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Sample records for absorption x-ray photoelectron

  1. Photoelectron and X-ray Absorption Spectroscopy Of Pu

    SciTech Connect

    Tobin, J; Chung, B; Schulze, R; Farr, J; Shuh, D

    2003-11-12

    We have performed Photoelectron Spectroscopy and X-Ray Absorption Spectroscopy upon highly radioactive samples of Plutonium at the Advanced Light Source in Berkeley, CA, USA. First results from alpha and delta Plutonium are reported as well as plans for future studies of actinide studies.

  2. Extended x-ray absorption fine structure in photoelectron emission

    SciTech Connect

    Rothberg, G.M.; Choudhary, K.M.; denBoer, M.L.; Williams, G.P.; Hecht, M.H.; Lindau, I.

    1984-09-17

    We report the first definitive measurements of extended x-ray absorption fine structure (EXAFS) made by monitoring the direct photoelectron emission as a function of photon energy. We have measured EXAFS associated with the Mn 3p and F 2s core levels in evaporated films of MnF/sub 2/ and found good agreement with bulk transmission EXAFS associated with the Mn 1s level. Photoelectron EXAFS makes possible surface-sensitive structural determinations using vacuum uv radiation on a virtually unlimited range of systems.

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

    SciTech Connect

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

    2013-07-15

    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.

  4. Correlation of magnetic dichroism in x-ray absorption and photoelectron emission using ultrathin magnetic alloy films

    SciTech Connect

    Tobin, J.G.; Goodman, K.W.; Mankey, G.J.; Willis, R.F.; Denlinger, J.D.; Rotenberg, E.; Warwick, A.

    1996-04-01

    We have begun a program to characterize magnetic alloy overlays using both magnetic x-ray circular dichroism (MXCD) and magnetic x-ray linear dichroism (MXLD). This will allow a direct comparison of MXCD-absorption and MXLD-photoelectron emission. First results from the Advanced Light Source will be presented.

  5. Electronic structure of fluorinated multiwalled carbon nanotubes studied using x-ray absorption and photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Brzhezinskaya, M. M.; Muradyan, V. E.; Vinogradov, N. A.; Preobrajenski, A. B.; Gudat, W.; Vinogradov, A. S.

    2009-04-01

    This paper presents the results of combined investigation of the chemical bond formation in fluorinated multiwalled carbon nanotubes (MWCNTs) with different fluorine contents (10-55wt%) and reference compounds (highly oriented pyrolytic graphite crystals and “white” graphite fluoride) using x-ray absorption and photoelectron spectroscopy at C1s and F1s thresholds. Measurements were performed at BESSY II (Berlin, Germany) and MAX-laboratory (Lund, Sweden). The analysis of the soft x-ray absorption and photoelectron spectra points to the formation of covalent chemical bonding between fluorine and carbon atoms in the fluorinated nanotubes. It was established that within the probing depth (˜15nm) of carbon nanotubes, the process of fluorination runs uniformly and does not depend on the fluorine concentration. In this case, fluorine atoms interact with MWCNTs through the covalent attachment of fluorine atoms to graphene layers of the graphite skeleton (phase 1) and this bonding is accompanied by a change in the hybridization of the 2s and 2p valence electron states of the carbon atom from the trigonal (sp2) to tetrahedral (sp3) hybridization and by a large electron transfer between carbon an fluorine atoms. In the MWCNT near-surface region the second fluorine-carbon phase with weak electron transfer is formed; it is located mainly within two or three upper graphene monolayers, and its contribution becomes much poorer as the probing depth of fluorinated multiwalled carbon nanotubes (F-MWCNTs) increases. The defluorination process of F-MWCNTs on thermal annealing has been investigated. The conclusion has been made that F-MWCNT defluorination without destruction of graphene layers is possible.

  6. 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.

  7. Hard X-ray photoelectron and X-ray absorption spectroscopy characterization of oxidized surfaces of iron sulfides

    NASA Astrophysics Data System (ADS)

    Mikhlin, Yuri; Tomashevich, Yevgeny; Vorobyev, Sergey; Saikova, Svetlana; Romanchenko, Alexander; Félix, Roberto

    2016-11-01

    Hard X-ray photoelectron spectroscopy (HAXPES) using an excitation energy range of 2 keV to 6 keV in combination with Fe K- and S K-edge XANES, measured simultaneously in total electron (TEY) and partial fluorescence yield (PFY) modes, have been applied to study near-surface regions of natural polycrystalline pyrite FeS2 and pyrrhotite Fe1-xS before and after etching treatments in an acidic ferric chloride solution. It was found that the following near-surface regions are formed owing to the preferential release of iron from oxidized metal sulfide lattices: (i) a thin, no more than 1-4 nm in depth, outer layer containing polysulfide species, (ii) a layer exhibiting less pronounced stoichiometry deviations and low, if any, concentrations of polysulfide, the composition and dimensions of which vary for pyrite and pyrrhotite and depend on the chemical treatment, and (iii) an extended almost stoichiometric underlayer yielding modified TEY XANES spectra, probably, due to a higher content of defects. We suggest that the extended layered structure should heavily affect the near-surface electronic properties, and processes involving the surface and interfacial charge transfer.

  8. 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.

  9. 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.

  10. X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure study of water adsorption on pyridine-terminated thiolate self-assembled monolayers.

    PubMed

    Zubavichus, Yan; Zharnikov, Michael; Yang, Yongjie; Fuchs, Oliver; Umbach, Eberhard; Heske, Clemens; Ulman, Abraham; Grunze, Michael

    2004-12-07

    Adsorption of water on self-assembled monolayers (SAMs) of 4-(4-mercaptophenyl)pyridine on gold at low temperatures under ultrahigh vacuum conditions is studied by synchrotron radiation X-ray photoelectron and absorption spectroscopy. Water adsorption induces a strong modification of the chemical state of the pyridine N atoms at the SAM/ice interface, indicative for strong H bonding and partial proton transfer between water molecules and pyridine moieties. Additionally, the initial molecular orientation within the SAM is changed upon formation of an adsorbed water multilayer.

  11. X-ray absorption and photoelectron spectroscopy studies on graphite and single-walled carbon nanotubes: Oxygen effect

    NASA Astrophysics Data System (ADS)

    Abbas, M.; Wu, Z. Y.; Zhong, J.; Ibrahim, K.; Fiori, A.; Orlanducci, S.; Sessa, V.; Terranova, M. L.; Davoli, Ivan

    2005-08-01

    We have investigated the electronic states of highly oriented pyrolitic graphite and single-walled carbon nanotubes using x-ray absorption spectroscopy (XAS) before and after annealing treatment in ultrahigh vacuum, and observed that the small peak between π* and σ* features, which has been previously assigned to free-electron-like interlayer states, disappears after in situ annealing treatment, suggesting that the signal may be assigned to a surface contamination, especially oxygen contamination introduced by chemical processing or gas adsorption. Additional experiments by photoelectron spectroscopy as well as XAS methods, performed after aging in air, fully support this interpretation.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  13. 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 (SiO2) 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 (Si2O), +2 (SiO) and +3 (Si2O3), 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

  14. Effect of gamma irradiation on X-ray absorption and photoelectron spectroscopy of Nd-doped phosphate glass.

    PubMed

    Rai, V N; Rajput, Parasmani; Jha, S N; Bhattacharyya, D; Raja Shekhar, B N; Deshpande, U P; Shripathi, T

    2016-11-01

    X-ray absorption near-edge structure (XANES) and X-ray photoelectron spectroscopy (XPS) of Nd-doped phosphate glasses have been studied before and after gamma irradiation. The intensity and the location of the white line peak of the L3-edge XANES of Nd are found to be dependent on the ratio O/Nd in the glass matrix. Gamma irradiation changes the elemental concentration of atoms in the glass matrix, which affects the peak intensity of the white line due to changes in the covalence of the chemical bonds with Nd atoms in the glass (structural changes). Sharpening of the Nd 3d5/2 peak profile in XPS spectra indicates a deficiency of oxygen in the glasses after gamma irradiation, which is supported by energy-dispersive X-ray spectroscopy measurements. The ratio of non-bridging oxygen to total oxygen in the glass after gamma radiation has been found to be correlated to the concentration of defects in the glass samples, which are responsible for its radiation resistance as well as for its coloration.

  15. Electronic structure of Fe2P(10 1 bar 0) studied by soft X-ray photoelectron spectroscopy and X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Sugizaki, Y.; Motoyama, H.; Edamoto, K.; Ozawa, K.

    2017-10-01

    The electronic structure of Fe2P(10 1 bar 0) has been investigated by photoelectron spectroscopy (PES) and X-ray absorption spectroscopy (XAS). The surface prepared by cycles of Ar+ ion sputtering and annealing at 500-800 °C showed a c(2 × 2) low-energy electron diffraction (LEED) pattern. An Fe 3d-P 3p hybrid band (main band) and a satellite were observed at 0-4 eV and 5-8 eV, respectively, in PES spectra of c(2 × 2) Fe2P(10 1 bar 0). The main band showed a clear cut-off at the Fermi edge, indicating the metallic nature of Fe2P. The satellite intensity showed a resonant maximum around the Fe 3p threshold, suggesting that the satellite is caused through a shake-up process. Three types of surface-shifted components were found in P 2p PES spectra. All the P 2p peaks have symmetric line shapes, while the Fe 2p PES and Fe L-edge XAS spectra have asymmetric line shapes, suggesting that the electronic states around the Fermi level are mostly composed of Fe 3d components. These results suggest that the stabilization of the electronic structure at metal sites through the bonding with P atoms is ineffective on Fe2P(10 1 bar 0), as in the case of Fe2P(0001).

  16. X-ray absorption and photoelectron spectroscopic study of plasma-nitrided SiO{sub 2} film

    SciTech Connect

    Song, H.J.; Shin, H.J.; Chung, Youngsu; Lee, J.C.; Lee, M.K.

    2005-06-01

    Plasma-nitrided SiO{sub 2} thin film has been analyzed by synchrotron-radiation-based x-ray absorption and photoelectron spectroscopies (XAS and XPS). High-resolution N 1s XAS and N 1s, O 1s, and Si 2p XPS spectral changes were obtained for different annealing temperatures. N 1s XPS and XAS spectra show that at room temperature, besides the main species of N[Si(O-){sub 3-x}]{sub 3}, there exist free moleculelike N{sub 2} and HN[Si(O-){sub 3}]{sub 2}, H{sub 2}NSi(O-){sub 3}, and N-Si{sub 2}O species with surface contaminants. The spectral intensities of the N{sub 2} and the HN[Si(O-){sub 3}]{sub 2}, H{sub 2}NSi(O-){sub 3}, and N-Si{sub 2}O species decrease as the annealing temperature increases, and finally the nitrogen exists dominantly in the form of N[Si(O){sub 3}]{sub 3} species above 820 K, indicating out-diffusion of molecular N{sub 2} and structural reconstruction to form a stable structure upon annealing. The Si 2p and O 1s XPS spectra show that Si{sup >4+} 2p peak and O 1s peak appear at 103.7 and 534.0 eV, respectively, which are higher binding energies than those of thermally grown oxynitride films with lower coverage on silicon. Upon annealing the sample, these peaks shift towards lower binding energy; {approx}0.3 eV for Si{sup >4+} and 0.4 eV for O 1s. The causes of the peaks appearance at relatively higher binding energy and the peak shift upon annealing are discussed.

  17. X-ray Absorption Spectroscopy

    SciTech Connect

    Yano, Junko; Yachandra, Vittal K.

    2009-07-09

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

  18. Electronic structure of nickel porphyrin NiP: Study by X-ray photoelectron and absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Svirskiy, G. I.; Sergeeva, N. N.; Krasnikov, S. A.; Vinogradov, N. A.; Sergeeva, Yu. N.; Cafolla, A. A.; Preobrajenski, A. B.; Vinogradov, A. S.

    2017-02-01

    Energy distributions and properties of the occupied and empty electronic states for a planar complex of nickel porphyrin NiP are studied by X-ray photoemission and absorption spectroscopy techniques. As a result of the analysis of the experimental spectra of valence photoemission, the nature and energy positions of the highest occupied electronic states were determined: the highest occupied state is formed mostly by atomic states of the porphine ligand; the following two states are associated with 3 d states of the nickel atom. It was found that the lowest empty state is specific and is described by the σ-type b 1 g MO formed by empty Ni3{d_{{x^2} - {y^2}}}-states and occupied 2 p-states of lone electron pairs of nitrogen atoms. This specific nature of the lowest empty state is a consequence of the donor-acceptor chemical bond in NiP.

  19. State of Co and Mn in Half-Metallic Ferromagnet Co2MnSi Explored by Magnetic Circular Dichroism in Hard X-Ray Photoelectron Emission and Soft X-Ray Absorption Spectroscopies

    NASA Astrophysics Data System (ADS)

    Fecher, Gerhard H.; Ebke, Daniel; Ouardi, Siham; Agrestini, Stefano; Kuo, Chang-Yang; Hollmann, Nils; Hu, Zhiwei; Gloskovskii, Andrei; Yakhou, Flora; Brookes, Nicholas B.; Felser, Claudia

    2014-01-01

    The half-metallic Heusler compound Co2MnSi is a very attractive material for spintronic devices because it exhibits very high tunnelling magnetoresistance ratios. This work reports on a spectroscopic investigation of thin Co2MnSi films as they are used as electrodes in magnetic tunnel junctions. The investigated films exhibit a remanent in-plane magnetization with a magnetic moment of about 5 μB when saturated, as expected. The low coercive field of only 4 mT indicates soft magnetic behavior. Magnetic dichroism in emission and absorption was measured at the Co and Mn 2p core levels. The photoelectron spectra were excited by circularly polarized hard X-rays with an energy of 6 keV and taken from the remanently magnetized film. The soft X-ray absorption spectra were taken in an induction field of 4 T. Both methods yielded large dichroism effects. An analysis reveals the localized character of the electrons and magnetic moments attributed to the Mn atoms, whereas the electrons related to the Co atoms contribute an itinerant part to the total magnetic moment.

  20. Atomic Layer Deposition of Hafnium(IV) Oxide on Graphene Oxide: Probing Interfacial Chemistry and Nucleation by using X-ray Absorption and Photoelectron Spectroscopies.

    PubMed

    Alivio, Theodore E G; De Jesus, Luis R; Dennis, Robert V; Jia, Ye; Jaye, Cherno; Fischer, Daniel A; Singisetti, Uttam; Banerjee, Sarbajit

    2015-07-27

    Interfacing graphene with metal oxides is of considerable technological importance for modulating carrier density through electrostatic gating as well as for the design of earth-abundant electrocatalysts. Herein, we probe the early stages of the atomic layer deposition (ALD) of HfO2 on graphene oxide using a combination of C and O K-edge near-edge X-ray absorption fine structure spectroscopies and X-ray photoelectron spectroscopy. Dosing with water is observed to promote defunctionalization of graphene oxide as a result of the reaction between water and hydroxyl/epoxide species, which yields carbonyl groups that further react with migratory epoxide species to release CO2 . The carboxylates formed by the reaction of carbonyl and epoxide species facilitate binding of Hf precursors to graphene oxide surfaces. The ALD process is accompanied by recovery of the π-conjugated framework of graphene. The delineation of binding modes provides a means to rationally assemble 2D heterostructures. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. An X-ray photoelectron spectroscopy study of the atomization of Mo from pyrolytic graphite platforms in Electrothermal Atomic Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ruiz, Frine; Benzo, Zully; Garaboto, Angel; León, Vladimir; Ruette, Fernando; Albornoz, Alberto; Brito, Joaquín L.

    2017-07-01

    X-ray photoelectron spectroscopy (XPS) was employed as the analytical tool for the identification of the solid state species formed during the atomization of molybdenum on a pyrolytic graphite surface used for electrothermal atomization in atomic absorption spectroscopy (ETAAS). As XPS is capable of probing the amounts of materials employed in actual ETAAS measurements, it was anticipated that it would allow obtaining more realistic results than those reported in previous works by means of techniques such as X-ray diffraction, which requires thousand-fold amounts of the analyte. The results obtained by XPS showed a distribution pattern of the oxidation states of Mo on the graphite surface as a function of the temperatures reached at each stage of the ETAAS procedure, which was correlated with the possible species formed during the drying, ashing and atomization steps. In light of the present results, a previously proposed atomization mechanism for Mo was revisited, which allowed to disprove the alleged presence of phases such as Mo4O11 at the ashing stage and of metallic Mo as a stable, intermediate phase during the Mo2C low temperature carbide formation at 1200-1900 °C. It is concluded that the XPS technique allows gaining an insight into the atomization mechanism of the analyte.

  2. Layered structure of the near-surface region of oxidized chalcopyrite (CuFeS2): hard X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and DFT+U studies.

    PubMed

    Mikhlin, Yuri; Nasluzov, Vladimir; Romanchenko, Alexander; Tomashevich, Yevgeny; Shor, Alexey; Félix, Roberto

    2017-01-25

    The depletion of oxidized metal sulfide surfaces in metals due to the preferential release of cations is a common, but as yet poorly understood phenomenon. Herein, X-ray photoelectron spectroscopy using excitation energies from 1.25 keV to 6 keV, and Fe K- and S K-edge X-ray absorption near-edge spectra in total electron and partial fluorescence yield modes was employed to study natural chalcopyrite oxidized in air and etched in an acidic ferric sulfate solution. The metal-depleted undersurface formed was found to consist of a thin, 1-4 nm, outer layer containing polysulfide species, a layer with a pronounced deficiency of metals, mainly iron, and an abundant disulfide content but negligible polysulfide content (about 20 nm thick after the chemical etching), and a defective underlayer which extended down to about a hundred nm. DFT+U was used to simulate chalcopyrite with increasing numbers of removed Fe atoms. It was found that the structure with disulfide anion near double Fe vacancies, and the 'defective' structure comprising Cu in the position of Fe and Cu vacancy are most energetically favorable, especially when using a higher Hubbard-type parameter U, and have a large density of states at the Fermi level, whereas polysulfide anions are stable only near the surface. We propose a mechanism explaining the formation of the layered undersurface and 'passivation' of metal sulfides by (i) arrested decomposition of a nearly stoichiometric sulfide surface, and (ii) faster interfacial transfer and solid diffusion of cations towards the surface; (iii) stability limits for specific defect structures, promoting their expansion in depth rather than through compositional changes, excluding surface layers; (iv) decay of surface polysulfide layer yielding elemental sulfur.

  3. Multimode Surface Functional Group Determination: Combining Steady-State and Time-Resolved Fluorescence with X-ray Photoelectron Spectroscopy and Absorption Measurements for Absolute Quantification.

    PubMed

    Fischer, Tobias; Dietrich, Paul M; Unger, Wolfgang E S; Rurack, Knut

    2016-01-19

    The quantitative determination of surface functional groups is approached in a straightforward laboratory-based method with high reliability. The application of a multimode BODIPY-type fluorescence, photometry, and X-ray photoelectron spectroscopy (XPS) label allows estimation of the labeling ratio, i.e., the ratio of functional groups carrying a label after reaction, from the elemental ratios of nitrogen and fluorine. The amount of label on the surface is quantified with UV/vis spectrophotometry based on the molar absorption coefficient as molecular property. The investigated surfaces with varying density are prepared by codeposition of 3-(aminopropyl)triethoxysilane (APTES) and cyanoethyltriethoxysilane (CETES) from vapor. These surfaces show high functional group densities that result in significant fluorescence quenching of surface-bound labels. Since alternative quantification of the label on the surface is available through XPS and photometry, a novel method to quantitatively account for fluorescence quenching based on fluorescence lifetime (τ) measurements is shown. Due to the complex distribution of τ on high-density surfaces, the stretched exponential (or Kohlrausch) function is required to determine representative mean lifetimes. The approach is extended to a commercial Rhodamine B isothiocyanate (RITC) label, clearly revealing the problems that arise from such charged labels used in conjunction with silane surfaces.

  4. Optimization of the X-ray incidence angle in photoelectron spectrometers.

    PubMed

    Strocov, Vladimir N

    2013-07-01

    The interplay between the angle-dependent X-ray reflectivity, X-ray absorption and the photoelectron attenuation length in the photoelectron emission process determines the optimal X-ray incidence angle that maximizes the photoelectron signal. Calculations in the wide VUV to the hard X-ray energy range show that the optimal angle becomes more grazing with increasing energy, from a few tens of degrees at 50 eV to about one degree at 3.5 keV. This is accompanied by an intensity gain of a few tens of times, as long as the X-ray footprint on the sample stays within the analyzer field of view. This trend is fairly material-independent. The obtained results bear immediate implications for the design of (synchrotron-based) photoelectron spectrometers.

  5. Optimization of the X-ray incidence angle in photoelectron spectrometers

    PubMed Central

    Strocov, Vladimir N.

    2013-01-01

    The interplay between the angle-dependent X-ray reflectivity, X-ray absorption and the photoelectron attenuation length in the photoelectron emission process determines the optimal X-ray incidence angle that maximizes the photoelectron signal. Calculations in the wide VUV to the hard X-ray energy range show that the optimal angle becomes more grazing with increasing energy, from a few tens of degrees at 50 eV to about one degree at 3.5 keV. This is accompanied by an intensity gain of a few tens of times, as long as the X-ray footprint on the sample stays within the analyzer field of view. This trend is fairly material-independent. The obtained results bear immediate implications for the design of (synchrotron-based) photoelectron spectrometers. PMID:23765292

  6. X-ray Photoelectron Spectroscopy Database (Version 4.1)

    National Institute of Standards and Technology Data Gateway

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

  7. Recent applications of hard x-ray photoelectron spectroscopy

    SciTech Connect

    Weiland, Conan; Woicik, Joseph C.; Rumaiz, Abdul K.; Pianetta, Piero

    2016-05-15

    Recent applications of hard x-ray photoelectron spectroscopy (HAXPES) demonstrate its many capabilities in addition to several of its limitations. Examples are given, including measurement of buried interfaces and materials under in situ or in operando conditions, as well as measurements under x-ray standing-wave and resonant excitation. Physical considerations that differentiate HAXPES from photoemission measurements utilizing soft x-ray and ultraviolet photon sources are also presented.

  8. Recent applications of hard x-ray photoelectron spectroscopy

    DOE PAGES

    Weiland, Conan; Rumaiz, Abdul K.; Pianetta, Piero; ...

    2016-05-05

    Recent applications of hard x-ray photoelectron spectroscopy (HAXPES) demonstrate its many capabilities in addition to several of its limitations. Examples are given, including measurement of buried interfaces and materials under in-situ or in-operando conditions, as well as measurements under x-ray standing-wave and resonant excitation. We also present physical considerations that differentiate HAXPES from photoemission measurements utilizing soft and ultraviolet x rays.

  9. Fixed energy X-ray absorption voltammetry.

    PubMed

    Minguzzi, Alessandro; Lugaresi, Ottavio; Locatelli, Cristina; Rondinini, Sandra; D'Acapito, Francesco; Achilli, Elisabetta; Ghigna, Paolo

    2013-08-06

    In this paper, the fixed energy X-ray absorption voltammetry (FEXRAV) is introduced. FEXRAV represents a novel in situ X-ray absorption technique for fast and easy preliminary characterization of electrode materials and consists of recording the absorption coefficient at a fixed energy while varying at will the electrode potential. The energy is chosen close to an X-ray absorption edge, in order to give the maximum contrast between different oxidation states of an element. It follows that any shift from the original oxidation state determines a variation of the absorption coefficient. Although the information given by FEXRAV obviously does not supply the detailed information of X-ray absorption near edge structure (XANES) or extended X-ray absorption fine structure (EXAFS), it allows to quickly map the oxidation states of the element under consideration within the selected potential windows. This leads to the rapid screening of several systems under different experimental conditions (e.g., nature of the electrolyte, potential window) and is preliminary to more deep X-ray absorption spectroscopy (XAS) characterizations, like XANES or EXAFS. In addition, the time-length of the experiment is much shorter than a series of XAS spectra and opens the door to kinetic analysis.

  10. Beyond hard x-ray photoelectron spectroscopy: Simultaneous combination with x-ray diffraction

    SciTech Connect

    Rubio-Zuazo, Juan; Castro, German R.

    2013-05-15

    Hard x-ray photoelectron spectroscopy (HAXPES) is a powerful and novel emerging technique for the nondestructive determination of electronic properties and chemical composition of bulk, buried interfaces and surfaces. It benefits from the exceptionally large escape depth of high kinetic energy photoelectrons, increasing the information depth up to several tens of nanometers. Complementing HAXPES with an atomic structure sensitive technique (such as x-ray diffraction) opens a new research field with major applications for materials science. At SpLine, the Spanish CRG beamline at the European Synchrotron Radiation Facility, we have developed a novel experimental set-up that combines HAXPES and x-ray diffraction (x-ray reflectivity, surface x-ray diffraction, grazing incidence x-ray diffraction, and reciprocal space maps). Both techniques can be operated simultaneously on the same sample and using the same excitation source. The set-up includes a robust 2S + 3D diffractometer hosting a ultrahigh vacuum chamber equipped with a unique photoelectron spectrometer (few eV < electron kinetic energy < 15 keV), x-ray tube (Mg/Ti), 15 keV electron gun, and auxiliary standard surface facilities (molecular beam epitaxy evaporator, ion gun, low energy electron diffraction, sample heating/cooling system, leak valves, load-lock sample transfer, etc.). This end-station offers the unique possibility of performing simultaneous HAXPES + x-ray diffraction studies. In the present work, we describe the experimental set-up together with two experimental examples that emphasize its outstanding capabilities: (i) nondestructive characterization of the Si/Ge and HfO{sub 2}/SiO{sub 2} interfaces on Ge-based CMOS devices, and (ii) strain study on La{sub 0.7}Ca{sub 0.3}MnO{sub 3} ultrathin films grown on SrTiO{sub 3}(001) substrate.

  11. Adsorption and stability of malonic acid on rutile TiO2 (110), studied by near edge X-ray absorption fine structure and photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Syres, Karen L.; Thomas, Andrew G.; Graham, Darren M.; Spencer, Ben F.; Flavell, Wendy R.; Jackman, Mark J.; Dhanak, Vinod R.

    2014-08-01

    The adsorption of malonic acid on rutile TiO2 (110) has been studied using photoelectron spectroscopy and C K-edge, near edge X-ray fine structure spectroscopy (NEXAFS). Analysis of the O 1s and Ti 2p spectra suggest that the molecule adsorbs dissociatively in a doubly-bidentate adsorption geometry as malonate. The data are unable to distinguish between a chelating bonding mode with the backbone of the molecule lying along the [001] azimuth or a bridging geometry along the direction. Work carried out on a wiggler beamline suggests that the molecule is unstable under irradiation by high-flux synchrotron radiation from this type of insertion device.

  12. X-ray photoelectron spectroscopy under real ambient pressure conditions

    NASA Astrophysics Data System (ADS)

    Takagi, Yasumasa; Nakamura, Takahiro; Yu, Liwei; Chaveanghong, Suwilai; Sekizawa, Oki; Sakata, Tomohiro; Uruga, Tomoya; Tada, Mizuki; Iwasawa, Yasuhiro; Yokoyama, Toshihiko

    2017-07-01

    We have developed an ambient pressure hard-X-ray photoelectron spectroscopic system equipped with a differential pumping system at BL36XU of SPring-8. Photoelectron spectra from a Au(111) surface were recorded using excitation light of 8 keV focused to 20 × 20 µm2 and adopting an aperture diameter of 30 µm at the entrance of the electron lens and a working distance of 60 µm. The Au 4f and 3d5/2 spectra were measured by increasing the ambient pressure from 1 Pa to atmospheric pressure and demonstrated that the instrument is capable of measuring the photoelectron spectrum under atmospheric pressure.

  13. Hard x-ray photoelectron spectroscopy and x-ray standing waves

    NASA Astrophysics Data System (ADS)

    Lee, Tien-Lin

    2006-03-01

    Using the brilliant undulator radiation available from the third generation synchrotron sources, hard x-ray photoelectron spectroscopy (HAXPES) has become an emerging field in the recent years. With the excitation energy used in HAXPES one can benefits from the large mean free path of fast electrons (˜ 5 nm for electrons of 6 keV kinetic energy) in probing the bulk electronic properties of materials. For high-resolution studies, photon energy bandwidth narrower than 100 meV is also readily achievable in the hard x-ray range with crystal monochromators. In addition, working with hard x-ray offers the possibility for combining photoelectron spectroscopy with x-ray standing wave (XSW) method. With the high spatial resolution from XSWs, this unique combination can provide site-specific, chemical and electronic information for studying surfaces, buried interfaces, thin films and bulk crystals. In this talk, I will briefly mention some HAXPES experiments detecting electrons up to 14.5 keV [1,2]. I will then sketch the principle of combining XSWs with HAXPES and present results from some recent applications using this combination: (1) chemical state-specific surface structure determination with core-level photoemission, (2) site-specific valence x-ray photoelectron spectroscopy and (3) XSW imaging with core-level photoemission. [1] S. Thiess, C. Kunz, B.C.C. Cowie, T.-L. Lee, M. Renier, and J. Zegenhagen. Solid State Communications 132, 589 (2004) [2] C. Kunz, S. Thiess, B.C.C. Cowie, T.-L. Lee, and J. Zegenhagen, Nuclear Instruments and Methods A 547, 73 (2005).

  14. Interpretation of nanoparticle X-ray photoelectron intensities

    SciTech Connect

    Werner, Wolfgang S. M. Chudzicki, Maksymillian; Smekal, Werner; Powell, Cedric J.

    2014-06-16

    X-ray photoelectron (XPS) intensities have been simulated for spherical core-shell nanoparticles (NPs) in different geometrical arrangements in order to investigate the validity of commonly made assumptions for the interpretation of XPS NP intensities. The single-sphere approximation is valid for a powder sample when all spatial coordinates of the NP positions are uncorrelated. Correlations along either the depth coordinate or the lateral coordinates lead to features in the angular distribution that provide information on these correlations. The XPS intensity is proportional to the surface-to-volume ratio of nanoparticles but only for NP sizes exceeding the inelastic mean free path of the photoelectrons.

  15. Probing deeper by hard x-ray photoelectron spectroscopy

    SciTech Connect

    Risterucci, P.; Renault, O. Martinez, E.; Delaye, V.; Detlefs, B.; Zegenhagen, J.; Gaumer, C.; Grenet, G.; Tougaard, S.

    2014-02-03

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

  16. Electronic structure of self-doped layered Eu3F4Bi2S4 material revealed by x-ray absorption spectroscopy and photoelectron spectromicroscopy

    NASA Astrophysics Data System (ADS)

    Paris, E.; Sugimoto, T.; Wakita, T.; Barinov, A.; Terashima, K.; Kandyba, V.; Proux, O.; Kajitani, J.; Higashinaka, R.; Matsuda, T. D.; Aoki, Y.; Yokoya, T.; Mizokawa, T.; Saini, N. L.

    2017-01-01

    We have studied the electronic structure of Eu3F4Bi2S4 using a combination of Eu L3-edge x-ray absorption spectroscopy (XAS) and space-resolved angle-resolved photoemission spectroscopy (ARPES). From the Eu L3-edge XAS, we have found that the Eu in this system is in mixed valence state with coexistence of Eu2 +/Eu3 + . The bulk charge doping was estimated to be ˜0.3 per Bi site in Eu3F4Bi2S4 , which corresponds to the nominal x in a typical REO1 -xFxBiS2 system (RE: rare-earth elements). From the space-resolved ARPES, we have ruled out the possibility of any microscale phase separation of Eu valence in the system. Using a microfocused beam we have observed the band structure as well as the Fermi surface that appeared similar to other compounds of this family with disconnected rectangular electronlike pockets around the X point. The Luttinger volume analysis gives the effective carrier to be 0.23 electrons per Bi site in Eu3F4Bi2S4 , indicating that the system is likely to be in the underdoped region of its superconducting phase diagram.

  17. Effect of X-ray flux on polytetrafluoroethylene in X-ray photoelectron spectroscopy

    NASA Technical Reports Server (NTRS)

    Wheeler, D. R.; Pepper, S. V.

    1982-01-01

    The effect of the X-ray flux in X-ray photoelectron spectroscopy (STAT) on the constitution of the polytetrafluoroethylene (PTFE) surface has been examined. The radiation dose rate for our specimen was about 10 to the 7th rad/s. The structure, magnitude and binding energy of the C(1s) and F(1s) features of the XPS spectrum and the mass spectrum of gaseous species evolved during irradiation are observed. The strong time dependence of these signals over a period of several hours indicated that the surface constitution of PTFE is greatly affected by this level of radiation dose. The results are consistent with the development of a heavily cross-linked or branched structure in the PTFE surface region and the evolution of short chain fragments into the gas phase.

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

    PubMed

    Ptasińska, Sylwia; Stypczyńska, Agnieszka; Nixon, Tony; Mason, Nigel J; Klyachko, Dimitri V; Sanche, Léon

    2008-08-14

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

  19. Effect of X-ray flux on polytetrafluoroethylene in X-ray photoelectron spectroscopy

    NASA Technical Reports Server (NTRS)

    Wheeler, D. R.; Pepper, S. V.

    1982-01-01

    The effect of the X-ray flux in X-ray photoelectron spectroscopy (STAT) on the constitution of the polytetrafluoroethylene (PTFE) surface has been examined. The radiation dose rate for our specimen was about 10 to the 7th rad/s. The structure, magnitude and binding energy of the C(1s) and F(1s) features of the XPS spectrum and the mass spectrum of gaseous species evolved during irradiation are observed. The strong time dependence of these signals over a period of several hours indicated that the surface constitution of PTFE is greatly affected by this level of radiation dose. The results are consistent with the development of a heavily cross-linked or branched structure in the PTFE surface region and the evolution of short chain fragments into the gas phase.

  20. X-ray photoelectron spectroscopy in the hard x-ray regime

    NASA Astrophysics Data System (ADS)

    Fadley, Charles S.

    2006-03-01

    Photoelectron spectroscopy is by now a very widely used tool for the study of atoms, molecules, solids, surfaces, and nanoscale structures. Until very recently, the exciting radiation has been limited to the energy range below about 2 keV. However, within the past few years, a few experimental projects have been initiated in which photon energies in the 5-15 keV range are employed. By matching the characteristics of undulator beamlines at third-generation synchrotron radiation sources to the optical properties of the electron spectrometer, it has proven possible to overcome the reduced photoelectric cross sections at such high energies and to study both core and valence electronic levels with resolutions down to ca. 50 meV [1]. Such hard x-ray photoelectron spectroscopy (HXPS or HAXPES) has the advantage of being more bulk sensitive, with electron inelastic attenuation lengths in the 50-150 Angstrom range. In this talk, I will discuss the advantages and disadvantages of this new direction, including highlights from recent work, as well as suggested future avenues for HXPS studies. [1] Nuclear Instruments and Methods A 547, 24 (2005), special issue dedicated to hard x-ray photoelectron spectroscopy, edited by J. Zegenhagen and C. Kunz.

  1. X-ray Photoelectron Spectroscopy of Isolated Nanoparticles.

    PubMed

    Sublemontier, Olivier; Nicolas, Christophe; Aureau, Damien; Patanen, Minna; Kintz, Harold; Liu, Xiaojing; Gaveau, Marc-André; Le Garrec, Jean-Luc; Robert, Emmanuel; Barreda, Flory-Anne; Etcheberry, Arnaud; Reynaud, Cécile; Mitchell, James B; Miron, Catalin

    2014-10-02

    X-ray photoelectron spectroscopy (XPS) is a very efficient and still progressing surface analysis technique. However, when applied to nano-objects, this technique faces drawbacks due to interactions with the substrate and sample charging effects. We present a new experimental approach to XPS based on coupling soft X-ray synchrotron radiation with an in-vacuum beam of free nanoparticles, focused by an aerodynamic lens system. The structure of the Si/SiO2 interface was probed without any substrate interaction or charging effects for silicon nanocrystals previously oxidized in ambient air. Complete characterization of the surface was obtained. The Si 2p core level spectrum reveals a nonabrupt interface.

  2. 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.

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

    SciTech Connect

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

    2006-09-25

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

  4. Effects of rare-earth substitution in the oxyarsenides REFeAsO (RE=Ce, Pr, Nd, Sm, Gd) and CeNiAsO by X-ray photoelectron and absorption spectroscopy

    SciTech Connect

    Blanchard, Peter E.R.; Cavell, Ronald G.; Mar, Arthur

    2010-08-16

    X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES) have been applied to examine the electronic structure of the rare-earth transition-metal oxyarsenides REFeAsO (RE=Ce, Pr, Nd, Sm, Gd) and CeNiAsO. Within the metal-arsenic layer [MAs], the bonding character is predominantly covalent and the As atoms are anionic, as implied by the small energy shifts in the M 2p and As 3d XPS spectra. Within the rare-earth-oxygen layer [REO], the bonding character is predominantly ionic, as implied by the similarity of the O 1s binding energies to those in highly ionic oxides. Substitution with a smaller RE element increases the O 1s binding energy, a result of an enhanced Madelung potential. The Ce 3d XPS and Ce L{sub 3}-edge XANES spectra have lineshapes and energies that confirm the presence of trivalent cerium in CeFeAsO and CeNiAsO. A population analysis of the valence band spectrum of CeNiAsO supports the formal charge assignment [Ce{sup 3+}O{sup 2-}][Ni{sup 2+}As{sup 3-}].

  5. Study Of Soot Growth And Nucleation By A Time-Resolved Synchrotron Radiation Based X-Ray Absorption Method

    DTIC Science & Technology

    2001-07-05

    soot density structure in a heavily sooting flame using x-ray absorption and photoelectron detection and (c) determine the influence of enhanced...particle photoemission yields (b) map out the soot density structure in a heavily sooting flame using x-ray absorption and photoelectron detection and

  6. X-ray photoelectron spectra of iron-sulphur proteins.

    PubMed Central

    Andrews, P T; Johnson, C E; Wallbank, B; Cammack, R; Hall, D O; Rao, K K

    1975-01-01

    The X-ray photoelectron spectra of the 2p, 3s and 3p levels of iron in oxidized Clostridium pasteurianum ferredoxin indicate that the eight iron atoms in the molecule are indistinguishable. Their magnetic state is indicated both by core polarization splitting of the 3s electrons, and by "shake-up' satellites on the 2p lines. Similar satellites are observed in the 2p lines of reduced Chromatium high-potential iron-sulphur proteins and oxidized spinach ferredoxin, indicating that there too the iron atoms are magnetic. The low observed magnetic susceptibility of these proteins is therefore due to spin-coupling between the iron atoms in the active centre. PMID:1180907

  7. 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 ~106 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 >107 laser pulses, we also presentmore » 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

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

    PubMed Central

    Miaja-Avila, L.; O'Neil, G. C.; Uhlig, J.; Cromer, C. L.; Dowell, M. L.; Jimenez, R.; Hoover, A. S.; Silverman, K. L.; Ullom, J. N.

    2015-01-01

    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 ∼106 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 >107 laser pulses, we 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. PMID:26798792

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

    PubMed

    Miaja-Avila, L; O'Neil, G C; Uhlig, J; Cromer, C L; Dowell, M L; Jimenez, R; Hoover, A S; Silverman, K L; Ullom, J N

    2015-03-01

    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, we 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.

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

    SciTech Connect

    Miaja-Avila, L.; O'Neil, G. C.; Uhlig, J.; Cromer, C. L.; Dowell, M. L.; Jimenez, R.; Hoover, A. S.; Silverman, K. L.; Ullom, J. N.

    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 ~106 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 >107 laser pulses, we 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.

  11. X-ray photoelectron spectra of MgH2

    NASA Astrophysics Data System (ADS)

    He, Z. X.; Pong, W.

    1990-06-01

    Measurements of X-ray photoemission from magnesium hydride MgH2 were made in an effort to further the fundamental understanding of the electronic structure of this metal hydride. The polycrystalline MgH2 was compressed onto a metal holder to provide a smooth solid surface in a dry nitrogen box and then transferred into a ESCA system without exposure to air. Measurements were made immediately after the surface was scrapped in the vacuum. The binding energies of the photoelectrons from Mg 2s and 2p states were found to be 88.9 ± 0.2eV, and 50.1 ± 0.2eV, respectively. The valence band spectrum shows an effective base width of approximately 8.8eV, which is in reasonable agreement with the recent band structure calculation for MgH2. The photoelectron spectra also display features that can be identified as volume plasmon energy loss of 14.6 ± 0.2eV. The data can be shown to be useful in calculating the average band gap energy (5.80eV) for MgH2.

  12. Theoretical Model For Photoelectron Transport In X-Ray Lithography Systems

    NASA Astrophysics Data System (ADS)

    Garth, J. C.

    1983-11-01

    We have developed a theoretical model for calculating the dose received by a resist behind an x-ray absorbing mask in an x-ray lithography system. The model enables the dose-depth profile due to photoelectrons entering the resist from the mask to be predicted as a function of x-ray target material, excitation voltage, mask material and thickness, and chemical composition of the resist. As an application, we have calculated the dose profile in the resist PBS next to a Au mask irradiated by x-rays from Ag and Al targets operated at 10 kilovolt beam voltage. The characteristic line and continuum spectrum from the targets are computed, the absorption by the Au mask obtained, and an approximate photoelectron and Auger electron spectrum in the gold and PBS is evaluated. The dose-depth curve next to the gold-resist interface is found using the analytic electron transport model developed by Burke and Garth (1979). The calculations show that the dose profiles obtained using bremsstrahlung-produced electrons extend deeper than profiles than are computed from characteristic photon radiation alone. At 10 kV, this effect is found to be much greater for Ag than for Al.

  13. Effects of Galactic absorption on soft X-ray surveys

    NASA Technical Reports Server (NTRS)

    Zamorani, G.; Gioia, I. M.; Maccacaro, T.; Wolter, A.

    1988-01-01

    A bias in the spectral distribution of X-ray sources detected in X-ray surveys is discussed which is due to the combination of the intrinsic characteristics of X-ray telescopes and the effects of low-energy photoelectric absorption within the Galaxy. A statistical method for obtaining information on the average spectrum of X-ray sources detected in well-defined surveys is presented. This method can be applied to surveys performed with X-ray telescopes working at relatively soft X-ray energies, such as Einstein, Exosat, and Rosat.

  14. X-ray photoelectron and X-ray Auger electron spectroscopy studies of heavy ion irradiated C 60 films

    NASA Astrophysics Data System (ADS)

    Kumar, Amit; Singh, F.; Govind; Shivaprasad, S. M.; Avasthi, D. K.; Pivin, J. C.

    2008-09-01

    The influence of 200 MeV Au ion irradiation on the surface properties of polycrystalline fullerene films has been investigated. The X-ray photoelectron and X-ray Auger electron spectroscopies are employed to study the ion-induced modification of the fullerene, near the surface region. The shift of C 1s core level and decrease in intensity of shake-up satellite were used to investigate the structural changes (like sp 2 to sp 3 conversion) and reduction of π electrons, respectively, under heavy ion irradiation. Further, X-ray Auger electron spectroscopy was employed to investigate hybridization conversion qualitatively as a function of ion fluence.

  15. Adsorption state and morphology of anthraquinone-2-carboxylic acid deposited from solution onto the atomically-smooth native oxide surface of Al(111) films studied by infrared reflection absorption spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy.

    PubMed

    Higo, Morihide; Miake, Takeshi; Mitsushio, Masaru; Yoshidome, Toshifumi; Ozono, Yoshihisa

    2008-03-01

    The adsorption state and morphology of anthraquinone-2-carboxylic acid (AQ-2-COOH) deposited from acetone solutions (0.02 - 1.00 mg ml(-1)) onto atomically-smooth native oxide surfaces of Al(111) films were investigated by infrared reflection absorption spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The atomically-smooth oxide surfaces were prepared by vacuum evaporation of Al on mica substrates at 350 degrees C, followed by oxidation in an oxygen-dc glow discharge at room temperature. It was found that AQ-2-COOH is adsorbed on the film surfaces in both the neutral and ionized state, where the amount of the neutral molecules increases with increasing concentration. This molecule is adsorbed as both a uniform nanometer-scale film, and as micrometer-sized particles with heights ranging from 10 to 200 nm above the film surface. The volumes of the particles of deposited AQ-2-COOH increased with increasing concentration. It is concluded that the particles are microcrystallites of neutral AQ-2-COOH and that the thin uniform film results from AQ-2-COOH anion formation on the film surfaces. A comparison of the results obtained by use of these surface analytical techniques clearly shows the features and advantages of these tools.

  16. X-ray absorption measurement by scanning capacitance microscopy

    NASA Astrophysics Data System (ADS)

    Ishii, Masashi; Uchihashi, Takayuki

    2003-12-01

    This paper describes a demonstration of scanning capacitance microscopy (SCM) as a technique for measuring X-ray absorption fine structure (XAFS) in what is called the SCM-XAFS method. This method achieves the simultaneous analysis of the electrical and chemical characteristics of surface-trapping centers. In obtaining the XAFS spectrum of trapping centers, the method takes advantage of the fact that the X-ray-induced photoemission of a localized electron leads to a change in capacitance. When the Fermi level corresponds to the trapping level, the photoemission process is sensitively detected. Therefore, a specific trapping center may be selectively observed by controlling the bias. From SCM-XAFS measurements of a GaAs surface, we found that gallium oxide trapping centers capture electrons in the positive bias voltage region. Moreover, experimental findings that resonant intra-transition and resonant scattering of emitted photoelectrons enhance the SCM-XAFS signal at particular X-ray photon energy reveal the local density of states of the gallium oxide and the complex structure of the trapping centers.

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

    SciTech Connect

    Hamad, Kimberly Sue

    2000-01-01

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

  18. Corrosion and degradation studies utilizing X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Hixson, Holly Gwyndolen

    1997-08-01

    This dissertation involves studies of corrosion behavior at the surface of various metal samples, as well as the degradation of wool fibers obtained from the Star-Spangled Banner. Molybdenum metal and iron-zinc alloys were examined under corrosive conditions, and the degradation of the wool fibers was studied. The behavior of a polished molybdenum metal surface upon exposure to both aerated and deaerated water and 1.0 M NaCl solution was studied by X-ray Photoelectron Spectroscopy (XPS). Exposure to deaerated water and NaCl failed to produce oxidation of the metal surfaces, but exposing the polished metal surface to aerated water produced significant oxidation. Metal surfaces cleaned by argon-ion etching were found to be inert to oxidation by aerated water. The etching process also appears to passivate the metal surface. The behavior of molybdenum metal in 0.5 M Hsb2SOsb4 treated at various potentials has been studied using core and valence band XPS. The study indicates that Mosp{IV} and Mosp{VI} (including possibly Mosp{V} in some cases) were formed as the potential of the system was increased within the active range of molybdenum. The corrosive behavior of iron-zinc alloys that have been electroplated on plain steel in both aerated and deaerated quadruply-distilled water has been studied using XPS. Several different iron-zinc alloys were electroplated for comparative purposes: an iron-rich alloy, a zinc-rich alloy, and an alloy of similar iron and zinc composition. Treatment in aerated water produces oxidation for the iron-rich and similar composition alloys, but the oxide is reduced for the zinc-rich alloy. Degradation of the fibers in the original Star-Spangled Banner has been monitored using XPS and Scanning Electron Microscopy (SEM). Comparison of white and red wool fibers and linen fibers from the flag with new, mechanically-abraded, and chemically-treated white, red, and linen fibers, respectively, was performed in an attempt to determine the fibers' levels

  19. Temperature dependent soft x-ray absorption spectroscopy of liquids

    NASA Astrophysics Data System (ADS)

    Meibohm, Jan; Schreck, Simon; Wernet, Philippe

    2014-10-01

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

  20. Temperature dependent soft x-ray absorption spectroscopy of liquids.

    PubMed

    Meibohm, Jan; Schreck, Simon; Wernet, Philippe

    2014-10-01

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

  1. X-ray Photoelectron Spectroscopy (XPS), Rutherford Back Scattering (RBS) studies

    NASA Technical Reports Server (NTRS)

    Neely, W. C.; Bozak, M. J.; Williams, J. R.

    1993-01-01

    X-ray photoelectron spectroscopy (XPS), Rutherford Back Scattering (RBS) studies of each of sample received were completed. Since low angle X-ray could not be performed because of instrumentation problems, Auger spectrometry was employed instead. The results of these measurements for each of the samples is discussed in turn.

  2. Photoelectron dynamics in x-ray free-electron-laser diffractive imaging of biological samples.

    PubMed

    Hau-Riege, Stefan P

    2012-06-08

    X-ray free electron lasers hold the promise of enabling atomic-resolution diffractive imaging of single biological molecules. We develop a hybrid continuum-particle model to describe the x-ray induced damage and find that the photoelectron dynamics and electrostatic confinement strongly affect the time scale of the damage processes. These phenomena are not fully captured in hydrodynamic modeling approaches.

  3. Evaluating Superconducting YBCO Film Properties Using X-Ray Photoelectron Spectroscopy (Postprint)

    DTIC Science & Technology

    2012-02-01

    AFRL-RZ-WP-TP-2012-0093 EVALUATING SUPERCONDUCTING YBCO FILM PROPERTIES USING X-RAY PHOTOELECTRON SPECTROSCOPY (POSTPRINT) Paul N. Barnes...2012 Conference Paper Postprint 01 January 2002 – 01 January 2004 4. TITLE AND SUBTITLE EVALUATING SUPERCONDUCTING YBCO FILM PROPERTIES USING X-RAY

  4. Synchrotron x-ray fluorescence and extended x-ray absorption fine structure analysis

    SciTech Connect

    Chen, J.R.; Gordon, B.M.; Hanson, A.L.; Jones, K.W.; Kraner, H.W.; Chao, E.C.T.; Minkin, J.A.

    1984-01-01

    The advent of dedicated synchrotron radiation sources has led to a significant increase in activity in many areas of science dealing with the interaction of x-rays with matter. Synchrotron radiation provides intense, linearly polarized, naturally collimated, continuously tunable photon beams, which are used to determine not only the elemental composition of a complex, polyatomic, dilute material but also the chemical form of the elements with improved accuracy. Examples of the application of synchrotron radiation include experiments in synchrotron x-ray fluorescence (SXRF) analysis and extended x-ray absorption fine structure (EXAFS) analysis. New synchrotron radiation x-ray microprobes for elemental analysis in the parts per billion range are under construction at several laboratories. 76 references, 24 figures.

  5. Photoelectron range limitations to the spatial resolution for x-rays in gas proportional chambers

    SciTech Connect

    Smith, G.C.; Fischer, J.; Radeka, V.

    1983-11-01

    Measurements have been made, for x-ray energies from a few keV to 18 keV, of the limiting spatial resolution caused by the finite range of the photoelectron, or electrons, created when an x-ray is absorbed in the gas of a proportional chamber. In hydrocarbon gases such as methane and ethane, where the photoelectron receives the bulk of the x-ray energy, the limiting spatial resolution is found to vary as a power law of x-ray energy. In argon and xenon, at an x-ray energy approximately twice that of the A/sub K/ edge and the Xe/sub L/ edge respectively, the measured limiting resolution is better than expected from an equivalent power law behavior.

  6. Soft X-ray Absorption Edges in LMXBs

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The XMM observation of LMC X-2 is part of our program to study X-ray absorption in the interstellar medium (ISM). This program includes a variety of bright X-ray binaries in the Galaxy as well as the Magellanic Clouds (LMC and SMC). LMC X-2 is located near the heart of the LMC. Its very soft X-ray spectrum is used to determine abundance and ionization fractions of neutral and lowly ionized oxygen of the ISM in the LMC. The RGS spectrum so far allowed us to determine the O-edge value to be for atomic O, the EW of O-I in the ls-2p resonance absorption line, and the same for O-II. The current study is still ongoing in conjunction with other low absorption sources like Sco X-1 and the recently observed X-ray binary 4U 1957+11.

  7. Combined surface plasmon resonance and X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Garcia, Miguel Angel; Serrano, Aida; Rodriguez de La Fuente, Oscar; Castro, German R.

    2012-02-01

    We present a system for the excitation and measurement of surface plasmons in metallic films based on the Kretschmann-Raether configuration that can be installed in a synchrotron beamline. The device was mounted an tested in a hard X-ray Absorption beamline, BM25 Spline at ESRF. Whit this device it is possible to carry on experiments combining surface plasmon and X-ray absorption spectroscopies. The surface plasmons can be use to monitor in situ changes induced by the X-rays in the metallic films or the dielectric overlayer. Similarly, the changes in the electronic configuration of the material when surface plasmons are excited can be measured by X-ray absorption spectroscopy. The resolution of the system allows to observe changes in the signals of the order of 10-3 to 10-5 depending on the particular experiment and used configuration. The system is available for experiments at the beamline.

  8. X-ray diffraction and X-ray K-absorption studies of copper doped complex

    NASA Astrophysics Data System (ADS)

    Sharma, P. K.; Mishra, Ashutosh; Kame, Rashmi; Malviya, Varsha; Malviya, P. K.

    2017-05-01

    Sample of Ni1-xCuxFe2O4where (x=0.05, 0.10, 0.15) has been prepared by root equation method. X-ray diffraction and K-absorption fine structural measurements have been carried out. The sample structure has been found to be cubic. X-ray diffraction measurements have been used to determine particle size and lattice parameter. EXAFS spectra has been recorded at 2.5Gev Indus -2 Synchrotron radiation source at RRCAT, Indore, India. EXAFS data have been analysed by computer software Athena.

  9. Femtosecond x-ray photoelectron diffraction on gas-phase dibromobenzene molecules

    NASA Astrophysics Data System (ADS)

    Rolles, D.; Boll, R.; Adolph, M.; Aquila, A.; Bostedt, C.; Bozek, J. D.; Chapman, H. N.; Coffee, R.; Coppola, N.; Decleva, P.; Delmas, T.; Epp, S. W.; Erk, B.; Filsinger, F.; Foucar, L.; Gumprecht, L.; Hömke, A.; Gorkhover, T.; Holmegaard, L.; Johnsson, P.; Kaiser, Ch; Krasniqi, F.; Kühnel, K.-U.; Maurer, J.; Messerschmidt, M.; Moshammer, R.; Quevedo, W.; Rajkovic, I.; Rouzée, A.; Rudek, B.; Schlichting, I.; Schmidt, C.; Schorb, S.; Schröter, C. D.; Schulz, J.; Stapelfeldt, H.; Stener, M.; Stern, S.; Techert, S.; Thøgersen, J.; Vrakking, M. J. J.; Rudenko, A.; Küpper, J.; Ullrich, J.

    2014-06-01

    We present time-resolved femtosecond photoelectron momentum images and angular distributions of dissociating, laser-aligned 1,4-dibromobenzene (C6H4Br2) molecules measured in a near-infrared pump, soft-x-ray probe experiment performed at an x-ray free-electron laser. The observed alignment dependence of the bromine 2p photoelectron angular distributions is compared to density functional theory calculations and interpreted in terms of photoelectron diffraction. While no clear time-dependent effects are observed in the angular distribution of the Br(2p) photoelectrons, other, low-energy electrons show a pronounced dependence on the time delay between the near-infrared laser and the x-ray pulse.

  10. X-ray absorption fine structure measurement with a 9 V electric battery x-ray emitter

    SciTech Connect

    Mitsuya, Shota; Ishii, Hideshi; Kawai, Jun; Tanaka, Keiichi

    2006-09-25

    X-ray absorption spectral analysis is a well known technique for analyzing the chemical environment of an element in a specimen. It has been believed that high intensity and monochromatized x rays such as the synchrotron radiation are required for an x-ray absorption experiment. In the present study, however, we demonstrate that the x-ray absorption spectral measurement of transition metal foils with an energy resolution of 10 eV is possible with a combination of a 9 V dry electric battery pyroelectric x-ray generator and a superconducting microcalorimeter.

  11. An X-ray diffraction and X-ray absorption spectroscopy joint study of neuroglobin.

    PubMed

    Arcovito, Alessandro; Moschetti, Tommaso; D'Angelo, Paola; Mancini, Giordano; Vallone, Beatrice; Brunori, Maurizio; Della Longa, Stefano

    2008-07-01

    Neuroglobin (Ngb) is a member of the globin family expressed in the vertebrate brain, involved in neuroprotection. A combined approach of X-ray diffraction (XRD) on single crystal and X-ray absorption spectroscopy (XAS) in solution, allows to determine the oxidation state and the structure of the Fe-heme both in the bis-histidine and the CO-bound (NgbCO) states. The overall data demonstrate that under X-ray the iron is photoreduced fairly rapidly, and that the previously reported X-ray structure of ferric Ngb [B. Vallone, K. Nienhaus, M. Brunori, G.U. Nienhaus, Proteins 56 (2004) 85-92] very likely refers to a photoreduced species indistinguishable from the dithionite reduced protein. Results from the XAS analysis of NgbCO in solution are in good agreement with XRD data on the crystal. However prolonged X-ray exposure at 15K determines CO release. This preliminary result paves the way to experiments aimed at the characterization of pentacoordinate ferrous Ngb, the only species competent in binding external ligands such as O2, CO or NO.

  12. X-ray photoelectron spectroscopy peak assignment for perfluoropolyether oils

    NASA Technical Reports Server (NTRS)

    Mori, Shigeyuki; Morales, Wilfredo

    1990-01-01

    Perfluoroalkylpolyether (PFPE) oils are increasingly being used as vacuum pump oils and as lubricants for magnetic recording media and instrumentation for satellites. In this paper, the relative binding energies of three PFPE oils are determined. When sample oils are continuously irradiated during X-ray spectroscopy (XPS) measurements, the relative peak intensity of the spectra is altered significantly, indicating that gaseous products form from the oils during XPS measurements. Thus, attention should be paid to chemical changes when XPE is used to characterize fluorinated carbons such as PFPE oils.

  13. TU-A-9A-07: X-Ray Acoustic Computed Tomography (XACT): 100% Sensitivity to X-Ray Absorption

    SciTech Connect

    Xiang, L; Ahmad, M; Nikoozadeh, A; Pratx, G; Khuri-Yakub, B; Xing, L

    2014-06-15

    Purpose: To assess whether X-ray acoustic computed tomography (XACT) is more sensitive to X-ray absorption than that of the conventional X-ray imaging. Methods: First, a theoretical model was built to analyze the X-ray absorption sensitivity of XACT imaging and conventional X-ray imaging. Second, an XACT imaging system was developed to evaluate the X-ray induced acoustic signal generation as well as the sensitivity improvement over transmission x-ray imaging. Ultra-short x-ray pulses (60-nanosecond) were generated from an X-ray source operated at the energy of 150 kVp with a 10-Hz repetition rate. The X-ray pulse was synchronized with the acoustic detection via a x-ray scintillation triggering to acquire the X-ray induced acoustic signal. Results: Theoretical analysis shows that X-ray induced acoustic signal is sensitive only to the X-ray absorption, while completely insensitive to out the X-ray scattering and fluorescence. XACT has reduced background and increased contrast-to-noise ratio, and therefore has increased sensitivity compared to transmission x-ray imaging. For a 50-μm size, gadolinium insertion in tissue exposed to 40 keV X-rays; the sensitivity of XACT imaging is about 28.9 times higher than that of conventional X-ray imaging. Conclusion: X-ray acoustic computer tomography (XACT) as a new imaging modality combines X-ray absorption contrast and high ultrasonic resolution in a single modality. It is feasible to improve the imaging sensitivity with XACT imaging compared with conventional X-ray imaging. Taking advantage of the high ultrasonic resolution, it is possible to perform 3-D imaging with a single x-ray pulse with arrays of transducers without any mechanical motion of the imaging system. This single-shot capability offers the potential of reducing radiation dose by a factor of 1000, and imaging 100 times faster when compared to the conventional X-ray CT, and thus revolutionizing x-ray imaging applications in medicine and biology. The authors

  14. 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.

  15. Polytetrafluoroethylene transfer film studied with X-ray photoelectron spectroscopy

    NASA Technical Reports Server (NTRS)

    Wheeler, D. R.

    1980-01-01

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

  16. Probing hot-electron effects in wide area plasmonic surfaces using X-ray photoelectron spectroscopy

    SciTech Connect

    Ayas, Sencer; Cupallari, Andi; Dana, Aykutlu

    2014-12-01

    Plasmon enhanced hot carrier formation in metallic nanostructures increasingly attracts attention due to potential applications in photodetection, photocatalysis, and solar energy conversion. Here, hot-electron effects in nanoscale metal-insulator-metal (MIM) structures are investigated using a non-contact X-ray photoelectron spectroscopy based technique using continuous wave X-ray and laser excitations. The effects are observed through shifts of the binding energy of the top metal layer upon excitation with lasers of 445, 532, and 650 nm wavelength. The shifts are polarization dependent for plasmonic MIM grating structures fabricated by electron beam lithography. Wide area plasmonic MIM surfaces fabricated using a lithography free route by the dewetting of evaporated Ag on HfO{sub 2} exhibit polarization independent optical absorption and surface photovoltage. Using a simple model and making several assumptions about the magnitude of the photoemission current, the responsivity and external quantum efficiency of wide area plasmonic MIM surfaces are estimated as 500 nA/W and 11 × 10{sup −6} for 445 nm illumination.

  17. Magnetic x-ray linear dichroism in the photoelectron spectroscopy of ultrathin magnetic alloy films

    NASA Astrophysics Data System (ADS)

    Tobin, J. G.; Goodman, K. W.; Mankey, G. J.; Willis, R. F.; Denlinger, J. D.; Rotenberg, E.; Warwick, A.

    1996-04-01

    The magnetic structure of nanoscale alloy films has been probed using the magnetic x-ray linear dichroism in photoelectron spectroscopy. FeNi and CoFe epitaxial films were grown on Cu(001), in situ and using molecular beam epitaxy techniques. The magnetic x-ray linear dichroism measurements were made at the Spectromicroscopy Facility of the Third Generation Advanced Light Source. Because soft x-rays were used to generate photoemission from the 3p core levels, both elemental selectivity and magnetic sensitivity were achieved simultaneously.

  18. 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

  19. X-Ray Weak Broad-Line Quasars: Absorption or Intrinsic X-Ray Weakness

    NASA Technical Reports Server (NTRS)

    Risaliti, Guido; Mushotzky, Richard F. (Technical Monitor)

    2004-01-01

    XMM observations of X-ray weak quasars have been performed during 2003. The data for all but the last observation are now available (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 these data, and obtained interesting preliminary scientific results. Out of the eight sources, 4 are confirmed to be extrimely X-ray weak, in agreement with the results of previous Chandra observations. 3 sources are confirmed to be highly variable both in flux (by factors 20-50) and in spectral properties (dramatic changes in spectral index). For both these groups of objects, an article is in preparation. Preliminary results have been presented at an international workshop on AGN surveys in December 2003, in Cozumel (Mexico). 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 will be performed in early 2004, and will complement the XMM data, in order to understand whether the X-ray weakness of these sources is an intrinsic property or is due to absorption by circumnuclear material.

  20. X-Ray Weak Broad-Line Quasars: Absorption or Intrinsic X-Ray Weakness

    NASA Technical Reports Server (NTRS)

    Risaliti, Guido; Mushotzky, Richard F. (Technical Monitor)

    2004-01-01

    XMM observations of X-ray weak quasars have been performed during 2003. The data for all but the last observation are now available (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 these data, and obtained interesting preliminary scientific results. Out of the eight sources, 4 are confirmed to be extrimely X-ray weak, in agreement with the results of previous Chandra observations. 3 sources are confirmed to be highly variable both in flux (by factors 20-50) and in spectral properties (dramatic changes in spectral index). For both these groups of objects, an article is in preparation. Preliminary results have been presented at an international workshop on AGN surveys in December 2003, in Cozumel (Mexico). 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 will be performed in early 2004, and will complement the XMM data, in order to understand whether the X-ray weakness of these sources is an intrinsic property or is due to absorption by circumnuclear material.

  1. Hard x-ray photoelectron spectroscopy of chalcopyrite solar cell components

    NASA Astrophysics Data System (ADS)

    Gloskovskii, A.; Jenkins, C. A.; Ouardi, S.; Balke, B.; Fecher, G. H.; Dai, X.-F.; Gruhn, T.; Johnson, B.; Lauermann, I.; Caballero, R.; Kaufmann, C. A.; Felser, C.

    2012-02-01

    Hard x-ray photoelectron spectroscopy is used to examine the partial density of states of Cu(In,Ga)Se2 (CIGSe), a semiconducting component of solar cells. The investigated, thin Cu(In,Ga)Se2 films were produced by multi-stage co-evaporation. Details of the measured core level and valence band spectra are compared to the calculated density of states. The semiconducting type electronic structure of Cu(In,Ga)Se2 is clearly resolved in the hard x-ray photoelectron spectra.

  2. Coherence based contrast enhancement in x-ray radiography with a photoelectron microscope

    NASA Astrophysics Data System (ADS)

    Hwu, Y.; Lai, B.; Mancini, D. C.; Je, J. H.; Noh, D. Y.; Bertolo, M.; Tromba, G.; Margaritondo, G.

    1999-10-01

    We show that a photoelectron spectromicroscope of the photoelectron emission microscope type can be used as an x-ray imaging detector for radiology. Using high penetration hard-x-ray photons (wavelength <0.1 nm), samples as thick as a few millimeters can be imaged with submicron resolution. The high imaging resolution enables us to substantially decrease the object-detector distance needed to observe coherent based contrast enhancement with respect to the standard film-based detection technique. Our result implies several advantages, the most important being a marked reduction of the required source emittance for contrast enhanced radiology.

  3. The Effect of X-Ray Absorption Fine Structure in Soft X-ray Astronomical Telescopes

    NASA Astrophysics Data System (ADS)

    Owens, Alan; Denby, Michael; Wells, Alan; Keay, Adam; Graessle, Dale E.; Blake, Richard L.

    1997-02-01

    Recent in-orbit measurements by high resolution soft X-ray telescopes have revealed low-level fine structure in target spectra that cannot be attributed to a celestial source. Ultimately, this can be traced to the ability of the new high spectral resolution silicon detectors to resolve X-ray absorption fine structure (XAFS) produced in the various detection subsystems. Based on measurements taken at the Daresbury Synchrotron Radiation Source (SRS) and the National Synchrotron Light Source (NSLS), we have modeled the full-up response function of the Joint European X-ray Telescope (JET-X), taking into account edge structure generated in the detectors, filters, and mirrors. It is found that unfolding celestial source spectra using a response function in which the detailed edge shapes are calculated from standard absorption cross sections leads to the generation of spectral artifacts at every absorption edge. These in turn produce unacceptably high values of χ2 in model fits for total source fluxes above ~4 × 104 counts. For JET-X, this corresponds to a source strength of ~0.4 millicrab observed for 105 s. Statistically significant ``linelike'' features are introduced into the derived source spectra with amplitudes as great as 10% of the source flux. For JET-X, these features rise above the 3 σ level for integral source exposures above ~5 × 104 source counts. The largest deviations in the residuals arise near 0.5 keV and 2.2 keV and are attributed to XAFS produced in the oxide surface layers of the CCD and the gold reflective surface of the mirrors, respectively. These results are significant for data interpretation tasks with the ASCA, JET-X, XMM, and Advanced X-Ray Astrophysics Facility (AXAF) telescopes.

  4. Diamond Photodetectors for X-Ray Absorption Spectroscopy Applications

    NASA Astrophysics Data System (ADS)

    Pace, Emanuele; De Sio, Antonio; Pan, Zhiyun; Wu, Ziyu; Marcelli, Augusto

    2010-06-01

    Synchrotron radiation (SR) is a fundamental tool for X-ray research. In particular, X-ray absorption spectroscopy (XAS) accesses information as electronic properties, local structure or chemical-physical state in condensed-matter studies. Ionization chambers (ICs) are the most widely used XAS detectors for transmission measurements because of their reliability, high linearity and good stability. Recently, solid-state detectors have been considered and Si p-i-n has been applied to high fluxes (1011 ph/s), where the linearity of ICs is no longer guaranteed. Silicon photodiodes exhibit an extremely linear response in at least 5 decades but show diffraction peaks. Diamond is an ideal substrate to produce radiation-hard, low dark current (<1 pA/cm2), visible-blind and fast-response X-ray detectors with a high S/N ratio. Diamond detectors were tested as SR monitor capable to withstand the high photon flux density of the 3rd generation SR sources. Being the lowest X-ray-absorbing solid-state dielectric material, diamond maximizes the flux through thin self-standing devices with minimal spectral effect down to the soft x-ray range. We will present results of X-ray tests of photoconductors based on different diamond substrates. The results will be compared to standard ICs for XAS applications in terms of spectral quality, noise and linearity in the 4-13 keV energy range.

  5. High ionisation absorption in low mass X-ray binaries

    NASA Astrophysics Data System (ADS)

    Ponti, G.; Bianchi, S.; Muñoz-Darias, T.; De, K.; Fender, R.; Merloni, A.

    2016-05-01

    The advent of the new generation of X-ray telescopes yielded a significant step forward in our understanding of ionised absorption generated in the accretion discs of X-ray binaries. It has become evident that these relatively weak and narrow absorption features, sporadically present in the X-ray spectra of some systems, are actually the signature of equatorial outflows, which might carry away more matter than that being accreted. Therefore, they play a major role in the accretion phenomenon. These outflows (or ionised atmospheres) are ubiquitous during the softer states but absent during the power-law dominated, hard states, suggesting a strong link with the state of the inner accretion disc, presence of the radio-jet and the properties of the central source. Here, we discuss the current understanding of this field.

  6. Total reflection X-ray photoelectron spectroscopy as a semiconductor lubricant elemental analysis method

    NASA Astrophysics Data System (ADS)

    Alshehabi, Abbas; Sasaki, Nobuharu; Kawai, Jun

    2015-12-01

    Photoelectron spectra from a typical hard disk storage media device (HDD) were measured at total reflection and non-total reflection at unburnished, acetone-cleaned, and argon-sputtered conditions. F, O, N, and C usually making the upper layer of a typical hard disk medium were detected. Enhancement of the photoelectron emission of the fluorocarbon lubricant was observed at total reflection. Pt and Co were only found by non-total X-ray photoelectron spectroscopy (XPS) because they are constituents of a deeper region than the top and interface regions. Argon-sputtered, ultrasonic acetone-cleaned, and unburnished top layers were compared at total and non-total reflection conditions. Total reflection X-ray photoelectron spectroscopy (TRXPS) is demonstrated to be a powerful tool for storage media lubrication layer chemical state analysis, reliable for industrial quality control application , and reproducible.

  7. Ultrafast absorption of intense x rays by nitrogen molecules

    SciTech Connect

    Buth, Christian; Liu Jicai; Chen, Mau Hsiung; Cryan, James P.; Fang Li; Hoener, Matthias; Berrah, Nora; Glownia, James M.; Coffee, Ryan N.

    2012-06-07

    We devise a theoretical description for the response of nitrogen molecules (N{sub 2}) to ultrashort and intense x rays from the free electron laser Linac Coherent Light Source (LCLS). We set out from a rate-equation description for the x-ray absorption by a nitrogen atom. The equations are formulated using all one-x-ray-photon absorption cross sections and the Auger and radiative decay widths of multiply-ionized nitrogen atoms. Cross sections are obtained with a one-electron theory and decay widths are determined from ab initio computations using the Dirac-Hartree-Slater (DHS) method. We also calculate all binding and transition energies of nitrogen atoms in all charge states with the DHS method as the difference of two self-consistent field (SCF) calculations ({Delta}SCF method). To describe the interaction with N{sub 2}, a detailed investigation of intense x-ray-induced ionization and molecular fragmentation are carried out. As a figure of merit, we calculate ion yields and the average charge state measured in recent experiments at the LCLS. We use a series of phenomenological models of increasing sophistication to unravel the mechanisms of the interaction of x rays with N{sub 2}: a single atom, a symmetric-sharing model, and a fragmentation-matrix model are developed. The role of the formation and decay of single and double core holes, the metastable states of N{sub 2}{sup 2+}, and molecular fragmentation are explained.

  8. In situ soft X-ray absorption spectroscopy of flames

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  9. X-ray photoelectron spectroscopy studies of the sodium chloride surface after laser exposure

    NASA Astrophysics Data System (ADS)

    Savintsev, A. P.; Gavasheli, Yu O.; Kalazhokov, Z. Kh; Kalazhokov, Kh Kh

    2016-11-01

    The surface of NaCl crystals outside and in the crater was examined using an x-ray photoelectron spectrometer. The comparative analysis of the XPS spectra showed that high- intensity laser irradiation has a significant impact on the state and composition of the surface of the ionic crystal.

  10. X-ray photoelectron spectroscopy for characterization of wood surfaces in adhesion studies

    Treesearch

    James F. Beecher; Charles R. Frihart

    2005-01-01

    X-ray photoelectron spectroscopy (XPS) is one of a set of tools that have been used to characterize wood surfaces. Among the advantages of XPS are surface sensitivity, identification of nearly all elements, and frequently, discrimination of bonding states. For these reasons, XPS seemed to be an appropriate tool to help explain the differences in bond strength under wet...

  11. Determining the Uncertainty of X-Ray Absorption Measurements

    PubMed Central

    Wojcik, Gary S.

    2004-01-01

    X-ray absorption (or more properly, x-ray attenuation) techniques have been applied to study the moisture movement in and moisture content of materials like cement paste, mortar, and wood. An increase in the number of x-ray counts with time at a location in a specimen may indicate a decrease in moisture content. The uncertainty of measurements from an x-ray absorption system, which must be known to properly interpret the data, is often assumed to be the square root of the number of counts, as in a Poisson process. No detailed studies have heretofore been conducted to determine the uncertainty of x-ray absorption measurements or the effect of averaging data on the uncertainty. In this study, the Poisson estimate was found to adequately approximate normalized root mean square errors (a measure of uncertainty) of counts for point measurements and profile measurements of water specimens. The Poisson estimate, however, was not reliable in approximating the magnitude of the uncertainty when averaging data from paste and mortar specimens. Changes in uncertainty from differing averaging procedures were well-approximated by a Poisson process. The normalized root mean square errors decreased when the x-ray source intensity, integration time, collimator size, and number of scanning repetitions increased. Uncertainties in mean paste and mortar count profiles were kept below 2 % by averaging vertical profiles at horizontal spacings of 1 mm or larger with counts per point above 4000. Maximum normalized root mean square errors did not exceed 10 % in any of the tests conducted. PMID:27366627

  12. Correlation of X-Ray Absorption Parameters with Schultz index

    NASA Astrophysics Data System (ADS)

    Kekre, Pravin A.; Khatri, Sunil; Mishra, A.; Joshi, K. P.

    2012-05-01

    A novel application of topological Index in estimating some X-ray parameters is described. X-Ray Absorption parameters (Chemical Shift and Effective Charge) are correlated with Schultz index. Some Cobalt (II) complexes were used to establish this type of correlation. The result have indicated that the chemical shift and effective charge are sensitive to the topological structure of coordinating ligand moieties. The topological understanding of molecular properties can lead to the development of new areas of present and future interest. i.e. designing of new drugs, tracking the effects of pollutants in environment and the prediction of carcinogenicity of a molecule.

  13. Simultaneous surface plasmon resonance and x-ray absorption spectroscopy

    SciTech Connect

    Serrano, A.; Rodriguez de la Fuente, O.; Collado, V.; Rubio-Zuazo, J.; Castro, G. R.; Monton, C.; Garcia, M. A.

    2012-08-15

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

  14. Determination of total x-ray absorption coefficient using non-resonant x-ray emission.

    PubMed

    Achkar, A J; Regier, T Z; Monkman, E J; Shen, K M; Hawthorn, D G

    2011-01-01

    An alternative measure of x-ray absorption spectroscopy (XAS) called inverse partial fluorescence yield (IPFY) has recently been developed that is both bulk sensitive and free of saturation effects. Here we show that the angle dependence of IPFY can provide a measure directly proportional to the total x-ray absorption coefficient, µ(E). In contrast, fluorescence yield (FY) and electron yield (EY) spectra are offset and/or distorted from µ(E) by an unknown and difficult to measure amount. Moreover, our measurement can determine µ(E) in absolute units with no free parameters by scaling to µ(E) at the non-resonant emission energy. We demonstrate this technique with measurements on NiO and NdGaO(3). Determining µ(E) across edge-steps enables the use of XAS as a non-destructive measure of material composition. In NdGaO(3), we also demonstrate the utility of IPFY for insulating samples, where neither EY or FY provide reliable spectra due to sample charging and self-absorption effects, respectively.

  15. Determination of total x-ray absorption coefficient using non-resonant x-ray emission

    PubMed Central

    Achkar, A. J.; Regier, T. Z.; Monkman, E. J.; Shen, K. M.; Hawthorn, D. G.

    2011-01-01

    An alternative measure of x-ray absorption spectroscopy (XAS) called inverse partial fluorescence yield (IPFY) has recently been developed that is both bulk sensitive and free of saturation effects. Here we show that the angle dependence of IPFY can provide a measure directly proportional to the total x-ray absorption coefficient, µ(E). In contrast, fluorescence yield (FY) and electron yield (EY) spectra are offset and/or distorted from µ(E) by an unknown and difficult to measure amount. Moreover, our measurement can determine µ(E) in absolute units with no free parameters by scaling to µ(E) at the non-resonant emission energy. We demonstrate this technique with measurements on NiO and NdGaO3. Determining µ(E) across edge-steps enables the use of XAS as a non-destructive measure of material composition. In NdGaO3, we also demonstrate the utility of IPFY for insulating samples, where neither EY or FY provide reliable spectra due to sample charging and self-absorption effects, respectively. PMID:22355697

  16. An XPS (X-Ray Photoelectron Spectroscopy) Study of the Composition of Thin Polyimide Films Formed by Vapor Deposition.

    DTIC Science & Technology

    1987-07-15

    Deposition, volycrystalline ? Silver, 0xidianiline (ODA), Benzenetetracarboxylic anhydride (PMDA), .- imidization, polymer , in situ, X-ray Photoelectron...imidization reaction leading to polymer formation was followed in situ with X-ray Photoelectron Spectroscopy. The uncertainties inherent in a...is an important polymer for application in solid state electronic technology because of its favorable dielectric properties and high thermal

  17. A method for normalization of X-ray absorption spectra

    SciTech Connect

    Weng, T.-C.; Waldo, G.S.; Penner-Hahn, J.E.

    2010-07-20

    Accurate normalization of X-ray absorption data is essential for quantitative analysis of near-edge features. A method, implemented as the program MBACK, to normalize X-ray absorption data to tabulated mass absorption coefficients is described. Comparison of conventional normalization methods with MBACK demonstrates that the new normalization method is not sensitive to the shape of the background function, thus allowing accurate comparison of data collected in transmission mode with data collected using fluorescence ion chambers or solid-state fluorescence detectors. The new method is shown to have better reliability and consistency and smaller errors than conventional normalization methods. The sensitivity of the new normalization method is illustrated by analysis of data collected during an equilibrium titration.

  18. Linear dimerized Se chains in cancrinite nanochannels: X-ray diffraction and photoelectron spectra

    NASA Astrophysics Data System (ADS)

    Poborchii, V. V.; Sato, M.; Shchukarev, A. V.

    1997-09-01

    Cancrinite crystals containing adsorbed selenium in 1-dimensional nanochannels (Can-Se) have been examined by X-ray diffraction, X-ray photoelectron spectroscopy and polarized infrared spectroscopy. It is found that adsorbed selenium forms Se 22- anions substituting OH - groups inside channels. Se 22- dimers are located in the center of the cancrinite channel and oriented along the channel. They interact with Na + cations located in the channels and with each other giving rise to a linear chain incommensurate to the cancrinite matrix. The arrangement of the dimers in the chain has been found to be dependent on the temperature.

  19. 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.

    2017-04-01

    Molecular inorganic materials are currently considered photoresists for extreme ultraviolet lithography (EUVL). Their high EUV absorption cross section and small building block size potentially allow 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. We 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 [SnBuO14OH]OH, which is spin-coated to thin layers of 20 nm. The core electronic structures (Sn 3d, O 1s, and C 1s) of unexposed and DUV exposed films were then investigated using synchrotron radiation-based hard x-ray photoelectron spectroscopy. Different chemical oxidation states and concentrations of atoms and atom types in the unexposed and exposed films were found. We observed that the exposure in a nitrogen atmosphere prevented the oxidation but still led to carbon loss, albeit with a smaller conversion. Finally, a mechanistic hypothesis for the basic DUV photoreactions in molecular tin-oxo cages is proposed.

  20. Extended X-ray absorption fine structure of bimetallic nanoparticles

    PubMed Central

    2011-01-01

    Summary Electronic and magnetic properties strongly depend on the structure of the material, especially on the crystal symmetry and chemical environment. In nanoparticles, the break of symmetry at the surface may yield different physical properties with respect to the corresponding bulk material. A useful tool to investigate the electronic structure, magnetic behaviour and local crystallographic structure is X-ray absorption spectroscopy. In this review, recent developments in the field of extended X-ray absorption fine structure measurements and in the analysis methods for structural investigations of bimetallic nanoparticles are highlighted. The standard analysis based on Fourier transforms is compared to the relatively new field of wavelet transforms that have the potential to outperform traditional analysis, especially in bimetallic alloys. As an example, the lattice expansion and inhomogeneous alloying found in FePt nanoparticles is presented, and this is discussed below in terms of the influence of employed density functional theory calculations on the magnetic properties. PMID:21977436

  1. 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.

  2. Nitrogen adsorption on supported size-selected tungsten nanoclusters as studied by X-ray photoelectron and X-ray excited Auger electron spectroscopies

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Wataru; Murakami, Junichi

    2003-09-01

    Adsorption states of nitrogen on tungsten pentamers supported on a highly oriented pyrolytic graphite surface have been investigated using X-ray photoelectron spectroscopy and X-ray excited Auger electron spectroscopy. An adsorption state that is not seen on a bulk polycrystalline tungsten surface was observed at temperatures below room temperature. It has been found that the adsorption state is a molecular state and is a precursor to dissociation of N 2 on the tungsten nanocluster.

  3. A lab-based ambient pressure x-ray photoelectron spectrometer with exchangeable analysis chambers

    SciTech Connect

    Newberg, John T. Arble, Chris; Goodwin, Chris; Khalifa, Yehia; Broderick, Alicia; Åhlund, John

    2015-08-15

    Ambient pressure X-ray photoelectron spectroscopy (APXPS) is a powerful spectroscopy tool that is inherently surface sensitive, elemental, and chemical specific, with the ability to probe sample surfaces under Torr level pressures. Herein, we describe the design of a new lab-based APXPS system with the ability to swap small volume analysis chambers. Ag 3d(5/2) analyses of a silver foil were carried out at room temperature to determine the optimal sample-to-aperture distance, x-ray photoelectron spectroscopy analysis spot size, relative peak intensities, and peak full width at half maximum of three different electrostatic lens modes: acceleration, transmission, and angular. Ag 3d(5/2) peak areas, differential pumping pressures, and pump performance were assessed under varying N{sub 2}(g) analysis chamber pressures up to 20 Torr. The commissioning of this instrument allows for the investigation of molecular level interfacial processes under ambient vapor conditions in energy and environmental research.

  4. A lab-based ambient pressure x-ray photoelectron spectrometer with exchangeable analysis chambers

    NASA Astrophysics Data System (ADS)

    Newberg, John T.; Åhlund, John; Arble, Chris; Goodwin, Chris; Khalifa, Yehia; Broderick, Alicia

    2015-08-01

    Ambient pressure X-ray photoelectron spectroscopy (APXPS) is a powerful spectroscopy tool that is inherently surface sensitive, elemental, and chemical specific, with the ability to probe sample surfaces under Torr level pressures. Herein, we describe the design of a new lab-based APXPS system with the ability to swap small volume analysis chambers. Ag 3d(5/2) analyses of a silver foil were carried out at room temperature to determine the optimal sample-to-aperture distance, x-ray photoelectron spectroscopy analysis spot size, relative peak intensities, and peak full width at half maximum of three different electrostatic lens modes: acceleration, transmission, and angular. Ag 3d(5/2) peak areas, differential pumping pressures, and pump performance were assessed under varying N2(g) analysis chamber pressures up to 20 Torr. The commissioning of this instrument allows for the investigation of molecular level interfacial processes under ambient vapor conditions in energy and environmental research.

  5. A lab-based ambient pressure x-ray photoelectron spectrometer with exchangeable analysis chambers.

    PubMed

    Newberg, John T; Åhlund, John; Arble, Chris; Goodwin, Chris; Khalifa, Yehia; Broderick, Alicia

    2015-08-01

    Ambient pressure X-ray photoelectron spectroscopy (APXPS) is a powerful spectroscopy tool that is inherently surface sensitive, elemental, and chemical specific, with the ability to probe sample surfaces under Torr level pressures. Herein, we describe the design of a new lab-based APXPS system with the ability to swap small volume analysis chambers. Ag 3d(5/2) analyses of a silver foil were carried out at room temperature to determine the optimal sample-to-aperture distance, x-ray photoelectron spectroscopy analysis spot size, relative peak intensities, and peak full width at half maximum of three different electrostatic lens modes: acceleration, transmission, and angular. Ag 3d(5/2) peak areas, differential pumping pressures, and pump performance were assessed under varying N2(g) analysis chamber pressures up to 20 Torr. The commissioning of this instrument allows for the investigation of molecular level interfacial processes under ambient vapor conditions in energy and environmental research.

  6. An X-Ray Photoelectron Spectroscopy (XPS) Study of Activated Carbons Impregnated with some Organocopper Complexes,

    DTIC Science & Technology

    1993-10-01

    AD-A282 721 l lllllll a Dfene Defence nationals AN X.RAY PHOTOELECTRON SPECTROSCOPY (XPS) STUDY OF ACTIVATED CARBONS IMPREGNATED WITH SOME... ammoniacal solution as a carrier into which all impregnants (except TEDA) were dissolved. Without a suitable carrier, and with the inherent low vapor...and will not be repeated here. All five complexes were synthesized at DREO using known methods. 2 2.2 IMPREGNATING PROCEDURES Two impregnating

  7. X-ray photoelectron spectroscopy of γ-ray-irradiated single-stranded DNA

    NASA Astrophysics Data System (ADS)

    Lee, Eunmo; Hong, W.; Han, J. H.; Choi, D. M.; Lee, Cheol Eui; Kim, H. D.; Kim, J.

    2015-07-01

    The effects of γ-ray irradiation on herring sperm single-stranded DNA have been studied by using X-ray photoelectron spectroscopy (XPS) in the view of the bonding configurations and the structural modifications. The significant changes in the hydrogen, carbon, nitrogen, and phosphorous bonding energies, as revealed by the XPS analysis, indicate that electron transfers result in the creation of radicals and in DNA strand breaks.

  8. Presence of monovalent oxygen anions in oxides demonstrated using X-ray photoelectron spectra

    SciTech Connect

    Wu, L. Q.; Li, Z. Z.; Tang, G. D. Qi, W. H.; Xue, L. C.; Ding, L. L.; Ge, X. S.; Li, S. Q.; Li, Y. C.

    2016-01-11

    The oxygen vacancy model has been used to explain the magnetic and electrical transport properties of dilute magnetic semiconductors and resistive switching. In particular, some authors have claimed that they found a symmetric peak corresponding to the oxygen vacancies in O1s photoelectron spectra. In this paper, using X-ray photoelectron spectra with argon ion etching, it is shown that this symmetric peak may also be interpreted as being related to O{sup 1−} anions, rather than to oxygen vacancies.

  9. Modeling Broadband X-Ray Absorption of Massive Star Winds

    NASA Technical Reports Server (NTRS)

    Leutenegger, Maurice A.; Cohen,David H.; Zsargo, Janos; Martell, Erin M.; MacArthur, James P.; Owocki, Stanley P.; Gagne, Marc; Hillier, D. John

    2010-01-01

    We present a method for computing the net transition of X-rays emitted by shock-heated plasma distributed throughout a partially optically thick stellar wind from a massive star. We find the transmission by an exact integration of the formal solution, assuming the emitting plasma and absorbing plasma are mixed at a constant mass ratio above some minimum radius, below which there is assumed to be no emission. This model is more realistic than either the slab absorption associated with a corona at the base of the wind or the exospheric approximation that assumes all observed X-rays are emitted without attenuation from above the radius of optical depth unity. Our model is implemented in XSPEC as a pre-calculated table that can be coupled to a user-defined table of the wavelength dependent wind opacity. We provide a default wind opacity model that is more representative of real wind opacities than the commonly used neutral ISM tabulation. Preliminary modeling of Chandra grating data indicates that the X-ray hardness trend of OB stars with spectral subtype cars largely be understood as a wind absorption effect.

  10. MODELING BROADBAND X-RAY ABSORPTION OF MASSIVE STAR WINDS

    SciTech Connect

    Leutenegger, Maurice A.; Zsargo, Janos; Martell, Erin M.; Owocki, Stanley P.; Gagne, Marc; Hillier, D. John

    2010-08-20

    We present a method for computing the net transmission of X-rays emitted by shock-heated plasma distributed throughout a partially optically thick stellar wind from a massive star. We find the transmission by an exact integration of the formal solution, assuming that the emitting plasma and absorbing plasma are mixed at a constant mass ratio above some minimum radius, below which there is assumed to be no emission. This model is more realistic than either the slab absorption associated with a corona at the base of the wind or the exospheric approximation that assumes that all observed X-rays are emitted without attenuation from above the radius of optical depth unity. Our model is implemented in XSPEC as a pre-calculated table that can be coupled to a user-defined table of the wavelength-dependent wind opacity. We provide a default wind opacity model that is more representative of real wind opacities than the commonly used neutral interstellar medium (ISM) tabulation. Preliminary modeling of Chandra grating data indicates that the X-ray hardness trend of OB stars with spectral subtype can largely be understood as a wind absorption effect.

  11. X-ray absorption studies of battery materials

    SciTech Connect

    McBreen, J.

    1996-10-01

    X-ray absorption spectroscopy (XAS) is ideal for {ital in}{ital situ} studies of battery materials because both the probe and signal are penetrating x rays. The advantage of XAS being element specific permits investigation of the environment of a constituent element in a composite material. This makes it very powerful for studying electrode additives and corrosion of individual components of complex metal hydride alloys. The near edge part of the spectrum (XANES) provides information on oxidation state and site symmetry of the excited atom. This is particularly useful in study of corrosion and oxidation changes in cathode materials during charge/discharge cycle. Extended fine structure (EXAFS) gives structural information. Thus the technique provides both chemical and structural information. Since XAS probes only short range order, it can be applied to study of amorphous electrode materials and electrolytes. This paper discusses advantages and limitations of the method, as well as some experimental aspects.

  12. 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...

  13. 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...

  14. Near Edge X-Ray Absorption Fine Structure Spectroscopy with X-Ray Free-Electron Lasers

    SciTech Connect

    Bernstein, D.P.; Acremann, Y.; Scherz, A.; Burkhardt, M.; Stohr, J.; Beye, M.; Schlotter, W.F.; Beeck, T.; Sorgenfrei, F.; Pietzsch, A.; Wurth, W.; Fohlisch, A.; /Hamburg U.

    2009-12-11

    We demonstrate the feasibility of Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy on solids by means of femtosecond soft x-ray pulses from a free-electron laser (FEL). Our experiments, carried out at the Free-Electron Laser at Hamburg (FLASH), used a special sample geometry, spectrographic energy dispersion, single shot position-sensitive detection and a data normalization procedure that eliminates the severe fluctuations of the incident intensity in space and photon energy. As an example we recorded the {sup 3}D{sub 1} N{sub 4,5}-edge absorption resonance of La{sup 3+}-ions in LaMnO{sub 3}. Our study opens the door for x-ray absorption measurements on future x-ray FEL facilities.

  15. X-RAY ABSORPTION OF HIGH-REDSHIFT QUASARS

    SciTech Connect

    Eitan, Assaf; Behar, Ehud E-mail: behar@physics.technion.ac.il

    2013-09-01

    The soft X-ray photoelectric absorption of high-z quasars has been known for two decades, but has no unambiguous astrophysical context. We construct the largest sample to date of 58 high-redshift quasars (z > 0.45) selected from the XMM-Newton archive based on a high photon count criterion (>1800). We measure the optical depth {tau} at 0.5 keV and find that 43% of the quasars show significant absorption. We aim to find which physical parameters of the quasars, e.g., redshift, radio luminosity, radio loudness, or X-ray luminosity, drive their observed absorption. We compare the absorption behavior with redshift with the pattern expected if the diffuse intergalactic medium (IGM) is responsible for the observed absorption. We also compare the absorption with a comparison sample of gamma-ray burst (GRB) X-ray afterglows. Although the z > 2 quasar opacity is consistent with diffuse IGM absorption, many intermediate-z (0.45 < z < 2) quasars are not sufficiently absorbed for this scenario, and are appreciably less absorbed than GRBs. Only 10/37 quasars at z < 2 are absorbed, and only 5/30 radio-quiet quasars are absorbed. We find a weak correlation between {tau} and z, and an even weaker correlation between {tau} and radio luminosity. These findings lead to the conclusion that although a diffuse IGM origin for the quasar absorption is unlikely, the optical depth does seem to increase with redshift, roughly as (1 + z){sup 2.2{+-}0.6}, tending to {tau} Almost-Equal-To 0.4 at high redshifts, similar to the high-z GRBs. This result can be explained by an ionized and clumpy IGM at z < 2, and a cold, diffuse IGM at higher redshift. If, conversely, the absorption occurs at the quasar, and owing to the steep L{sub x} {proportional_to}(1 + z){sup 7.1{+-}0.5} correlation in the present sample, the host column density scales as N{sub H}{proportional_to}L{sub x}{sup 0.7{+-}0.1}.

  16. High repetition rate laser produced soft x-ray source for ultrafast x-ray absorption near edge structure measurements.

    PubMed

    Fourmaux, S; Lecherbourg, L; Harmand, M; Servol, M; Kieffer, J C

    2007-11-01

    Recent progress in high intensity ultrafast laser systems provides the opportunity to produce laser plasma x-ray sources exhibiting broad spectrum and high average x-ray flux that are well adapted to x-ray absorption measurements. In this paper, the development of a laser based x-ray absorption near edge structure (XANES) beamline exhibiting high repetition rate by using the Advanced Laser Light Source (ALLS) facility 100 Hz laser system (100 mJ, 35 fs at 800 nm) is presented. This system is based on a broadband tantalum solid target soft x-ray source and a grazing incidence grating spectrometer in the 1-5 nm wavelength range. To demonstrate the high potential of this laser based XANES technique in condensed matter physics, material science, or biology, measurements realized with several samples are presented: VO2 vanadium L edge, Si3N4 nitrogen K edge, and BPDA/PPD polyimide carbon K edge. The characteristics of this laser based beamline are discussed in terms of brightness, signal to noise ratio, and compared to conventional synchrotron broadband x-ray sources which allow achieving similar measurements. Apart from the very compact size and the relative low cost, the main advantages of such a laser based soft x-ray source are the picosecond pulse duration and the perfect synchronization between this x-ray probe and a laser pulse excitation which open the way to the realization of time resolved x-ray absorption measurements with picosecond range time resolution to study the dynamics of ultrafast processes and phase transition.

  17. High repetition rate laser produced soft x-ray source for ultrafast x-ray absorption near edge structure measurements

    SciTech Connect

    Fourmaux, S.; Lecherbourg, L.; Harmand, M.; Servol, M.; Kieffer, J. C.

    2007-11-15

    Recent progress in high intensity ultrafast laser systems provides the opportunity to produce laser plasma x-ray sources exhibiting broad spectrum and high average x-ray flux that are well adapted to x-ray absorption measurements. In this paper, the development of a laser based x-ray absorption near edge structure (XANES) beamline exhibiting high repetition rate by using the Advanced Laser Light Source (ALLS) facility 100 Hz laser system (100 mJ, 35 fs at 800 nm) is presented. This system is based on a broadband tantalum solid target soft x-ray source and a grazing incidence grating spectrometer in the 1-5 nm wavelength range. To demonstrate the high potential of this laser based XANES technique in condensed matter physics, material science, or biology, measurements realized with several samples are presented: VO{sub 2} vanadium L edge, Si{sub 3}N{sub 4} nitrogen K edge, and BPDA/PPD polyimide carbon K edge. The characteristics of this laser based beamline are discussed in terms of brightness, signal to noise ratio, and compared to conventional synchrotron broadband x-ray sources which allow achieving similar measurements. Apart from the very compact size and the relative low cost, the main advantages of such a laser based soft x-ray source are the picosecond pulse duration and the perfect synchronization between this x-ray probe and a laser pulse excitation which open the way to the realization of time resolved x-ray absorption measurements with picosecond range time resolution to study the dynamics of ultrafast processes and phase transition.

  18. Advancements in time-resolved x-ray laser induced time-of-flight photoelectron spectroscopy

    SciTech Connect

    Nelson, A J; Dunn, J; Widmann, K; Ao, T; Ping, Y; Hunter, J; Ng, A

    2005-07-28

    Time-resolved soft x-ray photoelectron spectroscopy is used to probe the non-steady-state evolution of the valence band electronic structure of laser heated ultra-thin (50 nm) metal foils and bulk semiconductors. Single-shot soft x-ray laser induced time-of-flight photoelectron spectroscopy with picosecond time resolution was used in combination with optical measurements of the disassembly dynamics that have shown the existence of a metastable liquid phase in fs-laser heated metal foils persisting 4-5 ps. This metastable phase is studied using a 527 nm wavelength 400 fs laser pulse containing 0.3-2.5 mJ laser energy focused in a large 500 x 700 {micro}m{sup 2} spot to create heated conditions of 0.2-1.8 x 10{sup 12} W cm{sup -2} intensity. The unique LLNL COMET compact tabletop soft x-ray laser source provided the necessary high photon flux, highly monoenergetic, picosecond pulse duration, and coherence for observing the evolution of changes in the valence band electronic structure of laser heated metals and semiconductors with picosecond time resolution. This work demonstrates the continuing development of a powerful new technique for probing reaction dynamics and changes of local order on surfaces on their fundamental timescales including phenomena such as non-thermal melting, chemical bond formation, intermediate reaction steps, and the existence of transient reaction products.

  19. Advancements in time-resolved x-ray laser induced time-of-flight photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Nelson, A. J.; Dunn, J.; Widmann, K.; Ao, T.; Ping, Y.; Hunter, J.; Ng, A.

    2005-09-01

    Time-resolved soft x-ray photoelectron spectroscopy is used to probe the non-steady-state evolution of the valence band electronic structure of laser heated ultra-thin (50 nm) metal foils and bulk semiconductors. Single-shot soft x-ray laser induced time-of-flight photoelectron spectroscopy with picosecond time resolution was used in combination with optical measurements of the disassembly dynamics that have shown the existence of a metastable liquid phase in fs-laser heated metal foils persisting 4-5 ps. This metastable phase is studied using a 527 nm wavelength 400 fs laser pulse containing 0.3 - 2.5 mJ laser energy focused in a large 500 × 700 μm2 spot to create heated conditions of 0.2 - 1.8 × 1012 W cm-2 intensity. The unique LLNL COMET compact tabletop soft x-ray laser source provided the necessary high photon flux, highly monoenergetic, picosecond pulse duration, and coherence for observing the evolution of changes in the valence band electronic structure of laser heated metals and semiconductors with picosecond time resolution. This work demonstrates the continuing development of a powerful new technique for probing reaction dynamics and changes of local order on surfaces on their fundamental timescales including phenomena such as non-thermal melting, chemical bond formation, intermediate reaction steps, and the existence of transient reaction products.

  20. Extended x-ray absorption fine structure studies of hemoglobin

    SciTech Connect

    Shulman, R.G.

    1987-02-01

    Results of extended x-ray absorption fine structure (EXAFS) studies of the iron atom in deoxygenated hemoglobin are reviewed. It is shown that the iron-porphinato nitrogen distance has been determined to be 2.06 +/- 0.01 A by two independent investigations. Difficulties experienced in using this distance to calculate the iron's distance above the plane by triangulation are shown to be due to ignoring differences between ferrous and ferric hemes. It is concluded that the iron is 0.2 +/- 0.1/0.2 A above the plane of the nitrogens as originally shown.

  1. 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.

  2. X-ray absorption variability in NGC 4507

    NASA Astrophysics Data System (ADS)

    Marinucci, Andrea; Risaliti, Guido; Wang, Junfeng; Bianchi, Stefano; Elvis, Martin; Matt, Giorgio; Nardini, Emanuele; Braito, Valentina

    2013-03-01

    We present a complete spectral analysis of an XMM-Newton and Chandra campaign of the obscured AGN in NGC 4507, consisting of six observations spanning a period of six months, ranging from 2010 June to December. We detect strong absorption variability on time-scales between 1.5 and 4 months, suggesting that the obscuring material consists of gas clouds at parsec-scale distance. The lack of significant variability on shorter time-scales suggests that this event is not due to absorption by broad-line region (BLR) clouds, which was instead found in other studies of similar sources. This shows that a single, universal structure of the absorber (either BLR clouds, or the parsec-scale torus) is not enough to reproduce the observed complexity of the X-ray absorption features of this AGN.

  3. Size-induced changes in optical and X-ray photoelectron spectra of GaN nanoparticles deposited at lower substrate temperature.

    PubMed

    Mann, A K; Varandani, D; Mehta, B R; Malhotra, L K; Shivaprasad, S M

    2005-11-01

    This study reports the synthesis of GaN nanoparticles having hexagonal structure by a simple technique of activated reactive evaporation with substrates kept at comparatively lower temperatures than usually reported. By varying the substrate temperature from 30 degrees C to 350 degrees C, it is possible to vary nanoparticle sizes from 5-30 nm. X-ray diffraction and X-ray photoelectron spectroscopy analysis confirm the formation of GaN on quartz and silicon substrates at room temperature. The observed size dependent shift in energy position, large increase in full width at half maximum value of Ga 3d and N 1s X-ray photoelectron spectroscopy peaks and blue shift in the optical absorption edge are related to nanoparticle character.

  4. Extended x-ray-absorption fine structure—Auger process for surface structure analysis: Theoretical considerations of a proposed experiment

    PubMed Central

    Landman, Uzi; Adams, David L.

    1976-01-01

    A method for surface structure analysis is proposed. The proposed process combines x-ray photoabsorption and Auger electron emission. The extended x-ray-absorption fine structure, occurring for photon energies above an atomic absorption edge, contains structural information of the microscopic environment due to the coupling of the photoelectron final state with the atomic initial state. Measurement of the variations in the intensity of particular Auger lines, as a function of the incident radiation energy, provides a surface sensitive measure of the photoabsorption cross section in the media. Theoretical considerations of the physical processes underlying the proposed experiment and its feasibility, and a discussion of background contributions are presented. PMID:16592339

  5. Progress in the Theory and Interpretation of X-ray Absorption Spectra

    NASA Astrophysics Data System (ADS)

    Rehr, J. J.

    2002-03-01

    There has been dramatic progress in recent years in the understanding of x-ray absorption spectra (XAS) [1]. For example, modern real space multiple scattering theory has yielded a quantitative treatment of the extended fine structure in XAS. Crucial in the theory is a treatment of electronic excited states including many-body effects such as inelastic losses and Debye-Waller factors. These developments have led to ab initio codes which permit an interpretation of the spectra in terms of geometrical and electronic properties of materials [2]. Indeed, the availability of such codes has revolutionized experimental investigations based on synchrotron radiation x-ray sources. Algorithmic improvements have recently made possible fast, parallel calculations of the near edge structure (XANES) [3], and approximate treatments of local field effects and many-body amplitude factors. Related techniques have been applied to several other spectroscopies, e.g., anomalous x-ray scattering, x-ray magnetic circular dichroism, and photoelectron diffraction [4]. [1] J. J. Rehr and R. C. Albers, Rev. Mod. Phys. 72, 621 (2000); [2] A. L. Ankudinov, B. Ravel, J.J. Rehr, and S. Conradson, Phys. Rev. B 58, 7565 (1998); [3] A. L. Ankudinov, C. E. Bouldin, J. J. Rehr, J. Sims, and H. Hung, Phys. Rev. B, in press (2002); [4] F. J. Garcia de Abajo, M. A. Van Hove, C. S. Fadley, Phys. Rev. B 63, 075404 (2001).

  6. Hard x-ray photoelectron spectroscopy using an environmental cell with silicon nitride membrane windows

    SciTech Connect

    Tsunemi, Eika; Watanabe, Yoshio; Oji, Hiroshi; Cui, Yi-Tao; Son, Jin-Young

    2015-06-21

    We applied hard x-ray photoelectron spectroscopy (HAXPES) to a sample under ambient pressure conditions using an environmental cell with an approximately 24 nm-thick SiN{sub x} membrane window. As a model chemical substance, europium (II) iodide (EuI{sub 2}) sealed in the cell with argon gas was investigated with HAXPES to identify the chemical species present inside the cell. The optical and morphological properties of the sample within the cell were measured with optical and fluorescent microscopy, scanning electron microscopy, cathodoluminescence, and energy dispersive x-ray spectrometry. We confirmed the effectiveness of the gas barrier properties of the cell with the SiN{sub x} window and demonstrated its applicability to various other optical and electron measurements as well as HAXPES.

  7. An X-ray photoelectron spectroscopic study of the B-N-Ti system

    SciTech Connect

    Seal, S.; Barr, T.L.; Sobczak, N.; Benko, E.; Morgiel, J.

    1997-03-01

    Composite nitrides (such as BN, TiN) are widely used in various industrial applications because of their extreme wear and corrosion resistance, thermal and electrical properties. In order to obtain composite materials with these optimal properties, it is important to elucidate whether any chemical reactions occur at nitride/metal interfaces, e.g., those involving BN-Ti/TiN. Materials of interest include the deposition by PVD of Ti and TiN on BN substrates. Some of these systems were then subjected to varying degrees of physical and thermal alteration. Detailed X-ray photoelectron spectroscopy (XPS) has therefore been rendered of these interfaces using cross-sectional display and sputter etching. Resulting structural and morphological features have been investigated with transmission electron microscopy (TEM) and X-ray diffraction (XRD). Diffusion of the nitridation, oxynitride formation and interfacial growth are of general interest.

  8. 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.

  9. Comparison of hard and soft x-ray photoelectron spectra of silicon

    NASA Astrophysics Data System (ADS)

    Offi, F.; Werner, W. S. M.; Sacchi, M.; Torelli, P.; Cautero, M.; Cautero, G.; Fondacaro, A.; Huotari, S.; Monaco, G.; Paolicelli, G.; Smekal, W.; Stefani, G.; Panaccione, G.

    2007-08-01

    A detailed comparison of the surface sensitivity of x-ray photoemission spectroscopy for hard and soft x rays is presented and discussed. Electron scattering parameters and their energy dependence are given for Si and two Si spectra are analyzed: a MgKα (hν=1253.6eV) excited spectrum of the Si2p and 2s lines and a hard x-ray excited spectrum (hν=5925eV) of the Si1s line. The differential inelastic scattering characteristics for Si are extracted from reflection electron energy loss spectra taken at energies of 1500 and 4000eV . Using these scattering characteristics and electron mean free paths from the literature, simulated spectra are compared with experiment. The experimental spectra are deconvoluted to give the true intrinsic line shape corresponding to the theoretical collision statistics when interference effects between intrinsic and extrinsic scattering are neglected. The magnitude of interference effects cannot be assessed by our analysis. Within the (unknown) uncertainty introduced by neglecting interference effects, it is possible to determine the relative intensity of intrinsic and extrinsic excitations. In this way, it is found that in the case of the soft x-ray excited photoelectron spectrum of the shallower electronic shells ( 2p and 2s ), intrinsic plasmon creation is rather weak, and the apparent asymmetric line shape of the spectrum might be interpreted as the fact that electron-hole pair creation dominates the intrinsic loss spectrum, while an alternative explanation in terms of surface core level shifted components is also proposed. For the deeper core electronic shell, probed with hard x rays, the opposite situation is observed: while intrinsic electron-hole pair creation was not observed, a strong contribution of intrinsic plasmon losses of about 30% was seen.

  10. Imide photodissociation investigated by X-ray absorption spectroscopy.

    PubMed

    Johnson, Phillip S; Cook, Peter L; Liu, Xiaosong; Yang, Wanli; Bai, Yiqun; Abbott, Nicholas L; Himpsel, F J

    2012-06-21

    X-ray absorption spectroscopy is used to investigate the photodissociation of the imides PMDI (pyromellitic diimide) and SSMCC (sulfosuccinimidyl 4-(N-maleimidomethyl) cyclohexane-1-carboxylate). PMDI contains only one type of imide, and its photodissociation can be explained by a simple conversion from imide to a mix of imine and nitrile after desorption of the oxygens from the imide. SSMCC contains two different imides. One reacts like PMDI, the other in a more complex multistep process. Eventually, N(2) is formed in the bulk of the sample at high radiation density. The sequence of reactions is inferred from the π* peaks in total electron yield and fluorescence yield absorption spectra at the N 1s and O 1s edges. First-order rate equations are used to model the evolution of the peak areas versus radiation dose.

  11. X-ray photoelectron spectroscopy analysis of organic materials irradiated with gas cluster ion beam

    SciTech Connect

    Nakagiri, Motohiro; Toyoda, Noriaki; Yamada, Isao

    2011-01-07

    Irradiation effect of gas cluster ion beams (GCIB) on organic materials were studied with X-ray photoelectron spectroscopy by comparison to that with Ar-monomer ions. In the case of polyimide, the intensity of both N-C = O and -C-O- bond decreased with 500 eV Ar monomer ion irradiation. On the other hand, there was no significant change in the XPS spectra after Ar-GCIB irradiation. From the size-selected GCIB irradiation study, the damages in polyimide decreased with increasing the cluster size owing to the reduction of energy per atoms.

  12. X-ray photoelectron spectroscopy study of polyimide thin films with Ar cluster ion depth profiling

    SciTech Connect

    Miyayama, T.; Sanada, N.; Suzuki, M.; Hammond, J. S.; Si, S.-Q. D.; Takahara, A.

    2010-03-15

    X-ray photoelectron spectroscopy depth profiling of polyimide thin films on silicon substrates using an Ar cluster ion beam results in an extremely low degradation of the polyimide chemistry. In the range from 2.5 to 20 kV, a lower cluster ion energy produces a lower sputter induced damage to the polymer and results in an improved polyimide to silicon interface width. The sputtering rates of the polyimide are found to increase exponentially with an increase in the Ar cluster ion energy.

  13. X-ray photoelectron spectroscopy investigation of commercial passivated tinplate surface layer

    NASA Astrophysics Data System (ADS)

    Chen, Sheng; Xie, Long; Xue, Fei

    2013-07-01

    X-ray photoelectron spectroscopy (XPS) combined with the low energy Ar+ sputtering technique has been used to investigate the chemical compositions and chemical states of elements at different depths of commercial passivated tinplate surface layer. It is found that Cr2O3, SnO, Cr(OH)3, metallic Sn and a small amount of metallic Cr have been mixed in this layer. According to peak fitting and relative sensitivity factor method, the concentrations of elements in various chemical environments on different depth planes of the passivated tinplate surface layer have been obtained.

  14. 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.

  15. Sialolith characterization by scanning electron microscopy and X-ray photoelectron spectroscopy.

    PubMed

    Giray, C Bahadir; Dogan, Meral; Akalin, Ayse; Baltrusaitis, Jonas; Chan, Daniel C N; Skinner, H Catherine W; Dogan, A Umran

    2007-01-01

    The objective of this study has been to characterize sialolith, a calcium phosphate deposit that develops in the human oral cavity, by high-resolution field emission scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The morphological and chemical data obtained helped in the determination of their formation mechanism in salivary glands. Sialoliths in the submandibular salivary glands may arise secondary to sialodenitis, but not via a luminal organic nidus. We believe this is the first study that characterizes a sialolith by XPS.

  16. X-ray photoelectron spectroscopy study of the effects of ultrapure water on GaAs

    NASA Astrophysics Data System (ADS)

    Massies, J.; Contour, J. P.

    1985-06-01

    X-ray photoelectron spectroscopy has been used to investigate the effects of de-ionized water on chemical etched GaAs surfaces. When the treatment with water is performed in static conditions (stagnant water) a Ga-rich oxide layer is formed on GaAs at the rate of 10-20 Å h-1. In contrast, when the GaAs surface is treated in dynamic conditions (running water), no oxide buildup is observed. Moreover, running water can remove the oxide film formed in static conditions, as well as oxidized layers due to air exposure. These results are discussed in the framework of cleaning prior to molecular beam epitaxy.

  17. 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.

  18. Short-range order in amorphous SiO{sub x} by x ray photoelectron spectroscopy

    SciTech Connect

    Novikov, Yu. N.; Gritsenko, V. A.

    2011-07-01

    The Si 2p x ray photoelectron spectra of SiO{sub x} with a different composition of 0 {<=} x {<=} 2 have been studied experimentally and theoretically. The SiO{sub x} films were prepared by low-pressure chemical vapor deposition from SiH{sub 4} and N{sub 2}O source at 750 deg. C. Neither random bonding nor random mixture models can adequately describe the structure of these compounds. The interpretation of the experimental results is discussed according to a large scale potential fluctuation due to the spatial variation of chemical composition in SiO{sub x}.

  19. Ultrafast soft X-ray photoelectron spectroscopy at liquid water microjets.

    PubMed

    Faubel, M; Siefermann, K R; Liu, Y; Abel, B

    2012-01-17

    Since the pioneering work of Kai Siegbahn, electron spectroscopy for chemical analysis (ESCA) has been developed into an indispensable analytical technique for surface science. The value of this powerful method of photoelectron spectroscopy (PES, also termed photoemission spectroscopy) and Siegbahn's contributions were recognized in the 1981 Nobel Prize in Physics. The need for high vacuum, however, originally prohibited PES of volatile liquids, and only allowed for investigation of low-vapor-pressure molecules attached to a surface (or close to a surface) or liquid films of low volatility. Only with the invention of liquid beams of volatile liquids compatible with high-vacuum conditions was PES from liquid surfaces under vacuum made feasible. Because of the ubiquity of water interfaces in nature, the liquid water-vacuum interface became a most attractive research topic, particularly over the past 10 years. PES studies of these important aqueous interfaces remained significantly challenging because of the need to develop high-pressure PES methods. For decades, ESCA or PES (termed XPS, for X-ray photoelectron spectroscopy, in the case of soft X-ray photons) was restricted to conventional laboratory X-ray sources or beamlines in synchrotron facilities. This approach enabled frequency domain measurements, but with poor time resolution. Indirect access to time-resolved processes in the condensed phase was only achieved if line-widths could be analyzed or if processes could be related to a fast clock, that is, reference processes that are fast enough and are also well understood in the condensed phase. Just recently, the emergence of high harmonic light sources, providing short-wavelength radiation in ultrashort light pulses, added the dimension of time to the classical ESCA or XPS technique and opened the door to (soft) X-ray photoelectron spectroscopy with ultrahigh time resolution. The combination of high harmonic light sources (providing radiation with laserlike

  20. Spectromicroscope for the PHotoelectron Imaging of Nanostructures with X-rays (SPHINX): performance in biology, medicine and geology.

    PubMed

    Frazer, Bradley H; Girasole, Marco; Wiese, Lisa M; Franz, Torsten; De Stasio, Gelsomina

    2004-05-01

    Several X-ray PhotoElectron Emission spectroMicroscopes (X-PEEMs) exist around the world at this time. We present recent performance and resolution tests of one of them, the Spectromicroscope for PHotoelectron Imaging of Nanostructures with X-rays (SPHINX) X-PEEM, installed at the University of Wisconsin Synchrotron Radiation Center. With this state-of-the-art instrument we demonstrate chemical analysis capabilities on conducting and insulating specimens of diverse interests, and an unprecedented lateral resolution of 10 nm with monochromatic X-rays and 7.2 nm with ultraviolet illumination.

  1. Making use of x-ray optical effects in photoelectron-, Auger electron-, and x-ray emission spectroscopies: Total reflection, standing-wave excitation, and resonant effects

    SciTech Connect

    Yang, S.-H.; Gray, A. X.; Kaiser, A. M.; Mun, B. S.; Sell, B. C.; Kortright, J. B.; Fadley, C. S.

    2013-02-21

    We present a general theoretical methodology and related open-access computer program for carrying out the calculation of photoelectron, Auger electron, and x-ray emission intensities in the presence of several x-ray optical effects, including total reflection at grazing incidence, excitation with standing-waves produced by reflection from synthetic multilayers and at core-level resonance conditions, and the use of variable polarization to produce magnetic circular dichroism. Calculations illustrating all of these effects are presented, including in some cases comparisons to experimental results. Sample types include both semi-infinite flat surfaces and arbitrary multilayer configurations, with interdiffusion/roughness at their interfaces. These x-ray optical effects can significantly alter observed photoelectron, Auger, and x-ray intensities, and in fact lead to several generally useful techniques for enhancing surface and buried-layer sensitivity, including layer-resolved densities of states and depth profiles of element-specific magnetization. The computer program used in this study should thus be useful for a broad range of studies in which x-ray optical effects are involved or are to be exploited in next-generation surface and interface studies of nanoscale systems.

  2. Note: Construction of x-ray scattering and x-ray absorption fine structure beamline at the Pohang Light Source

    SciTech Connect

    Lee, Ik-Jae; Yu, Chung-Jong; Yun, Young-Duck; Lee, Chae-Soon; Seo, In Deuk; Kim, Hyo-Yun; Lee, Woul-Woo; Chae, Keun Hwa

    2010-02-15

    A new hard x-ray beamline, 10B KIST-PAL beamline (BL10B), has been designed and constructed at the Pohang Light Source (PLS) in Korea. The beamline, operated by Pohang Accelerator Laboratory-Korean Institute of Science and Technology consortium, is dedicated to x-ray scattering (XRS) and x-ray absorption fine structure (XAFS) experiments. X rays with photon energies from 4.0 to 16.0 keV are delivered to the experimental station passing a collimating mirror, a fixed-exit double-crystal Si(111) monochromator, and a toroidal mirror. Basic experimental equipments for XAFS measurement, a high resolution diffractometry, an image plate detector system, and a hot stage have been prepared for the station. From our initial commissioning and performance testing of the beamline, it is observed that BL10B beamline can perform XRS and XAFS measurements successfully.

  3. X-ray absorption in neon modulated by a strong laser pulse

    NASA Astrophysics Data System (ADS)

    Hertlein, M. P.; Glover, T. E.; Allison, T. K.; van Tilborg, J.; Rude, B. S.; Belkacem, A.; Southworth, S. H.; Kanter, E. P.; Krässig, B.; Varma, H. R.; Santra, R.; Young, L.

    2009-11-01

    We have measured the absorption of x-rays in neon gas in the presence of a strong laser pulse. The femtosecond x-rays were tuned to energies near the neon 1s-3p resonance, and the laser intensity of 1013 W/cm2 was below the intensity required to alone ionize neon. We observed strong modification of the x-ray absorption when the neon was subjected to laser light that was temporally overlapped with the x-rays.

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

    PubMed

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

    2015-01-01

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

  5. Interpretation of x-ray absorption spectroscopy in the presence of surface hybridization

    NASA Astrophysics Data System (ADS)

    Diller, Katharina; Maurer, Reinhard J.; Müller, Moritz; Reuter, Karsten

    2017-06-01

    X-ray absorption spectroscopy (XAS) yields direct access to the electronic and geometric structure of hybrid inorganic-organic interfaces formed upon adsorption of complex molecules at metal surfaces. The unambiguous interpretation of corresponding spectra is challenged by the intrinsic geometric flexibility of the adsorbates and the chemical interactions with the interface. Density-functional theory (DFT) calculations of the extended adsorbate-substrate system are an established tool to guide peak assignment in X-ray photoelectron spectroscopy of complex interfaces. We extend this to the simulation and interpretation of XAS data in the context of functional organic molecules on metal surfaces using dispersion-corrected DFT calculations within the transition potential approach. For the prototypical case of 2H-porphine adsorbed on Ag(111) and Cu(111) substrates, we follow the two main effects of the molecule/surface interaction onto the X-ray absorption signatures: (1) the substrate-induced chemical shift of the 1s core levels that dominates in physisorbed systems and (2) the hybridization-induced broadening and loss of distinct resonances that dominate in more chemisorbed systems.

  6. Boron Doped diamond films as electron donors in photovoltaics: An X-ray absorption and hard X-ray photoemission study

    SciTech Connect

    Kapilashrami, M.; Zegkinoglou, I.; Conti, G.; Nemšák, S.; Conlon, C. S.; Fadley, C. S.; Törndahl, T.; Fjällström, V.; Lischner, J.; Louie, Steven G.; Hamers, R. J.; Zhang, L.; Guo, J.-H.; Himpsel, F. J.

    2014-10-14

    Highly boron-doped diamond films are investigated for their potential as transparent electron donors in solar cells. Specifically, the valence band offset between a diamond film (as electron donor) and Cu(In,Ga)Se₂ (CIGS) as light absorber is determined by a combination of soft X-ray absorption spectroscopy and hard X-ray photoelectron spectroscopy, which is more depth-penetrating than standard soft X-ray photoelectron spectroscopy. In addition, a theoretical analysis of the valence band is performed, based on GW quasiparticle band calculations. The valence band offset is found to be small: VBO=VBM{sub CIGS} – VBM{sub diamond}=0.3 eV±0.1 eV at the CIGS/Diamond interface and 0.0 eV±0.1 eV from CIGS to bulk diamond. These results provide a promising starting point for optimizing the band offset by choosing absorber materials with a slightly lower valence band maximum.

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

    SciTech Connect

    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 et al. 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 et al. but not in detail. The predicted constancy in the shake-up contribution by Yarzhemsky et al. 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.

  8. X-Ray Photoelectron Diffraction Studies of Structural and Magnetic Disordering Transitions Near Surfaces

    NASA Astrophysics Data System (ADS)

    Tran, Thuy Thu

    This thesis deals with order/disorder transitions near solid surfaces as studied by x-ray photoelectron diffraction and photoelectron holography. Transitions involving both atomic positional order and magnetic order have been studied. Further evidence for a reversible high-temperature surface-disordering phase transition on Ge(111) has been found using Ge 3p x-ray photoelectron diffraction (a short -range-order probe of surface structure) and photoelectron holography. Azimuthal diffraction data at takeoff angles with respect to the surface of theta = 19^circ and theta = 55^circ show abrupt drops in intensity of ~30%-40% over the temperature interval of 900-1200 K. Photoelectron holographic near-neighbor images at temperatures below and above the transition region furthermore indicate an identical near-neighbor structure for all atoms present in ordered sites. These combined diffraction and holography data show that by 1200 K, the Ge(111) surface is covered by a completely disordered overlayer of about 2 Ge monolayers in thickness. The rate of growth of this overlayer with increasing temperature is in excellent agreement with recent medium-energy ion scattering results, although the thickness we find for the overlayer is 1.5-2.0x larger than that derived from ion scattering. Based on these data, a disordering model for the Ge(111) surface phase transition occurring at 1050 K is discussed. Spin-polarized photoelectron diffraction is a recently developed and promising application of photoelectron diffraction to the study of the magnetic structure near surfaces. This technique is based on an internal source of spin-polarized electrons as produced in core-level multiplet splittings and it is thus sensitive to the short-range magnetic order around a given type of emitter in the crystal. In prior studies, it has been applied to two antiferromagnets, KMnF_3 and MnO, and the effects seen at temperatures well above the Neel (or long-range -order) temperature have been

  9. Macroscopic and X-ray photoelectron spectroscopic investigation of interactions of arsenic with synthesized pyrite.

    PubMed

    Kim, Eun Jung; Batchelor, Bill

    2009-04-15

    Interactions of arsenic with synthesized pyrite were investigated using macroscopic (solution phase experiments) and microscopic (X-ray photoelectron spectroscopic investigation) approaches. Arsenic removal by pyrite was strongly dependent on pH and arsenic species. Both arsenite (As(III)) and arsenate (As(V)) had a strong affinity for the pyrite surface under acidic conditions, but As(III) was more effectively removed than As(V). A BET isotherm equation provided the best fit to arsenic removal data, suggesting that surface precipitation occurred at a high arsenic/pyrite ratio. The addition of competing ions did not substantially affect the ultimate distribution of arsenic between the pyrite surface and the solution, but changing the pH affected arsenic stability on pyrite. X-ray photoelectron spectroscopy (XPS) revealed that under acidic conditions, arsenic was removed by reaction with pyrite to form solid phases similar to As2S3 and As4S4. However, under neutral to alkaline conditions, arsenic was removed by sorption and precipitation to form solid phases that are similar to FeAsS and As2S3/As4S4.

  10. Quantitative spectromicroscopy from inelastically scattered photoelectrons in the hard X-ray range

    SciTech Connect

    Renault, O. Zborowski, C.; Risterucci, P.; Wiemann, C.; Schneider, C. M.; Grenet, G.; Tougaard, S.

    2016-07-04

    We demonstrate quantitative, highly bulk-sensitive x-ray photoelectron emission microscopy by analysis of inelastically scattered photoelectrons in the hard X-ray range, enabling elemental depth distribution analysis in deeply buried layers. We show results on patterned structures used in electrical testing of high electron mobility power transistor devices with an epitaxial Al{sub 0.25}Ga{sub 0.75}N channel and a Ti/Al metal contact. From the image series taken over an energy range of up to 120 eV in the Ti 1s loss feature region and over a typical 100 μm field of view, one can accurately retrieve, using background analysis together with an optimized scattering cross-section, the Ti depth distribution from 14 nm up to 25 nm below the surface. The method paves the way to multi-elemental, bulk-sensitive 3D imaging and investigation of phenomena at deeply buried interfaces and microscopic scales by photoemission.

  11. X-ray photoelectron spectroscopy of graphitic carbon nanomaterials doped with heteroatoms.

    PubMed

    Susi, Toma; Pichler, Thomas; Ayala, Paola

    2015-01-01

    X-ray photoelectron spectroscopy (XPS) is one of the best tools for studying the chemical modification of surfaces, and in particular the distribution and bonding of heteroatom dopants in carbon nanomaterials such as graphene and carbon nanotubes. Although these materials have superb intrinsic properties, these often need to be modified in a controlled way for specific applications. Towards this aim, the most studied dopants are neighbors to carbon in the periodic table, nitrogen and boron, with phosphorus starting to emerge as an interesting new alternative. Hundreds of studies have used XPS for analyzing the concentration and bonding of dopants in various materials. Although the majority of works has concentrated on nitrogen, important work is still ongoing to identify its precise atomic bonding configurations. In general, care should be taken in the preparation of a suitable sample, consideration of the intrinsic photoemission response of the material in question, and the appropriate spectral analysis. If this is not the case, incorrect conclusions can easily be drawn, especially in the assignment of measured binding energies into specific atomic configurations. Starting from the characteristics of pristine materials, this review provides a practical guide for interpreting X-ray photoelectron spectra of doped graphitic carbon nanomaterials, and a reference for their binding energies that are vital for compositional analysis via XPS.

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

    SciTech Connect

    Qin, Dongyang; Lu, Yafeng; Zhang, Kong; Liu, Qian; Zhou, Lian

    2012-11-15

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

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

    SciTech Connect

    Tobin, J G

    2011-03-17

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

  14. Investigating DNA Radiation Damage Using X-Ray Absorption Spectroscopy

    PubMed Central

    Czapla-Masztafiak, Joanna; Szlachetko, Jakub; Milne, Christopher J.; Lipiec, Ewelina; Sá, Jacinto; Penfold, Thomas J.; Huthwelker, Thomas; Borca, Camelia; Abela, Rafael; Kwiatek, Wojciech M.

    2016-01-01

    The biological influence of radiation on living matter has been studied for years; however, several questions about the detailed mechanism of radiation damage formation remain largely unanswered. Among all biomolecules exposed to radiation, DNA plays an important role because any damage to its molecular structure can affect the whole cell and may lead to chromosomal rearrangements resulting in genomic instability or cell death. To identify and characterize damage induced in the DNA sugar-phosphate backbone, in this work we performed x-ray absorption spectroscopy at the P K-edge on DNA irradiated with either UVA light or protons. By combining the experimental results with theoretical calculations, we were able to establish the types and relative ratio of lesions produced by both UVA and protons around the phosphorus atoms in DNA. PMID:27028640

  15. X-ray absorption spectroscopy of bacterial sulfur globules

    SciTech Connect

    George, Graham N.

    2002-08-01

    Sulfur K-edge X-ray absorption spectroscopy is a powerful in situ probe of sulfur biochemistry in intact cells and tissues. Under favorable circumstances the technique can provide quantitative information on the chemical identify of the sulfur species that are present in a sample. Prange et al. have recently reported an X-ray absorption spectroscopic study of bacterial sulfur storage globules. Unfortunately there are substantial problems with the experimental technique employed that, they contend, lead to completely erroneous conclusions. In the more recent of their two papers Prange et al. employed a curve-fitting method similar to that used by us (for more than 10 years). In essence, the method employs simply fitting a linear combination of the spectra of standard compounds to that of the unknown, in this case cultures of bacterial cells. This type of analysis can provide quantitative estimates of the individual sulfur types in the sample, but is critically dependent upon the choice of reference spectra. Prange et al. deduce substantial differences between the chemical forms of sulfur stored in the globules of different organisms; they conclude that the globules of Beggiatoa alba and Thiomargarita namibiensis contain cyclo-octasulfur (S{sub 8}), while those of other organisms contain polythionates (Acidithiobacillus ferrooxidans) and polymeric sulfur (e.g. Allochromatium vinosum). This is in contradiction with an earlier study, in which they found that sulfur in all globule species examined resembled that expected for various sized spherical particles of S{sub 8}. The discrepancy is due to an experimental artefact in the work of Prange et al. arising from their choice of transmittance detection, which is also discussed.

  16. X-ray absorption of Azotobacter vinelandii vanadium nitrogenase

    SciTech Connect

    George, G.N.; Coyle, C.L.; Hales, B.J.; Cramer, S.P.

    1988-06-08

    Evidence for the existence of a vanadium-containing nitrogenase has existed for more than half a century, but progress in understanding this enzyme has only come recently. In 1980, Bishop and co-workers proposed that an alternative nitrogen-fixing enzyme exists in Azotobacter vinelandii and subsequently proposed that vanadium was involved. In 1986, Robson et al. demonstrated clearly that the alternate nitrogenase from Azotobacter chroococcum, Acl*, contained vanadium instead of molybdenum. Hales et al. have shown the vanadium is also found in the Azotobacter vinelandii alternative component I, Avl'. The molybdenum and vanadium nitrogenase proteins are similar in many respects. Like the molybdenum enzyme, both Acl* and Avl' exhibit an EPR spectrum characteristic of a species with an S = 3/2 ground state; Avl' also contains the so-called P-clusters. Additionally Acl* has recently been shown to possess an N-methylformamide soluble cofactor, FeVco, analogous to the well-known iron-molybdenum cofactor FeMoco. Arber et al. have reported X-ray absorption spectra for the Acl* enzyme and interpreted the EXAFS as evidence for a V-Fe-S cluster. The local vanadium structure is proposed to resemble a recently synthesized cubane-like VFe/sub 3/S/sub 4/ cluster, and analogies are drawn with the EXAFS-derived structure reported for the molybdenum nitrogenases. The authors report herein an X-ray absorption spectroscopic study of A. vinelandii vanadium nitrogenase, Avl', which supports and extends the work of Arber et al.

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

    NASA Astrophysics Data System (ADS)

    Pauli, Mark Daniel

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

  18. Characterization of SiC fibers by soft x-ray photoelectron and photoabsorption spectroscopies and scanning Auger microscopy

    SciTech Connect

    Ma, Qing; McDowell, M.W.; Rosenberg, R.A.

    1996-08-01

    Synchrotron radiation soft x-ray photoelectron and photoabsorption spectroscopy was used to characterize commercially obtained SiC fibers produced by CVD on a W core and followed by a C passivating layer. Depth profiling of the fiber through the C/SiC interface was done by making Si 2p and C 1s core level PES and PAS, as well as scanning Auger microscopy, measurements following Ar{sup +} sputtering. No significant changes in either photoemission or absorption or Auger line shapes were observed versus depth, indicating no significant interfacial reaction. The line shapes of the carbonaceous coatings are predominantely graphite-like and those of the CVD SiC coatings are microcrystalline, with disorder present to some extent in both cases.

  19. Weak hard X-ray emission from broad absorption line quasars: evidence for intrinsic X-ray weakness

    SciTech Connect

    Luo, B.; Brandt, W. N.; Scott, A. E.; Alexander, D. M.; Gandhi, P.; Stern, D.; Teng, S. H.; Arévalo, P.; Bauer, F. E.; Boggs, S. E.; Craig, W. W.; Christensen, F. E.; Comastri, A.; Farrah, D.; Hailey, C. J.; Harrison, F. A.; Koss, M.; Ogle, P.; Puccetti, S.; Saez, C.; and others

    2014-10-10

    We report NuSTAR observations of a sample of six X-ray weak broad absorption line (BAL) quasars. These targets, at z = 0.148-1.223, are among the optically brightest and most luminous BAL quasars known at z < 1.3. However, their rest-frame ≈2 keV luminosities are 14 to >330 times weaker than expected for typical quasars. Our results from a pilot NuSTAR study of two low-redshift BAL quasars, a Chandra stacking analysis of a sample of high-redshift BAL quasars, and a NuSTAR spectral analysis of the local BAL quasar Mrk 231 have already suggested the existence of intrinsically X-ray weak BAL quasars, i.e., quasars not emitting X-rays at the level expected from their optical/UV emission. The aim of the current program is to extend the search for such extraordinary objects. Three of the six new targets are weakly detected by NuSTAR with ≲ 45 counts in the 3-24 keV band, and the other three are not detected. The hard X-ray (8-24 keV) weakness observed by NuSTAR requires Compton-thick absorption if these objects have nominal underlying X-ray emission. However, a soft stacked effective photon index (Γ{sub eff} ≈ 1.8) for this sample disfavors Compton-thick absorption in general. The uniform hard X-ray weakness observed by NuSTAR for this and the pilot samples selected with <10 keV weakness also suggests that the X-ray weakness is intrinsic in at least some of the targets. We conclude that the NuSTAR observations have likely discovered a significant population (≳ 33%) of intrinsically X-ray weak objects among the BAL quasars with significantly weak <10 keV emission. We suggest that intrinsically X-ray weak quasars might be preferentially observed as BAL quasars.

  20. X-ray-selected broad absorption line quasi-stellar objects

    NASA Astrophysics Data System (ADS)

    Page, M. J.; Carrera, F. J.; Ceballos, M.; Corral, A.; Ebrero, J.; Esquej, P.; Krumpe, M.; Mateos, S.; Rosen, S.; Schwope, A.; Streblyanska, A.; Symeonidis, M.; Tedds, J. A.; Watson, M. G.

    2017-02-01

    We study a sample of six X-ray-selected broad absorption line (BAL) quasi-stellar objects (QSOs) from the XMM-Newton Wide Angle Survey. All six objects are classified as BALQSOs using the classic balnicity index, and together they form the largest sample of X-ray-selected BALQSOs. We find evidence for absorption in the X-ray spectra of all six objects. An ionized absorption model applied to an X-ray spectral shape that would be typical for non-BAL QSOs (a power law with energy index α = 0.98) provides acceptable fits to the X-ray spectra of all six objects. The optical to X-ray spectral indices, αOX, of the X-ray-selected BALQSOs, have a mean value of <αOX> = 1.69 ± 0.05, which is similar to that found for X-ray-selected and optically selected non-BAL QSOs of a similar ultraviolet luminosity. In contrast, optically selected BALQSOs typically have much larger αOX and so are characterized as being X-ray weak. The results imply that X-ray selection yields intrinsically X-ray bright BALQSOs, but their X-ray spectra are absorbed by a similar degree to that seen in optically selected BALQSO samples; X-ray absorption appears to be ubiquitous in BALQSOs, but X-ray weakness is not. We argue that BALQSOs sit at one end of a spectrum of X-ray absorption properties in QSOs related to the degree of ultraviolet absorption in C IV 1550 Å.

  1. First in-flight synchrotron X-ray absorption and photoemission study of carbon soot nanoparticles

    NASA Astrophysics Data System (ADS)

    Ouf, F.-X.; Parent, P.; Laffon, C.; Marhaba, I.; Ferry, D.; Marcillaud, B.; Antonsson, E.; Benkoula, S.; Liu, X.-J.; Nicolas, C.; Robert, E.; Patanen, M.; Barreda, F.-A.; Sublemontier, O.; Coppalle, A.; Yon, J.; Miserque, F.; Mostefaoui, T.; Regier, T. Z.; Mitchell, J.-B. A.; Miron, C.

    2016-11-01

    Many studies have been conducted on the environmental impacts of combustion generated aerosols. Due to their complex composition and morphology, their chemical reactivity is not well understood and new developments of analysis methods are needed. We report the first demonstration of in-flight X-ray based characterizations of freshly emitted soot particles, which is of paramount importance for understanding the role of one of the main anthropogenic particulate contributors to global climate change. Soot particles, produced by a burner for several air-to-fuel ratios, were injected through an aerodynamic lens, focusing them to a region where they interacted with synchrotron radiation. X-ray photoelectron spectroscopy and carbon K-edge near-edge X-ray absorption spectroscopy were performed and compared to those obtained for supported samples. A good agreement is found between these samples, although slight oxidation is observed for supported samples. Our experiments demonstrate that NEXAFS characterization of supported samples provides relevant information on soot composition, with limited effects of contamination or ageing under ambient storage conditions. The highly surface sensitive XPS experiments of airborne soot indicate that the oxidation is different at the surface as compared to the bulk probed by NEXAFS. We also report changes in soot’s work function obtained at different combustion conditions.

  2. First in-flight synchrotron X-ray absorption and photoemission study of carbon soot nanoparticles.

    PubMed

    Ouf, F-X; Parent, P; Laffon, C; Marhaba, I; Ferry, D; Marcillaud, B; Antonsson, E; Benkoula, S; Liu, X-J; Nicolas, C; Robert, E; Patanen, M; Barreda, F-A; Sublemontier, O; Coppalle, A; Yon, J; Miserque, F; Mostefaoui, T; Regier, T Z; Mitchell, J-B A; Miron, C

    2016-11-24

    Many studies have been conducted on the environmental impacts of combustion generated aerosols. Due to their complex composition and morphology, their chemical reactivity is not well understood and new developments of analysis methods are needed. We report the first demonstration of in-flight X-ray based characterizations of freshly emitted soot particles, which is of paramount importance for understanding the role of one of the main anthropogenic particulate contributors to global climate change. Soot particles, produced by a burner for several air-to-fuel ratios, were injected through an aerodynamic lens, focusing them to a region where they interacted with synchrotron radiation. X-ray photoelectron spectroscopy and carbon K-edge near-edge X-ray absorption spectroscopy were performed and compared to those obtained for supported samples. A good agreement is found between these samples, although slight oxidation is observed for supported samples. Our experiments demonstrate that NEXAFS characterization of supported samples provides relevant information on soot composition, with limited effects of contamination or ageing under ambient storage conditions. The highly surface sensitive XPS experiments of airborne soot indicate that the oxidation is different at the surface as compared to the bulk probed by NEXAFS. We also report changes in soot's work function obtained at different combustion conditions.

  3. First in-flight synchrotron X-ray absorption and photoemission study of carbon soot nanoparticles

    PubMed Central

    Ouf, F.-X.; Parent, P.; Laffon, C.; Marhaba, I.; Ferry, D.; Marcillaud, B.; Antonsson, E.; Benkoula, S.; Liu, X.-J.; Nicolas, C.; Robert, E.; Patanen, M.; Barreda, F.-A.; Sublemontier, O.; Coppalle, A.; Yon, J.; Miserque, F.; Mostefaoui, T.; Regier, T. Z.; Mitchell, J.-B. A.; Miron, C.

    2016-01-01

    Many studies have been conducted on the environmental impacts of combustion generated aerosols. Due to their complex composition and morphology, their chemical reactivity is not well understood and new developments of analysis methods are needed. We report the first demonstration of in-flight X-ray based characterizations of freshly emitted soot particles, which is of paramount importance for understanding the role of one of the main anthropogenic particulate contributors to global climate change. Soot particles, produced by a burner for several air-to-fuel ratios, were injected through an aerodynamic lens, focusing them to a region where they interacted with synchrotron radiation. X-ray photoelectron spectroscopy and carbon K-edge near-edge X-ray absorption spectroscopy were performed and compared to those obtained for supported samples. A good agreement is found between these samples, although slight oxidation is observed for supported samples. Our experiments demonstrate that NEXAFS characterization of supported samples provides relevant information on soot composition, with limited effects of contamination or ageing under ambient storage conditions. The highly surface sensitive XPS experiments of airborne soot indicate that the oxidation is different at the surface as compared to the bulk probed by NEXAFS. We also report changes in soot’s work function obtained at different combustion conditions. PMID:27883014

  4. In situ Monitoring of Synchrotron X-Ray-Induced Radiolysis Effects on Chromium Species Using X-Ray Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Men, S.; Anderson, A. J.; Mayanovic, R. A.

    2017-05-01

    Synchrotron X-ray radiolysis-induced redox in a chromium aqueous solution was monitored using in situ X-ray absorption spectroscopy. The radiolysis in the fluid sample within a specifically designed hydrothermal diamond anvil cell caused the oxidation of Cr(III) to Cr(VI) upon heating from room temperature to 400°C, and reduction of Cr(VI) to Cr(III) at 500°C. The two fitted components of the pre-edge features of the Cr K-edge spectra were used to identify the presence of Cr(VI) in the solution.

  5. Quabantitative interpretation of molecular dynamics simulations for X-ray photoelectron spectroscopy of aqueous solutions

    PubMed Central

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

    2016-01-01

    Over the past decade, energy-dependent ambient pressure X-ray photoelectron spectroscopy (AP-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 at 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. PMID:27389231

  6. 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.

  7. Electronic Structures of Uranium Compounds Studied by Soft X-ray Photoelectron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Fujimori, Shin-ichi; Takeda, Yukiharu; Okane, Tetsuo; Saitoh, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; Yamamoto, Etsuji; Ōnuki, Yoshichika

    2016-06-01

    The electronic structures of uranium-based compounds have been studied by photoelectron spectroscopy with soft X-ray synchrotron radiation. Angle-resolved photoelectron spectroscopy with soft X-rays has made it possible to directly observe their bulk band structures and Fermi surfaces. It has been shown that the band structures and Fermi surfaces of itinerant compounds such as UB2, UN, and UFeGa5 are quantitatively described by a band-structure calculation treating all U 5f electrons as itinerant. Furthermore, the overall electronic structures of heavy-fermion compounds such as UPd2Al3, UNi2Al3, and URu2Si2 are also explained by a band-structure calculation, although some disagreements exist, which might originate from the electron correlation effect. This suggests that the itinerant description of U 5f states is an appropriate starting point for the description of their electronic structures. The situation is similar for ferromagnetic superconductors such as UGe2, URhGe, UCoGe, and UIr, although the complications from their low-symmetry crystal structures make it more difficult to describe their detailed electronic structures. The local electronic structures of the uranium site have been probed by core-level photoelectron spectroscopy with soft X-rays. The comparisons of core-level spectra of heavy-fermion compounds with typical itinerant and localized compounds suggest that the local electronic structures of most itinerant and heavy-fermion compounds are close to the U 5f3 configuration except for UPd2Al3 and UPt3. The core-level spectrum of UPd2Al3 has similarities to those of both itinerant and localized compounds, suggesting that it is located at the boundary between the itinerant and localized states. Moreover, the spectrum of UPt3 is very close to that of the localized compound UPd3, suggesting that it is nearly localized, although there are narrow quasi-particle bands in the vicinity of EF.

  8. High energy X-ray phase and dark-field imaging using a random absorption mask.

    PubMed

    Wang, Hongchang; Kashyap, Yogesh; Cai, Biao; Sawhney, Kawal

    2016-07-28

    High energy X-ray imaging has unique advantage over conventional X-ray imaging, since it enables higher penetration into materials with significantly reduced radiation damage. However, the absorption contrast in high energy region is considerably low due to the reduced X-ray absorption cross section for most materials. Even though the X-ray phase and dark-field imaging techniques can provide substantially increased contrast and complementary information, fabricating dedicated optics for high energies still remain a challenge. To address this issue, we present an alternative X-ray imaging approach to produce transmission, phase and scattering signals at high X-ray energies by using a random absorption mask. Importantly, in addition to the synchrotron radiation source, this approach has been demonstrated for practical imaging application with a laboratory-based microfocus X-ray source. This new imaging method could be potentially useful for studying thick samples or heavy materials for advanced research in materials science.

  9. Iron distances in hemoglobin: comparison of x-ray crystallographic and extended x-ray absorption fine structure studies

    SciTech Connect

    Fermi, G.; Perutz, M.F.; Shulman, R.G.

    1987-09-01

    A comparison is presented of the structures obtained around the iron atom in deoxyhemoglobin (Hb). The data come from extended x-ray absorption fine structure (EXAFS) studies of the iron, which gave Fe-porphyrin nitrogen distances of 2.06 +- 0.01 A, and from the most recent high-resolution x-ray crystallographic study, which gave exactly the same distance-2.06 +- 0.02 A. The distance of Fe above the plane of the porphyrin nitrogens was 0.38 +- 0.04 A from the crystallographic study; this value is not far from the upper limit of the distances 0.20 +- /sub 0.20//sup 0.10/ A calculated from the EXAFS experiment by triangulation. These distances above the nitrogen plane are shorter than those estimated in the earliest x-ray structures

  10. Charge transfer in nanocrystalline-Au /ZnO nanorods investigated by x-ray spectroscopy and scanning photoelectron microscopy

    NASA Astrophysics Data System (ADS)

    Chiou, J. W.; Ray, S. C.; Tsai, H. M.; Pao, C. W.; Chien, F. Z.; Pong, W. F.; Tsai, M.-H.; Wu, J. J.; Tseng, C. H.; Chen, C.-H.; Lee, J. F.; Guo, J.-H.

    2007-05-01

    O K- and Zn and Au L3-edge x-ray absorption near-edge structure (XANES), x-ray emission spectroscopy (XES), and scanning photoelectron microscopy (SPEM) are performed to investigate the electronic structure of ZnO nanorods with nanocrystalline (nc)-Au particles grown on the surfaces. The XANES spectra of nc-Au /ZnO nanorods reveal the decrease of the number of both O 2p and Zn 4s/3d unoccupied states with the increase of the nc-Au particle size. The number of Au 6s /5d unoccupied states increases when the size of nc-Au particle decreases, indicating that the deposition of nc-Au particles on the surface of ZnO nanorods promotes charge transfer from the ZnO nanorods to nc-Au particles. Excitation energy dependent XES and SPEM spectra show that the number of electrons in the valence band of O 2p-Zn 4sp hybridized states decreases as the nc-Au particle size increases, revealing that more electrons are excited from the valence band to the conduction band of ZnO nanorods and the storage of electrons in nc-Au particles.

  11. A Comprehensive X-Ray Absorption Model for Atomic Oxygen

    NASA Technical Reports Server (NTRS)

    Gorczyca, T. W.; Bautista, M. A.; Hasoglu, M. F.; Garcia, J.; Gatuzz, E.; Kaastra, J. S.; Kallman, T. R.; Manson, S. T.; Mendoza, C.; Raassen, A. J. J.; de Vries, C. P.; Zatsarinny, O.

    2013-01-01

    An analytical formula is developed to accurately represent the photoabsorption cross section of atomic Oxygen for all energies of interest in X-ray spectral modeling. In the vicinity of the K edge, a Rydberg series expression is used to fit R-matrix results, including important orbital relaxation effects, that accurately predict the absorption oscillator strengths below threshold and merge consistently and continuously to the above-threshold cross section. Further, minor adjustments are made to the threshold energies in order to reliably align the atomic Rydberg resonances after consideration of both experimental and observed line positions. At energies far below or above the K-edge region, the formulation is based on both outer- and inner-shell direct photoionization, including significant shake-up and shake-off processes that result in photoionization-excitation and double-photoionization contributions to the total cross section. The ultimate purpose for developing a definitive model for oxygen absorption is to resolve standing discrepancies between the astronomically observed and laboratory-measured line positions, and between the inferred atomic and molecular oxygen abundances in the interstellar medium from XSTAR and SPEX spectral models.

  12. A comprehensive X-ray absorption model for atomic oxygen

    SciTech Connect

    Gorczyca, T. W.; Bautista, M. A.; Mendoza, C.; Hasoglu, M. F.; García, J.; Gatuzz, E.; Kaastra, J. S.; Raassen, A. J. J.; De Vries, C. P.; Kallman, T. R.; Manson, S. T.; Zatsarinny, O.

    2013-12-10

    An analytical formula is developed to accurately represent the photoabsorption cross section of O I for all energies of interest in X-ray spectral modeling. In the vicinity of the K edge, a Rydberg series expression is used to fit R-matrix results, including important orbital relaxation effects, that accurately predict the absorption oscillator strengths below threshold and merge consistently and continuously to the above-threshold cross section. Further, minor adjustments are made to the threshold energies in order to reliably align the atomic Rydberg resonances after consideration of both experimental and observed line positions. At energies far below or above the K-edge region, the formulation is based on both outer- and inner-shell direct photoionization, including significant shake-up and shake-off processes that result in photoionization-excitation and double-photoionization contributions to the total cross section. The ultimate purpose for developing a definitive model for oxygen absorption is to resolve standing discrepancies between the astronomically observed and laboratory-measured line positions, and between the inferred atomic and molecular oxygen abundances in the interstellar medium from XSTAR and SPEX spectral models.

  13. Self-consistent aspects of x-ray absorption calculations.

    PubMed

    Bunău, O; Joly, Y

    2009-08-26

    We implemented a self-consistent, real-space x-ray absorption calculation within the FDMNES code. We performed the self-consistency within several schemes and identified which one is the most appropriate. We show a method that allows a rigorous setting of the Fermi level and thus an estimation of the energy cutoff for the identification and elimination of the occupied states. We investigated what are the structures where one can afford performing the self-consistent calculation at a lesser cluster radius than the absorption one. We exemplify the effects of the self-consistency at the K-edge and for several reference cases, including the copper Cu and the rutile TiO(2). We verified the robustness of our procedure on the transitional 3d and 4d elements. Although amelioration can be noticed, the self-consistency performed at the K-edge does not bring a major improvement of the calculated spectra. Taking into consideration a non-self-consistent, non-spherical potential gives better results than a self-consistent muffin-tin approximation calculation.

  14. An XPS (X-Ray Photoelectron Spectroscopy) Study of the Composition of Thin Polyimide Films Formed by Vapor Deposition.

    DTIC Science & Technology

    1987-07-15

    1985) 2857. 13. B. D. Silverman, J. W. Bartha, J. G. Clabes, P. S Ho and A. R. Rossi, J. Polym . Sci. Part A 24 (1986) 3325. 14. E. Cartier , P. Pfluger...Benzenetetracarboxylic anhydride (PMDA), imidization, polymer , in situ, X-ray Photoelectron Spectroscopy (XPS),Cu(111) 20. ABSTRACT (Continue an...ODA) and 1,2,4,5 Benzenetetracarboxylic anhydride (PMDA). The imidization reaction leading to polymer formation was followed in situ with X-ray

  15. X-ray absorption fine structure and X-ray excited optical luminescence studies of II-VI semiconducting nanostructures

    NASA Astrophysics Data System (ADS)

    Murphy, Michael Wayne

    2010-06-01

    Various II-VI semiconducting nanomaterials such as ZnO-ZnS nanoribbons (NRs), CdSxSe1-x nanostructures, ZnS:Mn NRs, ZnS:Mn,Eu nanoprsims (NPs), ZnO:Mn nanopowders, and ZnO:Co nanopowders were synthesized for study. These materials were characterized by techniques such as scanning electron microscopy, transmission electron microscopy, element dispersive X-ray spectroscopy, selected area electron diffraction, and X-ray diffraction. The electronic and optical properties of these nanomaterials were studied by X-ray absorption fine structure (XAFS) spectroscopy and X-ray excited optical luminescence (XEOL) techniques, using tuneable soft X-rays from a synchrotron light source. The complementary nature ofthe XAFS and XEOL techniques give site, element and chemical specific measurements which allow a better understanding of the interplay and role of each element in the system. Chemical vapour deposition (CVD) of ZnS powder in a limited oxygen environment resulted in side-by-side biaxial ZnO-ZnS NR heterostructures. The resulting NRs contained distinct wurtzite ZnS and wurtzite ZnO components with widths of 10--100 nm and 20 --500 nm, respectively and a uniform interface region of 5-15 nm. XAFS and XEOL measurements revealed the luminescence of ZnO-ZnS NRs is from the ZnO component. The luminescence of CdSxSe1-x nanostructures is shown to be dependent on the S to Se ratio, with the band-gap emission being tunable between that of pure CdS and CdSe. Excitation of the CdSxSe 1-x nanostructures by X-ray in XEOL has revealed new de-excitation channels which show a defect emission band not seen by laser excitation. CVD of Mn2+ doped ZnS results in nanostructures with luminescence dominated by the yellow Mn2+ emission due to energy transfer from the ZnS host to the Mn dopant sites. The addition of EuCl3 to the reactants in the CVD process results in a change in morphology from NR to NP. Zn1-xMnxO and Zn1-xCOxO nanopowders were prepared by sol-gel methods at dopant concentrations

  16. 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.

  17. 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.

  18. Enzymatic modification and X-ray photoelectron spectroscopy analysis of a functionalized polydiacetylene thin film

    SciTech Connect

    Wilson, T.E.; Spevak, W.; Bednarski, M.D. Lawrence Berkeley Lab., CA ); Charych, D.H. )

    1994-05-01

    The mild conditions and specificity of biological catalysts are attractive incentives for their use in the formation of surfaces with well-defined chemical functionality. Herein, we describe the synthesis, characterization, and enzymatic modification of a functionalized polymeric bilayer assembly. The assembly is composed of a self-assembled monolayer of octadecylsilane and a Langmuir-Blodgett monolayer of polydiacetylene functionalized with the dipeptide phenylalanine-alanine (Phe-Ala). We demonstrate via X-ray photoelectron spectroscopy surface analysis that the surface-bound Phe-Ala dipeptide is a substrate for specific cleavage by the enzyme subtilisin BPN[prime]. In-situ surface transformations via enzymatic synthesis or cleavage offer an alternative to chemical treatments of organic thin films. 28 refs., 4 figs.

  19. An x ray photoelectron spectroscopy study of Au(x)In(y) alloys

    NASA Technical Reports Server (NTRS)

    Jayne, Douglas T.; Fatemi, Navid S.; Weizer, Victor G.

    1990-01-01

    Four gold-indium alloys were studied by x ray photoelectron spectroscopy. The binding energies and intensity ratios of the Au 4f7/2 and In 3d5/2 core levels were determined for the bulk alloy compositions of Au(10 percent In), Au3In, AuIn, and AuIn2. These values were determined for the native oxides on the materials, for the surfaces prepared by ion bombardment to remove the oxide and for surfaces scraped in-situ with a ceramic tool to expose the bulk composition. These results furnish calibration values that allow determination of the composition of thin films of this alloy system. In addition the binding energies add to the data base for understanding the effect of alloying on core level binding energies. As an illustration, these results are used to determine the composition of a series of alloy films formed by incongruent evaporation of an alloy charge.

  20. X-ray photoelectron and Raman spectroscopic studies of MeV proton irradiated graphite

    NASA Astrophysics Data System (ADS)

    Mathew, S.; Joseph, B.; Sekhar, B. R.; Dev, B. N.

    2008-07-01

    Poly-crystalline graphite samples were irradiated using 2.25 MeV H + ions with a fluence of 2 × 10 17 ions/cm 2. Magnetic ordering in highly oriented pyrolytic graphite samples have been reported earlier under the similar irradiation conditions [Esquinazi et al., Phys. Rev. Lett. 91 (2003) 227201]. In that study, the authors attribute the observed irradiation induced magnetic ordering to the formation of a mixed sp 2-sp 3 hybridized carbon atoms. In the present study, we report the X-ray photoelectron and Raman spectroscopic studies on pristine and irradiated samples. Irradiated samples are found to show an increased number of sp 3 hybridized carbon atoms. However, the Raman spectrum, specially the second order data, do indicate that the nature of the graphene lattice structure has been preserved in the irradiated samples. The mechanisms for the irradiation induced enhancement in sp 3 hybridization are discussed.

  1. 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

  2. Second International Workshop on Ambient Pressure X-ray Photoelectron Spectroscopy

    SciTech Connect

    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 the 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.

  3. Uses of Auger and x ray photoelectron spectroscopy in the study of adhesion and friction

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    1990-01-01

    Three studies are described characterizing the possible contributions of surface science to tribology. These include surface contamination formed by the interaction of a surface with the environment, contaminants obtained with diffusion of compounds, and surface chemical changes resulting from selective thermal evaporation. Surface analytical tools such as Auger electron spectroscopy (AES) and x ray photoelectron spectroscopy (XPS) incorporated directly into adhesion and friction systems are primarily used to define the nature of tribological surfaces before and after tribological experimentation and to characterize the mechanism of solid-to-solid interaction. Emphasis is on fundamental studies involving the role of surfaces in controlling the adhesion and friction properties of materials emerging as a result of the surface analyses. The materials which were studied include metals and ceramics such as elemental metals, amorphous alloys (metallic glasses), and silicon-based ceramics.

  4. Determination of MgO/AlN heterojunction band offsets by x-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Yang, A. L.; Song, H. P.; Liu, X. L.; Wei, H. Y.; Guo, Y.; Zheng, G. L.; Jiao, C. M.; Yang, S. Y.; Zhu, Q. S.; Wang, Z. G.

    2009-02-01

    MgO is a promising gate dielectric and surface passivation film for GaN/AlGaN transistors, but little is known of the band offsets in the MgO/AlN system. X-ray photoelectron spectroscopy was used to measure the energy discontinuity in the valence band (ΔEv) of MgO/AlN heterostructures. A value of ΔEv=0.22±0.08 eV was obtained. Given the experimental band gap of 7.83 eV for MgO, a type-I heterojunction with a conduction band offset of ˜1.45 eV is found. The accurate determination of the valence and conduction band offsets is important for use of III-N alloys based electronic devices.

  5. Probing DNA hybridization efficiency and single base mismatch by X-ray photoelectron spectroscopy.

    PubMed

    Liu, Zheng-Chun; Zhang, Xin; He, Nong-Yue; Lu, Zu-Hong; Chen, Zhen-Cheng

    2009-07-01

    We demonstrated the use of X-ray photoelectron spectroscopy (XPS) to study DNA hybridization. Target DNA labeled with hexachloro-fluorescein (HEX) was hybridized to DNA arrays with four different probes. Each probe dot of the hybridized arrays was detected with XPS. The XPS Cl2p peak areas were found to decrease with an increase in mismatched bases in DNA probes. The Cl2p core-level peak area ratio of a probe perfectly matched to one, two and three base-mismatched probes accorded well with the results of conventional fluorescent imaging, which shows that XPS is a potential tool for analyzing DNA arrays. The DNA arrays' hybridization efficiency was assessed by the molar ratio of chlorine to phosphorus in a DNA strand, which was determined from the relevant XPS Cl2p and P2p core-level peak areas after hybridization. This could provide a new method to detect DNA hybridization efficiency.

  6. Early stages of surface graphitization on nanodiamond probed by x-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Petit, Tristan; Arnault, Jean-Charles; Girard, Hugues A.; Sennour, Mohamed; Bergonzo, Philippe

    2011-12-01

    We have investigated the early stages of graphitization on detonation nanodiamond during sequential annealing treatments under vacuum using x-ray photoelectron spectroscopy. Two different temperature-dependent regimes were observed. Below 900 °C, the nanodiamond surface reconstructs into graphitic domain but does not alter the diamond core. Above 900 °C, graphitization, i.e., carbon hybridization changes from sp3 to sp2, occurs from the nanodiamond surface toward the diamond core. Graphitization is observed at much lower temperatures on nanodiamonds than on bulk diamond due to the high concentration of structural defects on their surface. These results indicate that low-temperature annealing under vacuum is an efficient method to uncouple surface and bulk graphitization. Hybrid nanocarbons formed in these conditions, constituted of a diamond core with a thin graphitic outer shell, may have interesting catalytic and chemical properties.

  7. Assessment of the weathering of protective coatings using x-ray photoelectron spectroscopy

    SciTech Connect

    Wilson, G.R.; Skerry, B.S.

    1993-12-31

    Three fully formulated coatings systems: polyurethane, alkyd and latex, were exposed either outdoors to a natural industrial atmospheric environment or to an accelerated corrosion/weathering test incorporating UV-condensation exposures and wet/dry corrosion cycling or to an RF generated {open_quotes}in-glow{close_quotes} oxygen plasma. Changes in coating surface chemistry as a function of time in each environment were followed using X-ray photoelectron spectroscopy (XPS). XPS detected changes in the surface composition of all three systems for all three environmentS. Some of the trends in degradation detected on the exterior exposed samples were reproduced by both accelerated tests. The data obtained from this study also suggested that the corrosion/weathering test would benefit from an increase in the amount of UV exposure over that which is currently used. Oxygen plasma etching also appears to have some potential as a tool for accelerated weathering of paint systems.

  8. X-ray photoelectron spectroscopy study of catalyzed aluminum carbide formation at aluminum-carbon interfaces

    NASA Technical Reports Server (NTRS)

    Rabenberg, L.; Maruyama, Benji

    1990-01-01

    Aluminum carbide may form at aluminum-graphite interfaces during the high-temperature processing of graphite fiber-reinforced aluminum metal matrix composites. The chemical interactions leading to the formation of the aluminum carbide in the solid state involve the breaking of the carbon-carbon bonds within the graphite, the transport of the carbon atoms across the interface, and the reaction with the aluminum to form Al4C3. The aluminum carbide formation process has been followed using X-ray photoelectron spectroscopy of model, thin-film, reaction couples. The overall reaction is shown to be catalyzed by the presence of water vapor. Water at the interface increases reaction kinetics by apparently weakening the bonds between the surface carbon atoms and their substrate. This result is in general agreement with what is known to occur during the oxidation of graphite in air.

  9. X-ray photoelectron spectroscopy analysis of organic materials etched by charged water droplet impact

    SciTech Connect

    Sakai, Yuji; Iijima, Yoshitoki; Takaishi, Riou; Asakawa, Daiki; Hiraoka, Kenzo

    2009-07-15

    Electrospray droplet impact (EDI) has been developed for matrix-free secondary ion mass spectrometry for surface analysis. When a target is etched by EDI, the physical etching on the target is suppressed to minimal, i.e., the occurrence of shallow surface etching. A novel approach to shallow surface etching of polystyrene (PS) by EDI was investigated. The charged water droplets were irradiated to a bulk and a spin coated PS. After irradiation, these samples were analyzed by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy. It was found that XPS spectra for PS were independent on the irradiation time by EDI. This indicates that EDI is a unique technique for the surface etching of the organic materials without leaving any damage on the etched surface.

  10. The Rh oxide ultrathin film on Rh(100): an x-ray photoelectron diffraction study.

    PubMed

    Zhan, Rong Rong; Vesselli, Erik; Baraldi, Alessandro; Lizzit, Silvano; Comelli, Giovanni

    2010-12-07

    The surface and interface structure of the RhO(2) ultrathin film grown on Rh(100) is investigated by means of x-ray photoelectron diffraction. Experimental and simulated one- and two-dimensional angular distribution intensities of the O1s and Rh3d(5/2) chemically shifted core levels are quantitatively analyzed. The previously proposed O-Rh-O trilayer model is independently confirmed. A rippled buckling of the metal surface is observed at the oxide-metal interface, with a mean interfacial Rh-O distance which is 0.2 Å larger with respect to previous findings. The link between the local atomic rearrangement and the overall geometric and electronic properties of the oxide is discussed on the basis of a thorough comparison with the corresponding RhO(2) rutile structure.

  11. 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.

  12. Determination of band profiles in GaN films using hard X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Saito, Shinji; Yoshiki, Masahiko; Nunoue, Shinya; Sano, Nobuyuki

    2017-02-01

    We investigated band-profile control by introducing interlayers between a semiconductor and metal contact layers to improve the electrical properties of GaN-based semiconductor devices. We evaluated the electronic structure of the semiconductor surface and the metal/semiconductor interface by hard X-ray photoelectron spectroscopy. We also performed Monte Carlo simulations using the Boltzmann transport equation under the potential profile obtained using the Poisson equation. The band profile in the semiconductor substrate was then examined by comparing the energy spectra from the simulations with those from the experiments. We obtained good agreement between the two results. The present experimental and theoretical methods allow one to determine the band profile near the surface of a semiconductor as well as that in a metal interface. This approach may become a useful tool in the design and/or evaluation of processing conditions.

  13. Core-Hole Molecular Frame X-Ray Photoelectron Angular Distributions as Molecular Geometry Probes

    NASA Astrophysics Data System (ADS)

    Trevisan, Cynthia; Williams, Joshua; Menssen, Adrian; Weber, Thorsten; Rescigno, Thomas; McCurdy, Clyde; Landers, Allen

    2014-05-01

    We present experimental and theoretical results for the angular dependence of electrons ejected from the core orbitals of ethane (C2H6) and tetrafluoromethane (CF4) in an effort to understand the origin of the imaging effect by which the molecular frame photoelectron angular distributions (MFPADs) for removing an electron from a 1s orbital effectively image the geometry of a class of molecules. At low energies, our calculations predict the same imaging effect in X2H6 previously found in CH4, H2O and NH3. By contrast, in experiment and calculations CF4 displays an anti-imaging effect, whereby the electron ejected by core photoionization has the tendency to avoid molecular bonds, if averaged over directions of polarization of the incident X-ray beam. Our measurements employ the COLTRIMS method and the calculations were performed with the Complex Kohn Variational method.

  14. 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.

  15. 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.

  16. X-ray photoelectron spectroscopy for characterization of bionanocomposite functional materials for energy-harvesting technologies.

    PubMed

    Artyushkova, Kateryna; Atanassov, Plamen

    2013-07-22

    The analysis of hybrid multicomponent bioorganic and bioinorganic composite materials related to energy technologies by using X-ray photoelectron spectroscopy is discussed. The approaches and considerations of overcoming the difficulties of analyzing hybrid multicomponent materials are demonstrated for different types of materials used in bioenzyme fuel cells, that is, enzyme immobilization in a hybrid inorganic-organic matrix, analysis of peptide binding and structure in the mediation of silica nanoparticle formation, analysis of enzyme-polymeric multilayered architectures obtained through layer-by-layer assembly, and study of the mechanism of electropolymerization. Thorough optimization of experimental design through analysis of an adequate set of reference materials, relevant timescales of sample preparation and X-ray exposure, careful peak decomposition and cross-correlation between elemental speciation, results in a detailed understanding of the chemistry of nanocomposite constituents and interactions between them. The methodology presented and examples discussed are of significant importance to the scientific and engineering communities focused on the immobilization of enzymes, proteins, peptides, and other large biological molecules on solid substrates. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. X-Ray Photoelectron Spectroscopy Investigation of the Nitrogen Species in Photoactive Perfluorophenylazide-Modified Surfaces

    PubMed Central

    Zorn, Gilad; Liu, Li-Hong; Árnadóttir, Líney; Wang, Hui; Gamble, Lara J.; Castner, David G.; Yan, Mingdi

    2014-01-01

    X-ray Photoelectron Spectroscopy (XPS) was used to characterize the nitrogen species in perfluorophenylazide (PFPA) self-assembled monolayers. PFPA chemistry is a novel immobilization method for tailoring the surface properties of materials. It is a simple route for the efficient immobilization of graphene, proteins, carbohydrates and synthetic polymers onto a variety of surfaces. Upon light irradiation, the azido group in PFPA is converted to a highly reactive singlet nitrene species that readily undergoes CH insertion and C=C addition reactions. Here, the challenge of characterizing the PFPA modified surfaces was addressed by detailed XPS experimental analyses. The three nitrogen peaks detected in the XPS N1s spectra were assigned to amine/amide (400.5 eV) and azide (402.1 and 405.6 eV) species. The observed 2:1 ratio of the areas from the 402.1 eV to 405.6 eV peaks suggests the assignment of the peak at 402.1 eV to the two outer nitrogen atoms in the azido group and assignment of the peak at 405.6 eV to the central nitrogen atom in the azido group. The azide decomposition as the function of x-ray exposure was also determined. Finally, XPS analyses were conducted on patterned graphene to investigate the covalent bond formation between the PFPA and graphene. This study provides strong evidence for the formation of covalent bonds during the PFPA photocoupling process. PMID:24535931

  18. Depth-Resolved X-ray Absorption Spectroscopy by Means of Grazing Emission X-ray Fluorescence.

    PubMed

    Kayser, Yves; Sá, Jacinto; Szlachetko, Jakub

    2015-11-03

    Grazing emission X-ray fluorescence (GEXRF) is well suited for nondestructive elemental-sensitive depth-profiling measurements on samples with nanometer-sized features. By varying the grazing emission angle under which the X-ray fluorescence signal is detected, the probed depth range can be tuned from a few to several hundred nanometers. The dependence of the XRF intensity on the grazing emission angle can be assessed in a sequence of measurements or in a scanning-free approach using a position-sensitive area detector. Hereafter, we will show that the combination of scanning-free GEXRF and fluorescence detected X-ray absorption spectroscopy (XAS) allows for depth-resolved chemical speciation measurements with nanometer-scale accuracy. While the conventional grazing emission geometry is advantageous to minimize self-absorption effects, the use of a scanning-free setup makes the sequential scanning of the grazing emission angles obsolete and paves the way toward time-resolved depth-sensitive XAS measurements. The presented experimental approach was applied to study the surface oxidation of an Fe layer on the top of bulk Si and of a Ge bulk sample. Thanks to the penetrating properties and the insensitivity toward the electric conduction properties of the incident and emitted X-rays, the presented experimental approach is well suited for in situ sample surface studies in the nanometer regime.

  19. X-ray absorption spectroscopy using a self-seeded soft X-ray free-electron laser

    SciTech Connect

    Kroll, Thomas; Kern, Jan; Kubin, Markus; Ratner, Daniel; Gul, Sheraz; Fuller, Franklin D.; Löchel, Heike; Krzywinski, Jacek; Lutman, Alberto; Ding, Yuantao; Dakovski, Georgi L.; Moeller, Stefan; Turner, Joshua J.; Alonso-Mori, Roberto; Nordlund, Dennis L.; Rehanek, Jens; Weniger, Christian; Firsov, Alexander; Brzhezinskaya, Maria; Chatterjee, Ruchira; Lassalle-Kaiser, Benedikt; Sierra, Raymond G.; Laksmono, Hartawan; Hill, Ethan; Borovik, Andrew; Erko, Alexei; Föhlisch, Alexander; Mitzner, Rolf; Yachandra, Vittal K.; Yano, Junko; Wernet, Philippe; Bergmann, Uwe

    2016-09-19

    X-ray free electron lasers (XFELs) enable unprecedented new ways to study the electronic structure and dynamics of transition metal systems. L-edge absorption spectroscopy is a powerful technique for such studies and the feasibility of this method at XFELs for solutions and solids has been demonstrated. But, the required x-ray bandwidth is an order of magnitude narrower than that of self-amplified spontaneous emission (SASE), and additional monochromatization is needed. We compare L-edge x-ray absorption spectroscopy (XAS) of a prototypical transition metal system based on monochromatizing the SASE radiation of the linac coherent light source (LCLS) with a new technique based on self-seeding of LCLS. We demonstrate how L-edge XAS can be performed using the self-seeding scheme without the need of an additional beam line monochromator. Lastly, we show how the spectral shape and pulse energy depend on the undulator setup and how this affects the x-ray spectroscopy measurements.

  20. X-ray absorption spectroscopy using a self-seeded soft X-ray free-electron laser

    DOE PAGES

    Kroll, Thomas; Kern, Jan; Kubin, Markus; ...

    2016-09-19

    X-ray free electron lasers (XFELs) enable unprecedented new ways to study the electronic structure and dynamics of transition metal systems. L-edge absorption spectroscopy is a powerful technique for such studies and the feasibility of this method at XFELs for solutions and solids has been demonstrated. But, the required x-ray bandwidth is an order of magnitude narrower than that of self-amplified spontaneous emission (SASE), and additional monochromatization is needed. We compare L-edge x-ray absorption spectroscopy (XAS) of a prototypical transition metal system based on monochromatizing the SASE radiation of the linac coherent light source (LCLS) with a new technique based onmore » self-seeding of LCLS. We demonstrate how L-edge XAS can be performed using the self-seeding scheme without the need of an additional beam line monochromator. Lastly, we show how the spectral shape and pulse energy depend on the undulator setup and how this affects the x-ray spectroscopy measurements.« less

  1. X-ray absorption spectroscopy using a self-seeded soft X-ray free-electron laser

    PubMed Central

    Kroll, Thomas; Kern, Jan; Kubin, Markus; Ratner, Daniel; Gul, Sheraz; Fuller, Franklin D.; Löchel, Heike; Krzywinski, Jacek; Lutman, Alberto; Ding, Yuantao; Dakovski, Georgi L.; Moeller, Stefan; Turner, Joshua J.; Alonso-Mori, Roberto; Nordlund, Dennis L.; Rehanek, Jens; Weniger, Christian; Firsov, Alexander; Brzhezinskaya, Maria; Chatterjee, Ruchira; Lassalle-Kaiser, Benedikt; Sierra, Raymond G.; Laksmono, Hartawan; Hill, Ethan; Borovik, Andrew; Erko, Alexei; Föhlisch, Alexander; Mitzner, Rolf; Yachandra, Vittal K.; Yano, Junko; Wernet, Philippe; Bergmann, Uwe

    2016-01-01

    X-ray free electron lasers (XFELs) enable unprecedented new ways to study the electronic structure and dynamics of transition metal systems. L-edge absorption spectroscopy is a powerful technique for such studies and the feasibility of this method at XFELs for solutions and solids has been demonstrated. However, the required x-ray bandwidth is an order of magnitude narrower than that of self-amplified spontaneous emission (SASE), and additional monochromatization is needed. Here we compare L-edge x-ray absorption spectroscopy (XAS) of a prototypical transition metal system based on monochromatizing the SASE radiation of the linac coherent light source (LCLS) with a new technique based on self-seeding of LCLS. We demonstrate how L-edge XAS can be performed using the self-seeding scheme without the need of an additional beam line monochromator. We show how the spectral shape and pulse energy depend on the undulator setup and how this affects the x-ray spectroscopy measurements. PMID:27828320

  2. X-ray absorption spectroscopy of warm dense matter with betatron x-ray radiation (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Albert, Felicie

    2017-05-01

    Betatron x-ray radiation, driven by electrons from laser-wakefield acceleration, has unique properties to probe high energy density (HED) plasmas and warm dense matter. Betatron radiation is produced when relativistic electrons oscillate in the plasma wake of a laser pulse. Its properties are similar to those of synchrotron radiation, with a 1000 fold shorter pulse. This presentation will focus on the experimental challenges and results related to the development of betatron radiation for x-ray absorption spectroscopy of HED matter at large-scale laser facilities. A detailed presentation of the source mechanisms and characteristics in the blowout regime of laser-wakefield acceleration will be followed by a description of recent experiments performed at the Linac Coherent Light Source (LCLS). At LCLS, we have recently commissioned the betatron x-ray source driven by the MEC short pulse laser (1 J, 40 fs). The source is used as a probe for investigating the X-ray absorption near edge structure (XANES) spectrum at the K- or L-edge of iron and silicon oxide driven to a warm dense matter state (temperature of a few eV and solid densities). The driver is either LCLS itself or an optical laser. These experiments demonstrate the capability to study the electron-ion equilibration mechanisms in warm dense matter with sub-picosecond resolution.

  3. X-ray absorption spectroscopy using a self-seeded soft X-ray free-electron laser.

    PubMed

    Kroll, Thomas; Kern, Jan; Kubin, Markus; Ratner, Daniel; Gul, Sheraz; Fuller, Franklin D; Löchel, Heike; Krzywinski, Jacek; Lutman, Alberto; Ding, Yuantao; Dakovski, Georgi L; Moeller, Stefan; Turner, Joshua J; Alonso-Mori, Roberto; Nordlund, Dennis L; Rehanek, Jens; Weniger, Christian; Firsov, Alexander; Brzhezinskaya, Maria; Chatterjee, Ruchira; Lassalle-Kaiser, Benedikt; Sierra, Raymond G; Laksmono, Hartawan; Hill, Ethan; Borovik, Andrew; Erko, Alexei; Föhlisch, Alexander; Mitzner, Rolf; Yachandra, Vittal K; Yano, Junko; Wernet, Philippe; Bergmann, Uwe

    2016-10-03

    X-ray free electron lasers (XFELs) enable unprecedented new ways to study the electronic structure and dynamics of transition metal systems. L-edge absorption spectroscopy is a powerful technique for such studies and the feasibility of this method at XFELs for solutions and solids has been demonstrated. However, the required x-ray bandwidth is an order of magnitude narrower than that of self-amplified spontaneous emission (SASE), and additional monochromatization is needed. Here we compare L-edge x-ray absorption spectroscopy (XAS) of a prototypical transition metal system based on monochromatizing the SASE radiation of the linac coherent light source (LCLS) with a new technique based on self-seeding of LCLS. We demonstrate how L-edge XAS can be performed using the self-seeding scheme without the need of an additional beam line monochromator. We show how the spectral shape and pulse energy depend on the undulator setup and how this affects the x-ray spectroscopy measurements.

  4. X-ray photoelectron spectroscopy and luminescent properties of Y2O3:Bi3+ phosphor

    NASA Astrophysics Data System (ADS)

    Jafer, R. M.; Coetsee, E.; Yousif, A.; Kroon, R. E.; Ntwaeaborwa, O. M.; Swart, H. C.

    2015-03-01

    X-ray photoelectron spectroscopy (XPS) results provided proof for the blue and green emission of Bi3+ in the Y2O3:Bi3+ phosphor. The Y2O3:Bi3+ phosphor was successfully prepared by the combustion process during the investigation of down-conversion materials for Si solar cell application. The X-ray diffraction (XRD) patterns indicated that a single-phase cubic crystal structure with the Ia3 space group was formed. X-ray photoelectron spectroscopy (XPS) showed that the Bi3+ ion replaces the Y3+ ion in two different coordination sites in the Y2O3 crystal structure. The O 1s peak shows five peaks, two which correlate with the O2- ion in Y2O3 in the two different sites, two which correlate with O2- in Bi2O3 in the two different sites and the remaining peak relates to hydroxide. The Y 3d spectrum shows two peaks for the Y3+ ion in the Y2O3 structure in two different sites and the Bi 4f spectrum shows the Bi3+ ion in the two different sites in Bi2O3. The photoluminescence (PL) results showed three broad emission bands in the blue and green regions under ultraviolet excitation, which were also present for panchromatic cathodoluminescence (CL) results. These three peaks have maxima at ∼3.4, 3.0 and 2.5 eV. The PL emission ∼3.0 eV (blue emission) showed two excitation bands centered at ∼3.7 and 3.4 eV while the PL emission at ∼2.5 eV (green emission) showed a broad excitation band from ∼4 to 3.4 eV. The panchromatic CL images were obtained for selected wavelengths at (2.99 ± 0.08) eV (for blue emission) and (2.34 ± 0.06) eV (for green emission). These luminescence results correlate with the XPS results that show that there are two different Bi3+ sites in the host lattice.

  5. X-Ray Absorption Spectroscopy of Dinuclear Metallohydrolases

    PubMed Central

    Tierney, David L.; Schenk, Gerhard

    2014-01-01

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

  6. Near Edge X-ray Absorption Spectroscopy of Polymers

    NASA Astrophysics Data System (ADS)

    Dhez, Olivier; Ade, Harald; Urquhart, Stephen

    2001-03-01

    Synthetic and natural polymers exhibit a rich carbon, nitrogen and oxygen K-edge Near Edge X-ray Absorption Fine Structure (NEXAFS). The spectroscopic variations with chemical structure and composition are interesting in their own right. In addition, the large spectroscopic variability can be utilized for the compositional analysis of materials. This is particularly useful for high spatial resolution NEXAFS microanalysis at lateral spatial resolutions exceeding that achievable with more traditional compositional analysis tools such as Infrared and NMR spectroscopy. To increase our understanding of NEXAFS spectra and to start a database for microanalysis, we acquired carbon NEXAFS spectra of the following polymers: polycarbonate, poly(oxybenzoate-co-2,6oxynaphthoate), poly (p-phenylene terephtalamide), toluene diisocyanate polyurethane, toluene diisocyanate polyurea, 4,4'-methylene di-p-phenylene isocyanate polyurethane, 4,4'-methylene di-p-phenylene isocyanate polyurea, poly(ether ether ketone), poly(alpha-methylstyrene), poly-styrene, poly bromostyrene, poly(2-vinyl styrene), polyethylene, poly(ethylene oxide), polypropylene, poly(propylene oxide), polyisobutylene, ethylene propylene rubber, poly(methyl -metacrylate). These spectra were obtained in transmission with an energy resolution of 150 meV. The energy scale was carefully calibrated in-situ utilizing C02 gas as a reference. Spectral assignments are made based on model compounds and theoretical calculations.

  7. X-ray Absorption Spectroscopy of the Rare Earth orthophosphates

    SciTech Connect

    Shuh, D.K.; Terminello, L.J.; Boatner, L.A.; Abraham, M.M.

    1993-06-01

    X-ray Absorption Spectroscopy (XAS) of the Rare Earth (RE) 3d levels yields sharp peaks near the edges as a result of strong, quasi-atomic 3d{sup 10}4f{sup n} {yields} 3d-{sup 9}4f{sup n+1} transitions and these transitions exhibit a wealth of spectroscopic features. The XAS measurements of single crystal REPO{sub 4} (RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er) at the 3d edge were performed in the total yield mode at beam line 8-2 at the Stanford Synchrotron Radiation Laboratory (SSRL). The XAS spectra of the RE ions in the orthophosphate matrix generally resemble the XAS of the corresponding RE metal. This is not unexpected and emphasizes the major contribution of the trivalent state to the electronic transitions at the RE 3d edges. These spectra unequivocally identify the transitions originating from well-characterized RE cores and correlate well with previous theoretical investigations.

  8. Thomson Thick X-Ray Absorption in a Broad Absorption Line Quasar, PG 0946+301.

    PubMed

    Mathur; Green; Arav; Brotherton; Crenshaw; deKool; Elvis; Goodrich; Hamann; Hines; Kashyap; Korista; Peterson; Shields; Shlosman; van Breugel W; Voit

    2000-04-20

    We present a deep ASCA observation of a broad absorption line quasar (BALQSO) PG 0946+301. The source was clearly detected in one of the gas imaging spectrometers, but not in any other detector. If BALQSOs have intrinsic X-ray spectra similar to normal radio-quiet quasars, our observations imply that there is Thomson thick X-ray absorption (NH greater, similar1024 cm-2) toward PG 0946+301. This is the largest column density estimated so far toward a BALQSO. The absorber must be at least partially ionized and may be responsible for attenuation in the optical and UV. If the Thomson optical depth toward BALQSOs is close to 1, as inferred here, then spectroscopy in hard X-rays with large telescopes like XMM would be feasible.

  9. Surface structure of lithiated graphite by X-ray photoelectron diffraction

    NASA Astrophysics Data System (ADS)

    Lee, Choong Man; Yang, S.-H.; Mun, B.-J.; Ross, Philip N.

    2001-04-01

    The surface composition and structure of a stage-one lithium intercalation compound (Li-GIC) was studied by X-ray photoelectron diffraction (XPD) from Li 1s and C 1s core levels. The Li-GIC was prepared in situ by vapor phase intercalation of lithium into highly oriented pyrolitic graphite (HOPG) in an ultra-high vacuum system. Stage-one Li-GIC, LiC 6, having a characteristic golden color, was obtained using Li evaporation onto a HOPG substrate at 400 K, while a metallic lithium overlayer was observed at depositions below room temperature. XPD patterns of Li 1s and C 1s intensities as a function of the polar emission angle were obtained at a fixed photon energy of 1253.6 eV. The experimental XPD patterns on the HOPG and the stage-one Li-GIC were both in quite good agreement with calculated XPD patterns based on Rehr-Albers separable representation for scattering of the emitted photoelectrons. The structural model for the surface of the Li-GIC producing the best fit to the experimental data has the bulk LiC 6 lattice with surface termination in the graphene plane.

  10. GaN quantum dot polarity determination by X-ray photoelectron diffraction

    NASA Astrophysics Data System (ADS)

    Romanyuk, O.; Bartoš, I.; Brault, J.; Mierry, P. De; Paskova, T.; Jiříček, P.

    2016-12-01

    Growth of GaN quantum dots (QDs) on polar and semipolar GaN substrates is a promising technology for efficient nitride-based light emitting diodes (LED). The QDs crystal orientation typically repeats the polarity of the substrate. In case of non-polar or semipolar substrates, the polarity of QDs is not obvious. In this article, the polarity of GaN QDs and of underlying layers was investigated nondestructively by X-ray photoelectron diffraction (XPD). Polar and semipolar GaN/Al0.5Ga0.5N heterostructures were grown on the sapphire substrates with (0001) and (1 1 bar 00) orientations by molecular beam epitaxy (MBE). Polar angle dependence of N 1s core-level photoelectron intensities were measured from GaN QDs and compared with the corresponding experimental curves from free-standing GaN crystals. It is confirmed experimentally, that the crystalline orientation of polar (0001) GaN QDs follows the orientation of the (0001) sapphire substrate. In case of semipolar GaN QDs grown on (1 1 bar 00) sapphire substrate, the (11 2 bar 2) polarity of QDs was determined.

  11. Reactive ZnO/Ti/ZnO interfaces studied by hard x-ray photoelectron spectroscopy

    SciTech Connect

    Knut, Ronny Lindblad, Rebecka; Rensmo, Håkan; Karis, Olof; Grachev, Sergey; Faou, Jean-Yvon; Søndergård, Elin

    2014-01-28

    The chemistry and intermixing at buried interfaces in sputter deposited ZnO/Ti/ZnO thin layers were studied by hard x-ray photoelectron spectroscopy. The long mean free path of the photoelectrons allowed for detailed studies of the oxidation state, band bending effects, and intrinsic doping of the buried interfaces. Oxidation of the Ti layer was observed when ZnO was deposited on top. When Ti is deposited onto ZnO, Zn Auger peaks acquire a metallic character indicating a strong reduction of ZnO at the interface. Annealing of the stack at 200 °C results in further reduction of ZnO and oxidation of Ti. Above 300 °C, oxygen transport from the bulk of the ZnO layer takes place, leading to re-oxidation of ZnO at the interface and further oxidation of Ti layer. Heating above 500 °C leads to an intermixing of the layers and the formation of a Zn{sub x}TiO{sub y} compound.

  12. Characterisation of crystalline C-S-H phases by X-ray photoelectron spectroscopy

    SciTech Connect

    Black, Leon; Garbev, Krassimir; Stemmermann, Peter; Hallam, Keith R.; Allen, Geoffrey C

    2003-06-01

    We have prepared a number of crystalline calcium-silicate-hydrate (C-S-H) phases hydrothermally, with calcium-silicon ratios varying from approximately 0.5 (K-phase) to 2.0 (hillebrandite and {alpha}-dicalcium silicate hydrate). The phases were then analysed using X-ray photoelectron spectroscopy (XPS). Increasing calcium-silicon ratios resulted in decreased silicon binding energies. Additionally, changes in the O 1s spectra could be explained in terms of bridging (BO) and nonbridging oxygen (NBO) moieties. Finally, the modified Auger parameter has proved particularly useful in determining the extent of silicate anion polymerisation. Of note also are the apparently unusual spectra for 11 A tobermorite. The silicon and oxygen photoelectron spectra indicate a phase with a lower degree of silicate polymerisation than predicted from its composition. The main contributing factor is the intrinsic disorder within the tobermorite structure. This study has shown how XPS may be used to obtain valuable structural information from C-S-H phases, and our analysis of the crystalline phases is the first step towards the analysis of real C-S-H-based cement systems.

  13. The complementary nature of x-ray photoelectron spectroscopy and angle-resolved x-ray diffraction part II: Analysis of oxides on dental alloys

    NASA Astrophysics Data System (ADS)

    Kerber, S. J.; Barr, T. L.; Mann, G. P.; Brantley, W. A.; Papazoglou, E.; Mitchell, J. C.

    1998-06-01

    X-ray photoelectron spectroscopy (XPS) and angle-resolved x-ray diffraction (ARXRD) were used to analyze the oxide layer on three palladium-gallium-based dental casting alloys. The oxide layers were approximately 10 Μm thick. The use of the techniques helped to determine which mechanism was responsible for oxide formation—either (a) oxide layer growth via diffusion of oxygen through the scale to the metal, causing the scale to grow at the metal-oxide interface, or (b) an oxide layer formed by metal ions diffusing through the scale to the surface and reacting with oxygen, causing the scale to grow at the oxide-air interface. The oxide growth mechanisms were correlated to previous layer adhesion results determined with biaxial flexure testing.

  14. X-ray absorption in pillar shaped transmission electron microscopy specimens.

    PubMed

    Bender, H; Seidel, F; Favia, P; Richard, O; Vandervorst, W

    2017-03-07

    The dependence of the X-ray absorption on the position in a pillar shaped transmission electron microscopy specimen is modeled for X-ray analysis with single and multiple detector configurations and for different pillar orientations relative to the detectors. Universal curves, applicable to any pillar diameter, are derived for the relative intensities between weak and medium or strongly absorbed X-ray emission. For the configuration as used in 360° X-ray tomography, the absorption correction for weak and medium absorbed X-rays is shown to be nearly constant along the pillar diameter. Absorption effects in pillars are about a factor 3 less important than in planar specimens with thickness equal to the pillar diameter. A practical approach for the absorption correction in pillar shaped samples is proposed and its limitations discussed. The modeled absorption dependences are verified experimentally for pillars with HfO2 and SiGe stacks.

  15. Enhancement of X-ray dose absorption for medical applications

    NASA Astrophysics Data System (ADS)

    Lim, Sara; Nahar, S.; Pradhan, A.; Barth, R.

    2013-05-01

    A promising technique for cancer treatment is radiation therapy with high-Z (HZ) nanomoities acting as radio-sensitizers attached to tumor cells and irradiated with X-rays. But the efficacy of radiosenstization is highly energy dependent. We study the physical effects in using platinum (Pt) as the radio-sensitizing agent, coupled with commonly employed broadband x-ray sources with mean energies around 100 keV, as opposed to MeV energies produced by clinical linear accelerators (LINAC) used in radiation therapy. Numerical calculations, in vitro, and in vivo studies of F98 rat glioma (brain cancer) demonstrate that irradiation from a medium energy X-ray (MEX) 160 kV source is far more effective than from a high energy x-ray (HEX) 6 MV LINAC. We define a parameter to quantify photoionization by an x-ray source, which thereby provides a measure of subsequent Auger decays. The platinum (Z = 78) results are also relevant to ongoing studies on x-ray interaction with gold (Z = 79) nanoparticles, widely studied as an HZ contrast agent. The present study should be of additional interest for a combined radiation plus chemotherapy treatment since Pt compounds such cis-Pt and carbo-Pt are commonly used in chemotherapy.

  16. X-ray photoelectron spectra structure and chemical bond nature in NpO2

    NASA Astrophysics Data System (ADS)

    Teterin, Yu. A.; Teterin, A. Yu.; Ivanov, K. E.; Ryzhkov, M. V.; Maslakov, K. I.; Kalmykov, St. N.; Petrov, V. G.; Enina, D. A.

    2014-01-01

    Quantitative analysis was done of the x-ray photoelectron spectra structure in the binding energy (BE) range of 0 to ˜35 eV for neptunium dioxide (NpO2) valence electrons. The BEs and structure of the core electronic shells (˜35-1250 eV) as well as the relativistic discrete variation calculation results for the finite fragment of the NpO2 lattice and the data of other authors were taken into account. The experimental data show that the many-body effects and the multiplet splitting contribute to the spectral structure much less than the effects of formation of the outer (0-˜15 eV) and the inner (˜15-˜35 eV) valence molecular orbitals (OVMO and IVMO, respectively). The filled Np 5f electronic states were shown to form in the NpO2 valence band. The Np 6p electrons participate in formation of both the IVMO and the OVMO (bands). The filled Np 6p3/2 and the O 2s electronic shells were found to take the maximum part in the IVMO formation. The MO composition and the sequence order in the BE range 0-˜35 eV in NpO2 were established. The experimental and theoretical data allowed a quantitative MO scheme for NpO2, which is fundamental for both understanding the chemical bond nature in neptunium dioxide and the interpretation of other x-ray spectra of NpO2.

  17. 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.

  18. Laboratory-based high pressure X-ray photoelectron spectroscopy: A novel and flexible reaction cell approach

    NASA Astrophysics Data System (ADS)

    Kerherve, Gwilherm; Regoutz, Anna; Bentley, David; Hood, Colin; Feeley, Keith; Knight, Stewart; Robson, Anthony; Turner, Craig; Singh, Nick; Pontefract, John; Åhlund, John; Kahk, Juhan M.; Villar-Garcia, Ignacio J.; Payne, David J.

    2017-03-01

    The last 10-15 years have witnessed a resurgence in the application of high pressure X-ray photoelectron spectroscopy, mainly through the development of new electron energy analyser designs and the utilization of high-brilliance synchrotron radiation sources. To continue this expansion of the technique, it is crucial that instruments are developed for the home-laboratory, considering that this is where the vast majority of traditional ultra-high vacuum (UHV) X-ray photoelectron spectroscopy is performed. The research presented here introduces a new addition to the field, an instrument capable of performing spectroscopy measurements from UHV to high pressure (25 mbar), achieved using a retractable and modular reaction cell design. The ease of use, stability (of analyser, X-ray source, and gas delivery, etc.), and overall capability of the instrument will be demonstrated.

  19. First-principles core-level X-ray photoelectron spectroscopy calculation on arsenic defects in silicon crystal

    SciTech Connect

    Kishi, Hiroki; Miyazawa, Miki; Matsushima, Naoki; Yamauchi, Jun

    2014-02-21

    We investigate the X-ray photoelectron spectroscopy (XPS) binding energies of As 3d in Si for various defects in neutral and charged states by first-principles calculation. It is found that the complexes of a substitutional As and a vacancy in charged and neutral states explain the experimentally observed unknown peak very well.

  20. 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

  1. UV-Visible Absorption Spectroscopy Enhanced X-ray Crystallography at Synchrotron and X-ray Free Electron Laser Sources.

    PubMed

    Cohen, Aina E; Doukov, Tzanko; Soltis, Michael S

    2016-01-01

    This review describes the use of single crystal UV-Visible Absorption micro-Spectrophotometry (UV-Vis AS) to enhance the design and execution of X-ray crystallography experiments for structural investigations of reaction intermediates of redox active and photosensitive proteins. Considerations for UV-Vis AS measurements at the synchrotron and associated instrumentation are described. UV-Vis AS is useful to verify the intermediate state of an enzyme and to monitor the progression of reactions within crystals. Radiation induced redox changes within protein crystals may be monitored to devise effective diffraction data collection strategies. An overview of the specific effects of radiation damage on macromolecular crystals is presented along with data collection strategies that minimize these effects by combining data from multiple crystals used at the synchrotron and with the X-ray free electron laser.

  2. Electrochemical discharge of nanocrystalline magnetite: structure analysis using X-ray diffraction and X-ray absorption spectroscopy.

    PubMed

    Menard, Melissa C; Takeuchi, Kenneth J; Marschilok, Amy C; Takeuchi, Esther S

    2013-11-14

    Magnetite (Fe3O4) is an abundant, low cost, environmentally benign material with potential application in batteries. Recently, low temperature coprecipitation methods have enabled preparation of a series of nanocrystalline magnetite samples with a range of crystallite sizes. Electrochemical cells based on Li/Fe3O4 show a linear increase in capacity with decreasing crystallite size at voltages ≥1.2 V where a 2× capacity improvement relative to commercial (26.2 nm) magnetite is observed. In this report, a combination of X-ray powder diffraction (XRD) and X-ray absorption spectroscopy (XAS) is used to measure magnetite structural changes occurring upon electrochemical reduction, with parent Fe3O4 crystallite size as a variable. Notably, XAS provides evidence of metallic iron formation at high levels of electrochemical reduction.

  3. Microanalysis of iron oxidation state in iron oxides using X Ray Absorption Near Edge Structure (XANES)

    NASA Technical Reports Server (NTRS)

    Sutton, S. R.; Delaney, J.; Bajt, S.; Rivers, M. L.; Smith, J. V.

    1993-01-01

    An exploratory application of x ray absorption near edge structure (XANES) analysis using the synchrotron x ray microprobe was undertaken to obtain Fe XANES spectra on individual sub-millimeter grains in conventional polished sections. The experiments concentrated on determinations of Fe valence in a suite of iron oxide minerals for which independent estimates of the iron speciation could be made by electron microprobe analysis and x ray diffraction.

  4. Near-Edge X-ray Absorption Fine Structure Spectroscopy of Diamondoid Thiol Monolayers on Gold

    SciTech Connect

    Willey, T M; Fabbri, J; Lee, J I; Schreiner, P; Fokin, A A; Tkachenko, B A; Fokina, N A; Dahl, J; Carlson, B; Vance, A L; Yang, W; Terminello, L J; van Buuren, T; Melosh, N

    2007-11-27

    Diamondoids, hydrocarbon molecules with cubic-diamond-cage structures, have unique properties with potential value for nanotechnology. The availability and ability to selectively functionalize this special class of nanodiamond materials opens new possibilities for surface-modification, for high-efficiency field emitters in molecular electronics, as seed crystals for diamond growth, or as robust mechanical coatings. The properties of self-assembled monolayers (SAMs) of diamondoids are thus of fundamental interest for a variety of emerging applications. This paper presents the effects of thiol substitution position and polymantane order on diamondoid SAMs on gold using near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and X-ray photoelectron spectroscopy (XPS). A framework to determine both molecular tilt and twist through NEXAFS is presented and reveals highly ordered diamondoid SAMs, with the molecular orientation controlled by the thiol location. C 1s and S 2p binding energies are lower in adamantane thiol than alkane thiols on gold by 0.67 {+-} 0.05 eV and 0.16 {+-} 0.04 eV respectively. These binding energies vary with diamondoid monolayer structure and thiol substitution position, consistent with different amounts of steric strain and electronic interaction with the substrate. This work demonstrates control over the assembly, in particular the orientational and electronic structure, providing a flexible design of surface properties with this exciting new class of diamond clusters.

  5. Probing local structure of co doped polyvinylidene fluoride-ZnO thin films using X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Dey, Rajkumar; Yadav, Ashok Kumar; Bhunia, Ritamay; Jha, Shambhu Nath; Bhattacharyya, Dibyendu; Hussain, Shamima; Bhar, Radhaballav; Pal, Arun Kumar

    2017-05-01

    Nanocrystalline ZnO doped with cobalt (CoxZn1 - xO) as a filler was added to polyvinylidene fluoride (PVDF) host matrix to produce a free-standing flexible composite film by sol-gel technique. Three different amounts of cobalt (x = 0.01, 0.04, 0.07) were used in the above synthesis. The as-deposited and the poled composite Co-ZnO/PVDF films were subjected to extensive study by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy. Detailed information regarding the valence states of the host and the filler ions in the samples was derived from XPS and XANES (X-ray absorption near edge structure) studies. Local structures surrounding the Zn and Co sites were obtained from EXAFS (Extended X-ray absorption fine structure) data analysis. Combined XPS, XANES and EXAFS studies confirm that substitution of Zn sites by Co ions in wurtzite ZnO lattice without forming any significant metallic cluster phase in the samples.

  6. X-ray absorption spectroscopic studies of the active sites of nickel- and copper-containing metalloproteins

    SciTech Connect

    Tan, G.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, 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.

  7. Observation of Reverse Saturable Absorption of an X-ray Laser.

    PubMed

    Cho, B I; Cho, M S; Kim, M; Chung, H-K; Barbrel, B; Engelhorn, K; Burian, T; Chalupský, J; Ciricosta, O; Dakovski, G L; Hájková, V; Holmes, M; Juha, L; Krzywinski, J; Lee, R W; Nam, Chang Hee; Rackstraw, D S; Toleikis, S; Turner, J J; Vinko, S M; Wark, J S; Zastrau, U; Heimann, P A

    2017-08-18

    A nonlinear absorber in which the excited state absorption is larger than the ground state can undergo a process called reverse saturable absorption. It is a well-known phenomenon in laser physics in the optical regime, but is more difficult to generate in the x-ray regime, where fast nonradiative core electron transitions typically dominate the population kinetics during light matter interactions. Here, we report the first observation of decreasing x-ray transmission in a solid target pumped by intense x-ray free electron laser pulses. The measurement has been made below the K-absorption edge of aluminum, and the x-ray intensity ranges are 10^{16} -10^{17}  W/cm^{2}. It has been confirmed by collisional radiative population kinetic calculations, underscoring the fast spectral modulation of the x-ray pulses and charge states relevant to the absorption and transmission of x-ray photons. The processes shown through detailed simulations are consistent with reverse saturable absorption, which would be the first observation of this phenomena in the x-ray regime. These light matter interactions provide a unique opportunity to investigate optical transport properties in the extreme state of matters, as well as affording the potential to regulate ultrafast x-ray free-electron laser pulses.

  8. Observation of Reverse Saturable Absorption of an X-ray Laser

    DOE PAGES

    Cho, B. I.; Cho, M. S.; Kim, M.; ...

    2017-08-16

    A nonlinear absorber in which the excited state absorption is larger than the ground state can undergo a process called reverse saturable absorption. It is a well-known phenomenon in laser physics in the optical regime, but is more difficult to generate in the x-ray regime, where fast nonradiative core electron transitions typically dominate the population kinetics during light matter interactions. Here, we report the first observation of decreasing x-ray transmission in a solid target pumped by intense x-ray free electron laser pulses. The measurement has been made below the K-absorption edge of aluminum, and the x-ray intensity ranges are 1016more » –1017 W=cm2. It has been confirmed by collisional radiative population kinetic calculations, underscoring the fast spectral modulation of the x-ray pulses and charge states relevant to the absorption and transmission of x-ray photons. The processes shown through detailed simulations are consistent with reverse saturable absorption, which would be the first observation of this phenomena in the x-ray regime. These light matter interactions provide a unique opportunity to investigate optical transport properties in the extreme state of matters, as well as affording the potential to regulate ultrafast x-ray freeelectron laser pulses.« less

  9. Observation of Reverse Saturable Absorption of an X-ray Laser

    NASA Astrophysics Data System (ADS)

    Cho, B. I.; Cho, M. S.; Kim, M.; Chung, H.-K.; Barbrel, B.; Engelhorn, K.; Burian, T.; Chalupský, J.; Ciricosta, O.; Dakovski, G. L.; Hájková, V.; Holmes, M.; Juha, L.; Krzywinski, J.; Lee, R. W.; Nam, Chang Hee; Rackstraw, D. S.; Toleikis, S.; Turner, J. J.; Vinko, S. M.; Wark, J. S.; Zastrau, U.; Heimann, P. A.

    2017-08-01

    A nonlinear absorber in which the excited state absorption is larger than the ground state can undergo a process called reverse saturable absorption. It is a well-known phenomenon in laser physics in the optical regime, but is more difficult to generate in the x-ray regime, where fast nonradiative core electron transitions typically dominate the population kinetics during light matter interactions. Here, we report the first observation of decreasing x-ray transmission in a solid target pumped by intense x-ray free electron laser pulses. The measurement has been made below the K -absorption edge of aluminum, and the x-ray intensity ranges are 1016 - 1017 W /cm2 . It has been confirmed by collisional radiative population kinetic calculations, underscoring the fast spectral modulation of the x-ray pulses and charge states relevant to the absorption and transmission of x-ray photons. The processes shown through detailed simulations are consistent with reverse saturable absorption, which would be the first observation of this phenomena in the x-ray regime. These light matter interactions provide a unique opportunity to investigate optical transport properties in the extreme state of matters, as well as affording the potential to regulate ultrafast x-ray free-electron laser pulses.

  10. Surface composition analysis of HF vapour cleaned silicon by X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Ermolieff, A.; Martin, F.; Amouroux, A.; Marthon, S.; Westendorp, J. F. M.

    1991-06-01

    X-ray photoelectron spectroscopy (XPS) measurements on silicon surfaces treated by HF gaseous cleaning are described. Various cleaning recipes, which essentially differ by the amount of water present during the reaction were studied; the composition of the silicon surface was measured in terms of monolayer coverage of oxygen, fluorine and carbon. These gaseous cleaned surfaces are compared with those of commonly deglazed silicon samples by using an aqueous HF bath. The F(1s), O(1s), Si(2p), C(1s) photoelectron lines were monitored, and concentrations determined as usual by integration of the lines after removal of the non-linear backgroune. The F(1s), C(1s) and Si(2p) lines were decomposed into several components corresponding to different chemical bonds. The results show that the amount of fluorine is directly correlated with the amount of oxygen: the higher the oxygen level on the sample, the more important is the fluorine content till 0.7 ML, essentially in a O sbnd Si sbnd F bonding state. For more aggresive etching leaving less than one monolayer of oxygen, the Si sbnd F bond becomes predominant. The ratio of the SiF to OSiF concentrations is a significant signature of the deoxidation state of the surface. Hydrophobicity of the water appears in the range of 25% Si sbnd F bonds. With very aggresive etching processes, 67% Si sbnd F bonds and 33% O sbnd Si sbnd F bonds are reached and the total amount of fluoride drops below 0.3 ML. For comparison, only Si sbnd F bonds are observed after a wet etching in a dilute HF bath without a rinse with a much lower fluorine concentration. The balance between Si sbnd F and O sbnd Si sbnd F remains stable and seems to be representative of the surface states provided by the etching process.

  11. Characterization of oxidized platinum surfaces by X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Peuckert, M.; Bonzel, H. P.

    1984-09-01

    Various adlayers were grown on the (111) surface of a platinum crystal by four different oxidizing treatments. The resulting surface phases were characterized by X-ray photoelectron spectroscopy. According to the Pt 4f and O 1s XPS spectra, treatment in 0.1 MPa O 2 at 900 K yielded about two monolayers of PtO 2; anodic polarization in 0.5M H 2SO 4 acid electrolyte at 3 V versus standard hydrogen electrode gave a thick (> 5 nm) layer of Pt(OH) 4, while by polarization in 1M NaOH base electrolyte at 3 V versus Ag/AgCl reference electrode a thick film of an oxyhydroxide (approximately PtO(OH) 2) was formed. Etching in boiling conc. HNO 3 led to a thin layer of about 1 nm of a hydrated oxide, PtO 2 · xH 2O. Identification of the different surface phases was supported by comparative experiments with bulk PtO 2. The thermal stability of all compounds was investigated by heating the samples in ultrahigh vacuum. They all decomposed at about 400 K. Initially, not a pure metal phase was formed, but a mixed phase containing Pt metal and oxide, which was stable over a wide temperature range. No oxygen could be detected on the surface at 1070 K by XPS or Auger spectroscopy.

  12. X-ray photoelectron spectroscopy as a probe of rhodium-ligand interaction in ionic liquids

    NASA Astrophysics Data System (ADS)

    Men, Shuang; Lovelock, Kevin R. J.; Licence, Peter

    2016-02-01

    We use X-ray photoelectron spectroscopy (XPS) to identify the interaction between the rhodium atom and phosphine ligands in six 1-octyl-3-methylimidazolium-based ionic liquids ([C8C1Im][X]). The formation of a mono-phosphine rhodium complex based upon addition of triphenylphosphine (PPh3) is confirmed by XPS in all ionic liquids studied herein. Due to the electron donation effect of the ligand, the rhodium atom becomes more negatively charged and thus exhibits a lower measured binding energy. The influence of the anion basicity on the formation of different types of rhodium complexes is also investigated. By introducing a biphosphine ligand, a chelated diphosphine rhodium complex is formed in ionic liquids with more basic anions and verified by both XPS and Infrared Spectroscopy (IR). The measured Rh 3d binding energies are correlated to the reaction selectivity of a hydroformylation reaction which inspires a method to design a metal catalyst to control the chemical reaction towards desired products in the future.

  13. In Situ Ambient Pressure X-ray Photoelectron Spectroscopy Studies of Lithium-Oxygen Redox Reactions

    PubMed Central

    Lu, Yi-Chun; Crumlin, Ethan J.; Veith, Gabriel M.; Harding, Jonathon R.; Mutoro, Eva; Baggetto, Loïc; Dudney, Nancy J.; Liu, Zhi; Shao-Horn, Yang

    2012-01-01

    The lack of fundamental understanding of the oxygen reduction and oxygen evolution in nonaqueous electrolytes significantly hinders the development of rechargeable lithium-air batteries. Here we employ a solid-state Li4+xTi5O12/LiPON/LixV2O5 cell and examine in situ the chemistry of Li-O2 reaction products on LixV2O5 as a function of applied voltage under ultra high vacuum (UHV) and at 500 mtorr of oxygen pressure using ambient pressure X-ray photoelectron spectroscopy (APXPS). Under UHV, lithium intercalated into LixV2O5 while molecular oxygen was reduced to form lithium peroxide on LixV2O5 in the presence of oxygen upon discharge. Interestingly, the oxidation of Li2O2 began at much lower overpotentials (~240 mV) than the charge overpotentials of conventional Li-O2 cells with aprotic electrolytes (~1000 mV). Our study provides the first evidence of reversible lithium peroxide formation and decomposition in situ on an oxide surface using a solid-state cell, and new insights into the reaction mechanism of Li-O2 chemistry. PMID:23056907

  14. Chemistry of carbon polymer composite electrode - An X-ray photoelectron spectroscopy study

    NASA Astrophysics Data System (ADS)

    Andersen, Shuang Ma; Dhiman, Rajnish; Skou, Eivind

    2015-01-01

    Surface chemistry of the electrodes in a proton exchange membrane fuel cell is of great importance for the cell performance. Many groups have reported that electrode preparation condition has a direct influence on the resulting electrode properties. In this work, the oxidation state of electrode components and the composites (catalyst ionomer mixtures) in various electrode structures were systematically studied with X-ray photoelectron spectroscopy (XPS). Based on the spectra, when catalyst is physically mixed with Nafion ionomer, the resulting electrode surface chemistry is a combination of the two components. When the electrode is prepared with a lamination procedure, the ratio between fluorocarbon and graphitic carbon is decreased. Moreover, ether type oxide content is decreased although carbon oxide is slightly increased. This indicates structure change of the catalyst layer due to an interaction between the ionomer and the catalyst and possible polymer structural change during electrode fabrication. The surface of micro porous layer was found to be much more influenced by the lamination, especially when it is in contact with catalysts in the interphase. Higher amount of platinum oxide was observed in the electrode structures (catalyst ionomer mixture) compared to the catalyst powder. This also indicates a certain interaction between the functional groups in the polymer and platinum surface.

  15. 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.

  16. Chemical functionalization of nanodiamond by amino groups: an X-ray photoelectron spectroscopy study.

    PubMed

    Dhanak, V R; Butenko, Yu V; Brieva, A C; Coxon, P R; Alves, L; Siller, L

    2012-04-01

    The development of chemical functionalization techniques for diamond nanocrystallites opens up ways with a view to altering their solubility in different solvents, improve interfacial adhesion of nanodiamonds with a composite matrix in new materials, and provide new possibilities for the modification of the electronic properties of nanodiamond crystallites. In this work, we present results on the chemical functionalization of nanodiamonds by amino groups using ammonia as a nitrogenation agent. Nanodiamond material used was formed by the detonation technique with average crystallite sizes of 4-5 nm. The final materials and intermediates products were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Chemical functionalization of nanodiamonds by amino groups could enable the preparation of new nylon nano-composite materials. Presence of surface amino groups could alter pH of nanodiamond colloids towards basic values and improve colloidal stability of nanodiamond suspensions at pH close to 7. This could enable syntheses of new drug delivery systems based on nanodiamonds.

  17. Surface characterization of ginger powder examined by X-ray photoelectron spectroscopy and scanning electron microscopy.

    PubMed

    Zhao, Xiaoyan; Ao, Qiang; Du, Fangling; Zhu, Junqing; Liu, Jie

    2010-09-01

    The surface composition of five types of ginger powders with the particle sizes of 300, 149, 74, 37 and 8.34 microm was investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and various types of physical-chemical characteristics regarding material particle size distributions, discoloration and chemical composition. The results show that the color differences are greater for superfine ground ginger than for conventional comminuted ones; the values of crude fibre, neutral detergent fiber (NDF) and acid detergent fiber (ADF) decrease with decreasing ginger particle size. However, no relationship with the surface fat, crude protein, ash and total solids exists. With superfine grinding the XPS O/C ratios of the five ginger powders were similar since the surfaces were not oxidized. Correlations were observed between the XPS N/C ratios and the high resolution XPS N 1s spectra. SEM observations revealed that the surface of ginger powder with a particle size of 300 microm is rougher, while superfine ground powders with particle sizes of 149, 74, 37 and 8.34 microm are similar to each other. This roughness difference between these surfaces correlates with the differences in their O/C ratios and the surface morphology of five ginger powders. Copyright 2010 Elsevier B.V. All rights reserved.

  18. CHARACTERIZING SURFACE LAYERS IN NITINOL USING X-RAY PHOTOELECTRON SPECTROSCOPY

    SciTech Connect

    Christopfel, R.; Mehta, A.

    2008-01-01

    Nitinol is a shape memory alloy whose properties allow for large reversible deformations and a return to its original geometry. This nickel-titanium (NiTi) alloy has become a material used widely in the biomedical fi eld as a stent to open up collapsed arteries. Both ambient and biological conditions cause surface oxidation in these devices which in turn change its biocompatibility. The thickness of oxidized layers can cause fractures in the material if too large and can allow for penetration if too thin. Depending on the type and abundance of the chemical species on or near the surface, highly toxic metal ions can leak into the body causing cell damage or even cell death. Thus, biocompatibility of such devices is crucial. By using highly surface sensitive x-ray photoelectron spectroscopy to probe the surface of these structures, it is possible to decipher both layer composition and layer thickness. Two samples, both of which were mechanically polished, were investigated. Of the two samples, one was then exposed to a phosphate buffered saline (PBS) solution to mimic the chemical properties of blood, while the other remained unexposed. Although both samples were found to have oxide layers of appropriate thickness (on the order of a few nm), it was found that the sample exposed to the saline solution had a slightly thicker oxide layer and more signifi cantly, a phosphate layer very near the surface suggesting toxic metal components are well contained within the sample. These are considerable indications of a biocompatible device.

  19. 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 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, single bondO, single bondOHmore » and single bondF, in addition to OH-terminations relatively strongly bonded to H2O 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

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

    SciTech Connect

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

    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 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, single bondO, single bondOH and single bondF, in addition to OH-terminations relatively strongly bonded to H2O 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.

  1. Study on NiO/Fe interface with X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Feng, Chun; Zhang, Jing-Yan; Teng, Jiao; Wang, Fu-Ming

    2010-12-01

    Different monolayers (ML) of Fe atoms were deposited on NiO (001) substrates or NiO underlayers using molecular beam epitaxy (MBE), pulse laser deposition (PLD), and magnetron sputtering (MS). The magnetic properties and microstructure of the films were studied. The apparent magnetic dead layer (MDL) is found to exist at the NiO/Fe interfaces of the MBE sample (about 2 ML MDL), the PLD sample (about 3 ML MDL), and the MS sample (about 4 ML MDL). X-ray photoelectron spectroscopy indicates the presence of ionic Fe (Fe2+ or Fe3+) and metallic Ni at the NiO/Fe interfaces, which may be due to the chemical reactions between Fe and NiO layers. This also leads to the formation of MDL. The thickness of the MDL and the reaction products are related with the deposition energy of the atoms on the substrates. The interfacial reactions are effectively suppressed by inserting a thin Pt layer at the NiO/Fe interface.

  2. [Characterization of biochar by X-ray photoelectron spectroscopy and 13C nuclear magnetic resonance].

    PubMed

    Xu, Dong-yu; Jin, Jie; Yan, Yu; Han, Lan-fang; Kang, Ming-jie; Wang, Zi-ying; Zhao, Ye; Sun, Ke

    2014-12-01

    The wood (willow branch) and grass (rice straw) materials were pyrolyzed at different temperatures (300, 450 and 600 °C) to obtain the biochars used in the present study. The biochars were characterized using elementary analysis, X-ray photoelectron spectroscopy (XPS) and solid state 13C cross-polarization and magic angle spinning nuclear magnetic resonance spectroscopy (13C NMR) to illuminate the structure and composition of the biochars which were derived from the different thermal temperatures and biomass. The results showed that the H/C, O/C and (O+N)/C ratios of the biochars decreased with the increase in the pyrolysis temperatures. The surface polarity and ash content of the grass-derived biochars were higher than those of the wood-derived biochars. The minerals of the wood-derived biochars were mainly covered by the organic matter; in contrast, parts of the mineral surfaces of the grass-derived biochars were not covered by organic matter? The 13C NMR of the low temperature-derived biochars revealed a large contribution of aromatic carbon, aliphatic carbon, carboxyl and carbonyl carbon, while the high temperature-derived biochars contained a large amount of aromatic carbon. Moreover, the wood-derived biochars produced at low heat treatment temperatures contained more lignin residues than grass-derived ones, probably due to the existence of high lignin content in the feedstock soures of wood-derived biochars. The results of the study would be useful for environmental application of biochars.

  3. Quantitative characterization of DNA films by X-ray photoelectron spectroscopy.

    PubMed

    Petrovykh, Dmitri Y; Kimura-Suda, Hiromi; Tarlov, Michael J; Whitman, Lloyd J

    2004-01-20

    We describe the use of self-assembled films of thiolated (dT)25 single-stranded DNA (ssDNA) on gold as a model system for quantitative characterization of DNA films by X-ray photoelectron spectroscopy (XPS). We evaluate the applicability of a uniform and homogeneous overlayer-substrate model for data analysis, examine model parameters used to describe DNA films (e.g., density and electron attenuation length), and validate the results. The model is used to obtain quantitative composition and coverage information as a function of immobilization time. We find that when the electron attenuation effects are properly included in the XPS data analysis, excellent agreement is obtained with Fourier transform infrared (FTIR) measurements for relative values of the DNA coverage, and the calculated absolute coverage is consistent with a previous radiolabeling study. Based on the effectiveness of the analysis procedure for model (dT)25 ssDNA films, it should be generally valid for direct quantitative comparison of DNA films prepared under widely varying conditions.

  4. Angle-resolved X-ray photoelectron spectroscopy of the surface of imidazolium ionic liquids.

    PubMed

    Lockett, Vera; Sedev, Rossen; Bassell, Chris; Ralston, John

    2008-03-07

    The surfaces of three imidazolium based ionic liquids with a common anion were studied with angle-resolved X-ray photoelectron spectroscopy (XPS). The room temperature ionic liquids (RTILs): 1-butyl-3-methylimidazolium (bmim), 1-hexyl-3-methylimidazolium (hmim), and 1-octyl-3-methylimidazolium (omim) tetrafluoroborates, were meticulously purified and dried under vacuum. Survey and high-resolution spectra were obtained at different take-off angles (0-84 degrees ), thus increasing the surface sensitivity of the measurement. No impurities were detected and the survey spectra at normal emission (0 degrees ) confirmed the stoichiometric composition of the liquids. However, the spectra at take-off angles of 60, 70, 80 and 84 degrees indicated a higher amount of carbon. High resolution spectra of C1s, at these angles, showed an increased amount of aliphatic carbon when compared to the spectra at normal emission. The longer the side chain (R) of the imidazolium cation (Rmim), the larger was the amount of aliphatic carbon detected. Previous studies with other surface sensitive techniques have yielded contradictory conclusions about the surface orientation of the Rmim. We conclude unequivocally that the alkyl chain of the imidazolium ring of the investigated RTILs is oriented away from the liquid. Our study demonstrates the ability of XPS to probe the structure, along with the composition, of the free liquid surface by comparing signals from different penetration depths.

  5. Characterization of self-assembled organic films using differential charging in X-ray photoelectron spectroscopy.

    PubMed

    Dubey, Manish; Gouzman, Irina; Bernasek, Steven L; Schwartz, Jeffrey

    2006-05-09

    Differential charging is often regarded as a problem in X-ray photoelectron spectroscopic studies, especially for insulating or partially conducting samples. Application of a positive bias can reduce the effect of differential charging by attracting stray electrons from the system, thereby compensating for the electron loss. On the other hand, differential charging effect can be enhanced by the application of a negative bias to the sample during spectrum acquisition. The successful use of the differential charging technique to distinguish between multi- and monolayer organophosphonate films on oxide-covered silicon has been reported. A detailed description of this technique is now presented which shows how differential charging can be used as an important tool for the characterization of self-assembled films deposited on various surfaces. The dependence of this technique on the conductivity of the substrate has been investigated by studying the spectral behavior of the deposited films of phosphonic acid on conducting, semiconducting, and insulating samples (stainless steel, silicon, and glass). Application of either positive or negative dc electrical bias affects the carbon core-level (C1s) line shape and intensity, which is dependent on the atom's physical location above the surface.

  6. X-ray photoelectron spectroscopic study of the chemical vapor deposited W/Al interface

    NASA Astrophysics Data System (ADS)

    Ohshima, H.; Katayama, M.; Onoda, K.; Hattori, T.; Suzuki, H.; Tokuda, Y.

    1993-07-01

    The dependence of the amount of aluminum trifluoride (AlF3) piled up at the interface of chemical vapor deposited tungsten and the aluminum under layer on the deposition time and subsequent annealing in ultrahigh vacuum (UHV) or in monosilane (SiH4) gas has been studied. AlF3 is formed by the reaction of the aluminum under layer with tungsten hexafluoride (WF6) during the initial state of tungsten chemical vapor deposition. Tungsten was deposited on an Al layer under selective deposition conditions by SiH4 reduction at 250 °C. X-ray photoelectron spectroscopy measurement reveals that the amount of AlF3 decreases with an increase in the tungsten deposition time and that the reduction of AlF3 by volatilization of aluminum fluorides, which occurs at higher temperatures (≳400 °C) is not observed at low temperature (270 °C). Annealing in SiH4 gas after the tungsten deposition was effective to reduce the amount of AlF3 compared with annealing in UHV. This result and thermochemical data would suggest that the dependence of the amount of AlF3 on the tungsten deposition time is explained by the reduction of AlF3 with hydrogen atoms supplied from the dissociation of SiH4.

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

    SciTech Connect

    Aydogan, Pinar; Suzer, Sefik; Polat, Emre O.; Kocabas, Coskun

    2016-07-15

    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 specific 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.

  8. Closing the pressure gap in x-ray photoelectron spectroscopy by membrane hydrogenation

    SciTech Connect

    Delmelle, Renaud; Borgschulte, Andreas; Probst, Benjamin; Alberto, Roger; Züttel, Andreas; Bleiner, Davide

    2015-05-15

    Comprehensive studies of gas-solid reactions require the in-situ interaction of the gas at a pressure beyond the operating pressure of ultrahigh vacuum (UHV) X-ray photoelectron spectroscopy (XPS). The recent progress of near ambient pressure XPS allows to dose gases to the sample up to a pressure of 20 mbar. The present work describes an alternative to this experimental challenge, with a focus on H{sub 2} as the interacting gas. Instead of exposing the sample under investigation to gaseous hydrogen, the sample is in contact with a hydrogen permeation membrane, through which hydrogen is transported from the outside to the sample as atomic hydrogen. Thereby, we can reach local hydrogen concentrations at the sample inside an UHV chamber, which is equipped with surface science tools, and this corresponds to a hydrogen pressure up to 1 bar without affecting the sensitivity or energy resolution of the spectrometer. This experimental approach is validated by two examples, that is, the reduction of a catalyst precursor for CO{sub 2} hydrogenation and the hydrogenation of a water reduction catalyst for photocatalytic H{sub 2} production, but it opens the possibility of the new in situ characterisation of energy materials and catalysts.

  9. 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.

  10. Closing the pressure gap in x-ray photoelectron spectroscopy by membrane hydrogenation

    NASA Astrophysics Data System (ADS)

    Delmelle, Renaud; Probst, Benjamin; Alberto, Roger; Züttel, Andreas; Bleiner, Davide; Borgschulte, Andreas

    2015-05-01

    Comprehensive studies of gas-solid reactions require the in-situ interaction of the gas at a pressure beyond the operating pressure of ultrahigh vacuum (UHV) X-ray photoelectron spectroscopy (XPS). The recent progress of near ambient pressure XPS allows to dose gases to the sample up to a pressure of 20 mbar. The present work describes an alternative to this experimental challenge, with a focus on H2 as the interacting gas. Instead of exposing the sample under investigation to gaseous hydrogen, the sample is in contact with a hydrogen permeation membrane, through which hydrogen is transported from the outside to the sample as atomic hydrogen. Thereby, we can reach local hydrogen concentrations at the sample inside an UHV chamber, which is equipped with surface science tools, and this corresponds to a hydrogen pressure up to 1 bar without affecting the sensitivity or energy resolution of the spectrometer. This experimental approach is validated by two examples, that is, the reduction of a catalyst precursor for CO2 hydrogenation and the hydrogenation of a water reduction catalyst for photocatalytic H2 production, but it opens the possibility of the new in situ characterisation of energy materials and catalysts.

  11. X-ray photoelectron spectroscopic investigation of nanocrystalline calcium silicate hydrates synthesised by reactive milling

    SciTech Connect

    Black, Leon . E-mail: l.black@shu.ac.uk; Garbev, Krassimir; Beuchle, Guenter; Stemmermann, Peter; Schild, Dieter

    2006-06-15

    X-ray photoelectron spectroscopy (XPS) has been used to analyse a series of mechanochemically synthesised, nanocrystalline calcium silicate hydrates (C-S-H). The samples, with Ca/Si ratios of 0.2 to 1.5, showed structural features of C-S-H(I). XPS analysis revealed changes in the extent of silicate polymerisation. Si 2p, Ca 2p and O 1s spectra showed that, unlike for the crystalline calcium silicate hydrate phases studied previously, there was no evidence of silicate sheets (Q{sup 3}) at low Ca/Si ratios. Si 2p and O 1s spectra indicated silicate depolymerisation, expressed by decreasing silicate chain length, with increasing C/S. In all spectra, peak narrowing was observed with increasing Ca/Si, indicating increased structural ordering. The rapid changes of the slope of FWHM of Si 2p, {delta} {sub Ca-Si} and {delta} {sub NBO-BO} as function of C/S ratio indicated a possible miscibility gap in the C-S-H-solid solution series between C/S 5/6 and 1. The modified Auger parameter ({alpha}') of nanocrystalline C-S-H decreased with increasing silicate polymerisation, a trend already observed studying crystalline C-S-H. Absolute values of {alpha}' were shifted about - 0.7 eV with respect to crystalline phases of equal C/S ratio, due to reduced crystallinity.

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

    SciTech Connect

    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 COH alcohol group and CMe methyl groups in a 1 : 2 ratio, respectively. Coverage increased with 2-propanol partial pressure and followed first order Langmuir kinetics with a Langmuir constant of K = 6.3 × 103 Torr-1. The 1 : 2 ratio of COH : CMe 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.

  13. Quantum-classical calculations of X-ray photoelectron spectra of polymers-Polymethyl methacrylate revisited.

    PubMed

    Löytynoja, T; Harczuk, I; Jänkälä, K; Vahtras, O; Ågren, H

    2017-03-28

    In this work, we apply quantum mechanics/molecular mechanics (QM/MM) approach to predict core-electron binding energies and chemical shifts of polymers, obtainable via X-ray photoelectron spectroscopy(XPS), using polymethyl methacrylate as a demonstration example. The results indicate that standard parametrizations of the quantum part (basis sets, level of correlation) and the molecular mechanics parts (decomposed charges, polarizabilities, and capping technique) are sufficient for the QM/MM model to be predictive for XPS of polymers. It is found that the polymer environment produces contributions to the XPS binding energies that are close to monotonous with the number of monomer units, totally amounting to approximately an eV decrease in binding energies. In most of the cases, the order of the shifts is maintained, and even the relative size of the differential shifts is largely preserved. The coupling of the internal core-hole relaxation to the polymer environment is found to be weak in each case, amounting only to one or two tenths of an eV. The main polymeric effect is actually well estimated already at the frozen orbital level of theory, which in turn implies a substantial computational simplification. These conclusions are best represented by the cases where the ionized monomer and its immediate surrounding are treated quantum mechanically. If the QM region includes only a single monomer, a couple of anomalies are spotted, which are referred to the QM/MM interface itself and to the neglect of a possible charge transfer.

  14. Analysis of Band Offset in GaNAs/GaAs by X-Ray Photoelectron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Kitatani, Takeshi; Kondow, Masahiko; Kikawa, Takeshi; Yazawa, Yoshiaki; Okai, Makoto; Uomi, Kazuhisa

    1999-09-01

    We used X-ray photoelectron spectroscopy (XPS) to measure the energy discontinuity in the valence band (ΔEv) of Ga1-xNxAs/AlAs (x=0, 0.014, 0.034) and estimated ΔEv of GaNAs/GaAs by using the Al2p energy level as a reference. The change in ΔEv for GaNAs/GaAs with an increasing nitrogen content was -(0.019±0.053) eV/%N. This suggests that the valence-band edge (Ev) in GaNAs decreases in proportion to the nitrogen content. Based on the decrease in the bandgap energy of GaNAs, we found that the energy discontinuity in the conduction band (ΔEc) of GaNAs/GaAs is -(0.175±0.053) eV/%N. This large effect of bandgap bowing on the conduction band indicates that an ideal carrier confinement in the well can be obtained by using GaInNAs as an active layer in long-wavelength laser diodes.

  15. Depth-profiling X-ray photoelectron spectroscopy (XPS) analysis of interlayer diffusion in polyelectrolyte multilayers.

    PubMed

    Gilbert, Jonathan B; Rubner, Michael F; Cohen, Robert E

    2013-04-23

    Functional organic thin films often demand precise control over the nanometer-level structure. Interlayer diffusion of materials may destroy this precise structure; therefore, a better understanding of when interlayer diffusion occurs and how to control it is needed. X-ray photoelectron spectroscopy paired with C60(+) cluster ion sputtering enables high-resolution analysis of the atomic composition and chemical state of organic thin films with depth. Using this technique, we explore issues common to the polyelectrolyte multilayer field, such as the competition between hydrogen bonding and electrostatic interactions in multilayers, blocking interlayer diffusion of polymers, the exchange of film components with a surrounding solution, and the extent and kinetics of interlayer diffusion. The diffusion coefficient of chitosan (M = ∼100 kDa) in swollen hydrogen-bonded poly(ethylene oxide)/poly(acrylic acid) multilayer films was examined and determined to be 1.4*10(-12) cm(2)/s. Using the high-resolution data, we show that upon chitosan diffusion into the hydrogen-bonded region, poly(ethylene oxide) is displaced from the film. Under the conditions tested, a single layer of poly(allylamine hydrochloride) completely stops chitosan diffusion. We expect our results to enhance the understanding of how to control polyelectrolyte multilayer structure, what chemical compositional changes occur with diffusion, and under what conditions polymers in the film exchange with the solution.

  16. Depth-profiling X-ray photoelectron spectroscopy (XPS) analysis of interlayer diffusion in polyelectrolyte multilayers

    PubMed Central

    Gilbert, Jonathan B.; Rubner, Michael F.; Cohen, Robert E.

    2013-01-01

    Functional organic thin films often demand precise control over the nanometer-level structure. Interlayer diffusion of materials may destroy this precise structure; therefore, a better understanding of when interlayer diffusion occurs and how to control it is needed. X-ray photoelectron spectroscopy paired with C60+ cluster ion sputtering enables high-resolution analysis of the atomic composition and chemical state of organic thin films with depth. Using this technique, we explore issues common to the polyelectrolyte multilayer field, such as the competition between hydrogen bonding and electrostatic interactions in multilayers, blocking interlayer diffusion of polymers, the exchange of film components with a surrounding solution, and the extent and kinetics of interlayer diffusion. The diffusion coefficient of chitosan (M = ∼100 kDa) in swollen hydrogen-bonded poly(ethylene oxide)/poly(acrylic acid) multilayer films was examined and determined to be 1.4*10−12 cm2/s. Using the high-resolution data, we show that upon chitosan diffusion into the hydrogen-bonded region, poly(ethylene oxide) is displaced from the film. Under the conditions tested, a single layer of poly(allylamine hydrochloride) completely stops chitosan diffusion. We expect our results to enhance the understanding of how to control polyelectrolyte multilayer structure, what chemical compositional changes occur with diffusion, and under what conditions polymers in the film exchange with the solution. PMID:23569265

  17. X-ray photoelectron spectroscopy characterization of high dose carbon-implanted steel and titanium alloys

    NASA Astrophysics Data System (ADS)

    Viviente, J. L.; García, A.; Alonso, F.; Braceras, I.; Oñate, J. I.

    1999-04-01

    A study has been made of the depth dependence of the atomic fraction and chemical bonding states of AISI 440C martensitic stainless steel and Ti-6Al-4V alloy implanted with 75 keV C + at very high doses (above 10 18 ions cm -2), by means of X-ray photoelectron spectroscopy combined with an Ar + sputtering. A Gaussian-like carbon distribution was observed on both materials at the lowest implanted dose. More trapezoidal carbon depth-profiles were found with increasing implanted doses, and a pure carbon layer was observed only on the titanium alloy implanted at the highest dose. The implanted carbon was combined with both base metal and carbon itself to form metallic carbides and graphitic carbon. Furthermore, carbon-enriched carbides were also found by curve fitting the C 1s spectra. The titanium alloy showed a higher carbidic contribution than the steel implanted at the same C + doses. A critical carbon concentrations of about 33 at.% and 23 at.% were measured for the formation of C-C bonds in Ti-6Al-4V and steel samples, respectively. The carbon atoms were bound with metal to form carbidic compounds until these critical concentrations were reached; when this C concentration was exceeded the proportion of C-C bonds increased and resulted in the growth of carbonaceous layers.

  18. In Situ Ambient Pressure X-ray Photoelectron Spectroscopy Studies of Lithium-Oxygen Redox Reactions

    NASA Astrophysics Data System (ADS)

    Lu, Yi-Chun; Crumlin, Ethan J.; Veith, Gabriel M.; Harding, Jonathon R.; Mutoro, Eva; Baggetto, Loïc; Dudney, Nancy J.; Liu, Zhi; Shao-Horn, Yang

    2012-10-01

    The lack of fundamental understanding of the oxygen reduction and oxygen evolution in nonaqueous electrolytes significantly hinders the development of rechargeable lithium-air batteries. Here we employ a solid-state Li4+xTi5O12/LiPON/LixV2O5 cell and examine in situ the chemistry of Li-O2 reaction products on LixV2O5 as a function of applied voltage under ultra high vacuum (UHV) and at 500 mtorr of oxygen pressure using ambient pressure X-ray photoelectron spectroscopy (APXPS). Under UHV, lithium intercalated into LixV2O5 while molecular oxygen was reduced to form lithium peroxide on LixV2O5 in the presence of oxygen upon discharge. Interestingly, the oxidation of Li2O2 began at much lower overpotentials (~240 mV) than the charge overpotentials of conventional Li-O2 cells with aprotic electrolytes (~1000 mV). Our study provides the first evidence of reversible lithium peroxide formation and decomposition in situ on an oxide surface using a solid-state cell, and new insights into the reaction mechanism of Li-O2 chemistry.

  19. Characterization of peptide attachment on silicon nanowires by X-ray photoelectron spectroscopy and mass spectrometry.

    PubMed

    Kurylo, Ievgen; Dupré, Mathieu; Cantel, Sonia; Enjalbal, Christine; Drobecq, Hervé; Szunerits, Sabine; Melnyk, Oleg; Boukherroub, Rabah; Coffinier, Yannick

    2017-03-13

    In this paper, we report an original method to immobilize a model peptide on silicon nanowires (SiNWs) via a photolinker attached to the SiNWs' surface. The silicon nanowires were fabricated by a metal assisted chemical etching (MACE) method. Then, direct characterization of the peptide immobilization on SiNWs was performed either by X-ray photoelectron spectroscopy (XPS) or by laser-desorption/ionization mass spectrometry (LDI-MS). XPS allowed us to follow the peptide immobilization and its photorelease by recording the variation of the signal intensities of the different elements present on the SiNW surface. Mass spectrometry was performed without the use of an organic matrix and peptide ions were produced via a photocleavage mechanism. Indeed, thanks to direct photorelease achieved upon laser irradiation, a recorded predictable peak related to the molecular peptide ion has been detected, allowing the identification of the model peptide. Additional MS/MS experiments confirmed the photodissociation site and confirmed the N-terminal immobilization of the peptide on SiNWs.

  20. X-ray photoelectron spectroscopy surface analysis of aluminum ion stress in barley roots. [Hordeum vulgare

    SciTech Connect

    Millard, M.M.; Foy, C.D.; Coradetti, C.A.; Reinsel, M.D. )

    1990-06-01

    X-ray photoelectron spectroscopy (XPS) has been used to analyze root surface changes when Dayton barley (Hordeum vulgare) (Al tolerant) and Kearney barley (Al sensitive) seedlings were grown in nutrient solution in the presence and absence of 37.0 micromolar Al. The electron spectra from root surfaces contained strong lines in order of decreasing intensity from organic forms of carbon, oxygen, and nitrogen and weak lines due to inorganic elements in the form of anions and cations on the surface. The surface composition of root tips from Kearney was C, 65.6%; 0, 26.8%; N, 4.4% and tips from Dayton was C, 72.7%; O, 23.6%; N, 1.9%, grown in the absence of aluminum. Electron lines characteristic of nitrate, potassium, chloride, phosphate were also present in the spectra from those roots. Dayton roots grown in the presence of 37.0 micromolar aluminum contained 2.1% aluminum while Kearney contained 1.3% aluminum. The ratio of aluminum to phosphate was close to 1.0. Dayton roots usually contained twice as much aluminum phosphate in the surface region as Kearney. Dayton may be less susceptible to Al toxic effects by accumulation of aluminum phosphate on the root surface which then acts as a barrier to the transport of aluminum into the interior of the roots.

  1. Behavior of oxygen doped SiC thin films: An x-ray photoelectron spectroscopy study

    NASA Astrophysics Data System (ADS)

    Avila, A.; Montero, I.; Galán, L.; Ripalda, J. M.; Levy, R.

    2001-01-01

    Thin silicon carbide films have been deposited by chemical vapor deposition on p-type (100) silicon substrates. The composition and bonds formed in these films have been analyzed by x-ray photoelectron spectroscopy (XPS) and infrared spectroscopy. The native surface oxide on the silicon carbide surface induced by air exposure has also been studied. Several phases are detected in the near-surface region: elemental Si, Si oxides (mainly SiO2), Si carbide (SiC) and Si oxicarbides (SiOxCy). Quantitative XPS analysis results indicate that, for atomic oxygen fractions <0.15, the Si-C phases are dominant in the films. Above this value no silicon oxicarbide is observed, but a multiphase material formed by elemental Si, Si oxides and Si carbides is observed. In spite of the film being a complex phase mixture, a simple relationship is found between the overall carbon and oxygen compositions. The carbon atomic fraction in the film decreases quasilinearly as the oxygen content increases, with a slope of about -1. An overall composition of SiOxC3-x in the 0.5

  2. Surface characterization of various graphites by x-ray photoelectron, secondary ion mass, and Raman spectroscopies

    SciTech Connect

    Ashida, K.; Kanamori, K.; Watanabe, K.

    1988-07-01

    Graphite is the primary candidate for the first wall of magnetically confined fusion devices. For this purpose, it is important to know the surface properties of graphite to understand the plasma--surface interactions as well as vacuum properties of graphite. From this viewpoint, we examined the binding states of carbon atoms, inherent hydrogen content, and crystallinity of the surfaces of isotropic graphites prepared by several Japanese companies as well as anisotropic ones with x-ray photoelectron (XPS), secondary ion mass (SIMS), and Raman (RS) spectroscopies. Although no measurable difference in the binding state of carbon atoms was detected among the isotropic and anisotropic graphites with XPS, RS revealed that their crystallite sizes differed from each other. Namely, the crystallite sizes of the isotropic graphites were in the range from 100 to 300 A, whereas those of the anisotropic graphites were more than approx.1000 A. In addition, nongraphitized carbon which was not observed for the anisotropic graphites was present in the surface layers of the isotropic ones. SIMS revealed that the inherent hydrogen contents in the isotropic graphites were larger than those in the anisotropic ones. The results indicate that the larger hydrogen contents in the isotropic graphites are due to the presence of nongraphitized carbon which acts as the trapping site of hydrogen atoms.

  3. 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 COH alcohol group and CMe methyl groups in a 1 : 2 ratio, respectively. Coverage increased with 2-propanol partialmore » pressure and followed first order Langmuir kinetics with a Langmuir constant of K = 6.3 × 103 Torr-1. The 1 : 2 ratio of COH : CMe 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

  4. A versatile instrument for ambient pressure x-ray photoelectron spectroscopy: The Lund cell approach

    NASA Astrophysics Data System (ADS)

    Knudsen, Jan; Andersen, Jesper N.; Schnadt, Joachim

    2016-04-01

    During the past one and a half decades ambient pressure x-ray photoelectron spectroscopy (APXPS) has grown to become a mature technique for the real-time investigation of both solid and liquid surfaces in the presence of a gas or vapour phase. APXPS has been or is being implemented at most major synchrotron radiation facilities and in quite a large number of home laboratories. While most APXPS instruments operate using a standard vacuum chamber as the sample environment, more recently new instruments have been developed which focus on the possibility of custom-designed sample environments with exchangeable ambient pressure cells (AP cells). A particular kind of AP cell solution has been driven by the development of the APXPS instrument for the SPECIES beamline of the MAX IV Laboratory: the solution makes use of a moveable AP cell which for APXPS measurements is docked to the electron energy analyser inside the ultrahigh vacuum instrument. Only the inner volume of the AP cell is filled with gas, while the surrounding vacuum chamber remains under vacuum conditions. The design enables the direct connection of UHV experiments to APXPS experiments, and the swift exchange of AP cells allows different custom-designed sample environments. Moreover, the AP cell design allows the gas-filled inner volume to remain small, which is highly beneficial for experiments in which fast gas exchange is required. Here we report on the design of several AP cells and use a number of cases to exemplify the utility of our approach.

  5. Self-detection of x-ray Fresnel transmissivity using photoelectron-induced gas ionization

    SciTech Connect

    Stoupin, Stanislav

    2016-01-25

    Electric response of an x-ray mirror enclosed in a gas flow ionization chamber was studied under the conditions of total external reflection for hard x-rays. It is shown that the electric response of the system as a function of the incidence angle is defined by x-ray Fresnel transmissivity and photon-electron attenuation properties of the mirror material. A simple interpretation of quantum yield of the system is presented. The approach could serve as a basis for non-invasive in situ diagnostics of hard x-ray optics, easy access to complementary x-ray transmissivity data in x-ray reflectivity experiments, and might also pave the way to advanced schemes for angle and energy resolving x-ray detectors.

  6. Self-detection of x-ray Fresnel transmissivity using photoelectron-induced gas ionization

    NASA Astrophysics Data System (ADS)

    Stoupin, Stanislav

    2016-01-01

    Electric response of an x-ray mirror enclosed in a gas flow ionization chamber was studied under the conditions of total external reflection for hard x-rays. It is shown that the electric response of the system as a function of the incidence angle is defined by x-ray Fresnel transmissivity and photon-electron attenuation properties of the mirror material. A simple interpretation of quantum yield of the system is presented. The approach could serve as a basis for non-invasive in situ diagnostics of hard x-ray optics, easy access to complementary x-ray transmissivity data in x-ray reflectivity experiments, and might also pave the way to advanced schemes for angle and energy resolving x-ray detectors.

  7. Nonlinear Absorption of X-ray Free Electron Laser Pulses in Dense Aluminum Plasmas

    NASA Astrophysics Data System (ADS)

    Cho, Min Sang; Kim, M.; Chung, H.-K.; Cho, Byoung-Ick

    2016-10-01

    XFEL provides unique opportunities to generate and investigate dense plasmas. Here, we present the intensity dependent, nonlinear x-ray absorption in dense aluminum target using the collisional-radiative population kinetic calculations. With high peak intensity of XFEL pulses, even below K-absorption edge, x-ray photons could create excited states of which absorption is larger than the ground state absorption. At the resonant energy of neutral atom, increasing x-ray absorption in the intensity range of 1016 17 W/cm2 has been observed, and it is the reverse saturable absorption in the x-ray regime. The similar observations have been also made at the other resonant energies of higher charge states. At even higher XFEL intensities, bleaching a specific charge state could lead a transition from reverse saturable absorption to saturable absorption, so thus x-ray absorption is decreasing. Detailed population kinetics of charge states relevant to the absorption of x-ray photons, and fast modulation of XFEL spectrum will be discussed. This work is supported by Institute of Basic Science (IBS-R012-D1) and National Research Foundation of Korea (No. 2015R1A5A1009962 and 2016R1A2B4009631).

  8. Speciation of Gold Nanoparticles by Ex Situ Extended X-ray Absorption Fine Structure and X-ray Absorption Near Edge Structure.

    PubMed

    Giorgetti, Marco; Aquilanti, Giuliana; Ballarin, Barbara; Berrettoni, Mario; Cassani, Maria Cristina; Fazzini, Silvia; Nanni, Daniele; Tonelli, Domenica

    2016-07-05

    A combined X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) methodology is here presented on a series of partially and fully reduced Au(III) samples. This allows monitoring the relative fraction of Au(III) and Au(0) in the studied samples, displaying a consistent and independent outcome. The strategy followed is based, for the first time, on two structural models that can be fitted simultaneously, and it evaluates the correlation among strongly correlated parameters such as coordination number and the Debye-Waller factor. The results of the present EXAFS and XANES approach can be extended to studies based on X-ray absorption spectroscopy experiments for the in situ monitoring of the formation of gold nanoclusters.

  9. Isotope and temperature effects in liquid water probed by x-ray absorption and resonant x-ray emission spectroscopy.

    PubMed

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

    2008-01-18

    High-resolution x-ray absorption and emission spectra of liquid water exhibit a strong isotope effect. Further, the emission spectra show a splitting of the 1b1 emission line, a weak temperature effect, and a pronounced excitation-energy dependence. They can be described as a superposition of two independent contributions. By comparing with gas phase, ice, and NaOH/NaOD, we propose that the two components are governed by the initial state hydrogen bonding configuration and ultrafast dissociation on the time scale of the O 1s core hole decay.

  10. Phase Effects on Mesoscale Object X-ray Absorption Images

    SciTech Connect

    Martz, Jr., H E; Aufderheide, M B; Barty, A; Lehman, S K; Kozioziemski, B J; Schneberk, D J

    2004-09-24

    At Lawrence Livermore National Laboratory particular emphasis is being placed on the nondestructive characterization (NDC) of 'mesoscale' objects.[Martz and Albrecht 2003] We define mesoscale objects as objects that have mm extent with {micro}m features. Here we confine our discussions to x-ray imaging methods applicable to mesoscale object characterization. The goal is object recovery algorithms including phase to enable emerging high-spatial resolution x-ray imaging methods to ''see'' inside or image mesoscale-size materials and objects. To be successful our imaging characterization effort must be able to recover the object function to one micrometer or better spatial resolution over a few millimeters field-of-view with very high contrast.

  11. X-ray photoelectron emission microscopy and time-of-flight secondary ion mass spectrometry analysis of ultrathin fluoropolymer coatings for stent applications.

    PubMed

    Hale, Penelope; Turgeon, Stéphane; Horny, Paula; Lewis, François; Brack, Narelle; Van Riessen, Grant; Pigram, Paul; Mantovani, Diego

    2008-08-05

    Fluoropolymer plasma coatings have been investigated for application as stent coatings due to their chemical stability, conformability, and hydrophobic properties. The challenge resides in the capacity for these coatings to remain adherent, stable, and cohesive after the in vivo stent expansion, which can generate local plastic deformation of up to 25%. Plasma-coated samples have been prepared by a multistep process on 316L stainless steel substrates, and some coated samples were plastically deformed to mimic a stent expansion. Analyses were then performed by X-ray photoelectron spectroscopy (XPS), X-ray photoelectron emission microscopy (X-PEEM), and time-of-flight secondary ion mass spectrometry (TOF-SIMS) to determine the chemical and physical effects of such a deformation on both the coating and the interfacial region. While XPS analyses always showed a continuous coating with no significant effect of the deformation, TOF-SIMS and near-edge X-ray absorption fine structure (derived from X-PEEM) data indicated the presence of a certain density of porosity and pinholes in all coatings as well as sparse fissures and molecular fragmentation in the deformed ones. The smallness of the area fraction affected by the defects and the subtlety of the chemical changes could only be evidenced through the higher chemical sensitivity of these latter techniques.

  12. Discovery of an X-ray Violently Variable Broad Absorption Line Quasar

    NASA Technical Reports Server (NTRS)

    Ghosh, Kajal K.; Gutierrez, Carlos M.; Punsly, Brian; Chevallier, Loic; Goncalves, Anabela C.

    2006-01-01

    In this letter, we report on a quasar that is violently variable in the X-rays, XVV. It is also a broad absorption line quasar (BALQSO) that exhibits both high ionization and low ionization UV absorption lines (LoBALQSO). It is very luminous in the X-rays (approximately 10(exp 46) ergs s(sup -l) over the entire X-ray band). Surprisingly, this does not over ionize the LoBAL outflow. The X-rays vary by a factor of two within minutes in the quasar rest frame, which is shorter than 1/30 of the light travel time across a scale length equal to the black hole radius. We concluded that the X-rays are produced in a relativistic jet beamed toward earth in which variations in the Doppler enhancement produce the XVV behavior.

  13. Discovery of an X-ray Violently Variable Broad Absorption Line Quasar

    NASA Technical Reports Server (NTRS)

    Ghosh, Kajal K.; Gutierrez, Carlos M.; Punsly, Brian; Chevallier, Loic; Goncalves, Anabela C.

    2006-01-01

    In this letter, we report on a quasar that is violently variable in the X-rays, XVV. It is also a broad absorption line quasar (BALQSO) that exhibits both high ionization and low ionization UV absorption lines (LoBALQSO). It is very luminous in the X-rays (approximately 10(exp 46) ergs s(sup -l) over the entire X-ray band). Surprisingly, this does not over ionize the LoBAL outflow. The X-rays vary by a factor of two within minutes in the quasar rest frame, which is shorter than 1/30 of the light travel time across a scale length equal to the black hole radius. We concluded that the X-rays are produced in a relativistic jet beamed toward earth in which variations in the Doppler enhancement produce the XVV behavior.

  14. Optical and x-ray photoelectron spectroscopy studies of α-Al{sub 2}O{sub 3}

    SciTech Connect

    Prakash, Ram E-mail: ramprakash@smvdu.ac.in; Kumar, Sandeep; Kumar, Vinay; Choudhary, R. J.; Phase, D. M.

    2016-05-23

    α-Al{sub 2}O{sub 3} powder sample was synthesized at 550 °C via solution combustion synthesis (SCS) method using urea as an organic fuel. The sample was characterized by X-ray diffraction (XRD), Optical spectroscopy and X-ray photoelectron spectroscopy (XPS) without any further thermal treatment. XRD study reveals that the powder crystallized directly in the hexagons α-Al{sub 2}O{sub 3} phase. A band gap of 5.7 eV was estimated using diffuse reflectance spectra. For surface investigation X-ray photo electron spectroscopy (XPS) was carried out. The XPS survey scan study of α-Al{sub 2}O{sub 3} powder reveals that the sample is free from impurity. The core levels of Al-2s and O-1s are also reported.

  15. ASCITOVG - FORTRAN PROGRAM FOR X-RAY PHOTOELECTRON SPECTROSCOPY DATA REFORMATTING

    NASA Technical Reports Server (NTRS)

    Able, P. B.

    1994-01-01

    It is often desirable to use a central, more powerful computer to analyze data captured on a local machine. ASCITOVG is a program for use on an IBM PC series computer which creates binary format files from columns of ASCII-format numbers. The resultant files are suitable for interactive analysis on a DEC PDP-11/73 under the Micro-RSX operating system running the VGS-5000 Enhanced Data Processing (EDP) software package. EDP performs data analysis interactively with a color graphics display, speeding up the analysis considerably when compared with batch job processing. Its interactive analysis capabilities also allow the researcher to watch for spurious data that might go undetected when some form of automatic spectrum processing is used. The incompatibility in floating-point number representations of an IBM PC and a DEC computer were resolved by a FORTRAN subroutine that correctly converts single-precision, floating-point numbers on the PC so that they can be directly read by DEC computers, such as a VAX. The subroutine also can convert binary DEC files (single-precision, floating-point numbers) to IBM PC format. This may prove a more efficient method of moving data from, for instance, a VAX-cluster down to a local IBM PC for further examination, manipulation, or display. The input data file used by ASCITOVG is simply a text file in the form of a column of ASCII numbers, with each value followed by a carriage return. These can be the output of a data collection routine or can even be keyed in through the use of a program editor. The data file header required by the EDP programs for an x-ray photoelectron spectrum is also written to the file. The spectrum parameters, entered by the user when the program is run, are coded into the header format used internally by all of the VGS-5000 series EDP packages. Any file transfer protocol having provision for binary data can be used to transmit the resulting file from the PC to the DEC machine. Each EDP data file has at least

  16. ASCITOVG - FORTRAN PROGRAM FOR X-RAY PHOTOELECTRON SPECTROSCOPY DATA REFORMATTING

    NASA Technical Reports Server (NTRS)

    Able, P. B.

    1994-01-01

    It is often desirable to use a central, more powerful computer to analyze data captured on a local machine. ASCITOVG is a program for use on an IBM PC series computer which creates binary format files from columns of ASCII-format numbers. The resultant files are suitable for interactive analysis on a DEC PDP-11/73 under the Micro-RSX operating system running the VGS-5000 Enhanced Data Processing (EDP) software package. EDP performs data analysis interactively with a color graphics display, speeding up the analysis considerably when compared with batch job processing. Its interactive analysis capabilities also allow the researcher to watch for spurious data that might go undetected when some form of automatic spectrum processing is used. The incompatibility in floating-point number representations of an IBM PC and a DEC computer were resolved by a FORTRAN subroutine that correctly converts single-precision, floating-point numbers on the PC so that they can be directly read by DEC computers, such as a VAX. The subroutine also can convert binary DEC files (single-precision, floating-point numbers) to IBM PC format. This may prove a more efficient method of moving data from, for instance, a VAX-cluster down to a local IBM PC for further examination, manipulation, or display. The input data file used by ASCITOVG is simply a text file in the form of a column of ASCII numbers, with each value followed by a carriage return. These can be the output of a data collection routine or can even be keyed in through the use of a program editor. The data file header required by the EDP programs for an x-ray photoelectron spectrum is also written to the file. The spectrum parameters, entered by the user when the program is run, are coded into the header format used internally by all of the VGS-5000 series EDP packages. Any file transfer protocol having provision for binary data can be used to transmit the resulting file from the PC to the DEC machine. Each EDP data file has at least

  17. Scattering and absorption in soft X-ray selected AGN: an optical polarization survey

    NASA Astrophysics Data System (ADS)

    Grupe, D.; Wills, Beverley J.; Wills, D.; Beuermann, K.

    1998-05-01

    We have surveyed the optical linear polarization of a completely identified sample of 43 bright soft-X-ray-selected ROSAT AGN. Most (40) of these AGN show low polarization (~1%), and no clear optical reddening. This supports the suggestion from rapid X-ray variability, disk-like spectral energy distributions, and lack of cold X-ray absorption, that we are viewing a bare AGN disk. IRASF12397+3333 and IRAS13349+2438 show high polarization increasing to the UV - clear evidence for scattering. As well as steep, soft-X-ray spectra, they show optical reddening and rapid X-ray variability, but almost no cold X-ray absorption - a combination that suggests dusty ionized gas along the line-of-sight. Brandt et al. suggested and found these `warm absorbers' for IRAS13349+2438. IRASF12397+3333 is a new candidate. Combining our data with the optical and X-ray spectra of the high polarization narrow-line Seyfert 1 nuclei (NLSy1s) investigated by Goodrich reveals strong correlations among optical reddening indicators (alpha_opt and Hα /Hβ ), [OIII]/Hβ_b , and cold intrinsic X-ray absorption Delta N_H. Optical reddening underpredicts the cold X-ray absorption, suggesting dusty warm absorbers in all the highly polarized AGN. The existence of these scattering-polarized and reddened NLSy1s suggests an orientation Unified Scheme within the class of NLSy1s, analogous to that linking Seyfert 1 and Seyfert 2 nuclei. For some highly polarized and optically selected AGN we present new analysis of archival X-ray data, and for the highly polarized AGN new optical spectroscopy is presented in an appendix.

  18. X-ray-absorption spectroscopy and n-body distribution functions in condensed matter. I. Theory

    NASA Astrophysics Data System (ADS)

    Filipponi, Adriano; di Cicco, Andrea; Natoli, Calogero Renzo

    1995-12-01

    The general theoretical framework underlying the GNXAS multiple-scattering (MS) data-analysis method for x-ray absorption spectroscopy (XAS) is presented. The main approximations leading to the reduction of the many-body process in that of a photoelectron scattering in an effective potential are summarized. The methods available to expand the extended x-ray-absorption fine-structure χ(k) into physically meaningful terms are described. In particular, emphasis is given to the definition of the irreducible n-body signals γ(n) that can be calculated directly by means of linear combinations of continued fractions, or by using their respective multiple-scattering series. It is found that even for an infinite system the expansion of the χ(k) signal in terms of γ(n) has a better convergence rate than the MS series. Simple expressions for performing the configurational averages of the structural signals in the presence of thermal and structural disorder are derived. These can be used for the structural analysis of molecular, crystalline, or moderately disordered systems. It is shown that in the case of highly disordered systems the expansion in terms of the γ(n) signals is the natural framework for the interpretation of the XAS signal. General equations for the ensemble-averaged χ(k) signal as a function of a series of integrals over the n-body n>~2 distribution functions gn are provided and the possible use of advanced strategies for the inversion of the structural information is suggested.

  19. Inter-Diffusion of Copper and Hafnium as Studied by X-Ray Photoelectron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Pearson, Justin Seth

    The purpose of this study is to investigate the interdiffusion of copper and hafnium. 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. High purity samples have been used in this investigation. The deposition of the elements was done by the e-beam technique. The interfaces thus formed were annealed for a fixed time (30 minutes) at temperatures of 100, 200, and 300°C. The samples were characterized in situ by the x-ray photoelectron spectroscopy technique. To carry out the depth profiling of these samples a controlled amount of the over layer was removed and the spectral data were acquired. The argon ion sputtering technique was used to sputter the layers away. Spectral data in the copper 2p and hafnium 4f regions were investigated. The atomic concentration of the constituents as a function of depth across the interface was determined by analyzing the areas under the curves. The depth profiling data thus obtained was analyzed by the Matano-Boltzmann's procedure. For this analysis the Matano plane was determined based on the criteria of equal area on each side of the interface. The Fick's Law second law was used to calculate the interdiffuison coefficient for each of these interfaces. The interdiffusion coefficient as a function of temperature was determined from these analyses. From these coefficients the activation energy and the pre-exponential factor was determined by using the Arrhenius plot. The activation energy was found to be 0.128 eV/atom and the pre-exponential factor was 3.33E-14 cm2/s. The results from this investigation will be useful in the application of Cu/Hf interface in design and fabrication of semiconductor devices.

  20. 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.

  1. X-ray photoelectron spectroscopic analysis of Si nanoclusters in SiO2 matrix.

    PubMed

    Dane, Aykutlu; Demirok, U Korcan; Aydinli, Atilla; Suzer, Sefik

    2006-01-26

    We investigated silicon nanoclusters Si(nc) in a SiO2 matrix prepared by the plasma-enhanced chemical vapor deposition technique, using X-ray photoelectron spectroscopy (XPS) with external voltage stimuli in both static and pulsed modes. This method enables us to induce an additional charging shift of 0.8 eV between the Si2p peaks of the oxide and the underlying silicon, both in static and time-resolved modes, for a silicon sample containing a 6 nm oxide layer. In the case of the sample containing silicon nanoclusters, both Si2p peaks of Si(nc) and host SiO2 undergo a charging shift that is 1 order of magnitude larger (>15 eV), with no measurable difference between them (i.e., no differential charging between the silicon nanoclusters and the oxide matrix could be detected). By use of a measured Auger parameter, we estimate the relaxation energy of the Si(nc) in the SiO2 matrix as -0.4 eV, which yields a -0.6 eV shift in the binding energy of the Si(nc) with respect to that of bulk Si in the opposite direction of the expected quantum size effect. This must be related to the residual differential charging between the silicon nanoclusters and the oxide host. Therefore, differential charging is still the biggest obstacle for extracting size-dependent binding energy shifts with XPS when one uses the oxide peak as the reference.

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

    SciTech Connect

    Apostol, Nicoleta Georgiana

    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 are 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.

  3. Thermal desorption mass spectrometric and x-ray photoelectron studies of etched surfaces of polytetrafluoroethylene

    NASA Astrophysics Data System (ADS)

    Rye, R. R.; Kelber, J. A.

    1987-12-01

    The etching of polytetrafluoroethylene (PTFE) with Na solutions is known to lead to a loss of F, a loss which is correlated with enhanced adhesion. Subsequent heating partially restores surface F with a concurrent loss of adhesion strength. We have combined X-ray photoelectron spectroscopy (XPS) and gas phase mass spectroscopy for in situ measurements of the processes that occur as the fluorocarbon is heated. An array of volatile products, which vary with the specific treatment, desorb from etched PTFE. Among these are: N 2 and low molecular weight fluorocarbons, the amounts of which monotonically decrease with increasing exposure to the etching solution (and probably result from the bulk); species such as CO and CO 2, which in part result from surface impurities; and water and acetone which result from the rinse steps following the etching process. XPS measurements show that etching produces a major loss of surface F and a gain of surface O. The latter probably results from the subsequent rinse steps. Heating produces a substantial recovery in surface F with only a small decrease in the surface O, and the gain in surface F is shown to occur at a higher temperature than the desorption of any species from the surface. Thus, desorption of products from the surface is decoupled, in terms of both the distribution of products and their relative temperatures, from the surface changes as monitored by XPS. This decoupling suggests that the increase in surface F results from diffusion of low molecular weight fluorocarbons from the bulk or a transition region, or from a rearrangement of the sponge-like surface region produced in the etching process.

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

    NASA Astrophysics Data System (ADS)

    Apostol, Nicoleta Georgiana

    2014-11-01

    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 are 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 PbZr0.2Ti0.8O3(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.

  5. A new interpretation of the binding energies in X-ray photoelectron studies of oxides

    NASA Astrophysics Data System (ADS)

    Barr, Tery L.; Seal, Sudipta; Chen, Li Mei; Kao, Chi Chang

    1994-12-01

    Films and coatings applied to different substrates are often various types of oxides. The latter are employed for a number of reasons with particular emphasis on their lack of chemical and electrical porosity. It is generally important therefore to have some measure of the physical and chemical integrity of the resulting oxide films and their interfaces with the substrate. The latter is often realized by using X-ray photoelectron spectroscopy or electron spectroscopy for chemical analysis. In order to accomplish this, it is common practice to utilize the (now generally well accepted) binding energy data from the literature to verify and expand upon one's results. Unfortunately, close scrutiny reveals a number of major discrepancies in these literature results for certain key oxides. Thus, for example, a significant portion of the literature reports the Al 2p level of Al2O3at approximately 75.7+/-0.3 eV, whereas many others specify approximately 74.0+/-0.2 eV. Perhaps the greatest difficulty with this observation is that it can be shown that, based upon their respective methods of analysis, both results are equally valid. In the present investigation, we examine the extent and nature of this problem. We have discovered that there are particular types of oxides that exhibit this dichotomy in binding energies, whereas others do not. The role played by bonding and morphology in these differences is explored, as is the effect of the different methods of binding energy determination. Finally, we shall describe how the mechanism of the growth of oxides is the principal 'culprit' and a lack of understanding of the latter and its electronic implications may lead many to an incorrect interpretation of 'true' binding energies.

  6. Repair and Utilization of the Kratos XSAM 800 X-Ray Photoelectron Spectrometer (XPS)

    NASA Technical Reports Server (NTRS)

    Hampton, Michael D.

    2002-01-01

    The objectives for this summer faculty fellowship were first to repair the Kratos XSAM 800 X-ray Photoelectron Spectrometer (XPS) and then to utilize the instrument to participate in ongoing research projects at KSC and in the researcher's own laboratory at UCF. The first 6 weeks were used in repairing the instrument. Working both alone and with the Kratos service engineer, a number of hardware problems, largely associated with the sample stage control system, were corrected. Defective parts were identified and fixed in the computer driver boards, the stage power supply, and the driver interface. The power supply was completely replaced. After four weeks of work, the instrument was functional. This occurred on a Wednesday. The following Friday the instrument had to be completely shut down because the power to the O & C Building was to be turned off. The instrument was properly secured. On Monday, the instrument was powered up and the original problems returned. After another 2 weeks of work, a software problem was identified. This problem caused the computer to use a defective port for the sample stage control. It was circumvented by rewriting the startup routine. The final 3 weeks of the fellowship were spent using the XPS to analyze samples being studied in the Langley materials project (Martha Williams) and a catalyst project (Dr. Orlando Melendez). During this time, several sample analysis requests from other groups at KSC also came in and those samples were run as well. The summer faculty fellowship also allowed many contacts to be made. After meeting with the sensors group, two projects were identified for collaboration and white papers are being prepared. One project aims to develop small, very sensitive hydrogen detectors and the other to develop a broad area, easily monitored, zero power consumption hydrogen detector. In addition to the work mentioned above, the XPS was utilized in a study underway in Dr. Hampton's laboratory at UCF.

  7. Repair and Utilization of the Kratos XSAM 800 X-Ray Photoelectron Spectrometer (XPS)

    NASA Technical Reports Server (NTRS)

    Hampton, Michael D.

    2002-01-01

    The objectives for this summer faculty fellowship were first to repair the Kratos XSAM 800 X-ray Photoelectron Spectrometer (XPS) and then to utilize the instrument to participate in ongoing research projects at KSC and in the researcher's own laboratory at UCF. The first 6 weeks were used in repairing the instrument. Working both alone and with the Kratos service engineer, a number of hardware problems, largely associated with the sample stage control system, were corrected. Defective parts were identified and fixed in the computer driver boards, the stage power supply, and the driver interface. The power supply was completely replaced. After four weeks of work, the instrument was functional. This occurred on a Wednesday. The following Friday the instrument had to be completely shut down because the power to the O & C Building was to be turned off. The instrument was properly secured. On Monday, the instrument was powered up and the original problems returned. After another 2 weeks of work, a software problem was identified. This problem caused the computer to use a defective port for the sample stage control. It was circumvented by rewriting the startup routine. The final 3 weeks of the fellowship were spent using the XPS to analyze samples being studied in the Langley materials project (Martha Williams) and a catalyst project (Dr. Orlando Melendez). During this time, several sample analysis requests from other groups at KSC also came in and those samples were run as well. The summer faculty fellowship also allowed many contacts to be made. After meeting with the sensors group, two projects were identified for collaboration and white papers are being prepared. One project aims to develop small, very sensitive hydrogen detectors and the other to develop a broad area, easily monitored, zero power consumption hydrogen detector. In addition to the work mentioned above, the XPS was utilized in a study underway in Dr. Hampton's laboratory at UCF.

  8. Measuring the pK/pI of biomolecules using X-ray photoelectron spectroscopy.

    PubMed

    Fears, Kenan P

    2014-09-02

    Dissociation constants of GG-X-GG and X5 peptides (X = G, D, H, or K), and bovine albumin (BSA) and fibronectin (FN) were measured by X-ray photoelectron spectroscopy (XPS) in ultrahigh vacuum at room temperature. The biomolecules were deposited on Au substrates by drying 2.0 μL drops of 1.0 μg μL(-1) stock solutions in 100 mM sodium phosphate buffers (pH 1-12) at room temperature. Because of the ∼+1.3 eV shift in binding energy (BE) of protonated amines, pK values of basic amino acids were calculated by plotting the fraction of protonated amines as a function of solution pH. Similarly, the BE of carboxyl groups shifted ∼-1.3 eV upon deprotonation. While C 1s spectra were convoluted by the multiple chemical states of carbon present in the samples, the ratio of the C 1s components centered at BE = 289.0 ± 0.4 and BE = 287.9 ± 0.3 proved to reliably assess deprotonation of carboxyl groups. The pK values for the Asp (3.1 and 2.4), His (6.7), and Lys (11.3 and 10.6) peptides, and the pI of BSA (4.8) and FN (5.7), were consistent with published values; thus, these methods could potentially be used to determine the dissociation constants of surface-bound biomolecules.

  9. WEAK HARD X-RAY EMISSION FROM TWO BROAD ABSORPTION LINE QUASARS OBSERVED WITH NuSTAR: COMPTON-THICK ABSORPTION OR INTRINSIC X-RAY WEAKNESS?

    SciTech Connect

    Luo, B.; Brandt, W. N.; Alexander, D. M.; Hickox, R.; Harrison, F. A.; Fuerst, F.; Grefenstette, B. W.; Madsen, K. K.; Stern, D.; Bauer, F. E.; Boggs, S. E.; Craig, W. W.; Christensen, F. E.; Comastri, A.; Fabian, A. C.; Farrah, D.; Fiore, F.; Hailey, C. J.; Matt, G.; Ogle, P.; and others

    2013-08-01

    We present Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of two X-ray weak broad absorption line (BAL) quasars, PG 1004+130 (radio loud) and PG 1700+518 (radio quiet). Many BAL quasars appear X-ray weak, probably due to absorption by the shielding gas between the nucleus and the accretion-disk wind. The two targets are among the optically brightest BAL quasars, yet they are known to be significantly X-ray weak at rest-frame 2-10 keV (16-120 times fainter than typical quasars). We would expect to obtain Almost-Equal-To 400-600 hard X-ray ({approx}> 10 keV) photons with NuSTAR, provided that these photons are not significantly absorbed (N{sub H} {approx}< 10{sup 24} cm{sup -2}). However, both BAL quasars are only detected in the softer NuSTAR bands (e.g., 4-20 keV) but not in its harder bands (e.g., 20-30 keV), suggesting that either the shielding gas is highly Compton-thick or the two targets are intrinsically X-ray weak. We constrain the column densities for both to be N{sub H} Almost-Equal-To 7 Multiplication-Sign 10{sup 24} cm{sup -2} if the weak hard X-ray emission is caused by obscuration from the shielding gas. We discuss a few possibilities for how PG 1004+130 could have Compton-thick shielding gas without strong Fe K{alpha} line emission; dilution from jet-linked X-ray emission is one likely explanation. We also discuss the intrinsic X-ray weakness scenario based on a coronal-quenching model relevant to the shielding gas and disk wind of BAL quasars. Motivated by our NuSTAR results, we perform a Chandra stacking analysis with the Large Bright Quasar Survey BAL quasar sample and place statistical constraints upon the fraction of intrinsically X-ray weak BAL quasars; this fraction is likely 17%-40%.

  10. Weak Hard X-Ray Emission from Two Broad Absorption Line Quasars Observed with NuStar: Compton-Thick Absorption or Intrinsic X-Ray Weakness?

    NASA Technical Reports Server (NTRS)

    Luo, B.; Brandt, W. N.; Alexander, D. M.; Harrison, F. A.; Stern, D.; Bauer, F. E.; Boggs, S. E.; Christensen, F. E.; Comastri, A.; Craig, W. W..; Fabian, A. C.; Farrah, D.; Fiore, F.; Fuerst, F.; Grefenstette, B. W.; Hailey, C. J.; Hickox, R.; Madsen, K. K.; Matt, G.; Ogle, P.; Risaliti, G.; Saez, C.; Teng, S. H.; Walton, D. J.; Zhang, W. W.

    2013-01-01

    We present Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of two X-ray weak broad absorption line (BAL) quasars, PG 1004+130 (radio loud) and PG 1700+518 (radio quiet). Many BAL quasars appear X-ray weak, probably due to absorption by the shielding gas between the nucleus and the accretion-disk wind. The two targets are among the optically brightest BAL quasars, yet they are known to be significantly X-ray weak at rest-frame 2-10 keV (16-120 times fainter than typical quasars). We would expect to obtain approx. or equal to 400-600 hard X-ray (is greater than or equal to 10 keV) photons with NuSTAR, provided that these photons are not significantly absorbed N(sub H) is less than or equal to 10(exp24) cm(exp-2). However, both BAL quasars are only detected in the softer NuSTAR bands (e.g., 4-20 keV) but not in its harder bands (e.g., 20-30 keV), suggesting that either the shielding gas is highly Compton-thick or the two targets are intrinsically X-ray weak. We constrain the column densities for both to be N(sub H) 7 × 10(exp 24) cm(exp-2) if the weak hard X-ray emission is caused by obscuration from the shielding gas. We discuss a few possibilities for how PG 1004+130 could have Compton-thick shielding gas without strong Fe Ka line emission; dilution from jet-linked X-ray emission is one likely explanation. We also discuss the intrinsic X-ray weakness scenario based on a coronal-quenching model relevant to the shielding gas and disk wind of BAL quasars. Motivated by our NuSTAR results, we perform a Chandra stacking analysis with the Large Bright Quasar Survey BAL quasar sample and place statistical constraints upon the fraction of intrinsically X-ray weak BAL quasars; this fraction is likely 17%-40%.

  11. First-principles calculations of X-ray absorption spectra for warm dense methane

    NASA Astrophysics Data System (ADS)

    Li, Zi; Wang, Cong; Li, Dafang; Kang, Wei; Zhang, Ping

    2017-09-01

    X-ray absorption spectrum is a powerful tool for atomic structure detection on materials under extreme conditions. Here, we perform first-principles molecular dynamics and X-ray absorption spectrum calculations for warm dense methane under thermodynamical conditions along a Hugoniot curve. From the molecular dynamics trajectories, the detailed atomic structures are examined for each condition. The carbon K-shell X-ray absorption spectrum is calculated, and its change with temperature and pressure is discussed. The methane systems under extreme conditions may contain radicals CHx (x = 1,2,3), molecules CH4, and carbon chains CmHn (m,n >1). These various products show quite different contributions to the total X-ray spectrum due to the different atomic and electronic structures. The change of the total X-ray spectrum along the Hugoniot curve is then attributed to the change of the products induced by the temperature and pressure. Some clear signatures on the X-ray absorption spectrum under different thermodynamical conditions are proposed, which provide useful information for future X-ray experiments.

  12. X-Ray Attenuation and Absorption for Materials of Dosimetric Interest

    National Institute of Standards and Technology Data Gateway

    SRD 126 X-Ray Attenuation and Absorption for Materials of Dosimetric Interest (Web, free access)   Tables and graphs of the photon mass attenuation coefficient and the mass energy-absorption coefficient are presented for all of the elements Z = 1 to 92, and for 48 compounds and mixtures of radiological interest. The tables cover energies of the photon (x-ray, gamma ray, bremsstrahlung) from 1 keV to 20 MeV.

  13. Improved self-absorption correction for extended x-ray absorption fine-structure measurements

    SciTech Connect

    Booth, C.H.; Bridges, F.

    2003-06-04

    Extended x-ray absorption fine-structure (EXAFS) data collected in the fluorescence mode are susceptible to an apparent amplitude reduction due to the self-absorption of the fluorescing photon by the sample before it reaches a detector. Previous treatments have made the simplifying assumption that the effect of the EXAFS on the correction term is negligible, and that the samples are in the thick limit. We present a nearly exact treatment that can be applied for any sample thickness or concentration, and retains the EXAFS oscillations in the correction term.

  14. Multiple pre-edge structures in Cu K -edge x-ray absorption spectra of high- Tc cuprates revealed by high-resolution x-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Gougoussis, C.; Rueff, J.-P.; Calandra, M.; D'Astuto, M.; Jarrige, I.; Ishii, H.; Shukla, A.; Yamada, I.; Azuma, M.; Takano, M.

    2010-06-01

    Using high-resolution x-ray absorption spectroscopy and state-of-the-art electronic structure calculations we demonstrate that the pre-edge region at the Cu K edge of high- Tc cuprates is composed of several excitations invisible in standard x-ray absorption spectra. We consider in detail the case of Ca2-xCuO2Cl2 and show that the many pre-edge excitations (two for c -axis polarization, four for in-plane polarization and out-of-plane incident x-ray momentum) are dominated by off-site transitions and intersite hybridization. This demonstrates the relevance of approaches beyond the single-site model for the description of the pre edges of correlated materials. Finally, we show the occurrence of a doubling of the main edge peak that is most visible when the polarization is along the c axis. This doubling, that has not been seen in any previous absorption data in cuprates, is not reproduced by first-principles calculations. We suggest that this peak is due to many-body charge-transfer excitations while all the other visible far-edge structures are single particle in origin. Our work indicates that previous interpretations of the Cu K -edge x-ray absorption spectra in high- Tc cuprates can be profitably reconsidered.

  15. Coordination defects in bismuth-modified arsenic selenide glasses: High-resolution x-ray photoelectron spectroscopy measurements

    SciTech Connect

    Golovchak, Roman; Shpotyuk, Oleh

    2008-05-01

    The possibility of coordination defects formation in Bi-modified chalcogenide glasses is examined by high-resolution x-ray photoelectron spectroscopy. The results provide evidence for the formation of positively charged fourfold coordinated defects on As and Bi sites in glasses with low Bi concentration. At high Bi concentration, mixed As{sub 2}Se{sub 3}-Bi{sub 2}Se{sub 3} nanocrystallites are formed in the investigated Se-rich As-Se glasses.

  16. Monitoring potassium metal electrodeposition from an ionic liquid using in situ electrochemical-X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Wibowo, Rahmat; Aldous, Leigh; Jacobs, Robert M. J.; Manan, Ninie S. A.; Compton, Richard G.

    2011-06-01

    The real time electrodeposition of potassium has been monitored for the first time in an ionic liquid using in situ electrodeposition-X-ray photoelectron spectroscopy (XPS). The ionic liquid used was N-butyl- N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C 4mpyrr][ NTf 2]), and electrodeposition occurred at a nickel mesh electrode. Potassium electrochemistry was monitored at the ionic liquid-vacuum-electrode interface using a novel cell design.

  17. Characterization of carbonitrided and oxidized layers on low-carbon steel by conversion electron Moessbauer spectrometry, X-ray diffractometry, and X-ray photoelectron spectrometry

    SciTech Connect

    Kurosawa, K.; Li, H.L.; Ujihira, Y.; Nomura, K.

    1999-03-01

    The structures of low-carbon steel oxidized in an aqueous saline bath at 403 K and a fused salt bath at 673 K after carbonitriding were studied using conversion electron Moessbauer spectrometry (CEMS), x-ray diffractometry (XRD), and x-ray photoelectron spectrometry (XPS). Only a doublet peak caused by poor crystallinity of iron oxyhydroxides (FeOOH) or fine particles of iron oxides such as magnetite (Fe{sub 3}O{sub 4}) and maghemite ({gamma}-Fe{sub 2}O{sub 3}) was detected in the CEMS spectra of the surface of the carbonitrided steel oxidized in the aqueous saline bath. Corrosion resistance of the carbonitrided specimens was increased by oxidizing. The oxidized layers produced in the aqueous saline bath were superior to those produced in the fused salt bath as a result of pores in the carbonitrided zone being filled with finer particles of iron oxides and the production of tight, thick oxide layers of amorphous iron oxyhydroxides or fine iron oxides. Deformation of iron nitride ({gamma}{prime}-Fe{sub 4}N) crystals in the carbonitrided zone could not be detected by oxidizing in the aqueous saline bath but were detected in the fused salt bath at 673 K.

  18. X-Ray Absorption Spectroscopy of Uranium Dioxide

    SciTech Connect

    Tobin, J G

    2010-12-10

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

  19. Electron band bending and surface sensitivity: X-ray photoelectron spectroscopy of polar GaN surfaces

    NASA Astrophysics Data System (ADS)

    Bartoš, I.; Romanyuk, O.; Paskova, T.; Jiříček, P.

    2017-10-01

    The role of electron band bending and surface sensitivity in determining the core level binding energies by X-ray photoelectron spectroscopy is investigated. A dominating contribution of surface atomic layers to photoemission intensity is confirmed for normal photoemission. The energy of the photoelectron core level peak does not deviate from core level peak energies of electrons photoemitted from the surface atomic layers of the crystal. The higher surface sensitivity regime, achieved e.g. at off-normal photoelectron detection angle, can be used to study the surface potential barrier in just a few topmost atomic layers. In addition, it is demonstrated that core level binding energy measured by angle-resolved X-ray photoelectron spectroscopy reflect the electron attenuation anisotropy. In particular, core level binding energy changes with emission angle and correlates with the forward focusing directions in a crystal. This effect is demonstrated by measuring the polar angle dependence of Ga 3d core levels on clean GaN(0001) and GaN(000 1 bar) surfaces with a higher and a lower band bending, respectively. The effect is explained by variation of emission depth in a crystal for normal and off-normal photoelectron emission angles.

  20. Structure and Composition of Cu Doped CdSe Nanocrystals Using Soft X-ray Absorption Spectroscopy

    SciTech Connect

    Meulenberg, R W; van Buuren, T; Hanif, K M; Willey, T M; Strouse, G F; Terminello, L J

    2004-06-04

    The local structure and composition of Cu ions dispersed in CdSe nanocrystals is examined using soft x-ray absorption near edge spectroscopy (XANES). Using Cu L-edge XANES and X-ray photoelectron measurements (XPS), we find that the Cu ions exist in the Cu(I) oxidation state. We also find that the observed Cu L-edge XANES signal is directly proportional to the molar percent of Cu present in our final material. Se L-edge XANES indicates changes in the Se density of states with Cu doping, due to a chemical bonding effect, and supports a statistical doping mechanism. Photoluminescence (PL) measurements indicate the Cu ions may act as deep electron traps. We show that XANES, XPS, and PL are a powerful combination of methods to study the electronic and chemical structure of dopants in nanostructured materials.

  1. Theoretical study of Raman chirped adiabatic passage by X-ray absorption spectroscopy: Highly excited electronic states and rotational effects

    SciTech Connect

    Engin, Selma; Sisourat, Nicolas Selles, Patricia; Taïeb, Richard; Carniato, Stéphane

    2014-06-21

    Raman Chirped Adiabatic Passage (RCAP) is an efficient method to climb the vibrational ladder of molecules. It was shown on the example of fixed-in-space HCl molecule that selective vibrational excitation can thus be achieved by RCAP and that population transfer can be followed by X-ray Photoelectron spectroscopy [S. Engin, N. Sisourat, P. Selles, R. Taïeb, and S. Carniato, Chem. Phys. Lett. 535, 192–195 (2012)]. Here, in a more detailed analysis of the process, we investigate the effects of highly excited electronic states and of molecular rotation on the efficiency of RCAP. Furthermore, we propose an alternative spectroscopic way to monitor the transfer by means of X-ray absorption spectra.

  2. Solving the Structure of Reaction Intermediates by Time-Resolved Synchrotron X-ray Absorption Spectroscopy

    SciTech Connect

    Wang, Q.; Hanson, J; Frenkel, A

    2008-01-01

    We present a robust data analysis method of time-resolved x-ray absorption spectroscopy experiments suitable for chemical speciation and structure determination of reaction intermediates. Chemical speciation is done by principal component analysis (PCA) of the time-resolved x-ray absorption near-edge structure data. Structural analysis of intermediate phases is done by theoretical modeling of their extended x-ray absorption fine-structure data isolated by PCA. The method is demonstrated using reduction and reoxidation of Cu-doped ceria catalysts where we detected reaction intermediates and measured fine details of the reaction kinetics. This approach can be directly adapted to many time-resolved x-ray spectroscopy experiments where new rapid throughput data collection and analysis methods are needed.

  3. A sample holder for soft x-ray absorption spectroscopy of liquids in transmission mode.

    PubMed

    Schreck, Simon; Gavrila, Gianina; Weniger, Christian; Wernet, Philippe

    2011-10-01

    A novel sample holder for soft x-ray absorption spectroscopy of liquids in transmission mode based on sample cells with x-ray transparent silicon nitride membranes is introduced. The sample holder allows for a reliable preparation of ultrathin liquid films with an adjustable thickness in the nm-μm range. This enables measurements of high quality x-ray absorption spectra of liquids in transmission mode, as will be shown for the example of liquid H(2)O, aqueous solutions of 3d-transition metal ions and alcohol-water mixtures. The fine structure of the x-ray absorption spectra is not affected by the sample thickness. No effects of the silicon nitride membranes were observed in the spectra. It is shown how an inhomogeneous thickness of the sample affects the spectra and how this can be avoided.

  4. High energy X-ray phase and dark-field imaging using a random absorption mask

    PubMed Central

    Wang, Hongchang; Kashyap, Yogesh; Cai, Biao; Sawhney, Kawal

    2016-01-01

    High energy X-ray imaging has unique advantage over conventional X-ray imaging, since it enables higher penetration into materials with significantly reduced radiation damage. However, the absorption contrast in high energy region is considerably low due to the reduced X-ray absorption cross section for most materials. Even though the X-ray phase and dark-field imaging techniques can provide substantially increased contrast and complementary information, fabricating dedicated optics for high energies still remain a challenge. To address this issue, we present an alternative X-ray imaging approach to produce transmission, phase and scattering signals at high X-ray energies by using a random absorption mask. Importantly, in addition to the synchrotron radiation source, this approach has been demonstrated for practical imaging application with a laboratory-based microfocus X-ray source. This new imaging method could be potentially useful for studying thick samples or heavy materials for advanced research in materials science. PMID:27466217

  5. ON NEUTRAL ABSORPTION AND SPECTRAL EVOLUTION IN X-RAY BINARIES

    SciTech Connect

    Miller, J. M.; Cackett, E. M.; Reis, R. C.

    2009-12-10

    Current X-ray observatories make it possible to follow the evolution of transient and variable X-ray binaries across a broad range in luminosity and source behavior. In such studies, it can be unclear whether evolution in the low-energy portion of the spectrum should be attributed to evolution in the source, or instead to evolution in neutral photoelectric absorption. Dispersive spectrometers make it possible to address this problem. We have analyzed a small but diverse set of X-ray binaries observed with the Chandra High Energy Transmission Grating Spectrometer across a range in luminosity and different spectral states. The column density in individual photoelectric absorption edges remains constant with luminosity, both within and across source spectral states. This finding suggests that absorption in the interstellar medium strongly dominates the neutral column density observed in spectra of X-ray binaries. Consequently, evolution in the low-energy spectrum of X-ray binaries should properly be attributed to evolution in the source spectrum. We discuss our results in the context of X-ray binary spectroscopy with current and future X-ray missions.

  6. Interstellar dust grain composition from high-resolution X-ray absorption edge structure

    NASA Astrophysics Data System (ADS)

    Corrales, Lia

    2016-06-01

    X-ray light is sufficient to excite electrons from n=1 (K-shell) and n=2 (L-shell) energy levels of neutral interstellar metals, causing a sharp increase in the absorption cross-section. Near the ionization energy, the shape of the photoelectric absorption edge depends strongly on whether the atom is isolated or bound in molecules or minerals (dust). With high resolution X-ray spectroscopy, we can directly measure the state of metals and the mineral composition of dust in the interstellar medium. In addition, the scattering contribution to the X-ray extinction cross-section can be used to gauge grain size, shape, and filling factor. In order to fully take advantage of major advances in high resolution X-ray spectroscopy, lab measurements of X-ray absorption fine structure (XAFS) from suspected interstellar minerals are required. Optical constants derived from the absorption measurements can be used with Mie scattering or anomalous diffraction theory in order to model the full extinction cross-sections from the interstellar medium. Much like quasar spectra are used to probe other intergalactic gas, absorption spectroscopy of Galactic X-ray binaries and bright stars will yield key insights to the mineralogy and evolution of dust grains in the Milky Way.

  7. Ultrafast time-resolved X-ray absorption spectroscopy of ferrioxalate photolysis with a laser plasma X-ray source and microcalorimeter array

    DOE PAGES

    O’Neil, Galen C.; Miaja-Avila, Luis; Joe, Young Il; ...

    2017-02-17

    The detailed pathways of photoactivity on ultrafast time scales are a topic of contemporary interest. Using a tabletop apparatus based on a laser plasma X-ray source and an array of cryogenic microcalorimeter X-ray detectors, we measured a transient X-ray absorption spectrum during the ferrioxalate photoreduction reaction. With these high-efficiency detectors, we observe the Fe K edge move to lower energies and the amplitude of the extended X-ray absorption fine structure reduce, consistent with a photoreduction mechanism in which electron transfer precedes disassociation. We provide quantitative limits on the Fe–O bond length change. Lastly, we review potential improvements to our measurementmore » technique, highlighting the future potential of tabletop X-ray science using microcalorimeter sensors.« less

  8. 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)

  9. 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)

  10. The electronic structure study of titanium-nickel alloys by x-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Seabolt, Michael A.

    2002-01-01

    Purpose of the study. The purpose of the study was to investigate the electronic structure changes of titanium-nickel (Ti-Ni) alloys. The electronic structure was correlated with the physical property of shape memory effect demonstrated by 50% atomic nickel concentration Ti-Ni crystalline alloys. Methodology. The technique of x-ray photoelectron spectroscopy was used to collect spectra using an ESCA PHI 5100 system. The spectra were analyzed by measuring binding energies, Auger parameters, Shirley and Tougaard backgrounds, and electronegativity criteria. Changes in the density of state (DOS) at the Fermi level were modeled using binding energy shifts, Auger parameter changes, the intrinsic loss structure modeled from the Shirley and Tougaard background, and the electronegativity criteria. Results. Significant changes in binding energy (BE) were noted for alloys, but changes in BE could not be with electronegativity criteria. The Auger parameter demonstrated positive values for Ti and negative values for Ni with minimum values at the 50% atomic nickel concentration. This was interpreted as a transfer of charge from nickel to titanium. Wagner plots of the Auger parameter indicated Ti and Ni were in different chemical states in each of the alloys with a minimum for the 50% atomic concentration nickel, which correlates to the shape memory effect (SME). Chemical shifts indicated a shift in charge from Ni to Ti, correlating to the results yielded by the Auger parameter. Normalized background analysis (indicative of the intrinsic loss structure) obtained from Shirley and Tougaard methods correlated well with the Auger parameter and chemical shift results, indicating that background analysis is useful for studying changes in chemical state for these materials. Conclusions. This study demonstrated that BE shifts and electronegativity criteria can not be successfully used to model changes in chemical states for Ti-Ni alloys. The results from Auger parameter analysis

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

    SciTech Connect

    Axnanda, Stephanus; Crumlin, Ethan J.; Mao, Baohua; Rani, Sana; Chang, Rui; Karlsson, Patrik G.; Edwards, Mårten O. M.; Lundqvist, Måns; Moberg, Robert; Ross, Phil; Hussain, Zahid; Liu, Zhi

    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 liquid 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.

  12. Using "Tender" X-ray Ambient Pressure X-Ray Photoelectron Spectroscopy as A Direct Probe of Solid-Liquid Interface.

    PubMed

    Axnanda, Stephanus; Crumlin, Ethan J; Mao, Baohua; Rani, Sana; Chang, Rui; Karlsson, Patrik G; Edwards, Mårten O M; Lundqvist, Måns; Moberg, Robert; Ross, Phil; Hussain, Zahid; Liu, Zhi

    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 liquid 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 Pt(2+) and Pt(4+) 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.

  13. 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

  14. Evaluation of Two Methods for Determining Shell Thicknesses of Core-Shell Nanoparticles by X-ray Photoelectron Spectroscopy.

    PubMed

    Powell, C J; Werner, W S M; Shard, A G; Castner, D G

    2016-10-06

    We evaluated two methods for determining shell thicknesses of core-shell nanoparticles (NPs) by X-ray photoelectron spectroscopy (XPS). One of these methods had been developed for determining thicknesses of films on a planar substrate while the other was developed specifically for NPs. Our evaluations were based on simulated Cu 2p3/2 spectra from Cu-core/Cu-shell NPs with a wide range of core diameters and shell thicknesses. Copper was chosen for our tests because elastic-scattering effects for Cu 2p3/2 photoelectrons excited by Al Kα X-rays are known to be strong. Elastic scattering could also be switched off in our simulations so that the two methods could be evaluated in the limit of no elastic scattering. We found that the first method, based on both core and shell photoelectron intensities, was unsatisfactory for all conditions. The second method, based on an empirical equation for NPs developed by Shard, also utilized both core and shell photoelectron intensities and was found to be satisfactory for all conditions. The average deviation between shell thicknesses derived from the Shard equation and the true values was -4.1 % when elastic scattering was switched on and -2.2 % when elastic scattering was switched off. If elastic scattering was switched on, the effective attenuation length for a Cu film on a planar substrate was the appropriate length parameter while the inelastic mean free path was the appropriate parameter when elastic scattering was switched off.

  15. Femtosecond X-ray magnetic circular dichroism absorption spectroscopy at an X-ray free electron laser

    SciTech Connect

    Higley, Daniel J. Yuan, Edwin; Hirsch, Konstantin; Dakovski, Georgi L.; Jal, Emmanuelle; Lutman, Alberto A.; Coslovich, Giacomo; Hart, Philip; Hoffmann, Matthias C.; Mitra, Ankush; Moeller, Stefan; Ohldag, Hendrik; Seaberg, Matthew; Stöhr, Joachim; Nuhn, Heinz-Dieter; Reid, Alex H.; Dürr, Hermann A.; Schlotter, William F.; Liu, Tianmin; MacArthur, James P.; and others

    2016-03-15

    X-ray magnetic circular dichroism spectroscopy using an X-ray free electron laser is demonstrated with spectra over the Fe L{sub 3,2}-edges. The high brightness of the X-ray free electron laser combined with high accuracy detection of incident and transmitted X-rays enables ultrafast X-ray magnetic circular dichroism studies of unprecedented sensitivity. This new capability is applied to a study of all-optical magnetic switching dynamics of Fe and Gd magnetic sublattices in a GdFeCo thin film above its magnetization compensation temperature.

  16. X-ray two-photon absorption with high fluence XFEL pulses

    DOE PAGES

    Hoszowska, Joanna; Szlachetko, J.; Dousse, J. -Cl.; ...

    2015-09-07

    Here, we report on nonlinear interaction of solid Fe with intense femtosecond hard x-ray free-electron laser (XFEL) pulses. The experiment was performed at the CXI end-station of the Linac Coherent Light Source (LCLS) by means of high- resolution x-ray emission spectroscopy. The focused x-ray beam provided extreme fluence of ~105 photons/Å2. Two-photon absorption leading to K-shell hollow atom formation and to single K-shell ionization of solid Fe was investigated.

  17. X-ray two-photon absorption with high fluence XFEL pulses

    SciTech Connect

    Hoszowska, Joanna; Szlachetko, J.; Dousse, J. -Cl.; Błachucki, W.; Kayser, Y.; Milne, Ch.; Pajek, M.; Boutet, S.; Messerschmidt, M.; Williams, G.; Chantler, C. T.

    2015-09-07

    Here, we report on nonlinear interaction of solid Fe with intense femtosecond hard x-ray free-electron laser (XFEL) pulses. The experiment was performed at the CXI end-station of the Linac Coherent Light Source (LCLS) by means of high- resolution x-ray emission spectroscopy. The focused x-ray beam provided extreme fluence of ~105 photons/Å2. Two-photon absorption leading to K-shell hollow atom formation and to single K-shell ionization of solid Fe was investigated.

  18. Refraction and absorption of x rays by laser-dressed atoms.

    SciTech Connect

    Buth, C.; Santra, R.; Young, L.

    2010-06-01

    X-ray refraction and absorption by neon atoms under the influence of an 800 nm laser with an intensity of 10{sup 13} W/cm{sup 2} is investigated. For this purpose, we use an ab initio theory suitable for optical strong-field problems. Its results are interpreted in terms of a three-level model. On the Ne 1s {yields} 3p resonance, we find electromagnetically induced transparency (EIT) for x rays. Our work opens novel perspectives for ultrafast x-ray pulse shaping.

  19. Note: application of a pixel-array area detector to simultaneous single crystal X-ray diffraction and X-ray absorption spectroscopy measurements.

    PubMed

    Sun, Cheng-Jun; Zhang, Bangmin; Brewe, Dale L; Chen, Jing-Sheng; Chow, G M; Venkatesan, T; Heald, Steve M

    2014-04-01

    X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) are two main x-ray techniques in synchrotron radiation facilities. In this Note, we present an experimental setup capable of performing simultaneous XRD and XAS measurements by the application of a pixel-array area detector. For XRD, the momentum transfer in specular diffraction was measured by scanning the X-ray energy with fixed incoming and outgoing x-ray angles. By selecting a small fixed region of the detector to collect the XRD signal, the rest of the area was available for collecting the x-ray fluorescence for XAS measurements. The simultaneous measurement of XRD and X-ray absorption near edge structure for Pr0.67Sr0.33MnO3 film was demonstrated as a proof of principle for future time-resolved pump-probe measurements. A static sample makes it easy to maintain an accurate overlap of the X-ray spot and laser pump beam.

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

    SciTech Connect

    Sun, Cheng-Jun Brewe, Dale L.; Heald, Steve M.; Zhang, Bangmin; Chen, Jing-Sheng; Chow, G. M.; Venkatesan, T.

    2014-04-15

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

  1. Single-step absorption and phase retrieval with polychromatic x rays using a spectral detector.

    PubMed

    Gürsoy, Doğa; Das, Mini

    2013-05-01

    In this Letter, we present a single-step method to simultaneously retrieve x-ray absorption and phase images valid for a broad range of imaging energies and material properties. Our method relies on the availability of spectrally resolved intensity measurements, which is now possible using semiconductor x-ray photon counting detectors. The retrieval method is derived and presented, with results showing good agreement.

  2. Ultraintense X-Ray Induced Ionization, Dissociation, and Frustrated Absorption in Molecular Nitrogen

    SciTech Connect

    Hoener, M.; Fang, L.; Murphy, B.; Berrah, N.; Kornilov, O.; Gessner, O.; Pratt, S. T.; Kanter, E. P.; Guehr, M.; Bucksbaum, P. H.; Cryan, J.; Glownia, M.; McFarland, B.; Petrovic, V.; Blaga, C.; DiMauro, L.; Bostedt, C.; Bozek, J. D.; Coffee, R.; Messerschmidt, M.

    2010-06-25

    Sequential multiple photoionization of the prototypical molecule N{sub 2} is studied with femtosecond time resolution using the Linac Coherent Light Source (LCLS). A detailed picture of intense x-ray induced ionization and dissociation dynamics is revealed, including a molecular mechanism of frustrated absorption that suppresses the formation of high charge states at short pulse durations. The inverse scaling of the average target charge state with x-ray peak brightness has possible implications for single-pulse imaging applications.

  3. Ultraintense x-ray induced ionization, dissociation and frustrated absorption in molecular nitrogen.

    SciTech Connect

    Hoener, M.; Fang, L.; Kornilov, O.; Gessner, O.; Pratt, S. T.; Guhr, M.; Kanter, E. P.; Blaga, C.; Bostedt, C.; Bozek, J. D.; Bucksbaum, P. H.; Buth, C.; Chen, M.; Coffee, R.; Cryan, J.; DiMauro, L.; Glownia, M.; Hosler, E.; Kukk, E.; Leone, S. R.; McFarland, B.; Messerschmidt, M.; Murphy, B.; Petrovic, V.; Rolles, D.; Berrah, N.; Chemical Sciences and Engineering Division; Western Michigan Univ.; LBNL; Ohio State Univ.; Louisiana State Univ.; LLNL; Univ. of Turku; Univ. of California at Berkeley; Max Planck Advanced Study Group, CFEL; LCLS

    2010-06-23

    Sequential multiple photoionization of the prototypical molecule N2 is studied with femtosecond time resolution using the Linac Coherent Light Source (LCLS). A detailed picture of intense x-ray induced ionization and dissociation dynamics is revealed, including a molecular mechanism of frustrated absorption that suppresses the formation of high charge states at short pulse durations. The inverse scaling of the average target charge state with x-ray peak brightness has possible implications for single-pulse imaging applications.

  4. The 16th International Conference on X-ray Absorption Fine Structure (XAFS16)

    NASA Astrophysics Data System (ADS)

    Grunwaldt, J.-D.; Hagelstein, M.; Rothe, J.

    2016-05-01

    This preface of the proceedings volume of the 16th International Conference on X- ray Absorption Fine Structure (XAFS16) gives a glance on the five days of cutting-edge X-ray science which were held in Karlsruhe, Germany, August 23 - 28, 2015. In addition, several satellite meetings took place in Hamburg, Berlin and Stuttgart, a Sino-German workshop, three data analysis tutorials as well as special symposia on industrial catalysis and XFELs were held at the conference venue.

  5. XMM-Newton Spectroscopy of the X-ray Detected Broad Absorption Line QSO CSO 755

    NASA Technical Reports Server (NTRS)

    Brandt, Niel

    2005-01-01

    We present the results from XMM-Newton observations of the highly optically polarized broad absorption line quasar (BALQSO) CSO 755. By analyzing its X-ray spectrum with a total of approximately 3000 photons we find that this source has an X-ray continuum of "typical" radio-quiet quasars, with a photon index of Gamma=1.83, and a rather flat (X-ray bright) intrinsic optical-to-X-ray spectral slope of alpha_ox=- 1.51. The source shows evidence for intrinsic absorption, and fitting the spectrum with a neutral-absorption model gives a column density of N_H approximately 1.2x10^22 cm^{-2}; this is among the lowest X-ray columns measured for BALQSOs. We do not detect, with high significance, any other absorption features in the X-ray spectrum. Upper limits we place on the rest-frame equivalent width of a neutral (ionized) Fe K-alpha line, less than =180 eV (less than =120 eV), and on the Compton-reflection component parameter, R less than =0.2, suggest that most of the X-rays from the source are directly observed rather than being scattered or reflected; this is also supported by the relatively flat intrinsic alpha ox we measure. The possibility that most of the X-ray flux is scattered due to the high level of UV-optical polarization is ruled out. Considering data for 46 BALQSOs from the literature, including CSO 755, we have found that the UV-optical continuum polarization level of BALQSOs is not correlated with any of their X-ray properties. A lack of significant short-term and long-term X-ray flux variations in the source may be attributed to a large black-hole mass in CSO 755. We note that another luminous BALQSO, PG 2112+059, has both similar shallow C IV BALs and moderate X-ray absorption.

  6. XMM-Newton Spectroscopy of the X-ray Detected Broad Absorption Line QSO CSO 755

    NASA Technical Reports Server (NTRS)

    Brandt, Niel

    2005-01-01

    We present the results from XMM-Newton observations of the highly optically polarized broad absorption line quasar (BALQSO) CSO 755. By analyzing its X-ray spectrum with a total of approximately 3000 photons we find that this source has an X-ray continuum of "typical" radio-quiet quasars, with a photon index of Gamma=1.83, and a rather flat (X-ray bright) intrinsic optical-to-X-ray spectral slope of alpha_ox=- 1.51. The source shows evidence for intrinsic absorption, and fitting the spectrum with a neutral-absorption model gives a column density of N_H approximately 1.2x10^22 cm^{-2}; this is among the lowest X-ray columns measured for BALQSOs. We do not detect, with high significance, any other absorption features in the X-ray spectrum. Upper limits we place on the rest-frame equivalent width of a neutral (ionized) Fe K-alpha line, less than =180 eV (less than =120 eV), and on the Compton-reflection component parameter, R less than =0.2, suggest that most of the X-rays from the source are directly observed rather than being scattered or reflected; this is also supported by the relatively flat intrinsic alpha ox we measure. The possibility that most of the X-ray flux is scattered due to the high level of UV-optical polarization is ruled out. Considering data for 46 BALQSOs from the literature, including CSO 755, we have found that the UV-optical continuum polarization level of BALQSOs is not correlated with any of their X-ray properties. A lack of significant short-term and long-term X-ray flux variations in the source may be attributed to a large black-hole mass in CSO 755. We note that another luminous BALQSO, PG 2112+059, has both similar shallow C IV BALs and moderate X-ray absorption.

  7. 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

  8. Prospects for X-ray absorption with the super-bright light sources of the future.

    PubMed

    Norman, D

    2001-03-01

    The immense growth in applications of X-ray absorption spectroscopy (XAS) has been enabled by the widespread availability of intense tunable X-rays from synchrotron radiation sources. Recently, new concepts have been proposed for fourth-generation light sources, such as the SASE (self-amplified stimulated emission) X-ray free-electron lasers (XFELs) being pursued at Hamburg (TESLA) and Stanford (LCLS), and the recirculator ring (MARS) at Novosibirsk. These sources offer expected gains of many orders of magnitude in instantaneous brilliance, which will unlock opportunities for qualitatively different science. Examples of new or greatly expanded techniques in XAS could include Raman X-ray absorption fine structure (XAFS), pump-probe experiments, time-resolved XAFS and small-spot X-ray spectromicroscopy, although the limited tunability of the sources might not allow conventional XAFS measurements. Multi-photon X-ray absorption could become a new field of study. There should not be a collective stampede to these new sources, however, and it is likely that storage rings will continue to be necessary for most XAFS applications. The extreme brightness of these future light sources will present difficult challenges in instrumentation, especially detectors and sample containment. Practitioners will also have to exercise caution, because the intensity of the beam will surely destroy many samples and in some cases there will be so many photons absorbed per atom that XAFS will be impossible.

  9. Measurement of X-ray mass attenuation coefficient of nickel around the K-edge using synchrotron radiation based X-ray absorption study

    NASA Astrophysics Data System (ADS)

    Roy, Bunty Rani; Rajput, Parasmani; Jha, S. N.; Nageswara Rao, A. S.

    2015-09-01

    The work presents the X-ray absorption fine structure (XAFS) technique for measuring the X-ray mass attenuation coefficient of nickel metal foil in the X-ray energy range of 8271.2-8849.4 eV using scanning XAFS beam line (BL-09) at Indus-2 synchrotron radiation source facility, Raja Ramanna Centre for Advanced Technology (RRCAT) at Indore, India. The result represents the X-ray mass attenuation coefficient data for 0.02 mm thick Ni metal foil in the XAFS region of Ni K-edge. However, the results are compared to theoretical values using X-COM. There is a maximum deviation which is found exactly near the K-edge jump and decreases as we move away from the absorption edge. Oscillatory structure appears just above the observed absorption edge i.e., 8348.7 eV and is confined to around 250 eV above the edge.

  10. Oxidation of UO 2 fuel pellets in air at 503 and 543 K studied using X-ray photoelectron spectroscopy and X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Tempest, P. A.; Tucker, P. M.; Tyler, J. W.

    1988-02-01

    An understanding of the low temperature oxidation behaviour of UO 2 pellets in air is important in the unlikely event of gas ingress to a fuel can during handling or storage. The main parameter of concern is the production time of U 3O 8 particulate as a function of temperature. Factors which affect the UO2 → U3O8 transformation have been investigated by sequentially oxidising UO 2 fuel pellets in air at 503 and 543 K and monitoring the growth of U 3O and U 3O 7 using X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. Initially oxidation proceeded at a linear rate by the inward diffusion of oxygen to form a complete layer of substoichiometric U 3O 7. This phase was tetragonal with a {c}/{a} ratio of 1.015, significantly less than the value of 1.03 measured on UO 2 powder when oxidised under identical conditions. This difference and the preferred orientation exhibited by surface grains were caused by growth stresses induced in the pellet surface. Both intergranular and transgranular cracking occurred and became nucleation sites for the growth of U 3O 8. The linear oxidation period associated with U 3O 7 growth was much shorter at 543 than at 503 K and U 3O 8 nucleated earlier. Spallation and the production of particulate were only observed during the formation of U 3O 8 when a 30% increase in volume arose from the U3O7 → U3O8 phase change.

  11. 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

  12. Near edge X-ray absorption mass spectrometry on coronene

    SciTech Connect

    Reitsma, G.; Deuzeman, M. J.; Hoekstra, R.; Schlathölter, T.; Boschman, L.; Hoekstra, S.

    2015-01-14

    We have investigated the photoionization and photodissociation of free coronene cations C{sub 24}H{sub 12}{sup +} upon soft X-ray photoabsorption in the carbon K-edge region by means of a time-of-flight mass spectrometry approach. Core excitation into an unoccupied molecular orbital (below threshold) and core ionization into the continuum both leave a C 1s vacancy, that is subsequently filled in an Auger-type process. The resulting coronene dications and trications are internally excited and cool down predominantly by means of hydrogen emission. Density functional theory was employed to determine the dissociation energies for subsequent neutral hydrogen loss. A statistical cascade model incorporating these dissociation energies agrees well with the experimentally observed dehydrogenation. For double ionization, i.e., formation of intermediate C{sub 24}H{sub 12}{sup 3+⋆}trications, the experimental data hint at loss of H{sup +} ions. This asymmetric fission channel is associated with hot intermediates, whereas colder intermediates predominantly decay via neutral H loss.

  13. Time-resolved near-edge x-ray absorption fine structure spectroscopy on photo-induced phase transitions using a tabletop soft-x-ray spectrometer

    NASA Astrophysics Data System (ADS)

    Grossmann, P.; Rajkovic, I.; Moré, R.; Norpoth, J.; Techert, S.; Jooss, C.; Mann, Klaus

    2012-05-01

    We present a table-top soft-x-ray spectrometer for the wavelength range λ = 1-5 nm based on a stable laser-driven x-ray source, making use of a gas-puff target. With this setup, optical light-pump/soft-x-ray probe near-edge x-ray absorption fine structure (NEXAFS) experiments with a temporal resolution of about 230 ps are feasible. Pump-probe NEXAFS measurements were carried out in the "water-window" region (2.28 nm-4.36 nm) on the manganite Pr0.7Ca0.3MnO3, investigating diminutive changes of the oxygen K edge that derive from an optically induced phase transition. The results show the practicability of the table-top soft-x-ray spectrometer on demanding investigations so far exclusively conducted at synchrotron radiation sources.

  14. Time-resolved near-edge x-ray absorption fine structure spectroscopy on photo-induced phase transitions using a tabletop soft-x-ray spectrometer.

    PubMed

    Grossmann, P; Rajkovic, I; Moré, R; Norpoth, J; Techert, S; Jooss, C; Mann, Klaus

    2012-05-01

    We present a table-top soft-x-ray spectrometer for the wavelength range λ = 1-5 nm based on a stable laser-driven x-ray source, making use of a gas-puff target. With this setup, optical light-pump/soft-x-ray probe near-edge x-ray absorption fine structure (NEXAFS) experiments with a temporal resolution of about 230 ps are feasible. Pump-probe NEXAFS measurements were carried out in the "water-window" region (2.28 nm-4.36 nm) on the manganite Pr(0.7)Ca(0.3)MnO(3), investigating diminutive changes of the oxygen K edge that derive from an optically induced phase transition. The results show the practicability of the table-top soft-x-ray spectrometer on demanding investigations so far exclusively conducted at synchrotron radiation sources.

  15. Chemical shifts of K-X-ray absorption edges on copper in different compounds by X-ray absorption spectroscopy (XAS) with Synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Joseph, D.; Basu, S.; Jha, S. N.; Bhattacharyya, D.

    2012-03-01

    Cu K X-ray absorption edges were measured in compounds such as CuO, Cu(CH3CO2)2, Cu(CO3)2, and CuSO4 where Cu is present in oxidation state of 2+, using the energy dispersive EXAFS beamline at INDUS-2 Synchrotron radiation source at RRCAT, Indore. Energy shifts of ˜4-7 eV were observed for Cu K X-ray absorption edge in the above compounds compared to its value in elemental copper. The difference in the Cu K edge energy shifts in the different compounds having same oxidation state of Cu shows the effect of different chemical environments surrounding the cation in the above compounds. The above chemical effect has been quantitatively described by determining the effective charges on Cu cations in the above compounds.

  16. 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.

  17. An X-ray photoelectron spectroscopy study of the hydration of C{sub 2}S thin films

    SciTech Connect

    Rheinheimer, Vanessa; Casanova, Ignasi

    2014-06-01

    Electron-beam evaporation was used to produce thin films of β-dicalcium silicate. Chemical and mineralogical compositions were characterized by X-ray photoelectron spectroscopy (XPS) and grazing-angle X-ray diffraction (GAXRD), respectively. Results show that no fractionation occurs during evaporation and isostructural condensation of the material as synthesized films have the same composition as the initial bulk material. Samples were gradually hydrated under saturated water spray conditions and analyzed with XPS. Polymerization of the silicate chains due to hydration, and subsequent formation of C-S-H, has been monitored through evaluation of energy shifts on characteristic silicon peaks. Quantitative analyses show changes on the surface by the reduction of the Ca/Si ratio and an increase on the difference between binding energies of bridging and non-bridging oxygen. Finally, SEM/FIB observation shows clear differences between the surface and cross section of the initial sample and the reacted sample.

  18. Time-resolved x-ray photoelectron spectroscopy techniques for real-time studies of interfacial charge transfer dynamics

    NASA Astrophysics Data System (ADS)

    Shavorskiy, Andrey; Cordones, Amy; Vura-Weis, Josh; Siefermann, Katrin; Slaughter, Daniel; Sturm, Felix; Weise, Fabian; Bluhm, Hendrik; Strader, Matthew; Cho, Hana; Lin, Ming-Fu; Bacellar, Camila; Khurmi, Champak; Hertlein, Marcus; Guo, Jinghua; Tyliszczak, Tolek; Prendergast, David; Coslovich, Giacomo; Robinson, Joseph; Kaindl, Robert A.; Schoenlein, Robert W.; Belkacem, Ali; Weber, Thorsten; Neumark, Daniel M.; Leone, Stephen R.; Nordlund, Dennis; Ogasawara, Hirohito; Nilsson, Anders R.; Krupin, Oleg; Turner, Joshua J.; Schlotter, William F.; Holmes, Michael R.; Heimann, Philip A.; Messerschmidt, Marc; Minitti, Michael P.; Beye, Martin; Gul, Sheraz; Zhang, Jin Z.; Huse, Nils; Gessner, Oliver

    2013-04-01

    X-ray based spectroscopy techniques are particularly well suited to gain access to local oxidation states and electronic dynamics in complex systems with atomic pinpoint accuracy. Traditionally, these techniques are applied in a quasi-static fashion that usually highlights the steady-state properties of a system rather than the fast dynamics that often define the system function on a molecular level. Novel x-ray spectroscopy techniques enabled by free electron lasers (FELs) and synchrotron based pump-probe schemes provide the opportunity to monitor intramolecular and interfacial charge transfer processes in real-time and with element and chemical specificity. Two complementary time-domain xray photoelectron spectroscopy techniques are presented that are applied at the Linac Coherent Light Source (LCLS) and the Advanced Light Source (ALS) to study charge transfer processes in N3 dye-sensitized ZnO semiconductor nanocrystals, which are at the heart of emerging light-harvesting technologies.

  19. Time-resolved x-ray photoelectron spectroscopy techniques for real-time studies of interfacial charge transfer dynamics

    SciTech Connect

    Shavorskiy, Andrey; Hertlein, Marcus; Guo Jinghua; Tyliszczak, Tolek; Cordones, Amy; Vura-Weis, Josh; Siefermann, Katrin; Slaughter, Daniel; Sturm, Felix; Weise, Fabian; Khurmi, Champak; Belkacem, Ali; Weber, Thorsten; Gessner, Oliver; Bluhm, Hendrik; Strader, Matthew; Cho, Hana; Coslovich, Giacomo; Kaindl, Robert A.; Lin, Ming-Fu; and others

    2013-04-19

    X-ray based spectroscopy techniques are particularly well suited to gain access to local oxidation states and electronic dynamics in complex systems with atomic pinpoint accuracy. Traditionally, these techniques are applied in a quasi-static fashion that usually highlights the steady-state properties of a system rather than the fast dynamics that often define the system function on a molecular level. Novel x-ray spectroscopy techniques enabled by free electron lasers (FELs) and synchrotron based pump-probe schemes provide the opportunity to monitor intramolecular and interfacial charge transfer processes in real-time and with element and chemical specificity. Two complementary time-domain xray photoelectron spectroscopy techniques are presented that are applied at the Linac Coherent Light Source (LCLS) and the Advanced Light Source (ALS) to study charge transfer processes in N3 dye-sensitized ZnO semiconductor nanocrystals, which are at the heart of emerging light-harvesting technologies.

  20. Stability of thiol-passivated gold particles at elevated temperatures studied by X-ray photoelectron spectroscopy.

    PubMed

    Büttner, Michael; Belser, Thomas; Oelhafen, Peter

    2005-03-31

    The thermal stability of thiol-passivated gold colloids has been studied by means of X-ray photoelectron spectroscopy. Different colloids were chemically synthesized with thiol lengths from 3 to 8, and 16 carbon atoms. Depending on the synthesis parameters, the mean gold particle size varied from 1.6 to 4.9 nm for the particular colloid. Temperature-dependent measurements revealed a general tendency of shells with longer thiol chains (>5 carbon atoms) to be more stable in terms of desorption but to show a X-ray radiation-induced damage, which was absent with shorter thiols. Additionally, the self-assembling properties of the colloids were characterized by TEM, showing differences as a function of the chain lengths.

  1. Fabrication of 200 nanometer period centimeter area hard x-ray absorption gratings by multilayer deposition

    PubMed Central

    Lynch, S K; Liu, C; Morgan, N Y; Xiao, X; Gomella, A A; Mazilu, D; Bennett, E E; Assoufid, L; de Carlo, F; Wen, H

    2012-01-01

    We describe the design and fabrication trials of x-ray absorption gratings of 200 nm period and up to 100:1 depth-to-period ratios for full-field hard x-ray imaging applications. Hard x-ray phase-contrast imaging relies on gratings of ultra-small periods and sufficient depth to achieve high sensitivity. Current grating designs utilize lithographic processes to produce periodic vertical structures, where grating periods below 2.0 μm are difficult due to the extreme aspect ratios of the structures. In our design, multiple bilayers of x-ray transparent and opaque materials are deposited on a staircase substrate, and mostly on the floor surfaces of the steps only. When illuminated by an x-ray beam horizontally, the multilayer stack on each step functions as a micro-grating whose grating period is the thickness of a bilayer. The array of micro-gratings over the length of the staircase works as a single grating over a large area when continuity conditions are met. Since the layers can be nanometers thick and many microns wide, this design allows sub-micron grating periods and sufficient grating depth to modulate hard x-rays. We present the details of the fabrication process and diffraction profiles and contact radiography images showing successful intensity modulation of a 25 keV x-ray beam. PMID:23066175

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

    SciTech Connect

    Shavorskiy, Andrey; Slaughter, Daniel S.; Zegkinoglou, Ioannis; Rude, Bruce S.; Bluhm, Hendrik; Neppl, Stefan; Cryan, James P.; Siefermann, Katrin R.; Weise, Fabian; Lin, Ming-Fu; Bacellar, Camila; Ziemkiewicz, Michael P.; Fraund, Matthew W.; Khurmi, Champak; Wright, Travis W.; Schoenlein, Robert W.; Gessner, Oliver; Hertlein, Marcus P.; Tyliszczak, Tolek; Huse, Nils; and others

    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 of (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 angular

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

    NASA Astrophysics Data System (ADS)

    Shavorskiy, Andrey; Neppl, Stefan; Slaughter, Daniel S.; Cryan, James P.; Siefermann, Katrin R.; Weise, Fabian; Lin, Ming-Fu; Bacellar, Camila; Ziemkiewicz, Michael P.; Zegkinoglou, Ioannis; Fraund, Matthew W.; Khurmi, Champak; Hertlein, Marcus P.; Wright, Travis W.; Huse, Nils; Schoenlein, Robert W.; Tyliszczak, Tolek; Coslovich, Giacomo; Robinson, Joseph; Kaindl, Robert A.; Rude, Bruce S.; Ölsner, Andreas; Mähl, Sven; Bluhm, Hendrik; Gessner, Oliver

    2014-09-01

    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 of (780 ± 20) ps (FWHM) is demonstrated for a hemisphere pass energy Ep = 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 angular spread with

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

    PubMed

    Shavorskiy, Andrey; Neppl, Stefan; Slaughter, Daniel S; Cryan, James P; Siefermann, Katrin R; Weise, Fabian; Lin, Ming-Fu; Bacellar, Camila; Ziemkiewicz, Michael P; Zegkinoglou, Ioannis; Fraund, Matthew W; Khurmi, Champak; Hertlein, Marcus P; Wright, Travis W; Huse, Nils; Schoenlein, Robert W; Tyliszczak, Tolek; Coslovich, Giacomo; Robinson, Joseph; Kaindl, Robert A; Rude, Bruce S; Ölsner, Andreas; Mähl, Sven; Bluhm, Hendrik; Gessner, Oliver

    2014-09-01

    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 of (780 ± 20) ps (FWHM) is demonstrated for a hemisphere pass energy E(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 angular spread with

  5. Quadrupole effects in angular distributions of photoelectrons upon ionization of Kr by X-ray photons

    NASA Astrophysics Data System (ADS)

    Merem'yanin, A. V.; Chernov, V. E.; Gavrilov, G. E.; Naryshkin, Yu. G.; Zon, B. A.

    2017-05-01

    Implementation of promising control schemes for the intensity and position of X-ray-laser beams with a photon energy up to several tens of kiloelectronvolts requires knowledge of the angular dependence of cross sections for photoionization of noble gas atoms by hard photons. Estimates of quadrupole corrections to the cross section for photoionization of a Kr atom by X-ray photons with an energy of about 25 keV are reported in this paper. An analytic expression for the cross section of the process is parameterized in a compact form convenient for analyzing angular distributions with an arbitrary polarization of a photon beam.

  6. Non-destructive depth profiling using variable kinetic energy- x-ray photoelectron spectroscopy with maximum entropy regularization

    NASA Astrophysics Data System (ADS)

    Krajewski, James J.

    This study will describe a nondestructive method to determine compositional depth profiles of thicker films using Variable Kinetic Energy X-ray Photoelectron Spectroscopy (VKE-XPS) data by applying proven regularization methods successfully used in Angle-Resolved X-ray Photoelectron Spectroscopy (AR-XPS). To demonstrate the applicability of various regularization procedures to the experimental VKE-XPS data, simulated TiO2/Si film structures of two different thicknesses and known compositional profiles were "created" and then analyzed. It is found that superior results are attained when using a maximum entropy-like method with an initial model/prior knowledge of thickness is similar to the simulated film thickness. Other regularization functions, Slopes, Curvature and Total Variance Analysis (TVA) give acceptable results when there is no prior knowledge since they do not depend on an accurate initial model. The maximum entropy algorithm is then applied to two actual films of TiO2 deposited on silicon substrate. These results will show the applicability of generating compositional depth profiles with experimental VKE-XPS data. Accuracy of the profiles is confirmed by subjecting these actual films to a variety of "alternate" analytical thin film techniques including Sputtered Angle Resolved Photoelectron Spectroscopy, Auger Electron Spectroscopy, Rutherford Backscattering Spectroscopy, Focused Ion Beam Spectroscopy, Transmission and Scanning Electron Spectroscopy and Variable Angle Spectroscopic Ellipsometry. Future work will include applying different regularizations functions to better fit the MaxEnt composition depth profile other than those described in this study.

  7. A table-top femtosecond time-resolved soft x-ray transient absorption spectrometer

    SciTech Connect

    Leone, Stephen; Loh, Zhi-Heng; Khalil, Munira; Correa, Raoul E.; Leone, Stephen R.

    2008-05-21

    A laser-based, table-top instrument is constructed to perform femtosecond soft x-ray transient absorption spectroscopy. Ultrashort soft x-ray pulses produced via high-order harmonic generation of the amplified output of a femtosecond Ti:sapphire laser system are used to probe atomic core-level transient absorptions in atoms and molecules. The results provide chemically specific, time-resolved dynamics with sub-50-fs time resolution. In this setup, high-order harmonics generated in a Ne-filled capillary waveguide are refocused by a gold-coated toroidal mirror into the sample gas cell, where the soft x-ray light intersects with an optical pump pulse. The transmitted high-order harmonics are spectrally dispersed with a home-built soft x-ray spectrometer, which consists of a gold-coated toroidal mirror, a uniform-line spaced plane grating, and a soft x-ray CCD camera. The optical layout of the instrument, design of the soft x-ray spectrometer, and spatial and temporal characterization of the high-order harmonics are described. Examples of static and time-resolved photoabsorption spectra collected on this apparatus are presented.

  8. A tabletop femtosecond time-resolved soft x-ray transient absorption spectrometer

    NASA Astrophysics Data System (ADS)

    Loh, Zhi-Heng; Khalil, Munira; Correa, Raoul E.; Leone, Stephen R.

    2008-07-01

    A laser-based, tabletop instrument is constructed to perform femtosecond soft x-ray transient absorption spectroscopy. Ultrashort soft x-ray pulses produced via high-order harmonic generation of the amplified output of a femtosecond Ti:sapphire laser system are used to probe atomic core-level transient absorptions in atoms and molecules. The results provide chemically specific, time-resolved dynamics with sub-50-fs time resolution. In this setup, high-order harmonics generated in a Ne-filled capillary waveguide are refocused by a gold-coated toroidal mirror into the sample gas cell, where the soft x-ray light intersects with an optical pump pulse. The transmitted high-order harmonics are spectrally dispersed with a homebuilt soft x-ray spectrometer, which consists of a gold-coated toroidal mirror, a uniform-line spaced plane grating, and a soft x-ray charge coupled device camera. The optical layout of the instrument, design of the soft x-ray spectrometer, and spatial and temporal characterizations of the high-order harmonics are described. Examples of static and time-resolved photoabsorption spectra collected on this apparatus are presented.

  9. A tabletop femtosecond time-resolved soft x-ray transient absorption spectrometer.

    PubMed

    Loh, Zhi-Heng; Khalil, Munira; Correa, Raoul E; Leone, Stephen R

    2008-07-01

    A laser-based, tabletop instrument is constructed to perform femtosecond soft x-ray transient absorption spectroscopy. Ultrashort soft x-ray pulses produced via high-order harmonic generation of the amplified output of a femtosecond Ti:sapphire laser system are used to probe atomic core-level transient absorptions in atoms and molecules. The results provide chemically specific, time-resolved dynamics with sub-50-fs time resolution. In this setup, high-order harmonics generated in a Ne-filled capillary waveguide are refocused by a gold-coated toroidal mirror into the sample gas cell, where the soft x-ray light intersects with an optical pump pulse. The transmitted high-order harmonics are spectrally dispersed with a homebuilt soft x-ray spectrometer, which consists of a gold-coated toroidal mirror, a uniform-line spaced plane grating, and a soft x-ray charge coupled device camera. The optical layout of the instrument, design of the soft x-ray spectrometer, and spatial and temporal characterizations of the high-order harmonics are described. Examples of static and time-resolved photoabsorption spectra collected on this apparatus are presented.

  10. Surface characterization of lipid/chitosan nanoparticles assemblies, using X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry.

    PubMed

    Grenha, Ana; Seijo, Begoña; Serra, Carmen; Remuñán-López, Carmen

    2008-01-01

    Chitosan/tripolyphosphate nanoparticles are promising drug delivery systems, which show excellent capacity for protein entrapment and improvement of mucosal peptide absorption. We have recently developed a new drug delivery system consisting of assemblies formed between preformed chitosan nanoparticles and phospholipids (dipalmitoylphosphatidylcholine and dimiristoylphosphatidylglycerol) which are endogenous to the lung. These assemblies are prepared by lipid film hydration with a nanoparticles suspension. The aim of this work was to elucidate the architecture of these structures using sensitive surface analysis techniques such as X-ray photoelectron spectroscopy and static time-of-flight secondary ion mass spectrometry, as well as to determine their physicochemical characteristics. The combination of zeta potential measurements with the results obtained by X-ray photoelectron spectroscopy and static time-of-flight secondary ion mass spectrometry, demonstrated that a complete lipid coating of the nanoparticles can be achieved using a lipid film formed by both dipalmitoylphosphatidylcholine and dimiristoylphosphatidylglycerol, this way conferring to the lipid film a strong negative charge, which favors the interaction with the positively charged nanoparticles. Therefore, the major role of electrostatic interactions as driving forces to control the organisation of the lipid/nanoparticles assemblies was clearly evident. The implications of these findings for the structural organisation of the assemblies, for their in vitro behaviour, as well as for their mechanism of formation are discussed.

  11. An x-ray absorption spectroscopy study of Mo oxidation in Pb at elevated temperatures

    SciTech Connect

    Liu, Shanshan; Olive, Daniel; Terry, Jeff; Segre, Carlo U.

    2009-06-30

    The corrosion of fuel cladding and structural materials by lead and lead-bismuth eutectic in the liquid state at elevated temperatures is an issue that must be considered when designing advanced nuclear systems and high-power spallation neutron targets. In this work, lead corrosion studies of molybdenum were performed to investigate the interaction layer as a function of temperature by X-ray absorption spectroscopy. In situ X-ray absorption measurements on a Mo substrate with a 3-6 {micro}m layer of Pb deposited by thermal evaporation were performed at temperatures up to 900 C and at a 15{sup o} angle to the incident X-rays. The changes in the local atomic structure of the corrosion layer are visible in the difference extended X-ray absorption fine structure and the linear combination fitting of the X-ray absorption near-edge structure to as-deposited molybdenum sample and molybdenum oxide (MoO{sub 2} and MoO{sub 3}) standards. The data are consistent with the appearance of MoO{sub 3} in an intermediate temperature range (650-800 C) and the more stable MoO{sub 2} phase dominating at high and low temperatures.

  12. Interface of x-ray absorption package (XRAP) with ANSYS code

    SciTech Connect

    Wang, Zhibi; Kuzay, T.M.

    1996-03-01

    To analyze and design beamline components for third-generation synchrotron radiation facilities, knowledge of the heat load or the heat generation rate of x-rays absorbed inside different materials is needed. The absorption depends on their frequency, penetration depth, and the absorption material. X-rays Absorption Package (XRAP) is software which can generate an x-ray spectrum for bending magnets and insertion devices at synchrotron radiation facilities. XRAP can calculate the x-ray absorption distribution in geometric space and in frequency space. For a two dimensional structure, it can also perform heat transfer and thermal stress analyses. However, for cases such as a beamline component with a complex geometry or x-ray penetration effect, three dimensional analysis using a finite element method is needed. In these cases, XRAP can interface with a finite element code, such as ANSYS, to provide precise heat-load distribution inside a medium. XRAP can be executed interactively with its own graphical user interface, and it can be invoked within ANSYS to generate heat loads for heat transfer analysis. Other sources such as lasers, etc., can also be implemented similarly. This paper will present in detail the implementation of the interface of XRAP with ANSYS, and cases will be presented to illustrate this.

  13. Reduced absorption of neon-like bromine X-ray laser radiation in helium

    NASA Astrophysics Data System (ADS)

    Lu, P.; Fill, E. E.

    1999-10-01

    We have measured the absorption of the 19.47-nm neon like bromine (J=2-1) X-ray laser line in low-pressure helium. The experiment was motivated by the coincidence of this line with the low-absorption wing of an autoionizing transition in helium. We observe that, with 1 mbar of helium, the continuum background and another bromine X-ray laser line at 19.82 nm are strongly reduced, enhancing the relative strength of the 19.47-nm laser line. Increasing the helium pressure to 1.5 mbar makes the continuum virtually disappear, resulting in an almost monochromatic emission of the X-ray laser line. An estimate of the absorption cross section for the 19.47-nm line is given as ≈3.9×10-19 cm2 and for the nearby continuum as 0.9-1.3×10-18 cm2.

  14. Vanadium K-edge X-ray absorption spectroscopy of bromoperoxidase from Ascophyllum nodosum

    SciTech Connect

    Arber, J.M.; de Boer, E.; Garner, C.D.; Hasnain, S.S.; Wever, R. )

    1989-09-19

    Bromoperoxidase from Ascophyllum nodusum was the first vanadium-containing enzyme to be isolated. X-ray absorption spectra have now been collected in order to investigate the coordination of vanadium in the native, native plus bromide, native plus hydrogen peroxide, and dithionite-reduced forms of the enzyme. The edge and X-ray absorption near-edge structures show that, in the four samples studied, it is only on reduction of the native enzyme that the metal site is substantially altered. In addition, these data are consistent with the presence of vanadium(IV) in the reduced enzyme and vanadium(V) in the other samples. Extended X-ray absorption fine structure data confirm that there are structural changes at the metal site on reduction of the native enzyme, notably a lengthening of the average inner-shell distance, and the presence of terminal oxygen together with histidine and oxygen-donating residues.

  15. Photodissociation Structural Dynamics of TrirutheniumDodecacarbonyl Investigated by X-ray Transient Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Harpham, Michael R.; Stickrath, Andrew, B.; Zhang, Xiaoyi,; Huang, Jier; Mara, Michael W.; Chen, Lin X.; Liu, Di-Jia

    2013-10-01

    The molecular and electronic structures of the transient intermediates generated from the photolysis of trirutheniumdodecacarbonyl, Ru3(CO)12, by ultrafast UV (351 nm) laser excitation were investigated using X-ray transient absorption (XTA) spectroscopy. The electronic configuration change and nuclear rearrangement after the dissociation of carbonyls were observed at ruthenium K-edge X-ray absorption near edge structure and X-ray absorption fine structure spectra. Analysis of XTA data, acquired after 100, 200, and 400 ps and 300 ns time delay following the photoexcitation, identified the presence of three intermediate species with Ru3(CO)10 being the most dominating one. The results set an example of applying XTA in capturing both transient electronic and nuclear configurations in metal clusters simulating catalysts in chemical reactions.

  16. An X-ray-absorbed radio-quiet QSO with an intervening strong metal absorption-line system

    NASA Astrophysics Data System (ADS)

    Page, M. J.; Mittaz, J. P. D.; Carrera, F. J.

    2000-02-01

    We find evidence for significant X-ray absorption in the QSO RXJ005734.78-272827.4, along with strong absorption lines in its optical spectrum. We propose that the absorption lines are due to an intervening metal-line system at a redshift of z=0.628, and show that this intervening system is also the probable cause of the X-ray absorption. The intervening absorber is inferred to have an X-ray column of ~1022cm-2. This is the first time that an absorption-line system has been identified with an X-ray absorber in a radio-quiet object.

  17. Variable growth modes of CaF2 on Si(111) determined by x-ray photoelectron diffraction

    NASA Astrophysics Data System (ADS)

    Denlinger, J. D.; Rotenberg, Eli; Hessinger, Uwe; Leskovar, M.; Olmstead, Marjorie A.

    1993-04-01

    Chemical discrimination of bulk and interface Ca 2p x-ray photoelectron diffraction modulations is used to identify three growth regimes during the initial stages of CaF2 epitaxy on Si(111). Low flux, high temperature conditions produce island growth atop a nonwetting, chemically reacted Ca-F interface layer. Changing the growth kinetics by increasing the flux produces more laminar growth. Lowering the substrate temperature produces a more stoichiometric CaF2 interface layer that results in immediate wetting and laminar growth.

  18. X-ray Photoelectron Spectroscopy on Superconducting Tl2CaBa2Cu2O8 Thin Film

    NASA Astrophysics Data System (ADS)

    Zeng, Wensheng; Qiu, Ping; Yan, Shaolin; Li, Zengfa; Zhang, Guangyin

    1991-06-01

    We have prepared single-phase superconducting Tl2CaBa2Cu2O8 thin film by dc magnetron sputtering process and measured x-ray photoelectron spectra of the film at room and liquid nitrogen temperatures. From the relative intensities of the Ba3d, Tl4f. O1s and Cu2p spectra taken at different take-off angles, we have concluded that there is an adventitious contamination (nonsuperconducting phase) surface layer. After excluding contributions from these spurious phases, we have tentatively assigned which core-level shifts should be caused by the superconducting phase transition.

  19. Application of maximum-entropy spectral estimation to deconvolution of XPS data. [X-ray Photoelectron Spectroscopy

    NASA Technical Reports Server (NTRS)

    Vasquez, R. P.; Klein, J. D.; Barton, J. J.; Grunthaner, F. J.

    1981-01-01

    A comparison is made between maximum-entropy spectral estimation and traditional methods of deconvolution used in electron spectroscopy. The maximum-entropy method is found to have higher resolution-enhancement capabilities and, if the broadening function is known, can be used with no adjustable parameters with a high degree of reliability. The method and its use in practice are briefly described, and a criterion is given for choosing the optimal order for the prediction filter based on the prediction-error power sequence. The method is demonstrated on a test case and applied to X-ray photoelectron spectra.

  20. Band alignment at the interface of PbTe/SnTe heterojunction determined by X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Shu, Tianyu; Ye, Zhenyu; Lu, Pengqi; Chen, Lu; Xu, Gangyi; Zhou, Jie; Wu, Huizhen

    2016-11-01

    We report the determination of band alignment of PbTe/SnTe (111) heterojunction interfaces using X-ray photoelectron spectroscopy (XPS). Multiple core levels of Pb and Sn were utilized to determine the valence band offset (VBO) of the heterojunction. The XPS result shows a type-III band alignment with the VBO of 1.37+/- 0.18 \\text{eV} and the conduction band offset (CBO) of 1.23+/- 0.18 \\text{eV} . The experimental determination of the band alignment of the PbTe/SnTe heterojunction shall benefit the improvement of PbTe/SnTe-related optoelectronic and electronic devices.

  1. Origin of resistivity change in NiO thin films studied by hard x-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Calka, P.; Martinez, E.; Lafond, D.; Minoret, S.; Tirano, S.; Detlefs, B.; Roy, J.; Zegenhagen, J.; Guedj, C.

    2011-06-01

    We investigated origins of the resistivity change during the forming of NiO based resistive random access memories in a nondestructive way using hard x-ray photoelectron spectroscopy. Energy shifts and bandgap states observed after switching suggest that oxygen vacancies are created in the low resistive state. As a result conduction may occur via defects such as electrons traps and metallic nickel impurities. Migration of oxygen atoms seems to be the driving mechanism. This provides concrete evidence of the major role played by oxygen defects in decreasing resistivity. This is a key point since oxygen vacancies are particularly unstable and thus difficult to identify by physico-chemical analyses.

  2. Band alignment of InN/6H-SiC heterojunction determined by x-ray photoelectron spectroscopy

    SciTech Connect

    Jing, Qiang; Wu, Guoguang; Zhang, Yuantao; Gao, Fubin; Cai, Xupu; Zhao, Yang; Li, Wancheng Du, Guotong

    2014-08-11

    The valence band offset (VBO) of InN/6H-SiC heterojunction has been directly measured by x-ray photoelectron spectroscopy. The VBO is determined to be −0.10 ± 0.23 eV and the conduction band offset is deduced to be −2.47 ± 0.23 eV, indicating that the heterojunction has a type-II band alignment. The accurate determination of the valence and conduction band offsets is important for applications and analysis of InN/6H-SiC optoelectronic devices.

  3. Intracellular nanoparticles mass quantification by near-edge absorption soft X-ray nanotomography

    PubMed Central

    Conesa, Jose Javier; Otón, Joaquín; Chiappi, Michele; Carazo, Jose María; Pereiro, Eva; Chichón, Francisco Javier; Carrascosa, José L.

    2016-01-01

    We used soft X-ray three-dimensional imaging to quantify the mass of superparamagnetic iron oxide nanoparticles (SPION) within whole cells, by exploiting the iron oxide differential absorption contrast. Near-edge absorption soft X-ray nanotomography (NEASXT) combines whole-cell 3D structure determination at 50 nm resolution, with 3D elemental mapping and high throughput. We detected three-dimensional distribution of SPIONs within cells with 0.3 g/cm3 sensitivity, sufficient for detecting the density corresponding to a single nanoparticle. PMID:26960695

  4. Ab-initio method for X-ray absorption spectra simulation of hydride molecular ions

    NASA Astrophysics Data System (ADS)

    Puglisi, Alessandra; Sisourat, Nicolas; Carniato, Stéphane

    2017-03-01

    Soft X-ray absorption spectra of molecular ions are important data for the modeling and understanding of laboratory and astrophysical plasma. In this work, we present an ab-initio method, based on the Configuration Interaction (CI) approach, for the calculations of energy positions and oscillator strengths of X-ray absorption spectra. Furthermore, we investigate the effects of the choice of the nature and number of spin-orbitals used in the CI expansion on the spectra. The method is applied on three hydride molecular ions, namely CH+, OH+ and SiH+. However, the approach proposed here is general and may thus be applied to any kind of molecular ions.

  5. Intracellular nanoparticles mass quantification by near-edge absorption soft X-ray nanotomography.

    PubMed

    Conesa, Jose Javier; Otón, Joaquín; Chiappi, Michele; Carazo, Jose María; Pereiro, Eva; Chichón, Francisco Javier; Carrascosa, José L

    2016-03-10

    We used soft X-ray three-dimensional imaging to quantify the mass of superparamagnetic iron oxide nanoparticles (SPION) within whole cells, by exploiting the iron oxide differential absorption contrast. Near-edge absorption soft X-ray nanotomography (NEASXT) combines whole-cell 3D structure determination at 50 nm resolution, with 3D elemental mapping and high throughput. We detected three-dimensional distribution of SPIONs within cells with 0.3 g/cm(3) sensitivity, sufficient for detecting the density corresponding to a single nanoparticle.

  6. X ray absorption by dark nebulae (HEAO-2 guest investigator program)

    NASA Technical Reports Server (NTRS)

    Sanders, W. T.

    1991-01-01

    A study is described of data obtained from the Imaging Proportional Counter (IPC) x ray detector aboard the HEAO-2 satellite (Einstein Observatory). The research project involved a search for absorption of diffuse low energy x ray background emission by galactic dark nebulae. The commonly accepted picture that the bulk of the C band emission originates locally, closer that a few hundred parsec, and the bulk of the M band emission originates farther away than a few hundred parsec, was tested. The idea was to look for evidence of absorption of the diffuse background radiation by nearby interstellar clouds.

  7. Undistorted X-ray Absorption Spectroscopy Using s-Core-Orbital Emissions.

    PubMed

    Golnak, Ronny; Xiao, Jie; Atak, Kaan; Unger, Isaak; Seidel, Robert; Winter, Bernd; Aziz, Emad F

    2016-05-12

    Detection of secondary emissions, fluorescence yield (FY), or electron yield (EY), originating from the relaxation processes upon X-ray resonant absorption has been widely adopted for X-ray absorption spectroscopy (XAS) measurements when the primary absorption process cannot be probed directly in transmission mode. Various spectral distortion effects inherent in the relaxation processes and in the subsequent transportation of emitted particles (electron or photon) through the sample, however, undermine the proportionality of the emission signals to the X-ray absorption coefficient. In the present study, multiple radiative (FY) and nonradiative (EY) decay channels have been experimentally investigated on a model system, FeCl3 aqueous solution, at the excitation energy of the Fe L-edge. The systematic comparisons between the experimental spectra taken from various decay channels, as well as the comparison with the theoretically simulated Fe L-edge XA spectrum that involves only the absorption process, indicate that the detection of the Fe 3s → 2p partial fluorescence yield (PFY) gives rise to the true Fe L-edge XA spectrum. The two key characteristics generalized from this particular decay channel-zero orbital angular momentum (i.e., s orbital) and core-level emission-set a guideline for obtaining undistorted X-ray absorption spectra in the future.

  8. Ultrafast Time-Resolved X-ray Absorption Spectroscopy of Ferrioxalate Photolysis with a Laser Plasma X-ray Source and Microcalorimeter Array.

    PubMed

    O'Neil, Galen C; Miaja-Avila, Luis; Joe, Young Il; Alpert, Bradley K; Balasubramanian, Mahalingam; Sagar, D M; Doriese, William; Fowler, Joseph W; Fullagar, Wilfred K; Chen, Ning; Hilton, Gene C; Jimenez, Ralph; Ravel, Bruce; Reintsema, Carl D; Schmidt, Dan R; Silverman, Kevin L; Swetz, Daniel S; Uhlig, Jens; Ullom, Joel N

    2017-03-02

    The detailed pathways of photoactivity on ultrafast time scales are a topic of contemporary interest. Using a tabletop apparatus based on a laser plasma X-ray source and an array of cryogenic microcalorimeter X-ray detectors, we measured a transient X-ray absorption spectrum during the ferrioxalate photoreduction reaction. With these high-efficiency detectors, we observe the Fe K edge move to lower energies and the amplitude of the extended X-ray absorption fine structure reduce, consistent with a photoreduction mechanism in which electron transfer precedes disassociation. These results are compared to previously published transient X-ray absorption measurements on the same reaction and found to be consistent with the results from Ogi et al. and inconsistent with the results of Chen et al. ( Ogi , Y. ; et al. Struct. Dyn. 2015 , 2 , 034901 ; Chen , J. ; Zhang , H. ; Tomov , I. V. ; Ding , X. ; Rentzepis , P. M. Chem. Phys. Lett. 2007 , 437 , 50 - 55 ). We provide quantitative limits on the Fe-O bond length change. Finally, we review potential improvements to our measurement technique, highlighting the future potential of tabletop X-ray science using microcalorimeter sensors.

  9. High Resolution X-Ray Absorption Spectroscopy: Distribution of Matter in and around Galaxies

    NASA Astrophysics Data System (ADS)

    Schulz, Norbert; MIT/CAT Team

    2015-10-01

    The chemical evolution of the Universe embraces aspects that reachdeep into modern astrophysics and cosmology. We want to know how present and past matter is affected by various levels and types of nucleo-synthesis and stellar evolution. Three major categories were be identified: 1. The study of pre-mordial star formation including periods of super-massive black hole formation, 2. The embedded evolution of the intergalactic medium IGM, 3. The status and evolution of stars and the interstellar medium ISM in galaxies. Today a fourth category relates to our understanding of dark matter in relationwith these three categories. The X-ray band is particularly sensitive to K- and L-shell absorption and scattering from high abundant elements like C, N, O, Ne, Mg, Si, S,Ar, Ca, Fe, and Ni. Like the Lyman alpha forest in the optical band, absorbers in the IGM produce an X-ray line forest along the line of sight in the X-rayspectrum of a background quasar. Similary bright X-ray sources within galaxies and the Milky Way produce a continuum, which is being absorbed by elements invarious phases of the ISM. High resolution X-ray absorption surveys are possible with technologies ready for flight within decade. == high efficiency X-ray optics with optical performance 3== high resolution X-ray gratings with R 3000 for E 1.5 keV== X-ray micro-calorimeters with R 2000 for E 1.5 keV. The vision for the next decade needs to lead to means and strategies which allows us to perform such absorption surveys as effectively as surveys are now or in very near future quite common in astronomy pursued in other wave length bands such as optical, IR, and sub-mm.

  10. Photochemically Generated Thiyl Free Radicals Observed by X-ray Absorption Spectroscopy

    DOE PAGES

    Sneeden, Eileen Y.; Hackett, Mark J.; Cotelesage, Julien J. H.; ...

    2017-07-27

    Sulfur-based thiyl radicals are known to be involved in a wide range of chemical and biological processes, but they are often highly reactive, which makes them difficult to observe directly. We report herein X-ray absorption spectra and analysis that support the direct observation of two different thiyl species generated photochemically by X-ray irradiation. The thiyl radical sulfur K-edge X-ray absorption spectra of both species are characterized by a uniquely low energy transition at about 2465 eV, which occurs at a lower energy than any previously observed feature at the sulfur K-edge and corresponds to a 1s → 3p transition tomore » the singly occupied molecular orbital of the free radical. In conclusion, our results constitute the first observation of substantial levels of thiyl radicals generated by X-ray irradiation and detected by sulfur K-edge X-ray absorption spectroscopy.« less

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

    SciTech Connect

    Isomura, N. Kataoka, K.; Horibuchi, K.; Dohmae, K.; Kitazumi, K.; Takahashi, N.; Kimoto, Y.; Oji, H.; Cui, Y.-T.; Son, J.-Y.

    2016-07-27

    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 both 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.

  12. Oxygen, Neon, and Iron X-Ray Absorption in the Local Interstellar Medium

    NASA Technical Reports Server (NTRS)

    Gatuzz, Efrain; Garcia, Javier; Kallman, Timothy R.; Mendoza, Claudio

    2016-01-01

    We present a detailed study of X-ray absorption in the local interstellar medium by analyzing the X-ray spectra of 24 galactic sources obtained with the Chandra High Energy Transmission Grating Spectrometer and the XMM-Newton Reflection Grating Spectrometer. Methods. By modeling the continuum with a simple broken power-law and by implementing the new ISMabs X-ray absorption model, we have estimated the total H, O, Ne, and Fe column densities towards the observed sources. Results. We have determined the absorbing material distribution as a function of source distance and galactic latitude longitude. Conclusions. Direct estimates of the fractions of neutrally, singly, and doubly ionized species of O, Ne, and Fe reveal the dominance of the cold component, thus indicating an overall low degree of ionization. Our results are expected to be sensitive to the model used to describe the continuum in all sources.

  13. On the relation of optical obscuration and X-ray absorption in Seyfert galaxies

    NASA Astrophysics Data System (ADS)

    Burtscher, L.; Davies, R. I.; Graciá-Carpio, J.; Koss, M. J.; Lin, M.-Y.; Lutz, D.; Nandra, P.; Netzer, H.; Orban de Xivry, G.; Ricci, C.; Rosario, D. J.; Veilleux, S.; Contursi, A.; Genzel, R.; Schnorr-Müller, A.; Sternberg, A.; Sturm, E.; Tacconi, L. J.

    2016-02-01

    The optical classification of a Seyfert galaxy and whether it is considered X-ray absorbed are often used interchangeably. There are many borderline cases, however, and also numerous examples where the optical and X-ray classifications appear to be in disagreement. In this article we revisit the relation between optical obscuration and X-ray absorption in active galactic nuclei (AGNs). We make use of our "dust colour" method to derive the optical obscuration AV, and consistently estimated X-ray absorbing columns using 0.3-150 keV spectral energy distributions. We also take into account the variable nature of the neutral gas column NH and derive the Seyfert subclasses of all our objects in a consistent way. We show in a sample of 25 local, hard-X-ray detected Seyfert galaxies (log LX/ (erg / s) ≈ 41.5-43.5) that there can actually be a good agreement between optical and X-ray classification. If Seyfert types 1.8 and 1.9 are considered unobscured, the threshold between X-ray unabsorbed and absorbed should be chosen at a column NH = 1022.3 cm-2 to be consistent with the optical classification. We find that NH is related to AV and that the NH/AV ratio is approximately Galactic or higher in all sources, as indicated previously. However, in several objects we also see that deviations from the Galactic ratio are only due to a variable X-ray column, showing that (1) deviations from the Galactic NH/AV can be simply explained by dust-free neutral gas within the broad-line region in some sources; that (2) the dust properties in AGNs can be similar to Galactic dust and that (3) the dust colour method is a robust way to estimate the optical extinction towards the sublimation radius in all but the most obscured AGNs.

  14. Search for correlated UV and x ray absorption of NGC 3516

    NASA Technical Reports Server (NTRS)

    Martin, Christopher; Halpern, Jules P.; Kolman, Michiel

    1991-01-01

    NGC 3516, a low-luminosity Seyfert galaxy, is one of a small fraction of Seyfert galaxies that exhibit broad absorption in a resonance line. In order to determine whether the UV and x ray absorption in NGC 3516 are related, 5 IUE observations were obtained, quasi-simultaneously with 4 Ginga observations. The results are presented and discussed. The following subject areas are covered: short-term UV variability; emission lines; galactic absorption lines; the C IV, N V, and Si IV absorption features; lower limit on the carbon column density; estimate of the distance from the absorber to the continuum source; variability in the continuum and absorption; a comparison with BAL QSO's; and the x ray-UV connection.

  15. Silicon nanocrystals with high boron and phosphorus concentration hydrophilic shell—Raman scattering and X-ray photoelectron spectroscopic studies

    SciTech Connect

    Fujii, Minoru Sugimoto, Hiroshi; Hasegawa, Masataka; Imakita, Kenji

    2014-02-28

    Boron (B) and phosphorus (P) codoped silicon (Si) nanocrystals, which exhibit very wide range tunable luminescence due to the donor to acceptor transitions and can be dispersed in polar liquids without organic ligands, are studied by Raman scattering and X-ray photoelectron spectroscopies. Codoped Si nanocrystals exhibit a Raman spectrum significantly different from those of intrinsic ones. First, the Raman peak energy is almost insensitive to the size and is very close to that of bulk Si crystal in the diameter range of 2.7 to 14 nm. Second, the peak is much broader than that of intrinsic ones. Furthermore, an additional broad peak, the intensity of which is about 20% of the main peak, appears around 650 cm{sup −1}. The peak can be assigned to local vibrational modes of substitutional B and B-P pairs, B clusters, B-interstitial clusters, etc. in Si crystal. The Raman and X-ray photoelectron spectroscopic studies suggest that a crystalline shell heavily doped with these species is formed at the surface of a codoped Si nanocrystal and it induces the specific properties, i.e., hydrophilicity, high-stability in water, high resistance to hydrofluoric acid, etc.

  16. X-ray photoelectron spectroscopy study of irradiation-induced amorphizaton of Gd2Ti2O7

    NASA Astrophysics Data System (ADS)

    Chen, J.; Lian, J.; Wang, L. M.; Ewing, R. C.; Boatner, L. A.

    2001-09-01

    The radiation-induced evolution of the microstructure of Gd2Ti2O7, an important pyrochlore phase in radioactive waste disposal ceramics and a potential solid electrolyte and oxygen gas sensor, has been characterized using transmission electron microscopy and x-ray photoelectron spectroscopy. Following the irradiation of a Gd2Ti2O7 single crystal with 1.5 MeV Xe+ ions at a fluence of 1.7×1014Xe+/cm2, cross-sectional transmission electron microscopy revealed a 300-nm-thick amorphous layer at the specimen surface. X-ray photoelectron spectroscopy analysis of the Ti 2p and O 1s electron binding energy shifts of Gd2Ti2O7 before and after amorphization showed that the main results of ion-irradiation-induced disorder are a decrease in the coordination number of titanium and a transformation of the Gd-O bond. These features resemble those occurring in titanate glass formation, and they have implications for the chemical stability and electronic properties of pyrochlores subjected to displacive radiation damage.

  17. Forward scattering in hard X-ray photoelectron spectroscopy: Structural investigation of buried Mn–Ga films

    SciTech Connect

    ViolBarbosa, Carlos E. Ouardi, Siham; Fecher, Gerhard H. Felser, Claudia; Kubota, Takahide; Mizukami, Shigemi; Miyazaki, Terunobu; Ikenaga, Eiji

    2015-02-02

    X-ray photoelectron diffraction (XPD) in combination with hard X-ray photoelectron spectroscopy (HAXPES) has been used to study the structure of buried layers in thin multilayer films. A detailed layer-by-layer investigation was performed using the element-specific, local-probe character of XPD. In the present work, angular-resolved HAXPES at a photon energy of 7.94 keV photon energy was used to investigate a Cr/Mn{sub 62}Ga{sub 38}/Mg/MgO multilayer system. Differences in the angular distributions of electrons emitted from Mn and Ga atoms revealed that the structure of Mn{sub 62}Ga{sub 38} changes from L1{sub 0} towards D0{sub 22} for increasing annealing temperatures. A c/a ratio of 1.81 ± 0.06 was determined for the buried Mn{sub 62}Ga{sub 38} layer in a D0{sub 22} structure from the XPD experiment. The improvement of the structural order of the Mn{sub 62}Ga{sub 38} layer is accompanied by an improvement of the structure of the overlying MgO layer.

  18. 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.

  19. Near-edge x-ray absorption fine structure spectroscopy at atmospheric pressure with a table-top laser-induced soft x-ray source

    SciTech Connect

    Kühl, Frank-Christian Müller, Matthias Schellhorn, Meike; Mann, Klaus; Wieneke, Stefan; Eusterhues, Karin

    2016-07-15

    The authors present a table-top soft x-ray absorption spectrometer, accomplishing investigations of the near-edge x-ray absorption fine structure (NEXAFS) in a laboratory environment. The system is based on a low debris plasma ignited by a picosecond laser in a pulsed krypton gas jet, emitting soft x-ray radiation in the range from 1 to 5 nm. For absorption spectroscopy in and around the “water window” (2.3–4.4 nm), a compact helium purged sample compartment for experiments at atmospheric pressure has been constructed and tested. NEXAFS measurements on CaCl{sub 2} and KMnO{sub 4} samples were conducted at the calcium and manganese L-edges, as well as at the oxygen K-edge in air, atmospheric helium, and under vacuum, respectively. The results indicate the importance of atmospheric conditions for an investigation of sample hydration processes.

  20. High Resolution Spectroscopy of X-ray Quasars: Searching for the X-ray Absorption from the Warm-Hot Intergalactic Medium

    NASA Technical Reports Server (NTRS)

    Fang, Taotao; Canizares, Claude R.; Marshall, Herman L.

    2004-01-01

    We present a survey of six low to moderate redshift quasars with Chandra and XMM-Newton. The primary goal is to search for the narrow X-ray absorption lines produced by highly ionized metals in the Warm-Hot Intergalactic Medium. All the X-ray spectra can be well fitted by a power law with neutral hydrogen absorption. Only one feature is detected at above 3-sigma level in all the spectra, which is consistent with statistic fluctuation. We discuss the implications in our understanding of the baryon content of the universe. We also discuss the implication of the non-detection of the local (z approx. 0) X-ray absorption.

  1. Application of x-ray absorption spectroscopy to the study of corrosion and inhibition

    SciTech Connect

    Davenport, A.J.; Isaacs, H.S.

    1991-01-01

    X-ray absorption spectroscopy is a powerful technique for determination of valency and coordination. Measurements can be made in air or in situ under electrochemical control. The technique will be described and its application to the analysis of passive oxide films, corrosion products, and inhibitors will be reviewed.

  2. High Pressure X-ray Absorption Studies on Correlated-Electron Systems

    SciTech Connect

    Cornelius, Andrew L.

    2016-08-26

    This project used high pressure to alter the electron-electron and electron-lattice interactions in rare earth and actinide compounds. Knowledge of these properties is the starting points for a first-principles understanding of electronic and electronically related macroscopic properties. The research focused on a systematic study of x-ray absorption measurements on rare earth and actinide compounds.

  3. Ligand effects on the X-ray absorption of a nickel porphyrin complex: a simulation study

    NASA Astrophysics Data System (ADS)

    Campbell, Luke; Tanaka, Satoshi; Mukamel, Shaul

    2004-04-01

    We present a simulation of the X-ray absorption near-edge spectrum (XANES) of the metal porphyrin NiTPP (nickel tetraphenylporphyrin) and investigate the changes to the spectrum caused by adding piperidine ligands to the metal atom. The main features in the experimental spectrum (Chen et al., Science 292 (2001) 262) are interpreted in terms of changes in the electronic structure.

  4. Sequential electronic and structural transitions in VO2 observed using X-ray absorption spectromicroscopy.

    PubMed

    Kumar, Suhas; Strachan, John Paul; Pickett, Matthew D; Bratkovsky, Alexander; Nishi, Yoshio; Williams, R Stanley

    2014-11-26

    The popular dual electronic and structural transitions in VO2 are explored using X-ray absorption spectromicroscopy with high spatial and spectral resolutions. It is found that during both heating and cooling, the electronic transition always precedes the structural Peierls transition. Between the two transitions, there are intermediate states that are spectrally isolated here.

  5. Status of the X-Ray Absorption Spectroscopy (XAS) Beamline at the Australian Synchrotron

    NASA Astrophysics Data System (ADS)

    Glover, C.; McKinlay, J.; Clift, M.; Barg, B.; Boldeman, J.; Ridgway, M.; Foran, G.; Garret, R.; Lay, P.; Broadbent, A.

    2007-02-01

    We present herein the current status of the X-ray Absorption Spectroscopy (XAS) Beamline at the 3 GeV Australian Synchrotron. The optical design and performance, details of the insertion device (Wiggler), end station capabilities and construction and commissioning timeline are given.

  6. LISA: the Italian CRG beamline for x-ray Absorption Spectroscopy at ESRF

    NASA Astrophysics Data System (ADS)

    d'Acapito, F.; Trapananti, A.; Puri, A.

    2016-05-01

    LISA is the acronym of Linea Italiana per la Spettroscopia di Assorbimento di raggi X (Italian beamline for X-ray Absorption Spectroscopy) and is the upgrade of the former GILDA beamline installed on the BM08 bending magnet port of European Synchrotron Radiation Facility (ESRF). Within this contribution a full description of the project is provided.

  7. Picosecond-resolved X-ray absorption spectroscopy at low signal contrast using a hard X-ray streak camera

    SciTech Connect

    Adams, Bernhard W.; Rose-Petruck, Christoph; Jiao, Yishuo

    2015-06-24

    A picosecond-resolving hard-X-ray streak camera has been in operation for several years at Sector 7 of the Advanced Photon Source (APS). Several upgrades have been implemented over the past few years to optimize integration into the beamline, reduce the timing jitter, and improve the signal-to-noise ratio. These include the development of X-ray optics for focusing the X-rays into the sample and the entrance slit of the streak camera, and measures to minimize the amount of laser light needed to generate the deflection-voltage ramp. For the latter, the photoconductive switch generating the deflection ramp was replaced with microwave power electronics. With these, the streak camera operates routinely at 88 MHz repetition rate, thus making it compatible with all of the APS fill patterns including use of all the X-rays in the 324-bunch mode. Sample data are shown to demonstrate the performance.

  8. X-Ray Dichroism in Photoelectron Spectroscopy for Direct Element Specific Surface Magnetometry of Nanomagnetic Structures

    NASA Astrophysics Data System (ADS)

    Tobin, James G.

    1997-03-01

    Element specific surface magnetometry remains a central goal of synchrotron radiation based studies of nanomagnetic structures. One appealing possibility is the combination of xray absorption dichroism measurements and the theoretical framework provided by the "sum rules."[1] Unfortunately, sum rule analyses are hampered by several limitations [2], including delocalization of the final state, multi-electronic phenomena and the presence of surface dipoles. An alternative experiment, Magnetic Xray Dichroism in Photoelectron Spectroscopy, holds out promise based upon its elemental specificity, surface sensitivity and high resolution. Computational simulations by Tamura et al [3] demonstrated the relationship between exchange and spin orbit splittings and experimental data of linear and circular dichroisms. Now we [4] 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 [5], 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 [6], 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. [7,8] This work was performed under the auspices of the U.S. Department of Energy by LLNL under contract No. W-7405-ENG-48. 1. B.T. Thole et al, Phys. Rev. Lett. 68,1943 (1992); P. Carra et al. Phys. Rev. Lett. 70, 694 (1993). 2. J.G. Tobin et al Phys. Rev. B 52, 6530 (1995). 3. E. Tamura et al, Phys. Rev. Lett 73, 1533 (1994) 4. J.G. Tobin, K.W. Goodman, F.O. Schumann, R.F. Willis, J

  9. Discovery of Broad Soft X-ray Absorption Lines from the Quasar Wind in PDS 456

    NASA Astrophysics Data System (ADS)

    Reeves, J. N.; Braito, V.; Nardini, E.; Behar, E.; O'Brien, P. T.; Tombesi, F.; Turner, T. J.; Costa, M. T.

    2016-06-01

    High-resolution soft X-ray spectroscopy of the prototype accretion disk wind quasar, PDS 456, is presented. Here, the XMM-Newton reflection grating spectrometer spectra are analyzed from the large 2013-2014 XMM-Newton campaign, consisting of five observations of approximately 100 ks in length. During the last observation (OBS. E), the quasar is at a minimum flux level, and broad absorption line (BAL) profiles are revealed in the soft X-ray band, with typical velocity widths of {σ }{{v}}˜ {{10,000}} km s-1. During a period of higher flux in the third and fourth observations (OBS. C and D, respectively), a very broad absorption trough is also present above 1 keV. From fitting the absorption lines with models of photoionized absorption spectra, the inferred outflow velocities lie in the range ˜ 0.1{--}0.2c. The absorption lines likely originate from He and H-like neon and L-shell iron at these energies. A comparison with earlier archival data of PDS 456 also reveals a similar absorption structure near 1 keV in a 40 ks observation in 2001, and generally the absorption lines appear most apparent when the spectrum is more absorbed overall. The presence of the soft X-ray BALs is also independently confirmed by an analysis of the XMM-Newton EPIC spectra below 2 keV. We suggest that the soft X-ray absorption profiles could be associated with a lower ionization and possibly clumpy phase of the accretion disk wind, where the latter is known to be present in this quasar from its well-studied iron K absorption profile and where the wind velocity reaches a typical value of 0.3c.

  10. Experimental investigation of X-ray spectral absorption coefficients in heated Al and Ge on the Iskra-5 laser facility

    SciTech Connect

    Bondarenko, S V; Garanin, Sergey G; Zhidkov, N V; Pinegin, A V; Suslov, N A

    2012-01-31

    We set forth the data of experimental investigation of X-ray spectral absorption coefficients in the 1.1 - 1.6 keV photon energy range for Al and Ge specimens bulk heated by soft X-ray radiation. Two experimental techniques are described: with the use of one facility channel and the heating of specimens by the X-ray radiation from a plane burnthrough target, as well as with the use of four channels and the heating by the radiation from two cylindrical targets with internal input of laser radiation. The X-ray radiation absorption coefficients were studied by way of transmission absorption spectroscopy using backlighting X-ray radiation from a point source. The results of investigation of X-ray spectral absorption coefficients on the 1s - 2p transitions in Al atoms and the 2p - 3d transitions in Ge atoms are presented.

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

    SciTech Connect

    Jolley, J.G.; Geesey, G.G.; Hankins, M.R.; Wright, R.B.; Wichlacz, P.L.

    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 into the polymer matrix. Thus biocorrosion of copper was exhibited by the Gum Arabic, BCS and Pseudomonas atlantica exopolymer. 14 refs., 4 figs., 3 tabs.

  12. Surface extended x-ray absorption fine structure of low-Z absorbates using fluorescence detection

    SciTech Connect

    Stoehr, J.; Kollin, E.B.; Fischer, D.A.; Hastings, J.B.; Zaera, F.; Sette, F.

    1985-05-01

    Comparison of x-ray fluorescence yield (FY) and electron yield surface extended x-ray absorption fine structure spectra above the S K-edge for c(2 x 2) S on Ni(100) reveals an order of magnitude higher sensitivity of the FY technique. Using FY detection, thiophene (C/sub 4/H/sub 4/S) chemisorption on Ni(100) is studied with S coverages down to 0.08 monolayer. The molecule dissociates at temperatures as low as 100K by interaction with fourfold hollow Ni sites. Blocking of these sites by oxygen leaves the molecule intact.

  13. A ubiquitous absorption feature in the X-ray spectra of BL Lacertae objects

    NASA Technical Reports Server (NTRS)

    Madejski, Greg M.; Mushotzky, Richard F.; Weaver, Kimberly A.; Arnaud, Keith A.; Urry, C. Megan

    1991-01-01

    The paper presents the broadband (0.5-20-keV) X-ray spectra of five X-ray bright BL Lac objects observed with the Einstein Observatory Solid State Spectrometer (SSS) and Monitor Proportional Counter (MPC) detectors. The combination of moderate energy resolution and broad spectral coverage makes it possible to confirm the presence of an absorption feature at an energy of 650 eV in the BL Lac object PKS 2155-304, originally reported by Canizares and Kruper (1984) based on higher resolution Einstein Objective Grating Spectrometer (OGS) data.

  14. Observing heme doming in myoglobin with femtosecond X-ray absorption spectroscopy

    DOE PAGES

    Levantino, M.; Lemke, H. T.; Schirò, G.; ...

    2015-07-01

    We report time-resolved X-ray absorption measurements after photolysis of carbonmonoxy myoglobin performed at the LCLS X-ray free electron laser with nearly 100 fs (FWHM) time resolution. Data at the Fe K-edge reveal that the photoinduced structural changes at the heme occur in two steps, with a faster (~70 fs) relaxation preceding a slower (~400 fs) one. We tentatively attribute the first relaxation to a structural rearrangement induced by photolysis involving essentially only the heme chromophore and the second relaxation to a residual Fe motion out of the heme plane that is coupled to the displacement of myoglobin F-helix.

  15. X-Ray Absorption Fine Structure Study for Fe60Ni40 Alloy

    SciTech Connect

    Yang, Dong-Seok; Oh, Kyuseung; Na, Wonkyung; Kim, Nayoung; Yoo, Yong-Goo; Min, Seung-Gi; Yu, Seong-Cho

    2007-02-02

    Fe60Ni40 alloys were fabricated by the mechanical alloying process with process periods of 1, 2, 4, 6, 12 and 24 hours, respectively. The formation of alloy and the structural evolution of the alloy were examined by X-ray diffraction and extended X-ray absorption fine structure methods. With increase of alloying time the BCC phase of iron was changed significantly during the mechanical alloying process. The alloying was activated in about 6 hours and completed in about 24 hours.

  16. X-ray absorption Debye-Waller factors from ab initio molecular dynamics

    NASA Astrophysics Data System (ADS)

    Vila, F. D.; Lindahl, V. E.; Rehr, J. J.

    2012-01-01

    An ab initio equation of motion method is introduced to calculate the temperature-dependent mean-square vibrational amplitudes σ2 which appear in the Debye-Waller factors in x-ray absorption, x-ray scattering, and related spectra. The approach avoids explicit calculations of phonon modes, and is based instead on calculations of the displacement-displacement time correlation function from ab initio density functional theory molecular dynamics simulations. The method also yields the vibrational density of states and thermal quantities such as the lattice free energy. Illustrations of the method are presented for a number of systems and compared with other methods and experiment.

  17. X-ray absorption in GaGdN: A study of local structure

    NASA Astrophysics Data System (ADS)

    Martínez-Criado, G.; Sancho-Juan, O.; Garro, N.; Sans, J. A.; Cantarero, A.; Susini, J.; Roever, M.; Mai, D.-D.; Bedoya-Pinto, A.; Malindretos, J.; Rizzi, A.

    2008-07-01

    In this study, we report on the incorporation of dilute Gd amounts into GaN films grown by molecular beam epitaxy. A combination of x-ray fluorescence with x-ray absorption spectroscopic techniques enabled us to examine not only the distribution of rare earth atoms in the GaN matrix but also the short-range structural order. Our results show Gd atoms in a trivalent state with tetrahedral coordination, thus substituting Ga in the wurtzite GaN structure.

  18. Photoelectronic radiology 1983; X-ray imaging with the computer-assisted technologies

    NASA Astrophysics Data System (ADS)

    Chalaqui, Jean; Sylvestre, Jacques; Robillard, Pierre; Dussault, Robert

    The development of the discipline of radiology has continued to progress from initial images depicting the structure of organs, to the exploration of dynamic and physiologic phenomena, improvements in the power of X-ray generators and with the refinement of non-toxic contrast media. Until the early part of the 1970s, radiology consisted in extrapolations from a two-dimensional image of a three-dimensional organ, and advances in diagnostic quality related chiefly to improvements in spatial resolution of the flat image. With the advent of cross-sectional imaging using computer reconstruction the emphasis has shifted to contrast resolution, to the acquisition of "pure" images in the XY plane and to an area-related approach in diagnosis, rather than to the traditional organ-oriented method. This new trend has only been made possible because of the influence of recent developments in the digital and electronics industry. This history of diagnostic radiology up to 1972 is reviewed, followed by a discussion of the major areas of interaction between X-rays and the computer, as represented by the major leading edge technologies that have already received broad acceptance by the health care profession.

  19. 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.

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

    SciTech Connect

    Citron, Robert; Kropf, A.J.

    2008-01-01

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

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

    PubMed

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

    2016-10-14

    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.

  2. The magnetic field of an isolated neutron star from X-ray cyclotron absorption lines.

    PubMed

    Bignami, G F; Caraveo, P A; De Luca, A; Mereghetti, S

    2003-06-12

    Isolated neutron stars are highly magnetized, fast-rotating objects that form as an end point of stellar evolution. They are directly observable in X-ray emission, because of their high surface temperatures. Features in their X-ray spectra could in principle reveal the presence of atmospheres, or be used to estimate the strength of their magnetic fields through the cyclotron process, as is done for X-ray binaries. Almost all isolated neutron star spectra observed so far appear as featureless thermal continua. The only exception is 1E1207.4-5209 (refs 7-9), where two deep absorption features have been detected, but with insufficient definition to permit unambiguous interpretation. Here we report a long X-ray observation of the same object in which the star's spectrum shows three distinct features, regularly spaced at 0.7, 1.4 and 2.1 keV, plus a fourth feature of lower significance, at 2.8 keV. These features vary in phase with the star's rotation. The logical interpretation is that they are features from resonant cyclotron absorption, which allows us to calculate a magnetic field strength of 8 x 10(10) G, assuming the absorption arises from electrons.

  3. 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.

  4. Simulation of X-ray transient absorption for following vibrations in coherently ionized F2 molecules

    NASA Astrophysics Data System (ADS)

    Dutoi, Anthony D.; Leone, Stephen R.

    2017-01-01

    Femtosecond and attosecond X-ray transient absorption experiments are becoming increasingly sophisticated tools for probing nuclear dynamics. In this work, we explore and develop theoretical tools needed for interpretation of such spectra,in order to characterize the vibrational coherences that result from ionizing a molecule in a strong IR field. Ab initio data for F2 is combined with simulations of nuclear dynamics, in order to simulate time-resolved X-ray absorption spectra for vibrational wavepackets after coherent ionization at 0 K and at finite temperature. Dihalogens pose rather difficult electronic structure problems, and the issues encountered in this work will be reflective of those encountered with any core-valence excitation simulation when a bond is breaking. The simulations reveal a strong dependence of the X-ray absorption maximum on the locations of the vibrational wave packets. A Fourier transform of the simulated signal shows features at the overtone frequencies of both the neutral and the cation, which reflect spatial interferences of the vibrational eigenstates. This provides a direct path for implementing ultrafast X-ray spectroscopic methods to visualize coherent nuclear dynamics.

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

    SciTech Connect

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

    2001-03-25

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

  6. The effects of dust scattering on high-resolution X-ray absorption edge structure

    NASA Astrophysics Data System (ADS)

    Corrales, Lia; Garcia, Javier; Wilms, Joern; Baganoff, Frederick K.

    2016-04-01

    In high resolution X-ray spectroscopy, dust scattering significantly enhances the total extinction optical depth and alters the shape of photoelectric absorption edges. This effect is modulated by the dust grain size distribution, spatial location along the line of sight, and the imaging resolution of the X-ray telescope. We focus in particular on the Fe L-edge at 0.7 keV, fitting a template for the total extinction to the high resolution spectrum of three X-ray binaries from the Chandra archive: GX 9+9, XTE J1817-330, and Cyg X-1. In cases where dust is intrinsic to the source, a covering factor based on the angular extent of the dusty material must be applied to the extinction curve, regardless of imaging resolution. We discuss the various astrophysical cases in which scattering effects need to be taken into account.

  7. ISMabs: A COMPREHENSIVE X-RAY ABSORPTION MODEL FOR THE INTERSTELLAR MEDIUM

    SciTech Connect

    Gatuzz, E.; Mendoza, C.; García, J.; Kallman, T. R.; Gorczyca, T. W. E-mail: claudio@ivic.gob.ve E-mail: timothy.r.kallman@nasa.gov

    2015-02-10

    We present an X-ray absorption model for the interstellar medium, to be referred to as ISMabs, that takes into account both neutral and ionized species of cosmically abundant elements, and includes the most accurate atomic data available. Using high-resolution spectra from eight X-ray binaries obtained with the Chandra High Energy Transmission Grating Spectrometer, we proceed to benchmark the atomic data in the model particularly in the neon K-edge region. Compared with previous photoabsorption models, which solely rely on neutral species, the inclusion of ions leads to improved spectral fits. Fit parameters comprise the column densities of abundant contributors that allow direct estimates of the ionization states. ISMabs is provided in the appropriate format to be implemented in widely used X-ray spectral fitting packages such as XSPEC, ISIS, and SHERPA.

  8. ISMabs: A Comprehensive X-Ray Absorption Model for the Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Gatuzz, E.; García, J.; Kallman, T. R.; Mendoza, C.; Gorczyca, T. W.

    2015-02-01

    We present an X-ray absorption model for the interstellar medium, to be referred to as ISMabs, that takes into account both neutral and ionized species of cosmically abundant elements, and includes the most accurate atomic data available. Using high-resolution spectra from eight X-ray binaries obtained with the Chandra High Energy Transmission Grating Spectrometer, we proceed to benchmark the atomic data in the model particularly in the neon K-edge region. Compared with previous photoabsorption models, which solely rely on neutral species, the inclusion of ions leads to improved spectral fits. Fit parameters comprise the column densities of abundant contributors that allow direct estimates of the ionization states. ISMabs is provided in the appropriate format to be implemented in widely used X-ray spectral fitting packages such as XSPEC, ISIS, and SHERPA.

  9. Analytic model of energy-absorption response functions in compound X-ray detector materials.

    PubMed

    Yun, Seungman; Kim, Ho Kyung; Youn, Hanbean; Tanguay, Jesse; Cunningham, Ian A

    2013-10-01

    The absorbed energy distribution (AED) in X-ray imaging detectors is an important factor that affects both energy resolution and image quality through the Swank factor and detective quantum efficiency. In the diagnostic energy range (20-140 keV), escape of characteristic photons following photoelectric absorption and Compton scatter photons are primary sources of absorbed-energy dispersion in X-ray detectors. In this paper, we describe the development of an analytic model of the AED in compound X-ray detector materials, based on the cascaded-systems approach, that includes the effects of escape and reabsorption of characteristic and Compton-scatter photons. We derive analytic expressions for both semi-infinite slab and pixel geometries and validate our approach by Monte Carlo simulations. The analytic model provides the energy-dependent X-ray response function of arbitrary compound materials without time-consuming Monte Carlo simulations. We believe this model will be useful for correcting spectral distortion artifacts commonly observed in photon-counting applications and optimal design and development of novel X-ray detectors.

  10. X-Ray Absorption Toward the Einstein Ring Source PKS 1830-211

    NASA Technical Reports Server (NTRS)

    Mathur, Smita; Nair, Sunita

    1997-01-01

    PKS 1830-211 is an unusually radio-loud gravitationally lensed quasar. In the radio spectrum, the system appears as two compact, dominant features surrounded by relatively extended radio emission that forms an Einstein ring. As the line of sight to it passes close to our Galactic center, PKS 1830-211 has not been detected in wave bands other than the radio and X-ray so far. Here we present X-ray data of PKS 1830-211 observed with ROSAT Position Sensitive Proportional Counter. The X-ray spectrum shows that absorption in excess of the Galactic contribution is highly likely, which at the redshift of the lensing galaxy (z(sub t)=0.886) corresponds to N(sub H)=3.5((sup 0.6)(sub -0.5))x10(exp 22) atoms sq cm. The effective optical extinction is large, A(sub V)(observed) is greater than or approximately 5.8. When corrected for this additional extinction, the two-point optical to X-ray slope alpha(sub ox) of PKS 1830-211 lies just within the observed range of quasars. It is argued here that both compact images must be covered by the X-ray absorber(s) that we infer to be the lensing galaxy (galaxies). The dust-to-gas ratio along the line of sight within the lensing galaxy is likely to be somewhat larger than for our Galaxy.

  11. Determination of the texture of arrays of aligned carbon nanotubes from the angular dependence of the X-ray emission and X-ray absorption spectra

    SciTech Connect

    Okotrub, A. V. Belavin, V. V.; Bulusheva, L. G.; Gusel'nikov, A. V.; Kudashov, A. G.; Vyalikh, D. V.; Molodtsov, S. L.

    2008-09-15

    The properties of materials containing carbon nanotubes depend on the degree of alignment and the internal structure of nanotubes. It is shown that the degree of misorientation of carbon nanotubes in samples can be evaluated from the measurements of the angular dependences of the carbon X-ray emission and carbon X-ray absorption spectra. The CK{sub {alpha}} emission and CK X-ray absorption spectra of the array of multiwalled carbon nanotubes synthesized by catalytic thermolysis of a mixture of fullerene and ferrocene are measured. A comparison of the calculated model dependences of the relative intensities of the {pi} and {sigma} bands in the spectra with the experimental results makes it possible to evaluate the degree of misorientation of nanotubes in the sample and their internal texture.

  12. X-ray emission and photoelectron spectra of Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3}

    SciTech Connect

    Kurmaev, E.Z.; Korotin, M.A.; Galakhov, V.R.; Finkelstein, L.D.; Zabolotzky, E.I.; Efremova, N.N.; Lobachevskaya, N.I.; Stadler, S.; Ederer, D.L.; Callcott, T.A.; Zhou, L.; Moewes, A.; Bartkowski, S.; Neumann, M.; Matsuno, J.; Mizokawa, T.; Fujimori, A.; Mitchell, J.

    1999-05-01

    The results of measurements of x-ray photoelectron (XPS), x-ray emission (XES), and x-ray absorption spectra and local spin-density approximation band structure (LSDA) calculations of Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3} are presented. The excitation energy dependence of Mn L{sub 2,3} and O K{alpha} x-ray emission spectra of Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3} is measured using tunable synchrotron radiation. The XES measurements yielded no photon energy dependence for the O K{alpha} spectra, but the Mn L{sub 2,3} spectra yielded inelastic scattering losses of 2 and 6 eV, corresponding to features in the structure of the occupied part of the valence band. Comparing XPS and XES measurements with LSDA band-structure calculations, one concludes that the electronic structure of the compound consists mainly of Mn 3d and O 2p states. States of 3d character localized at the Mn site predominate near the top of the valence band (VB). Some differences in the Mn 3d distribution in this part of the XPS valence band and Mn L{sub 3} XES with {ital d} symmetry due to spin-selection rules that govern the Mn L{sub 3} XES. In addition, the Mn 3d states distribution is hybridized with the O 2p part of the VB. Mn L{sub 3} XES spectra were determined relative to the Fermi energy by assuming normal x-ray emission begins from the lowest level of the p{sup 5}d{sup n+1}L intermediate state (which is the Mn 2p ionizatation threshold). From the local spin-density approximation, the orbital character of the Mn 3d electrons can be assigned e{sub g} symmetry at the top of the valence band T{sub 2g} in the central part of the VB, and equal contributions of e{sub g} and t{sub 2g} states at the bottom of the valence band. {copyright} {ital 1999} {ital The American Physical Society}

  13. 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.

  14. X-ray absorption spectroscopy on the basis of hybrid X-pinch radiation

    SciTech Connect

    Tilikin, I. N. Shelkovenko, T. A.; Pikuz, S. A.; Knapp, P. F.; Hammer, D. A.

    2015-07-15

    Results of experiments on X-ray absorption spectroscopy carried out at the BIN (270 kA, 100 ns) and XP (450 kA, 45 ns) facilities are presented. Continuum radiation of a Mo hybrid X-pinch was used as probing radiation, against which absorption lines of the plasma of exploded Al wires placed in the return current circuit of a hybrid X-pinch, as well as in a two- and four-wire array, were observed. The experiments have demonstrated that the radiation of a hybrid X-pinch hot spot can be used as probing radiation for X-ray absorption spectroscopy and that, in many parameters, such a source surpasses those on the basis of laser-produced plasma. The plasma parameters in arrays made of two and four Al wires were studied experimentally.

  15. Novel angular encoder for a quick-extended x-ray absorption fine structure monochromator

    SciTech Connect

    Stoetzel, J.; Luetzenkirchen-Hecht, D.; Frahm, R.; Fonda, E.; De Oliveira, N.; Briois, V.

    2008-08-15

    New concepts for time-resolved x-ray absorption spectroscopy using the quick-extended x-ray absorption fine structure (QEXAFS) method are presented. QEXAFS is a powerful tool to gain structural information about, e.g., fast chemical reactions or phase transitions on a subsecond scale. This can be achieved with a monochromator design that employs a channel-cut crystal on a cam driven tilt table for rapid angular oscillations of the Bragg angle. A new angular encoder system and a new data acquisition were described and characterized that were applied to a QEXAFS monochromator to get spectra with a directly measured accurate energy scale. New electronics were designed to allow a fast acquisition of the Bragg angle values and the absorption data during the measurements simultaneously.

  16. Electronic structure of warm dense copper studied by ultrafast x-ray absorption spectroscopy.

    PubMed

    Cho, B I; Engelhorn, K; Correa, A A; Ogitsu, T; Weber, C P; Lee, H J; Feng, J; Ni, P A; Ping, Y; Nelson, A J; Prendergast, D; Lee, R W; Falcone, R W; Heimann, P A

    2011-04-22

    We use time-resolved x-ray absorption spectroscopy to investigate the unoccupied electronic density of states of warm dense copper that is produced isochorically through the absorption of an ultrafast optical pulse. The temperature of the superheated electron-hole plasma, which ranges from 4000 to 10 000 K, was determined by comparing the measured x-ray absorption spectrum with a simulation. The electronic structure of warm dense copper is adequately described with the high temperature electronic density of state calculated by the density functional theory. The dynamics of the electron temperature is consistent with a two-temperature model, while a temperature-dependent electron-phonon coupling parameter is necessary.

  17. X-ray absorption spectroscopy on the basis of hybrid X-pinch radiation

    NASA Astrophysics Data System (ADS)

    Tilikin, I. N.; Shelkovenko, T. A.; Pikuz, S. A.; Knapp, P. F.; Hammer, D. A.

    2015-07-01

    Results of experiments on X-ray absorption spectroscopy carried out at the BIN (270 kA, 100 ns) and XP (450 kA, 45 ns) facilities are presented. Continuum radiation of a Mo hybrid X-pinch was used as probing radiation, against which absorption lines of the plasma of exploded Al wires placed in the return current circuit of a hybrid X-pinch, as well as in a two- and four-wire array, were observed. The experiments have demonstrated that the radiation of a hybrid X-pinch hot spot can be used as probing radiation for X-ray absorption spectroscopy and that, in many parameters, such a source surpasses those on the basis of laser-produced plasma. The plasma parameters in arrays made of two and four Al wires were studied experimentally.

  18. Quantitative analysis of deconvolved X-ray absorption near-edge structure spectra: a tool to push the limits of the X-ray absorption spectroscopy technique.

    PubMed

    D'Angelo, Paola; Migliorati, Valentina; Persson, Ingmar; Mancini, Giordano; Della Longa, Stefano

    2014-09-15

    A deconvolution procedure has been applied to K-edge X-ray absorption near-edge structure (XANES) spectra of lanthanoid-containing solid systems, namely, hexakis(dmpu)praseodymium(III) and -gadolinium(III) iodide. The K-edges of lanthanoids cover the energy range 38 (La)-65 (Lu) keV, and the large widths of the core-hole states lead to broadening of spectral features, reducing the content of structural information that can be extracted from the raw X-ray absorption spectra. Here, we demonstrate that deconvolution procedures allow one to remove most of the instrumental and core-hole lifetime broadening in the K-edge XANES spectra of lanthanoid compounds, highlighting structural features that are lost in the raw data. We show that quantitative analysis of the deconvolved K-edge XANES spectra can be profitably used to gain a complete local structural characterization of lanthanoid-containing systems not only for the nearest neighbor atoms but also for higher-distance coordination shells.

  19. Geometric Structure Determination of N694C Lipoxygenase: a Comparative Near-Edge X-Ray Absorption Spectroscopy And Extended X-Ray Absorption Fine Structure Study

    SciTech Connect

    Sarangi, R.; Hocking, R.K.; Neidig, M.L.; Benfatto, M.; Holman, T.R.; Solomon, E.I.; Hodgson, K.O.; Hedman, B.

    2009-05-27

    The mononuclear nonheme iron active site of N694C soybean lipoxygenase (sLO1) has been investigated in the resting ferrous form using a combination of Fe-K-pre-edge, near-edge (using the minuit X-ray absorption near-edge full multiple-scattering approach), and extended X-ray absorption fine structure (EXAFS) methods. The results indicate that the active site is six-coordinate (6C) with a large perturbation in the first-shell bond distances in comparison to the more ordered octahedral site in wild-type sLO1. Upon mutation of the asparigine to cystiene, the short Fe-O interaction with asparigine is replaced by a weak Fe-(H{sub 2}O), which leads to a distorted 6C site with an effective 5C ligand field. In addition, it is shown that near-edge multiple scattering analysis can give important three-dimensional structural information, which usually cannot be accessed using EXAFS analysis. It is further shown that, relative to EXAFS, near-edge analysis is more sensitive to partial coordination numbers and can be potentially used as a tool for structure determination in a mixture of chemical species.

  20. X-ray structure analysis of a metalloprotein with enhanced active-site resolution using in situ x-ray absorption near edge structure spectroscopy.

    PubMed

    Arcovito, Alessandro; Benfatto, Maurizio; Cianci, Michele; Hasnain, S Samar; Nienhaus, Karin; Nienhaus, G Ulrich; Savino, Carmelinda; Strange, Richard W; Vallone, Beatrice; Della Longa, Stefano

    2007-04-10

    X-ray absorption spectroscopy is exquisitely sensitive to the coordination geometry of an absorbing atom and therefore allows bond distances and angles of the surrounding atomic cluster to be measured with atomic resolution. By contrast, the accuracy and resolution of metalloprotein active sites obtainable from x-ray crystallography are often insufficient to analyze the electronic properties of the metals that are essential for their biological functions. Here, we demonstrate that the combination of both methods on the same metalloprotein single crystal yields a structural model of the protein with exceptional active-site resolution. To this end, we have collected an x-ray diffraction data set to 1.4-A resolution and Fe K-edge polarized x-ray absorption near edge structure (XANES) spectra on the same cyanomet sperm whale myoglobin crystal. The XANES spectra were quantitatively analyzed by using a method based on the multiple scattering approach, which yielded Fe-heme structural parameters with +/-(0.02-0.07)-A accuracy on the atomic distances and +/-7 degrees on the Fe-CN angle. These XANES-derived parameters were subsequently used as restraints in the crystal structure refinement. By combining XANES and x-ray diffraction, we have obtained an cyanomet sperm whale myoglobin structural model with a higher precision of the bond lengths and angles at the active site than would have been possible with crystallographic analysis alone.

  1. X-ray photoelectron spectroscopy analysis of aluminum and copper cleaning procedures for the Advanced Photon Source

    SciTech Connect

    Rosenberg, R.A.; McDowell, M.W.; Noonan, J.R. )

    1994-07-01

    The Advanced Photon Source (APS), presently under construction, will produce x rays of unprecedented brightness. The storage ring where the x rays will be produced will be constructed from an extruded 6063 aluminum alloy, while transition pieces (flanges, etc.) will be made from a 2219 aluminum alloy. In addition, cooled photon absorbers will be placed in strategic locations throughout the ring to intercept the majority of the unused high power-density radiation. These will be made of either CDA-101 (OFHC) copper or glidcop (a dispersion strengthened copper alloy). Before any of these components can be assembled they must be cleaned to remove surface contaminants so that the ultrahigh vacuum ([lt]0.1 nTorr) necessary for successful operation can be achieved. Many recipes for cleaning aluminum and copper exist; however, most of them involve the use of chemicals that present safety and/or environmental concerns. We have undertaken an x-ray photoelectron spectroscopy study of the effects of a variety of commercially available cleaners on the surface cleanliness of aluminum and copper. Several important results have been identified in this study. A simple alkaline detergent in an ultrasonic bath cleans aluminum alloys as effectively as the more aggressive cleaning solutions. The detergent can be used at 65 [degree]C to clean the 6063 alloy and at 50 [degree]C to clean the 2219 alloy. A citric acid based cleaner was found to be effective at cleaning copper, although the surface oxidizes rapidly. To date, we have been unable to find a universal cleaning procedure, i.e., one that is optimal for cleaning both Al and Cu.

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

    PubMed Central

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

    2011-01-01

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

  3. Complex X-ray Absorption and the Fe K(alpha) Profile in NGC 3516

    NASA Technical Reports Server (NTRS)

    Turner, T. J.; Kraemer, S. B.; George, I. M.; Reeves, J. N.; Botorff, M. C.

    2004-01-01

    We present data from simultaneous Chandra, XMM-Newton and BeppoSAX observations of the Seyfert 1 galaxy NGC 3516, taken during 2001 April and November. We have investigated the nature of the very flat observed X-ray spectrum. Chandra grating data show the presence of X-ray absorption lines, revealing two distinct components of the absorbing gas, one which is consistent with our previous model of the UV/X-ray absorber while the other, which is outflowing at a velocity of approximately 1100 kilometers per second, has a larger column density and is much more highly ionized. The broad-band spectral characteristics of the X-ray continuum observed with XMM during 2001 April, reveal the presence of a third layer of absorption consisting of a very large column (approximately 2.5 x 10(exp 23) per square centimeter) of highly ionized gas with a covering fraction approximately 50%. This low covering fraction suggests that the absorber lies within a few 1t-days of the X-ray source and/or is filamentary in structure. Interestingly, these absorbers are not in thermal equilibrium with one another. The two new components are too highly ionized to be radiatively accelerated, which we suggest is evidence for a hydromagnetic origin for the outflow. Applying our model to the November dataset, we can account for the spectral variability primarily by a drop in the ionization states of the absorbers, as expected by the change in the continuum flux. When this complex absorption is accounted for we find the underlying continuum to be typical of Seyfert 1 galaxies. The spectral curvature attributed to the high column absorber, in turn, reduces estimates of the flux and extent of any broad Fe emission line from the accretion disk.

  4. 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).

  5. Employing X-ray Photoelectron Spectroscopy for Determining Layer Homogeneity in Mixed Polar Self-Assembled Monolayers

    PubMed Central

    2016-01-01

    Self-assembled monolayers (SAMs) containing embedded dipolar groups offer the particular advantage of changing the electronic properties of a surface without affecting the SAM–ambient interface. Here we show that such systems can also be used for continuously tuning metal work functions by growing mixed monolayers consisting of molecules with different orientations of the embedded dipolar groups. To avoid injection hot-spots when using the SAM-modified electrodes in devices, a homogeneous mixing of the two components is crucial. We show that a combination of high-resolution X-ray photoelectron spectroscopy with state-of-the-art simulations is an ideal tool for probing the electrostatic homogeneity of the layers and thus for determining phase separation processes in polar adsorbate assemblies down to inhomogeneities at the molecular level. PMID:27429041

  6. Employing X-ray Photoelectron Spectroscopy for Determining Layer Homogeneity in Mixed Polar Self-Assembled Monolayers.

    PubMed

    Hehn, Iris; Schuster, Swen; Wächter, Tobias; Abu-Husein, Tarek; Terfort, Andreas; Zharnikov, Michael; Zojer, Egbert

    2016-08-04

    Self-assembled monolayers (SAMs) containing embedded dipolar groups offer the particular advantage of changing the electronic properties of a surface without affecting the SAM-ambient interface. Here we show that such systems can also be used for continuously tuning metal work functions by growing mixed monolayers consisting of molecules with different orientations of the embedded dipolar groups. To avoid injection hot-spots when using the SAM-modified electrodes in devices, a homogeneous mixing of the two components is crucial. We show that a combination of high-resolution X-ray photoelectron spectroscopy with state-of-the-art simulations is an ideal tool for probing the electrostatic homogeneity of the layers and thus for determining phase separation processes in polar adsorbate assemblies down to inhomogeneities at the molecular level.

  7. 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.

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

    SciTech Connect

    Fan, Haibo E-mail: liusz@snnu.edu.cn; Yang, Zhou; Ren, Xianpei; Gao, Fei; Yin, Mingli; Liu, Shengzhong E-mail: liusz@snnu.edu.cn

    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-voltage test has verified that the band alignment has a significant effect on the current transport of the heterojunction.

  9. Surface characterization of immunosensor conjugated with gold nanoparticles based on cyclic voltammetry and X-ray photoelectron spectroscopy.

    PubMed

    Lai, Lee-Jene; Yang, Yaw-Wen; Lin, Yao-Kwang; Huang, Li-Ling; Hsieh, Yi-Heui

    2009-02-01

    This investigation describes the surface characterization of rabbit immunoglobulin G (IgG) conjugated with gold nanoparticles. Goat anti-rabbit immunoglobulin G tagged with 5nm gold nanoparticles was applied to detect the IgG. Then, the autocatalyzed deposition of Au(3+) onto the surface of anti-IgGAu increased the surface area per gold nanoparticle. The immobilization chemistries and the atomic concentrations of Au(4f), P(2p), S(2p), C(1s), N(1s) and O(1s) of the resulting antibody-modified Au electrodes were determined by X-ray photoelectron spectroscopy (XPS). The sulfur that is involved in the cysteamine binding and the enlargement of the gold nanoparticles are identified using cyclic voltammetry. The results reveal that the surface area per gold particle, following the autocatalyzed deposition Au(3+) on the surface of anti-IgGAu, was approximately seven times higher than that before deposition.

  10. Electronic structure of Al- and Ga-doped ZnO films studied by hard X-ray photoelectron spectroscopy

    SciTech Connect

    Gabás, M.; Ramos Barrado, José R.; Torelli, P.; Barrett, N. T.

    2014-01-01

    Al- and Ga-doped sputtered ZnO films (AZO, GZO) are semiconducting and metallic, respectively, despite the same electronic valence structure of the dopants. Using hard X-ray photoelectron spectroscopy we observe that both dopants induce a band in the electronic structure near the Fermi level, accompanied by a narrowing of the Zn 3d/O 2p gap in the valence band and, in the case of GZO, a substantial shift in the Zn 3d. Ga occupies substitutional sites, whereas Al dopants are in both substitutional and interstitial sites. The latter could induce O and Zn defects, which act as acceptors explaining the semiconducting character of AZO and the lack of variation in the optical gap. By contrast, mainly substitutional doping is consistent with the metallic-like behavior of GZO.

  11. Application of ESCA to the determination of stoichiometry in sputtered coatings and interface regions. [X-ray photoelectron spectroscopy

    NASA Technical Reports Server (NTRS)

    Wheeler, D. R.

    1978-01-01

    X-ray Photoelectron Spectroscopy (XPS) was used to characterize radiofrequency sputter deposited films of several refractory compounds. Both the bulk film properties such as purity and stoichiometry and the character of the interfacial region between the film and substrate were examined. The materials were CrB2, MoS2, Mo2C, and Mo2B5 deposited on 440C steel. It was found that oxygen from the sputtering target was the primary impurity in all cases. Biasing improves the film purity. The effect of biasing on film stoichiometry is different for each compound. Comparison of the interfacial composition with friction data suggests that adhesion of these films is improved if a region of mixed film and iron oxides can be formed.

  12. 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.

  13. 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.

  14. Effects of proton irradiation on single-stranded DNA studied by using X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, E.; Lee, Cheol Eui; Han, J. H.

    2016-08-01

    X-ray photoelectron spectroscopy (XPS) has been employed in order to study the effects of proton irradiation on herring sperm single-stranded DNA. Systematic changes of the chemical shifts in the C, N, O, and P XPS line components as functions of the irradiation dose were observed, indicative of the bonding configurations in the DNA system. While the C 1 s XPS lines showed weak blueshifts, the N 1 s, O 1 s, and P 2 p XPS lines showed blueshifts with a marked dependence on the irradiation dose in a prominent manner. Our results show that linear energy transfer by charged particles and photons may have distinct molecular-level effects as the C 1 s, N 1 s, O 1 s, and P 2 p XPS lines showed redshifts in our previous study of effects of the γ-ray irradiation on the same system.

  15. Negatively charged gold atoms in subnanometric particles: experimental evidence from an X-ray photoelectron spectroscopy study.

    PubMed

    Boccia, Alice; Zanoni, Robertino; Arduini, Arturo; Pescatori, Luca; Secchi, Andrea

    2012-11-01

    The results of an X-ray Photoelectron Spectroscopy study conducted on a series of gold nanoparticles recently reported by us, stabilized by monodentate, bidentate, tridentate and tetradentate thiolate calix[n]arene ligands, are presented here. By virtue of the different denticity of the ligands, the nuclearity of the resulting particles can be tuned down to the subnanometric range. From the present XPS results, a clear correlation among the experimental binding energy of single Au 4f peak components and the specific Au state of charge is proposed, where the smaller (i.e., nanometer) fraction of the series selectively shows negatively charged Au atoms. Our findings are relevant for the open discussion of a specific role played by negatively charged Au atoms in catalytic reactions, especially at low temperatures.

  16. Energy-dispersive and x-ray photoelectron spectroscopy and electron microscopy of new quininium-plastic membrane electrodes.

    PubMed

    Shoukry, Adel F; Maraffie, Hayat M; Al-Shatti, Laila A

    2007-10-01

    New quininium (Qn) plastic membrane electrodes of the conventional type were constructed and characterized. They are based on incorporation of Qn-reineckate (QnRn) ion-pair, Qn-phosphotungstate (Qn3-PT), or Qn-phosphomolybdate (Qn3PM) ion associate into a poly(vinyl chloride) membrane. The electrodes are selective for Qn and have been successfully used for the determination of Qn2SO4 in pharmaceutical tablets. Nevertheless, they showed, as almost all other ion-selective electrodes, limited life times. Energy dispersive- (EDS) and X-ray photoelectron spectroscopy (XPS), as well as electron microscopy were applied to investigate the cause of this limitation in the life times of the electrodes. The results indicated that the electrodes lose their activity after prolonged soaking as a result of leaching of the ion exchanger from the membranes into the test solution in addition to deformation at the surface of the expired electrode.

  17. Probing the electronic environment of binary and ternary ionic liquid mixtures by X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Men, Shuang; Licence, Peter

    2017-10-01

    X-ray photoelectron spectroscopy is used to probe the electronic environment of cations and anions for three binary and one ternary chlorostannate ionic liquid mixtures. The impact of the weighting of Cl- on the electronic environment of the cation-based nitrogen atom is revealed in detail. With the increasing of the concentration of Cl-, the N 1s binding energy is decreased. The electronic environment of the anion-based component is also compared based upon Sn 3d5/2 and Cl 2p3/2 binding energies. It is found that with the increasing of the weighting of Cl-, binding energies of Sn 3d5/2 and Cl 2p3/2 both decrease.

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

    SciTech Connect

    Kreil, Justin; Ellingsworth, Edward; Szulczewski, Greg

    2013-11-15

    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 is 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.

  19. Native target chemistry during reactive dc magnetron sputtering studied by ex-situ x-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Greczynski, G.; Mráz, S.; Schneider, J. M.; Hultman, L.

    2017-07-01

    We report x-ray photoelectron spectroscopy (XPS) analysis of native Ti target surface chemistry during magnetron sputtering in an Ar/N2 atmosphere. To avoid air exposure, the target is capped immediately after sputtering with a few-nm-thick Al overlayers; hence, information about the chemical state of target elements as a function of N2 partial pressure pN2 is preserved. Contrary to previous reports, which assume stoichiometric TiN formation, we present direct evidence, based on core-level XPS spectra and TRIDYN simulations, that the target surface is covered by TiNx with x varying in a wide range, from 0.27 to 1.18, depending on pN2. This has far-reaching consequences both for modelling of the reactive sputtering process and for everyday thin film growth where detailed knowledge of the target state is crucial.

  20. Understanding Chemical versus Electrostatic Shifts in X-ray Photoelectron Spectra of Organic Self-Assembled Monolayers

    PubMed Central

    2016-01-01

    The focus of the present article is on understanding the insight that X-ray photoelectron spectroscopy (XPS) measurements can provide when studying self-assembled monolayers. Comparing density functional theory calculations to experimental data on deliberately chosen model systems, we show that both the chemical environment and electrostatic effects arising from a superposition of molecular dipoles influence the measured core-level binding energies to a significant degree. The crucial role of the often overlooked electrostatic effects in polar self-assembled monolayers (SAMs) is unambiguously demonstrated by changing the dipole density through varying the SAM coverage. As a consequence of this effect, care has to be taken when extracting chemical information from the XP spectra of ordered organic adsorbate layers. Our results, furthermore, imply that XPS is a powerful tool for probing local variations in the electrostatic energy in nanoscopic systems, especially in SAMs. PMID:26937264

  1. 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.

  2. Application of ESCA to the determination of stoichiometry in sputtered coatings and interface regions. [X-ray photoelectron spectroscopy

    NASA Technical Reports Server (NTRS)

    Wheeler, D. R.

    1978-01-01

    X-ray Photoelectron Spectroscopy (XPS) was used to characterize radiofrequency sputter deposited films of several refractory compounds. Both the bulk film properties such as purity and stoichiometry and the character of the interfacial region between the film and substrate were examined. The materials were CrB2, MoS2, Mo2C, and Mo2B5 deposited on 440C steel. It was found that oxygen from the sputtering target was the primary impurity in all cases. Biasing improves the film purity. The effect of biasing on film stoichiometry is different for each compound. Comparison of the interfacial composition with friction data suggests that adhesion of these films is improved if a region of mixed film and iron oxides can be formed.

  3. Annealing dependence of diamond-metal Schottky barrier heights probed by hard x-ray photoelectron spectroscopy

    SciTech Connect

    Gaowei, M.; Muller, E. M.; Rumaiz, A. K.; Weiland, C.; Cockayne, E.; Woicik, J. C.; Jordan-Sweet, J.; Smedley, J.

    2012-05-14

    Hard x-ray photoelectron spectroscopy was applied to investigate the diamond-metal Schottky barrier heights for several metals and diamond surface terminations. The position of the diamond valence-band maximum was determined by theoretically calculating the diamond density of states and applying cross section corrections. The diamond-platinum Schottky barrier height was lowered by 0.2 eV after thermal annealing, indicating annealing may increase carrier injection in diamond devices leading to photoconductive gain. The platinum contacts on oxygen-terminated diamond was found to provide a higher Schottky barrier and therefore a better blocking contact than that of the silver contact in diamond-based electronic devices.

  4. In situ X-ray photoelectron and Auger electron spectroscopic characterization of reaction mechanisms during Li-ion cycling.

    PubMed

    Tang, Ching-Yen; Haasch, Richard T; Dillon, Shen J

    2016-11-03

    The complex nature of Li-ion battery reactions along with their sensitivity to environmental exposure necessitates in situ characterization, particularly for surface sensitive methods. In this work, we demonstrate in situ X-ray photoelectron spectroscopy and in situ Auger electron spectroscopy applied to characterize the evolution of bonding and chemistry during cycling of nanoparticle electrodes. We apply the method to study the conversion reaction associated with Li insertion and extraction from CuO nanoparticle electrodes. This approach circumvents the need for ion sputtering and mechanical erosion, previously required to remove solid electrolyte interphase during ex situ measurements. This allows the elucidation of the changes in Cu oxidation state, during initial Li insertion, without the introduction of artifacts that have caused prior disagreement in the published literature.

  5. Band alignment at a MgO/GaSb heterointerface using x-ray photoelectron spectroscopy measurements

    NASA Astrophysics Data System (ADS)

    Li, Ruxue; Wei, Zhipeng; Liu, Xue; Li, Yongfeng; Fang, Xuan; Tang, Jilong; Fang, Dan; Gao, Xian; Wang, Dengkui; Hao, Yongqin; Yao, Bin; Ma, Xiaohui; Wang, Xiaohua

    2016-07-01

    The valence band offset (ΔE V) of a MgO/GaSb heterostructure was determined using x-ray photoelectron spectroscopy measurements. A ΔE V value of 2.84 ± 0.10 eV was calculated by using Ga 3d3/2 and Mg 2p1/2 binding energies as references. Taking the empirical band gaps of 7.83 eV and 0.73 eV for MgO and GaSb thin films into consideration, respectively, we obtained the type-I band alignment of a MgO/GaSb heterostructure with a conduction band offset (ΔE c) of 4.26 ± 0.10 eV, suggesting a nested interface band alignment.

  6. Valence band offset of MgO /InN heterojunction measured by x-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, P. F.; Liu, X. L.; Zhang, R. Q.; Fan, H. B.; Song, H. P.; Wei, H. Y.; Jiao, C. M.; Yang, S. Y.; Zhu, Q. S.; Wang, Z. G.

    2008-01-01

    MgO may be a promising gate dielectric and surface passivation film for InN based devices and the valence band offset of MgO /InN heterojunction has been measured by x-ray photoelectron spectroscopy. The valence band offset is determined to be 1.59±0.23eV. Given the experimental band gap of 7.83 for the MgO, a type-I heterojunction with a conduction band offset of 5.54±0.23eV is found. The accurate determination of the valence and conduction band offsets is important for use of MgO /InN electronic devices.

  7. pH-induced protonation of lysine in aqueous solution causes chemical shifts in X-ray photoelectron spectroscopy.

    PubMed

    Nolting, Dirk; Aziz, Emad F; Ottosson, Niklas; Faubel, Manfred; Hertel, Ingolf V; Winter, Bernd

    2007-11-14

    We demonstrate the applicability of X-ray photoelectron spectroscopy to obtain charge- and site-specific electronic structural information of biomolecules in aqueous solution. Changing the pH of an aqueous solution of lysine from basic to acidic results in nitrogen 1s and carbon 1s chemical shifts to higher binding energies. These shifts are associated with the sequential protonation of the two amino groups, which affects both charge state and hydrogen bonding to the surrounding water molecules. The N1s chemical shift is 2.2 eV, and for carbon atoms directly neighboring a nitrogen the shift for C1s is approximately 0.4 eV. The experimental binding energies agree reasonably with our calculated energies of lysine(aq) for different pH values.

  8. Mixed adlayer of alkanethiol and peptide on GaAs(100): quantitative characterization by X-ray photoelectron spectroscopy.

    PubMed

    Wampler, Heeyeon P; Zemlyanov, Dmitry Y; Lee, Kangho; Janes, David B; Ivanisevic, Albena

    2008-04-01

    Homogeneous and mixed adlayers composed of an alkanethiol (1-octadecanethiol, ODT) and a peptide (CGISYGRKKRRQRRR) on GaAs(100) were formed in two different solvent systems: phosphate-buffered saline (PBS) and N,N-dimethylformamide (DMF). The chemical composition of each adlayer was characterized by X-ray photoelectron spectroscopy (XPS). The data showed that the makeup of the adlayer and its stability largely depends on the solvent used. Angle-resolved XPS also revealed that the adlayer thickness and tilt angles were different from values obtained from ellipsometry measurements and vastly varied between the two solvents used. The coverage data extracted from the XPS measurements indicated that homogeneous adlayers of peptide in PBS buffer form a multilayered film. Homogeneous alkanethiol adlayers exhibited monolayer coverage under all solvent treatments. Coadsorbed layers containing both alkanethiol and peptide have fractional monolayer coverage in both solvents.

  9. Conformational studies of covalently grafted poly(ethylene glycol) on modified solid matrices using X-ray photoelectron spectroscopy.

    PubMed

    Damodaran, Vinod Babu; Fee, Conan J; Ruckh, Tim; Popat, Ketul C

    2010-05-18

    Amine functionalized poly(ethylene glycols) (PEGs) with molecular weights 2000 and 4000 Da were covalently grafted onto carboxy modified hydrophilic Sephadex derivatives and hydrophobic polystyrene derivatives using anhydrous amine conjugation methods. Varying PEG surface concentration and layer thickness were achieved by controlling the reaction parameters and were analyzed by X-ray photoelectron spectroscopy (XPS). C-O intensities obtained from high resolution C 1s scans were correlated using the standard overlay model to study the grafting kinetics as well as conformational properties of grafted polymer chains. A detailed and systematic comparison of PEG layer thickness and distance between grafted chains with the Flory radius of surface grafted PEG resulted in valuable information regarding conformational behavior of the polymer. The influence of the nature of the solid matrix on grafting kinetics and conformational properties of the grafted polymer chain was also established from the XPS results.

  10. X-ray photoelectron spectroscopy of trihalide ionic liquids: Comparison to halide-based analogues, anion basicity and beam damage

    NASA Astrophysics Data System (ADS)

    Men, Shuang; Lovelock, Kevin R. J.; Licence, Peter

    2017-07-01

    X-ray photoelectron spectroscopy is used to investigate two 1-octyl-3-methylimidazolium trihalide ionic liquids, with anions including triiodide and iododibromide. The electronic environment of each element present in ionic liquids studied herein is analysed and compared to their halide-based analogous. The anion basicity is compared based upon the measured N 1s binding energy. The iododibromide ionic liquid is studied as a representative sample to illustrate the beam damage effect. Due to the beam damage, there is a new formed bromine component observed. This effect is calculated and demonstrated for all elements present within the ionic liquid. It suggests that the beam induced decomposition caused a stoichiometric loss of bromine atom and iodine atom.

  11. X-ray photoelectron spectroscopy analysis of cleaning procedures for synchrotron radiation beamline materials at the Advanced Photon Source

    SciTech Connect

    Li, Y.; Ryding, D.; Liu, C.; Kuzay, T.M.; McDowell, M.W.; Rosenberg, R.A.

    1994-12-31

    TZM (a high temperature molybdenum alloy), machinable tungsten, and 304 stainless steel were cleaned using environmentally safe, commercially available cleaning detergents. The surface cleanliness was evaluated by x-ray photoelectron spectroscopy (XPS). It was found that a simple alkaline detergent is very effective at removal of organic and inorganic surface contaminants or foreign particle residue from machining processes. The detergent can be used with ultrasonic agitation at 140 F to clean the TZM molybdenum, machinable tungsten, and 304 stainless steel. A citric-acid-based detergent was also found to be effective at cleaning metal oxides, such as iron oxide, molybdenum oxide, as well as tungsten oxides at mild temperatures with ultrasonic agitation, and it can be used to replace strong inorganic acids to improve cleaning safety and minimize waste disposal and other environmental problems. The efficiency of removing the metal oxides depends on both cleaning temperature and time.

  12. 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.

  13. 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.

  14. Understanding Chemical versus Electrostatic Shifts in X-ray Photoelectron Spectra of Organic Self-Assembled Monolayers.

    PubMed

    Taucher, Thomas C; Hehn, Iris; Hofmann, Oliver T; Zharnikov, Michael; Zojer, Egbert

    2016-02-18

    The focus of the present article is on understanding the insight that X-ray photoelectron spectroscopy (XPS) measurements can provide when studying self-assembled monolayers. Comparing density functional theory calculations to experimental data on deliberately chosen model systems, we show that both the chemical environment and electrostatic effects arising from a superposition of molecular dipoles influence the measured core-level binding energies to a significant degree. The crucial role of the often overlooked electrostatic effects in polar self-assembled monolayers (SAMs) is unambiguously demonstrated by changing the dipole density through varying the SAM coverage. As a consequence of this effect, care has to be taken when extracting chemical information from the XP spectra of ordered organic adsorbate layers. Our results, furthermore, imply that XPS is a powerful tool for probing local variations in the electrostatic energy in nanoscopic systems, especially in SAMs.

  15. Investigation of passive films on {alpha}{sub 2} and {gamma} titanium aluminides by X-ray photoelectron spectroscopy

    SciTech Connect

    Ziomek-Moroz, M.; Su, W.; Covino, B.S. Jr.

    1999-07-01

    Passive films on {alpha}{sub 2} and {gamma} titanium aluminide formed potentiostatically in sodium hydroxide (NaOH) and sulfuric acid (H{sub 2}SO{sub 4}) solutions were studied by x-ray photoelectron spectroscopy (XPS). In NaOH, potentiostatic experiments showed that titanium aluminides had very similar passive current densities to that of Ti. XPS sputter depth profile showed nearly no Al present in the outer layer of the passive films. In H{sub 2}SO{sub 4}, passive current densities increased for specimens with increasing Al content. XPS sputter depth profile showed that Al was enriched in outer layers of the passive films. These results indicated that the passive film dissolution rates increased with increasing amounts of Al in the passive film for titanium aluminides.

  16. Investigation of passive films on alpha2 and gamma titanium aluminides by X-ray photoelectron spectroscopy

    SciTech Connect

    Ziomek-Moroz, M.; Su, W.; Covino, Bernard S., Jr.

    1999-07-01

    Passive films on alpha2 and gamma titanium aluminide formed potentiostatically in sodium hydroxide (NaOH) and sulfuric acid (H2SO4) solutions were studied by x-ray photoelectron microscopy (XPS). In NaOH, potentiostatic experiments showed that titanium aluminides had very similar passive current densities to that of Ti. XPS sputter depth profile showed nearly no Al present in the outer layer of the passive films. In H2SO4, passive current densities increased for specimens with increasing Al content. XPS sputter depth profile showed that Al was enriched in outer layers of the passive films. These results indicated that the passive film dissolution rate increased with increasing amounts of Al in the passive film for titanium aluminides.

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

    SciTech Connect

    Yasuno, Satoshi Koganezawa, Tomoyuki; Watanabe, Takeshi; Oji, Hiroshi

    2016-07-27

    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.

  18. Probing buried organic-organic and metal-organic heterointerfaces by hard x-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Shibuta, Masahiro; Eguchi, Toyoaki; Watanabe, Yoshio; Son, Jin-Young; Oji, Hiroshi; Nakajima, Atsushi

    2012-11-01

    We present a nondestructive characterization method for buried hetero-interfaces for organic/organic and metal/organic systems using hard x-ray photoelectron spectroscopy (HAXPES) which can probe electronic states at depths deeper than ˜10 nm. A significant interface-derived signal showing a strong chemical interaction is observed for Au deposited onto a C60 film, while there is no such additional feature for copper phthalocyanine deposited onto a C60 film reflecting the weak interaction between the molecules in the latter case. A depth analysis with HAXPES reveals that a Au-C60 intermixed layer with a thickness of 5.1 nm is formed at the interface.

  19. 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.

  20. X-ray photoelectron spectroscopy study on the chemistry involved in tin oxide film growth during chemical vapor deposition processes

    SciTech Connect

    Mannie, Gilbere J. A.; Gerritsen, Gijsbert; Abbenhuis, Hendrikus C. L.; Deelen, Joop van; Niemantsverdriet, J. W.; Thuene, Peter C.

    2013-01-15

    The chemistry of atmospheric pressure chemical vapor deposition (APCVD) processes is believed to be complex, and detailed reports on reaction mechanisms are scarce. Here, the authors investigated the reaction mechanism of monobutyl tinchloride (MBTC) and water during SnO{sub 2} thin film growth using x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). XPS results indicate an acid-base hydrolysis reaction mechanism, which is tested with multilayer experiments, demonstrating self-terminating growth. In-house developed TEM wafers are used to visualize nucleation during these multilayer experiments, and results are compared with TEM results of APCVD samples. Results show almost identical nucleation behavior implying that their growth mechanism is identical. Our experiments suggest that in APCVD, when using MBTC and water, SnO{sub 2} film growth occurs via a heterolytic bond splitting of the Sn-Cl bonds without the need to invoke gas-phase radical or coordination chemistry of the MBTC precursor.

  1. Liquid-Jet X-ray Photoelectron Spectra of TiO(2) Nanoparticles in an Aqueous Electrolyte Solution.

    PubMed

    Makowski, Michael J; Galhenage, Randima P; Langford, Joel; Hemminger, John C

    2016-05-05

    Titania has attracted significant interest due to its broad catalytic applications, many of which involve titania nanoparticles in contact with aqueous electrolyte solutions. Understanding the titania nanoparticle/electrolyte interface is critical for the rational development of such systems. Here, we have employed liquid-jet ambient pressure X-ray photoelectron spectroscopy (AP-XPS) to investigate the solid/electrolyte interface of 20 nm diameter TiO2 nanoparticles in 0.1 M aqueous nitric acid solution. The Ti 2p line shape and absolute binding energy reflect a fully oxidized stoichiometric titania lattice. Further, by increasing the X-ray excitation energy, the difference in O 1s binding energies between that of liquid water (O 1sliq) and the titania lattice (O 1slat) oxygen was measured as a function of probe depth into the particles. The titania lattice, O 1slat, binding energy decreases by 250 meV when probing from the particle surface into the bulk. This is interpreted as downward band bending at the interface.

  2. Synthesis and Characterization of Ca and Ba Doped LAMOX Materials and Surface Study by X-ray Photoelectron Spectroscopy.

    PubMed

    Khaled, Ammar; Pireaux, Jean-Jacques; Khelili, Smail

    2012-12-01

    (La1-xCax)2Mo2O9-d and (La1-xBax)2Mo2O9-d (x = 0.05, 0.1, 0.15, 0.2) materials were prepared at 800 °C by co-precipitation method and characterized by X-ray diffraction and scanning electron microscope. The XRD diagrams showed the presence of CaMoO4 and BaMoO4 secondary phases only at high contents of the dopants. X-ray photoelectron spectroscopy was used to study the surface chemical structure of doped and undoped materials (La2Mo2O9). It was found that the La and Mo atoms had 3+ and 6+ valence states, respectively. The absence of carbides and carbonates at surface suggests that, the unavoidable carbon contamination did not interact with the metal atoms, which allows applications using carbonaceous fuels, and, that the formation of secondary phases did not influence the surface state. XPS spectra show that the covalent character of the La-O bond was enhanced with calcium doping as compared to barium, predicting interesting conductive and catalytic properties of the materials.

  3. Adsorption, X-ray Diffraction, Photoelectron, and Atomic Emission Spectroscopy Benchmark Studies for the Eighth Industrial Fluid Properties Simulation Challenge.

    PubMed

    Ross, Richard B; Aeschliman, David B; Ahmad, Riaz; Brennan, John K; Brostrom, Myles L; Frankel, Kevin A; Moore, Jonathan D; Moore, Joshua D; Mountain, Raymond D; Poirier, Derrick M; Thommes, Matthias; Shen, Vincent K; Schultz, Nathan E; Siderius, Daniel W; Smith, Kenneth D

    2016-02-01

    The primary goal of the eighth industrial fluid properties simulation challenge was to test the ability of molecular simulation methods to predict the adsorption of organic adsorbates in activated carbon materials. The challenge focused on the adsorption of perfluorohexane in the activated carbon standard BAM-P109 (Panne and Thünemann 2010). Entrants were challenged to predict the adsorption of perfluorohexane in the activated carbon at a temperature of 273 K and at relative pressures of 0.1, 0.3, and 0.6. The relative pressure (P/Po) is defined as that relative to the bulk saturation pressure predicted by the fluid model at a given temperature (273 K in this case). The predictions were judged by comparison to a set of experimentally determined values, which are published here for the first time and were not disclosed to the entrants prior to the challenge. Benchmark experimental studies, described herein, were also carried out and provided to entrants in order to aid in the development of new force fields and simulation methods to be employed in the challenge. These studies included argon, carbon dioxide, and water adsorption in the BAM-P109 activated carbon as well as X-ray diffraction, X-ray microtomography, photoelectron spectroscopy, and atomic emission spectroscopy studies of BAM-P109. Several concurrent studies were carried out for the BAM-P108 activated carbon (Panne and Thünemann 2010). These are included in the current manuscript for comparison.

  4. Adsorption, X-ray Diffraction, Photoelectron, and Atomic Emission Spectroscopy Benchmark Studies for the Eighth Industrial Fluid Properties Simulation Challenge*+

    PubMed Central

    Ross, Richard B.; Aeschliman, David B.; Ahmad, Riaz; Brennan, John K.; Brostrom, Myles L.; Frankel, Kevin A.; Moore, Jonathan D.; Moore, Joshua D.; Mountain, Raymond D.; Poirier, Derrick M.; Thommes, Matthias; Shen, Vincent K.; Schultz, Nathan E.; Siderius, Daniel W.; Smith, Kenneth D.

    2016-01-01

    The primary goal of the eighth industrial fluid properties simulation challenge was to test the ability of molecular simulation methods to predict the adsorption of organic adsorbates in activated carbon materials. The challenge focused on the adsorption of perfluorohexane in the activated carbon standard BAM-P109 (Panne and Thünemann 2010). Entrants were challenged to predict the adsorption of perfluorohexane in the activated carbon at a temperature of 273 K and at relative pressures of 0.1, 0.3, and 0.6. The relative pressure (P/Po) is defined as that relative to the bulk saturation pressure predicted by the fluid model at a given temperature (273 K in this case). The predictions were judged by comparison to a set of experimentally determined values, which are published here for the first time and were not disclosed to the entrants prior to the challenge. Benchmark experimental studies, described herein, were also carried out and provided to entrants in order to aid in the development of new force fields and simulation methods to be employed in the challenge. These studies included argon, carbon dioxide, and water adsorption in the BAM-P109 activated carbon as well as X-ray diffraction, X-ray microtomography, photoelectron spectroscopy, and atomic emission spectroscopy studies of BAM-P109. Several concurrent studies were carried out for the BAM-P108 activated carbon (Panne and Thünemann 2010). These are included in the current manuscript for comparison. PMID:27840543

  5. Interface investigations of a commercial lithium ion battery graphite anode material by sputter depth profile X-ray photoelectron spectroscopy.

    PubMed

    Niehoff, Philip; Passerini, Stefano; Winter, Martin

    2013-05-14

    Here we provide a detailed X-ray photoelectron spectroscopy (XPS) study of the electrode/electrolyte interface of a graphite anode from commercial NMC/graphite cells by intense sputter depth profiling using a polyatomic ion gun. The uniqueness of this method lies in the approach using 13-step sputter depth profiling (SDP) to obtain a detailed model of the film structure, which forms at the electrode/electrolyte interface often noted as the solid electrolyte interphase (SEI). In addition to the 13-step SDP, several reference experiments of the untreated anode before formation with and without electrolyte were carried out to support the interpretation. Within this work, it is shown that through charging effects during X-ray beam exposure chemical components cannot be determined by the binding energy (BE) values only, and in addition, that quantification by sputter rates is complicated for composite electrodes. A rough estimation of the SEI thickness was carried out by using the LiF and graphite signals as internal references.

  6. 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.

  7. X-Ray Photoelectron Spectroscopy Applied to the Characterization of Surfaces at Pressures of up to 0.1 Mbar.

    NASA Astrophysics Data System (ADS)

    Kong, Chang-Wha

    The thesis describes the design principles, operation and an X-Ray Photoelectron Spectrometer capable of analyzing surfaces under "in situ" conditions in the pressure range of 10^{-11} to 1 mbar. Measurements at pressures exceeding 10^{-5} mbar are carried out by placing a differentially pumped aperture system between sample surface and the hemispherical electron energy analyzer. The reduction of signal intensity due to the aperture is, depending on the operation mode and resolution of the analyzer, between a factor of 5-12. Measurements at pressures as high as 6 times 10^{-1} mbar show that the sensitivity of the apparatus is sufficient to detect coverages as low as ~.1 monolayers. The experimental work described in this thesis relates to the interaction of sulfur dioxide with metallic copper and CuO and Cu_2O surfaces. Adsorption and reaction of SO_2 with these surfaces comprise one of the elemental steps in the flue gas cleanup process from a duct stream using copper oxide particles. The adsorption and reaction of SO_2 with copper and copper oxide surfaces was studied by in situ x-ray photoelectron spectroscopy between 173 K-473 K and pressures ranging from UHV to 10^ {-1} mbar. It was found that a Cu _2 SO_3^ecies acts as an intermediate in the formation of CuSO_4 at T < 300 K, and at T > 300 K, in the formation of coppersulfide. The presence of gas phase oxygen was found to accelerate the surface reaction between SO_2 and the substrates. Contrary to previous suggestions, we find that a copper sulfate is found only under conditions which are far removed from the conditions in a duct-pipe. Under temperature and partial pressure conditions resembling the industrial process, a copper sulfide is formed.

  8. Electronic ground states of Fe2(+) and Co2(+) as determined by x-ray absorption and x-ray magnetic circular dichroism spectroscopy.

    PubMed

    Zamudio-Bayer, V; Hirsch, K; Langenberg, A; Ławicki, A; Terasaki, A; V Issendorff, B; Lau, J T

    2015-12-28

    The (6)Π electronic ground state of the Co2 (+) diatomic molecular cation has been assigned experimentally by x-ray absorption and x-ray magnetic circular dichroism spectroscopy in a cryogenic ion trap. Three candidates, (6)Φ, (8)Φ, and (8)Γ, for the electronic ground state of Fe2 (+) have been identified. These states carry sizable orbital angular momenta that disagree with theoretical predictions from multireference configuration interaction and density functional theory. Our results show that the ground states of neutral and cationic diatomic molecules of 3d transition elements cannot generally be assumed to be connected by a one-electron process.

  9. Determining crystal phase purity in c-BP through X-ray absorption spectroscopy.

    PubMed

    Huber, S P; Medvedev, V V; Gullikson, E; Padavala, B; Edgar, J H; van de Kruijs, R W E; Bijkerk, F; Prendergast, D

    2017-02-02

    We employ X-ray absorption near-edge spectroscopy at the boron K-edge and the phosphorus L2,3-edge to study the structural properties of cubic boron phosphide (c-BP) samples. The X-ray absorption spectra are modeled from first-principles within the density functional theory framework using the excited electron core-hole (XCH) approach. A simple structural model of a perfect c-BP crystal accurately reproduces the P L2,3-edge, however it fails to describe the broad and gradual onset of the B K-edge. Simulations of the spectroscopic signatures in boron 1s excitations of intrinsic point defects and the hexagonal BP crystal phase show that these additions to the structural model cannot reproduce the broad pre-edge of the experimental spectrum. Calculated formation enthalpies show that, during the growth of c-BP, it is possible that amorphous boron phases can be grown in conjunction with the desired boron phosphide crystalline phase. In combination with experimental and theoretically obtained X-ray absorption spectra of an amorphous boron structure, which have a similar broad absorption onset in the B K-edge spectrum as the cubic boron phosphide samples, we provide evidence for the presence of amorphous boron clusters in the synthesized c-BP samples.

  10. Picosecond x-ray laser photoelectron spectroscopy of room temperature and heated materials

    SciTech Connect

    Dunn, J; Nelson, A J; van Buuren, T; Hunter, J R

    2004-08-03

    An 84.5 eV Ni-like Pd ion 4d - 4p x-ray laser source generated by the LLNL Compact Multipulse Terawatt (COMET) tabletop system has been used to probe the electronic structure of various metals and semiconductors. In addition to the {approx}4 - 5 ps time resolution, the probe provides the necessary high photon flux (>10{sup 12}/pulse), narrow line width ({Delta}E/E{approx}2 x 10{sup -5}) and coherence for studying valence band and shallow core electronic structure levels in a single shot. We show some preliminary results of room temperature and heated thin foil samples consisting of 50 nm Cu coated on a 20 nm C substrate. A 527 nm wavelength 400 fs laser pulse containing 0.1 - 2.5 mJ laser energy is focused in a large 500 x 700 {micro}m{sup 2} (FWHM) spot to create heated conditions of 0.07 - 1.8 x 1012 W cm{sup -2} intensity.

  11. X-ray photoelectron spectra and electronic structure of rare-earth orthovanadates

    NASA Astrophysics Data System (ADS)

    Ryzhkov, M. V.; Kostikov, S. P.; Ivanov, I. K.; Gubanov, V. A.

    1981-08-01

    Photoelectron spectra of 4 d and valence states in RVO 4 ( R = Y, Nd, Eu, Gd, Tb, Dy, Yb) have been investigated. The experimental spectra are interpreted using the results of the Xα discrete variational method calculations for orthovanadates. Transformations of electronic structure and covalency in the RVO 4 series are discussed. It is shown that lanthanide 4 f orbitals significantly mix with the O 2 pAO's and hybridize with the rare-earths 5 pAO's. The 5 p levels spin-orbital splitting in orthovanadates has been evaluated.

  12. A structural study of bone changes in knee osteoarthritis by synchrotron-based X-ray fluorescence and X-ray absorption spectroscopy techniques

    NASA Astrophysics Data System (ADS)

    Sindhupakorn, Bura; Thienpratharn, Suwittaya; Kidkhunthod, Pinit

    2017-10-01

    Osteoarthritis (OA) is characterized by degeneration of articular cartilage and thickening of subchondral bone. The present study investigated the changing of biochemical components of cartilage and bone compared between normal and OA people. Using Synchrotron-based X-ray fluorescence (SR-XRF) and X-ray absorption spectroscopy (XAS) techniquesincluding X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) were employed for the bone changes in kneeosteoarthritisstudies. The bone samples were collected from various osteoarthritis patients with both male and female in the ages range between 20 and 74 years old. SR-XRF results excited at 4240 eV for Ca elements show a majority three main groups, based on their XRF intensities, 20-36 years, 40-60 years and over 70 years, respectively. By employing XAS techniques, XANES features can be used to clearly explain in term of electronic transitions occurring in bone samples which are affected from osteoarthritis symptoms. Moreover, a structural change around Ca ions in bone samples is obviously obtained by EXAFS results indicating an increase of Ca-amorphous phase when the ages increase.

  13. Electron and x-ray fluorescence yield measurements of the Cu L2,3-edge x-ray absorption fine structures: A comparative study

    NASA Astrophysics Data System (ADS)

    Hiraya, A.; Watanabe, M.; Sham, T. K.

    1995-02-01

    The Cu L2,3-edge x-ray absorption fine structures (XAFS) of a series of Cu samples have been recorded at the BL1A beamline of UVSOR using both electron yield and x-ray fluorescence yield techniques. XAFS measurements were simultaneously recorded in three modes: total electron yield (TEY) with specimen current, total electron yield with a channeltron electron multiplier and x-ray fluorescence yield (FLY) with an Ar/CH4 gas proportional counter. While both TEY measurements produce essentially identical spectra, a comparison between TEY and FLY results shows a drastic difference in the sensitivity of the techniques towards sampling depth. These results and their implications are discussed.

  14. Identifying anthropogenic uranium compounds using soft X-ray near-edge absorption spectroscopy

    SciTech Connect

    Ward, Jesse D.; Bowden, Mark; Tom Resch, C.; Eiden, Gregory C.; Pemmaraju, C. D.; Prendergast, David; Duffin, Andrew M.

    2017-01-01

    Uranium ores mined for industrial use are typically acid-leached to produce yellowcake and then converted into uranium halides for enrichment and purification. These anthropogenic chemical forms of uranium are distinct from their mineral counterparts. The purpose of this study is to use soft X-ray absorption spectroscopy to characterize several common anthropogenic uranium compounds important to the nuclear fuel cycle. Non-destructive chemical analyses of these compounds is important for process and environmental monitoring and X-ray absorption techniques have several advantages in this regard, including element-specificity, chemical sensitivity, and high spectral resolution. Oxygen K-edge spectra were collected for uranyl nitrate, uranyl fluoride, and uranyl chloride, and fluorine K-edge spectra were collected for uranyl fluoride and uranium tetrafluoride. Interpretation of the data is aided by comparisons to calculated spectra. These compounds have unique spectral signatures that can be used to identify unknown samples.

  15. X-ray absorption fine structure study of heavily P doped (111) and (001) diamond

    NASA Astrophysics Data System (ADS)

    Shikata, Shinichi; Yamaguchi, Koji; Fujiwara, Akihiko; Tamenori, Yusuke; Yahiro, Jumpei; Kunisu, Masahiro; Yamada, Takatoshi

    2017-02-01

    X-ray absorption fine structure (XANES) measurements were carried out for P doped (111) and (001) diamond films, and the results were compared with those from simulations. For the (111) spectrum, the main strong peak observed at 2147.0 eV and three broad peaks centered at 2150 eV, 2157 eV, and 2165 eV were observed. The assignment with the estimation by the simulation of the XANES peaks showed the interstitial sites additional to the substitutional site. The Extended X-ray Absorption Fine Structure (EXAFS) result of the P doped (111) diamond showed that the first and second neighboring peaks are observed at 1.21 A and 2.0 A, respectively. The assignment with the estimation by the simulation of the EXAFS peaks also showed the interstitial sites additional to the substitutional site. Overall, P in diamonds presumably has dopant sites in both the substitutional and interstitial sites.

  16. X-ray absorption spectroscopic studies of mononuclear non-heme iron enzymes

    SciTech Connect

    Westre, Tami E.

    1996-01-01

    Fe-K-edge X-ray absorption spectroscopy (XAS) has been used to investigate the electronic and geometric structure of the iron active site in non-heme iron enzymes. A new theoretical extended X-ray absorption fine structure (EXAFS) analysis approach, called GNXAS, has been tested on data for iron model complexes to evaluate the utility and reliability of this new technique, especially with respect to the effects of multiple-scattering. In addition, a detailed analysis of the 1s→3d pre-edge feature has been developed as a tool for investigating the oxidation state, spin state, and geometry of iron sites. Edge and EXAFS analyses have then been applied to the study of non-heme iron enzyme active sites.

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

    PubMed

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

    2014-10-01

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

  18. Single shot near edge x-ray absorption fine structure spectroscopy in the laboratory

    SciTech Connect

    Mantouvalou, I. Witte, K.; Martyanov, W.; Jonas, A.; Grötzsch, D.; Kanngießer, B.; Streeck, C.; Löchel, H.; Rudolph, I.; Erko, A.; Stiel, H.

    2016-05-16

    With the help of adapted off-axis reflection zone plates, near edge X-ray absorption fine structure spectra at the C and N K-absorption edge have been recorded using a single 1.2 ns long soft X-ray pulse. The transmission experiments were performed with a laser-produced plasma source in the laboratory rendering time resolved measurements feasible independent on large scale facilities. A resolving power of E/ΔE ∼ 950 at the respective edges could be demonstrated. A comparison of single shot spectra with those collected with longer measuring time proves that all features of the used reference samples (silicon nitrate and polyimide) can be resolved in 1.2 ns. Hence, investigations of radiation sensitive biological specimen become possible due to the high efficiency of the optical elements enabling low dose experiments.

  19. Multiple-electron excitation in X-ray absorption: a simple generic model.

    PubMed

    Roy, M; Lindsay, J D; Louch, S; Gurman, S J

    2001-07-01

    The probability of multiple-electron excitation in X-ray absorption is calculated using a simple generic model. The model permits calculations to be made for all atoms with little input data or computing effort. The high-energy limit of this probability, which gives the usual EXAFS amplitude reduction factor, is calculated in the 'sudden approximation' using Slater orbitals. Good agreement with experiment is found. The energy dependence of this probability is also calculated using a simple model form of perturbing potential and found to agree well with experiment for rare gas atoms. The effect on the X-ray absorption coefficient of including multiple-electron excitations is also determined and is found to be small, again in agreement with observation.

  20. Solution spectroelectrochemical cell for in situ X-ray absorption fine structure

    SciTech Connect

    Antonio, M.R.; Soderholm, L.; Song, I.

    1995-06-12

    A purpose-built spectroelectrochemical cell for in situ fluorescence XAFS (X-ray Absorption Fine Structure) measurements of bulk solution species during constant-potential electrolysis is described. The cell performance was demonstrated by the collection of europium L{sub 3}-edge XANES (X-ray Absorption Near Edge Structure) throughout the course of electrolysis of an aqueous solution of EuCl{sub 3}{center_dot}6H{sub 2}O in 1 M H{sub 2}SO{sub 4}. The europium L{sub 3}-edge resonances reported here for the Eu{sup III} and Eu{sup II} ions demonstrate that their 2p{sub 3/2} {yields} 5d electronic transition probabilities are not the same.

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

    SciTech Connect

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

    2014-10-15

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

  2. The nature of arsenic in uranium mill tailings by X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Cutler, J. N.; Chen, N.; Jiang, D. T.; Demopoulos, G. P.; Jia, Y.; Rowson, J. W.

    2003-05-01

    In order to understand the evolving world of environmental issues, the ability to characterize and predict the stability and bioavailability of heavy métal contaminants in mine waste is becoming increasingly more important. X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopies were used to characterize a series of synthetic and natural samples associated with mine tailings processing. XANES was shown to be excellent as a tool to rapidly differentiate oxidation states of arsenic within the samples. The EXAFS spectra provided information on the mineralogy of the precipitated raffinate and tailings and showed that these samples are composed of a mixture of amorphous ferric arsenates, adsorbed arsenates and a mixture of other poorly ordered arsenates.

  3. Randic and Schultz molecular topological indices and their correlation with some X-ray absorption parameters

    NASA Astrophysics Data System (ADS)

    Khatri, Sunil; Kekre, Pravin A.; Mishra, Ashutosh

    2016-10-01

    The properties of a molecular system are affected by the topology of molecule. Therefore many studies have been made where the various physic-chemical properties are correlated with the topological indices. These studies have shown a very good correlation demonstrating the utility of the graph theoretical approach. It is, therefore, very natural to expect that the various physical properties obtained by the X-ray absorption spectra may also show correlation with the topological indices. Some complexes were used to establish correlation between topological indices and some X-ray absorption parameters like chemical shift. The chemical shift is on the higher energy side of the metal edge in these complexes. The result obtained in these studies shows that the topological indices of organic molecule acting as a legands can be used for estimating edge shift theoretically.

  4. Analytical description of partially coherent propagation and absorption losses in x-ray planar waveguides.

    PubMed

    Tsanaktsidis, K J; Paganin, D M; Pelliccia, D

    2013-06-01

    We present an analytical approach to describe field propagation along a planar x-ray waveguide (WG) in the presence of absorption losses. The method utilizes the complete expression for the complex index of refraction in solving the Helmholtz equation describing the guided modes. In this way, the propagation modes for the WG are no longer imposed to be standing waves and the energy flow from the core to the cladding, a consequence of the absorption in the cladding, can be calculated. In addition, the method accurately describes the field coupling between a plane wave and the WG, reproducing the self-imaging phenomenon. The case of partially coherent illumination has also been calculated for a realistic laboratory x-ray source.

  5. Polarized x-ray-absorption spectroscopy of the uranyl ion: Comparison of experiment and theory

    SciTech Connect

    Hudson, E.A.; Allen, P.G.; Terminello, L.J.; Denecke, M.A.; Reich, T.

    1996-07-01

    The x-ray linear dichroism of the uranyl ion (UO{sub 2}{sup 2+}) in uranium {ital L}{sub 3}-edge extended x-ray-absorption fine structure (EXAFS), and {ital L}{sub 1}- and {ital L}{sub 3}-edge x-ray-absorption near-edge structure (XANES), has been investigated both by experiment and theory. A striking polarization dependence is observed in the experimental XANES and EXAFS for an oriented single crystal of uranyl acetate dihydrate [UO{sub 2}(CH{sub 3}CO{sub 2}){sub 2}{center_dot}2H{sub 2}O], with the x-ray polarization vector aligned either parallel or perpendicular to the bond axis of the linear uranyl cation (O-U-O). Single-crystal results are compared to experimental spectra for a polycrystalline uranyl acetate sample and to calculations using the {ital ab} {ital initio} multiple-scattering (MS) code FEFF 6. Theoretical XANES spectra for uranyl fluoride (UO{sub 2}F{sub 2}) reproduce all the features of the measured uranyl acetate spectra. By identifying scattering paths which contribute to individual features in the calculated spectrum, a detailed understanding of the {ital L}{sub 1}-edge XANES is obtained. MS paths within the uranyl cation have a notable influence upon the XANES. The measured {ital L}{sub 3}-edge EXAFS is also influenced by MS, especially when the x-ray polarization is parallel to the uranyl species. These MS contributions are extracted from the total EXAFS and compared to calculations. The best agreement with the isolated MS signal is obtained by using nonoverlapped muffin-tin spheres in the FEFF 6 calculation. This contrasts the {ital L}{sub 1}-edge XANES calculations, in which overlapping was required for the best agreement with experiment. {copyright} {ital 1996 The American Physical Society.}

  6. Electronic structure transformation in small bare Au clusters as seen by x-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Andersson, T.; Zhang, C.; Björneholm, O.; Mikkelä, M.-H.; Jänkälä, K.; Anin, D.; Urpelainen, S.; Huttula, M.; Tchaplyguine, M.

    2017-01-01

    Free bare gold clusters in the size range from few tens to few hundred atoms (≤1 nm dimensions) have been produced in a beam, and the size-dependent development of their full valence band including the 5d and 6s parts has been mapped ‘on the fly’ by synchrotron-based photoelectron spectroscopy. The Au 4f core level has been also probed, and the cluster-specific Au 4f ionization energies have been used to estimate the cluster size. The recorded in the present work valence spectra of the small clusters are compared with the spectra of the large clusters ( N ∼ 103) created by us using a magnetron-based gas aggregation source. The comparison shows a substantially narrower 5d valence band and the decrease in its splitting for gold clusters in the size range of few hundred atoms and below. Our DFT calculations involving the pseudopotential method show that the 5d band width of the ground state increases with the cluster size and by the size N = 20 becomes comparable with the experimental width of the valence photoelectron spectrum. Similar to the earlier observations on supported clusters we interpret our experimental and theoretical results as due to the undercoordination of a large fraction of atoms in the clusters with N ∼ 102 and below. The consequences of such electronic structure of small gold clusters are discussed in connection with their specific physical and chemical properties related to nanoplasmonics and nanocatalysis.

  7. Excited state molecular structure determination in disordered media using laser pump/x-ray probe time-domain x-ray absorption spectroscopy.

    SciTech Connect

    Chen, L. X.; Chemistry

    2003-01-01

    Advances in X-ray technologies provide opportunities for solving structures of photoexcited state molecules with short lifetimes. Using X-ray pulses from a modern synchrotron source, the structure of a metal-to-ligand-charge-transfer (MLCT) excited state of CuI(dmp)2+ (dmp 1/4 2,9-dimethyl-1,10-phenanthroline) was investigated by laser pump/X-ray probe X-ray absorption fine structure (LPXP-XAFS) in fluid solution at room temperature on a nanosecond time scale. The experimental requirements for such pump-probe XAFS are described in terms of technical challenges: (1) conversion of optimal excited state population, (2) synchronization of the pump laser pulse and probe Xray pulse, and (3) timing of the detection. Using a laser pump pulse for the photoexcitation, a photoluminescent MLCT excited state of CuI(dmp)2(BArF), (dmp 1/4 2,9-dimethyl-1,10-phenanthroline), BArF 1/4 tetrakis(3,5-bis(trifluoromethylphenyl)borate) with a lifetime of 98{+-}5 ns was created. Probing the structure of this state at its optimal concentration using an X-ray pulse cluster with a total duration of 14.2 ns revealed that (1) a Cu{sup II} center was generated via a whole charge transfer; (2) the copper in the MLCT state bound an additional ligand to form a penta-coordinate complex with a likely trigonal bipyramidal geometry; and (3) the average Cu-N bond length increases in the MLCT excited state by 0.07 . In contrast to previously reported literature, the photoluminescence of this pentacoordinate MLCT state was not quenched upon ligation with the fifth ligand. On the basis of experimental results, we propose that the absorptive and emissive states have distinct geometries. The results represent X-ray characterization of a molecular excited state in fluid solution on a nanosecond time scale.

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

    SciTech Connect

    Paesler, M.; Sayers, D.

    1988-12-01

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

  9. X-ray absorption spectroscopy beyond the core-hole lifetime

    SciTech Connect

    Haemaelaeinen, K.; Hastings, J.B.; Siddons, D.P.; Berman, L.

    1992-01-01

    A new technique to overcome the core-hole lifetime broadening in x-ray absorption spectroscopy is presented. It utilizes a high resolution fluorescence spectrometer which can be used to analyze the fluorescence photon energy with better resolution than the natural lifetime width. Furthermore, the high resolution spectrometer can also be used to select the final state in the fluorescence process which can offer spin selectivity even without long range magnetic order in the sample.

  10. X-ray absorption spectroscopy beyond the core-hole lifetime

    SciTech Connect

    Haemaelaeinen, K.; Hastings, J.B.; Siddons, D.P.; Berman, L.

    1992-10-01

    A new technique to overcome the core-hole lifetime broadening in x-ray absorption spectroscopy is presented. It utilizes a high resolution fluorescence spectrometer which can be used to analyze the fluorescence photon energy with better resolution than the natural lifetime width. Furthermore, the high resolution spectrometer can also be used to select the final state in the fluorescence process which can offer spin selectivity even without long range magnetic order in the sample.

  11. Characterizing trace metal impurities in optical waveguide materials using x-ray absorption

    SciTech Connect

    Citrin, P.H.; Northrup, P.A.; Atkins, R.M.; Niu, L.; Marcus, M.A.; Jacobson, D.C.; Glodis, P.F.

    1998-12-31

    X-ray absorption measurements are described for identifying metal impurities in silica preforms, the rod-like starting materials from which hair-like optical fibers are drawn. The results demonstrate the effectiveness of this approach as a non-destructive, quantitative, element-selective, position-sensitive, and chemical-state-specific means for characterizing transition metals in the concentration regime of parts per billion.

  12. X-ray absorption study of ceria nanorods promoting the disproportionation of hydrogen peroxide.

    PubMed

    Wu, Tai-Sing; Zhou, Yunyun; Sabirianov, Renat F; Mei, Wai-Ning; Soo, Yun-Liang; Cheung, Chin Li

    2016-04-11

    A quasi in situ X-ray absorption study demonstrated that the disproportionation of hydrogen peroxide (H2O2) promoted by ceria nanorods was associated with a reversible Ce(3+)/Ce(4+) reaction and structural transformations in ceria. The direction of this reversible reaction was postulated to depend on the H2O2 concentration and the fraction of Ce(3+) species in ceria nanorods.

  13. Orientation and electronic structure of ion exchanged dye molecules on mica: An X-ray absorption study

    SciTech Connect

    Fischer, D.; Caseri, W.R.; Haehner, G.

    1998-02-15

    Dye molecules are frequently used to determine the specific surface area and the ion exchange capacity of high-surface-area materials such as mica. The organic molecules are often considered to be planar and to adsorb in a flat orientation. In the present study the authors have investigated the orientation and electronic structure of crystal violet (CV) and malachite green (MG) on muscovite mica, prepared by immersing the substrates for extended periods into aqueous solutions of the dyes of various concentrations. The K{sup +} ions of the mica surface are replaced by the organic cations via ion exchange. X-ray photoelectron spectroscopy reveals that only one amino group is involved in the interaction of CV and MG with the muscovite surface, i.e., certain resonance structures are abolished upon adsorption. With near edge X-ray absorption fine structure spectroscopy a significant tilt angle with respect to the surface was found for all investigated species. A flat orientation, as has often been proposed before, can effectively be ruled out. Hence, results are in marked contrast to the often quoted orientation and suggest that the specific surface areas determined with dyes may, in general, be overestimated.

  14. On the relation between X-ray absorption and optical extinction in AGN

    NASA Astrophysics Data System (ADS)

    Ordovás-Pascual, I.; Mateos, S.; Carrera, F. J.; Wiersema, K.; Caccianiga, A.; Della Ceca, R.; Severgnini, P.; Moretti, A.; Ballo, L.

    2017-03-01

    According to the Unified Model of Active Galactic Nuclei (AGN), an X-ray unabsorbed AGN should appear as unobscured in the optical band (the so called type-1 AGN). However, there is an important fraction (10-30%) of AGN whose optical and X-ray classifications do not match. To provide insight into the origin of such apparent discrepancies, we have conducted two types of analysis: 1) a detailed study of the UV-to-near-IR emission of two X-ray low absorbed AGN with high optical extinction drawn from the Bright Ultra-Hard XMM-Newton Survey (BUXS); 2) a statistical analysis of the optical obscuration and X-ray absorption properties of 159 type-1 AGN drawn from BUXS to determine the distribution of dust-to-gas ratios in AGN over a broad range of luminosities and redshifts. We have determined the impact of contamination from the AGN hosts in their optical classification (detection or lack of detection of rest-frame UV-optical broad emission lines). This is an on-going project, but our preliminary results, reported below, are very promising.

  15. Toward picosecond time-resolved X-ray absorption studies of interfacial photochemistry

    NASA Astrophysics Data System (ADS)

    Gessner, Oliver; Mahl, Johannes; Neppl, Stefan

    2016-05-01

    We report on the progress toward developing a novel picosecond time-resolved transient X-ray absorption spectroscopy (TRXAS) capability for time-domain studies of interfacial photochemistry. The technique is based on the combination of a high repetition rate picosecond laser system with a time-resolved X-ray fluorescent yield setup that may be used for the study of radiation sensitive materials and X-ray spectroscopy compatible photoelectrochemical (PEC) cells. The mobile system is currently deployed at the Advanced Light Source (ALS) and may be used in all operating modes (two-bunch and multi-bunch) of the synchrotron. The use of a time-stamping technique enables the simultaneous recording of TRXAS spectra with delays between the exciting laser pulses and the probing X-ray pulses spanning picosecond to nanosecond temporal scales. First results are discussed that demonstrate the viability of the method to study photoinduced dynamics in transition metal-oxide semiconductor (SC) samples under high vacuum conditions and at SC-liquid electrolyte interfaces during photoelectrochemical water splitting. Opportunities and challenges are outlined to capture crucial short-lived intermediates of photochemical processes with the technique. This work was supported by the Department of Energy Office of Science Early Career Research Program.

  16. Chemical Modification of Graphene Oxide by Nitrogenation: An X-ray Absorption and Emission Spectroscopy Study

    NASA Astrophysics Data System (ADS)

    Chuang, Cheng-Hao; Ray, Sekhar C.; Mazumder, Debarati; Sharma, Surbhi; Ganguly, Abhijit; Papakonstantinou, Pagona; Chiou, Jau-Wern; Tsai, Huang-Ming; Shiu, Hung-Wei; Chen, Chia-Hao; Lin, Hong-Ji; Guo, Jinghua; Pong, Way-Faung

    2017-02-01

    Nitrogen-doped graphene oxides (GO:Nx) were synthesized by a partial reduction of graphene oxide (GO) using urea [CO(NH2)2]. Their electronic/bonding structures were investigated using X-ray absorption near-edge structure (XANES), valence-band photoemission spectroscopy (VB-PES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). During GO:Nx synthesis, different nitrogen-bonding species, such as pyrrolic/graphitic-nitrogen, were formed by replacing of oxygen-containing functional groups. At lower N-content (2.7 at%), pyrrolic-N, owing to surface and subsurface diffusion of C, N and NH is deduced from various X-ray spectroscopies. In contrast, at higher N-content (5.0 at%) graphitic nitrogen was formed in which each N-atom trigonally bonds to three distinct sp2-hybridized carbons with substitution of the N-atoms for C atoms in the graphite layer. Upon nitrogen substitution, the total density of state close to Fermi level is increased to raise the valence-band maximum, as revealed by VB-PES spectra, indicating an electron donation from nitrogen, molecular bonding C/N/O coordination or/and lattice structure reorganization in GO:Nx. The well-ordered chemical environments induced by nitrogen dopant are revealed by XANES and RIXS measurements.

  17. Chemical Modification of Graphene Oxide by Nitrogenation: An X-ray Absorption and Emission Spectroscopy Study

    PubMed Central

    Chuang, Cheng-Hao; Ray, Sekhar C.; Mazumder, Debarati; Sharma, Surbhi; Ganguly, Abhijit; Papakonstantinou, Pagona; Chiou, Jau-Wern; Tsai, Huang-Ming; Shiu, Hung-Wei; Chen, Chia-Hao; Lin, Hong-Ji; Guo, Jinghua; Pong, Way-Faung

    2017-01-01

    Nitrogen-doped graphene oxides (GO:Nx) were synthesized by a partial reduction of graphene oxide (GO) using urea [CO(NH2)2]. Their electronic/bonding structures were investigated using X-ray absorption near-edge structure (XANES), valence-band photoemission spectroscopy (VB-PES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). During GO:Nx synthesis, different nitrogen-bonding species, such as pyrrolic/graphitic-nitrogen, were formed by replacing of oxygen-containing functional groups. At lower N-content (2.7 at%), pyrrolic-N, owing to surface and subsurface diffusion of C, N and NH is deduced from various X-ray spectroscopies. In contrast, at higher N-content (5.0 at%) graphitic nitrogen was formed in which each N-atom trigonally bonds to three distinct sp2-hybridized carbons with substitution of the N-atoms for C atoms in the graphite layer. Upon nitrogen substitution, the total density of state close to Fermi level is increased to raise the valence-band maximum, as revealed by VB-PES spectra, indicating an electron donation from nitrogen, molecular bonding C/N/O coordination or/and lattice structure reorganization in GO:Nx. The well-ordered chemical environments induced by nitrogen dopant are revealed by XANES and RIXS measurements. PMID:28186190

  18. Chemical Modification of Graphene Oxide by Nitrogenation: An X-ray Absorption and Emission Spectroscopy Study.

    PubMed

    Chuang, Cheng-Hao; Ray, Sekhar C; Mazumder, Debarati; Sharma, Surbhi; Ganguly, Abhijit; Papakonstantinou, Pagona; Chiou, Jau-Wern; Tsai, Huang-Ming; Shiu, Hung-Wei; Chen, Chia-Hao; Lin, Hong-Ji; Guo, Jinghua; Pong, Way-Faung

    2017-02-10

    Nitrogen-doped graphene oxides (GO:Nx) were synthesized by a partial reduction of graphene oxide (GO) using urea [CO(NH2)2]. Their electronic/bonding structures were investigated using X-ray absorption near-edge structure (XANES), valence-band photoemission spectroscopy (VB-PES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). During GO:Nx synthesis, different nitrogen-bonding species, such as pyrrolic/graphitic-nitrogen, were formed by replacing of oxygen-containing functional groups. At lower N-content (2.7 at%), pyrrolic-N, owing to surface and subsurface diffusion of C, N and NH is deduced from various X-ray spectroscopies. In contrast, at higher N-content (5.0 at%) graphitic nitrogen was formed in which each N-atom trigonally bonds to three distinct sp(2)-hybridized carbons with substitution of the N-atoms for C atoms in the graphite layer. Upon nitrogen substitution, the total density of state close to Fermi level is increased to raise the valence-band maximum, as revealed by VB-PES spectra, indicating an electron donation from nitrogen, molecular bonding C/N/O coordination or/and lattice structure reorganization in GO:Nx. The well-ordered chemical environments induced by nitrogen dopant are revealed by XANES and RIXS measurements.

  19. Chemical Modification of Graphene Oxide by Nitrogenation: An X-ray Absorption and Emission Spectroscopy Study

    DOE PAGES

    Chuang, Cheng-Hao; Ray, Sekhar C.; Mazumder, Debarati; ...

    2017-02-10

    Nitrogen-doped graphene oxides (GO:N x) were synthesized by a partial reduction of graphene oxide (GO) using urea [CO(NH 2) 2 ]. Their electronic/bonding structures were investigated using X-ray absorption near-edge structure (XANES), valence-band photoemission spectroscopy (VB-PES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). During GO:N x synthesis, different nitrogen-bonding species, such as pyrrolic/graphitic-nitrogen, were formed by replacing of oxygen-containing functional groups. At lower N-content (2.7 at%), pyrrolic-N, owing to surface and subsurface diffusion of C, N and NH is deduced from various X-ray spectroscopies. In contrast, at higher N-content (5.0 at%) graphitic nitrogen was formed in whichmore » each N-atom trigonally bonds to three distinct sp 2 -hybridized carbons with substitution of the N-atoms for C atoms in the graphite layer. Upon nitrogen substitution, the total density of state close to Fermi level is increased to raise the valence-band maximum, as revealed by VB-PES spectra, indicating an electron donation from nitrogen, molecular bonding C/N/O coordination or/and lattice structure reorganization in GO:N x . The well-ordered chemical environments induced by nitrogen dopant are revealed by XANES and RIXS measurements.« less

  20. Synchrotron X-ray Powder Diffraction and Absorption Spectroscopy in Pulsed Magnetic Fields with Milliseconds Duration

    NASA Astrophysics Data System (ADS)

    Vanacken, J.; Detlefs, C.; Mathon, O.; Frings, P.; Duc, F.; Lorenzo, J. E.; Nardone, M.; Billette, J.; Zitouni, A.; Dominguez, M.-C.; Herczeg, J.; Bras, W.; Moshchalkov, V. V.; Rikken, G.

    2007-03-01

    X-ray Powder Diffraction and X-ray Absorption Spectroscopy experiments (WAS) and X-ray magnetic circular dichroism (XMCD) experiments were carried out at the ESRF DUBBLE beam line (BM26) and at the energy dispersive beam line (ID24), respectively. A mobile pulse generator, developed at the LNCMP, delivered 110kJ to the load coil, which was sufficient to generate peak fields of 30T with a rise time of about 5 ms. A liquid He flow cryostat allowed us to vary the sample temperature accurately between 4.2K and 300K. Powder diffraction patterns of TbVO4 were recorded in a broad temperature range using 21 keV monochromatic X-rays and using an on-line image plate detector. We observed the suppression of the Jahn-Teller structural distortion in TbVO4 due to the high magnetic pulsed field. XAS spectra could be measured and finite XMCD signals, directly proportional to the magnetic moment on the Gd absorber atom, were measured in thin Gd foils. Thanks to its element and orbital selectivity, XMCD proofs to be very useful in probing the magnetic properties and due to the strong brilliance of the synchrotron beam, the signals can be measured even in the ms range.