Probing molecular orientations in thin films by x-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Li, Y.; Li, P.; Lu, Z.-H.

2018-03-01

A great number of functional organic molecules in active thin-film layers of optoelectronic devices have highly asymmetric structures, such as plate-like, rod-like, etc. This makes molecular orientation an important aspect in thin-films as it can significantly affect both the optical and electrical performance of optoelectronic devices. With a combination of in-situ ultra violet photoelectron spectroscopy (UPS) and x-ray photoelectron spectroscopy (XPS) investigations for organic molecules having a broad range of structural properties, we discovered a rigid connection of core levels and frontier highest occupied molecular orbital levels at organic interfaces. This finding opens up opportunities of using X-ray photoemission spectroscopy as an alternative tool to UPS for providing an easy and unambiguous data interpretation in probing molecular orientations.

Analysis of electronic structure of amorphous InGaZnO/SiO{sub 2} interface by angle-resolved X-ray photoelectron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ueoka, Y.; Ishikawa, Y.; Maejima, N.

2013-10-28

The electronic structures of amorphous indium gallium zinc oxide (a-IGZO) on a SiO{sub 2} layers before and after annealing were observed by constant final state X-ray photoelectron spectroscopy (CFS-XPS) and X-ray adsorption near-edge structure spectroscopy (XANES). From the results of angle-resolved CFS-XPS, the change in the electronic state was clearly observed in the a-IGZO bulk rather than in the a-IGZO/SiO{sub 2} interface. This suggests that the electronic structures of the a-IGZO bulk strongly affected the thin-film transistor characteristics. The results of XANES indicated an increase in the number of tail states upon atmospheric annealing (AT). We consider that the increasemore » in the number of tail states decreased the channel mobility of AT samples.« less

Ab Initio Theory of Dynamical Core-Hole Screening in Graphite from X-Ray Absorption Spectra

NASA Astrophysics Data System (ADS)

Wessely, O.; Katsnelson, M. I.; Eriksson, O.

2005-04-01

We have implemented the effect of dynamical core-hole screening, as given by Mahan, Nozières, and De Dominicis, in a first-principles based method and applied the theory to the x-ray absorption (XA) spectrum of graphite. It turns out that two of the conspicuous peaks of graphite are well described, both regarding the position, shape, and relative intensity, whereas one peak is absent in the theory. Only by incorporation of both excitonic and delocalized processes can a full account of the experimental spectrum be obtained theoretically, and we interpret the XA spectrum in graphite to be the result of a well screened and a poor screened process, much in the same way as is done for core level x-ray photoelectron spectroscopy.

Annealing induced atomic rearrangements on (Ga,In) (N,As) probed by hard X-ray photoelectron spectroscopy and X-ray absorption fine structure.

PubMed

Ishikawa, Fumitaro; Higashi, Kotaro; Fuyuno, Satoshi; Morifuji, Masato; Kondow, Masahiko; Trampert, Achim

2018-04-13

We study the effects of annealing on (Ga 0.64 ,In 0.36 ) (N 0.045 ,As 0.955 ) using hard X-ray photoelectron spectroscopy and X-ray absorption fine structure measurements. We observed surface oxidation and termination of the N-As bond defects caused by the annealing process. Specifically, we observed a characteristic chemical shift towards lower binding energies in the photoelectron spectra related to In. This phenomenon appears to be caused by the atomic arrangement, which produces increased In-N bond configurations within the matrix, as indicated by the X-ray absorption fine structure measurements. The reduction in the binding energies of group-III In, which occurs concomitantly with the atomic rearrangements of the matrix, causes the differences in the electronic properties of the system before and after annealing.

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.

PubMed

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

2013-07-01

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 α 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.

Valence change detection in memristive oxide based heterostructure cells by hard X-ray photoelectron emission spectroscopy

NASA Astrophysics Data System (ADS)

Kindsmüller, A.; Schmitz, C.; Wiemann, C.; Skaja, K.; Wouters, D. J.; Waser, R.; Schneider, C. M.; Dittmann, R.

2018-04-01

The switching mechanism of valence change resistive memory devices is widely accepted to be an ionic movement of oxygen vacancies resulting in a valence change of the metal cations. However, direct experimental proofs of valence changes in memristive devices are scarce. In this work, we have employed hard X-ray photoelectron emission microscopy (PEEM) to probe local valence changes in Pt/ZrOx/Ta memristive devices. The use of hard X-ray radiation increases the information depth, thus providing chemical information from buried layers. By extracting X-ray photoelectron spectra from different locations in the PEEM images, we show that zirconia in the active device area is reduced compared to a neighbouring region, confirming the valence change in the ZrOx film during electroforming. Furthermore, we succeeded in measuring the Ta 4f spectrum for two different resistance states on the same device. In both states, as well as outside the device region, the Ta electrode is composed of different suboxides without any metallic contribution, hinting to the formation of TaOx during the deposition of the Ta thin film. We observed a reduction of the Ta oxidation state in the low resistance state with respect to the high resistive state. This observation is contradictory to the established model, as the internal redistribution of oxygen between ZrOx and the Ta electrode during switching would lead to an oxidation of the Ta layer in the low resistance state. Instead, we have to conclude that the Ta electrode takes an active part in the switching process in our devices and that oxygen is released and reincorporated in the ZrOx/TaOx bilayer during switching. This is confirmed by the degradation of the high resistance state during endurance measurements under vacuum.

Inter-diffusion of copper and hafnium as studied by x-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Pearson, Justin; Chourasia, A. R.

The Cu/Hf interface has been characterized by x-ray photoelectron spectroscopy. Thin films (thicknesses ranging from 100 nm to 150 nm) of hafnium were deposited on a silicon substrate. About 80 nm of copper was then deposited on such samples. The e-beam method was used for the deposition. The samples were annealed for 30 min at temperatures of 100, 200, 300, 400, and 500°C. The inter-diffusion of copper and hafnium was investigated by sequential sputter depth profiling and x-ray photoelectron spectroscopy. The interdiffusion in each case was analyzed by the Matano-Boltzmann's procedure using the Fick's second law. The interdiffusion coefficients and the width of the interface as determined from the data have been correlated with the annealing temperature. Supported by Organized Research, TAMU-Commerce.

Second International Workshop on Ambient Pressure X-ray Photoelectron Spectroscopy

DOE PAGES

Bluhm, Hendrik; Crumlin, Ethan J.

2016-05-03

The Second International Workshop on Ambient Pressure X-ray Photoelectron Spectroscopy (APXPS) was held at Lawrence Berkeley National Laboratory (LBNL) in Berkeley, CA, from December 7-9, 2015. It brought together more than 100 participants from 17 countries. The workshop followed the inaugural meeting at the French synchrotron SOLEIL in December 2014, which was organized by François Rochet. The strong interest in these workshops reflects the growth of the APXPS community over the last decade, with instruments now operational at more than 12 synchrotrons around the world (see SRN, Vol. 27, No. 2, pp. 14–23 (2014)), and a steady increase in themore » number of laboratory instruments. Finally, APXPS has established itself as an important method for the investigation of surfaces and interfaces under in situ and operando conditions, including liquid/vapor and liquid/solid interfaces.« less

Analysis of Ti and TiO2 nanolayers by total reflection X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Kubala-Kukuś, A.; Banaś, D.; Stabrawa, I.; Szary, K.; Sobota, D.; Majewska, U.; Wudarczyk-Moćko, J.; Braziewicz, J.; Pajek, M.

2018-07-01

Total reflection X-ray photoelectron spectroscopy (TRXPS) is applied in the analysis of Ti and TiO2 nanolayers deposited on silicon and silicon dioxide substrates. The idea of application of total-reflection phenomenon for exciting X-ray used in the XPS technique is briefly discussed. The experimental setup and measurement conditions for the studied Ti and TiO2 layers are presented. The XPS spectra were registered both for the non-total and total reflection regimes. The survey spectra and C1s, N1s, Ti2p and O1s photoelectron peaks are shown. For energy calibration, the position of C1s photoelectron peak was applied (C-C component, binding energy 284.8 eV). The peak to background ratios are discussed as regards the dependence of the excitation angle. An increase of this ratio for the glancing angle 1°, being below critical angle of the X-ray beam and sample material, results in an improvement of XPS detection limit by factor up to 2. In the case of the Ti nanolayer, additionally, the thickness of the overlayer TiO2 is determined. As an example of applying the TRXPS technique, the analysis of Ti nanolayers implanted by highly charged Xe35+ ions of 280 keV energy is discussed. The Xe3d and O1s photoelectron peaks are presented and discussed.

Examination of U valence states in the brannerite structure by near-infrared diffuse reflectance and X-ray photoelectron spectroscopies

NASA Astrophysics Data System (ADS)

Finnie, Kim S.; Zhang, Zhaoming; Vance, Eric R.; Carter, Melody L.

2003-04-01

The valence state of uranium doped into a f 0 thorium analog of brannerite (i.e., thorutite) has been examined using near-infrared (NIR) diffuse reflectance (DRS) and X-ray photoelectron (XPS) spectroscopies. NIR transitions of U 4+, which are not observed in spectra of brannerite, have been detected in the samples of U xTh 1- xTi 2O 6, and we propose that strong specular reflectance is responsible for the lack of U 4+ features in UTi 2O 6. Characteristic U 5+ bands have been identified in samples in which sufficient Ca 2+ has been added to nominally effect complete oxidation to U 5+. XPS results support the assignments of U 4+ and U 5+ by DRS. The presence of residual U 4+ bands in the spectra of the Ca-doped samples is consistent with segregation of Ca 2+ to the grain boundaries during high temperature sintering.

X-Ray photoelectron diffraction and photoelectron holography as methods for investigating the local atomic structure of the surface of solids

NASA Astrophysics Data System (ADS)

Kuznetsov, M. V.; Ogorodnikov, I. I.; Vorokh, A. S.

2014-01-01

The state-of-the-art theory and experimental applications of X-ray photoelectron diffraction (XPD) and photoelectron holography (PH) are discussed. These methods are rapidly progressing and serve to examine the surface atomic structure of solids, including nanostructures formed on surfaces during adsorption of gases, epitaxial film growth, etc. The depth of analysis by these methods is several nanometres, which makes it possible to characterize the positions of atoms localized both on and beneath the surface. A remarkable feature of the XPD and PH methods is their sensitivity to the type of examined atoms and, in the case of high energy resolution, to the particular chemical form of the element under study. The data on experimental applications of XPD and PH to studies of various surface structures are analyzed and generalized. The bibliography includes 121 references.

X-Ray Photoelectron Spectroscopic Characterization of Iron Oxide Nanoparticles

NASA Astrophysics Data System (ADS)

Radu, T.; Iacovita, C.; Benea, D.; Turcu, R.

2017-05-01

We report X-ray photoelectron spectroscopy (XPS) results on iron oxide magnetic nanoparticle (Fe3O4) synthesized using solvothermal reduction in the presence of polyethylene glycol. The magnetite obtained was employed as precursor for the synthesis of γ-Fe2O3 (by oxygen dissociation) which in turn was transformed into α-Fe2O3. We confirmed the magnetite, maghemite and hematite structure by Fourier Transformed Spectroscopy (FTIR) and X-ray diffraction (XRD). The analysis of the XPS core level and valence band (VB) photoemission spectra for all investigated samples is discussed in terms of the degree of iron oxidation. This is of fundamental importance to better understand the electronic structure of the obtained iron oxide nanoparticles in order to control and improve their quality for specific biomedical applications. Moreover, theoretical band structure calculations are performed for magnetite and the separate contributions of Fe in tetragonal and octahedral environment are shown.

Interactions of gaseous molecules with X-ray photons and photoelectrons in AP-XPS study of solid surface in gas phase.

PubMed

Tao, Franklin Feng; Nguyen, Luan

2018-04-18

Studies of the surface of a catalyst in the gas phase via photoelectron spectroscopy is an important approach to establish a correlation between the surface of a catalyst under reaction conditions or during catalysis and its corresponding catalytic performance. Unlike the well understood interactions between photoelectrons and the atomic layers of a surface in ultrahigh vacuum (UHV) and the well-developed method of quantitative analysis of a solid surface in UHV, a fundamental understanding of the interactions between X-ray photons and gaseous molecules and between photoelectrons and molecules of the gas phase in ambient pressure X-ray photoelectron spectroscopy (AP-XPS) is lacking. Through well designed experiments, here the impact of the interactions between photoelectrons and gaseous molecules and interactions between X-ray photons and gaseous molecules on the intensity of the collected photoelectrons have been explored. How the changes in photoelectron intensity resulting from these interactions influence measurement of the authentic atomic ratio of element M to A of a solid surface has been discussed herein, and methods to correct the measured nominal atomic ratio of two elements of a solid surface upon travelling through a gas phase to its authentic atomic ratio have been developed.

Catalytic Properties of Surfaces Sites on Metal Oxides and Their Characterization by X-Ray Photoelectron Spectroscopy

DTIC Science & Technology

1974-01-01

gas now supplies one third of our 9 national energy needs and its use is the fastest growing of all fossil fuels , conversion of coal to...the possibilities of profiling oxidation states and to gain further insight into the mechanism of the bombarding process . (2) Application of ESCA to...the surface sites—which will be measured using x-ray photoelectron spectroscopy. This technique has general applicability to a large atttibM of

In situ study of an oxidation reaction on a Pt/C electrode by ambient pressure hard X-ray photoelectron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takagi, Yasumasa, E-mail: ytakagi@ims.ac.jp; Uemura, Yohei; Yokoyama, Toshihiko

2014-09-29

We have constructed an ambient pressure X-ray photoelectron spectroscopy instrument that uses hard X-ray radiation at the high-performance undulator beamline BL36XU of SPring-8. The dependence of the Au 4f peak intensity from Au foil on the ambient N{sub 2} pressure was measured. At a photon energy of 7.94 keV, the Au 4f peak intensity maintained 40% at 3000 Pa compared with that at high vacuum. We designed a polymer electrolyte fuel cell that allows us to perform X-ray photoelectron spectroscopy measurements of an electrode under working conditions. The oxidized Pt peaks were observed in the Pt 3d{sub 5/2} level of Pt nanoparticlesmore » in the cathode, and the peaks clearly depended on the applied voltage between the anode and cathode. Our apparatus can be applied as a valuable in situ tool for the investigation of the electronic states and adsorbed species of polymer electrolyte fuel cell electrode catalysts under the reaction conditions.« less

Digital imaging with solid state x-ray image intensifiers

NASA Astrophysics Data System (ADS)

Damento, Michael A.; Radspinner, Rachel; Roehrig, Hans

1999-10-01

X-ray cameras in which a CCD is lens coupled to a large phosphor screen are known to suffer from a loss of x-ray signal due to poor light collection from conventional phosphors, making them unsuitable for most medical imaging applications. By replacing the standard phosphor with a solid-state image intensifier, it may be possible to improve the signal-to-noise ratio of the images produced with these cameras. The solid-state x-ray image intensifier is a multi- layer device in which a photoconductor layer controls the light output from an electroluminescent phosphor layer. While prototype devices have been used for direct viewing and video imaging, they are only now being evaluated in a digital imaging system. In the present work, the preparation and evaluation of intensifiers with a 65 mm square format are described. The intensifiers are prepared by screen- printing or doctor blading the following layers onto an ITO coated glass substrate: ZnS phosphor, opaque layer, CdS photoconductor, and carbon conductor. The total thickness of the layers is approximately 350 micrometers , 350 VAC at 400 Hz is applied to the device for operation. For a given x-ray dose, the intensifiers produce up to three times the intensity (after background subtracting) of Lanex Fast Front screens. X-ray images produced with the present intensifiers are somewhat noisy and their resolution is about half that of Lanex screens. Modifications are suggested which could improve the resolution and noise of the intensifiers.

Electronic structure of β-Ga2O3 single crystals investigated by hard X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Li, Guo-Ling; Zhang, Fabi; Cui, Yi-Tao; Oji, Hiroshi; Son, Jin-Young; Guo, Qixin

2015-07-01

By combination of hard X-ray photoelectron spectroscopy (HAXPES) and first-principles band structure calculations, the electronic states of β-Ga2O3 were investigated to deepen the understanding of bulk information for this compound. The valence band spectra of HAXPES presented the main contribution from Ga 4sp, which are well represented by photoionization cross section weighted partial density of states. The experimental data complemented with the theoretical study yield a realistic picture of the electronic structure for β-Ga2O3.

Theory of time-resolved x-ray photoelectron diffraction from transient conformational molecules

NASA Astrophysics Data System (ADS)

Tsuru, Shota; Sako, Tokuei; Fujikawa, Takashi; Yagishita, Akira

2017-04-01

We formulate x-ray photoelectron diffraction (XPD) from molecules undergoing photochemical reactions induced by optical laser pulses, and then apply the formula to the simulation of time-dependent XPD profiles from both dissociating I2 molecules and bending C S2 molecules. The dependence of nuclear wave-packet motions on the intensity and shape of the optical laser pulses is examined. As a result, the XPD simulations based on such nuclear wave-packet calculations are observed to exhibit characteristic features, which are compared with the XPD profiles due to classical trajectories of nuclear motions. The present study provides a methodology toward creating "molecular movies" of ultrafast photochemical reactions by means of femtosecond XPD with x-ray free-electron lasers.

Soft X-ray spectroscopy of nanoparticles by velocity map imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kostko, O.; Xu, B.; Jacobs, M. I.

Velocity map imaging (VMI), a technique traditionally used to study chemical dynamics in the gas phase, is applied to study X-ray photoemission from aerosol nanoparticles. Soft X-rays from the Advanced Light Source synchrotron, probe a beam of nanoparticles, and the resulting photoelectrons are velocity mapped to obtain their kinetic energy distributions. A new design of the VMI spectrometer is described. The spectrometer is benchmarked by measuring vacuum ultraviolet photoemission from gas phase xenon and squalene nanoparticles followed by measurements using soft X-rays. It is demonstrated that the photoelectron distribution from X-ray irradiated squalene nanoparticles is dominated by secondary electrons. Bymore » scanning the photon energies and measuring the intensities of these secondary electrons, a near edge X-ray absorption fine structure (NEXAFS) spectrum is obtained. The NEXAFS technique is used to obtain spectra of aqueous nanoparticles at the oxygen K edge. By varying the position of the aqueous nanoparticle beam relative to the incident X-ray beam, evidence is presented such that the VMI technique allows for NEXAFS spectroscopy of water in different physical states. Finally, we discuss the possibility of applying VMI methods to probe liquids and solids via X-ray spectroscopy.« less

Soft X-ray spectroscopy of nanoparticles by velocity map imaging

DOE PAGES

Kostko, O.; Xu, B.; Jacobs, M. I.; ...

2017-05-05

Velocity map imaging (VMI), a technique traditionally used to study chemical dynamics in the gas phase, is applied to study X-ray photoemission from aerosol nanoparticles. Soft X-rays from the Advanced Light Source synchrotron, probe a beam of nanoparticles, and the resulting photoelectrons are velocity mapped to obtain their kinetic energy distributions. A new design of the VMI spectrometer is described. The spectrometer is benchmarked by measuring vacuum ultraviolet photoemission from gas phase xenon and squalene nanoparticles followed by measurements using soft X-rays. It is demonstrated that the photoelectron distribution from X-ray irradiated squalene nanoparticles is dominated by secondary electrons. Bymore » scanning the photon energies and measuring the intensities of these secondary electrons, a near edge X-ray absorption fine structure (NEXAFS) spectrum is obtained. The NEXAFS technique is used to obtain spectra of aqueous nanoparticles at the oxygen K edge. By varying the position of the aqueous nanoparticle beam relative to the incident X-ray beam, evidence is presented such that the VMI technique allows for NEXAFS spectroscopy of water in different physical states. Finally, we discuss the possibility of applying VMI methods to probe liquids and solids via X-ray spectroscopy.« less

Investigation of nanoparticulate silicon as printed layers using scanning electron microscopy, transmission electron microscopy, X-ray absorption spectroscopy and X-ray photoelectron spectroscopy

DOE PAGES

Unuigbe, David M.; Harting, Margit; Jonah, Emmanuel O.; ...

2017-08-21

The presence of native oxide on the surface of silicon nanoparticles is known to inhibit charge transport on the surfaces. Scanning electron microscopy (SEM) studies reveal that the particles in the printed silicon network have a wide range of sizes and shapes. High-resolution transmission electron microscopy reveals that the particle surfaces have mainly the (111)- and (100)-oriented planes which stabilizes against further oxidation of the particles. X-ray absorption spectroscopy (XANES) and X-ray photoelectron spectroscopy (XPS) measurements at the O 1s-edge have been utilized to study the oxidation and local atomic structure of printed layers of silicon nanoparticles which were milledmore » for different times. XANES results reveal the presence of the +4 (SiO 2) oxidation state which tends towards the +2 (SiO) state for higher milling times. Si 2pXPS results indicate that the surfaces of the silicon nanoparticles in the printed layers are only partially oxidized and that all three sub-oxide, +1 (Si 2O), +2 (SiO) and +3 (Si 2O 3), states are present. The analysis of the change in the sub-oxide peaks of the silicon nanoparticles shows the dominance of the +4 state only for lower milling times.« less

Spectroscopic imaging, diffraction, and holography with x-ray photoemission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1992-02-01

X-ray probes are capable of determining the spatial structure of an atom in a specific chemical state, over length scales from about a micron all the way down to atomic resolution. Examples of these probes include photoemission microscopy, energy-dependent photoemission diffraction, photoelectron holography, and X-ray absorption microspectroscopy. Although the method of image formation, chemical-state sensitivity, and length scales can be very different, these X-ray techniques share a common goal of combining a capability for structure determination with chemical-state specificity. This workshop will address recent advances in holographic, diffraction, and direct imaging techniques using X-ray photoemission on both theoretical and experimentalmore » fronts. A particular emphasis will be on novel structure determinations with atomic resolution using photoelectrons.« less

X-ray photoelectron spectroscopy study of chemically-etched Nd-Ce-Cu-O surfaces

NASA Technical Reports Server (NTRS)

Vasquez, R. P.; Gupta, A.; Kussmaul, A.

1991-01-01

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.

Bandpass x-ray diode and x-ray multiplier detector

DOEpatents

Wang, C.L.

1982-09-27

An absorption-edge of an x-ray absorption filter and a quantum jump of a photocathode determine the bandpass characteristics of an x-ray diode detector. An anode, which collects the photoelectrons emitted by the photocathode, has enhanced amplification provided by photoelectron-multiplying means which include dynodes or a microchannel-plate electron-multiplier. Suppression of undesired high frequency response for a bandpass x-ray diode is provided by subtracting a signal representative of energies above the passband from a signal representative of the overall response of the bandpass diode.

Photoelectron Diffraction from Valence States of Oriented Molecules

NASA Astrophysics Data System (ADS)

Krüger, Peter

2018-06-01

The angular distribution of photoelectrons emitted from valence states of oriented molecules is investigated. The principles underlying the angular pattern formation are explained in terms of photoelectron wave interference, caused by initial state delocalization and final state photoelectron scattering. Computational approaches to photoelectron spectroscopy from molecules are briefly reviewed. Here a combination of molecular orbital calculations for the initial state and multiple scattering theory for the photoelectron final state is used and applied to the 3σ and 4σ orbitals of nitrogen and the highest occupied molecular orbital of pentacene. Appreciable perpendicular emission and circular dichroism in angular distributions is found, two effects that cannot be described by the popular plane wave approximation to the photoelectron final state.

Near Edge X-Ray Absorption and X-Ray Photoelectron Diffraction Studies of the Structural Environment of Ge-Si Systems

NASA Astrophysics Data System (ADS)

Castrucci, P.; Gunnella, R.; Pinto, N.; Bernardini, R.; de Crescenzi, M.; Sacchi, M.

Near edge X-ray absorption spectroscopy (XAS), X-ray photoelectron diffraction (XPD) and Auger electron diffraction (AED) are powerful techniques for the qualitative study of the structural and electronic properties of several systems. The recent development of a multiple scattering approach to simulating experimental spectra opened a friendly way to the study of structural environments of solids and surfaces. This article reviews recent X-ray absorption experiments using synchrotron radiation which were performed at Ge L edges and core level electron diffraction measurements obtained using a traditional X-ray source from Ge core levels for ultrathin Ge films deposited on silicon substrates. Thermodynamics and surface reconstruction have been found to play a crucial role in the first stages of Ge growth on Si(001) and Si(111) surfaces. Both techniques show the occurrence of intermixing processes even for room-temperature-grown Ge/Si(001) samples and give a straightforward measurement of the overlayer tetragonal distortion. The effects of Sb as a surfactant on the Ge/Si(001) interface have also been investigated. In this case, evidence of layer-by-layer growth of the fully strained Ge overlayer with a reduced intermixing is obtained when one monolayer of Sb is predeposited on the surface.

Quantitative interpretation of molecular dynamics simulations for X-ray photoelectron spectroscopy of aqueous solutions

NASA Astrophysics Data System (ADS)

Olivieri, Giorgia; Parry, Krista M.; Powell, Cedric J.; Tobias, Douglas J.; Brown, Matthew A.

2016-04-01

Over the past decade, energy-dependent ambient pressure X-ray photoelectron spectroscopy (XPS) has emerged as a powerful analytical probe of the ion spatial distributions at the vapor (vacuum)-aqueous electrolyte interface. These experiments are often paired with complementary molecular dynamics (MD) simulations in an attempt to provide a complete description of the liquid interface. There is, however, no systematic protocol that permits a straightforward comparison of the two sets of results. XPS is an integrated technique that averages signals from multiple layers in a solution even at the lowest photoelectron kinetic energies routinely employed, whereas MD simulations provide a microscopic layer-by-layer description of the solution composition near the interface. Here, we use the National Institute of Standards and Technology database for the Simulation of Electron Spectra for Surface Analysis (SESSA) to quantitatively interpret atom-density profiles from MD simulations for XPS signal intensities using sodium and potassium iodide solutions as examples. We show that electron inelastic mean free paths calculated from a semi-empirical formula depend strongly on solution composition, varying by up to 30% between pure water and concentrated NaI. The XPS signal thus arises from different information depths in different solutions for a fixed photoelectron kinetic energy. XPS signal intensities are calculated using SESSA as a function of photoelectron kinetic energy (probe depth) and compared with a widely employed ad hoc method. SESSA simulations illustrate the importance of accounting for elastic-scattering events at low photoelectron kinetic energies (<300 eV) where the ad hoc method systematically underestimates the preferential enhancement of anions over cations. Finally, some technical aspects of applying SESSA to liquid interfaces are discussed.

Photoelectron Spectroscopy for Identification of Chemical States

NASA Technical Reports Server (NTRS)

Novakov, T.

1971-01-01

The technique of X-ray photoelectron spectroscopy and the fundamental electronic interactions constituting the basis of the method will be discussed. The method provides information about chemical states ("oxidation states") of atoms in molecules. In addition, quantitative elemental analysis can be performed using the same method. On the basis of this information identification of chemical species is possible. Examples of applications are discussed with particular references to the study of smog particulate matter.

Ambient-Pressure X-ray Photoelectron Spectroscopy to Characterize the Solid/Liquid Interface: Probing the Electrochemical Double Layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Favaro, Marco; Liu, Zhi; Crumlin, Ethan J.

Ambient-pressure X-ray photoelectron spectroscopy (APXPS) has contributed greatly to a wide range of research fields, including environmental science, catalysis, and electrochemistry, to name a few. The use of this technique at synchrotron facilities primarily focused on probing the solid/gas interface; however, it quickly advanced to the probing of liquid/vapor interfaces and solid/liquid interfaces through an X-ray-transparent window. Most recently, combining APXPS with “Tender” X-rays (~2.5 keV to 8 keV) on beamline 9.3.1 at the Advanced Light Source in Lawrence Berkeley National Laboratory (which can generate photoelectrons with much longer inelastic mean free paths) has enabled us to probe the solid/liquidmore » interface without needing a window. This innovation allows us to probe interfacial chemistries of electrochemically controlled solid/liquid interfaces undergoing charge transfer reactions. Lastly, these advancements have transitioned APXPS from a traditional surface science tool to an essential interface science technique.« less

Ambient-Pressure X-ray Photoelectron Spectroscopy to Characterize the Solid/Liquid Interface: Probing the Electrochemical Double Layer

DOE PAGES

Favaro, Marco; Liu, Zhi; Crumlin, Ethan J.

2017-03-31

Ambient-pressure X-ray photoelectron spectroscopy (APXPS) has contributed greatly to a wide range of research fields, including environmental science, catalysis, and electrochemistry, to name a few. The use of this technique at synchrotron facilities primarily focused on probing the solid/gas interface; however, it quickly advanced to the probing of liquid/vapor interfaces and solid/liquid interfaces through an X-ray-transparent window. Most recently, combining APXPS with “Tender” X-rays (~2.5 keV to 8 keV) on beamline 9.3.1 at the Advanced Light Source in Lawrence Berkeley National Laboratory (which can generate photoelectrons with much longer inelastic mean free paths) has enabled us to probe the solid/liquidmore » interface without needing a window. This innovation allows us to probe interfacial chemistries of electrochemically controlled solid/liquid interfaces undergoing charge transfer reactions. Lastly, these advancements have transitioned APXPS from a traditional surface science tool to an essential interface science technique.« less

X-ray photoelectron spectroscopic study of water adsorption on iron sulphide minerals

NASA Astrophysics Data System (ADS)

Knipe, S. W.; Mycroft, J. R.; Pratt, A. R.; Nesbitt, H. W.; Bancroff, G. M.

1995-03-01

Samples of natural pyrrhotite and pyrite were fractured within the analytical chamber of an X-ray photoelectron spectrometer. The pristine mineral surfaces were then exposed, in the absence of oxygen, to total doses of 100, 200, 400, 800, 1400, 28,000, and 300,000 Langmuirs (L) of D2O. X-ray photoelectron spectroscopic (XPS) analyses were performed between each water dose, to investigate the interaction of these iron sulphide surfaces with water vapour. Recorded Fe and S photoelectron spectra showed no evidence of oxidation products on either mineral, even at highest D2O doses, nor could an oxide oxygen signal be fitted in the spectra for either mineral. On pyrrhotite, the O 1s spectra are composed of contributions from dominantly hydroxyl (at 532.0 ± 0.2 eV ) and subordinate chemisorbed water (at 533.5 ± 0.2 eV) signals. The main O is peak on pyrite is also formed from hydroxyl (531.0 ± 0.3 eV) and adsorbed water/hydroxyl (at 532.3 eV) signals. However, some O is spectra recorded on pyrite have peaks at anomalously high binding energies (>535 eV ). The anomalous high binding energy species are attributed to electrically-isolated OH/H2O, as reported elsewhere, and to liquid-like water, which has not previously been described in the literature. Pyrrhotite and pyrite interact with water via fundamentally different processes. Pyrrhotite reaction involves the donation of electron charge through Fe vacancies, whereas the water species detected on pyrite interact with the Fe 3d (eg) molecular orbital, and it is suggested that hydrogen bonding with the disulphide moiety may be important.

Reduction of Vanadium Oxide (VOx) under High Vacuum Conditions as Investigated by X-Ray Photoelectron Spectroscopy

NASA Astrophysics Data System (ADS)

Chourasia, A.

2015-03-01

Vanadium oxide thin films were formed by depositing thin films of vanadium on quartz substrates and oxidizing them in an atmosphere of oxygen. The deposition was done by the e-beam technique. The oxide films were annealed at different temperatures for different times under high vacuum conditions. The technique of x-ray photoelectron spectroscopy has been employed to study the changes in the oxidation states of vanadium and oxygen in such films. The spectral features in the vanadium 2p, oxygen 1s, and the x-ray excited Auger regions were investigated. The Auger parameter has been utilized to study the changes. The complete oxidation of elemental vanadium to V2O5 was observed to occur at 700°C. At any other temperature, a mixture of oxides consisting of V2O5 and VO2 was observed in the films. Annealing of the films resulted in the gradual loss of oxygen followed by reduction in the oxidation state from +5 to 0. The reduction was observed to depend upon the annealing temperature and the annealing time. Organized Research, TAMU-Commerce.

Summary: Update to ASTM Guide E 1523 to Charge Control and Charge Referencing Techniques in X-ray Photoelectron Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baer, Donald R.

2005-04-22

An updated version of the ASTM guide E1523 to the methods to charge control and charge referencing techniques in x-ray photoelectron spectroscopy has been released by ASTM. The guide is meant to acquaint x-ray photoelectron spectroscopy (XPS) users with the various charge control and charge referencing techniques that are and have been used in the acquisition and interpretation of XPS data from surfaces of insulating specimens. The current guide has been expanded to include new references as well as recommendations for reporting information on charge control and charge referencing. The previous version of the document had been published in 1997.

Composition of RF-sputtered refractory compounds determined by X-ray photoelectron spectroscopy

NASA Technical Reports Server (NTRS)

Wheeler, D. R.; Brainard, W. A.

1978-01-01

RF-sputtered coatings of CrB2, MoSi2, Mo2C, TiC, and MoS2 were examined by X-ray photoelectron spectroscopy (XPS). Data on stoichiometry, impurity content, and chemical bonding were obtained. The influences of sputtering target history, deposition time, RF power level, and substrate bias were studied. Significant deviations from stoichiometry and high oxide levels were related to target outgassing. The effect of substrate bias depended on the particular coating material studied.

X ray screening at entry and systematic screening for the control of tuberculosis in a highly endemic prison.

PubMed

Sanchez, Alexandra; Massari, Veronique; Gerhardt, Germano; Espinola, Ana Beatriz; Siriwardana, Mahinda; Camacho, Luiz Antonio B; Larouzé, Bernard

2013-10-20

Tuberculosis (TB) is a major issue in prisons of low and middle income countries where TB incidence rates are much higher in prison populations as compared with the general population. In the Rio de Janeiro (RJ) State prison system, the TB control program is limited to passive case-finding and supervised short duration treatment. The aim of this study was to measure the impact of X-ray screening at entry associated with systematic screening on the prevalence and incidence of active TB. We followed up for 2 years a RJ State prison for adult males (1429 inmates at the beginning of the study) and performed, in addition to passive case-finding, 1) two "cross-sectional" X-ray systematic screenings: the first at the beginning of the study period and the second 13 months later; 2) X-ray screening of inmates entering the prison during the 2 year study period. Bacteriological examinations were performed in inmates presenting any pulmonary, pleural or mediastinal X-ray abnormality or spontaneously attending the prison clinic for symptoms suggestive of TB. Overall, 4326 X-rays were performed and 246 TB cases were identified. Prevalence among entering inmates remained similar during 1st and the 2nd year of the study: 2.8% (21/754) and 2.9% (28/954) respectively, whereas prevalence decreased from 6.0% (83/1374) to 2.8% (35/1244) between 1st and 2nd systematic screenings (p < 0.0001). Incidence rates of cases identified by passive case-finding decreased from 42 to 19 per 1000 person-years between the 1st and the 2nd year (p < 0.0001). Cases identified by screenings were less likely to be bacteriologically confirmed as compared with cases identified by passive-case finding. The strategy investigated, which seems highly effective, should be considered in highly endemic confined settings such as prisons.

X-Ray Photoelectron Spectroscopy of Stabilized Zirconia Films with Embedded Au Nanoparticles Formed under Irradiation with Gold Ions

NASA Astrophysics Data System (ADS)

Zubkov, S. Yu.; Antonov, I. N.; Gorshkov, O. N.; Kasatkin, A. P.; Kryukov, R. N.; Nikolichev, D. E.; Pavlov, D. A.; Shenina, M. E.

2018-03-01

Nanosized films of stabilized zirconia with Au nanoparticles formed by implanting Au ions are studied by X-ray photoelectron spectroscopy and transmission electron microscopy. The effect of irradiation of films with Au ions and postimplantation annealing on the distribution of chemical elements and zirconium- containing ZrO x compounds over the depth of the films is studied. Based on the data on the dimensional shift of the Au 4 f photoelectron line, the average value of the nanoparticle size is determined.

Photochemical conversion of tin-oxo cage compounds studied using hard x-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Zhang, Yu; Haitjema, Jarich; Liu, Xiaomeng; Johansson, Fredrik; Lindblad, Andreas; Castellanos, Sonia; Ottosson, Niklas; Brouwer, Albert M.

2017-03-01

Several metal-containing molecular inorganic materials are currently considered as photoresists for extreme ultraviolet lithography (EUVL). This is primarily due to their high EUV absorption cross section and small building block size, properties which potentially allow both high sensitivity and resolution as well as low line-edge roughness. The photochemical reaction mechanisms that allow these kinds of materials to function as photoresists, however, are still poorly understood. As a step in this direction, we here discuss photochemical reactions upon deep UV (DUV) irradiation of a model negative-tone EUV photoresist material, namely the well-defined molecular tin-oxo cage compound [(SnR)12O14(OH)6]X2 (R = organic group; X = anion) which is spin coated to thin layers of 20 nm. The core electronic structure (Sn 3d, O 1s and C 1s) of fresh and DUV exposed films were then investigated using synchrotron radiationbased hard X-ray photoelectron spectroscopy (HAXPES). This method provides information about the structure and chemical state of the respective atoms in the material. We performed a comparative HAXPES study of the composition of the tin-oxo cage compound [(SnR)12O14(OH)6](OH)2, either fresh directly after spin-coated vs. DUV-exposed materials under either ambient condition or under a dry N2 atmosphere. Different chemical oxidation states and concentrations of atoms and atom types in the fresh and exposed films were found. We further found that the chemistry resulting from exposure in air and N2 is strikingly different, clearly illustrating the influence of film-gas interactions on the (photo)chemical processes that eventually determine the photoresist. Finally, a mechanistic hypothesis for the basic DUV photoreactions in molecular tin-oxo cages is proposed.

3D X-Ray Luggage-Screening System

NASA Technical Reports Server (NTRS)

Fernandez, Kenneth

2006-01-01

A three-dimensional (3D) x-ray luggage- screening system has been proposed to reduce the fatigue experienced by human inspectors and increase their ability to detect weapons and other contraband. The system and variants thereof could supplant thousands of xray scanners now in use at hundreds of airports in the United States and other countries. The device would be applicable to any security checkpoint application where current two-dimensional scanners are in use. A conventional x-ray luggage scanner generates a single two-dimensional (2D) image that conveys no depth information. Therefore, a human inspector must scrutinize the image in an effort to understand ambiguous-appearing objects as they pass by at high speed on a conveyor belt. Such a high level of concentration can induce fatigue, causing the inspector to reduce concentration and vigilance. In addition, because of the lack of depth information, contraband objects could be made more difficult to detect by positioning them near other objects so as to create x-ray images that confuse inspectors. The proposed system would make it unnecessary for a human inspector to interpret 2D images, which show objects at different depths as superimposed. Instead, the system would take advantage of the natural human ability to infer 3D information from stereographic or stereoscopic images. The inspector would be able to perceive two objects at different depths, in a more nearly natural manner, as distinct 3D objects lying at different depths. Hence, the inspector could recognize objects with greater accuracy and less effort. The major components of the proposed system would be similar to those of x-ray luggage scanners now in use. As in a conventional x-ray scanner, there would be an x-ray source. Unlike in a conventional scanner, there would be two x-ray image sensors, denoted the left and right sensors, located at positions along the conveyor that are upstream and downstream, respectively (see figure). X-ray illumination

A Chemical View on X-ray Photoelectron Spectroscopy: the ESCA Molecule and Surface-to-Bulk XPS Shifts.

PubMed

Delesma, Francisco A; Van den Bossche, Maxime; Grönbeck, Henrik; Calaminici, Patrizia; Köster, Andreas M; Pettersson, Lars G M

2018-01-19

In this paper we remind the reader of a simple, intuitive picture of chemical shifts in X-ray photoelectron spectroscopy (XPS) as the difference in chemical bonding between the probed atom and its neighbor to the right in the periodic table, the so called Z+1 approximation. We use the classical ESCA molecule, ethyl trifluoroacetate, and 4d-transition metals to explicitly demonstrate agreement between core-level shifts computed as differences between final core-hole states and the approach where each core-ionized atom is replaced by a Z+1 atom. In this final state, or total energy picture, the XPS shift arises due to the more or less unfavorable chemical bonding of the effective nitrogen in the carbon geometry for the ESCA molecule. Surface core level shifts in metals are determined by whether the Z+1 atom as an alloy segregates to the surface or is more soluble in the bulk. As further illustration of this more chemical picture, we compare the geometry of C 1s and O 1s core-ionized CO with that of, respectively, NO + and CF + . The scope is not to propose a new method to compute XPS shifts but rather to stress the validity of this simple interpretation. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hard X-ray photoelectron spectroscopy of Li{sub x}Ni{sub 1−x}O epitaxial thin films with a high lithium content

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumara, L. S. R., E-mail: KUMARA.Rosantha@nims.go.jp; Yang, Anli; Sakata, Osami, E-mail: SAKATA.Osami@nims.go.jp

2014-07-28

The core-level and valence-band electronic structures of Li{sub x}Ni{sub 1−x}O epitaxial thin films with x = 0, 0.27, and 0.48 were studied by hard X-ray photoelectron spectroscopy. A double peak structure, consisting of a main peak and a shoulder peak, and a satellite structure were observed in the Ni 2p{sub 3/2} core-level spectra. The intensity ratio of the shoulder to main peak in this double peak structure increased with increasing lithium content in Li{sub x}Ni{sub 1−x}O. This lithium doping dependence of the Ni 2p{sub 3/2} core-level spectra was investigated using an extended cluster model, which included the Zhang–Rice (ZR) doubletmore » bound states arising from a competition between O 2p – Ni 3d hybridization and the Ni on-site Coulomb interaction. The results indicated that the change in the intensity ratio in the main peak is because of a reduction in the ZR doublet bound states from lithium substitutions. This strongly suggests that holes compensating Li doping in Li{sub x}Ni{sub 1−x}O are of primarily ZR character.« less

Characterization of CuHal-intercalated carbon nanotubes with x-ray absorption spectroscopy combined with x-ray photoelectron and resonant photoemission spectroscopies

NASA Astrophysics Data System (ADS)

Brzhezinskaya, M.; Generalov, A.; Vinogdradov, A.; Eliseev, A.

2013-04-01

Encapsulated single-walled carbon nanotubes (SWCNTs) with inner channels filled by different compounds present the new class of composite materials. Such CNTs give opportunity to form 1D nanocrystals as well as quantum nanowires with new physical and chemical properties inside the tubes. The present study is aimed to characterize the possible chemical interaction between CuHal (Hal=I, Cl, Br) and SWCNTs in CuHal@SWCNTs and electronic structure of the latter using high-resolution near edge X-ray absorption fine structure (NEXAFS) spectroscopy combined with high-resolution X-ray photoelectron spectroscopy and resonant photoemission spectroscopy. The present study has shown that there is a chemical interaction between the filler and π-electron subsystem of CNTs which is accompanied by changes of the atomic and electronic structure of the filler during the encapsulating it inside CNTs.

Native State Mass Spectrometry, Surface Plasmon Resonance, and X-ray Crystallography Correlate Strongly as a Fragment Screening Combination.

PubMed

Woods, Lucy A; Dolezal, Olan; Ren, Bin; Ryan, John H; Peat, Thomas S; Poulsen, Sally-Ann

2016-03-10

Fragment-based drug discovery (FBDD) is contingent on the development of analytical methods to identify weak protein-fragment noncovalent interactions. Herein we have combined an underutilized fragment screening method, native state mass spectrometry, together with two proven and popular fragment screening methods, surface plasmon resonance and X-ray crystallography, in a fragment screening campaign against human carbonic anhydrase II (CA II). In an initial fragment screen against a 720-member fragment library (the "CSIRO Fragment Library") seven CA II binding fragments, including a selection of nonclassical CA II binding chemotypes, were identified. A further 70 compounds that comprised the initial hit chemotypes were subsequently sourced from the full CSIRO compound collection and screened. The fragment results were extremely well correlated across the three methods. Our findings demonstrate that there is a tremendous opportunity to apply native state mass spectrometry as a complementary fragment screening method to accelerate drug discovery.

Combined soft and hard X-ray ambient pressure photoelectron spectroscopy studies of semiconductor/electrolyte interfaces

DOE PAGES

Starr, David E.; Favaro, Marco; Abdi, Fatwa F.; ...

2017-05-18

The development of solar fuel generating materials would greatly benefit from a molecular level understanding of the semiconductor/electrolyte interface and changes in the interface induced by an applied potential and illumination by solar light. Ambient pressure photoelectron spectroscopy techniques with both soft and hard X-rays, AP-XPS and AP-HAXPES respectively, have the potential to markedly contribute to this understanding. In this paper we initially provide two examples of current challenges in solar fuels material development that AP-XPS and AP-HAXPES can directly a ddress. This will be followed by a brief description of the distinguishing and complementary characteristics of soft and hardmore » X-ray AP-XPS and AP-HAXPES and best approaches to achieving monolayer sensitivity in solid/aqueous electrolyte studies. In particular we focus on the detection of surface adsorbed hydroxyl groups in the presence of aqueous hydroxide anions in the electrolyte, a common situation when investigating photoanodes for solar fuel generating applications. Finally, the article concludes by providing an example of a combined AP-XPS and AP-HAXPES study of a semiconductor/aqueous electrolyte interface currently used in water splitting devices specifically the BiVO 4/aqueous potassium phosphate electrolyte interface.« less

X-ray photoelectron spectroscopy and atomic force microscopy characterization of the effects of etching Zn xCd 1- xTe surfaces

NASA Astrophysics Data System (ADS)

George, M. A.; Azoulay, M.; Jayatirtha, H. N.; Burger, A.; Collins, W. E.; Silberman, E.

1993-10-01

X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) was used for the first time to characterize the chemical composition of modified surfaces of Zn xCd 1- xTe single crystals. These surface treatments were selected for their relevance to device preparation procedures. The XPS peaks indicated an increase of the tellurium and a depletion of the cadmium concentrations upon etching in bromine methanol solution. AFM revealed the formation of pronounced Te inclusions. Higher x values correlated with a decrease in residual bromine left on the surface, while cut and polished samples had higher oxide concentrations and increased bromination of the surface than cleaved samples.

p-Type dopant incorporation and surface charge properties of catalyst-free GaN nanowires revealed by micro-Raman scattering and X-ray photoelectron spectroscopy.

PubMed

Wang, Q; Liu, X; Kibria, M G; Zhao, S; Nguyen, H P T; Li, K H; Mi, Z; Gonzalez, T; Andrews, M P

2014-09-07

Micro-Raman scattering and X-ray photoelectron spectroscopy were employed to investigate Mg-doped GaN nanowires. With the increase of Mg doping level, pronounced Mg-induced local vibrational modes were observed. The evolution of longitudinal optical phonon-plasmon coupled mode, together with detailed X-ray photoelectron spectroscopy studies, show that the near-surface region of nanowires can be transformed from weakly n-type to p-type with the increase of Mg doping.

Hard x-ray photoelectron spectroscopy equipment developed at beamline BL46XU of SPring-8 for industrial researches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yasuno, Satoshi, E-mail: yasuno@spring8.or.jp; Koganezawa, Tomoyuki; Watanabe, Takeshi

Hard X-ray photoelectron spectroscopy (HAXPES) is a powerful tool for investigating the chemical and electronic states of bulk and buried interface in a non-destructive manner due to the large probing depth of this technique. At BL46XU of SPring-8, there are two HAXPES systems equipped with different electron spectrometers, which can be utilized appropriately according to the purpose in various industrial researches. In this article, these systems are outlined, and two typical examples of HAXPES studies performed by them are presented, which focus on the silicidation at Ni/SiC interface and the energy distribution of interface states at SiO{sub 2}/a-InGaZnO.

Fortran Program for X-Ray Photoelectron Spectroscopy Data Reformatting

NASA Technical Reports Server (NTRS)

Abel, Phillip B.

1989-01-01

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.

Characterization of Colloidal Quantum Dot Ligand Exchange by X-ray Photoelectron Spectroscopy

NASA Astrophysics Data System (ADS)

Atewologun, Ayomide; Ge, Wangyao; Stiff-Roberts, Adrienne D.

2013-05-01

Colloidal quantum dots (CQDs) are chemically synthesized semiconductor nanoparticles with size-dependent wavelength tunability. Chemical synthesis of CQDs involves the attachment of long organic surface ligands to prevent aggregation; however, these ligands also impede charge transport. Therefore, it is beneficial to exchange longer surface ligands for shorter ones for optoelectronic devices. Typical characterization techniques used to analyze surface ligand exchange include Fourier-transform infrared spectroscopy, x-ray diffraction, transmission electron microscopy, and nuclear magnetic resonance spectroscopy, yet these techniques do not provide a simultaneously direct, quantitative, and sensitive method for evaluating surface ligands on CQDs. In contrast, x-ray photoelectron spectroscopy (XPS) can provide nanoscale sensitivity for quantitative analysis of CQD surface ligand exchange. A unique aspect of this work is that a fingerprint is identified for shorter surface ligands by resolving the regional XPS spectrum corresponding to different types of carbon bonds. In addition, a deposition technique known as resonant infrared matrix-assisted pulsed laser evaporation is used to improve the CQD film uniformity such that stronger XPS signals are obtained, enabling more accurate analysis of the ligand exchange process.

The surface of 1-euro coins studied by X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Gou, F.; Gleeson, M. A.; Villette, J.; Kleyn, S. E. F.; Kleyn, A. W.

2004-03-01

The two alloy surfaces (pill and ring) that are present on 1-euro coins have been studied by X-ray photoelectron spectroscopy (XPS). Comparison is made between coins from general circulation and coin surfaces that have been subjected to a variety of cleaning and oxidation treatments. The concentrations and possible oxidation states of the metals (nickel, copper and zinc) at the surface were derived from analysis of the 2p 3/2 core levels. The surface atomic ratios measured for the pill and the ring parts of the euro coins were compared to the official bulk ratios. This study shows a clear nickel enrichment of both pill and ring surfaces. Nickel at surface seems to be present mainly in hydroxide form although the chloride form cannot be excluded. A small concentration of zinc was present on the surface of the pill, even though it is not present in the bulk alloy. Evidence of both nickel and zinc surface enrichment is observed for the ring. No surface enrichment is observed for the atomically clean or oxidized alloy surfaces over a 60-h time scale.

X-ray Photoelectron Spectroscopy of High-κ Dielectrics

NASA Astrophysics Data System (ADS)

Mathew, A.; Demirkan, K.; Wang, C.-G.; Wilk, G. D.; Watson, D. G.; Opila, R. L.

2005-09-01

Photoelectron spectroscopy is a powerful technique for the analysis of gate dielectrics because it can determine the elemental composition, the chemical states, and the compositional depth profiles non-destructively. The sampling depth, determined by the escape depth of the photoelectrons, is comparable to the thickness of current gate oxides. A maximum entropy algorithm was used to convert photoelectron collection angle dependence of the spectra to compositional depth profiles. A nitrided hafnium silicate film is used to demonstrate the utility of the technique. The algorithm balances deviations from a simple assumed depth profile against a calculated depth profile that best fits the angular dependence of the photoelectron spectra. A flow chart of the program is included in this paper. The development of the profile is also shown as the program is iterated. Limitations of the technique include the electron escape depths and elemental sensitivity factors used to calculate the profile. The technique is also limited to profiles that extend to the depth of approximately twice the escape depth. These limitations restrict conclusions to comparison among a family of similar samples. Absolute conclusions about depths and concentrations must be used cautiously. Current work to improve the algorithm is also described.

X-ray monitoring optical elements

DOEpatents

Stoupin, Stanislav; Shvydko, Yury; Katsoudas, John; Blank, Vladimir D.; Terentyev, Sergey A.

2016-12-27

An X-ray article and method for analyzing hard X-rays which have interacted with a test system. The X-ray article is operative to diffract or otherwise process X-rays from an input X-ray beam which have interacted with the test system and at the same time provide an electrical circuit adapted to collect photoelectrons emitted from an X-ray optical element of the X-ray article to analyze features of the test system.

GEMS X-ray Polarimeter Performance Simulations

NASA Technical Reports Server (NTRS)

Baumgartner, Wayne H.; Strohmayer, Tod; Kallman, Tim; Black, J. Kevin; Hill, Joanne; Swank, Jean

2012-01-01

The Gravity and Extreme Magnetism Small explorer (GEMS) is an X-ray polarization telescope selected as a NASA small explorer satellite mission. The X-ray Polarimeter on GEMS uses a Time Projection Chamber gas proportional counter to measure the polarization of astrophysical X-rays in the 2-10 keV band by sensing the direction of the track of the primary photoelectron excited by the incident X-ray. We have simulated the expected sensitivity of the polarimeter to polarized X-rays. We use the simulation package Penelope to model the physics of the interaction of the initial photoelectron with the detector gas and to determine the distribution of charge deposited in the detector volume. We then model the charge diffusion in the detector,and produce simulated track images. Within the track reconstruction algorithm we apply cuts on the track shape and focus on the initial photoelectron direction in order to maximize the overall sensitivity of the instrument, using this technique we have predicted instrument modulation factors nu(sub 100) for 100% polarized X-rays ranging from 10% to over 60% across the 2-10 keV X-ray band. We also discuss the simulation program used to develop and model some of the algorithms used for triggering, and energy measurement of events in the polarimeter.

Flow method and apparatus for screening chemicals using micro x-ray fluorescence

DOEpatents

Warner, Benjamin P [Los Alamos, NM; Havrilla, George J [Los Alamos, NM; Miller, Thomasin C [Bartlesville, OK; Lewis, Cris [Los Alamos, NM; Mahan, Cynthia A [Los Alamos, NM; Wells, Cyndi A [Los Alamos, NM

2009-04-14

Method and apparatus for screening chemicals using micro x-ray fluorescence. A method for screening a mixture of potential pharmaceutical chemicals for binding to at least one target binder involves flow-separating a solution of chemicals and target binders into separated components, exposing them to an x-ray excitation beam, detecting x-ray fluorescence signals from the components, and determining from the signals whether or not a binding event between a chemical and target binder has occurred.

Flow method and apparatus for screening chemicals using micro x-ray fluorescence

DOEpatents

Warner, Benjamin P [Los Alamos, NM; Havrilla, George J [Los Alamos, NM; Miller, Thomasin C [Bartlesville, OK; Lewis, Cris [Los Alamos, NM; Mahan, Cynthia A [Los Alamos, NM; Wells, Cyndi A [Los Alamos, NM

2011-04-26

Method and apparatus for screening chemicals using micro x-ray fluorescence. A method for screening a mixture of potential pharmaceutical chemicals for binding to at least one target binder involves flow separating a solution of chemicals and target binders into separated components, exposing them to an x-ray excitation beam, detecting x-ray fluorescence signals from the components, and determining from the signals whether or not a binding event between a chemical and target binder has occurred.

Summary: Update to ASTM guide E 1523 to charge control and charge referencing techniques in x-ray photoelectron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baer, D.R.

2005-05-01

An updated version of the American Society for Testing and Materials (ASTM) guide E 1523 to the methods to charge control and charge referencing techniques in x-ray photoelectron spectroscopy has been released by ASTM [Annual Book of ASTM Standards Surface Analysis (American Society for Testing and Materials, West Conshohocken, PA, 2004), Vol. 03.06]. The guide is meant to acquaint x-ray photoelectron spectroscopy (XPS) users with the various charge control and charge referencing techniques that are and have been used in the acquisition and interpretation of XPS data from surfaces of insulating specimens. The current guide has been expanded to includemore » new references as well as recommendations for reporting information on charge control and charge referencing. The previous version of the document had been published in 1997 [D. R. Baer and K. D. Bomben, J. Vac. Sci. Technol. A 16, 754 (1998)].« less

Electronic Structure of the Organic Semiconductor Alq3 (aluminum tris-8-hydroxyquinoline) from Soft X-ray Spectroscopies and Density Functional Theory Calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeMasi, A.; Piper, L; Zhang, Y

2008-01-01

The element-specific electronic structure of the organic semiconductor aluminum tris-8-hydroxyquinoline (Alq3) has been studied using a combination of resonant x-ray emission spectroscopy, x-ray photoelectron spectroscopy, x-ray absorption spectroscopy, and density functional theory (DFT) calculations. Resonant and nonresonant x-ray emission spectroscopy were used to measure directly the carbon, nitrogen and oxygen 2p partial densities of states in Alq3, and good agreement was found with the results of DFT calculations. Furthermore, resonant x-ray emission at the carbon K-edge is shown to be able to measure the partial density of states associated with individual C sites. Finally, comparison of previous x-ray emission studiesmore » and the present data reveal the presence of clear photon-induced damage in the former.« less

Electronic structure of the organic semiconductor Alq3 (aluminum tris-8-hydroxyquinoline) from soft x-ray spectroscopies and density functional theory calculations.

PubMed

DeMasi, A; Piper, L F J; Zhang, Y; Reid, I; Wang, S; Smith, K E; Downes, J E; Peltekis, N; McGuinness, C; Matsuura, A

2008-12-14

The element-specific electronic structure of the organic semiconductor aluminum tris-8-hydroxyquinoline (Alq(3)) has been studied using a combination of resonant x-ray emission spectroscopy, x-ray photoelectron spectroscopy, x-ray absorption spectroscopy, and density functional theory (DFT) calculations. Resonant and nonresonant x-ray emission spectroscopy were used to measure directly the carbon, nitrogen and oxygen 2p partial densities of states in Alq(3), and good agreement was found with the results of DFT calculations. Furthermore, resonant x-ray emission at the carbon K-edge is shown to be able to measure the partial density of states associated with individual C sites. Finally, comparison of previous x-ray emission studies and the present data reveal the presence of clear photon-induced damage in the former.

X-ray photoelectron spectroscopy study of excimer laser treated alumina films

NASA Astrophysics Data System (ADS)

Georgiev, D. G.; Kolev, K.; Laude, L. D.; Mednikarov, B.; Starbov, N.

1998-01-01

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.

Inelastic losses in X-ray absorption theory

NASA Astrophysics Data System (ADS)

Campbell, Luke Whalin

There is a surprising lack of many body effects observed in XAS (X-ray Absorption Spectroscopy) experiments. While collective excitations and other satellite effects account for between 20% and 40% of the spectral weight of the core hole and photoelectron excitation spectrum, the only commonly observed many body effect is a relatively structureless amplitude reduction to the fine structure, typically no more than a 10% effect. As a result, many particle effects are typically neglected in the XAS codes used to predict and interpret modern experiments. To compensate, the amplitude reduction factor is simply fitted to experimental data. In this work, a quasi-boson model is developed to treat the case of XAS, when the system has both a photoelectron and a core hole. We find that there is a strong interference between the extrinsic and intrinsic losses. The interference reduces the excitation amplitudes at low energies where the core hole and photo electron induced excitations tend to cancel. At high energies, the interference vanishes, and the theory reduces to the sudden approximation. The x-ray absorption spectrum including many-body excitations is represented by a convolution of the one-electron absorption spectrum with an energy dependent spectral function. The latter has an asymmetric quasiparticle peak and broad satellite structure. The net result is a phasor sum, which yields the many body amplitude reduction and phase shift of the fine structure oscillations (EXAFS), and possibly additional satellite structure. Calculations for several cases of interest are found to be in reasonable agreement with experiment. Edge singularity effects and deviations from the final state rule arising from this theory are also discussed. The ab initio XAS code FEFF has been extended for calculations of the many body amplitude reduction and phase shift in x-ray spectroscopies. A new broadened plasmon pole self energy is added. The dipole matrix elements are modified to include a

Band bending at magnetic Ni/Ge(001) interface investigated by X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Bocîrnea, Amelia Elena; Tănase, Liviu Cristian; Costescu, Ruxandra Maria; Apostol, Nicoleta Georgiana; Teodorescu, Cristian Mihail

2017-12-01

We report the molecular beam epitaxy growth of Ni on a clean Ge(001) surface with an intermediate NiGe layer forming at the interface at room temperature. The crystallinity of the substrate is lost after the deposition of more than 2 Ni monolayers. The Schottky barrier formation is investigated by X-ray photoelectron spectroscopy. The method allows us to infer a 0.39-0.45 eV band bending at the interface between the compound and Ge(001). Magneto-optical Kerr effect measurements were conclusive in detecting the ferromagnetic ordering of Ni outermost layers.

Valence band offset of β-Ga2O3/wurtzite GaN heterostructure measured by X-ray photoelectron spectroscopy.

PubMed

Wei, Wei; Qin, Zhixin; Fan, Shunfei; Li, Zhiwei; Shi, Kai; Zhu, Qinsheng; Zhang, Guoyi

2012-10-10

A sample of the β-Ga2O3/wurtzite GaN heterostructure has been grown by dry thermal oxidation of GaN on a sapphire substrate. X-ray diffraction measurements show that the β-Ga2O3 layer was formed epitaxially on GaN. The valence band offset of the β-Ga2O3/wurtzite GaN heterostructure is measured by X-ray photoelectron spectroscopy. It is demonstrated that the valence band of the β-Ga2O3/GaN structure is 1.40 ± 0.08 eV.

X ray photoelectron spectroscopy (XPS) analysis of Photosensitive ZrO2 array

NASA Astrophysics Data System (ADS)

Li, Y.; Zhao, G.; Zhu, R.; Kou, Z.

2018-03-01

Based on organic zirconium source as the starting material, by adding chemical modifiers which are made up with photosensitive ZrO2 sol. A uniformed ZrO2 array dot was fabricated with a mean diameter of around 800 nm. By using UV-vis spectra and X-ray photoelectron spectroscopy analysis method, studies the photosensitive ZrO2 gel film of photochemical reaction process and the photosensitive mechanism, to determine the zirconium atom centered chelate structure, reaction formed by metal chelate Zr atom for the center, and to establish the molecular model of the chelate. And studied the ultraviolet light in the process of the variation of the XPS spectra, Zr3d5/2 to 184.9 eV corresponding to the binding energy of the as the combination of state peak gradually reduce; By combining with the status of Zr-O peak gradually increase; The strength of the peak is gradually decline. This suggests that in the process of ultraviolet light photo chemical reaction happened. This study is of great significance to the micro fabrication of ZrO2 array not only to the memory devices but also to the optical devices.

Ultrafast X-Ray Spectroscopy of Conical Intersections

NASA Astrophysics Data System (ADS)

Neville, Simon P.; Chergui, Majed; Stolow, Albert; Schuurman, Michael S.

2018-06-01

Ongoing developments in ultrafast x-ray sources offer powerful new means of probing the complex nonadiabatically coupled structural and electronic dynamics of photoexcited molecules. These non-Born-Oppenheimer effects are governed by general electronic degeneracies termed conical intersections, which play a key role, analogous to that of a transition state, in the electronic-nuclear dynamics of excited molecules. Using high-level ab initio quantum dynamics simulations, we studied time-resolved x-ray absorption (TRXAS) and photoelectron spectroscopy (TRXPS) of the prototypical unsaturated organic chromophore, ethylene, following excitation to its S2(π π*) state. The TRXAS, in particular, is highly sensitive to all aspects of the ensuing dynamics. These x-ray spectroscopies provide a clear signature of the wave packet dynamics near conical intersections, related to charge localization effects driven by the nuclear dynamics. Given the ubiquity of charge localization in excited state dynamics, we believe that ultrafast x-ray spectroscopies offer a unique and powerful route to the direct observation of dynamics around conical intersections.

Taguchi's technique: an effective method for improving X-ray medical radiographic screen performance.

PubMed

Vlachogiannis, J G

2003-01-01

Taguchi's technique is a helpful tool to achieve experimental optimization of a large number of decision variables with a small number of off-line experiments. The technique appears to be an ideal tool for improving the performance of X-ray medical radiographic screens under a noise source. Currently there are very many guides available for improving the efficiency of X-ray medical radiographic screens. These guides can be refined using a second-stage parameter optimization. based on Taguchi's technique, selecting the optimum levels of controllable X-ray radiographic screen factors. A real example of the proposed technique is presented giving certain performance criteria. The present research proposes the reinforcement of X-ray radiography by Taguchi's technique as a novel hardware mechanism.

Investigation of electronic structure of tri- and tetranuclear molybdenum clusters by X-ray photoelectron and emission spectroscopies and quantum chemical methods

NASA Astrophysics Data System (ADS)

Kryuchkova, Natalya A.; Syrokvashin, Mikhail M.; Gushchin, Artem L.; Korotaev, Evgeniy V.; Kalinkin, Alexander V.; Laricheva, Yuliya A.; Sokolov, Maxim N.

2018-02-01

Charge state studies of compounds [Mo3S4(tu)8(H2O)]Cl4·4H2O (1), [Mo3S4Cl3(dbbpy)3]Cl·5H2O (2), [Mo3S4(CuCl)Cl3(dbbpy)3][CuCl2] (3), containing {Mo3S4}4+ and {Mo3CuS4}5+ cluster cores bearing terminal thiourea (tu) or 4,4‧-di-tert-butyl-2,2‧-bipyridine (dbbpy) ligands, have been performed by X-ray photoelectron and X-ray emission spectroscopies combined with quantum chemical calculations. The best agreement between theory and experiments has been obtained using the B3LYP method. According to the experimental and calculated data, the Mo atoms are in the oxidation state 4+ for all compounds. The energies and shapes of the Cu2p lines indicate formal oxidation states of Cu as 1+. The coordination of Cu(I) to the cluster {Mo3S4} in 3 does not lead to significant changes in the charge state of the molybdenum atoms and the {Mo3S4} unit can be considered as a tridentate metallothia crown ether.

Development of a single-shot CCD-based data acquisition system for time-resolved X-ray photoelectron spectroscopy at an X-ray free-electron laser facility

PubMed Central

Oura, Masaki; Wagai, Tatsuya; Chainani, Ashish; Miyawaki, Jun; Sato, Hiromi; Matsunami, Masaharu; Eguchi, Ritsuko; Kiss, Takayuki; Yamaguchi, Takashi; Nakatani, Yasuhiro; Togashi, Tadashi; Katayama, Tetsuo; Ogawa, Kanade; Yabashi, Makina; Tanaka, Yoshihito; Kohmura, Yoshiki; Tamasaku, Kenji; Shin, Shik; Ishikawa, Tetsuya

2014-01-01

In order to utilize high-brilliance photon sources, such as X-ray free-electron lasers (XFELs), for advanced time-resolved photoelectron spectroscopy (TR-PES), a single-shot CCD-based data acquisition system combined with a high-resolution hemispherical electron energy analyzer has been developed. The system’s design enables it to be controlled by an external trigger signal for single-shot pump–probe-type TR-PES. The basic performance of the system is demonstrated with an offline test, followed by online core-level photoelectron and Auger electron spectroscopy in ‘single-shot image’, ‘shot-to-shot image (image-to-image storage or block storage)’ and ‘shot-to-shot sweep’ modes at soft X-ray undulator beamline BL17SU of SPring-8. In the offline test the typical repetition rate for image-to-image storage mode has been confirmed to be about 15 Hz using a conventional pulse-generator. The function for correcting the shot-to-shot intensity fluctuations of the exciting photon beam, an important requirement for the TR-PES experiments at FEL sources, has been successfully tested at BL17SU by measuring Au 4f photoelectrons with intentionally controlled photon flux. The system has also been applied to hard X-ray PES (HAXPES) in ‘ordinary sweep’ mode as well as shot-to-shot image mode at the 27 m-long undulator beamline BL19LXU of SPring-8 and also at the SACLA XFEL facility. The XFEL-induced Ti 1s core-level spectrum of La-doped SrTiO3 is reported as a function of incident power density. The Ti 1s core-level spectrum obtained at low power density is consistent with the spectrum obtained using the synchrotron source. At high power densities the Ti 1s core-level spectra show space-charge effects which are analysed using a known mean-field model for ultrafast electron packet propagation. The results successfully confirm the capability of the present data acquisition system for carrying out the core-level HAXPES studies of condensed matter induced by the

X-ray Photoelectron Spectroscopy Study of Argon-Plasma-Treated Fluoropolymers

NASA Technical Reports Server (NTRS)

Golub, Morton A.; Lopata, Eugene S.; Finney, Lorie S.

1994-01-01

Films of poly(tetrafluoroethylene) (PTFE) and of a tetrafluoroethylene-perfluoroalkyl vinyl ether (approximately 49:1) copolymer (PFA) were exposed to a radio-frequency argon plasma and then examined by X-ray photoelectron spectroscopy (XPS). The use of fluoropolymer films nearly free of surface hydrocarbon contamination as well as the use of a monochromatized X-ray source for XPS removed two factors contributing to conflicting reports on the effect of exposure time on the fluorine-to-carbon (F/C) and oxygen-to-carbon (O/C) ratios for several Ar-plasma-treated fluoropolymers. Contrary to literature indications, a common pattern was found for PTFE and PFA: a moderate decrease in F/C ratio (from 1.99 to 1.40, and from 1.97 to 1.57, respectively), together with a moderate increase in O/C ratio (from negligible to about 0.10, and from 0.012 to about O.10, respectively) at very short exposures, after which the F/C ratios remained essentially constant on prolonged exposures, while the O/C ratios for PTFE and PFA leveled off at 0.11 and 0.15, respectively. The XPS C(sub 1s), spectra for these polymers exposed to the Ar plasma for 20 min were similar and presented, besides a prominent peak at 292.0 eV (CF2,) and a minor peak at 294.0 or 294.1 eV (CF3), a composite band of four curve-resolved peaks (approximately 285-290 eV) representing various CH, CC, CO, CN, and CF functionalities.

Femtosecond profiling of shaped x-ray pulses

NASA Astrophysics Data System (ADS)

Hoffmann, M. C.; Grguraš, I.; Behrens, C.; Bostedt, C.; Bozek, J.; Bromberger, H.; Coffee, R.; Costello, J. T.; DiMauro, L. F.; Ding, Y.; Doumy, G.; Helml, W.; Ilchen, M.; Kienberger, R.; Lee, S.; Maier, A. R.; Mazza, T.; Meyer, M.; Messerschmidt, M.; Schorb, S.; Schweinberger, W.; Zhang, K.; Cavalieri, A. L.

2018-03-01

Arbitrary manipulation of the temporal and spectral properties of x-ray pulses at free-electron lasers would revolutionize many experimental applications. At the Linac Coherent Light Source at Stanford National Accelerator Laboratory, the momentum phase-space of the free-electron laser driving electron bunch can be tuned to emit a pair of x-ray pulses with independently variable photon energy and femtosecond delay. However, while accelerator parameters can easily be adjusted to tune the electron bunch phase-space, the final impact of these actuators on the x-ray pulse cannot be predicted with sufficient precision. Furthermore, shot-to-shot instabilities that distort the pulse shape unpredictably cannot be fully suppressed. Therefore, the ability to directly characterize the x-rays is essential to ensure precise and consistent control. In this work, we have generated x-ray pulse pairs via electron bunch shaping and characterized them on a single-shot basis with femtosecond resolution through time-resolved photoelectron streaking spectroscopy. This achievement completes an important step toward future x-ray pulse shaping techniques.

Femtosecond profiling of shaped x-ray pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoffmann, M. C.; Grguras, I.; Behrens, C.

Arbitrary manipulation of the temporal and spectral properties of x-ray pulses at free-electron lasers would revolutionize many experimental applications. At the Linac Coherent Light Source at Stanford National Accelerator Laboratory, the momentum phase-space of the free-electron laser driving electron bunch can be tuned to emit a pair of x-ray pulses with independently variable photon energy and femtosecond delay. However, while accelerator parameters can easily be adjusted to tune the electron bunch phase-space, the final impact of these actuators on the x-ray pulse cannot be predicted with sufficient precision. Furthermore, shot-to-shot instabilities that distort the pulse shape unpredictably cannot be fullymore » suppressed. Therefore, the ability to directly characterize the x-rays is essential to ensure precise and consistent control. In this work, we have generated x-ray pulse pairs via electron bunch shaping and characterized them on a single-shot basis with femtosecond resolution through time-resolved photoelectron streaking spectroscopy. Furthermore, this achievement completes an important step toward future x-ray pulse shaping techniques.« less

Femtosecond profiling of shaped x-ray pulses

DOE PAGES

Hoffmann, M. C.; Grguras, I.; Behrens, C.; ...

2018-03-26

Arbitrary manipulation of the temporal and spectral properties of x-ray pulses at free-electron lasers would revolutionize many experimental applications. At the Linac Coherent Light Source at Stanford National Accelerator Laboratory, the momentum phase-space of the free-electron laser driving electron bunch can be tuned to emit a pair of x-ray pulses with independently variable photon energy and femtosecond delay. However, while accelerator parameters can easily be adjusted to tune the electron bunch phase-space, the final impact of these actuators on the x-ray pulse cannot be predicted with sufficient precision. Furthermore, shot-to-shot instabilities that distort the pulse shape unpredictably cannot be fullymore » suppressed. Therefore, the ability to directly characterize the x-rays is essential to ensure precise and consistent control. In this work, we have generated x-ray pulse pairs via electron bunch shaping and characterized them on a single-shot basis with femtosecond resolution through time-resolved photoelectron streaking spectroscopy. Furthermore, this achievement completes an important step toward future x-ray pulse shaping techniques.« less

Electronic structure of the dilute magnetic semiconductor G a1 -xM nxP from hard x-ray photoelectron spectroscopy and angle-resolved photoemission

NASA Astrophysics Data System (ADS)

Keqi, A.; Gehlmann, M.; Conti, G.; Nemšák, S.; Rattanachata, A.; Minár, J.; Plucinski, L.; Rault, J. E.; Rueff, J. P.; Scarpulla, M.; Hategan, M.; Pálsson, G. K.; Conlon, C.; Eiteneer, D.; Saw, A. Y.; Gray, A. X.; Kobayashi, K.; Ueda, S.; Dubon, O. D.; Schneider, C. M.; Fadley, C. S.

2018-04-01

We have investigated the electronic structure of the dilute magnetic semiconductor (DMS) G a0.98M n0.02P and compared it to that of an undoped GaP reference sample, using hard x-ray photoelectron spectroscopy (HXPS) and hard x-ray angle-resolved photoemission spectroscopy (HARPES) at energies of about 3 keV. We present experimental data, as well as theoretical calculations, to understand the role of the Mn dopant in the emergence of ferromagnetism in this material. Both core-level spectra and angle-resolved or angle-integrated valence spectra are discussed. In particular, the HARPES experimental data are compared to free-electron final-state model calculations and to more accurate one-step photoemission theory. The experimental results show differences between G a0.98M n0.02P and GaP in both angle-resolved and angle-integrated valence spectra. The G a0.98M n0.02P bands are broadened due to the presence of Mn impurities that disturb the long-range translational order of the host GaP crystal. Mn-induced changes of the electronic structure are observed over the entire valence band range, including the presence of a distinct impurity band close to the valence-band maximum of the DMS. These experimental results are in good agreement with the one-step photoemission calculations and a prior HARPES study of G a0.97M n0.03As and GaAs [Gray et al., Nat. Mater. 11, 957 (2012), 10.1038/nmat3450], demonstrating the strong similarity between these two materials. The Mn 2 p and 3 s core-level spectra also reveal an essentially identical state in doping both GaAs and GaP.

X-ray photoelectron spectroscopy of select multi-layered transition metal carbides (MXenes)

DOE PAGES

Halim, Joseph; Cook, Kevin M.; Naguib, Michael; ...

2015-12-01

A detailed high resolution X-ray photoelectron spectroscopy (XPS) analysis is presented in this work for select MXenes—a recently discovered family of two-dimensional (2D) carbides and carbonitrides. Given their 2D nature, understanding their surface chemistry is paramount. Thus we identify and quantify the surface groups present before, and after, sputter-cleaning as well as freshly prepared vs. aged multi-layered cold pressed discs. The nominal compositions of the MXenes studied here are Ti 3C 2T x, Ti 2CT x, Ti 3CNTx, Nb 2CT x and Nb 4C 3T x, where T represents surface groups that this work attempts to quantify. In all themore » cases, the presence of three surface terminations, single bondO, single bondOH and single bondF, in addition to OH-terminations relatively strongly bonded to H 2O molecules, was confirmed. Moreover, from XPS peak fits, it was possible to establish the average sum of the negative charges of the terminations for the aforementioned MXenes. Based on this work, it is now possible to quantify the nature of the surface terminations. This information can, in turn, be used to better design and tailor these novel 2D materials for various applications.« less

Valence band offset of β-Ga2O3/wurtzite GaN heterostructure measured by X-ray photoelectron spectroscopy

PubMed Central

2012-01-01

A sample of the β-Ga2O3/wurtzite GaN heterostructure has been grown by dry thermal oxidation of GaN on a sapphire substrate. X-ray diffraction measurements show that the β-Ga2O3 layer was formed epitaxially on GaN. The valence band offset of the β-Ga2O3/wurtzite GaN heterostructure is measured by X-ray photoelectron spectroscopy. It is demonstrated that the valence band of the β-Ga2O3/GaN structure is 1.40 ± 0.08 eV. PMID:23046910

Electronic structure of the (Nd{sub 1−x}Dy{sub x}){sub 2}Fe{sub 14}B (0 ≤ x ≤ 1) system studied by X-ray photoelectron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jing; Liang, Le; Yang, Bin

2015-09-15

Systematic characterization of electronic structures in the (Nd{sub 1−x}Dy{sub x}){sub 2}Fe{sub 14}B system, especially the 4f behavior, provides an insight to the physical nature of the evolution of magnetic properties. A series of X-ray photoelectron spectroscopy (XPS) core-level and valence-band spectra were used to study the electronic structures. It was found that substitution of Dy for Nd in Nd{sub 2}Fe{sub 14}B results in a nonlinear variation in the evolution of electronic structures. Only the finite coupling between the Nd 4f states and the Fe 3d states is found at both the Nd-rich regime and the Dy-rich regime. When the Dymore » concentration and the Nd concentration approach to be equal, a strong coupling between the Nd 4f states and the Fe 3d states is found, which results in a bonding state between them. Additionally, the 4f components in the (Nd{sub 1−x}Dy{sub x}){sub 2}Fe{sub 14}B system are ascribed to three parts: 1) the individual contribution of the Dy 4f states, which emerges just after the Dy-substitution; 2) the contribution of the coupling between the Nd 4f states and the Dy 4f states, which arises only when 0.4 ≤ x ≤ 0.6; 3) the associated contributions of the Nd 4f states and the Dy 4f states, where the contribution of the Nd 4f states and that of the Dy 4f states are prominent in the Nd-rich regime and Dy-rich regime, respectively.« less

Stress-induced cortisol secretion impairs detection performance in x-ray baggage screening for hidden weapons by screening novices.

PubMed

Thomas, Livia; Schwaninger, Adrian; Heimgartner, Nadja; Hedinger, Patrik; Hofer, Franziska; Ehlert, Ulrike; Wirtz, Petra H

2014-09-01

Aviation security strongly depends on screeners' performance in the detection of threat objects in x-ray images of passenger bags. We examined for the first time the effects of stress and stress-induced cortisol increases on detection performance of hidden weapons in an x-ray baggage screening task. We randomly assigned 48 participants either to a stress or a nonstress group. The stress group was exposed to a standardized psychosocial stress test (TSST). Before and after stress/nonstress, participants had to detect threat objects in a computer-based object recognition test (X-ray ORT). We repeatedly measured salivary cortisol and X-ray ORT performance before and after stress/nonstress. Cortisol increases in reaction to psychosocial stress induction but not to nonstress independently impaired x-ray detection performance. Our results suggest that stress-induced cortisol increases at peak reactivity impair x-ray screening performance. Copyright © 2014 Society for Psychophysiological Research.

X-Ray Photoelectron Spectroscopy and Tribology Studies of Annealed Fullerene-like WS2 Nanoparticles

NASA Astrophysics Data System (ADS)

Kopnov, F.; Tenne, R.; Späth, B.; Jägermann, W.; Cohen, H.; Feldman, Y.; Zak, A.; Moshkovich, A.; Rapoport, L.

The temporal chemical changes occurring at the surface of fullerene-like (IF) nanoparticles of WS2 were investigated using X-ray photo-electron spectroscopy (XPS) and compared to those of bulk powder (2H) of the same material. It is possible to follow the long term (surface oxidation and carbonization) occurring at defects on the outermost surface (0001) layer of the fullerene-like nanoparticles. Similar but perhaps more distinctive changes are observed on the prismatic (hk0) surfaces of the 2H powder. Vacuum annealing is shown to remove most of these changes and bring the surface close to its stoichiometric composition. In accordance with previous measurements, further evidence is obtained for the existence of water molecules which are entrapped in the hollow core and interstitial defects of the fullerene-like nanoparticles during the synthesis. They are also shown to be removed by the vacuum annealing process. Chemically resolved electrical measurements (CREM) in the XPS show that the vacuum annealed IF samples become more intrinsic. Finally, tribological measurements show that the vacuum annealed IF samples perform better as an additive to oil than the non-annealed IF samples and the bulk (2H) platelets powder.

Determination of the radiation resistance order of high explosives by the two dimensional correlation X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Sui, Heliang; Hao, Xiaofei; Luo, Yiwei; Xu, Jinjiang; Zhong, Fachun; Xu, Ruijuan

2017-09-01

Two-dimensional X-ray photoelectron spectroscopy (2DXPS) was employed to obtain the radiation resistance order of high explosives. Mixed hexanitrohexaazaisowurtzitane (CL-20) and 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) were irradiated by X-ray radiation. The time-dependent N1s XPS spectra were collected. 2DXPS was used to analyze the variation of the binding energy peaks. The main degradation time of TATB was longer than that of CL-20. CL-20 changes occurred prior to that of TATB during radiation. These changes suggest that TATB exhibited higher radiation resistance property than CL-20. 2DXPS is a very useful method to distinguish the radiation resistance orders of materials.

Chemical state analysis of heavily phosphorus-doped epitaxial silicon films grown on Si (1 0 0) by X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Lee, Minhyeong; Kim, Sungtae; Ko, Dae-Hong

2018-06-01

In this work, we investigated the chemical bonding states in highly P-doped Si thin films epitaxially grown on Si (0 0 1) substrates using high-resolution X-ray photoelectron spectroscopy (HR-XPS). HR-XPS P 2p core-level spectra clearly show spin-orbital splitting between P 2p1/2 and P 2p3/2 peaks in Si films doped with a high concentration of P. Moreover, the intensities of P 2p1/2 and P 2p3/2 peaks for P-doped Si films increase with P concentrations, while their binding energies remained almost identical. These results indicate that more P atoms are incorporated into the substitutional sites of the Si lattice with the increase of P concentrations. In order to identify the chemical states of P-doped Si films shown in XPS Si 2p spectra, the spectra of bulk Si were subtracted from those of Si:P samples, which enables us to clearly identify the new chemical state related to Sisbnd P bonds. We observed that the presence of the two well-resolved new peaks only for the Si:P samples at the binding energy higher than those of a Sisbnd Si bond, which is due to the strong electronegativity of P than that of Si. Experimental findings in this study using XPS open up new doors for evaluating the chemical states of P-doped Si materials in fundamental researches as well as in industrial applications.

Ethene adsorption and dehydrogenation on clean and oxygen precovered Ni(111) studied by high resolution x-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Lorenz, M. P. A.; Fuhrmann, T.; Streber, R.; Bayer, A.; Bebensee, F.; Gotterbarm, K.; Kinne, M.; Tränkenschuh, B.; Zhu, J. F.; Papp, C.; Denecke, R.; Steinrück, H.-P.

2010-07-01

The adsorption and thermal evolution of ethene (ethylene) on clean and oxygen precovered Ni(111) was investigated with high resolution x-ray photoelectron spectroscopy using synchrotron radiation at BESSY II. The high resolution spectra allow to unequivocally identify the local environment of individual carbon atoms. Upon adsorption at 110 K, ethene adsorbs in a geometry, where the two carbon atoms within the intact ethene molecule occupy nonequivalent sites, most likely hollow and on top; this new result unambiguously solves an old puzzle concerning the adsorption geometry of ethene on Ni(111). On the oxygen precovered surface a different adsorption geometry is found with both carbon atoms occupying equivalent hollow sites. Upon heating ethene on the clean surface, we can confirm the dehydrogenation to ethine (acetylene), which adsorbs in a geometry, where both carbon atoms occupy equivalent sites. On the oxygen precovered surface dehydrogenation of ethene is completely suppressed. For the identification of the adsorbed species and the quantitative analysis the vibrational fine structure of the x-ray photoelectron spectra was analyzed in detail.

Discovery of novel inhibitors for DHODH via virtual screening and X-ray crystallographic structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

McLean, Larry R.; Zhang, Ying; Degnen, William

2010-10-28

Amino-benzoic acid derivatives 1-4 were found to be inhibitors for DHODH by virtual screening, biochemical, and X-ray crystallographic studies. X-ray structures showed that 1 and 2 bind to DHODH as predicted by virtual screening, but 3 and 4 were found to be structurally different from the corresponding compounds initially identified by virtual screening.

Using “Tender” x-ray ambient pressure x-Ray photoelectron spectroscopy as a direct probe of solid-liquid interface

DOE PAGES

Axnanda, Stephanus; Crumlin, Ethan J.; Mao, Baohua; ...

2015-05-07

We report a new method to probe the solid-liquid interface through the use of a thin liquid layer on a solid surface. An ambient pressure XPS (AP-XPS) endstation that is capable of detecting high kinetic energy photoelectrons (7 keV) at a pressure up to 110 Torr has been constructed and commissioned. Additionally, we have deployed a “dip & pull” method to create a stable nanometers-thick aqueous electrolyte on platinum working electrode surface. Combining the newly constructed AP-XPS system, “dip & pull” approach, with a “tender” X-ray synchrotron source (2 keV–7 keV), we are able to access the interface between liquidmore » and solid dense phases with photoelectrons and directly probe important phenomena occurring at the narrow solid-liquid interface region in an electrochemical system. Using this approach, we have performed electrochemical oxidation of the Pt electrode at an oxygen evolution reaction (OER) potential. Under this potential, we observe the formation of both Pt²⁺ and Pt⁴⁺ interfacial species on the Pt working electrode in situ. We believe this thin-film approach and the use of “tender” AP-XPS highlighted in this study is an innovative new approach to probe this key solid-liquid interface region of electrochemistry.« less

Using “Tender” x-ray ambient pressure x-Ray photoelectron spectroscopy as a direct probe of solid-liquid interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Axnanda, Stephanus; Crumlin, Ethan J.; Mao, Baohua

We report a new method to probe the solid-liquid interface through the use of a thin liquid layer on a solid surface. An ambient pressure XPS (AP-XPS) endstation that is capable of detecting high kinetic energy photoelectrons (7 keV) at a pressure up to 110 Torr has been constructed and commissioned. Additionally, we have deployed a “dip & pull” method to create a stable nanometers-thick aqueous electrolyte on platinum working electrode surface. Combining the newly constructed AP-XPS system, “dip & pull” approach, with a “tender” X-ray synchrotron source (2 keV–7 keV), we are able to access the interface between liquidmore » and solid dense phases with photoelectrons and directly probe important phenomena occurring at the narrow solid-liquid interface region in an electrochemical system. Using this approach, we have performed electrochemical oxidation of the Pt electrode at an oxygen evolution reaction (OER) potential. Under this potential, we observe the formation of both Pt²⁺ and Pt⁴⁺ interfacial species on the Pt working electrode in situ. We believe this thin-film approach and the use of “tender” AP-XPS highlighted in this study is an innovative new approach to probe this key solid-liquid interface region of electrochemistry.« less

Effect of iron oxide reductive dissolution on the transformation and immobilization of arsenic in soils: New insights from X-ray photoelectron and X-ray absorption spectroscopy.

PubMed

Fan, Jian-Xin; Wang, Yu-Jun; Liu, Cun; Wang, Li-Hua; Yang, Ke; Zhou, Dong-Mei; Li, Wei; Sparks, Donald L

2014-08-30

The geochemical behavior and speciation of arsenic (As) in paddy soils is strongly controlled by soil redox conditions and the sequestration by soil iron oxyhydroxides. Hence, the effects of iron oxide reductive dissolution on the adsorption, transformation and precipitation of As(III) and As(V) in soils were investigated using batch experiments and synchrotron based techniques to gain a deeper understanding at both macroscopic and microscopic scales. The results of batch sorption experiments revealed that the sorption capacity of As(V) on anoxic soil was much higher than that on control soil. Synchrotron based X-ray fluorescence (μ-XRF) mapping studies indicated that As was heterogeneously distributed and was mainly associated with iron in the soil. X-ray absorption near edge structure (XANES), micro-X-ray absorption near edge structure (μ-XANES) and X-ray photoelectron spectroscopy (XPS) analyses revealed that the primary speciation of As in the soil is As(V). These results further suggested that, when As(V) was introduced into the anoxic soil, the rapid coprecipitation of As(V) with ferric/ferrous ion prevented its reduction to As(III), and was the main mechanism controlling the immobilization of As. This research could improve the current understanding of soil As chemistry in paddy and wetland soils. Copyright © 2014 Elsevier B.V. All rights reserved.

Distinguishability of N Composition Profiles In SiON Films On Si By Angle-Resolved X-ray Photoelectron Spectroscopy

NASA Astrophysics Data System (ADS)

Powell, C. J.; Werner, W. S. M.; Smekal, W.

2007-09-01

We report on the use of the NIST Database for the Simulation of Electron Spectra for Surface Analysis (SESSA) to determine N 1s, O 1s, and Si 2p3/2 photoelectron intensities for a 25 Å SiON film on a Si substrate with different distributions of N in the film. These simulations were made to assess the distinguishability of angle-resolved x-ray photoelectron spectroscopy (ARXPS) signals for each N distribution. Our approach differs from conventional simulations of ARXPS data in that we do not neglect elastic scattering of the photoelectrons and the finite solid angle of the analyzer. Appreciable dispersion of the photoelectron intensities was found only for the N 1s intensities at an emission angle of 75° (with respect to the surface normal). Conventional analyses of ARXPS data that include such large emission angles are unlikely to be valid due to angle-dependent changes of the attenuation length. We demonstrate the magnitude of elastic-scattering and analyzer solid-angle effects on the calculated angular distributions.

An X-ray photoelectron spectroscopy study of the thermal nitridation of SiO2/Si

NASA Technical Reports Server (NTRS)

Vasquez, R. P.; Madhukar, A.; Grunthaner, F. J.; Naiman, M. L.

1986-01-01

The dependence of the nitrogen distribution in thermally nitrided SiO2 films on the nitridation time and temperature has been studied by means of X-ray photoelectron spectroscopy (XPS). The photoelectron peak intensities were measured by fitting Voigt profiles to the XPS spectra and were used to calculate the film composition as a function of film depth, applying an analytical method described in detail. The times of appearance of the maxima in interfacial nitrogen concentration are shown for 800, 1000, and 1150 C, and the data are related to a kinetic model of Vasquez and Madhukar (1985), which considers the effect of interfacial strain on the nitridation kinetics. In addition, the intensity of a fluorine marker (from the HF used in the etching step) was found to correlate with the nitrogen concentration. It is postulated that the F bonds preferentially to defects. This hypothesis and the measured F intensities are consistent with the proposed strain-dependent energy of defect formation.

X-ray position detector and implementation in a mirror pointing servo system

DOEpatents

Rabedeau, Thomas A.; Van Campen, Douglas G.; Stefan, Peter M.

2016-04-05

An X-ray beam position and stability detector is provided having a first metal blade collinear with a second metal blade, where an edge of the first metal blade is opposite an edge of the second metal blade, where the first metal blade edge and the second metal blade edge are disposed along a centerline with respect to each other, where the metal blades are capable of photoelectron emission when exposed to an x-ray beam, a metal coating on the metal blades that is capable of enhancing the photoelectron emission, or suppressing energy-resonant contaminants, or enhancing the photoelectron emission and suppressing energy-resonant contaminants, a background shielding element having an electrode capable of suppressing photoelectron emission from spurious x-rays not contained in an x-ray beam of interest, and a photoelectron emission detector having an amplifier capable of detecting the photoelectron emission as a current signal.

X-ray photoelectron spectroscopic evidence for bacteria-enhanced dissolution of hornblende

NASA Astrophysics Data System (ADS)

Kalinowski, B. E.; Liermann, L. J.; Brantley, S. L.; Barnes, A.; Pantano, C. G.

2000-04-01

An Arthrobacter species capable of extracting Fe from hornblende was isolated from a soil from the Adirondacks, NY (USA). This bacteria isolate, used in batch experiments with hornblende, accelerated the release of Fe from hornblende without measurably affecting Al release. The isolate produces both low molecular weight organic acids (LMWOA) and a catecholate siderophore. Polished hornblende (glass and crystal) discs were analyzed with X-ray photoelectron spectroscopy (XPS) before and after incubation with growing Arthrobacter sp. to investigate whether the bacteria caused a distinguishable chemical signature on the upper 100 Å of mineral surface. After removal of the arthrobacter grown on hornblende crystal or glass substrates using lysozyme, XPS revealed surface depletion of Fe for samples grown for several days in buffered (crystal) and unbuffered (crystal and glass) media. Fe/Si ratios of hornblende surfaces dissolved under biotic conditions are significantly lower than Fe/Si ratios on surfaces dissolved under abiotic conditions for similar amounts of time. Enhanced Fe release and the formation of Fe-depleted surfaces is inferred to be caused by catechol complexation at the mineral surface. Because natural siderophore was not isolated in sufficient quantities to run bacteria-free leaching experiments, parallel investigations were run with a commercially available siderophore (desferrioxamine B). Desferrioxamine B was observed to enhance release of Fe, Si, and Al from hornblende both with and without added bacteria. Formation of desferrioxamine-Fe surface complexes were probed by studying the multiple splitting and shift in intensities of the N 1s line analyzed by XPS on siderophore ± Fe on gold surfaces and siderophore + hornblende crystal surfaces. Based upon the observed formation of an hydroxamate (desferrioxamine) surface complex on hornblende, we infer that catecholate siderophores, such as those produced by the arthrobacter, also complex on the

Structure determination of a multilayer with an island-like overlayer using hard x-ray photoelectron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Isomura, N., E-mail: isomura@mosk.tytlabs.co.jp; Kataoka, K.; Horibuchi, K.

We use hard X-ray photoelectron spectroscopy (HAXPES) to obtain the surface structure of a multilayer Au/SiO{sub 2}/Si substrate sample with an island-like overlayer. Photoelectron intensities are measured as a function of incident photon energy (PE) and take-off angle (TOA, measured from the sample surface). The Au layer coverage and Au and SiO{sub 2} layer thicknesses are obtained by the PE dependence, and are used for the following TOA analysis. The Au island lateral width in the cross section is obtained by the TOA dependence, including information about surface roughness, in consideration of the island shadowing at small TOAs. In bothmore » cases, curve-fitting analysis is conducted. The surface structure, which consists of layer thicknesses, overlayer coverage and island width, is determined nondestructively by a combination of PE and TOA dependent HAXPES measurements.« less

Magnetic x-ray dichroism in ultrathin epitaxial films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tobin, J.G.; Goodman, K.W.; Cummins, T.R.

1997-04-01

The authors have used Magnetic X-ray Linear Dichroism (MXLD) and Magnetic X-ray Circular Dichroism (MXCD) to study the magnetic properties of epitaxial overlayers in an elementally specific fashion. Both MXLD and MXCD Photoelectron Spectroscopy were performed in a high resolution mode at the Spectromicroscopy Facility of the ALS. Circular Polarization was obtained via the utilization of a novel phase retarder (soft x-ray quarter wave plate) based upon transmission through a multilayer film. The samples were low temperature Fe overlayers, magnetic alloy films of NiFe and CoNi, and Gd grown on Y. The authors results include a direct comparison of highmore » resolution angle resolved Photoelectron Spectroscopy performed in MXLD and MXCD modes as well as structural studies with photoelectron diffraction.« less

Hydrazine reduction of transition metal oxides - In situ characterization using X-ray photoelectron spectroscopy

NASA Technical Reports Server (NTRS)

Littrell, D. M.; Tatarchuk, B. J.

1986-01-01

The transition metal oxides (TMOs) V2O5, FeO3, Co3O4, NiO, CuO, and ZnO were exposed to hydrazine at various pressures. The metallic surfaces were surveyed by in situ X-ray photoelectron spectroscopy to determine the irrelative rate of reduction by hydrazine. The most easily reducible oxide, CuO, could be reduced to the metallic state at room temperature and 10 to the -6th torr. The reaction is first order with respect to CuO, with an activation energy of about 35 kJ/mol. Two types of adsorption were seen to occur at 295 K: (1) a reversible component in which the measured N:Cu ratio increased to 0.60 at hydrazine pressures up to 0.5 torr, and (2) an irreversible component, with a N:Cu ratio of 0.28, which could not be removed by extended vacuum pumping. The results of this study are useful for the identification of TMO's that can be used as solid neatallizers of hydrazine spills, and for the preparation of metal surfaces for electroplating and evaporative thin-film coating.

Ion bombardment and adsorption studies on ilmenite (FeTiO3) by X-ray photoelectron spectroscopy

NASA Technical Reports Server (NTRS)

Schulze, P. D.

1983-01-01

The effects of 5 KeV argon and oxygen ion bombardment on FeTiO3 (ilmenite) at low temperatures have been studied using X-ray photoelectron spectroscopy (XPS). Also, using this same technique, the adsorption of O2, NO, N2O, and CO at 300 K and the adsorption of O2 and D2O at 150K have been studied. Argon and oxygen ion bombardment of ilmenite have confirmed earlier studies on metal oxides that argon ions generally reduce the anion species while oxygen ions generally oxidize the anion species. The two iron states involved were Fe sup +2 and Fe sup O. The reduction of Ti sup +4 was not verified although a significant shift in the Ti(2p1,3) binding energies toward the metallic state was observed after oxygen ion bombardment at low temperatures. At temperatures above 150K, O2 adsorbs dissociatively on ilmenite while D2O adsorbs molecularly below 170K. Above 300 K No, N2O, and CO do not appear to adsorb dissociatively. Low temperature adsorption of D2O was found to be inhibited by predosing the ilmenite with O2.

Evolution of Cygnus X-3 through its Radio and X-ray States

NASA Astrophysics Data System (ADS)

Szostek, A.; Zdziarski, A. A.; McCollough, M. L.

2009-05-01

Based on X-ray spectra and studies of the long-term correlated behavior between radio and soft X-ray, we present a detailed evolution of Cyg X-3 through its radio and X-ray states. We comment on the nature of the hard X-ray tail and possible Simbol X contribution in constraining the models.

Combining X-ray and neutron crystallography with spectroscopy.

PubMed

Kwon, Hanna; Smith, Oliver; Raven, Emma Lloyd; Moody, Peter C E

2017-02-01

X-ray protein crystallography has, through the determination of the three-dimensional structures of enzymes and their complexes, been essential to the understanding of biological chemistry. However, as X-rays are scattered by electrons, the technique has difficulty locating the presence and position of H atoms (and cannot locate H + ions), knowledge of which is often crucially important for the understanding of enzyme mechanism. Furthermore, X-ray irradiation, through photoelectronic effects, will perturb the redox state in the crystal. By using single-crystal spectrophotometry, reactions taking place in the crystal can be monitored, either to trap intermediates or follow photoreduction during X-ray data collection. By using neutron crystallography, the positions of H atoms can be located, as it is the nuclei rather than the electrons that scatter neutrons, and the scattering length is not determined by the atomic number. Combining the two techniques allows much greater insight into both reaction mechanism and X-ray-induced photoreduction.

Lab-based ambient pressure X-ray photoelectron spectroscopy from past to present

NASA Astrophysics Data System (ADS)

Arble, Chris; Jia, Meng; Newberg, John T.

2018-05-01

Chemical interactions which occur at a heterogeneous interface between a gas and substrate are critical in many technological and natural processes. Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) is a powerful spectroscopy tool that is inherently surface sensitive, elemental and chemical specific, with the ability to probe sample surfaces in the presence of a gas phase. In this review, we discuss the evolution of lab-based AP-XPS instruments, from the first development by Siegbahn and coworkers up through modern day systems. A comprehensive overview is given of heterogeneous experiments investigated to date via lab-based AP-XPS along with the different instrumental metrics that affect the quality of sample probing. We conclude with a discussion of future directions for lab-based AP-XPS, highlighting the efficacy for this in-demand instrument to continue to expand in its ability to significantly advance our understanding of surface chemical processes under in situ conditions in a technologically multidisciplinary setting.

X-ray photoelectron spectroscopy study of radiofrequency-sputtered refractory compound steel interfaces

NASA Technical Reports Server (NTRS)

Wheeler, D. R.; Brainard, W. A.

1978-01-01

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.

X-ray photoelectron spectroscopic study of the interaction of xanthate with coal pyrite and mineral pyrite surfaces

NASA Astrophysics Data System (ADS)

Khan, S. U. M.; Baltrus, J. P.; Lai, R. W.; Richardson, A. G.

1991-06-01

Coal pyrite and mineral pyrite surfaces were examined by X-ray photoelectron spectroscopy (XPS) before and after treatment in acidic and basic solutions of sodium ethyl xanthate (NaEtX). XPS showed that the degree of oxidation of coal and mineral pyrite surfaces increased when these pyrites were conditioned in basic solutions. However, conditioning in acidic solutions led to partial removal of surface oxidation from the pyrites. Addition of NaEtX to the acidic and basic solutions enhanced the removal of oxidation from pyrite surfaces. Pretreatment with sulfur dioxide further enhanced the removal of surface oxidation in the presence of NaEtX. Surface oxidation was typically less on mineral pyrite than coal pyrite surfaces following identical treatments. The flotation recoveries of the pyrites in the presence of NaEtX are greatest for the pyrites with the least amount of surface oxidation.

High resolution X-ray photoelectron spectroscopy of styrene oxide adsorption and reaction on Ag(1 1 1)

NASA Astrophysics Data System (ADS)

Piao, H.; Enever, M. C. N.; Adib, K.; Hrbek, J.; Barteau, M. A.

2004-11-01

Synchrotron-based X-ray photoelectron spectroscopy (XPS) has been used to investigate the adsorption and reaction of styrene oxide on Ag(1 1 1). When adsorption is carried out at 250 K or above, ring opening of styrene oxide forms a stable surface oxametallacycle intermediate which eventually reacts at 485 K to regenerate styrene oxide. High resolution XPS is capable of distinguishing the oxametallacycle from molecularly adsorbed and condensed styrene oxide on the basis of different C1s peak separations. The observed separations are well accounted for by the results of DFT calculations.

Nonlocal heat transport and improved target design for x-ray heating studies at x-ray free electron lasers

NASA Astrophysics Data System (ADS)

Hoidn, Oliver; Seidler, Gerald T.

2018-01-01

The extremely high-power densities and short durations of single pulses of x-ray free electron lasers (XFELs) have opened new opportunities in atomic physics, where complex excitation-relaxation chains allow for high ionization states in atomic and molecular systems, and in dense plasma physics, where XFEL heating of solid-density targets can create unique dense states of matter having temperatures on the order of the Fermi energy. We focus here on the latter phenomena, with special emphasis on the problem of optimum target design to achieve high x-ray heating into the warm dense matter (WDM) state. We report fully three-dimensional simulations of the incident x-ray pulse and the resulting multielectron relaxation cascade to model the spatial energy density deposition in multicomponent targets, with particular focus on the effects of nonlocal heat transport due to the motion of high energy photoelectrons and Auger electrons. We find that nanoscale high-Z /low-Z multicomponent targets can give much improved energy density deposition in lower-Z materials, with enhancements reaching a factor of 100. This has three important benefits. First, it greatly enlarges the thermodynamic parameter space in XFEL x-ray heating studies of lower-Z materials. Second, it allows the use of higher probe photon energies, enabling higher-information content x-ray diffraction (XRD) measurements such as in two-color XFEL operations. Third, while this is merely one step toward optimization of x-ray heating target design, the demonstration of the importance of nonlocal heat transport establishes important common ground between XFEL-based x-ray heating studies and more traditional laser plasma methods.

Band alignment of SiO2/(AlxGa1-x)2O3 (0 ≤ x ≤ 0.49) determined by X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Feng, Zhaoqing; Feng, Qian; Zhang, Jincheng; Li, Xiang; Li, Fuguo; Huang, Lu; Chen, Hong-Yan; Lu, Hong-Liang; Hao, Yue

2018-03-01

In this work, we report the investigation of the band alignment of SiO2/(AlxGa1-x)2O3 (0 ≤ x ≤ 0.49) utilizing the high resolution X-ray photoelectron spectroscopy (XPS) measurements. The single crystallinity and orientation of β-(AlxGa1-x)2O3 films grown on sapphire by pulsed laser deposition were studied with the high resolution X-ray diffraction. The Ga 2p3/2 and Si 2p core-level spectra as well as valence band spectra were used in the analysis of band alignment. As the mole fraction x of Al increases from 0 to 0.49, the bandgap and conduction band offset values of SiO2/(AlxGa1-x)2O3 increases from 4.9 to 5.6 eV and from 1.5 to 2.1 eV, respectively, while that of valence band offset decreases from 2.2 to 0.9 eV. From the results obtained, the energy band diagram of the studied SiO2/(AlxGa1-x)2O3 (0 ≤ x ≤ 0.49) interfaces is found to be of type I. Energy band lineups of SiO2/(AlxGa1-x)2O3 were thus determined which can be used as for Ga2O3 based power device technology.

In Situ X-Ray Photoelectron Spectroscopy of Model Catalysts: At the Edge of the Gap

NASA Astrophysics Data System (ADS)

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.

2013-03-01

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 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 setup.

Development of x-ray imaging technique for liquid screening at airport

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sulaiman, Nurhani binti, E-mail: nhani.sulaiman@gmail.com; Srisatit, Somyot, E-mail: somyot.s@chula.ac.th

2016-01-22

X-ray imaging technology is a viable option to recognize flammable liquids for the purposes of aviation security. In this study, an X-ray imaging technology was developed whereby, the image viewing system was built with the use of a digital camera coupled with a gadolinium oxysulfide (GOS) fluorescent screen. The camera was equipped with a software for remote control setting of the camera via a USB cable which allows the images to be captured. The image was analysed to determine the average grey level using a software designed by Microsoft Visual Basic 6.0. The data was obtained for various densities ofmore » liquid thickness of 4.5 cm, 6.0 cm and 7.5 cm respectively for X-ray energies ranging from 70 to 200 kVp. In order to verify the reliability of the constructed calibration data, the system was tested with a few types of unknown liquids. The developed system could be conveniently employed for security screening in order to discriminate between a threat and an innocuous liquid.« less

Development of x-ray imaging technique for liquid screening at airport

NASA Astrophysics Data System (ADS)

Sulaiman, Nurhani binti; Srisatit, Somyot

2016-01-01

X-ray imaging technology is a viable option to recognize flammable liquids for the purposes of aviation security. In this study, an X-ray imaging technology was developed whereby, the image viewing system was built with the use of a digital camera coupled with a gadolinium oxysulfide (GOS) fluorescent screen. The camera was equipped with a software for remote control setting of the camera via a USB cable which allows the images to be captured. The image was analysed to determine the average grey level using a software designed by Microsoft Visual Basic 6.0. The data was obtained for various densities of liquid thickness of 4.5 cm, 6.0 cm and 7.5 cm respectively for X-ray energies ranging from 70 to 200 kVp. In order to verify the reliability of the constructed calibration data, the system was tested with a few types of unknown liquids. The developed system could be conveniently employed for security screening in order to discriminate between a threat and an innocuous liquid.

Microgap x-ray detector

DOEpatents

Wuest, Craig R.; Bionta, Richard M.; Ables, Elden

1994-01-01

An x-ray detector which provides for the conversion of x-ray photons into photoelectrons and subsequent amplification of these photoelectrons through the generation of electron avalanches in a thin gas-filled region subject to a high electric potential. The detector comprises a cathode (photocathode) and an anode separated by the thin, gas-filled region. The cathode may comprise a substrate, such a beryllium, coated with a layer of high atomic number material, such as gold, while the anode can be a single conducting plane of material, such as gold, or a plane of resistive material, such as chromium/silicon monoxide, or multiple areas of conductive or resistive material, mounted on a substrate composed of glass, plastic or ceramic. The charge collected from each electron avalanche by the anode is passed through processing electronics to a point of use, such as an oscilloscope.

Quantitative x-ray photoelectron spectroscopy: Quadrupole effects, shake-up, Shirley background, and relative sensitivity factors from a database of true x-ray photoelectron spectra

NASA Astrophysics Data System (ADS)

Seah, M. P.; Gilmore, I. S.

2006-05-01

An analysis is provided of the x-ray photoelectron spectroscopy (XPS) intensities measured in the National Physical Laboratory (NPL) XPS database for 46 solid elements. This present analysis does not change our previous conclusions concerning the excellent correlation between experimental intensities, following deconvolving the spectra with angle-averaged reflection electron energy loss data, and the theoretical intensities involving the dipole approximation using Scofield’s cross sections. Here, more recent calculations for cross sections by Trzhaskovskaya involving quadrupole terms are evaluated and it is shown that their cross sections diverge from the experimental database results by up to a factor of 5. The quadrupole angular terms lead to small corrections that are close to our measurement limit but do appear to be supported in the present analysis. Measurements of the extent of shake-up for the 46 elements broadly agree with the calculations of Yarzhemsky but not in detail. The predicted constancy in the shake-up contribution by Yarzhemsky implies that the use of the Shirley background will lead to a peak area that is a constant fraction of the true peak area including the shake-up intensities. However, the measured variability of the shake-up contribution makes the Shirley background invalid for quantification except for situations where the sensitivity factors are from reference samples similar to those being analyzed.

Investigations on surface chemical analysis using X-ray photoelectron spectroscopy and optical properties of Dy3+-doped LiNa3P2O7 phosphor

NASA Astrophysics Data System (ADS)

Munirathnam, K.; Dillip, G. R.; Chaurasia, Shivanand; Joo, S. W.; Deva Prasad Raju, B.; John Sushma, N.

2016-08-01

Near white-light emitting LiNa3P2O7:Dy3+ phosphors were prepared by a conventional solid-state reaction method. The orthorhombic crystal structure of the phosphors was confirmed using X-ray diffraction (XRD), and the valence states of the surface elements were determined from the binding energies of Li 1s, O 1s, Na 1s, P 2p, and Dy 3d by X-ray photoelectron spectroscopy (XPS). Attenuated total reflectance (ATR) - Fourier transform infrared (FT-IR) spectroscopy was employed to identify the pyrophosphate groups in the phosphors. Diffuse reflectance spectra (DRS) show the absorption bands of the Dy3+ ions in the host material. Intense blue (481 nm) and yellow (575 nm) emissions were obtained at an excitation wavelength of 351 nm and are attributed to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ions, respectively. The combination of these two intense bands generates light emission in the near-white region of the chromaticity diagram.

Photoelectron diffraction from single oriented molecules: Towards ultrafast structure determination of molecules using x-ray free-electron lasers

NASA Astrophysics Data System (ADS)

Kazama, Misato; Fujikawa, Takashi; Kishimoto, Naoki; Mizuno, Tomoya; Adachi, Jun-ichi; Yagishita, Akira

2013-06-01

We provide a molecular structure determination method, based on multiple-scattering x-ray photoelectron diffraction (XPD) calculations. This method is applied to our XPD data on several molecules having different equilibrium geometries. Then it is confirmed that, by our method, bond lengths and bond angles can be determined with a resolution of less than 0.1 Å and 10∘, respectively. Differently from any other scenario of ultrafast structure determination, we measure the two- or three-dimensional XPD of aligned or oriented molecules in the energy range from 100 to 200 eV with a 4π detection velocity map imaging spectrometer. Thanks to the intense and ultrashort pulse properties of x-ray free-electron lasers, our approach exhibits the most probable method for obtaining ultrafast real-time structural information on small to medium-sized molecules consisting of light elements, i.e., a “molecular movie.”

Investigation of the surface composition of electrodeposited black chromium by X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Survilienė, S.; Češūnienė, A.; Jasulaitienė, V.; Jurevičiūtė, I.

2015-01-01

The paper reviews black chromium electrodeposited from a trivalent chromium bath containing ZnO as a second main component. The chemical compositions of the top layers of the black chromium coatings were studied by the X-ray photoelectron spectroscopy method. The surface of black chromium was found to be almost entirely covered with organic substances. To gain information on the state of each element in the deposit bulk, the layer-by-layer etching of the black chromium surface with argon gas was used. Analysis of XPS spectra has shown that the top layers of black chromium without zinc are composed of various Cr(III) components, organic substances and metallic Cr, whereas metallic Cr is almost absent in black chromium containing some amount of Zn(II) compounds. The ratios of metal/oxide phases were found to be 10/27 and 2/28 for black chromium without and with zinc, respectively. It has been determined that owing to the presence of ZnO in the Cr(III) bath, the percentage of metallic chromium is substantially reduced in black chromium which is quite important for good solar selective characteristics of the coating. The results confirm some of earlier observations and provide new information on the composition of the near-surface layers.

Evidences for dry deintercalation in layered compounds upon controlled surface charging in x-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Feldman, Y.; Zak, A.; Tenne, R.; Cohen, H.

2003-09-01

Pronounced surface diffusion is observed during x-ray photoelectron spectroscopy measurements of 2H platelets and inorganic fullerene-like (IF) MS2 (M=W,Mo) powders, intercalated with alkaline (A=K,Na) elements. Using controlled surface charging the intercalants migrate towards the surface, where they oxidize. This dry deintercalation is controllable via external charging parameters, yet showing that internal chemical and structural parameters play an important role in the process. Diffusion rates out of 2H matrixes are generally higher than in corresponding IF samples. Clear differences are also found between Mo and W-based systems. Application of this approach into surface modification and processing is proposed.

Study of average valence and valence electron distribution of several oxides using X-ray photoelectron spectra

NASA Astrophysics Data System (ADS)

Ding, L. L.; Wu, L. Q.; Ge, X. S.; Du, Y. N.; Qian, J. J.; Tang, G. D.; Zhong, W.

2018-06-01

X-ray photoelectron spectra of the O 1s electrons of MnFe2O4, ZnFe2O4, ZnO, and CaO were used to estimate the average valence, ValO, of the oxygen anions in these samples. The absolute values of ValO for these samples were found to be distinctly lower than the traditional value of 2.0, suggesting that the total average valences of the cations are also lower than the conventionally accepted values owing to valence balance in the compounds. In addition, we analyzed the valence band spectra of the samples and investigated the distribution characteristics of the valence electrons.

Sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy setup for pulsed and constant wave X-ray light sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shavorskiy, Andrey; Slaughter, Daniel S.; Zegkinoglou, Ioannis

2014-09-15

An apparatus for sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy studies with pulsed and constant wave X-ray light sources is presented. A differentially pumped hemispherical electron analyzer is equipped with a delay-line detector that simultaneously records the position and arrival time of every single electron at the exit aperture of the hemisphere with ∼0.1 mm spatial resolution and ∼150 ps temporal accuracy. The kinetic energies of the photoelectrons are encoded in the hit positions along the dispersive axis of the two-dimensional detector. Pump-probe time-delays are provided by the electron arrival times relative to the pump pulse timing. An average time-resolution ofmore » (780 ± 20) ps (FWHM) is demonstrated for a hemisphere pass energy E{sub p} = 150 eV and an electron kinetic energy range KE = 503–508 eV. The time-resolution of the setup is limited by the electron time-of-flight (TOF) spread related to the electron trajectory distribution within the analyzer hemisphere and within the electrostatic lens system that images the interaction volume onto the hemisphere entrance slit. The TOF spread for electrons with KE = 430 eV varies between ∼9 ns at a pass energy of 50 eV and ∼1 ns at pass energies between 200 eV and 400 eV. The correlation between the retarding ratio and the TOF spread is evaluated by means of both analytical descriptions of the electron trajectories within the analyzer hemisphere and computer simulations of the entire trajectories including the electrostatic lens system. In agreement with previous studies, we find that the by far dominant contribution to the TOF spread is acquired within the hemisphere. However, both experiment and computer simulations show that the lens system indirectly affects the time resolution of the setup to a significant extent by inducing a strong dependence of the angular spread of electron trajectories entering the hemisphere on the retarding ratio. The scaling of the

Oxidation and deprotonation of synthetic Fe{sup II}-Fe{sup III} (oxy)hydroxycarbonate Green Rust: An X-ray photoelectron study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mullet, M.; Guillemin, Y.; Ruby, C.

X-ray photoelectron spectroscopy (XPS) was used to investigate chemical bonding and distribution of iron and oxygen species at the surface of Green Rusts (GRs). GRs with variable composition, i.e. Fe{sup II}{sub 6(1-x)}Fe{sup III}{sub 6x}O{sub 12}H{sub 2(7-3x)} CO{sub 3}.3H{sub 2}O where the Fe{sup III} molar fraction of the positively charged hydroxide sheets, x=[Fe(III)]/[Fe(total)] belongs to [1/3, 1], were synthesised under an inert atmosphere. The broadened Fe(2p{sub 3/2}) spectra were fitted using Gupta and Sen multiplets peaks and additional satellite and surface features. The [Fe(III)]/[Fe(total)] surface atomic ratios closely agree with the x ratios expected from the bulk composition, which gives amore » high degree of confidence on the validity of the proposed fitting procedure. The valence band spectra are also reported and show dependencies on iron speciation. The O(1s) spectra revealed the presence of O{sup 2-}, OH{sup -} species and adsorbed water. The hydroxyl component decreases with increasing x values, i.e. with the amount of ferric iron, while the oxide component increases. This study provides direct spectroscopic evidence of the deprotonation of hydroxyl groups that occurs simultaneously with the oxidation of ferrous iron within the GR structure. - Graphical abstract: X-ray photoelectron spectroscopy (XPS) is used to investigate chemical bonding and distribution of iron and oxygen species at the surface of Green Rust (GR) compounds. First spectroscopic evidence of the deprotonation of hydroxyls groups occurring simultaneously to the oxidation of Fe(II) into Fe(III) species is provided.« less

Deduction of the chemical state and the electronic structure of Nd{sub 2}Fe{sub 14}B compound from X-ray photoelectron spectroscopy core-level and valence-band spectra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jing; Liang, Le; Zhang, Lanting, E-mail: lantingzh@sjtu.edu.cn, E-mail: lmsun@sjtu.edu.cn

2014-10-28

Characterization of chemical state and electronic structure of the technologically important Nd{sub 2}Fe{sub 14}B compound is attractive for understanding the physical nature of its excellent magnetic properties. X-ray photoelectron spectroscopy (XPS) study of such rare-earth compound is important and also challenging due to the easy oxidation of surface and small photoelectron cross-sections of rare-earth 4f electrons and B 2p electrons, etc. Here, we reported an investigation based on XPS spectra of Nd{sub 2}Fe{sub 14}B compound as a function of Ar ion sputtering time. The chemical state of Fe and that of B in Nd{sub 2}Fe{sub 14}B compound can be clearlymore » determined to be 0 and −3, respectively. The Nd in Nd{sub 2}Fe{sub 14}B compound is found to have the chemical state of close to +3 instead of +3 as compared with the Nd in Nd{sub 2}O{sub 3}. In addition, by comparing the valence-band spectrum of Nd{sub 2}Fe{sub 14}B compound to that of the pure Fe, the contributions from Nd, Fe, and B to the valence-band structure of Nd{sub 2}Fe{sub 14}B compound is made more clear. The B 2p states and B 2s states are identified to be at ∼11.2 eV and ∼24.6 eV, respectively, which is reported for the first time. The contribution from Nd 4f states can be identified both in XPS core-level spectrum and XPS valence-band spectrum. Although Nd 4f states partially hybridize with Fe 3d states, Nd 4f states are mainly localized in Nd{sub 2}Fe{sub 14}B compound.« less

Assigning Oxidation States to Organic Compounds via Predictions from X-Ray Photoelectron Spectroscopy: A Discussion of Approaches and Recommended Improvements

ERIC Educational Resources Information Center

Gupta, Vipul; Ganegoda, Hasitha; Engelhard, Mark H.; Terry, Jeff; Linford, Matthew R.

2014-01-01

The traditional assignment of oxidation states to organic molecules is problematic. Accordingly, in 1999, Calzaferri proposed a simple and elegant solution that is based on the similar electronegativities of carbon and hydrogen: hydrogen would be assigned an oxidation state of zero when bonded to carbon. Here, we show that X-ray photoelectron…

Auger electron and X-ray photoelectron spectroscopic study of the biocorrosion of copper by alginic acid polysaccharide

NASA Astrophysics Data System (ADS)

Jolley, John G.; Geesey, Gill G.; Hankins, Michael R.; Wright, Randy B.; Wichlacz, Paul L.

1989-08-01

Thin films (3.4 nm) of copper on germanium substrates were exposed to 2% alginic acid polysaccharide aqueous solution. Pre- and post-exposure characterization were done by Auger electron spectroscopy and X-ray photoelectron spectroscopy. Ancillary graphite furnace atomic absorption spectroscopy was used to monitor the removal process of the copper thin film from the germanium substrate. Results indicate that some of the copper was oxidized by the alginic acid solution. Some of the copper was removed from the Cu/Ge interface and incorporated into the polymer matrix. Thus, biocorrosion of copper was exhibited by the alginic acid polysaccharide.

Effects of the carrier concentration on polarity determination in Ga-doped ZnO films by hard x-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Song, Huaping; Makino, Hisao; Kobata, Masaaki; Nomoto, Junichi; Kobayashi, Keisuke; Yamamoto, Tetsuya

2018-03-01

Core level (CL) and valence band (VB) spectra of heavily Ga-doped ZnO (GZO) films with carrier concentrations (Ne) ranging from 1.8 × 1020 to 1.0 × 1021 cm-3 were measured by high-resolution Al Kα (hν = 1486.6 eV) x-ray photoelectron spectroscopy (XPS) and Cr Kα (hν = 5414.7 eV) hard x-ray photoelectron spectroscopy (HAXPES). The CL spectra of the GZO films measured by XPS had little dependence on Ne. In contrast, clear differences in asymmetric broadening were observed in the HAXPES spectra owing to the large probing depth. The asymmetry in the Zn 2p3/2 and O 1s HAXPES spectra is mainly attributed to the energy loss of the conduction electron plasmon caused by the high Ne of the GZO films. Similar asymmetry was also observed in the VB spectra of these GZO films. It was found that such asymmetry plays a crucial role in the determination of crystal polarity. With increasing Ne, the intensity of the sub-peak at a binding energy Eb of about 5 eV in the VB spectrum decreased and the sub-peak became indistinguishable. We clarified the limitation of the criterion using the sub-peak and proposed an alternative method for polarity determination.

Evaluation of band alignment of α-Ga2O3/α-(Al x Ga1‑ x )2O3 heterostructures by X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Uchida, Takayuki; Jinno, Riena; Takemoto, Shu; Kaneko, Kentaro; Fujita, Shizuo

2018-04-01

The band alignment at an α-Ga2O3/α-(Al x Ga1‑ x )2O3 heterointerface, with different Al compositions (x), grown on a c-plane sapphire substrate was evaluated by X-ray photoelectron spectroscopy. The experimental results show that the heterointerface has the type-I band discontinuity with the valence band offsets of 0.090, 0.12, and 0.14 eV, and the conduction band offsets of 0.34, 0.79, and 1.87 eV, for x values of 0.1, 0.4, and 0.8, respectively. The small band offset for the valence band is attributed to the fact that the valence band of oxides is constituted by the localized O 2p level, which is dominated by the nature of oxygen atoms. The type-I band discontinuity is desirable for a variety of heterostructure devices.

Microgap x-ray detector

DOEpatents

Wuest, C.R.; Bionta, R.M.; Ables, E.

1994-05-03

An x-ray detector is disclosed which provides for the conversion of x-ray photons into photoelectrons and subsequent amplification of these photoelectrons through the generation of electron avalanches in a thin gas-filled region subject to a high electric potential. The detector comprises a cathode (photocathode) and an anode separated by the thin, gas-filled region. The cathode may comprise a substrate, such a beryllium, coated with a layer of high atomic number material, such as gold, while the anode can be a single conducting plane of material, such as gold, or a plane of resistive material, such as chromium/silicon monoxide, or multiple areas of conductive or resistive material, mounted on a substrate composed of glass, plastic or ceramic. The charge collected from each electron avalanche by the anode is passed through processing electronics to a point of use, such as an oscilloscope. 3 figures.

Photoelectron angular distributions from rotationally resolved autoionizing states of N 2

DOE PAGES

Chartrand, A. M.; McCormack, E. F.; Jacovella, U.; ...

2017-12-08

The single-photon, photoelectron-photoion coincidence spectrum of N 2 has been recorded at high (~1.5 cm -1) resolution in the region between the N 2 + X 2Σ g +, v + = 0 and 1 ionization thresholds by using a double imaging spectrometer and intense vacuum-ultraviolet light from the Synchrotron SOLEIL. This approach provides the relative photoionization cross section, the photoelectron energy distribution, and the photoelectron angular distribution as a function of photon energy. The region of interest contains autoionizing valence states, vibrationally autoionizing Rydberg states converging to vibrationally excited levels of the N 2 + X 2Σ g +more » ground state, and electronically autoionizing states converging to the N 2 + A 2Π and B 2Σ u + states. The wavelength resolution is sufficient to resolve rotational structure in the autoionizing states, but the electron energy resolution is insufficient to resolve rotational structure in the photoion spectrum. Here, a simplified approach based on multichannel quantum defect theory is used to predict the photoelectron angular distribution parameters, β, and the results are in reasonably good agreement with experiment.« less

Computational Studies of X-ray Framing Cameras for the National Ignition Facility

DTIC Science & Technology

2013-06-01

Livermore National Laboratory 7000 East Avenue Livermore, CA 94550 USA Abstract The NIF is the world’s most powerful laser facility and is...a phosphor screen where the output is recorded. The x-ray framing cameras have provided excellent information. As the yields at NIF have increased...experiments on the NIF . The basic operation of these cameras is shown in Fig. 1. Incident photons generate photoelectrons both in the pores of the MCP and

Scanning electron and atomic force microscopy, and raman and x-ray photoelectron spectroscopy characterization of near-isogenic soft and hard wheat kernels and corresponding flours

USDA-ARS?s Scientific Manuscript database

Atomic force microscopy (AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) are used to investigate vitreous (hard) and non-vitreous (soft) wheat kernels and their corresponding wheat flours. AFM data reveal two different microstructures. The vitreous kernel reveals a granular text...

Angularly resolved X-ray photoelectron spectroscopy investigation of PTFE after prolonged space exposure

NASA Technical Reports Server (NTRS)

Dalins, I.; Karimi, M.

1992-01-01

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.

Structure determination of molecules in an alignment laser field by femtosecond photoelectron diffraction using an X-ray free-electron laser

PubMed Central

Minemoto, Shinichirou; Teramoto, Takahiro; Akagi, Hiroshi; Fujikawa, Takashi; Majima, Takuya; Nakajima, Kyo; Niki, Kaori; Owada, Shigeki; Sakai, Hirofumi; Togashi, Tadashi; Tono, Kensuke; Tsuru, Shota; Wada, Ken; Yabashi, Makina; Yoshida, Shintaro; Yagishita, Akira

2016-01-01

We have successfully determined the internuclear distance of I2 molecules in an alignment laser field by applying our molecular structure determination methodology to an I 2p X-ray photoelectron diffraction profile observed with femtosecond X-ray free electron laser pulses. Using this methodology, we have found that the internuclear distance of the sample I2 molecules in an alignment Nd:YAG laser field of 6 × 1011 W/cm2 is elongated by from 0.18 to 0.30 Å “in average” relatively to the equilibrium internuclear distance of 2.666 Å. Thus, the present experiment constitutes a critical step towards the goal of femtosecond imaging of chemical reactions and opens a new direction for the study of ultrafast chemical reaction in the gas phase. PMID:27934891

An Electrochemical, Microtopographical and Ambient Pressure X-Ray Photoelectron Spectroscopic Investigation of Si/TiO 2/Ni/Electrolyte Interfaces

DOE PAGES

Lichterman, Michael F.; Richter, Matthias H.; Hu, Shu; ...

2015-12-05

The electrical and spectroscopic properties of the TiO 2/Ni protection layer system, which enables stabilization of otherwise corroding photoanodes, have been investigated in contact with electrolyte solutions by scanning-probe microscopy, electrochemistry and in-situ ambient pressure X-ray photoelectron spectroscopy (AP-XPS). Specifically, the energy-band relations of the p +-Si/ALD-TiO 2/Ni interface have been determined for a selected range of Ni thicknesses. AP-XPS measurements using tender X-rays were performed in a three-electrode electrochemical arrangement under potentiostatic control to obtain information from the semiconductor near-surface region, the electrochemical double layer (ECDL) and the electrolyte beyond the ECDL. The degree of conductivity depended on themore » chemical state of the Ni on the TiO 2 surface. At low loadings of Ni, the Ni was present primarily as an oxide layer and the samples were not conductive, although the TiO 2 XPS core levels nonetheless displayed behavior indicative of a metal-electrolyte junction. In contrast, as the Ni thickness increased, the Ni phase was primarily metallic and the electrochemical behavior became highly conductive, with the AP-XPS data indicative of a metal-electrolyte junction. Electrochemical and microtopographical methods have been employed to better define the nature of the TiO 2/Ni electrodes and to contextualize the AP-XPS results.« less

X-ray screening seems to reduce gastric cancer mortality by half in a community-controlled trial in Costa Rica

PubMed Central

Rosero-Bixby, L; Sierra, R

2007-01-01

X-ray screening of gastric cancer is broadly used in Japan, although no controlled trial has proved its effectiveness. This study evaluates the impact of an X-ray screening demonstrative intervention to reduce gastric cancer mortality in a Costa Rican region. The evaluation follows a quasi-experimental, community-controlled design, with measures before and after. About 7000 individuals participated by invitation in the two-wave screening programme. X-ray screening was followed by videoendoscopy and gastric biopsies. Treatment included resection with or without lymph node dissection. Comparisons with two control groups estimate that gastric cancer mortality was halved in the period from 2 to 7 years after the first screening visit. Validity of X-rays as used in this intervention had 88% sensitivity, 80% specificity, and 3% predictive value for individuals with two screening visits. Incidence in the screened group increased up to four times. Case survival was 85% in the intervention group after 5 years, compared to 12% among the controls before the intervention and 35% among the controls in the same region after the intervention. Although X-ray mass screening seems able to reduce stomach cancer mortality, its high cost may be an obstacle for scaling up this intervention in a non-rich country like Costa Rica. PMID:17912238

X-ray photoelectron spectrometry and binding energies of Be 1s and O 1s core levels in clinobarylite, BaBe{sub 2}Si{sub 2}O{sub 7}, from Khibiny massif, Kola peninsula

DOE Office of Scientific and Technical Information (OSTI.GOV)

Atuchin, V.V.; Kesler, V.G.; Sapozhnikov, V.K.

2008-09-15

The electronic structure of BaBe{sub 2}Si{sub 2}O{sub 7}, clinobarylite, has been investigated by means of X-ray photoelectron spectroscopy (XPS). The valence band of the crystal is mainly formed by Ba 5p, Ba 3s and O 2s states. At higher binding energies the emission lines related to the Si 2p, Be 1s, Si 2s, O 1s and numerous Ba-related states were analyzed in the photoemission spectrum. The Si KLL Auger line has been measured under excitation by the bremsstrahlung X-rays from the Al anode. Chemical bonding effects for Be 1s core level have been considered by comparison with electronic parameters measuredmore » for other beryllium containing oxides.« less

Rapid X-ray variability properties during the unusual very hard state in neutron-star low-mass X-ray binaries

NASA Astrophysics Data System (ADS)

Wijnands, R.; Parikh, A. S.; Altamirano, D.; Homan, J.; Degenaar, N.

2017-11-01

Here, we study the rapid X-ray variability (using XMM-Newton observations) of three neutron-star low-mass X-ray binaries (1RXS J180408.9-342058, EXO 1745-248 and IGR J18245-2452) during their recently proposed very hard spectral state. All our systems exhibit a strong to very strong noise component in their power density spectra (rms amplitudes ranging from 34 per cent to 102 per cent) with very low characteristic frequencies (as low as 0.01 Hz). These properties are more extreme than what is commonly observed in the canonical hard state of neutron-star low-mass X-ray binaries observed at X-ray luminosities similar to those we observe from our sources. This suggests that indeed the very hard state is a spectral-timing state distinct from the hard state, although we argue that the variability behaviour of IGR J18245-2452 is very extreme and possibly this source was in a very unusual state. We also compare our results with the rapid X-ray variability of the accreting millisecond X-ray pulsars IGR J00291+5934 and Swift J0911.9-6452 (also using XMM-Newton data) for which previously similar variability phenomena were observed. Although their energy spectra (as observed using the Swift X-ray telescope) were not necessarily as hard (i.e. for Swift J0911.9-6452) as for our other three sources, we conclude that likely both sources were also in very similar state during their XMM-Newton observations. This suggests that different sources that are found in this new state might exhibit different spectral hardness and one has to study both the spectral and the rapid variability to identify this unusual state.

X-ray photoelectron spectroscopy and paramagnetic resonance evidence for shock-induced intramolecular bond breaking in some energetic solids

NASA Astrophysics Data System (ADS)

Owens, F. J.; Sharma, J.

1980-03-01

Solid samples of 1,3,5, trinitro 1,3,5, triazacyclohexane (RDX), trinitrotoluene (TNT), and ammonium nitrate were subjected to shock pulses of strength and duration less than the threshold to cause detonation. The recovered shocked samples were studied by x-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). The results of these measurements indicate that the shock pulse either broke or altered the internal bonds of the molecules of the solid. The results of the shock decomposition are compared with measurements of the uv and slow thermal decomposition of these materials using the same experimental techniques.

Probing buried layers by photoelectron spectromicroscopy with hard x-ray excitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiemann, C.; Patt, M.; Cramm, S.

We report about a proof-of-principle experiment which explores the perspectives of performing hard x-ray photoemission spectromicroscopy with high lateral resolution. Our results obtained with an energy-filtered photoemission microscope at the PETRA III storage ring facility using hard x-ray excitation up to 6.5 keV photon energy demonstrate that it is possible to obtain selected-area x-ray photoemission spectra from regions less than 500 nm in diameter.

Characterization of copper oxides, iron oxides, and zinc copper ferrite desulfurization sorbents by X-ray photoelectron spectroscopy and scanning electron microscopy

NASA Astrophysics Data System (ADS)

Siriwardane, Ranjani V.; Poston, James A.

1993-05-01

Characterization of copper oxides, iron oxides, and zinc copper ferrite desulfurization sorbents was performed by X-ray photoelectron spectroscopy and scanning electron microscopy/energy-dispersive spectroscopy at temperatures of 298 to 823 K. Analysis of copper oxides indicated that the satellite structure of the Cu22p region was absent in the Cu(I) state but was present in the Cu(II) state. Reduction of CuO at room temperature was observed when the ion gauge was placed close to the sample. The satellite structure was absent in all the copper oxides at 823 K in vacuum. Differentiation of the oxidation state of copper utilizing both Cu(L 3M 4,5M 4,5) X-ray-induced Auger lines and Cu2p satellite structure, indicated that the copper in zinc copper ferrite was in the + 1 oxidation state at 823 K. This + 1 state of copper was not significantly changed after exposure to H 2, CO, and H 2O. There was an increase in Cu/Zn ratio and a decrease in Fe/Zn ratio on the surface of zinc copper ferrite at 823 K compared to that at room temperature. These conditions of copper offered the best sulfidation equilibrium for the zinc copper ferrite desulfurization sorbent. Analysis of iron oxides indicated that there was some reduction of both Fe 2O 3 and FeO at 823K. The iron in zinc copper ferrite was similar to that of Fe 2O 3 at room temperature but there was some reduction of this Fe(III) state to Fe(II) at 823 K. This reduction was more enhanced in the presence of H 2 and CO. Reduction to Fe(II) may not be desirable for the lifetime of the sorbent.

X-ray photoelectron spectroscopic study of the oxide film on an aluminum-tin alloy in 3.5% sodium chloride solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Venugopal, A.; Selvam, P.; Raja, V.S.

1997-10-01

Oxide films on Al and an Al-Sn alloy were analyzed by x-ray photoelectron spectroscopy (XPS) after immersion in 3.5% sodium chloride (NaCl) solution. Results showed Sn exhibited both Sn{sup 2+} and Sn{sup 4+} oxidation stats in the oxide film. It was proposed that incorporation of these cations in the film would result in generation of more anionic and cationic vacancies in aluminum oxide (Al{sub 2}O{sub 3}), leading to active dissolution of Al.

Attosecond time-energy structure of X-ray free-electron laser pulses

NASA Astrophysics Data System (ADS)

Hartmann, N.; Hartmann, G.; Heider, R.; Wagner, M. S.; Ilchen, M.; Buck, J.; Lindahl, A. O.; Benko, C.; Grünert, J.; Krzywinski, J.; Liu, J.; Lutman, A. A.; Marinelli, A.; Maxwell, T.; Miahnahri, A. A.; Moeller, S. P.; Planas, M.; Robinson, J.; Kazansky, A. K.; Kabachnik, N. M.; Viefhaus, J.; Feurer, T.; Kienberger, R.; Coffee, R. N.; Helml, W.

2018-04-01

The time-energy information of ultrashort X-ray free-electron laser pulses generated by the Linac Coherent Light Source is measured with attosecond resolution via angular streaking of neon 1s photoelectrons. The X-ray pulses promote electrons from the neon core level into an ionization continuum, where they are dressed with the electric field of a circularly polarized infrared laser. This induces characteristic modulations of the resulting photoelectron energy and angular distribution. From these modulations we recover the single-shot attosecond intensity structure and chirp of arbitrary X-ray pulses based on self-amplified spontaneous emission, which have eluded direct measurement so far. We characterize individual attosecond pulses, including their instantaneous frequency, and identify double pulses with well-defined delays and spectral properties, thus paving the way for X-ray pump/X-ray probe attosecond free-electron laser science.

X-ray photoelectron spectroscopy of select multi-layered transition metal carbides (MXenes)

NASA Astrophysics Data System (ADS)

Halim, Joseph; Cook, Kevin M.; Naguib, Michael; Eklund, Per; Gogotsi, Yury; Rosen, Johanna; Barsoum, Michel W.

2016-01-01

In this work, a detailed high resolution X-ray photoelectron spectroscopy (XPS) analysis is presented for select MXenes-a recently discovered family of two-dimensional (2D) carbides and carbonitrides. Given their 2D nature, understanding their surface chemistry is paramount. Herein we identify and quantify the surface groups present before, and after, sputter-cleaning as well as freshly prepared vs. aged multi-layered cold pressed discs. The nominal compositions of the MXenes studied here are Ti3C2Tx, Ti2CTx, Ti3CNTx, Nb2CTx and Nb4C3Tx, where T represents surface groups that this work attempts to quantify. In all the cases, the presence of three surface terminations, sbnd O, sbnd OH and sbnd F, in addition to OH-terminations relatively strongly bonded to H2O molecules, was confirmed. From XPS peak fits, it was possible to establish the average sum of the negative charges of the terminations for the aforementioned MXenes. Based on this work, it is now possible to quantify the nature of the surface terminations. This information can, in turn, be used to better design and tailor these novel 2D materials for various applications.

X-ray Variations at the Orbital Period from Cygnus X-1 IN the High/Soft State

NASA Astrophysics Data System (ADS)

Boroson, Bram; Vrtilek, Saeqa Dil

2010-02-01

Orbital variability has been found in the X-ray hardness of the black hole candidate Cygnus X-1 during the soft/high X-ray state using light curves provided by the Rossi X-ray Timing Explorer's All-Sky Monitor. We are able to set broad limits on how the mass-loss rate and X-ray luminosity vary between the hard and soft states. The folded light curve shows diminished flux in the soft X-ray band at phi = 0 (defined as the time of the superior conjunction of the X-ray source). Models of the orbital variability provide slightly superior fits when the absorbing gas is concentrated in neutral clumps and better explain the strong variability in hardness. In combination with the previously established hard/low state dips, our observations give a lower limit to the mass-loss rate in the soft state (\\dot{M}<2× 10^{-6} M_{⊙} yr-1) than the limit in the hard state (\\dot{M}<4× 10^{-6} M_{⊙} yr-1). Without a change in the wind structure between X-ray states, the greater mass-loss rate during the low/hard state would be inconsistent with the increased flaring seen during the high-soft state.

Elucidating the electronic structure of supported gold nanoparticles and its relevance to catalysis by means of hard X-ray photoelectron spectroscopy

DOE PAGES

Reinecke, Benjamin N.; Kuhl, Kendra P.; Ogasawara, Hirohito; ...

2015-12-31

We report on the electronic structure of Au (gold) nanoparticles supported onto TiO 2 with a goal of elucidating the most important effects that contribute to their high catalytic activity. We synthesize and characterize with high resolution transmission electron microscopy (HRTEM) 3.4, 5.3, and 9.5 nm diameter TiO 2-supported Au nanoparticles with nearly spherical shape and measure their valence band using Au 5d subshell sensitive hard X-ray photoelectron spectroscopy (HAXPES) conducted at Spring-8. Based on density functional theory (DFT) calculations of various Au surface structures, we interpret the observed changes in the Au 5d valence band structure as a functionmore » of size in terms of an increasing percentage of Au atoms at corners/edges for decreasing particle size. Finally, this work elucidates how Au coordination number impacts the electronic structure of Au nanoparticles, ultimately giving rise to their well-known catalytic activity.« less

Combined use of backscattered and transmitted images in x-ray personnel screening systems

NASA Astrophysics Data System (ADS)

Tracey, B.; Schiefele, Markus; Alvino, Christopher; Miller, Eric; Al-Kofani, Omar

2012-06-01

Current aviation security relies heavily on personnel screening using X-ray backscatter systems or other advanced imaging technologies. Passenger privacy concerns and screening times can be reduced through the use of low-dose twosided X-ray backscatter (Bx) systems, which also have the ability to collect transmission (Tx) X-ray. Bx images reveal objects placed on the body, such as contraband and security threats, as well as anatomical features at or close to the surface, such as lungs cavities and bones. While the quality of the transmission images is lower than medical imagery due to the low X-ray dose, Tx images can be of significant value in interpreting features in the Bx images, such as lung cavities, which can cause false alarms in automated threat detection (ATD) algorithms. Here we demonstrate an ATD processing chain fusing both Tx and BX images. The approach employs automatically extracted fiducial points on the body and localized active contour methods to segments lungs in acquired Tx and Bx images. Additionally, we derive metrics from the Tx image can be related to the probability of observing internal body structure in the Bx image. The combined use of Tx and Bx data can enable improved overall system performance.

Depth-resolved electronic structure of spintronic nanostructures and complex materials with soft and hard x-ray photoemission

NASA Astrophysics Data System (ADS)

Gray, Alexander

second aspect of this dissertation, depth selectivity is achieved by setting-up an x-ray standing wave field in the sample by growing it on a synthetic periodic multilayer mirror substrate, which in first-order Bragg reflection acts as the standing-wave generator. The antinodes of the standing wave function as "epicenters" for photoemission, and can be moved in the direction perpendicular to the sample surface by either scanning the incidence angle thetainc, or the photon energy through the Bragg condition. Alternatively, provided that one of the underlying layers in the structure is grown in a shape of a wedge with varying thickness, the standing wave can be scanned vertically though the sample simply by moving the sample laterally under the x-ray measurement spot. We present the first study in which the chemical and electronic-structure profiles of a magnetic tunnel junction La 0.7Sr0.3MnO3/SrTiO3 (LSMO/STO) have been quantitatively determined by a combination of soft and hard x-ray standing-wave excited photoemission. By comparing experiment to x-ray optical calculations, the detailed chemical profile of the constituent layers and their interfaces is quantitatively derived with Angstrom precision. Combined with core-hole multiplet theory incorporating Jahn-Teller distortion, these results indicate a change in the Mn bonding state near the LSMO/STO interface. Our results thus further clarify the reduced performance of LSMO/STO magnetic tunnel junction compared to ideal theoretical expectations. Finally, we demonstrate the addition of depth resolution to the usual two-dimensional images in photoelectron emission microscopy (PEEM) as a further aspect of standing-wave photoemission. We show that standing-wave excited photoelectron microscopy can be used to produce element-specific and depth-selective images of patterned samples. In conjunction with x-ray optical theoretical modeling, quantitative information about the depth-dependent chemical composition of the sample can

Chemical-state-selective mapping at nanometer scale using synchrotron radiation and photoelectron emission microscopy.

PubMed

Hirao, Norie; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Honda, Mitsunori

2010-01-01

For surface analyses of semiconductor devices and various functional materials, it has become indispensable to analyze valence states at nanometer scale due to the rapid developments of nanotechnology. Since a method for microscopic mapping dependent on the chemical bond states has not been established so far, we have developed a photoelectron emission microscopy (PEEM) system combined with synchrotron soft X-ray excitation. The samples investigated were Si/SiO(x) micro-patterns prepared by O(2)(+) ion implantation in Si(001) wafer using a mask. PEEM images excited by various photon energies around the Si K-edge were observed. The lateral spatial resolution of the system was about 41 nm. The brightness of each spot in PEEM images changed depending on the photon energy, due to the X-ray absorption intensity of the respective chemical state. Since the surface of this sample was topographically flat, it has been demonstrated that the present method can be applied to observations of the microscopic pattern, depending not on the morphology, but only on the valence states of silicon. We have also in-situ measured the changes of the PEEM images upon annealing, and elucidated the mechanism of the lateral diffusion of oxygen and valence states of silicon at the nanometer scale.

Thermal stability of electron-irradiated poly(tetrafluoroethylene) - X-ray photoelectron and mass spectroscopic study

NASA Technical Reports Server (NTRS)

Wheeler, Donald R.; Pepper, Stephen V.

1990-01-01

Polytetrafluoroethylene (PTFE) was subjected to 3 keV electron bombardment and then heated in vacuum to 300 C. The behavior of the material as a function of radiation dose and temperature was studied by X-ray photoelectron spectroscopy (XPS) of the surface and mass spectroscopy of the species evolved. Lightly damaged material heated to 300 C evolved saturated fluorocarbon species, whereas unsaturated fluorocarbon species were evolved from heavily damaged material. After heating the heavily damaged material, those features in the XPS spectrum that were associated with damage diminished, giving the appearance that the radiation damage had annealed. The observations were interpreted by incorporating mass transport of severed chain fragments and thermal decomposition of severely damaged material into the branched and cross-linked network model of irradiated PTFE. The apparent annealing of the radiation damage was due to covering of the network by saturated fragments that easily diffused through the decomposed material to the surface region upon heating.

A convolutional neural network-based screening tool for X-ray serial crystallography

PubMed Central

Ke, Tsung-Wei; Brewster, Aaron S.; Yu, Stella X.; Ushizima, Daniela; Yang, Chao; Sauter, Nicholas K.

2018-01-01

A new tool is introduced for screening macromolecular X-ray crystallography diffraction images produced at an X-ray free-electron laser light source. Based on a data-driven deep learning approach, the proposed tool executes a convolutional neural network to detect Bragg spots. Automatic image processing algorithms described can enable the classification of large data sets, acquired under realistic conditions consisting of noisy data with experimental artifacts. Outcomes are compared for different data regimes, including samples from multiple instruments and differing amounts of training data for neural network optimization. PMID:29714177

A convolutional neural network-based screening tool for X-ray serial crystallography.

PubMed

Ke, Tsung Wei; Brewster, Aaron S; Yu, Stella X; Ushizima, Daniela; Yang, Chao; Sauter, Nicholas K

2018-05-01

A new tool is introduced for screening macromolecular X-ray crystallography diffraction images produced at an X-ray free-electron laser light source. Based on a data-driven deep learning approach, the proposed tool executes a convolutional neural network to detect Bragg spots. Automatic image processing algorithms described can enable the classification of large data sets, acquired under realistic conditions consisting of noisy data with experimental artifacts. Outcomes are compared for different data regimes, including samples from multiple instruments and differing amounts of training data for neural network optimization. open access.

A convolutional neural network-based screening tool for X-ray serial crystallography

DOE PAGES

Ke, Tsung-Wei; Brewster, Aaron S.; Yu, Stella X.; ...

2018-04-24

A new tool is introduced for screening macromolecular X-ray crystallography diffraction images produced at an X-ray free-electron laser light source. Based on a data-driven deep learning approach, the proposed tool executes a convolutional neural network to detect Bragg spots. Automatic image processing algorithms described can enable the classification of large data sets, acquired under realistic conditions consisting of noisy data with experimental artifacts. Outcomes are compared for different data regimes, including samples from multiple instruments and differing amounts of training data for neural network optimization.

A convolutional neural network-based screening tool for X-ray serial crystallography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ke, Tsung-Wei; Brewster, Aaron S.; Yu, Stella X.

A new tool is introduced for screening macromolecular X-ray crystallography diffraction images produced at an X-ray free-electron laser light source. Based on a data-driven deep learning approach, the proposed tool executes a convolutional neural network to detect Bragg spots. Automatic image processing algorithms described can enable the classification of large data sets, acquired under realistic conditions consisting of noisy data with experimental artifacts. Outcomes are compared for different data regimes, including samples from multiple instruments and differing amounts of training data for neural network optimization.

X-ray Photoelectron Spectroscopy Analysis of Gold Surfaces after Removal of Thiolated DNA Oligomers by Ultraviolet/Ozone Treatment

PubMed Central

Mirsaleh-Kohan, Nasrin; Bass, Andrew D.; Sanche, Léon

2012-01-01

Well ordered films of molecular DNA can be formed by the attachment of thiolated DNA oligonucleotides to a supporting gold substrate. The gold substrate represents a significant fraction of the total cost of preparing such films and it is thus important to determine whether such substrates can be reused. Here we investigate with X-ray Photoelectron Spectroscopy the suitability of UV/ozonolysis previously employed to remove alkanethiols from gold, for removing 40-mer, single and double stranded synthetic DNA. We find that while UV/O3 can indeed remove thiolated DNA from gold slides, the treatment times required permit the implantation of additional organic contaminants. PMID:20000594

X-ray photoelectron spectroscopy analysis of gold surfaces after removal of thiolated DNA oligomers by ultraviolet/ozone treatment.

PubMed

Mirsaleh-Kohan, Nasrin; Bass, Andrew D; Sanche, Léon

2010-05-04

Well-ordered films of molecular DNA can be formed by the attachment of thiolated DNA oligonucleotides to a supporting gold substrate. The gold substrate represents a significant fraction of the total cost of preparing such films, and it is thus important to determine whether such substrates can be reused. Here, we investigate with X-ray photoelectron spectroscopy the suitability of UV/ozonolysis previously employed to remove alkanethiols from gold, for removing 40-mer, single- and double-stranded synthetic DNA. We find that while UV/O(3) can indeed remove thiolated DNA from gold slides, the treatment times required permit the implantation of additional organic contaminants.

Segmented-spectrum detection mechanism for medical x-ray in CdTe

NASA Astrophysics Data System (ADS)

Shi, Zaifeng; Meng, Qingzhen; Cao, Qingjie; Yao, Suying

2016-01-01

This paper presents a segmented X-ray spectrum detection method based on a layered X-ray detector in Cadmium Telluride (CdTe) substrate. We describe the three-dimensional structure of proposed detector pixel and investigate the matched spectrum-resolving method. Polychromatic X-ray beam enter the CdTe substrate edge on and will be absorbed completely in different thickness varying with photon energy. Discrete potential wells are formed under external controlling voltage to collect the photo-electrons generated in different layers, and segmented X-ray spectrum can be deduced from the quantity of photo-electrons. In this work, we verify the feasibility of the segmented-spectrum detection mechanism by simulating the absorption of monochromatic X-ray in a CdTe substrate. Experiments in simulation show that the number of photo-electrons grow exponentially with the increase of incident thickness, and photons with different energy will be absorbed in various thickness. The charges generated in different layers are collected into adjacent potential wells, and collection efficiency is estimated to be about 87% for different incident intensity under the 40000V/cm electric field. Errors caused by charge sharing between neighboring layers are also analyzed, and it can be considered negligible by setting appropriate size of electrodes.

Modified Oxygen Defect Chemistry at Transition Metal Oxide Heterostructures Probed by Hard X-ray Photoelectron Spectroscopy and X-ray Diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Yan; Fong, Dillon D.; Herbert, F. William

Transition metal oxide hetero-structures are interesting due to the distinctly different properties that can arise from their interfaces, such as superconductivity, high catalytic activity and magnetism. Oxygen point defects can play an important role at these interfaces in inducing potentially novel properties. The design of oxide hetero-structures in which the oxygen defects are manipulated to attain specific functionalities requires the ability to resolve the state and concentration of local oxygen defects across buried interfaces. In this work, we utilized a novel combination of hard x-ray photoelectron spectroscopy (HAXPES) and high resolution xray diffraction (HRXRD) to probe the local oxygen defectmore » distribution across the buried interfaces of oxide heterolayers. This approach provides a non-destructive way to qualitatively probe locally the oxygen defects in transition metal oxide hetero-structures. We studied two trilayer structures as model systems - the La 0.8Sr 0.2CoO 3-δ/(La 0.5Sr 0.5) 2CoO 4/La 0.8Sr 0.2CoO 3-δ (LSC 113/LSC 214) and the La 0.8Sr 0.2CoO 3-δ/La 2NiO 4+δ/La 0.8Sr 0.2CoO 3-δ (LSC 113/LNO 214) on SrTiO 3(001) single crystal substrates. We found that the oxygen defect chemistry of these transition metal oxides was strongly impacted by the presence of interfaces and the properties of the adjacent phases. Under reducing conditions, the LSC 113 in the LSC 113/LNO 214 tri-layer had less oxygen vacancies than the LSC 113 in the LSC 113/LSC 214 tri-layer and the LSC 113 single phase film. On the other hand, LSC 214 and LNO 214 were more reduced in the two tri-layer structures when in contact with the LSC 113 layer compared to their single phase counterparts. Furthermore, the results point out a potential way to modify the local oxygen defect states at oxide hetero-interfaces.« less

Modified Oxygen Defect Chemistry at Transition Metal Oxide Heterostructures Probed by Hard X-ray Photoelectron Spectroscopy and X-ray Diffraction

DOE PAGES

Chen, Yan; Fong, Dillon D.; Herbert, F. William; ...

2018-04-17

Transition metal oxide hetero-structures are interesting due to the distinctly different properties that can arise from their interfaces, such as superconductivity, high catalytic activity and magnetism. Oxygen point defects can play an important role at these interfaces in inducing potentially novel properties. The design of oxide hetero-structures in which the oxygen defects are manipulated to attain specific functionalities requires the ability to resolve the state and concentration of local oxygen defects across buried interfaces. In this work, we utilized a novel combination of hard x-ray photoelectron spectroscopy (HAXPES) and high resolution xray diffraction (HRXRD) to probe the local oxygen defectmore » distribution across the buried interfaces of oxide heterolayers. This approach provides a non-destructive way to qualitatively probe locally the oxygen defects in transition metal oxide hetero-structures. We studied two trilayer structures as model systems - the La 0.8Sr 0.2CoO 3-δ/(La 0.5Sr 0.5) 2CoO 4/La 0.8Sr 0.2CoO 3-δ (LSC 113/LSC 214) and the La 0.8Sr 0.2CoO 3-δ/La 2NiO 4+δ/La 0.8Sr 0.2CoO 3-δ (LSC 113/LNO 214) on SrTiO 3(001) single crystal substrates. We found that the oxygen defect chemistry of these transition metal oxides was strongly impacted by the presence of interfaces and the properties of the adjacent phases. Under reducing conditions, the LSC 113 in the LSC 113/LNO 214 tri-layer had less oxygen vacancies than the LSC 113 in the LSC 113/LSC 214 tri-layer and the LSC 113 single phase film. On the other hand, LSC 214 and LNO 214 were more reduced in the two tri-layer structures when in contact with the LSC 113 layer compared to their single phase counterparts. Furthermore, the results point out a potential way to modify the local oxygen defect states at oxide hetero-interfaces.« less

Low Mass X-ray Binary 4U1705-44 Exiting an Extended High X-ray State

NASA Astrophysics Data System (ADS)

Phillipson, Rebecca; Boyd, Patricia T.; Smale, Alan P.

2017-09-01

The neutron-star low-mass X-ray binary 4U1705-44, which exhibited high amplitude long-term X-ray variability on the order of hundreds of days during the 16-year continuous monitoring by the RXTE ASM (1995-2012), entered an anomalously long high state in July 2012 as observed by MAXI (2009-present).

Comparative study of GeO 2/Ge and SiO 2/Si structures on anomalous charging of oxide films upon water adsorption revealed by ambient-pressure X-ray photoelectron spectroscopy

DOE PAGES

Mori, Daichi; Oka, Hiroshi; Hosoi, Takuji; ...

2016-09-02

The energy difference between the oxide and bulk peaks in X-ray photoelectron spectroscopy (XPS) spectra was investigated in this paper for both GeO 2/Ge and SiO 2/Si structures with thickness-controlled water films. This was achieved by obtaining XPS spectra at various values of relative humidity (RH) of up to ~15%. The increase in the energy shift is more significant for thermal GeO 2 on Ge than for thermal SiO 2 on Si above ~10 -4% RH, which is due to the larger amount of water molecules that infiltrate into the GeO 2 film to form hydroxyls. Analyzing the origins ofmore » this energy shift, we propose that the positive charging of a partially hydroxylated GeO 2 film, which is unrelated to X-ray irradiation, causes the larger energy shift for GeO 2/Ge than for SiO 2/Si. A possible microscopic mechanism of this intrinsic positive charging is the emission of electrons from adsorbed water species in the suboxide layer of the GeO 2 film to the Ge bulk, leaving immobile cations or positively charged states in the oxide. Finally, this may be related to the reported negative shift of flat band voltages in metal-oxide-semiconductor diodes with an air-exposed GeO 2 layer.« less

X-ray photoelectron spectroscopic study of surface chemistry of dibenzyl-disulfide on steel under mild and severe wear conditions

NASA Technical Reports Server (NTRS)

Wheeler, D. R.

1977-01-01

Wear tests were performed on 304 stainless steel lubricated with pure mineral oil with and without dibenzyl-disulfide. Both mild and severe wear were observed. The type of wear was distinguished by a marked change in wear rate, friction coefficient, and wear scar appearance. The chemical composition of the wear scar surface was examined with X-ray photoelectron spectroscopy in conjunction with argon ion sputter etching. In severe wear scars, a sulfide was formed at the expense of the normal oxide layer. In mild wear scars, there were only superficial sulfur compounds, but there was a substantial increase in the oxide thickness.

X-ray photoelectron spectroscopy study of radiofrequency sputtered chromium bromide, molybdenum disilicide, and molybdenum disulfide coatings and their friction properties

NASA Technical Reports Server (NTRS)

Wheeler, D. R.; Brainard, W. A.

1977-01-01

Radiofrequency sputtered coatings of CRB2, MOSI2, and MOS2 were examined by X-ray photoelectron spectroscopy. The effects of sputtering target history, deposition time, RF power level, and substrate bias on film composition were studied. Friction tests were run on RF sputtered surfaces of 440-C steel to correlate XPS data with lubricating properties. Significant deviations from stoichiometry and high oxide levels for all three compounds were related to target outgassing. The effect of biasing on these two factors depended on the compound. Improved stoichiometry correlated well with good friction and wear properties.

Dimethyl methylphosphonate adsorption and decomposition on MoO2 as studied by ambient pressure x-ray photoelectron spectroscopy and DFT calculations

NASA Astrophysics Data System (ADS)

Head, Ashley R.; Tsyshevsky, Roman; Trotochaud, Lena; Yu, Yi; Karslıoǧlu, Osman; Eichhorn, Bryan; Kuklja, Maija M.; Bluhm, Hendrik

2018-04-01

Organophosphonates range in their toxicity and are used as pesticides, herbicides, and chemical warfare agents (CWAs). Few laboratories are equipped to handle the most toxic molecules, thus simulants such as dimethyl methylphosphonate (DMMP), are used as a first step in studying adsorption and reactivity on materials. Benchmarked by combined experimental and theoretical studies of simulants, calculations offer an opportunity to understand how molecular interactions with a surface changes upon using a CWA. However, most calculations of DMMP and CWAs on surfaces are limited to adsorption studies on clusters of atoms, which may differ markedly from the behavior on bulk solid-state materials with extended surfaces. We have benchmarked our solid-state periodic calculations of DMMP adsorption and reactivity on MoO2 with ambient pressure x-ray photoelectron spectroscopy studies (APXPS). DMMP is found to interact strongly with a MoO2 film, a model system for the MoO x component in the ASZM-TEDA© gas filtration material. Density functional theory modeling of several adsorption and decomposition mechanisms assist the assignment of APXPS peaks. Our results show that some of the adsorbed DMMP decomposes, with all the products remaining on the surface. The rigorous calculations benchmarked with experiments pave a path to reliable and predictive theoretical studies of CWA interactions with surfaces.

Electronic properties and bonding in Zr Hx thin films investigated by valence-band x-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Magnuson, Martin; Schmidt, Susann; Hultman, Lars; Högberg, Hans

2017-11-01

The electronic structure and chemical bonding in reactively magnetron sputtered Zr Hx (x =0.15 , 0.30, 1.16) thin films with oxygen content as low as 0.2 at.% are investigated by 4d valence band, shallow 4p core-level, and 3d core-level x-ray photoelectron spectroscopy. With increasing hydrogen content, we observe significant reduction of the 4d valence states close to the Fermi level as a result of redistribution of intensity toward the H 1s-Zr 4d hybridization region at ˜6 eV below the Fermi level. For low hydrogen content (x =0.15 , 0.30), the films consist of a superposition of hexagonal closest-packed metal (α phase) and understoichiometric δ -Zr Hx (Ca F2 -type structure) phases, while for x =1.16 , the films form single-phase Zr Hx that largely resembles that of stoichiometric δ -Zr H2 phase. We show that the cubic δ -Zr Hx phase is metastable as thin film up to x =1.16 , while for higher H contents the structure is predicted to be tetragonally distorted. For the investigated Zr H1.16 film, we find chemical shifts of 0.68 and 0.51 eV toward higher binding energies for the Zr 4 p3 /2 and 3 d5 /2 peak positions, respectively. Compared to the Zr metal binding energies of 27.26 and 178.87 eV, this signifies a charge transfer from Zr to H atoms. The change in the electronic structure, spectral line shapes, and chemical shifts as a function of hydrogen content is discussed in relation to the charge transfer from Zr to H that affects the conductivity by charge redistribution in the valence band.

Hydrolysis condensation reactions of titanium alkoxides in thin films: A study of the steric hindrance effect by X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Barlier, Vincent; Bounor-Legaré, Véronique; Boiteux, Gisèle; Davenas, Joël; Léonard, Didier

2008-06-01

An original approach based on X-ray photoelectron spectroscopy (XPS) is proposed to study the influence of the surrounding humidity on the hydrolysis-condensation reactions of five titanium alkoxides in thin films. More precisely, the influence of the nature of the ligands (propoxide, butoxide, isopropoxide, phenoxide, and 9H-carbazole-9-yl-ethyl-oxy) on the reaction rate was evidenced. The reaction advancement was evaluated by comparing XPS chemical compositions to theoretical compositions calculated for all the possible rates. XPS chemical environment information allowed validating the reliability of this approach through the evaluation of the condensation state. In both approaches, the influence of the steric hindrance on the reactivity of titanium alkoxides was highlighted to be similar to what has been previously observed in solution. Theses results corroborate the validity of our XPS approach to determine titanium alkoxide hydrolysis-condensation reactions in the specific application of thin films.

Observing the Electrochemical Oxidation of Co Metal at the Solid/Liquid Interface Using Ambient Pressure X-ray Photoelectron Spectroscopy

DOE PAGES

Han, Yong; Axnanda, Stephanus; Crumlin, Ethan J.; ...

2017-08-28

Some rcent advances of ambient pressure X-ray photoelectron spectroscopy (AP-XPS) have enabled the chemical composition and the electrical potential profile at a liquid/electrode interface under electrochemical reaction conditions to be directly probed. In this work, we apply this operando technique to study the surface chemical composition evolution on a Co metal electrode in 0.1 M KOH aqueous solution under various electrical biases. It is found that an ~12.2 nm-thick layer of Co(OH) 2 forms at a potential of about -0.4 V Ag/AgCl, and upon increasing the anodic potential to about +0.4 V Ag/AgCl, this layer is partially oxidized into cobaltmore » oxyhydroxide (CoOOH). A CoOOH/Co(OH) 2 mixture layer is formed on the top of the electrode surface. Finally, the oxidized surface layer can be reduced to Co0 at a cathodic potential of -1.35 VAg/Cl. Our observations indicate that the ultrathin layer containing cobalt oxyhydroxide is the active phase for oxygen evolution reaction (OER) on a Co electrode in an alkaline electrolyte, consistent with previous studies.« less

Investigation on the interfacial chemical state and band alignment for the sputtering-deposited CaF2/p-GaN heterojunction by angle-resolved X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Zhang, Kexiong; Liao, Meiyong; Sumiya, Masatomo; Koide, Yasuo; Sang, Liwen

2016-11-01

The interfacial chemical state and the band alignment of the sputtering-deposited CaF2/p-GaN hetero-structure were investigated by angle-resolved X-ray photoelectron spectroscopy. The dependence of Ga 3p core-level positions on the collection angles proves that the downward band bending of p-GaN is reduced from 1.51 to 0.85 eV after the deposition of CaF2, which may be due to the reduction of Mg-Ga-O-related interface states by the oxygen-free deposition of CaF2. The band gap of sputtering-deposited CaF2 is estimated to be about 7.97 eV with a potential gradient of 0.48 eV obtained by the variation of the Ca 2p3/2 position on different collection angles. By taking into account the p-GaN surface band bending and potential gradient in the CaF2 layer, large valence and conduction band offsets of 2.66 ± 0.20 and 1.92 ± 0.20 eV between CaF2 and p-GaN are obtained. These results indicate that CaF2 is a promising gate dielectric layer on the p-GaN for the application of metal-insulator-semiconductor devices.

Cryotomography x-ray microscopy state

DOEpatents

Le Gros, Mark; Larabell, Carolyn A.

2010-10-26

An x-ray microscope stage enables alignment of a sample about a rotation axis to enable three dimensional tomographic imaging of the sample using an x-ray microscope. A heat exchanger assembly provides cooled gas to a sample during x-ray microscopic imaging.

X-ray transparent microfluidic chips for high-throughput screening and optimization of in meso membrane protein crystallization

PubMed Central

Schieferstein, Jeremy M.; Pawate, Ashtamurthy S.; Wan, Frank; Sheraden, Paige N.; Broecker, Jana; Ernst, Oliver P.; Gennis, Robert B.

2017-01-01

Elucidating and clarifying the function of membrane proteins ultimately requires atomic resolution structures as determined most commonly by X-ray crystallography. Many high impact membrane protein structures have resulted from advanced techniques such as in meso crystallization that present technical difficulties for the set-up and scale-out of high-throughput crystallization experiments. In prior work, we designed a novel, low-throughput X-ray transparent microfluidic device that automated the mixing of protein and lipid by diffusion for in meso crystallization trials. Here, we report X-ray transparent microfluidic devices for high-throughput crystallization screening and optimization that overcome the limitations of scale and demonstrate their application to the crystallization of several membrane proteins. Two complementary chips are presented: (1) a high-throughput screening chip to test 192 crystallization conditions in parallel using as little as 8 nl of membrane protein per well and (2) a crystallization optimization chip to rapidly optimize preliminary crystallization hits through fine-gradient re-screening. We screened three membrane proteins for new in meso crystallization conditions, identifying several preliminary hits that we tested for X-ray diffraction quality. Further, we identified and optimized the crystallization condition for a photosynthetic reaction center mutant and solved its structure to a resolution of 3.5 Å. PMID:28469762

Probing interfacial characteristics of rubrene/pentacene and pentacene/rubrene bilayers with soft X-ray spectroscopy.

PubMed

Seo, J H; Pedersen, T M; Chang, G S; Moewes, A; Yoo, K-H; Cho, S J; Whang, C N

2007-08-16

The electronic structure of rubrene/pentacene and pentacene/rubrene bilayers has been investigated using soft X-ray absorption spectroscopy, resonant X-ray emission spectroscopy, and density-functional theory calculations. X-ray absorption and emission measurements reveal that it has been possible to alter the lowest unoccupied and the highest occupied molecular orbital states of rubrene in rubrene/pentacene bilayer. In the reverse case, one gets p* molecular orbital states originating from the pentacene layer. Resonant X-ray emission spectra suggest a reduction in the hole-transition probabilities for the pentacene/rubrene bilayer in comparison to reference pentacene layer. For the rubrenepentacene structure, the hole-transition probability shows an increase in comparison to the rubrene reference. We also determined the energy level alignment of the pentacene-rubrene interface by using X-ray and ultraviolet photoelectron spectroscopy. From these comparisons, it is found that the electronic structure of the pentacene-rubrene interface has a strong dependence on interface characteristics which depends on the order of the layers used.

On the nature of citrate-derived surface species on Ag nanoparticles: Insights from X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Mikhlin, Yuri L.; Vorobyev, Sergey A.; Saikova, Svetlana V.; Vishnyakova, Elena A.; Romanchenko, Alexander S.; Zharkov, Sergey M.; Larichev, Yurii V.

2018-01-01

Citrate is an important stabilizing, reducing, and complexing reagent in the wet chemical synthesis of nanoparticles of silver and other metals, however, the exact nature of adsorbates, and its mechanism of action are still uncertain. Here, we applied X-ray photoelectron spectroscopy, soft X-ray absorption near-edge spectroscopy, and other techniques in order to determine the surface composition and to specify the citrate-related species at Ag nanoparticles immobilized from the dense hydrosol prepared using room-temperature reduction of aqueous Ag+ ions with ferrous ions and citrate as stabilizer (Carey Lea method). It was found that, contrary to the common view, the species adsorbed on the Ag nanoparticles are, in large part, products of citrate decomposition comprising an alcohol group and one or two carboxylate bound to the surface Ag, and minor unbound carboxylate group; these may also be mixtures of citrate with lower molecular weight anions. No ketone groups were specified, and very minor surface Ag(I) and Fe (mainly, ferric oxyhydroxides) species were detected. Moreover, the adsorbates were different at AgNPs having various size and shape. The relation between the capping and the particle growth, colloidal stability of the high-concentration sol and properties of AgNPs is briefly considered.

Spectral state transitions of the Ultraluminous X-ray Source IC 342 X-1

NASA Astrophysics Data System (ADS)

Marlowe, H.; Kaaret, P.; Lang, C.; Feng, H.; Grisé, F.; Miller, N.; Cseh, D.; Corbel, S.; Mushotzky, R. F.

2014-10-01

We observed the Ultraluminous X-ray Source (ULX) IC 342 X-1 simultaneously in X-ray and radio with Chandra and the JVLA to investigate previously reported unresolved radio emission coincident with the ULX. The Chandra data reveal a spectrum that is much softer than observed previously and is well modelled by a thermal accretion disc spectrum. No significant radio emission above the rms noise level was observed within the region of the ULX, consistent with the interpretation as a thermal state though other states cannot be entirely ruled out with the current data. We estimate the mass of the black hole using the modelled inner disc temperature to be 30 M_{⊙} ≲ M√{cosi}≲ 200 M_{⊙} based on a Shakura-Sunyaev disc model. Through a study of the hardness and high-energy curvature of available X-ray observations, we find that the accretion state of X-1 is not determined by luminosity alone.

Band bending at ferroelectric surfaces and interfaces investigated by x-ray photoelectron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Apostol, Nicoleta Georgiana, E-mail: nicoleta.apostol@infim.ro

2014-11-24

This work reports on the use of X-ray photoelectron spectroscopy to quantify band bending at ferroelectric free surfaces and at their interfaces with metals. Surfaces exhibiting out-of-plane ferroelectric polarization are characterized by a band bending, due to the formation of a dipole layer at the surface, composed by the uncompensated polarization charges (due to ionic displacement) and to the depolarization charge sheet of opposite sign, composed by mobile charge carriers, which migrate near surface, owing to the depolarization electric field. To this surface band bending due to out-of-plane polarization states, metal-semiconductor Schottky barriers must be considered additionally when ferroelectrics aremore » covered by metal layers. It is found that the net band bending is not always an algebraic sum of the two effects discussed above, since sometimes the metal is able to provide additional charge carriers, which are able to fully compensate the surface charge of the ferroelectric, up to the vanishing of the ferroelectric band bending. The two cases which will be discussed in more detail are Au and Cu deposited by molecular beam epitaxy on PbZr{sub 0.2}Ti{sub 0.8}O{sub 3}(001) single crystal thin layers, prepared by pulsed laser deposition. Gold forms unconnected nanoparticles, and their effect on the band bending is the apparition of a Schottky band bending additional to the band bending due to the out-of-plane polarization. Copper, starting with a given thickness, forms continuous metal layers connected to the ground of the system, and provide electrons in sufficient quantity to compensate the band bending due to the out-of-plane polarization.« less

A search for X-ray polarization in cosmic X-ray sources. [binary X-ray sources and supernovae remnants

NASA Technical Reports Server (NTRS)

Hughes, J. P.; Long, K. S.; Novick, R.

1983-01-01

Fifteen strong X-ray sources were observed by the X-ray polarimeters on board the OSO-8 satellite from 1975 to 1978. The final results of this search for X-ray polarization in cosmic sources are presented in the form of upper limits for the ten sources which are discussed elsewhere. These limits in all cases are consistent with a thermal origin for the X-ray emission.

Surface chemical composition of human maxillary first premolar as assessed by X-ray photoelectron spectroscopy (XPS)

NASA Astrophysics Data System (ADS)

Lou, Leo; Nelson, Alan E.; Heo, Giseon; Major, Paul W.

2008-08-01

The surface chemical composition of dental enamel has been postulated as a contributing factor in the variation of bond strength of brackets bonded to teeth, and hence, the probability of bracket failure during orthodontic treatment. This study systematically investigated the chemical composition of 98 bonding surfaces of human maxillary premolars using X-ray photoelectron spectroscopy (XPS) to ascertain compositional differences between right and left first premolars. The major elements detected in all samples were calcium, phosphorus, oxygen, nitrogen and carbon. Surface compositions were highly variable between samples and several elements were found to be highly correlated. No statistical significant difference in the chemical composition of the maxillary right and left first premolars was found ( p > 0.05). Knowledge of the chemical composition of enamel surfaces will facilitate future studies that relate this information to the variations in dental enamel bond strength.

X-Ray Photoelectron Spectroscopy Study of the Heating Effects on Pd/6H-SiC Schottky Structure

NASA Technical Reports Server (NTRS)

Chen, Liang-Yu; Hunter, Gary W.; Neudeck, Philip G.; Knight, Dak

1998-01-01

X-ray photoelectron spectroscopy is used to study the effects of heat treatment on the Pd/6H-SiC Schottky diode structure. After heating the structure at 425 C for 140 h, a very thin surface layer of PdO mixed with SiO(x) formed on the palladium surface of the Schottky structure. Heat treatment promoted interfacial diffusion and reaction which significantly broadened the interfacial region. In the interfacial region, the palladium concentration decreases with depth, and the interfacial products are Pd(x)Si (x = 1,2,3,4). In the high Pd concentration regions, Pd4Si is the major silicide component while gr and Pd2Si are major components in the low Pd concentration region. At the center of the interface, where the total palladium concentration equals that of silicon, the concentrations of palladium associated with various palladium silicides (Pd(x)Si, x= 1,2,3,4) are approximately equal. The surface passivation layer composed of PdO and SiO, may significantly affect the electronic and catalytic properties of the surface of the Schottky diode which plays a major role in gas detection. The electronic properties of the Schottky structure may be dominated by a (Pd+Pd(x)Si)/SiC interface. In order to stabilize the properties of the Schottky structure the surface and interface diffusion and reactions must be controlled.

X-ray photoelectron spectroscopy investigations of band offsets in Ga0.02Zn0.98O/ZnO heterojunction for UV photodetectors

NASA Astrophysics Data System (ADS)

Singh, Karmvir; Rawal, Ishpal; Punia, Rajesh; Dhar, Rakesh

2017-10-01

Here, we report the valence and conduction band offset measurements in pure ZnO and the Ga0.02Zn0.98O/ZnO heterojunction by X-Ray photoelectron spectroscopy studies for UV photodetector applications. For detailed investigations on the band offsets and UV photodetection behavior of Ga0.02Zn0.98O/ZnO heterostructures, thin films of pristine ZnO, Ga-doped ZnO (Ga0.02Zn0.98O), and heterostructures of Ga-doped ZnO with ZnO (Ga0.02Zn0.98O/ZnO) were deposited using a pulsed laser deposition technique. The deposited thin films were characterized by X-ray diffraction, atomic force microscopy, and UV-Vis spectroscopy. X-ray photoelectron spectroscopy studies were carried out on all the thin films for the investigation of valence and conduction band offsets. The valence band was found to be shifted by 0.28 eV, while the conduction band has a shifting of -0.272 eV in the Ga0.02Zn0.98O/ZnO heterojunction as compared to pristine ZnO thin films. All the three samples were analyzed for photoconduction behavior under UVA light of the intensity of 3.3 mW/cm2, and it was observed that the photoresponse of pristine ZnO (19.75%) was found to increase with 2 wt. % doping of Ga (22.62%) and heterostructured thin films (29.10%). The mechanism of UV photodetection in the deposited samples has been discussed in detail, and the interaction of chemisorbed oxygen on the ZnO surface with holes generated by UV light exposure has been the observed mechanism for the change in electrical conductivity responsible for UV photoresponse on the present deposited ZnO films.

Energetic (above 60 eV) atmospheric photoelectrons

NASA Technical Reports Server (NTRS)

Winningham, J. D.; Decker, D. T.; Kozyra, J. U.; Nagy, A. F.; Jasperse, J. R.

1989-01-01

Data from low altitude plasma instrument (LAPI) on Dynamics Explorer 2 document a population of high-energy (up to 800 eV) atmospheric photoelectrons that has not been reported in the published literature. The source of these photoelectrons is postulated to be the soft X-ray portion of the whole sun spectrum. This conclusion is supported by sunrise-sunset characteristics that track those of the classical (below 60 eV) EUV-produced photoelectrons, and theoretical results from two models that incorporate the soft X-ray portion of the solar spectrum. The models include K-shell ionization effects and predict peaks in the photoelectron spectrum due to Auger electrons emitted from oxygen and nitrogen. The peak for nitrogen is observed as predicted, but the peak for oxygen is barely observable. Excellent quantitative agreement is achieved between theory and experiment by using reasonable adjustments to the few published soft X-ray spectra based on solar activity. The upflowing energetic photoelectrons provide a heretofore unknown source of electrons to the magnetosphere. They occur whenever and wherever the sun is up, that is, at all invariant latitudes. Their density is low, but they are steady and ubiquitous. If scattering and trapping occur on closed field lines, then photoelectrons could contribute as a significant particle source and thus represent a new facet of magnetosphere-ionosphere coupling.

The superslow pulsation X-ray pulsars in high mass X-ray binaries

NASA Astrophysics Data System (ADS)

Wang, Wei

2013-03-01

There exists a special class of X-ray pulsars that exhibit very slow pulsation of P spin > 1000 s in the high mass X-ray binaries (HMXBs). We have studied the temporal and spectral properties of these superslow pulsation neutron star binaries in hard X-ray bands with INTEGRAL observations. Long-term monitoring observations find spin period evolution of two sources: spin-down trend for 4U 2206+54 (P spin ~ 5560 s with Ṗ spin ~ 4.9 × 10-7 s s-1) and long-term spin-up trend for 2S 0114+65 (P spin ~ 9600 s with Ṗ spin ~ -1 × 10-6 s s-1) in the last 20 years. A Be X-ray transient, SXP 1062 (P spin ~ 1062 s), also showed a fast spin-down rate of Ṗ spin ~ 3 × 10-6 s s-1 during an outburst. These superslow pulsation neutron stars cannot be produced in the standard X-ray binary evolution model unless the neutron star has a much stronger surface magnetic field (B > 1014 G). The physical origin of the superslow spin period is still unclear. The possible origin and evolution channels of the superslow pulsation X-ray pulsars are discussed. Superslow pulsation X-ray pulsars could be younger X-ray binary systems, still in the fast evolution phase preceding the final equilibrium state. Alternatively, they could be a new class of neutron star system - accreting magnetars.

X-ray photoelectron spectroscopic analysis of rice kernels and flours: Measurement of surface chemical composition.

PubMed

Nawaz, Malik A; Gaiani, Claire; Fukai, Shu; Bhandari, Bhesh

2016-12-01

The objectives of this study were to evaluate the ability of X-ray photoelectron spectroscopy (XPS) to differentiate rice macromolecules and to calculate the surface composition of rice kernels and flours. The uncooked kernels and flours surface composition of the two selected rice varieties, Thadokkham-11 (TDK11) and Doongara (DG) demonstrated an over-expression of lipids and proteins and an under-expression of starch compared to the bulk composition. The results of the study showed that XPS was able to differentiate rice polysaccharides (mainly starch), proteins and lipids in uncooked rice kernels and flours. Nevertheless, it was unable to distinguish components in cooked rice samples possibly due to complex interactions between gelatinized starch, denatured proteins and lipids. High resolution imaging methods (Scanning Electron Microscopy and Confocal Laser Scanning Microscopy) were employed to obtain complementary information about the properties and location of starch, proteins and lipids in rice kernels and flours. Copyright © 2016. Published by Elsevier Ltd.

X-ray photoelectron and mass spectroscopic study of electron irradiation and thermal stability of polytetrafluoroethylene

NASA Technical Reports Server (NTRS)

Wheeler, Donald R.; Pepper, Stephen V.

1990-01-01

Polytetrafluoroethylene (PTFE) was subjected to 3 keV electron bombardment and then heated in vacuum to 300 C. The behavior of the material as a function of radiation dose and temperature was studied by X-ray photoelectron spectroscopy (XPS) of the surface and mass spectroscopy of the species evolved. A quantitative comparison of the radiation dose rate with that in other reported studies showed that, for a given total dose, the damage observed by XPS is greater for higher dose rates. Lightly damaged material heated to 300 C evolved saturated fluorocarbon species, whereas unsaturated fluorocarbon species evolved from heavily damaged material. After heating the heavily damaged material, those features in the XPS that were associated with damage diminished, giving the appearance that the radiation damage annealed. The apparent annealing of the radiation damage was found to be due to the covering of the network by saturated fragments that easily diffused through the decomposed material to the surface region upon heating.

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

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

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/ΔE 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/ΔE > 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

The hypersoft state of Cygnus X-3. A key to jet quenching in X-ray binaries?

NASA Astrophysics Data System (ADS)

Koljonen, K. I. I.; Maccarone, T.; McCollough, M. L.; Gurwell, M.; Trushkin, S. A.; Pooley, G. G.; Piano, G.; Tavani, M.

2018-04-01

Context. Cygnus X-3 is a unique microquasar in the Galaxy hosting a Wolf-Rayet companion orbiting a compact object that most likely is a low-mass black hole. The unique source properties are likely due to the interaction of the compact object with the heavy stellar wind of the companion. Aim. In this paper, we concentrate on a very specific period of time prior to the massive outbursts observed from the source. During this period, Cygnus X-3 is in a so-called hypersoft state, in which the radio and hard X-ray fluxes are found to be at their lowest values (or non-detected), the soft X-ray flux is at its highest values, and sporadic γ-ray emission is observed. We use multiwavelength observations to study the nature of the hypersoft state. Methods: We observed Cygnus X-3 during the hypersoft state with Swift and NuSTAR in X-rays and SMA, AMI-LA, and RATAN-600 in the radio. We also considered X-ray monitoring data from MAXI and γ-ray monitoring data from AGILE and Fermi. Results: We found that the spectra and timing properties of the multiwavelength observations can be explained by a scenario in which the jet production is turned off or highly diminished in the hypersoft state and the missing jet pressure allows the wind to refill the region close to the black hole. The results provide proof of actual jet quenching in soft states of X-ray binaries.

Surface studies of solids using integral X-ray-induced photoemission yield

PubMed Central

Stoupin, Stanislav; Zhernenkov, Mikhail; Shi, Bing

2016-01-01

X-ray induced photoemission yield contains structural information complementary to that provided by X-ray Fresnel reflectivity, which presents an advantage to a wide variety of surface studies if this information is made easily accessible. Photoemission in materials research is commonly acknowledged as a method with a probing depth limited by the escape depth of the photoelectrons. Here we show that the integral hard-X-ray-induced photoemission yield is modulated by the Fresnel reflectivity of a multilayer structure and carries structural information that extends well beyond the photoelectron escape depth. A simple electric self-detection of the integral photoemission yield and Fourier data analysis permit extraction of thicknesses of individual layers. The approach does not require detection of the reflected radiation and can be considered as a framework for non-invasive evaluation of buried layers with hard X-rays under grazing incidence. PMID:27874041

Surface studies of solids using integral x-ray-induced photoemission yield

DOE PAGES

Stoupin, Stanislav; Zhernenkov, Mikhail; Shi, Bing

2016-11-22

X-ray induced photoemission yield contains structural information complementary to that provided by X-ray Fresnel reflectivity, which presents an advantage to a wide variety of surface studies if this information is made easily accessible. Photoemission in materials research is commonly acknowledged as a method with a probing depth limited by the escape depth of the photoelectrons. Here we show that the integral hard-X-ray-induced photoemission yield is modulated by the Fresnel reflectivity of a multilayer structure and carries structural information that extends well beyond the photoelectron escape depth. A simple electric self-detection of the integral photoemission yield and Fourier data analysis permitmore » extraction of thicknesses of individual layers. The approach does not require detection of the reflected radiation and can be considered as a framework for non-invasive evaluation of buried layers with hard X-rays under grazing incidence.« less

Table-top laser-driven ultrashort electron and X-ray source: the CIBER-X source project

NASA Astrophysics Data System (ADS)

Girardeau-Montaut, Jean-Pierre; Kiraly, Bélà; Girardeau-Montaut, Claire; Leboutet, Hubert

2000-09-01

We report on the development of a new laser-driven table-top ultrashort electron and X-ray source, also called the CIBER-X source . X-ray pulses are produced by a three-step process which consists of the photoelectron emission from a thin metallic photocathode illuminated by 16 ps duration laser pulses at 213 nm. The e-gun is a standard Pierce diode electrode type, in which electrons are accelerated by a cw electric field of ˜11 MV/m up to a hole made in the anode. The photoinjector produces a train of 70-80 keV electron pulses of ˜0.5 nC and 20 A peak current at a repetition rate of 10 Hz. The electrons are then transported outside the diode along a path of 20 cm length, and are focused onto a target of thullium by magnetic fields produced by two electromagnetic coils. X-rays are then produced by the impact of electrons on the target. Simulations of geometrical, electromagnetic fields and energetic characteristics of the complete source were performed previously with the assistance of the code PIXEL1 also developed at the laboratory. Finally, experimental electron and X-ray performances of the CIBER-X source as well as its application to very low dose imagery are presented and discussed. source Compacte d' Impulsions Brèves d' Electrons et de Rayons X

X-Ray and Radio Studies of Black Hole X-Ray Transients During Outburst Decay

NASA Technical Reports Server (NTRS)

Tomsick, John A.

2005-01-01

unexpectedly, that the radio jet does not turn on until the hard X-ray emission is well past its peak hard state level, strongly constraining theoretical models for hard X-ray production and the spectrum emitted by the jet. Finally, the X-ray/radio results in A2 led us to propose a general picture about the relationship between jet production and X-ray spectral states .

XRIndex: a brief screening tool for individual differences in security threat detection in x-ray images

PubMed Central

Rusconi, Elena; Ferri, Francesca; Viding, Essi; Mitchener-Nissen, Timothy

2015-01-01

X-ray imaging is a cost-effective technique at security checkpoints that typically require the presence of human operators. We have previously shown that self-reported attention to detail can predict threat detection performance with small-vehicle x-ray images (Rusconi et al., 2012). Here, we provide evidence for the generality of such a link by having a large sample of naïve participants screen more typical dual-energy x-ray images of hand luggage. The results show that the Attention to Detail score from the autism-spectrum quotient (AQ) questionnaire (Baron-Cohen et al., 2001) is a linear predictor of threat detection accuracy. We then develop and fine-tune a novel self-report scale for security screening: the XRIndex, which improves on the Attention to Detail scale for predictive power and opacity to interpretation. The XRIndex is not redundant with any of the Big Five personality traits. We validate the XRIndex against security x-ray images with an independent sample of untrained participants and suggest that the XRIndex may be a useful aid for the identification of suitable candidates for professional security training with a focus on x-ray threat detection. Further studies are needed to determine whether this can also apply to trained professionals. PMID:26321935

Understanding the Oxygen Evolution Reaction Mechanism on CoO x using Operando Ambient-Pressure X-ray Photoelectron Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Favaro, Marco; Yang, Jinhui; Nappini, Silvia

Photoelectrochemical water splitting is a promising approach for renewable production of hydrogen from solar energy and requires interfacing advanced water-splitting catalysts with semiconductors. Understanding the mechanism of function of such electrocatalysts at the atomic scale and under realistic working conditions is a challenging, yet important, task for advancing efficient and stable function. This is particularly true for the case of oxygen evolution catalysts and, here, we study a highly active Co 3O 4/Co(OH) 2 biphasic electrocatalyst on Si by means of operando ambient-pressure X-ray photoelectron spectroscopy performed at the solid/liquid electrified interface. Spectral simulation and multiplet fitting reveal that themore » catalyst undergoes chemical-structural transformations as a function of the applied anodic potential, with complete conversion of the Co(OH) 2 and partial conversion of the spinel Co 3O 4 phases to CoO(OH) under precatalytic electrochemical conditions. Furthermore, we observe new spectral features in both Co 2p and O 1s core-level regions to emerge under oxygen evolution reaction conditions on CoO(OH). The operando photoelectron spectra support assignment of these newly observed features to highly active Co 4+ centers under catalytic conditions. Comparison of these results to those from a pure phase spinel Co 3O 4 catalyst supports this interpretation and reveals that the presence of Co(OH) 2 enhances catalytic activity by promoting transformations to CoO(OH). The direct investigation of electrified interfaces presented in this work can be extended to different materials under realistic catalytic conditions, thereby providing a powerful tool for mechanism discovery and an enabling capability for catalyst design.« less

Understanding the Oxygen Evolution Reaction Mechanism on CoO x using Operando Ambient-Pressure X-ray Photoelectron Spectroscopy

DOE PAGES

Favaro, Marco; Yang, Jinhui; Nappini, Silvia; ...

2017-06-09

Photoelectrochemical water splitting is a promising approach for renewable production of hydrogen from solar energy and requires interfacing advanced water-splitting catalysts with semiconductors. Understanding the mechanism of function of such electrocatalysts at the atomic scale and under realistic working conditions is a challenging, yet important, task for advancing efficient and stable function. This is particularly true for the case of oxygen evolution catalysts and, here, we study a highly active Co 3O 4/Co(OH) 2 biphasic electrocatalyst on Si by means of operando ambient-pressure X-ray photoelectron spectroscopy performed at the solid/liquid electrified interface. Spectral simulation and multiplet fitting reveal that themore » catalyst undergoes chemical-structural transformations as a function of the applied anodic potential, with complete conversion of the Co(OH) 2 and partial conversion of the spinel Co 3O 4 phases to CoO(OH) under precatalytic electrochemical conditions. Furthermore, we observe new spectral features in both Co 2p and O 1s core-level regions to emerge under oxygen evolution reaction conditions on CoO(OH). The operando photoelectron spectra support assignment of these newly observed features to highly active Co 4+ centers under catalytic conditions. Comparison of these results to those from a pure phase spinel Co 3O 4 catalyst supports this interpretation and reveals that the presence of Co(OH) 2 enhances catalytic activity by promoting transformations to CoO(OH). The direct investigation of electrified interfaces presented in this work can be extended to different materials under realistic catalytic conditions, thereby providing a powerful tool for mechanism discovery and an enabling capability for catalyst design.« less

X-ray photoelectron spectroscopy study of para-substituted benzoic acids chemisorbed to aluminum oxide thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kreil, Justin; Ellingsworth, Edward; Szulczewski, Greg

A series of para-substituted, halogenated (F, Cl, Br, and I) benzoic acid monolayers were prepared on the native oxide of aluminum surfaces by solution self-assembly and spin-coating techniques. The monolayers were characterized by x-ray photoelectron spectroscopy (XPS) and water contact angles. Several general trends are apparent. First, the polarity of the solvent is critical to monolayer formation. Protic polar solvents produced low coverage monolayers; in contrast, nonpolar solvents produced higher coverage monolayers. Second, solution deposition yields a higher surface coverage than spin coating. Third, the thickness of the monolayers determined from XPS suggests the plane of the aromatic ring ismore » perpendicular to the surface with the carboxylate functional group most likely binding in a bidentate chelating geometry. Fourth, the saturation coverage (∼2.7 × 10{sup 14} molecules cm{sup −2}) is independent of the para-substituent.« less

Study of fission-product segregation in used CANDU fuel by X-ray photoelectron spectroscopy (XPS) II

NASA Astrophysics Data System (ADS)

Hocking, William H.; Duclos, A. Michael; Johnson, Lawrence H.

1994-03-01

A thorough investigation of the grain-boundary chemistry of used CANDU fuel from one intact element has been conducted by X-ray photoelectron spectroscopy (XPS). Selected findings from more extensive XPS measurements on other used CANDU fuels exposed to storage conditions are included for comparison. Cesium, rubidium, tellurium and barium have been commonly observed, often reaching high degrees of surface enrichment, although their relative abundances can vary widely with a complex dependence on the fuel irradiation history. Lower concentrations of cadmium, molybdenum, strontium and iodine have also been occasionally detected. Except for iodine, chemical-shift data are indicative of oxidized species, possibly uranates. Segregation at monolayer-level coverages has been demonstrated by sequential XPS analysis and argon-ion sputtering. Calculations based on an idealized thin-film model are consistent with the depth profiles. The interpretation of these results is discussed in the context of previous studies, especially on LWR fuels.

Can laptops be left inside passenger bags if motion imaging is used in X-ray security screening?

PubMed

Mendes, Marcia; Schwaninger, Adrian; Michel, Stefan

2013-01-01

This paper describes a study where a new X-ray machine for security screening featuring motion imaging (i.e., 5 views of a bag are shown as an image sequence) was evaluated and compared to single view imaging available on conventional X-ray screening systems. More specifically, it was investigated whether with this new technology X-ray screening of passenger bags could be enhanced to such an extent that laptops could be left inside passenger bags, without causing a significant impairment in threat detection performance. An X-ray image interpretation test was created in four different versions, manipulating the factors packing condition (laptop and bag separate vs. laptop in bag) and display condition (single vs. motion imaging). There was a highly significant and large main effect of packing condition. When laptops and bags were screened separately, threat item detection was substantially higher. For display condition, a medium effect was observed. Detection could be slightly enhanced through the application of motion imaging. There was no interaction between display and packing condition, implying that the high negative effect of leaving laptops in passenger bags could not be fully compensated by motion imaging. Additional analyses were carried out to examine effects depending on different threat categories (guns, improvised explosive devices, knives, others), the placement of the threat items (in bag vs. in laptop) and viewpoint (easy vs. difficult view). In summary, although motion imaging provides an enhancement, it is not strong enough to allow leaving laptops in bags for security screening.

Can laptops be left inside passenger bags if motion imaging is used in X-ray security screening?

PubMed Central

Mendes, Marcia; Schwaninger, Adrian; Michel, Stefan

2013-01-01

This paper describes a study where a new X-ray machine for security screening featuring motion imaging (i.e., 5 views of a bag are shown as an image sequence) was evaluated and compared to single view imaging available on conventional X-ray screening systems. More specifically, it was investigated whether with this new technology X-ray screening of passenger bags could be enhanced to such an extent that laptops could be left inside passenger bags, without causing a significant impairment in threat detection performance. An X-ray image interpretation test was created in four different versions, manipulating the factors packing condition (laptop and bag separate vs. laptop in bag) and display condition (single vs. motion imaging). There was a highly significant and large main effect of packing condition. When laptops and bags were screened separately, threat item detection was substantially higher. For display condition, a medium effect was observed. Detection could be slightly enhanced through the application of motion imaging. There was no interaction between display and packing condition, implying that the high negative effect of leaving laptops in passenger bags could not be fully compensated by motion imaging. Additional analyses were carried out to examine effects depending on different threat categories (guns, improvised explosive devices, knives, others), the placement of the threat items (in bag vs. in laptop) and viewpoint (easy vs. difficult view). In summary, although motion imaging provides an enhancement, it is not strong enough to allow leaving laptops in bags for security screening. PMID:24151457

Diagnosis of Plasma States in X-Ray Laser Experiments

DTIC Science & Technology

1992-10-01

J e AD-A256 909 FOREIGN AEROSPACE SCIENCE AND TECHNOLOGY CENTER DTIC 4 OCT 2 6 1992’ DIAGNOSIS OF PLASMA STATES IN X-RAY LASER EXPERIMENTS by Yang ...0619-92 HUMAN TRANSLATION FASTC-ID(RS)T-0619-92 8 October 1992 DIAGNOSIS OF PLASMA STATES IN X-RAY LASER EXPERIMENTS By: Yang Shangjin, Cai Yuqin, Chunyu... Yang Shangjin, Cai Yuqin, and Chunyu Shutai China Academy of Engineering Physics Abstract At an LF-12 laser installation, an Nd glass laser of

XPS studies of structure-induced radiation effects at the Si/SiO2 interface. [X ray Photoelectron Spectroscopy

NASA Technical Reports Server (NTRS)

Grunthaner, F. J.; Lewis, B. F.; Zamini, N.; Maserjian, J.; Madhukar, A.

1980-01-01

The interfacial structures of radiation hard and soft oxides grown by dry and wet processes on silicon substrates have been examined by high-resolution X-ray photoelectron spectroscopy. It is found that the primary difference in the local atomic structure at the Si/SiO2 interface is the significantly higher concentration of strained 120 deg SiO2 bonds and SiO interfacial species in soft samples. Results of in situ radiation damage experiments using low energy electrons (0-20 eV) are reported which correlate with the presence of a strained layer of SiO2 (20 A) at the interface. The results are interpreted in terms of a structural model for hole and electron trap generation by ionizing radiation.

X-ray photoelectron spectroscopy characterization of a nonsuperconducting Y-Ba-Cu-O superconductor-normal-metal-superconductor barrier material

NASA Technical Reports Server (NTRS)

Vasquez, R. P.; Hunt, B. D.; Foote, M. C.; Bajuk, L. J.

1992-01-01

A film of a novel nonsuperconducting Y-Ba-Cu-O (YBCO) barrier material was grown using conditions similar to those reported by Agostinelli et al. (1991) for forming a cubic semiconducting (c-YBCO) phase, and the material was characterized using X-ray photoelectron spectroscopy (XPS). A comparison of the XPS spectra of this material to those obtained from the orthorhombic and tetragonal phases of YBCO (o-YBCO and t-YBCO, respectively) showed that the barrier material had spectral characteristics different from those of o-YBCO and t-YBCO, particularly in the O 1s region. Features associated with the Cu-O chain and surface-reconstructed Cu-O planes were absent, consistent with expectations for the simple perovskite crystal structure of c-YBCO proposed by Agostinelli et al.

X-ray Photoelectron Spectroscopy of Pyridinium-Based Ionic Liquids: Comparison to Imidazolium- and Pyrrolidinium-Based Analogues.

PubMed

Men, Shuang; Mitchell, Daniel S; Lovelock, Kevin R J; Licence, Peter

2015-07-20

We investigate eight 1-alkylpyridinium-based ionic liquids of the form [Cn Py][A] by using X-ray photoelectron spectroscopy (XPS). The electronic environment of each element of the ionic liquids is analyzed. In particular, a reliable fitting model is developed for the C 1s region that applies to each of the ionic liquids. This model allows the accurate charge correction of binding energies and the determination of reliable and reproducible binding energies for each ionic liquid. Shake-up/off phenomena are determinedfor both C 1s and N 1s spectra. The electronic interaction between cations and anions is investigated for both simple ionic liquids and an example of an ionic-liquid mixture; the effect of the anion on the electronic environment of the cation is also explored. Throughout the study, a detailed comparison is made between [C8 Py][A] and analogues including 1-octyl-1-methylpyrrolidinium- ([C8 C1 Pyrr][A]), and 1-octyl-3-methylimidazolium- ([C8 C1 Im][A]) based samples, where X is common to all ionic liquids. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

X-ray excited Auger transitions of Pu compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nelson, Art J., E-mail: nelson63@llnl.gov; Grant, William K.; Stanford, Jeff A.

2015-05-15

X-ray excited Pu core–valence–valence and core–core–valence Auger line-shapes were used in combination with the Pu 4f photoelectron peaks to characterize differences in the oxidation state and local electronic structure for Pu compounds. The evolution of the Pu 4f core-level chemical shift as a function of sputtering depth profiling and hydrogen exposure at ambient temperature was quantified. The combination of the core–valence–valence Auger peak energies with the associated chemical shift of the Pu 4f photoelectron line defines the Auger parameter and results in a reliable method for definitively determining oxidation states independent of binding energy calibration. Results show that PuO{sub 2},more » Pu{sub 2}O{sub 3}, PuH{sub 2.7}, and Pu have definitive Auger line-shapes. These data were used to produce a chemical state (Wagner) plot for select plutonium oxides. This Wagner plot allowed us to distinguish between the trivalent hydride and the trivalent oxide, which cannot be differentiated by the Pu 4f binding energy alone.« less

Miniaturized, High-Speed, Modulated X-Ray Source

NASA Technical Reports Server (NTRS)

Gendreau, Keith; Arzoumanian, Zaven; Kenyon, Steve; Spartana, Nick

2013-01-01

A low-cost, miniature x-ray source has been developed that can be modulated in intensity from completely off to full intensity on nanosecond timescales. This modulated x-ray source (MXS) has no filaments and is extremely rugged. The energy level of the MXS is adjustable from 0 to more than 100 keV. It can be used as the core of many new devices, providing the first practical, arbitrarily time-variable source of x-rays. The high-speed switching capability and miniature size make possible many new technologies including x-ray-based communication, compact time-resolved x-ray diffraction, novel x-ray fluorescence instruments, and low- and precise-dose medical x-rays. To make x-rays, the usual method is to accelerate electrons into a target material held at a high potential. When the electrons stop in the target, x-rays are produced with a spectrum that is a function of the target material and the energy to which the electrons are accelerated. Most commonly, the electrons come from a hot filament. In the MXS, the electrons start off as optically driven photoelectrons. The modulation of the x-rays is then tied to the modulation of the light that drives the photoelectron source. Much of the recent development has consisted of creating a photoelectrically-driven electron source that is robust, low in cost, and offers high intensity. For robustness, metal photocathodes were adopted, including aluminum and magnesium. Ultraviolet light from 255- to 350-nm LEDs (light emitting diodes) stimulated the photoemissions from these photocathodes with an efficiency that is maximized at the low-wavelength end (255 nm) to a value of roughly 10(exp -4). The MXS units now have much higher brightness, are much smaller, and are made using a number of commercially available components, making them extremely inexpensive. In the latest MXS design, UV efficiency is addressed by using a high-gain electron multiplier. The photocathode is vapor-deposited onto the input cone of a Burle Magnum

Proton transfer mediated by the vibronic coupling in oxygen core ionized states of glyoxalmonoxime studied by infrared-X-ray pump-probe spectroscopy.

PubMed

Felicíssimo, V C; Guimarães, F F; Cesar, A; Gel'mukhanov, F; Agren, H

2006-11-30

The theory of IR-X-ray pump-probe spectroscopy beyond the Born-Oppenheimer approximation is developed and applied to the study of the dynamics of intramolecular proton transfer in glyoxalmonoxime leading to the formation of the tautomer 2-nitrosoethenol. Due to the IR pump pulses the molecule gains sufficient energy to promote a proton to a weakly bound well. A femtosecond X-ray pulse snapshots the wave packet route and, hence, the dynamics of the proton transfer. The glyoxalmonoxime molecule contains two chemically nonequivalent oxygen atoms that possess distinct roles in the hydrogen bond, a hydrogen donor and an acceptor. Core ionizations of these form two intersecting core-ionized states, the vibronic coupling between which along the OH stretching mode partially delocalizes the core hole, resulting in a hopping of the core hole from one site to another. This, in turn, affects the dynamics of the proton transfer in the core-ionized state. The quantum dynamical simulations of X-ray photoelectron spectra of glyoxalmonoxime driven by strong IR pulses demonstrate the general applicability of the technique for studies of intramolecular proton transfer in systems with vibronic coupling.

The X-ray photoelectron spectroscopy depth profiling and tribological characterization of ion-plated gold on various metals

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Spalvins, T.; Buckley, D. H.

1983-01-01

For the case of ion-plated gold, the graded interface between gold and a nickel substrate and a nickel substrate, such tribological properties as friction and microhardness are examined by means of X-ray photoelectron spectroscopy analysis and depth profiling. Sliding was conducted against SiC pins in both the adhesive process, where friction arises from adhesion between sliding surfaces, and abrasion, in which friction is due to pin indentation and groove-plowing. Both types of friction are influenced by coating depth, but with opposite trends: the graded interface exhibited the highest adhesion, but the lowest abrasion. The coefficient of friction due to abrasion is inversely related to hardness. Graded interface microhardness values are found to be the highest, due to an alloying effect. There is almost no interface gradation between the vapor-deposited gold film and the substrate.

Surface Evaluation by X-Ray Photoelectron Spectroscopy of High Performance Polyimide Foams After Exposure to Oxygen Plasma

NASA Technical Reports Server (NTRS)

Melendez, Orlando; Hampton, Michael D.; Williams, Martha K.; Brown, Sylvia F.; Nelson, Gordon L.; Weiser, Erik S.

2002-01-01

Aromatic polyimides have been attractive in the aerospace and electronics industries for applications such as cryogenic insulation, flame retardant panels and structural subcomponents. Newer to the arena of polyimides is the synthesis of polyimide foams and their applications. In the present work, three different, closely related, polyimide foams developed by NASA Langley Research Center (LaRC) are studied by X-ray Photoelectron Spectroscopy (XPS) after exposure to radio frequency generated Oxygen Plasma. Although polyimide films exposure to atomic oxygen and plasma have been studied previously and reported, the data relate to films and not foams. Foams have much more surface area and thus present new information to be explored. Understanding degradation mechanisms and properties versus structure, foam versus solid is of interest and fundamental to the application and protection of foams exposed to atomic oxygen in Low Earth Orbit (LEO).

X-ray diffraction imaging with the Multiple Inverse Fan Beam topology: principles, performance and potential for security screening.

PubMed

Harding, G; Fleckenstein, H; Kosciesza, D; Olesinski, S; Strecker, H; Theedt, T; Zienert, G

2012-07-01

The steadily increasing number of explosive threat classes, including home-made explosives (HMEs), liquids, amorphous and gels (LAGs), is forcing up the false-alarm rates of security screening equipment. This development can best be countered by increasing the number of features available for classification. X-ray diffraction intrinsically offers multiple features for both solid and LAGs explosive detection, and is thus becoming increasingly important for false-alarm and cost reduction in both carry-on and checked baggage security screening. Following a brief introduction to X-ray diffraction imaging (XDI), which synthesizes in a single modality the image-forming and material-analysis capabilities of X-rays, the Multiple Inverse Fan Beam (MIFB) XDI topology is described. Physical relationships obtaining in such MIFB XDI components as the radiation source, collimators and room-temperature detectors are presented with experimental performances that have been achieved. Representative X-ray diffraction profiles of threat substances measured with a laboratory MIFB XDI system are displayed. The performance of Next-Generation (MIFB) XDI relative to that of the 2nd Generation XRD 3500TM screener (Morpho Detection Germany GmbH) is assessed. The potential of MIFB XDI, both for reducing the exorbitant cost of false alarms in hold baggage screening (HBS), as well as for combining "in situ" liquid and solid explosive detection in carry-on luggage screening is outlined. Copyright © 2011 Elsevier Ltd. All rights reserved.

Adsorption of 2-propanol on ice probed by ambient pressure X-ray photoelectron spectroscopy

DOE PAGES

Newberg, John T.; Bluhm, Hendrik

2015-08-18

The interaction of 2-propanol with ice was examined via ambient pressure X-ray photoelectron spectroscopy (APXPS), a surface sensitive technique that probes the adsorbed 2-propanol directly with submonolayer resolution. Isothermal uptake experiments were performed on vapor deposited ice at 227 K in the presence of the equilibrium water vapor pressure of 0.05 Torr and 2-propanol partial pressures ranging from 5 × 10 -5 to 2 × 10 -3 Torr. The C 1s APXPS spectra of adsorbed 2-propanol showed two characteristic peaks associated with the C OH alcohol group and C Me methyl groups in a 1 : 2 ratio, respectively. Coveragemore » increased with 2-propanol partial pressure and followed first order Langmuir kinetics with a Langmuir constant of K = 6.3 × 10 3 Torr -1. The 1 : 2 ratio of C OH : C Me remained constant with increasing coverage, indicating there is no chemical reaction upon adsorption. The observed Langmuir kinetics using APXPS is consistent with previous observations of other small chain alcohols via indirect adsorption methods using, e.g., Knudsen cell and coated wall flow tube reactors.« less

Technique charts for Kodak EC-L film screen system for portal localization in a 6MV X-ray beam.

PubMed

Sandilos, P; Antypas, C; Paraskevopoulou, C; Kouvaris, J; Vlachos, L

2006-01-01

Port films are used in radiotherapy for visual evaluation of the radiation fields and subsequent quantitative analysis. Common port films suffer from poor image quality compared to the simulator-diagnostic films and is desirable to determine the appropriate exposure required for the best image contrast. The aim of this work is to generate technique charts for the Kodak EC-L film screen system for use in a 6MV x-ray beam. Three homogeneous water phantoms were used to simulate head-neck, thorax and abdomen dimensions of adult human, correspondingly. The film screen system was calibrated in a 6MV x-ray beam and under various irradiation conditions. The film screen system behavior was studied as a function of phantom thickness, field size and air gap between the phantom and the film screen system. In each case the optimum film exposure which produces the maximum image contrast was determined. The generated technique charts for the EC-L film screen system and for a 6 MV x-ray beam are used in our radiotherapy department for daily quality assurance of the radiotherapy procedure.

Excited state X-ray absorption spectroscopy: Probing both electronic and structural dynamics

NASA Astrophysics Data System (ADS)

Neville, Simon P.; Averbukh, Vitali; Ruberti, Marco; Yun, Renjie; Patchkovskii, Serguei; Chergui, Majed; Stolow, Albert; Schuurman, Michael S.

2016-10-01

We investigate the sensitivity of X-ray absorption spectra, simulated using a general method, to properties of molecular excited states. Recently, Averbukh and co-workers [M. Ruberti et al., J. Chem. Phys. 140, 184107 (2014)] introduced an efficient and accurate L 2 method for the calculation of excited state valence photoionization cross-sections based on the application of Stieltjes imaging to the Lanczos pseudo-spectrum of the algebraic diagrammatic construction (ADC) representation of the electronic Hamiltonian. In this paper, we report an extension of this method to the calculation of excited state core photoionization cross-sections. We demonstrate that, at the ADC(2)x level of theory, ground state X-ray absorption spectra may be accurately reproduced, validating the method. Significantly, the calculated X-ray absorption spectra of the excited states are found to be sensitive to both geometric distortions (structural dynamics) and the electronic character (electronic dynamics) of the initial state, suggesting that core excitation spectroscopies will be useful probes of excited state non-adiabatic dynamics. We anticipate that the method presented here can be combined with ab initio molecular dynamics calculations to simulate the time-resolved X-ray spectroscopy of excited state molecular wavepacket dynamics.

Interface Energy Alignment of Atomic-Layer-Deposited VOx on Pentacene: an in Situ Photoelectron Spectroscopy Investigation.

PubMed

Zhao, Ran; Gao, Yuanhong; Guo, Zheng; Su, Yantao; Wang, Xinwei

2017-01-18

Ultrathin atomic-layer-deposited (ALD) vanadium oxide (VO x ) interlayer has recently been demonstrated for remarkably reducing the contact resistance in organic electronic devices (Adv. Funct. Mater. 2016, 26, 4456). Herein, we present an in situ photoelectron spectroscopy investigation (including X-ray and ultraviolet photoelectron spectroscopies) of ALD VO x grown on pentacene to understand the role of the ALD VO x interlayer for the improved contact resistance. The in situ photoelectron spectroscopy characterizations allow us to monitor the ALD growth process of VO x and trace the evolutions of the work function, pentacene HOMO level, and VO x defect states during the growth. The initial VO x growth is found to be partially delayed on pentacene in the first ∼20 ALD cycles. The underneath pentacene layer is largely intact after ALD. The ALD VO x is found to contain a high density of defect states starting from 0.67 eV below the Fermi level, and the energy level of these defect states is in excellent alignment with the HOMO level of pentacene, which therefore allows these VO x defect states to provide an efficient hole-injection pathway at the contact interface.

Dynamic light scattering and X-ray photoelectron spectroscopy characterization of PEGylated polymer nanocarriers: internal structure and surface properties.

PubMed

Celasco, Edvige; Valente, Ilaria; Marchisio, Daniele L; Barresi, Antonello A

2014-07-22

In this work, nanospheres and nanocapsules are precipitated in confined impinging jet mixers through solvent displacement and characterized. Acetone and water are used as the solvent and antisolvent, respectively, together with polymethoxypolyethylene glycol cyanoacrylate-co-hexadecylcyanoacrylate and Miglyol as the copolymer and oil, respectively. Characterization is performed with dynamic light scattering, with electrophoretic measurements, and for the first time with X-ray photoelectron spectroscopy. Results show that the presence of polyethylene glycol chains seems to be more pronounced on the surface of nanospheres than on that of nanocapsules. The thickness of the copolymer layer in nanocapsules ranges from 1 to 10 nm, depending on the value of the oil:copolymer mass ratio. Fast dilution is confirmed to have a positive effect in suppressing aggregation but can induce further copolymer precipitation.

State interference in resonance Auger and x-ray emission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cesar, A.; Agren, H.

1992-03-01

Starting from a scattering-theory formulation, cross sections for Auger and x-ray decay from energetically shifted inner-shell states are derived. Two situations are studied: (i) when there are several close-lying intermediate core-hole states with no vibrational excitations, in which case a {ital state} {ital interference} effect is identified; and (ii) when there are several close-lying intermediate states with vibrational excitations, in which case a {ital vibronic} {ital interference} effect is identified. In the latter case, the present formalism is a many-state generalization of the {ital vibrational} {ital interference} {ital effects} derived from the same type of scattering formalism in our previousmore » paper (A. Cesar, H. Agren, and V. Carravetta, Phys. Rev. A 40, 187 (1989)). Applications are carried out for spectra of some few-state model systems. It is found that a conventional analysis in terms of discrete noninteracting (noninterfering) states, such as the one-center decomposition model, is only valid when the ratio ({ital R}) between energy shift and lifetime is sufficiently large. For states with small {ital R}, a more complete theoretical account must be undertaken, including, e.g., the calculation of phases of the respective transition moments. The presented formalism applies to resonance Auger or x-ray emission spectra, to Auger and x-ray emission from core-electron shake-up states, and also, under certain circumstances, to emission from chemically shifted core-hole states.« less

Combined angle-resolved X-ray photoelectron spectroscopy, density functional theory and kinetic study of nitridation of gallium arsenide

NASA Astrophysics Data System (ADS)

Mehdi, H.; Monier, G.; Hoggan, P. E.; Bideux, L.; Robert-Goumet, C.; Dubrovskii, V. G.

2018-01-01

The high density of interface and surface states that cause the strong Fermi pinning observed on GaAs surfaces can be reduced by depositing GaN ultra-thin films on GaAs. To further improve this passivation, it is necessary to investigate the nitridation phenomena by identifying the distinct steps occurring during the process and to understand and quantify the growth kinetics of GaAs nitridation under different conditions. Nitridation of the cleaned GaAs substrate was performed using N2 plasma source. Two approaches have been combined. Firstly, an AR-XPS (Angle Resolved X-ray Photoelectron Spectroscopy) study is carried out to determine the chemical environments of the Ga, As and N atoms and the composition depth profile of the GaN thin film which allow us to summarize the nitridation process in three steps. Moreover, the temperature and time treatment have been investigated and show a significant impact on the formation of the GaN layer. The second approach is a refined growth kinetic model which better describes the GaN growth as a function of the nitridation time. This model clarifies the exchange mechanism of arsenic with nitrogen atoms at the GaN/GaAs interface and the phenomenon of quasi-saturation of the process observed experimentally.

Direct surface magnetometry with photoemission magnetic x-ray dichroism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tobin, J.G.; Goodman, K.W.; Schumann, F.O.

1997-04-01

Element specific surface magnetometry remains a central goal of synchrotron radiation based studies of nanomagnetic structures. One appealing possibility is the combination of x-ray absorption dichroism measurements and the theoretical framework provided by the {open_quotes}sum rules.{close_quotes} Unfortunately, sum rule analysis are hampered by several limitations including delocalization of the final state, multi-electronic phenomena and the presence of surface dipoles. An alternative experiment, Magnetic X-Ray Dichroism in Photoelectron Spectroscopy, holds out promise based upon its elemental specificity, surface sensitivity and high resolution. Computational simulations by Tamura et al. demonstrated the relationship between exchange and spin orbit splittings and experimental data ofmore » linear and circular dichroisms. Now the authors have developed an analytical framework which allows for the direct extraction of core level exchange splittings from circular and linear dichroic photoemission data. By extending a model initially proposed by Venus, it is possible to show a linear relation between normalized dichroism peaks in the experimental data and the underlying exchange splitting. Since it is reasonable to expect that exchange splittings and magnetic moments track together, this measurement thus becomes a powerful new tool for direct surface magnetometry, without recourse to time consuming and difficult spectral simulations. The theoretical derivation will be supported by high resolution linear and circular dichroism data collected at the Spectromicroscopy Facility of the Advanced Light Source.« less

Internal structure of InP/ZnS nanocrystals unraveled by high-resolution soft X-ray photoelectron spectroscopy.

PubMed

Huang, Kai; Demadrille, Renaud; Silly, Mathieu G; Sirotti, Fausto; Reiss, Peter; Renault, Olivier

2010-08-24

High-energy resolution photoelectron spectroscopy (DeltaE < 200 meV) is used to investigate the internal structure of semiconductor quantum dots containing low Z-contrast elements. In InP/ZnS core/shell nanocrystals synthesized using a single-step procedure (core and shell precursors added at the same time), a homogeneously alloyed InPZnS core structure is evidenced by quantitative analysis of their In3d(5/2) spectra recorded at variable excitation energy. When using a two-step method (core InP nanocrystal synthesis followed by subsequent ZnS shell growth), XPS analysis reveals a graded core/shell interface. We demonstrate the existence of In-S and S(x)-In-P(1-x) bonding states in both types of InP/ZnS nanocrystals, which allows a refined view on the underlying reaction mechanisms.

Hard state neutron star and black hole X-ray binaries in the radio:X-ray luminosity plane

NASA Astrophysics Data System (ADS)

Gallo, Elena; Degenaar, Nathalie; van den Eijnden, Jakob

2018-07-01

Motivated by the large body of literature around the phenomenological properties of accreting black hole (BH) and neutron star (NS) X-ray binaries in the radio:X-ray luminosity plane, we carry out a comparative regression analysis on 36 BHs and 41 NSs in hard X-ray states, with data over 7 dex in X-ray luminosity for both. The BHs follow a radio to X-ray (logarithmic) luminosity relation with slope β = 0.59 ± 0.02, consistent with the NSs' slope (β =0.44^{+0.05}_{-0.04}) within 2.5σ. The best-fitting intercept for the BHs significantly exceeds that for the NSs, cementing BHs as more radio loud, by a factor ˜22. This discrepancy cannot be fully accounted for by the mass or bolometric correction gap, or by the NS boundary layer contribution to the X-rays, and is likely to reflect physical differences in the accretion flow efficiency, or the jet powering mechanism. Once importance sampling is implemented to account for the different luminosity distributions, the slopes of the non-pulsating and pulsating NS subsamples are formally inconsistent (>3σ), unless the transitional millisecond pulsars (whose incoherent radio emission mechanism is not firmly established) are excluded from the analysis. We confirm the lack of a robust partitioning of the BH data set into separate luminosity tracks.

Hard state neutron star and black hole X-ray binaries in the radio:X-ray luminosity plane

NASA Astrophysics Data System (ADS)

Gallo, Elena; Degenaar, Nathalie; van den Eijnden, Jakob

2018-05-01

Motivated by the large body of literature around the phenomenological properties of accreting black hole (BH) and neutron star (NS) X-ray binaries in the radio:X-ray luminosity plane, we carry out a comparative regression analysis on 36 BHs and 41 NSs in hard X-ray states, with data over 7 dex in X-ray luminosity for both. The BHs follow a radio to X-ray (logarithmic) luminosity relation with slope β = 0.59 ± 0.02, consistent with the NSs' slope (β =0.44^{+0.05}_{-0.04}) within 2.5σ. The best-fitting intercept for the BHs significantly exceeds that for the NSs, cementing BHs as more radio loud, by a factor ˜22. This discrepancy can not be fully accounted for by the mass or bolometric correction gap, nor by the NS boundary layer contribution to the X-rays, and is likely to reflect physical differences in the accretion flow efficiency, or the jet powering mechanism. Once importance sampling is implemented to account for the different luminosity distributions, the slopes of the non-pulsating and pulsating NS subsamples are formally inconsistent (>3σ), unless the transitional millisecond pulsars (whose incoherent radio emission mechanism is not firmly established) are excluded from the analysis. We confirm the lack of a robust partitioning of the BH data set into separate luminosity tracks.

Reply to ``Comment on `Relation between copper {ital L} x-ray fluorescence and 2{ital p} x-ray photoelectron spectroscopies` ``

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawai, J.; Maeda, K.; Nakajima, K.

1995-08-15

Ohno`s preceding Comment [Phys. Rev. B 52, 6127 (1995)] was based on experimental raw spectra of copper {ital L} x-ray emission. The Cu {ital L} x-ray emission spectra were, however, heavily smeared by the self-absorption effect, which was a source of contradiction. The electronic structure of divalent copper oxide was calculated placing one core hole and two 3{ital d} holes, with the result that the spectator 3{ital d} holes were delocalized in the adiabatic limit. This implies that the spectator 3{ital d} hole produced by the {ital L}{sub 1,2}{ital L}{sub 3}{ital M}{sub 4,5} Coster-Kronig transition preceding the {ital L}{sub 3}-{italmore » M} x-ray emission will be mostly delocalized at the time of the {ital L}{sub 3}-{ital M} x-ray emission, and thus the spectator satellite will be weaker than is expected for the free atom. Ohno did not consider this delocalization, which was another source of contradiction.« less

Electronic structure and optical properties of Cs2HgCl4: DFT calculations and X-ray photoelectron spectroscopy measurements

NASA Astrophysics Data System (ADS)

Lavrentyev, A. A.; Gabrelian, B. V.; Vu, V. T.; Parasyuk, O. V.; Fedorchuk, A. O.; Khyzhun, O. Y.

2016-10-01

A high-quality single crystal of cesium mercury tetrabromide, Cs2HgCl4, was synthesized by using the vertical Bridgman-Stockbarger method and its electronic structure was studied from both experimental and theoretical viewpoints. In particular, X-ray photoelectron spectra were measured for both pristine and Ar+ ion-bombarded Cs2HgCl4 single crystal surfaces. The present XPS measurements indicate that the Cs2HgCl4 single crystal surface is sensitive with respect to Ar+ ion-bombardment: such a treatment changes substantially its elemental stoichiometry. With the aim of exploring total and partial densities of states within the valence band and conduction band regions of the Cs2HgCl4 compound, band-structure calculations based on density functional theory (DFT) using the augmented plane wave + local orbitals (APW + lo) method as incorporated within the WIEN2k package are performed. The calculations indicate that the Cl 3p states are the principal contributors in the upper portion of the valence band, while the Hg 5d and Cs 5p states dominate in its lower portion. In addition, the calculations allow for concluding that the unoccupied Cl p and Hg s states are the main contributors to the bottom of the conduction band. Furthermore, main optical characteristics of Cs2HgCl4, namely dispersion of the absorption coefficient, real and imaginary parts of dielectric function, electron energy-loss spectrum, refractive index, extinction coefficient and optical reflectivity, are elucidated based on the DFT calculations.

X-ray spectra and electronic structure of the Ca3Ga2Ge3О12 compound

NASA Astrophysics Data System (ADS)

Shcherba, I. D.; Kostyk, L. V.; Noga, H.; Bekenov, L. V.; Uskokovich, D.; Jatsyk, B. M.

2017-09-01

The band structure of Ca3Ga2Ge3О12 with the garnet structure has been determined for the first time by X-ray emission and photoelectron spectroscopy. It has been established that the bottom of the valence band is formed by Ge d states, which are not dominant in the chemical bonding. Strong hybridization of oxygen 2s states with 4p states of Ga and Ge revealed by the presence of an extra structure in the X-ray emission spectra has been found. The middle of the valence band has been demonstrated to be occupied by d states of Ga, while Ga and Ge 4рstates with a considerable admixture of oxygen 2p states form the top of the valence band.

Bulk sensitive hard x-ray photoemission electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patt, M., E-mail: m.patt@fz-juelich.de; Wiemann, C.; Weber, N.

Hard x-ray photoelectron spectroscopy (HAXPES) has now matured into a well-established technique as a bulk sensitive probe of the electronic structure due to the larger escape depth of the highly energetic electrons. In order to enable HAXPES studies with high lateral resolution, we have set up a dedicated energy-filtered hard x-ray photoemission electron microscope (HAXPEEM) working with electron kinetic energies up to 10 keV. It is based on the NanoESCA design and also preserves the performance of the instrument in the low and medium energy range. In this way, spectromicroscopy can be performed from threshold to hard x-ray photoemission. Themore » high potential of the HAXPEEM approach for the investigation of buried layers and structures has been shown already on a layered and structured SrTiO{sub 3} sample. Here, we present results of experiments with test structures to elaborate the imaging and spectroscopic performance of the instrument and show the capabilities of the method to image bulk properties. Additionally, we introduce a method to determine the effective attenuation length of photoelectrons in a direct photoemission experiment.« less

Correlations Between Variations in Solar EUV and Soft X-Ray Irradiance and Photoelectron Energy Spectra Observed on Mars and Earth

NASA Technical Reports Server (NTRS)

Peterson, W. K.; Brain, D. A.; Mitchell, D. L.; Bailey, S. M.; Chamberlin, P. C.

2013-01-01

Solar extreme ultraviolet (EUV; 10-120 nm) and soft X-ray (XUV; 0-10 nm) radiation are major heat sources for the Mars thermosphere as well as the primary source of ionization that creates the ionosphere. In investigations of Mars thermospheric chemistry and dynamics, solar irradiance models are used to account for variations in this radiation. Because of limited proxies, irradiance models do a poor job of tracking the significant variations in irradiance intensity in the EUV and XUV ranges over solar rotation time scales when the Mars-Sun-Earth angle is large. Recent results from Earth observations show that variations in photoelectron energy spectra are useful monitors of EUV and XUV irradiance variability. Here we investigate photoelectron energy spectra observed by the Mars Global Surveyor (MGS) Electron Reflectometer (ER) and the FAST satellite during the interval in 2005 when Earth, Mars, and the Sun were aligned. The Earth photoelectron data in selected bands correlate well with calculations based on 1 nm resolution observations above 27 nm supplemented by broadband observations and a solar model in the 0-27 nm range. At Mars, we find that instrumental and orbital limitations to the identifications of photoelectron energy spectra in MGS/ER data preclude their use as a monitor of solar EUV and XUV variability. However, observations with higher temporal and energy resolution obtained at lower altitudes on Mars might allow the separation of the solar wind and ionospheric components of electron energy spectra so that they could be used as reliable monitors of variations in solar EUV and XUV irradiance than the time shifted, Earth-based, F(10.7) index currently used.

Correlations between variations in solar EUV and soft X-ray irradiance and photoelectron energy spectra observed on Mars and Earth

NASA Astrophysics Data System (ADS)

Peterson, W. K.; Brain, D. A.; Mitchell, D. L.; Bailey, S. M.; Chamberlin, P. C.

2013-11-01

extreme ultraviolet (EUV; 10-120 nm) and soft X-ray (XUV; 0-10 nm) radiation are major heat sources for the Mars thermosphere as well as the primary source of ionization that creates the ionosphere. In investigations of Mars thermospheric chemistry and dynamics, solar irradiance models are used to account for variations in this radiation. Because of limited proxies, irradiance models do a poor job of tracking the significant variations in irradiance intensity in the EUV and XUV ranges over solar rotation time scales when the Mars-Sun-Earth angle is large. Recent results from Earth observations show that variations in photoelectron energy spectra are useful monitors of EUV and XUV irradiance variability. Here we investigate photoelectron energy spectra observed by the Mars Global Surveyor (MGS) Electron Reflectometer (ER) and the FAST satellite during the interval in 2005 when Earth, Mars, and the Sun were aligned. The Earth photoelectron data in selected bands correlate well with calculations based on 1 nm resolution observations above 27 nm supplemented by broadband observations and a solar model in the 0-27 nm range. At Mars, we find that instrumental and orbital limitations to the identifications of photoelectron energy spectra in MGS/ER data preclude their use as a monitor of solar EUV and XUV variability. However, observations with higher temporal and energy resolution obtained at lower altitudes on Mars might allow the separation of the solar wind and ionospheric components of electron energy spectra so that they could be used as reliable monitors of variations in solar EUV and XUV irradiance than the time shifted, Earth-based, F10.7 index currently used.

X-ray photoelectron spectroscopy analysis for the chemical impact of solvent addition rate on electromagnetic shielding effectiveness of HCl-doped polyaniline nanopowders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tantawy, Hesham Ramzy; Aston, D. Eric, E-mail: aston@uidaho.edu; Kengne, Blaise-Alexis F.

2015-11-07

An in-depth analysis of the chemical functionality in HCl-doped polyaniline (PANI) nanopowders is discussed through interpretations of x-ray photoelectron spectra. The distinctions between three PANI sample types, produced under varied synthesis conditions, are compared on the basis correlations between newly collected electron spectra for chemical analysis (or also x-ray photoelectron spectroscopy) and electromagnetic (EM) shielding effectiveness (SE) within two frequency bands (100–1500 MHz and ∼2–14 GHz). The findings are discussed with reference to previous data analysis of electrical conductivities and Raman and UV-vis spectra analyzed from replicates of the same PANI nanopowders, where only the 8–12 GHz range for SE was tested.more » They further corroborate previous results for limited-solvent conditions that enhance EM shielding. The three nanopowder types show distinctive differences in polaron, bipolaron, and polar lattice contributions. The collective findings describe the chemical connections between controlling and, most importantly, limiting the available solvent for polymerization with simultaneously doping and how it is that the newly developed solvent-limited approach for HCl-PANI nanopowders provides better shielding than traditionally solvent-rich methods by having more extended and perhaps even faster polaron delocalization than other PANI-based products. The maximum oxidation (50%) and doping (49%) levels obtained in the solvent-free nanopowders also produced the highest SE values of 37.3 ± 3.7 dB (MHz band) and 68.6 ± 4.6 dB (GHz band)« less

Development of a mercuric iodide solid state spectrometer for X-ray astronomy

NASA Technical Reports Server (NTRS)

Vallerga, J.

1983-01-01

Mercuric iodide detectors, experimental development for astronomical use, X ray observations of the 1980 Cygnus X-1 High State, astronomical had X ray detectors in current use, detector development, balloon flight of large area (1500 sq cm) Phoswich detectors, had X ray telescope design, shielded mercuric iodide background measurement, Monte Carlo analysis, measurements with a shielded mercuric iodide detector are discussed.

Dark jets in the soft X-ray state of black hole binaries?

NASA Astrophysics Data System (ADS)

Drappeau, S.; Malzac, J.; Coriat, M.; Rodriguez, J.; Belloni, T. M.; Belmont, R.; Clavel, M.; Chakravorty, S.; Corbel, S.; Ferreira, J.; Gandhi, P.; Henri, G.; Petrucci, P.-O.

2017-04-01

X-ray binary observations led to the interpretation that powerful compact jets, produced in the hard state, are quenched when the source transitions to its soft state. The aim of this paper is to discuss the possibility that a powerful dark jet is still present in the soft state. Using the black hole X-ray binaries GX339-4 and H1743-322 as test cases, we feed observed X-ray power density spectra in the soft state of these two sources to an internal shock jet model. Remarkably, the predicted radio emission is consistent with current upper limits. Our results show that for these two sources, a compact dark jet could persist in the soft state with no major modification of its kinetic power compared to the hard state.

Final Report - X-ray Studies of Highly Correlated Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burns, Clement

2017-11-27

The overall goal of the research was to improve the capabilities of x-ray synchrotron instrumentation to enable cutting-edge research in condensed matter physics. The main goal of the current grant cycle was to find a method to measure the polarization of the scattered x-ray in resonant inelastic x-ray scattering. To do this, we developed a polarization analysis apparatus using a thin, toroidally bent single crystal, which could be set to reflect one or the other of the two polarization components in the scattered x-ray beam. Resonant x-ray scattering measurements were also carried out on interfaces and the charge density wavemore » in high temperature superconducting materials.« less

Graphene oxide windows for in situ environmental cell photoelectron spectroscopy.

PubMed

Kolmakov, Andrei; Dikin, Dmitriy A; Cote, Laura J; Huang, Jiaxing; Abyaneh, Majid Kazemian; Amati, Matteo; Gregoratti, Luca; Günther, Sebastian; Kiskinova, Maya

2011-08-28

The performance of new materials and devices often depends on processes taking place at the interface between an active solid element and the environment (such as air, water or other fluids). Understanding and controlling such interfacial processes require surface-specific spectroscopic information acquired under real-world operating conditions, which can be challenging because standard approaches such as X-ray photoelectron spectroscopy generally require high-vacuum conditions. The state-of-the-art approach to this problem relies on unique and expensive apparatus including electron analysers coupled with sophisticated differentially pumped lenses. Here, we develop a simple environmental cell with graphene oxide windows that are transparent to low-energy electrons (down to 400 eV), and demonstrate the feasibility of X-ray photoelectron spectroscopy measurements on model samples such as gold nanoparticles and aqueous salt solution placed on the back side of a window. These proof-of-principle results show the potential of using graphene oxide, graphene and other emerging ultrathin membrane windows for the fabrication of low-cost, single-use environmental cells compatible with commercial X-ray and Auger microprobes as well as scanning or transmission electron microscopes.

Application of X-ray photoelectron spectroscopy to the analysis of stainless-steel welding aerosols

NASA Astrophysics Data System (ADS)

Tandon, R. K.; Payling, R.; Chenhall, B. E.; Crisp, P. T.; Ellis, J.; Baker, R. S.

1985-02-01

Aerosol particles ("fume") from manual metal arc welding of stainless steel with E316L-16 electrodes were analysed by X-ray photoelectron spectroscopy. The inherent complexity of the particles required the use of a wide range of experimental techniques. These included IR spectrophotometry, TGA/DTA, XRF, XRD, AAS and electron microprobe analysis. The surface of the fume particles comprised ≈ 50 at% NaF and KF, ≈ 8 at.% soluble (probably K) chromate, ≈ 30 at% SiO 2 and several at.% transition-metal oxides, hydroxides or silicates. The fluorides and chromates were removed by washing to reveal a surface which was predominantly SiO 2 (≈ 60 at%) with the remainder comprising of transition-metal oxides, silicates and fluorides. Approximately 6 at% F remained on the surface of the water-washed particles, presumably as transition-metal fluoro-complexes. The water-soluble fraction of the fume contained K +, Na +, F - and CrO 2-4 ions in the mole ratio 5:5:4:3. When aerosol particles are deposited in lung tissues, water-soluble constituents would be expected to dissolve rapidly. In view of the suspected carcinogenicity of stainless steel welding fume, a bio-medical study of the combined effects of F - and CrO 2-4 ions on lung tissue is warranted.

X-ray photoelectron spectroscopy for identification of morphological defects and disorders in graphene devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aydogan, Pinar; Suzer, Sefik, E-mail: suzer@fen.bilkent.edu.tr; Polat, Emre O.

The progress in the development of graphene devices is promising, and they are now considered as an option for the current Si-based electronics. However, the structural defects in graphene may strongly influence the local electronic and mechanical characteristics. Although there are well-established analytical characterization methods to analyze the chemical and physical parameters of this material, they remain incapable of fully understanding of the morphological disorders. In this study, x-ray photoelectron spectroscopy (XPS) with an external voltage bias across the sample is used for the characterization of morphological defects in large area of a few layers graphene in a chemically specificmore » fashion. For the XPS measurements, an external +6 V bias applied between the two electrodes and areal analysis for three different elements, C1s, O1s, and Au4f, were performed. By monitoring the variations of the binding energy, the authors extract the voltage variations in the graphene layer which reveal information about the structural defects, cracks, impurities, and oxidation levels in graphene layer which are created purposely or not. Raman spectroscopy was also utilized to confirm some of the findings. This methodology the authors offer is simple but provides promising chemically specific electrical and morphological information.« less

Combined use of atomic force microscopy, X-ray photoelectron spectroscopy, and secondary ion mass spectrometry for cell surface analysis.

PubMed

Dague, Etienne; Delcorte, Arnaud; Latgé, Jean-Paul; Dufrêne, Yves F

2008-04-01

Understanding the surface properties of microbial cells is a major challenge of current microbiological research and a key to efficiently exploit them in biotechnology. Here, we used three advanced surface analysis techniques with different sensitivity, probing depth, and lateral resolution, that is, in situ atomic force microscopy, X-ray photoelectron spectroscopy, and secondary ion mass spectrometry, to gain insight into the surface properties of the conidia of the human fungal pathogen Aspergillus fumigatus. We show that the native ultrastructure, surface protein and polysaccharide concentrations, and amino acid composition of three mutants affected in hydrophobin production are markedly different from those of the wild-type, thereby providing novel insight into the cell wall architecture of A. fumigatus. The results demonstrate the power of using multiple complementary techniques for probing microbial cell surfaces.

Kinetic study of GeO disproportionation into a GeO{sub 2}/Ge system using x-ray photoelectron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Shengkai; Department of Materials Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656; CREST, Japan Science and Technology Agency

2012-08-06

GeO disproportionation into GeO{sub 2} and Ge is studied through x-ray photoelectron spectroscopy. Direct evidence for the reaction 2GeO {yields} GeO{sub 2} + Ge after annealing in ultra-high vacuum is presented. Activation energy for GeO disproportionation is found to be about 0.7 {+-} 0.2 eV through kinetic and thermodynamic calculations. A kinetic model of GeO disproportionation is established by considering oxygen transfer in the GeO network. The relationship between GeO disproportionation and GeO desorption induced by GeO{sub 2}/Ge interfacial reaction is discussed, and the apparent contradiction between GeO desorption via interfacial redox reaction and GeO disproportionation into Ge and GeO{submore » 2} is explained by considering the oxygen vacancy.« less

Effect of Space Radiation Processing on Lunar Soil Surface Chemistry: X-Ray Photoelectron Spectroscopy Studies

NASA Technical Reports Server (NTRS)

Dukes, C.; Loeffler, M.J.; Baragiola, R.; Christoffersen, R.; Keller, J.

2009-01-01

Current understanding of the chemistry and microstructure of the surfaces of lunar soil grains is dominated by a reference frame derived mainly from electron microscopy observations [e.g. 1,2]. These studies have shown that the outermost 10-100 nm of grain surfaces in mature lunar soil finest fractions have been modified by the combined effects of solar wind exposure, surface deposition of vapors and accretion of impact melt products [1,2]. These processes produce surface-correlated nanophase Feo, host grain amorphization, formation of surface patinas and other complex changes [1,2]. What is less well understood is how these changes are reflected directly at the surface, defined as the outermost 1-5 atomic monolayers, a region not easily chemically characterized by TEM. We are currently employing X-ray Photoelectron Spectroscopy (XPS) to study the surface chemistry of lunar soil samples that have been previously studied by TEM. This work includes modification of the grain surfaces by in situ irradiation with ions at solar wind energies to better understand how irradiated surfaces in lunar grains change their chemistry once exposed to ambient conditions on earth.

X-ray variability of Cygnus X-1 in its soft state

NASA Technical Reports Server (NTRS)

Cui, W.; Zhang, S. N.; Jahoda, K.; Focke, W.; Swank, J.; Heindl, W. A.; Rothschild, R. E.

1997-01-01

Observations from the Rossi X-ray Timing Explorer (RXTE) of Cyg X-1 in the soft state and during the soft to hard transition are examined. The results of this analysis confirm previous conclusions that for this source there is a settling period (following the transition from the hard to soft state during which the low energy spectrum varies significantly, while the high energy portion changes little) during which the source reaches nominal soft state brightness. This behavior can be characterized by a soft low energy spectrum and significant low frequency 1/f noise and white noise on the power density spectrum, which becomes softer upon reaching the true soft state. The low frequency 1/f noise is not observed when Cyg X-1 is in the hard state, and therefore appears to be positively correlated with the disk mass accretion rate. The difference in the observed spectral and timing properties between the hard and soft states is qualitatively consistent with a fluctuating corona model.

Photoelectron interference fringes by super intense x-ray laser pulses

NASA Astrophysics Data System (ADS)

Toyota, Koudai; Tolstikhin, Oleg I.; Morishita, Toru; Watanabe, Shinichi

2009-09-01

The photoelectron spectra of H- produced by circularly polarized strong high-frequency laser pulses are theoretically studied. An oscillating substructure in the above-threshold ionization (ATI) peaks is observed, which extends the validity of the earlier findings in the 1D calculations [K. Toyota et al., Phys. Rev. A 76, 043418 (2007)] and 3D calculations for linear polarization [O. I. Tolstikhin, Phys. Rev. A 77, 032712 (2008)]. Its origin is due to an interference between a pair of photoelectron wave packets created in the rising and falling part of the pulse, which appears clearly in the stabilization regime.

Surface study of stainless steel electrode deposition from soil electrokinetic (EK) treatment using X-ray photoelectron spectroscopy (XPS)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Embong, Zaidi, E-mail: zaidi@uthm.edu.my; Research Centre for Soft Soils; Johar, Saffuwan

2015-04-29

Electrokinetic (EK) remediation relies upon application of a low-intensity direct current through the soil between stainless steel electrodes that are divided into a cathode array and an anode array. This mobilizes charged species, causing ions and water to move toward the electrodes. Metal ions and positively charged organic compounds move toward the cathode. Anions such as chloride, fluoride, nitrate, and negatively charged organic compounds move toward the anode. Here, this remediation techniques lead to a formation of a deposition at the both cathode and anode surface that mainly contributed byanion and cation from the remediated soil. In this research, Renggam-Jerangaumore » soil species (HaplicAcrisol + RhodicFerralsol) with a surveymeter reading of 38.0 ± 3.9 μR/hr has been investigation in order to study the mobility of the anion and cation under the influence electric field. Prior to the EK treatment, the elemental composition of the soil and the stainless steel electrode are measured using XRF analyses. Next, the soil sample is remediated at a constant electric potential of 30 V within an hour of treatment period. A surface study for the deposition layer of the cathode and anode using X-ray Photoelectron spectroscopy (XPS) revealed that a narrow photoelectron signal from oxygen O 1s, carbon, C 1s silica, Si 2p, aluminium, Al 2p and chromium, Cr 2p exhibited on the electrode surface and indicate that a different in photoelectron intensity for each element on both electrode surface. In this paper, the mechanism of Si{sup 2+} and Al{sup 2+} cation mobility under the influence of voltage potential between the cathode and anode will be discussed in detail.« less

Toward better Li-ion batteries: hard x-ray photoelectron spectroscopy investigation of binder materials for Si-based anodes

NASA Astrophysics Data System (ADS)

Young, Benjamin; Heskett, David; Nguyen, Cao Cuong; Woicik, Joseph; Lucht, Brett

From portable electronics to space exploration, the desire for more capable rechargeable batteries is driving a search for high capacity anodes. There is much interest in incorporating silicon as a partial or full replacement for the current graphite material in the most popular batteries because it could potentially hold much more charge. There is a significant challenge, however, in that storing so much more lithium in either electrode as the battery is charged and discharged as this causes an accompanying increase in the physical size fluctuation of the electrodes. Specifically, in the anode where this investigation focuses, the active material may experience a 300% volume change between the charged and discharged state. This makes a long lifetime difficult to achieve because the passivation layer protecting the electrolyte material from decomposition is compromised upon each cycle. One approach to accommodating the large volumetric fluctuation without sacrificing lifetime is to find a better material to include in the anode substrate to act as a binder. Ideally, such a material would permit the anode to fluctuate without breaking. Polyvinylidene fluoride (PVdF) is not successful for silicon-based anodes and we present Hard X-ray photoelectron spectroscopy studies of batteries incorporating three alternatives. The alternative binders outperform the PVdF and we present possible explanations. DOE EPSCoR and RI College Faculty Research Fund.

Characterization of photocatalytic TiO 2 powder under varied environments using near ambient pressure X-ray photoelectron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krishnan, Padmaja; Liu, Minghui; Itty, Pierre A.

Consecutive eight study phases under the successive presence and absence of UV irradiation, water vapor, and oxygen were conducted to characterize surface changes in the photocatalytic TiO2 powder using near-ambient-pressure X-ray photoelectron spectroscopy (XPS). Both Ti 2p and O 1s spectra show hysteresis through the experimental course. Under all the study environments, the bridging hydroxyl (OH br) and terminal hydroxyl (OH t) are identified at 1.1–1.3 eV and 2.1–2.3 eV above lattice oxygen, respectively. This enables novel and complementary approach to characterize reactivity of TiO 2 powder. The dynamic behavior of surface-bound water molecules under each study environment is identified,more » while maintaining a constant distance of 1.3 eV from the position of water vapor. In the dark, the continual supply of both water vapor and oxygen is the key factor retaining the activated state of the TiO 2 powder for a time period. Two new surface peaks at 1.7–1.8 and 4.0–4.2 eV above lattice oxygen are designated as peroxides (OOH/H 2O 2) and H 2O 2 dissolved in water, respectively. The persistent peroxides on the powder further explain previously observed prolonged oxidation capability of TiO 2 powder without light irradiation.« less

Characterization of photocatalytic TiO 2 powder under varied environments using near ambient pressure X-ray photoelectron spectroscopy

DOE PAGES

Krishnan, Padmaja; Liu, Minghui; Itty, Pierre A.; ...

2017-02-27

Consecutive eight study phases under the successive presence and absence of UV irradiation, water vapor, and oxygen were conducted to characterize surface changes in the photocatalytic TiO2 powder using near-ambient-pressure X-ray photoelectron spectroscopy (XPS). Both Ti 2p and O 1s spectra show hysteresis through the experimental course. Under all the study environments, the bridging hydroxyl (OH br) and terminal hydroxyl (OH t) are identified at 1.1–1.3 eV and 2.1–2.3 eV above lattice oxygen, respectively. This enables novel and complementary approach to characterize reactivity of TiO 2 powder. The dynamic behavior of surface-bound water molecules under each study environment is identified,more » while maintaining a constant distance of 1.3 eV from the position of water vapor. In the dark, the continual supply of both water vapor and oxygen is the key factor retaining the activated state of the TiO 2 powder for a time period. Two new surface peaks at 1.7–1.8 and 4.0–4.2 eV above lattice oxygen are designated as peroxides (OOH/H 2O 2) and H 2O 2 dissolved in water, respectively. The persistent peroxides on the powder further explain previously observed prolonged oxidation capability of TiO 2 powder without light irradiation.« less

Anti-Stokes resonant x-ray Raman scattering for atom specific and excited state selective dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kunnus, Kristjan; Josefsson, Ida; Rajkovic, Ivan

Here, ultrafast electronic and structural dynamics of matter govern rate and selectivity of chemical reactions, as well as phase transitions and efficient switching in functional materials. Since x-rays determine electronic and structural properties with elemental, chemical, orbital and magnetic selectivity, short pulse x-ray sources have become central enablers of ultrafast science. Despite of these strengths, ultrafast x-rays have been poor at picking up excited state moieties from the unexcited ones. With time-resolved anti-Stokes resonant x-ray Raman scattering (AS-RXRS) performed at the LCLS, and ab initio theory we establish background free excited state selectivity in addition to the elemental, chemical, orbitalmore » and magnetic selectivity of x-rays. This unparalleled selectivity extracts low concentration excited state species along the pathway of photo induced ligand exchange of Fe(CO)5 in ethanol. Conceptually a full theoretical treatment of all accessible insights to excited state dynamics with AS-RXRS with transform-limited x-ray pulses is given—which will be covered experimentally by upcoming transform-limited x-ray sources.« less

Anti-Stokes resonant x-ray Raman scattering for atom specific and excited state selective dynamics

DOE PAGES

Kunnus, Kristjan; Josefsson, Ida; Rajkovic, Ivan; ...

2016-10-07

Here, ultrafast electronic and structural dynamics of matter govern rate and selectivity of chemical reactions, as well as phase transitions and efficient switching in functional materials. Since x-rays determine electronic and structural properties with elemental, chemical, orbital and magnetic selectivity, short pulse x-ray sources have become central enablers of ultrafast science. Despite of these strengths, ultrafast x-rays have been poor at picking up excited state moieties from the unexcited ones. With time-resolved anti-Stokes resonant x-ray Raman scattering (AS-RXRS) performed at the LCLS, and ab initio theory we establish background free excited state selectivity in addition to the elemental, chemical, orbitalmore » and magnetic selectivity of x-rays. This unparalleled selectivity extracts low concentration excited state species along the pathway of photo induced ligand exchange of Fe(CO)5 in ethanol. Conceptually a full theoretical treatment of all accessible insights to excited state dynamics with AS-RXRS with transform-limited x-ray pulses is given—which will be covered experimentally by upcoming transform-limited x-ray sources.« less

Direct evaluation of electrical dipole moment and oxygen density ratio at high-k dielectrics/SiO2 interface by X-ray photoelectron spectroscopy analysis

NASA Astrophysics Data System (ADS)

Fujimura, Nobuyuki; Ohta, Akio; Ikeda, Mitsuhisa; Makihara, Katsunori; Miyazaki, Seiichi

2018-04-01

The electrical dipole moment at an ultrathin high-k (HfO2, Al2O3, TiO2, Y2O3, and SrO)/SiO2 interface and its correlation with the oxygen density ratio at the interface have been directly evaluated by X-ray photoelectron spectroscopy (XPS) under monochromatized Al Kα radiation. The electrical dipole moment at the high-k/SiO2 interface has been measured from the change in the cut-off energy of secondary photoelectrons. Moreover, the oxygen density ratio at the interface between high-k and SiO2 has been estimated from cation core-line signals, such as Hf 4f, Al 2p, Y 3d, Ti 2p, Sr 3d, and Si 2p. We have experimentally clarified the relationship between the measured electrical dipole moment and the oxygen density ratio at the high-k/SiO2 interface.

Solar Absorber Cu 2 ZnSnS 4 and its Parent Multilayers ZnS/SnS 2 /Cu 2 S Synthesized by Atomic Layer Deposition and Analyzed by X-ray Photoelectron Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baryshev, Sergey V.; Riha, Shannon C.; Zinovev, Alexander V.

2015-06-01

Presented here are results of x-ray photoelectron spectroscopy (XPS) on multilayers of metal-sulfide binaries ZnS, SnS2, and Cu2S grown by atomic layer deposition (ALD) on Si substrates, and of Cu2ZnSnS4 (CZTS) formed upon 450 °C annealing of the parent multilayer ZnS/SnS2/Cu2S. Survey and detailed spectral analysis of the multilayer ZnS/SnS2/Cu2S are presented step-wise, as each layer was sequentially added by ALD. The set of data is finalized with spectra of the resulting alloy CZTS. XPS analyses indicate significant mixing between SnS2 and Cu2S, which favors CZTS formation within the ALD approach.

X-ray outbursts and high-state episodes of HETE J1900.1-2455

NASA Astrophysics Data System (ADS)

Šimon, Vojtěch

2018-06-01

HETE J1900.1-2455 is an ultra-compact low-mass X-ray binary that underwent a long-lasting (about 10 yr) active state. The analysis presented here of its activity uses the observations of RXTE/ASM, Swift/BAT, and ISS/MAXI for investigating this active state and the relation of time evolution of fluxes in the hard and medium X-ray bands. We show that the variations of the flux of HETE J1900.1-2455 on the time-scales of days and weeks have the form both of the outbursts and occasional high-state episodes. These outbursts are accompanied by the large changes of the hardness of the spectrum in the surroundings of the peaks of their soft X-ray flux. The very strong peaks of these outbursts occur in the soft X-ray band (2-4 keV) and are accompanied by a large depression in the 15-50 keV band flux. We interpret these events as an occasional occurrence of a thermal-viscous instability of the accretion disc that gives rise to the outbursts similar to those in the soft X-ray transients. On the other hand, the 2-4 and the 15-50 keV band fluxes are mutually correlated in the high-state episodes, much longer than the outbursts. In the interpretation, the episodes of the X-ray high states of HETE J1900.1-2455 during the active state bear some analogy with the standstills in the Z Cam type of cataclysmic variables.

Band alignment of TiO{sub 2}/FTO interface determined by X-ray photoelectron spectroscopy: Effect of annealing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, Haibo, E-mail: hbfan@nwu.edu.cn, E-mail: liusz@snnu.edu.cn; School of Physics, Northwest University, Xi’an 710069; Yang, Zhou

2016-01-15

The energy band alignment between pulsed-laser-deposited TiO{sub 2} and FTO was firstly characterized using high-resolution X-ray photoelectron spectroscopy. A valence band offset (VBO) of 0.61 eV and a conduction band offset (CBO) of 0.29 eV were obtained across the TiO{sub 2}/FTO heterointerface. With annealing process, the VBO and CBO across the heterointerface were found to be -0.16 eV and 1.06 eV, respectively, with the alignment transforming from type-I to type-II. The difference in the band alignment is believed to be dominated by the core level down-shift of the FTO substrate, which is a result of the oxidation of Sn. Current-voltagemore » test has verified that the band alignment has a significant effect on the current transport of the heterojunction.« less

X-ray photoelectron spectroscopy and friction studies of nickel-zinc and manganese-zinc ferrites in contact with metals

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1983-01-01

X-ray photoelectron spectroscopy analysis and sliding friction experiments were conducted with hot-pressed, polycrystalline Ni-Zn and Mn-Zn ferrites in sliding contact with various transition metals at room temperature in a vacuum of 30 nPa. The results indicate that the coefficients of friction for Ni-Zn and Mn-Zn ferrites in contact with metals are related to the relative chemical activity in these metals: the more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites correlate with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite surfaces increases the coefficients of friction for the Ni-Zn and Mn-Zn ferrite-metal interfaces.

Detailed Characterization of a Nanosecond-Lived Excited State: X-ray and Theoretical Investigation of the Quintet State in Photoexcited [Fe(terpy)2]2+

PubMed Central

2015-01-01

Theoretical predictions show that depending on the populations of the Fe 3dxy, 3dxz, and 3dyz orbitals two possible quintet states can exist for the high-spin state of the photoswitchable model system [Fe(terpy)2]2+. The differences in the structure and molecular properties of these 5B2 and 5E quintets are very small and pose a substantial challenge for experiments to resolve them. Yet for a better understanding of the physics of this system, which can lead to the design of novel molecules with enhanced photoswitching performance, it is vital to determine which high-spin state is reached in the transitions that follow the light excitation. The quintet state can be prepared with a short laser pulse and can be studied with cutting-edge time-resolved X-ray techniques. Here we report on the application of an extended set of X-ray spectroscopy and scattering techniques applied to investigate the quintet state of [Fe(terpy)2]2+ 80 ps after light excitation. High-quality X-ray absorption, nonresonant emission, and resonant emission spectra as well as X-ray diffuse scattering data clearly reflect the formation of the high-spin state of the [Fe(terpy)2]2+ molecule; moreover, extended X-ray absorption fine structure spectroscopy resolves the Fe–ligand bond-length variations with unprecedented bond-length accuracy in time-resolved experiments. With ab initio calculations we determine why, in contrast to most related systems, one configurational mode is insufficient for the description of the low-spin (LS)–high-spin (HS) transition. We identify the electronic structure origin of the differences between the two possible quintet modes, and finally, we unambiguously identify the formed quintet state as 5E, in agreement with our theoretical expectations. PMID:25838847

Detailed Characterization of a Nanosecond-Lived Excited State: X-ray and Theoretical Investigation of the Quintet State in Photoexcited [Fe(terpy) 2 ] 2+

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vankó, György; Bordage, Amélie; Pápai, Mátyás

2015-03-19

Theoretical predictions show that depending on the populations of the Fe 3dxy, 3dxz, and 3dyz orbitals two possible quintet states can exist for the high-spin state of the photoswitchable model system [Fe(terpy)2]2+. The differences in the structure and molecular properties of these 5B2 and 5E quintets are very small and pose a substantial challenge for experiments to resolve them. Yet for a better understanding of the physics of this system, which can lead to the design of novel molecules with enhanced photoswitching performance, it is vital to determine which high-spin state is reached in the transitions that follow the lightmore » excitation. The quintet state can be prepared with a short laser pulse and can be studied with cutting-edge time-resolved X-ray techniques. Here we report on the application of an extended set of X-ray spectroscopy and scattering techniques applied to investigate the quintet state of [Fe(terpy)2]2+ 80 ps after light excitation. High-quality X-ray absorption, nonresonant emission, and resonant emission spectra as well as X-ray diffuse scattering data clearly reflect the formation of the high-spin state of the [Fe(terpy)2]2+ molecule; moreover, extended X-ray absorption fine structure spectroscopy resolves the Fe-ligand bond-length variations with unprecedented bondlength accuracy in time-resolved experiments. With ab initio calculations we determine why, in contrast to most related systems, one configurational mode is insufficient for the description of the low-spin (LS)-high-spin (HS) transition. We identify the electronic structure origin of the differences between the two possible quintet modes, and finally, we unambiguously identify the formed quintet state as 5E, in agreement with our theoretical expectations.« less

Detailed Characterization of a Nanosecond-Lived Excited State: X-ray and Theoretical Investigation of the Quintet State in Photoexcited [Fe(terpy) 2 ] 2+

DOE PAGES

Vanko, Gyorgy; Bordage, Amelie; Papai, Matyas; ...

2015-03-19

Theoretical predictions show that depending on the populations of the Fe 3d xy, 3d xz, and 3d yz orbitals two possible quintet states can exist for the high-spin state of the photoswitchable model system [Fe(terpy) 2] 2+. The differences in the structure and molecular properties of these 5B2 and 5E quintets are very small and pose a substantial challenge for experiments to resolve them. Yet for a better understanding of the physics of this system, which can lead to the design of novel molecules with enhanced photoswitching performance, it is vital to determine which high-spin state is reached in themore » transitions that follow the light excitation. The quintet state can be prepared with a short laser pulse and can be studied with cutting-edge time-resolved X-ray techniques. Here we report on the application of an extended set of X-ray spectroscopy and scattering techniques applied to investigate the quintet state of [Fe(terpy) 2] 2+ 80 ps after light excitation. High-quality X-ray absorption, nonresonant emission, and resonant emission spectra as well as X-ray diffuse scattering data clearly reflect the formation of the high-spin state of the [Fe(terpy) 2] 2+ molecule; moreover, extended X-ray absorption fine structure spectroscopy resolves the Fe–ligand bond-length variations with unprecedented bond-length accuracy in time-resolved experiments. With ab initio calculations we determine why, in contrast to most related systems, one configurational mode is insufficient for the description of the low-spin (LS)–high-spin (HS) transition. We identify the electronic structure origin of the differences between the two possible quintet modes, and finally, we unambiguously identify the formed quintet state as 5E, in agreement with our theoretical expectations.« less

Automation in visual inspection tasks: X-ray luggage screening supported by a system of direct, indirect or adaptable cueing with low and high system reliability.

PubMed

Chavaillaz, Alain; Schwaninger, Adrian; Michel, Stefan; Sauer, Juergen

2018-05-25

The present study evaluated three automation modes for improving performance in an X-ray luggage screening task. 140 participants were asked to detect the presence of prohibited items in X-ray images of cabin luggage. Twenty participants conducted this task without automatic support (control group), whereas the others worked with either indirect cues (system indicated the target presence without specifying its location), or direct cues (system pointed out the exact target location) or adaptable automation (participants could freely choose between no cue, direct and indirect cues). Furthermore, automatic support reliability was manipulated (low vs. high). The results showed a clear advantage for direct cues regarding detection performance and response time. No benefits were observed for adaptable automation. Finally, high automation reliability led to better performance and higher operator trust. The findings overall confirmed that automatic support systems for luggage screening should be designed such that they provide direct, highly reliable cues.

A novel x-ray imaging system and its imaging performance

NASA Astrophysics Data System (ADS)

Yu, Chunyu; Chang, Benkang; Wang, Shiyun; Zhang, Junju; Yao, Xiao

2006-09-01

Since x-ray was discovered and applied to the imaging technology, the x-ray imaging techniques have experienced several improvements, from film-screen, x-ray image intensifier, CR to DR. To store and transmit the image information conveniently, the digital imaging is necessary for the imaging techniques in medicine and biology. Usually as the intensifying screen technique as for concerned, to get the digital image signals, the CCD was lens coupled directly to the screen, but which suffers from a loss of x-ray signal and resulted in the poor x-ray image perfonnance. Therefore, to improve the image performance, we joined the brightness intensifier, which, was named the Low Light Level (LLL) image intensifier in military affairs, between the intensifying screen and the CCD and designed the novel x-ray imaging system. This design method improved the image performance of the whole system thus decreased the x-ray dose. Comparison between two systems with and without the brightness intensifier was given in detail in this paper. Moreover, the main noise source of the image produced by the novel system was analyzed, and in this paper, the original images produced by the novel x-ray imaging system and the processed images were given respectively. It was clear that the image performance was satisfied and the x-ray imaging system can be used in security checking and many other nondestructive checking fields.

An update on X-ray reflection gratings developed for future missions

NASA Astrophysics Data System (ADS)

Miles, Drew

2018-01-01

X-ray reflection gratings are a key technology being studied for future X-ray spectroscopy missions, including the Lynx X-ray mission under consideration for the 2020 Decadal Survey. We present an update on the status of X-ray reflection gratings being developed at Penn State University, including current fabrication techniques and mass-replication processes and the latest diffraction efficiency results and resolving power measurements. Individual off-plane X-ray reflection gratings have exceeded the current Lynx requirements for both effective area and resolving power. Finally, we discuss internal projects that will advance the technology readiness level of these gratings.

X-ray spectral analysis of the steady states of GRS 1915+105

NASA Astrophysics Data System (ADS)

Peris, Charith; Remillard, Ronald A.; Steiner, James F.; Vrtilek, Saeqa Dil; Varniere, Peggy; Rodriguez, Jerome; Pooley, Guy G.

2016-04-01

Of the black hole binaries (BHBs) discovered thus far, GRS 1915+105 stands out as an exceptional source primarily due to its wild X-ray variability, the diversity of which has not been replicated in any other stellar-mass black hole. Although extreme variability is commonplace in its light-curve, about half of the observations of GRS1915+105 show fairly steady X-ray intensity. We report on the X-ray spectral behavior within these steady observations. Our work is based on a vast RXTE/PCA data set obtained on GRS 1915+105 during the course of its entire mission and 10 years of radio data from the Ryle Telescope, which overlap the X-ray data. We find that the steady observations within the X-ray data set naturally separate into two regions in a color-color diagram, which we refer to as steady-soft and steady-hard. GRS 1915+105 displays significant curvature in the Comptonization component within the PCA band pass suggesting significantly heating from a hot disk present in all states. A new Comptonization model 'simplcut' was developed in order to model this curvature to best effect. A majority of the steady-soft observations display a roughly constant inner disk radius, remarkably reminiscent of canonical soft state black hole binaries. In contrast, the steady-hard observations display a growing disk truncation that is correlated to the mass accretion rate through the disk, which suggests a magnetically truncated disk. A comparison of X-ray model parameters to the canonical state definitions show that almost all steady-soft observations match the criteria of either thermal or steep power law state, while the thermal state observations dominate the constant radius branch. A large portion 80 % of the steady-hard observations matches the hard state criteria when the disk fraction constraint is neglected. These results combine to suggest that within the complexity of this source is a simpler underlying basis of states, which map to those observed in canonical BHBs.

X-ray photoelectron spectrum and electronic properties of a noncentrosymmetric chalcopyrite compound HgGa(2)S(4): LDA, GGA, and EV-GGA.

PubMed

Reshak, Ali Hussain; Khenata, R; Kityk, I V; Plucinski, K J; Auluck, S

2009-04-30

An all electron full potential linearized augmented plane wave method has been applied for a theoretical study of the band structure, density of states, and electron charge density of a noncentrosymmetric chalcopyrite compound HgGa(2)S(4) using three different approximations for the exchange correlation potential. Our calculations show that the valence band maximum (VBM) and conduction band minimum (CBM) are located at Gamma resulting in a direct energy gap of about 2.0, 2.2, and 2.8 eV for local density approximation (LDA), generalized gradient approximation (GGA), and Engel-Vosko (EVGGA) compared to the experimental value of 2.84 eV. We notice that EVGGA shows excellent agreement with the experimental data. This agreement is attributed to the fact that the Engel-Vosko GGA formalism optimizes the corresponding potential for band structure calculations. We make a detailed comparison of the density of states deduced from the X-ray photoelectron spectra with our calculations. We find that there is a strong covalent bond between the Hg and S atoms and Ga and S atoms. The Hg-Hg, Ga-Ga, and S-S bonds are found to be weaker than the Hg-S and Ga-S bonds showing that a covalent bond exists between Hg and S atoms and Ga and S atoms.

Bulk electronic structure of non-centrosymmetric EuTGe 3 (T=Co, Ni, Rh, Ir) studied by hard x-ray photoelectron spectroscopy

DOE PAGES

Utsumi, Yuki; Kasinathan, Deepa; Swatek, Przemys?aw; ...

2018-03-15

Non-centrosymmetric EuTGe 3 ( T = Co, Ni, Rh, and Ir) possesses magnetic Eu 2+ ions, and antiferromagnetic ordering appears at low temperatures. Transition-metal substitution leads to changes in the unit-cell volume and in the magnetic ordering. However, the magnetic ordering temperature does not scale with the volume change, and the Eu valence is expected to remain divalent. Here we study the bulk electronic structure of non-centrosymmetric Eu T Ge 3 ( T = Co, Ni, Rh, and Ir) by hard x-ray photoelectron spectroscopy. The Eu 3d core-level spectrum confirms the robust Eu 2+ valence state against the transition-metal substitutionmore » with a small contribution from Eu 3+ . The estimated Eu mean valence is around 2.1 in these compounds, as confirmed by multiplet calculations. In contrast, the Ge 2p spectrum shifts to higher binding energy upon cha nging the transition metal from 3d to 4d to 5d elements, hinting at a change in the Ge- T bonding strength. The valence bands of the different compounds are found to be well reproduced by ab initio band structure calculations.« less

Degradation of all-vanadium redox flow batteries (VRFB) investigated by electrochemical impedance and X-ray photoelectron spectroscopy: Part 2 electrochemical degradation

NASA Astrophysics Data System (ADS)

Derr, Igor; Bruns, Michael; Langner, Joachim; Fetyan, Abdulmonem; Melke, Julia; Roth, Christina

2016-09-01

Electrochemical degradation (ED) of carbon felt electrodes was investigated by cycling of a flow through all-vanadium redox flow battery (VRFB) and conducting half-cell measurements with two reference electrodes inside the test bench. ED was detected using half-cell and full-cell electrochemical impedance spectroscopy (EIS) at different states of charge (SOC). Reversing the polarity of the battery to recover cell performance was performed with little success. Renewing the electrolyte after a certain amount of cycles restored the capacity of the battery. X-ray photoelectron spectroscopy (XPS) reveals that the amount of surface functional increases by more than a factor of 3 for the negative side as well as for the positive side. Scanning electron microscope (SEM) images show a peeling of the fiber surface after cycling the felts, which leads to a loss of electrochemically active surface area (ECSA). Long term cycling shows that ED has a stronger impact on the negative half-cell [V(II)/V(III)] than the positive half-cell [V(IV)/V(V)] and that the negative half-cell is the rate-determining half-cell for the VRFB.

Bulk electronic structure of non-centrosymmetric EuTGe 3 (T=Co, Ni, Rh, Ir) studied by hard x-ray photoelectron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Utsumi, Yuki; Kasinathan, Deepa; Swatek, Przemys?aw

Non-centrosymmetric EuTGe 3 ( T = Co, Ni, Rh, and Ir) possesses magnetic Eu 2+ ions, and antiferromagnetic ordering appears at low temperatures. Transition-metal substitution leads to changes in the unit-cell volume and in the magnetic ordering. However, the magnetic ordering temperature does not scale with the volume change, and the Eu valence is expected to remain divalent. Here we study the bulk electronic structure of non-centrosymmetric Eu T Ge 3 ( T = Co, Ni, Rh, and Ir) by hard x-ray photoelectron spectroscopy. The Eu 3d core-level spectrum confirms the robust Eu 2+ valence state against the transition-metal substitutionmore » with a small contribution from Eu 3+ . The estimated Eu mean valence is around 2.1 in these compounds, as confirmed by multiplet calculations. In contrast, the Ge 2p spectrum shifts to higher binding energy upon cha nging the transition metal from 3d to 4d to 5d elements, hinting at a change in the Ge- T bonding strength. The valence bands of the different compounds are found to be well reproduced by ab initio band structure calculations.« less

Photoelectron imaging using an ellipsoidal display analyzer

NASA Astrophysics Data System (ADS)

Dütemeyer, T.; Quitmann, C.; Kitz, M.; Dörnemann, K.; Johansson, L. S. O.; Reihl, B.

2001-06-01

speed it is possible to study the electronic structure of solids as a function of an external parameter (i.e., temperature) or to make animated movies showing, for example, the evolution of electronic states in reciprocal space. After installation of this EDA at a synchrotron providing tunable photon energy, the full power of the instrument will come into play by adding techniques like constant final state or constant initial state spectroscopy, and x-ray photoelectron diffraction.

X-ray laser

DOEpatents

Nilsen, Joseph

1991-01-01

An X-ray laser (10) that lases between the K edges of carbon and oxygen, i.e. between 44 and 23 Angstroms, is provided. The laser comprises a silicon (12) and dysprosium (14) foil combination (16) that is driven by two beams (18, 20) of intense line focused (22, 24) optical laser radiation. Ground state nickel-like dysprosium ions (34) are resonantly photo-pumped to their upper X-ray laser state by line emission from hydrogen-like silicon ions (32). The novel X-ray laser should prove especially useful for the microscopy of biological specimens.

Interatomic scattering in energy dependent photoelectron spectra of Ar clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patanen, M.; Benkoula, S.; Nicolas, C.

2015-09-28

Soft X-ray photoelectron spectra of Ar 2p levels of atomic argon and argon clusters are recorded over an extended range of photon energies. The Ar 2p intensity ratios between atomic argon and clusters’ surface and bulk components reveal oscillations similar to photoelectron extended X-ray absorption fine structure signal (PEXAFS). We demonstrate here that this technique allows us to analyze separately the PEXAFS signals from surface and bulk sites of free-standing, neutral clusters, revealing a bond contraction at the surface.

Investigation on Surface Polarization of Al2O3-capped GaN/AlGaN/GaN Heterostructure by Angle-Resolved X-ray Photoelectron Spectroscopy.

PubMed

Duan, Tian Li; Pan, Ji Sheng; Wang, Ning; Cheng, Kai; Yu, Hong Yu

2017-08-17

The surface polarization of Ga-face gallium nitride (GaN) (2 nm)/AlGaN (22 nm)/GaN channel (150 nm)/buffer/Si with Al 2 O 3 capping layer is investigated by angle-resolved X-ray photoelectron spectroscopy (ARXPS). It is found that the energy band varies from upward bending to downward bending in the interface region, which is believed to be corresponding to the polarization variation. An interfacial layer is formed between top GaN and Al 2 O 3 due to the occurrence of Ga-N bond break and Ga-O bond forming during Al 2 O 3 deposition via the atomic layer deposition (ALD). This interfacial layer is believed to eliminate the GaN polarization, thus reducing the polarization-induced negative charges. Furthermore, this interfacial layer plays a key role for the introduction of the positive charges which lead the energy band downward. Finally, a N 2 annealing at 400 °C is observed to enhance the interfacial layer growth thus increasing the density of positive charges.

Thickness measurement of a thin hetero-oxide film with an interfacial oxide layer by X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Kim, Kyung Joong; Lee, Seung Mi; Jang, Jong Shik; Moret, Mona

2012-02-01

The general equation Tove = L cos θ ln(Rexp/R0 + 1) for the thickness measurement of thin oxide films by X-ray photoelectron spectroscopy (XPS) was applied to a HfO2/SiO2/Si(1 0 0) as a thin hetero-oxide film system with an interfacial oxide layer. The contribution of the thick interfacial SiO2 layer to the thickness of the HfO2 overlayer was counterbalanced by multiplying the ratio between the intensity of Si4+ from a thick SiO2 film and that of Si0 from a Si(1 0 0) substrate to the intensity of Si4+ from the HfO2/SiO2/Si(1 0 0) film. With this approximation, the thickness levels of the HfO2 overlayers showed a small standard deviation of 0.03 nm in a series of HfO2 (2 nm)/SiO2 (2-6 nm)/Si(1 0 0) films. Mutual calibration with XPS and transmission electron microscopy (TEM) was used to verify the thickness of HfO2 overlayers in a series of HfO2 (1-4 nm)/SiO2 (3 nm)/Si(1 0 0) films. From the linear relation between the thickness values derived from XPS and TEM, the effective attenuation length of the photoelectrons and the thickness of the HfO2 overlayer could be determined.

Quantitative X-ray photoelectron spectroscopy-based depth profiling of bioleached arsenopyrite surface by Acidithiobacillus ferrooxidans

NASA Astrophysics Data System (ADS)

Zhu, Tingting; Lu, Xiancai; Liu, Huan; Li, Juan; Zhu, Xiangyu; Lu, Jianjun; Wang, Rucheng

2014-02-01

In supergene environments, microbial activities significantly enhance sulfide oxidation and result in the release of heavy metals, causing serious contamination of soils and waters. As the most commonly encountered arsenic mineral in nature, arsenopyrite (FeAsS) accounts for arsenic contaminants in various environments. In order to investigate the geochemical behavior of arsenic during microbial oxidation of arsenopyrite, (2 3 0) surfaces of arsenopyrite slices were characterized after acidic (pH 2.00) and oxidative decomposition with or without an acidophilic microorganism Acidithiobacillus ferrooxidans. The morphology as well as chemical and elemental depth profiles of the oxidized arsenopyrite surface were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. With the mediation of bacteria, cell-shaped and acicular pits were observed on the reacted arsenopyrite surface, and the concentration of released arsenic species in solution was 50 times as high as that of the abiotic reaction after 10 days reaction. Fine-scale XPS depth profiles of the reacted arsenopyrite surfaces after both microbial and abiotic oxidation provided insights into the changes in chemical states of the elements in arsenopyrite surface layers. Within the 450 nm surface layer of abiotically oxidized arsenopyrite, Fe(III)-oxides appeared and gradually increased towards the surface, and detectable sulfite and monovalent arsenic appeared above 50 nm. In comparison, higher contents of ferric sulfate, sulfite, and arsenite were found in the surface layer of approximately 3 μm of the microbially oxidized arsenopyrite. Intermediates, such as Fe(III)-AsS and S0, were detectable in the presence of bacteria. Changes of oxidative species derived from XPS depth profiles show the oxidation sequence is Fe > As = S in abiotic oxidation, and Fe > S > As in microbial oxidation. Based on these results, a possible reaction path of microbial oxidation was proposed in a concept model.

Penn State University ground software support for X-ray missions.

NASA Astrophysics Data System (ADS)

Townsley, L. K.; Nousek, J. A.; Corbet, R. H. D.

1995-03-01

The X-ray group at Penn State is charged with two software development efforts in support of X-ray satellite missions. As part of the ACIS instrument team for AXAF, the authors are developing part of the ground software to support the instrument's calibration. They are also designing a translation program for Ginga data, to change it from the non-standard FRF format, which closely parallels the original telemetry format, to FITS.

Anisotropic imaging performance in indirect x-ray imaging detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Badano, Aldo; Kyprianou, Iacovos S.; Sempau, Josep

We report on the variability in imaging system performance due to oblique x-ray incidence, and the associated transport of quanta (both x rays and optical photons) through the phosphor, in columnar indirect digital detectors. The analysis uses MANTIS, a combined x-ray, electron, and optical Monte Carlo transport code freely available. We describe the main features of the simulation method and provide some validation of the phosphor screen models considered in this work. We report x-ray and electron three-dimensional energy deposition distributions and point-response functions (PRFs), including optical spread in columnar phosphor screens of thickness 100 and 500 {mu}m, for 19,more » 39, 59, and 79 keV monoenergetic x-ray beams incident at 0 deg., 10 deg., and 15 deg. . In addition, we present pulse-height spectra for the same phosphor thickness, x-ray energies, and angles of incidence. Our results suggest that the PRF due to the phosphor blur is highly nonsymmetrical, and that the resolution properties of a columnar screen in a tomographic, or tomosynthetic imaging system varies significantly with the angle of x-ray incidence. Moreover, we find that the noise due to the variability in the number of light photons detected per primary x-ray interaction, summarized in the information or Swank factor, is somewhat independent of thickness and incidence angle of the x-ray beam. Our results also suggest that the anisotropy in the PRF is not less in screens with absorptive backings, while the noise introduced by variations in the gain and optical transport is larger. Predictions from MANTIS, after additional validation, can provide the needed understanding of the extent of such variations, and eventually, lead to the incorporation of the changes in imaging performance with incidence angle into the reconstruction algorithms for volumetric x-ray imaging systems.« less

X-ray generator

DOEpatents

Dawson, John M.

1976-01-01

Apparatus and method for producing coherent secondary x-rays that are controlled as to direction by illuminating a mixture of high z and low z gases with an intense burst of primary x-rays. The primary x-rays are produced with a laser activated plasma, and these x-rays strip off the electrons of the high z atoms in the lasing medium, while the low z atoms retain their electrons. The neutral atoms transfer electrons to highly excited states of the highly striped high z ions giving an inverted population which produces the desired coherent x-rays. In one embodiment, a laser, light beam provides a laser spark that produces the intense burst of coherent x-rays that illuminates the mixture of high z and low z gases, whereby the high z atoms are stripped while the low z ones are not, giving the desired mixture of highly ionized and neutral atoms. To this end, the laser spark is produced by injecting a laser light beam, or a plurality of beams, into a first gas in a cylindrical container having an adjacent second gas layer co-axial therewith, the laser producing a plasma and the intense primary x-rays in the first gas, and the second gas containing the high and low atomic number elements for receiving the primary x-rays, whereupon the secondary x-rays are produced therein by stripping desired ions in a neutral gas and transfer of electrons to highly excited states of the stripped ions from the unionized atoms. Means for magnetically confining and stabilizing the plasma are disclosed for controlling the direction of the x-rays.

Accretion states in X-ray binaries and their connection to GeV emission

NASA Astrophysics Data System (ADS)

Koerding, Elmar

Accretion onto compact objects is intrinsically a multi-wavelength phenomenon: it shows emis-sion components visible from the radio to GeV bands. In X-ray binaries one can well observe the evolution of a single source under changes of the accretion rate and thus study the interplay between the different emission components.I will introduce the phenomenology of X-ray bina-ries and their accretion states and present our current understanding of the interplay between the optically thin and optically thick part of the accretion flow and the jet.The recent detection of the Fermi Large Area Telescope of a variable high-energy source coinciding with the position of the x-ray binary Cygnus X-3 will be presented. Its identification with Cygnus X-3 has been secured by the detection of its orbital period in gamma rays, as well as the correlation of the LAT flux with radio emission from the relativistic jets of Cygnus X-3. This will be interpreted in the context of the accretion states of the X-ray binary.

X-Ray photoelectron spectroscopy study of radiofrequency-sputtered titanium, carbide, molybdenum carbide, and titanium boride coatings and their friction properties

NASA Technical Reports Server (NTRS)

Brainard, W. A.; Wheeler, D. R.

1977-01-01

Radiofrequency sputtered coatings of titanium carbide, molybdenum carbide and titanium boride were tested as wear resistant coatings on stainless steel in a pin on disk apparatus. X-ray photoelectron spectroscopy (XPS) was used to analyze the sputtered films with regard to both bulk and interface composition in order to obtain maximum film performance. Significant improvements in friction behavior were obtained when properly biased films were deposited on deliberately preoxidized substrates. XPS depth profile data showed thick graded interfaces for bias deposited films even when adherence was poor. The addition of 10 percent hydrogen to the sputtering gas produced coatings with thin poorly adherent interfaces. Results suggest that some of the common practices in the field of sputtering may be detrimental to achieving maximum adherence and optimum composition for these refractory compounds.

X-ray source for mammography

DOEpatents

Logan, Clinton M.

1994-01-01

An x-ray source utilizing anode material which shifts the output spectrum to higher energy and thereby obtains higher penetrating ability for screening mammography application, than the currently utilized anode material. The currently used anode material (molybdenum) produces an energy x-ray spectrum of 17.5/19.6 keV, which using the anode material of this invention (e.g. silver, rhodium, and tungsten) the x-ray spectrum would be in the 20-35 keV region. Thus, the anode material of this invention provides for imaging of breasts with higher than average x-ray opacity without increase of the radiation dose, and thus reduces the risk of induced breast cancer due to the radiation dose administered for mammograms.

Small Angle X-Ray Scattering Detector

DOEpatents

Hessler, Jan P.

2004-06-15

A detector for time-resolved small-angle x-ray scattering includes a nearly constant diameter, evacuated linear tube having an end plate detector with a first fluorescent screen and concentric rings of first fiber optic bundles for low angle scattering detection and an annular detector having a second fluorescent screen and second fiber optic bundles concentrically disposed about the tube for higher angle scattering detection. With the scattering source, i.e., the specimen under investigation, located outside of the evacuated tube on the tube's longitudinal axis, scattered x-rays are detected by the fiber optic bundles, to each of which is coupled a respective photodetector, to provide a measurement resolution, i.e., dq/q, where q is the momentum transferred from an incident x-ray to an x-ray scattering specimen, of 2% over two (2) orders of magnitude in reciprocal space, i.e., q.sub.max /q.sub.min.congruent.100.

Initial and steady-state Ru growth by atomic layer deposition studied by in situ Angle Resolved X-ray Photoelectron Spectroscopy

NASA Astrophysics Data System (ADS)

Egorov, Konstantin V.; Lebedinskii, Yury Yu.; Soloviev, Anatoly A.; Chouprik, Anastasia A.; Azarov, Alexander Yu.; Markeev, Andrey M.

2017-10-01

The clear substrate-dependent growth and delayed film continuity are essential challenges of Ru atomic layer deposition (ALD) demanding adequate and versatile approaches for their study. Here, we report on the application of in situ Angle Resolved X-ray Phototelectron Spectroscopy (ARXPS) for investigation of initial and steady-state ALD growth of Ru using Ru(EtCp)2 and O2 as precursors. Using ARXPS surface analysis technique we determine such parameters of Ru ALD initial growth as incubation period, fractional coverage and the thickness of islands/film depending on the substrate chemical state, governed by the presence/absence of NH3/Ar plasma pretreatment. It was demonstrated that NH3/Ar plasma pretreatment allows to obtain the lowest incubation period (∼7 ALD cycles) resulting in a continuous ultrathin (∼20 Å) and smooth Ru films after 70 ALD cycles. In situ XPS at UHV was used at steady state Ru growth for analysis of half-cycle reactions that revealed formation of RuOx (x ≈ 2) layer with thickness of ∼8 Å after O2 pulse (first half-cycle). It was also shown that oxygen of RuOx layer combusts Ru(EtCp)2 ligands in the second half-cycle reaction and the observed Ru growth of ∼0.34 Å per cycle is in a good agreement with the amount of oxygen in the RuOx layer.

Compositional depth profile of a native oxide LPCVD MNOS structure using X-ray photoelectron spectroscopy and chemical etching

NASA Technical Reports Server (NTRS)

Wurzbach, J. A.; Grunthaner, F. J.

1983-01-01

It is pointed out that there is no report of an unambiguous analysis of the composition and interfacial structure of MNOS (metal-nitride oxide semiconductor) systems, despite the technological importance of these systems. The present investigation is concerned with a study of an MNOS structure on the basis of a technique involving the use of X-ray photoelectron spectroscopy (XPS) with a controlled stopped-flow chemical-etching procedure. XPS is sensitive to the structure of surface layers, while stopped-flow etching permits the controlled removal of overlying material on a scale of atomic layers, to expose new surface layers as a function of thickness. Therefore, with careful analysis of observed intensities at measured depths, this combination of techniques provides depth resolution between 5 and 10 A. According to the obtained data there is intact SiO2 at the substrate interface. There appears to be a thin layer containing excess bonds to silicon on top of the SiO2.

X-ray photoelectron spectroscopy study of the stability of Fomblin Z25 on the native oxide of aluminum

NASA Technical Reports Server (NTRS)

Herrera-Fierro, Pilar; Pepper, Stephen V.; Jones, William R.

1992-01-01

Thin films of Fomblin Z25, a perfluoropolyalkylether lubricant, were vapor deposited onto clean, oxidized aluminum, and onto sapphire surfaces, and their behavior at different temperatures was studied using X-ray photoelectron spectroscopy and temperature desorption spectroscopy (TDS). The interfacial fluid molecules decompose on the native oxide at room temperature, and continue to decompose at elevated temperatures, as previous studies had shown to occur on the clean metal. TDS indicated that different degradation mechanisms were operative for clean and oxidized aluminum. On sapphire substrates, no reaction was observed at room temperature. The native oxide of aluminum is neither passive nor protective towards Fomblin Z25. At higher temperatures (150 C), degradation of the polymer on sapphire produced a debris layer at the interface with a chemical composition similar to the one formed on aluminum oxide. Rubbing a Fomblin film on a single crystal sapphire also induced the decomposition of the lubricant in contact with the interface and the formation of a debris layer.

X-ray natural widths, level widths and Coster-Kronig transition probabilities

NASA Astrophysics Data System (ADS)

Papp, T.; Campbell, J. L.; Varga, D.

1997-01-01

A critical review is given for the K-N7 atomic level widths. The experimental level widths were collected from x-ray photoelectron spectroscopy (XPS), x-ray emission spectroscopy (XES), x-ray spectra fluoresced by synchrotron radiation, and photoelectrons from x-ray absorption (PAX). There are only limited atomic number ranges for a few atomic levels where data are available from more than one source. Generally the experimental level widths have large scatter compared to the reported error bars. The experimental data are compared with the recent tabulation of Perkins et al. and of Ohno et al. Ohno et al. performed a many body approach calculation for limited atomic number ranges and have obtained reasonable agreement with the experimental data. Perkins et al. presented a tabulation covering the K-Q1 shells of all atoms, based on extensions of the Scofield calculations for radiative rates and extensions of the Chen calculations for non-radiative rates. The experimental data are in disagreement with this tabulation, in excess of a factor of two in some cases. A short introduction to the experimental Coster-Kronig transition probabilities is presented. It is our opinion that the different experimental approaches result in systematically different experimental data.

Fiber fed x-ray/gamma ray imaging apparatus

DOEpatents

Hailey, C.J.; Ziock, K.P.

1992-06-02

X-ray/gamma ray imaging apparatus is disclosed for detecting the position, energy, and intensity of x-ray/gamma ray radiation comprising scintillation means disposed in the path of such radiation and capable of generating photons in response to such radiation; first photodetection means optically bonded to the scintillation means and capable of generating an electrical signal indicative of the intensity, and energy of the radiation detected by the scintillation means; second photodetection means capable of generating an electrical signal indicative of the position of the radiation in the radiation pattern; and means for optically coupling the scintillation means to the second photodetection means. The photodetection means are electrically connected to control and storage means which may also be used to screen out noise by rejecting a signal from one photodetection means not synchronized to a signal from the other photodetection means; and also to screen out signals from scattered radiation. 6 figs.

X-Tip: a New Tool for Nanoscience or How to Combine X-Ray Spectroscopies to Local Probe Analysis

NASA Astrophysics Data System (ADS)

Olivier, Dhez; Mario, Rodrigues; Fabio, Comin; Roberto, Felici; Joel, Chevrier

2007-01-01

With the advent of nanoscale science, the need of tools able to image samples and bring the region of interest to the X-ray beam is essential. We show the possibility of using the high resolution imaging capability of a scanning probe microscope to image and align a sample relative to the X-ray beam, as well as the possibility to record the photoelectrons emitted by the sample.

Ray-trace analysis of glancing-incidence X-ray optical systems

NASA Technical Reports Server (NTRS)

Foreman, J. W., Jr.; Cardone, J. M.

1976-01-01

The results of a ray-trace analysis of several glancing-incidence X-ray optical systems are presented. The object of the study was threefold. First, the vignetting characteristics of the S-056 X-ray telescope were calculated using experimental data to determine mirror reflectivities. Second, a small Wolter Type I X-ray telescope intended for possible use in the Geostationary Operational Environmental Satellite program was designed and ray traced. Finally, a ray-trace program was developed for a Wolter-Schwarzschild X-ray telescope.

X-Ray Toolkit

DOE Office of Scientific and Technical Information (OSTI.GOV)

2015-10-20

Radiographic Image Acquisition & Processing Software for Security Markets. Used in operation of commercial x-ray scanners and manipulation of x-ray images for emergency responders including State, Local, Federal, and US Military bomb technicians and analysts.

Quantitative analysis of trace levels of surface contamination by X-ray photoelectron spectroscopy Part I: statistical uncertainty near the detection limit.

PubMed

Hill, Shannon B; Faradzhev, Nadir S; Powell, Cedric J

2017-12-01

We discuss the problem of quantifying common sources of statistical uncertainties for analyses of trace levels of surface contamination using X-ray photoelectron spectroscopy. We examine the propagation of error for peak-area measurements using common forms of linear and polynomial background subtraction including the correlation of points used to determine both background and peak areas. This correlation has been neglected in previous analyses, but we show that it contributes significantly to the peak-area uncertainty near the detection limit. We introduce the concept of relative background subtraction variance (RBSV) which quantifies the uncertainty introduced by the method of background determination relative to the uncertainty of the background area itself. The uncertainties of the peak area and atomic concentration and of the detection limit are expressed using the RBSV, which separates the contributions from the acquisition parameters, the background-determination method, and the properties of the measured spectrum. These results are then combined to find acquisition strategies that minimize the total measurement time needed to achieve a desired detection limit or atomic-percentage uncertainty for a particular trace element. Minimization of data-acquisition time is important for samples that are sensitive to x-ray dose and also for laboratories that need to optimize throughput.

X-ray photoelectron spectroscopy characterization of gold nanoparticles functionalized with amine-terminated alkanethiols

PubMed Central

Techane, Sirnegeda D.; Gamble, Lara J.; Castner, David G.

2011-01-01

Gold nanoparticles (AuNPs) functionalized with a short chain amine-terminated alkanethiol (HS-(CH2)2NH2 or C2 NH2-thiol) are prepared via a direct synthesis method and then ligand-exchanged with a long chain amine-terminated alkanethiol (HS-(CH2)11NH2 or C11 NH2-thiol). Transmission electron microscopy analysis showed the AuNPs were relatively spherical with a median diameter of 24.2±4.3 nm. X-ray photoelectron spectroscopy was used to determine surface chemistry of the functionalized and purified AuNPs. The ligand-exchange process was monitored within the time range from 30 min to 61 days. By the fourth day of exchange all the C2 NH2-thiol molecules had been replaced by C11 NH2-thiol molecules. C11 NH2-thiol molecules continued to be incorporated into the C11 NH2 self-assembled monolayer between days 4 and 14 of ligand-exchange. As the length of the exchange time increased, the functionalized AuNPs became more stable against aggregation. The samples were purified by a centrifugation and resuspension method. The C2 NH2 covered AuNPs aggregated immediately when purification was attempted. The C11 NH2 covered AuNPs could be purified with minimal or no aggregation. Small amounts of unbound thiol (∼15%) and oxidized sulfur (∼20%) species were detected on the ligand-exchanged AuNPs. Some of the unbound thiol and all of the oxidized sulfur could be removed by treating the functionalized AuNPs with HCl. PMID:21974680

Generation of High Brightness X-rays with the PLEIADES Thomson X-ray Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, W J; Anderson, S G; Barty, C P J

2003-05-28

The use of short laser pulses to generate high peak intensity, ultra-short x-ray pulses enables exciting new experimental capabilities, such as femtosecond pump-probe experiments used to temporally resolve material structural dynamics on atomic time scales. PLEIADES (Picosecond Laser Electron InterAction for Dynamic Evaluation of Structures) is a next generation Thomson scattering x-ray source being developed at Lawrence Livermore National Laboratory (LLNL). Ultra-fast picosecond x-rays (10-200 keV) are generated by colliding an energetic electron beam (20-100 MeV) with a high intensity, sub-ps, 800 nm laser pulse. The peak brightness of the source is expected to exceed 10{sup 20} photons/s/0.1% bandwidth/mm2/mrad2. Simulationsmore » of the electron beam production, transport, and final focus are presented. Electron beam measurements, including emittance and final focus spot size are also presented and compared to simulation results. Measurements of x-ray production are also reported and compared to theoretical calculations.« less

X-ray source for mammography

DOEpatents

Logan, C.M.

1994-12-20

An x-ray source is described utilizing anode material which shifts the output spectrum to higher energy and thereby obtains higher penetrating ability for screening mammography application, than the currently utilized anode material. The currently used anode material (molybdenum) produces an energy x-ray spectrum of 17.5/19.6 keV, which using the anode material of this invention (e.g. silver, rhodium, and tungsten) the x-ray spectrum would be in the 20-35 keV region. Thus, the anode material of this invention provides for imaging of breasts with higher than average x-ray opacity without increase of the radiation dose, and thus reduces the risk of induced breast cancer due to the radiation dose administered for mammograms. 6 figures.

Enhanced Adsorption of p-Arsanilic Acid from Water by Amine-Modified UiO-67 as Examined Using Extended X-ray Absorption Fine Structure, X-ray Photoelectron Spectroscopy, and Density Functional Theory Calculations.

PubMed

Tian, Chen; Zhao, Jian; Ou, Xinwen; Wan, Jieting; Cai, Yuepeng; Lin, Zhang; Dang, Zhi; Xing, Baoshan

2018-03-20

p-Arsanilic acid ( p-ASA) is an emerging organoarsenic pollutant comprising both inorganic and organic moieties. For the efficient removal of p-ASA, adsorbents with high adsorption affinity are urgently needed. Herein, amine-modified UiO-67 (UiO-67-NH 2 ) metal-organic frameworks (MOFs) were synthesized, and their adsorption affinities toward p-ASA were 2 times higher than that of the pristine UiO-67. Extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculation results revealed adsorption through a combination of As-O-Zr coordination, hydrogen bonding, and π-π stacking, among which As-O-Zr coordination was the dominant force. Amine groups played a significant role in enhancing the adsorption affinity through strengthening the As-O-Zr coordination and π-π stacking, as well as forming new adsorption sites via hydrogen bonding. UiO-67-NH 2 s could remove p-ASA at low concentrations (<5 mg L -1 ) in simulated natural and wastewaters to an arsenic level lower than that of the drinking water standard of World Health Organization (WHO) and the surface water standard of China, respectively. This work provided an emerging and promising method to increase the adsorption affinity of MOFs toward pollutants containing both organic and inorganic moieties, via modifying functional groups based on the pollutant structure to achieve synergistic adsorption effect.

Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy

DOE PAGES

Miaja-Avila, L.; O'Neil, G. C.; Uhlig, J.; ...

2015-03-02

We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ~10 6 photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >10 7 laser pulses, wemore » also present data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments.« less

Photoelectron studies of machined brass surfaces

NASA Astrophysics Data System (ADS)

Potts, A. W.; Merrison, J. P.; Tournas, A. D.; Yacoot, A.

UV photoelectron spectroscopy has been used to determine the surface composition of machined brass. The results show a considerable change between the photoelectron surface composition and the bulk composition of the same sample determined by energy-dispersive X-ray fluorescence. On the surface the lead composition is increased by ˜900 G. This is consistent with the important part that lead is believed to play in improving the machinability of this alloy.

Bulk electronic structure of non-centrosymmetric Eu T Ge3 (T =Co , Ni, Rh, Ir) studied by hard x-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Utsumi, Yuki; Kasinathan, Deepa; Swatek, Przemysław; Bednarchuk, Oleksandr; Kaczorowski, Dariusz; Ablett, James M.; Rueff, Jean-Pascal

2018-03-01

Non-centrosymmetric Eu T Ge3 (T = Co, Ni, Rh, and Ir) possesses magnetic Eu2 + ions, and antiferromagnetic ordering appears at low temperatures. Transition-metal substitution leads to changes in the unit-cell volume and in the magnetic ordering. However, the magnetic ordering temperature does not scale with the volume change, and the Eu valence is expected to remain divalent. Here we study the bulk electronic structure of non-centrosymmetric Eu T Ge3 (T = Co, Ni, Rh, and Ir) by hard x-ray photoelectron spectroscopy. The Eu 3 d core-level spectrum confirms the robust Eu2 + valence state against the transition-metal substitution with a small contribution from Eu3 +. The estimated Eu mean valence is around 2.1 in these compounds, as confirmed by multiplet calculations. In contrast, the Ge 2 p spectrum shifts to higher binding energy upon changing the transition metal from 3 d to 4 d to 5 d elements, hinting at a change in the Ge-T bonding strength. The valence bands of the different compounds are found to be well reproduced by ab initio band structure calculations.

State Switching of the X-Ray/Radio Transitional Millisecond Pulsar

NASA Astrophysics Data System (ADS)

Shang, Lun-Hua; Zhang, Cheng-Min; Li, Di; Wang, De-Hua; Wang, Shuang-Qiang; Wang, Pei; Pan, Yuan-Yue; Yang, Yi-Yan; Zhi, Qi-Jun

2017-11-01

PSR J1023+0038 is a known transitional pulsar, which switches between the accretion-powered X-ray pulsar state and the rotation-powered radio millisecond pulsar (MSP) state. Here, we study the conditions for its state transition by ascribing ˜GHz radio pulse emission to the plasma cutoff oscillation frequency at the magnetosphere, which depends on the plasma density or accretion rate. With the accretion X-ray luminosity declining fromhigh to low state (e.g., ˜ {10}35 erg s-1 to ˜ {10}32 erg s-1), the magnetosphere boundary expands to the light cylinder, where the plasma density is low enough to permit the emission of radio waves at the several-GHz frequency band. Thus, for a sufficiently low accretion-rate state (˜ {10}32 erg s-1), the radio emission at the several-GHz band is not blocked by the plasma, and the radio pulsar can be detected in the favored “observational windows,” I.e., the L band (1-2 GHz), S band (2-4 GHz), and C band (4-8 GHz). Furthermore, to evaluate the penetration characteristics of the outgoing radio wave of low frequency, we calculate its skin depth, which is found to be a couple of centimeters for the low X-ray luminosity of {10}34{--}{10}32 erg s-1, a scale that is much shorter than the light cylinder radius of about 100 km for MSPs.

FPGA-Based X-Ray Detection and Measurement for an X-Ray Polarimeter

NASA Technical Reports Server (NTRS)

Gregory, Kyle; Hill, Joanne; Black, Kevin; Baumgartner, Wayne

2013-01-01

This technology enables detection and measurement of x-rays in an x-ray polarimeter using a field-programmable gate array (FPGA). The technology was developed for the Gravitational and Extreme Magnetism Small Explorer (GEMS) mission. It performs precision energy and timing measurements, as well as rejection of non-x-ray events. It enables the GEMS polarimeter to detect precisely when an event has taken place so that additional measurements can be made. The technology also enables this function to be performed in an FPGA using limited resources so that mass and power can be minimized while reliability for a space application is maximized and precise real-time operation is achieved. This design requires a low-noise, charge-sensitive preamplifier; a highspeed analog to digital converter (ADC); and an x-ray detector with a cathode terminal. It functions by computing a sum of differences for time-samples whose difference exceeds a programmable threshold. A state machine advances through states as a programmable number of consecutive samples exceeds or fails to exceed this threshold. The pulse height is recorded as the accumulated sum. The track length is also measured based on the time from the start to the end of accumulation. For track lengths longer than a certain length, the algorithm estimates the barycenter of charge deposit by comparing the accumulator value at the midpoint to the final accumulator value. The design also employs a number of techniques for rejecting background events. This innovation enables the function to be performed in space where it can operate autonomously with a rapid response time. This implementation combines advantages of computing system-based approaches with those of pure analog approaches. The result is an implementation that is highly reliable, performs in real-time, rejects background events, and consumes minimal power.

X-ray lasers

NASA Astrophysics Data System (ADS)

Elton, Raymond C.

Theoretical and practical aspects of X-ray lasers are discussed in an introduction emphasizing recent advances. Chapters are devoted to the unique optical properties of the X-ray spectral region, the principles of short-wavelength lasers, pumping by exciting plasma ions, pumping by electron capture into excited ionic states, pumping by ionization of atoms and ions, and alternative approaches. The potential scientific, technical, biological, and medical applications of X-ray lasers are briefly characterized.

Development of a simulation method for dynamics of electrons ejected from DNA molecules irradiated with X-rays.

PubMed

Kai, Takeshi; Higuchi, Mariko; Fujii, Kentaro; Watanabe, Ritsuko; Yokoya, Akinari

2012-12-01

To develop a method for simulating the dynamics of the photoelectrons and Auger electrons ejected from DNA molecules irradiated with pulsed monochromatic X-rays. A 30-base-pair (bp) DNA molecule was used as the target model, and the X-rays were assumed to have a Gaussian-shaped time distribution. Photoionization and Auger decay were considered as the atomic processes. The atoms from which the photoelectrons or Auger electrons were emitted were specified in the DNA molecule (or DNA ion) using the Monte Carlo method, and the trajectory of each electron in the electric field formed around the positively charged DNA molecule was calculated with a Newtonian equation. The kinetics of the electrons produced by irradiation with X-rays at an intensity ranging from 1 × 10(12) to 1 × 10(16) photons/mm(2) and energies of 380 eV (below the carbon K-edge), 435 eV (above the nitrogen K-edge), and 560 eV (above the oxygen K-edge) were evaluated. It was found that at an X-ray intensity of 1 × 10(14) photons/mm(2) or less, all the produced electrons escaped from the target. However, above an X-ray intensity of 1 × 10(15) photons/mm(2) and an energy of 560 eV, some photoelectrons that were ejected from the oxygen atoms were trapped near the target DNA. A simulation method for studying the trajectories of electrons ejected from a 30-bp DNA molecule irradiated with pulsed monochromatic X-rays has been developed. The present results show that electron dynamics are strongly dependent on the charged density induced in DNA by pulsed X-ray irradiation.

Working alone or in the presence of others: exploring social facilitation in baggage X-ray security screening tasks.

PubMed

Yu, Rui-feng; Wu, Xin

2015-01-01

This study investigated whether the mere presence of a human audience would evoke a social facilitation effect in baggage X-ray security screening tasks. A 2 (target presence: present vs. absent) ×  2 (task complexity: simple vs. complex) ×  2 (social presence: alone vs. human audience) within-subject experiment simulating a real baggage screening task was conducted. This experiment included 20 male participants. The participants' search performance in this task was recorded. The results showed that the presence of a human audience speeded up responses in simple tasks and slowed down responses in complex tasks. However, the social facilitation effect produced by the presence of a human audience had no effect on response accuracy. These findings suggested that the complexity of screening tasks should be considered when designing work organisation modes for security screening tasks. Practitioner summary: This study investigated whether the presence of a human audience could evoke a social facilitation effect in baggage X-ray security screening tasks. An experimental simulation was conducted. The results showed that the presence of a human audience facilitated the search performance of simple tasks and inhibited the performance of complex tasks.

Auger electron spectroscopy and x-ray photoelectron spectroscopy of the biocorrosion of copper by Gum Arabic, BCS and Pseudomonas atlantica exopolymer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jolley, J.G.; Geesey, G.G.; Hankins, M.R.

1987-01-01

Thin films (3.4 nm) of copper on germanium substrates were exposed to 10% Gum Arabic aqueous solution, 1% BCS (aqueous and simulated sea water solutions) and 0.5% Pseudomonas atlantica exopolymer (aqueous and simulated sea water solutions). Pre- and post-exposure characterization were done by Auger electron spectroscopy and x-ray photoelectron spectroscopy. Ancillary graphite furnace atomic absorption spectroscopy was used to monitor the removal process of the copper thin film from the germanium substrate. Results indicate that the copper was oxidized by the Gum Arabic and BCS, and some was removed from the Cu/Ge interface by all three polymers and incorporated intomore » the polymer matrix. Thus biocorrosion of copper was exhibited by the Gum Arabic, BCS and Pseudomonas atlantica exopolymer. 14 refs., 4 figs., 3 tabs.« less

Comparison of gold leaf thickness in Namban folding screens using X-ray fluorescence

NASA Astrophysics Data System (ADS)

Pessanha, Sofia; Madeira, Teresa I.; Manso, Marta; Guerra, Mauro; Le Gac, Agnès; Carvalho, Maria Luisa

2014-09-01

In this work, the thickness of the gold leaf applied in six Japanese folding screens is compared using a nondestructive approach. Four screens belonging to the Momoyama period (~1573-1603) and two screens belonging to the early Edo period (~1603-1868) were analyzed in situ using energy dispersive X-ray fluorescence, and the thickness of the applied gold leaf was evaluated using a methodology based on the attenuation of the different characteristic lines of gold in the gold leaf layer. Considering that the leaf may well not be made of pure gold, we established that, for the purpose of comparing the intensity ratios of the Au lines, layers made with gold leaf of high grade can be considered identical. The gold leaf applied in one of the screens from the Edo period was found to be thinner than the gold leaf applied in the other ones. This is consistent with the development of the beating technology to obtain ever more thin gold leafs.

Analyse de l'interface cuivre/Teflon AF1600 par spectroscopie des photoelectrons rayons x

NASA Astrophysics Data System (ADS)

Popovici, Dan

The speed of electrical signals through the microelectronic multilevel interconnects depends of the delay time R x C. In order to improve the transmission speed of future microdevices, the microelectronics industry requires the use of metals having lower resistivities and insulators having lower permittivities. Copper and fluoropolymers are interesting candidates for the replacement of the presently used Al/polyimide technology. This thesis presents an X-ray photoelectron spectroscopy (XPS) analysis of the Cu/Teflon AF1600 interface, in order to have a better understanding of those interfacial interactions leading to improved adhesion. Several deposition methods, such as evaporation, sputtering and laser-induced chemical deposition were analyzed and compared. X-ray photoelectron spectroscopy (XPS) was used as the primary characterization technique of the different surfaces and interfaces. In the case of evaporation and sputtering, the loss of fluorine and oxygen atoms leads to graphitization and the crosslinking of carbon chains. The extent of damage caused by copper deposition is higher for sputter deposition because of the higher energies of the incidents atoms. This energy (two orders of magnitude higher than the energy involved in the evaporation) is also responsible for the total reaction of Cu with F and C. For the physical depositions (sputtering and evaporation), an angle-resolved XPS diffusion study showed the copper distribution as a function of depth. (i) For sputter deposition, this distribution is uniform. (ii) In the case of evaporation, we computed the concentration profile using the inverse Laplace transform. Several samples, annealed at different temperatures, were used to calculate the diffusion coefficients for the Cu/Teflon AF1600 interface. The study of interactions at the interface between Teflon AF1600 and copper deposited by different metallization techniques permitted us to elucidate some aspects related to the chemistry and structure of

X-ray photoelectron spectroscopic study of the oxide removal mechanism of GaAs /100/ molecular beam epitaxial substrates in in situ heating

NASA Technical Reports Server (NTRS)

Vasquez, R. P.; Lewis, B. F.; Grunthaner, F. J.

1983-01-01

A standard cleaning procedure for GaAs (100) molecular beam epitaxial (MBE) substrates is a chemical treatment with a solution of H2SO4/H2O2/H2O, followed by in situ heating prior to MBE growth. X-ray photoelectron spectroscopic (XPS) studies of the surface following the chemical treatment show that the oxidized As is primarily As(+ 5). Upon heating to low temperatures (less than (350 C) the As(+ 5) oxidizes the substrate to form Ga2O3 and elemental As, and the As(+ 5) is reduced to As(+ 3) in the process. At higher temperatures (500 C), the As(+ 3) and elemental As desorb, while the Ga(+ 3) begins desorbing at about 600 C.

Final Report on X-ray Yields from OMEGA II Targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fournier, K B; May, M J; MacLaren, S A

2007-06-20

We present details about X-ray yields measured with Lawrence Livermore National Laboratory (LLNL) and Sandia National Laboratories (SNL) diagnostics in soft and moderately hard X-ray bands from laser-driven, doped-aerogel targets shot on 07/14/06 during the OMEGA II test series. Yields accurate to {+-}25% in the 5-15 keV band are measured with Livermore's HENWAY spectrometer. Yields in the sub-keV to 3.2 keV band are measured with LLNL's DANTE diagnostic, the DANTE yields are accurate to 10-15%. SNL ran a PCD-based diagnostic that also measured X-ray yields in the spectral region above 4 keV, and also down to the sub-keV range. Themore » PCD and HENWAY and DANTE numbers are compared. The time histories of the moderately hard (h{nu} > 4 keV) X-ray signals are measured with LLNL's H11 PCD, and from two SNL PCDs with comparable filtration. There is general agreement between the H11 PCD and SNL PCD measured FWHM except for two of the shorter-laser-pulse shots, which is shown not to be due to analysis techniques. The recommended X-ray waveform is that from the SNL PCD p66k10, which was recorded on a fast, high-bandwidth TDS 6804 oscilloscope. X-ray waveforms from target emission in two softer spectral bands are also shown; the X-ray emissions have increasing duration as the spectral content gets softer.« less

Circular polarization of X-ray radiation emitted by longitudinally polarized electron impact excitation: Under a screened Coulomb interaction

NASA Astrophysics Data System (ADS)

Chen, Zhan-Bin

2017-12-01

Longitudinally polarized electron impact excitation from the ground state 1s2 to the excited state 1s2l (l =s,p) levels of highly charged He-like Fe24+ ions in weakly coupled hot-dense plasmas is investigated using a fully relativistic distorted-wave method. The Debye-Hückel potential is used to describe the plasma screening. Benchmark results such as the total cross sections, the magnetic sublevels cross sections, and the circular polarizations of corresponding X-ray radiations are presented. For the excitation process, results show that the plasma screening has an effect in reducing both the total and magnetic sublevels cross sections. For the de-excitation process, it is found that while the plasma screening as a slightly effect on the circular polarizations of radiations for the 1 s 2 s 3S1 → 1 s21S0,1 s 2 p 3P2 → 1 s21S0 , and 1 s 2 p 1P1 → 1 s21S0 transition lines, it gives a substantial contribution for the same properties of the 1 s 2 p 3P1 → 1 s21S0 line.

Imaging local electric fields produced upon synchrotron X-ray exposure

DOE PAGES

Dettmar, Christopher M.; Newman, Justin A.; Toth, Scott J.; ...

2014-12-31

Electron–hole separation following hard X-ray absorption during diffraction analysis of soft materials under cryogenic conditions produces substantial local electric fields visualizable by second harmonic generation (SHG) microscopy. Monte Carlo simulations of X-ray photoelectron trajectories suggest the formation of substantial local electric fields in the regions adjacent to those exposed to X-rays, indicating a possible electric-field–induced SHG (EFISH) mechanism for generating the observed signal. In studies of amorphous vitreous solvents, analysis of the SHG spatial profiles following X-ray microbeam exposure was consistent with an EFISH mechanism. Within protein crystals, exposure to 12-keV (1.033-Å) X-rays resulted in increased SHG in the regionmore » extending ~3 μm beyond the borders of the X-ray beam. Moderate X-ray exposures typical of those used for crystal centering by raster scanning through an X-ray beam were sufficient to produce static electric fields easily detectable by SHG. The X-ray–induced SHG activity was observed with no measurable loss for longer than 2 wk while maintained under cryogenic conditions, but disappeared if annealed to room temperature for a few seconds. In conclusion, these results provide direct experimental observables capable of validating simulations of X-ray–induced damage within soft materials. Additionally, X-ray–induced local fields may potentially impact diffraction resolution through localized piezoelectric distortions of the lattice.« less

Coherent Multidimensional Core Spectroscopy of Molecules with Multiple X-ray pulses

NASA Astrophysics Data System (ADS)

Mukamel, Shaul

2017-04-01

Multidimensional spectroscopy uses sequences of optical pulses to study dynamical processes in complex molecules through correlation plots involving several time delay periods. Extensions of these techniques to the x-ray regime will be discussed. Ultrafast nonlinear x-ray spectroscopy is made possible by newly developed free electron laser and high harmonic generation sources. The attosecond duration of X-ray pulses and the atomic selectivity of core X-ray excitations offer a uniquely high spatial and temporal resolution. We demonstrate how stimulated Raman detection of an X-ray probe may be used to monitor the phase and dynamics of the nonequilibrium valence electronic state wavepacket created by e.g. photoexcitation, photoionization and Auger processes. Spectroscopy of multiplecore excitations provides a new window into electron correlations. Applications will be presented to long-range charge transfer in proteins and to excitation energy transfer in porphyrin arrays. Conical intersections (CoIn) dominate the pathways and outcomes of virtually all photophysical and photochemical molecular processes. Despite extensive experimental and theoretical effort CoIns have not been directly observed yet and the experimental evidence is being inferred from fast reaction rates and some vibrational signatures. Novel ultrafast X ray probes for these processes will be presented. Short X-ray pulses can directly detect the passage through a CoIn with the adequate temporal and spectral sensitivity. The technique is based on a coherent Raman process that employs a composite femtosecond/attosecond X-ray pulse to directly detect the electronic coherences (rather than populations) that are generated as the system passes through the CoIn. Streaking of time-resolved photoelectron spectroscopy (TRPES) signals offers another powerful window into the joint electronic/vibrational dynamics at concial intersections. Strong coupling of molecules to the vacuum field of micro cavities can modify

Total photoelectron yield spectroscopy of energy distribution of electronic states density at GaN surface and SiO2/GaN interface

NASA Astrophysics Data System (ADS)

Ohta, Akio; Truyen, Nguyen Xuan; Fujimura, Nobuyuki; Ikeda, Mitsuhisa; Makihara, Katsunori; Miyazaki, Seiichi

2018-06-01

The energy distribution of the electronic state density of wet-cleaned epitaxial GaN surfaces and SiO2/GaN structures has been studied by total photoelectron yield spectroscopy (PYS). By X-ray photoelectron spectroscopy (XPS) analysis, the energy band diagram for a wet-cleaned epitaxial GaN surface such as the energy level of the valence band top and electron affinity has been determined to obtain a better understanding of the measured PYS signals. The electronic state density of GaN surface with different carrier concentrations in the energy region corresponding to the GaN bandgap has been evaluated. Also, the interface defect state density of SiO2/GaN structures was also estimated by not only PYS analysis but also capacitance–voltage (C–V) characteristics. We have demonstrated that PYS analysis enables the evaluation of defect state density filled with electrons at the SiO2/GaN interface in the energy region corresponding to the GaN midgap, which is difficult to estimate by C–V measurement of MOS capacitors.

Global Properties of X-Ray Flashes and X-Ray-Rich Gamma-Ray Bursts Observed by Swift

NASA Astrophysics Data System (ADS)

Sakamoto, Takanori; Yamazaki, Ryo; Barthelmy, Scott; Gehrels, Neil; Osborne, Julian; Hullinger, Derek; Sato, Goro; Barbier, Louis; Cummings, Jay; Fenimore, Ed; Krimm, Hans; Lamb, Don; Markwardt, Craig; Palmer, David; Parsons, Ann; Stamatikos, Michael; Tueller, Jack

Takanori Sakamoto, Taka.Sakamoto@nasa.gov NASA Goddard Space Flight Center, Greenbelt, Maryland, United States Ryo Yamazaki, ryo@theo.phys.sci.hiroshima-u.ac.jp Hiroshima University, Higashi-Hiroshima, Japan Scott Barthelmy, scott@milkyway.gsfc.nasa.gov NASA GSFC, Greenbelt, Maryland, United States Neil Gehrels, gehrels@milkyway.gsfc.nasa.gov NASA Goddard Space Flight Center, Greenbelt, Maryland, United States Julian Osborne, julo@star.le.ac.uk University of Leicester, Leicester, United Kingdom Derek Hullinger, derek.hullinger@gmail.com Moxtek, Inc, Orem, Utah, United States Goro Sato, Goro.Sato@nasa.gov Goddard Space Flight Center, Greenbelt, Maryland, United States Louis Barbier, lmb@milkyway.gsfc.nasa.gov Goddard Space Flight Center, Greenbelt, Maryland, United States Jay Cummings, jayc@milkyway.gsfc.nasa.gov Goddard Space Flight Center, Greenbelt, Maryland, United States Ed Fenimore, efenimore@lanl.gov Los Alamos National Laboratory, Los Alamos, California, United States Hans Krimm, hans.krimm@nasa.gov Goddard Space Flight Center, Greenbelt, Maryland, United States Don Lamb, d-lamb@uchicago.edu University of Chicago, Chicago, Illinois, United States Craig Markwardt, Craig.Markwardt@nasa.gov Goddard Space Flight Center, Greenbelt, Maryland, United States David Palmer, palmer@lanl.gov Los Alamos National Laboratory, Los Alamos, California, United States Ann Parsons, Ann.M.Parsons@nasa.gov Goddard Space Flight Center, Greenbelt, Maryland, United States Michael Stamatikos, michael@milkyway.gsfc.nasa.gov Goddard Space Flight Center, Greenbelt, Maryland, United States Jack Tueller, jack.tueller@nasa.gov Goddard Space Flight Center, Greenbelt, Maryland, United States We present the spectral and temporal characteristics of the prompt emission and X-ray afterglow emission of X-ray flashes (XRFs) and X-ray-rich gamma-ray bursts (XRRs) detected and observed by Swift between December 2004 and September 2006. We compare these characteristics to a sample of conventional

X-ray emission from high temperature plasmas

NASA Technical Reports Server (NTRS)

Harries, W. L.

1974-01-01

X-rays from a 25-hJ plasma focus apparatus were observed with pinhole cameras. The cameras consist of 0.4 mm diameter pinholes in 2 cm thick lead housing enclosing an X-ray intensifying screen at the image plane. Pictures recorded through thin aluminum foils or plastic sheets for X-ray energies sub gamma smaller than 15 keV show distributed X-ray emissions from the focussed plasma and from the anode surface. However, when thick absorbers are used, radial filamentary structure in the X-ray emission from the anode surface is revealed. Occasionally larger structures are observed in addition to the filaments. Possible mechanisms for the filamentary structure are discussed.

Investigation of polydopamine coatings by X-ray Photoelectron Spectroscopy as an effective tool for improving biomolecule conjugation

NASA Astrophysics Data System (ADS)

Rella, Simona; Mazzotta, Elisabetta; Caroli, Antonio; De Luca, Maria; Bucci, Cecilia; Malitesta, Cosimino

2018-07-01

Polydopamine (PDA) films have attracted a rapidly increasing research attention during the last years due to its simple and rapid deposition under alkaline conditions in substrate independent manner providing a universal coating for materials with different chemical and physical properties. Furthermore, this polymerized layer is enriched with functional groups that enable immobilization of primary amine or thiol-based biomolecules via a simple dipping process. Although these aspects justify PDA wide and successful application as a versatile coating for biomolecule immobilization, several aspects have not been deeply investigated leaving some key details unclear and thus limiting PDA practical applications. A number of approaches are commonly used for the growth of PDA, but the effect of deposition conditions on film properties, which in turn influence biomolecule immobilization has not been systematically investigated yet. In the present work, an extensive characterization by X-ray Photoelectron Spectroscopy (XPS) is performed on PDA coatings grown under different experimental conditions. Comparison of XPS data about elemental composition, distribution of functional groups and thickness of PDA coatings provided valuable information for identifying more suitable PDA coating for biomolecule anchoring, further explored by in vitro experiments.

Cosmic x ray physics

NASA Technical Reports Server (NTRS)

Mccammon, Dan; Cox, D. P.; Kraushaar, W. L.; Sanders, W. T.

1992-01-01

This final report covers the period 1 January 1985 - 31 March 1992. It is divided into the following sections: the soft x-ray background; proportional counter and filter calibrations; sounding rocket flight preparations; new sounding rocket payload: x-ray calorimeter; and theoretical studies. Staff, publications, conference proceedings, invited talks, contributed talks, colloquia and seminars, public service lectures, and Ph. D. theses are listed.

Soft X-ray spectroscopy of transition metal compounds: a theoretical perspective

NASA Astrophysics Data System (ADS)

Bokarev, S. I.; Hilal, R.; Aziz, S. G.; Kühn, O.

2017-01-01

To date, X-ray spectroscopy has become a routine tool that can reveal highly local and element-specific information on the electronic structure of atoms in complex environments. Here, we report on the development of an efficient and versatile theoretical methodology for the treatment of soft X-ray spectra of transition metal compounds based on the multi-configurational self-consistent field electronic structure theory. A special focus is put on the L-edge photon-in/photon-out and photon-in/electron-out processes, i.e. X-ray absorption, resonant inelastic scattering, partial fluorescence yield, and photoelectron spectroscopy, all treated on the same theoretical footing. The investigated systems range from small prototypical coordination compounds and catalysts to aggregates of biomolecules.

X-Ray Laser Program Final Report for FY91

DTIC Science & Technology

1992-09-16

from a Na z pinch is used to photoionize Ne to the He-like ground state and radiation from the Na 1 s 2-1 s2p 1P1 transition is used to resonantly...creating photopumped x-ray lasers2 , imploding inertial confinement fusion capsules, 3 and studying the photoionization kinetics of plasmas in intense...has received extensive theoretical study, 5 -8 employs radiation from the 1s2 -1s2p 1P1 transition at 11.0027 A in He-like Na to resonantly photoexcite

Fluence thresholds for grazing incidence hard x-ray mirrors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aquila, A.; Ozkan, C.; Sinn, H.

2015-06-15

X-ray Free Electron Lasers (XFELs) have the potential to contribute to many fields of science and to enable many new avenues of research, in large part due to their orders of magnitude higher peak brilliance than existing and future synchrotrons. To best exploit this peak brilliance, these XFEL beams need to be focused to appropriate spot sizes. However, the survivability of X-ray optical components in these intense, femtosecond radiation conditions is not guaranteed. As mirror optics are routinely used at XFEL facilities, a physical understanding of the interaction between intense X-ray pulses and grazing incidence X-ray optics is desirable. Wemore » conducted single shot damage threshold fluence measurements on grazing incidence X-ray optics, with coatings of ruthenium and boron carbide, at the SPring-8 Angstrom compact free electron laser facility using 7 and 12 keV photon energies. The damage threshold dose limits were found to be orders of magnitude higher than would naively be expected. The incorporation of energy transport and dissipation via keV level energetic photoelectrons accounts for the observed damage threshold.« less

Growth of an Ultrathin Zirconia Film on Pt3Zr Examined by High-Resolution X-ray Photoelectron Spectroscopy, Temperature-Programmed Desorption, Scanning Tunneling Microscopy, and Density Functional Theory.

PubMed

Li, Hao; Choi, Joong-Il Jake; Mayr-Schmölzer, Wernfried; Weilach, Christian; Rameshan, Christoph; Mittendorfer, Florian; Redinger, Josef; Schmid, Michael; Rupprechter, Günther

2015-02-05

Ultrathin (∼3 Å) zirconium oxide films were grown on a single-crystalline Pt 3 Zr(0001) substrate by oxidation in 1 × 10 -7 mbar of O 2 at 673 K, followed by annealing at temperatures up to 1023 K. The ZrO 2 films are intended to serve as model supports for reforming catalysts and fuel cell anodes. The atomic and electronic structure and composition of the ZrO 2 films were determined by synchrotron-based high-resolution X-ray photoelectron spectroscopy (HR-XPS) (including depth profiling), low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and density functional theory (DFT) calculations. Oxidation mainly leads to ultrathin trilayer (O-Zr-O) films on the alloy; only a small area fraction (10-15%) is covered by ZrO 2 clusters (thickness ∼0.5-10 nm). The amount of clusters decreases with increasing annealing temperature. Temperature-programmed desorption (TPD) of CO was utilized to confirm complete coverage of the Pt 3 Zr substrate by ZrO 2 , that is, formation of a closed oxide overlayer. Experiments and DFT calculations show that the core level shifts of Zr in the trilayer ZrO 2 films are between those of metallic Zr and thick (bulklike) ZrO 2 . Therefore, the assignment of such XPS core level shifts to substoichiometric ZrO x is not necessarily correct, because these XPS signals may equally well arise from ultrathin ZrO 2 films or metal/ZrO 2 interfaces. Furthermore, our results indicate that the common approach of calculating core level shifts by DFT including final-state effects should be taken with care for thicker insulating films, clusters, and bulk insulators.

Exploring coherent electron excitation and migration dynamics by electron diffraction with ultrashort X-ray pulses.

PubMed

Yuan, Kai-Jun; Bandrauk, André D

2017-10-04

Exploring ultrafast charge migration is of great importance in biological and chemical reactions. We present a scheme to monitor attosecond charge migration in molecules by electron diffraction with spatial and temporal resolutions from ab initio numerical simulations. An ultraviolet pulse creates a coherent superposition of electronic states, after which a time-delayed attosecond X-ray pulse is used to ionize the molecule. It is found that diffraction patterns in the X-ray photoelectron spectra show an asymmetric structure, which is dependent on the time delay between the pump-probe pulses, encoding the information of molecular orbital symmetry and chemical bonding. We describe these phenomena by developing an electronic time-dependent ultrafast molecular photoionization model of a coherent superposition state. The periodical distortion of electron diffraction patterns illustrates the evolution of the electronic coherence, providing a tool for attosecond imaging of ultrafast molecular reaction processes.

The utility of chest X-ray as a screening tool for blunt thoracic aortic injury.

PubMed

Gutierrez, Adam; Inaba, Kenji; Siboni, Stefano; Effron, Zachary; Haltmeier, Tobias; Jaffray, Paul; Reddy, Sravanthi; Lofthus, Alexander; Benjamin, Elizabeth; Dubose, Joseph; Demetriades, Demetrios

2016-01-01

The early and accurate identification of patients with blunt thoracic aortic injury (BTAI) remains a challenge. Traditionally, a portable AP chest X-ray (CXR) is utilized as the initial screening modality for BTAI, however, there is controversy surrounding its sensitivity. The purpose of this study was to assess the sensitivity of CXR as a screening modality for BTAI. After IRB approval, all adult (≥18 yo) blunt trauma patients admitted to LAC+USC (01/2011-12/2013) who underwent CXR and chest CT were retrospectively reviewed. Final radiology attending CXR readings were reviewed for mediastinal abnormalities (widened mediastinum, mediastinal to chest width ratio greater than 0.25, irregular aortic arch, blurred aortic contour, opacification of the aortopulmonary window, and apical pleural haematoma) suggestive of aortic injury. Chest CT final attending radiologist readings were utilized as the gold standard for diagnosis of BTAI. The primary outcome analyzed was CXR sensitivity. A total of 3728 patients were included in the study. The majority of patients were male (72.6%); mean age was 43 (SD 20). Median ISS was 9 (IQR 4-17) and median GCS was 15 (IQR 14-15). The most common mechanism of injury was MVC (48.0%), followed by fall (20.6%), and AVP (16.9%). The total number of CXRs demonstrating a mediastinal abnormality was 200 (5.4%). Widened mediastinum was present on 191 (5.1%) of CXRs, blurred aortic contour on 10 (0.3%), and irregular aortic arch on 4 (0.1%). An acute aortic injury confirmed by chest CT was present in 17 (0.5%) patients. Only 7 of these with CT-confirmed BTAI had a mediastinal abnormality identified on CXR, for a sensitivity of 41% (95% CI: 19-67%). The results from this study suggest that CXR alone is not a reliable screening modality for BTAI. A combination of screening CXR and careful consideration of other factors, such as mechanism of injury, will be required to effectively discriminate between those who should and should not undergo chest

Soft X-ray scanning transmission X-ray microscopy (STXM) of actinide particles.

PubMed

Nilsson, Hans J; Tyliszczak, Tolek; Wilson, Richard E; Werme, Lars; Shuh, David K

2005-09-01

A descriptive account is given of our most recent research on the actinide dioxides with the Advanced Light Source Molecular Environmental Science (ALS-MES) Beamline 11.0.2 soft X-ray scanning transmission X-ray microscope (STXM) at the Lawrence Berkeley National Laboratory (LBNL). The ALS-MES STXM permits near-edge X-ray absorption fine structure (NEXAFS) and imaging with 30-nm spatial resolution. The first STXM spectromicroscopy NEXAFS spectra at the actinide 4d5/2 edges of the imaged transuranic particles, NpO2 and PuO2, have been obtained. Radiation damage induced by the STXM was observed in the investigation of a mixed oxidation state particle (Np(V,VI)) and was minimized during collection of the actual spectra at the 4d5/2 edge of the Np(V,VI) solid. A plutonium elemental map was obtained from an irregular PuO2 particle with the dimensions of 650 x 650 nm. The Pu 4d5/2 NEXAFS spectra were collected at several different locations from the PuO2 particle and were identical. A representative oxygen K-edge spectrum from UO2 was collected and resembles the oxygen K-edge from the bulk material. The unique and current performance of the ALS-MES STXM at extremely low energies (ca. 100 eV) that may permit the successful measurement of the actinide 5d edge is documented. Finally, the potential of STXM as a tool for actinide investigations is briefly discussed.

Evaluating the solid electrolyte interphase formed on silicon electrodes: A comparison of ex situ X-ray photoelectron spectroscopy and in situ neutron reflectometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doucet, Mathieu; Browning, Jim; Baldwin, J. K.

This work details the in situ characterization of the interface between a silicon electrode and an electrolyte using a linear fluorinated solvent molecule, 0.1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in deuterated dimethyl perfluoroglutarate (d6-PF5M 2) (1.87 x 10 -2 mS/cm -1). The solid electrolyte interphase (SEI) composition and thickness determined via in situ neutron reflectometry (NR) and ex situ X-ray photoelectron spectroscopy (XPS) were compared. The data show that SEI expansion and contraction (breathing) during electrochemical cycling was observed via both techniques; however, ex situ XPS suggests that the SEI thickness increases during Si lithiation and decreases during delithiation, while inmore » situ NR suggests the opposite. The most likely cause of this discrepancy is the selective removal of SEI components (top 20 nm of the SEI) during the electrode rinse process, required to remove electrolyte residue prior to ex situ analysis, demonstrating the necessity of performing SEI characterizations in situ.« less

Evaluating the solid electrolyte interphase formed on silicon electrodes: A comparison of ex situ X-ray photoelectron spectroscopy and in situ neutron reflectometry

DOE PAGES

Doucet, Mathieu; Browning, Jim; Baldwin, J. K.; ...

2016-04-15

This work details the in situ characterization of the interface between a silicon electrode and an electrolyte using a linear fluorinated solvent molecule, 0.1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in deuterated dimethyl perfluoroglutarate (d6-PF5M 2) (1.87 x 10 -2 mS/cm -1). The solid electrolyte interphase (SEI) composition and thickness determined via in situ neutron reflectometry (NR) and ex situ X-ray photoelectron spectroscopy (XPS) were compared. The data show that SEI expansion and contraction (breathing) during electrochemical cycling was observed via both techniques; however, ex situ XPS suggests that the SEI thickness increases during Si lithiation and decreases during delithiation, while inmore » situ NR suggests the opposite. The most likely cause of this discrepancy is the selective removal of SEI components (top 20 nm of the SEI) during the electrode rinse process, required to remove electrolyte residue prior to ex situ analysis, demonstrating the necessity of performing SEI characterizations in situ.« less

X-ray photoelectron spectroscopy (XPS) investigation of the surface film on magnesium powders.

PubMed

Burke, Paul J; Bayindir, Zeynel; Kipouros, Georges J

2012-05-01

Magnesium (Mg) and its alloys are attractive for use in automotive and aerospace applications because of their low density and good mechanical properties. However, difficulty in forming magnesium and the limited number of available commercial alloys limit their use. Powder metallurgy may be a suitable solution for forming near-net-shape parts. However, sintering pure magnesium presents difficulties due to surface film that forms on the magnesium powder particles. The present work investigates the composition of the surface film that forms on the surface of pure magnesium powders exposed to atmospheric conditions and on pure magnesium powders after compaction under uniaxial pressing at a pressure of 500 MPa and sintering under argon at 600 °C for 40 minutes. Initially, focused ion beam microscopy was utilized to determine the thickness of the surface layer of the magnesium powder and found it to be ~10 nm. The X-ray photoelectron analysis of the green magnesium sample prior to sintering confirmed the presence of MgO, MgCO(3)·3H(2)O, and Mg(OH)(2) in the surface layer of the powder with a core of pure magnesium. The outer portion of the surface layer was found to contain MgCO(3)·3H(2)O and Mg(OH)(2), while the inner portion of the layer is primarily MgO. After sintering, the MgCO(3)·3H(2)O was found to be almost completely absent, and the amount of Mg(OH)(2) was also decreased significantly. This is postulated to occur by decomposition of the compounds to MgO and gases during the high temperature of sintering. An increase in the MgO content after sintering supports this theory.

The influence of methanol on the chemical state of PtRu anodes in a high-temperature direct methanol fuel cell studied in situ by synchrotron-based near-ambient pressure x-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Saveleva, Viktoriia A.; Daletou, Maria K.; Savinova, Elena R.

2017-01-01

Synchrotron radiation-based near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS) has recently become a powerful tool for the investigation of interfacial phenomena in electrochemical power sources such as batteries and fuel cells. Here we present an in situ NAP-XPS study of the anode of a high-temperature direct methanol fuel cell with a phosphoric acid-doped hydrocarbon membrane, which reveals an enhanced flooding of the Pt3Ru anode with phosphoric acid in the presence of methanol. An analysis of the electrode surface composition depending on the cell voltage and on the presence of methanol reveals the strong influence of the latter on the extent of Pt oxidation and on the transformation of Ru into Ru (IV) hydroxide.

Electronic structure of the polymer-cathode interface of an organic electroluminescent device investigated using operando hard x-ray photoelectron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ikeuchi, J.; Hamamatsu, H.; Miyamoto, T.

2015-08-28

The electronic structure of a polymer-cathode interface of an operating organic light-emitting diode (OLED) was directly investigated using hard X-ray photoelectron spectroscopy (HAXPES). The potential distribution profile of the light-emitting copolymer layer as a function of the depth under the Al/Ba cathode layer in the OLED depended on the bias voltage. We found that band bending occurred in the copolymer of 9,9-dioctylfluorene (50%) and N-(4-(2-butyl)-phenyl)diphenylamine (F8-PFB) layer near the cathode at 0 V bias, while a linear potential distribution formed in the F8-PFB when a bias voltage was applied to the OLED. Direct observation of the built-in potential and that bandmore » bending formed in the F8-PFB layer in the operating OLED suggested that charges moved in the F8-PFB layer before electron injection from the cathode.« less

X-Ray Photoelectron Spectroscopy and Ultrahigh Vacuum Contactless Capacitance-Voltage Characterization of Novel Oxide-Free InP Passivation Process Using a Silicon Surface Quantum Well

NASA Astrophysics Data System (ADS)

Takahashi, Hiroshi; Hashizume, Tamotsu; Hasegawa, Hideki

1999-02-01

In order to understand and optimize a novel oxide-free InP passivation process using a silicon surface quantum well, a detailed in situ X-ray photoelectron spectroscopy (XPS) and ultrahigh vacuum (UHV) contactless capacitance-voltage (C-V) study of the interface was carried out. Calculation of quantum levels in the silicon quantum well was performed on the basis of the band lineup of the strained Si3N4/Si/InP interface and the result indicated that the interface should become free of gap states when the silicon layer thickness is below 5 Å. Experimentally, such a delicate Si3N4/Si/InP structure was realized by partial nitridation of a molecular beam epitaxially (MBE) grown pseudomorphic silicon layer using an electron cyclotron resonance (ECR) N2 plasma. The progress of nitridation was investigated in detail by angle-resolved XPS. A newly developed UHV contactless C-V method realized in situ characterization of surface electronic properties of InP at each processing step for passivation. It was found that the interface state density decreased substantially into the 1010 cm-2 eV-1 range by optimizing the nitridation process of the silicon layer. It was concluded that both the surface bond termination and state removal by quantum confinement are responsible for the NSS reduction.

TRACING THE REVERBERATION LAG IN THE HARD STATE OF BLACK HOLE X-RAY BINARIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Marco, B.; Ponti, G.; Nandra, K.

2015-11-20

We report results obtained from a systematic analysis of X-ray lags in a sample of black hole X-ray binaries, with the aim of assessing the presence of reverberation lags and studying their evolution during outburst. We used XMM-Newton and simultaneous Rossi X-ray Timing Explorer (RXTE) observations to obtain broadband energy coverage of both the disk and the hard X-ray Comptonization components. In most cases the detection of reverberation lags is hampered by low levels of variability-power signal-to-noise ratio (typically when the source is in a soft state) and/or short exposure times. The most detailed study was possible for GX 339-4more » in the hard state, which allowed us to characterize the evolution of X-ray lags as a function of luminosity in a single source. Over all the sampled frequencies (∼0.05–9 Hz), we observe the hard lags intrinsic to the power-law component, already well known from previous RXTE studies. The XMM-Newton soft X-ray response allows us to detail the disk variability. At low frequencies (long timescales) the disk component always leads the power-law component. On the other hand, a soft reverberation lag (ascribable to thermal reprocessing) is always detected at high frequencies (short timescales). The intrinsic amplitude of the reverberation lag decreases as the source luminosity and the disk fraction increase. This suggests that the distance between the X-ray source and the region of the optically thick disk where reprocessing occurs gradually decreases as GX 339-4 rises in luminosity through the hard state, possibly as a consequence of reduced disk truncation.« less

X-Ray Computed Tomography Monitors Damage in Composites

NASA Technical Reports Server (NTRS)

Baaklini, George Y.

1997-01-01

The NASA Lewis Research Center recently codeveloped a state-of-the-art x-ray CT facility (designated SMS SMARTSCAN model 100-112 CITA by Scientific Measurement Systems, Inc., Austin, Texas). This multipurpose, modularized, digital x-ray facility includes an imaging system for digital radiography, CT, and computed laminography. The system consists of a 160-kV microfocus x-ray source, a solid-state charge-coupled device (CCD) area detector, a five-axis object-positioning subassembly, and a Sun SPARCstation-based computer system that controls data acquisition and image processing. The x-ray source provides a beam spot size down to 3 microns. The area detector system consists of a 50- by 50- by 3-mm-thick terbium-doped glass fiber-optic scintillation screen, a right-angle mirror, and a scientific-grade, digital CCD camera with a resolution of 1000 by 1018 pixels and 10-bit digitization at ambient cooling. The digital output is recorded with a high-speed, 16-bit frame grabber that allows data to be binned. The detector can be configured to provide a small field-of-view, approximately 45 by 45 mm in cross section, or a larger field-of-view, approximately 60 by 60 mm in cross section. Whenever the highest spatial resolution is desired, the small field-of-view is used, and for larger samples with some reduction in spatial resolution, the larger field-of-view is used.

Graphene Membranes for Atmospheric Pressure Photoelectron Spectroscopy.

PubMed

Weatherup, Robert S; Eren, Baran; Hao, Yibo; Bluhm, Hendrik; Salmeron, Miquel B

2016-05-05

Atmospheric pressure X-ray photoelectron spectroscopy (XPS) is demonstrated using single-layer graphene membranes as photoelectron-transparent barriers that sustain pressure differences in excess of 6 orders of magnitude. The graphene serves as a support for catalyst nanoparticles under atmospheric pressure reaction conditions (up to 1.5 bar), where XPS allows the oxidation state of Cu nanoparticles and gas phase species to be simultaneously probed. We thereby observe that the Cu(2+) oxidation state is stable in O2 (1 bar) but is spontaneously reduced under vacuum. We further demonstrate the detection of various gas-phase species (Ar, CO, CO2, N2, O2) in the pressure range 10-1500 mbar including species with low photoionization cross sections (He, H2). Pressure-dependent changes in the apparent binding energies of gas-phase species are observed, attributable to changes in work function of the metal-coated grids supporting the graphene. We expect atmospheric pressure XPS based on this graphene membrane approach to be a valuable tool for studying nanoparticle catalysis.

An adjustable short-focal length, high-gradient PMQ electron-beam final-focus system for the PLEIADES ultra-fast x-ray Thomson source

NASA Astrophysics Data System (ADS)

Lim, Jae-Ku

In the span of a 100 year since the discovery of first x-rays by Roentgen that won him the first Nobel prize in physics, several types of radiation sources have been developed. Currently, radiations at extremely short wavelengths have only been accessed at synchrotron radiation sources. However, the current 3rd generation synchrotron sources can only produce x-rays of energy up to 60 keV and pulse lengths of several picoseconds long. But needs for shorter wavelength and shorter pulse duration radiations demanded by scientists to understand the nature of matter at atomic/molecular scale initiated the new scientific research for the production of sub-picosecond, hard x-rays. At the Lawrence Livermore National Laboratory, a Thomson x-ray source in the backscattering mode---a head-on collision between a high intensity Ti:Sapphire Chirped Pulse Amplification laser and a relativistic electron beam---called the PLEIADES (Picosecond Laser-Electron Inter-Action for the Dynamical Evaluation of Structures) laboratory has been developed. Early works demonstrated the production of quasi-monochromatic, femto-second long, hard x-rays. Initially reported x-ray flux was in the low range of 105--10 6 photons per shot. During the early stage of PLEIADES experiments, 15 T/m electromagnet final focusing quadrupoles (in a triplet lattice configuration) were employed to focus the beam to a 40-50 mum spot-size. A larger focal spot-size beam has a low-density of electron particles available at the interaction with incident photons, which leads to a low scattering probability. The current dissertation shows that by employing a 560 T/m PMQ (Permanent-Magnet Quadrupole) final focus system, an electron beam as small as 10-20 mum can be achieved. The implementation of this final focus system demonstrated the improvement of the total x-ray flux by two orders of magnitude. The PMQ final focus system also produced small electron beams consistently over 30-100 MeV electron beam energy, which

Dynamical effects in x-ray absorption spectra of graphene and monolayered h -BN on Ni(111)

NASA Astrophysics Data System (ADS)

Rusz, J.; Preobrajenski, A. B.; Ng, May Ling; Vinogradov, N. A.; Mårtensson, N.; Wessely, O.; Sanyal, B.; Eriksson, O.

2010-02-01

We present first-principles calculations of x-ray absorption spectra of graphene and hexagonal BN monolayer on the Ni(111) substrate. Including dynamical core-hole screening effects according to the theory of Mahan-Nozières-de Dominics (MND) results in an overall good agreement with previously published experimental data and our new observations. This approach provides a unified first-principles description of the electronic structure and core excitations in the sp2 -bonded materials on metal surfaces and a better insight into the dynamics of screening effects. We demonstrate in particular that the observed spectral features of graphene and hexagonal BN can be well reproduced with the MND theory, and that they are determined by a delicate balance between initial and final-state effects.

X-Ray Absorption Microspectroscopy with Electrostatic Force Microscopy and its Application to Chemical States Mapping

NASA Astrophysics Data System (ADS)

Ishii, M.; Rigopoulos, N.; Poolton, N. R. J.; Hamilton, B.

2007-02-01

A new technique named X-EFM that measures the x-ray absorption fine structure (XAFS) of nanometer objects was developed. In X-EFM, electrostatic force microscopy (EFM) is used as an x-ray absorption detector, and photoionization induced by x-ray absorption of surface electron trapping sites is detected by EFM. An EFM signal with respect to x-ray photon energy provides the XAFS spectra of the trapping sites. We adopted X-EFM to observe Si oxide thin films. An edge jump shift intrinsic to the X-EFM spectrum was found, and it was explained with a model where an electric field between the trapping site and probe deepens the energy level of the inner-shell. A scanning probe under x-rays with fixed photon energy provided the chemical state mapping on the surface.

Conduction band offset at GeO{sub 2}/Ge interface determined by internal photoemission and charge-corrected x-ray photoelectron spectroscopies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, W. F.; Nishimula, T.; Nagashio, K.

2013-03-11

We report a consistent conduction band offset (CBO) at a GeO{sub 2}/Ge interface determined by internal photoemission spectroscopy (IPE) and charge-corrected X-ray photoelectron spectroscopy (XPS). IPE results showed that the CBO value was larger than 1.5 eV irrespective of metal electrode and substrate type variance, while an accurate determination of valence band offset (VBO) by XPS requires a careful correction of differential charging phenomena. The VBO value was determined to be 3.60 {+-} 0.2 eV by XPS after charge correction, thus yielding a CBO (1.60 {+-} 0.2 eV) in excellent agreement with the IPE results. Such a large CBO (>1.5more » eV) confirmed here is promising in terms of using GeO{sub 2} as a potential passivation layer for future Ge-based scaled CMOS devices.« less

X-ray photoelectron spectroscopy and secondary electron yield analysis of Al and Cu samples exposed to an accelerator environment

NASA Astrophysics Data System (ADS)

Rosenberg, R. A.; McDowell, M. W.; Ma, Q.; Harkay, K. C.

2003-09-01

It is well known that exposure to an accelerator environment can cause ``conditioning'' of the vacuum chamber surfaces. In order to understand the manner in which the surface structure might influence the production of gases and electrons in the accelerator, such surfaces should be studied both before and after exposure to accelerator conditions. Numerous studies have been performed on representative materials prior to being inserted into an accelerator, but very little has been done on materials that have ``lived'' in the accelerator for extended periods. In the present work, we mounted Al and Cu coupons at different positions in a section of the Advanced Photon Source storage ring and removed them following exposures ranging from 6 to 18 months. X-ray photoelectron spectroscopy (XPS) of the surface was performed before and after exposure. Changes were observed that depended on the location and whether the coupon was facing the chamber interior or chamber wall. These results will be presented and compared to XPS and secondary electron yield data obtained from laboratory measurements meant to simulate the accelerator conditions.

Electronic structure of ZrX2 (X = Se, Te)

NASA Astrophysics Data System (ADS)

Shkvarin, A. S.; Merentsov, A. I.; Shkvarina, E. G.; Yarmoshenko, Yu. M.; Píš, I.; Nappini, S.; Titov, A. N.

2018-03-01

The electronic structure of the ZrX2 (X = Se, Te) compounds has been studied using photoelectron, resonant photoelectron and X-ray absorption spectroscopy, theoretical calculations of the X-ray absorption spectra, and density of electronic states. It was found that the absorption spectra and valence band spectra are influenced by the chalcogen type. The results of the multiplet calculation of the Zr4+ atom show that the change in the splitting in the crystal field, which is described by the 10Dq parameter, is due to the change in the ratio of covalent and ionic contributions to the chemical bond. The resonance band near the Fermi level in the valence band spectra is observed for ZrTe2 in the Zr 3p-4d resonant excitation mode. The extent of photon energy indicates the charge localization on the Zr atom. Similar resonance band for ZrSe2 is absent; it indicates the presence of a gap at the Fermi level.

Photoelectron spectroscopy of aqueous solutions: Streaming potentials of NaX (X = Cl, Br, and I) solutions and electron binding energies of liquid water and X{sup −}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurahashi, Naoya; Horio, Takuya; Suzuki, Toshinori, E-mail: suzuki@kuchem.kyoto-u.ac.jp

2014-05-07

The streaming potentials of liquid beams of aqueous NaCl, NaBr, and NaI solutions are measured using soft X-ray, He(I), and laser multiphoton ionization photoelectron spectroscopy. Gaseous molecules are ionized in the vicinity of liquid beams and the photoelectron energy shifts are measured as a function of the distance between the ionization point and the liquid beam. The streaming potentials change their polarity with concentration of electrolytes, from which the singular points of concentration eliminating the streaming potentials are determined. The streaming currents measured in air also vanish at these concentrations. The electron binding energies of liquid water and I{sup −},more » Br{sup −}, and Cl{sup −} anions are revisited and determined more accurately than in previous studies.« less

X-Ray Spectral Analysis of the Steady States of GRS1915+105

NASA Astrophysics Data System (ADS)

Peris, Charith S.; Remillard, Ronald A.; Steiner, James F.; Vrtilek, Saeqa D.; Varnière, Peggy; Rodriguez, Jerome; Pooley, Guy

2016-05-01

We report on the X-ray spectral behavior within the steady states of GRS1915+105. Our work is based on the full data set of the source obtained using the Proportional Counter Array (PCA) on the Rossi X-ray Timing Explorer (RXTE) and 15 GHz radio data obtained using the Ryle Telescope. The steady observations within the X-ray data set naturally separated into two regions in the color-color diagram and we refer to these regions as steady-soft and steady-hard. GRS1915+105 displays significant curvature in the coronal component in both the soft and hard data within the RXTE/PCA bandpass. A majority of the steady-soft observations displays a roughly constant inner disk radius ({R}{{in}}), while the steady-hard observations display an evolving disk truncation which is correlated to the mass accretion rate through the disk. The disk flux and coronal flux are strongly correlated in steady-hard observations and very weakly correlated in the steady-soft observations. Within the steady-hard observations, we observe two particular circumstances when there are correlations between the coronal X-ray flux and the radio flux with log slopes η ˜ 0.68+/- 0.35 and η ˜ 1.12+/- 0.13. They are consistent with the upper and lower tracks of Gallo et al. (2012), respectively. A comparison of the model parameters to the state definitions shows that almost all of the steady-soft observations match the criteria of either a thermal or steep power-law state, while a large portion of the steady-hard observations match the hard-state criteria when the disk fraction constraint is neglected.

Real-time 3-D X-ray and gamma-ray viewer

NASA Technical Reports Server (NTRS)

Yin, L. I. (Inventor)

1983-01-01

A multi-pinhole aperture lead screen forms an equal plurality of invisible mini-images having dissimilar perspectives of an X-ray and gamma-ray emitting object (ABC) onto a near-earth phosphor layer. This layer provides visible light mini-images directly into a visible light image intensifier. A viewing screen having an equal number of dissimilar perspective apertures distributed across its face in a geometric pattern identical to the lead screen, provides a viewer with a real, pseudoscopic image (A'B'C') of the object with full horizontal and vertical parallax. Alternatively, a third screen identical to viewing screen and spaced apart from a second visible light image intensifier, may be positioned between the first image intensifier and the viewing screen, thereby providing the viewer with a virtual, orthoscopic image (A"B"C") of the object (ABC) with full horizontal and vertical parallax.

Band alignment of ZnO/multilayer MoS{sub 2} interface determined by x-ray photoelectron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Xinke, E-mail: xkliu@szu.edu.cn, E-mail: liuwj@szu.edu.cn; He, Jiazhu; Chen, Le

2016-08-15

The energy band alignment between ZnO and multilayer (ML)-MoS{sub 2} was characterized using high-resolution x-ray photoelectron spectroscopy. The ZnO film was deposited using an atomic layer deposition tool, and ML-MoS{sub 2} was grown by chemical vapor deposition. A valence band offset (VBO) of 3.32 eV and a conduction band offset (CBO) of 1.12 eV were obtained for the ZnO/ML-MoS{sub 2} interface without any treatment. With CHF{sub 3} plasma treatment, a VBO and a CBO across the ZnO/ML-MoS{sub 2} interface were found to be 3.54 eV and 1.34 eV, respectively. With the CHF{sub 3} plasma treatment, the band alignment of the ZnO/ML-MoS{sub 2} interface hasmore » been changed from type II or staggered band alignment to type III or misaligned one, which favors the electron-hole pair separation. The band alignment difference is believed to be dominated by the down-shift in the core level of Zn 2p or the interface dipoles, which is caused by the interfacial layer rich in F.« less

Synchrotron radiation x-ray photoelectron spectroscopy study on the interface chemistry of high-k PrxAl2-xO3 (x=0-2) dielectrics on TiN for dynamic random access memory applications

NASA Astrophysics Data System (ADS)

Schroeder, T.; Lupina, G.; Sohal, R.; Lippert, G.; Wenger, Ch.; Seifarth, O.; Tallarida, M.; Schmeisser, D.

2007-07-01

Engineered dielectrics combined with compatible metal electrodes are important materials science approaches to scale three-dimensional trench dynamic random access memory (DRAM) cells. Highly insulating dielectrics with high dielectric constants were engineered in this study on TiN metal electrodes by partly substituting Al in the wide band gap insulator Al2O3 by Pr cations. High quality PrAlO3 metal-insulator-metal capacitors were processed with a dielectric constant of 19, three times higher than in the case of Al2O3 reference cells. As a parasitic low dielectric constant interface layer between PrAlO3 and TiN limits the total performance gain, a systematic nondestructive synchrotron x-ray photoelectron spectroscopy study on the interface chemistry of PrxAl2-xO3 (x =0-2) dielectrics on TiN layers was applied to unveil its chemical origin. The interface layer results from the decreasing chemical reactivity of PrxAl2-xO3 dielectrics with increasing Pr content x to reduce native Ti oxide compounds present on unprotected TiN films. Accordingly, PrAlO3 based DRAM capacitors require strict control of the surface chemistry of the TiN electrode, a parameter furthermore of importance to engineer the band offsets of PrxAl2-xO3/TiN heterojunctions.

Improved performances of CIBER-X: a new tabletop laser-driven electron and x-ray source

NASA Astrophysics Data System (ADS)

Girardeau-Montaut, Jean-Pierre; Kiraly, Bela; Girardeau-Montaut, Claire

2000-11-01

We present the most recent data concerning the performances of the table-top laser driven electron and x-ray source developed in our laboratory. X-ray pulses are produced by a three-step process which consists of the photoelectron emission from a thin metallic photocathode illuminated by 16 ps duration laser pulse at 213 nm. The e-gun is a standard pierce diode electrode type, in which electrons are accelerated by a cw electric fields of 12 MV/m. The photoinjector produced a train of 90 - 100 keV electron pulses of approximately 1 nC and 40 A peak current at a repetition rate of 10 Hz. The electrons, transported outside the diode, are focused onto a target of thulium by magnetic fields produced by two electromagnetic coils to produce x-rays. Applications to low dose imagery of inert and living materials are also presented.

Atomic force microscopy and X-ray photoelectron spectroscopy study of NO2 reactions on CaCO3 (1014) surfaces in humid environments.

PubMed

Baltrusaitis, Jonas; Grassian, Vicki H

2012-09-13

In this study, alternating current (AC) mode atomic force microscopy (AFM) combined with phase imaging and X-ray photoelectron spectroscopy (XPS) were used to investigate the effect of nitrogen dioxide (NO2) adsorption on calcium carbonate (CaCO3) (101̅4) surfaces at 296 K in the presence of relative humidity (RH). At 70% RH, CaCO3 (101̅4) surfaces undergo rapid formation of a metastable amorphous calcium carbonate layer, which in turn serves as a substrate for recrystallization of a nonhydrated calcite phase, presumably vaterite. The adsorption of nitrogen dioxide changes the surface properties of CaCO3 (101̅4) and the mechanism for formation of new phases. In particular, the first calcite nucleation layer serves as a source of material for further island growth; when it is depleted, there is no change in total volume of nitrocalcite, Ca(NO3)2, particles formed whereas the total number of particles decreases. This indicates that these particles are mobile and coalesce. Phase imaging combined with force curve measurements reveals areas of inhomogeneous energy dissipation during the process of water adsorption in relative humidity experiments, as well as during nitrocalcite particle formation. Potential origins of the different energy dissipation modes within the sample are discussed. Finally, XPS analysis confirms that NO2 adsorbs on CaCO3 (101̅4) in the form of nitrate (NO3(-)) regardless of environmental conditions or the pretreatment of the calcite surface at different relative humidity.

The effect of Sr and Bi on the Si(100) surface oxidation - Auger electron spectroscopy, low energy electron diffraction, and X-ray photoelectron spectroscopy study

NASA Technical Reports Server (NTRS)

Fan, W. C.; Mesarwi, A.; Ignatiev, A.

1990-01-01

The effect of Sr and Bi on the oxidation of the Si(100) surface has been studied by Auger electron spectroscopy, low electron diffraction, and X-ray photoelectron spectroscopy. A dramatic enhancement, by a factor of 10, of the Si oxidation has been observed for Si(100) with a Sr overlayer. The SR-enhanced Si oxidation has been studied as a function of O2 exposure and Sr coverage. In contrast to the oxidation promotion of Sr on Si, it has been also observed that a Bi overlayer on Si(100) reduced Si oxidation significantly. Sr adsorption on the Si(100) with a Bi overlayer enhances Si oxidation only at Sr coverage of greater than 0.3 ML.

Control Scheme for Quickly Starting X-ray Tube

NASA Astrophysics Data System (ADS)

Nakahama, Masayuki; Nakanishi, Toshiki; Ishitobi, Manabu; Ito, Tuyoshi; Hosoda, Kenichi

A control scheme for quickly starting a portable X-ray generator used in the livestock industry is proposed in this paper. A portable X-ray generator used to take X-ray images of animals such as horses, sheep and dogs should be capable of starting quickly because it is difficult for veterinarians to take X-ray images of animals at their timing. In order to develop a scheme for starting the X-ray tube quickly, it is necessary to analysis the X-ray tube. However, such an analysis has not been discussed until now. First, the states of an X-ray tube are classified into the temperature-limited state and the space-charge-limited state. Furthermore, existence of “mixed state” that comprises both is newly proposed in this paper. From these analyses, a novel scheme for quickly starting an X-ray generator is proposed; this scheme is considered with the characteristics of the X-ray tube. The proposed X-ray system that is capable of starting quickly is evaluated on the basis of experimental results.

Time-dependent nonequilibrium soft x-ray response during a spin crossover

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Veenendaal, Michel

The rapid development of high-brilliance pulsed X-ray sources with femtosecond time resolution has created a need for a better theoretical understanding of the time-dependent soft-X-ray response of dissipative many-body quantum systems. It is demonstrated how soft-X-ray spectroscopies, such as X-ray absorption and resonant inelastic X-ray scattering at transition-metal L-edges, can provide insight into intersystem crossings, such as a spin crossover. The photoinduced doublet-to-quartet spin crossover on cobalt in Fe-Co Prussian blue analogues is used as an example to demonstrate how the X-ray response is affected by the dissipative nonequilibrium dynamics. The time-dependent soft-X-ray spectra provide a wealth of information thatmore » reflect the changes in the nonequilibrium initial state via continuously changing spectral lineshapes that cannot be decomposed into initial photoexcited and final metastable spectra, strong broadenings, a collapse of clear selection rules during the intersystem crossing, strong fluctuations in the isotropic branching ratio in X-ray absorption, and crystal-field collapse/oscillations and strongly time-dependent anti-Stokes processes in RIXS.« less

The use of C-near edge X-ray absorption fine structure spectroscopy for the elaboration of chemistry in lignocellulosics

Treesearch

Lucian A. Lucia; Hiroki Nanko; Alan W. Rudie; Doug G. Mancosky; Sue Wirick

2006-01-01

The research presented elucidates the oxidation chemistry occurring in hydrogen peroxide bleached kraft pulp fibers by employing carbon near edge x-ray absorption fine structure spectroscopy (C-NEXAFS). C-NEXAFS is a soft x-ray technique that selectively interrogates atomic moieties using photoelectrons (Xrays) of variable energies. The X1A beam line at the National...

Novel visualization studies of lignocellulosic oxidation chemistry by application of C-near edge X-ray absorption fine structure spectroscopy

Treesearch

Douglas G. Mancosky; Lucian A. Lucia; Hiroki Nanko; Sue Wirick; Alan W. Rudie; Robert Braun

2005-01-01

The research presented herein is the first attempt to probe the chemical nature of lignocellulosic samples by the application of carbon near edge X-ray absorption fine structure spectroscopy (C-NEXAFS). C-NEXAFS is a soft X-ray technique that principally provides selective interrogation of discrete atomic moieties using photoelectrons of variable energies. The X1A beam...

Development of a New X-Ray Polarization Detection Device

NASA Astrophysics Data System (ADS)

Thompson, Jahreem R.; Hill, Joanne E.; Jahoda, Keith; Black, Kevin; Querrard, Rodney

2018-01-01

The aim of this research is to confirm the functionality of a Gas Electron Multiplier made of stainless steel in a detection medium of carbon dioxide and nitromethane through a series of X-ray tests in a vacuum chamber. Utilizing the photoelectric effect with carbon dioxide and nitromethane, we can confirm polarization of X-rays emitted from the most extreme astronomical conditions. We chose to use CO2 because we can confirm that it works well with the stainless-steel detector based on previous tests and nitromethane because we suspect that the ionization electrons created by the photoelectron during the photoelectric effect will experience less diffusion if they are bonded to a large molecule such as nitromethane as they diffuse towards the drift plate. The development of these new X-ray polarimeters will help to further the study of gravitational fields near black holes, their effects on matter they encounter, and the magnetic fields of neutron stars.

Characterization of thin films on the nanometer scale by Auger electron spectroscopy and X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Powell, C. J.; Jablonski, A.; Werner, W. S. M.; Smekal, W.

2005-01-01

We describe two NIST databases that can be used to characterize thin films from Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) measurements. First, the NIST Electron Effective-Attenuation-Length Database provides values of effective attenuation lengths (EALs) for user-specified materials and measurement conditions. The EALs differ from the corresponding inelastic mean free paths on account of elastic-scattering of the signal electrons. The database supplies "practical" EALs that can be used to determine overlayer-film thicknesses. Practical EALs are plotted as a function of film thickness, and an average value is shown for a user-selected thickness. The average practical EAL can be utilized as the "lambda parameter" to obtain film thicknesses from simple equations in which the effects of elastic-scattering are neglected. A single average practical EAL can generally be employed for a useful range of film thicknesses and for electron emission angles of up to about 60°. For larger emission angles, the practical EAL should be found for the particular conditions. Second, we describe a new NIST database for the Simulation of Electron Spectra for Surface Analysis (SESSA) to be released in 2004. This database provides data for many parameters needed in quantitative AES and XPS (e.g., excitation cross-sections, electron-scattering cross-sections, lineshapes, fluorescence yields, and backscattering factors). Relevant data for a user-specified experiment are automatically retrieved by a small expert system. In addition, Auger electron and photoelectron spectra can be simulated for layered samples. The simulated spectra, for layer compositions and thicknesses specified by the user, can be compared with measured spectra. The layer compositions and thicknesses can then be adjusted to find maximum consistency between simulated and measured spectra, and thus, provide more detailed characterizations of multilayer thin-film materials. SESSA can also

Local X-ray magnetic circular dichroism study of Fe/Cu(111) using a tunneling smart tip

PubMed Central

DiLullo, Andrew; Shirato, Nozomi; Cummings, Marvin; Kersell, Heath; Chang, Hao; Rosenmann, Daniel; Miller, Dean; Freeland, John W.; Hla, Saw-Wai; Rose, Volker

2016-01-01

Localized spectroscopy with simultaneous topographic, elemental and magnetic information is presented. A synchrotron X-ray scanning tunneling microscope has been employed for the local study of the X-ray magnetic circular dichroism at the Fe L 2,3-edges of a thin iron film grown on Cu(111). Polarization-dependent X-ray absorption spectra have been obtained through a tunneling smart tip that serves as a photoelectron detector. In contrast to conventional spin-polarized scanning tunneling microscopy, X-ray excitations provide magnetic contrast even with a non-magnetic tip. Intensity variations in the photoexcited tip current point to chemical variations within a single magnetic Fe domain. PMID:26917146

Local X-ray magnetic circular dichroism study of Fe/Cu(111) using a tunneling smart tip

DOE PAGES

DiLullo, Andrew; Shirato, Nozomi; Cummings, Marvin; ...

2016-01-28

Localized spectroscopy with simultaneous topographic, elemental and magnetic information is presented. A synchrotron X-ray scanning tunneling microscope has been employed for the local study of the X-ray magnetic circular dichroism at the FeL 2,3-edges of a thin iron film grown on Cu(111). Polarization-dependent X-ray absorption spectra have been obtained through a tunneling smart tip that serves as a photoelectron detector. In contrast to conventional spin-polarized scanning tunneling microscopy, X-ray excitations provide magnetic contrast even with a non-magnetic tip. Intensity variations in the photoexcited tip current point to chemical variations within a single magnetic Fe domain.

Local X-ray magnetic circular dichroism study of Fe/Cu(111) using a tunneling smart tip.

PubMed

DiLullo, Andrew; Shirato, Nozomi; Cummings, Marvin; Kersell, Heath; Chang, Hao; Rosenmann, Daniel; Miller, Dean; Freeland, John W; Hla, Saw-Wai; Rose, Volker

2016-03-01

Localized spectroscopy with simultaneous topographic, elemental and magnetic information is presented. A synchrotron X-ray scanning tunneling microscope has been employed for the local study of the X-ray magnetic circular dichroism at the Fe L2,3-edges of a thin iron film grown on Cu(111). Polarization-dependent X-ray absorption spectra have been obtained through a tunneling smart tip that serves as a photoelectron detector. In contrast to conventional spin-polarized scanning tunneling microscopy, X-ray excitations provide magnetic contrast even with a non-magnetic tip. Intensity variations in the photoexcited tip current point to chemical variations within a single magnetic Fe domain.

Digital Dental X-ray Database for Caries Screening

NASA Astrophysics Data System (ADS)

Rad, Abdolvahab Ehsani; Rahim, Mohd Shafry Mohd; Rehman, Amjad; Saba, Tanzila

2016-06-01

Standard database is the essential requirement to compare the performance of image analysis techniques. Hence the main issue in dental image analysis is the lack of available image database which is provided in this paper. Periapical dental X-ray images which are suitable for any analysis and approved by many dental experts are collected. This type of dental radiograph imaging is common and inexpensive, which is normally used for dental disease diagnosis and abnormalities detection. Database contains 120 various Periapical X-ray images from top to bottom jaw. Dental digital database is constructed to provide the source for researchers to use and compare the image analysis techniques and improve or manipulate the performance of each technique.

Portable total reflection x-ray fluorescence analysis in the identification of unknown laboratory hazards

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Ying, E-mail: liu.ying.48r@st.kyoto-u.ac.jp; Imashuku, Susumu; Sasaki, Nobuharu

In this study, a portable total reflection x-ray fluorescence (TXRF) spectrometer was used to analyze unknown laboratory hazards that precipitated on exterior surfaces of cooling pipes and fume hood pipes in chemical laboratories. With the aim to examine the accuracy of TXRF analysis for the determination of elemental composition, analytical results were compared with those of wavelength-dispersive x-ray fluorescence spectrometry, scanning electron microscope and energy-dispersive x-ray spectrometry, energy-dispersive x-ray fluorescence spectrometry, inductively coupled plasma atomic emission spectrometry, x-ray diffraction spectrometry (XRD), and x-ray photoelectron spectroscopy (XPS). Detailed comparison of data confirmed that the TXRF method itself was not sufficient tomore » determine all the elements (Z > 11) contained in the samples. In addition, results suggest that XRD should be combined with XPS in order to accurately determine compound composition. This study demonstrates that at least two analytical methods should be used in order to analyze the composition of unknown real samples.« less

Applications of time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) to study interactions of genetically engineered proteins with noble metal films

NASA Astrophysics Data System (ADS)

Suzuki, Noriaki

Genetically engineered proteins for inorganics (GEPIs) belong to a new class of polypeptides that are designed to have specific affinities to inorganic materials. A "gold binding protein (GBP)" was chosen as a model protein for GEPIs to study the molecular origins of binding specificity to gold using Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS). TOF-SIMS, a surface-sensitive analytical instrument with extremely high mass resolutions, provides information on specific amino acid-surface interactions. We used "principal component analysis (PCA)" to analyze the data. We also introduced a new multivariate technique, "hierarchical cluster analysis (HCA)" to organize the data into meaningful structures by measuring a degree of "similarity" and "dissimilarity" of the data. This report discusses a combined use of PCA and HCA to elucidate the binding specificity of GBP to Au. Based on the knowledge gained from TOF-SIMS measurements, we further investigated the nature of the interaction between selected amino acids and noble metal surfaces by using X-ray photoelectron spectroscopy (XPS). We developed a unique capability to introduce water vapor during the adsorption of a single amino acid and applied this method to study the intrinsic nature of sidechain/Au interactions. To further apply this unique research protocol, we characterized another type of GEPI, "quartz binding protein (QBP)," to identify the possible binding sites. This thesis research aims to provide experimental protocols for analyzing short peptide-substrate interface from complex spectroscopic data by using multivariate analysis techniques.

Experimental validation of Monte Carlo (MANTIS) simulated x-ray response of columnar CsI scintillator screens

DOE Office of Scientific and Technical Information (OSTI.GOV)

Freed, Melanie; Miller, Stuart; Tang, Katherine

Purpose: MANTIS is a Monte Carlo code developed for the detailed simulation of columnar CsI scintillator screens in x-ray imaging systems. Validation of this code is needed to provide a reliable and valuable tool for system optimization and accurate reconstructions for a variety of x-ray applications. Whereas previous validation efforts have focused on matching of summary statistics, in this work the authors examine the complete point response function (PRF) of the detector system in addition to relative light output values. Methods: Relative light output values and high-resolution PRFs have been experimentally measured with a custom setup. A corresponding set ofmore » simulated light output values and PRFs have also been produced, where detailed knowledge of the experimental setup and CsI:Tl screen structures are accounted for in the simulations. Four different screens were investigated with different thicknesses, column tilt angles, and substrate types. A quantitative comparison between the experimental and simulated PRFs was performed for four different incidence angles (0 deg., 15 deg., 30 deg., and 45 deg.) and two different x-ray spectra (40 and 70 kVp). The figure of merit (FOM) used measures the normalized differences between the simulated and experimental data averaged over a region of interest. Results: Experimental relative light output values ranged from 1.456 to 1.650 and were in approximate agreement for aluminum substrates, but poor agreement for graphite substrates. The FOMs for all screen types, incidence angles, and energies ranged from 0.1929 to 0.4775. To put these FOMs in context, the same FOM was computed for 2D symmetric Gaussians fit to the same experimental data. These FOMs ranged from 0.2068 to 0.8029. Our analysis demonstrates that MANTIS reproduces experimental PRFs with higher accuracy than a symmetric 2D Gaussian fit to the experimental data in the majority of cases. Examination of the spatial distribution of differences between the

Coordinated X-ray and optical observations of Scorpius X-1

NASA Technical Reports Server (NTRS)

Augusteijn, T.; Karatasos, K.; Papadakis, M.; Paterakis, G.; Kikuchi, S.; Brosch, N.; Leibowitz, E.; Hertz, P.; Mitsuda, K.; Dotani, T.

1992-01-01

We present the results of coordinated, partly simultaneous, optical and X-ray (Ginga) observations of the low-mass X-ray binary Sco X-1. We find that the division between the optically bright and faint state, at a blue magnitude B = 12.8, corresponds to the change from the normal to the flaring branch in the X-ray color-color diagram as proposed by Priedhorsky et al. (1986). From archival Walraven data we find that in both optical states the orbital light curve is approximately sinusoidal, and have a similar amplitudes.

Direct time-domain observation of attosecond final-state lifetimes in photoemission from solids

DOE PAGES

Tao, Z.; Chen, C.; Szilvasi, T.; ...

2016-06-01

Attosecond spectroscopic techniques have made it possible to measure differences in transport times for photoelectrons from localized core levels and delocalized valence bands in solids. Here, we report the application of attosecond pulse trains to directly and unambiguously measure the difference in lifetimes between photoelectrons born into free electron–like states and those excited into unoccupied excited states in the band structure of nickel (111). An enormous increase in lifetime of 212 ± 30 attoseconds occurs when the final state coincides with a short-lived excited state. Moreover, a strong dependence of this lifetime on emission angle is directly related to themore » final-state band dispersion as a function of electron transverse momentum. Our finding underscores the importance of the material band structure in determining photoelectron lifetimes and corresponding electron escape depths.« less

X-ray analyses of thermally grown and reactively sputtered tantalum oxide films on NiTi alloy

NASA Astrophysics Data System (ADS)

McNamara, Karrina; Tofail, Syed A. M.; Conroy, Derek; Butler, James; Gandhi, Abbasi A.; Redington, Wynette

2012-08-01

Sputter deposition of tantalum (Ta) on the surface of NiTi alloy is expected to improve the alloy's corrosion resistance and biocompatibility. Tantalum is a well-known biomaterial which is not affected by body fluids and is not irritating to human tissue. Here we compare the oxidation chemistry crystal structure evolution of tantalum oxide films grown on NiTi by reactive O2 sputtering and by thermal oxidation of sputter deposited Ta films. The effect of sputtering parameters and post-sputtering treatments on the morphology, oxidation state and crystal structure of the tantalum oxide layer have been investigated by field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The study has found that it may be better to avoid oxidation at and above 600 °C. The study establishes that reactive sputtering in presence of low oxygen mixture yields thicker film with better control of the film quality except that the surface oxidation state of Ta is slightly lower.

VizieR Online Data Catalog: Sample of faint X-ray pulsators (Israel+, 2016)

NASA Astrophysics Data System (ADS)

Israel, G. L.; Esposito, P.; Rodriguez Castillo, G. A.; Sidoli, L.

2018-04-01

As of 2015 December 31, we extracted about 430000 time series from sources with more than 10 counts (after background subtraction); ~190000 of them have more than 50 counts and their PSDs were searched for significant peaks. At the time of writing, the total number of searched Fourier frequencies was about 4.3x109. After a detailed screening, we obtained a final sample of 41 (42) new X-ray pulsators (signals), which are listed in Table 1. (1 data file).

Electronic Structure of Tl2Ba2CuO(6+Delta) Epitaxial Films Measured by X-Ray Photoemission

NASA Technical Reports Server (NTRS)

Vasquez, R. P.; Ren, Z. F.; Wang, J. H.

1996-01-01

The valence electronic structure and core levels of Tl2Ba2CuO(6 + delta) (Tl-2201) epitaxial films have been measured with X-ray photoelectron spectroscopy and are compared to those of Tl2Ba2CaCu2O(8 + delta) (Tl-2212). Changes in the Tl-2201 core-level binding energies with oxygen doping are consistent with a change in the chemical potential. Differences between the Tl-2201 and Tl-2212 measured densities of states are consistent with the calculated Cu 3d and Tl 6s partial densities of states.

X-ray absorption spectroscopic studies of the active sites of nickel- and copper-containing metalloproteins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Grace O.

1993-06-01

X-ray absorption spectroscopy (XAS) is a useful tool for obtaining structural and chemical information about the active sites of metalloproteins and metalloenzymes. Information may be obtained from both the edge region and the extended X-ray absorption fine structure (EXAFS) or post-edge region of the K-edge X-ray absorption spectrum of a metal center in a compound. The edge contains information about the valence electronic structure of the atom that absorbs the X-rays. It is possible in some systems to infer the redox state of the metal atom in question, as well as the geometry and nature of ligands connected to it,more » from the features in the edge in a straightforward manner. The EXAFS modulations, being produced by the backscattering of the ejected photoelectron from the atoms surrounding the metal atom, provide, when analyzed, information about the number and type of neighbouring atoms, and the distances at which they occur. In this thesis, analysis of both the edge and EXAFS regions has been used to gain information about the active sites of various metalloproteins. The metalloproteins studied were plastocyanin (Pc), laccase and nickel carbon monoxide dehydrogenase (Ni CODH). Studies of Cu(I)-imidazole compounds, related to the protein hemocyanin, are also reported here.« less

Monitoring X-Ray Emission from X-Ray Bursters

NASA Technical Reports Server (NTRS)

Halpern, Jules P.; Kaaret, Philip

1999-01-01

The scientific goal of this project was to monitor a selected sample of x-ray bursters using data from the All-Sky Monitor (ASM) on the Rossi X-Ray Timing Explorer together with data from the Burst and Transient Source Experiment (BATSE) on the Compton Gamma-Ray Observatory to study the long-term temporal evolution of these sources in the x-ray and hard x-ray bands. The project was closely related to "Long-Term Hard X-Ray Monitoring of X-Ray Bursters", NASA project NAG5-3891, and and "Hard x-ray emission of x-ray bursters", NASA project NAG5-4633, and shares publications in common with both of these. The project involved preparation of software for use in monitoring and then the actual monitoring itself. These efforts have lead to results directly from the ASM data and also from Target of Opportunity Observations (TOO) made with the Rossi X-Ray Timing Explorer based on detection of transient hard x-ray outbursts with the ASM and BATSE.

X-Ray Observations of VY Scl-Type Nova-Like Binaries in the High and Low State

NASA Technical Reports Server (NTRS)

Zemko, P.; Orio, M.; Mukai, K.; Shugarov, S.

2014-01-01

Four VY Scl-type nova-like systems were observed in X-rays during both the low- and the high-optical states. We examined Chandra, ROSAT, Swift and Suzaku archival observations of BZ Cam, MV Lyr, TT Ari and V794 Aql. The X-ray flux of BZ Cam is higher during the low state, but there is no supersoft X-ray source (SSS) as hypothesized in previous articles. No SSS was detected in the low state of the any of the other systems, with the X-ray flux decreasing by a factor between 2 and 50. The best fit to the Swift X-ray spectra is obtained with a multicomponent model of plasma in collisional ionization equilibrium. The high-state high-resolution spectra of TT Ari taken with Chandra Advanced CCD Imaging Spectrometer (ACIS-S) and the Chandra High Energy Transmission Grating (HETG) shows a rich emission line spectrum, with prominent lines of Mg, Si, Ne and S. The complexity of this spectrum seems to have origin in more than one region, or more than one single physical mechanism. While several emission lines are consistent with a cooling flow in an accretion stream, there is at least an additional component. We discuss the origin of this component, which is probably arising in a wind from the system. We also examine the possibility that the VY Scl systems may be intermediate polars, and that while the boundary layer of the accretion disc emits only in the extreme ultraviolet, part of the X-ray flux may be due to magnetically driven accretion.

The Hard X-Ray Emission from Scorpius X-1 Seen by INTEGRAL

NASA Technical Reports Server (NTRS)

Sturner, Steve; Shrader, C. R.

2008-01-01

We present the results of our hard X-ray and gamma-ray study of the LMXB Sco X-1 utilizing INTEGRAL data as well as contemporaneous RXTE PCA data. We have investigated the hard X-ray spectral properties of Sco X-1 including the nature of the high-energy, nonthermal component and its possible correlations with the location of the source on the soft X-ray color-color diagram. We find that Sco X-1 follows two distinct spectral tracks when the 20-40 keV count rate is greater than 130 counts/second. One state is a hard state which exhibits a significant high-energy, powerlaw tail to the lower energy thermal spectrum. The other state shows a much less significant high-energy component. We found suggestive evidence for a correlation of these hard and soft high-energy states with the position of Sco X-1 on the low-energy X-ray color-color diagram. We have searched for similar behavior in 2 other Z sources: GX 17+2 and GX 5-1 with negative results.

X-ray photoelectron-diffraction study of intermixing and morphology at the Ge/Si(001) and Ge/Sb/Si(001) interface

NASA Astrophysics Data System (ADS)

Gunnella, R.; Castrucci, P.; Pinto, N.; Davoli, I.; Sébilleau, D.; de Crescenzi, M.

1996-09-01

We used the XPD (x-ray photoelectron diffraction) and AED (Auger electron diffraction) from Ge core levels to probe the crystalline structure of 3 and 6 ML of Ge epitaxially grown by molecular-beam epitaxy on the Si(001) surface. In order to check the film tetragonal distortion and the pseudomorphic growth morphology, we used two different temperatures of the substrate during the deposition: room temperature and 400 °C. Evidence for an interfacial intermixing has been found by means of the observation of the angular behavior of the intensity of the emitted electrons. We also investigated the effects of Sb as a surfactant on such an interface. In this case indications of a laminar growth of strained Ge overlayer with reduced intermixing is obtained when 1 ML of Sb is predeposited on the substrate. Furthermore making use of a multiple-scattering approach to reproduce the experimental XPD patterns, a higher amount of accessible information on the morphology of the interface, beyond the determination of the strain content, is obtained.

An XPS study of the stability of Fomblin Z25 on the native oxide of aluminum. [x ray photoelectron spectroscopy

NASA Technical Reports Server (NTRS)

Herrera-Fierro, Pilar; Pepper, Stephen V.; Jones, William R.

1991-01-01

Thin films of Fomblin Z25, a perfluoropolyalkylether lubricant, were vapor deposited onto clean, oxidized aluminum and sapphire surfaces, and their behavior at different temperatures was studied using x ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS). It was found that the interfacial fluid molecules decompose on the native oxide at room temperature, and continue to decompose at elevated temperatures, as previous studies had shown to occur on clean metal. TDS indicated that different degradation mechanisms were operative for clean and oxidized aluminum. On sapphire substrates, no reaction was observed at room temperature. Our conclusion is that the native oxide of aluminum is neither passive nor protective towards Fomblin Z25. At high temperatures (150 C) degradation of the polymer on sapphire produced a debris layer at the interface with a chemical composition similar to the one formed on aluminum oxide. Rubbing a Fomblin film on a single crystal sapphire also induced the decomposition of the lubricant in contact with the interface and the formulation of a debris layer.

Band bending at the heterointerface of GaAs/InAs core/shell nanowires monitored by synchrotron X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Khanbabaee, B.; Bussone, G.; Knutsson, J. V.; Geijselaers, I.; Pryor, C. E.; Rieger, T.; Demarina, N.; Grützmacher, D.; Lepsa, M. I.; Timm, R.; Pietsch, U.

2016-10-01

Unique electronic properties of semiconductor heterostructured nanowires make them useful for future nano-electronic devices. Here, we present a study of the band bending effect at the heterointerface of GaAs/InAs core/shell nanowires by means of synchrotron based X-ray photoelectron spectroscopy. Different Ga, In, and As core-levels of the nanowire constituents have been monitored prior to and after cleaning from native oxides. The cleaning process mainly affected the As-oxides and was accompanied by an energy shift of the core-level spectra towards lower binding energy, suggesting that the As-oxides turn the nanowire surfaces to n-type. After cleaning, both As and Ga core-levels revealed an energy shift of about -0.3 eV for core/shell compared to core reference nanowires. With respect to depth dependence and in agreement with calculated strain distribution and electron quantum confinement, the observed energy shift is interpreted by band bending of core-levels at the heterointerface between the GaAs nanowire core and the InAs shell.

X-ray photoelectron spectroscopy characterization of composite TiO 2-poly(vinylidenefluoride) films synthesised for applications in pesticide photocatalytic degradation

NASA Astrophysics Data System (ADS)

Losito, I.; Amorisco, A.; Palmisano, F.; Zambonin, P. G.

2005-02-01

X-ray photoelectron spectroscopy (XPS) was adopted for the analytical characterization of composite titanium dioxide-poly(vinylidenefluoride) (TiO 2-PVDF) films developed for applications in the photocatalytic degradation of pollutants. The composites were deposited on glass substrates by casting or spin coating from TiO 2-PVDF suspensions in dimethylformamide (DMF). XPS data on the TiO 2-PVDF surface composition were used to optimize preparation conditions (composition of the TiO 2/PVDF suspension, deposition technique) in terms of titanium dioxide surface amount and film stability. The use of spin-coating deposition and the increase of TiO 2 amount in the DMF suspensions were found to improve the titanium surface content, although high TiO 2/PVDF ratios led to film instability. PVDF-TiO 2 films were also used in preliminary photocatalytic degradation tests on isoproturon, a phenylurea herbicide, under solar UV irradiation; the results were compared to direct photolysis to evaluate the catalytic efficiency of immobilized TiO 2 and the role played by the PVDF film during the degradation process.

5.8 X-ray Calorimeters

NASA Technical Reports Server (NTRS)

Porter, F. Scott

2008-01-01

X-ray calorimeter instruments for astrophysics have seen rapid development since they were invented in 1984. The prime instrument on all currently planned X-ray spectroscopic observatories is based on calorimeter technology. This relatively simple detection concept that senses the energy of an incident photon by measuring the temperature rise of an absorber material at very low temperatures, can form the basis of a very high performance, non-dispersive spectrometer. State-of-the-art calorimeter instruments have resolving powers of over 3000, large simultaneous band-passes, and near unit efficiency. This coupled with the intrinsic imaging capability of a pixilated x-ray calorimeter array, allows true spectral-spatial instruments to be constructed. In this chapter I briefly review the detection scheme, the state-of-the-art in X-ray calorimeter instruments and the future outlook for this technology.

High performance x-ray anti-scatter grid

DOEpatents

Logan, Clinton M.

1995-01-01

An x-ray anti-scatter grid for x-ray imaging, particularly for screening mammography, and method for fabricating same, x-rays incident along a direct path pass through a grid composed of a plurality of parallel or crossed openings, microchannels, grooves, or slots etched in a substrate, such as silicon, having the walls of the microchannels or slots coated with a high opacity material, such as gold, while x-rays incident at angels with respect to the slots of the grid, arising from scatter, are blocked. The thickness of the substrate is dependent on the specific application of the grid, whereby a substrate of the grid for mammography would be thinner than one for chest radiology. Instead of coating the walls of the slots, such could be filed with an appropriate liquid, such as mercury.

Band Offset Measurements in Atomic-Layer-Deposited Al2O3/Zn0.8Al0.2O Heterojunction Studied by X-ray Photoelectron Spectroscopy.

PubMed

Yan, Baojun; Liu, Shulin; Heng, Yuekun; Yang, Yuzhen; Yu, Yang; Wen, Kaile

2017-12-01

Pure aluminum oxide (Al 2 O 3 ) and zinc aluminum oxide (Zn x Al 1-x O) thin films were deposited by atomic layer deposition (ALD). The microstructure and optical band gaps (E g ) of the Zn x Al 1-x O (0.2 ≤ x ≤ 1) films were studied by X-ray diffractometer and Tauc method. The band offsets and alignment of atomic-layer-deposited Al 2 O 3 /Zn 0.8 Al 0.2 O heterojunction were investigated in detail using charge-corrected X-ray photoelectron spectroscopy. In this work, different methodologies were adopted to recover the actual position of the core levels in insulator materials which were easily affected by differential charging phenomena. Valence band offset (ΔE V ) and conduction band offset (ΔE C ) for the interface of the Al 2 O 3 /Zn 0.8 Al 0.2 O heterojunction have been constructed. An accurate value of ΔE V  = 0.82 ± 0.12 eV was obtained from various combinations of core levels of heterojunction with varied Al 2 O 3 thickness. Given the experimental E g of 6.8 eV for Al 2 O 3 and 5.29 eV for Zn 0.8 Al 0.2 O, a type-I heterojunction with a ΔE C of 0.69 ± 0.12 eV was found. The precise determination of the band alignment of Al 2 O 3 /Zn 0.8 Al 0.2 O heterojunction is of particular importance for gaining insight to the design of various electronic devices based on such heterointerface.

Toward Adaptive X-Ray Telescopes

NASA Technical Reports Server (NTRS)

O'Dell, Stephen L.; Atkins, Carolyn; Button, Tim W.; Cotroneo, Vincenzo; Davis, William N.; Doel, Peer; Feldman, Charlotte H.; Freeman, Mark D.; Gubarev, Mikhail V.; Kolodziejczak, Jeffrey J.;

Toward active x-ray telescopes

NASA Astrophysics Data System (ADS)

O'Dell, Stephen L.; Atkins, Carolyn; Button, Timothy W.; Cotroneo, Vincenzo; Davis, William N.; Doel, Peter; Feldman, Charlotte H.; Freeman, Mark D.; Gubarev, Mikhail V.; Kolodziejczak, Jeffery J.; Michette, Alan G.; Ramsey, Brian D.; Reid, Paul B.; Rodriguez Sanmartin, Daniel; Saha, Timo T.; Schwartz, Daniel A.; Trolier-McKinstry, Susan; Wilke, Rudeger H. T.; Willingale, Richard; Zhang, William W.

2011-09-01

Future x-ray observatories will require high-resolution (< 1") optics with very-large-aperture (> 25 m2) areas. Even with the next generation of heavy-lift launch vehicles, launch-mass constraints and aperture-area requirements will limit the areal density of the grazing-incidence mirrors to about 1 kg/m2 or less. Achieving sub-arcsecond x-ray imaging with such lightweight mirrors will require excellent mirror surfaces, precise and stable alignment, and exceptional stiffness or deformation compensation. Attaining and maintaining alignment and figure control will likely involve active (in-space adjustable) x-ray optics. In contrast with infrared and visible astronomy, active optics for x-ray astronomy is in its infancy. In the middle of the past decade, two efforts began to advance technologies for adaptive x-ray telescopes: The Smart X-ray Optics (SXO) Basic Technology project in the United Kingdom (UK) and the Generation-X (Gen-X) concept studies in the United States (US). This paper discusses relevant technological issues and summarizes progress toward active x-ray telescopes.

Improved adhesion of Ni films on X-ray damaged polytetrafluoroethylene

NASA Technical Reports Server (NTRS)

Wheeler, D. R.; Pepper, S. V.

1981-01-01

The considered investigation shows that the adhesion of evaporated Ni on polytetrafluoroethylene (PTFE) is enhanced by irradiating the PTFE surface prior to evaporation. Evidence obtained with the aid of X-ray photoelectron spectroscopy is presented concerning the association of the enhanced adhesion with an interfacial chemical reaction. Evaporated Ni clearly adheres better to the X-ray damaged PTFE surface than to the undamaged surface. There is evidence that the improved adhesion is not related to the Ni-C bond, but rather to the NiF2. A possible mechanism which may be consistent with the data is the formation of a F-Ni-C complex, where C is a member of the polymer chain.

Inter-satellites x-ray communication system

NASA Astrophysics Data System (ADS)

Mou, Huan; Li, Bao-quan

2017-02-01

An inter-satellite X-ray communication system is presented in this paper. X-ray has a strong penetrating power without almost attenuation for transmission in outer space when the energy of X-ray photons is more than 10KeV and the atmospheric pressure is lower than 10-1 Pa, so it is convincing of x-ray communication in inter-satellite communication and deep space exploration. Additionally, using X-ray photons as information carriers can be used in some communication applications that laser communication and radio frequency (RF) communication are not available, such as ionization blackout area communication. The inter-satellites X-ray communication system, including the grid modulated X-ray source, the high-sensitivity X-ray detector and the transmitting and receiving antenna, is described explicitly. As the X-ray transmitter, a vacuum-sealed miniature modulated X-ray source has been fabricated via the single-step brazing process in a vacuum furnace. Pulse modulation of X-rays, by means of controlling the voltage value of the grid electrode, is realized. Three focusing electrodes, meanwhile, are used to make the electron beam converge and finally 150μm focusing spot diameter is obtained. The X-ray detector based on silicon avalanche photodiodes (APDs) is chosen as the communication receiver on account of its high temporal resolution and non-vacuum operating environment. Furthermore, considering x-ray emission characteristic and communication distance of X-rays, the multilayer nested rotary parabolic optics is picked out as transmitting and receiving antenna. And as a new concept of the space communication, there will be more important scientific significance and application prospects, called "Next-Generation Communications".

Surface Termination Conversion during SrTiO3 Thin Film Growth Revealed by X-ray Photoelectron Spectroscopy

PubMed Central

Baeumer, Christoph; Xu, Chencheng; Gunkel, Felix; Raab, Nicolas; Heinen, Ronja Anika; Koehl, Annemarie; Dittmann, Regina

2015-01-01

Emerging electrical and magnetic properties of oxide interfaces are often dominated by the termination and stoichiometry of substrates and thin films, which depend critically on the growth conditions. Currently, these quantities have to be measured separately with different sophisticated techniques. This report will demonstrate that the analysis of angle dependent X-ray photoelectron intensity ratios provides a unique tool to determine both termination and stoichiometry simultaneously in a straightforward experiment. Fitting the experimental angle dependence with a simple analytical model directly yields both values. The model is calibrated through the determination of the termination of SrTiO3 single crystals after systematic pulsed laser deposition of sub-monolayer thin films of SrO. We then use the model to demonstrate that during homoepitaxial SrTiO3 growth, excess Sr cations are consumed in a self-organized surface termination conversion before cation defects are incorporated into the film. We show that this termination conversion results in insulating properties of interfaces between polar perovskites and SrTiO3 thin films. These insights about oxide thin film growth can be utilized for interface engineering of oxide heterostructures. In particular, they suggest a recipe for obtaining two-dimensional electron gases at thin film interfaces: SrTiO3 should be deposited slightly Ti-rich to conserve the TiO2-termination. PMID:26189436

Reaction of Hydroquinone with Hematite I. Study of Adsorption by Electrochemical-Scanning Tunneling Microscopy and X-ray Photoelectron Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stack, Andrew G; Eggleston, Carrick M; Engelhard, Mark H

2004-06-15

The reaction of hematite with quinones and the quinone moieties of larger molecules may be an important factor in limiting the rate ofreductive dissolution, especially by iron-reducing bacteria. Here, the electrochemical and physical properties of hydroquinone adsorbed on hematite surfaces at pH 2.5–3 were investigated with cyclic voltammetry (CV), electrochemical-scanning tunneling microscopy (EC-STM), and X-ray photoelectron spectroscopy (XPS). An oxidation peak for hydroquinone was observed in the CV experiments, as well as (photo)reduction of iron and decomposition of the solvent. The EC-STM results indicate that hydroquinone sometimes forms an ordered monolayer with ~1.1 H₂/nm², but can be fairly disordered (especiallymore » when viewed at larger scales). XPS results indicate that hydroquinone and benzoquinone are retained at the interface in increasing amounts as the reaction proceeds, but reduced iron is not observed. These results suggest that quinones do not adsorb by an inner-sphere complex where adsorbate–surface interactions determine the adsorbate surface structure, but rather in an outer-sphere complex where interactions among the adsorbate molecules dominate.« less

Reaction of hydroquinone with hematite I. Study of asdsorption by electrochemical-scanning tunneling microscopy and X-ray photoelectron spectroscopy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stack, Andrew G; Eggleston, Carrick M; Engelhard, Mark H

2003-12-01

The reaction of hematite with quinones and the quinone moieties of larger molecules may be an important factor in limiting the rate of reductive dissolution, especially by iron-reducing bacteria. Here, the electrochemical and physical properties of hydroquinone adsorbed on hematite surfaces at pH 2.5-3 were investigated with cyclic voltammetry (CV), electrochemical-scanning tunneling microscopy (EC-STM), and X-ray photoelectron spectroscopy (XPS). An oxidation peak for hydroquinone was observed in the CV experiments, as well as (photo)reduction of iron and decomposition of the solvent. The EC-STM results indicate that hydroquinone sometimes forms an ordered monolayer with {approx}1.1 QH{sub 2}/nm{sup 2}, but can bemore » fairly disordered (especially when viewed at larger scales). XPS results indicate that hydroquinone and benzoquinone are retained at the interface in increasing amounts as the reaction proceeds, but reduced iron is not observed. These results suggest that quinones do not adsorb by an inner-sphere complex where adsorbate-surface interactions determine the adsorbate surface structure, but rather in an outer-sphere complex where interactions among the adsorbate molecules dominate.« less

A temperature-programmed X-ray photoelectron spectroscopy (TPXPS) study of chlorine adsorption and diffusion on Ag(1 1 1)

NASA Astrophysics Data System (ADS)

Piao, H.; Adib, K.; Barteau, Mark A.

2004-05-01

Synchrotron-based temperature programmed X-ray photoelectron spectroscopy (TPXPS) has been used to investigate the surface chloridation of Ag(1 1 1) to monolayer coverages. At 100 K both atomic and molecular chlorine species are present on the surface; adsorption at 300 K or annealing the adlayer at 100 K to this temperature generates adsorbed Cl atoms. As the surface is heated from 300 to 600 K, chlorine atoms diffuse below the surface, as demonstrated by attenuation of the Cl2p signals in TPXPS experiments. Quantitative analysis of the extent of attenuation is consistent with chlorine diffusion below the topmost silver layer. For coverages in the monolayer and sub-monolayer regime, chlorine diffusion to and from the bulk appears not to be significant, in contrast to previous results obtained at higher chlorine loadings. Chlorine is removed from the surface at 650-780 K by desorption as AgCl. These results demonstrate that chlorine diffusion beneath the surface does occur at coverages and temperatures relevant to olefin epoxidation processes carried out on silver catalysts with chlorine promoters. The surface sensitivity advantages of synchrotron-based XPS experiments were critical to observing Cl diffusion to the sub-surface at low coverages.

The Hard X-ray Emission from Scorpius X-1 as Seen by INTEGRAL

NASA Technical Reports Server (NTRS)

Sturner, S. J.; Shrader, C. R.; Weidenspointner, G.

2008-01-01

We present the results of our hard X-ray and gamma-ray study of the LMXB Sco X-1 utilizing INTEGRAL data as well as contemporaneous RXTE PCA data. We have concentrated on investigating the hard X-ray spectral properties of Sco X-1 including the nature of the high-energy, nonthermal component of the spectrum and its possible correlations with the location of the source on the X-ray color-color diagram. We find that Sco X-1 has two distinct spectral when the 20-40 keV count rate is greater than 140 counts/second. One state is a hard state which exhibits a significant high-energy, powerlaw tail to the lower energy thermal spectrum. The other state shows no evidence for a powerlaw tail whatsoever. We found suggestive evidence for a correlation of these hard and soft high-energy states with the position of Sco X-1 on the low-energy X-ray color-color diagram.

VETA-I x ray test analysis

NASA Technical Reports Server (NTRS)

Brissenden, R. J. V.; Chartas, G.; Freeman, M. D.; Hughes, J. P.; Kellogg, E. M.; Podgorski, W. A.; Schwartz, D. A.; Zhao, P.

1992-01-01

This interim report presents some definitive results from our analysis of the VETA-I x-ray testing data. It also provides a description of the hardware and software used in the conduct of the VETA-I x-ray test program performed at the MSFC x-ray Calibration Facility (XRCF). These test results also serve to supply data and information to include in the TRW final report required by DPD 692, DR XC04. To provide an authoritative compendium of results, we have taken nine papers as published in the SPIE Symposium, 'Grazing Incidence X-ray/EUV Optics for Astronomy and Projection Lithography' and have reproduced them as the content of this report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hardman, P.J.; Wincott, P.L.; Thornton, G.

Full-hemispherical x-ray photoelectron (Ti2p/O1s) and x-ray stimulated Auger electron (TiL{sub 3}M{sub 23}M{sub 23}/O&hthinsp;KVV) intensity distributions have been measured from TiO{sub 2}(100)1{times}1 at relatively high-angular resolution ({plus_minus}1.8{degree}). The results are compared with theoretical calculations using a multipole {ital R}-factor analysis. Multiple scattering up to fifth order and a slab thickness of {approximately}16 {Angstrom} are needed to obtain optimum agreement with experimental photoelectron distributions. We also investigate the contribution of the final state wave function in the Auger-electron diffraction patterns and show that it is possible to determine the symmetry of the final state angular momenta for oxides such as TiO{sub 2}.more » Both the x-ray photoelectron diffraction and the x-ray stimulated Auger intensity distributions are found to be insensitive to details of the surface structure. {copyright} {ital 1999} {ital The American Physical Society}« less

X-ray Photoelectron Spectroscopy as a tool to investigate silane-based coatings for the protection of outdoor bronze: The role of alloying elements

NASA Astrophysics Data System (ADS)

Masi, G.; Balbo, A.; Esvan, J.; Monticelli, C.; Avila, J.; Robbiola, L.; Bernardi, E.; Bignozzi, M. C.; Asensio, M. C.; Martini, C.; Chiavari, C.

2018-03-01

Application of a protective coating is the most widely used conservation treatment for outdoor bronzes (cast Cu-Sn-Zn-Pb-Sb alloys). However, improving coating protectiveness requires detailed knowledge of the coating/substrate chemical bonding. This is particularly the case for 3-mercapto-propyl-trimethoxy-silane (PropS-SH) applied on bronze, exhibiting a good protective behaviour in outdoor simulated conditions. The present work deals with X-Ray Photoelectron Spectroscopy (XPS) and Electron Microscopy (FEG-SEM + FIB (Focused Ion Beam)) characterization of a thin PropS-SH film on bronze. In particular, in order to better understand the influence of alloying elements on coating performance, PropS-SH was studied first on pure Cu and Sn substrates then on bronzes with increasing alloy additions: Cu8Sn as well as a quinary Cu-Sn-Zn-Pb-Sb bronze. Moreover, considering the real application of this coating on historical bronze substrates, previously artificially aged ("patinated") bronze samples were prepared and a comparison between bare and "patinated" quinary bronzes was performed. In the case of coated quinary bronze, the free surface of samples was analysed by High Resolution Photoelectron Spectroscopy using Synchrotron Radiation (HR-SRPES) at ANTARES (Synchrotron SOLEIL), which offers a higher energy and lateral resolution. By compiling complementary spectroscopic and imaging information, a deeper insight into the interactions between the protective coating and the bronze substrate was achieved.

In-flight calibration of Hitomi Soft X-ray Spectrometer. (1) Background

NASA Astrophysics Data System (ADS)

Kilbourne, Caroline A.; Sawada, Makoto; Tsujimoto, Masahiro; Angellini, Lorella; Boyce, Kevin R.; Eckart, Megan E.; Fujimoto, Ryuichi; Ishisaki, Yoshitaka; Kelley, Richard L.; Koyama, Shu; Leutenegger, Maurice A.; Loewenstein, Michael; McCammon, Dan; Mitsuda, Kazuhisa; Nakashima, Shinya; Porter, Frederick S.; Seta, Hiromi; Takei, Yoh; Tashiro, Makoto S.; Terada, Yukikatsu; Yamada, Shinya; Yamasaki, Noriko Y.

2018-03-01

The X-Ray Spectrometer (XRS) instrument of Suzaku provided the first measurement of the non-X-ray background (NXB) of an X-ray calorimeter spectrometer, but the data set was limited. The Soft X-ray Spectrometer (SXS) instrument of Hitomi was able to provide a more detailed picture of X-ray calorimeter background, with more than 360 ks of data while pointed at the Earth, and a comparable amount of blank-sky data. These data are important not only for analyzing SXS science data, but also for categorizing the contributions to the NXB in X-ray calorimeters as a class. In this paper, we present the contributions to the SXS NXB, the types and effectiveness of the screening, the interaction of the screening with the broad-band redistribution, and the residual background spectrum as a function of magnetic cut-off rigidity. The orbit-averaged SXS NXB in the range 0.3-12 keV was 4 × 10-2 counts s-1 cm-2. This very low background in combination with groundbreaking spectral resolution gave SXS unprecedented sensitivity to weak spectral lines.

Detection of contraband concealed on the body using x-ray imaging

NASA Astrophysics Data System (ADS)

Smith, Gerald J.

1997-01-01

In an effort to avoid detection, smugglers and terrorists are increasingly using the body as a vehicle for transporting illicit drugs, weapons, and explosives. This trend illustrates the natural tendency of traffickers to seek the path of least resistance, as improved interdiction technology and operational effectiveness have been brought to bear on other trafficking avenues such as luggage, cargo, and parcels. In response, improved technology for human inspection is being developed using a variety of techniques. ASE's BodySearch X-ray Inspection Systems uses backscatter x-ray imaging of the human body to quickly, safely, and effectively screen for drugs, weapons, and explosives concealed on the body. This paper reviews the law enforcement and social issues involved in human inspections, and briefly describes the ASE BodySearch systems. Operator training, x-ray image interpretation, and maximizing systems effectiveness are also discussed. Finally, data collected from operation of the BodySearch system in the field is presented, and new law enforcement initiatives which have come about due to recent events are reviewed.

Charge-exchange x-ray spectra: Evidence for significant contributions from radiative decays of doubly excited states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ali, R.; Beiersdorfer, P.; Harris, C. L.

2016-01-21

Charge-exchange collisions of slow Ne 10+ ions with He, Ne, and Ar targets were studied with simultaneous x-ray and cold-target recoil-ion-momentum spectroscopy proving the contribution of several mechanisms to the radiative stabilization of apparent (4,4) doubly excited states for He and Ne targets and of (5,6) states for Ar. In particular, the stabilization efficiency of the mechanism of dynamic auto-transfer to Rydberg states is confirmed. Moreover, we present evidence for direct radiative decays of (4,4) states populated in collisions with He, which is an experimental indication of the population of so-called unnatural-parity states in such collisions. Lastly, these mechanisms leadmore » to the emission of x-rays that have considerably higher energies than those predicted by current spectral models and may explain recent observations of anomalously large x-ray emission from Rydberg levels.« less

Theoretical investigations of X-ray bursts

NASA Technical Reports Server (NTRS)

Taam, Ronald E.

1987-01-01

Current theoretical understanding of the X-ray burst phenomenon is reviewed, providing a framework in which the burst radiation can be used as a diagnostic of the fundamental properties of the underlying neutron star. The typical Type I X-ray burst is detected as a rapid increase in emission to a level about a factor of 10 above that seen during the quiescent state and recurs on time scales which range from several hours to several days. The thermonuclear flash model has successfully reproduced the basic features of the X-ray burst phenomenon and thereby provided strong theoretical evidence that neutron stars are involved. Topics covered include: theory of the emission spectrum; oscillation modes and prospects for diagnosing the thermal state of neutron stars through experiments on board the X-Ray Timing Explorer or the Advanced X-Ray Astrophysics Facility; applications to the mass and radius of a neutron star.

X-Ray Timing Analysis of Cyg X-3 Using AstroSat/LAXPC: Detection of Milli-hertz Quasi-periodic Oscillations during the Flaring Hard X-Ray State

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pahari, Mayukh; Misra, Ranjeev; Antia, H M

We present here results from the X-ray timing and spectral analysis of the X-ray binary Cyg X-3 using observations from the Large Area X-ray proportional Counter on board AstroSat . Consecutive light curves observed over a period of one year show the binary orbital period of 17253.56 ± 0.19 s. Another low-amplitude, slow periodicity of the order of 35.8 ± 1.4 days is observed, which may be due to the orbital precession as suggested earlier by Molteni et al. During the rising binary phase, power density spectra from different observations during the flaring hard X-ray state show quasi-periodic oscillations (QPOs)more » at ∼5–8 mHz, ∼12–14 mHz, and ∼18–24 mHz frequencies at the minimum confidence of 99%. However, during the consecutive binary decay phase, no QPO is detected up to 2 σ significance. Energy-dependent time-lag spectra show soft lag (soft photons lag hard photons) at the mHz QPO frequency and the fractional rms of the QPO increases with the photon energy. During the binary motion, the observation of mHz QPOs during the rising phase of the flaring hard state may be linked to the increase in the supply of the accreting material in the disk and corona via stellar wind from the companion star. During the decay phase, the compact source moves in the outer wind region causing the decrease in supply of material for accretion. This may cause weakening of the mHz QPOs below the detection limit. This is also consistent with the preliminary analysis of the orbital phase-resolved energy spectra presented in this paper.« less

Demonstration of Laser Plasma X-Ray Source with X-Ray Collimator Final Report CRADA No. TC-1564-99

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lane, S. M.; Forber, R. A.

2017-09-28

This collaborative effort between the University of California, Lawrence Livermore National Laboratory (LLNL) and JMAR Research, Inc. (JRI), was to demonstrate that LLNL x-ray collimators can effectively increase the wafer throughput of JRI's laser based x-ray lithography systems. The technical objectives were expected to be achieved by completion of the following tasks, which are separated into two task lists by funding source. The organization (LLNL or JMAR) having primary responsibility is given parenthetically for each task.

X-ray filter for x-ray powder diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sinsheimer, John Jay; Conley, Raymond P.; Bouet, Nathalie C. D.

Technologies are described for apparatus, methods and systems effective for filtering. The filters may comprise a first plate. The first plate may include an x-ray absorbing material and walls defining first slits. The first slits may include arc shaped openings through the first plate. The walls of the first plate may be configured to absorb at least some of first x-rays when the first x-rays are incident on the x-ray absorbing material, and to output second x-rays. The filters may comprise a second plate spaced from the first plate. The second plate may include the x-ray absorbing material and wallsmore » defining second slits. The second slits may include arc shaped openings through the second plate. The walls of the second plate may be configured to absorb at least some of second x-rays and to output third x-rays.« less

High performance x-ray anti-scatter grid

DOEpatents

Logan, C.M.

1995-05-23

Disclosed are an x-ray anti-scatter grid for x-ray imaging, particularly for screening mammography, and method for fabricating same, x-rays incident along a direct path pass through a grid composed of a plurality of parallel or crossed openings, microchannels, grooves, or slots etched in a substrate, such as silicon, having the walls of the microchannels or slots coated with a high opacity material, such as gold, while x-rays incident at angels with respect to the slots of the grid, arising from scatter, are blocked. The thickness of the substrate is dependent on the specific application of the grid, whereby a substrate of the grid for mammography would be thinner than one for chest radiology. Instead of coating the walls of the slots, such could be filed with an appropriate liquid, such as mercury. 4 Figs.

X-Ray Laser Program Report for FY 1989

DTIC Science & Technology

1990-05-24

theoretical photopumped x-ray laser program also involves the use of a neon lasant plasma. However, that is the only similarity to the Na/Ne scheme described...K-shell neon Z pinch photons of energy hv > 900 eV, photoionize inner K-shell electrons from the neutral neon, leading to Auger decay from Ne II to...is generated by electrons which are produced in the photoionization of Ne I. For example, ionization by the Ly-a line produces 150-eV photoelectrons

X-Ray Photoelectron Spectroscopy and the Role of Relaxation Energy in Understanding Chemical Shifts

ERIC Educational Resources Information Center

Ellison, Frank O.; White, Michael G.

1976-01-01

Discusses the measurement of electrons ejected from a system which is being irradiated with X-rays or ultraviolet photons, and a theoretical model for calculating core-electron ionization energies. (MLH)

Comparative study of the oxidation of NiAl(100) by molecular oxygen and water vapor using ambient-pressure X-ray photoelectron spectroscopy

DOE PAGES

Liu, Qianqian; Qin, Hailang; Boscoboinik, Jorge Anibal; ...

2016-10-11

The oxidation behavior of NiAl(100) by molecular oxygen and water vapor under a near-ambient pressure of 0.2 Torr is monitored using ambient-pressure X-ray photoelectron spectroscopy. O 2 exposure leads to the selective oxidation of Al at temperatures ranging from 40 to 500 °C. By contrast, H 2O exposure results in the selective oxidation of Al at 40 and 200 °C, and increasing the oxidation temperature above 300 °C leads to simultaneous formation of both Al and Ni oxides. Furthermore, these results demonstrate that the O 2 oxidation forms a nearly stoichiometric Al 2O 3 structure that provides improved protection tomore » the metallic substrate by barring the outward diffusion of metals. By contrast, the H 2O oxidation results in the formation of a defective oxide layer that allows outward diffusion of Ni at elevated temperatures for simultaneous NiO formation.« less

Impact of water vapour and carbon dioxide on surface composition of C{sub 3}A polymorphs studied by X-ray photoelectron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dubina, E.; Plank, J.; Black, L., E-mail: l.black@leeds.ac.uk

2015-07-15

The surface specific analytical method, X-ray photoelectron spectroscopy (XPS), has been used to study the effects of water vapour and CO{sub 2} on the cubic and orthorhombic polymorphs of C{sub 3}A. Significant differences between the two polymorphs were observed in the XPS spectra. Upon exposure to water vapour, both polymorphs produced C{sub 4}AH{sub 13} on their surfaces. Additionally, the sodium-doped o-C{sub 3}A developed NaOH and traces of C{sub 3}AH{sub 6} on its surface. Subsequent carbonation yielded mono carboaluminate on both polymorphs. Large amounts of Na{sub 2}CO{sub 3} also formed on the surface of o-C{sub 3}A as a result of carbonationmore » of NaOH. Furthermore, the extent of carbonation was much more pronounced for o-C{sub 3}A{sub o} than for c-C{sub 3}A.« less

Comparative study of the oxidation of NiAl(100) by molecular oxygen and water vapor using ambient-pressure X-ray photoelectron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Qianqian; Qin, Hailang; Boscoboinik, Jorge Anibal

The oxidation behavior of NiAl(100) by molecular oxygen and water vapor under a near-ambient pressure of 0.2 Torr is monitored using ambient-pressure X-ray photoelectron spectroscopy. O 2 exposure leads to the selective oxidation of Al at temperatures ranging from 40 to 500 °C. By contrast, H 2O exposure results in the selective oxidation of Al at 40 and 200 °C, and increasing the oxidation temperature above 300 °C leads to simultaneous formation of both Al and Ni oxides. Furthermore, these results demonstrate that the O 2 oxidation forms a nearly stoichiometric Al 2O 3 structure that provides improved protection tomore » the metallic substrate by barring the outward diffusion of metals. By contrast, the H 2O oxidation results in the formation of a defective oxide layer that allows outward diffusion of Ni at elevated temperatures for simultaneous NiO formation.« less

Influence of polymolybdate adsorbates on electrooxidation of ethanol at PtRu nanoparticles: Combined electrochemical, mass spectrometric and X-ray photoelectron spectroscopic studies

NASA Astrophysics Data System (ADS)

Gralec, Barbara; Lewera, Adam; Kulesza, Pawel J.

2016-05-01

The role Keggin-type phosphomolybdate (PMo12O403-) ions (adsorbed on carbon-supported PtRu, PtRu/C) on electrooxidation of ethanol is addressed here. The combined results obtained using Differential Electrochemical Mass Spectrometry, X-ray Photoelectron Spectroscopy and Cyclic Voltammetry are consistent with the view that presence of the Keggin-type polyoxometallate, phosphomolybdate, ions (adsorbates) leads to enlargement of the current densities associated with electrooxidation of ethanol at potentials greater than 700 mV vs. RHE. This increase of the anodic currents is correlated with the higher acetaldehyde yield which is likely to reflect changes in the reaction kinetics (e.g. more dynamic dehydrogenation of ethanol leading to acetaldehyde) or in the reaction mechanism defined by the preferential surface modification resulting not only in faster kinetics but also in higher selectivity with respect to acetaldehyde production. It is apparent from the spectroscopic data that modification of PtRu/C nanoparticles with phosphomolybdate ions leads to suppression of the formation of Ru surface oxides.

Band offsets and growth mode of molecular beam epitaxy grown MgO (111) on GaN (0002) by x-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Craft, H. S.; Collazo, R.; Losego, M. D.; Mita, S.; Sitar, Z.; Maria, J.-P.

2007-10-01

MgO is a proposed dielectric for use as a tunneling barrier in devices integrating GaN and ferroelectric oxides. In this study, we present data regarding the growth mode and band offsets of MgO grown epitaxially on GaN (0002) surfaces using molecular beam epitaxy. Using in situ x-ray photoelectron spectroscopy (XPS) and molecular beam epitaxy, we determine, from sequential growth experiments, that the growth of MgO proceeds via the Volmer-Weber (three-dimensional) mode, and full coalescence of the film does not occur until approximately 12nm of MgO has been deposited. The observation of a three-dimensional growth mode is in agreement with previously published data. For the valence band offset, we find a value of 1.2±0.2eV, which corresponds to a 3.2eV conduction band offset. XPS measurements suggest a chemically abrupt interface and no effect on band lineup due to the slow coalescence behavior.

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 K-edge X-ray Absorption Near-Edge Spectroscopy, X-ray Photoelectron Spectroscopy, and Time-Resolved X-ray Diffraction Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Do Heui; Szanyi, Janos; Kwak, Ja Hun

2009-04-03

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 experiments is not proportional to the amount of initial sulfur loading. The results of both in-situ sulfur K-edge XANES and TR-XRD show that at low sulfur loadings, sulfates were transformed to a BaS phase and remained in the catalyst, rathermore » than being removed as H2S. On the other hand, when the deposited sulfur level exceeded a certain threshold (at least S/Ba = 0.31) sulfates were reduced to form H2S, and the relative amount of the residual sulfide species in the catalyst was much less than at low sulfur loading. Unlike samples with high sulfur loading (e.g., S/Ba = 0.62), H2O did not promote the desulfation for the sample with S/Ba of 0.12, implying that the formed BaS species originating from the reduction of sulfates at low sulfur loading are more stable to hydrolysis. The results of this combined spectroscopy investigation provide clear evidence to show that sulfates at low sulfur loadings are less likely to be removed as H2S and have a greater tendency to be transformed to BaS on the material, leading to the conclusion that desulfation behavior of Pt BaO/Al2O3 lean NOx trap catalysts is markedly dependent on the sulfation levels.« less

GAMMA-RAY OBSERVATIONS OF CYGNUS X-1 ABOVE 100 MeV IN THE HARD AND SOFT STATES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sabatini, S.; Tavani, M.; Del Santo, M.

2013-04-01

We present the results of multi-year gamma-ray observations by the AGILE satellite of the black hole binary system Cygnus X-1. In a previous investigation we focused on gamma-ray observations of Cygnus X-1 in the hard state during the period mid-2007/2009. Here we present the results of the gamma-ray monitoring of Cygnus X-1 during the period 2010/mid-2012 which includes a remarkably prolonged 'soft state' phase (2010 June-2011 May). Previous 1-10 MeV observations of Cyg X-1 in this state hinted at a possible existence of a non-thermal particle component with substantial modifications of the Comptonized emission from the inner accretion disk. Ourmore » AGILE data, averaged over the mid-2010/mid-2011 soft state of Cygnus X-1, provide a significant upper limit for gamma-ray emission above 100 MeV of F{sub soft} < 20 Multiplication-Sign 10{sup -8} photons cm{sup -2} s{sup -1} , excluding the existence of prominent non-thermal emission above 100 MeV during the soft state of Cygnus X-1. We discuss theoretical implications of our findings in the context of high-energy emission models of black hole accretion. We also discuss possible gamma-ray flares detected by AGILE. In addition to a previously reported episode observed by AGILE in 2009 October during the hard state, we report a weak but important candidate for enhanced emission which occurred at the end of 2010 June (2010 June 30 10:00-2010 July 2 10:00 UT) exactly coinciding with a hard-to-soft state transition and before an anomalous radio flare. An appendix summarizes all previous high-energy observations and possible detections of Cygnus X-1 above 1 MeV.« less

Increased photoelectron transmission in High-pressure photoelectron spectrometers using "swift acceleration"

NASA Astrophysics Data System (ADS)

Edwards, Mårten O. M.; Karlsson, Patrik G.; Eriksson, Susanna K.; Hahlin, Maria; Siegbahn, Hans; Rensmo, Håkan; Kahk, Juhan M.; Villar-Garcia, Ignacio J.; Payne, David J.; Åhlund, John

2015-06-01

A new operation mode of a HPXPS (high-pressure X-ray photoelectron spectroscopy) analyzer is evaluated on a HPXPS system fitted with an Al Kα X-ray source. A variety of metal foil samples (gold, silver and copper) were measured in different sample gas environments (N2 and H2O), and a front aperture diameter of 0.8 mm. The new design concept is based upon "swiftly" accelerating the photoelectrons to kinetic energies of several keV after they pass the analyzer front aperture. Compared to the standard mode, in which the front section between the two first apertures is field-free, this gives a wider angular collection and a lower tendency for electron losses in collisions with gas molecules within the analyzer. With the swift-acceleration mode we attain, depending on the experimental conditions, up to about 3 times higher peak intensities in vacuum and about 10 to 20 times higher peak intensities in the 6-9 mbar regime, depending on kinetic energy. These experimental findings agree well with simulated transmission functions for the analyzer. The new mode of operation enables faster data acquisition than the standard mode of operation, particularly valuable in a home laboratory environment. Further demonstrations of performance are highlighted by measurements of the valence band structure in dye-sensitized solar cell photoelectrodes under a 2 mbar H2O atmosphere, a molecularly modified surface of interest in photoelectrochemical devices.

Electronic structures of U X3 (X =Al , Ga, and In) studied by photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Fujimori, Shin-ichi; Kobata, Masaaki; Takeda, Yukiharu; Okane, Tetsuo; Saitoh, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; Yamamoto, Etsuji; Ōnuki, Yoshichika

2017-09-01

The electronic structures of U X3 (X =Al , Ga , and In ) were studied by photoelectron spectroscopy to understand the relationship between their electronic structures and magnetic properties. The band structures and Fermi surfaces of UAl3 and UGa3 were revealed experimentally by angle-resolved photoelectron spectroscopy (ARPES), and they were compared with the result of band-structure calculations. The topologies of the Fermi surfaces and the band structures of UAl3 and UGa3 were explained reasonably well by the calculation, although bands near the Fermi level (EF) were renormalized owing to the finite electron correlation effect. The topologies of the Fermi surfaces of UAl3 and UGa3 are very similar to each other, except for some minor differences. Such minor differences in their Fermi surface or electron correlation effect might take an essential role in their different magnetic properties. No significant changes were observed between the ARPES spectra of UGa3 in the paramagnetic and antiferromagnetic phases, suggesting that UGa3 is an itinerant weak antiferromagnet. The effect of chemical pressure on the electronic structures of U X3 compounds was also studied by utilizing the smaller lattice constants of UAl3 and UGa3 than that of UIn3. The valence band spectrum of UIn3 is accompanied by a satellitelike structure on the high-binding-energy side. The core-level spectrum of UIn3 is also qualitatively different from those of UAl3 and UGa3. These findings suggest that the U 5 f states in UIn3 are more localized than those in UAl3 and UGa3.

The adsorption of methyl iodide on uranium and uranium dioxide: Surface characterization using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES)

NASA Astrophysics Data System (ADS)

Dillard, J. G.; Moers, H.; Klewe-Nebenius, H.; Kirch, G.; Pfennig, G.; Ache, H. J.

1984-09-01

The adsorption of methyl iodide on uranium and on uranium dioxide has been studied at 25 °C. Surfaces of the substrates were characterized before and after adsorption by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The XPS binding energy results indicate that CH 3I adsorption on uranium yields a carbide-type carbon, UC, and uranium iodide, UI 3. On uranium dioxide the carbon electron binding energy measurements are consistent with the formation of a hydrocarbon, —CH 3-type moiety. The interpretation of XPS and AES spectral features for CH 3I adsorption on uranium suggest that a complex dissociative adsorption reaction takes place. Adsorption of CH 3I on UO 2 occurs via a dissociative process. Saturation coverage occurs on uranium at approximately two langmuir (1 L = 10 -6 Torr s) exposure whereas saturation coverage on uranium dioxide is found at about five langmuir.

Elemental content of enamel and dentin after bleaching of teeth (a comparative study between laser-induced breakdown spectroscopy and x-ray photoelectron spectroscopy)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Imam, H.; Ahmed, Doaa; Eldakrouri, Ashraf

2013-06-21

The elemental content of the superficial and inner enamel as well as that of dentin was analyzed using laser-induced breakdown spectroscopy (LIBS) and x-ray photoelectron spectroscopy (XPS) of bleached and unbleached tooth specimens. It is thus clear from the spectral analysis using both the LIBS and XPS technique that elemental changes (though insignificant within the scopes of this study) of variable intensities do occur on the surface of the enamel and extend deeper to reach dentin. The results of the LIBS revealed a slight reduction in the calcium levels in the bleached compared to the control specimens in all themore » different bleaching groups and in both enamel and dentin. The good correlation found between the LIBS and XPS results demonstrates the possibility of LIBS technique for detection of minor loss in calcium and phosphorus in enamel and dentin.« less

Measurements of reciprocity law failure in green-sensitive X-ray films.

PubMed

Arnold, B A; Eisenberg, H; Bjärngard, B E

1978-02-01

Reciprocity law failure was measured for four brands of medical x-ray films exposed with intensifying screens. Three of the films are green light-sensitized for use in combination with green light-emitting rare-earth screens. These films showed larger reciprocity failure effects than one conventional blue-sensitive film, Dupont Cronex-2. Development conditions had a small effect on reciprocity failure. As part of the investigation, a detector was constructed with a response that accurately monitors the light emission from the double screen-cassette combination over a wide range of x-ray photon energies.

X-Ray Study of Variable Gamma-Ray Pulsar PSR J2021+4026

NASA Astrophysics Data System (ADS)

Wang, H. H.; Takata, J.; Hu, C.-P.; Lin, L. C. C.; Zhao, J.

2018-04-01

PSR J2021+4026 showed a sudden decrease in the gamma-ray emission at the glitch that occurred around 2011 October 16, and a relaxation of the flux to the pre-glitch state at around 2014 December. We report X-ray analysis results of the data observed by XMM-Newton on 2015 December 20 in the post-relaxation state. To examine any change in the X-ray emission, we compare the properties of the pulse profiles and spectra at the low gamma-ray flux state and at the post-relaxation state. The phase-averaged spectra for both states can be well described by a power-law component plus a blackbody component. The former is dominated by unpulsed emission and probably originated from the pulsar wind nebula as reported by Hui et al. The emission property of the blackbody component is consistent with the emission from the polar cap heated by the back-flow bombardment of the high-energy electrons or positrons that were accelerated in the magnetosphere. We found no significant change in the X-ray emission properties between two states. We suggest that the change of the X-ray luminosity is at an order of ∼4%, which is difficult to measure with the current observations. We model the observed X-ray light curve with the heated polar cap emission, and we speculate that the observed large pulsed fraction is owing to asymmetric magnetospheric structure.

Electron and fluorescence spectra of a water molecule irradiated by an x-ray free-electron laser pulse

NASA Astrophysics Data System (ADS)

Schäfer, Julia M.; Inhester, Ludger; Son, Sang-Kil; Fink, Reinhold F.; Santra, Robin

2018-05-01

With the highly intense x-ray light generated by x-ray free-electron lasers (XFELs), molecular samples can be ionized many times in a single pulse. Here we report on a computational study of molecular spectroscopy at the high x-ray intensity provided by XFELs. Calculated photoelectron, Auger electron, and x-ray fluorescence spectra are presented for a single water molecule that reaches many electronic hole configurations through repeated ionization steps. The rich details shown in the spectra depend on the x-ray pulse parameters in a nonintuitive way. We discuss how the observed trends can be explained by the competition of microscopic electronic transition processes. A detailed comparison between spectra calculated within the independent-atom model and within the molecular-orbital framework highlights the chemical sensitivity of the spectral lines of multiple-hole configurations. Our results demonstrate how x-ray multiphoton ionization-related effects such as charge-rearrangement-enhanced x-ray ionization of molecules and frustrated absorption manifest themselves in the electron and fluorescence spectra.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

1990-04-01

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-raymore » 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.« less

Revealing the electronic structure of LiC 6 by soft X-ray spectroscopy

DOE PAGES

Zhang, L.; Li, X.; Augustsson, A.; ...

2017-03-09

The electronic structure of LiC 6 has been investigated in this paper by soft X-ray absorption and emission spectroscopies. The results reveal that upon full lithiation of graphite, the Li 2s electrons are transferred into the carbon π* states in a near rigid-band behavior, resulting in the increased density of states near E F and the shift of σ* states to lower energies. Finally, in addition, the resonant inelastic X-ray scattering spectra of LiC 6 do not show strong dispersive features as that of graphite, indicating that the crystal momentum is not conserved during the scattering process due to themore » delocalization of electrons in the intermediate state.« less

Rebonding of Se to As and Ge in Ge33As12Se55 films upon thermal annealing: Evidence from x-ray photoelectron spectra investigations

NASA Astrophysics Data System (ADS)

Wang, R. P.; Choi, D. Y.; Rode, A. V.; Madden, S. J.; Luther-Davies, B.

2007-06-01

We have measured and analyzed x-ray photoelectron spectra (XPS) of as-grown and annealed Ge33As12Se55 films compared with bulk material. We found that the as-grown film contains a large number of separated Se clusters which can coalesce with As and Ge after annealing at high temperatures. In addition, both the Ge and As 3d spectra show the presence of oxides. While the Ge oxidation increases with an increasing annealing temperature, As oxidation is almost unaffected by annealing. The difference could be due to their different electro-negativities. Our results suggest that, while thermal annealing is effective to move the film toward the bond structure of bulk glass, the simultaneous surface oxidation must be suppressed in order to achieve high quality films.

Effects of Sulfation Level on the Desulfation Behavior of Presulfated Pt-BaO/Al2O3 Lean NOx Trap Catalysts: A Combined H2 Temperature-Programmed Reaction, in Situ Sulfur K-Edge X-ray Absorption Near-Edge Spectroscopy, X-ray Photoelectron Spectroscopy, and Time-Resolved X-ray Diffraction Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, D.H.; Hanson, J.; Szanyi, J.

2009-04-30

Desulfation by hydrogen of presulfated Pt (2 wt %)-BaO(20 wt %)/Al{sub 2}O{sub 3} with various sulfur loading (S/Ba = 0.12, 0.31, and 0.62) were investigated by combining H{sub 2} 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 H{sub 2}S desorbed during the desulfation in the H{sub 2} TPRX experiments is not proportional to the amount of initial sulfur loading. The results of both in situ sulfur K-edge XANES and TR-XRD show that at low sulfur loadings, sulfates weremore » transformed to a BaS phase and remained in the catalyst rather than being removed as H{sub 2}S. On the other hand, when the deposited sulfur level exceeded a certain threshold (at least S/Ba = 0.31) sulfates were reduced to form H{sub 2}S, and the relative amount of the residual sulfide species in the catalyst was much less than at low sulfur loading. Unlike samples with high sulfur loading (e.g., S/Ba = 0.62), H{sub 2}O did not promote the desulfation for the sample with S/Ba of 0.12, implying that the formed BaS species originating from the reduction of sulfates at low sulfur loading are more stable to hydrolysis. The results of this combined spectroscopy investigation provide clear evidence to show that sulfates at low sulfur loadings are less likely to be removed as H{sub 2}S and have a greater tendency to be transformed to BaS on the material, leading to the conclusion that desulfation behavior of Pt-BaO/Al{sub 2}O{sub 3} lean NO{sub x} trap catalysts is markedly dependent on the sulfation levels.« less

Configuring and Characterizing X-Rays for Laser-Driven Compression Experiments at the Dynamic Compression Sector

NASA Astrophysics Data System (ADS)

Li, Y.; Capatina, D.; D'Amico, K.; Eng, P.; Hawreliak, J.; Graber, T.; Rickerson, D.; Klug, J.; Rigg, P. A.; Gupta, Y. M.

2017-06-01

Coupling laser-driven compression experiments to the x-ray beam at the Dynamic Compression Sector (DCS) at the Advanced Photon Source (APS) of Argonne National Laboratory requires state-of-the-art x-ray focusing, pulse isolation, and diagnostics capabilities. The 100J UV pulsed laser system can be fired once every 20 minutes so precise alignment and focusing of the x-rays on each new sample must be fast and reproducible. Multiple Kirkpatrick-Baez (KB) mirrors are used to achieve a focal spot size as small as 50 μm at the target, while the strategic placement of scintillating screens, cameras, and detectors allows for fast diagnosis of the beam shape, intensity, and alignment of the sample to the x-ray beam. In addition, a series of x-ray choppers and shutters are used to ensure that the sample is exposed to only a single x-ray pulse ( 80ps) during the dynamic compression event and require highly precise synchronization. Details of the technical requirements, layout, and performance of these instruments will be presented. Work supported by DOE/NNSA.

Valence shell threshold photoelectron spectroscopy of the CHxCN (x = 0-2) and CNC radicals.

PubMed

Garcia, Gustavo A; Krüger, Julia; Gans, Bérenger; Falvo, Cyril; Coudert, Laurent H; Loison, Jean-Christophe

2017-07-07

We present the photoelectron spectroscopy of four radical species, CH x CN (x = 0-2) and CNC, formed in a microwave discharge flow-tube reactor by consecutive H abstractions from CH 3 CN (CH x CN + F → CH x-1 CN + HF (x = 1-3)). The spectra were obtained combining tunable vacuum ultraviolet synchrotron radiation with double imaging electron/ion coincidence techniques, which yielded mass-selected threshold photoelectron spectra. The results obtained for H 2 CCN complement existing ones while for the other radicals the data represent the first observation of their (single-photon) ionizing transitions. In the case of H 2 CCN, Franck-Condon calculations have been performed in order to assign the vibrational structure of the X + 1 A 1 ←X 2 B 1 ionizing transition. A similar treatment for the HCCN, CCN, and CNC radicals appeared to be more complicated mainly because a Renner-Teller effect strongly affects the vibrational levels of the ground electronic state of the HCCN + , CCN, and CNC species. Nevertheless, the first adiabatic ionization energies of these radicals are reported and compared to our ab initio calculated values, leading to new values for enthalpies of formation (Δ f H 298 0 (HCCN + (X 2 A ' ))=1517±12kJmol -1 ,Δ f H 298 0 (CCN(X 2 Π))=682±13kJmol -1 , and Δ f H 298 0 (CNC(X 2 Πg))=676±12kJmol -1 ), which are of fundamental importance for astrochemistry.

Interatomic interactions in M2(C8H4O4)2C6H12N2 (M = Zn, Cu, Co, Ni) metal-organic framework polymers: X-ray photoelectron spectroscopy, QTAIM and ELF study

NASA Astrophysics Data System (ADS)

Kozlova, S. G.; Ryzhikov, M. R.; Samsonenko, D. G.; Kalinkin, A. V.

2017-12-01

Interatomic interactions in M2(C8H4O4)2C6H12N2 (M = Co, Ni, Cu, Zn) metal-organic framework polymers have been studied with the methods of quantum chemistry and X-ray photoelectron spectroscopy. Interactions of C6H12N2 molecules and C8H4O42- anions with metal atoms are shown to be of closed-shell type. C6H12N2 molecules are positively charged, the value of the charge slightly depends on the type of the metal atoms. Msbnd M interactions are described as "intermediate interactions" with some covalence contribution which reaches maximum for the interactions between cobalt atoms. The obtained quantum-chemical data agree with those obtained from photoelectron spectroscopy measurements.

Laser-produced lithium plasma as a narrow-band extended ultraviolet radiation source for photoelectron spectroscopy.

PubMed

Schriever, G; Mager, S; Naweed, A; Engel, A; Bergmann, K; Lebert, R

1998-03-01

Extended ultraviolet (EUV) emission characteristics of a laser-produced lithium plasma are determined with regard to the requirements of x-ray photoelectron spectroscopy. The main features of interest are spectral distribution, photon flux, bandwidth, source size, and emission duration. Laser-produced lithium plasmas are characterized as emitters of intense narrow-band EUV radiation. It can be estimated that the lithium Lyman-alpha line emission in combination with an ellipsoidal silicon/molybdenum multilayer mirror is a suitable EUV source for an x-ray photoelectron spectroscopy microscope with a 50-meV energy resolution and a 10-mum lateral resolution.

Regulation of X-Ray Security Scanners in Michigan.

PubMed

Parry, Donald E

2016-02-01

In January of 2013 the Transportation Security Administration (TSA) ordered the removal of x-ray security scanners from airports by June of 2013. Since that time several of these scanners have been purchased at a reduced cost by various state and county governments for use in screening individuals entering or leaving their facilities. To address this issue the Radiation Safety Section of the State of Michigan drafted a set of registration conditions for facilities to follow when using these security scanners. Inspection procedures and measurement protocols were developed to estimate the dose to screened individuals. Inspections were performed on nine of the 16 registered backscatter scanners in the state and the one transmission scanner. The average estimated effective dose to screened individuals was ∼11 nSv for a two view scan from a backscatter system. The effective dose was 0.446 μSv, 0.330 μSv, and 0.150 μSv for a transmission system operated in the high, medium, and low dose modes, respectively. The limit suggested in the new registration condition is 0.25 μSv for a general use system and 10 μSv for a limited use system.

Characterization of aluminum nitride based films with high resolution X-ray fluorescence spectroscopy

NASA Astrophysics Data System (ADS)

Anagnostopoulos, D. F.; Siozios, A.; Patsalas, P.

2018-02-01

X-ray fluorescence spectra of Al based films are measured, using a lab-scale wavelength dispersive flat crystal spectrometer. Various structures of AlN films were studied, like single layered, capped, stratified, nanostructured, crystalline, or amorphous. By optimizing the set-up for enhanced energy resolution and detection efficiency, the measured line shapes of Κα, Kβ, and KLL radiative Auger transitions are shown to be adequately detailed to allow chemical characterization. The chemistry identification is based on the pattern comparison of the emitted line shape from the chemically unknown film and the reference line shapes from standard materials, recorded under identical experimental conditions. The ultimate strength of lab-scale high resolution X-ray fluorescence spectroscopy on film analysis is verified, in cases that ordinary applied techniques like X-ray photoelectron and X-ray diffraction fail, while the characterization refers to the non-destructive determination of the bulk properties of the film and not to its surface, as the probed depth is in the micrometer range.

Time-resolved x-ray absorption spectroscopy: Watching atoms dance

NASA Astrophysics Data System (ADS)

Milne, Chris J.; Pham, Van-Thai; Gawelda, Wojciech; van der Veen, Renske M.; El Nahhas, Amal; Johnson, Steven L.; Beaud, Paul; Ingold, Gerhard; Lima, Frederico; Vithanage, Dimali A.; Benfatto, Maurizio; Grolimund, Daniel; Borca, Camelia; Kaiser, Maik; Hauser, Andreas; Abela, Rafael; Bressler, Christian; Chergui, Majed

2009-11-01

The introduction of pump-probe techniques to the field of x-ray absorption spectroscopy (XAS) has allowed the monitoring of both structural and electronic dynamics of disordered systems in the condensed phase with unprecedented accuracy, both in time and in space. We present results on the electronically excited high-spin state structure of an Fe(II) molecular species, [FeII(bpy)3]2+, in aqueous solution, resolving the Fe-N bond distance elongation as 0.2 Å. In addition an analysis technique using the reduced χ2 goodness of fit between FEFF EXAFS simulations and the experimental transient absorption signal in energy space has been successfully tested as a function of excited state population and chemical shift, demonstrating its applicability in situations where the fractional excited state population cannot be determined through other measurements. Finally by using a novel ultrafast hard x-ray 'slicing' source the question of how the molecule relaxes after optical excitation has been successfully resolved using femtosecond XANES.

Observational Aspects of Hard X-ray Polarimetry

NASA Astrophysics Data System (ADS)

Chattopadhyay, Tanmoy

2016-04-01

Sensitive polarization measurements in X-ray may address a wealth of astrophysical phenomena, which so far remain beyond our understanding through available X-ray spectroscopic, imaging, and timing studies. Though scientific potential of X-ray polarimetry was realized long ago, there has not been any significant advancement in this field for the last four decades since the birth of X-ray astronomy. The only successful polarization measurement in X-rays dates back to 1976, when a Bragg polarimeter onboard OSO-8 measured polarization of Crab nebula. Primary reason behind the lack in progress is its extreme photon hungry nature, which results in poor sensitivity of the polarimeters. Recently, in the last decade or so, with the advancement in detection technology, X-ray polarimetry may see a significant progress in near future, especially in soft X-rays with the invention of photoelectron tracking polarimeters. Though photoelectric polarimeters are expected to provide sensitive polarization measurements of celestial X-ray sources, they are sensitive only in soft X-rays, where the radiation from the sources is dominated by thermal radiation and therefore expected to be less polarized. On the other hand, in hard X-rays, sources are ex-pected to be highly polarized due to the dominance of nonthermal emission over its thermal counterpart. Moreover, polarization measurements in hard X-rays promises to address few interesting scientific issues regarding geometry of corona for black hole sources, emission mechanism responsible for the higher energy peak in the blazars, accretion geometry close to the magnetic poles in accreting neutron star systems and acceleration mechanism in solar flares. Compton polarimeters provide better sensitivity than photoelectric polarimeters in hard X-rays with a broad energy band of operation. Recently, with the development of hard X-ray focusing optics e.g. NuSTAR, Astro-H, it is now possible to conceive Compton polarimeters at the focal plane

Utilizing broadband X-rays in a Bragg coherent X-ray diffraction imaging experiment

DOE PAGES

Cha, Wonsuk; Liu, Wenjun; Harder, Ross; ...

2016-07-26

A method is presented to simplify Bragg coherent X-ray diffraction imaging studies of complex heterogeneous crystalline materials with a two-stage screening/imaging process that utilizes polychromatic and monochromatic coherent X-rays and is compatible with in situ sample environments. Coherent white-beam diffraction is used to identify an individual crystal particle or grain that displays desired properties within a larger population. A three-dimensional reciprocal-space map suitable for diffraction imaging is then measured for the Bragg peak of interest using a monochromatic beam energy scan that requires no sample motion, thus simplifyingin situchamber design. This approach was demonstrated with Au nanoparticles and will enable,more » for example, individual grains in a polycrystalline material of specific orientation to be selected, then imaged in three dimensions while under load.« less

Utilizing broadband X-rays in a Bragg coherent X-ray diffraction imaging experiment.

PubMed

Cha, Wonsuk; Liu, Wenjun; Harder, Ross; Xu, Ruqing; Fuoss, Paul H; Hruszkewycz, Stephan O

2016-09-01

A method is presented to simplify Bragg coherent X-ray diffraction imaging studies of complex heterogeneous crystalline materials with a two-stage screening/imaging process that utilizes polychromatic and monochromatic coherent X-rays and is compatible with in situ sample environments. Coherent white-beam diffraction is used to identify an individual crystal particle or grain that displays desired properties within a larger population. A three-dimensional reciprocal-space map suitable for diffraction imaging is then measured for the Bragg peak of interest using a monochromatic beam energy scan that requires no sample motion, thus simplifying in situ chamber design. This approach was demonstrated with Au nanoparticles and will enable, for example, individual grains in a polycrystalline material of specific orientation to be selected, then imaged in three dimensions while under load.

Soft x-ray contact imaging of biological specimens using a laser-produced plasma as an x-ray source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, P.C.

The use of a laser-produced plasma as an x-ray source provides significant advantages over other types of sources for x-ray microradiography of, particularly, living biological specimens. The pulsed nature of the x-rays enables imaging of the specimen in a living state, and the small source size minimizes penumbral blurring. This makes it possible to make an exposure close to the source, thereby increasing the x-ray intensity. In this article, we will demonstrate the applications of x-ray contact microradiography in structural and developmental botany such as the localization of silica deposition and the floral morphologenesis of maize.

Band alignment of 2D WS2/HfO2 interfaces from x-ray photoelectron spectroscopy and first-principles calculations

NASA Astrophysics Data System (ADS)

Zhu, H. L.; Zhou, C. J.; Tang, B. S.; Yang, W. F.; Chai, J. W.; Tay, W. L.; Gong, H.; Pan, J. S.; Zou, W. D.; Wang, S. J.; Chi, D. Z.

2018-04-01

We report on the growth of two-dimensional (2D) WS2 on high-k HfO2/Si substrates by reactive sputtering deposition. Raman, x-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy characterizations indicate that the 2D WS2 layers exhibit high-quality crystallinity and exact stoichiometry. Through high-resolution XPS valence spectra, we find a type I alignment at the interface of monolayer WS2/HfO2 with a valence band offset (VBO) of 1.95 eV and a conduction band offset (CBO) of 1.57 eV. The VBO and CBO are also found to increase up to 2.24 eV and 2.09 eV, respectively, with increasing WS2 layers. This is consistent with the results obtained from our first-principles calculations. Our theoretical calculations reveal that the remarkable splitting and shift of the W 5 d z 2 orbital originating from interlayer orbital coupling in thicker WS2 films induce a reduction of its bandgap, leading to an increase in both the VBO and CBO. This observation can be attributed to the asymmetric splitting at different high symmetric k-points caused by the interlayer orbital coupling.

Study of mesoporous CdS-quantum-dot-sensitized TiO2 films by using X-ray photoelectron spectroscopy and AFM

PubMed Central

Wojcieszak, Robert; Raj, Gijo

2014-01-01

Summary CdS quantum dots were grown on mesoporous TiO2 films by successive ionic layer adsorption and reaction processes in order to obtain CdS particles of various sizes. AFM analysis shows that the growth of the CdS particles is a two-step process. The first step is the formation of new crystallites at each deposition cycle. In the next step the pre-deposited crystallites grow to form larger aggregates. Special attention is paid to the estimation of the CdS particle size by X-ray photoelectron spectroscopy (XPS). Among the classical methods of characterization the XPS model is described in detail. In order to make an attempt to validate the XPS model, the results are compared to those obtained from AFM analysis and to the evolution of the band gap energy of the CdS nanoparticles as obtained by UV–vis spectroscopy. The results showed that XPS technique is a powerful tool in the estimation of the CdS particle size. In conjunction with these results, a very good correlation has been found between the number of deposition cycles and the particle size. PMID:24605274

Recent X-ray hybrid CMOS detector developments and measurements

NASA Astrophysics Data System (ADS)

Hull, Samuel V.; Falcone, Abraham D.; Burrows, David N.; Wages, Mitchell; Chattopadhyay, Tanmoy; McQuaide, Maria; Bray, Evan; Kern, Matthew

2017-08-01

The Penn State X-ray detector lab, in collaboration with Teledyne Imaging Sensors (TIS), have progressed their efforts to improve soft X-ray Hybrid CMOS detector (HCD) technology on multiple fronts. Having newly acquired a Teledyne cryogenic SIDECARTM ASIC for use with HxRG devices, measurements were performed with an H2RG HCD and the cooled SIDECARTM. We report new energy resolution and read noise measurements, which show a significant improvement over room temperature SIDECARTM operation. Further, in order to meet the demands of future high-throughput and high spatial resolution X-ray observatories, detectors with fast readout and small pixel sizes are being developed. We report on characteristics of new X-ray HCDs with 12.5 micron pitch that include in-pixel CDS circuitry and crosstalk-eliminating CTIA amplifiers. In addition, PSU and TIS are developing a new large-scale array Speedster-EXD device. The original 64 × 64 pixel Speedster-EXD prototype used comparators in each pixel to enable event driven readout with order of magnitude higher effective readout rates, which will now be implemented in a 550 × 550 pixel device. Finally, the detector lab is involved in a sounding rocket mission that is slated to fly in 2018 with an off-plane reflection grating array and an H2RG X-ray HCD. We report on the planned detector configuration for this mission, which will increase the NASA technology readiness level of X-ray HCDs to TRL 9.

Angle resolved x-ray photoelectron spectroscopy (ARXPS) analysis of lanthanum oxide for micro-flexography printing

NASA Astrophysics Data System (ADS)

Hassan, S.; Yusof, M. S.; Embong, Z.; Maksud, M. I.

2016-01-01

Micro-flexography printing was developed in patterning technique from micron to nano scale range to be used for graphic, electronic and bio-medical device on variable substrates. In this work, lanthanum oxide (La2O3) has been used as a rare earth metal candidate as depositing agent. This metal deposit was embedded on Carbon (C) and Silica (Si) wafer substrate using Magnetron Sputtering technique. The choose of Lanthanum as a target is due to its wide application in producing electronic devices such as thin film battery and printed circuit board. The La2O3 deposited on the surface of Si wafer substrate was then analyzed using Angle Resolve X-Ray Photoelectron Spectroscopy (ARXPS). The position for each synthetic component in the narrow scan of Lanthanum (La) 3d and O 1s are referred to the electron binding energy (eV). The La 3d narrow scan revealed that the oxide species of this particular metal is mainly contributed by La2O3 and La(OH)3. The information of oxygen species, O2- component from O 1s narrow scan indicated that there are four types of species which are contributed from the bulk (O2-), two chemisorb component (La2O3) and La(OH)3 and physisorp component (OH). Here, it is proposed that from the adhesive and surface chemical properties of La, it is suitable as an alternative medium for micro-flexography printing technique in printing multiple fine solid lines at nano scale. Hence, this paper will describe the capability of this particular metal as rare earth metal for use in of micro-flexography printing practice. The review of other parameters contributing to print fine lines will also be described later.

Angle resolved x-ray photoelectron spectroscopy (ARXPS) analysis of lanthanum oxide for micro-flexography printing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hassan, S., E-mail: suhaimihas@uthm.edu.my; Yusof, M. S., E-mail: mdsalleh@uthm.edu.my; Maksud, M. I., E-mail: midris1973@gmail.com

2016-01-22

Micro-flexography printing was developed in patterning technique from micron to nano scale range to be used for graphic, electronic and bio-medical device on variable substrates. In this work, lanthanum oxide (La{sub 2}O{sub 3}) has been used as a rare earth metal candidate as depositing agent. This metal deposit was embedded on Carbon (C) and Silica (Si) wafer substrate using Magnetron Sputtering technique. The choose of Lanthanum as a target is due to its wide application in producing electronic devices such as thin film battery and printed circuit board. The La{sub 2}O{sub 3} deposited on the surface of Si wafer substratemore » was then analyzed using Angle Resolve X-Ray Photoelectron Spectroscopy (ARXPS). The position for each synthetic component in the narrow scan of Lanthanum (La) 3d and O 1s are referred to the electron binding energy (eV). The La 3d narrow scan revealed that the oxide species of this particular metal is mainly contributed by La{sub 2}O{sub 3} and La(OH){sub 3}. The information of oxygen species, O{sup 2-} component from O 1s narrow scan indicated that there are four types of species which are contributed from the bulk (O{sup 2−}), two chemisorb component (La{sub 2}O{sub 3}) and La(OH){sub 3} and physisorp component (OH). Here, it is proposed that from the adhesive and surface chemical properties of La, it is suitable as an alternative medium for micro-flexography printing technique in printing multiple fine solid lines at nano scale. Hence, this paper will describe the capability of this particular metal as rare earth metal for use in of micro-flexography printing practice. The review of other parameters contributing to print fine lines will also be described later.« less

X-ray absorption spectroscopy and X-ray photoelectron spectroscopy studies of CaSO 4:Dy thermoluminescent phosphors

NASA Astrophysics Data System (ADS)

Bakshi, A. K.; Jha, S. N.; Olivi, L.; Phase, D. M.; Kher, R. K.; Bhattacharyya, D.

2007-11-01

Extended X-ray absorption fine structure (EXAFS) measurements have been carried out on CaSO4:Dy phosphor samples at the Dy L3 edge with synchrotron radiation. Measurements were carried out on a set of samples which were subjected to post-preparation annealing at different temperatures and for different cycles. The EXAFS data have been analysed to find the Dy-S and Dy-O bond lengths in the neighbourhood of the Dy atoms in a CaSO4 matrix. The observations from EXAFS measurements were verified with XANES and XPS techniques. On the basis of these measurements, efforts were made to explain the loss of thermoluminescence sensitivity of CaSO4:Dy phosphors after repeated cycles of annealing at 400 °C in air for 1 h.

Calculation of density of states of transition metals: From bulk sample to nanocluster

NASA Astrophysics Data System (ADS)

Krasavin, Andrey V.; Borisyuk, Petr V.; Vasiliev, Oleg S.; Zhumagulov, Yaroslav V.; Kashurnikov, Vladimir A.; Kurelchuk, Uliana N.; Lebedinskii, Yuriy Yu.

2018-03-01

A technique is presented of restoring the electronic density of states of the valence band from data of X-ray photoelectron spectroscopy (XPS). The originality of the technique consists in using a stochastic procedure to solve an integral equation relating the density of states and the experimental X-ray photoelectron spectra via the broadening function. To obtain the broadening function, only the XPS spectra of the core levels are needed. The results are presented for bulk sample of gold and tungsten and nanoclusters of tantalum; the possibility of using the results to determine the density of states of low-dimensional structures, including ensembles of metal nanoclusters, is demonstrated.

Forcing Cesium into Higher Oxidation States Using Useful hard x-ray Induced Chemistry under High Pressure

NASA Astrophysics Data System (ADS)

Sneed, D.; Pravica, M.; Kim, E.; Chen, N.; Park, C.; White, M.

2017-10-01

This paper discusses our attempt to synthesize higher oxidation forms of cesium fluoride by pressurizing cesium fluoride in a fluorine-rich environment created via the x-ray decomposition of potassium tetrafluoroborate. This was done in order to confirm recent theoretical predictions of higher oxidation forms of CsFn. We discuss the development of a technique to produce molecular fluorine in situ via useful hard x-ray photochemistry, and the attempt to utilize this technique to form higher oxidation states of cesium fluoride. In order to verify the formation of the novel stoichiometric species of CsFn. X-ray Absorption Near Edge Spectroscopy (XANES) centered on the cesium K-edge was performed to probe the oxidation state of cesium as well as the local molecular coordination around Cs.

Stimulated Electronic X-Ray Raman Scattering

NASA Astrophysics Data System (ADS)

Weninger, Clemens; Purvis, Michael; Ryan, Duncan; London, Richard A.; Bozek, John D.; Bostedt, Christoph; Graf, Alexander; Brown, Gregory; Rocca, Jorge J.; Rohringer, Nina

2013-12-01

We demonstrate strong stimulated inelastic x-ray scattering by resonantly exciting a dense gas target of neon with femtosecond, high-intensity x-ray pulses from an x-ray free-electron laser (XFEL). A small number of lower energy XFEL seed photons drive an avalanche of stimulated resonant inelastic x-ray scattering processes that amplify the Raman scattering signal by several orders of magnitude until it reaches saturation. Despite the large overall spectral width, the internal spiky structure of the XFEL spectrum determines the energy resolution of the scattering process in a statistical sense. This is demonstrated by observing a stochastic line shift of the inelastically scattered x-ray radiation. In conjunction with statistical methods, XFELs can be used for stimulated resonant inelastic x-ray scattering, with spectral resolution smaller than the natural width of the core-excited, intermediate state.

X-ray microscopy of live biological micro-organisms

NASA Astrophysics Data System (ADS)

Raja Al-Ani, Ma'an Nassar

Real-time, compact x-ray microscopy has the potential to benefit many scientific fields, including microbiology, pharmacology, organic chemistry, and physics. Single frame x-ray micro-radiography, produced by a compact, solid-state laser plasma source, allows scientists to use x-ray emission for elemental analysis, and to observe biological specimens in their natural state. In this study, x-ray images of mouse kidney tissue, live bacteria, Pseudomonas aeruginosa and Burkholderia cepacia, and the bacteria's interaction with the antibiotic gentamicin, are examined using x-ray microscopy. For the purposes of comparing between confocal microscopy and x-ray microscopy, we introduced to our work the technique of gold labeling. Indirect immunofluorescence staining and immuno-gold labeling were applied on human lymphocytes and human tumor cells. Differential interference contrast microscopy (DIC) showed the lymphocyte body and nucleus, as did x-ray microscopy. However, the high resolution of x-ray microscopy allows us to differentiate between the gold particles bound to the antibodies and the free gold. A compact, tabletop Nd: glass laser is used in this study to produce x-rays from an Yttrium target. An atomic force microscope is used to scan the x-ray images from the developed photo-resist. The use of compact, tabletop laser plasma sources, in conjunction with x-ray microscopy, is a new technique that has great potential as a flexible, user-friendly scientific research tool.

X-ray Weak Broad-line Qquasars: Absorption or Intrinsic X-ray Weakness

NASA Technical Reports Server (NTRS)

Mushotzky, Richard (Technical Monitor); Risaliti, Guida

2005-01-01

XMM observations of X-ray weak quasars have been performed during 2003 and 2004. The data for all the observations have become available in 2004 (there has been a delay of several months on the initial schedule, due to high background flares which contaminated the observations: as a consequence, most of them had to be rescheduled). We have reduced and analyzed all the data, and obtained interesting scientific results. Out of the eight sources, 4 are confirmed to be extremely X-ray weak, in agreement with the results of previous Chandra observations. 3 sources are confined to be highly variable both in flux (by factor 20-50) and in spectral properties (dramatic changes in spectral index). For both these groups of objects we are completing a publication: 1) For the X-ray weak sources, a paper is submitted with a complete analysis of the X-ray spectra both from Chandra and XMM-Newton, and a comparison with optical and near-IR photometry obtained from all-sky surveys. Possible models for the unusual spectral energy distribution of these sources are also presented. 2) For the variable sources, a paper is being finalized where the X-ray spectra obtained with XMM-Newton are compared with previous X-ray observations and with observations at other wavelengths. It is shown that these sources are high luminosity and extreme cases of the highly variable class of narrow-line Seyfert Is. In order to further understand the nature of these X-ray weak quasars, we submitted proposals for spectroscopy at optical and infrared telescopes. We obtained time at the TNG 4 meter telescope for near-IR observations and at the Hobby-Eberly Telescope for optical high-resolution spectroscopy. These observations have been performed in early 2004. They will complement the XMM data and will lead to understanding of whether the X-ray weakness of these sources is an intrinsic property or is due to absorption by circum-nuclear material. The infrared spectra of the variable sources have been already