data System (ADS)

X-ray absorption fine structure (XAFS) measurements are widely used for the analysis of electronic structure. Generally, XAFS in the soft X-ray region is measured under vacuum, but chemical structures under vacuum are typically different from those under operando conditions, where chemical species exhibit their function. Here, we developed an XAFS measurement instrument, as a step toward operando fluorescent, which yields XAFS measurement using synchrotron radiation in the soft X-ray region. We applied this method to analyze the local electronic structure of the sulfur atoms in L-cysteine in different pH solutions. In water at pH 7, the hydrogen atom does not dissociate from the thiol (-SH) group in L-cysteine, which forms a structure surrounded by and interacting with water molecules. The XAFS spectrum of L-cysteine in solution was altered by changing the pH. At pH 9, the hydrogen atom dissociated and a thiolate anion was formed. Although the -SH group was oxidized to SO42- when L-cysteine was adsorbed on a metal surface and dried, no oxidation was observed in solution. This may be because the water molecules were densely packed and protected the -SH group from oxidation. Our results show that this instrument aimed toward operando fluorescence XAFS measurements in the soft X-ray region is useful for structural analysis of sulfur atoms in organic molecules in air and in solution. The instrument will be applied to the structural analysis of materials containing elements that have absorption edges in soft X-ray region, such as phosphorus and alkali metals (potassium and cesium). It will be also particularly useful for the analysis of samples that are difficult to handle under vacuum and materials that have specific functions in solution.

Honda, M.; Baba, Y.; Shimoyama, I.; Sekiguchi, T.

2015-03-01

349

Resolution enhancement in coherent x-ray diffraction imaging by overcoming instrumental noise.  

PubMed

We report that reference objects, strong scatterers neighboring weak phase objects, enhance the phase retrieval and spatial resolution in coherent x-ray diffraction imaging (CDI). A CDI experiment with Au nano-particles exhibited that the reference objects amplified the signal-to-noise ratio in the diffraction intensity at large diffraction angles, which significantly enhanced the image resolution. The interference between the diffracted x-ray from reference objects and a specimen also improved the retrieval of the phase of the diffraction signal. The enhancement was applied to image NiO nano-particles and a mitochondrion and confirmed in a simulation with a bacteria phantom. We expect that the proposed method will be of great help in imaging weakly scattering soft matters using coherent x-ray sources including x-ray free electron lasers. PMID:25402155

Kim, Chan; Kim, Yoonhee; Song, Changyong; Kim, Sang Soo; Kim, Sunam; Kang, Hyon Chol; Hwu, Yeukuang; Tsuei, Ku-Ding; Liang, Keng San; Noh, Do Young

2014-11-17

350

28 CFR 552.13 - X-ray, major instrument, fluoroscope, or surgical intrusion.  

Code of Federal Regulations, 2010 CFR

...may direct X-rays of inanimate objects where the inmate is not exposed. [45 FR 75134, Nov. 13, 1980, as amended at 48 FR 48970, Oct. 21, 1983. Redesignated and amended at 56 FR 20136, 20137, May 6,...

2010-07-01

351

A New Route to Phase-Resolved Spectroscopy of Pulsations and QPOs in X-ray Binaries  

NASA Astrophysics Data System (ADS)

The accretion disks in neutron star and stellar-mass black hole X-ray binaries provide an opportunity to study matter in strong gravitational fields. In particular, using spectral-timing measurements of X-ray emission, we can analyze the inner parts of the accretion disk and corona. Here we present the application of a new spectral-timing technique to carry out phase-resolved spectroscopy of rapid periodic and quasi-periodic signals from X-ray binaries. This technique measures relative phase and does not require ephemerides or exactly periodic signals, so it is applicable to a wide range of data, from X-ray millisecond pulsations to kHz and low-frequency QPOs. The method gives new insight into the physical mechanisms underlying these signals as well as the geometry of the emitting regions.

Stevens, A.; Uttley, P.; van der Klis, M.

2014-07-01

352

Soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering spectroscopy below 100 eV: probing first-row transition-metal M-edges in chemical complexes.  

PubMed

X-ray absorption and scattering spectroscopies involving the 3d transition-metal K- and L-edges have a long history in studying inorganic and bioinorganic molecules. However, there have been very few studies using the M-edges, which are below 100 eV. Synchrotron-based X-ray sources can have higher energy resolution at M-edges. M-edge X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) could therefore provide complementary information to K- and L-edge spectroscopies. In this study, M2,3-edge XAS on several Co, Ni and Cu complexes are measured and their spectral information, such as chemical shifts and covalency effects, are analyzed and discussed. In addition, M2,3-edge RIXS on NiO, NiF2 and two other covalent complexes have been performed and different d-d transition patterns have been observed. Although still preliminary, this work on 3d metal complexes demonstrates the potential to use M-edge XAS and RIXS on more complicated 3d metal complexes in the future. The potential for using high-sensitivity and high-resolution superconducting tunnel junction X-ray detectors below 100 eV is also illustrated and discussed. PMID:23765304

Wang, Hongxin; Young, Anthony T; Guo, Jinghua; Cramer, Stephen P; Friedrich, Stephan; Braun, Artur; Gu, Weiwei

2013-07-01

353

Soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering spectroscopy below 100?eV: probing first-row transition-metal M-edges in chemical complexes  

PubMed Central

X-ray absorption and scattering spectroscopies involving the 3d transition-metal K- and L-edges have a long history in studying inorganic and bioinorganic molecules. However, there have been very few studies using the M-edges, which are below 100?eV. Synchrotron-based X-ray sources can have higher energy resolution at M-edges. M-edge X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) could therefore provide complementary information to K- and L-edge spectroscopies. In this study, M 2,3-edge XAS on several Co, Ni and Cu complexes are measured and their spectral information, such as chemical shifts and covalency effects, are analyzed and discussed. In addition, M 2,3-edge RIXS on NiO, NiF2 and two other covalent complexes have been performed and different d–d transition patterns have been observed. Although still preliminary, this work on 3d metal complexes demonstrates the potential to use M-edge XAS and RIXS on more complicated 3d metal complexes in the future. The potential for using high-sensitivity and high-resolution superconducting tunnel junction X-ray detectors below 100?eV is also illustrated and discussed. PMID:23765304

Wang, Hongxin; Young, Anthony T.; Guo, Jinghua; Cramer, Stephen P.; Friedrich, Stephan; Braun, Artur; Gu, Weiwei

2013-01-01

354

Determination of uranyl incorporation into biogenic manganese oxides using X-ray absorption spectroscopy and scattering  

USGS Publications Warehouse

Biogenic manganese oxides are common and an important source of reactive mineral surfaces in the environment that may be potentially enhanced in bioremediation cases to improve natural attenuation. Experiments were performed in which the uranyl ion, UO22+ (U(VI)), at various concentrations was present during manganese oxide biogenesis. At all concentrations, there was strong uptake of U onto the oxides. Synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray diffraction (XRD) studies were carried out to determine the molecular-scale mechanism by which uranyl is incorporated into the oxide and how this incorporation affects the resulting manganese oxide structure and mineralogy. The EXAFS experiments show that at low concentrations (2 mol % U, >4 ??M U(VI) in solution), the presence of U(VI) affects the stability and structure of the Mn oxide to form poorly ordered Mn oxide tunnel structures, similar to todorokite. EXAFS modeling shows that uranyl is present in these oxides predominantly in the tunnels of the Mn oxide structure in a tridentate complex. Observations by XRD corroborate these results. Structural incorporation may lead to more stable U(VI) sequestration that may be suitable for remediation uses. These observations, combined with the very high uptake capacity of the Mn oxides, imply that Mn-oxidizing bacteria may significantly influence dissolved U(VI) concentrations in impacted waters via sorption and incorporation into Mn oxide biominerals. ?? 2006 American Chemical Society.

Webb, S.M.; Fuller, C.C.; Tebo, B.M.; Bargar, J.R.

2006-01-01

355

X-Ray Intensity Fluctuation Spectroscopy Studies of Colloids and Polymers  

NASA Astrophysics Data System (ADS)

X-ray intensity fluctuation spectroscopy (XIFS) using coherent beams available from high brightness synchrotron sources can be used to measure the low-frequency equilibrium dynamics of disordered systems. Conventional techniques using visible light are limited to wavevectors below ~ 4 × 10-3Åfor transparent media. Both colloidal and polymer systems are expected to exhibit slow dynamics for wavevectors q ~ 0.01ÅIn this range the bandpass of the x-ray radiation can be relaxed, producing sufficient intensity in the coherent beam for practical measurements of XIFS. At the Troïka (ID10A) beamline of the European Synchrotron Radiation Facility we have measured the dynamics of colloidal palladium dispersed in glycerol in the time range from 10-4s to 10^2s using a digital autocorrelator. The measured relaxation rates are proportional to q^2 and scale inversely with the viscosity, as expected for a translational diffusion process. XIFS measurements of concentrated polymer micelle liquids composed of polystyrene-polyisoprene block copolymers in a polystyrene homopolymer matrix show that the diffusion coefficient is wavevector dependent. The morphology of the micelles also has significant effects on the equilibrium dynamics of such systems.

Abernathy, Douglas L.

1997-03-01

356

Millisecond Kinetics of Nanocrystal Cation Exchange UsingMicrofluidic X-ray Absorption Spectroscopy  

SciTech Connect

We describe the use of a flow-focusing microfluidic reactorto measure the kinetics of theCdSe-to-Ag2Se nanocrystal cation exchangereaction using micro-X-ray absorption spectroscopy (mu XAS). The smallmicroreactor dimensions facilitate the millisecond mixing of CdSenanocrystal and Ag+ reactant solutions, and the transposition of thereaction time onto spatial coordinates enables the in situ observation ofthe millisecond reaction with mu XAS. XAS spectra show the progression ofCdSe nanocrystals to Ag2Se over the course of 100 ms without the presenceof long-lived intermediates. These results, along with supporting stoppedflow absorption experiments, suggest that this nanocrystal cationexchange reaction is highly efficient and provide insight into how thereaction progresses in individual particles. This experiment illustratesthe value and potential of in situ microfluidic X-ray synchrotrontechniques for detailed studies of the millisecond structuraltransformations of nanoparticles and other solution-phase reactions inwhich diffusive mixing initiates changes in local bond structures oroxidation states.

Chan, Emory M.; Marcus, Matthew A.; Fakra, Sirine; Elnaggar,Mariam S.; Mathies, Richard A.; Alivisatos, A. Paul

2007-05-07

357

X-ray absorption spectroscopy and EPR studies of oriented spinach thylakoid preparations  

SciTech Connect

In this study, oriented Photosystem II (PS II) particles from spinach chloroplasts are studied with electron paramagnetic resonance (EPR) and x-ray absorption spectroscopy (XAS) to determine more details of the structure of the oxygen evolving complex (OEC). The nature of halide binding to Mn is also studied with Cl K-edge and Mn EXAFS (extended x-ray absorption fine structure) of Mn-Cl model compounds, and with Mn EXAFS of oriented PS II in which Br has replaced Cl. Attention is focused on the following: photosynthesis and the oxygen evolving complex; determination of mosaic spread in oriented photosystem II particles from signal II EPR measurement; oriented EXAFS--studies of PS II in the S{sub 2} state; structural changes in PS II as a result of treatment with ammonia: EPR and XAS studies; studies of halide binding to Mn: Cl K-edge and Mn EXAFS of Mn-Cl model compounds and Mn EXAFS of oriented Br-treated photosystem II.

Andrews, J.C. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; [Lawrence Berkeley Lab., CA (United States). Structural Biology Div.

1995-08-01

358

Mossbauer spectroscopy and X-ray diffraction of samples from the Santa Catharina iron meteorite  

NASA Technical Reports Server (NTRS)

Conversion electron Mossbauer spectroscopy (CEMS) of samples from the Santa Catharina iron meteorite shows the presence of the ordered iron-nickel phase with 50% Ni, tetrataenite, and of the paramagnetic iron-nickel phase with 25% Ni. The FeNi phase with 50% Ni amounts to 70% of the iron-nickel alloys. Futhermore, the CEM spectra show the presence of small peaks from one or more spinel compounds. These small peaks are more pronounced when regions near the rim of the samples are analyzed. The X-ray diffraction of different areas of the samples, both optically dark and optically light areas, shows the presence of a diffraction pattern from a single f.c.c. lattice with a lattice parameter of a=3.58A This means that the two different Fe-Ni phases seen in the CEMS analysis occupy the same lattice. The X-ray photographs also show the presence of super-structure reflections from the ordered FeNi phase, and that the orientation of the f.c.c. lattice is the same within the whole sample.

Roy-Poulsen, H.; Clarke, R. S., Jr.; Jensen, G. B.; Knudsen, J. M.; Larsen, L.; Roy-Poulsen, N. O.; Vistisen, L.

1984-01-01

359

Americium characterization by X-ray fluorescence and absorption spectroscopy in plutonium uranium mixed oxide  

NASA Astrophysics Data System (ADS)

Plutonium uranium mixed oxide (MOX) fuels are currently used in nuclear reactors. The actinides in these fuels need to be analyzed after irradiation for assessing their behaviour with regard to their environment and the coolant. In this work the study of the atomic structure and next-neighbour environment of Am in the (Pu,U)O2 lattice in an irradiated (60 MW d kg-1) MOX sample was performed employing micro-X-ray fluorescence (µ-XRF) and micro-X-ray absorption fine structure (µ-XAFS) spectroscopy. The chemical bonds, valences and stoichiometry of Am (˜0.66 wt%) are determined from the experimental data gained for the irradiated fuel material examined in its peripheral zone (rim) of the fuel. In the irradiated sample Am builds up as Am3+ species within an [AmO8]13- coordination environment (e.g. >90%) and no (<10%) Am(IV) or (V) can be detected in the rim zone. The occurrence of americium dioxide is avoided by the redox buffering activity of the uranium dioxide matrix.

Degueldre, Claude; Cozzo, Cedric; Martin, Matthias; Grolimund, Daniel; Mieszczynski, Cyprian

2013-06-01

360

Electronic structures of silicon monoxide film probed by X-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Electronic structures of thin films of silicon monoxides (SiO) deposited on a solid surface have been in-situ investigated by X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS). As a substrate, a highly oriented pyrolytic graphite (HOPG) was used because the hybridization between molecules and substrate can be excluded due to the inertness of the surface. For thin films with less than monolayer, XPS spectrum showed that the binding energy of the Si 1s is located just between those of the elemental silicon (Si0) and SiO2 (Si4 +). The result indicates that the stable divalent silicon surely exists in the deposited SiO layer. For the Si K-edge XAFS spectrum of the SiO thin film, the energy of the core-to-valence resonance peak is also located between those of the elemental silicon (Si0) and SiO2 (Si4 +). The polarization dependence of the Si K-edge XAFS spectra for the SiO film revealed that the SiO molecules are well-ordered and almost perpendicularly oriented on HOPG surface. The XAFS results also support the existence of the silicon divalent states in the deposited SiO films. The obtained well-ordered SiO films with divalent silicon will become an excellent starting material for the synthesis of low-dimensional SiOx films.

Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie

2013-06-01

361

X-Ray Photoelectron Spectroscopy Investigation of the Nitrogen Species in Photoactive Perfluorophenylazide-Modified Surfaces  

PubMed Central

X-ray Photoelectron Spectroscopy (XPS) was used to characterize the nitrogen species in perfluorophenylazide (PFPA) self-assembled monolayers. PFPA chemistry is a novel immobilization method for tailoring the surface properties of materials. It is a simple route for the efficient immobilization of graphene, proteins, carbohydrates and synthetic polymers onto a variety of surfaces. Upon light irradiation, the azido group in PFPA is converted to a highly reactive singlet nitrene species that readily undergoes CH insertion and C=C addition reactions. Here, the challenge of characterizing the PFPA modified surfaces was addressed by detailed XPS experimental analyses. The three nitrogen peaks detected in the XPS N1s spectra were assigned to amine/amide (400.5 eV) and azide (402.1 and 405.6 eV) species. The observed 2:1 ratio of the areas from the 402.1 eV to 405.6 eV peaks suggests the assignment of the peak at 402.1 eV to the two outer nitrogen atoms in the azido group and assignment of the peak at 405.6 eV to the central nitrogen atom in the azido group. The azide decomposition as the function of x-ray exposure was also determined. Finally, XPS analyses were conducted on patterned graphene to investigate the covalent bond formation between the PFPA and graphene. This study provides strong evidence for the formation of covalent bonds during the PFPA photocoupling process. PMID:24535931

Zorn, Gilad; Liu, Li-Hong; Árnadóttir, Líney; Wang, Hui; Gamble, Lara J.; Castner, David G.; Yan, Mingdi

2014-01-01

362

X-ray emission spectroscopy of bulk liquid water in "no-man's land".  

PubMed

The structure of bulk liquid water was recently probed by x-ray scattering below the temperature limit of homogeneous nucleation (TH) of ?232 K [J. A. Sellberg et al., Nature 510, 381-384 (2014)]. Here, we utilize a similar approach to study the structure of bulk liquid water below TH using oxygen K-edge x-ray emission spectroscopy (XES). Based on previous XES experiments [T. Tokushima et al., Chem. Phys. Lett. 460, 387-400 (2008)] at higher temperatures, we expected the ratio of the 1b1' and 1b1? peaks associated with the lone-pair orbital in water to change strongly upon deep supercooling as the coordination of the hydrogen (H-) bonds becomes tetrahedral. In contrast, we observed only minor changes in the lone-pair spectral region, challenging an interpretation in terms of two interconverting species. A number of alternative hypotheses to explain the results are put forward and discussed. Although the spectra can be explained by various contributions from these hypotheses, we here emphasize the interpretation that the line shape of each component changes dramatically when approaching lower temperatures, where, in particular, the peak assigned to the proposed disordered component would become more symmetrical as vibrational interference becomes more important. PMID:25637993

Sellberg, Jonas A; McQueen, Trevor A; Laksmono, Hartawan; Schreck, Simon; Beye, Martin; DePonte, Daniel P; Kennedy, Brian; Nordlund, Dennis; Sierra, Raymond G; Schlesinger, Daniel; Tokushima, Takashi; Zhovtobriukh, Iurii; Eckert, Sebastian; Segtnan, Vegard H; Ogasawara, Hirohito; Kubicek, Katharina; Techert, Simone; Bergmann, Uwe; Dakovski, Georgi L; Schlotter, William F; Harada, Yoshihisa; Bogan, Michael J; Wernet, Philippe; Föhlisch, Alexander; Pettersson, Lars G M; Nilsson, Anders

2015-01-28

363

An x-ray absorption spectroscopy study of Ni-Mn-Ga shape memory alloys.  

PubMed

The austenite to martensite phase transition in Ni-Mn-Ga ferromagnetic shape memory alloys was studied by extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) spectroscopy. The spectra at all the three elements', namely, Mn, Ga and Ni, K-edges in several Ni-Mn-Ga samples (with both Ni and Mn excess) were analyzed at room temperature and low temperatures. The EXAFS analysis suggested a displacement of Mn and Ga atoms in opposite direction with respect to the Ni atoms when the compound transforms from the austenite phase to the martensite phase. The first coordination distances around the Mn and Ga atoms remained undisturbed on transition, while the second and subsequent shells showed dramatic changes indicating the presence of a modulated structure. The Mn rich compounds showed the presence of antisite disorder of Mn and Ga. The XANES results showed remarkable changes in the unoccupied partial density of states corresponding to Mn and Ni, while the electronic structure of Ga remained unperturbed across the martensite transition. The post-edge features in the Mn K-edge XANES spectra changed from a double peak like structure to a flat peak like structure upon phase transition. The study establishes strong correlation between the crystal structure and the unoccupied electronic structure in these shape memory alloys. PMID:23238326

Sathe, V G; Dubey, Aditi; Banik, Soma; Barman, S R; Olivi, L

2013-01-30

364

An x-ray absorption spectroscopy study of Ni-Mn-Ga shape memory alloys  

NASA Astrophysics Data System (ADS)

The austenite to martensite phase transition in Ni-Mn-Ga ferromagnetic shape memory alloys was studied by extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) spectroscopy. The spectra at all the three elements’, namely, Mn, Ga and Ni, K-edges in several Ni-Mn-Ga samples (with both Ni and Mn excess) were analyzed at room temperature and low temperatures. The EXAFS analysis suggested a displacement of Mn and Ga atoms in opposite direction with respect to the Ni atoms when the compound transforms from the austenite phase to the martensite phase. The first coordination distances around the Mn and Ga atoms remained undisturbed on transition, while the second and subsequent shells showed dramatic changes indicating the presence of a modulated structure. The Mn rich compounds showed the presence of antisite disorder of Mn and Ga. The XANES results showed remarkable changes in the unoccupied partial density of states corresponding to Mn and Ni, while the electronic structure of Ga remained unperturbed across the martensite transition. The post-edge features in the Mn K-edge XANES spectra changed from a double peak like structure to a flat peak like structure upon phase transition. The study establishes strong correlation between the crystal structure and the unoccupied electronic structure in these shape memory alloys.

Sathe, V. G.; Dubey, Aditi; Banik, Soma; Barman, S. R.; Olivi, L.

2013-01-01

365

The Chemistry os Spent Nuclear Fuel From X-Ray Absorption Spectroscopy  

SciTech Connect

Present and future nuclear fuel cycles will require an understanding of the complex chemistry of trace fission products and transuranium actinides in spent nuclear fuel (SNF). Because of the unique analytical challenges presented by SNF to the materials scientist, many of its fundamental physical and chemical properties remain poorly understood, especially on the microscopic scale. Such an understanding of the chemical states of radionuclides in SNF would benefit development of technologies for fuel monitoring, fuel performance improvement and modeling, fuel reprocessing, and spent fuel storage and disposal. We have recently demonstrated the use of synchrotron x-ray absorption spectroscopy (XAS) to examine crystal chemical properties of actinides and fission products in extracted specimens of SNF. Information obtained includes oxidation state, chemical bond coordination, and quantitative elemental concentration and distribution. We have also used XAS in a scanning mode to obtain x-ray spectral micrographs with resolution approaching 1 micron. A brief overview of the technique will be presented, along with findings on uranium, plutonium, neptunium, technetium, and molybdenum in commercial PWR SNF specimens.

F.A. Fortner; A.J. Kropf; J.C. Cunnane

2006-09-21

366

High Spatial Resolution X-Ray Spectroscopy of Cas A with Chandra  

NASA Astrophysics Data System (ADS)

We present high spatial resolution X-ray spectroscopy of the supernova remnant Cassiopeia A with the Chandra observations. The X-ray emitting region of this remnant was divided into 38 × 34 pixels of 10?× 10? each. Spectra of 960 pixels were created and fitted with an absorbed two component non-equilibrium ionization model. From the results of the spectral analysis we obtained maps of absorbing column density, temperatures, ionization ages, and the abundances of Ne, Mg, Si, S, Ca and Fe. The Si, S and possibly Ca abundance maps show obvious jet structures, while Fe does not follow the jet but seems to be distributed perpendicular to it. The abundances of Si, S and Ca show tight correlations between one another over a range of about two dex. This suggests that they are ejecta from explosive O-burning and incomplete Si-burning. Meanwhile, the Ne abundance is well correlated with that of Mg, indicating them to be the ashes of explosive C/Ne burning. The Fe abundance is positively correlated with that of Si when the latter is lower than 3 times the solar value, and is negatively correlated when higher. We suggest that such a two phase correlation is due to the different ways in which Fe was synthesized.

Yang, Xue-Juan; Lu, Fang-Jun; Chen, Li

2008-08-01

367

Nitrogen chemical structure in DNA and related molecules by X-ray absorption spectroscopy.  

PubMed

The electronic environment of nitrogen in nucleic acid bases, nucleotides, polynucleotides and DNA has been studied, for the first time using X-Ray Absorption Near-Edge Spectroscopy (XANES). Generally, the spectra of these complex molecules consist of low energy bands corresponding to 1s-->pi* transitions and high energy bands corresponding to 1s-->sigma* transition, as illustrated using several nitrogen model compounds. The 1s-->pi* transitions show particular sensitivity to the chemical environment of the nitrogen. Oxygen substitution on ring carbon atoms generally results in a significant blue shift of the lowest 1s-->pi* bands while halogen substitution results in a small blue shift. These observations illustrate the significance of the disturbance of the aromatic ring system produced by exocyclic carbonyl groups. Direct substitution on the nitrogen frequently results in significant spectral perturbations. Differences between the spectra of the polynucleotides and the sums of spectra of the individual nucleotides point to the effects of hydrogen-bonding in complementary double-helix structures. The XANES spectrum of a DNA sample with a known ratio of the polynucleotides is equivalent to the weighted sum of the spectra of individual polynucleotides, indicating that the difference in base stacking interactions produces negligible spectral effects. The variability of nitrogen K-edge spectra in these samples and in protein may be useful for chemically specific imaging using X-ray microscopes. PMID:1420304

Kirtley, S M; Mullins, O C; Chen, J; van Elp, J; George, S J; Chen, C T; O'Halloran, T; Cramer, S P

1992-10-20

368

The Constellation-X Spectroscopy X-ray Telescope: recent technology development  

NASA Astrophysics Data System (ADS)

We describe recent progress in the technology development program for the mirror system for the Constellation-X Spectroscopy X-ray Telescope (SXT). Development of this mirror represents a significant technology challenge, as it must provide a combination of large effective area (3 sq. m) and modest angular resolution (15 arc second half power diameter requirement; 5 arc second goal) with a limited mass allocation. The baseline design incorporates over 200 nested Wolter 1 mirrors. Each of these in turn is segmented in order to simplify handling of the mirrors and facilitate mass production. The X-ray reflecting surfaces are fabricated from thin, thermally formed glass sheets. Production improvements have yielded mirror segments that approach the performance requirement without the need for epoxy replication. A mounting and alignment approach incorporating piezoelectric actuators has been shown to manipulate mirror segments with the required precision without introducing significant distortion. Substantial improvements in metrology methodology have provided insights into the mirror segment forming and alignment processes. We describe the technical advances made over the past year and summarize near-term plans.

Petre, Robert; Lehan, John; O'Dell, Stephen; Owens, Scott; Reid, Paul B.; Saha, Timo; Stewart, Jeff; Jones, William D.; Zhang, William

2006-06-01

369

X-ray photoelectron spectroscopy of graphitic carbon nanomaterials doped with heteroatoms  

PubMed Central

Summary X-ray photoelectron spectroscopy (XPS) is one of the best tools for studying the chemical modification of surfaces, and in particular the distribution and bonding of heteroatom dopants in carbon nanomaterials such as graphene and carbon nanotubes. Although these materials have superb intrinsic properties, these often need to be modified in a controlled way for specific applications. Towards this aim, the most studied dopants are neighbors to carbon in the periodic table, nitrogen and boron, with phosphorus starting to emerge as an interesting new alternative. Hundreds of studies have used XPS for analyzing the concentration and bonding of dopants in various materials. Although the majority of works has concentrated on nitrogen, important work is still ongoing to identify its precise atomic bonding configurations. In general, care should be taken in the preparation of a suitable sample, consideration of the intrinsic photoemission response of the material in question, and the appropriate spectral analysis. If this is not the case, incorrect conclusions can easily be drawn, especially in the assignment of measured binding energies into specific atomic configurations. Starting from the characteristics of pristine materials, this review provides a practical guide for interpreting X-ray photoelectron spectra of doped graphitic carbon nanomaterials, and a reference for their binding energies that are vital for compositional analysis via XPS. PMID:25671162

Pichler, Thomas; Ayala, Paola

2015-01-01

370

Double-core-hole spectroscopy for chemical analysis with an intense X-ray femtosecond laser  

PubMed Central

Theory predicts that double-core-hole (DCH) spectroscopy can provide a new powerful means of differentiating between similar chemical systems with a sensitivity not hitherto possible. Although DCH ionization on a single site in molecules was recently measured with double- and single-photon absorption, double-core holes with single vacancies on two different sites, allowing unambiguous chemical analysis, have remained elusive. Here we report that direct observation of double-core holes with single vacancies on two different sites produced via sequential two-photon absorption, using short, intense X-ray pulses from the Linac Coherent Light Source free-electron laser and compare it with theoretical modeling. The observation of DCH states, which exhibit a unique signature, and agreement with theory proves the feasibility of the method. Our findings exploit the ultrashort pulse duration of the free-electron laser to eject two core electrons on a time scale comparable to that of Auger decay and demonstrate possible future X-ray control of physical inner-shell processes. PMID:21969540

Berrah, Nora; Fang, Li; Murphy, Brendan; Osipov, Timur; Ueda, Kiyoshi; Kukk, Edwin; Feifel, Raimund; van der Meulen, Peter; Salen, Peter; Schmidt, Henning T.; Thomas, Richard D.; Larsson, Mats; Richter, Robert; Prince, Kevin C.; Bozek, John D.; Bostedt, Christoph; Wada, Shin-ichi; Piancastelli, Maria N.; Tashiro, Motomichi; Ehara, Masahiro

2011-01-01

371

X-ray emission spectroscopy of bulk liquid water in "no-man's land"  

NASA Astrophysics Data System (ADS)

The structure of bulk liquid water was recently probed by x-ray scattering below the temperature limit of homogeneous nucleation (TH) of ˜232 K [J. A. Sellberg et al., Nature 510, 381-384 (2014)]. Here, we utilize a similar approach to study the structure of bulk liquid water below TH using oxygen K-edge x-ray emission spectroscopy (XES). Based on previous XES experiments [T. Tokushima et al., Chem. Phys. Lett. 460, 387-400 (2008)] at higher temperatures, we expected the ratio of the 1b1' and 1b1? peaks associated with the lone-pair orbital in water to change strongly upon deep supercooling as the coordination of the hydrogen (H-) bonds becomes tetrahedral. In contrast, we observed only minor changes in the lone-pair spectral region, challenging an interpretation in terms of two interconverting species. A number of alternative hypotheses to explain the results are put forward and discussed. Although the spectra can be explained by various contributions from these hypotheses, we here emphasize the interpretation that the line shape of each component changes dramatically when approaching lower temperatures, where, in particular, the peak assigned to the proposed disordered component would become more symmetrical as vibrational interference becomes more important.

Sellberg, Jonas A.; McQueen, Trevor A.; Laksmono, Hartawan; Schreck, Simon; Beye, Martin; DePonte, Daniel P.; Kennedy, Brian; Nordlund, Dennis; Sierra, Raymond G.; Schlesinger, Daniel; Tokushima, Takashi; Zhovtobriukh, Iurii; Eckert, Sebastian; Segtnan, Vegard H.; Ogasawara, Hirohito; Kubicek, Katharina; Techert, Simone; Bergmann, Uwe; Dakovski, Georgi L.; Schlotter, William F.; Harada, Yoshihisa; Bogan, Michael J.; Wernet, Philippe; Föhlisch, Alexander; Pettersson, Lars G. M.; Nilsson, Anders

2015-01-01

372

Lattice instability in high temperature superconducting cuprates probed by x-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

In contrast to conventionl superconductivity where phonons lead to the formation of Cooper pairs, in high-tempratures superconductivity (HTSC), the role of electron-phonon coupling has long been neglected. The in-plane Cu-O bonds in HTSC cuprates show unconventionalbroadening at low temperature as carier are doped. Here we focus on high-quality polarized x-ray absorption spectroscopy (XAS)data for a model HTSC system, (La,Sr)2CuO4 (LSCO). Thin film signal crystal samples were prepared by state-of-the-arts MBE, precisely controlling compositions. High quality data was obtained by use of a segmented x-ray detector. the inplane CuO radial distribution function (RDF)in LSCO (x = 0.15)shows broadening as temprature is lowered, which shows a sharp drop at the critical temprature which is followed by a gradual increase (disorder). Comparing the data with resistivity, we find a remarkeble coinsidence between the sharpening and the onset supercondectivity. Since the sharpening of RDF is interpreated as correleted motion of oxyzen atoms (phase coherence due to supercondectivity), the result demonstrate that the super conducting state directly relates to the unconventionl oxyzen displacements in a bond stretching mode. The result will be discussed in relation to the local models of distortion of the diffrent nature (metallic vs. insulating) that is strongly influnced by strain.

Oyanagi, H.; Zhang, C.; Tsukada, A.; Naito, M.

2008-03-01

373

X-ray absorption spectroscopy study of a copper-containing material after thermal treatment.  

PubMed

Thermal immobilization of copper contaminant in a copper-containing solid material collected from local copper smelting and foundry area is investigated in the present work. X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) are employed for copper speciation. XAS results indicate that cupric hydroxide is the major copper species in the solid material dried at 105 degrees C. After being subjected to a 500 degrees C thermal process, cupric hydroxide still remains as the main copper species, but some Cu(II) is chemically reduced to Cu(I). More cupric hydroxide is progressively converted to Cu(I) as the sample was heated at 1100 degrees C than that heated at 500 degrees C. The sample heated at 500 degrees C is in its original powder form. However, thermal treatment at 1100 degrees C transforms the powder into a hardened granule-like form that is much bigger in size and difficult to be ground into powders. The sample is sintered with the sparingly soluble cuprous oxide and elemental copper being encapsulated inside. Toxicity characteristic leaching procedure (TCLP) results depict that amount of copper leached from the sample (containing 133,000 mg copper kg-1) heated at 1100 degrees C for 2 h is considerably minor, being 367 mg copper kg-1. PMID:16257485

Wei, Y-L; Huang, M-Y; Wang, H-C; Huang, H-C; Lee, J-F

2006-04-17

374

X-ray photoelectron spectroscopy of graphitic carbon nanomaterials doped with heteroatoms.  

PubMed

X-ray photoelectron spectroscopy (XPS) is one of the best tools for studying the chemical modification of surfaces, and in particular the distribution and bonding of heteroatom dopants in carbon nanomaterials such as graphene and carbon nanotubes. Although these materials have superb intrinsic properties, these often need to be modified in a controlled way for specific applications. Towards this aim, the most studied dopants are neighbors to carbon in the periodic table, nitrogen and boron, with phosphorus starting to emerge as an interesting new alternative. Hundreds of studies have used XPS for analyzing the concentration and bonding of dopants in various materials. Although the majority of works has concentrated on nitrogen, important work is still ongoing to identify its precise atomic bonding configurations. In general, care should be taken in the preparation of a suitable sample, consideration of the intrinsic photoemission response of the material in question, and the appropriate spectral analysis. If this is not the case, incorrect conclusions can easily be drawn, especially in the assignment of measured binding energies into specific atomic configurations. Starting from the characteristics of pristine materials, this review provides a practical guide for interpreting X-ray photoelectron spectra of doped graphitic carbon nanomaterials, and a reference for their binding energies that are vital for compositional analysis via XPS. PMID:25671162

Susi, Toma; Pichler, Thomas; Ayala, Paola

2015-01-01

375

"Live" Prussian blue fading by time-resolved X-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Prussian blue (PB) is an artists' pigment that has been frequently used in many artworks but poses several problems of conservation because of its fading under light and anoxia treatment. PB fading is due to the reduction of iron(III) into iron(II) and depends a lot on the object investigated. Due to the complexity of the structure, the precise physico-chemical mechanisms behind the redox process remain obscure. In this paper, we present a procedure to investigate light- and anoxia-induced fading of PB-paper samples by means of time resolved X-ray absorption spectroscopy performed at the Fe K-edge. A system composed of a visible light source and a flux-controlled environmental cell allowed light, gas and humidity to be modified in situ. The synchrotron X-ray beam was evidenced to induce a reduction of PB and to play a major role in the kinetics. The analysis of the PB fading kinetics of a sample submitted to various gas and light environments showed that both synchrotron beam and anoxia were influencing PB reduction in a correlated way. In comparison, light was found to play a minor role. Finally, we have demonstrated that the type of paper substrate could influence significantly the kinetics of reduction. Several hypotheses to explain the correlation between PB reduction mechanism and substrate are presented.

Gervais, Claire; Languille, Marie-Angélique; Reguer, Solenn; Gillet, Martine; Vicenzi, Edward P.; Chagnot, Sébastien; Baudelet, François; Bertrand, Loïc

2013-04-01

376

A Suborbital Payload for Soft X-ray Spectroscopy of Extended Sources  

NASA Astrophysics Data System (ADS)

This thesis details the intent, design and results of an X-ray suborbital rocket payload whose scientific target was the Cygnus Loop Supernova Remnant. The payload consists of wire grid collimators, off-plane gratings arrays and gaseous electron multiplier (GEM) detectors. The system was designed for measurements in the 17-107 Å bandpass with a resolution up to ? 60 (?=??). This instrument was christened the Extended X-ray Off-plane Spectrometer (EXOS) and was launched on a Terrier-Black Brant rocket on November 13th, 2009 from White Sands Missile Range and obtained 340 seconds of useable scientific data. The emission is dominated by O VII and O VIII, including the He-like O VII triplet at ?22 Å. Another feature at ?45 Å is composed primarily of Si XI and Si XII. The best-fit model to this spectrum is an equilibrium plasma model at a temperature of log(T) = 6.4 (0.23 keV).

Oakley, Phillip Henry Howard

377

The sub-micron resolution X-ray spectroscopy beamline at NSLS-II  

NASA Astrophysics Data System (ADS)

For many research areas such as life, environmental, earth or material sciences, novel analytical resources have to be developed for an advance understanding of complex natural and engineered systems that are heterogeneous on the micron to the tenths of microns scale. NSLS-II at BNL will be a synchrotron radiation source with an ultra-high brilliance delivering a high current (500 mA). One of the 1st six NSLS-II beamlines will be the Sub-micron Resolution X-ray spectroscopy beamline (SRX), dedicated as an analytical tool to study complex systems on a sub-micron length scale. SRX will comprise two branches thanks to a canted setup with two undulators: the first branch using Kirkpatrick-Baez mirrors as focusing optics will cover the energy range of 4.65-23 keV, allowing for XANES experiments from the Ti to the Rh K-edge. Thanks to a horizontally deflecting double crystal monochromator with maximum stability, a set of slits located on the secondary source, and two sets of complementary and quickly interchangeable KB mirrors, spectroscopy with very high spectral and spatial resolution will be achieved. The spot size will almost fully cover a range from 60×60 to 1300×500 nm 2, providing an attractive adaptability of the observation scale. A 1.5 m long IVU21 will serve as a light source. The expected high flux in a sub-micron-spot (5×10 12 and 7×10 13 ph s -1 at maximum and lowest resolutions) will open new possibilities for spectromicroscopy of trace elements. The 2nd canted undulator will serve as an independent light source for the second branch designed for experiments with X-ray energies in the range of 2-15 keV. Using Fresnel zone plates, the spatial resolution aimed for is around 30 nm with up to 7×10 9 ph s -1 in the spot. This branch would be attractive for many biological applications from life and environmental science due to low-Z elements of interest within that energy range. In both experimental stations, X-ray fluorescence will be used for imaging, spectroscopy, tomography and ?-diffraction experiments.

De Andrade, V.; Thieme, J.; Northrup, P.; Yao, Y.; Lanzirotti, A.; Eng, P.; Shen, Q.

2011-09-01

378

The Focusing Optics X-ray Solar Imager (FOXSI): Instrument and First Flight  

NASA Astrophysics Data System (ADS)

Understanding electron acceleration in solar flares requires hard X-ray studies with greater sensitivity and dynamic range than are available with current solar hard X-ray observers (i.e. the RHESSI spacecraft). Both these capabilities can be advanced by the use of direct focusing optics instead of the indirect Fourier methods of current and previous generations. The Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket payload demonstrates the feasibility and usefulness of hard X-ray focusing optics for solar observation. FOXSI flew for the first time on 2012 November 2, producing images and spectra of a microflare and performing a search for nonthermal X-rays from the quiet Sun. Such measurements are important for characterizing the impact of small "nanoflares" on the solar coronal heating problem. A spaceborne solar observer featuring similar optics could make detailed observations of hard X-rays from flare-accelerated electrons, identifying and characterizing particle acceleration sites and mapping out paths of energetic electrons as they leave these sites and propagate throughout the solar corona. Solar observations from NuSTAR are also expected to be an important step in this direction.

Glesener, Lindsay; Christe, S.; Ishikawa, S.; Ramsey, B.; Takahashi, T.; Saito, S.; Lin, R. P.; Krucker, S.; FOXSI Team

2013-04-01

379

Effects of sulfation level on the desulfation behavior of pre-sulfated Pt BaO\\/Al2O3 lean NOx trap catalysts: a combined H2 Temperature-Programmed Reaction, in-situ sulfur Kedge X-ray Absorption Near-Edge Spectroscopy, X-ray Photoelectron Spectroscopy, and Time-Resolved X-ray Diffraction Study  

Microsoft Academic Search

Desulfation by hydrogen of pre-sulfated Pt(2wt%) BaO(20wt%)\\/Al2O3 with various sulfur loading (S\\/Ba = 0.12, 0.31 and 0.62) were investigated by combining H2 temperature programmed reaction (TPRX), x-ray photoelectron spectroscopy (XPS), in-situ sulfur K-edge x-ray absorption near-edge spectroscopy (XANES), and synchrotron time-resolved x-ray diffraction (TR-XRD) techniques. We find that the amount of H2S desorbed during the desulfation in the H2 TPRX

Do Heui Kim; Janos Szanyi; Ja Hun Kwak; Xianqin Wang; Jonathan C. Hanson; Mark H. Engelhard; Charles HF Peden

2009-01-01

380

Unveiling the nature of INTEGRAL objects through optical spectroscopy. IX. Twenty two more identifications, and a glance into the far hard X-ray Universe  

NASA Astrophysics Data System (ADS)

Since its launch in October 2002, the INTEGRAL satellite has revolutionized our knowledge of the hard X-ray sky thanks to its unprecedented imaging capabilities and source detection positional accuracy above 20 keV. Nevertheless, many of the newly-detected sources in the INTEGRAL sky surveys are of unknown nature. The combined use of available information at longer wavelengths (mainly soft X-rays and radio) and of optical spectroscopy on the putative counterparts of these new hard X-ray objects allows us to pinpoint their exact nature. Continuing our long-standing program that has been running since 2004, and using 6 different telescopes of various sizes together with data from an online spectroscopic survey, here we report the classification through optical spectroscopy of 22 more unidentified or poorly studied high-energy sources detected with the IBIS instrument onboard INTEGRAL. We found that 16 of them are active galactic nuclei (AGNs), while the remaining 6 objects are within our Galaxy. Among the identified extragalactic sources, the large majority (14) is made up of type 1 AGNs (i.e. with broad emission lines); of these, 6 lie at redshift larger than 0.5 and one (IGR J12319-0749) has z = 3.12, which makes it the second farthest object detected in the INTEGRAL surveys up to now. The remaining AGNs are of type 2 (that is, with narrow emission lines only), and one of the two cases is confirmed as a pair of interacting Seyfert 2 galaxies. The Galactic objects are identified as two cataclysmic variables, one high-mass X-ray binary, one symbiotic binary and two chromospherically active stars, possibly of RS CVn type. The main physical parameters of these hard X-ray sources were also determined using the multiwavelength information available in the literature. We thus still find that AGNs are the most abundant population among hard X-ray objects identified through optical spectroscopy. Moreover, we note that the higher sensitivity of the more recent INTEGRAL surveys is now enabling the detection of high-redshift AGNs, thus allowing the exploration of the most distant hard X-ray emitting sources and possibly of the most extreme blazars. Based on observations collected at the following observatories: Cerro Tololo Interamerican Observatory (Chile); Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (Canary Islands, Spain); Astronomical Observatory of Bologna in Loiano (Italy); Astronomical Observatory of Asiago (Italy); Observatorio Astronómico Nacional (San Pedro Mártir, Mexico); Anglo-Australian Observatory (Siding Spring, Australia).

Masetti, N.; Parisi, P.; Jiménez-Bailón, E.; Palazzi, E.; Chavushyan, V.; Bassani, L.; Bazzano, A.; Bird, A. J.; Dean, A. J.; Galaz, G.; Landi, R.; Malizia, A.; Minniti, D.; Morelli, L.; Schiavone, F.; Stephen, J. B.; Ubertini, P.

2012-02-01

381

High-rate x-ray spectroscopy in mammography with a CdTe detector: A digital pulse processing approach  

SciTech Connect

Purpose:Direct measurement of mammographic x-ray spectra under clinical conditions is a difficult task due to the high fluence rate of the x-ray beams as well as the limits in the development of high resolution detection systems in a high counting rate environment. In this work we present a detection system, based on a CdTe detector and an innovative digital pulse processing (DPP) system, for high-rate x-ray spectroscopy in mammography. Methods: The DPP system performs a digital pile-up inspection and a digital pulse height analysis of the detector signals, digitized through a 14-bit, 100 MHz digitizer, for x-ray spectroscopy even at high photon counting rates. We investigated on the response of the digital detection system both at low (150 cps) and at high photon counting rates (up to 500 kcps) by using monoenergetic x-ray sources and a nonclinical molybdenum anode x-ray tube. Clinical molybdenum x-ray spectrum measurements were also performed by using a pinhole collimator and a custom alignment device. Results: The detection system shows excellent performance up to 512 kcps with an energy resolution of 4.08% FWHM at 22.1 keV. Despite the high photon counting rate (up to 453 kcps), the molybdenum x-ray spectra, measured under clinical conditions, are characterized by a low number of pile-up events. The agreement between the attenuation curves and the half value layer values, obtained from the measured spectra, simulated spectra, and from the exposure values directly measured with an ionization chamber, also shows the accuracy of the measurements. Conclusions: These results make the proposed detection system a very attractive tool for both laboratory research and advanced quality controls in mammography.

Abbene, L.; Gerardi, G.; Principato, F.; Del Sordo, S.; Ienzi, R.; Raso, G. [Dipartimento di Fisica e Tecnologie Relative, Universita di Palermo, Viale delle Scienze, Edificio 18, Palermo 90128 (Italy) and INAF/IASF Palermo, Via Ugo La Malfa 153, 90146 Palermo (Italy); Dipartimento di Fisica e Tecnologie Relative, Universita di Palermo, Viale delle Scienze, Edificio 18, Palermo 90128 (Italy); INAF/IASF Palermo, Via Ugo La Malfa 153, 90146 Palermo (Italy); Istituto di Radiologia, Policlinico, 90100 Palermo (Italy); Dipartimento di Fisica e Tecnologie Relative, Universita di Palermo, Viale delle Scienze, Edificio 18, Palermo 90128 (Italy)

2010-12-15

382

Where Water is Oxidized to Dioxygen: Structure of the Photosynthetic Mn4Ca Cluster from X-ray Spectroscopy  

SciTech Connect

Light-driven oxidation of water to dioxygen in plants, algae and cyanobacteria iscatalyzed within photosystem II (PS II) by a Mn4Ca cluster. Although the cluster has been studied by many different methods, the structure and the mechanism have remained elusive. X-ray absorption and emission spectroscopy and EXAFS studies have been particularly useful in probing the electronic and geometric structure, and the mechanism of the water oxidation reaction. Recent progress, reviewed here, includes polarized X-ray absorption spectroscopy measurements of PS II single crystals. Analysis of those results has constrained the Mn4Ca cluster geometry to a setof three similar high-resolution structures. The structure of the cluster from the present study is unlike either the 3.0 or 3.5 Angstrom-resolution X-ray structures or other previously proposed models. The differences between the models derived from X-rayspectroscopy and crystallography are predominantly because of damage to the Mn4Ca cluster by X-rays under the conditions used for structure determination by X-ray crystallography. X-ray spectroscopy studies are also used for studying the changes in the structure of the Mn4Ca catalytic center as it cycles through the five intermediate states known as the Si-states (i=0-4). The electronic structure of the Mn4Ca cluster has been studied more recently using resonant inelastic X-ray scattering spectroscopy (RIXS), in addition to the earlier X-ray absorption and emission spectroscopy methods. These studies are revealing that the assignment of formaloxidation states is overly simplistic. A more accurate description should consider the charge density on the Mn atoms that includes the covalency of the bonds and delocalization of the charge over the cluster. The geometric and electronic structure of the Mn4Ca cluster in the S-states derived from X-ray spectroscopy are leading to a detailed understanding of the mechanism of the O-O bond formation during the photosynthetic water splitting process.

Yano, Junko; Yano, Junko; Yachandra, Vittal K.

2007-10-24

383

Picosecond laser-pump, x-ray probe spectroscopy of GaAs  

Microsoft Academic Search

A laser-pump, x-ray probe spectroscopic experiment is described, and the results are shown. The Ga K? x-ray fluorescence following x-ray absorption, at the Ga K absorption edge was measured, and its increase due to excitation with subpicosecond pulses of laser light at 4.6 eV photon energy was determined. The x-ray absorption, and thus the fluorescence, is increased for about 200

B. W. Adams; M. F. DeCamp; E. M. Dufresne; D. A. Reis

2002-01-01

384

Picosecond laser-pump, x-ray probe spectroscopy of GaAs  

Microsoft Academic Search

A laser-pump, x-ray probe spectroscopic experiment is described, and the results are shown. The Ga Kalpha x-ray fluorescence following x-ray absorption, at the Ga K absorption edge was measured, and its increase due to excitation with subpicosecond pulses of laser light at 4.6 eV photon energy was determined. The x-ray absorption, and thus the fluorescence, is increased for about 200

B. W. Adams; M. F. Decamp; E. M. Dufresne; D. A. Reis

2002-01-01

385

A Fully Bayesian Method for Jointly Fitting Instrumental Calibration and X-Ray Spectral Models  

NASA Astrophysics Data System (ADS)

Owing to a lack of robust principled methods, systematic instrumental uncertainties have generally been ignored in astrophysical data analysis despite wide recognition of the importance of including them. Ignoring calibration uncertainty can cause bias in the estimation of source model parameters and can lead to underestimation of the variance of these estimates. We previously introduced a pragmatic Bayesian method to address this problem. The method is "pragmatic" in that it introduced an ad hoc technique that simplified computation by neglecting the potential information in the data for narrowing the uncertainty for the calibration product. Following that work, we use a principal component analysis to efficiently represent the uncertainty of the effective area of an X-ray (or ?-ray) telescope. Here, however, we leverage this representation to enable a principled, fully Bayesian method that coherently accounts for the calibration uncertainty in high-energy spectral analysis. In this setting, the method is compared with standard analysis techniques and the pragmatic Bayesian method. The advantage of the fully Bayesian method is that it allows the data to provide information not only for estimation of the source parameters but also for the calibration product—here the effective area, conditional on the adopted spectral model. In this way, it can yield more accurate and efficient estimates of the source parameters along with valid estimates of their uncertainty. Provided that the source spectrum can be accurately described by a parameterized model, this method allows rigorous inference about the effective area by quantifying which possible curves are most consistent with the data.

Xu, Jin; van Dyk, David A.; Kashyap, Vinay L.; Siemiginowska, Aneta; Connors, Alanna; Drake, Jeremy; Meng, Xiao-Li; Ratzlaff, Pete; Yu, Yaming

2014-10-01

386

Analysis of photographs and photo-paintings by energy-dispersive X-ray fluorescence spectroscopy  

NASA Astrophysics Data System (ADS)

A collection of Brazilian family photographs and photo-paintings from the beginning of the XX Century was analyzed by portable EDXRF (Energy-Dispersive X-Ray Fluorescence) spectroscopy. The spectrometer uses a Si-drift Amptek detector and an Oxford Cr-tube or an Oxford W-tube. For every region under analysis, spectra obtained with the W-tube were used to detect all the elements above Al, while the Cr-tube was used to obtain more accurate results for elements between Al and V. Thirty nine elements were identified in the photos, and the origin of the most important ones was discussed. These results can be used for cataloging, preservation and restoring procedures.

Neiva, Augusto Camara; Marcondes, Marli A.; Pinto, Herbert Prince Favero; Almeida, Paula Aline Durães

2014-02-01

387

High-resolution detectors for imaging and spectroscopy at ultraviolet and soft X-ray wavelengths  

NASA Technical Reports Server (NTRS)

The Multi-Anode Microchannel Arrays (MAMAs) are a family of pulse-counting imaging array detectors designed specifically for astrophysical investigations in space. The MAMAs have a number of unique performance characteristics which make them particularly suitable for imaging and spectroscopy at ultraviolet and soft X-ray wavelengths. First, they employ 'solar blind' photocathodes eliminating the 'red leak' problem associated with solid state arrays such as the CCDs. Second, they operate with zero readout noise, yielding photon-statistics limited signals. Third, they utilize a random readout technique and can determine both the location of a detected photon and also its arrival time to an accuracy of the order of 100 ns. This paper gives an overview of the construction, mode of operation, and performance characteristics of the MAMA detectors and describes the current status of the development program.

Timothy, J. G.; Morgan, J. S.; Slater, D. C.

1988-01-01

388

In situ x-ray photoelectron spectroscopy of model catalysts: at the edge of the gap.  

PubMed

We present high-pressure x-ray photoelectron spectroscopy (HP-XPS) and first-principles kinetic Monte Carlo study addressing the nature of the active surface in CO oxidation over Pd(100). Simultaneously measuring the chemical composition at the surface and in the near-surface gas phase, we reveal both O-covered pristine Pd(100) and a surface oxide as stable, highly active phases in the near-ambient regime accessible to HP-XPS. Surprisingly, no adsorbed CO can be detected during high CO(2) production rates, which can be explained by a combination of a remarkably short residence time of the CO molecule on the surface and mass-transfer limitations in the present setup. PMID:25166577

Blomberg, S; Hoffmann, M J; Gustafson, J; Martin, N M; Fernandes, V R; Borg, A; Liu, Z; Chang, R; Matera, S; Reuter, K; Lundgren, E

2013-03-15

389

X-Ray Absorption Spectroscopy Of Thin Foils Irradiated By An Ultra-short Laser Pulse  

SciTech Connect

Point-projection K-shell absorption spectroscopy has been used to measure absorption spectra of transient plasma created by an ultra-short laser pulse. The 1s-2p and 1s-3p absorption lines of weakly ionized aluminum and the 2p-3d absorption lines of bromine were measured over an extended range of densities in a low-temperature regime. Independent plasma characterization was obtained using frequency domain interferometry diagnostic (FDI) that allows the interpretation of the absorption spectra in terms of spectral opacities. Assuming local thermodynamic equilibrium, spectral opacity calculations have been performed using the density and temperature inferred from the FDI diagnostic to compare to the measured absorption spectra. A good agreement is obtained when non-equilibrium effects due to non-stationary atomic physics are negligible at the x-ray probe time.

Renaudin, P.; Blancard, C.; Cosse, P.; Faussurier, G. [Departement de Physique Theorique et Appliquee, Centre DAM Ile-de-France, BP12, 91680 Bruyeres-le-Chatel Cedex (France); Lecherbourg, L. [Laboratoire pour l'Utilisation des Lasers Intenses, UMR 7605, CNRS-CEA-Universite Paris VI-Ecole Polytechnique, 91128 Palaiseau (France); Universite du Quebec, INRS Energie et Materiaux, Varennes, Quebec (Canada); Audebert, P.; Bastiani-Ceccotti, S.; Geindre, J.-P. [Laboratoire pour l'Utilisation des Lasers Intenses, UMR 7605, CNRS-CEA-Universite Paris VI-Ecole Polytechnique, 91128 Palaiseau (France); Shepherd, R. [Lawrence Livermore National Laboratory, University of California, Livermore, CA 94550 (United States)

2007-08-02

390

X-Ray Absorption Spectroscopy Of Thin Foils Irradiated By An Ultra-short Laser Pulse  

NASA Astrophysics Data System (ADS)

Point-projection K-shell absorption spectroscopy has been used to measure absorption spectra of transient plasma created by an ultra-short laser pulse. The 1s-2p and 1s-3p absorption lines of weakly ionized aluminum and the 2p-3d absorption lines of bromine were measured over an extended range of densities in a low-temperature regime. Independent plasma characterization was obtained using frequency domain interferometry diagnostic (FDI) that allows the interpretation of the absorption spectra in terms of spectral opacities. Assuming local thermodynamic equilibrium, spectral opacity calculations have been performed using the density and temperature inferred from the FDI diagnostic to compare to the measured absorption spectra. A good agreement is obtained when non-equilibrium effects due to non-stationary atomic physics are negligible at the x-ray probe time.

Renaudin, P.; Lecherbourg, L.; Blancard, C.; Cossé, P.; Faussurier, G.; Audebert, P.; Bastiani-Ceccotti, S.; Geindre, J.-P.; Shepherd, R.

2007-08-01

391

Precision spectroscopy of light kaonic atom X-rays in the SIDDHARTA experiment  

SciTech Connect

The KN system at rest makes a sensitive testing ground for low energy QCD. At the DA{Phi}NE electron-positron collider of Laboratori Nazionali di Frascati we study kaonic atoms, taking advantage of the low-energy kaons from {Phi}-mesons decaying nearly at rest. The DEAR (DA{Phi}NE Exotic Atom Research) experiment at LNF delivered the most precise data on kaonic hydrogen up to now. DEAR and its follow-up experiment SIDDHARTA (Silicon Drift Detector for Hadronic Atom Research by Timing Application) are using X-ray spectroscopy of kaonic atoms to measure the strong interaction induced shift and width of the ground state. SIDDHARTA is the first experiment on kaonic helium-3 and deuterium ever, and kaonic hydrogen was remeasured with improved precision.

Cargnelli, M.; Ishiwatari, T.; Marton, J.; Widmann, E.; Zmeskal, J. [Stefan Meyer Institut of the Austrian Academy of Sciences, Vienna, 1090, Boltzmanngasse 3 (Austria); Bazzi, M.; Bragadireanu, A. M.; Curceanu, C.; Guaraldo, C.; Iliescu, M.; Sandri, P. Levi; Lucherini, V.; Okada, S.; Pietreanu, D.; Vidal, A. Romero; Scordo, A.; Sirghi, D. L.; Sirghi, F; Doce, O. Vazquez [INFN, Laboratori Nazionali di Frascati, C.P. 13, Via E. Fermi 40,I-00044 Frascati, Roma (Italy); Beer, G. [Dep. of Physics and Astronomy, University of Victoria, P.O.Box 3055, Victoria B.C. V8W3P6 (Canada)

2011-10-24

392

Tin Valence and Local Environments in Silicate Glasses as Determined From X-ray Absorption Spectroscopy  

SciTech Connect

X-ray absorption spectroscopy (XAS) was used to characterize the tin (Sn) environments in four borosilicate glass nuclear waste formulations, two silicate float glasses, and three potassium aluminosilicate glasses. Sn K-edge XAS data of most glasses investigated indicate Sn4+O6 units with average Sn-O distances near 2.03 Angstroms. XAS data for a float glass fabricated under reducing conditions show a mixture of Sn4+O6 and Sn2+O4 sites. XAS data for three glasses indicate Sn-Sn distances ranging from 3.43 to 3.53 Angstroms, that suggest Sn4+O6 units linking with each other, while the 4.96 Angstroms Sn-Sn distance for one waste glass suggests clustering of unlinked Sn4+O6 units.

McKeown,D.; Buechele, A.; Gan, H.; Pegg, I.

2008-01-01

393

Zinc ligands in the metal hyperaccumulator Thlaspi caerulescens as determined using X-ray absorption spectroscopy  

SciTech Connect

Using the noninvasive technique of X-ray absorption spectroscopy (XAS), the authors have been able to determine the ligand environment of Zn in different tissues of the Zn-hyperaccumulator Thlaspi caerulescens. The majority of intracellular Zn in roots of T. caerulescens was found to be coordinated with histidine. In the xylem sap Zn was found to be transported mainly as the free hydrated Zn{sup 2+} cation with a smaller proportion coordinated with organic acids. In the shoots, Zn coordination occurred mainly via organic acids, with a smaller proportion present as the hydrated cation and coordinated with histidine and the cell wall. Their data suggest that histidine plays an important role in Zn homeostasis in the roots, whereas organic acids are involved in xylem transport and Zn storage in shoots.

Salt, D.E. [Northern Arizona Univ., Flagstaff, AZ (United States). Chemistry Dept.] [Northern Arizona Univ., Flagstaff, AZ (United States). Chemistry Dept.; Prince, R.C. [Exxon Research and Engineering, Annandale, NJ (United States)] [Exxon Research and Engineering, Annandale, NJ (United States); Baker, A.J.M. [Univ. of Sheffield (United Kingdom). Dept. of Animal and Plant Sciences] [Univ. of Sheffield (United Kingdom). Dept. of Animal and Plant Sciences; Raskin, I. [Rutgers Univ., New Brunswick, NJ (United States)] [Rutgers Univ., New Brunswick, NJ (United States); Pickering, I.J. [Stanford Synchrotron Radiation Lab., CA (United States)] [Stanford Synchrotron Radiation Lab., CA (United States)

1999-03-01

394

X-ray photoelectron spectroscopy study of radiofrequency-sputtered refractory compound steel interfaces  

NASA Technical Reports Server (NTRS)

Radiofrequency sputtering was used to deposit Mo2C, Mo2B5, and MoSi2 coatings on 440C steel substrates. Both sputter etched and preoxidized substrates were used, and the films were deposited with and without a substrate bias of -300 V. The composition of the coatings was measured as a function of depth by X-ray photoelectron spectroscopy combined with argon ion etching. In the interfacial region there was evidence that bias produced a graded interface in Mo2B5 but not in Mo2C. Oxides of iron and of all film constituents except carbon were presented in all cases but the iron oxide concentration was higher and the layer thicker on the preoxidized substrates. The film and iron oxides were mixed in the MoSi2 and Mo2C films but layered in the Mo2B5 film. The presence of mixed oxides correlates with enhanced film adhesion.

Wheeler, D. R.; Brainard, W. A.

1978-01-01

395

Room temperature oxidation kinetics of Si nanoparticles in air, determined by x-ray photoelectron spectroscopy  

SciTech Connect

The air oxidation kinetics of low coverages of {approx}5 nm Si nanoparticles, deposited by pulsed excimer laser ablation (KrF, 248 nm) in He, have been characterized by x-ray photoelectron spectroscopy. A simple model, based on the evolution of the Si 2p spectral components during oxidation, has been developed to determine the nanoparticle oxide thickness. It is found that the short-term oxide thickness is greater, and the long-term room-temperature air oxidization rate of these nanoparticles is less, than those reported for bulk a-Si and c-Si. The results are also consistent with an earlier transmission electron microscope observation of the oxidation of larger Si particles at higher temperatures. The greater short-term oxide thickness may be attributed to surface defects on the prepared Si nanoparticles, and lower long-term oxidation rate is due to the nonlinear decrease of oxygen diffusion in spherical systems.

Yang, D.-Q.; Gillet, Jean-Numa; Meunier, M.; Sacher, E. [Regroupement Quebecois des Materiaux de Pointe and Departement de Genie Physique, Ecole Polytechnique Case Postale 6079, succursale Centre-Ville, Montreal, Quebec H3C 3A7 (Canada)

2005-01-15

396

In situ X-ray photoelectron spectroscopy of model catalysts: At the edge of the gap  

E-print Network

We present a High-Pressure X-ray Photoelectron Spectroscopy (HP-XPS) and first-principles kinetic Monte Carlo study addressing the nature of the active surface in CO oxidation over Pd(100). Simultaneously measuring the chemical composition at the surface and in the near-surface gas-phase, we reveal both O-covered pristine Pd(100) and a surface oxide as stable, highly active phases in the near-ambient regime accessible to HP-XPS. Surprisingly, no adsorbed CO can be detected during high CO2 production rates, which can be explained by a combination of a remarkably short residence time of the CO molecule on the surface and mass-transfer limitations in the present set-up.

Blomberg, S; Gustafson, J; Martin, N M; Fernandes, V R; Borg, A; Liu, Z; Chang, R; Matera, S; Reuter, K; Lundgren, E

2013-01-01

397

Surface properties of SmB6 from x-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

We have investigated the properties of cleaved SmB6 single crystals by x-ray photoelectron spectroscopy. At low temperatures and freshly cleaved samples a surface core level shift is observed which vanishes when the temperature is increased. A Sm valence between 2.5 and 2.6 is derived from the relative intensities of the Sm2 + and Sm3 + multiplets. The B/Sm intensity ratio obtained from the core levels is always larger than the stoichiometric value. Possible reasons for this deviation are discussed. The B 1s signal shows an unexpected complexity: An anomalous low energy component appears with increasing temperature and is assigned to the formation of a suboxide at the surface. While several interesting intrinsic and extrinsic properties of the SmB6 surface are elucidated in this manuscript, no clear indication of a trivial mechanism for the prominent surface conductivity is found.

Heming, N.; Treske, U.; Knupfer, M.; Büchner, B.; Inosov, D. S.; Shitsevalova, N. Y.; Filipov, V. B.; Krause, S.; Koitzsch, A.

2014-11-01

398

The irradiation of ammonia ice studied by near edge x-ray absorption spectroscopy  

SciTech Connect

A vapor-deposited NH{sub 3} ice film irradiated at 20 K with 150 eV photons has been studied with near-edge x-ray absorption fine structure (NEXAFS) spectroscopy at the nitrogen K-edge. Irradiation leads to the formation of high amounts (12%) of molecular nitrogen N{sub 2}, whose concentration as a function of the absorbed energy has been quantified to 0.13 molecule/eV. The stability of N{sub 2} in solid NH{sub 3} has been also studied, showing that N{sub 2} continuously desorbs between 20 and 95 K from the irradiated ammonia ice film. Weak concentrations (<1%) of other photoproducts are also detected. Our NEXAFS simulations show that these features own to NH{sub 2}, N{sub 2}H{sub 2}, and N{sub 3}{sup -}.

Parent, Ph.; Bournel, F.; Lasne, J.; Laffon, C.; Carniato, S. [Laboratoire de Chimie Physique, CNRS, UMR 7614, Matiere et Rayonnement, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Lacombe, S. [Laboratoire des Collisions Atomiques et Moleculaires (LCAM), CNRS, 91405 Orsay Cedex, France and Universite Paris Sud 11, Bat 351, 91405 Orsay Cedex (France); Strazzulla, G. [INAF-Ossevatorio Astrofisico, Via S. Sofia 78, 95123 Catania (Italy); Gardonio, S.; Lizzit, S. [Sincrotrone Trieste S.C.p.A., S. S. 14 Km 163.5, Basovizza, 34012 Trieste (Italy); Kappler, J.-P. [Institut de Physique et Chimie des Materiaux de Strasbourg, UMR 7504, ULP-CNRS, 23 rue du Loess, BP 43, F-67034 Strasbourg Cedex 2 (France); Joly, L. [Institut de Physique et Chimie des Materiaux de Strasbourg, UMR 7504, ULP-CNRS, 23 rue du Loess, BP 43, F-67034 Strasbourg Cedex 2 (France); Swiss Light Source, Paul Scherrer Institut, Villigen PSI, 5232 Villigen (Switzerland)

2009-10-21

399

Angularly resolved X-ray photoelectron spectroscopy investigation of PTFE after prolonged space exposure  

NASA Technical Reports Server (NTRS)

Monochromatized angularly resolved X-ray photoelectron spectroscopy (ARXPS) was used to study PTFE (Teflon) that had been exposed to an earth orbital environment for approximately six years. The primary interest of the research is on a very reactive component of this environment (atomic oxygen) which, because of the typical orbital velocities of a spacecraft, impinge on exposed surfaces with 5 eV energy. This presentation deals with the method of analysis, the findings as they pertain to a rather complex carbon, oxygen, and fluorine XPS peak analysis, and the character of the valence bands. An improved bias referencing method, based on ARXPS, is also demonstrated for evaluating specimen charging effects. It was found that the polymer molecule tends to resist the atomic oxygen attack by reorienting itself, so that the most electronegative CF3 groups are facing the incoming hyperthermal oxygen atoms. The implications of these findings to ground-based laboratory studies are discussed.

Dalins, I.; Karimi, M.

1992-01-01

400

X-ray photoelectron spectroscopy study of chemically-etched Nd-Ce-Cu-O surfaces  

NASA Technical Reports Server (NTRS)

Acetic acid, Br2, and HCl solutions are investigated for removing insulating species from Nd(1.85)Ce(0.15)CuO(4-delta) (NCCO) thin film surfaces. X-ray photoelectron spectroscopy (XPS) shows that the HCl etch is most effective, yielding O 1s spectra comparable to those obtained from samples cleaned in vacuum and a clear Fermi edge in the valence band region. Reduction and oxidation reversibly induces and eliminates, respectively, Fermi level states for undoped samples, but has no clearly observable effect on the XPS spectra for doped samples. Reactivity to air is much less for NCCO compared to hole superconductors, which is attributed to the lack of reactive alkaline earth elements in NCCO.

Vasquez, R. P.; Gupta, A.; Kussmaul, A.

1991-01-01

401

Photosynthetic Dioxygen Formation Monitored by Time-Resolved X-Ray Spectroscopy  

SciTech Connect

Photosynthetic water oxidation provides the dioxygen of the atmosphere. Its partial reactions proceed at a Mn4Ca complex bound to photosystem II of plants and cyanobacteria. Understanding the mechanism of this biological oxidation of water molecules to O2 is one of the major challenges in life sciences. We have developed and employed X-ray absorption Spectroscopy (XAS) techniques facilitating measurements on metalloenzymes at room temperature. By these techniques, we were able to resolve structural changes at the Mn ions, to follow oxidation-state changes in the microseconds time domain, and to detect a novel and likely crucial intermediate in the oxygen-evolving step of the catalytic cycle of the Mn complex. Based on the obtained results, we replace the classic S-state model of the catalytic cycle by a more elaborated reaction scheme which solves apparent inconsistencies of earlier models, explains a large body of experimental results, and provides a fresh twist in photosynthesis research.

Haumann, Michael; Dau, Holger [Freie Universitaet Berlin, Inst. f. Experimentalphysik, Arnimallee 14, D-14195 Berlin (Germany)

2007-02-02

402

Fast X-ray Photon Correlation Spectroscopy measurements from the diffusion of concentrated Alpha Crystallin suspensions  

NASA Astrophysics Data System (ADS)

Alpha Crystallin constitute up to half of the total protein found in the mammalian eye lens. It has chaperone like behavior and may play a key role in maintaining lens transparency by preventing condensation of other lens proteins. We report here Fast X-ray Photon Correlation Spectroscopy (XPCS) measurements of protein diffusion within concentrated suspensions of Alpha Crystallin. Bovine calf eye lens cortices were homogenized, centrifuged and ultra-filtered to obtain concentrated Alpha Crystallin suspensions. Diffusion of proteins within these suspensions was measured as a function of temperature. The overall observed diffusion rates imply that the proteins exist in a glassy or gel phase, even at concentrations where equivalent hard sphere system would still be liquid. We interpret these results within the context of strongly interacting proteins, with protein-protein interactions possibly mediated by subunit exchange among Alpha Crystallin oligormers.

Nuwan Karunaratne, Vidanage; Debartolo, Janae; Berry, Justin; Lurio, Laurence; Thurston, George; Narayanan, Suresh; Sandy, Alec; Weizeorick, John

2011-03-01

403

Probing DNA hybridization efficiency and single base mismatch by X-ray photoelectron spectroscopy.  

PubMed

We demonstrated the use of X-ray photoelectron spectroscopy (XPS) to study DNA hybridization. Target DNA labeled with hexachloro-fluorescein (HEX) was hybridized to DNA arrays with four different probes. Each probe dot of the hybridized arrays was detected with XPS. The XPS Cl2p peak areas were found to decrease with an increase in mismatched bases in DNA probes. The Cl2p core-level peak area ratio of a probe perfectly matched to one, two and three base-mismatched probes accorded well with the results of conventional fluorescent imaging, which shows that XPS is a potential tool for analyzing DNA arrays. The DNA arrays' hybridization efficiency was assessed by the molar ratio of chlorine to phosphorus in a DNA strand, which was determined from the relevant XPS Cl2p and P2p core-level peak areas after hybridization. This could provide a new method to detect DNA hybridization efficiency. PMID:19282155

Liu, Zheng-Chun; Zhang, Xin; He, Nong-Yue; Lu, Zu-Hong; Chen, Zhen-Cheng

2009-07-01

404

X-ray photoelectron spectroscopy study of excimer laser treated alumina films  

NASA Astrophysics Data System (ADS)

Amorphous alumina layers are deposited on a single crystal Si substrate by a e-gun evaporation technique. These films are then thermally annealed in oxygen to be crystallized and, further, irradiated with an excimer laser beam. At each stage of the film preparation, an x-ray photoelectron spectroscopy analysis is performed at the film surface and in depth, upon ion beam grinding. Results give evidence for the formation of an aluminosilicate upon thermal annealing of the film in oxygen. At the surface itself, this compound is observed to decompose upon excimer laser irradiation at energy densities exceeding 1.75 J/cm2, giving rise to free Si atoms and SiO2, however with complete disappearance of Al atoms. Model photochemical reactions are proposed to explain such transformations.

Georgiev, D. G.; Kolev, K.; Laude, L. D.; Mednikarov, B.; Starbov, N.

1998-01-01

405

Comparative study of bandwidths in copper delafossites from x-ray emission spectroscopy  

NASA Astrophysics Data System (ADS)

The widths of the valence bands in the copper (I) delafossites CuGaO2 , CuInO2 , and CuScO2 have been measured by OK -shell x-ray emission spectroscopy and are compared with previous experimental work on CuAlO2 and CuCrO2 . In agreement with recent density-functional theory calculations it is found that the bandwidth decreases in the series CuAlO2>CuGaO2>CuInO2>CuScO2 . It is shown that states at the top of the valence band are of dominant Cu3dz2 atomic character but with significant mixing with O2p states.

Shin, D.; Foord, J. S.; Payne, D. J.; Arnold, T.; Aston, D. J.; Egdell, R. G.; Godinho, K. G.; Scanlon, D. O.; Morgan, B. J.; Watson, G. W.; Mugnier, E.; Yaicle, C.; Rougier, A.; Colakerol, L.; Glans, P. A.; Piper, L. F. J.; Smith, K. E.

2009-12-01

406

Insufficiency of O and Cu holes for oxide superconductivity: X-ray absorption spectroscopy  

SciTech Connect

We have studied the electronic properties of YBa/sub 2/Cu/sub 3/O/sub 7/ and EuBa/sub 2/Cu/sub 3/O/sub 7/ superconductors with soft x-ray absorption spectroscopy (XAS) at BESSY. Electronic transitions to unoccupied states (holes) of 2p and 3d character on O and Cu, respectively, are found in superconducting specimens. In samples with reduced oxygen content, superconductivity is suppressed, and a decrease in the intensity of transitions to these unoccupied states is observed. However, there is little change in these features when Zn sufficient to suppress supercondicutivity is substituted for Cu. We conclude that O 2p and Cu 3d holes are necessary but not sufficient for superconductivity.

denBoer, M.L.; Chang, C.L.; Petersen, H.; Schaible, M.; Reilly, K.; Horn, S.

1988-10-01

407

Local structure of liquid and undercooled liquid Cu probed by x-ray absorption spectroscopy.  

NASA Astrophysics Data System (ADS)

In this work we report about a recent XAS (x-ray absorption spectroscopy) experiment aimed to study the local structure of liquid and undercooled copper, a typical close-packed liquid metal, under high-pressure conditions. In our study we have obtained new experimental data of liquid Cu under high pressure and high-temperature conditions using synchrotron radiation at the ESRF and a large-volume Paris-Edinburgh cell. We have studied the extension of the undercooling region as well as possible modifications of the local structure as a function of pressure, using XAS data-analysis. Liquid copper has been undercooled up to 300°C below the melting point at high pressures up to 3.3 GPa.

Coppari, F.; Di Cicco, A.; Filipponi, A.; Trapananti, A.; Aquilanti, G.; Panfilis, S. D.

2008-07-01

408

Atomic-scale chemical quantification of oxide interfaces using energy-dispersive X-ray spectroscopy  

SciTech Connect

Atomic-scale quantification of chemical composition across oxide interfaces is important for understanding physical properties of epitaxial oxide nanostructures. Energy-dispersive X-ray spectroscopy (EDS) in an aberration-corrected scanning transmission electron microscope was used to quantify chemical composition across the interface of ferromagnetic La{sub 0.7}Sr{sub 0.3}MnO{sub 3} and antiferromagnetic BiFeO{sub 3} quantum structure. This research demonstrates that chemical composition at atomic columns can be quantified by Gaussian peak-fitting of EDS compositional profiles across the interface. Cation diffusion was observed at both A- and B-sublattice sites; and asymmetric chemical profiles exist across the interface, consistent with the previous studies.

Lu, Ping; Van Benthem, Mark [Sandia National Laboratories, P.O. Box 5800, MS 1411, Albuquerque, New Mexico 87185-1411 (United States)] [Sandia National Laboratories, P.O. Box 5800, MS 1411, Albuquerque, New Mexico 87185-1411 (United States); Xiong, Jie; Jia, Quanxi [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2013-04-29

409

Localized high spin states in transition-metal dimers: X-ray absorption spectroscopy study  

SciTech Connect

X-ray absorption spectroscopy provides direct evidence for localized valence electrons in Cr{sub 2}{sup +}, Mn{sub 2}{sup +}, and CrMn{sup +} dimer cations. Bonding in these transition-metal molecules is predominantly mediated by 4s electrons. This behavior is markedly different from other 3d transition-metal dimers with open 3d subshells and can be ascribed to the highly stable 3d{sup 5}({sup 6}S) configuration of the 3d subshell in chromium and manganese atoms and ions. In Cr{sub 2}{sup +}, Mn{sub 2}{sup +}, and CrMn{sup +}, 3d electron localization indicates local high spin states.

Lau, J. T.; Hirsch, K.; Langenberg, A.; Probst, J.; Richter, R.; Rittmann, J.; Vogel, M.; Zamudio-Bayer, V.; Moeller, T.; Issendorff, B. von [Institut fuer Optik und Atomare Physik, Technische Universitaet Berlin, EW 3-1, Hardenbergstrasse 36, D-10623 Berlin (Germany); Fakultaet fuer Physik, FMF, Universitaet Freiburg, Stefan-Meier-Strasse 21, D-79104 Freiburg (Germany)

2009-06-15

410

Development of Kilo-Pixel Arrays of Transition-Edge Sensors for X-Ray Spectroscopy  

NASA Technical Reports Server (NTRS)

We are developing kilo-pixel arrays of transition-edge sensor (TES) microcalorimeters for future X-ray astronomy observatories or for use in laboratory astrophysics applications. For example, Athena/XMS (currently under study by the european space agency) would require a close-packed 32x32 pixel array on a 250-micron pitch with < 3.0 eV full-width-half-maximum energy resolution at 6 keV and at count-rates of up to 50 counts/pixel/second. We present characterization of 32x32 arrays. These detectors will be readout using state of the art SQUID based time-domain multiplexing (TDM). We will also present the latest results in integrating these detectors and the TDM readout technology into a 16 row x N column field-able instrument.

Adams, J. S.; Bandler, S. R.; Busch, S. E.; Chervenak, J. A.; Chiao, M. P.; Eckart, M. E.; Ewin, A. J.; Finkbeiner, F. M.; Kelley, R. L.; Kelly, D. P.; Kilbourne, C. A.; Leutenegger, M. A.; Porst, J.-P.; Porter, F. S.; Ray, C. A.; Sadleir, J. E.; Smith, S. J.; Wassell, E. J.; Doriese, W. B.; Fowler, J. W.; Hilton, G. C.; Irwin, K. D.; Reintsema, C. D.; Smith, D. R.; Swetz, D. S.

2012-01-01

411

Testing of High-Resolution SI and GE Analyzers for X-Ray Raman Scattering and X-Ray Emission Spectroscopy  

SciTech Connect

A project at Stanford Linear Accelerator Center (SLAC) is currently underway for the building of a new multi-crystal x-ray spectrometer that will be used to probe the fundamental structures of light elements, including water, as well as 3d transition metals, such as metalloproteins, in dilute systems. Experimentation for determining the focal lengths for the prospective high-resolution, spherically-curved silicon (Si) and germanium (Ge) analyzers for the instrument and the energy resolutions at their respective focal points is described. The focal lengths of the Si and Ge analyzers being sampled were found by minimizing the focal size made from a diffused helium-neon (HeNe) gas laser operating at 632 nm (0.95 meV). Afterwards, the energy resolutions were determined by using synchrotron radiation (SR), in the range from 6-16 keV energies. The experiments were performed at Beamline 10-2 at the Stanford Synchrotron Radiation Laboratory (SSRL), a division of SLAC. This data, along with the energies of the incident beams, was used to determine which samples are most effective at focusing x-rays to the highest spatial and energy resolution. Sample Si (440)A, with a focal length of 1015.2 mm, had the best energy resolution. Furthermore, a new multi-crystal goniometer was tested and commissioned. As part of this work, the device was prealigned into Rowland geometry, in order to facilitate the process of finding a single high-energy resolution x-ray focus for all 7 analyzers.

Reynolds, K.W.; Bergmann, U.

2005-01-01

412

Characterization of interfacially electronic structures of gold-magnetite heterostructures using X-ray absorption spectroscopy.  

PubMed

Gold-magnetite heterostructures are novel nanomaterials which can rapidly catalyze the reduction reaction of nitroaromatics. In this study, the interfacially structural and electronic properties of various morphologies of Au-Fe3O4 heterostructures were systematically investigated using X-ray absorbance spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS). The effect of change in electronic structure and charge transfer on electrochemically catalytic activity of Au-Fe3O4 heterostructures was further evaluated by oxygen reduction reaction (ORR). The shifts in binding energy of Au4f and Fe2p peaks in XPS spectra indicate the charge transfer between the Au and Fe3O4 nanoparticles. The increase in d-hole population of Au seeds after the conjugation with iron oxides follows the order flower-like Au-Fe3O4 (FLNPs)>dumbbell-like Au-Fe3O4 (DBNPs)>Au seeds. In addition, the Fe(2+) valence state increases in Au-Fe3O4 heterostructures, which provides evidence to support the hypothesis of charge transfer between Au and Fe3O4 nanoparticles. The theoretical simulation of Au L3-edge XAS further confirms the production of Au-Fe and Au-O bonds at the interface of Au/Fe3O4 and the epitaxial linkage relationship between Au and Fe3O4 nanoparticles. In addition, the electron deficient of Au seeds increases upon increasing Fe3O4 nanoparticles on a single Au seed, and subsequently decreases the catalytic activity of Au in the Au-Fe3O4 heterostructures. The catalytic activity of Au-Fe3O4 toward ORR follows the order Au seeds>Au-Fe3O4 DBNPs>Au-Fe3O4 FLNPs, which is positively correlated to the extent of electronic deficiency of Au in Au-Fe3O4 heterostructures. PMID:24407694

Lin, Fang-hsin; Doong, Ruey-an

2014-03-01

413

Oxidation and surface segregation of chromium in Fe-Cr alloys studied by Mössbauer and X-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

The room temperature 57Fe Mössbauer and XPS spectra were measured for polycrystalline iron-based Fe-Cr alloys. The spectra were collected using three techniques: the transmission Mössbauer spectroscopy (TMS), the conversion electron Mössbauer spectroscopy (CEMS) and the X-ray photoelectron spectroscopy (XPS). The combination of these experimental techniques allows to determine changes in Cr concentration and the presence of oxygen in bulk, in the 300 nm pre-surface layer and on the surface of the studied alloys.

Idczak, R.; Idczak, K.; Konieczny, R.

2014-09-01

414

A study of the elemental composition of diabases by instrumental neutron activation and X-ray fluorescence analysis  

Microsoft Academic Search

The distribution of the elemental composition was studied mainly for microelements in the diabases of the Pechenga suite subjected\\u000a to various changes. Investigations were conducted by a combination of instrumental neutron activation INAA and X-ray fluoresence\\u000a XRFA analyses. The INAA was conducted with sample weights of 20–100 mg exposed to irradiation in a nuclear reactor by a flux\\u000a of neutrons

A. V. Gurevich; Z. V. Vikhrova; V. Ya Vyropayev; V. I. Drynkin; D. I. Leipunskaya; I. Ya. Shirokova

1980-01-01