WorldWideScience

Sample records for structure x-ray spectra

  1. Invisible structures in the X-ray absorption spectra of actinides

    NARCIS (Netherlands)

    Kvashnina, Kristina O.; De Groot, Frank M F

    The X-ray absorption spectra of actinides are discussed with an emphasis on the fundamental effects that influence their spectral shape, including atomic multiplet theory, charge transfer theory and crystal field theory. Many actinide spectra consist of a single peak and it is shown that the use of

  2. Electronic Structures of Purple Bronze KMo6O17 Studied by X-Ray Photoemission Spectra

    Science.gov (United States)

    Qin, Xiaokui; Wei, Junyin; Shi, Jing; Tian, Mingliang; Chen, Hong; Tian, Decheng

    X-ray photoemission spectroscopy study has been performed for the purple bronze KMo6O17. The structures of conduction band and valence band are analogous to the results of ultraviolet photoemission spectra and are also consistent with the model of Travaglini et al., but the gap between conduction and valence band is insignificant. The shape of asymmetric and broadening line of O-1s is due to unresolved contributions from the many inequivalent oxygen sites in this crystal structure. Mo 3d core-level spectrum reveals that there are two kinds of valence states of Molybdenum (Mo+5 and Mo+6). The calculated average valence state is about +5.6, which is consistent with the expectation value from the composition of this material. The tail of Mo-3d spectrum toward higher binding energy is the consequence of the excitation of electron-hole pairs with singularity index of 0.21.

  3. X-ray photoelectron spectra structure and chemical bonding in AmO2

    Directory of Open Access Journals (Sweden)

    Teterin Yury A.

    2015-01-01

    Full Text Available Quantitative analysis was done of the X-ray photoelectron spectra structure in the binding energy range of 0 eV to ~35 eV for americium dioxide (AmO2 valence electrons. The binding energies and structure of the core electronic shells (~35 eV-1250 eV, as well as the relativistic discrete variation calculation results for the Am63O216 and AmO8 (D4h cluster reflecting Am close environment in AmO2 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 binding energy and the inner (~15 eV-~35 eV binding energy valence molecular orbitals. The filled Am 5f electronic states were shown to form in the AmO2 valence band. The Am 6p electrons participate in formation of both the inner and the outer valence molecular orbitals (bands. The filled Am 6p3/2 and the O 2s electronic shells were found to make the largest contributions to the formation of the inner valence molecular orbitals. Contributions of electrons from different molecular orbitals to the chemical bond in the AmO8 cluster were evaluated. Composition and sequence order of molecular orbitals in the binding energy range 0-~35 eV in AmO2 were established. The experimental and theoretical data allowed a quantitative scheme of molecular orbitals for AmO2, which is fundamental for both understanding the chemical bond nature in americium dioxide and the interpretation of other X-ray spectra of AmO2.

  4. Analysis of fine structure of X-ray spectra from laser-irradiated gold dot

    International Nuclear Information System (INIS)

    Yang Guohong; Zhang Jiyan; Zhang Baohan; Zhou Yuqing; Li Jun

    2000-01-01

    The X-ray emission spectra from highly stripped plasma of gold has been observed by focusing a Nd-glass frequency tripled laser beam onto the surface of the gold dot at the XINGGUANG II laser facilities. The spectra of gold ions in the range of 0.0003 nm-0.0004 nm was recorded using the plate PET (2d = 0.8742 nm) crystal spectrometer. The code of average energy of relativistic sub-arrays was built on the basis of the code MCDF (Multi-Configuration-Dirac-Fock). Using the spin-orbit-split-arrays (SOSA) formalism, mean wavelengths and full widths at half height of isolated peaks of sub-arrays of lower charged gold ions, isoelectronic with Cu, Zn, Ga and Ge, was calculated. Twenty-six lines are interpreted, they pertain mainly to transitions of 3d-nf (n = 5,6,7) of gold ions from Ni-like to As-like. These results of experiment and calculation have important application in plasma diagnostics and examination of high Z elemental atomic structure calculation

  5. Theoretically predicted soft x-ray emission and absorption spectra of graphitic-structured BC2N

    Science.gov (United States)

    Muramatsu, Yasuji

    Theoretical B K, C K and N K x-ray emission/absorption spectra of three possible graphitic-structured BC2N clusters are predicted based on the B2p-, C2p-, and N2p- density-of-states (DOS) calculated by discrete variational (DV)-X[alpha] molecular orbital calculations. Several prominent differences in DOS spectral features among BC2Ns, h-BN, and graphite are confirmed from comparison of calculated B2p-, C2p-, and N2p-DOS spectra. These variations in the spectra allow BC2N structures to be positively identified by high-resolution x-ray emission/absorption spectroscopy in the B K, C K, and N K regions.

  6. The effect of SNR structure on non-equilibrium X-ray spectra

    International Nuclear Information System (INIS)

    Hamilton, A.J.S.; Sarazin, C.L.

    1983-01-01

    A technique is presented for characterizing the ionization structure and consequent thermal X-ray emission of a SNR when non-equilibrium ionization effects are important. The technique allows different theoretical SNR models to be compared and contrasted rapidly in advance of detailed numerical computations. In particular it is shown that the spectrum of a Sedov remnant can probably be applied satisfactorily in a variety of SNR structures, including the reverse shock model advocated by Chevalier (1982) for Type I SN, the isothermal similarity solution of Solinger, Rappaport and Buff (1975), and various inhomogenous or 'messy' structures. (Auth.)

  7. Influence of changes in the valence electronic configuration on the structure of L-X-ray spectra of molybdenum

    International Nuclear Information System (INIS)

    Polasik, M; Koziol, K; Slabkowska, K; Czarnota, M; Pajek, M

    2009-01-01

    Extensive multiconfiguration Dirac-Fock (MCDF) calculations with the inclusion of the transverse (Breit) interaction and QED corrections have been carried out on molybdenum to explain the dependence of the structure of Lα 1,2 and Lβ 1 lines on the changes in configurations of the valence electrons belonging to two different configuration types: three open-shell 4d 6-r 5s r (r = 2,1,0) configurations and one closed-shell 4d 4 3/2 5s 2 configuration. It has been found that the MCDF predictions for open-shell valence configurations (4d 4 5s 2 , 4d 5 5s 1 , 4d 6 5s 0 ) much better reproduce observed structure of Lα 1,2 lines in X-ray spectra of molybdenum than closed-shell 4d 4 3/2 5s 2 valence configuration. The influence of changes in the valence electronic configuration on the structure of L-X-ray spectra of molybdenum is noticeable. Moreover, the observation of the shapes of L-X-ray spectra seems to be very good method to investigate the changes of the valence electronic configuration caused by the chemical environment.

  8. X-ray photoelectron spectra structure of actinide compounds stipulated by electrons of the inner valence molecular orbitals (IVMO)

    International Nuclear Information System (INIS)

    Teterin, Yu. A.; Ivanov, K. E.

    1997-01-01

    Development of precise X-ray photoelectron spectroscopy using X-ray radiation hν< 1.5 KeV allowed to carry out immediate investigations of fine spectra structure of both weakly bond and deep electrons. Based on the experiments and the obtained results it may be concluded: 1. Under favourable conditions the inner valence molecular orbitals (IVMO) may form in all actinide compounds. 2. The XPS spectra fine structure stipulated by IVMO electrons allows to judge upon the degree of participation of the filled AO electrons in the chemical bond, on the structure o considered atom close environment and the bond lengths in compounds. For amorphous compounds the obtaining of such data based on X-ray structure analysis is restricted. 3. The summary contribution of IVMO electrons to the absolute value of the chemical bonding is comparable with the corresponding value of OMO electrons contribution to the atomic bonding. This fact is very important and new in chemistry. (author)

  9. X-ray spectra and electronic structure of the Ca3Ga2Ge3О12 compound

    Science.gov (United States)

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

    2017-09-01

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

  10. Structure of the X-ray photoelectron spectra of fluorides and oxides of lanthanides connected with the dynamic effect

    International Nuclear Information System (INIS)

    Teterin, Yu.A.; Teterin, A.Yu.; Lebedev, A.M.; Utkin, I.O.; Nikitin, A.S.

    1998-01-01

    Impact of dynamic effect on the fine structure of the X-ray electron spectra of the lanthanide oxides and fluorides is considered. Significant complication of the Ln4p-electrons occurs due to interaction of configurations of the basic single-hole and additional two-hole finite states of the 4p 5 4d 10 4f n ↔ 4p 6 4d 8 4f n+1 type. Impact of the atoms nature of the nearest surrounding of the lanthanides ions on the parameters of such fine structure is evaluated [ru

  11. Theory of X-ray absorption and emission spectra

    International Nuclear Information System (INIS)

    Mukoyama, Takeshi

    2004-01-01

    Theoretical studies on X-ray absorption and emission spectroscopy are discussed. Simple expressions for X-ray emission rate and X-ray absorption cross section are presented in the dipole approximation. Various atomic models to obtain realistic wave functions and theoretical calculations for X-ray absorption cross sections and X-ray emission rates are described. In the case of molecules and solids, molecular orbital methods for electronic structures and molecular wave functions are discussed. The emphasis is on the procedures to obtain the excited-state and continuum wave functions for molecules and to calculate the multi-center dipole matrix elements. The examples of the calculated X-ray absorption and emission spectra are shown and compared with the experimental results

  12. Soft x-ray absorption and emission spectra and the electronic structure of some exotic materials

    International Nuclear Information System (INIS)

    Ederer, D.L.; Canfield, L.R.; Callcott, T.A.; Tsang, K.L.; Zhang, C.H.; Arakawa, E.T.

    1988-01-01

    The technique of soft x-ray fluorescence spectroscopy (SXE) is complimentary to that of photoemission spectroscopy (PES). SXE probes the local partial density of states (PDOS), selects dipole allowed symmetries, and is not necessarily surface sensitive. PES on the other hand, averages over the DOS and can be used to measure the dispersion of the energy bands. PES is also very surface sensitive. We present measurements on the high T/sub c/ superconductors, the quasicrystalline phase of AlMn, and the LiAl intermetallic alloy. These measurements provide insight for theoretical modeling. In the case of the high T/sub c/ compound and the intermetallic compound the measurements are in good agreement with the theory. However, for the quasicrystals the measurements provide new insights to challenge theory. 13 refs., 3 figs

  13. Secondary electronic processes and the structure of X-ray photoelectron spectra of lanthanides in oxygen-containing compounds

    International Nuclear Information System (INIS)

    Teterin, Yu.A.; Teterin, A.Yu.; Lebedev, A.M.; Ivanov, K.E.

    2004-01-01

    X-ray photoelectron spectra of lanthanide compounds in the binding energy range 0-1250 eV beside the spin-orbitally split doublets exhibit fine structure. In particular, in the low-energy spectral range 0-50 eV such structure appears most likely due to the formation of the inner (IVMO) and outer (OVMO) valence molecular orbitals. The many-body perturbation shows up in the spectra of all the studied electronic shells but with different probabilities, while the multiplet splitting and dynamic effect in the spectra of just some inner shells. The present work studies the X-ray photoelectron spectral structure of lanthanide (La-Lu except for Pm) oxides and orthoniobates due to the secondary electronic processes accompanying the photoemission from the inner shells: many-body perturbation and dynamic effect. As a result, for example, the relative intensity of the line due to the many-body perturbation (shake-up process) with ΔE sat ∼4 eV for LaNbO 4 was found to decrease with decreasing of the binding energy of the inner electrons from 0.72 (E b for La 3d 5/2 =834.8 eV) to 0.28 (E b for La 4d 5/2 =102.9 eV). The full-width at half-maximum of the Ln 3d 5/2 line of lanthanide oxides and orthoniobates decreases as the atomic number Z of lanthanide grows in the range 58≤Z≤67 to the middle of the lanthanide row, and then increases. This agrees with the fact that for the beginning of the lanthanide row the Ln 3d 5/2 photoemission is accompanied by the shake-up process, while for the second half of the row--by the shake-down. It is important to note that it is connected with the Ln 4f binding energy change relative to the OVMO in compounds. The present work also confirms experimentally that the dynamic effect due to the gigantic Coster-Kronig transitions observed in the Ln 4p spectra takes place within the inner Ln 4p, 4d and outer Ln 4f shells with formation of the additional two-hole final state Ln 4p 6 4d 8 4f n+1 . The influence of the chemical environment on the Ln 4

  14. X-ray photoelectron spectra and electronic structure of quasi-one-dimensional SbSeI crystals

    Directory of Open Access Journals (Sweden)

    J.Grigas

    2007-01-01

    Full Text Available The paper presents the X-ray photoelectron spectra (XPS of the valence band (VB and of the principal core levels from the (110 and (001 crystal surfaces for the quasi-one-dimensional high permittivity SbSeI single crystal isostructural to ferroelectric SbSI. The XPS were measured with monochromatized Al Ka radiation in the energy range of 0-1400 eV at room temperature. The VB is located from 1.6 to 20 eV below the Fermi level. Experimental energies of the VB and core levels are compared with the results of theoretical ab initio calculations of the molecular model of the SbSeI crystal. The electronic structure of the VB is revealed. Shifts in the core-level binding energies of surface atoms relative to bulk ones, which show a dependency on surface crystallography, have been observed. The chemical shifts of the core levels (CL in the SbSeI crystal for the Sb, I and Se states are obtained.

  15. Soft x-ray absorption spectra of ilmenite family.

    Science.gov (United States)

    Agui, A; Mizumaki, M; Saitoh, Y; Matsushita, T; Nakatani, T; Fukaya, A; Torikai, E

    2001-03-01

    We have carried out soft x-ray absorption spectroscopy to study the electronic structure of ilmenite family, such as MnTiO3, FeTiO3, and CoTiO3 at the soft x-ray beamline, BL23SU, at the SPring-8. The Ti and M L2,3 absorption spectra of MTiO3 (M=Mn, Fe, and Co) show spectra of Ti4+ and M2+ electron configurations, respectively. Except the Fe L2,3 spectrum, those spectra were understood within the O(h) symmetry around the transition metal ions. The Fe L3-edge spectrum clearly shows a doublet peak at the L3 edge, which is attributed to Fe2+ state, moreover the very high-resolution the L-edge spectra of transition metals show fine structures. The spectra of those ilmenites are compared.

  16. High-resolution x-ray photoemission spectra of silver

    DEFF Research Database (Denmark)

    Barrie, A.; Christensen, N. E.

    1976-01-01

    An electron spectrometer fitted with an x-ray monochromator for Al Kα1,2 radiation (1486.6 eV) has been used to record high-resolution x-ray photoelectron spectra for the 4d valence band as well as the 3d spin doublet in silver. The core-level spectrum has a line shape that can be described...... successfully in terms of the many-body theory of Mahan, Nozières, and De Dominicis. The 4d spectrum agrees well with predictions based on a relativistic-augmented-plane-wave band-structure calculation....

  17. Indirect measurements of X-ray spectra

    International Nuclear Information System (INIS)

    Mainardi, R.T.

    2006-01-01

    To the effects of measuring the spectral distribution of the radiation emitted by the x-ray tubes and electron accelerators, numerous procedures that are grouped in two big categories exist at the present time: direct and indirect methods. The first ones use high resolution detectors that should be positioned, together with the appropriate collimator, in the direction of the x ray beam. The user should be an expert in the use and correction of the obtained data by the different effects that affect the detector operation such as efficiency and resolution in terms of the energy of the detected radiation. The indirect procedures, although its are more simple to use, its also require a considerable space along the beam to position the ionization chamber and the necessary absorbents to construct by this way the denominated attenuation curve. We will analyze the operation principle of the indirect methods and a new proposal in which such important novelties are introduced as the beam dispersion to avoid to measure along the main beam and that of determination of the attenuation curve in simultaneous form. By this way, with a single shot of the tube, the attenuation curve is measured, being necessary at most a shot of additional calibration to know the relative response of the detectors used in the experimental array. The physical processes involved in the obtaining of an attenuation curve are very well well-known and this it finishes it can be theoretically calculated if the analytic form of the spectrum is supposed well-known. Finally, we will see a spectra reconstruction example with the Kramers parametric form and comparisons with numeric simulations carried out with broadly validated programs as well as the possibility of the use of solid state dosemeters in the obtention of the attenuation curve. (Author)

  18. X-ray, MP2 and DFT studies of the structure and vibrational spectra of trigonellinium chloride

    International Nuclear Information System (INIS)

    Szafran, M.; Koput, J.; Dega-Szafran, Z.; Katrusiak, A.; Pankowski, M.; Stobiecka, K.

    2003-01-01

    The effects of hydrogen bonding, inter- and intramolecular electrostatic interactions on the conformation of trigonellinium chloride, TRGH...Cl, in the crystal and on that of a single molecule have been studied by X-ray diffraction, FT-IR, Raman, 1 H and 13 C NMR spectroscopies, and by MP2 and DFT calculations. In the crystal, the Cl - anion is connected with protonated trigonelline via hydrogen bond, O-H...Cl - =2.915(3) Angst, and three N + ...Cl - intermolecular electrostatic interactions. In a single molecule, the Cl - anion is also engaged in a slightly longer hydrogen bond, O-H...Cl - =2.948-3.019 Angst, but only in one type of intramolecular electrostatic interaction. The optimized bond lengths and bond angles at the MP2 and B3LYP levels of theory are in good agreement with the X-ray data, except conformation of the COOH group, which is cis (syn) in the crystal and trans (anti) in the single molecule. The probable assignments for the experimental solid state vibrational spectra of TRGH.Cl and TRGD.Cl based on the calculated MP2/cc-pVDZ frequencies and intensities were made. The effect of quaternization of nicotinic acid, its salt and amide on chemical shifts of the ring protons and carbons is analyzed

  19. Tetrahedral hydrocarbon nanoparticles in space: X-ray spectra

    Science.gov (United States)

    Bilalbegović, G.; Maksimović, A.; Valencic, L. A.

    2018-06-01

    It has been proposed, or confirmed, that diamond nanoparticles exist in various environments in space: close to active galactic nuclei, in the vicinity of supernovae and pulsars, in the interior of several planets in the Solar system, in carbon planets, and other exoplanets, carbon-rich stars, meteorites, in X-ray active Herbig Ae/Be stars, and in the interstellar medium. Using density functional theory methods, we calculate the carbon K-edge X-ray absorption spectrum of two large tetrahedral nanodiamonds: C26H32 and C51H52. We also study and test our methods on the astrophysical molecule CH4, the smallest C-H tetrahedral structure. A possible detection of nanodiamonds from X-ray spectra by future telescopes, such as the project Arcus, is proposed. Simulated spectra of the diffuse interstellar medium using Cyg X-2 as a source show that nanodiamonds studied in this work can be detected by Arcus, a high-resolution X-ray spectrometer mission selected by NASA for a Phase A concept study.

  20. X-ray spectra, chemical bonding, and electron structure of ScM2Si2 (M = Fe, Co, Ni)

    International Nuclear Information System (INIS)

    Shcherba, I.D.; Kotur, B.Ya.

    1990-01-01

    In a study of the interaction of the components in the ternary systems Sc-M-Si (where M is a 3d transition metal) it was established that there are compounds of the empirical formula ScM 2 Si 2 (M = Fe, Co, Ni). They crystallize in two structural types, HfFe 2 Si 2 (the compound ScFe 2 Si 2 ) and CeGa 2 Al 2 (ScCo 2 Si 2 and ScNi 2 Si 2 ) (ref. 1), leading to different coordination environment of the atoms in the structures of the compounds. With the aim of investigating the electron structure and the type ofin these compounds, they authors made a systematic x-ray spectral investigation with simultaneous analysis of the crystal structures of ScM 2 Si 2

  1. Wavelength dispersive X-ray absorption fine structure imaging by parametric X-ray radiation

    International Nuclear Information System (INIS)

    Inagaki, Manabu; Sakai, Takeshi; Sato, Isamu; Hayakawa, Yasushi; Nogami, Kyoko; Tanaka, Toshinari; Hayakawa, Ken; Nakao, Keisuke

    2008-01-01

    The parametric X-ray radiation (PXR) generator system at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University is a monochromatic and coherent X-ray source with horizontal wavelength dispersion. The energy definition of the X-rays, which depends on the horizontal size of the incident electron beam on the generator target crystal, has been investigated experimentally by measuring the X-ray absorption near edge structure (XANES) spectra on Cu and CuO associated with conventional X-ray absorption imaging technique. The result demonstrated the controllability of the spectrum resolution of XANES by adjusting of the horizontal electron beam size on the target crystal. The XANES spectra were obtained with energy resolution of several eV at the narrowest case, which is in qualitative agreement with the energy definition of the PXR X-rays evaluated from geometrical consideration. The result also suggested that the wavelength dispersive X-ray absorption fine structure measurement associated with imaging technique is one of the promising applications of PXR. (author)

  2. Structure of X-ray photoelectron spectra of low-energy and core electrons of Ln(C6H4OCH3COO-3

    Directory of Open Access Journals (Sweden)

    Teterin Yury A.

    2005-01-01

    Full Text Available This paper deals with the results of an X-ray photo electron spectroscopy of lanthanide ortho-metoxybenzoates Ln(C6H4OCH3COO-3, where Ln represents lanthanides La through Lu except for Pm and C6H4OCH3COO- - residuum of ortho-metoxybenzoic acid. The core and outer electron X-ray photo electron spectroscopy spectra in the binding energy range of 0-1250 eV were shown to exhibit a complex, fine structure. The said structure was established due to the outer (0-15 eV binding energy and inner (15-50 eV binding energy valence molecular orbital from the filled Ln5p and O2s atomic shells multiple splitting, many-body perturbation, dynamic effect, etc. The mechanisms of such a fine structure formation were shown to manifest different probabilities in the spectrum of a certain electronic shell. There fore, the fine X-ray photo electron spectroscopy spectral structure resulting from a certain mechanism can be interpreted and its quantitative parameters related to the physical and chemical properties of the studied com pounds (degree of delocalization and participation of Ln4f electrons in the chemical bond, electronic configuration and oxidation states, density of uncoupled electrons on paramagnetic ions, degree of participation of the low binding energy filled electronic shells of lanthanide and ligands information of the outer and in nervalence molecular orbitals, lanthanide close environment structure in amorphous materials, etc.

  3. Chemical effects in x-ray emission spectra

    International Nuclear Information System (INIS)

    Fernandes, N.G.

    1982-01-01

    The chemical bond influence in X-ray emission spectra of hafnium, iodine, iron, sulphur, aluminium and magnesium is detected. The position of one X-ray emission line is determined by three methods: parabolic profile; Gaussian distribution and extra-heavy maximum. (author)

  4. X ray spectra of X Per. [oso-8 observations

    Science.gov (United States)

    Becker, R. H.; Boldt, E. A.; Holt, S. S.; Pravdo, S. H.; Robinson-Saba, J.; Serlemitsos, P. J.; Swank, J. H.

    1978-01-01

    The cosmic X-ray spectroscopy experiment on OSO-8 observed X Per for twenty days during two observations in Feb. 1976 and Feb. 1977. The spectrum of X Per varies in phase with its 13.9 min period, hardening significantly at X-ray minimum. Unlike other X-ray binary pulsar spectra, X Per's spectra do not exhibit iron line emission or strong absorption features. The data show no evidence for a 22 hour periodicity in the X-ray intensity of X Per. These results indicate that the X-ray emission from X Per may be originating from a neutron star in a low density region far from the optically identified Be star.

  5. Diversity of soft X-ray spectra in quasars

    International Nuclear Information System (INIS)

    Elvis, M.; Wilkes, B.J.; Tananbaum, H.

    1985-01-01

    Soft X-ray spectra for three quasars obtained with the Einstein Imaging Proportional Counter covering the 0.1-4.0 keV band are reported. Power-law fits to these spectra have best-fit energy indices of 1.2 +0.6 or -0.2, for the quasar NAB 0205 + 024, 0.6 +0.3 or -0.2 for the quasar B2 1028 + 313, and 2.2 + or -0.4 for the quasar PG 1211 + 143. None of the quasars shows any evidence for a column density of cold matter in excess of the galactic values. The derived spectra demonstrate that there is no single universal power law slope for quasar X-ray spectra. The implications of these results for the X-ray background, X-ray continuum emission mechanisms, and the production of the optical/UV emission lines are briefly discussed. 46 references

  6. The high energy X-ray spectra of supernova remnants

    Science.gov (United States)

    Pravdo, S. H.; Nugent, J. J.

    The results of fitting an ionization-nonequilibrium (INE) model to the high-energy (above 5-keV) X-ray spectra of the young supernova remnants Cas A and Tycho are presented. As an additional constraint, the models must simultaneously fit lower-energy, higher-resolution data. For Cas A, a single INE component cannot adequately reproduce the features for the entire X-ray spectrum because the ionization structure of iron ions responsible for the K emission is inconsistent with that of the ions responsible for the lower-energy lines, and the flux of the highest-energy X-rays is underestimated. The iron K line and the high-energy continuum could arise from the same INE component, but the identification of this component with either the blast wave or the ejecta in the standard model is difficult. In Tycho, the high-energy data rule out a class of models for the lower-energy data which have too large a continuum contribution.

  7. Assignment of near-edge x-ray absorption fine structure spectra of metalloporphyrins by means of time-dependent density-functional calculations

    International Nuclear Information System (INIS)

    Schmidt, Norman; Fink, Rainer; Hieringer, Wolfgang

    2010-01-01

    The C 1s and N 1s near-edge x-ray absorption fine structure (NEXAFS) spectra of three prototype tetraphenyl porphyrin (TPP) molecules are discussed in the framework of a combined experimental and theoretical study. We employ time-dependent density-functional theory (TDDFT) to compute the NEXAFS spectra of the open- and closed-shell metalloporphyrins CoTPP and ZnTPP as well as the free-base 2HTPP in realistic nonplanar conformations. Using Becke's well-known half-and-half hybrid functional, the computed core excitation spectra are mostly in good agreement with the experimental data in the low-energy region below the appropriate ionization threshold. To make these calculations feasible, we apply a new, simple scheme based on TDDFT using a modified single-particle input spectrum. This scheme is very easy to implement in standard codes and allows one to compute core excitation spectra at a similar cost as ordinary UV/vis spectra even for larger molecules. We employ these calculations for a detailed assignment of the NEXAFS spectra including subtle shifts in certain peaks of the N 1s spectra, which depend on the central coordination of the TPP ligand. We furthermore assign the observed NEXAFS resonances to the individual molecular subunits of the investigated TPP molecules.

  8. X-ray spectra of PG quasars. I. The continuum from X-rays to infrared

    International Nuclear Information System (INIS)

    Elvis, M.; Green, R.F.; Bechtold, J.; Schmidt, M.; Neugebauer, G.; Kitt Peak National Observatory, Tucson, AZ; Steward Observatory, Tucson, AZ; Palomar Observatory, Pasadena, CA)

    1986-01-01

    Einstein IPC X-ray spectra for a sample of eight optically selected quasars from the Palomar Bright Quasar survey are presented. The quasars have a mean power law energy slope which in five individual cases is inconsistent with the value found in hard X-ray selection criterion rather than luminosity, redshift, or U-B color. New IUE and optical continuum spectra and infrared photometry are presented for these quasars. The data are combined into log vf(v) and log v distributions which support the decomposition of the overall quasar spectrum into a power law plus a superposed optical-UV big bump which may be due to an accretion disk. At least six of the quasars have vf(v)s which are roughly constant between their infrared and X-ray power laws, suggesting a strong link between the two regions. 104 references

  9. Monte Carlo simulation of x-ray spectra in mammography

    Energy Technology Data Exchange (ETDEWEB)

    Ng, K.P. [Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China). E-mail: benngkp at netvigator.com; Kwok, C.S.; Ng, K.P.; Tang, F.H. [Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China)

    2000-05-01

    A model for generating x-ray spectra in mammography is presented. This model used the ITS version 3 Monte Carlo code for simulating the radiation transport. Various target/filter combinations such as tungsten/aluminium, molybdenum/molybdenum, molybdenum/rhodium and rhodium/rhodium were used in the simulation. Both bremsstrahlung and characteristic x-ray production were included in the model. The simulated x-ray emission spectra were compared with two sets of spectra, those of Boone et al (1997 Med. Phys. 24 1863-74) and IPEM report 78. The {chi}{sup 2} test was used for the overall goodness of fit of the spectral data. There is good agreement between the simulated x-ray spectra and the comparison spectra as the test yielded a probability value of nearly 1. When the transmitted x-ray spectra for specific target/filter combinations were generated and compared with a measured molybdenum/rhodium spectrum and spectra generated in IPEM report 78, close agreement is also observed. This was demonstrated by the probability value for the {chi}{sup 2} test being almost 1 for all the cases. However, minor differences between the simulated spectra and the 'standard' ones are observed. (author)

  10. Monte Carlo simulation of x-ray spectra in mammography

    International Nuclear Information System (INIS)

    Ng, K.P.

    2000-01-01

    A model for generating x-ray spectra in mammography is presented. This model used the ITS version 3 Monte Carlo code for simulating the radiation transport. Various target/filter combinations such as tungsten/aluminium, molybdenum/molybdenum, molybdenum/rhodium and rhodium/rhodium were used in the simulation. Both bremsstrahlung and characteristic x-ray production were included in the model. The simulated x-ray emission spectra were compared with two sets of spectra, those of Boone et al (1997 Med. Phys. 24 1863-74) and IPEM report 78. The χ 2 test was used for the overall goodness of fit of the spectral data. There is good agreement between the simulated x-ray spectra and the comparison spectra as the test yielded a probability value of nearly 1. When the transmitted x-ray spectra for specific target/filter combinations were generated and compared with a measured molybdenum/rhodium spectrum and spectra generated in IPEM report 78, close agreement is also observed. This was demonstrated by the probability value for the χ 2 test being almost 1 for all the cases. However, minor differences between the simulated spectra and the 'standard' ones are observed. (author)

  11. X-ray Spectra of Distant Clusters

    Science.gov (United States)

    Ellingson, E.

    1998-01-01

    The masses of galaxy clusters are dominated by dark matter, and a robust determination of their temperatures and masses has the potential of indicating how much dark matter exists on large scales in the universe, and the cosmological parameter Omega. X-ray observations of galaxy clusters provide a direct measure of both the gas mass in the intra-cluster medium, and also the total gravitating mass of the cluster. We used new and archival ASCA and ROSAT observations to measure these quantities for a sample of intermediate redshift clusters which have also been subject to intensive dynamical studies, in order to compare the mass estimates from different methods. We used data from 12 of the CNOC cluster sample at 0.18 less than z less than 0.55 for this study. A direct comparison of dynamical mass estimates from Carlberg, Yee & Ellingson (1997) yielded surprisingly good results. The X-ray/dynamical mass ratios have a mean of 0.96+/- 0.10, indicating that for this sample, both methods are probably yielding very robust mass estimates. Comparison with mass estimates from gravitational lensing studies from the literature showed a small systematic with weak lensing estimates, and large discrepancies with strong lensing estimates. This latter is not surprising, given that these measurements are made close to the central core, where optical and Xray estimates are less certain, and where substructure and the effects of individual galaxies will be more pronounced. These results are presented in Lewis, Ellingson, Morris \\& Carlberg, 1998, submitted to the Astrophysical Journal.

  12. Compton spectra of atoms at high x-ray intensity

    Science.gov (United States)

    Son, Sang-Kil; Geffert, Otfried; Santra, Robin

    2017-03-01

    Compton scattering is the nonresonant inelastic scattering of an x-ray photon by an electron and has been used to probe the electron momentum distribution in gas-phase and condensed-matter samples. In the low x-ray intensity regime, Compton scattering from atoms dominantly comes from bound electrons in neutral atoms, neglecting contributions from bound electrons in ions and free (ionized) electrons. In contrast, in the high x-ray intensity regime, the sample experiences severe ionization via x-ray multiphoton multiple ionization dynamics. Thus, it becomes necessary to take into account all the contributions to the Compton scattering signal when atoms are exposed to high-intensity x-ray pulses provided by x-ray free-electron lasers (XFELs). In this paper, we investigate the Compton spectra of atoms at high x-ray intensity, using an extension of the integrated x-ray atomic physics toolkit, xatom. As the x-ray fluence increases, there is a significant contribution from ionized electrons to the Compton spectra, which gives rise to strong deviations from the Compton spectra of neutral atoms. The present study provides not only understanding of the fundamental XFEL-matter interaction but also crucial information for single-particle imaging experiments, where Compton scattering is no longer negligible. , which features invited work from the best early-career researchers working within the scope of J. Phys. B. This project is part of the Journal of Physics series’ 50th anniversary celebrations in 2017. Sang-Kil Son was selected by the Editorial Board of J. Phys. B as an Emerging Leader.

  13. Comparison of various molecular forms of bovine trypsin: Correlation of infrared spectra with X-ray crystal structures

    Energy Technology Data Exchange (ETDEWEB)

    Prestrelski, S.J. (Mount Sinai School of Medicine of the City Univ. of New York (USA)); Byler, D.M. (U.S. Department of Agriculture, Philadelphia, PA (USA)); Liebman, M.N. (AMOCO Technology Corporation, Naperville, IL (USA))

    1991-01-01

    Fourier-transform infrared spectroscopy is a valuable method for the study of protein conformation in solution primarily because of the sensitivity to conformation of the amide I band (1700-1620 cm{sup {minus}1}) which arises from the backbone C{double bond}O stretching vibration. Combined with resolution-enhancement techniques such as derivative spectroscopy and self-deconvolution, plus the application of iterative curve-fitting techniques, this method provides a wealth of information concerning protein secondary structure. Further extraction of conformational information from the amide I band is dependent upon discerning the correlations between specific conformation types and component bands in the amide I region. In this paper the authors report spectra-structure correlations derived from conformational perturbations in bovine trypsin which arise from autolytic processing, zymogen activation, and active-site inhibition. IR spectra were collected for the single-chain ({beta}-trypsin) and once-cleaved, double-chain ({alpha}-trypsin) forms as well as at various times during the course of autolysis and also for zymogen, trypsinogen, and {beta}-trypsin inhibited with diisopropyl fluorophosphate. Spectral differences among the various molecular forms were interpreted in light of previous biochemical studies of autolysis and the known three-dimensional structures of the zymogen, the active enzyme, and the DIP-inhibited form. The spectroscopic results from these proteins in D{sub 2}O imply that certain loop structures may absorb in the region of 1655 cm{sup {minus}1}. They estimate that this approach to data analysis and interpretation is sensitive to changes of 0.01 unit or less in the relative integrated intensities of component bands in spectra whose peaks are well resolved.

  14. Nitrogen K-edge X-ray absorption near edge structure (XANES) spectra of purine-containing nucleotides in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Shimada, Hiroyuki; Fukao, Taishi; Minami, Hirotake; Ukai, Masatoshi [Department of Applied Physics, Tokyo University of Agriculture and Technology, Koganei-shi, Tokyo 184-8588 (Japan); Fujii, Kentaro; Yokoya, Akinari [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Fukuda, Yoshihiro; Saitoh, Yuji [Synchrotron Radiation Research Center, Japan Atomic Energy Agency, Sayo-gun, Hyougo 679-5148 (Japan)

    2014-08-07

    The N K-edge X-ray absorption near edge structure (XANES) spectra of the purine-containing nucleotide, guanosine 5{sup ′}-monophosphate (GMP), in aqueous solution are measured under various pH conditions. The spectra show characteristic peaks, which originate from resonant excitations of N 1s electrons to π* orbitals inside the guanine moiety of GMP. The relative intensities of these peaks depend on the pH values of the solution. The pH dependence is explained by the core-level shift of N atoms at specific sites caused by protonation and deprotonation. The experimental spectra are compared with theoretical spectra calculated by using density functional theory for GMP and the other purine-containing nucleotides, adenosine 5{sup ′}-monophosphate, and adenosine 5{sup ′}-triphosphate. The N K-edge XANES spectra for all of these nucleotides are classified by the numbers of N atoms with particular chemical bonding characteristics in the purine moiety.

  15. Pyrimidine and halogenated pyrimidines near edge x-ray absorption fine structure spectra at C and N K-edges: experiment and theory

    International Nuclear Information System (INIS)

    Bolognesi, P.; O'Keeffe, P.; Ovcharenko, Y.; Coreno, M.; Avaldi, L.; Feyer, V.; Plekan, O.; Prince, K. C.; Zhang, W.; Carravetta, V.

    2010-01-01

    The inner shell excitation of pyrimidine and some halogenated pyrimidines near the C and N K-edges has been investigated experimentally by near edge x-ray absorption fine structure spectroscopy and theoretically by density functional theory calculations. The selected targets, 5-Br-pyrimidine, 2-Br-pyrimidine, 2-Cl-pyrimidine, and 5-Br-2-Cl-pyrimidine, allow the effects of the functionalization of the pyrimidine ring to be studied either as a function of different halogen atoms bound to the same molecular site or as a function of the same halogen atom bound to different molecular sites. The results show that the individual characteristics of the different spectra of the substituted pyrimidines can be rationalized in terms of variations in electronic and geometrical structures of the molecule depending on the localization and the electronegativity of the substituent.

  16. X-ray metrology for ULSI structures

    International Nuclear Information System (INIS)

    Bowen, D. K.; Matney, K. M.; Wormington, M.

    1998-01-01

    Non-destructive X-ray metrological methods are discussed for application to both process development and process control of ULSI structures. X-ray methods can (a) detect the unacceptable levels of internal defects generated by RTA processes in large wafers, (b) accurately measure the thickness and roughness of layers between 1 and 1000 nm thick and (c) can monitor parameters such as crystallographic texture and the roughness of buried interfaces. In this paper we review transmission X-ray topography, thin film texture measurement, grazing-incidence X-ray reflectivity and high-resolution X-ray diffraction. We discuss in particular their suitability as on-line sensors for process control

  17. Analysis of X-Ray (L) spectra of heavy elements

    International Nuclear Information System (INIS)

    Souza Coelho, L.F. de.

    1976-08-01

    The general problem of obtaining and analysing spectra is presented, with emphasis in the comparison of methods for the analysis of gamma rays and X rays. The method proposed to obtain a standard and later the intensities of lines of an X-ray (L) spectrum is discussed. The good eesults obtained by the program RAIOXL, when simulated spectra are used, and by the program RAIXL1, when doublets are decomposed, are shown. In annex A, the listings of the programs used are presented, and in annex B a review is made of the analytical formulae used for adjustment of the pulses. (I.C.R.) [pt

  18. LINE FORMATION IN SPECTRA OF X-RAY NOVAE

    OpenAIRE

    Suleimanov, V. F.; Shimansky, V. V.

    2017-01-01

    Results of X-ray Novae (XN) optical spectra computation are presented. The continuum and Balmer line are calculated. The model of XN as a self-irradiated accretion disk is used. Local (for given radius) disk atmospheres as model stellar atmospheres, heated due to external X-ray radiation are treated. Changes of spectra shape and equivalent widths of the Balmer lines depending from the luminosity and some others accretion disk parameters are investigated. The comparison of GRO JO422+32 observe...

  19. Model independent method to deconvolve hard X-ray spectra

    Energy Technology Data Exchange (ETDEWEB)

    Polcaro, V.F.; Bazzano, A.; Ubertini, P.; La Padula, C. (Consiglio Nazionale delle Ricerche, Frascati (Italy). Lab. di Astrofisica Spaziale); Manchanda, R.K. (Tata Inst. of Fundamental Research, Bombay (India))

    1984-07-01

    A general purpose method to deconvolve the energy spectra detected by means of the use of a hard X-ray telescope is described. The procedure does not assume any form of input spectrum and the observed energy loss spectrum is directly deconvolved into the incident photon spectrum, the form of which can be determined independently of physical interpretation of the data. Deconvolution of the hard X-ray spectrum of Her X-1, detected during the HXR 81M experiment, by the method independent method is presented.

  20. On hard X-ray spectra of accreting neutron stars

    International Nuclear Information System (INIS)

    Zheleznyakov, V.V.

    1982-01-01

    Formation of the spectra of X-ray pulsars and gamma bursters is investigated. Interpretation of a hard X-ray spectrum of pulsars containing cyclotron lines is feasible on the basis of an isothermal model of a polar spot heated due to acccretion to a neutron star. It has been ascertained that in the regions responsible for the formation of continuum radiation and lines the mode polarization is determined by a magnetized vacuum rather than by a plasma. Bearing this in mind, the influence of the magnetic field of a star on the wide wings of the cyclotron line and on its depth is discussed. The part played by the accreting column in the case of strong accretion (approx. equal to 10 19 el cm -3 ) needed for long sustaining of the high level of X-rays from a neutron star-pulsar is studied. There occur the gaps in spectrum at frequencies close to the electron gyro-frequency and its harmonics due to the screening of the hot spot by the opaque gyro-resonant layer located within the accreting column. These gaps ensure the formation of cyclotron lines in absorption irrespective of the presence of such lines in the X-ray spectrum of a polar hot spot. (orig./WL)

  1. The X-ray electronic spectra of TiC-NbC solid solution

    International Nuclear Information System (INIS)

    Cherkashenko, V.M.; Ezhov, A.V.; Nazarova, S.Z.; Kurmaev, Eh.Z.; Nojmann, M.

    2001-01-01

    X-ray photoelectronic spectra of inner levels and valency lands in TiC-NbC solid solutions were studied. Results of combining TiL α -, NbL β2.15 -, CK α - X-ray emission spectra and photoelectronic spectra of valency bands in one energy scale in reference to the Fermi level were analyzed. It is shown that a change in crystal lattice parameters, as well as charge redistribution between titanium and niobium atoms, produce a strong effect on electronic structure formation in the mixed carbides mentioned [ru

  2. X-ray absorption spectra and emission spectra of plasmas

    International Nuclear Information System (INIS)

    Peng Yonglun; Yang Li; Wang Minsheng; Li Jiaming

    2002-01-01

    The author reports a theoretical method to calculate the resolved absorption spectra and emission spectra (optically thin) of hot dense plasmas. Due to its fully relativistic treatment incorporated with the quantum defect theory, it calculates the absorption spectra and emission spectra for single element or multi-element plasmas with little computational efforts. The calculated absorption spectra of LTE gold plasmas agree well with the experimental ones. It also calculates the optical thin emission spectra of LTE gold plasmas, which is helpful to diagnose the plasmas of relevant ICF plasmas. It can also provide the relevant parameters such as population density of various ionic stages, precise radiative properties for ICF studies

  3. X-ray scattering in X-ray fluorescence spectra with X-ray tube excitation - Modelling, experiment, and Monte-Carlo simulation

    International Nuclear Information System (INIS)

    Hodoroaba, V.-D.; Radtke, M.; Vincze, L.; Rackwitz, V.; Reuter, D.

    2010-01-01

    X-ray scattering may contribute significantly to the spectral background of X-ray fluorescence (XRF) spectra. Based on metrological measurements carried out with a scanning electron microscope (SEM) having attached a well characterised X-ray source (polychromatic X-ray tube) and a calibrated energy dispersive X-ray spectrometer (EDS) the accuracy of a physical model for X-ray scattering is systematically evaluated for representative samples. The knowledge of the X-ray spectrometer efficiency, but also of the spectrometer response functions makes it possible to define a physical spectral background of XRF spectra. Background subtraction relying on purely mathematical procedures is state-of-the-art. The results produced by the analytical model are at least as reliable as those obtained by Monte-Carlo simulations, even without considering the very challenging contribution of multiple scattering. Special attention has been paid to Compton broadening. Relevant applications of the implementation of the analytical model presented in this paper are the prediction of the limits of detection for particular cases or the determination of the transmission of X-ray polycapillary lenses.

  4. The Soft X-Ray Spectra of Sulfur Compounds.

    Science.gov (United States)

    Zhou, Ling

    1995-01-01

    The sulfur compounds including CdS, ZnS, rm MoS_2, WS_2, NiS, FeS, GaS, SnS, MgS and Alloy rm ZnS_{x }Se_{1-x} were investigated by using photon/e-beam excited soft x-ray spectroscopy through SXA, SXE, SXF and inelastic Resonant Raman scattering and resonant elastic scattering processes. For valence bands, the PDOS of S L_{2,3}, Zn M_{2,3}, Se M _{4,5}, bands locations, band gaps Eg, core level spin splitting, the lifetime broadening of valence band t_{1/2}, branching ratio of rm L_2/L_3 and shallow d level and exciton state were measured in some of these materials respectively. The excitation mechanism or threshold effects were studied for CdS, ZnS, MoS_2, WS_2, FeS, NiS, and alloy. In photon excited S L_ {2,3}^ectra, local core levels with spin splitting were found to charge threshold effects. The threshold effects are also found to be influenced by resonant elastic and inelastic scattering process. A simple model and the second order perturbation theory are used to explain the observed inelastic Raman scattering of Zn M _{2,3} spectra near d threshold. The d participation in the chemical bonding and interactions was studied. Atomiclike d bands were found in FeS and NiS from strong d-d and d-p couplings. Two groups of d bands were observed in Transitional Metal Sulfides (TMS) and the no-bonding group with a few d bands was found to across whole valence bands in TMS. The direct connection between valence bands and conduction bands is built and some conduction bands were studied. A study of alloy was included briefly. These experiments provide a rich information about TMS, and prove that Soft X-ray Spectroscopy is a powerful, precise and reliable tool in the study of fine electronic band structure in solids.

  5. Structure and dynamics in liquid water from x-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Wernet, Philippe

    2009-01-01

    Oxygen K-edge x-ray absorption spectra of water are discussed. The spectra of gas-phase water, liquid water and ice illustrate the sensitivity of oxygen K-edge x-ray absorption spectroscopy to hydrogen bonding in water. Transmission mode spectra of amorphous and crystalline ice are compared to x-ray Raman spectra of ice. The good agreement consolidates the experimental spectrum of crystalline ice and represents an incentive for theoretical calculations of the oxygen K-edge absorption spectrum of crystalline ice. Time-resolved infrared-pump and x-ray absorption probe results are finally discussed in the light of this structural interpretation.

  6. Spatially resolved X-ray spectra of coronal active regions

    International Nuclear Information System (INIS)

    Catura, R.C.; Acton, L.W.; Joki, E.G.; Rapley, C.G.; Culhane, J.L.

    1975-01-01

    X-ray spectra from a number of coronal active regions were obtained during ATM support rocket flights carried out by the Lockheed group on June 11 and December 19, 1973. Multi-grid collimators were used to provide fields of view of 40ins. diameter and 90ins. diameter for a number of scanning crystal spectrometers and a bent crystal spectrometer which employed a position sensitive proportional counter to register the diffracted spectrum. A solar image was produced on film and on a TV camera on board the rocket with the aid of a 1 A Hα filter. A small part of the X-ray collimator was used to generate a multiple spot diffraction pattern which was superimposed on the Hα image and the composite picture was transmitted to the ground. Pre-launch calibrations allowed the spot corresponding to the X-ray collimator axis to be identified and so the collimator pointing direction on the solar disc was controlled from the ground by means of commands sent to the rocket. (Auth.)

  7. Indirect measure of X-rays spectra using TLDs

    International Nuclear Information System (INIS)

    Bonzi, E. V.; Mainardi, R. T.

    2011-10-01

    A methodology of indirect measure of X-rays spectra, emitted by conventional tubes, was developed recently and its feasibility verified in the first place by Monte Carlo simulations. For that case is intended to measure, by means of plastic scintillators, attenuation curves of dispersed beams previously. In this work were carried out measurements of attenuation curves with thermoluminescent dosimeters (TLD) to verify the kindness of the indirect measure method. The attenuation curve was also measured using an ionization chamber brand Capintec (model 192) with the purpose of making a comparison. The results of the attenuation curve measured with both dosimeters present a good resolution inside the statistical fluctuations and the spectral reconstruction using diverse parametric functions is carried out in a quick and simple way with excellent resolutions in the functional form. For this reconstruction method are of fundamental importance the following properties of the used dosimeter: in the first place the repetition of the measures, property that could check; in second place the precision of the measured data and lastly the dosimeter response, this is, the increase of the thermoluminescent signal before an increase of the photons flow of X-rays. This parameter is the gradient of the curve thermoluminescent signal versus the dose imparted to the dosimeter. The measures were realized with a generator of X-rays brand Kevex provided of a conventional tube with tungsten anti cathode that polarizes with high tension to a maximum value of 50 kV and current of 0.5 ma. (Author)

  8. Quantum chemistry interpretation of x-ray spectra

    International Nuclear Information System (INIS)

    Bocharov, D.; Kuzmin, A.

    2005-01-01

    Full text: In this study, we present the results of ab initio computer simulations on X-ray absorption spectra of some perovskite-type tungsten oxides. For our calculations, we combine a periodic bulk model with Hartree-Fock method including a posteriori electron correlation corrections, as implemented in CRYSTAL98 computer code [1]. First, we describe the results of calculations performed on some bulk properties of the tungsten oxides (lattice constant and bulk modulus), in order to achieve the necessary level of agreement with available experimental and theoretical data. Our calculations on the densities of oneelectron energy states (DOS) for models of tungsten oxides are verified by experimental X-ray absorption spectra, which allow us to make correct qualitative interpretation of the latter. The main difficulties appearing during our first principles simulations will be discussed. [1] V.R. Saunders, R. Dovesi, C. Roetti, M. Causi, N.M. Harrison, R. Orlando, and C.M. Zicovich-Wilson, CRYSTAL-98 User Manual, University of Turin, 1999

  9. Many-body effects on the x-ray spectra of metals

    International Nuclear Information System (INIS)

    Satpathy, S.S.

    1982-01-01

    The effects of band structure, of a solid surface, of temperature, and of disorder on the many-electron x-ray spectra of metals are evaluated in a change-of-mean-field approximation using a one-dimensional nearest-neighbor tight-binding model of a metal. The x-ray spectral shapes are determined by both the band structure and the final-state interactions. The effect of the band being non-free-electron-like is not felt at the x-ray threshold, but away from it such effects are noticeable. When the core hole is created at the surface, the spectra at the edge exhibit a Nozieres-de Dominicis-type singularity with the appropriate surface phase-shifts. At energies away from the edge, the one-particle effects are prominent with the x-ray emission and absorption spectra closely reflecting the local one-electron density of states. The recoil spectrum of a Fermi sea at a non-zero temperature has less asymmetry than the zero-temperature case. It was found that at ordinary temperatures the reduction of the asymmetry due to the thermal distribution of one-electron states is not very significant. Finally, using a one-dimensional Anderson model, the effect of lattice disorder on the x-ray absorption spectra is studied for the first time. There are two effects: (1) the strong infrared divergence peak is gradually quenched as disorder is increased, and (2) the threshold is broadened because the threshold energies for absorption at different sites in the crystal depend on the varying local lattice environment. It is proposed that the x-ray spectra may be useful as a tool for studying the degree of electron localization in disordered many-electron systems

  10. Vibrational spectra, powder X-ray diffractions and physical properties of cyanide complexes with 1-ethylimidazole

    Science.gov (United States)

    Kürkçüoğlu, Güneş Süheyla; Kiraz, Fulya Çetinkaya; Sayın, Elvan

    2015-10-01

    The heteronuclear tetracyanonickelate(II) complexes of the type [M(etim)Ni(CN)4]n (hereafter, abbreviated as M-Ni-etim, M = Mn(II), Fe(II) or Co(II); etim = 1-ethylimidazole, C5H8N2) were prepared in powder form and characterized by FT-IR and Raman spectroscopy, powder X-ray diffraction (PXRD), thermal (TG; DTG and DTA), and elemental analysis techniques. The structures of these complexes were elucidated using vibrational spectra and powder X-ray diffraction patterns with the peak assignment to provide a better understanding of the structures. It is shown that the spectra are consistent with a proposed crystal structure for these compounds derived from powder X-ray diffraction measurements. Vibrational spectra of the complexes were presented and discussed with respect to the internal modes of both the etim and the cyanide ligands. The C, H and N analyses were carried out for all the complexes. Thermal behaviors of these complexes were followed using TG, DTG and DTA curves in the temperature range 30-700 °C in the static air atmosphere. The FT-IR, Raman spectra, thermal and powder X-ray analyses revealed no significant differences between the single crystal and powder forms. Additionally, electrical and magnetic properties of the complexes were investigated. The FT-IR and Raman spectroscopy, PXRD, thermal and elemental analyses results propose that these complexes are similar in structure to the Hofmann-type complexes.

  11. Optimization and energy spectra of x-ray to be used for imaging

    International Nuclear Information System (INIS)

    Nakamori, Nobuyuki; Kanamori, Hitoshi

    1979-01-01

    The relations of the spectra of X-ray used for diagnosis to the absorbed dose of patients and X-ray information are now being investigated by a number of investigators. Here the problems and the trends of the investigations at present are described. Advent of semiconductor detectors has improved the accuracy of measuring X-ray spectra very rapidly. However, since the semiconductor detectors themselves utilize X-ray photon absorption, calibration curves must be prepared for obtaining the true X-ray spectra. Though there are methods of theoretically determining X-ray spectra, no definite theoretical formula is found. Thus, the derivation of an empirical equation based on measured data would be the most fundamental problem. Interactions in an object and the change of X-ray spectra are described on the case of monochromatic and continuous X-ray irradiation. As mentioned above, beam hardening occurs when X-ray enters a matter deep, because the interactions between X-ray and the matter depend upon the photon energy. There are a few methods for correcting the variation of CT (computed tomography) number due to beam hardening. However, prior to this, there are two methods of representing continuous X-ray with single energy, and the unification of the methods or a new way of defining X-ray quality is needed. It has been and is always desirable that monochromatic X-ray source becomes to be useable, and various methods are proposed. (Wakatsuki, Y.)

  12. A model of tungsten anode x-ray spectra

    Energy Technology Data Exchange (ETDEWEB)

    Hernández, G.; Fernández, F., E-mail: fdz@usal.es [Física Fundamental, Universidad de Salamanca, Salamanca 37008 (Spain)

    2016-08-15

    Purpose: A semiempirical model for x-ray production in tungsten thick-targets was evaluated using a new characterization of electron fluence. Methods: Electron fluence is modeled taking into account both the energy and angular distributions, each of them adjusted to Monte Carlo simulated data. Distances were scaled by the CSDA range to reduce the energy dependence. Bremsstrahlung production was found by integrating the cross section with the fluence in a 1D penetration model. Characteristic radiation was added using a semiempirical law whose validity was checked. The results were compared the experimental results of Bhat et al., with the SpekCalc numerical tool, and with MCNPX simulation results from the work of Hernandez and Boone. Results: The model described shows better agreement with the experimental results than the SpekCalc predictions in the sense of area between the spectra. A general improvement of the predictions of half-value layers is also found. The results are also in good agreement with the simulation results in the 50–640 keV energy range. Conclusions: A complete model for x-ray production in thick bremsstrahlung targets has been developed, improving the results of previous works and extending the energy range covered to the 50–640 keV interval.

  13. Probing symmetry and symmetry breaking in resonant soft-x-ray fluorescence spectra of molecules

    Energy Technology Data Exchange (ETDEWEB)

    Glans, P.; Gunnelin, K.; Guo, J. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    Conventional non-resonant soft X-ray emission brings about information about electronic structure through its symmetry and polarization selectivity, the character of which is governed by simple dipole rules. For centro-symmetric molecules with the emitting atom at the inversion center these rules lead to selective emission through the required parity change. For the more common classes of molecules which have lower symmetry or for systems with degenerate core orbitals (delocalized over identical sites), it is merely the local symmetry selectivity that provides a probe of the local atomic orbital contribution to the molecular orbital. For instance, in X-ray spectra of first row species the intensities essentially map the p-density at each particular atomic site, and, in a molecular orbital picture, the contribution of the local p-type atomic orbitals in the LCAO description of the molecular orbitals. The situation is different for resonant X-ray fluorescence spectra. Here strict parity and symmetry selectivity gives rise to a strong frequency dependence for all molecules with an element of symmetry. In addition to symmetry selectivity the strong frequency dependence of resonant X-ray emission is caused by the interplay between the shape of a narrow X-ray excitation energy function and the lifetime and vibrational broadenings of the resonantly excited core states. This interplay leads to various observable effects, such as linear dispersion, resonance narrowing and emission line (Stokes) doubling. Also from the point of view of polarization selectivity, the resonantly excited X-ray spectra are much more informative than the corresponding non-resonant spectra. Examples are presented for nitrogen, oxygen, and carbon dioxide molecules.

  14. OSO 8 X-ray spectra of clusters of galaxies. II - Discussion

    Science.gov (United States)

    Smith, B. W.; Mushotzky, R. F.; Serlemitsos, P. J.

    1979-01-01

    An observational description of X-ray clusters of galaxies is given based on OSO 8 X-ray results for spatially integrated spectra of 20 such clusters and various correlations obtained from these results. It is found from a correlation between temperature and velocity dispersion that the X-ray core radius should be less than the galaxy core radius or, alternatively, that the polytropic index is about 1.1 for most of the 20 clusters. Analysis of a correlation between temperature and emission integral yields evidence that more massive clusters accumulate a larger fraction of their mass as intracluster gas. Galaxy densities and optical morphology, as they correlate with X-ray properties, are reexamined for indications as to how mass injection by galaxies affects the density structure of the gas. The physical arguments used to derive iron abundances from observed equivalent widths of iron line features in X-ray spectra are critically evaluated, and the associated uncertainties in abundances derived in this manner are estimated to be quite large.

  15. Dynamical and Radiative Properties of X-Ray Pulsar Accretion Columns: Phase-averaged Spectra

    Energy Technology Data Exchange (ETDEWEB)

    West, Brent F. [Department of Electrical and Computer Engineering, United States Naval Academy, Annapolis, MD (United States); Wolfram, Kenneth D. [Naval Research Laboratory (retired), Washington, DC (United States); Becker, Peter A., E-mail: bwest@usna.edu, E-mail: kswolfram@gmail.com, E-mail: pbecker@gmu.edu [Department of Physics and Astronomy, George Mason University, Fairfax, VA (United States)

    2017-02-01

    The availability of the unprecedented spectral resolution provided by modern X-ray observatories is opening up new areas for study involving the coupled formation of the continuum emission and the cyclotron absorption features in accretion-powered X-ray pulsar spectra. Previous research focusing on the dynamics and the associated formation of the observed spectra has largely been confined to the single-fluid model, in which the super-Eddington luminosity inside the column decelerates the flow to rest at the stellar surface, while the dynamical effect of gas pressure is ignored. In a companion paper, we have presented a detailed analysis of the hydrodynamic and thermodynamic structure of the accretion column obtained using a new self-consistent model that includes the effects of both gas and radiation pressures. In this paper, we explore the formation of the associated X-ray spectra using a rigorous photon transport equation that is consistent with the hydrodynamic and thermodynamic structure of the column. We use the new model to obtain phase-averaged spectra and partially occulted spectra for Her X-1, Cen X-3, and LMC X-4. We also use the new model to constrain the emission geometry, and compare the resulting parameters with those obtained using previously published models. Our model sheds new light on the structure of the column, the relationship between the ionized gas and the photons, the competition between diffusive and advective transport, and the magnitude of the energy-averaged cyclotron scattering cross-section.

  16. Structure determination by X-ray crystallography

    CERN Document Server

    Ladd, M F C

    1995-01-01

    X-ray crystallography provides us with the most accurate picture we can get of atomic and molecular structures in crystals. It provides a hard bedrock of structural results in chemistry and in mineralogy. In biology, where the structures are not fully crystalline, it can still provide valuable results and, indeed, the impact here has been revolutionary. It is still an immense field for young workers, and no doubt will provide yet more striking develop­ ments of a major character. It does, however, require a wide range of intellectual application, and a considerable ability in many fields. This book will provide much help. It is a very straightforward and thorough guide to every aspect of the subject. The authors are experienced both as research workers themselves and as teachers of standing, and this is shown in their clarity of exposition. There are plenty of iliustrations and worked examples to aid the student to obtain a real grasp of the subject.

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

    Science.gov (United States)

    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.

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

    International Nuclear Information System (INIS)

    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

  19. X-ray spectra of clusters of galaxies

    Science.gov (United States)

    Sarazin, Craig L.

    1990-01-01

    X-ray line observations of clusters of galaxies have shown that the X-ray emission in clusters is mainly thermal emission from hot diffuse gas, and that much of this gas has come out of stars, probably having been ejected from galaxies in the cluster. Future high resolution observations should allow us to determine the physical state of the gas. X-ray line measurements and abundance determinations can lead to strong constraints on the origin of the intracluster gas, and on the chemical evolution and history of galaxies. Some of the stronger resonant X-ray lines may be observable as absorption lines against a background quasar. Such X-ray absorption line measurement can be used to directly derive distances to clusters, using a technique similar to (and possibly complementary to) that the well-known method using the Zel'dovich-Syunyaev effect.

  20. Automated generation and ensemble-learned matching of X-ray absorption spectra

    Science.gov (United States)

    Zheng, Chen; Mathew, Kiran; Chen, Chi; Chen, Yiming; Tang, Hanmei; Dozier, Alan; Kas, Joshua J.; Vila, Fernando D.; Rehr, John J.; Piper, Louis F. J.; Persson, Kristin A.; Ong, Shyue Ping

    2018-03-01

    X-ray absorption spectroscopy (XAS) is a widely used materials characterization technique to determine oxidation states, coordination environment, and other local atomic structure information. Analysis of XAS relies on comparison of measured spectra to reliable reference spectra. However, existing databases of XAS spectra are highly limited both in terms of the number of reference spectra available as well as the breadth of chemistry coverage. In this work, we report the development of XASdb, a large database of computed reference XAS, and an Ensemble-Learned Spectra IdEntification (ELSIE) algorithm for the matching of spectra. XASdb currently hosts more than 800,000 K-edge X-ray absorption near-edge spectra (XANES) for over 40,000 materials from the open-science Materials Project database. We discuss a high-throughput automation framework for FEFF calculations, built on robust, rigorously benchmarked parameters. FEFF is a computer program uses a real-space Green's function approach to calculate X-ray absorption spectra. We will demonstrate that the ELSIE algorithm, which combines 33 weak "learners" comprising a set of preprocessing steps and a similarity metric, can achieve up to 84.2% accuracy in identifying the correct oxidation state and coordination environment of a test set of 19 K-edge XANES spectra encompassing a diverse range of chemistries and crystal structures. The XASdb with the ELSIE algorithm has been integrated into a web application in the Materials Project, providing an important new public resource for the analysis of XAS to all materials researchers. Finally, the ELSIE algorithm itself has been made available as part of veidt, an open source machine-learning library for materials science.

  1. Multiscale structural study using scanning X-ray microscope

    International Nuclear Information System (INIS)

    Ohsumi, Hiroyuki; Arima, Taka-hisa

    2016-01-01

    Correspondence between structures at the atomic- and meso-scales can be given by scanning X-ray microscopy integrated with polarized X-ray diffractometry. Symmetry is the common structural feature available across multiple hierarchies. This article introduces a symmetry evaluation technique based on polarized X-ray diffractometry and describes two embodiments: chirality domain observation and antiferromagnetic domain observation. Multiscale structural studies would play an important role in uncovering universality of hierarchical structure. (author)

  2. Quasar X-Ray Spectra At z=1.5

    Science.gov (United States)

    Siemiginowska, Aneta

    2001-01-01

    The predicted counts for ASCA observation was much higher than actually observed counts in the quasar. However, there are three weak hard x-ray sources in the GIS field. We are adding them to the source counts in modeling of hard x-ray background. The work is in progress. We have published a paper in Ap.J. on the luminosity function and the quasar evolution. Based on the theory described in this paper we are predicting a number of sources and their contribution to the x-ray background at different redshifts. These model predictions will be compared to the observed data in the final paper.

  3. Time-resolved x-ray spectra of laser irradiated high-Z targets

    International Nuclear Information System (INIS)

    Lee, P.H.Y.; Attwood, D.T.; Boyle, M.J.; Campbell, E.M.; Coleman, L.C.; Kornblum, H.N.

    1977-01-01

    Recent results obtained by using the Livermore 15 psec x-ray streak camera to record x-ray emission from laser-irradiated high-z targets in the 1-20 keV range are reported. Nine to eleven K-edge filter channels were used for the measurements. In the lower energy channels, a dynamic range of x-ray emission intensity of better than three orders of magnitude have been recorded. Data will be presented which describe temporally and spectrally resolved x-ray spectra of gold disk targets irradiated by laser pulses from the Argus facility, including the temporal evolution of the superthermal x-ray tail

  4. Changes of soft X-ray emission spectra of oxygen and copper in high Tc superconductors

    International Nuclear Information System (INIS)

    Fukushima, Sei; Gohshi, Yohichi; Kohiki, Shigemi; Saitoh, Naoki

    1989-01-01

    X-ray induced soft X-ray emission spectroscopy is one of the bulk analysis methods used to characterize high-Tc superconductor. In this report, some observations on the changes in O Kα and Cu L spectra of thin layer LnBa 2 Cu 3 O 7-δ (Ln=Er,Gd) samples are presented. From the measurement of O Kα, no discernible difference was found between those of Gd compounds which were composed single phase or not. It may be said that the electronic structure of p state localized on the O is not sensitive to the change of Tc or zero-resistance temperature. From the measurement of Cu L spectra, it was found that Cu Lα of only Gd containing compounds has a low energy shoulder

  5. X-ray measurements on wood - spectra measurements

    DEFF Research Database (Denmark)

    Jensen, Signe Kamp; Thygesen, Lisbeth Garbrecht; Gerward, Leif

    The report concerns simultaneous non-destructive measurements of water content and density of wood. Theoretically, this should be possible using a x-ray equipment newly build at BKM, and this work is an attempt to use the equipment for assessing water content and density of wood samples under...... laboratory conditions. A number of wood samples with different densities are placed at different relative humidities from 0.5 to 97 %RH. When equilibrium is obtained the samples are measured with the x-ray equipment such that 10 points are measured in the sample followed by measurements outside the sample...... (free-scanning). In this way 100 points are measured for each wood sample. This produces information about moisture content and density of the samples as water and wood attenuations of the x-rays are different for the different energy levels contained in the x-rays. The "real" density and moisture...

  6. Structure determination by X-ray crystallography

    CERN Document Server

    Ladd, M F C

    1977-01-01

    Crystallography may be described as the science of the structure of materi­ als, using this word in its widest sense, and its ramifications are apparent over a broad front of current scientific endeavor. It is not surprising, therefore, to find that most universities offer some aspects of crystallography in their undergraduate courses in the physical sciences. It is the principal aim of this book to present an introduction to structure determination by X-ray crystal­ lography that is appropriate mainly to both final-year undergraduate studies in crystallography, chemistry, and chemical physics, and introductory post­ graduate work in this area of crystallography. We believe that the book will be of interest in other disciplines, such as physics, metallurgy, biochemistry, and geology, where crystallography has an important part to play. In the space of one book, it is not possible either to cover all aspects of crystallography or to treat all the subject matter completely rigorously. In particular, certain ...

  7. Theory of pump–probe ultrafast photoemission and X-ray absorption spectra

    Energy Technology Data Exchange (ETDEWEB)

    Fujikawa, Takashi, E-mail: tfujikawa@faculty.chiba-u.jp; Niki, Kaori

    2016-01-15

    Highlights: • Pump–probe ultrafast XAFS and XPS spectra are theoretically studied. • Keldysh Green's function theory is applied. • Important many-body effects are explicitly included. - Abstract: Keldysh Green's function approach is extensively used in order to derive practical formulas to analyze pump–probe ultrafast photoemission and X-ray absorption spectra. Here the pump pulse is strong enough whereas the probe X-ray pulse can be treated by use of a perturbation theory. We expand full Green's function in terms of renormalized Green's function without the interaction between electrons and probe pulse. The present theoretical formulas allow us to handle the intrinsic and extrinsic losses, and furthermore resonant effects in X-ray Absorption Fine Structures (XAFS). To understand the radiation field screening in XPS spectra, we have to use more sophisticated theoretical approach. In the ultrafast XPS and XAFS analyses the intrinsic and extrinsic loss effects can interfere as well. In the XAFS studies careful analyses are necessary to handle extrinsic losses in terms of damped photoelectron propagation. The nonequilibrium dynamics after the pump pulse irradiation is well described by use of the time-dependent Dyson orbitals. Well above the edge threshold, ultrafast photoelectron diffraction and extended X-ray absorption fine structure (EXAFS) provide us with transient structural change after the laser pump excitations. In addition to these slow processes, the rapid oscillation in time plays an important role related to pump electronic excitations. Near threshold detailed information could be obtained for the combined electronic and structural dynamics. In particular high-energy photoemission and EXAFS are not so influenced by the details of excited states by pump pulse. Random-Phase Approximation (RPA)-boson approach is introduced to derive some practical formulas for time-dependent intrinsic amplitudes.

  8. Measurement of spectra for intra-oral X-ray beams using biological materials as attenuator

    International Nuclear Information System (INIS)

    Zenóbio, Madelon A.F.; Nogueira-Tavares, Maria S.; Zenóbio, Elton G.; Squair, Peterson Lima; Santos, Marcus A.P.; Silva, Teógenes A. da

    2011-01-01

    In diagnostic radiology, the radiation interaction probability in matter is a strong function of the X-ray energy. The knowledge of the X-ray energy spectral distribution allows optimizing the radiographic imaging system in order to obtain high quality images with as low as reasonably achievable patient doses. In this study, transmitted X-ray spectra through dentin and enamel that are existing materials in intra-oral radiology were experimentally determined in an X-ray equipment with 40–70 kV variable range. Dentin and enamel samples with 0.4–3.8 and 0.6–2.6 mm thick were used as attenuators. X-ray transmitted spectra were measured with XR-100T model CdTe detector and half-value layers (HVL) were determined. Characteristics of both dentin and enamel transmitted spectra showed that they have differences in the penetration power in matter and in the spectrum distribution. The results will be useful for phantom developments based on dentin and enamel for image quality control in dental radiology. - Highlights: ► The X-ray energy spectral distribution, optimize the radiographic imaging system. Transmitted X-ray spectra through dentin and enamel were experimentally determined. X-ray transmitted spectra were measured (XR-100T model CdTe detector). The transmitted spectra showed differences in the penetration power and spectrum distribution. Dentin and enamel transmitted spectra will be useful for phantom developments.

  9. Copper L X-ray spectra measured by a high resolution ion-induced X-ray spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Ryohei; Hamaguchi, Dai; Kageyama, Hiroyoshi [Kyoto Inst. of Tech. (Japan); and others

    1997-03-01

    High resolution L X-ray emission spectra of Cu have been measured by 0.75 MeV/u H, He, and F, 0.73 MeV/u Ar, 0.64 MeV/u Si, and 0.073 MeV/u Si ion impacts with a crystal spectrometer. The X-ray transition energies in the Cu target for L{iota}, L{eta}, L{alpha}{sub 1,2}, L{beta}{sub 1}, and L{beta}{sub 3,4} diagram lines induced by light ion impacts are determined, which are in good agreement with those given in the reference. The difference in L X-ray emission spectra produced by H, He, F, Si, and Ar ions are considered and the L{alpha}{sub 1,2} and L{beta}{sub 1} emission spectra are compared with the calculated ones based on the multiconfiguration Dirac-Fock method. (author)

  10. Electronic structure of nanoscale Cu/Pt alloys: A combined X-ray diffraction and X-ray absorption investigations

    International Nuclear Information System (INIS)

    Chen Xing; Chu Wangsheng; Cai Quan; Xia Dingguo; Wu Zhonghua; Wu Ziyu

    2006-01-01

    PVP-protected Cu/Pt clusters were prepared by glycol/water reduction method and characterized with transmission electron microscopy (TEM), X-ray diffraction (XRD) and absorption spectra. TEM and XRD analysis show that the Cu/Pt clusters with different molar ratio have fcc structure with particle size of about 4 nm, while the lattice parameters in these clusters reduce with increasing Cu concentration. From the X-ray absorption near edge structure (XANES) at Cu-K edge and Pt-L 2,3 edge, we demonstrate that the d-electronic states of Cu and Pt are affected by the local environment as a function of Cu/Pt molar ratio. With increasing Cu concentration, Pt loses a fraction of 5d electrons and the hybridization between p- and d-states at Cu sites is enhanced

  11. Electronic structure of nanoscale Cu/Pt alloys: A combined X-ray diffraction and X-ray absorption investigations

    Energy Technology Data Exchange (ETDEWEB)

    Chen Xing [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, CAS, Beijing (China); Graduate School of the Chinese Academy of Sciences, 100864 Beijing (China); Chu Wangsheng [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, CAS, Beijing (China); University of Science and Technology of China, Hefei, 230036 (China); Cai Quan [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, CAS, Beijing (China); Graduate School of the Chinese Academy of Sciences, 100864 Beijing (China); Xia Dingguo [College of Environmental and Energy Engineering, Beijing University of Technology, 100022 Beijing (China); Wu Zhonghua [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, CAS, Beijing (China); Wu Ziyu [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, CAS, Beijing (China) and National Center for Nanoscience and Technology (China)]. E-mail: wuzy@ihep.ac.cn

    2006-11-15

    PVP-protected Cu/Pt clusters were prepared by glycol/water reduction method and characterized with transmission electron microscopy (TEM), X-ray diffraction (XRD) and absorption spectra. TEM and XRD analysis show that the Cu/Pt clusters with different molar ratio have fcc structure with particle size of about 4 nm, while the lattice parameters in these clusters reduce with increasing Cu concentration. From the X-ray absorption near edge structure (XANES) at Cu-K edge and Pt-L{sub 2,3} edge, we demonstrate that the d-electronic states of Cu and Pt are affected by the local environment as a function of Cu/Pt molar ratio. With increasing Cu concentration, Pt loses a fraction of 5d electrons and the hybridization between p- and d-states at Cu sites is enhanced.

  12. INTEGRAL hard X-ray spectra of the cosmic X-ray background and Galactic ridge emission

    Science.gov (United States)

    Türler, M.; Chernyakova, M.; Courvoisier, T. J.-L.; Lubiński, P.; Neronov, A.; Produit, N.; Walter, R.

    2010-03-01

    Aims: We derive the spectra of the cosmic X-ray background (CXB) and of the Galactic ridge X-ray emission (GRXE) in the ~20-200 keV range from the data of the IBIS instrument aboard the INTEGRAL satellite obtained during the four dedicated Earth-occultation observations in early 2006. Methods: We analyze the modulation of the IBIS/ISGRI detector counts induced by the passage of the Earth through the field of view of the instrument. Unlike previous studies, we do not fix the spectral shape of the various contributions, but model instead their spatial distribution and derive for each of them the expected modulation of the detector counts. The spectra of the diffuse emission components are obtained by fitting the normalizations of the model lightcurves to the observed modulation in different energy bins. Because of degeneracy, we guide the fits with a realistic choice of the input parameters and a constraint for spectral smoothness. Results: The obtained CXB spectrum is consistent with the historic HEAO-1 results and falls slightly below the spectrum derived with Swift/BAT. A 10% higher normalization of the CXB cannot be completely excluded, but it would imply an unrealistically high albedo of the Earth. The derived spectrum of the GRXE confirms the presence of a minimum around 80 keV with improved statistics and yields an estimate of ~0.6 M⊙ for the average mass of white dwarfs in the Galaxy. The analysis also provides updated normalizations for the spectra of the Earth's albedo and the cosmic-ray induced atmospheric emission. Conclusions: This study demonstrates the potential of INTEGRAL Earth-occultation observations to derive the hard X-ray spectra of three fundamental components: the CXB, the GRXE and the Earth emission. Further observations would be extremely valuable to confirm our results with improved statistics.

  13. Singularities in x-ray spectra of metals

    International Nuclear Information System (INIS)

    Mahan, G.D.

    1987-08-01

    The x-ray spectroscopies discussed are absorption, emission, and photoemission. The singularities show up in each of them in a different manner. In absorption and emission they show up as power law singularities at the thresholds frequencies. This review will emphasize two themes. First a simple model is proposed to describe this phenomena, which is now called the MND model after MAHAN-NOZIERES-DeDOMINICIS. Exact analytical solutions are now available for this model for the three spectroscopies discussed above. These analytical models can be evaluated numerically in a simple way. The second theme of this review is that great care must be used when comparing the theory to experiment. A number of factors influence the edge shapes in x-ray spectroscopy. The edge singularities play an important role, and are observed in many matals. Quantitative fits of the theory to experiment require the consideration of other factors. 51 refs

  14. X-ray structure analysis of soil compositions

    International Nuclear Information System (INIS)

    Tillaev, T.; Kalonov, M.; Kuziev, Sh.; Khatamov, Sh.; Suvanov, M.

    1998-01-01

    The analytic characteristics of techniques developed to analyse soil structure by means of X-ray diffraction method are presented. Presence of 8 minerals in Fergana valley soils have been established. It is shown that X-ray structure analysis of soils gives rise to new original possibilities to determine not only their structure but also quantative content and type of chemical compound of element in soil. (author)

  15. Ab initio theory and calculations of X-ray spectra

    International Nuclear Information System (INIS)

    Rehr, J.J.; Kas, J.J.; Prange, M.P.; Sorini, A.P.; Takimoto, Y.; Vila, F.

    2009-01-01

    There has been dramatic progress in recent years both in the calculation and interpretation of various x-ray spectroscopies. However, current theoretical calculations often use a number of simplified models to account for many-body effects, in lieu of first principles calculations. In an effort to overcome these limitations we describe in this article a number of recent advances in theory and in theoretical codes which offer the prospect of parameter free calculations that include the dominant many-body effects. These advances are based on ab initio calculations of the dielectric and vibrational response of a system. Calculations of the dielectric function over a broad spectrum yield system dependent self-energies and mean-free paths, as well as intrinsic losses due to multielectron excitations. Calculations of the dynamical matrix yield vibrational damping in terms of multiple-scattering Debye-Waller factors. Our ab initio methods for determining these many-body effects have led to new, improved, and broadly applicable x-ray and electron spectroscopy codes. (authors)

  16. High-resolution Al L2,3-edge x-ray absorption near edge structure spectra of Al-containing crystals and glasses: coordination number and bonding information from edge components

    International Nuclear Information System (INIS)

    Weigel, C; Calas, G; Cormier, L; Galoisy, L; Henderson, G S

    2008-01-01

    High-resolution Al L 2,3 -edge x-ray absorption near edge structure (XANES) spectra have been measured in selected materials containing aluminium in 4-, 5- and 6-coordination. A shift of 1.5 eV is observed between the onset of [4] Al and [6] Al L 2,3 -edge XANES, in agreement with the magnitude of the shift observed at the Al K-edge. The differences in the position and shape of low-energy components of Al L 2,3 -edge XANES spectra provide a unique fingerprint of the geometry of the Al site and of the nature of Al-O chemical bond. The high resolution allows the calculation of electronic parameters such as the spin-orbit coupling and exchange energy using intermediate coupling theory. The electron-hole exchange energy decreases in tetrahedral as compared to octahedral symmetry, in relation with the increased screening of the core hole in the former. Al L 2,3 -edge XANES spectra confirm a major structural difference between glassy and crystalline NaAlSi 2 O 6 , with Al in 4- and 6-coordination, respectively, Al coordination remaining unchanged in NaAl 1-x Fe x Si 2 O 6 glasses, as Fe is substituted for Al

  17. Structure of polysaccharide and structural analysis by x-ray

    International Nuclear Information System (INIS)

    Yuguchi, Yoshiaki

    2010-01-01

    Polysaccharides occur in plants and the living body in the solid, gel, or liquid. They have a highly structural diversity and possess the potential to be used for development of new materials and energy sources. So it is very important to understand their molecular structure under various conditions. This review introduces the structural characteristics of polysaccharides and the examples of their analysis by the X-ray scattering method. (author)

  18. Broadband X-ray spectra of the ultraluminous x-ray source Holmberg IX X-1 observed with NuSTAR, XMM-Newton, and Suzaku

    DEFF Research Database (Denmark)

    Walton, D. J.; Harrison, F. A.; Grefenstette, B. W.

    2014-01-01

    We present results from the coordinated broadband X-ray observations of the extreme ultraluminous X-ray source Holmberg IX X-1 performed by NuSTAR, XMM-Newton, and Suzaku in late 2012. These observations provide the first high-quality spectra of Holmberg IX X-1 above 10 keV to date, extending the...

  19. X-ray photoelectron spectra of γ-irradiated perfluorobenzene

    International Nuclear Information System (INIS)

    Sunder, S.; Sagert, N.H.; Wood, D.D.; Miller, N.H.

    1990-01-01

    The effect of γ-radiolysis on perfluorobenzene (PFB) was investigated using low-temperature X-ray photoelectron spectroscopy (XPS). PFB was irradiated in fluorine-passivated nickel cells using Co 60 γ-rays in an Atomic Energy of Canada Limited Gammacell at a dose rate of about 2.6 Gy·s -1 and for a total dose of about 50 kGy. The γ-radiolysis of PFB not only results in cross-linkage but also in the formation of saturated carbon centers in the PFB, as indicated by the presence of CF 2 and CF 3 groups. The relative abundance of CF, CF 2 and CF 3 groups, in the irradiated PFB, was estimated to be about 86, 9 and 5%, respectively

  20. Structure in galactic soft X-ray features

    International Nuclear Information System (INIS)

    Davelaar, J.

    1979-01-01

    Observations are described of the soft X-ray background in a part of the northern hemisphere in the energy range 0.06 - 3.0 keV. The X-ray instruments, placed onboard a sounding rocket, are a one-dimensional focusing collector with multi-cell proportional counters in the focal plane and eight large area counters on deployable panels. A description of the instruments and their preflight calibration is given. Precautions were taken to prevent UV sensitivity of the X-ray instruments. The observation program, which consisted of a number of pre-programmed slow scans, is outlined. The spectral date on the soft X-ray background in these and previous observations showed that at least two components of different temperature are present. A low temperature component of approximately (3-10)x10 5 is found all over the sky. Components of higher temperature approximately 3x10 6 K are found in regions of soft X-ray enhancement; The North Polar Spur has been observed in two scans at the galactic latitude b=25 0 and b=75 0 . The X-ray ridge structure is found to be strongly energy dependent. The low energy data ( 0 reveals two separate emission features on the ridge, both probably of finite extensions (approximately equal to 0 0 .5). A wider X-ray ridge (approximately equal to 10 0 ) is observed above 0.4 keV. (Auth.)

  1. First Principles Calculations for X-ray Resonant Spectra and Elastic Properties

    International Nuclear Information System (INIS)

    Yongbin Lee

    2006-01-01

    In this thesis, we discuss applications of first principles methods to x-ray resonant spectra and elastic properties calculation. We start with brief reviews about theoretical background of first principles methods, such as density functional theory, local density approximation (LDA), LDA+U, and the linear augmented plane wave (LAPW) method to solve Kohn-Sham equations. After that we discuss x-ray resonant scattering (XRMS), x-ray magnetic circular dichroism (XMCD) and the branching problem in the heavy rare earths Ledges. In the last chapter we discuss the elastic properties of the second hardest material AlMgB 14

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

    Energy Technology Data Exchange (ETDEWEB)

    Seidler, G. T., E-mail: seidler@uw.edu; Mortensen, D. R.; Remesnik, A. J.; Pacold, J. I.; Ball, N. A.; Barry, N.; Styczinski, M.; Hoidn, O. R. [Physics Department, University of Washington, Seattle, Washington 98195-1560 (United States)

    2014-11-15

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

  3. Modeling of X-ray images and energy spectra produced by stepping lightning leaders

    OpenAIRE

    Xu , Wei; Marshall , Robert A.; Celestin , Sébastien; Pasko , Victor P.

    2017-01-01

    International audience; Recent ground-based measurements at the International Center for Lightning Research and Testing (ICLRT) have greatly improved our knowledge of the energetics, fluence, and evolution of X-ray emissions during natural cloud-to-ground (CG) and rocket-triggered lightning flashes. In this paper, using Monte Carlo simulations and the response matrix of unshielded detectors in the Thunderstorm Energetic Radiation Array (TERA), we calculate the energy spectra of X-rays as woul...

  4. High-energy X-ray spectra of Cygnus XR-1 observed from OSO 8

    Science.gov (United States)

    Dolan, J. F.; Crannell, C. J.; Dennis, B. R.; Frost, K. J.; Orwig, L. E.

    1979-01-01

    X-ray spectra of Cygnus XR-1 were measured with the scintillation spectrometer aboard the OSO 8 satellite during a period of one-and-one-half to three weeks in each of the years from 1975 to 1977. Typical spectra of the source between 15 and 250 keV are presented and the spectra are found to be well represented by a single power-law expression whose photon number spectral index is different for the two intensity states that were considered. The observed pivoting effect is consistent with two-temperature accretion disk models of the X-ray emitting region.

  5. SU-F-I-76: Fluoroscopic X-Ray Beam Profiles for Spectra Incorporating Copper Filtration

    Energy Technology Data Exchange (ETDEWEB)

    Wunderle, K [Cleveland Clinic Foundation, Cleveland, OH (United States); Wayne State University School of Medicine, Detroit, MI (United States); Godley, A; Shen, Z; Dong, F [Cleveland Clinic Foundation, Cleveland, OH (United States); Rakowski, J [Wayne State University School of Medicine, Detroit, MI (United States)

    2016-06-15

    Purpose: The purpose of this investigation is to characterize and quantify X-ray beam profiles for fluoroscopic x-ray beam spectra incorporating spectral (copper) filtration. Methods: A PTW (Freiburg, Germany) type 60016 silicon diode detector and PTW MP3 water tank were used to measure X-ray beam profiles for 60, 80, 100 and 120 kVp x-ray beams at five different copper filtration thicknesses ranging from 0–0.9 mm at 22 and 42 cm fields of view and depths of 1, 5, and 10 cm in both the anode-cathode axis (inplane) and cross-plane directions. All measurements were acquired on a Siemens (Erlangen, Germany) Artis ZeeGo fluoroscope inverted from the typical orientation providing an x-ray beam originating from above the water surface with the water level set at 60 cm from the focal spot. Results: X-ray beam profiles for beam spectra without copper filtration compared well to previously published data by Fetterly et al. [Med Phys, 28, 205 (2001)]. Our data collection benefited from the geometric orientation of the fluoroscope, providing a beam perpendicular to the tank water surface, rather than through a thin side wall as did the previously mentioned study. Profiles for beams with copper filtration were obtained which have not been previously investigated and published. Beam profiles in the anode-cathode axis near the surface and at lower x-ray energy exhibited substantial heel effect, which became less pronounced at greater depth. At higher energy with copper filtration in the beam, the dose falloff out-of-field became less pronounced, as would be anticipated given higher scatter photon energy. Conclusion: The x-ray beam profile data for the fluoroscopic x-ray beams incorporating copper filtration are intended for use as reference data for estimating doses to organs or soft tissue, including fetal dose, involving similar beam qualities or for comparison with mathematical models.

  6. Finite temperature effects on the X-ray absorption spectra of energy related materials

    Science.gov (United States)

    Pascal, Tod; Prendergast, David

    2014-03-01

    We elucidate the role of room-temperature-induced instantaneous structural distortions in the Li K-edge X-ray absorption spectra (XAS) of crystalline LiF, Li2SO4, Li2O, Li3N and Li2CO3 using high resolution X-ray Raman spectroscopy (XRS) measurements and first-principles density functional theory calculations within the eXcited electron and Core Hole (XCH) approach. Based on thermodynamic sampling via ab-initio molecular dynamics (MD) simulations, we find calculated XAS in much better agreement with experiment than those computed using the rigid crystal structure alone. We show that local instantaneous distortion of the atomic lattice perturbs the symmetry of the Li 1 s core-excited-state electronic structure, broadening spectral line-shapes and, in some cases, producing additional spectral features. This work was conducted within the Batteries for Advanced Transportation Technologies (BATT) Program, supported by the U.S. Department of Energy Vehicle Technologies Program under Contract No. DE-AC02-05CH11231.

  7. The Zone of Avoidance as an X-ray absorber - the role of the galactic foreground modelling Swift XRT spectra

    Science.gov (United States)

    Racz, I. I.; Bagoly, Z.; Tóth, L. V.; Balázs, L. G.; Horvath, I.; Zahorecz, S.

    2018-05-01

    Gamma-ray bursts (GRBs) are the most powerful explosive events in the Universe. The prompt gamma emission is followed by an X-ray afterglow that is also detected for over nine hundred GRBs by the Swift BAT and XRT detectors. The X-ray afterglow spectrum bears essential information about the burst, and the surrounding interstellar medium (ISM). Since the radiation travels through the line of sight intergalactic medium and the ISM in the Milky Way, the observed emission is influenced by extragalactic and galactic components. The column density of the Galactic foreground ranges several orders of magnitudes, due to both the large scale distribution of ISM and its small scale structures. We examined the effect of local HI column density on the penetrating X-ray emission, as the first step towards a precise modeling of the measured X-ray spectra. We fitted the X-ray spectra using the Xspec software, and checked how the shape of the initially power low spectrum changes with varying input Galactic HI column density. The total absorbing HI column is a sum of the intrinsic and Galactic component. We also investigated the model results for the intrinsic component varying the Galactic foreground. We found that such variations may alter the intrinsic hydrogen column density up to twenty-five percent. We will briefly discuss its consequences.

  8. Modeling of X-ray Images and Energy Spectra Produced by Stepping Lightning Leaders

    Science.gov (United States)

    Xu, Wei; Marshall, Robert A.; Celestin, Sebastien; Pasko, Victor P.

    2017-11-01

    Recent ground-based measurements at the International Center for Lightning Research and Testing (ICLRT) have greatly improved our knowledge of the energetics, fluence, and evolution of X-ray emissions during natural cloud-to-ground (CG) and rocket-triggered lightning flashes. In this paper, using Monte Carlo simulations and the response matrix of unshielded detectors in the Thunderstorm Energetic Radiation Array (TERA), we calculate the energy spectra of X-rays as would be detected by TERA and directly compare with the observational data during event MSE 10-01. The good agreement obtained between TERA measurements and theoretical calculations supports the mechanism of X-ray production by thermal runaway electrons during the negative corona flash stage of stepping lightning leaders. Modeling results also suggest that measurements of X-ray bursts can be used to estimate the approximate range of potential drop of lightning leaders. Moreover, the X-ray images produced during the leader stepping process in natural negative CG discharges, including both the evolution and morphological features, are theoretically quantified. We show that the compact emission pattern as recently observed in X-ray images is likely produced by X-rays originating from the source region, and the diffuse emission pattern can be explained by the Compton scattering effects.

  9. Diagnostic x-ray spectra measurements using a silicon surface barrier detector

    International Nuclear Information System (INIS)

    Pani, R.; Laitano, R.F.

    1987-01-01

    A silicon surface barrier detector having a low efficiency for x-ray is used to analyse diagnostic x-ray spectra. This characteristic is advantageous in overcoming experimental problems caused by high fluence rates typical of diagnostic x-ray beams. The pulse height distribution obtained with silicon surface barrier detectors is very different from the true photon spectra because of the presence of escaped Compton photons and the fact that detection efficiency falls abruptly when photon energy increases. A detailed analysis of the spurious effects involved in detection is made by a Monte Carlo method. A stripping procedure is described for implementation on a personal computer. The validity of this method is tested by comparison with experimental results obtained with a Ge detector. The spectra obtained with the Si detector are in fairly good agreement with the analogous spectra measured with a Ge detector. The advantages of using Si as opposed to Ge detectors in x-ray spectrometry are: its simplicity of use, its greater economy for use in routine diagnostic x-ray spectroscopy and the possibility that the stripping procedure can be implemented on a personal computer. (author)

  10. Phase-dependent absorption features in X-ray spectra of X-ray Dim Isolated Neutron Stars

    Science.gov (United States)

    Borghese, A.; Rea, N.; Coti Zelati, F.; Turolla, R.; Tiengo, A.; Zane, S.

    2017-12-01

    A detailed phase-resolved spectroscopy of archival XMM-Newton observations of X-ray Dim Isolated Neutron Stars (XDINSs) led to the discovery of narrow and strongly phase-dependent absorption features in two of these sources. The first was discovered in the X-ray spectrum of RX J0720.4-3125, followed by a new possible candidate in RX J1308.6+2127. Both spectral lines have similar properties: they are detected for only ˜ 20% of the rotational cycle and appear to be stable over the timespan covered by the observations. We performed Monte Carlo simulations to test the significance of these phase-variable features and in both cases the outcome has confirmed the detection with a confidence level > 4.6σ. Because of the narrow width and the strong dependence on the pulsar rotational phase, the most likely interpretation for these spectral features is in terms of resonant proton cyclotron absorption scattering in a confined high-B structure close to the stellar surface. Within the framework of this interpretation, our results provide evidence for deviations from a pure dipole magnetic field on small scales for highly magnetized neutron stars and support the proposed scenario of XDINSs being aged magnetars, with a strong non-dipolar crustal B-field component.

  11. Effects of phonon broadening on x-ray near-edge spectra in molecular crystals

    Science.gov (United States)

    Vinson, John; Jach, Terrence; Elam, Tim; Denlinger, Jonathon

    2014-03-01

    Calculations of near-edge x-ray spectra are often carried out using the average atomic coordinates from x-ray or neutron scattering experiments or from density functional theory (DFT) energy minimization. This neglects disorder from thermal and zero-point vibrations. Here we look at the nitrogen K-edge of ammonium chloride and ammonium nitrate, comparing Bethe-Salpeter calculations of absorption and fluorescence to experiment. We find that intra-molecular vibrational effects lead to significant, non-uniform broadening of the spectra, and that for some features zero-point motion is the primary source of the observed shape.

  12. Lifetime-vibrational interference effects in resonantly excited x-ray emission spectra of CO

    Energy Technology Data Exchange (ETDEWEB)

    Skytt, P.; Glans, P.; Gunnelin, K. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    The parity selection rule for resonant X-ray emission as demonstrated for O{sub 2} and N{sub 2} can be seen as an effect of interference between coherently excited degenerate localized core states. One system where the core state degeneracy is not exact but somewhat lifted was previously studied at ALS, namely the resonant X-ray emission of amino-substituted benzene (aniline). It was shown that the X-ray fluorescence spectrum resulting from excitation of the C1s at the site of the {open_quotes}aminocarbon{close_quotes} could be described in a picture separating the excitation and the emission processes, whereas the spectrum corresponding to the quasi-degenerate carbons could not. Thus, in this case it was necessary to take interference effects between the quasi-degenerate intermediate core excited states into account in order to obtain agreement between calculations and experiment. The different vibrational levels of core excited states in molecules have energy splittings which are of the same order of magnitude as the natural lifetime broadening of core excitations in the soft X-ray range. Therefore, lifetime-vibrational interference effects are likely to appear and influence the band shapes in resonant X-ray emission spectra. Lifetime-vibrational interference has been studied in non-resonant X-ray emission, and in Auger spectra. In this report the authors discuss results of selectively excited soft X-ray fluorescence spectra of molecules, where they focus on lifetime-interference effects appearing in the band shapes.

  13. X-Ray, IR, NMR, UV-visible spectra and DFT analysis of 5-aryloxy-(1H-tetrazoles, structure, conformation and tautomerism

    Directory of Open Access Journals (Sweden)

    Nader Noroozi Pesyan

    2014-03-01

    Full Text Available The predominant tautomeric forms of N1–H, N2–H of 5-(2,6-dimethyl- and 5-(2,6-diisopropylphenoxy-(1H-tetrazoles were analyzed at B3LYP method using 6-311G(d,p basis set in the gas phase. The N1–H form of tetrazoles was found to be more stable than N2–H form in both solid and gas phases. Crystal structures of both tetrazoles show an intermolecular H-bond between N1-H and N4 atom of other tetrazole space. The hydrogen bonds between each tautomer of tetrazoles were evaluated at B3LYP/6-311G(d,p level. The geometrical parameters and spectral data of tetrazoles and their variation were studied in both solid and gas phases.

  14. X-ray structure based evaluation of analogs of citalopram

    DEFF Research Database (Denmark)

    Topiol, Sid; Bang-Andersen, Benny; Sanchez, Connie

    2017-01-01

    The recent publication of X-ray structures of SERT includes structures with the potent antidepressant S-Citalopram (S-Cit). Earlier predictions of ligand binding at both a primary (S1) and an allosteric modulator site (S2), were confirmed. We provide herein examples of a series of Citalopram anal...

  15. Sensitivity Analysis of X-ray Spectra from Scanning Electron Microscopes

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Thomas Martin [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Patton, Bruce W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Weber, Charles F. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Bekar, Kursat B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2014-10-01

    The primary goal of this project is to evaluate x-ray spectra generated within a scanning electron microscope (SEM) to determine elemental composition of small samples. This will be accomplished by performing Monte Carlo simulations of the electron and photon interactions in the sample and in the x-ray detector. The elemental inventories will be determined by an inverse process that progressively reduces the difference between the measured and simulated x-ray spectra by iteratively adjusting composition and geometric variables in the computational model. The intended benefit of this work will be to develop a method to perform quantitative analysis on substandard samples (heterogeneous phases, rough surfaces, small sizes, etc.) without involving standard elemental samples or empirical matrix corrections (i.e., true standardless quantitative analysis).

  16. Time-resolved soft x-ray spectra from laser-produced Cu plasma

    International Nuclear Information System (INIS)

    Cone, K.V.; Dunn, J.; Baldis, H.A.; May, M.J.; Purvis, M.A.; Scott, H.A.; Schneider, M.B.

    2012-01-01

    The volumetric heating of a thin copper target has been studied with time resolved x-ray spectroscopy. The copper target was heated from a plasma produced using the Lawrence Livermore National Laboratory's Compact Multipulse Terrawatt (COMET) laser. A variable spaced grating spectrometer coupled to an x-ray streak camera measured soft x-ray emission (800-1550 eV) from the back of the copper target to characterize the bulk heating of the target. Radiation hydrodynamic simulations were modeled in 2-dimensions using the HYDRA code. The target conditions calculated by HYDRA were post-processed with the atomic kinetics code CRETIN to generate synthetic emission spectra. A comparison between the experimental and simulated spectra indicates the presence of specific ionization states of copper and the corresponding electron temperatures and ion densities throughout the laser-heated copper target.

  17. Astrophysical extended X-ray absorption fine-structure analysis

    International Nuclear Information System (INIS)

    Woo, J.W.; Forrey, R.C.; Cho, K.; Department of Physics and Division of Applied Sciences, Harvard University)

    1997-01-01

    We present an astrophysical extended X-ray absorption fine-structure (EXAFS) analysis (AEA) tool. The AEA tool is designed to generate a numerical model of the modification to the X-ray absorption coefficient due to the EXAFS phenomenon. We have constructed a complete database (elements up to the atomic number 92) of EXAFS parameters: central atom phase shift (2δ 1 ), backscattering phase shift (φ b ), and backscattering amplitude (F). Using the EXAFS parameter data base, the AEA tool can generate a numerical model of any compound when the atomic numbers of neighboring atoms and their distances to the central X-ray-absorbing atom are given. copyright 1997 The American Astronomical Society

  18. New Spectral Model for Constraining Torus Covering Factors from Broadband X-Ray Spectra of Active Galactic Nuclei

    Science.gov (United States)

    Baloković, M.; Brightman, M.; Harrison, F. A.; Comastri, A.; Ricci, C.; Buchner, J.; Gandhi, P.; Farrah, D.; Stern, D.

    2018-02-01

    The basic unified model of active galactic nuclei (AGNs) invokes an anisotropic obscuring structure, usually referred to as a torus, to explain AGN obscuration as an angle-dependent effect. We present a new grid of X-ray spectral templates based on radiative transfer calculations in neutral gas in an approximately toroidal geometry, appropriate for CCD-resolution X-ray spectra (FWHM ≥ 130 eV). Fitting the templates to broadband X-ray spectra of AGNs provides constraints on two important geometrical parameters of the gas distribution around the supermassive black hole: the average column density and the covering factor. Compared to the currently available spectral templates, our model is more flexible, and capable of providing constraints on the main torus parameters in a wider range of AGNs. We demonstrate the application of this model using hard X-ray spectra from NuSTAR (3–79 keV) for four AGNs covering a variety of classifications: 3C 390.3, NGC 2110, IC 5063, and NGC 7582. This small set of examples was chosen to illustrate the range of possible torus configurations, from disk-like to sphere-like geometries with column densities below, as well as above, the Compton-thick threshold. This diversity of torus properties challenges the simple assumption of a standard geometrically and optically thick toroidal structure commonly invoked in the basic form of the unified model of AGNs. Finding broad consistency between our constraints and those from infrared modeling, we discuss how the approach from the X-ray band complements similar measurements of AGN structures at other wavelengths.

  19. The X-ray spectra of clusters of galaxies and their relationship to other cluster properties

    International Nuclear Information System (INIS)

    Mitchell, R.J.; Dickens, R.J.; Burnell, S.J.B.; Culhane, J.L.

    1979-01-01

    New observations with the MSSL proportional counter spectrometer on the Ariel V satellite of the X-ray spectra of 20 candidate clusters of galaxies are reported. The data are compared with the results from the OSO-8 satellite and the combined sample of some 30 cluster X-ray spectra are analysed. The present study finds generally larger values of Lsub(X) than do Uhuru or the SSI, which, because of the larger field of view, may indicate significant amounts of hot gas away from the cluster centres. The validity of all X-ray cluster identifications has been examined, and sources have been classified according to certainty of identification. The incidence of X-ray line emission from the clusters has been investigated and temperatures, kTsub(X), have been derived on the basis of an isothermal model. Relationships between X-ray, optical and radio properties of the clusters have been studied. The more massive, centrally condensed clusters generally contain higher temperature gas and have a greater luminosity than the less massive, more irregular clusters. (author)

  20. Transmission properties of barite mortar using X-ray spectra measured with Cd Te detector

    Energy Technology Data Exchange (ETDEWEB)

    Santos, J. C.; Mariano, L.; Costa, P. R. [Universidade de Sao Paulo, Instituto de Fisica, Rua do Matao Travessa R. 187, Cidade Universitaria, 05508-090 Sao Paulo (Brazil); Tomal, A., E-mail: josilene@usp.br [Universidade Federal de Goias, Instituto de Fisica, Campus Samambaia, 74001-970 Goiania (Brazil)

    2014-08-15

    Current methods for calculating X-ray shielding barriers do not take into account spectral distribution of the beam transmitted by the protective material. This consideration is important in dose estimations for radiation workers and general public in diagnostic radiology facilities. The aim of the present study was to estimate barite mortar attenuation curves using X-ray spectra weighted by a workload distribution. These curves were described in units of ambient dose equivalent (H (10)), since it is the radiation quantity adopted by IAEA for dose assessment in medical environment. Attenuation curves were determined using the optimized model for shielding evaluation presented by Costa and Caldas (2002). Workload distribution presented by Simpkin (1996), measured primary spectra and mass attenuation coefficients of barite mortar were used as input data in this model. X-ray beams in diagnostic energy range were generated by an industrial X-ray tube with 3 mm of aluminum additional filtration. Primary experimental spectra were measured by a Cd Te detector and corrected by the response function of detector by means of a stripping procedure. Air kerma measurements were performed using an ionization chamber for normalization purpose of the spectra. The corrected spectra presented good agreement with spectra generated by a semi-empirical model. The variation of the ambient dose equivalent as a function of barite mortar thickness was calculated. Using these data, it was estimated the optimized thickness of protective barrier needed for shielding a particular area in an X-ray imaging facility. The results obtained for primary protective barriers exhibit qualitative agreement with those presented in literature. (Author)

  1. Measurement of X-ray spectra by PIN photodiode: comparative study

    International Nuclear Information System (INIS)

    Costa, Paulo R.; Furquim, Tania A.C.; Herdade, Silvio B.

    1996-01-01

    Two different approaches for the evaluation of diagnostic X-ray spectra are presented : one based on a semiempirical model and other based on measurements using a silicon PIN photodiode. Measured and calculated values using typical kVp and filter combinations are compared

  2. X-ray satellite spectra of Ti, V, Cr and Mn induced by photons

    Indian Academy of Sciences (India)

    K X-ray emission spectra of Ti, V, Cr and Mn generated by photon excitation have been studied with a crystal spectrometer. The measured energy shifts of K satellite relative to the diagram line are compared with values obtained by electron excitation and with different theoretical estimates. The present experimental ...

  3. X-ray spectra from the Cornell Electron-Beam Ion Source (CEBIS I)

    International Nuclear Information System (INIS)

    Johnson, B.M.; Jones, K.W.; Kostroun, V.O.; Ghanbari, E.; Janson, S.W.

    1985-01-01

    Radiation emitted from the Cornell electron beam ion source (CEBIS I) has been surveyed with a Si(Li) x-ray detector. These spectra can be used to estimate backgrounds from electron bremsstrahlung and to evaluate the feasibility of atomic physics experiments using the CEBIS I source in this configuration. 1 ref., 2 figs

  4. Core-hole effects in the x-ray-absorption spectra of transition-metal silicides

    NARCIS (Netherlands)

    WEIJS, PJW; CZYZYK, MT; VANACKER, JF; SPEIER, W; GOEDKOOP, JB; VANLEUKEN, H; HENDRIX, HJM; DEGROOT, RA; VANDERLAAN, G; BUSCHOW, KHJ; WIECH, G; FUGGLE, JC

    1990-01-01

    We report systematic differences between the shape of the Si K x-ray-absorption spectra of transition-metal silicides and broadened partial densities of Si p states. We use a variety of calculations to show that the origin of these discrepancies is the core-hole potential appropriate to the final

  5. Nano structured materials studied by coherent X-ray diffraction

    International Nuclear Information System (INIS)

    Gulden, Johannes

    2013-03-01

    Structure determination with X-rays in crystallography is a rapidly evolving field. Crystallographic methods for structure determination are based on the assumptions about the crystallinity of the sample. It is vital to understand the structure of possible defects in the crystal, because they can influence the structure determination. All conventional methods to characterize defects require a modelling through simulated data. No direct methods exist to image the core of defects in crystals. Here a new method is proposed, which will enable to visualize the individual scatterers around and at defects in crystals. The method is based on coherent X-ray scattering. X-rays are perfectly suited since they can penetrate thick samples and buried structures can be investigated Recent developments increased the coherent flux of X-Ray sources such as synchrotrons by orders of magnitude. As a result, the use of the coherent properties of X-rays is emerging as a new aspect of X-ray science. New upcoming and operating X-ray laser sources will accelerate this trend. One new method which has the capacity to recover structural information from the coherently scattered photons is Coherent X-ray Diffraction Imaging (CXDI). The main focus of this thesis is the investigation of the structure and the dynamics of colloidal crystals. Colloidal crystals can be used as a model for atomic crystals in order to understand the growth and defect structure. Despite the large interest in these structures, many details are still unknown.Therefore, it is vital to develop new approaches to measure the core of defects in colloidal crystals. After an introduction into the basics of the field of coherent X-ray scattering, this thesis introduces a novel method, Small Angle Bragg Coherent Diffractive Imaging, (SAB-CDI). This new measurement technique which besides the relevance to colloidal crystals can be applied to a large variety of nano structured materials. To verify the experimental possibilities the

  6. Nano structured materials studied by coherent X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Gulden, Johannes

    2013-03-15

    Structure determination with X-rays in crystallography is a rapidly evolving field. Crystallographic methods for structure determination are based on the assumptions about the crystallinity of the sample. It is vital to understand the structure of possible defects in the crystal, because they can influence the structure determination. All conventional methods to characterize defects require a modelling through simulated data. No direct methods exist to image the core of defects in crystals. Here a new method is proposed, which will enable to visualize the individual scatterers around and at defects in crystals. The method is based on coherent X-ray scattering. X-rays are perfectly suited since they can penetrate thick samples and buried structures can be investigated Recent developments increased the coherent flux of X-Ray sources such as synchrotrons by orders of magnitude. As a result, the use of the coherent properties of X-rays is emerging as a new aspect of X-ray science. New upcoming and operating X-ray laser sources will accelerate this trend. One new method which has the capacity to recover structural information from the coherently scattered photons is Coherent X-ray Diffraction Imaging (CXDI). The main focus of this thesis is the investigation of the structure and the dynamics of colloidal crystals. Colloidal crystals can be used as a model for atomic crystals in order to understand the growth and defect structure. Despite the large interest in these structures, many details are still unknown.Therefore, it is vital to develop new approaches to measure the core of defects in colloidal crystals. After an introduction into the basics of the field of coherent X-ray scattering, this thesis introduces a novel method, Small Angle Bragg Coherent Diffractive Imaging, (SAB-CDI). This new measurement technique which besides the relevance to colloidal crystals can be applied to a large variety of nano structured materials. To verify the experimental possibilities the

  7. Theoretical approaches to x-ray absorption fine structure

    International Nuclear Information System (INIS)

    Rehr, J. J.; Albers, R. C.

    2000-01-01

    Dramatic advances in the understanding of x-ray absorption fine structure (XAFS) have been made over the past few decades, which have led ultimately to a highly quantitative theory. This review covers these developments from a unified multiple-scattering viewpoint. The authors focus on extended x-ray absorption fine structure (EXAFS) well above an x-ray edge, and, to a lesser extent, on x-ray absorption near-edge structure (XANES) closer to an edge. The discussion includes both formal considerations, derived from a many-electron formulation, and practical computational methods based on independent-electron models, with many-body effects lumped into various inelastic losses and energy shifts. The main conceptual issues in XAFS theory are identified and their relative importance is assessed; these include the convergence of the multiple-scattering expansion, curved-wave effects, the scattering potential, inelastic losses, self-energy shifts, and vibrations and structural disorder. The advantages and limitations of current computational approaches are addressed, with particular regard to quantitative experimental comparisons. (c) 2000 The American Physical Society

  8. Structured scintillators for X-ray imaging with micrometre resolution

    DEFF Research Database (Denmark)

    Olsen, Ulrik Lund; Schmidt, Søren; Poulsen, Henning Friis

    2009-01-01

    A 3D X-ray detector for imaging of 30–200 keV photons is described. It comprises a stack of semitransparent structured scintillators, where each scintillator is a regular array of waveguides in silicon, and with pores filled with CsI. The performance of the detector is described theoretically...

  9. Structural Investigations of Nanowires Using X-Ray Diffraction

    DEFF Research Database (Denmark)

    Stankevic, Tomas

    Advancements in growth of the nanowire-based devices opened another dimension of possible structures and material combinations, which nd their applications in a wide variety of elds, including everyday life. Characterization of such devices brings its own challenges and here we show that X-rays oer...

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

    Science.gov (United States)

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

    2018-04-13

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

  11. Envelope method for background elimination from X-ray fluorescence spectra

    International Nuclear Information System (INIS)

    Monakhov, V.V.; Naumenko, P.A.; Chashinskaya, O.A.

    2006-01-01

    The influence of the background noise caused by Bremsstrahlung on the accuracy of the envelope method at x-ray fluorescence spectra processing is studied. This is carried out by the example of model spectra at different forms of Bremsstrahlung noise as well as at the presence of background noise in spectra. The interpolation by parabolic splines is used for the estimation of the error of the envelope method for the elimination of continuos background noise. It is found out that the error of the proposed method constitutes decimal parts of percent. It is shown that the envelope method is the effective technique for the elimination of the continuous Bremsstrahlung from x-ray fluorescence spectra of the first order [ru

  12. Quasar energy distributions. I. Soft X-ray spectra of quasars

    International Nuclear Information System (INIS)

    Wilkes, B.J.; Elvis, M.

    1987-01-01

    As the initial stage of a study of quasar energy distributions (QEDs), Einstein IPC spectra of 24 quasars are presented. These are combined with previously reported IPC spectra to form a sample of 33 quasars with well-determined soft X-ray slopes. A correlation analysis shows that radio loudness, rather than redshift or luminosity, is fundamentally related to the X-ray slope. This correlation is not followed by higher energy spectra of active galaxies. Two components are required to explain both sets of results. The best-fit column densities are systematically smaller than the Galactic values. The same effect is not present in a sample of BL Lac objects, implying that the effect is intrinsic to the quasars and is caused by a low-energy turnup in the quasar spectra. 74 references

  13. An analysis of the MO X-ray spectra in U92+-Pb collisions

    International Nuclear Information System (INIS)

    Schulze, K.; Anton, J.; Sepp, W.-D.; Fricke, B.

    1999-01-01

    The investigation of quasimolecular X-rays from superheavy collision systems with bare or H-like projectiles seems to be a promising approach to get information about the behaviour of inner shell electrons with energy eigenvalues in the vicinity of the negative continuum. We present calculations of the MO X-ray spectra for the system U 92+ -Pb for varying impact energies. Furthermore we analyse the contributions due to electrons in higher lying states. The results are discussed with respect to the experimental determination of the transition energies in the superheavy quasimolecule. (orig.)

  14. A color display device recording X ray spectra, especially intended for medical radiography

    International Nuclear Information System (INIS)

    Boulch, J.-M.

    1975-01-01

    Said invention relates to a color display recording device for X ray spectra intended for medical radiography. The video signal of the X ray camera receiving the radiation having passed through the patient is amplified and transformed into a color coding according to the energy spectrum received by the camera. In a first version, the energy spectrum from the camera gives directly an image on the color tube. In a second version the energy spectrum, after having been transformed into digital signals, is first sent into a memory, then into a computer used as a spectrum analyzer, and finally into the color display device [fr

  15. Spectra transmitted by mortar barite in X-Ray qualities applied in diagnostic radiology as shielding

    Energy Technology Data Exchange (ETDEWEB)

    Almeida Junior, Airton T., E-mail: airton.almeida@fundacentro.gov.br [Fundacaoo Jorge Duprat Figueiredo de Seguranca e Medicina do Trabalho (FUNDACENTRO), Belo Horizonte, MG (Brazil); Araujo, F.G.S. [Universidade Federal de Ouro Preto (REDEMAT/UFOP), MG (Brazil); Nogueira, M.S., E-mail: mnogue@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Santos, M.A.P. [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil)

    2015-07-01

    Concrete which contains water, cement and aggregate, is widely used in building construction such as medical hospitals. The CdZnTe spectrometry system was used to acquire the transmitted spectra in the RQR qualities and the stripping procedure was performed by taking into account both the contributions of efficiency and x-ray escape fraction, experimentally determined. The samples were prepared in rectangular plate format with dimensions of (5 x 5) cm with thicknesses varying from 0.2cm to 2cm and exposed to x-ray beams generated. The HVL and the mean energy in this energy range was determined. (author)

  16. Coronal temperature diagnostics from high-resolution soft X-ray spectra

    Science.gov (United States)

    Strong, K. T.; Claflin, E. S.; Lemen, J. R.; Linford, G. A.

    1988-01-01

    The problem of deriving the temperature of the coronal plasma from soft X-ray spectra is discussed. Spectral atlas scans of the soft X-ray spectrum from the Flat Crystal Spectrometer on the Solar Maximum Mission are compared with theoretical predictions of the relative intensities of some of the brighter lines to determine which line intensity ratios give the most reliable temperature diagnostics. The techniques considered include line widths, He-like G ratios, intensity ratios, and ratios of lines formed by different elements. It is found that the best temperature diagnostics come from the ratios of lines formed by successive ionization stages of the same element.

  17. A model independent method to deconvolve hard X-ray spectra

    International Nuclear Information System (INIS)

    Polcaro, V.F.; Bazzano, A.; Ubertini, P.; La Padula, C.

    1984-01-01

    A general purpose method to deconvolve the energy spectra detected by means of the use of a hard X-ray telescope is described. The procedure does not assume any form of input spectrum and the observed energy loss spectrum is directly deconvolved into the incident photon spectrum, the form of which can be determined independently of physical interpretation of the data. Deconvolution of the hard X-ray spectrum of Her X-1, detected during the HXR 81M experiment, by the method independent method is presented. (orig.)

  18. Influence of smoothing of X-ray spectra on parameters of calibration model

    International Nuclear Information System (INIS)

    Antoniak, W.; Urbanski, P.; Kowalska, E.

    1998-01-01

    Parameters of the calibration model before and after smoothing of X-ray spectra have been investigated. The calibration model was calculated using multivariate procedure - namely the partial least square regression (PLS). Investigations have been performed on an example of six sets of various standards used for calibration of some instruments based on X-ray fluorescence principle. The smoothing methods were compared: regression splines, Savitzky-Golay and Discrete Fourier Transform. The calculations were performed using a software package MATLAB and some home-made programs. (author)

  19. X-Ray Absorption Spectra of Amorphous Ices from GW Quasiparticle Calculation

    Science.gov (United States)

    Kong, Lingzhu; Car, Roberto

    2013-03-01

    We use a GW approach[2] to compute the x-ray absorption spectra of model low- and high-density amorphous ice structures(LDA and HDA)[3]. We include the structural effects of quantum zero point motion using colored-noise Langevin molecular dynamics[4]. The calculated spectra differences in the main and post edge region between LDA and HDA agree well with experimental observations. We attribute these differences to the presence of interstitial molecules within the first coordination shell range in HDA. This assignment is further supported by a calculation of the spectrum of ice VIII, a high-pressure structure that maximizes the number of interstitial molecules and, accordingly, shows a much weaker post-edge feature. We further rationalize the spectral similarity between HDA and liquid water, and between LDA and ice Ih in terms of the respective similarities in the H-bond network topology and bond angle distributions. Supported by grants DOE-DE-SC0005180, DOE DE-SC0008626 and NSF-CHE-0956500.

  20. Analysis of neon soft x-ray spectra from short-pulse laser-produced plasmas

    International Nuclear Information System (INIS)

    Abare, A.C.; Keane, C.J.; Crane, J.K.; DaSilva, L.B.; Lee, R.W.; Perry, M.D.; Falcone, R.W.

    1993-04-01

    We report preliminary results from the analysis of streaked soft x-ray neon spectra a gas jet target. In obtained from the interaction of a picosecond Nd:glass laser with these experiments streaked spectra show prompt harmonic emission followed by longer time duration soft x-ray line emission. The majority of the line emission observed was found to originate from Li- and Be-like Ne and the major transitions in the observed spectra have been identified. Li-like emission lines were observed to decay faster in time than Be-like transitions, suggesting that recombination is taking place. Line ratios of n=4-2 and n=3-2 transitions supported the view that these lines were optically thin and thick, respectively. The time history of Li-like Ne 2p-4d and 2p-3d lines is in good agreement with a simple adiabatic expansion model coupled to a time dependent collisional-radiative code. Further x-ray spectroscopic analysis is underway which is aimed at diagnosing plasma conditions and assessing the potential of this recombining neon plasma as a quasi-steady-state recombination x-ray laser medium

  1. Determination of x-ray spectra incident on and transmitted through whole excised breast for improved mammographic exposing technique

    International Nuclear Information System (INIS)

    Haus, A.G.; Metz, C.E.; Doi, K.; Bernstein, J.

    1976-01-01

    Measurements were made of x-ray spectra incident on and transmitted through whole excised fresh breast tissue. The spectra and corresponding radiographs show that hardening of the x-ray beam from a molybdenum anode x-ray tube by a 0.5 mm Al filter instead of the conventional 0.03 mm Mo filter allows shorter exposure times and reduces patient radiation exposure. With the Al filter, acceptable image contrast is preserved in mammography of thick or dense breasts

  2. Galactic and extragalactic hydrogen in the X-ray spectra of Gamma Ray Bursts

    Science.gov (United States)

    Rácz, I. I.; Bagoly, Z.; Tóth, L. V.; Balázs, L. G.; Horváth, I.; Pintér, S.

    2017-07-01

    Two types of emission can be observed from gamma-ray bursts (GRBs): the prompt emission from the central engine which can be observed in gamma or X-ray (as a low energy tail) and the afterglow from the environment in X-ray and at shorter frequencies. We examined the Swift XRT spectra with the XSPEC software. The correct estimation of the galactic interstellar medium is very important because we observe the host emission together with the galactic hydrogen absorption. We found that the estimated intrinsic hydrogen column density and the X-ray flux depend heavily on the redshift and the galactic foreground hydrogen. We also found that the initial parameters of the iteration and the cosmological parameters did not have much effect on the fitting result.

  3. High resolution krypton M/sub 4,5/ x-ray emission spectra

    International Nuclear Information System (INIS)

    Perera, R.C.C.; Hettrick, M.C.; Lindle, D.W.

    1987-10-01

    High resolution M/sub 4,5/ (3d → 4p) x-ray emission spectra from a krypton plasma were measured using a recently developed grazing-incidence reflection-grating monochromator/spectrometer with very high flux rates at extreme ultraviolet and soft x-ray wave lengths. The nominal resolving power of the instrument, E/ΔE, is about 300 in this energy range (∼80 eV). Three dipole-allowed 3d → 4p emission lines were observed at 80.98 eV, 80.35 eV and 79.73 eV. A broad peak at about 82.3 eV is tentatively assigned to transitions resulting from Kr 2+ , and effects of excitation energy on M/sub 4,5/ x-ray emission were observed. 9 refs., 3 figs., 1 tab

  4. Restricted active space calculations of L-edge X-ray absorption spectra: from molecular orbitals to multiplet states.

    Science.gov (United States)

    Pinjari, Rahul V; Delcey, Mickaël G; Guo, Meiyuan; Odelius, Michael; Lundberg, Marcus

    2014-09-28

    The metal L-edge (2p → 3d) X-ray absorption spectra are affected by a number of different interactions: electron-electron repulsion, spin-orbit coupling, and charge transfer between metal and ligands, which makes the simulation of spectra challenging. The core restricted active space (RAS) method is an accurate and flexible approach that can be used to calculate X-ray spectra of a wide range of medium-sized systems without any symmetry constraints. Here, the applicability of the method is tested in detail by simulating three ferric (3d(5)) model systems with well-known electronic structure, viz., atomic Fe(3+), high-spin [FeCl6](3-) with ligand donor bonding, and low-spin [Fe(CN)6](3-) that also has metal backbonding. For these systems, the performance of the core RAS method, which does not require any system-dependent parameters, is comparable to that of the commonly used semi-empirical charge-transfer multiplet model. It handles orbitally degenerate ground states, accurately describes metal-ligand interactions, and includes both single and multiple excitations. The results are sensitive to the choice of orbitals in the active space and this sensitivity can be used to assign spectral features. A method has also been developed to analyze the calculated X-ray spectra using a chemically intuitive molecular orbital picture.

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

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jing; Liang, Le [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Zhang, Lanting, E-mail: lantingzh@sjtu.edu.cn, E-mail: lmsun@sjtu.edu.cn [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Hirano Institute for Materials Innovation, Shanghai Jiao Tong University, Shanghai 200240 (China); Sun, Limin, E-mail: lantingzh@sjtu.edu.cn, E-mail: lmsun@sjtu.edu.cn [Instrumental Analysis Center, Shanghai Jiao Tong University, Shanghai 200240 (China); Hirano, Shinichi [Hirano Institute for Materials Innovation, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2014-10-28

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

  6. X-ray lasers for structural and dynamic biology

    International Nuclear Information System (INIS)

    Spence, J C H; Weierstall, U; Chapman, H N

    2012-01-01

    Research opportunities and techniques are reviewed for the application of hard x-ray pulsed free-electron lasers (XFEL) to structural biology. These include the imaging of protein nanocrystals, single particles such as viruses, pump–probe experiments for time-resolved nanocrystallography, and snapshot wide-angle x-ray scattering (WAXS) from molecules in solution. The use of femtosecond exposure times, rather than freezing of samples, as a means of minimizing radiation damage is shown to open up new opportunities for the molecular imaging of biochemical reactions at room temperature in solution. This is possible using a ‘diffract-and-destroy’ mode in which the incident pulse terminates before radiation damage begins. Methods for delivering hundreds of hydrated bioparticles per second (in random orientations) to a pulsed x-ray beam are described. New data analysis approaches are outlined for the correlated fluctuations in fast WAXS, for protein nanocrystals just a few molecules on a side, and for the continuous x-ray scattering from a single virus. Methods for determining the orientation of a molecule from its diffraction pattern are reviewed. Methods for the preparation of protein nanocrystals are also reviewed. New opportunities for solving the phase problem for XFEL data are outlined. A summary of the latest results is given, which now extend to atomic resolution for nanocrystals. Possibilities for time-resolved chemistry using fast WAXS (solution scattering) from mixtures is reviewed, toward the general goal of making molecular movies of biochemical processes. (key issues reviews)

  7. Surface extended x-ray absorption fine structure of low-Z absorbates using fluorescence detection

    International Nuclear Information System (INIS)

    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 4 H 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

  8. Measurements of ionic structure in shock compressed lithium hydride from ultrafast x-ray Thomson scattering.

    Science.gov (United States)

    Kritcher, A L; Neumayer, P; Brown, C R D; Davis, P; Döppner, T; Falcone, R W; Gericke, D O; Gregori, G; Holst, B; Landen, O L; Lee, H J; Morse, E C; Pelka, A; Redmer, R; Roth, M; Vorberger, J; Wünsch, K; Glenzer, S H

    2009-12-11

    We present the first ultrafast temporally, spectrally, and angularly resolved x-ray scattering measurements from shock-compressed matter. The experimental spectra yield the absolute elastic and inelastic scattering intensities from the measured density of free electrons. Laser-compressed lithium-hydride samples are well characterized by inelastic Compton and plasmon scattering of a K-alpha x-ray probe providing independent measurements of temperature and density. The data show excellent agreement with the total intensity and structure when using the two-species form factor and accounting for the screening of ion-ion interactions.

  9. Theoretical modeling of Comptonized X-ray spectra of super-Eddington accretion flow: Origin of hard excess in ultraluminous X-ray sources

    Science.gov (United States)

    Kitaki, Takaaki; Mineshige, Shin; Ohsuga, Ken; Kawashima, Tomohisa

    2017-12-01

    X-ray continuum spectra of super-Eddington accretion flow are studied by means of Monte Carlo radiative transfer simulations based on the radiation hydrodynamic simulation data, in which both thermal- and bulk-Compton scatterings are taken into account. We compare the calculated spectra of accretion flow around black holes with masses of MBH = 10, 102, 103, and 104 M⊙ for a fixed mass injection rate (from the computational boundary at 103 rs) of 103 LEdd/c2 (with rs, LEdd, and c being the Schwarzschild radius, the Eddington luminosity, and the speed of light, respectively). The soft X-ray spectra exhibit mass dependence in accordance with the standard-disk relation; the maximum surface temperature is scaled as T ∝ M_{ BH}^{ -1/4}. The spectra in the hard X-ray band, by contrast with soft X-ray, look to be quite similar among different models, if we normalize the radiation luminosity by MBH. This reflects that the hard component is created by thermal- and bulk-Compton scatterings of soft photons originating from an accretion flow in the overheated and/or funnel regions, the temperatures of which have no dependence on mass. The hard X-ray spectra can be reproduced by a Wien spectrum with the temperature of T ˜ 3 keV accompanied by a hard excess at photon energy above several keV. The excess spectrum can be fitted well with a power law with a photon index of Γ ˜ 3. This feature is in good agreement with that of the recent NuSTAR observations of ULXs (ultra-luminous X-ray sources).

  10. The development of structural x-ray crystallography

    Science.gov (United States)

    Woolfson, M. M.

    2018-03-01

    From its birth in 1912, when only the simplest structures could be solved, x-ray structural crystallography is now able to solve macromolecular structures containing many thousands of independent non-hydrogen atoms. This progress has depended on, and been driven by, great technical advances in the development of powerful synchrotron x-ray sources, advanced automated equipment for the collection and storage of large data sets and powerful computers to deal with everything from data processing to running programmes employing complex algorithms for the automatic solution of structures. The sheer number of developments in the subject over the past century makes it impossible for this review to be exhaustive, but it will describe some major developments that will enable the reader to understand how the subject has grown from its humble beginnings to what it is today.

  11. Modeling X-ray Spectra of Astrophysical Plasmas: Current Status and Future Needs

    Science.gov (United States)

    Smith, Randall

    Existing high-resolution astrophysical X-ray spectra has exposed the need for high-quality atomic data of all stripes: wavelengths, collisional and absorption cross sections, and radiative rates. The Astro-H soft X-ray spectrometer (2015 launch) will vastly increase the number and type of high-resolution X-ray spectra available and likely expose a number of shortcomings in our models. I will describe recent advances in theoretical calculations and laboratory measurements, as well as a number of existing needs in the field. These include accurate soft X-ray wavelengths for L-shell ions, diagnostic emission line ratios with estimated error bars, and high-resolution absorption cross sections for abundant ions and molecules. Finally, new models of emission from non-equilibrium ionization plasmas and astrophysical charge exchange will be discussed. This latter emission arises due to the interaction of highly charged ions with neutral atoms, forming a diffuse background in the case of solar wind ions and possibly also arising in more distant environments.

  12. X ray spectra and qualities for use in diagnostic radiology and equipment calibration

    International Nuclear Information System (INIS)

    Souza, Karla Cristina de

    1996-12-01

    The goal of this work was the standardization of radiation qualities of diagnostic X ray equipment of the Assay Laboratory of the Institute for Radiation Protection and Dosimetry (IRD) of the National Commission of Nuclear Energy, Brazil. X ray spectra were determined from pulse height distribution measured directly on the primary beam using a high pure planar Ge detector. A program was developed to convert pulse height distribution into radiation spectra in the range from 20 to 150 keV. X ray qualities based on those used by the 'Physikalish-Technish Bundesantalt' (PTB) primary laboratory were implanted in three radiological equipment of the Assay Laboratory. These qualities simulate radiation beams on patients submitted to typical radiological examinations. Besides the spectrometric system, a reference measurement system based on an ionization chamber calibrated in air kerma was used to establish parameters such as kilovoltage, first and second half-value layer, mean energy, effective energy and inherent filtration. Our data have shown that the implantation of these radiation qualities in the Assay Laboratory results on a metrological basis for calibration of dose measurement assemblies and kV-meters, like those used by IRD to evaluate the parameters of X ray equipment around the country. A catalogue of spectral data resulting from this work is a data bank that allows various applications like dose calculation using Monte Carlo simulation techniques. (author)

  13. Diffraction anomalous fine structure using X-ray anomalous dispersion

    International Nuclear Information System (INIS)

    Soejima, Yuji; Kuwajima, Shuichiro

    1998-01-01

    A use of X-ray anomalous dispersion effects for structure investigation has recently been developed by using synchrotron radiation. One of the interesting method is the observation of anomalous fine structure which arise on diffraction intensity in energy region of incident X-ray at and higher than absorption edge. The phenomenon is so called Diffraction Anomalous Fine Structure (DAFS). DAFS originates in the same physical process an that of EXAFS: namely photoelectric effect at the corresponding atom and the interaction of photoelectron waves between the atom and neighboring atoms. In contrast with EXAFS, the method is available for only the crystalline materials, but shows effective advantages of the structure investigations by a use of diffraction: one is the site selectivity and the other is space selectivity. In the present study, demonstrations of a use of X-ray anomalous dispersion effect for the superstructure determination will be given for the case of PbZrO 3 , then recent trial investigations of DAFS in particular on the superlattice reflections will be introduced. In addition, we discuss about Forbidden Reflection near Edge Diffraction (FRED) which is more recently investigated as a new method of the structure analysis. (author)

  14. Application of the X-ray diffractometer DRON to the study of long period structures

    International Nuclear Information System (INIS)

    Gordelij, V.I.; Lushchikov, V.I.; Syrykh, A.G.; Cherezon, V.G.

    1991-01-01

    It is shown that the stock-produced X-ray diffractometer DRON can be adapted for the study of long period structures up to ∼150 A. The experimental data on small-angle diffraction spectra, measured on it, from both lamellar and lateral structures of biological and lipid membranes are reported. The data show that lattice constants of these structures could be determined within the accuracy of 1 A. 15 refs.; 7 figs

  15. A method to unfold the efficiency of gaseous detectors exposed to broad X-ray spectra

    International Nuclear Information System (INIS)

    Almeida, Gevaldo L. de; Souza, Maria Ines S. de; Lopes, Ricardo T.

    2000-01-01

    A method to obtain the efficiency of a gaseous detector exposed to broad energy X-ray spectra was developed. It consists in the de-convolution of the integrated detector response using the shapes of those spectra as a tool to unfold the aimed detector efficiency curve. For this purpose, the spectra emitted by a X-ray tube under several anode voltages, were properly characterized through measurements with a NaI(Tl) spectrometer. A Lorentz function was then fitted to each of the spectra, and their parameters expressed as a function of the anode voltage, by using polynomial and gaussian fittings. The integral of the product of each Lorentz function, by another unknown Lorentz function, expressing the detector efficiency curve, represents the response of the detector for each anode tension, e.g., each X-ray spectrum. The symbolical integration of that product, produces a general function containing the unknown parameters of the unknown efficiency curve. A non-linear fitting of this general function, to the detector response points, as experimentally obtained, generates the aimed parameters for the efficiency curve. The final detector efficiency curve is obtained after normalization procedures. (author)

  16. Parallelization for X-ray crystal structural analysis program

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Hiroshi [Japan Atomic Energy Research Inst., Tokyo (Japan); Minami, Masayuki; Yamamoto, Akiji

    1997-10-01

    In this report we study vectorization and parallelization for X-ray crystal structural analysis program. The target machine is NEC SX-4 which is a distributed/shared memory type vector parallel supercomputer. X-ray crystal structural analysis is surveyed, and a new multi-dimensional discrete Fourier transform method is proposed. The new method is designed to have a very long vector length, so that it enables to obtain the 12.0 times higher performance result that the original code. Besides the above-mentioned vectorization, the parallelization by micro-task functions on SX-4 reaches 13.7 times acceleration in the part of multi-dimensional discrete Fourier transform with 14 CPUs, and 3.0 times acceleration in the whole program. Totally 35.9 times acceleration to the original 1CPU scalar version is achieved with vectorization and parallelization on SX-4. (author)

  17. Dynamical X-ray scattering from the relaxed structures

    International Nuclear Information System (INIS)

    Benediktovitch, A.; Feranchuk, I.; Ulyanenkov, A.

    2009-01-01

    High-resolution X-ray diffraction is now widely used analytical tool for investigation of nano scale multilayered structures in semiconductor and optical technologies. The HRXRD method delivers unique information on the crystallographic lattice of the samples, concentration of solid solutions, lattice mismatches, layer thicknesses, defect distribution, and relaxation degree of the epitaxial layers. The evaluation of the experimental results, however, requires a robust and precise theory due to complex dynamical scattering of X-rays from near perfect crystallographic structure of the samples. Usually, the Takagi-Taupin approach [1] or the recurrent matrix methods [2] are used for the simulation of the X-ray diffraction profiles from the epitaxial multilayered structures. The use of these theories, however, becomes essentially difficult, when the lateral lattice mismatches are present in multilayers, for example, in the case of partially or fully relaxed epitaxially grown samples. In the present work, the general solution of this problem is found analytically. The angular divergence of the incident beam is also considered and the algorithm for the diffracted profile mapping in the reciprocal space is developed. The experimental reciprocal space mapping of typical AlGaN/GaN/AlN samples with partially relaxed layers is compared to the simulated maps, which describe well the location and character of the diffraction spots caused by different layers. (author)

  18. An iterative method for unfolding time-resolved soft x-ray spectra of laser plasmas

    International Nuclear Information System (INIS)

    Tang Yongjian; Shen Kexi; Xu Hepin

    1991-01-01

    Dante-recorded temporal waveforms have been unfolded by using Fast Fourier transformation (FFT) and the inverted convolution theorem of Fourier analysis. The conversion of the signals to time-dependent soft x-ray spectra is accomplished on the IBM-PC/XT-286 microcomputer system with the code DTSP including SAND II reported by W.N.Mcelory et al.. An amplitude-limited iterative and periodic smoothing technique has been developed in the code DTSP. Time-resolved soft x-ray spectra with sixteen time-cell, and time-dependent radiation, [T R (t)], have been obtained for hohlraum targets irradiated with laser beams (λ = 1.06 μm) on LF-12 in 1989

  19. Optimization of tungsten x-ray spectra for digital mammography: a comparison of model to experiment

    Science.gov (United States)

    Andre, Michael P.; Spivey, Brett A.

    1997-05-01

    Tungsten (W) target x-rays tubes are being studied for use in digital mammography to improve x-ray flux, reduce noise and increase tube heat capacity. A parametric model was developed for digital mammography to evaluate optimization of x-ray spectra for a particular sensor. The model computes spectra and mean glandular doses (MGD) for combinations of W target, beam filters, kVp, breast type and thickness. Two figures of merit were defined: (signal/noise)2/MGD and spectral quantum efficiency; these were computed as a means to approach optimization of object contrast. The model is derived from a combination of classic equations, XCOM from NBS, and published data. X-ray spectra were calculated and measured for filters of Al, Sn, Rh, Mo and Ag on a Eureka tube. (Signal/noise)2/MGD was measured for a filtered W target tube and a digital camera employing CsI scintillator optically coupled to a CCD for which the detective quantum efficiency (DQE) was known. A 3-mm thick acrylic disk was imaged on thickness of 3-8 cm of acrylic and the results were compared to the predictions of the model. The relative error between predicted and measured spectra was +/- 2 percent from 24 to 34 kVp. Calculated MGD as a function of breast thickness, half-value layer and beam filter compares very well to published data. Best performance was found for the following combinations: Mo filter with 30 mm breast, Ag filter with 45 mm, Sn filter for 60 mm, and Al filter for 75 mm thick breast. The parametric model agrees well with measurement and provides a means to explore optimum combinations of kVp and beam filter. For a particular detector, this data may be used with the DQE to estimate total system signal-to-noise ratio for a particular imaging task.

  20. X-ray electron spectra of chalcogenide glasses and polycrystalline alloys of Ge-Te and As-Te systems

    International Nuclear Information System (INIS)

    Panus, V.R.

    1990-01-01

    Comparative investigation into structures of crystals and glasses in Ge-Te and As-Te two-component systems was conducted. Analysis of x-ray electron spectra of Ge-Te and As-Te systems indicates, that processes of dissociation-association resulting in formation of new structure units occur in telluride melts at synthesis temperatures. Structural chemical composition of binary glass-like alloys of Ge-Te and As-Te systems differs essentially from the one that corresponds to fusibility equilibrium curve. Oxygen doping into tellurium-base glasses results mainly in occurence of structures forecasted due to thermochemical calculation

  1. Quantitative X-ray determination of CFRP micro structures

    International Nuclear Information System (INIS)

    Hentschel, Manfred P.; Mueller, Bernd R.; Lange, Axel; Wald, Oliver

    2008-01-01

    Beyond imaging the mass distribution of materials by X-ray absorption techniques recent synchrotron and laboratory X-ray refraction techniques provide interface contrast imaging of micro structures. This is of specific relevance to carbon fibre composites (CFRP) which constitute advanced aerospace components. Apart from merely finding isolated flaws like cracks or pores within the natural high interface density only the quantitative measurement of the differences after defined mechanical treatment provides a reliable understanding of the related macroscopic properties. The contribution of the fibre matrix interface of CFRP laminates to the mechanical properties is investigated by relating the mechanical damage to the additional fibre debonding after impact and fatigue. Composites of industrially sized carbon fibres for aerospace applications and of unsized fibres are compared. (orig.)

  2. Colliding Stellar Winds Structure and X-ray Emission

    Science.gov (United States)

    Pittard, J. M.; Dawson, B.

    2018-04-01

    We investigate the structure and X-ray emission from the colliding stellar winds in massive star binaries. We find that the opening angle of the contact discontinuity (CD) is overestimated by several formulae in the literature at very small values of the wind momentum ratio, η. We find also that the shocks in the primary (dominant) and secondary winds flare by ≈20° compared to the CD, and that the entire secondary wind is shocked when η ≲ 0.02. Analytical expressions for the opening angles of the shocks, and the fraction of each wind that is shocked, are provided. We find that the X-ray luminosity Lx∝η, and that the spectrum softens slightly as η decreases.

  3. Extended X-ray absorption fine structure and X-ray diffraction studies on supported Ni catalysts

    International Nuclear Information System (INIS)

    Aldea, N.; Marginean, P.; Yaning, Xie; Tiandou, Hu; Tao, Liu; Wu, Zhongua; ZhenYa, Dai

    1999-01-01

    In the first part of this paper, we present a study based on EXAFS spectroscopy. This method can yield structural information about the local environment around a specific atomic constituent in the amorphous materials, the location and chemical state of any catalytic atom on any support or point defect structures, in alloys and composites. EXAFS is a specific technique of the scattering of X-ray on materials. The present study is aimed toward elucidation of the local structure of Ni atoms and their interaction with oxide support. The second goal of the paper consists in X-ray diffraction on the same samples. X-ray diffraction method that is capable to determine average particle size, microstrains, probability of faults as well as particle size distribution function of supported Ni catalysts is presented. The method is based on the Fourier analysis of a single X-Ray diffraction profile. The results obtained on supported nickel catalysts, which are used in H/D isotopic exchange reactions are reported. The global structure is obtained with a new fitting method based on the Generalised Fermi Function facilities for approximation and Fourier transform of the experimental X-Ray line profiles. Both types of measurements were performed on Beijing Synchrotron Radiation Facilities (BSRF). (authors)

  4. Structural enzymology using X-ray free electron lasers

    Directory of Open Access Journals (Sweden)

    Christopher Kupitz

    2017-07-01

    Full Text Available Mix-and-inject serial crystallography (MISC is a technique designed to image enzyme catalyzed reactions in which small protein crystals are mixed with a substrate just prior to being probed by an X-ray pulse. This approach offers several advantages over flow cell studies. It provides (i room temperature structures at near atomic resolution, (ii time resolution ranging from microseconds to seconds, and (iii convenient reaction initiation. It outruns radiation damage by using femtosecond X-ray pulses allowing damage and chemistry to be separated. Here, we demonstrate that MISC is feasible at an X-ray free electron laser by studying the reaction of M. tuberculosis ß-lactamase microcrystals with ceftriaxone antibiotic solution. Electron density maps of the apo-ß-lactamase and of the ceftriaxone bound form were obtained at 2.8 Å and 2.4 Å resolution, respectively. These results pave the way to study cyclic and non-cyclic reactions and represent a new field of time-resolved structural dynamics for numerous substrate-triggered biological reactions.

  5. Electron-electron correlation, resonant photoemission and X-ray emission spectra

    International Nuclear Information System (INIS)

    Parlebas, J.C.; Kotani, Akio; Tanaka, Satoshi.

    1991-01-01

    In this short review paper we essentially focus on the high energy spectroscopies which involve second order quantum processes, i.e., resonance photoemission, Auger and X-ray emission spectroscopies, denoted respectively by RXPS, AES and XES. First, we summarize the main 3p-RXPS and AES results obtained in Cu and Ni metals; especially we recall that the satellite near the 3p-threshold in the spectra, which arises from a d-hole pair bound state, needs a careful treatment of the electron-electron correlation. Then we analyze the RXPS spectra in a few Ce compounds (CeO 2 , Ce 2 O 3 and CeF 3 ) involving 3d or 4d core levels and we interpret the spectra consistently with the other spectroscopies, such as core XPS and XAS which are first order quantum processes. Finally within the same one-impurity model and basically with the same sets of parameters, we review a theory for the Ce 5p→3d XES, as well as for the corresponding RXES, where (1) the incident X-ray is tuned to resonate with the 3d→4f transition and (2) the X-ray emission due to the 5p→3d transition is actually observed. The paper ends with a general discussion. (author) 77 refs

  6. Experimental and Monte Carlo simulated spectra of a liquid-metal-jet x-ray source

    International Nuclear Information System (INIS)

    Marziani, M.; Gambaccini, M.; Di Domenico, G.; Taibi, A.; Cardarelli, P.

    2014-01-01

    A prototype x-ray system based on a liquid-metal-jet anode was evaluated within the framework of the LABSYNC project. The generated spectrum was measured using a CZT-based spectrometer and was compared with spectra simulated by three Monte Carlo codes: MCNPX, PENELOPE and EGS5. Notable differences in the simulated spectra were found. These are mainly attributable to differences in the models adopted for the electron-impact ionization cross section. The simulation that more closely reproduces the experimentally measured spectrum was provided by PENELOPE. - Highlights: • The x-ray spectrum of a liquid-jet x-ray anode was measured with a CZT spectrometer. • Results were compared with Monte Carlo simulations using MCNPX, PENELOPE, EGS5. • Notable differences were found among the Monte Carlo simulated spectra. • The key role was played by the electron-impact ionization cross-section model used. • The experimentally measured spectrum was closely reproduced by the PENELOPE code

  7. Absorption spectra response of XRQA radiochromic film to x-ray radiation

    International Nuclear Information System (INIS)

    Alnawaf, Hani; Cheung, Tsang; Butson, Martin J.; Yu, Peter K.N.

    2010-01-01

    Gafchromic XRQA, radiochromic film is a high sensitivity auto developing x-ray analysis films designed and available for kilovoltage x-ray, dose and QA assessment applications. The film is designed for reflective analysis with a yellow transparent top filter and white opaque backing materials. This allows the film to be visually inspected for colour changes with a higher level of contrast than clear coated radiochromic films such as Gafchromic EBT version 1. The spectral absorption properties in the visible wavelengths have been investigated and results show two main peaks in absorption located at 636 nm and 585 nm. These peaks are located in the same position as EBT Gafchromic film highlighting a similar chemical monomer/polymer for radiation sensitivity. A much higher sensitivity however is found at kilovoltage energies with an average 1.55 OD units per 20 cGy irradiation variation measured at 636 nm using 150 kVp x-rays. This is compared to approximately 0.12 OD units per 20 cGy measured at 636 nm for EBT film at 6 MV x-ray energy. That is, the XRQA film is more than 10 times more sensitive than EBT1 film. The visual colour change is enhanced by the yellow polyester coating. However this does not affect the absorption spectra properties in the red region of analysis which is the main area for use using desktop scanners in reflection mode.

  8. SpekCalc: a program to calculate photon spectra from tungsten anode x-ray tubes

    International Nuclear Information System (INIS)

    Poludniowski, G; Evans, P M; Landry, G; DeBlois, F; Verhaegen, F

    2009-01-01

    A software program, SpekCalc, is presented for the calculation of x-ray spectra from tungsten anode x-ray tubes. SpekCalc was designed primarily for use in a medical physics context, for both research and education purposes, but may also be of interest to those working with x-ray tubes in industry. Noteworthy is the particularly wide range of tube potentials (40-300 kVp) and anode angles (recommended: 6-30 deg.) that can be modelled: the program is therefore potentially of use to those working in superficial/orthovoltage radiotherapy, as well as diagnostic radiology. The utility is free to download and is based on a deterministic model of x-ray spectrum generation (Poludniowski 2007 Med. Phys. 34 2175). Filtration can be applied for seven materials (air, water, Be, Al, Cu, Sn and W). In this note SpekCalc is described and illustrative examples are shown. Predictions are compared to those of a state-of-the-art Monte Carlo code (BEAMnrc) and, where possible, to an alternative, widely-used, spectrum calculation program (IPEM78). (note)

  9. Study of soft X-ray energy spectra from gas-puff Z-pinch plasma

    International Nuclear Information System (INIS)

    Zou Xiaobing; Wang Xinxin; Zhang Guixin; Han Min; Luo Chengmu

    2006-01-01

    A ROSS-FILTER-PIN spectrometer in the spectral range of 0.28 keV-1.56 keV was developed to study the soft X-ray radiation emitted from gas-puff Z-pinch plasma. It is composed of five channels covering the energy interval of interest without gaps. Soft X-ray spectral energy cuts were determined by the L absorption edges of selected filter elements (K absorption edges being used for light filter elements), and the optimum thickness of filter material was designed using computer code. To minimize the residual sensitivity outside the sensitivity range of each channel, element of the first filter was added into the second filter of all the Ross pair. To diminish the area of each filter, PIN detector with small sensitive area of 1 mm 2 was adopted for the spectrometer. A filter with small area is easy to fabricate and would be helpful to withstand the Z-pinch discharge shock wave. With this ROSS-FILTER-PIN spectrometer, the energy spectra of soft X-ray from a small gas-puff Z-pinch were investigated, and the correlation between the soft X-ray yield and the plasma implosion state was also studied. (authors)

  10. X-ray diffraction and X-ray standing-wave study of the lead stearate film structure

    Energy Technology Data Exchange (ETDEWEB)

    Blagov, A. E.; Dyakova, Yu. A.; Kovalchuk, M. V.; Kohn, V. G.; Marchenkova, M. A.; Pisarevskiy, Yu. V.; Prosekov, P. A., E-mail: prosekov@crys.ras.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2016-05-15

    A new approach to the study of the structural quality of crystals is proposed. It is based on the use of X-ray standing-wave method without measuring secondary processes and considers the multiwave interaction of diffraction reflections corresponding to different harmonics of the same crystallographic reflection. A theory of multiwave X-ray diffraction is developed to calculate the rocking curves in the X-ray diffraction scheme under consideration for a long-period quasi-one-dimensional crystal. This phase-sensitive method is used to study the structure of a multilayer lead stearate film on a silicon substrate. Some specific structural features are revealed for the surface layer of the thin film, which are most likely due to the tilt of the upper layer molecules with respect to the external normal to the film surface.

  11. Quantum many-body effects in x-ray spectra efficiently computed using a basic graph algorithm

    Science.gov (United States)

    Liang, Yufeng; Prendergast, David

    2018-05-01

    The growing interest in using x-ray spectroscopy for refined materials characterization calls for an accurate electronic-structure theory to interpret the x-ray near-edge fine structure. In this work, we propose an efficient and unified framework to describe all the many-electron processes in a Fermi liquid after a sudden perturbation (such as a core hole). This problem has been visited by the Mahan-Noziéres-De Dominicis (MND) theory, but it is intractable to implement various Feynman diagrams within first-principles calculations. Here, we adopt a nondiagrammatic approach and treat all the many-electron processes in the MND theory on an equal footing. Starting from a recently introduced determinant formalism [Phys. Rev. Lett. 118, 096402 (2017), 10.1103/PhysRevLett.118.096402], we exploit the linear dependence of determinants describing different final states involved in the spectral calculations. An elementary graph algorithm, breadth-first search, can be used to quickly identify the important determinants for shaping the spectrum, which avoids the need to evaluate a great number of vanishingly small terms. This search algorithm is performed over the tree-structure of the many-body expansion, which mimics a path-finding process. We demonstrate that the determinantal approach is computationally inexpensive even for obtaining x-ray spectra of extended systems. Using Kohn-Sham orbitals from two self-consistent fields (ground and core-excited state) as input for constructing the determinants, the calculated x-ray spectra for a number of transition metal oxides are in good agreement with experiments. Many-electron aspects beyond the Bethe-Salpeter equation, as captured by this approach, are also discussed, such as shakeup excitations and many-body wave function overlap considered in Anderson's orthogonality catastrophe.

  12. Soft x-ray absorption spectroscopy on Co doped ZnO: structural distortions and electronic structure

    International Nuclear Information System (INIS)

    Kowalik, I A; Guziewicz, E; Godlewski, M; Arvanitis, D

    2016-01-01

    We present soft x-ray absorption spectra from a series of Co doped ZnO films. We discuss systematic variations of the Co L-edge white line intensity and multiplet features for this series of samples. We document sizeable differences in the electronic state of the Co ionic cores, as well as in the local environment of the host lattice atoms, characterised by means of x-ray absorption spectra at the O K-edge and Zn L-edges. Model calculations allow to correlate the observed effects to small structural distortions of the ZnO lattice. (paper)

  13. New developments in the simultaneous measurement system of wide-angle and small-angle x-ray scatterings and vibrational spectra for the static and dynamic analyses of the hierarchical structures of polymer solids

    International Nuclear Information System (INIS)

    Tashiro, Kohji; Yamamoto, Hiroko; Yoshioka, Taiyo; Ninh, Tran Hai; Shimada, Shigeru; Nakatani, Takeshi; Iwamoto, Hiroyuki; Ohta, Noboru; Masunaga, Hiroyasu

    2012-01-01

    A simultaneous measurement system of wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS) and Raman or transmission-type infrared spectroscopy was developed by us. Its purposes is to clarify the static and dynamic structural changes of polymer materials subjected to the various external condition changes. Some examples described here include the study of the stretch-induced reorientation phenomenon of a-axially-oriented polyethylene, the study of structural change in photo-induced solid-state polymerization reaction of muconic acid ester monomer crystal, the study of the two-stage high-temperature phase transitions of aliphatic nylons, the study of stress-induced crystalline phase transition of an oriented poly(tetramethylene terephthalate) sample and its relation to the higher-order structural change, and the study of structural regularization process of poly(L-lactic acid) in the isothermal crystallization of the meso phase. These case studies in the clarification of hierarchical structural changes of polymer materials have proven that the simultaneous measurement systems can be useful to examine the structural changes in polymer systems. (author)

  14. HIGHER ORDER SPECIATION EFFECTS ON PLUTONIUM L3 X-RAY ABSORPTION NEAR EDGE SPECTRA.

    Energy Technology Data Exchange (ETDEWEB)

    Conradson, Steven D.; Abney, Kent D.; Begg, Bruce D.; Brady, Erik D.; Clark, David L.; den Auwer, Christophe; Ding, Mei; Dorhout, Peter K.; Espinosa-Faller, Francisco J.; Gordon, Pamela L.; Hess, Nancy J.; Hess, Ryan F.; Keogh, D. Webster; Lander, Gerard H.; Lupinetti, Anthony J.; Neu, Mary P.; Palmer, Phillip D.; Paviet-Hartmann, Patricia; Reilly, Sean D.; Runde, Wolfgang H.; Tait, C. Drew; Veirs, D. Kirk

    2003-06-09

    Pu L{sub 3} X-ray Near Edge Absorption Spectra for Pu(0-VII) are reported for more than 50 chalcogenides, chlorides, hydrates, hydroxides, nitrates, carbonates, oxy-hydroxides, and other compounds both as solids and in solution, and substituted in zirconlite, perovksite, and borosilicate glass. This large data base extends the known correlations between the energy and shape of these spectra from the usual association of the XANES with valence and site symmetry to higher order chemical effects. Because of the large number of compounds of these different types a number of novel and unexpected behaviors are observed.

  15. High-Resolution X-Ray Spectra of the Symbiotic Star SS73 17

    Science.gov (United States)

    Eze, R. N. C.; Luna, G. J. M.; Smith, R. K.

    2010-01-01

    SS73 17 was an innocuous Mira-type symbiotic star until the International Gamma-Ray Astrophysics Laboratory and Swift discovered its bright hard X-ray emission, adding it to the small class of "hard X-ray emitting symbiotics." Suzaku observations in 2006 then showed it emits three bright iron lines as well, with little to no emission in the 0.3-2.0 keV bandpass. We present here follow-up observations with the Chandra High Energy Transmission Grating and Suzaku that confirm the earlier detection of strong emission lines of Fe K(alpha) fluorescence, Fe XXV and Fe XXVI but also show significantly more soft X-ray emission. The high-resolution spectrum also shows emission lines of other highly ionized ions as Si xiv and possibly S XVI. In addition, a re-analysis of the 2006 Suzaku data using the latest calibration shows that the hard (15-50 keV) X-ray emission is brighter than previously thought and remains constant in both the 2006 and 2008 data. The G ratio calculated from the Fe xxv lines shows that these lines are thermal, not photoionized, in origin.With the exception of the hard X-ray emission, the spectra from both epochs can be fit using thermal radiation assuming a differential emission measure based on a cooling-flow model combined with a full and partial absorber. We show that acceptable fits can be obtained for all the data in the 1-10 keV band varying only the partial absorber. Based on the temperature and accretion rate, the thermal emission appears to be arising from the boundary layer between the accreting white dwarf and the accretion disk.

  16. HIGH-RESOLUTION X-RAY SPECTRA OF THE SYMBIOTIC STAR SS73 17

    International Nuclear Information System (INIS)

    Eze, R. N. C.; Luna, G. J. M.; Smith, R. K.

    2010-01-01

    SS73 17 was an innocuous Mira-type symbiotic star until the International Gamma-Ray Astrophysics Laboratory and Swift discovered its bright hard X-ray emission, adding it to the small class of 'hard X-ray emitting symbiotics'. Suzaku observations in 2006 then showed it emits three bright iron lines as well, with little to no emission in the 0.3-2.0 keV bandpass. We present here follow-up observations with the Chandra High Energy Transmission Grating and Suzaku that confirm the earlier detection of strong emission lines of Fe Kα fluorescence, Fe XXV and Fe XXVI but also show significantly more soft X-ray emission. The high-resolution spectrum also shows emission lines of other highly ionized ions as Si XIV and possibly S XVI. In addition, a re-analysis of the 2006 Suzaku data using the latest calibration shows that the hard (15-50 keV) X-ray emission is brighter than previously thought and remains constant in both the 2006 and 2008 data. The G ratio calculated from the Fe XXV lines shows that these lines are thermal, not photoionized, in origin. With the exception of the hard X-ray emission, the spectra from both epochs can be fit using thermal radiation assuming a differential emission measure based on a cooling-flow model combined with a full and partial absorber. We show that acceptable fits can be obtained for all the data in the 1-10 keV band varying only the partial absorber. Based on the temperature and accretion rate, the thermal emission appears to be arising from the boundary layer between the accreting white dwarf and the accretion disk.

  17. X-ray spectra of PG quasars. II - the X-ray-ultraviolet excess of PG 1211 + 143

    International Nuclear Information System (INIS)

    Bechtold, J.; Czerny, B.; Elvis, M.; Fabbiano, G.; Green, R.F.; Harvard-Smithsonian Center for Astrophysics, Cambridge, MA; Kitt Peak National Observatory, Tucson, AZ)

    1987-01-01

    Observations of the quasar PG 1211 + 143 are presented and its continuum is modelled in terms of an accretion disk and an underlying power law. The X-ray spectrum in the Einstein imaging proportional counter band is well described by a power law with the very steep spectral index 2.2 + or - 0.4. The overall continuum spectral energy distribution can be described as a power law with alpha roughly 1.2 from the infrared to about 1 keV, with the optical, ultraviolet, and soft X-rays forming a large excess above this power law. If the soft X-ray excess is attributed to emission from a physically thin, optically thick accretion disk, then the implied accretion rate is super-Eddington, from which it is concluded that the application of this simple model is not valid. The observed broad-line ratios in PG 1211 + 143 imply broad-line cloud densities that are somewhat higher than those usually derived for quasars. 82 references

  18. X-ray crystal structure and small-angle X-ray scattering of sheep liver sorbitol dehydrogenase

    DEFF Research Database (Denmark)

    Yennawar, Hemant; Møller, Magda; Gillilan, Richard

    2011-01-01

    The X-ray crystal structure of sheep liver sorbitol dehydrogenase (slSDH) has been determined using the crystal structure of human sorbitol dehydrogenase (hSDH) as a molecular-replacement model. slSDH crystallized in space group I222 with one monomer in the asymmetric unit. A conserved tetramer...

  19. Spatial power-spectra from Yohkoh soft X-ray images

    Science.gov (United States)

    Martens, Petrus C. H.; Gomez, Daniel O.

    1992-01-01

    We analyze three sequences of images from active regions, and a full disk image obtained by Yohkoh's Soft X-ray Telescope. Two sequences are from a region at center disk observed through different filters, and one sequence is from the limb. After Fourier-transforming the X-ray intensity of the images we find nearly isotropic power-spectra with an azimuthally integrated slope of -2.1 for the center disk, and -2.8 for the limb images. The full-disk picture yields a spectrum of -2.4. These results are different from the active region spectra obtained with the Normal Incidence X-ray Telescope which have a slope of the order of -3.0, and we ascribe this to the difference in temperature response between the instruments. However, both the SXT and NIXT results are consistent with coronal heating as the end result of a downward quasistatic cascade (in lengthscales) of free magnetic energy in the corona, driven by footpoint motions in the photosphere.

  20. Calculations of magnetic x-ray dichroism in the 3d absorption spectra of rare-earth compounds

    NARCIS (Netherlands)

    GOEDKOOP, JB; THOLE, BT; VANDERLAAN, G; SAWATZKY, GA; DEGROOT, FMF; FUGGLE, JC; de Groot, Frank|info:eu-repo/dai/nl/08747610X

    1988-01-01

    We present atomic calculations for the recently discovered magnetic x-ray dichroism (MXD) displayed by the 3d x-ray-absorption spectra of rare-earth compounds. The spectral shapes expected at T=0 K for linear polarization parallel and normal to the local magnetic field is given, together with the

  1. Testing ion structure models with x-ray Thomson scattering

    Directory of Open Access Journals (Sweden)

    Wünsch K.

    2013-11-01

    Full Text Available We investigate the influence of various ionic structure models on the interpretation of the X-ray Thomson scattering signal. For the calculation of the ion structure, classical hypernetted chain equations are used applying different effective inter-particle potentials. It is shown that the different models lead to significant discrepancies in the theoretically predicted weight of the Rayleigh peak, in particular for small k-values where correlation effects are important. Here, we propose conditions which might allow for an experimental verification of the theories under consideration of experimental constraints of k-vector blurring.

  2. Automatic protein structure solution from weak X-ray data

    Science.gov (United States)

    Skubák, Pavol; Pannu, Navraj S.

    2013-11-01

    Determining new protein structures from X-ray diffraction data at low resolution or with a weak anomalous signal is a difficult and often an impossible task. Here we propose a multivariate algorithm that simultaneously combines the structure determination steps. In tests on over 140 real data sets from the protein data bank, we show that this combined approach can automatically build models where current algorithms fail, including an anisotropically diffracting 3.88 Å RNA polymerase II data set. The method seamlessly automates the process, is ideal for non-specialists and provides a mathematical framework for successfully combining various sources of information in image processing.

  3. Krypton K-shell X-ray spectra recorded by the HENEX spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Seely, J.F. [Naval Research Laboratory, Space Science Division, Washington DC 20375 (United States)]. E-mail: john.seely@nrl.navy.mil; Back, C.A. [Lawrence Livermore National Laboratory, Livermore CA 94550 (United States); Constantin, C. [Lawrence Livermore National Laboratory, Livermore CA 94550 (United States); Lee, R.W. [Lawrence Livermore National Laboratory, Livermore CA 94550 (United States); Chung, H.-K. [Lawrence Livermore National Laboratory, Livermore CA 94550 (United States); Hudson, L.T. [National Institute of Standards and Technology, Gaithersburg MD 20899 (United States); Szabo, C.I. [National Institute of Standards and Technology, Gaithersburg MD 20899 (United States); Henins, A. [National Institute of Standards and Technology, Gaithersburg MD 20899 (United States); Holland, G.E. [SFA Inc., 9315 Largo Drive West Suite 200, Largo MD 20774 (United States); Atkin, R. [Tiger Innovations, L.L.C., 3610 Vacation Lane, Arlington VA 22207 (United States); Marlin, L. [Naval Research Laboratory, Space Science Division, Washington DC 20375 (United States)

    2006-05-15

    High-resolution X-ray spectra were recorded by the High-Energy Electronic X-ray (HENEX) spectrometer from a variety of targets irradiated by the Omega laser at the Laboratory for Laser Energetics. The HENEX spectrometer utilizes four reflection crystals covering the 1-20keV energy range and one quartz(10-11) transmission crystal (Laue geometry) covering the 11-40keV range. The time-integrated spectral images were recorded on five CMOS X-ray detectors. In the spectra recorded from krypton-filled gasbag and hohlraum targets, the helium-like K-shell transitions n=1-2, 1-3, and 1-4 appeared in the 13-17keV energy range. A number of additional spectral features were observed at energies lower than the helium-like n=1-3 and n=1-4 transitions. Based on computational simulations of the spectra using the FLYCHK/FLYSPEC codes, which included opacity effects, these additional features are identified to be inner-shell transitions from the Li-like through N-like krypton charge states. The comparisons of the calculated and observed spectra indicate that these transitions are characteristic of the plasma conditions immediately after the laser pulse when the krypton density is 2x10{sup 18}cm{sup -3} and the electron temperature is in the range 2.8-3.2keV. These spectral features represent a new diagnostic for the charge state distribution, the density and electron temperature, and the plasma opacity. Laboratory experiments indicate that it is feasible to record K-shell spectra from gold and higher Z targets in the >60keV energy range using a Ge(220) transmission crystal.

  4. single crystal growth, x-ray structure analysis, optical band gap

    African Journals Online (AJOL)

    2015-09-01

    Sep 1, 2015 ... Hg...Hgand Cl...Cl interactions are stabilizing the structures in 3D pattern. UV-vis absorption spectra illustrate the change in opticalband gap from 3.01eVto 3.42eV on replacing the metal halide group.Raman and Hyper-Raman tensors calculations were performed based on single crystal X-ray data and the ...

  5. X-ray crystal structure and small-angle X-ray scattering of sheep liver sorbitol dehydrogenase

    Energy Technology Data Exchange (ETDEWEB)

    Yennawar, Hemant [Pennsylvania State University, 8 Althouse Laboratory, University Park, PA 16802 (United States); Møller, Magda [Cornell High Energy Synchrotron Source, Ithaca, NY 14853 (United States); University of Copenhagen, DK-2100 Copenhagen (Denmark); Gillilan, Richard [Cornell High Energy Synchrotron Source, Ithaca, NY 14853 (United States); Yennawar, Neela, E-mail: nhy1@psu.edu [Pennsylvania State University, 8 Althouse Laboratory, University Park, PA 16802 (United States)

    2011-05-01

    The X-ray crystal structure and a small-angle X-ray scattering solution structure of sheep liver sorbitol dehydrogenase have been determined. The details of the interactions that enable the tetramer scaffold to be the functional biological unit have been analyzed. The X-ray crystal structure of sheep liver sorbitol dehydrogenase (slSDH) has been determined using the crystal structure of human sorbitol dehydrogenase (hSDH) as a molecular-replacement model. slSDH crystallized in space group I222 with one monomer in the asymmetric unit. A conserved tetramer that superposes well with that seen in hSDH (despite belonging to a different space group) and obeying the 222 crystal symmetry is seen in slSDH. An acetate molecule is bound in the active site, coordinating to the active-site zinc through a water molecule. Glycerol, a substrate of slSDH, also occupies the substrate-binding pocket together with the acetate designed by nature to fit large polyol substrates. The substrate-binding pocket is seen to be in close proximity to the tetramer interface, which explains the need for the structural integrity of the tetramer for enzyme activity. Small-angle X-ray scattering was also used to identify the quaternary structure of the tetramer of slSDH in solution.

  6. Neutron and X-ray diffraction from modulated structures

    International Nuclear Information System (INIS)

    Harris, P.

    1994-07-01

    This thesis describes X-ray and neutron scattering experiments performed on two examples of modulated structures. After an introduction to the subject of modulated structures, the thesis is divided in three parts. A single crystal elastic neutron scattering experiment between 4.2 and 115 Κ has been performed and four-circle X-ray data have been collected at 8 Κ for the monoclinic low-temperature phase of the layered perovskite PAMC. The results from the neutron scattering experiment indicate that magnetoelastic effects influence the ordering of the crystal. The X-ray experiments have made it possible to determine the crystal structure in the low-temperature phase. The superspace group is P2 1 /b(β-30)Os, with β = 1/3. A small-angle neutron scattering experiment has been performed on the magnetic structure of manganese silicide. When a magnetic field is applied, the modulation vectors turn towards the field direction, showing domain growth and diverging peak widths as they approach the field direction. Phase 'A' is established to have the modulation vectors directed perpendicular to the field direction. Cooling in zero field shows increasing peak widths at low temperatures, indicating a lock-in transition below the lowest reached temperature. To be able to analyse the data of the magnetic order in MnSi, and analytical calculation of the three dimensional resolution function for a small-angle neutron scattering spectrometer has been performed. The calculation is done by application of a combination of phase space analysis and Gaussian approximations for the neutron distribution as well as for the transmission functions of the different apertures. A finite mosaic spread of the crystal and finite correlation widths of the Bragg reflections have been included in the cross section. (au) (3 tabs., 48 ills., 100 refs.)

  7. Studies of the X-ray absorption spectra of some methylcyano esters

    International Nuclear Information System (INIS)

    Takahashi, Osamu; Saito, Ko; Mitani, Masaki; Yoshida, Hiroaki; Tahara, Fumitaka; Sunami, Tetsuji; Waki, Keiichiro; Senba, Yasunori; Hiraya, Atsunari; Pettersson, Lars G.M.

    2005-01-01

    Density functional theory (DFT) has been applied to simulate core-excited photoabsorption spectra for some methylcyano esters within a transition potential (TP) framework. Our calculations for methylcyano formate at the N and O K-edges are consistent with previous experimental spectra. For methylcyano acetate the photoabsorption spectra at the N and O K-edges were reinvestigated experimentally. Contrary to the previous experiment, only one main peak was observed at the N K-edge and this peak was assigned to N(1s) ->π* excitation. This result was supported by our theoretical calculations. The general trends in the X-ray absorption spectra and the site-specific bond scission of methylcyano esters at the N and O K-edges are also discussed

  8. Acemetacin cocrystal structures by powder X-ray diffraction

    Science.gov (United States)

    Bolla, Geetha

    2017-01-01

    Cocrystals of acemetacin drug (ACM) with nicotinamide (NAM), p-aminobenzoic acid (PABA), valerolactam (VLM) and 2-pyridone (2HP) were prepared by melt crystallization and their X-ray crystal structures determined by high-resolution powder X-ray diffraction. The powerful technique of structure determination from powder data (SDPD) provided details of molecular packing and hydrogen bonding in pharmaceutical cocrystals of acemetacin. ACM–NAM occurs in anhydrate and hydrate forms, whereas the other structures crystallized in a single crystalline form. The carboxylic acid group of ACM forms theacid–amide dimer three-point synthon R 3 2(9)R 2 2(8)R 3 2(9) with three different syn amides (VLM, 2HP and caprolactam). The conformations of the ACM molecule observed in the crystal structures differ mainly in the mutual orientation of chlorobenzene fragment and the neighboring methyl group, being anti (type I) or syn (type II). ACM hydrate, ACM—NAM, ACM–NAM-hydrate and the piperazine salt of ACM exhibit the type I conformation, whereas ACM polymorphs and other cocrystals adopt the ACM type II conformation. Hydrogen-bond interactions in all the crystal structures were quantified by calculating their molecular electrostatic potential (MEP) surfaces. Hirshfeld surface analysis of the cocrystal surfaces shows that about 50% of the contribution is due to a combination of strong and weak O⋯H, N⋯H, Cl⋯H and C⋯H interactions. The physicochemical properties of these cocrystals are under study. PMID:28512568

  9. Acemetacin cocrystal structures by powder X-ray diffraction

    Directory of Open Access Journals (Sweden)

    Geetha Bolla

    2017-05-01

    Full Text Available Cocrystals of acemetacin drug (ACM with nicotinamide (NAM, p-aminobenzoic acid (PABA, valerolactam (VLM and 2-pyridone (2HP were prepared by melt crystallization and their X-ray crystal structures determined by high-resolution powder X-ray diffraction. The powerful technique of structure determination from powder data (SDPD provided details of molecular packing and hydrogen bonding in pharmaceutical cocrystals of acemetacin. ACM–NAM occurs in anhydrate and hydrate forms, whereas the other structures crystallized in a single crystalline form. The carboxylic acid group of ACM forms theacid–amide dimer three-point synthon R32(9R22(8R32(9 with three different syn amides (VLM, 2HP and caprolactam. The conformations of the ACM molecule observed in the crystal structures differ mainly in the mutual orientation of chlorobenzene fragment and the neighboring methyl group, being anti (type I or syn (type II. ACM hydrate, ACM—NAM, ACM–NAM-hydrate and the piperazine salt of ACM exhibit the type I conformation, whereas ACM polymorphs and other cocrystals adopt the ACM type II conformation. Hydrogen-bond interactions in all the crystal structures were quantified by calculating their molecular electrostatic potential (MEP surfaces. Hirshfeld surface analysis of the cocrystal surfaces shows that about 50% of the contribution is due to a combination of strong and weak O...H, N...H, Cl...H and C...H interactions. The physicochemical properties of these cocrystals are under study.

  10. Monte Carlo simulation of x-ray spectra in diagnostic radiology and mammography using MCNP4C

    Energy Technology Data Exchange (ETDEWEB)

    Ay, M R [Department of Physics and Nuclear Sciences, AmirKabir University of Technology, Tehran (Iran, Islamic Republic of); Shahriari, M [Department of Nuclear Engineering, Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Sarkar, S [Department of Medical Physics, Tehran University of Medical Science, Tehran (Iran, Islamic Republic of); Adib, M [TPP Co., GE Medical Systems, Iran Authorized Distributor, Tehran (Iran, Islamic Republic of); Zaidi, H [Division of Nuclear Medicine, Geneva University Hospital, 1211 Geneva (Switzerland)

    2004-11-07

    The general purpose Monte Carlo N-particle radiation transport computer code (MCNP4C) was used for the simulation of x-ray spectra in diagnostic radiology and mammography. The electrons were transported until they slow down and stop in the target. Both bremsstrahlung and characteristic x-ray production were considered in this work. We focus on the simulation of various target/filter combinations to investigate the effect of tube voltage, target material and filter thickness on x-ray spectra in the diagnostic radiology and mammography energy ranges. The simulated x-ray spectra were compared with experimental measurements and spectra calculated by IPEM report number 78. In addition, the anode heel effect and off-axis x-ray spectra were assessed for different anode angles and target materials and the results were compared with EGS4-based Monte Carlo simulations and measured data. Quantitative evaluation of the differences between our Monte Carlo simulated and comparison spectra was performed using student's t-test statistical analysis. Generally, there is a good agreement between the simulated x-ray and comparison spectra, although there are systematic differences between the simulated and reference spectra especially in the K-characteristic x-rays intensity. Nevertheless, no statistically significant differences have been observed between IPEM spectra and the simulated spectra. It has been shown that the difference between MCNP simulated spectra and IPEM spectra in the low energy range is the result of the overestimation of characteristic photons following the normalization procedure. The transmission curves produced by MCNP4C have good agreement with the IPEM report especially for tube voltages of 50 kV and 80 kV. The systematic discrepancy for higher tube voltages is the result of systematic differences between the corresponding spectra.

  11. Monte Carlo simulation of x-ray spectra in diagnostic radiology and mammography using MCNP4C

    Science.gov (United States)

    Ay, M. R.; Shahriari, M.; Sarkar, S.; Adib, M.; Zaidi, H.

    2004-11-01

    The general purpose Monte Carlo N-particle radiation transport computer code (MCNP4C) was used for the simulation of x-ray spectra in diagnostic radiology and mammography. The electrons were transported until they slow down and stop in the target. Both bremsstrahlung and characteristic x-ray production were considered in this work. We focus on the simulation of various target/filter combinations to investigate the effect of tube voltage, target material and filter thickness on x-ray spectra in the diagnostic radiology and mammography energy ranges. The simulated x-ray spectra were compared with experimental measurements and spectra calculated by IPEM report number 78. In addition, the anode heel effect and off-axis x-ray spectra were assessed for different anode angles and target materials and the results were compared with EGS4-based Monte Carlo simulations and measured data. Quantitative evaluation of the differences between our Monte Carlo simulated and comparison spectra was performed using student's t-test statistical analysis. Generally, there is a good agreement between the simulated x-ray and comparison spectra, although there are systematic differences between the simulated and reference spectra especially in the K-characteristic x-rays intensity. Nevertheless, no statistically significant differences have been observed between IPEM spectra and the simulated spectra. It has been shown that the difference between MCNP simulated spectra and IPEM spectra in the low energy range is the result of the overestimation of characteristic photons following the normalization procedure. The transmission curves produced by MCNP4C have good agreement with the IPEM report especially for tube voltages of 50 kV and 80 kV. The systematic discrepancy for higher tube voltages is the result of systematic differences between the corresponding spectra.

  12. Structure determination of spider silk from X-ray images

    Energy Technology Data Exchange (ETDEWEB)

    Ulrich, Stephan; Zippelius, Annette [Universitaet Goettingen, Institut fuer Theoretische Physik (Germany); Meling, Martin [Max-Planck-Institut fuer biophysikalische Chemie, Goettingen (Germany); Glisovic, Anja; Salditt, Tim [Universitaet Goettingen, Institut fuer Roentgenphysik (Germany)

    2008-07-01

    Spider silk consists of interconnected crystallites, which are typically aligned along the fiber axis. We present a method to systematically determine the structure of these crystallites. Hereby we introduce a model that calculates the scattering function G(q) which is fitted to the measured X-ray image (silk from nephila clavipes). With it, the crystallites' size, the constitution and dimensions of their unit cell, as well as their tilt with respect to the fiber axis is identified, and furthermore the effect of coherent scattering from different crystallites is investigated. The shown methods and the presented model can easily be generalized to a wide class of composite materials.

  13. Status and limitations of multilayer X-ray interference structures

    International Nuclear Information System (INIS)

    Kortright, J.B.

    1996-01-01

    Trends in the performance of x-ray multilayer interference structures with periods ranging from 9 to 130 (angstrom) are reviewed. Analysis of near-normal incidence reflectance data vs photon energy reveals that the effective interface with σ in a static Debye-Waller model, describing interdiffusion and roughness, decreases as the multilayer period decreases, and reaches a lower limit of roughly 2 (angstrom). Specular reflectance and diffuse scattering from uncoated and multilayer-coated substrates having different roughness suggest that this lower limit results largely from substrate roughness. The increase in interface width with period thus results from increasing roughness of interdiffusion as the layer thickness increases

  14. The influence of magnetic field geometry on magnetars X-ray spectra

    International Nuclear Information System (INIS)

    Viganò, D; Pons, J A; Miralles, J A; Parkins, N; Zane, S; Turolla, R

    2012-01-01

    Nowadays, the analysis of the X-ray spectra of magnetically powered neutron stars or magnetars is one of the most valuable tools to gain insight into the physical processes occurring in their interiors and magnetospheres. In particular, the magnetospheric plasma leaves a strong imprint on the observed X-ray spectrum by means of Compton up-scattering of the thermal radiation coming from the star surface. Motivated by the increased quality of the observational data, much theoretical work has been devoted to develop Monte Carlo (MC) codes that incorporate the effects of resonant Compton scattering (RCS) in the modeling of radiative transfer of photons through the magnetosphere. The two key ingredients in this simulations are the kinetic plasma properties and the magnetic field (MF) configuration. The MF geometry is expected to be complex, but up to now only mathematically simple solutions (self-similar solutions) have been employed. In this work, we discuss the effects of new, more realistic, MF geometries on synthetic spectra. We use new force-free solutions [14] in a previously developed MC code [9] to assess the influence of MF geometry on the emerging spectra. Our main result is that the shape of the final spectrum is mostly sensitive to uncertain parameters of the magnetospheric plasma, but the MF geometry plays an important role on the angle-dependence of the spectra.

  15. Changes in X-ray photoelectron spectra of yttria-tetragonal zirconia polycrystal by ion sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Eiko; Yoshinari, Masao [Tokyo Dental College, Oral Health Science Center, Tokyo, Chiyoda-ku (Japan)

    2016-04-15

    This paper reports changes in X-ray photoelectron spectroscopy spectra of yttria-tetragonal zirconia polycrystal (Y-TZP) brought about by Ar ion sputtering. The changes in the core-level spectra of Y-TZP suggest that preferential sputtering of oxygen occurred. A new peak was observed near 0 eV binding energy accompanied with changes in the core-level spectra by the sputtering. After 18 h in a high vacuum following the sputtering, the spectra changed by the sputtering were returned to their original shapes. In contrast, the color of Y-TZP was changed from white to pale brown by X-ray irradiation and was changed from pale brown to dark gray by ion sputtering. However, when the new peak near 0 eV decreased after 18 h, no color change was observed. Therefore, it is thought that the new peak was mainly derived from electrons trapped in various kinds of oxygen vacancies created by the sputtering in other than color centers. (orig.)

  16. Laboratory Studies of X-ray Spectra Formed by Charge Exchange

    Science.gov (United States)

    Beiersdorfer, Peter; Ali, R.; Brown, G. V.; Koutroumpa, D.; Kelley, R. L.; Kilbourne, C.; Leutenegger, M. A.; Porter, F.

    2013-04-01

    Charge exchange between ions and neutral atoms or molecules has been accepted at an important soft producing process in our solar system. By extension, charge exchange may contribute to the X-ray emission of circumstellar material. It may also produce X-ray emission at the boundaries of supernova ejecta and star burst galaxies, or whenever hot plasma collides with neutral matter. X-ray spectra of K-shell and L-shell ions formed by charge exchange have now been studied in a variety of laboratory settings. These experiments have shown several characteristic features of line formation by charge exchange when compared to the X-ray emission produced by electron-impact excitation, e.g., enhancement emission of forbidden lines and of lines from levels with high principal quantum number. They have also shown a dependence on the interaction gas and on the energy of the ion-neutral collision. Moreover, the transfer of multiple electrons is typically preferred, provided the donor molecules or atoms have multiple valence-shell electrons. The laboratory measurements are in qualitative agreement with theory. However, the details of the observed X-ray spectra, especially those recorded with high spectral resolution, can differ substantially from predictions, especially for spectra produced at collision velocities equal to or lower than those found in thermal plasmas or produced with neutral gases other than atomic hydrogen. Puzzling discrepancies can be noted, such as enhanced emission from an upper level with the 'wrong' principal quantum number. Even more puzzling is a recent experiment in which two, co-mixed bare ion species of similar atomic number produce very different Lyman series emission upon charge exchange with a given neutral gas, defying both theoretical predictions and empirical scaling. Laboratory measurements have also shown that some of the characteristic features of charge exchange can be reproduced by radiative electron capture, i.e., by capture of a continuum

  17. X-ray structure determination and deuteration of nattokinase

    International Nuclear Information System (INIS)

    Yanagisawa, Yasuhide; Chatake, Toshiyuki; Naito, Sawa; Ohsugi, Tadanori; Yatagai, Chieko; Sumi, Hiroyuki; Kawaguchi, Akio; Chiba-Kamosida, Kaori; Ogawa, Megumi; Adachi, Tatsumi; Morimoto, Yukio

    2013-01-01

    X-ray structure determination and deuteration of nattokinase were performed to facilitate neutron crystallographic analysis. Nattokinase (NK) is a strong fibrinolytic enzyme, which is produced in abundance by Bacillus subtilis natto. Although NK is a member of the subtilisin family, it displays different substrate specificity when compared with other subtilisins. The results of molecular simulations predict that hydrogen arrangements around Ser221 at the active site probably account for the substrate specificity of NK. Therefore, neutron crystallographic analysis should provide valuable information that reveals the enzymatic mechanism of NK. In this report, the X-ray structure of the non-hydrogen form of undeuterated NK was determined, and the preparation of deuterated NK was successfully achieved. The non-hydrogen NK structure was determined at 1.74 Å resolution. The three-dimensional structures of NK and subtilisin E from Bacillus subtilis DB104 are near identical. Deuteration of NK was carried out by cultivating Bacillus subtilis natto in deuterated medium. The D 2 O resistant strain of Bacillus subtilis natto was obtained by successive cultivation rounds, in which the concentration of D 2 O in the medium was gradually increased. NK was purified from the culture medium and its activity was confirmed by the fibrin plate method. The results lay the framework for neutron protein crystallography analysis

  18. X-ray structure determination and deuteration of nattokinase

    Energy Technology Data Exchange (ETDEWEB)

    Yanagisawa, Yasuhide [Chiba Institute of Science, 15-8 Shiomi-cho, Cho-shi, Chiba 288-025 (Japan); Chatake, Toshiyuki [Kyoto University, Asashironishi 2, Kumatori, Osaka 590-0494 (Japan); Naito, Sawa; Ohsugi, Tadanori; Yatagai, Chieko; Sumi, Hiroyuki [Kurashiki University of Science and the Arts, 2640 Nishinoura, Tsurajima-cho, Kurashiki, Okayama 712-8505 (Japan); Kawaguchi, Akio [Kyoto University, Asashironishi 2, Kumatori, Osaka 590-0494 (Japan); Chiba-Kamosida, Kaori [Nippon Advanced Technology Co. Ltd, J-PARC, 2-4 Shirane Shirakata, Tokai, Ibaraki 319-1195 (Japan); Ogawa, Megumi; Adachi, Tatsumi [Chiba Institute of Science, 15-8 Shiomi-cho, Cho-shi, Chiba 288-025 (Japan); Morimoto, Yukio [Kyoto University, Asashironishi 2, Kumatori, Osaka 590-0494 (Japan)

    2013-11-01

    X-ray structure determination and deuteration of nattokinase were performed to facilitate neutron crystallographic analysis. Nattokinase (NK) is a strong fibrinolytic enzyme, which is produced in abundance by Bacillus subtilis natto. Although NK is a member of the subtilisin family, it displays different substrate specificity when compared with other subtilisins. The results of molecular simulations predict that hydrogen arrangements around Ser221 at the active site probably account for the substrate specificity of NK. Therefore, neutron crystallographic analysis should provide valuable information that reveals the enzymatic mechanism of NK. In this report, the X-ray structure of the non-hydrogen form of undeuterated NK was determined, and the preparation of deuterated NK was successfully achieved. The non-hydrogen NK structure was determined at 1.74 Å resolution. The three-dimensional structures of NK and subtilisin E from Bacillus subtilis DB104 are near identical. Deuteration of NK was carried out by cultivating Bacillus subtilis natto in deuterated medium. The D{sub 2}O resistant strain of Bacillus subtilis natto was obtained by successive cultivation rounds, in which the concentration of D{sub 2}O in the medium was gradually increased. NK was purified from the culture medium and its activity was confirmed by the fibrin plate method. The results lay the framework for neutron protein crystallography analysis.

  19. X-ray spectra and time variability of active galactic nuclei

    International Nuclear Information System (INIS)

    Mushotzky, R.F.

    1984-02-01

    The X-ray spectra of broad line active galactic nuclei (AGN) of all types (Seyfert I's, NELG's, broadline radio galaxies) are well fit by a power law in the .5 to 100 keV band of man energy slope alpha .68 + or - .15. There is, as yet, no strong evidence for time variability of this slope in a given object. The constraints that this places on simple models of the central energy source are discussed. BL Lac objects have quite different X-ray spectral properties and show pronounced X-ray spectral variability. On time scales longer than 12 hours most radio quiet AGN do not show strong, delta I/I .5, variability. The probability of variability of these AGN seems to be inversely related to their luminosity. However characteristics timescales for variability have not been measured for many objects. This general lack of variability may imply that most AGN are well below the Eddington limit. Radio bright AGN tend to be more variable than radio quiet AGN on long, tau approx 6 month, timescales

  20. On the Weak-Wind Problem in Massive Stars: X-Ray Spectra Reveal a Massive Hot Wind in mu Columbae

    Science.gov (United States)

    Huenemoerder, David P.; Oskinova, Lidia M.; Ignace, Richard; Waldron, Wayne L.; Todt, Helge; Hamaguchi, Kenji; Kitamoto, Shunji

    2012-01-01

    Mu Columbae is a prototypical weak-wind O star for which we have obtained a high-resolution X-ray spectrum with the Chandra LETG/ACIS instrument and a low-resolution spectrum with Suzaku. This allows us, for the first time, to investigate the role of X-rays on the wind structure in a bona fide weak-wind system and to determine whether there actually is a massive hot wind. The X-ray emission measure indicates that the outflow is an order of magnitude greater than that derived from UV lines and is commensurate with the nominal wind-luminosity relationship for O stars. Therefore, the "weak-wind problem"--identified from cool wind UV/optical spectra--is largely resolved by accounting for the hot wind seen in X-rays. From X-ray line profiles, Doppler shifts, and relative strengths, we find that this weak-wind star is typical of other late O dwarfs. The X-ray spectra do not suggest a magnetically confined plasma-the spectrum is soft and lines are broadened; Suzaku spectra confirm the lack of emission above 2 keV. Nor do the relative line shifts and widths suggest any wind decoupling by ions. The He-like triplets indicate that the bulk of the X-ray emission is formed rather close to the star, within five stellar radii. Our results challenge the idea that some OB stars are "weak-wind" stars that deviate from the standard wind-luminosity relationship. The wind is not weak, but it is hot and its bulk is only detectable in X-rays.

  1. Quantitative x-ray structure determination of superlattices and interfaces

    International Nuclear Information System (INIS)

    Schuller, I.K.; Fullerton, E.E.

    1990-01-01

    This paper presents a general procedure for quantitative structural refinement of superlattice structures. To analyze a wide range of superlattices, the authors have derived a general kinematical diffraction formula that includes random, continuous and discrete fluctuations from the average structure. By implementing a non-linear fitting algorithm to fit the entire x-ray diffraction profile, refined parameters that describe the average superlattice structure, and deviations from this average are obtained. The structural refinement procedure is applied to a crystalline/crystalline Mo/Ni superlattices and crystalline/amorphous Pb/Ge superlattices. Roughness introduced artificially during growth in Mo/Ni superlattices is shown to be accurately reproduced by the refinement

  2. Monte Carlo Simulation of Complete X-Ray Spectra for Use in Scanning Electron Microscopy Analysis

    International Nuclear Information System (INIS)

    Roet, David; Van Espen, Piet

    2003-01-01

    Full Text: The interactions of keV electrons and photons with matter can be simulated accurately with the aid of the Monte Carlo (MC) technique. In scanning electron microscopy x-ray analysis (SEM-EDX) such simulations can be used to perform quantitative analysis using a Reverse Monte Carlo method even if the samples have irregular geometry. Alternatively the MC technique can generate spectra of standards for use in quantization with partial least squares regression. The feasibility of these alternatives to the more classical ZAF or phi-rho-Z quantification methods has been proven already. In order to be applicable for these purposes the MC-code needs to generate accurately only the characteristic K and L x-ray lines, but also the Bremsstrahlung continuum, i.e. the complete x-ray spectrum need to be simulated. Currently two types of MC simulation codes are available. Programs like Electron Flight Simulator and CASINO simulate characteristic x-rays due to electron interaction in a fast and efficient way but lack provision for the simulation of the continuum. On the other hand, programs like EGS4, MCNP4 and PENELOPE, originally developed for high energy (MeV- GeV) applications, are more complete but difficult to use and still slow, even on todays fastest computers. We therefore started the development of a dedicated MC simulation code for use in quantitative SEM-EDX work. The selection of the most appropriate cross section for the different interactions will be discussed and the results obtained will be compared with those obtained with existing MC programs. Examples of the application of MC simulations for quantitative analysis of samples with various composition will be given

  3. New Observations of Soft X-ray (0.5-5 keV) Solar Spectra

    Science.gov (United States)

    Caspi, A.; Woods, T. N.; Mason, J. P.; Jones, A. R.; Warren, H. P.

    2013-12-01

    The solar corona is the brightest source of X-rays in the solar system, and the X-ray emission is highly variable on many time scales. However, the actual solar soft X-ray (SXR) (0.5-5 keV) spectrum is not well known, particularly during solar quiet periods, as, with few exceptions, this energy range has not been systematically studied in many years. Previous observations include high-resolution but very narrow-band spectra from crystal spectrometers (e.g., Yohkoh/BCS), or integrated broadband irradiances from photometers (e.g., GOES/XRS, TIMED/XPS, etc.) that lack detailed spectral information. In recent years, broadband measurements with moderate energy resolution (~0.5-0.7 keV FWHM) were made by SphinX on CORONAS-Photon and SAX on MESSENGER, although they did not extend to energies below ~1 keV. We present observations of solar SXR emission obtained using new instrumentation flown on recent SDO/EVE calibration rocket underflights. The photon-counting spectrometer, a commercial Amptek X123 with a silicon drift detector and an 8 μm Be window, measures the solar disk-integrated SXR emission from ~0.5 to >10 keV with ~0.15 keV FWHM resolution and 1 s cadence. A novel imager, a pinhole X-ray camera using a cooled frame-transfer CCD (15 μm pixel pitch), Ti/Al/C filter, and 5000 line/mm Au transmission grating, images the full Sun in multiple spectral orders from ~0.1 to ~5 nm with ~10 arcsec/pixel and ~0.01 nm/pixel spatial and spectral detector scales, respectively, and 10 s cadence. These instruments are prototypes for future CubeSat missions currently being developed. We present new results of solar observations on 04 October 2013 (NASA sounding rocket 36.290). We compare with previous results from 23 June 2012 (NASA sounding rocket 36.286), during which solar activity was low and no signal was observed above ~4 keV. We compare our spectral and imaging measurements with spectra and broadband irradiances from other instruments, including SDO/EVE, GOES/XRS, TIMED

  4. Reconstruction of X-rays spectra of clinical linear accelerators using the generalized simulated annealing method

    International Nuclear Information System (INIS)

    Manrique, John Peter O.; Costa, Alessandro M.

    2016-01-01

    The spectral distribution of megavoltage X-rays used in radiotherapy departments is a fundamental quantity from which, in principle, all relevant information required for radiotherapy treatments can be determined. To calculate the dose delivered to the patient who make radiation therapy, are used treatment planning systems (TPS), which make use of convolution and superposition algorithms and which requires prior knowledge of the photon fluence spectrum to perform the calculation of three-dimensional doses and thus ensure better accuracy in the tumor control probabilities preserving the normal tissue complication probabilities low. In this work we have obtained the photon fluence spectrum of X-ray of the SIEMENS ONCOR linear accelerator of 6 MV, using an character-inverse method to the reconstruction of the spectra of photons from transmission curves measured for different thicknesses of aluminum; the method used for reconstruction of the spectra is a stochastic technique known as generalized simulated annealing (GSA), based on the work of quasi-equilibrium statistic of Tsallis. For the validation of the reconstructed spectra we calculated the curve of percentage depth dose (PDD) for energy of 6 MV, using Monte Carlo simulation with Penelope code, and from the PDD then calculate the beam quality index TPR_2_0_/_1_0. (author)

  5. On the origin of X-ray spectra in luminous blazars

    International Nuclear Information System (INIS)

    Sikora, Marek; Janiak, Mateusz; Moderski, Rafał; Nalewajko, Krzysztof; Madejski, Greg M.

    2013-01-01

    Gamma-ray luminosities of some quasar-associated blazars imply jet powers reaching values comparable to the accretion power even if assuming very strong Doppler boosting and very high efficiency of gamma-ray production. With much lower radiative efficiencies of protons than of electrons, and the recent reports of very strong coupling of electrons with shock-heated protons indicated by particle-in-cell simulations, the leptonic models seem to be strongly favored over the hadronic ones. However, the electron-proton coupling combined with the external-radiation-Compton (ERC) models of gamma-ray production in leptonic models predict extremely hard X-ray spectra, with energy indices α x ∼ 0. This is inconsistent with the observed 2-10 keV slopes of blazars, which cluster around α x ∼ 0.6. This problem can be resolved by assuming that electrons can be efficiently cooled down radiatively to non-relativistic energies, or that blazar spectra are entirely dominated by the synchrotron self-Compton (SSC) component up to at least 10 keV. Here, we show that the required cooling can be sufficiently efficient only at distances r < 0.03 pc. SSC spectra, on the other hand, can be produced roughly co-spatially with the observed synchrotron and ERC components, which are most likely located roughly at a parsec scale. We show that the dominant SSC component can also be produced much further than the dominant synchrotron and ERC components, at distances of ≳ 10 pc. Hence, depending on the spatial distribution of the energy dissipation along the jet, one may expect to see γ-ray/optical events with either correlated or uncorrelated X-rays. In all cases the number of e + e – pairs per proton is predicted to be very low. The direct verification of the proposed SSC scenario, and particularly the question of the co-spatiality of the SSC component with other spectral components, requires sensitive observations in the hard X-ray band. This is now possible with the deployment of the Nu

  6. Determining misorientation of graphite grains from the angular dependence of X-ray emission spectra

    International Nuclear Information System (INIS)

    Belavin, V. V.; Okotrub, A. V.; Bulusheva, L. G.; Kotosonov, A. S.; Vyalykh, D. V.; Molodtsov, S. L.

    2006-01-01

    Angular-resolved X-ray absorption spectra were measured for pyrolytic graphite samples of various quality. A new approach to determining the misorientation of graphite grains in polycrystalline samples is proposed, which is based on calculations of the angular dependence of the relative intensity of a peak corresponding to the π* state for a normal distribution of grains. The experimental values are used to construct theoretical angular dependences using partial densities of the π* and σ* states determined from the nonempirical calculations for graphite

  7. Application of direct peak analysis to energy dispersive x-ray fluorescence spectra

    International Nuclear Information System (INIS)

    Nielson, K.K.

    1977-07-01

    A modified Covell method for direct peak analysis has been applied to energy dispersive x-ray fluorescence spectra. The method is background independent and is well-suited to computerized data reduction. It provides acceptable precision, minimizes errors from instrumental gain shift, and permits peak overlap correction. Peak overlap errors exhibit both positive and negative nodes as a function of peak separation distance, and are corrected using concentration ratios determined from thin, single-element standards. Peak precisions and overlaps are evaluated as a function of window width to aid in width selection. Least-square polynomial smoothing prior to peak analysis significantly improves peak area precisions without significantly affecting their accuracies

  8. Calculation of x-ray spectra emerging from an x-ray tube. Part I. Electron penetration characteristics in x-ray targets

    International Nuclear Information System (INIS)

    Poludniowski, Gavin G.; Evans, Philip M.

    2007-01-01

    The penetration characteristics of electron beams into x-ray targets are investigated for incident electron kinetic energies in the range 50-150 keV. The frequency densities of electrons penetrating to a depth x in a target, with a fraction of initial kinetic energy, u, are calculated using Monte Carlo methods for beam energies of 50, 80, 100, 120 and 150 keV in a tungsten target. The frequency densities for 100 keV electrons in Al, Mo and Re targets are also calculated. A mixture of simple modeling with equations and interpolation from data is used to generalize the calculations in tungsten. Where possible, parameters derived from the Monte Carlo data are compared to experimental measurements. Previous electron transport approximations in the semiempirical models of other authors are discussed and related to this work. In particular, the crudity of the use of the Thomson-Whiddington law to describe electron penetration and energy loss is highlighted. The results presented here may be used towards calculating the target self-attenuation correction for bremsstrahlung photons emitted within a tungsten target

  9. X-Ray Spectra from MHD Simulations of Accreting Black Holes

    Science.gov (United States)

    Schnittman, Jeremy D.; Krolik, Julian H.; Noble, Scott C.

    2012-01-01

    We present the results of a new global radiation transport code coupled to a general relativistic magneto-hydrodynamic simulation of an accreting, nonrotating black hole. For the first time, we are able to explain from first principles in a self-consistent way the X-ray spectra observed from stellar-mass black holes, including a thermal peak, Compton reflection hump, power-law tail, and broad iron line. Varying only the mass accretion rate, we are able to reproduce the low/hard, steep power-law, and thermal-dominant states seen in most galactic black hole sources. The temperature in the corona is T(sub e) 10 keV in a boundary layer near the disk and rises smoothly to T(sub e) greater than or approximately 100 keV in low-density regions far above the disk. Even as the disk's reflection edge varies from the horizon out to approximately equal to 6M as the accretion rate decreases, we find that the shape of the Fe Ka line is remarkably constant. This is because photons emitted from the plunging region are strongly beamed into the horizon and never reach the observer. We have also carried out a basic timing analysis of the spectra and find that the fractional variability increases with photon energy and viewer inclination angle, consistent with the coronal hot spot model for X-ray fluctuations.

  10. EMISSION LINES BETWEEN 1 AND 2 keV IN COMETARY X-RAY SPECTRA

    Energy Technology Data Exchange (ETDEWEB)

    Ewing, Ian; Christian, Damian J. [Department of Physics and Astronomy, California State University, 18111 Nordhoff Street, Northridge, CA 91330 (United States); Bodewits, Dennis [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Dennerl, Konrad [Max-Planck-Institut fuer extraterrestrische Physik, Postfach 1312, D-85741 Garching Germany (Germany); Lisse, Carey M. [Planetary Exploration Group, Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 (United States); Wolk, Scott J., E-mail: ian.ewing.794@my.csun.edu, E-mail: daman.christian@csun.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2013-01-20

    We present the detection of new cometary X-ray emission lines in the 1.0-2.0 keV range using a sample of comets observed with the Chandra X-Ray Observatory and ACIS spectrometer. We have selected five comets from the Chandra sample with good signal-to-noise spectra. The surveyed comets are C/1999 S4 (LINEAR), C/1999 T1 (McNaught-Hartley), 153P/2002 (Ikeya-Zhang), 2P/2003 (Encke), and C/2008 8P (Tuttle). We modeled the spectra with an extended version of our solar wind charge exchange (SWCX) emission model. Above 1 keV, we find Ikeya-Zhang to have strong emission lines at 1340 and 1850 eV which we identify as being created by SWCX lines of Mg XI and Si XIII, respectively, and weaker emission lines at 1470, 1600, and 1950 eV formed by SWCX of Mg XII, Mg XI, and Si XIV, respectively. The Mg XI and XII and Si XIII and XIV lines are detected at a significant level for the other comets in our sample (LS4, MH, Encke, 8P), and these lines promise additional diagnostics to be included in SWCX models. The silicon lines in the 1700-2000 eV range are detected for all comets, but with the rising background and decreasing cometary emission, we caution that these detections need further confirmation with higher resolution instruments.

  11. X-RAY REFLECTED SPECTRA FROM ACCRETION DISK MODELS. I. CONSTANT DENSITY ATMOSPHERES

    International Nuclear Information System (INIS)

    Garcia, J.; Kallman, T. R.

    2010-01-01

    We present new models for illuminated accretion disks, their structure, and reprocessed emission. We consider the effects of incident X-rays on the surface of an accretion disk by simultaneously solving the equations of radiative transfer, energy balance, and ionization equilibrium over a large range of column densities. We assume plane-parallel geometry and azimuthal symmetry, such that each calculation corresponds to a ring at a given distance from the central object. Our models include recent and complete atomic data for K-shell processes of the iron and oxygen isonuclear sequences. We examine the effect on the spectrum of fluorescent Kα line emission and absorption in the emitted spectrum. We also explore the dependence of the spectrum on the strength of the incident X-rays and other input parameters, and discuss the importance of Comptonization on the emitted spectrum.

  12. X-ray structural analysis of some Indian coals

    International Nuclear Information System (INIS)

    Binoy K Saikia, B.K.

    2009-01-01

    Coal is one of the most abundant energy resources and has the capability to meet future energy needs with high reliability. The use of coal as an energy source and as a source of organic chemicals feedstock may become more important in the future. It is physically and chemically a heterogeneous and carbonaceous rock which consists of organic and inorganic materials. Assam coal has been, and continuous to be, a valuable energy source, especially for the various industry in India and for liquefactions of coal. The basic chemical structure of coal that has been widely accepted today was built up from the synthesis of results obtained from X-ray diffraction data. The present paper reports a comparative investigation of coals from different collieries/areas of Makum coal field, Assam viz. Ledo, Tikak, Baragolai, Tipong and Tirap collieries Makum coal field, Assam with the help of X-ray diffraction (XRD). The X-ray diffraction patterns indicate that the coals are amorphous in nature. The present XRD method includes the evaluation of Function of Radial Distribution of Atoms (FRDA) and structural interpretations of the coals from their Radial Distribution Function (RDF) plots after proper corrections for air scatter, absorption by sample and polarization. The curve intensity profiles in FRDA clearly show quite regular molecular packets for these coals. The first maxima in the FRDA curves was obtained at r= 0.4 Amstrong for Ledo, Baragolai and Tipong coals whereas for Tikak coal it was observed at r= 0.5 Amstrong. The first maximum in the pair distribution function plots, G (r) of Ledo, Tikak, and Tipong coals was obtained at r=0.15 nm whereas for Baragolai and Tirap coals it was observed at r=0.14 nm and r=0.12 nm respectively, which relates to the C=C (aliphatic/aromatic) bonds in coal matrix. The Assam coal samples from Ledo, Tikak, Baragolai, Tipong and Tirap collieries of Makum coalfield have almost the same RDF inter-atomic distances except slight differences. This

  13. Construction of a catalog of X-ray spectra for mammography simulations

    International Nuclear Information System (INIS)

    Santos, L.C.S.; Vieira, J.W.

    2017-01-01

    Computational Exposure Models (MCEs) allow the simulation of the interaction of radiation with matter by means of Monte Carlo (MC) techniques. Generally, MCEs are composed of phantom, simulator algorithms of radioactive sources and an MC code to simulate the transport, interaction of the radiation with matter and to evaluate the energy deposited in regions of interest. To compose an MCE for simulations in mammography, the construction of a catalog of X-ray spectra was started, based on the catalog model constructed and using until then in MCEs by the Group of Research in Numerical Dosimetry and by the Group of Research in Computational Dosimetry & Embedded Systems (both referenced in this work as GDN). Potential of 25 kV and 35 kV and used target / filter were applied to the tube: Mo / Mo. The file containing the spectra was read correctly by EGSnrc

  14. Studies of cluster X-ray sources. Energy spectra for the Perseus, Virgo, and Coma clusters

    International Nuclear Information System (INIS)

    Kellogg, E.; Baldwin, J.R.; Koch, D.

    1975-01-01

    We present the final Uhuru X-ray differential-energy spectra for the Perseus, Virgo, and Coma clusters of galaxies. The power-law and isothermal bremsstrahlung model forms, both with a low-energy cutoff, are given. For bremsstrahlung, the energy-dependent Gaunt factor is calculated by an improved method. The spectra, best fits to the Uhuru 2-10 keV data, are also compared with other observations of these sources in the energy range 0.1-100 keV. For Perseus, the data above 20 keV favor the bremsstrahlung fit marginally. For Virgo, the data of Catura et al. between 0.25 and 1.0 keV clearly favor the bremsstrahlung curve. For Coma, the weakest of the three sources, the data are less precise, but there is some evidence for a low-energy turnover or cutoff. The implications of such a cutoff are discussed briefly

  15. Equivalent half-value thickness and mean energies of filtered X-ray bremsstrahlung spectra

    International Nuclear Information System (INIS)

    Seelentag, W.W.; Panzer, W.

    1980-01-01

    X-ray beam qualities are often conveniently described by half-value thicknesses (in connection with tube voltage and filtration). Aluminium and copper are commonly used as half-value thickness materials, and either material may be used in a large intermediate energy range. Data comparisons frequently require conversions from values in Al to values in Cu. Equivalent half-value thicknesses for polychromatic radiations depend on the shapes of the spectra, but spectrometry is too expensive for routine application. Half-value thicknesses in both Al and Cu have been determined for some 250 spectra (tube potentials 10 to 300 kV). The results are tabulated, and these results together with a nomogram enable conversion with an accuracy of better than +- 5% in most cases. (UK)

  16. Structural studies using X-ray absorption and scattering techniques

    International Nuclear Information System (INIS)

    Ericson, Agneta.

    1989-01-01

    The thesis presents extended X-ray absorption fine structure, EXAFS, and large angle X-ray scattering, LAXS, techniques; instrumentation, data collection and reduction, and applications. These techniques have been used to determine the structures of magnesium halides and organomagnesium halides in diethyl ether and tetrahydrofuran solution. The iodides were used for the LAXS measurements and Br K edge EXAFS data were collected for the corresponding bromides. Two different complexes are present in the diethyl ether solution of magnesium iodide; a polymeric chain-type structure where magnesium is tetrahedrally coordinated, as well as dimeric complex with octahedrally coordinated magnesium. Solvated MgI + is the dominating species in tetrahydrofuran solution. The organomagnesium halides are present in diethyl ether solution as both solvated monomeric and dimeric complexes. Magnesium coordinates a halide ion, an alkyl or aryl group and four solvent molecules octahedrally in the monomeric complex. In the dimeric complex magnesium is octahedrally coordinated by two bridging halide ions, an alkyl or aryl group and three solvent molecules. The distribution of monomeric and dimeric complexes in various solutions are given by a dimerisation constant, K dl . The results indicate that the Schlenk equilibrium is present in these solutions, however, in an extended form. In diethyl ether solution, where MgX 2 does not dissociate, no MgX 2 complex and thereby no Schlenk equilibrium has been observed. In tetrahydrofuran solution MgI 2 has dissociated into mainly MgI + and I - . This indicates that the concentration of MgI 2 is low and that the Schlenk equilibrium should be expanded even further to include the dissociation equilibrium of the magnesium halide. In the thesis Fe K edge EXAFS data collected for the semireduced form of protein A of methane monooxygenase from Methylococcus capsulatus, are also presented. (139 refs.)

  17. The supersoft X-ray source in V5116 Sagittarii. I. The high resolution spectra

    Science.gov (United States)

    Sala, G.; Ness, J. U.; Hernanz, M.; Greiner, J.

    2017-05-01

    Context. Classical nova explosions occur on the surface of an accreting white dwarf in a binary system. After ejection of a fraction of the envelope and when the expanding shell becomes optically thin to X-rays, a bright source of supersoft X-rays arises, powered by residual H burning on the surface of the white dwarf. While the general picture of the nova event is well established, the details and balance of accretion and ejection processes in classical novae are still full of unknowns. The long-term balance of accreted matter is of special interest for massive accreting white dwarfs, which may be promising supernova Ia progenitor candidates. Nova V5116 Sgr 2005b was observed as a bright and variable supersoft X-ray source by XMM-Newton in March 2007, 610 days after outburst. The light curve showed a periodicity consistent with the orbital period. During one third of the orbit the luminosity was a factor of seven brighter than during the other two thirds of the orbital period. Aims: In the present work we aim to disentangle the X-ray spectral components of V5116 Sgr and their variability. Methods: We present the high resolution spectra obtained with XMM-Newton RGS and Chandra LETGS/HRC-S in March and August 2007. Results: The grating spectrum during the periods of high-flux shows a typical hot white dwarf atmosphere dominated by absorption lines of N VI and N VII. During the low-flux periods, the spectrum is dominated by an atmosphere with the same temperature as during the high-flux period, but with several emission features superimposed. Some of the emission lines are well modeled with an optically thin plasma in collisional equilibrium, rich in C and N, which also explains some excess in the spectra of the high-flux period. No velocity shifts are observed in the absorption lines, with an upper limit set by the spectral resolution of 500 km s-1, consistent with the expectation of a non-expanding atmosphere so late in the evolution of the post-nova. Based on

  18. X-ray absorption study of the electronic structure of Mn-doped amorphous Si

    Energy Technology Data Exchange (ETDEWEB)

    Arenholz, Elke; Zeng, Li; Huegel, A.; Helgren, E.; Hellman, F.; Piamonteze, C.; Arenholz, E.

    2008-03-08

    The electronic structure of Mn in amorphous Si (a-Mn{sub x}Si{sub 1?x}) is studied by X-ray absorption spectroscopy at the Mn L{sub 3,2} edges for x = 0.005-0.18. Except the x = 0.005 sample, which shows a slight signature of Mn{sup 2+} atomic multiplets associated with a local Mn moment, all samples have broad and featureless L{sub 3,2} absorption peaks, corresponding to an itinerant state for all 3d electrons. The broad X-ray absorption spectra exclude the possibility of a localized 3d moment and explain the unexpectedly quenched Mn moment in this magnetically-doped amorphous semiconductor. Such a fully delocalized d state of Mn dopant in Si has not been previously suggested.

  19. Lα1 satellites in X-ray emission spectra of higher - Z elements

    International Nuclear Information System (INIS)

    Poonia, S.

    2004-01-01

    Full text: The X-ray satellite spectra arising due to 2p 3/2 -1 3x -1 - 3x -1 3d -1 (x ≡ s, p, d) transition array, in elements with Z 74 to 92, have been calculated. While the energies of various transitions of the array have been determined by using available Hartree-Fock-Slater data on 1s -1 - 2p -1 3x -1 and 2p 3/2 -1 - 3x -1 , 3x' -1 Auger transition energies and their relative intensities have been estimated by considering cross - sections of singly ionized 2x -1 (x ≡ s, p) states and then of subsequent Coster-Kronig and shake off processes. The calculated spectra have been compared with the measured satellite energies in Lα1 spectra. Their intense peaks have been identified as the observed satellite lines. The one to one correspondence between the peaks in calculated spectra and the satellites in measured spectra has been established on the basis of the agreement between the separations in the peak energies and those in the measured satellite energies. It has been established that three satellites observed in the Lα 1 region of the X-ray spectra of various elements and named α', α ix and α x in order of increasing energy are mainly emitted by 2p 3/2 -1 3d -1 - 3d -2 transitions. It is observed that the satellite α' in all these spectra can be assigned to the superposition of 3 F 4 - 3 F 4 transition and that this must be most intense one out of all these satellites, contributing in order of decreasing intensity. The line α ix , has been assigned to mainly the 1 F 3 - 1 G 4 , 1 P 1 - 1 D 2 and 1 F 3 - 1 D 2 transitions. Finally, the satellite α x , reported in the spectra of elements with Z = 74-92, has been associated with the transition 3 D 3 - 3 F 4 . The possible contributions of other transitions of the 2p 3/2 -1 3x -1 - 3x -1 3d -1 (x ≡ s, p, d) array having appreciable intensities, have also been discussed

  20. Traditional x-ray imaging

    International Nuclear Information System (INIS)

    Hay, G.A.

    1982-01-01

    Methods of imaging x-rays, with particular reference to medicine, are reviewed. The history and nature of x-rays, their production and spectra, contrast, shapes and fine structure, image transducers, including fluorescent screens, radiography, fluoroscopy, and image intensifiers, image detection, perception and enhancement and clinical applications are considered. (U.K.)

  1. X-ray Absorption Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    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.

  2. Discovery of Spatial and Spectral Structure in the X-Ray Emission from the Crab Nebula

    Science.gov (United States)

    Weisskopf, Martin C.; Hester, J. Jeff; Tennant, Allyn F.; Elsner, Ronald F.; Schulz, Norbert S.; Marshall, Herman L.; Karovska, Margarita; Nichols, Joy S.; Swartz, Douglas A.; Kolodziejczak, Jeffery J.

    2000-01-01

    The Chandra X-Ray Observatory observed the Crab Nebula and pulsar during orbital calibration. Zeroth-order images with the High-Energy Transmission Grating (HETG) readout by the Advanced Charge Coupled Devices (CCD) Imaging Spectrometer spectroscopy array (ACIS-S) show a striking richness of X-ray structure at a resolution comparable to that of the best ground-based visible-light observations. The HETG-ACIS-S images reveal, for the first time, an X-ray inner ring within the X-ray torus, the suggestion of a hollow-tube structure for the torus, and X-ray knots along the inner ring and (perhaps) along the inward extension of the X-ray jet. Although complicated by instrumental effects and the brightness of the Crab Nebula, the spectrometric analysis shows systematic variations of the X-ray spectrum throughout the nebula.

  3. Discovery of Spatial and Spectral Structure in the X-Ray Emission from the Crab Nebula.

    Science.gov (United States)

    Weisskopf; Hester; Tennant; Elsner; Schulz; Marshall; Karovska; Nichols; Swartz; Kolodziejczak; O'Dell

    2000-06-20

    The Chandra X-Ray Observatory observed the Crab Nebula and pulsar during orbital calibration. Zeroth-order images with the High-Energy Transmission Grating (HETG) readout by the Advanced CCD Imaging Spectrometer spectroscopy array (ACIS-S) show a striking richness of X-ray structure at a resolution comparable to that of the best ground-based visible-light observations. The HETG-ACIS-S images reveal, for the first time, an X-ray inner ring within the X-ray torus, the suggestion of a hollow-tube structure for the torus, and X-ray knots along the inner ring and (perhaps) along the inward extension of the X-ray jet. Although complicated by instrumental effects and the brightness of the Crab Nebula, the spectrometric analysis shows systematic variations of the X-ray spectrum throughout the nebula.

  4. On the origin of cyclotron lines in the spectra of X-ray pulsars

    Directory of Open Access Journals (Sweden)

    Mushtukov A. A.

    2014-01-01

    Full Text Available Cyclotron resonance scattering features are observed in the spectra of some X-ray pulsars and show significant changes in the line energy with the pulsar luminosity. In a case of bright sources, the line centroid energy is anti-correlated with the luminosity. Such a behaviour is often associated with the onset and growth of the accretion column, which is believed to be the origin of the observed emission and the cyclotron lines. However, this scenario inevitably implies large gradient of the magnetic field strength within the line-forming region, and it makes the formation of the observed line-like features problematic. Moreover, the observed variation of the cyclotron line energy is much smaller than could be anticipated for the corresponding luminosity changes. We argue that a more physically realistic situation is that the cyclotron line forms when the radiation emitted by the accretion column is reflected from the neutron star surface. The idea is based on the facts that a substantial part of column luminosity is intercepted by the neutron star surface and the reflected radiation should contain absorption features. The reflection model is developed and applied to explain the observed variations of the cyclotron line energy in a bright X-ray pulsar V 0332+53 over a wide range of luminosities.

  5. Comparison of hard X-ray spectra obtained by spectrometers on Hinotori and SMM and detection of 'superhot' component

    Science.gov (United States)

    Nitta, Nariaki

    1988-01-01

    Hard X-ray spectra in solar flares obtained by the broadband spectrometers aboard Hinotori and SMM are compared. Within the uncertainty brought about by assuming the typical energy of the background X-rays, spectra by the Hinotori spectrometer are usually consistent with those by the SMM spectrometer for flares in 1981. On the contrary, flares in 1982 persistently show 20-50-percent higher flux by Hinotori than by SMM. If this discrepancy is entirely attributable to errors in the calibration of energy ranges, the errors would be about 10 percent. Despite such a discrepancy in absolute flux, in the the decay phase of one flare, spectra revealed a hard X-ray component (probably a 'superhot' component) that could be explained neither by emission from a plasma at about 2 x 10 to the 7th K nor by a nonthermal power-law component. Imaging observations during this period show hard X-ray emission nearly cospatial with soft X-ray emission, in contrast with earlier times at which hard and soft X-rays come from different places.

  6. Directional fine structure in absorption of white x rays: A tomographic interpretation

    International Nuclear Information System (INIS)

    Korecki, P.; Szymonski, M.; Tolkiehn, M.; Novikov, D. V.; Materlik, G.

    2006-01-01

    We discuss directional fine structure in absorption of white x rays for tomographic imaging of crystal structure at the atomic level. The interference between a direct x-ray beam and the secondary waves coherently scattered inside a specimen modifies the total wave field at the position of the absorbing atoms. For a white x-ray beam, the wave field variations cancel out by energy integration for all directions, except for the near forward scattering components, coinciding with the incident beam. Therefore, two-dimensional patterns of the angular-dependent fine structure in absorption of white x rays can be interpreted as real-space projections of atomic structure. In this work, we present a theory describing the directional fine structure in white x-ray absorption and a tomographic approach for crystal structure retrieval developed on its basis. The tomographic algorithm is applied to the experimental x-ray absorption data recorded for GaP crystals

  7. X-ray Structure of the Mature Ectodomain of Phogrin

    Energy Technology Data Exchange (ETDEWEB)

    Noguera, M. E. [National Univ. of Quilmes, Buenos Aires (Argentina); Primo, M. [Univ. of Buenos Aires (Argentina); Jakoncic, J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Poskus, E. [Univ. of Buenos Aires (Argentina); Solimena, M. [Dresden Univ. of Technology and Max Planck Inst. of Molecular Cell Biology and Genetics (Germany); Ermacora, M. R. [National Univ. of Quilmes and Multidisciplinary Inst. of Cellular Biology, Buenos Aires (Argentina)

    2014-11-26

    Phogrin/IA-2β and ICA512/IA-2 are two paralogs receptor-type protein-tyrosine phosphatases (RPTP) that localize in secretory granules of various neuroendocrine cells. In pancreatic islet β-cells, they participate in the regulation of insulin secretion, ensuring proper granulogenesis, and β-cell proliferation. The role of their cytoplasmic tail has been partially unveiled, while that of their luminal region remains unclear. To advance the understanding of its structure–function relationship, the X-ray structure of the mature ectodomain of phogrin (ME phogrin) at pH 7.4 and 4.6 has been solved at 1.95- and 2.01-Å resolution, respectively. Likewise to the ME of ICA512, ME phogrin adopts a ferredoxin-like fold: a sheet of four antiparallel β-strands packed against two α-helices. Furthermore, sequence conservation among vertebrates, plants and insects suggests that the structural similarity extends to all the receptor family. Crystallized ME phogrin is monomeric, in agreement with solution studies but in striking contrast with the behavior of homodimeric ME ICA512. The structural details that may cause the quaternary structure differences are analyzed. The results provide a basis for building models of the overall orientation and oligomerization state of the receptor in biological membranes.

  8. Interpretation of magnetic circular dichroism of X-ray emission spectra

    International Nuclear Information System (INIS)

    Takayama, Yasuhiro; Yoshida, Tetsuo; Nakamura, Satoshi; Sasaki, Naoya; Ishii, Hiroyoshi; Miyahara, Tsuneaki

    2006-01-01

    We have measured the dependence of the magnetic circular dichroism (MCD) of the X-ray emission spectra (XES) on the temperature and incident angle for a Gd thin film. The energy of the incident photon for the XES was 138.25eV, which corresponded to the resonant excitation to the 8 D 9/2 intermediate state. The dependence of the observed MCD on the temperature and incident angle was quite different from that of the magnetic moment estimated with a SQUID magnetometer. By considering the reflection, saturation effect, self-absorption effect and magnetic anisotropy of the thin film, the agreement of the two behaviors was considerably improved. This result shows that the revisions of the MCD of the XES are extremely important for the quantitative estimation of the magnetic moment from the MCD of the XES. (author)

  9. Fundamental quantification procedure for total reflection X-ray fluorescence spectra analysis and elements determination

    International Nuclear Information System (INIS)

    Wegrzynek, D.; Holynska, B.

    1997-01-01

    A method for the determination of the concentrations of elements in particulate-like samples measured in total reflection geometry is proposed. In the proposed method the fundamental parameters are utilized for calculating the sensitivities of elements and an internal standard is used to account for the unknown mass per unit area of a sample and geometrical constant of the spectrometer. The modification of the primary excitation spectrum on its way to a sample has been taken into consideration. The concentrations of the elements to be determined are calculated simultaneously with the spectra deconvolution procedure. In the process of quantitative analysis the intensities of all X-ray peaks corresponding to K and L-series lines present in the analyzed spectrum are taken into account. (Author)

  10. X-ray absorption near edge structure (XANES) study of some hydroxamic mixed ligand copper complexes

    International Nuclear Information System (INIS)

    Mishra, A; Parsai, N; Shrivastava, B D; Soni, N

    2012-01-01

    With the advent of modern bright synchrotron radiation sources, X-ray absorption spectra has emerged as a powerful technique for local structure determination, which can be applied to any type of material. The X-ray absorption measurements of four hydroxamic mixed ligand copper complexes have been performed at the recently developed BL-8 Dispersive EXAFS beamline at 2.5 GeV Indus-2 synchrotron at RRCAT, Indore, India. The X-ray absorption near edge structure (XANES) data obtained has been processed using data analysis program Athena. The energies of the K absorption edge, chemical shifts, edge-widths, shifts of the principal absorption maximum in the complexes have been determined. The values of the chemical shift suggest that copper is in oxidation state +2 in all of the complexes. The chemical shift data has been utilized to estimate effective nuclear charge on copper atom. The order of the chemical shifts has been correlated to the relative ionic character of the bonding in these complexes.

  11. X-Ray Absorption Spectra of Water from First Principles Calculations

    International Nuclear Information System (INIS)

    Prendergast, David; Galli, Giulia

    2006-01-01

    We present a series of ab initio calculations of the x-ray absorption cross section (XAS) of ice and liquid water at ambient conditions. Our results show that all available experimental data and theoretical results are consistent with the standard model of the liquid as comprising molecules with approximately four hydrogen bonds. Our simulations of ice XAS including the lowest lying excitonic state are in excellent agreement with experiment and those of a quasitetrahedral model of water are in reasonable agreement with recent measurements. Hence we propose that the standard, quasitetrahedral model of water, although approximate, represents a reasonably accurate description of the local structure of the liquid

  12. X-ray structure determination and deuteration of nattokinase.

    Science.gov (United States)

    Yanagisawa, Yasuhide; Chatake, Toshiyuki; Naito, Sawa; Ohsugi, Tadanori; Yatagai, Chieko; Sumi, Hiroyuki; Kawaguchi, Akio; Chiba-Kamosida, Kaori; Ogawa, Megumi; Adachi, Tatsumi; Morimoto, Yukio

    2013-11-01

    Nattokinase (NK) is a strong fibrinolytic enzyme, which is produced in abundance by Bacillus subtilis natto. Although NK is a member of the subtilisin family, it displays different substrate specificity when compared with other subtilisins. The results of molecular simulations predict that hydrogen arrangements around Ser221 at the active site probably account for the substrate specificity of NK. Therefore, neutron crystallographic analysis should provide valuable information that reveals the enzymatic mechanism of NK. In this report, the X-ray structure of the non-hydrogen form of undeuterated NK was determined, and the preparation of deuterated NK was successfully achieved. The non-hydrogen NK structure was determined at 1.74 Å resolution. The three-dimensional structures of NK and subtilisin E from Bacillus subtilis DB104 are near identical. Deuteration of NK was carried out by cultivating Bacillus subtilis natto in deuterated medium. The D2O resistant strain of Bacillus subtilis natto was obtained by successive cultivation rounds, in which the concentration of D2O in the medium was gradually increased. NK was purified from the culture medium and its activity was confirmed by the fibrin plate method. The results lay the framework for neutron protein crystallography analysis.

  13. Fast synchrotron X-ray tomography study of the rod packing structures

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xiaodan; Xia Chengjie; Sun Haohua; Wang Yujie [Department of Physics, Shanghai Jiao Tong University, 800 Dong Chuan Road, Shanghai 200240 (China)

    2013-06-18

    We present a fast synchrotron X-ray tomography study of the packing structures of rods under tapping. Utilizing the high flux of the X-rays generated from the third-generation synchrotron source, we can complete a tomography scan within several seconds, after which the three-dimensional (3D) packing structure can be obtained for the subsequent structural analysis. Due to the high-energy nature of the X-ray beam, special image processing steps including image phase-retrieval has been implemented. Overall, this study suggests the possibility of acquiring statistically significant static packing structures within a reasonable time scale using high-intensity X-ray sources.

  14. OSO 8 X-ray spectra of clusters of galaxies. I - Observations of twenty clusters: Physical correlations

    Science.gov (United States)

    Mushotzky, R. F.; Serlemitsos, P. J.; Boldt, E. A.; Holt, S. S.; Smith, B. W.

    1978-01-01

    OSO 8 X-ray spectra from 2 to 20 keV have been analyzed for 26 clusters of galaxies. For 20 clusters temperatures, emission integrals, iron abundances, and low-energy absorption measurements are presented. The data give, in general, better fits to thermal bremsstrahlung than to power-law models. Eight clusters have positive iron emission-line detections at the 90% confidence level, and all 20 cluster spectra are consistent with Fe/H = 0.000014 by number with the possible exception of Virgo. Thus it is confirmed that X-ray emission in this energy band is predominantly thermal radiation from hot intracluster gas rather than inverse Compton radiation. Physical correlations between X-ray spectral parameters and other cluster properties are examined. It is found that (1) the X-ray temperature is approximately proportional to the square of the velocity dispersion of the galaxies; (2) the emission integral is a strong function of the X-ray temperature; (3) the X-ray temperature and emission integral are better correlated with cluster central-galaxy density than with richness; and (4) the fraction of galaxies which are spirals is correlated with the observed ram pressure in the cluster core.

  15. THE XMM-NEWTON X-RAY SPECTRA OF THE MOST X-RAY LUMINOUS RADIO-QUIET ROSAT BRIGHT SURVEY-QSOs: A REFERENCE SAMPLE FOR THE INTERPRETATION OF HIGH-REDSHIFT QSO SPECTRA

    International Nuclear Information System (INIS)

    Krumpe, M.; Markowitz, A.; Lamer, G.; Corral, A.

    2010-01-01

    We present the broadband X-ray properties of four of the most X-ray luminous (L X ≥ 10 45 erg s -1 in the 0.5-2 keV band) radio-quiet QSOs found in the ROSAT Bright Survey. This uniform sample class, which explores the extreme end of the QSO luminosity function, exhibits surprisingly homogenous X-ray spectral properties: a soft excess with an extremely smooth shape containing no obvious discrete features, a hard power law above 2 keV, and a weak narrow/barely resolved Fe Kα fluorescence line for the three high signal-to-noise ratio (S/N) spectra. The soft excess can be well fitted with only a soft power law. No signatures of warm or cold intrinsic absorbers are found. The Fe Kα centroids and the line widths indicate emission from neutral Fe (E = 6.4 keV) originating from cold material from distances of only a few light days or further out. The well-constrained equivalent widths (EW) of the neutral Fe lines are higher than expected from the X-ray Baldwin effect which has been only poorly constrained at very high luminosities. Taking into account our individual EW measurements, we show that the X-ray Baldwin effect flattens above L X ∼ 10 44 erg s -1 (2-10 keV band) where an almost constant (EW) of ∼100 eV is found. We confirm the assumption of having very similar X-ray active galactic nucleus properties when interpreting stacked X-ray spectra. Our stacked spectrum serves as a superb reference for the interpretation of low S/N spectra of radio-quiet QSOs with similar luminosities at higher redshifts routinely detected by XMM-Newton and Chandra surveys.

  16. Electronic structure of human hemoglobin: ultrasoft X-ray emission study

    International Nuclear Information System (INIS)

    Soldatov, A.V.; Kravtsova, A.N.; Fedorovich, E.N.; Kurmaev, E.Z.; Moewes, A.

    2004-01-01

    Full text: The iron L 2,3 and carbon, nitrogen and oxygen Kα X-ray emission spectra (XES) of human hemoglobin have been recorded at the soft X-ray spectroscopy endstation on Undulator Beam line 8.0 at Advanced Light Source (ALS) located at the Lawrence Berkeley National Laboratory. The theoretical calculations of Fe L 3 -XES have been performed using ab initio code FEFF8.2. The calculations have been carried out for the structure of hemoglobin presented in PDB (entry 3HHB) as well as for the molecule with symmetrical heme plane. It was found that the Fe L 3 emission spectrum calculated for the ideal molecule agrees slightly better with the experiment as compared with those calculated for the real molecule. Thus, one can use the structure of the ideal molecule for theoretical Fe L 3 -XES simulations. The theoretical analysis has shown that the fist peak of experimental Fe L 3 - emission spectrum is enhanced by the nearest nitrogen atoms lying in heme plane around the central iron atom. The theoretical C K- and N K-XES spectra of hemoglobin have been calculated. A good agreement between theoretical and experimental spectra has been obtained. The distribution of the partial electronic densities of states in the valence and conduction bands of hemoglobin has been determined

  17. X-ray photoemission spectroscopy (XPS) and extended x-ray absorption fine structure (EXAFS) studies of silicate based glasses

    International Nuclear Information System (INIS)

    Karim, D.; Lam, D.J.

    1979-01-01

    The application of the x-ray photoemission spectroscopy (XPS) technique to study the electronic structure and bonding of heavy metal oxides in alkali- and alkali-earth-silicate glasses had been demonstrated. The bonding characteristics of the iron oxide and uranium oxide in sodium silicate glasses were deduced from the changes in the oxygen 1s levels and the heavy metal core levels. It is reasonable to expect that the effect of leaching on the heavy metal ions can be monitored using the appropriate core levels of these ions. To study the effect of leaching on the glass forming network, the valence band structure of the bridging and nonbridging oxygens in sodium silicate glasses were investigated. The measurement of extended x-ray absorption fine-structure (EXAFS) is a relatively new analytical technique for obtaining short range (<5 A) structural information around atoms of a selected species in both solid and fluid systems. Experiments have recently begun to establish the feasibility of using EXAFS to study the bonding of actinides in silicate glasses. Because of the ability of EXAFS to yield specific structural data even in complex multicomponent systems, it could prove to be an invaluable tool in understanding glass structure

  18. Excited state electron and energy relays in supramolecular dinuclear complexes revealed by ultrafast optical and X-ray transient absorption spectroscopy† †Electronic supplementary information (ESI) available: Synthesis schemes, experimental methods, NMR spectra, X-ray crystallographic information, emission spectra, cyclic voltammetry, electronic structure calculations, data analysis and numerical methods, and other additional figures. CCDC 1561879. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc04055e

    Science.gov (United States)

    Kohler, Lars; Hadt, Ryan G.; Zhang, Xiaoyi; Liu, Cunming

    2017-01-01

    The kinetics of photoinduced electron and energy transfer in a family of tetrapyridophenazine-bridged heteroleptic homo- and heterodinuclear copper(i) bis(phenanthroline)/ruthenium(ii) polypyridyl complexes were studied using ultrafast optical and multi-edge X-ray transient absorption spectroscopies. This work combines the synthesis of heterodinuclear Cu(i)–Ru(ii) analogs of the homodinuclear Cu(i)–Cu(i) targets with spectroscopic analysis and electronic structure calculations to first disentangle the dynamics at individual metal sites by taking advantage of the element and site specificity of X-ray absorption and theoretical methods. The excited state dynamical models developed for the heterodinuclear complexes are then applied to model the more challenging homodinuclear complexes. These results suggest that both intermetallic charge and energy transfer can be observed in an asymmetric dinuclear copper complex in which the ground state redox potentials of the copper sites are offset by only 310 meV. We also demonstrate the ability of several of these complexes to effectively and unidirectionally shuttle energy between different metal centers, a property that could be of great use in the design of broadly absorbing and multifunctional multimetallic photocatalysts. This work provides an important step toward developing both a fundamental conceptual picture and a practical experimental handle with which synthetic chemists, spectroscopists, and theoreticians may collaborate to engineer cheap and efficient photocatalytic materials capable of performing coulombically demanding chemical transformations. PMID:29629153

  19. Anatomy of the AGN in NGC 5548. IX. Photoionized emission features in the soft X-ray spectra

    Science.gov (United States)

    Mao, Junjie; Kaastra, J. S.; Mehdipour, M.; Gu, Liyi; Costantini, E.; Kriss, G. A.; Bianchi, S.; Branduardi-Raymont, G.; Behar, E.; Di Gesu, L.; Ponti, G.; Petrucci, P.-O.; Ebrero, J.

    2018-04-01

    The X-ray narrow emission line region (NELR) of the archetypal Seyfert 1 galaxy NGC 5548 has been interpreted as a single-phase photoionized plasma that is absorbed by some of the warm absorber components. This scenario requires those overlaying warm absorber components to have larger distance (to the central engine) than the X-ray NELR, which is not fully consistent with the distance estimates found in the literature. Therefore, we reanalyze the high-resolution spectra obtained in 2013-2014 with the Reflection Grating Spectrometer (RGS) aboard XMM-Newton to provide an alternative interpretation of the X-ray narrow emission features. We find that the X-ray narrow emission features in NGC 5548 can be described by a two-phase photoionized plasma with different ionization parameters (logξ = 1.3 and 0.1) and kinematics (vout = -50 and -400 km s-1), and no further absorption by the warm absorber components. The X-ray and optical NELR might be the same multi-phase photoionized plasma. Both X-ray and optical NELR have comparable distances, asymmetric line profiles, and the underlying photoionized plasma is turbulent and compact in size. The X-ray NELR is not the counterpart of the UV/X-ray absorber outside the line of sight because their distances and kinematics are not consistent. In addition, X-ray broad emission features that we find in the spectrum can be accounted for by a third photoionized emission component. The RGS spectrum obtained in 2016 is analyzed as well, where the luminosity of most prominent emission lines (the O VII forbidden line and O VIII Lyα line) are the same (at a 1σ confidence level) as in 2013-2014.

  20. Revisiting the total ion yield x-ray absorption spectra of liquid water microjets

    International Nuclear Information System (INIS)

    Saykally, Richard J; Cappa, Chris D.; Smith, Jared D.; Wilson, Kevin R.; Saykally, Richard J.

    2008-01-01

    Measurements of the total ion yield (TIY) x-ray absorption spectrum (XAS) of liquid water by Wilson et al. (2002 J. Phys.: Condens. Matter 14 L221 and 2001 J. Phys. Chem. B 105 3346) have been revisited in light of new experimental and theoretical efforts by our group. Previously, the TIY spectrum was interpreted as a distinct measure of the electronic structure of the liquid water surface. However, our new results indicate that the previously obtained spectrum may have suffered from as yet unidentified experimental artifacts. Although computational results indicate that the liquid water surface should exhibit a TIY-XAS that is fundamentally distinguishable from the bulk liquid XAS, the new experimental results suggest that the observable TIY-XAS is actually nearly identical in appearance to the total electron yield (TEY-)XAS, which is a bulk probe. This surprising similarity between the observed TIY-XAS and TEY-XAS likely results from large contributions from x-ray induced electron stimulated desorption of ions, and does not necessarily indicate that the electronic structure of the bulk liquid and liquid surface are identical

  1. Dynamical correlation effects in a weakly correlated material: Inelastic x-ray scattering and photoemission spectra of beryllium

    Science.gov (United States)

    Seidu, Azimatu; Marini, Andrea; Gatti, Matteo

    2018-03-01

    Beryllium is a weakly correlated simple metal. Still we find that dynamical correlation effects, beyond the independent-particle picture, are necessary to successfully interpret the electronic spectra measured by inelastic x-ray scattering (IXS) and photoemission spectroscopies (PES). By combining ab initio time-dependent density-functional theory (TDDFT) and many-body Green's function theory in the G W approximation (G W A ), we calculate the dynamic structure factor, the quasiparticle (QP) properties and PES spectra of bulk Be. We show that band-structure effects (i.e., due to interaction with the crystal potential) and QP lifetimes (LT) are both needed in order to explain the origin of the measured double-peak features in the IXS spectra. A quantitative agreement with experiment is obtained only when LT are supplemented to the adiabatic local-density approximation (ALDA) of TDDFT. Besides the valence band, PES spectra display a satellite, a signature of dynamical correlation due to the coupling of QPs and plasmons, which we are able to reproduce thanks to the combination of the G W A for the self-energy with the cumulant expansion of the Green's function.

  2. X-ray structural analysis of plasma sprayed europium oxide

    Energy Technology Data Exchange (ETDEWEB)

    Gorshkov, B.N.; Loskutov, V.S.; Gavrish, A.A.; Shakh, G.E.

    1981-12-01

    An X-ray structure microanalysis is made for europium oxide powder produced by sintering and plasmic spheroidization for plasma spraying. The technique of concern is shown not to alter chemical composition of the powder. It is stated that a rise in the plasma jet enthalpy while spraying does not result in dissociation of europium oxide and its interaction with the plasma flux. The coating (to 15.2 kWxs/g) is found to have only a high-temperature (monoclinic) europium oxide phase and there appears a low-temperature (cubic) phase with a subsequent increase in the enthalpy. The plasma jet enthalpy increasing the grain size and the crystal lattice c parameter of the sprayed europium oxide are shown to decrease; the a parameter reduces with an enthalpy growth to 16.2 kW s/g and then smoothly increases with the enthalpy further growth. It is noticed that the europium oxide coating does not interact with an aluminium D16 alloy substrate.

  3. Electronic structure and X-ray spectroscopic properties of YbNi_2P_2

    International Nuclear Information System (INIS)

    Shcherba, I.D.; Bekenov, L.V.; Antonov, V.N.; Noga, H.; Uskokovic, D.; Zhak, O.; Kovalska, M.V.

    2016-01-01

    Highlights: • We present new experimental and theoretical data for YbNi_2P_2. • The presence of divalent and trivalent Yb ion found in YbNi_2P_2. • The calculation show good agreement with the experimental measurements. - Abstract: X-ray absorption spectrum at the Yb L_3 edge and X-ray emission spectra of Ni and P at the K and L_2_,_3 edges have been studied experimentally and theoretically in the mixed valent compound YbNi_2P_2 with ThCr_2Si_2 type crystal structure. The electronic structure of YbNi_2P_2 is investigated using the fully relativistic Dirac linear muffin-tin orbital (LMTO) band-structure method. The effect of the spin–orbit (SO) interaction and Coulomb repulsion U on the electronic structure of YbNi_2P_2 is examined in the frame of the LSDA + SO + U method. The core-hole effect in the final states as well as the effect of the electric quadrupole E_2 transitions have been investigated. A good agreement between the theory and the experiment was found. Both the trivalent and the divalent Yb ions in YbNi_2P_2 are reflected in the experimentally measured Yb L_3 X-ray absorption spectrum simultaneously. We found that the best agreement between the experimental spectrum and sum of the theoretically calculated Yb"2"+ and Yb"3"+ spectra is achieved with 73% ytterbium ions in 2+ state and 27% ions in 3+ state.

  4. Parallel of semi-empirical results simulated by MCNP of X-ray spectra with a semiconductor

    International Nuclear Information System (INIS)

    Santos, L.R.; Vivolo, V.; Potiens, M.P.A.; Navarro, M.V.T.; Santos, W.S.

    2016-01-01

    The aim of this study was to use the MCNPX radiation transport code to simulate X-ray spectra generated by a constant voltage system in a CdTe semiconductor detector. As part of the validation process, we obtained a series of experimental spectra. Comparatively, in all cases there is a good correlation between the two spectra. There were no statistically significant differences between the experimental results with the simulated. (author)

  5. Examination of X-ray spectra from the antiprotonic helium isotopes 3He and 4He

    International Nuclear Information System (INIS)

    Schneider, M.

    1987-05-01

    Using the high intensity antiprotonic LEAR beam at CERN (Geneva), several measurements were done to investigate the X-ray spectra of the antiprotonic Helium isotopes 3 He and 4 He. For the first time antiprotons were stopped in gases at low pressures (600, 375, 72 and 36 mbar), which permitted observations on nearly isolated atoms. A newly developed method for stopping the antiprotons in gases by means of a focusing cyclotron field surrounding the target gas was used. The field was supplied by a superconducting magnet ('cyclotron trap'). The antiprotons were tangentially injected into the cyclotron field, where they slowed down by ionising the target gas. The inhomogeneous magnetic field guided the antiprotons in spiral orbits to the magnetic center. Thus, even at low pressures a very small stopping volume could be achieved. To detect the X-rays different Si(Li)- and Ge-semiconductor detectors were used, some of which were furnished with 'guard-rings'. They were used to investigate the effects of the strong interaction between the antiproton and the nucleus in the (3d → 2p) transition in both isotopes. The analyzis of this transition permitted directly the determination of the shift and width of the 2p-level. The width of the 3d-level could be determined only indirectly using an intensity balance. The utilization of gases with different pressures permitted investigations of the pressure dependence of the antiprotonic deexcitation process. The results for the widths and shifts were compared with earlier measurements and theoretical predictions. The theory agrees only partly with the measurements. The evaluation of a complex scattering length using an optical model contradicts some of the results of calculations. (orig.) [de

  6. Indirect measurements of X-ray spectra; Mediciones indirectas de espectros de rayos X

    Energy Technology Data Exchange (ETDEWEB)

    Mainardi, R.T. [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, X5000HUA Cordoba (Argentina)

    2006-07-01

    To the effects of measuring the spectral distribution of the radiation emitted by the x-ray tubes and electron accelerators, numerous procedures that are grouped in two big categories exist at the present time: direct and indirect methods. The first ones use high resolution detectors that should be positioned, together with the appropriate collimator, in the direction of the x ray beam. The user should be an expert in the use and correction of the obtained data by the different effects that affect the detector operation such as efficiency and resolution in terms of the energy of the detected radiation. The indirect procedures, although its are more simple to use, its also require a considerable space along the beam to position the ionization chamber and the necessary absorbents to construct by this way the denominated attenuation curve. We will analyze the operation principle of the indirect methods and a new proposal in which such important novelties are introduced as the beam dispersion to avoid to measure along the main beam and that of determination of the attenuation curve in simultaneous form. By this way, with a single shot of the tube, the attenuation curve is measured, being necessary at most a shot of additional calibration to know the relative response of the detectors used in the experimental array. The physical processes involved in the obtaining of an attenuation curve are very well well-known and this it finishes it can be theoretically calculated if the analytic form of the spectrum is supposed well-known. Finally, we will see a spectra reconstruction example with the Kramers parametric form and comparisons with numeric simulations carried out with broadly validated programs as well as the possibility of the use of solid state dosemeters in the obtention of the attenuation curve. (Author)

  7. First-principles calculations of K-shell X-ray absorption spectra for warm dense nitrogen

    International Nuclear Information System (INIS)

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

    2016-01-01

    X-ray absorption spectrum is a powerful tool for atomic structure detection on warm dense matter. Here, we perform first-principles molecular dynamics and X-ray absorption spectrum calculations on warm dense nitrogen along a Hugoniot curve. From the molecular dynamics trajectory, the detailed atomic structures are examined for each thermodynamical condition. The K-shell X-ray absorption spectrum is calculated, and its changes with temperature and pressure along the Hugoniot curve are discussed. The warm dense nitrogen systems may contain isolated nitrogen atoms, N 2 molecules, and nitrogen clusters, which show quite different contributions to the total X-ray spectrum due to their different electron density of states. The changes of X-ray spectrum along the Hugoniot curve are caused by the different nitrogen structures induced by the temperature and the pressure. Some clear signatures on X-ray spectrum for different thermodynamical conditions are pointed out, which may provide useful data for future X-ray experiments.

  8. Broadband X-ray spectra of the ultraluminous X-ray source Holmberg IX X-1 observed with NuSTAR, XMM-Newton, and Suzaku

    Energy Technology Data Exchange (ETDEWEB)

    Walton, D. J.; Harrison, F. A.; Grefenstette, B. W.; Fuerst, F.; Madsen, K. K.; Rana, V.; Stern, D. [Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125 (United States); Miller, J. M. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042 (United States); Bachetti, M.; Barret, D.; Webb, N. [Universite de Toulouse, UPS-OMP, IRAP, Toulouse (France); Boggs, S. E.; Craig, W. W. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Christensen, F. E. [DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Fabian, A. C.; Parker, M. L. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Hailey, C. J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Ptak, A.; Zhang, W. W., E-mail: dwalton@srl.caltech.edu [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2014-09-20

    We present results from the coordinated broadband X-ray observations of the extreme ultraluminous X-ray source Holmberg IX X-1 performed by NuSTAR, XMM-Newton, and Suzaku in late 2012. These observations provide the first high-quality spectra of Holmberg IX X-1 above 10 keV to date, extending the X-ray coverage of this remarkable source up to ∼30 keV. Broadband observations were undertaken at two epochs, between which Holmberg IX X-1 exhibited both flux and strong spectral variability, increasing in luminosity from L {sub X} = (1.90 ± 0.03) × 10{sup 40} erg s{sup –1} to L {sub X} = (3.35 ± 0.03) × 10{sup 40} erg s{sup –1}. Neither epoch exhibits a spectrum consistent with emission from the standard low/hard accretion state seen in Galactic black hole binaries, which would have been expected if Holmberg IX X-1 harbors a truly massive black hole accreting at substantially sub-Eddington accretion rates. The NuSTAR data confirm that the curvature observed previously in the 3-10 keV bandpass does represent a true spectral cutoff. During each epoch, the spectrum appears to be dominated by two optically thick thermal components, likely associated with an accretion disk. The spectrum also shows some evidence for a nonthermal tail at the highest energies, which may further support this scenario. The available data allow for either of the two thermal components to dominate the spectral evolution, although both scenarios require highly nonstandard behavior for thermal accretion disk emission.

  9. Origins of extreme broadening mechanisms in near-edge x-ray spectra of nitrogen compounds

    Science.gov (United States)

    Vinson, John; Jach, Terrence; Elam, W. T.; Denlinger, J. D.

    2014-11-01

    We demonstrate the observation of many-body lifetime effects in valence-band x-ray emission. A comparison of the N K α emission of crystalline ammonium nitrate to molecular-orbital calculations revealed an unexpected, extreme broadening of the NO σ recombination—so extensively as to virtually disappear. GW calculations establish that this disappearance is due to a large imaginary component of the self-energy associated with the NO σ orbitals. Building upon density-functional theory, we have calculated radiative transitions from the nitrogen 1 s level of ammonium nitrate and ammonium chloride using a Bethe-Salpeter method to include electron-hole interactions. The absorption and emission spectra of both crystals evince large, orbital-dependent sensitivity to molecular dynamics. We demonstrate that many-body effects as well as thermal and zero-point motion are vital for understanding observed spectra. A computational approach using average atomic positions and uniform broadening to account for lifetime and phonon effects is unsatisfactory.

  10. Temperature effect on X-ray photoelectron spectra of 3d transition metal ions

    International Nuclear Information System (INIS)

    Kochur, A.G.; Kozakov, A.T.; Yavna, V.A.; Daniel, Ph.

    2014-01-01

    Highlights: • 2p XPS of 3d metal ions are calculated in an isolated ion approximation. • 2p XPS of Ti, V, Cr, Mn, Fe ions are temperature dependent even at room temperature. • Temperature effect on 3p XPS is slight. • No temperature effect on 3s XPS is discovered. - Abstract: Temperature effect on 2p- 3s- and 3p X-ray photoelectron spectra (XPS) of various ions of Ti, V, Cr, Mn and Fe is studied theoretically within an isolated ion approximation. It is shown that the 2p XPS of those ions are temperature dependent even at room temperature due to a very slight energy splitting between the ground-state-term total-momentum J-components which can be thermally populated. Most significant temperature effect is expected in the 2p-spectra of Ti 2+ (3d 2 ), V 2+ (3d 3 ), Cr 2+ (3d 4 ), Mn 3+ (3d 4 ), and Mn 3+ (3d 4 ) ions. The temperature effect on 3p XPS is slight. No temperature effect on 3s XPS is expected

  11. The atomic structure of Fe100-xCux nanoalloys: X-ray absorption analysis

    International Nuclear Information System (INIS)

    Kravtsova, A.N.; Yalovega, G.E.; Soldatov, A.V.; Yan, W.S.; Wei, S.Q.

    2009-01-01

    The local atomic structure of Fe 100-x Cu x nanoalloys (x = 0, 10, 20, 40, 60, 70, 80 and 100%) has been investigated by X-ray absorption near edge structure (XANES) analysis. Local environment around copper and iron atoms in Fe 100-x Cu x has been studied by comparing the experimental XANES with corresponding theoretical spectra calculated for several structural models. It has been established that the most probable structure of the Fe 100-x Cu x nanoalloys for a low concentration of copper (x = 10-20%) is a homogenous bcc structure, for a high copper concentration (x = 60-80%)-a homogenous fcc structure, while at an intermediate copper concentration (about 40%) the nanoalloys have an inhomogeneous structure consisting of clusters of fcc solid solution (90%) and of clusters of bcc solid solution (10%)

  12. Cost and sensitivity of restricted active-space calculations of metal L-edge X-ray absorption spectra.

    Science.gov (United States)

    Pinjari, Rahul V; Delcey, Mickaël G; Guo, Meiyuan; Odelius, Michael; Lundberg, Marcus

    2016-02-15

    The restricted active-space (RAS) approach can accurately simulate metal L-edge X-ray absorption spectra of first-row transition metal complexes without the use of any fitting parameters. These characteristics provide a unique capability to identify unknown chemical species and to analyze their electronic structure. To find the best balance between cost and accuracy, the sensitivity of the simulated spectra with respect to the method variables has been tested for two models, [FeCl6 ](3-) and [Fe(CN)6 ](3-) . For these systems, the reference calculations give deviations, when compared with experiment, of ≤1 eV in peak positions, ≤30% for the relative intensity of major peaks, and ≤50% for minor peaks. When compared with these deviations, the simulated spectra are sensitive to the number of final states, the inclusion of dynamical correlation, and the ionization potential electron affinity shift, in addition to the selection of the active space. The spectra are less sensitive to the quality of the basis set and even a double-ζ basis gives reasonable results. The inclusion of dynamical correlation through second-order perturbation theory can be done efficiently using the state-specific formalism without correlating the core orbitals. Although these observations are not directly transferable to other systems, they can, together with a cost analysis, aid in the design of RAS models and help to extend the use of this powerful approach to a wider range of transition metal systems. © 2015 Wiley Periodicals, Inc.

  13. Observation of soft X-ray spectra from a Seyfert 1 and a narrow emission-line galaxy

    International Nuclear Information System (INIS)

    Singh, K.P.; Garmire, G.P.; Nousek, J.

    1985-01-01

    The 0.2-40 keV X-ray spectra of the Seyfert 1 galaxy Mrk 509 and the narrow emission-line galaxy NGC 2992 are analyzed. The results suggest the presence of a steep soft X-ray component in Mrk 509 in addition to the well-known Gamma = 1.7 component found in other active galactic nuclei in the 2-40 keV energy range. The soft X-ray component is interpreted as due to thermal emission from a hot gas, probably associated with the highly ionized gas observed to be outflowing from the galaxy. The X-ray spectrum of NGC 2992 does not show any steepening in the soft X-ray band and is consistent with a single power law (Gamma = 1.78) with very low absorbing column density of 4 x 10 to the 21st/sq cm. A model with partial covering of the nuclear X-ray source is preferred, however, to a simple model with a single power law and absorption. 34 references

  14. An accurate method for computer-generating tungsten anode x-ray spectra from 30 to 140 kV.

    Science.gov (United States)

    Boone, J M; Seibert, J A

    1997-11-01

    A tungsten anode spectral model using interpolating polynomials (TASMIP) was used to compute x-ray spectra at 1 keV intervals over the range from 30 kV to 140 kV. The TASMIP is not semi-empirical and uses no physical assumptions regarding x-ray production, but rather interpolates measured constant potential x-ray spectra published by Fewell et al. [Handbook of Computed Tomography X-ray Spectra (U.S. Government Printing Office, Washington, D.C., 1981)]. X-ray output measurements (mR/mAs measured at 1 m) were made on a calibrated constant potential generator in our laboratory from 50 kV to 124 kV, and with 0-5 mm added aluminum filtration. The Fewell spectra were slightly modified (numerically hardened) and normalized based on the attenuation and output characteristics of a constant potential generator and metal-insert x-ray tube in our laboratory. Then, using the modified Fewell spectra of different kVs, the photon fluence phi at each 1 keV energy bin (E) over energies from 10 keV to 140 keV was characterized using polynomial functions of the form phi (E) = a0[E] + a1[E] kV + a2[E] kV2 + ... + a(n)[E] kVn. A total of 131 polynomial functions were used to calculate accurate x-ray spectra, each function requiring between two and four terms. The resulting TASMIP algorithm produced x-ray spectra that match both the quality and quantity characteristics of the x-ray system in our laboratory. For photon fluences above 10% of the peak fluence in the spectrum, the average percent difference (and standard deviation) between the modified Fewell spectra and the TASMIP photon fluence was -1.43% (3.8%) for the 50 kV spectrum, -0.89% (1.37%) for the 70 kV spectrum, and for the 80, 90, 100, 110, 120, 130 and 140 kV spectra, the mean differences between spectra were all less than 0.20% and the standard deviations were less than approximately 1.1%. The model was also extended to include the effects of generator-induced kV ripple. Finally, the x-ray photon fluence in the units of

  15. Coupled-cluster response theory for near-edge x-ray-absorption fine structure of atoms and molecules

    DEFF Research Database (Denmark)

    Coriani, Sonia; Christiansen, Ove; Fransson, Thomas

    2012-01-01

    triple corrected excitation energies CCSDR(3). This work is a first step toward the extension of these theoretical electronic structure methods of well-established high accuracy in UV-vis absorption spectroscopies to applications concerned with x-ray radiation. From the imaginary part of the linear...... response function, the near K-edge x-ray absorption spectra of neon, water, and carbon monoxide are determined and compared with experiment. Results at the CCSD level show relative peak intensities in good agreement with experiment with discrepancies in transition energies due to incomplete treatment...

  16. Understanding reliability and some limitations of the images and spectra reconstructed from a multi-monochromatic x-ray imager

    Science.gov (United States)

    Nagayama, T.; Mancini, R. C.; Mayes, D.; Tommasini, R.; Florido, R.

    2015-11-01

    Temperature and density asymmetry diagnosis is critical to advance inertial confinement fusion (ICF) science. A multi-monochromatic x-ray imager (MMI) is an attractive diagnostic for this purpose. The MMI records the spectral signature from an ICF implosion core with time resolution, 2-D space resolution, and spectral resolution. While narrow-band images and 2-D space-resolved spectra from the MMI data constrain temperature and density spatial structure of the core, the accuracy of the images and spectra depends not only on the quality of the MMI data but also on the reliability of the post-processing tools. Here, we synthetically quantify the accuracy of images and spectra reconstructed from MMI data. Errors in the reconstructed images are less than a few percent when the space-resolution effect is applied to the modeled images. The errors in the reconstructed 2-D space-resolved spectra are also less than a few percent except those for the peripheral regions. Spectra reconstructed for the peripheral regions have slightly but systematically lower intensities by ˜6% due to the instrumental spatial-resolution effects. However, this does not alter the relative line ratios and widths and thus does not affect the temperature and density diagnostics. We also investigate the impact of the pinhole size variation on the extracted images and spectra. A 10% pinhole size variation could introduce spatial bias to the images and spectra of ˜10%. A correction algorithm is developed, and it successfully reduces the errors to a few percent. It is desirable to perform similar synthetic investigations to fully understand the reliability and limitations of each MMI application.

  17. Understanding reliability and some limitations of the images and spectra reconstructed from a multi-monochromatic x-ray imager

    International Nuclear Information System (INIS)

    Nagayama, T.; Mancini, R. C.; Mayes, D.; Tommasini, R.; Florido, R.

    2015-01-01

    Temperature and density asymmetry diagnosis is critical to advance inertial confinement fusion (ICF) science. A multi-monochromatic x-ray imager (MMI) is an attractive diagnostic for this purpose. The MMI records the spectral signature from an ICF implosion core with time resolution, 2-D space resolution, and spectral resolution. While narrow-band images and 2-D space-resolved spectra from the MMI data constrain temperature and density spatial structure of the core, the accuracy of the images and spectra depends not only on the quality of the MMI data but also on the reliability of the post-processing tools. Here, we synthetically quantify the accuracy of images and spectra reconstructed from MMI data. Errors in the reconstructed images are less than a few percent when the space-resolution effect is applied to the modeled images. The errors in the reconstructed 2-D space-resolved spectra are also less than a few percent except those for the peripheral regions. Spectra reconstructed for the peripheral regions have slightly but systematically lower intensities by ∼6% due to the instrumental spatial-resolution effects. However, this does not alter the relative line ratios and widths and thus does not affect the temperature and density diagnostics. We also investigate the impact of the pinhole size variation on the extracted images and spectra. A 10% pinhole size variation could introduce spatial bias to the images and spectra of ∼10%. A correction algorithm is developed, and it successfully reduces the errors to a few percent. It is desirable to perform similar synthetic investigations to fully understand the reliability and limitations of each MMI application

  18. Understanding reliability and some limitations of the images and spectra reconstructed from a multi-monochromatic x-ray imager.

    Science.gov (United States)

    Nagayama, T; Mancini, R C; Mayes, D; Tommasini, R; Florido, R

    2015-11-01

    Temperature and density asymmetry diagnosis is critical to advance inertial confinement fusion (ICF) science. A multi-monochromatic x-ray imager (MMI) is an attractive diagnostic for this purpose. The MMI records the spectral signature from an ICF implosion core with time resolution, 2-D space resolution, and spectral resolution. While narrow-band images and 2-D space-resolved spectra from the MMI data constrain temperature and density spatial structure of the core, the accuracy of the images and spectra depends not only on the quality of the MMI data but also on the reliability of the post-processing tools. Here, we synthetically quantify the accuracy of images and spectra reconstructed from MMI data. Errors in the reconstructed images are less than a few percent when the space-resolution effect is applied to the modeled images. The errors in the reconstructed 2-D space-resolved spectra are also less than a few percent except those for the peripheral regions. Spectra reconstructed for the peripheral regions have slightly but systematically lower intensities by ∼6% due to the instrumental spatial-resolution effects. However, this does not alter the relative line ratios and widths and thus does not affect the temperature and density diagnostics. We also investigate the impact of the pinhole size variation on the extracted images and spectra. A 10% pinhole size variation could introduce spatial bias to the images and spectra of ∼10%. A correction algorithm is developed, and it successfully reduces the errors to a few percent. It is desirable to perform similar synthetic investigations to fully understand the reliability and limitations of each MMI application.

  19. THE BROADBAND XMM-NEWTON AND NuSTAR X-RAY SPECTRA OF TWO ULTRALUMINOUS X-RAY SOURCES IN THE GALAXY IC 342

    Energy Technology Data Exchange (ETDEWEB)

    Rana, Vikram; Harrison, Fiona A.; Walton, Dominic J.; Furst, Felix; Grefenstette, Brian W.; Madsen, Kristin K. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Bachetti, Matteo; Barret, Didier; Webb, Natalie A. [Université de Toulouse, UPS-OMP, IRAP, Toulouse (France); Miller, Jon M. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042 (United States); Fabian, Andrew C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Boggs, Steven E.; Craig, William W. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Christensen, Finn C. [DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Hailey, Charles J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Ptak, Andrew F.; Zhang, William W. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2015-02-01

    We present results for two ultraluminous X-ray sources (ULXs), IC 342 X-1 and IC 342 X-2, using two epochs of XMM-Newton and NuSTAR observations separated by ∼7 days. We observe little spectral or flux variability above 1 keV between epochs, with unabsorbed 0.3-30 keV luminosities being 1.04{sub −0.06}{sup +0.08}×10{sup 40} erg s{sup –1} for IC 342 X-1 and 7.40 ± 0.20 × 10{sup 39} erg s{sup –1} for IC 342 X-2, so that both were observed in a similar, luminous state. Both sources have a high absorbing column in excess of the Galactic value. Neither source has a spectrum consistent with a black hole binary in low/hard state, and both ULXs exhibit strong curvature in their broadband X-ray spectra. This curvature rules out models that invoke a simple reflection-dominated spectrum with a broadened iron line and no cutoff in the illuminating power-law continuum. X-ray spectrum of IC 342 X-1 can be characterized by a soft disk-like blackbody component at low energies and a cool, optically thick Comptonization continuum at high energies, but unique physical interpretation of the spectral components remains challenging. The broadband spectrum of IC 342 X-2 can be fit by either a hot (3.8 keV) accretion disk or a Comptonized continuum with no indication of a seed photon population. Although the seed photon component may be masked by soft excess emission unlikely to be associated with the binary system, combined with the high absorption column, it is more plausible that the broadband X-ray emission arises from a simple thin blackbody disk component. Secure identification of the origin of the spectral components in these sources will likely require broadband spectral variability studies.

  20. X-Ray and Neutron Scattering Study of the Magnetic Structure of Neodymium Metal

    DEFF Research Database (Denmark)

    Lebech, Bente; Als-Nielsen, Jens Aage; McEwen, K. A.

    1979-01-01

    A combined x-ray and neutron diffraction study has shown that the so-called "triple-q⃗" structure is not the correct model of the magnetic structure of neodymium. The x-ray data showed only the Bragg reflections originating from the double-hcp lattice. Hence, all additional reflections observed...

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

    Energy Technology Data Exchange (ETDEWEB)

    McLean, Larry R.; Zhang, Ying; Degnen, William; Peppard, Jane; Cabel, Dasha; Zou, Chao; Tsay, Joseph T.; Subramaniam, Arun; Vaz, Roy J.; Li, Yi (Sanofi)

    2010-10-28

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

  2. Synthesis and X-ray structure of the dysprosium(III) complex derived ...

    African Journals Online (AJOL)

    Synthesis and X-ray structure of the dysprosium(III) complex derived from the ligand 5-chloro-1 ... Bulletin of the Chemical Society of Ethiopia ... synthesized and its crystal structure determined by single X-ray diffraction at room temperature.

  3. Determination of half value layer and applied voltage from emitted spectra by an X-ray tube

    International Nuclear Information System (INIS)

    Santos, Josilene C.; Gonzales, Alejandro H.L.; Terini, Ricardo A.; Costa, Paulo R.

    2016-01-01

    This work describes a method for assessment of half value layer (HVL) and peak tube voltage (kVp) applied in an X-ray tube by means of experimental X-ray spectra measured using a CdTe detector. It was assessed some parameters that can affect the evaluation of these quantities such as dead time, count rate and tube current (mA). For this study, two sets of X-ray spectra were measured: Set A), spectra measurements using Cu filters with different thicknesses (1.8 - 5.4 mm) and fixed tube current; Set B), spectra measurements keeping a fixed Cu filtration and varying tube current (0.5 - 3.0 mA). The experimental setup for the Set A spectra measurements allowed the assessment of the HVL and kVp for different count rates and dead time in the detection system, while the Set B setup allowed to assess the dependence of these quantities with the tube current. The spectrometer was energy calibrated using standard X/γ rays radioactive sources. The tube voltage values were estimated by means of experimental measured X-ray spectra, using linear regression in order to search the end point of each spectrum. The spectra correction was performed using the stripping procedure developed for the Matlab® software and the HVL values were derived from these corrected spectra. For comparison, HVL was also determined using a 30 cm"3 ion chamber and high purity Al filters. The results show that it is possible to determine the kVp with accuracy and reproducibility using spectra with dead time of up to 10%. In spite of this, the values obtained showed a deviation of up to 7 kV, for spectra measured using the same nominal tube voltage different tube current values, indicating dependence between these two parameters. (author)

  4. X-ray CT analysis of pore structure in sand

    Science.gov (United States)

    Mukunoki, Toshifumi; Miyata, Yoshihisa; Mikami, Kazuaki; Shiota, Erika

    2016-06-01

    The development of microfocused X-ray computed tomography (CT) devices enables digital imaging analysis at the pore scale. The applications of these devices are diverse in soil mechanics, geotechnical and geoenvironmental engineering, petroleum engineering, and agricultural engineering. In particular, the imaging of the pore space in porous media has contributed to numerical simulations for single-phase and multiphase flows or contaminant transport through the pore structure as three-dimensional image data. These obtained results are affected by the pore diameter; therefore, it is necessary to verify the image preprocessing for the image analysis and to validate the pore diameters obtained from the CT image data. Moreover, it is meaningful to produce the physical parameters in a representative element volume (REV) and significant to define the dimension of the REV. This paper describes the underlying method of image processing and analysis and discusses the physical properties of Toyoura sand for the verification of the image analysis based on the definition of the REV. On the basis of the obtained verification results, a pore-diameter analysis can be conducted and validated by a comparison with the experimental work and image analysis. The pore diameter is deduced from Young-Laplace's law and a water retention test for the drainage process. The results from previous study and perforated-pore diameter originally proposed in this study, called the voxel-percolation method (VPM), are compared in this paper. In addition, the limitations of the REV, the definition of the pore diameter, and the effectiveness of the VPM for an assessment of the pore diameter are discussed.

  5. Simulation of pulse height analysis soft X-ray spectra expected from W7-X

    Science.gov (United States)

    Jabłoński, S.; Czarnecka, A.; Kubkowska, M.; Ryć, L.; Weller, A.; Biedermann, C.; König, R.; W7-X Team

    2015-10-01

    A computer code named RayX has been developed for checking the performance of a spectroscopy system and optimizing individual parts, like detectors and filters for the pulse height analysis (PHA) diagnostic system designed for the stellarator W7-X. Using the code, the intensity and shape of the X-ray spectra are simulated for different plasma scenarios characterized by varying the temperature and density profiles as well as the electron cyclotron resonance heating (ECRH) power over a wide range. In the simulations of the recorded spectra, the influence of geometrical configuration changes of the diagnostic system (pinhole size, detector size, location of each diagnostic component), of the timing of data collection, as well as of the type and thickness of filters are being investigated. The atomic processes of free-free (bremsstrahlung), free-bound (recombination radiation), and bound-bound emission (line radiation) are considered. For the impurities fractional abundancies of 3% carbon (C), 0.5% oxygen (O) and 0.002% iron (Fe) are taken into account. Information about the number of photons which reach the detector and the current generated inside the detector is given. It is shown that the distance between pinhole and detector has a larger impact on the registered spectra (intensity and total number of photons) than the distance between plasma and pinhole. Based on the results of the simulations, the expected optimal positions of the individual components (pinholes, detectors) were defined for the PHA W7-X diagnostic system. A shorter version of this contribution is due to be published in PoS at: 1st EPS conference on Plasma Diagnostics

  6. Steep Hard-X-ray Spectra Indicate Extremely High Accretion Rates in Weak Emission-Line Quasars

    Science.gov (United States)

    Marlar, Andrea; Shemmer, Ohad; Anderson, Scott F.; Brandt, W. Niel; Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; Luo, Bin; Plotkin, Richard; Richards, Gordon T.; Schneider, Donald P.; Wu, Jianfeng

    2018-06-01

    We present XMM-Newton imaging spectroscopy of ten weak emission-line quasars (WLQs) at 0.928 ≤ z ≤ 3.767, six of which are radio quiet and four which are radio intermediate. The new X-ray data enabled us to measure the hard-X-ray power-law photon index (Γ) in each source with relatively high accuracy. These measurements allowed us to confirm previous reports that WLQs have steeper X-ray spectra, therefore indicating higher accretion rates with respect to "typical" quasars. A comparison between the Γ values of our radio-quiet WLQs and those of a carefully-selected, uniform sample of 84 quasars shows that the first are significantly higher, at the ≥ 3σ level. Collectively, the four radio-intermediate WLQs have lower Γ values with respect to the six radio-quiet WLQs, as may be expected if the spectra of the first group are contaminated by X-ray emission from a jet. These results suggest that, in the absence of significant jet emission along our line of sight, WLQs constitute the extreme high end of the accretion rate distribution in quasars. We detect soft excess emission in our lowest-redshift radio-quiet WLQ, in agreement with previous findings suggesting that the prominence of this feature is associated with a high accretion rate. We have not detected signatures of Compton reflection, Fe Kα lines, or strong variability between two X-ray epochs in any of our WLQs.

  7. Applying a physical continuum model to describe the broadband X-ray spectra of accreting pulsars at high luminosity

    Science.gov (United States)

    Pottschmidt, Katja; Hemphill, Paul B.; Wolff, Michael T.; Cheatham, Diana M.; Iwakiri, Wataru; Gottlieb, Amy M.; Falkner, Sebastian; Ballhausen, Ralf; Fuerst, Felix; Kuehnel, Matthias; Ferrigno, Carlo; Becker, Peter A.; Wood, Kent S.; Wilms, Joern

    2018-01-01

    A new window for better understanding the accretion onto strongly magnetized neutron stars in X-ray binaries is opening. In these systems the accreted material follows the magnetic field lines as it approaches the neutron star, forming accretion columns above the magnetic poles. The plasma falls toward the neutron star surface at near-relativistic speeds, losing energy by emitting X-rays. The X-ray spectral continua are commonly described using phenomenological models, i.e., power laws with different types of curved cut-offs at higher energies. Here we consider high luminosity pulsars. In these systems the mass transfer rate is high enough that the accreting plasma is thought to be decelerated in a radiation-dominated radiative shock in the accretion columns. While the theory of the emission from such shocks had already been developed by 2007, a model for direct comparison with X-ray continuum spectra in xspec or isis has only recently become available. Characteristic parameters of this model are the accretion column radius and the plasma temperature, among others. Here we analyze the broadband X-ray spectra of the accreting pulsars Centaurus X-3 and 4U 1626-67 obtained with NuSTAR. We present results from traditional empirical modeling as well as successfully apply the radiation-dominated radiative shock model. We also take the opportunity to compare to similar recent analyses of both sources using these and other observations.

  8. CHARGE-TRANSFER SATELLITES AND MULTIPLET SPLITTING IN X-RAY PHOTOEMISSION SPECTRA OF LATE TRANSITION-METAL HALIDES

    NARCIS (Netherlands)

    OKADA, K; KOTANI, A; THOLE, BT

    1992-01-01

    Core-level X-ray photoemission spectra (XPS) are calculated for Ni and Co dihalides with an MX6 cluster model (M = Ni, Co; X = F, Cl, Br), where intra-atomic multiplet coupling as well as covalency mixing is taken into account. The effects of the intra-atomic configuration interaction between

  9. Determination of semi-reducing layer and applied stress through spectra emitted by an X-ray tube

    International Nuclear Information System (INIS)

    Santos, Josilene C.; Gonzalez, Alejandro H.L.; Terini, Ricardo A.; Costa, Paulo R.

    2016-01-01

    This work describes a method for assessment of half value layer (HVL) and peak tube voltage (kVp) by means of experimental x-ray spectra measured using a CdTe detector. The work also evaluated spectrometry parameters such as dead time and count rate, and x-ray tube characteristics that can affect the assessment of these quantities. Two sets of x-ray spectra were measured: A) using Cu filters with different thicknesses and fixed tube current, and B) keeping a fixed Cu filtration and different tube current and, so, ranging the count rates. The spectrometer was energy calibrated using standard radioactive sources. kVp value was estimated by means of experimental measured x-ray spectra, using linear regression in order to search the end point of each spectrum. HVL was estimated after the correction of the measured spectra, using an analytical method implemented using Matlab® software. For comparison, HVL was also determined using a 30 cm"3 ion chamber and high purity Al filters. (author)

  10. Quantifying the effect of anode surface roughness on diagnostic x-ray spectra using Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Mehranian, A.; Ay, M. R.; Alam, N. Riyahi; Zaidi, H. [Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, P.O. Box 14155-6447, Tehran (Iran, Islamic Republic of) and Research Center for Science and Technology in Medicine, Tehran University of Medical Sciences, P.O. Box 14185-615, Tehran (Iran, Islamic Republic of); Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, P.O. Box 14155-6447, Tehran (Iran, Islamic Republic of); Research Center for Science and Technology in Medicine, Tehran University of Medical Sciences, P.O. Box 14185-615, Tehran (Iran, Islamic Republic of) and Research Institute for Nuclear Medicine, Tehran University of Medical Sciences, P.O. Box 14155-6447, Tehran (Iran, Islamic Republic of); Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, P.O. Box 14155-6447, Tehran (Iran, Islamic Republic of); Division of Nuclear Medicine, Geneva University Hospital, CH-1211 Geneva (Switzerland) and Geneva Neuroscience Center, Geneva University, CH-1205 Geneva (Switzerland)

    2010-02-15

    Purpose: The accurate prediction of x-ray spectra under typical conditions encountered in clinical x-ray examination procedures and the assessment of factors influencing them has been a long-standing goal of the diagnostic radiology and medical physics communities. In this work, the influence of anode surface roughness on diagnostic x-ray spectra is evaluated using MCNP4C-based Monte Carlo simulations. Methods: An image-based modeling method was used to create realistic models from surface-cracked anodes. An in-house computer program was written to model the geometric pattern of cracks and irregularities from digital images of focal track surface in order to define the modeled anodes into MCNP input file. To consider average roughness and mean crack depth into the models, the surface of anodes was characterized by scanning electron microscopy and surface profilometry. It was found that the average roughness (R{sub a}) in the most aged tube studied is about 50 {mu}m. The correctness of MCNP4C in simulating diagnostic x-ray spectra was thoroughly verified by calling its Gaussian energy broadening card and comparing the simulated spectra with experimentally measured ones. The assessment of anode roughness involved the comparison of simulated spectra in deteriorated anodes with those simulated in perfectly plain anodes considered as reference. From these comparisons, the variations in output intensity, half value layer (HVL), heel effect, and patient dose were studied. Results: An intensity loss of 4.5% and 16.8% was predicted for anodes aged by 5 and 50 {mu}m deep cracks (50 kVp, 6 deg. target angle, and 2.5 mm Al total filtration). The variations in HVL were not significant as the spectra were not hardened by more than 2.5%; however, the trend for this variation was to increase with roughness. By deploying several point detector tallies along the anode-cathode direction and averaging exposure over them, it was found that for a 6 deg. anode, roughened by 50 {mu}m deep

  11. Structural analysis of radiation damage in zircon and thorite: An X-ray absorption spectroscopic study

    International Nuclear Information System (INIS)

    Farges, F.; Calas, G.

    1991-01-01

    Metamictization effects have been investigated in zircon, thorite, uranothorite, and thorogummite using X-ray absorption spectroscopy at Zr-K, Th-L III edges. Extended X-ray absorption fine structure (EXAFS) spectra of metamict samples are characterized by a major contribution due to the O nearest neighbors with some contributions from next-nearest neighbors (Si and Zr in zircon, Si in thorite). In zircon, Zr-O distances decrease by ∼0.1 angstrom while the coordination number of Zr decreases from 8 to 7. In contrast, the eightfold coordination of Th in crystalline thorite is preserved in metamict thorite, Si second neighbors around Zr or Th are generally observed in metamict samples with distances close to those measured in crystalline phases. No other contribution to EXAFS is observed in thorite, but Zr-Zr distances are observed in zircon. They decrease by ca. 0.3 Angstrom as a function of zircon metamictization. Metamictization processes are characterized by a loss of medium range order. There is no evidence for decomposition into crystalline oxides. The structural interpretation of EXAFS data must take into account the creation of O vacancies arising from a displacement or tilting of the SiO 4 tetrahedra during metamictization of zircon-like structures. If the cation can take a lower coordination number (as in the case of Zr), a coordination change allows the local structure to be partly maintained during metamictization. If not, as for Th, the local structure is rapidly destroyed

  12. Hard X-ray irradiation of cosmic silicate analogs: structural evolution and astrophysical implications

    Science.gov (United States)

    Gavilan, L.; Jäger, C.; Simionovici, A.; Lemaire, J. L.; Sabri, T.; Foy, E.; Yagoubi, S.; Henning, T.; Salomon, D.; Martinez-Criado, G.

    2016-03-01

    Context. Protoplanetary disks, interstellar clouds, and active galactic nuclei contain X-ray-dominated regions. X-rays interact with the dust and gas present in such environments. While a few laboratory X-ray irradiation experiments have been performed on ices, X-ray irradiation experiments on bare cosmic dust analogs have been scarce up to now. Aims: Our goal is to study the effects of hard X-rays on cosmic dust analogs via in situ X-ray diffraction. By using a hard X-ray synchrotron nanobeam, we seek to simulate cumulative X-ray exposure on dust grains during their lifetime in these astrophysical environments and provide an upper limit on the effect of hard X-rays on dust grain structure. Methods: We prepared enstatite (MgSiO3) nanograins, which are analogs to cosmic silicates, via the melting-quenching technique. These amorphous grains were then annealed to obtain polycrystalline grains. These were characterized via scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) before irradiation. Powder samples were prepared in X-ray transparent substrates and were irradiated with hard X-rays nanobeams (29.4 keV) provided by beamline ID16B of the European Synchrotron Radiation Facility (Grenoble). X-ray diffraction images were recorded in transmission mode, and the ensuing diffractograms were analyzed as a function of the total X-ray exposure time. Results: We detected the amorphization of polycrystalline silicates embedded in an organic matrix after an accumulated X-ray exposure of 6.4 × 1027 eV cm-2. Pure crystalline silicate grains (without resin) do not exhibit amorphization. None of the amorphous silicate samples (pure and embedded in resin) underwent crystallization. We analyze the evolution of the polycrystalline sample embedded in an organic matrix as a function of X-ray exposure. Conclusions: Loss of diffraction peak intensity, peak broadening, and the disappearance of discrete spots and arcs reveal the amorphization

  13. X-ray tomography investigations on pebble bed structures

    International Nuclear Information System (INIS)

    Reimann, J.; Rolli, R.; Pieritz, R.A.; Ferrero, C.; Di Michiel, M.

    2007-01-01

    Granular materials (pebbles) are used in present ceramic breeder blankets both for the ceramic breeder material and beryllium. The thermal-mechanical behaviour of these pebble beds strongly depends on the arrangement of the pebbles in the bed, their contacts and contact surfaces with other pebbles and with walls. The influence of these quantities is most pronounced for beryllium pebble beds because of the large thermal conductivity ratio of beryllium to helium gas atmosphere. At present, the data base for the pebble bed thermal conductivity (k) and heat transfer coefficient (h) is quite limited for compressed beds and significant discrepancies exist in respect to h. The detailed knowledge of the pebble bed topology is, therefore, essential to better understand the heat transfer mechanisms. In the present work, results from detailed X-ray tomography investigations are reported on pebble topology in i) the pebble bed bulk (which is relevant for k), and ii) the region close to walls with thicknesses of several pebble diameters (relevant for h). At Forschungszentrum Karlsruhe, pebble beds consisting of aluminium spheres with diameters of 2.3 and 5 mm, respectively, (simulating the blanket relevant 1 mm beryllium pebbles), were uniaxially compressed at different pressure levels. High resolution three-dimensional microtomography (MT) experiments were subsequently performed at the European Synchrotron Radiation Facility, Grenoble. Radial and axial void fraction distributions were found to be oscillatory next to the walls and non-oscillatory in the bulk. For non-compressed pebble beds, the bulk void fraction is fairly constant; for compressed beds, a gradient exists along the compression axis. In the bulk, the angular distribution of pebble contacts was found to be fairly constant, indicating that no regular packing structure is induced. In the wall region, the pebble layer touching the wall is composed of zones with hexagonal structures as shown clearly by MT images. This

  14. Accounting for nanometer-thick adventitious carbon contamination in X-ray absorption spectra of carbon-based materials.

    Science.gov (United States)

    Mangolini, Filippo; McClimon, J Brandon; Rose, Franck; Carpick, Robert W

    2014-12-16

    Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is a powerful technique for characterizing the composition and bonding state of nanoscale materials and the top few nanometers of bulk and thin film specimens. When coupled with imaging methods like photoemission electron microscopy, it enables chemical imaging of materials with nanometer-scale lateral spatial resolution. However, analysis of NEXAFS spectra is often performed under the assumption of structural and compositional homogeneity within the nanometer-scale depth probed by this technique. This assumption can introduce large errors when analyzing the vast majority of solid surfaces due to the presence of complex surface and near-surface structures such as oxides and contamination layers. An analytical methodology is presented for removing the contribution of these nanoscale overlayers from NEXAFS spectra of two-layered systems to provide a corrected photoabsorption spectrum of the substrate. This method relies on the subtraction of the NEXAFS spectrum of the overlayer adsorbed on a reference surface from the spectrum of the two-layer system under investigation, where the thickness of the overlayer is independently determined by X-ray photoelectron spectroscopy (XPS). This approach is applied to NEXAFS data acquired for one of the most challenging cases: air-exposed hard carbon-based materials with adventitious carbon contamination from ambient exposure. The contribution of the adventitious carbon was removed from the as-acquired spectra of ultrananocrystalline diamond (UNCD) and hydrogenated amorphous carbon (a-C:H) to determine the intrinsic photoabsorption NEXAFS spectra of these materials. The method alters the calculated fraction of sp(2)-hybridized carbon from 5 to 20% and reveals that the adventitious contamination can be described as a layer containing carbon and oxygen ([O]/[C] = 0.11 ± 0.02) with a thickness of 0.6 ± 0.2 nm and a fraction of sp(2)-bonded carbon of 0.19 ± 0.03. This

  15. Monte Carlo derivation of filtered tungsten anode X-ray spectra for dose computation in digital mammography*

    Science.gov (United States)

    Paixão, Lucas; Oliveira, Bruno Beraldo; Viloria, Carolina; de Oliveira, Marcio Alves; Teixeira, Maria Helena Araújo; Nogueira, Maria do Socorro

    2015-01-01

    Objective Derive filtered tungsten X-ray spectra used in digital mammography systems by means of Monte Carlo simulations. Materials and Methods Filtered spectra for rhodium filter were obtained for tube potentials between 26 and 32 kV. The half-value layer (HVL) of simulated filtered spectra were compared with those obtained experimentally with a solid state detector Unfors model 8202031-H Xi R/F & MAM Detector Platinum and 8201023-C Xi Base unit Platinum Plus w mAs in a Hologic Selenia Dimensions system using a direct radiography mode. Results Calculated HVL values showed good agreement as compared with those obtained experimentally. The greatest relative difference between the Monte Carlo calculated HVL values and experimental HVL values was 4%. Conclusion The results show that the filtered tungsten anode X-ray spectra and the EGSnrc Monte Carlo code can be used for mean glandular dose determination in mammography. PMID:26811553

  16. Monte Carlo derivation of filtered tungsten anode X-ray spectra for dose computation in digital mammography

    Directory of Open Access Journals (Sweden)

    Lucas Paixão

    2015-12-01

    Full Text Available Abstract Objective: Derive filtered tungsten X-ray spectra used in digital mammography systems by means of Monte Carlo simulations. Materials and Methods: Filtered spectra for rhodium filter were obtained for tube potentials between 26 and 32 kV. The half-value layer (HVL of simulated filtered spectra were compared with those obtained experimentally with a solid state detector Unfors model 8202031-H Xi R/F & MAM Detector Platinum and 8201023-C Xi Base unit Platinum Plus w mAs in a Hologic Selenia Dimensions system using a direct radiography mode. Results: Calculated HVL values showed good agreement as compared with those obtained experimentally. The greatest relative difference between the Monte Carlo calculated HVL values and experimental HVL values was 4%. Conclusion: The results show that the filtered tungsten anode X-ray spectra and the EGSnrc Monte Carlo code can be used for mean glandular dose determination in mammography.

  17. Simulation of X-ray absorption spectra with orthogonality constrained density functional theory.

    Science.gov (United States)

    Derricotte, Wallace D; Evangelista, Francesco A

    2015-06-14

    Orthogonality constrained density functional theory (OCDFT) [F. A. Evangelista, P. Shushkov and J. C. Tully, J. Phys. Chem. A, 2013, 117, 7378] is a variational time-independent approach for the computation of electronic excited states. In this work we extend OCDFT to compute core-excited states and generalize the original formalism to determine multiple excited states. Benchmark computations on a set of 13 small molecules and 40 excited states show that unshifted OCDFT/B3LYP excitation energies have a mean absolute error of 1.0 eV. Contrary to time-dependent DFT, OCDFT excitation energies for first- and second-row elements are computed with near-uniform accuracy. OCDFT core excitation energies are insensitive to the choice of the functional and the amount of Hartree-Fock exchange. We show that OCDFT is a powerful tool for the assignment of X-ray absorption spectra of large molecules by simulating the gas-phase near-edge spectrum of adenine and thymine.

  18. X-Ray Diffraction and the Discovery of the Structure of DNA

    Science.gov (United States)

    Crouse, David T.

    2007-01-01

    A method is described for teaching the analysis of X-ray diffraction of DNA through a series of steps utilizing the original methods used by James Watson, Francis Crick, Maurice Wilkins and Rosalind Franklin. The X-ray diffraction pattern led to the conclusion of the basic helical structure of DNA and its dimensions while basic chemical principles…

  19. ROSAT Energy Spectra of Low-Mass X-Ray Binaries

    Science.gov (United States)

    Schulz, N. S.

    1999-01-01

    The 0.1-2.4 keV bandpass of the ROSAT Position Sensitive Proportional Counter (PSPC) offers an opportunity to study the very soft X-ray continuum of bright low-mass X-ray binaries (LMXBs). In 46 pointed observations, 23 LMXBs were observed with count rates between 0.4 and 165.4 counts s-1. The survey identified a total of 29 different luminosity levels, which are compared with observations and identified spectral states from other missions. The atoll source 4U 1705-44 was observed near Eddington luminosities in an unusually high intensity state. Spectral analysis provided a measure of the interstellar column density for all 49 observations. The sensitivity of spectral fits depends strongly on column density. Fits to highly absorbed spectra are merely insensitive toward any particular spectral model. Sources with column densities well below 1022 cm-2 are best fitted by power laws, while the blackbody model gives clearly worse fits to the data. Most single-component fits from sources with low column densities, however, are not acceptable at all. The inclusion of a blackbody component in eight sources can improve the fits significantly. The obtained emission radii of less than 5 km suggest emission from the neutron star surface. In 10 sources acceptable fits can only be achieved by including soft-line components. With a spectral resolution of the PSPC of 320-450 eV, between 0.6 and 1.2 keV unresolved broad-line features were detected around 0.65, 0.85, and 1.0 keV. The line fluxes range within 10-11 and 10-12 ergs cm-2 s-1, with equivalent widths between 24 and 210 eV. In LMC X-2, 2S 0918-549, and 4U 1254-690, line emission is indicated for the first time. The soft emission observed in 4U 0614+091 compares with recent ASCA results, with a new feature indicated at 1.31 keV. The deduced line fluxes in 4U 1820-30 and Cyg X-2 showed variability of a factor of 2 within timescales of 1-2 days. Average fluxes of line components in 4U 1820-30 varied by the same factor over a

  20. Structural investigations of LiFePO4 electrodes and in situ studies by Fe X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

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

    2005-01-01

    Fe K-edge X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) have been performed on electrodes containing LiFePO 4 to determine the local atomic and electronic structure and their stability with electrochemical cycling. A versatile electrochemical in situ cell has been constructed for long-term soft and hard X-ray experiments for the structural investigation on battery electrodes during the lithium-insertion/extraction processes. The device is used here for an X-ray absorption spectroscopic study of lithium insertion/extraction in a LiFePO 4 electrode, where the electrode contained about 7.7 mg of LiFePO 4 on a 20 μm thick Al-foil. Fe K-edge X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) have been performed on this electrode to determine the local atomic and electronic structure and their stability with electrochemical cycling. The initial state (LiFePO 4 ) showed iron to be in the Fe 2+ state corresponding to the initial state (0.0 mAh) of the cell, whereas in the delithiated state (FePO 4 ) iron was found to be in the Fe 3+ state corresponding to the final charged state (3 mAh). XANES region of the XAS spectra revealed a high spin configuration for the two states (Fe (II), d 6 and Fe (III), d 5 ). The results confirm that the olivine structure of the LiFePO 4 and FePO 4 is retained by the electrodes in agreement with the XRD observations reported previously. These results confirm that LiFePO 4 cathode material retains good structural short-range order leading to superior cycling capability

  1. Serial data acquisition for the X-ray plasma diagnostics with selected GEM detector structures

    International Nuclear Information System (INIS)

    Czarski, T.; Chernyshova, M.; Pozniak, K.T.; Kasprowicz, G.; Zabolotny, W.; Kolasinski, P.; Krawczyk, R.; Wojenski, A.; Zienkiewicz, P.

    2015-01-01

    The measurement system based on GEM—Gas Electron Multiplier detector is developed for X-ray diagnostics of magnetic confinement tokamak plasmas. The paper is focused on the measurement subject and describes the fundamental data processing to obtain reliable characteristics (histograms) useful for physicists. The required data processing have two steps: 1—processing in the time domain, i.e. events selections for bunches of coinciding clusters, 2—processing in the planar space domain, i.e. cluster identification for the given detector structure. So, it is the software part of the project between the electronic hardware and physics applications. The whole project is original and it was developed by the paper authors. The previous version based on 1-D GEM detector was applied for the high-resolution X-ray crystal spectrometer KX1 in the JET tokamak. The current version considers 2-D detector structures for the new data acquisition system. The fast and accurate mode of data acquisition implemented in the hardware in real time can be applied for the dynamic plasma diagnostics. Several detector structures with single-pixel sensors and multi-pixel (directional) sensors are considered for two-dimensional X-ray imaging. Final data processing is presented by histograms for selected range of position, time interval and cluster charge values. Exemplary radiation source properties are measured by the basic cumulative characteristics: the cluster position distribution and cluster charge value distribution corresponding to the energy spectra. A shorter version of this contribution is due to be published in PoS at: 1 st EPS conference on Plasma Diagnostics

  2. Serial data acquisition for the X-ray plasma diagnostics with selected GEM detector structures

    Science.gov (United States)

    Czarski, T.; Chernyshova, M.; Pozniak, K. T.; Kasprowicz, G.; Zabolotny, W.; Kolasinski, P.; Krawczyk, R.; Wojenski, A.; Zienkiewicz, P.

    2015-10-01

    The measurement system based on GEM—Gas Electron Multiplier detector is developed for X-ray diagnostics of magnetic confinement tokamak plasmas. The paper is focused on the measurement subject and describes the fundamental data processing to obtain reliable characteristics (histograms) useful for physicists. The required data processing have two steps: 1—processing in the time domain, i.e. events selections for bunches of coinciding clusters, 2—processing in the planar space domain, i.e. cluster identification for the given detector structure. So, it is the software part of the project between the electronic hardware and physics applications. The whole project is original and it was developed by the paper authors. The previous version based on 1-D GEM detector was applied for the high-resolution X-ray crystal spectrometer KX1 in the JET tokamak. The current version considers 2-D detector structures for the new data acquisition system. The fast and accurate mode of data acquisition implemented in the hardware in real time can be applied for the dynamic plasma diagnostics. Several detector structures with single-pixel sensors and multi-pixel (directional) sensors are considered for two-dimensional X-ray imaging. Final data processing is presented by histograms for selected range of position, time interval and cluster charge values. Exemplary radiation source properties are measured by the basic cumulative characteristics: the cluster position distribution and cluster charge value distribution corresponding to the energy spectra. A shorter version of this contribution is due to be published in PoS at: 1st EPS conference on Plasma Diagnostics

  3. Electronic structure of polycrystalline cadmium dichloride studied by X-ray spectroscopies and ab initio calculations

    International Nuclear Information System (INIS)

    Demchenko, I.N.; Chernyshova, M.; Stolte, W.C.; Speaks, D.T.; Derkachova, A.

    2012-01-01

    The electronic structure of cadmium dichloride has been studied by X-ray absorption near edge structure (XANES) and, for the first time, by resonant inelastic X-ray scattering (RIXS) at the Cl K edge. Good agreement was obtained between the non-resonant X-ray emission (XES) along with XANES experimental spectra and the calculated Cl 3p local partial density of states (DOS). The calculations were performed using the full-potential linearized-augmented-plane-wave with the local orbitals (FP-(L)APW l o) method utilized in the WIEN2k code. It was shown that the position of the RIXS band in CdCl 2 follows a linear dispersion according to the Raman–Stokes law if the excitation energy is tuned below the absorption threshold. The situation changes for core excitation above the photoabsorption threshold where the dispersion relation is split into two branches. The position of the resonant contribution does not depend on the excitation energy, while the excitonic sideband follows the Raman–Stoke law. Combined XANES and RIXS measurements compared to calculated band structure allowed us to determine the direct band gap of CdCl 2 to be at 5.7 ± 0.05 eV. -- Highlights: ► XANES at the K edge of Cl and related emission KV band interpreted within the ab initio DFT formalism. ► Two dominant contributions observed in RIXS data: the resonant and the excitonic ones. ► The dispersion relation below the absorption threshold follows Raman–Stokes law. ► Dispersion above the threshold splits into two qualitatively different relations. ► Overlapping of XAS spectrum with RIXS one makes possible to estimate direct band gap value to be 5.7 eV.

  4. Effects of proton irradiation on structure of NdFeB permanent magnets studied by X-ray diffraction and X-ray absorption fine structure

    International Nuclear Information System (INIS)

    Yang, L.; Zhen, L.; Xu, C.Y.; Sun, X.Y.; Shao, W.Z.

    2011-01-01

    The effects of proton irradiation on the structure of NdFeB permanent magnet were investigated by X-ray diffraction and X-ray absorption fine structure (XAFS). The results reveal that proton irradiation has no effect on the long-range structure, but significantly affects the atomic local structure of the NdFeB magnet. The alignment degree of the magnet decreases and the internal stress of the lattice increases after proton irradiation. XAFS results show that the coordination number of Fe-Nd in the first neighboring coordination shell of the Fe atoms decreases and the disorder degree increases.

  5. Effects of proton irradiation on structure of NdFeB permanent magnets studied by X-ray diffraction and X-ray absorption fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Yang, L. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Zhen, L., E-mail: lzhen@hit.edu.c [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Xu, C.Y.; Sun, X.Y.; Shao, W.Z. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2011-01-15

    The effects of proton irradiation on the structure of NdFeB permanent magnet were investigated by X-ray diffraction and X-ray absorption fine structure (XAFS). The results reveal that proton irradiation has no effect on the long-range structure, but significantly affects the atomic local structure of the NdFeB magnet. The alignment degree of the magnet decreases and the internal stress of the lattice increases after proton irradiation. XAFS results show that the coordination number of Fe-Nd in the first neighboring coordination shell of the Fe atoms decreases and the disorder degree increases.

  6. Dose and absorption spectra response of EBT2 Gafchromic film to high energy X-rays

    International Nuclear Information System (INIS)

    Butson, M.J.; Cheung, T.; Yu, P.K.N.; Alnawaf, H.

    2009-01-01

    Full text: With new advancements in radiochromic film designs and sensitivity to suit different niche applications, EBT2 is the latest offering for the megavoltage radiotherapy market. New construction specifications including different physical construction and the use of a yellow coloured dye has provided the next generation radiochromic film for therapy applications. The film utilises the same active chemical for radiation measurement as its predecessor, EBT Gafchromic. Measurements have been performed using photo spectrometers to analyse the absorption spectra properties of this new EBT2 Gafchromic, radiochromic film. Results have shown that whilst the physical coloration or absorption spectra of the film, which turns yellow to green as compared to EBT film, (clear to blue) is significantly different due to the added yellow dye, the net change in absorption spectra properties for EBT2 are similar to the original EBT film. Absorption peaks are still located at 636 n m and 585 n m positions. A net optical density change of 0.590 ± 0.020 (2SD) for a 1 Gy radiation absorbed dose using 6 MV x-rays when measured at the 636 n m absorption peak was found. This is compared to 0.602 ± 0.025 (2SD) for the original EBT film (2005 Batch) and 0.557 ± 0.027 (2009 Batch) at the same absorption peak. The yellow dye and the new coating material produce a significantly different visible absorption spectra results for the EBT2 film compared to EBT at wavelengths especially below approximately 550 n m. At wavelengths above 550 n m differences in absolute OD are seen however, when dose analysis is performed at wavelengths above 550 n m using net optical density changes, no significant variations are seen. If comparing results of the late production EBT to new production EBT2 film, net optical density variations of approximately 10 % to 15 % are seen. As all new film batches should be calibrated for sensitivity upon arrival this should not be of concern.

  7. Dynamics of hot spots in the DPF-78 plasma focus from x-ray spectra and REB emission

    International Nuclear Information System (INIS)

    Schmidt, H.; Wang, X.X.

    1995-01-01

    The X-ray emission from hot spots in the plasma focus DPF-78 was investigated with the help of two X-ray quartz crystal spectrometers of the Johann type and a 4 fold magnifying X-ray pinhole camera. In the experiments the working gas was chosen to be 300 Pa deuterium with 20 Pa argon admixture. X-ray spectra in the wavelength range from 3.55 angstrom to 4.0 angstrom, including H-like and He-like Argon lines, were recorded on Kodak DEF-2 film. From the spatially resolved spectra recorded side-on, a relative spectral shift between different hot spots of the same shot was often observed. The shift could be attributed to the Doppler shift. From spectral characteristics such as intensities and FWHM of Ar resonant and intercombination lines electron densities of up to 3 x 10 27 m -3 were determined. Radial dimensions of the hot spots ranging from about 140 microm to 300 microm were found from pinhole pictures applying the penumbra method. Usually two pulses of relativistic electron beams were observed using Cherenkov detectors in a magnetic spectrometer. The energy of the first pulse, which was emitted at the time of maximum compression, was higher than that of the second pulse. The measured FWHM of the REB pulses ranges from 3 ns to about 10 ns. The characteristics of the time-integrated X-ray spectra and the time resolved REB spectra and their dependence on the composition of the filling gas are discussed

  8. Correcting X-ray spectra obtained from the AXAF VETA-I mirror calibration for pileup, continuum, background and deadtime

    Science.gov (United States)

    Chartas, G.; Flanagan, K.; Hughes, J. P.; Kellogg, E. M.; Nguyen, D.; Zombek, M.; Joy, M.; Kolodziejezak, J.

    1993-01-01

    The VETA-I mirror was calibrated with the use of a collimated soft X-ray source produced by electron bombardment of various anode materials. The FWHM, effective area and encircled energy were measured with the use of proportional counters that were scanned with a set of circular apertures. The pulsers from the proportional counters were sent through a multichannel analyzer that produced a pulse height spectrum. In order to characterize the properties of the mirror at different discrete photon energies one desires to extract from the pulse height distribution only those photons that originated from the characteristic line emission of the X-ray target source. We have developed a code that fits a modeled spectrum to the observed X-ray data, extracts the counts that originated from the line emission, and estimates the error in these counts. The function that is fitted to the X-ray spectra includes a Prescott function for the resolution of the detector a second Prescott function for a pileup peak and a X-ray continuum function. The continuum component is determined by calculating the absorption of the target Bremsstrahlung through various filters, correcting for the reflectivity of the mirror and convolving with the detector response.

  9. Structural study on Ni nanowires in an anodic alumina membrane by using in situ heating extended x-ray absorption fine structure and x-ray diffraction techniques

    International Nuclear Information System (INIS)

    Cai Quan; Chen Xing; Chen Zhongjun; Wang Wei; Mo Guang; Wu Zhonghua; Zhang Junxi; Zhang Lide; Pan Wei

    2008-01-01

    Polycrystalline Ni nanowires have been prepared by electrochemical deposition in an anodic alumina membrane template with a nanopore size of about 60 nm. In situ heating extended x-ray absorption fine structure and x-ray diffraction techniques are used to probe the atomic structures. The nanowires are identified as being mixtures of nanocrystallites and amorphous phase. The nanocrystallites have the same thermal expansion coefficient, of 1.7 x 10 -5 K -1 , as Ni bulk; however, the amorphous phase has a much larger thermal expansion coefficient of 3.5 x 10 -5 K -1 . Details of the Ni nanowire structures are discussed in this paper

  10. A structural study of ceramic oxides by X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Akhtar, M.J.

    1995-01-01

    A detailed structural study of ceramic oxides is presented by employing X-ray Absorption Spectroscopy (XAS). In the present work X-ray Absorption Near Edge Structure (XANES) is used for the investigation of valence state of metal cations; whereas, Extended X-ray Absorption Fine Structure EXAFS) is employed for the determination for bond lengths, coordination numbers and nature of the elements present in the near neighbour shells surrounding the absorbing atom. These results show that local environment of dopant and host cations are different; and this variation in local structure depends on the nature and concentration of the dopant ions. (author)

  11. Hydrogen atoms in protein structures: high-resolution X-ray diffraction structure of the DFPase

    Science.gov (United States)

    2013-01-01

    Background Hydrogen atoms represent about half of the total number of atoms in proteins and are often involved in substrate recognition and catalysis. Unfortunately, X-ray protein crystallography at usual resolution fails to access directly their positioning, mainly because light atoms display weak contributions to diffraction. However, sub-Ångstrom diffraction data, careful modeling and a proper refinement strategy can allow the positioning of a significant part of hydrogen atoms. Results A comprehensive study on the X-ray structure of the diisopropyl-fluorophosphatase (DFPase) was performed, and the hydrogen atoms were modeled, including those of solvent molecules. This model was compared to the available neutron structure of DFPase, and differences in the protein and the active site solvation were noticed. Conclusions A further examination of the DFPase X-ray structure provides substantial evidence about the presence of an activated water molecule that may constitute an interesting piece of information as regard to the enzymatic hydrolysis mechanism. PMID:23915572

  12. PROBING WOLF–RAYET WINDS: CHANDRA/HETG X-RAY SPECTRA OF WR 6

    Energy Technology Data Exchange (ETDEWEB)

    Huenemoerder, David P.; Schulz, N. S. [Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research, 70 Vassar St., Cambridge, MA 02139 (United States); Gayley, K. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Hamann, W.-R.; Oskinova, L.; Shenar, T. [Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, D-14476 Potsdam (Germany); Ignace, R. [Department of Physics and Astronomy, East Tennessee State University, Johnson City, TN 37614 (United States); Nichols, J. S. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS 34, Cambridge, MA 02138 (United States); Pollock, A. M. T., E-mail: dph@space.mit.edu, E-mail: ken.gayley@gmail.com, E-mail: wrh@astro.physik.uni-potsdam.de, E-mail: lida@astro.physik.uni-potsdam.de, E-mail: shtomer@astro.physik.uni-potsdam.de, E-mail: ignace@mail.etsu.edu, E-mail: jnichols@cfa.harvard.edu [European Space Agency, ESAC, Apartado 78, E-28691 Villanueva de la Cañada (Spain)

    2015-12-10

    With a deep Chandra/HETGS exposure of WR 6, we have resolved emission lines whose profiles show that the X-rays originate from a uniformly expanding spherical wind of high X-ray-continuum optical depth. The presence of strong helium-like forbidden lines places the source of X-ray emission at tens to hundreds of stellar radii from the photosphere. Variability was present in X-rays and simultaneous optical photometry, but neither were correlated with the known period of the system or with each other. An enhanced abundance of sodium revealed nuclear-processed material, a quantity related to the evolutionary state of the star. The characterization of the extent and nature of the hot plasma in WR 6 will help to pave the way to a more fundamental theoretical understanding of the winds and evolution of massive stars.

  13. Sub-keV, subnanosecond measurements of x-ray spectra from laser-produced plasmas

    International Nuclear Information System (INIS)

    Kornblum, H.N.; Koppel, L.N.; Slivinsky, V.W.; Glaros, S.S.; Ahlstrom, H.G.; Larsen, J.T.

    1977-01-01

    As part of the effort to extend our x-ray diagnostic capabilities, we have made x-ray spectral measurements of laser-produced plasmas for photon energies down to 100 eV with a time response of 0.5 nsec. Fast, windowless x-ray diodes were used in conjunction with critical angle reflecting mirrors and thin filters for energy definition for two channels, 300 to 600 eV and 800 to 1300 eV. A third channel, using only an x-ray diode and filter, provided spectral information in the 100 to 300 eV region. Results from exploding pusher targets will be presented and compared with those of other diagnostic techniques and Lasnex calculations. Future expansion and modifications of the present system will be discussed

  14. The Intrinsically X-Ray-weak Quasar PHL 1811. II. Optical and UV Spectra and Analysis

    Science.gov (United States)

    Leighly, Karen M.; Halpern, Jules P.; Jenkins, Edward B.; Casebeer, Darrin

    2007-11-01

    This is the second of two papers reporting observations and analysis of the unusually bright (mb=14.4), luminous (MB=-25.5), nearby (z=0.192) narrow-line quasar PHL 1811. The first paper reported that PHL 1811 is intrinsically X-ray-weak and presented a spectral energy distribution (SED). Here we present HST STIS optical and UV spectra, and ground-based optical spectra. The optical and UV line emission is very unusual. There is no evidence for forbidden or semiforbidden lines. The near-UV spectrum is dominated by very strong Fe II and Fe III, and unusual low-ionization lines such as Na I D and Ca II H and K are observed. High-ionization lines are very weak; C IV has an equivalent width of 6.6 Å, a factor of ~5 smaller than measured from quasar composite spectra. An unusual feature near 1200 Å can be deblended in terms of Lyα, N V, Si II, and C III* using the blueshifted C IV profile as a template. Photoionization modeling shows that the unusual line emission can be explained qualitatively by the unusually soft SED. Principally, a low gas temperature results in inefficient emission of collisionally excited lines, including the semiforbidden lines generally used as density diagnostics. The emission resembles that of high-density gas; in both cases this is a consequence of inefficient cooling. PHL 1811 is very unusual, but we note that quasar surveys may be biased against finding similar objects. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with proposal 9181. Based on observations obtained at Kitt Peak National Observatory, a division of the National Optical Astronomy Observatories, which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.

  15. An optimal ross filter system for soft X-ray spectra measurement

    International Nuclear Information System (INIS)

    Huang Tianxuan; Zheng Zhijian; Sun Kexu; Jiang Shaoen

    2000-01-01

    A broadband Ross filter spectrometer is described for measuring soft X-ray radiation (0.1∼1.5 keV) emitted from laser plasma. It consists of a number of channels, each representing a Ross filter pair in conjunction with Al cathode X-ray diodes. An optimal channel has flat response within the sensitivity band, and minimal response outside it. The effect of some uncertainties on the accuracy of measurements is calculated

  16. X-ray spectroscopy of electronic structure of amorphous silicon and silicyne

    International Nuclear Information System (INIS)

    Mashin, A.I.; Khokhlov, A.F.; Mashin, N.I.; Domashevskaya, Eh.P.; Terekhov, V.A.

    2001-01-01

    SiK β and SiL 23 emission spectra of crystalline silicon (c-Si), amorphous hydrogenated silicon (α-Si:H) and silicyne have been studied by X-ray and ultrasoft X-ray spectroscopy. It is observed that SiL 23 emission spectra of silicyne displays not two maximums, as it usually observed for the c-Si and α-Si:H, but three ones. The third one is seen at high energies near 95.7 eV, and has an intensity about 75%. An additional maximum in the short- wave part of SiK β emission spectrum is observed. This difference of shapes of X-ray spectra between α-Si:H and silicyne is explained by the presence in silicyne a strong π-component of chemical bonds of a silicon atoms in silicyne [ru

  17. X-ray spectroscopy of electronic structure of amorphous silicon and silicyne

    CERN Document Server

    Mashin, A I; Mashin, N I; Domashevskaya, E P; Terekhov, V A

    2001-01-01

    SiK subbeta and SiL sub 2 sub 3 emission spectra of crystalline silicon (c-Si), amorphous hydrogenated silicon (alpha-Si:H) and silicyne have been studied by X-ray and ultrasoft X-ray spectroscopy. It is observed that SiL sub 2 sub 3 emission spectra of silicyne displays not two maximums, as it usually observed for the c-Si and alpha-Si:H, but three ones. The third one is seen at high energies near 95.7 eV, and has an intensity about 75%. An additional maximum in the short- wave part of SiK subbeta emission spectrum is observed. This difference of shapes of X-ray spectra between alpha-Si:H and silicyne is explained by the presence in silicyne a strong pi-component of chemical bonds of a silicon atoms in silicyne

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

    Science.gov (United States)

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

    2018-04-01

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

  19. Radiative electron rearrangement and polarization in target K x-ray spectra

    International Nuclear Information System (INIS)

    Jamison, K.A.

    1978-01-01

    Two topics in the atomic physics of ion-atom collisions are studied. The first is an investigation of a free-atom decay process that is shown to be a two-electron one-photon decay. This two-electron decay requires an initial state with multiple inner-shell vacancies that has a high probability of creation in ion-atom collisions. Because this decay promotes one electron to a higher shell while allowing the other to fall to a lower shell, it is referred to as radiative electron rearrangement (RER). The investigation of this process includes the experimental study of the x-ray spectra region approx. 150 eV below the characteristic Kα 1 2 target radiation in third period elements when bombarded by various ion beams in the energy range 1 to 2 MeV/amu. Theoretical calculations of the transition energies, line strengths, and line widths are performed to verify the origin of the RER lines. The second topic of consideration is the study of the polarization of Kα satellite radiation from targets of Al and Si. It is shown that the polarization, which is observed experimentally with a curved-crystal polarimeter, is due to the nonstatistical population of the magnetic substates created in specific ion-atom collisions. Further, the polarization of the RER lines is studied. The connection between the polarization of the normal Kα satellite radiation and the polarization of the RER lines adds final proof to their origin as two-electron one-photon transitions

  20. Optimization of x-ray spectra in digital mammography through Monte Carlo simulations.

    Science.gov (United States)

    Cunha, D M; Tomal, A; Poletti, M E

    2012-04-07

    In this work, a Monte Carlo code was used to investigate the performance of different x-ray spectra in digital mammography, through a figure of merit (FOM), defined as FOM = CNR²/(¯)D(g), with CNR being the contrast-to-noise ratio in image and [Formula: see text] being the average glandular dose. The FOM was studied for breasts with different thicknesses t (2 cm ≤ t ≤ 8 cm) and glandular contents (25%, 50% and 75% glandularity). The anode/filter combinations evaluated were those traditionally employed in mammography (Mo/Mo, Mo/Rh, Rh/Rh), and a W anode combined with Al or K-edge filters (Zr, Mo, Rh, Pd, Ag, Cd, Sn), for tube potentials between 22 and 34 kVp. Results show that the W anode combined with K-edge filters provides higher values of FOM for all breast thicknesses investigated. Nevertheless, the most suitable filter and tube potential depend on the breast thickness, and for t ≥ 6 cm, they also depend on breast glandularity. Particularly for thick and dense breasts, a W anode combined with K-edge filters can greatly improve the digital technique, with the values of FOM up to 200% greater than that obtained with the anode/filter combinations and tube potentials traditionally employed in mammography. For breasts with t < 4 cm, a general good performance was obtained with the W anode combined with 60 μm of the Mo filter at 24-25 kVp, while 60 μm of the Pd filter provided a general good performance at 24-26 kVp for t = 4 cm, and at 28-30 and 29-31 kVp for t = 6 and 8 cm, respectively.

  1. Probing chemistry within the membrane structure of wood with soft X-ray spectral microscopy

    International Nuclear Information System (INIS)

    Cody, George D.

    2000-01-01

    Scanning Transmission Soft X-ray spectral microscopy on Carbon's 1s absorption edge reveals the distribution of structural biopolymers within cell membrane regions of modern cedar and oak. Cellulose is extremely susceptible to beam damage. Spectroscopic studies of beam damage reveals that the chemical changes resulting from secondary electron impact may be highly selective and is consistent with hydroxyl eliminations and structural rearrangement of pyranose rings in alpha-cellulose to hydroxyl substituted γ pyrones. A study of acetylated cellulose demonstrates significantly different chemistry; principally massive decarboxylation. Defocusing the beam to a 2 μm spot size allows for the acquisition of 'pristine' cellulose spectra. Spectral deconvolution is used to assess the distribution of lignin and cellulose in the different regions of the cell membrane. Using the intensity of the hydroxylated aromatic carbons 1s-π * transition, the ratio of coniferyl and syringyl based lignin within the middle lamellae and secondary cell wall of oak, an angiosperm can be determined

  2. Natural widths and Coster-Kronig transitions of L X-ray spectra in elements between Pd and Sb

    International Nuclear Information System (INIS)

    Sakakura, Shusuke; Oohashi, Hirofumi; Ito, Yoshiaki; Tochio, Tatsunori; Vlaicu, Aurel M.; Yoshikawa, Hideki; Ikenaga, Eiji; Kobayashi, Keisuke

    2006-01-01

    The Lα and Lβ X-ray emission spectra in the elements between Pd (Z=46) and Sb (Z=51) were measured using a high-resolution double-crystal vacuum spectrometer. The relative intensities of satellite structures, which originate in L 1 L 3 M 4,5 Coster-Kronig transitions, were estimated to that of each diagram line, and compared with calculated values. According to the work of Chen et al. [1977a. Theoretical L-shell Coster-Kronig energies 11≤Z≤103. At. Data Nucl. Data Tables 19, 97-151], Salgueiro et al. [1987. J. Phys. (Paris) 48 Colloq. C9, 609] and Vlaicu et al. [1998. Investigation of the 74W L emission spectra and satellites. Phys. Rev. A 58, 3544] L 1 L 3 M 4 Coster-Kronig transition is forbidden for 50≤Z≤77, and L 1 L 3 M 5 Coster-Kronig transition is forbidden for 50≤Z≤73. The results suggest that L 1 L 3 M 4,5 Coster-Kronig transitions may be allowed even for Sn (Z=50) and Sb (Z=51)

  3. Use of X-Ray Absorption Spectra as a ``Fingerprint'' of the Local Environment in Complex Chalcogenides

    Science.gov (United States)

    Branci, C.; Womes, M.; Lippens, P. E.; Olivier-Fourcade, J.; Jumas, J. C.

    2000-03-01

    The local environment of tin, titanium, iron, and sulfur in spinel compounds Cu2FeSn3S8 and Cu2FeTi3S8 was studied by X-ray absorption spectroscopy (XAS) at the titanium, iron, sulfur K edges, and the tin LI-edge. As detailed calculations of the electronic structure of these compounds are difficult to carry out due to the large number of atoms contained in the unit cell, the XAS spectra of the spinels are compared to those of relatively simple binary sulfides like SnS2, TiS2, and FeS. Indeed, the metal environments in these binary compounds are very similar to those in the spinels, and they can be considered good model compounds allowing the interpretation of electronic transitions observed in the spectra of quaternary phases. In the latter, the bottom of the conduction band is mainly formed by Sn 5s-S 3p, Sn 5p-S 3p antibonding states for the tin-based compounds and by Ti 3dt2g-S 3p, Ti 3deg-S 3p antibonding states for the titanium-based compounds. It it shown that the local environment of iron atoms remains unchanged when substituting tin with titanium atoms, according to a topotactic substitution.

  4. Soft X-ray absorption spectra of aqueous salt solutions with highly charged cations in liquid microjets

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, Craig P.; Uejio, Janel S.; Duffin, Andrew M.; Drisdell, Walter S.; Smith, Jared D.; Saykally, Richard J.

    2010-03-11

    X-ray absorption spectra of 1M aqueous solutions of indium (III) chloride, yttrium (III) bromide, lanthanum (III) chloride, tin (IV) chloride and chromium (III) chloride have been measured at the oxygen K-edge. Relatively minor changes are observed in the spectra compared to that of pure water. SnCl{sub 4} and CrCl{sub 3} exhibit a new onset feature which is attributed to formation of hydroxide or other complex molecules in the solution. At higher energy, only relatively minor, but salt-specific changes in the spectra occur. The small magnitude of the observed spectral changes is ascribed to offsetting perturbations by the cations and anions.

  5. X-Ray Absorption with Transmission X-Ray Microscopes

    NARCIS (Netherlands)

    de Groot, F.M.F.

    2016-01-01

    In this section we focus on the use of transmission X-ray microscopy (TXM) to measure the XAS spectra. In the last decade a range of soft X-ray and hard X-ray TXM microscopes have been developed, allowing the measurement of XAS spectra with 10–100 nm resolution. In the hard X-ray range the TXM

  6. The complex ion structure of warm dense carbon measured by spectrally resolved x-ray scattering

    Energy Technology Data Exchange (ETDEWEB)

    Kraus, D.; Barbrel, B.; Falcone, R. W. [Department of Physics, University of California, Berkeley, California 94720 (United States); Vorberger, J. [Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Straße 38, 01187 Dresden (Germany); Helfrich, J.; Frydrych, S.; Ortner, A.; Otten, A.; Roth, F.; Schaumann, G.; Schumacher, D.; Siegenthaler, K.; Wagner, F.; Roth, M. [Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstraße 9, 64289 Darmstadt (Germany); Gericke, D. O.; Wünsch, K. [Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Bachmann, B.; Döppner, T. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Bagnoud, V.; Blažević, A. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße 1, 64291 Darmstadt (Germany); and others

    2015-05-15

    We present measurements of the complex ion structure of warm dense carbon close to the melting line at pressures around 100 GPa. High-pressure samples were created by laser-driven shock compression of graphite and probed by intense laser-generated x-ray sources with photon energies of 4.75 keV and 4.95 keV. High-efficiency crystal spectrometers allow for spectrally resolving the scattered radiation. Comparing the ratio of elastically and inelastically scattered radiation, we find evidence for a complex bonded liquid that is predicted by ab-initio quantum simulations showing the influence of chemical bonds under these conditions. Using graphite samples of different initial densities we demonstrate the capability of spectrally resolved x-ray scattering to monitor the carbon solid-liquid transition at relatively constant pressure of 150 GPa. Showing first single-pulse scattering spectra from cold graphite of unprecedented quality recorded at the Linac Coherent Light Source, we demonstrate the outstanding possibilities for future high-precision measurements at 4th Generation Light Sources.

  7. Finite difference method calculations of X-ray absorption fine structure for copper

    Energy Technology Data Exchange (ETDEWEB)

    Bourke, J.D. [School of Physics, University of Melbourne, Parkville, Vic 3010 (Australia); Chantler, C.T. [School of Physics, University of Melbourne, Parkville, Vic 3010 (Australia)]. E-mail: chantler@physics.unimelb.edu.au; Witte, C. [School of Physics, University of Melbourne, Parkville, Vic 3010 (Australia)

    2007-01-15

    The finite difference method is extended to calculate X-ray absorption fine structure (XAFS) for solid state copper. These extensions include the incorporation of a Monte Carlo frozen phonon technique to simulate the effect of thermal vibrations under a correlated Debye-Waller model, and the inclusion of broadening effects from inelastic processes. Spectra are obtained over an energy range in excess of 300 eV above the K absorption edge-more than twice the greatest energy range previously reported for a solid state calculation using this method. We find this method is highly sensitive to values of the photoelectron inelastic mean free path, allowing us to probe the accuracy of current models of this parameter, particularly at low energies. We therefore find that experimental data for the photoelectron inelastic mean free path can be obtained by this method. Our results compare favourably with high precision measurements of the X-ray mass attenuation coefficient for copper, reaching agreement to within 3%, and improving previous results using the finite difference method by an order of magnitude.

  8. Analysis of kiwi fruit (Accented deliciosa) by energy dispersive X-ray fluorescence spectra

    International Nuclear Information System (INIS)

    Oliveira, Ana Claudia S.; Oliveira, Marcia L. de; Silva, Lucia C.A.S.; Arthur, Valter; Almeida, Eduardo

    2011-01-01

    The search for a healthy life has led consumers to eat fruits and vegetables in place of manufactured products, however, the demand for minimally processed products has evolved rapidly. The kiwi has at least eight nutrients beneficial to health: calcium, magnesium, manganese, phosphorus, iron, potassium, sodium and has also high vitamin C, which has wide acceptance in consumer markets. Energy dispersive spectroscopy X-ray (EDX) is the analytical technique used for elemental analysis or chemical characterization of a sample. It is a variant of fluorescence spectroscopy X-ray based on the sample through an investigation of interactions between electromagnetic radiation and matter, analyzing X-rays emitted by matter in response to being struck by charged particles. The aim of this study were to determine potassium, calcium, iron and bromine (K, Ca, Fe and Br, respectively) present in kiwifruit using the technique of fluorescence X-ray energy dispersive (EDXRF). Kiwifruit were peeled, washed and cut into slices and freeze-dried. After drying the sample was held digestion and subsequent reading of the same equipment in the X-ray fluorescence energy dispersive (EDXRF). The results indicated that the contents of potassium, calcium, iron and bromine are present in kiwifruit as expected when compared to Brazilian Table of Food Composition. (author)

  9. The structure of the coronal soft X-ray source associated with the dark filament disappearance of 1991 September 28 using the Yohkoh Soft X-ray Telescope

    Science.gov (United States)

    Mcallister, Alan; Uchida, Yutaka; Tsuneta, Saku; Strong, Keith T.; Acton, Loren W.; Hiei, Eijiro; Bruner, Marilyn E.; Watanabe, Takashi; Shibata, Kazunari

    1992-01-01

    The structure of the coronal soft X-ray source associated with the dark filament disappearance on September 28, 1991, observed with the Soft X-ray Telescope, is examined as a possible example of the 'eruption-reconnection' model of filament disappearance. The results suggest, however, that this model may not fit. There is a strong possibility that much of the dark filament mass remains in the heated unwinding axial field.

  10. Synthesis, X-ray crystal structure, DNA binding and Nuclease activity ...

    Indian Academy of Sciences (India)

    s12039-016-1125-x. Synthesis, X-ray crystal structure, DNA binding and Nuclease activity of lanthanide(III) complexes of 2-benzoylpyridine acetylhydrazone. KARREDDULA RAJA, AKKILI SUSEELAMMA and KATREDDI HUSSAIN REDDY. ∗.

  11. Extracting ion emission lines from femtosecond-laser plasma x-ray spectra heavily contaminated by spikes

    International Nuclear Information System (INIS)

    Gasilov, S. V.; Faenov, A. Ya.; Pikuz, T. A.; Villoresi, P.; Poletto, L.; Stagira, S.; Calegari, F.; Vozzi, C.; Nisoli, M.

    2007-01-01

    Nowadays charged-coupled device (CCD) detectors are widely used for the registration of multicharged ions x-ray spectra. These spectra are generated in a plasma during interaction of ultrashort, ultraintense laser pulses with solid targets. Strong parasitic radiation from the plasma affects CCD detectors and contaminates resulting spectra, so that spectral features can be completely covered by noise even during measurements with a very short accumulation time. In this work we propose a ''mean to median'' (M2M) algorithm for noise suppression in femtosecond laser plasma x-ray spectra. Series of spectra is necessary for the identification of corrupted data points by the developed method. The algorithm was tested with model spectra which reflect main features of experimental data. In practice we used it for extracting information about spectral lines of Ne-like Fe ions and He-like Al ions which allowed us to calculate plasma parameters. It is demonstrated that M2M method is able to clean spectra with more than 10% of corrupted pixels. Fluctuations in intensity of spectral lines induced by laser instability do not affect validity of the proposed method

  12. Peculiar time dependence of unexpected lines in delayed beam-foil X-ray spectra of V, Fe and Ni

    International Nuclear Information System (INIS)

    Ahmad, Nissar; Karn, Ranjeet K.; Marketos, Pan; Nandi, T.

    2005-01-01

    Delayed beam-foil X-ray spectra of highly charged ions of V, Fe and Ni show a few lines at energies higher than the H-like Lyman α-line of the respective projectile ions. These can only be attributed to heavier ions. Further the time dependence of such unexpected lines display a peculiar behavior. This work presents the experimental observations systematically

  13. Jupiter's X-ray Auroral Pulsations and Spectra During Juno Perijove 7

    Science.gov (United States)

    Dunn, W.; Branduardi-Raymont, G.; Ray, L. C.; Jackman, C. M.; Kraft, R.; Gladstone, R.; Yao, Z.; Rae, J.; Gray, R.; Elsner, R.; Grodent, D. C.; Nichols, J. D.; Ford, P. G.; Ness, J. U.; Kammer, J.; Rodriguez, P.

    2017-12-01

    Jupiter's X-ray aurora is concentrated into a bright and dynamic hot spot that is produced by precipitating 10 MeV ions [Gladstone et al. 2002; Elsner et al. 2005; Branduardi-Raymont et al. 2007]. These highly energetic emissions exhibit pulsations over timescales of 10s of minutes and change morphology, intensity and precipitating particle populations from observation to observation and pole to pole [e.g. Dunn et al. 2016; in-press]. The acceleration process/es that allow Jupiter to produce these high-energy ion charge exchange emissions are not well understood, but are concentrated in the most poleward regions of the aurora, where field lines map to the outer magnetosphere and possibly beyond [Vogt et al. 2015; Kimura et al. 2016]. On July 11th 2017, NASA's Juno spacecraft conducted its 7th perijove flyby of Jupiter and is predicted to have flown directly through field lines that map to the Northern and Southern X-ray hot spots. During this unique flight, the XMM-Newton observatory conducted 40 hours of continuous time-tagged X-ray observations. We present the results from these X-ray observations, showing that Jupiter's X-ray aurora varies significantly from one planetary rotation to the next and that the spectral signatures, indicative of the precipitating ion and electron populations producing the emission, also vary. We measure the Doppler broadening of the spectral lines to calculate the ion energies at the point when they impact the ionosphere, in order that these might be compared with in-situ data to constrain Jovian auroral acceleration processes. Finally, we compare X-ray signatures from the last decade of observations with UV polar emissions at similar times to further enrich multi-wavelength connections and deepen our understanding of how Jupiter is able to generate its highly energetic polar auroral precipitations.

  14. Studies of momentum transfer and X-ray spectra in a laser-produced plasma

    International Nuclear Information System (INIS)

    Leroy, Pierre

    Studies of momentum transfer from a ballistic pendulum appear to give satisfactory results for absorbed laser energies in excess of 200 mJ i.e. for fluxes in the 3.10 10 to 3.10 12 W.cm -2 range. A hard X-ray component attributed to fast electrons was revealed by an X-ray spectrometer with a PM system of greater sensitivity than PIN diodes. The laser energy is however too weak to enable studies to be conducted as a function of laser flux or measurements to be performed on targets of low Z [fr

  15. Photovoltaic X-ray detectors based on epitaxial GaAs structures

    Energy Technology Data Exchange (ETDEWEB)

    Achmadullin, R.A. [Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 1 Ac. Vvedenski square, Fryazino 141190, Moscow region (Russian Federation); Artemov, V.V. [Shubnikov Institute of Crystallography, Russian Academy of Sciences, 59 Leninski pr., Moscow B-333, 117333 (Russian Federation); Dvoryankin, V.F. [Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 1 Ac. Vvedenski square, Fryazino 141190, Moscow region (Russian Federation)]. E-mail: vfd217@ire216.msk.su; Dvoryankina, G.G. [Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 1 Ac. Vvedenski square, Fryazino 141190, Moscow region (Russian Federation); Dikaev, Yu.M. [Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 1 Ac. Vvedenski square, Fryazino 141190, Moscow region (Russian Federation); Ermakov, M.G. [Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 1 Ac. Vvedenski square, Fryazino 141190, Moscow region (Russian Federation); Ermakova, O.N. [Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 1 Ac. Vvedenski square, Fryazino 141190, Moscow region (Russian Federation); Chmil, V.B. [Scientific State Center, High Energy Physics Institute, Protvino, Moscow region (Russian Federation); Holodenko, A.G. [Scientific State Center, High Energy Physics Institute, Protvino, Moscow region (Russian Federation); Kudryashov, A.A.; Krikunov, A.I.; Petrov, A.G.; Telegin, A.A. [Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 1 Ac. Vvedenski square, Fryazino 141190, Moscow region (Russian Federation); Vorobiev, A.P. [Scientific State Center, High Energy Physics Institute, Protvino, Moscow region (Russian Federation)

    2005-12-01

    A new type of the photovoltaic X-ray detector based on epitaxial p{sup +}-n-n'-n{sup +} GaAs structures which provides a high efficiency of charge collection in the non-bias operation mode at room temperature is proposed. The GaAs epitaxial structures were grown by vapor-phase epitaxy on heavily doped n{sup +}-GaAs(1 0 0) substrates. The absorption efficiency of GaAs X-ray detector is discussed. I-V and C-V characteristics of the photovoltaic X-ray detectors are analyzed. The built-in electric field profiles in the depletion region of epitaxial structures are measured by the EBIC method. Charge collection efficiency to {alpha}-particles and {gamma}-radiation are measured. The application of X-ray detectors is discussed.

  16. Hard X-ray Microscopy with Elemental, Chemical and Structural Contrast

    International Nuclear Information System (INIS)

    Schroer, C.G.; Boye, P.; Feldkamp, J.P.

    2010-01-01

    We review hard X-ray microscopy techniques with a focus on scanning microscopy with synchrotron radiation. Its strength compared to other microscopies is the large penetration depth of hard x rays in matter that allows one to investigate the interior of an object without destructive sample preparation. In combination with tomography, local information from inside of a specimen can be obtained, even from inside special non-ambient sample environments. Different X-ray analytical techniques can be used to produce contrast, such as X-ray absorption, fluorescence, and diffraction, to yield chemical, elemental, and structural information about the sample, respectively. This makes X-ray microscopy attractive to many fields of science, ranging from physics and chemistry to materials, geo-, and environmental science, biomedicine, and nanotechnology. Our scanning microscope based on nanofocusing refractive X-ray lenses has a routine spatial resolution of about 100 nm and supports the contrast mechanisms mentioned above. In combination with coherent X-ray diffraction imaging, the spatial resolution can be improved to the 10 nm range. The current state-of-the-art of this technique is illustrated by several examples, and future prospects of the technique are given. (author)

  17. Inner Disk Structure of Dwarf Novae in the Light of X-Ray Observations

    Directory of Open Access Journals (Sweden)

    S. Balman

    2015-02-01

    Full Text Available Diversity of the X-ray observations of dwarf nova are still not fully understood. I review the X-ray spectral characteristics of dwarf novae during the quiescence in general explained by cooling flow models and the outburst spectra that show hard X-ray emission dominantly with few sources that reveal soft X-ray/EUV blackbody emission. The nature of aperiodic time variability of brightness of dwarf novae shows band limited noise, which can be adequately described in the framework of the model of propagating fluctuations. The frequency of the break (1-6 mHz indicates inner disk truncation of the optically thick disk with a range of radii (3.0-10.0×109 cm. The RXTE and optical (RTT150 data of SS Cyg in outburst and quiescence reveal that the inner disk radius moves towards the white dwarf and receeds as the outburst declines to quiescence. A preliminary analysis of SU UMa indicates a similar behaviour. In addition, I find that the outburst spectra of WZ Sge shows two component spectrum of only hard X-ray emission, one of which may be fitted with a power law suggesting thermal Comptonization occuring in the system. Cross-correlations between the simultaneous UV and X-ray light curves (XMM −Newton of five DNe in quiescence show time lags in the X-rays of 96-181 sec consistent with travel time of matter from a truncated inner disk to the white dwarf surface. All this suggests that dwarf novae and other plausible nonmagnetic systems have truncated accretion disks indicating that the disks may be partially evaporated and the accretion may occur through hot (coronal flows in the disk.

  18. Electronic structure analysis of UO2 by X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Ozkendir, O.M.

    2009-01-01

    Full text: Due to the essential role of Actinides in nuclear science and technology, electronic and structural investigations of actinide compounds attract major interest in science. Electronic structure of actinide compounds have important properties due to narrow 5f states which play key role in bonding with anions. The properties of Uranium has been a subject of enduring interest due to its being a major importance as a nuclear fuel and is the highest numbered element which can be found naturally on earth. UO 2 forms as a secondary uranyl group occurred during metamictization of uranium oxide compounds [1].Uranium oxide thin films have been investigated by X-ray Absorption Fine Structure spectroscopy (XAFS) [2]. The full multiple scattering approach has been applied to the calculation of U L3 edge spectra of UO 2 . The calculations are based on different choices of one electron potentials according to Uranium coordinations by using the real space multiple scattering method FEFF 8.2 code [3,4]. U L3-edge absorption spectrum in UO 2 is compared with U L3-edges in USiO 4 and UTe which are chosen due to their different electronic and chemical structures.We have found prominent changes in the XANES spectra of Uranium oxide thin films due to valency properties. Such observed changes are explained by considering the structural, electronic and spectroscopic properties. (author)

  19. Simulations of iron K pre-edge X-ray absorption spectra using the restricted active space method.

    Science.gov (United States)

    Guo, Meiyuan; Sørensen, Lasse Kragh; Delcey, Mickaël G; Pinjari, Rahul V; Lundberg, Marcus

    2016-01-28

    The intensities and relative energies of metal K pre-edge features are sensitive to both geometric and electronic structures. With the possibility to collect high-resolution spectral data it is important to find theoretical methods that include all important spectral effects: ligand-field splitting, multiplet structures, 3d-4p orbital hybridization, and charge-transfer excitations. Here the restricted active space (RAS) method is used for the first time to calculate metal K pre-edge spectra of open-shell systems, and its performance is tested against on six iron complexes: [FeCl6](n-), [FeCl4](n-), and [Fe(CN)6](n-) in ferrous and ferric oxidation states. The method gives good descriptions of the spectral shapes for all six systems. The mean absolute deviation for the relative energies of different peaks is only 0.1 eV. For the two systems that lack centrosymmetry [FeCl4](2-/1-), the ratios between dipole and quadrupole intensity contributions are reproduced with an error of 10%, which leads to good descriptions of the integrated pre-edge intensities. To gain further chemical insight, the origins of the pre-edge features have been analyzed with a chemically intuitive molecular orbital picture that serves as a bridge between the spectra and the electronic structures. The pre-edges contain information about both ligand-field strengths and orbital covalencies, which can be understood by analyzing the RAS wavefunction. The RAS method can thus be used to predict and rationalize the effects of changes in both the oxidation state and ligand environment in a number of hard X-ray studies of small and medium-sized molecular systems.

  20. 5 K extended X-ray absorption fine structure and 40 K 10-s resolved extended X-ray absorption fine structure studies of photolyzed carboxymyoglobin

    International Nuclear Information System (INIS)

    Teng, T.Y.; Huang, H.W.; Olah, G.A.

    1987-01-01

    A previous extended X-ray absorption fine structure (EXAFS) study of photolyzed carboxymyoglobin (MbCO) has provoked much discussion on the heme structure of the photoproduct (Mb*CO). The EXAFS interpretation that the Fe-Co distance increases by no more than 0.05 A following photodissociation has been regarded as inconsistent with optical, infrared, and magnetic susceptibility studies. The present experiment was performed with well-characterized dry film samples in which MbCO molecules were embedded in a poly(vinyl alcohol) matrix. The sample had a high protein concentration (12 mM) to yield adequate EXAFS signals but was very thin (40 μm) so that complete photolysis could be easily achieved by a single flash from a xenon lamp. Although the electronic state of Mb*CO resembles that of deoxymyoglobin (deoxy-Mb), direct comparison of EXAFS spectra indicates that structurally Mb*CO is much closer to MbCO than to deoxy-Mb. Our EXAFS analysis shows that photolysis of MbCO at 5 K leads to a stable intermediate state in which CO has moved away from iron by a distance of 0.27-0.45 A, but the 5-coordinate heme structure is strained in a form similar to that of MbCO; the resolution of the CO position depends on the structure parameters of MbCO which we use as a reference for the analysis of Mb*CO. At 40 K, from 1 to 10 s after photolysis, 42% of the photoproduct has relaxed to the ground state, and the EXAFS spectrum of the remaining photoproduct is indistinguishable from that of the 5 K photoproduct

  1. X-rays in protoplanetary disks : Their impact on the thermal and chemical structure, a grid of models

    NARCIS (Netherlands)

    Aresu, G.; Kamp, I.; Meijerink, R.; Woitke, P.; Thi, W. F.; Spaans, M.C.

    X-rays impact protoplanetary disks hydrostatic, thermal and chemical structure. The range of efficiency of X-rays is explored using a grid modelling approach: different parameters affects the structure of the disk, this determines different contribution of the X-ray radiation to the chemistry and

  2. Fast spectral fitting of hard X-ray bremsstrahlung from truncated power-law electron spectra

    Czech Academy of Sciences Publication Activity Database

    Brown, J. C.; Kašparová, Jana; Massone, A.M.; Piana, M.

    2008-01-01

    Roč. 486, č. 3 (2008), s. 1023-1029 ISSN 0004-6361 R&D Projects: GA ČR GP205/06/P135 Institutional research plan: CEZ:AV0Z10030501 Keywords : sun flares * X-rays * gamma rays Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.153, year: 2008

  3. Multiplet splitting of x-ray photoemission spectra core levels in magnetic metals

    International Nuclear Information System (INIS)

    Kowalczyk, S.P.; McFeely, F.R.; Ley, L.; Shirley, D.A.

    1975-01-01

    The results of high resolution x-ray photoemission studies of the multiplet splitting of the 3s core levels in the 3d transition metals and the 4s, 5s and 4d core levels in the lanthanide metals are reported

  4. Bone structure investigation using X-ray and neutron radiography techniques

    International Nuclear Information System (INIS)

    Kamali Moghaddam, K.; Taheri, T.; Ayubian, M.

    2008-01-01

    In this paper we report a study of the periodic variation of bone tissue humidity immediately after death using both neutron and X-ray radiography techniques. After death, bone tissue experiences sequential change over time. This change consists of organic and inorganic phase variations of the bone structure, as well as gradual reduction of the bone's water content. These variations are investigated by periodically imaging dead bone using X-ray and neutron radiography. Chemical separation techniques such as calcification and decalcification were used to separate the organic and inorganic phases of the bone. Comparison between X-ray and neutron radiographs of bone following phase separation can be potentially used to investigate the bone disease or to determine a cause of death. In our experiments, we use adult rat femur bones, and the interpretations of these results are presented based on our understanding of bone structure and images produced by neutron and X-ray photon interactions

  5. Bone structure investigation using X-ray and neutron radiography techniques

    Energy Technology Data Exchange (ETDEWEB)

    Kamali Moghaddam, K. [Nuclear Research Center (NRC), Atomic Energy Organization of Iran (AEOI), P.O. Box 11365-8486, Tehran (Iran, Islamic Republic of)], E-mail: kkamali@aeoi.org.ir; Taheri, T.; Ayubian, M. [Nuclear Research Center (NRC), Atomic Energy Organization of Iran (AEOI), P.O. Box 11365-8486, Tehran (Iran, Islamic Republic of)

    2008-01-15

    In this paper we report a study of the periodic variation of bone tissue humidity immediately after death using both neutron and X-ray radiography techniques. After death, bone tissue experiences sequential change over time. This change consists of organic and inorganic phase variations of the bone structure, as well as gradual reduction of the bone's water content. These variations are investigated by periodically imaging dead bone using X-ray and neutron radiography. Chemical separation techniques such as calcification and decalcification were used to separate the organic and inorganic phases of the bone. Comparison between X-ray and neutron radiographs of bone following phase separation can be potentially used to investigate the bone disease or to determine a cause of death. In our experiments, we use adult rat femur bones, and the interpretations of these results are presented based on our understanding of bone structure and images produced by neutron and X-ray photon interactions.

  6. Noninvasive 3D Structural Analysis of Arthropod by Synchrotron X-Ray Phase Contrast Tomography

    International Nuclear Information System (INIS)

    Yao, S.; Zong, Y.; Fan, J.; Sun, Z.; Jiang, H.

    2015-01-01

    X-ray imaging techniques significantly advanced our understanding of materials and biology, among which phase contrast X-ray microscopy has obvious advantages in imaging biological specimens which have low contrast by conventional absorption contrast microscopy. In this paper, three-dimensional microstructure of arthropod with high contrast has been demonstrated by synchrotron X-ray in-line phase contrast tomography. The external morphology and internal structures of an earthworm were analyzed based upon tomographic reconstructions with and without phase retrieval. We also identified and characterized various fine structural details such as the musculature system, the digestive system, the nervous system, and the circulatory system. This work exhibited the high efficiency, high precision, and wide potential applications of synchrotron X-ray phase contrast tomography in nondestructive investigation of low-density materials and biology.

  7. NEWFIT, a computer program for the analysis of alpha, X-ray and gamma-ray spectra

    International Nuclear Information System (INIS)

    Welch, R.B.; Gyger, F.; Jost, D.T.; Gunten, H.R. von; Kraehenbuehl, U.

    1988-01-01

    The computer program NEWFIT has been developed for analysis of gamma-ray, X-ray and alpha spectra. The general shape used for the analysis of activity peaks is a Gaussian function. An exponential tail can be added for use in alpha spectra analysis. The algorithms to analyze the peak shapes and the program operation are presented. Special features include the ability to create realistic peak shapes based on the systematic deviations of the real peaks from the theoretical Gaussian shape, as well as the option to constrain the calculated areas of peaks from a given emitting nuclide to their relative branching ratios. The program is available from the authors. (orig.)

  8. Analysis of the X-ray emission spectra of copper, germanium and rubidium plasmas produced at the Phelix laser facility

    Science.gov (United States)

    Comet, M.; Pain, J.-C.; Gilleron, F.; Piron, R.; Denis-Petit, D.; Méot, V.; Gosselin, G.; Morel, P.; Hannachi, F.; Gobet, F.; Tarisien, M.; Versteegen, M.

    2017-03-01

    We present the analysis of X-ray emission spectra of copper, germanium and rubidium plasmas measured at the Phelix laser facility. The laser intensity was around 6×1014 W.cm-2. The analysis is based on the hypothesis of an homogeneous plasma in local thermodynamic equilibrium using an effective temperature. This temperature is deduced from hydrodynamic simulations and collisional-radiative computations. Spectra are then calculated using the LTE opacity codes OPAMCDF and SCO-RCG and compared to experimental data.

  9. Ultrafast Structural Dynamics in InSb Probed by Time-Resolved X-Ray Diffraction

    International Nuclear Information System (INIS)

    Chin, A.H.; Shank, C.V.; Chin, A.H.; Schoenlein, R.W.; Shank, C.V.; Glover, T.E.; Leemans, W.P.; Balling, P.

    1999-01-01

    Ultrafast structural dynamics in laser-perturbed InSb are studied using time-resolved x-ray diffraction with a novel femtosecond x-ray source. We report the first observation of a delay in the onset of lattice expansion, which we attribute to energy relaxation processes and lattice strain propagation. In addition, we observe direct indications of ultrafast disordering on a subpicosecond time scale. copyright 1999 The American Physical Society

  10. Structural investigation of GaInP nanowires using X-ray diffraction

    DEFF Research Database (Denmark)

    Kriegner, D.; Persson, Johan Mikael; Etzelstorfer, T.

    2013-01-01

    In this work the structure of ternary GaxIn1−xP nanowires is investigated with respect to the chemical composition and homogeneity. The nanowires were grown by metal–organic vapor-phase epitaxy. For the investigation of ensemble fluctuations on several lateral length scales, X-ray diffraction...... gradients along the sample by recording diffraction patterns at different positions. In addition, compositional variations were found also within single nanowires in X-ray energy dispersive spectroscopy measurements....

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

    Science.gov (United States)

    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.

  12. Extended x-ray absorption fine structure spectroscopy and x-ray absorption near edge spectroscopy study of aliovalent doped ceria to correlate local structural changes with oxygen vacancies clustering

    Energy Technology Data Exchange (ETDEWEB)

    Shirbhate, S. C.; Acharya, S. A., E-mail: saha275@yahoo.com [Department of Physics, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur 440033 (India); Yadav, A. K. [Atomic and molecular Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2016-04-04

    This study provides atomic scale insight to understand the role of aliovalent dopants on oxygen vacancies clustering and dissociation mechanism in ceria system in order to enhance the performance of oxy-ion conductor. Dopants induced microscale changes in ceria are probed by extended X-ray absorption fine structure spectroscopy, X-ray absorption near edge spectra, and Raman spectroscopy. The results are explored to establish a correlation between atomic level structural changes (coordination number, interatomic spacing) → formation of dimer and trimer type cation-oxygen vacancies defect complex (intrinsic and extrinsic) → dissociation of oxygen vacancies from defect cluster → ionic conductivity temperature. It is a strategic approach to understand key physics of ionic conductivity mechanism in order to reduce operating temperature of electrolytes for intermediate temperature (300–450 °C) electrochemical devices for the first time.

  13. Local structure studies of Fe{sub 2}TeO{sub 6} using x-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Harishchandra, E-mail: singh85harish@gmail.com [Homi Bhabha National Institute, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India); Indus Synchrotron Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India); Yadav, A. K. [Atomic & Molecular Physics Division Bhabha Atomic Research Centre, Mumbai – 400 094 (India)

    2016-05-23

    In the present study, we have performed EXAFS measurements on powder samples of Fe{sub 2}TeO{sub 6} (FTO) to probe the local structure surrounding at the Fe site. The structural parameters (atomic coordination and lattice parameters) of FTO used for simulation of theoretical EXAFS spectra of the samples have been obtained from Rietveld refined structure on synchrotron X-ray Diffraction (SXRD) data. Quite similar and satisfactory structural parameters have been obtained from both the study, indicating goodness of synchrotron structural analysis over EXAFS analysis. SXRD and EXAFS results shows absence of any secondary phase proves current synthesis superior over reported techniques.

  14. Comparative Analysis and Variability of the Jovian X-Ray Spectra Detected by the Chandra and XMM-Newton Observatories

    Energy Technology Data Exchange (ETDEWEB)

    Hui, Yawei [ORNL; Schultz, David Robert [ORNL; Kharchenko, Vasili A [ORNL; Bhardwaj, Anil [Vikram Sarabhai Space Center, Trivandrum, India; Branduardi-Raymont, Graziella [University College, London; Stancil, Phillip C. [University of Georgia, Athens, GA; Cravens, Thomas E. E. [University of Kansas; Lisse, Carey M. [Johns Hopkins University; Dalgarno, A. [Harvard-Smithsonian Center for Astrophysics

    2010-01-01

    Expanding upon recent work, a more comprehensive spectral model based on charge exchange induced X-ray emission by ions precipitating into the Jovian atmosphere is used to provide new understanding of the polar auroras. In conjunction with the Xspec spectral fitting software, the model is applied to analyze observations from both Chandra and XMM-Newton by systematically varying the initial precipitating ion parameters to obtain the best fit model for the observed spectra. In addition to the oxygen and sulfur ions considered previously, carbon is included to discriminate between solar wind and Jovian magnetospheric ion origins, enabled by the use of extensive databases of both atomic collision cross sections and radiative transitions. On the basis of fits to all the Chandra observations, we find that carbon contributes negligibly to the observed polar X-ray emission suggesting that the highly accelerated precipitating ions are of magnetospheric origin. Most of the XMM-Newton fits also favor this conclusion with one exception that implies a possible carbon contribution. Comparison among all the spectra from these two observatories in light of the inferred initial energies and relative abundances of precipitating ions from the modeling show that they are significantly variable in time (observation date) and space (north and south polar X-ray auroras).

  15. Determination of Al concentration in Al doped ZnO using Auger spectra excited by Mo X-rays

    International Nuclear Information System (INIS)

    Toth, J.; Koever, L.; Cserny, I.; Varga, D.

    2006-01-01

    Complete text of publication follows. A good conductor with excellent transparency is of crucial importance for the window layer of CIGS solar cells. Al doped ZnO is a good candidate for this purpose, its conductivity depends on the concentration and chemical state of the Al dopant atoms. It was demonstrated that the non-conventional XPS using Mo X-rays for excitation is a very sensitive tool for the detection of Al, P, Si [1, 2, 3]. The present paper compares the experimental ratios for Zn/Al photoinduced peak intensity ratios obtained using both Al and Mo X-ray excitations. The Mo excited Zn/Al intensity ratios can be determined with higher selectivity and sensitivity than the Zn/Al intensity ratios excited by Al X-rays. The experiments were performed with a hemispherical deflector electron spectrometer [4]. The chemical state of the Al was identified to be close to that in Al 2 O 3 . The atomic concentrations were determined using a calibration curve based on ZnO/Al samples with known composition of Al. The energy dependent efficiency of the electron spectrometer was determined comparing REELS spectra of Cu specimen to standard spectra measured by K. Goto (Nagoya Institute of Technology, Japan). For evaluation of the Al atomic concentrations from the measured photoelectron intensities the photoionisation cross-sections of Band et al [5] and the IMFP data of S. Tanuma et al [6] and C.J. Powell and A. Jablonski [7] were used. (author)

  16. Analysis of X-ray Spectra of High-Z Elements obtained on Nike with high spectral and spatial resolution

    Science.gov (United States)

    Aglitskiy, Yefim; Weaver, J. L.; Karasik, M.; Serlin, V.; Obenschain, S. P.; Ralchenko, Yu.

    2014-10-01

    The spectra of multi-charged ions of Hf, Ta, W, Pt, Au and Bi have been studied on Nike krypton-fluoride laser facility with the help of two kinds of X-ray spectrometers. First, survey instrument covering a spectral range from 0.5 to 19.5 angstroms which allows simultaneous observation of both M- and N- spectra of above mentioned elements with high spectral resolution. Second, an imaging spectrometer with interchangeable spherically bent Quartz crystals that added higher efficiency, higher spectral resolution and high spatial resolution to the qualities of the former one. Multiple spectral lines with X-ray energies as high as 4 keV that belong to the isoelectronic sequences of Fe, Co, Ni, Cu and Zn were identified with the help of NOMAD package developed by Dr. Yu. Ralchenko and colleagues. In our continuous effort to support DOE-NNSA's inertial fusion program, this campaign covered a wide range of plasma conditions that result in production of relatively energetic X-rays. Work supported by the US DOE/NNSA.

  17. Analysis of the electronic structure of human hemoglobin from soft X-ray emission

    International Nuclear Information System (INIS)

    Soldatov, A.V.; Kravtsova, A.N.; Fedorovich, E.N.; Ankudinov, A.; Moewes, A.; Kurmaev, E.Z.

    2005-01-01

    We present X-ray emission spectra (XES) of human hemoglobin excited near the iron L 2,3 threshold and the nitrogen and carbon K-edges. The experiment is compared with our calculations of the corresponding spectra and gives good agreement. We find that the Fe L 3 emission is affected by the nearest nitrogen atoms located in the heme plane around the central iron atom. The distribution of the partial electronic densities of states of hemoglobin is determined

  18. Monte Carlo derivation of filtered tungsten anode X-ray spectra for dose computation in digital mammography

    Energy Technology Data Exchange (ETDEWEB)

    Paixao, L.; Oliveira, B. B.; Nogueira, M. do S. [Centro de Desenvolvimento da Tecnologia Nuclear, Post-graduation in Science and Technology of Radiations, Minerals and Materials, Pte. Antonio Carlos 6.627, Pampulha, 31270-901 Belo Horizonte (Brazil); Viloria, C. [UFMG, Departamento de Engenharia Nuclear, Post-graduation in Nuclear Sciences and Techniques, Pte. Antonio Carlos 6.627, Pampulha, 31270-901 Belo Horizonte (Brazil); Alves de O, M. [UFMG, Department of Anatomy and Imaging, Prof. Alfredo Balena 190, 30130-100 Belo Horizonte (Brazil); Araujo T, M. H., E-mail: lpr@cdtn.br [Dr Maria Helena Araujo Teixeira Clinic, Guajajaras 40, 30180-100 Belo Horizonte (Brazil)

    2014-08-15

    It is widely accepted that the mean glandular dose (D{sub G}) for the glandular tissue is the more useful magnitude for characterizing the breast cancer risk. The procedure to estimate the D{sub G}, for being difficult to measure it directly in the breast, it is to make the use of conversion factors that relate incident air kerma (K{sub i}) at this dose. Generally, the conversion factors vary with the x-ray spectrum half-value layer and the breast composition and thickness. Several authors through computer simulations have calculated such factors by the Monte Carlo (Mc) method. Many spectral models for D{sub G} computer simulations purposes are available in the diagnostic range. One of the models available generates unfiltered spectra. In this work, the Monte Carlo EGSnrc code package with the C++ class library (eg spp) was employed to derive filtered tungsten x-ray spectra used in digital mammography systems. Filtered spectra for rhodium and aluminium filters were obtained for tube potentials between 26 and 32 kV. The half-value layer of simulated filtered spectra were compared with those obtained experimentally with a solid state detector Unfors model 8202031-H Xi R/F and Mam Detector Platinum and 8201023-C Xi Base unit Platinum Plus w m As in a Hologic Selenia Dimensions system using a Direct Radiography mode. Calculated half-value layer values showed good agreement compared to those obtained experimentally. These results show that the filtered tungsten anode x-ray spectra and the EGSnrc Mc code can be used for D{sub G} determination in mammography. (Author)

  19. Monte Carlo derivation of filtered tungsten anode X-ray spectra for dose computation in digital mammography

    International Nuclear Information System (INIS)

    Paixao, L.; Oliveira, B. B.; Nogueira, M. do S.; Viloria, C.; Alves de O, M.; Araujo T, M. H.

    2014-08-01

    It is widely accepted that the mean glandular dose (D G ) for the glandular tissue is the more useful magnitude for characterizing the breast cancer risk. The procedure to estimate the D G , for being difficult to measure it directly in the breast, it is to make the use of conversion factors that relate incident air kerma (K i ) at this dose. Generally, the conversion factors vary with the x-ray spectrum half-value layer and the breast composition and thickness. Several authors through computer simulations have calculated such factors by the Monte Carlo (Mc) method. Many spectral models for D G computer simulations purposes are available in the diagnostic range. One of the models available generates unfiltered spectra. In this work, the Monte Carlo EGSnrc code package with the C++ class library (eg spp) was employed to derive filtered tungsten x-ray spectra used in digital mammography systems. Filtered spectra for rhodium and aluminium filters were obtained for tube potentials between 26 and 32 kV. The half-value layer of simulated filtered spectra were compared with those obtained experimentally with a solid state detector Unfors model 8202031-H Xi R/F and Mam Detector Platinum and 8201023-C Xi Base unit Platinum Plus w m As in a Hologic Selenia Dimensions system using a Direct Radiography mode. Calculated half-value layer values showed good agreement compared to those obtained experimentally. These results show that the filtered tungsten anode x-ray spectra and the EGSnrc Mc code can be used for D G determination in mammography. (Author)

  20. Microbeam high-resolution diffraction and x-ray standing wave methods applied to semiconductor structures

    International Nuclear Information System (INIS)

    Kazimirov, A; Bilderback, D H; Huang, R; Sirenko, A; Ougazzaden, A

    2004-01-01

    A new approach to conditioning x-ray microbeams for high angular resolution x-ray diffraction and scattering techniques is introduced. We combined focusing optics (one-bounce imaging capillary) and post-focusing collimating optics (miniature Si(004) channel-cut crystal) to generate an x-ray microbeam with a size of 10 μm and ultimate angular resolution of 14 μrad. The microbeam was used to analyse the strain in sub-micron thick InGaAsP epitaxial layers grown on an InP(100) substrate by the selective area growth technique in narrow openings between the oxide stripes. For the structures for which the diffraction peaks from the substrate and the film overlap, the x-ray standing wave technique was applied for precise measurements of the strain with a Δd/d resolution of better than 10 -4 . (rapid communication)

  1. Laser plasmas as x-ray sources for lithographic imaging of submicron structures

    International Nuclear Information System (INIS)

    Bijkerk, F.; van Dorssen, G.E.; van der Wiel, M.J.

    1988-01-01

    Laser radiation can be used efficiently to generate x-rays for lithographic imaging of submicron patterns, e.g., for VLSI device fabrication. Due to their short wavelength and high average power, excimer lasers show much potential for this application. Results are presented of scaling studies for high repetition rate excimer laser application, using the frequency doubled output of a low repetition rate Nd:YAG/Glass laser. Spectral and spatial characteristics of x-ray emission of the laser plasma are shown. The power density in the laser focus was 3 x 10 12 W/cm 2 . With this source Si x-ray masks with submicron Au absorber profiles are imaged into high sensitivity x-ray photoresist. For the exposures 80 laser shots sufficed to yield high quality submicron structures. Extrapolation of the results to a high power excimer laser reduces the exposure time of the photoresists to several seconds, enabling a wafer throughput at an industrial level

  2. Implications for gravitational lensing and the dark matter content in clusters of galaxies from spatially resolved x-ray spectra

    Science.gov (United States)

    Loewenstein, M.

    1994-01-01

    A simple method for deriving well-behaved temperature solutions to the equation of hydrostatic equilibrium for intracluster media with X-ray imaging observations is presented and applied to a series of generalized models as well as to observations of the Perseus cluster and Abell 2256. In these applications the allowed range in the ratio of nonbaryons to baryons as a function of radius is derived, taking into account the uncertainties and crude spatial resolution of the X-ray spectra and considering a range of physically reasonable mass models with various scale heights. Particular attention is paid to the central regions of the cluster, and it is found that the dark matter can be sufficiently concentrated to be consistent with the high central mass surface densities for moderate-redshift clusters from their gravitational lensing properties.

  3. Simultaneous acquisition of X-ray spectra using a multi-wire, position-sensitive gas flow detector

    International Nuclear Information System (INIS)

    Beaven, Peter A.; Marmotti, Mauro; Kampmann, Reinhard; Knoth, Joachim; Schwenke, Heinrich

    2003-01-01

    A multi-wire, gas-filled position-sensitive detector has been developed for the simultaneous recording of wavelength-dispersed X-ray signals that enables X-ray fluorescence spectrometry with a limited multi-element capability in the low Z element range. Details of the modular construction of the detector are given. The detector performance was characterized using Al-Kα radiation and a variable slit system. The detector has been applied in a laboratory spectrometer equipped with an electron source and a double multilayer mirror device as the wavelength-dispersing element. Spectra from Al and Si obtained in the simultaneous acquisition mode show good agreement with calculations performed using a ray-tracing model

  4. X-ray laser diffraction for structure determination of the rhodopsin-arrestin complex

    Science.gov (United States)

    Zhou, X. Edward; Gao, Xiang; Barty, Anton; Kang, Yanyong; He, Yuanzheng; Liu, Wei; Ishchenko, Andrii; White, Thomas A.; Yefanov, Oleksandr; Han, Gye Won; Xu, Qingping; de Waal, Parker W.; Suino-Powell, Kelly M.; Boutet, Sébastien; Williams, Garth J.; Wang, Meitian; Li, Dianfan; Caffrey, Martin; Chapman, Henry N.; Spence, John C. H.; Fromme, Petra; Weierstall, Uwe; Stevens, Raymond C.; Cherezov, Vadim; Melcher, Karsten; Xu, H. Eric

    2016-04-01

    Serial femtosecond X-ray crystallography (SFX) using an X-ray free electron laser (XFEL) is a recent advancement in structural biology for solving crystal structures of challenging membrane proteins, including G-protein coupled receptors (GPCRs), which often only produce microcrystals. An XFEL delivers highly intense X-ray pulses of femtosecond duration short enough to enable the collection of single diffraction images before significant radiation damage to crystals sets in. Here we report the deposition of the XFEL data and provide further details on crystallization, XFEL data collection and analysis, structure determination, and the validation of the structural model. The rhodopsin-arrestin crystal structure solved with SFX represents the first near-atomic resolution structure of a GPCR-arrestin complex, provides structural insights into understanding of arrestin-mediated GPCR signaling, and demonstrates the great potential of this SFX-XFEL technology for accelerating crystal structure determination of challenging proteins and protein complexes.

  5. ERX: a software for editing files containing X-ray spectra to be used in exposure computational models

    International Nuclear Information System (INIS)

    Cabral, Manuela O.M.; Vieira, Jose W.; Silva, Alysson G.; Leal Neto, Viriato; Oliveira, Alex C.H.; Lima, Fernando R.A.

    2011-01-01

    Exposure Computational Models (ECMs) are utilities that simulate situations in which occurs irradiation in a given environment. An ECM is composed primarily by an anthropomorphic model (phantom), and a Monte Carlo code (MC). This paper presents a tutorial of the software Espectro de Raios-X (ERX). This software performs reading and numerical and graphical analysis of text files containing diagnostic X-ray spectra for use in algorithms of radioactive sources in the ECMs of a Grupo de Dosimetria Numerica. The ERX allows the user to select one among several X-ray spectrums in the energy range Diagnostic radiology X-Ray most commonly used in radiology clinics. In the current version of the ERX there are two types of input files: the contained in mspectra.dat file and the resulting of MC simulations in Geant4. The software allows the construction of charts of the Probability Density Function (PDF) and Cumulative Distribution Function (CDF) of a selected spectrum as well as the table with the values of these functions and the spectrum. In addition, the ERX allows the user to make comparative analysis between the PDF graphics of the two catalogs of spectra available, besides being can perform dosimetric evaluations with the selected spectrum. A software of this kind is an important computational tool for researchers in numerical dosimetry because of the diversity of Diagnostic radiology X-Ray machines, which implies in a mass of input data highly diverse. And because of this, the ERX provides independence to the group related to the data origin that is contained in the catalogs created, not being necessary to resort to others. (author)

  6. Electronic structure of multiferroic BiFeO3 by resonant soft-x-ray emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Higuchi, Tohru; Higuchi, T.; Liu, Y.-S.; Yao, P.; Glans, P.-A.; Guo, Jinghua; Chang, C.; Wu, Z.; Sakamoto, W.; Itoh, N.; Shimura, T.; Yogo, T.; Hattori, T.

    2008-07-11

    The electronic structure of multiferroic BiFeO{sub 3} has been studied using soft-X-ray emission spectroscopy. The fluorescence spectra exhibit that the valence band is mainly composed of O 2p state hybridized with Fe 3d state. The band gap corresponding to the energy separation between the top of the O 2p valence band and the bottom of the Fe 3d conduction band is 1.3 eV. The soft-X-ray Raman scattering reflects the features due to charge transfer transition from O 2p valence band to Fe 3d conduction band. These findings are similar to the result of electronic structure calculation by density functional theory within the local spin-density approximation that included the effect of Coulomb repulsion between localized d states.

  7. Correction of diagnostic x-ray spectra measured with CdTe and CdZnTe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, M [Osaka Univ., Suita (Japan). Medical School; Kanamori, H; Toragaito, T; Taniguchi, A

    1996-07-01

    We modified the formula of stripping procedure presented by E. Di. Castor et al. We added the Compton scattering and separated K{sub {alpha}} radiation of Cd and Te (23 and 27keV, respectively). Using the new stripping procedure diagnostic x-ray spectra (object 4mm-Al) of tube voltage 50kV to 100kV for CdTe and CdZnTe detectors are corrected with comparison of those spectra for the Ge detector. The corrected spectra for CdTe and CdZnTe detectors coincide with those for Ge detector at lower tube voltage than 70kV. But the corrected spectra at higher tube voltage than 70kV do not coincide with those for Ge detector. The reason is incomplete correction for full energy peak efficiencies of real CdTe and CdZnTe detectors. (J.P.N.)

  8. High-resolution X-ray spectra from low-temperature, highly charged ions

    International Nuclear Information System (INIS)

    Beiersdorfer, P.

    1996-09-01

    The electron beam ion traps (EBIT) at Livermore were designed for studying the x-ray emission of highly charged ions produced and excited by a monoenergetic electron beam. The precision with which the x-ray emission can be analyzed has recently been increased markedly when it became possible to decouple the temperature of the ions from the energy of the electron beam by several orders of magnitude. By adjusting the trap parameters, ion temperatures as low as 15.8±4.4 eV for Ti 20+ and 59.4±9.9 eV for Cs 45+ were achieved. These temperatures were more than two orders of magnitude lower than the energy of the multi-keV electron beam used for the production and excitation of the ions. A discussion of the techniques used to produce and study low-temperature highly charged ions is presented in this progress report. The low ion temperatures enabled measurements heretofore impossible. As an example, a direct observation of the natural line width of fast electric dipole allowed x-ray transitions is described. From the observed natural line width and b making use of the time-energy relations of the uncertainty principle we were able to determine a radiative transition rate of 1.65 fs for the 2p-3d resonance transition in neonlike Cs 45+ . A brief discussion of other high-precision measurements enabled by our new technique is also given

  9. High-resolution x-ray spectroscopy of coherent bremsstrahlung fine structure

    International Nuclear Information System (INIS)

    Lund, M.W.

    1989-01-01

    The aim of this research was to provide experimental evidence for fine structure due to umklapp by distinct reciprocal lattice vectors in coherent bremsstrahlung spectra. The spontaneous emission of photons by relativistic electrons transversing thin crystals is made possible by recoil of the crystal, which absorbs momentum in multiples of ℎG where G is a reciprocal lattice vector. Previous work in the MeV-GeV beam energy range used detectors whose energy resolution was greater than 10%. By fitting a Johann wavelength dispersive spectrometer to a transmission electron microscope the author obtained coherent bremsstrahlung spectra of very high quality with energy resolution of 1%. Important to this result were also the fine angular collimation, small energy width of the electron beam in the microscope, and the accurate control of crystal orientation possible in a modern goniometer stage. The theory of the design of bent crystal x-ray spectrometers is extended to include effects of defocus and aberrations. The theory for diffraction from a stationary three dimensional grating due to a dipole radiator moving at relativistic speeds is derived as well as several other broadening mechanisms stemming from experimental variables. This dissertation provides the first experimental observations and corresponding theoretical background for the fine structure of coherent bremsstrahlung due to umklapp by different G-vectors in the same reciprocal lattice plane

  10. Isolation, Characterization and X-ray Structure Determination of the ...

    African Journals Online (AJOL)

    NICO

    2014-12-20

    Dec 20, 2014 ... applications in diverse areas.1 They can be used in laser materials, as 1H NMR shift reagents, ... spectra were measured at 400.22 and 100.63 MHz, respectively, ..... tions in solutions and in the gas phase, J. Mol. Struct., 2001 ...

  11. X-ray absorption fine structure (XAFS) studies of cobalt silicide thin films

    International Nuclear Information System (INIS)

    Naftel, S.J.; Coulthard, I.; Hu, Y.; Sham, T.K.; Zinke-Allmang, M.

    1998-01-01

    Cobalt silicide thin films, prepared on Si(100) wafers, have been studied by X-ray absorption near edge structures (XANES) at the Si K-, L 2,3 - and Co K-edges utilizing both total electron (TEY) and fluorescence yield (FLY) detection as well as extended X-ray absorption fine structure (EXAFS) at the Co K-edge. Samples made using DC sputter deposition on clean Si surfaces and MBE were studied along with a bulk CoSi 2 sample. XANES and EXAFS provide information about the electronic structure and morphology of the films. It was found that the films studied have essentially the same structure as bulk CoSi 2 . Both the spectroscopy and materials characterization aspects of XAFS (X-ray absorption fine structures) are discussed

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

    Energy Technology Data Exchange (ETDEWEB)

    Hamad, Kimberly Sue [Univ. of California, Berkeley, CA (United States)

    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.

  13. Indirect measure of X-rays spectra using TLDs; Medicion indirecta de espectros de rayos X utilizando TLDs

    Energy Technology Data Exchange (ETDEWEB)

    Bonzi, E. V.; Mainardi, R. T. [Universidad Nacional de Cordoba, Facultad de Matematica, Astronomia y Fisica, Av. Haya de la Torre y Av. Medina Allende s/n, Ciudad Universitaria, X5016LEA Cordoba (Argentina)

    2011-10-15

    A methodology of indirect measure of X-rays spectra, emitted by conventional tubes, was developed recently and its feasibility verified in the first place by Monte Carlo simulations. For that case is intended to measure, by means of plastic scintillators, attenuation curves of dispersed beams previously. In this work were carried out measurements of attenuation curves with thermoluminescent dosimeters (TLD) to verify the kindness of the indirect measure method. The attenuation curve was also measured using an ionization chamber brand Capintec (model 192) with the purpose of making a comparison. The results of the attenuation curve measured with both dosimeters present a good resolution inside the statistical fluctuations and the spectral reconstruction using diverse parametric functions is carried out in a quick and simple way with excellent resolutions in the functional form. For this reconstruction method are of fundamental importance the following properties of the used dosimeter: in the first place the repetition of the measures, property that could check; in second place the precision of the measured data and lastly the dosimeter response, this is, the increase of the thermoluminescent signal before an increase of the photons flow of X-rays. This parameter is the gradient of the curve thermoluminescent signal versus the dose imparted to the dosimeter. The measures were realized with a generator of X-rays brand Kevex provided of a conventional tube with tungsten anti cathode that polarizes with high tension to a maximum value of 50 kV and current of 0.5 ma. (Author)

  14. Fabrication of high-aspect-ratio nano structures using a nano x-ray shadow mask

    International Nuclear Information System (INIS)

    Kim, Yong Chul; Lee, Seung S

    2008-01-01

    This paper describes a novel method for the fabrication of high-aspect-ratio nano structures (HAR-nano structures) using a nano x-ray shadow mask and deep x-ray lithography (DXRL). The nano x-ray shadow mask is fabricated by depositing an x-ray absorber layer (Au, 3 µm) onto the back side of a nano shadow mask. The nano shadow mask is produced with nano-sized apertures whose dimensions are reduced to several tens of nanometers by the accumulation of low-stress silicon nitride (Si x N y ) using the LPCVD process on the shadow mask. A shadow mask containing apertures with a size of 1 µm is fabricated on a bulk micromachined Si x N y membrane. The thickness of an absorber layer must be in the range of several tens of micrometers in order to obtain a contrast of more than 100 for the conventional DXRL process at the Pohang Light Source (PLS). However, a 3 µm thick absorber layer can provide a sufficient contrast if the modified DXRL of the central beam-stop method is used, which blocks high-energy x-rays. A nano shadow mask with 30 nm sized apertures is fabricated and a nano x-ray shadow mask with 250 nm sized apertures is fabricated by depositing a 3 µm thick absorber layer on a nano shadow mask with 500 nm sized apertures. HAR-nano structures (circles with a diameter of 420 nm and lines with a width of 274 nm) with aspect ratios of over 10:1 on a 3.2 µm SU-8 are successfully fabricated by using the nano x-ray shadow mask and the central beam-stop method

  15. Modeling Radiation Effects of Ultrasoft X Rays on the Basis of Amorphous Track Structure.

    Science.gov (United States)

    Buch, Tamara; Scifoni, Emanuele; Krämer, Michael; Durante, Marco; Scholz, Michael; Friedrich, Thomas

    2018-01-01

    There is experimental evidence that ultrasoft X rays (0.1-5 keV) show a higher biological effectiveness than high-energy photons. Similar to high-LET radiation, this is attributed to a rather localized dose distribution associated with a considerably smaller range of secondary electrons, which results in an increasing yield of double-strand breaks (DSBs) and potentially more complex lesions. We previously reported on the application of the Giant LOop Binary LEsion (GLOBLE) model to ultrasoft X rays, in which experimental values of the relative biological effectiveness (RBE) for DSB induction were used to show that this increasing DSB yield was sufficient to explain the enhanced effectiveness in the cell inactivation potential of ultrasoft X rays. Complementary to GLOBLE, we report here on a modeling approach to predict the increased DSB yield of ultrasoft X rays on the basis of amorphous track structure formed by secondary electrons, which was derived from Monte Carlo track structure simulations. This procedure is associated with increased production of single-strand break (SSB) clusters, which are caused by the highly localized energy deposition pattern induced by low-energy photons. From this, the RBE of ultrasoft X rays can be determined and compared to experimental data, showing that the inhomogeneity of the energy deposition pattern represents the key variable to describe the increased biological effectiveness of ultrasoft X rays. Thus, this work demonstrates an extended applicability of the amorphous track structure concept and tests its limits with respect to its predictive power. The employed model mechanism offers a possible explanation for how the cellular response to ultrasoft X rays is directly linked to the energy deposition properties on the nanometric scale.

  16. 3D visualization of subcellular structures of Schizosaccharomyces pombe by hard X-ray tomography.

    Science.gov (United States)

    Yang, Y; Li, W; Liu, G; Zhang, X; Chen, J; Wu, W; Guan, Y; Xiong, Y; Tian, Y; Wu, Z

    2010-10-01

    Cellular structures of the fission yeast, Schizosaccharomyces pombe, were examined by using hard X-ray tomography. Since cells are nearly transparent to hard X-rays, Zernike phase contrast and heavy metal staining were introduced to improve image contrast. Through using such methods, images taken at 8 keV displayed sufficient contrast for observing cellular structures. The cell wall, the intracellular organelles and the entire structural organization of the whole cells were visualized in three-dimensional at a resolution better than 100 nm. Comparison between phase contrast and absorption contrast was also made, indicating the obvious advantage of phase contrast for cellular imaging at this energy. Our results demonstrate that hard X-ray tomography with Zernike phase contrast is suitable for cellular imaging. Its unique abilities make it have potential to become a useful tool for revealing structural information from cells, especially thick eukaryotic cells. © 2010 The Authors Journal compilation © 2010 The Royal Microscopical Society.

  17. X-ray-to-current signal conversion characteristics of trench-structured photodiodes for direct-conversion-type silicon X-ray sensor

    International Nuclear Information System (INIS)

    Ariyoshi, Tetsuya; Funaki, Shota; Sakamoto, Kenji; Baba, Akiyoshi; Arima, Yutaka

    2017-01-01

    To reduce the radiation dose required in medical X-ray diagnoses, we propose a high-sensitivity direct-conversion-type silicon X-ray sensor that uses trench-structured photodiodes. This sensor is advantageous in terms of its long device lifetime, noise immunity, and low power consumption because of its low bias voltage. With this sensor, it is possible to detect X-rays with almost 100% efficiency; sensitivity can therefore be improved by approximately 10 times when compared with conventional indirect-conversion-type sensors. In this study, a test chip was fabricated using a single-poly single-metal 0.35 μm process. The formed trench photodiodes for the X-ray sensor were approximately 170 and 300 μm deep. At a bias voltage of 25 V, the absorbed X-ray-to-current signal conversion efficiencies were 89.3% (theoretical limit; 96.7%) at a trench depth of 170 μm and 91.1% (theoretical limit; 94.3%) at a trench depth of 300 μm. (author)

  18. Spectroscopic and X-ray Diffraction Study of Structural Disorder in Cryomilled and Amorphous Griseofulvin

    International Nuclear Information System (INIS)

    Zarow, A.; Zhou, B.; Wang, X.; Pinal, R.; Iqbal, Z.

    2011-01-01

    Structural disorder induced by cryogenic milling and by heating to the amorphous phase in the active pharmaceutical ingredient Griseofulvin has been studied using Raman spectroscopy, X-ray powder diffraction (XRPD), and fluorescence spectroscopy. A broad, exciting-frequency-independent scattering background in the Raman spectra and changes in intensities and splitting of some of the Raman lines due to lattice and molecular modes have been observed. In the cryomilled samples this strong background is deconvoluted into two components: one due to lattice disorder induced by cryomilling and the other due to Mie scattering from nanosized crystallites. A single-component background scattering attributed to lattice disorder is seen in the Raman spectrum of the amorphous sample. Fluorescence measurements showed an intrinsic fluorescence signal in as-received Griseofulvin that does not correspond to the inelastic background in the Raman spectra and, moreover, decreases in intensity upon cryomilling, thus excluding an assignment of the Raman background intensity to impurity- or molecular-defect-induced fluorescence. Wide-angle XRPD measurements on cryomilled Griseofulvin shows a broad two-component background consistent with the background-scattering component in the Raman data associated with lattice disorder, but at longer correlation lengths. Persistence of this disorder to even longer lengths is evident in small-angle synchrotron XRPD data on micronized Griseofulvin taken as a function of temperature from the crystalline to the amorphous phase.

  19. X-ray Emitting GHz-Peaked Spectrum Galaxies: Testing a Dynamical-Radiative Model with Broad-Band Spectra

    International Nuclear Information System (INIS)

    Ostorero, L.; Moderski, R.; Stawarz, L.; Diaferio, A.; Kowalska, I.; Cheung, C.C.; Kataoka, J.; Begelman, M.C.; Wagner, S.J.

    2010-01-01

    In a dynamical-radiative model we recently developed to describe the physics of compact, GHz-Peaked-Spectrum (GPS) sources, the relativistic jets propagate across the inner, kpc-sized region of the host galaxy, while the electron population of the expanding lobes evolves and emits synchrotron and inverse-Compton (IC) radiation. Interstellar-medium gas clouds engulfed by the expanding lobes, and photoionized by the active nucleus, are responsible for the radio spectral turnover through free-free absorption (FFA) of the synchrotron photons. The model provides a description of the evolution of the GPS spectral energy distribution (SED) with the source expansion, predicting significant and complex high-energy emission, from the X-ray to the γ-ray frequency domain. Here, we test this model with the broad-band SEDs of a sample of eleven X-ray emitting GPS galaxies with Compact-Symmetric-Object (CSO) morphology, and show that: (i) the shape of the radio continuum at frequencies lower than the spectral turnover is indeed well accounted for by the FFA mechanism; (ii) the observed X-ray spectra can be interpreted as non-thermal radiation produced via IC scattering of the local radiation fields off the lobe particles, providing a viable alternative to the thermal, accretion-disk dominated scenario. We also show that the relation between the hydrogen column densities derived from the X-ray (N H ) and radio (N HI ) data of the sources is suggestive of a positive correlation, which, if confirmed by future observations, would provide further support to our scenario of high-energy emitting lobes.

  20. Multifractal Analysis of Seismically Induced Soft-Sediment Deformation Structures Imaged by X-Ray Computed Tomography

    Science.gov (United States)

    Nakashima, Yoshito; Komatsubara, Junko

    Unconsolidated soft sediments deform and mix complexly by seismically induced fluidization. Such geological soft-sediment deformation structures (SSDSs) recorded in boring cores were imaged by X-ray computed tomography (CT), which enables visualization of the inhomogeneous spatial distribution of iron-bearing mineral grains as strong X-ray absorbers in the deformed strata. Multifractal analysis was applied to the two-dimensional (2D) CT images with various degrees of deformation and mixing. The results show that the distribution of the iron-bearing mineral grains is multifractal for less deformed/mixed strata and almost monofractal for fully mixed (i.e. almost homogenized) strata. Computer simulations of deformation of real and synthetic digital images were performed using the egg-beater flow model. The simulations successfully reproduced the transformation from the multifractal spectra into almost monofractal spectra (i.e. almost convergence on a single point) with an increase in deformation/mixing intensity. The present study demonstrates that multifractal analysis coupled with X-ray CT and the mixing flow model is useful to quantify the complexity of seismically induced SSDSs, standing as a novel method for the evaluation of cores for seismic risk assessment.

  1. Processing and quantification of x-ray energy dispersive spectra in the Analytical Electron Microscope

    International Nuclear Information System (INIS)

    Zaluzec, N.J.

    1988-08-01

    Spectral processing in x-ray energy dispersive spectroscopy deals with the extraction of characteristic signals from experimental data. In this text, the four basic procedures for this methodology are reviewed and their limitations outlined. Quantification, on the other hand, deals with the interpretation of the information obtained from spectral processing. Here the limitations are for the most part instrumental in nature. The prospects of higher voltage operation does not, in theory, present any new problems and may in fact prove to be more desirable assuming that electron damage effects do not preclude analysis. 28 refs., 6 figs

  2. Detailed analysis of hollow ions spectra from dense matter pumped by X-ray emission of relativistic laser plasma

    International Nuclear Information System (INIS)

    Hansen, S. B.; Colgan, J.; Abdallah, J.; Faenov, A. Ya.; Pikuz, S. A.; Skobelev, I. Yu.; Wagenaars, E.; Culfa, O.; Dance, R. J.; Tallents, G. J.; Rossall, A. K.; Woolsey, N. C.; Booth, N.; Lancaster, K. L.; Evans, R. G.; Gray, R. J.; McKenna, P.; Kaempfer, T.; Schulze, K. S.; Uschmann, I.

    2014-01-01

    X-ray emission from hollow ions offers new diagnostic opportunities for dense, strongly coupled plasma. We present extended modeling of the x-ray emission spectrum reported by Colgan et al. [Phys. Rev. Lett. 110, 125001 (2013)] based on two collisional-radiative codes: the hybrid-structure Spectroscopic Collisional-Radiative Atomic Model (SCRAM) and the mixed-unresolved transition arrays (MUTA) ATOMIC model. We show that both accuracy and completeness in the modeled energy level structure are critical for reliable diagnostics, investigate how emission changes with different treatments of ionization potential depression, and discuss two approaches to handling the extensive structure required for hollow-ion models with many multiply excited configurations

  3. Pulsator-like Spectra from Ultraluminous X-Ray Sources and the Search for More Ultraluminous Pulsars

    International Nuclear Information System (INIS)

    Pintore, F.; Mereghetti, S.; Zampieri, L.; Stella, L.; Israel, G. L.; Wolter, A.

    2017-01-01

    Ultraluminous X-ray sources (ULXs) are a population of extragalactic objects whose luminosity exceeds the Eddington limit for a 10 M ⊙ black hole (BH). Their properties have been widely interpreted in terms of accreting stellar-mass or intermediate-mass BHs. However at least three neutron stars (NSs) have been recently identified in ULXs through the discovery of periodic pulsations. Motivated by these findings we studied the spectral properties of a sample of bright ULXs using a simple continuum model which was extensively used to fit the X-ray spectra of accreting magnetic NSs in the Galaxy. We found that such a model, consisting of a power-law with a high-energy exponential cut-off, fits most of the ULX spectra analyzed here very well, at a level comparable to that of models involving an accreting BH. On these grounds alone we suggest that other non-pulsating ULXs may host NSs. We also found that above 2 keV the spectrum of known pulsating ULXs is harder than that of the majority of the other ULXs of the sample, with only IC 342 X-1 and Ho IX X-1 displaying spectra of comparable hardness. We thus suggest that these two ULXs may host an accreting NS and encourage searches for periodic pulsations in the flux.

  4. Pulsator-like Spectra from Ultraluminous X-Ray Sources and the Search for More Ultraluminous Pulsars

    Energy Technology Data Exchange (ETDEWEB)

    Pintore, F.; Mereghetti, S. [INAF-IASF Milano, via E. Bassini 15, I-20133 Milano (Italy); Zampieri, L. [INAF-Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova (Italy); Stella, L.; Israel, G. L. [INAF—Osservatorio astronomico di Roma, Via Frascati 44, I-00078, Monteporzio Catone (Italy); Wolter, A. [INAF, Osservatorio Astronomico di Brera, via Brera 28, I-20121 Milano (Italy)

    2017-02-10

    Ultraluminous X-ray sources (ULXs) are a population of extragalactic objects whose luminosity exceeds the Eddington limit for a 10 M {sub ⊙} black hole (BH). Their properties have been widely interpreted in terms of accreting stellar-mass or intermediate-mass BHs. However at least three neutron stars (NSs) have been recently identified in ULXs through the discovery of periodic pulsations. Motivated by these findings we studied the spectral properties of a sample of bright ULXs using a simple continuum model which was extensively used to fit the X-ray spectra of accreting magnetic NSs in the Galaxy. We found that such a model, consisting of a power-law with a high-energy exponential cut-off, fits most of the ULX spectra analyzed here very well, at a level comparable to that of models involving an accreting BH. On these grounds alone we suggest that other non-pulsating ULXs may host NSs. We also found that above 2 keV the spectrum of known pulsating ULXs is harder than that of the majority of the other ULXs of the sample, with only IC 342 X-1 and Ho IX X-1 displaying spectra of comparable hardness. We thus suggest that these two ULXs may host an accreting NS and encourage searches for periodic pulsations in the flux.

  5. Rapid X-ray crystal structure analysis in few second measurements using microstrip gas chamber

    CERN Document Server

    Ochi, A; Tanimori, T; Ohashi, Y; Toyokawa, H; Nishi, Y; Nishi, Y; Nagayoshi, T; Koishi, S

    2001-01-01

    X-ray crystal structure analysis using microstrip gas chamber was successfully carried out in a measurement time within a few seconds. The continuous rotation photograph method, in which most of the diffraction peaks can be obtained within one continuous rotation of the sample crystal (without stopping or oscillation), was applied for this measurement. As an example, the structure of a single crystal of ammonium bitartrate (r=1 mm, spherical) was measured. Diffraction spots from the sample, which were sufficient to obtain crystal structure, were successfully obtained by taking only 2 s measurements with a commercially available laboratory X-ray source.

  6. New structural studies of liquid crystal by reflectivity and resonant X-ray diffraction

    International Nuclear Information System (INIS)

    Fernandes, P.

    2007-04-01

    This memory presents three structural studies of smectic Liquid Crystals by reflectivity and resonant diffraction of X-rays. It is divided in five chapters. In the first a short introduction to Liquid Crystals is given. In particular, the smectic phases that are the object of this study are presented. The second chapter is consecrated to the X-ray experimental techniques that were used in this work. The three last chapters present the works on which this thesis can be divided. Chapter three demonstrates on free-standing films of MHPOBC (historic liquid crystal that possesses the antiferroelectric sub-phases) the possibility to extend the technique of resonant X-ray diffraction to liquid crystals without resonant element. In the fourth chapter the structure of the B 2 liquid crystal phase of bent-core molecules (or banana molecules) is elucidated by using resonant X-ray diffraction combined with polarization analysis of the diffracted beam. A model of the polarization of the resonant beam diffracted by four different structures proposed for the B 2 phase is developed in this chapter. In the fifth chapter a smectic binary mixture presenting a very original critical point of phase separation is studied by X-ray reflectivity and optical microscopy. A concentration gradient in the direction perpendicular to the plane of the film seems to be induced by the free-standing film geometry. The results of a simplified model of the system are compatible with this interpretation

  7. X-Ray structure and biophysical properties of rabbit fibroblast growth factor 1

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jihun; Blaber, Sachiko I.; Irsigler, Andre; Aspinwall, Eric; Blaber, Michael; (FSU)

    2010-01-14

    The rabbit is an important and de facto animal model in the study of ischemic disease and angiogenic therapy. Additionally, fibroblast growth factor 1 (FGF-1) is emerging as one of the most important growth factors for novel pro-angiogenic and pro-arteriogenic therapy. However, despite its significance, the fundamental biophysical properties of rabbit FGF-1, including its X-ray structure, have never been reported. Here, the cloning, crystallization, X-ray structure and determination of the biophysical properties of rabbit FGF-1 are described. The X-ray structure shows that the amino-acid differences between human and rabbit FGF-1 are solvent-exposed and therefore potentially immunogenic, while the biophysical studies identify differences in thermostability and receptor-binding affinity that distinguish rabbit FGF-1 from human FGF-1.

  8. The rotation of accretion-disks and the power spectra of X-rays 'flickering'

    International Nuclear Information System (INIS)

    Zhang Xiaohe; Bao Gang

    1990-07-01

    The X-ray producing, inner region of the accretion disk in Active Galactic Nuclei (AGN) is likely to be non-stationary and non-axisymmetric. This non-stationarity and non-axisymmetry in disk surface brightness may be modeled by considering the pre-sense of many 'hot spots' on a steady, axisymmetric disk. As long as a 'spot' can survive for a few orbital periods, its orbital frequency can be introduced into the light curve either by relativistic orbital motion or by eclipsing of the spot by the disk. These rotational effects vary with the local properties of the spot population. Depending on the radial variation of spot brightness, lifetime and number density, the observed variability power spectrum may differ from that due to the intrinsic variability of spots alone, within the orbital frequency range in which these spots occur. In this paper, we explore the relation between properties assumed for the spot population and the resulting predictions for the observed variability. The implications of our results for the 'flickering' of X-ray sources powered by accretion disks (both AGN and galactic sources) are also discussed. (author). 24 refs, 6 figs

  9. Compton scattering artifacts in electron excited X-ray spectra measured with a silicon drift detector.

    Science.gov (United States)

    Ritchie, Nicholas W M; Newbury, Dale E; Lindstrom, Abigail P

    2011-12-01

    Artifacts are the nemesis of trace element analysis in electron-excited energy dispersive X-ray spectrometry. Peaks that result from nonideal behavior in the detector or sample can fool even an experienced microanalyst into believing that they have trace amounts of an element that is not present. Many artifacts, such as the Si escape peak, absorption edges, and coincidence peaks, can be traced to the detector. Others, such as secondary fluorescence peaks and scatter peaks, can be traced to the sample. We have identified a new sample-dependent artifact that we attribute to Compton scattering of energetic X-rays generated in a small feature and subsequently scattered from a low atomic number matrix. It seems likely that this artifact has not previously been reported because it only occurs under specific conditions and represents a relatively small signal. However, with the advent of silicon drift detectors and their utility for trace element analysis, we anticipate that more people will observe it and possibly misidentify it. Though small, the artifact is not inconsequential. Under some conditions, it is possible to mistakenly identify the Compton scatter artifact as approximately 1% of an element that is not present.

  10. Experimental and theoretical study of electronic structure of aluminum in extreme conditions with X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Festa, Floriane

    2013-01-01

    Matter in extreme conditions belongs to Warm Dense Matter regime which lays between dense plasma regime and condensed matter. This regime is still not well known, indeed it is very complex to generate such plasma in the laboratory to get experimental data and validate models. The goal of this thesis is to study electronic structure of aluminum in extreme conditions with X-ray absorption spectroscopy. Experimentally aluminum has reached high densities and high temperatures, up to now unexplored. An X-ray source has also been generated to probe highly compressed aluminum. Two spectrometers have recorded aluminum absorption spectra and aluminum density and temperature conditions have been deduced thanks to optical diagnostics. Experimental spectra have been compared to ab initio spectra, calculated in the same conditions. The theoretical goal was to validate the calculation method in high densities and high temperatures regime with the study of K-edge absorption modifications. We also used absorption spectra to study the metal-non metal transition which takes place at low density (density ≤ solid density). This transition could be study with electronic structure modifications of the system. (author) [fr

  11. Estimation of identification limit for a small-type OSL dosimeter on the medical images by measurement of X-ray spectra.

    Science.gov (United States)

    Takegami, Kazuki; Hayashi, Hiroaki; Okino, Hiroki; Kimoto, Natsumi; Maehata, Itsumi; Kanazawa, Yuki; Okazaki, Tohru; Hashizume, Takuya; Kobayashi, Ikuo

    2016-07-01

    Our aim in this study is to derive an identification limit on a dosimeter for not disturbing a medical image when patients wear a small-type optically stimulated luminescence (OSL) dosimeter on their bodies during X-ray diagnostic imaging. For evaluation of the detection limit based on an analysis of X-ray spectra, we propose a new quantitative identification method. We performed experiments for which we used diagnostic X-ray equipment, a soft-tissue-equivalent phantom (1-20 cm), and a CdTe X-ray spectrometer assuming one pixel of the X-ray imaging detector. Then, with the following two experimental settings, corresponding X-ray spectra were measured with 40-120 kVp and 0.5-1000 mAs at a source-to-detector distance of 100 cm: (1) X-rays penetrating a soft-tissue-equivalent phantom with the OSL dosimeter attached directly on the phantom, and (2) X-rays penetrating only the soft-tissue-equivalent phantom. Next, the energy fluence and errors in the fluence were calculated from the spectra. When the energy fluence with errors concerning these two experimental conditions was estimated to be indistinctive, we defined the condition as the OSL dosimeter not being identified on the X-ray image. Based on our analysis, we determined the identification limit of the dosimeter. We then compared our results with those for the general irradiation conditions used in clinics. We found that the OSL dosimeter could not be identified under the irradiation conditions of abdominal and chest radiography, namely, one can apply the OSL dosimeter to measurement of the exposure dose in the irradiation field of X-rays without disturbing medical images.

  12. Charge exchange recombination in X-ray spectra of He-like argon measured at the tokamak TEXTOR

    Energy Technology Data Exchange (ETDEWEB)

    Schlummer, Tobias

    2014-06-16

    Charge exchange recombination between ions and atomic hydrogen is an important atomic process in magnetically confined fusion plasmas. Besides radiative cooling of the plasma edge, charge exchange causes modifications of the ionization balance and the population densities of excited ion states. The central goal of this work is to investigate the influence of charge exchange on X-ray spectra measured at the tokamak TEXTOR. A new 2D X-ray spectrometer developed for future use at the stellarator W7-X was recently installed at TEXTOR. The spectrometer is optimized for measuring the K{sub α}-spectrum of He-like argon (1s2l - 1s{sup 2}) at wavelengths close to 4 Aa. K{sub α}-spectroscopy on He-like impurity ions is an established diagnostic for electron and ion temperature measurements in fusion plasmas. Still, up to now the observed intensity ratios of the K{sub α}-lines and their associated satellites are not fully understood. They show significant deviations from the predictions made by basic corona models. In the past charge exchange with the neutral particle background and radial impurity transport have been discussed as likely explanations. Yet a detailed description of the experimental spectra still has not been achieved. To reconstruct the 2D K{sub α}-spectra measured at TEXTOR the radial argon ion distribution is modeled using an impurity transport code. The model accounts for charge exchange and transport on basis of given radial profiles of the neutral particle density n{sub 0}(r) and the diffusion coefficient D {sub perpendicular} {sub to} (r). The theoretical spectrum is then constructed based on the processes relevant for line emission. Within an iterative procedure n{sub 0}(r) and D {sub perpendicular} {sub to} (r) are varied until consistency between the theoretical and the experimental spectra is achieved. It is shown that the 2D K{sub α}-spectra allow a clear distinction of charge exchange and transport effects, ensuring unique solutions for n

  13. Communication: The electronic structure of matter probed with a single femtosecond hard x-ray pulse

    Directory of Open Access Journals (Sweden)

    J. Szlachetko

    2014-03-01

    Full Text Available Physical, biological, and chemical transformations are initiated by changes in the electronic configuration of the species involved. These electronic changes occur on the timescales of attoseconds (10−18 s to femtoseconds (10−15 s and drive all subsequent electronic reorganization as the system moves to a new equilibrium or quasi-equilibrium state. The ability to detect the dynamics of these electronic changes is crucial for understanding the potential energy surfaces upon which chemical and biological reactions take place. Here, we report on the determination of the electronic structure of matter using a single self-seeded femtosecond x-ray pulse from the Linac Coherent Light Source hard x-ray free electron laser. By measuring the high energy resolution off-resonant spectrum (HEROS, we were able to obtain information about the electronic density of states with a single femtosecond x-ray pulse. We show that the unoccupied electronic states of the scattering atom may be determined on a shot-to-shot basis and that the measured spectral shape is independent of the large intensity fluctuations of the incoming x-ray beam. Moreover, we demonstrate the chemical sensitivity and single-shot capability and limitations of HEROS, which enables the technique to track the electronic structural dynamics in matter on femtosecond time scales, making it an ideal probe technique for time-resolved X-ray experiments.

  14. Texture, residual stress and structural analysis of thin films using a combined X-ray analysis

    International Nuclear Information System (INIS)

    Lutterotti, L.; Chateigner, D.; Ferrari, S.; Ricote, J.

    2004-01-01

    Advanced thin films for today's industrial and research needs require highly specialized methodologies for a successful quantitative characterization. In particular, in the case of multilayer and/or unknown phases a global approach is necessary to obtain some or all the required information. A full approach has been developed integrating novel texture and residual stress methodologies with the Rietveld method (Acta Cryst. 22 (1967) 151) (for crystal structure analysis) and it has been coupled with the reflectivity analysis. The complete analysis can be done at once and offers several benefits: the thicknesses obtained from reflectivity can be used to correct the diffraction spectra, the phase analysis help to identify the layers and to determine the electron density profile for reflectivity; quantitative texture is needed for quantitative phase and residual stress analyses; crystal structure determination benefits of the previous. To achieve this result, it was necessary to develop some new methods, especially for texture and residual stresses. So it was possible to integrate them in the Rietveld, full profile fitting of the patterns. The measurement of these spectra required a special reflectometer/diffractometer that combines a thin parallel beam (for reflectivity) and a texture/stress goniometer with a curved large position sensitive detector. This new diffraction/reflectivity X-ray machine has been used to test the combined approach. Several spectra and the reflectivity patterns have been collected at different tilting angles and processed at once by the special software incorporating the aforementioned methodologies. Some analysis examples will be given to show the possibilities offered by the method

  15. Electronic states in Li/sub c/Mg/sub l-c/ alloys: soft x-ray emission spectra

    International Nuclear Information System (INIS)

    Stocks, G.M.; Tagle, J.A.; Callcott, T.A.; Arakawa, E.T.

    1980-01-01

    A first principles theory is developed for Li-Mg alloy systems which avoids the use of pseudo-potentials and, more importantly, low-order perturbation theory and which can be checked quantitatively against detailed probes of the electronic structure such as soft x-ray spectroscopy. These calculations can then be used as a base against which the psuedo-potential methods can, in the future, be checked

  16. Photovoltaic x-ray detectors based on the GaAs epitaxial structures

    CERN Document Server

    Akhmadullin, R A; Dvoryankina, G G; Dikaev, Y M; Ermakov, M G; Ermakova, O N; Krikunov, A I; Kudryashov, A A; Petrov, A G; Telegin, A A

    2002-01-01

    The new photovoltaic detector of the X-ray radiation is proposed on the basis of the GaAs epitaxial structures, which operates with high efficiency of the charge carriers collection without shift voltage and at the room temperature. The structures are grown by the method of the gas-phase epitaxy on the n sup + -type highly-alloyed substrates. The range of sensitivity to the X-ray radiation is within the range of effective energies from 8 up to 120 keV. The detector maximum response in the current short circuit mode is determined

  17. Solution spectroelectrochemical cell for in situ X-ray absorption fine structure

    International Nuclear Information System (INIS)

    Antonio, M.R.; Soderholm, L.

    1995-01-01

    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 3 -edge XANES (X-ray Absorption Near Edge Structure) throughout the course of electrolysis of an aqueous solution of EuCl 3 ·6H 2 O in 1 M H 2 SO 4 . The europium L 3 -edge resonances reported here for the Eu III and Eu II ions demonstrate that their 2p 3/2 → 5d electronic transition probabilities are not the same

  18. Method of evaluation of structural (screen) and quantum graininess of X-ray pictures

    Energy Technology Data Exchange (ETDEWEB)

    Gurvich, A M; Shamanov, A A; Erofeeva, N D [Nauchno-Issledovatel' skij Inst. Rentgenologii i Radiologii, Moscow (USSR)

    1979-03-01

    Proposed is a method for quantitative determination of graininess of X-ray pictures (gamma-ray images), the graininess being conditioned by the structure of amplifying screens and quantum fluctuations. The method is based on the determination of threshold brightness at which the picture graininess becomes obvious. It is shown that at low effective quantum energy (Esub(eff.) <= 50 keV) the graininess observed is for the most part structural (screen). Its growth is connected with quantum fluctuations when increasing Esub(eff.) up to 150 keV and using screens with high output values of X-ray luminescence and the coefficient of spectral accordance to the film.

  19. X-ray absorption in GaGdN: A study of local structure

    Science.gov (United States)

    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.

  20. X-ray absorption in GaGdN: A study of local structure

    International Nuclear Information System (INIS)

    Martinez-Criado, G.; Sans, J. A.; Susini, J.; Sancho-Juan, O.; Cantarero, A.; Garro, N.; Roever, M.; Mai, D.-D.; Bedoya-Pinto, A.; Malindretos, J.; Rizzi, A.

    2008-01-01

    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

  1. Structural mechanics of the solar-A Soft X-ray Telescope

    Science.gov (United States)

    Jurcevich, B. K.; Bruner, M. E.; Gowen, K. F.

    1992-01-01

    The Soft X-ray Telescope (SXT) is one of four major instruments that constitute the payload of the NASA-Japanese mission YOHKOH (formerly known as Solar-A), scheduled to be launched in August, 1991. This paper describes the design of the SXT, the key system requirements, and the SXT optical and structural systems. Particular attention is given to the design considerations for stiffness and dimensional stability, temperature compensation, and moisture sensitivyty control. Consideration is also given to the X-ray mirror, the aspect telescope, the entrance filters, the mechanical structure design, the aft support plate and mount, the SXT finite element model, and other subsystems.

  2. Purification, crystallization and preliminary X-ray structure analysis of the laccase from Ganoderma lucidum

    International Nuclear Information System (INIS)

    Lyashenko, Andrey V.; Belova, Oksana; Gabdulkhakov, Azat G.; Lashkov, Alexander A.; Lisov, Alexandr V.; Leontievsky, Alexey A.; Mikhailov, Al’bert M.

    2011-01-01

    The purification, crystallization and preliminary X-ray structure analysis of the laccase from G. lucidum are reported. The ligninolytic enzymes of the basidiomycetes play a key role in the global carbon cycle. A characteristic property of these enzymes is their broad substrate specificity, which has led to their use in various biotechnologies, thus stimulating research into the three-dimensional structures of ligninolytic enzymes. This paper presents the purification, crystallization and preliminary X-ray analysis of the laccase from the ligninolytic basidiomycete Ganoderma lucidum

  3. X-ray diffraction study of the structure of detonation nanodiamonds

    International Nuclear Information System (INIS)

    Ozerin, A. N.; Kurkin, T. S.; Ozerina, L. A.; Dolmatov, V. Yu.

    2008-01-01

    The spatial structure of aggregates formed by detonation nanodiamonds is investigated using the wide-angle and small-angle X-ray scattering techniques. The effective sizes of crystallites and the crystallite size distribution function are determined. The shape of scattering aggregates is restored from the small-angle X-ray scattering data. An analysis of the results obtained allowed the conclusion that the nanodiamond aggregates have an extended spatial structure composed of nine to ten clusters, each involving four to five crystallites with a crystal lattice of the diamond type

  4. Reflections on hard X-ray photon-in/photon-out spectroscopy for electronic structure studies

    Energy Technology Data Exchange (ETDEWEB)

    Glatzel, Pieter, E-mail: glatzel@esrf.fr [European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, 38043 Grenoble (France); Weng, Tsu-Chien; Kvashnina, Kristina; Swarbrick, Janine; Sikora, Marcin [European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, 38043 Grenoble (France); Gallo, Erik [European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, 38043 Grenoble (France); Department of Inorganic, Physical and Materials Chemistry, INSTM Reference Center and NIS Centre of Excellence, Università di Torino, Via P. Giuria 7, I-10125 Torino (Italy); Smolentsev, Nikolay [European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, 38043 Grenoble (France); Research Center for Nanoscale Structure of Matter, Southern Federal University, str. Zorge 5, 344090 Rostov-on-Don (Russian Federation); Mori, Roberto Alonso [European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, 38043 Grenoble (France)

    2013-06-15

    Highlights: ► Overview of some recent developments in hard X-ray RXES/RIXS. ► Evaluation of spectral line broadening in RXES/RIXS. ► Modelling of RXES/RIXS by ground state DFT calculations. ► Discussion on when HERFD provides a good approximation to XAS. -- Abstract: An increasing community of researchers in various fields of natural sciences is combining X-ray absorption with X-ray emission spectroscopy (XAS–XES) to study electronic structure. With the applications becoming more diverse, the objectives and the requirements in photon-in/photon-out spectroscopy are becoming broader. It is desirable to find simple experimental protocols, robust data reduction and theoretical tools that help the experimentalist to understand their data and learn about the electronic structure. This article presents a collection of considerations on non-resonant and resonant XES with the aim to guide the experimentalist to make good use of this technique.

  5. Investigation of nanoscale structures by small-angle X-ray scattering in a radiochromic dosimeter

    DEFF Research Database (Denmark)

    Skyt, Peter Sandegaard; Jensen, Grethe Vestergaard; Wahlstedt, Isak Hannes

    2014-01-01

    This study examines the nanoscale structures in a radiochromic dosimeter that was based on leuco-malachite-green dye and the surfactant sodium dodecyl sulfate (SDS) suspended in a gelatin matrix. Small-angle X-ray scattering was used to investigate the structures of a range of compositions...

  6. X-ray structure amplitudes for GaAs and InP

    International Nuclear Information System (INIS)

    Pietsch, U.

    1985-01-01

    The structure amplitudes of GaAs and InP are calculated taking into account the nonspherical parts of the valence electron density by means of a static bond charge model. The best known temperature factors and dispersion coefficients are employed. The calculated structure amplitudes should help determining exactly the shape of X-ray diffraction patterns. (author)

  7. Composite structure of helicopter rotor blades studied by neutron- and X-ray radiography

    International Nuclear Information System (INIS)

    Balasko, M.; Veres, I.; Molnar, Gy.; Balasko, Zs.; Svab, E.

    2004-01-01

    In order to inspect the possible defects in the composite structure of helicopter rotor blades combined neutron- and X-ray radiography investigations were performed at the Budapest Research Reactor. Imperfections in the honeycomb structure, resin rich or starved areas at the core-honeycomb surfaces, inhomogeneities at the adhesive filling and water percolation at the sealing interfaces of the honeycomb sections were discovered

  8. Composite structure of helicopter rotor blades studied by neutron- and X-ray radiography

    Science.gov (United States)

    Balaskó, M.; Veres, I.; Molnár, Gy.; Balaskó, Zs.; Sváb, E.

    2004-07-01

    In order to inspect the possible defects in the composite structure of helicopter rotor blades combined neutron- and X-ray radiography investigations were performed at the Budapest Research Reactor. Imperfections in the honeycomb structure, resin rich or starved areas at the core-honeycomb surfaces, inhomogeneities at the adhesive filling and water percolation at the sealing interfaces of the honeycomb sections were discovered.

  9. X-ray propagation through a quasi-ordered multilayered structure ...

    African Journals Online (AJOL)

    We investigate the propagation of short wavelength transverse electric x-rays through a quasiordered (Fibonacci) atomically commensurate multilayered structure using a transfer matrix model which treats each atomic plane as a diffraction unit. The reflectance spectrum has a rich structure being dominated by peaks ...

  10. X-ray detectors for structure investigations constructed at JINR

    Energy Technology Data Exchange (ETDEWEB)

    Chernenko, S P [LHE Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Cheremukhina, G A [LHE Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Fateev, O V [LHE Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Smykov, L P [LHE Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Vasiliev, S E [LHE Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Zanevsky, Yu V [LHE Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Kheiker, D M [Institute of Crystallography, Leninsky prosp. 59, 117333 Moscow (Russian Federation); Popov, A N [Institute of Crystallography, Leninsky prosp. 59, 117333 Moscow (Russian Federation)

    1994-09-01

    The performance characteristics of a few high resolution position-sensitive detectors constructed at JINR are presented. The detectors supplied with original software operate with an IBM PC/AT. One of these devices has been succesfully applied for protein molecule structure investigations and the other for studies of the structure-forming process during combustion. The preliminary parameters of the high count rate MWPC with parallel electronics and the testing results of the microstrip detector are given. ((orig.))

  11. A structural study of bone changes in knee osteoarthritis by synchrotron-based X-ray fluorescence and X-ray absorption spectroscopy techniques

    Science.gov (United States)

    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.

  12. Target surface structure effects on x-ray generation from laser produced plasma

    Energy Technology Data Exchange (ETDEWEB)

    Nishikawa, Tadashi; Nakano, Hidetoshi; Uesugi, Naoshi [NTT Basic Research Laboratories, Atsugi, Kanagawa (Japan)

    2000-03-01

    We demonstrated two different methods to increase the x-ray conversion efficiency of laser-produced plasma by modifying the target surface structure. One way is making a rectangular groove on a target surface and confining a laser-produced plasma in it. By the plasma collision process, a time and wavelength (4-10 nm) integrated soft x-ray fluence enhancement of 35 times was obtained at a groove width of 20 {mu}m and a groove depth of 100 {mu}m on a Nd-doped glass target. The other way is making an array of nanoholes on an alumina target and increasing the laser interaction depth with it. The x-ray fluence enhancement increases as the ionization level of Al becomes higher and the x-ray wavelength becomes shorter. Over 50-fold enhancement was obtained at a soft x-ray wavelength around 6 nm, which corresponds to the emission from Al{sup 8+,9+} ions. (author)

  13. Target surface structure effects on x-ray generation from laser produced plasma

    International Nuclear Information System (INIS)

    Nishikawa, Tadashi; Nakano, Hidetoshi; Uesugi, Naoshi

    2000-01-01

    We demonstrated two different methods to increase the x-ray conversion efficiency of laser-produced plasma by modifying the target surface structure. One way is making a rectangular groove on a target surface and confining a laser-produced plasma in it. By the plasma collision process, a time and wavelength (4-10 nm) integrated soft x-ray fluence enhancement of 35 times was obtained at a groove width of 20 μm and a groove depth of 100 μm on a Nd-doped glass target. The other way is making an array of nanoholes on an alumina target and increasing the laser interaction depth with it. The x-ray fluence enhancement increases as the ionization level of Al becomes higher and the x-ray wavelength becomes shorter. Over 50-fold enhancement was obtained at a soft x-ray wavelength around 6 nm, which corresponds to the emission from Al 8+,9+ ions. (author)

  14. A hydrodynamical model of Kepler's supernova remnant constrained by x-ray spectra

    International Nuclear Information System (INIS)

    Ballet, J.; Arnaud, M.; Rothinfluo, R.; Chieze, J.P.; Magne, B.

    1988-01-01

    The remnant of the historical supernova observed by Kepler in 1604 was recently observed in x-rays by the EXOSAT satellite up to 10 keV. A strong Fe K emission line around 6.5 keV is readily apparent in the spectrum. From an analysis of the light curve of the SN, reconstructed from historical descriptions, a previous study proposed to classify it as type I. Standard models of SN I based on carbon deflagration of white dwarf predict the synthesis of about 0.5 M circle of iron in the ejecta. Observing the iron line is a crucial check for such models. It has been argued that the light curve of Sn II-L is very similar to that of SN I and that the original observations are compatible with either type. In view of this uncertainty the authors have run a hydrodynamics-ionization code for both SN II and SN I remnants

  15. Electronic structure of titania aerogels: Soft x-ray absorption study

    International Nuclear Information System (INIS)

    Kucheyev, S.O.; Van Buuren, T.V.; Baumann, T.F.; Satcher, J.H.; Willey, T.M.; Muelenberg, R.W.; Felter, T.E.; Poco, J.E.; Gammon, S.A.; Terminello, L.J.

    2004-01-01

    Full text: Titania aerogels - a somewhat extreme form of nanoporous TiO 2 - are open-cell solid foams derived from highly crosslinked gels by drying them under supercritical conditions. In this presentation, the unoccupied electronic states of TiO 2 aerogels are studied by soft x-ray absorption near-edge structure (XANES) spectroscopy. High-resolution O K-edge and Ti L 2,3 -edge XANES spectra of aerogels are compared with those of rutile, anatase, and unrelaxed amorphous phases of full- density TiO 2 . Results show that all the main spectroscopic features of aerogels, reflecting the element-specific partial density of empty electronic states and correlation effects, can be attributed to the absence of long-range order in stoichiometric amorphous TiO 2 . Based on these results, we discuss the effects of short- and long-range order on the electronic structure of TiO 2 . This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48

  16. Synthesis, X-ray Structure, Spectroscopic Properties and DFT Studies of a Novel Schiff Base

    Directory of Open Access Journals (Sweden)

    Kew-Yu Chen

    2014-10-01

    Full Text Available A series of Schiff bases, salicylideneaniline derivatives 1–4, was synthesized under mild conditions and characterized by 1H NMR, HRMS, UV-Vis and fluorescence spectra, and single-crystal X-ray diffraction. In solid and aprotic solvents 1–4 exist mainly as E conformers that possess an intramolecular six-membered-ring hydrogen bond. A weak intramolecular C–H×××F hydrogen bond is also observed in fluoro-functionalized Schiff base 4, which generates another S(6 ring motif. The C–H×××F hydrogen bond further stabilizes its structure and leads it to form a planar configuration. Compounds 1–3 exhibit solely a long-wavelength proton-transfer tautomer emission, while dipole-functionalized Schiff base 4 shows remarkable dual emission originated from the excited-state intramolecular charge transfer (ESICT and excited-state intramolecular proton transfer (ESIPT states. Furthermore, the geometric structures, frontier molecular orbitals (MOs and the potential energy curves for 1–4 in the ground and the first singlet excited state were fully rationalized by density functional theory (DFT and time-dependent DFT calculations.

  17. Structural and dynamical properties of chlorinated hydrocarbons studied with resonant inelastic x-ray scattering

    Science.gov (United States)

    Bohinc, R.; Žitnik, M.; Bučar, K.; Kavčič, M.; Carniato, S.; Journel, L.; Guillemin, R.; Marchenko, T.; Kawerk, E.; Simon, M.; Cao, W.

    2016-04-01

    We present a theoretical and experimental study of resonant inelastic x-ray scattering on a large group of chlorinated hydrocarbons: CH3Cl, CH2Cl2, CHCl3, CCl4, CH3CH2Cl, ClCH2CH2Cl, CH3CHCl2, CH3CCl3, C2H2Cl2-iso, C2H2Cl2-cis, C2H2Cl2-trans, and C6H5Cl. Differences in structural and dynamical properties of the molecules generated by diverse chemical environments are observed in the measured Cl(Kα) spectral maps as well as in the Cl(K) total fluorescence yield spectra. The energy position, relative intensity, and the width of the Franck-Condon distribution of low-lying σ∗ and π∗ resonances are extracted by a fitting procedure taking into account the experimental broadening. The theoretical values obtained with the transition potential and Δ Kohn-Sham methods are in good agreement with the experimental parameters indicating subtle differences due to variations in the molecular structure.

  18. Resonant inelastic X-ray scattering spectra at the Ir L-edge in Na{sub 2}IrO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Igarashi, Jun-ichi, E-mail: junichi.igarashi.kiryu@vc.ibaraki.ac.jp [Faculty of Science, Ibaraki University, Mito, Ibaraki 310-8512 (Japan); Nagao, Tatsuya, E-mail: nagao@gunma-u.ac.jp [Faculty of Engineering, Gunma University, Kiryu, Gunma 376-8515 (Japan)

    2016-10-15

    Highlights: • A theoretical framework of resonant inelastic X-ray scattering (RIXS) on the basis of the itinerant electron scheme has been developed. • The RIXS theory is applied to iridate Na{sub 2}IrO{sub 3}. • The origins of the multi-peak structure of the excitation spectra found in the RIXS experiment have been assigned to the magnetic and excitonic excitations. - Abstract: We analyze resonant X-ray scattering (RIXS) spectra in Na{sub 2}IrO{sub 3} on the basis of the itinerant electron picture. Employing a multi-orbital tight-binding model on a honeycomb lattice, we find that the zigzag magnetic order is the most stable with sizable energy gap in the one-electron band within the Hartree–Fock approximation. We derive the RIXS spectra, which are connected to the generalized density–density correlation function. We calculate the spectra as a function of excitation energy ω, within the random phase approximation. The spectra consist of the peaks with ω < 20 meV, and of the peaks with 0.4 < ω < 0.8 eV. The former peaks are composed of four bound states in the density–density correlation function, and may be identified as the magnetic excitations, while the latter peaks are composed of 16 bound states below the energy continuum of individual electron–hole pair excitations, and may be identified as the excitonic excitations. The calculated spectra agree qualitatively with the recent RIXS experiment.

  19. Vibrational, X-ray absorption, and Mössbauer spectra of sulfate minerals from the weathered massive sulfide deposit at Iron Mountain, California

    Science.gov (United States)

    Majzlan, Juraj; Alpers, Charles N.; Bender Koch, Christian; McCleskey, R. Blaine; Myneni, Satish B.C.; Neil, John M.

    2014-01-01

    The Iron Mountain Mine Superfund site in California is a prime example of an acid mine drainage (AMD) system with well developed assemblages of sulfate minerals typical for such settings. Here we present and discuss the vibrational (infrared), X-ray absorption, and Mössbauer spectra of a number of these phases, augmented by spectra of a few synthetic sulfates related to the AMD phases. The minerals and related phases studied in this work are (in order of increasing Fe2O3/FeO): szomolnokite, rozenite, siderotil, halotrichite, römerite, voltaite, copiapite, monoclinic Fe2(SO4)3, Fe2(SO4)3·5H2O, kornelite, coquimbite, Fe(SO4)(OH), jarosite and rhomboclase. Fourier transform infrared spectra in the region 750–4000 cm−1 are presented for all studied phases. Position of the FTIR bands is discussed in terms of the vibrations of sulfate ions, hydroxyl groups, and water molecules. Sulfur K-edge X-ray absorption near-edge structure (XANES) spectra were collected for selected samples. The feature of greatest interest is a series of weak pre-edge peaks whose position is determined by the number of bridging oxygen atoms between Fe3+ octahedra and sulfate tetrahedra. Mössbauer spectra of selected samples were obtained at room temperature and 80 K for ferric minerals jarosite and rhomboclase and mixed ferric–ferrous minerals römerite, voltaite, and copiapite. Values of Fe2+/[Fe2+ + Fe3+] determined by Mössbauer spectroscopy agree well with those determined by wet chemical analysis. The data presented here can be used as standards in spectroscopic work where spectra of well-characterized compounds are required to identify complex mixtures of minerals and related phases.

  20. Large-area soft x-ray projection lithography using multilayer mirrors structured by RIE

    Science.gov (United States)

    Rahn, Steffen; Kloidt, Andreas; Kleineberg, Ulf; Schmiedeskamp, Bernt; Kadel, Klaus; Schomburg, Werner K.; Hormes, F. J.; Heinzmann, Ulrich

    1993-01-01

    SXPL (soft X-ray projection lithography) is one of the most promising applications of X-ray reflecting optics using multilayer mirrors. Within our collaboration, such multilayer mirrors were fabricated, characterized, laterally structured and then used as reflection masks in a projecting lithography procedure. Mo/Si-multilayer mirrors were produced by electron beam evaporation in UHV under thermal treatment with an in-situ X-ray controlled thickness in the region of 2d equals 14 nm. The reflectivities measured at normal incidence reached up to 54%. Various surface analysis techniques have been applied in order to characterize and optimize the X-ray mirrors. The multilayers were patterned by reactive ion etching (RIE) with CF(subscript 4), using a photoresist as the etch mask, thus producing X-ray reflection masks. The masks were tested in the synchrotron radiation laboratory of the electron accelerator ELSA at the Physikalisches Institut of Bonn University. A double crystal X-ray monochromator was modified so as to allow about 0.5 cm(superscript 2) of the reflection mask to be illuminated by white synchrotron radiation. The reflected patterns were projected (with an energy of 100 eV) onto the resist (Hoechst AZ PF 514), which was mounted at an average distance of about 7 mm. In the first test-experiments, structure sizes down to 8 micrometers were nicely reproduced over the whole of the exposed area. Smaller structures were distorted by Fresnel-diffraction. The theoretically calculated diffraction images agree very well with the observed images.

  1. Structure investigation, spectral, thermal, X-ray and mass characterization of piroxicam and its metal complexes

    Science.gov (United States)

    Zayed, M. A.; Nour El-Dien, F. A.; Mohamed, Gehad G.; El-Gamel, Nadia E. A.

    2004-10-01

    [M(H 2L) 2](A) 2. yH 2O (where H 2L: neutral piroxicam (Pir), A: Cl - in case of Ni(II) or acetate anion in case of Cu(II) and Zn(II) ions and y=0-2.5) and [M(H 2L) 3](A) z. yH 2O (A: SO 42- in case of Fe(II) ion ( z=1) or Cl - in case of Fe(III) ( z=3) and Co(II) ions ( z=2) and y=1-4) chelates are prepared and characterized using elemental analyses, IR, magnetic and electronic reflectance measurements, mass spectra and thermal analyses. IR spectra reveal that Pir behaves a neutral bidentate ligand coordinated to the metal ions through the pyridyl-N and carbonyl-O of the amide moiety. The reflectance and magnetic moment measurements reveal that these chelates have tetrahedral, square planar and octahedral geometrical structures. Mass spectra and thermal analyses are also used to confirm the proposed formulae and the possible fragments resulted from fragmentation of Pir and its chelates. The thermal behaviour of the chelates (TGA and DTA) are discussed in detail and the thermal stability of the anhydrous chelates follow the order Ni(II)≅Cu(II)X-ray powder diffraction was also used as a confirmatory tool to elucidate the crystallinity of the chelates.

  2. Ab initio structure determination via powder X-ray diffraction

    Indian Academy of Sciences (India)

    Unknown

    Although the method of structure completion when once the starting model is provided is ... In this article a survey of the recent development in this area is ..... The Monte Carlo method 4,9 differs from the traditional approaches as it operates in.

  3. Forming a structure of the CoNiFe alloys by X-ray irradiation

    Science.gov (United States)

    Valko, Natalia; Kasperovich, Andrey; Koltunowicz, Tomasz N.

    The experimental data of electrodeposition kinetics researches and structure formation of ternary CoNiFe alloys deposited onto low-carbon steel 08kp in the presence of X-rays are presented. Relations of deposit rate, current efficiencies, element and phase compositions of CoNiFe coatings formed from sulfate baths with respect to cathode current densities (0.5-3A/dm2), electrolyte composition and irradiation were obtained. It is shown that, the CoNiFe coatings deposited by the electrochemical method involving exposure of the X-rays are characterized by more perfect morphology surfaces with less developed surface geometry than reference coatings. The effect of the X-ray irradiation on the electrodeposition of CoNiFe coatings promotes formatting of alloys with increased electropositive component and modified phase composition.

  4. Structure investigation of metal ions clustering in dehydrated gel using x-ray anomalous dispersion effect

    CERN Document Server

    Soejima, Y; Sugiyama, M; Annaka, M; Nakamura, A; Hiramatsu, N; Hara, K

    2003-01-01

    The structure of copper ion clusters in dehydrated N-isopropylacrylamide/sodium acrylate (NIPA/SA) gel has been studied by means of small angle X-ray scattering (SAXS) method. In order to distinguish the intensity scattered by Cu ions, the X-ray anomalous dispersion effect around the Cu K absorption edge has been coupled with SAXS. It is found that the dispersion effect dependent on the incident X-ray energy is remarkable only at the momentum transfer q = 0.031 A sup - sup 1 , where a SAXS peak is observed. The results indicate that copper ions form clusters in the dehydrated gel, and that the mean size of clusters is the same as that of SA clusters produced by microphase separation. It is therefore naturally presumed that copper ions are adsorbed into the SA molecules. On the basis of the presumption, a mechanism is proposed for microphase-separation and clustering of Cu ions.

  5. Two-dimensional imaging detectors for structural biology with X-ray lasers.

    Science.gov (United States)

    Denes, Peter

    2014-07-17

    Our ability to harness the advances in microelectronics over the past decade(s) for X-ray detection has resulted in significant improvements in the state of the art. Biology with X-ray free-electron lasers present daunting detector challenges: all of the photons arrive at the same time, and individual high peak power pulses must be read out shot-by-shot. Direct X-ray detection in silicon pixel detectors--monolithic or hybrid--are the standard for XFELs today. For structural biology, improvements are needed for today's 10-100 Hz XFELs, and further improvements are required for tomorrow's 10+ kHz XFELs. This article will discuss detector challenges, why they arise and ways to overcome them, along with the current state of the art. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  6. Single crystal X-ray structure of the artists’ pigment zinc yellow

    DEFF Research Database (Denmark)

    Simonsen, Kim Pilkjær; Christiansen, Marie Bitsch; Vinum, Morten Gotthold

    2017-01-01

    electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and powder X-ray diffraction (PXRD), showed that the synthesised products and the industrial pigment were identical. Single-crystal X-ray crystallography......The artists’ pigment zinc yellow is in general described as a complex potassium zinc chromate with the empirical formula 4ZnCrO4·K2O·3H2O. Even though the pigment has been in use since the second half of the 19th century also in large-scale industrial applications, the exact structure had hitherto...... been unknown. In this work, zinc yellow was synthesised by precipitation from an aqueous solution of zinc nitrate and potassium chromate under both neutral and basic conditions, and the products were compared with the pigment used in industrial paints. Analyses by Raman microscopy (MRS), scanning...

  7. Rapid characterization of a nanomaterial structure using X-ray reciprocal-lattice-space imaging

    International Nuclear Information System (INIS)

    Sakata, Osami; Yoshimoto, Mamoru; Miki, Kazushi

    2006-01-01

    The X-ray reciprocal-lattice-space imaging method is able to record the reciprocal-lattice-space of nanostructure by sample-and-detector fixed geometry. This method was developed by the surface structure analysis beam line BL13XU of SPring-8. Outline of the X-ray diffraction method and basic principles of the X-ray reciprocal-lattice-space imaging method, and application examples are stated. The method is able to find out the Bragg conditions of nanostructure of surface in the atmosphere. The reciprocal-lattice of the embedded trace atomic wires was observed. The trace atoms of Bi atomic wires embedded in silicone showed the diffraction signal and image by a short exposure time. This method is useful at rapid non-destructive measurement of nanostructure. (S.Y.)

  8. Parameter study of self-absorption effects in Total Reflection X-ray Fluorescence-X-ray Absorption Near Edge Structure analysis of arsenic

    International Nuclear Information System (INIS)

    Meirer, F.; Pepponi, G.; Streli, C.; Wobrauschek, P.; Kregsamer, P.; Zoeger, N.; Falkenberg, G.

    2008-01-01

    Total reflection X-ray Fluorescence (TXRF) analysis in combination with X-ray Absorption Near Edge Structure (XANES) analysis is a powerful method to perform chemical speciation studies at trace element levels. However, when measuring samples with higher concentrations and in particular standards, damping of the oscillations is observed. In this study the influence of self-absorption effects on TXRF-XANES measurements was investigated by comparing measurements with theoretical calculations. As(V) standard solutions were prepared at various concentrations and dried on flat substrates. The measurements showed a correlation between the damping of the oscillations and the As mass deposited. A Monte-Carlo simulation was developed using data of the samples shapes obtained from confocal white light microscopy. The results showed good agreement with the measurements; they confirmed that the key parameters are the density of the investigated atom in the dried residues and the shape of the residue, parameters that combined define the total mass crossed by a certain portion of the incident beam. The study presents a simple approach for an a priori evaluation of the self-absorption in TXRF X-ray absorption studies. The consequences for Extended X-ray Absorption Fine Structure (EXAFS) and XANES measurements under grazing incidence conditions are discussed, leading to the conclusion that the damping of the oscillations seems to make EXAFS of concentrated samples non feasible. For XANES 'fingerprint' analysis samples should be prepared with a deposited mass and sample shape leading to an acceptable absorption for the actual investigation

  9. Synthesis, characterization, x-ray structure and antimicrobial activity ...

    African Journals Online (AJOL)

    intermolecular N3—H1N1•••O1 hydrogen bonds. (Table 2), resulting in the formation of zigzag layers lying parallel to (100) (Fig. 2b). The existence of π•••π interactions involving the centroid of the N4/C9-C13 pyridine ring (π•••π distance = 3.5108(18) Å) further stabilize the molecular packing. The structure of compound 2.

  10. Covering complete proteomes with X-ray structures: a current snapshot

    Energy Technology Data Exchange (ETDEWEB)

    Mizianty, Marcin J.; Fan, Xiao; Yan, Jing; Chalmers, Eric; Woloschuk, Christopher [University of Alberta, Edmonton, Alberta T6G 2V4 (Canada); Joachimiak, Andrzej, E-mail: andrzejj@anl.gov [Argonne National Laboratory, Argonne, IL 60439 (United States); Kurgan, Lukasz, E-mail: andrzejj@anl.gov [University of Alberta, Edmonton, Alberta T6G 2V4 (Canada)

    2014-11-01

    The current and the attainable coverage by X-ray structures of proteins and their functions on the scale of the ‘protein universe’ are estimated. A detailed analysis of the coverage across nearly 2000 proteomes from all superkingdoms of life and functional annotations is performed, with particular focus on the human proteome and the family of GPCR proteins. Structural genomics programs have developed and applied structure-determination pipelines to a wide range of protein targets, facilitating the visualization of macromolecular interactions and the understanding of their molecular and biochemical functions. The fundamental question of whether three-dimensional structures of all proteins and all functional annotations can be determined using X-ray crystallography is investigated. A first-of-its-kind large-scale analysis of crystallization propensity for all proteins encoded in 1953 fully sequenced genomes was performed. It is shown that current X-ray crystallographic knowhow combined with homology modeling can provide structures for 25% of modeling families (protein clusters for which structural models can be obtained through homology modeling), with at least one structural model produced for each Gene Ontology functional annotation. The coverage varies between superkingdoms, with 19% for eukaryotes, 35% for bacteria and 49% for archaea, and with those of viruses following the coverage values of their hosts. It is shown that the crystallization propensities of proteomes from the taxonomic superkingdoms are distinct. The use of knowledge-based target selection is shown to substantially increase the ability to produce X-ray structures. It is demonstrated that the human proteome has one of the highest attainable coverage values among eukaryotes, and GPCR membrane proteins suitable for X-ray structure determination were determined.

  11. Covering complete proteomes with X-ray structures: a current snapshot

    International Nuclear Information System (INIS)

    Mizianty, Marcin J.; Fan, Xiao; Yan, Jing; Chalmers, Eric; Woloschuk, Christopher; Joachimiak, Andrzej; Kurgan, Lukasz

    2014-01-01

    The current and the attainable coverage by X-ray structures of proteins and their functions on the scale of the ‘protein universe’ are estimated. A detailed analysis of the coverage across nearly 2000 proteomes from all superkingdoms of life and functional annotations is performed, with particular focus on the human proteome and the family of GPCR proteins. Structural genomics programs have developed and applied structure-determination pipelines to a wide range of protein targets, facilitating the visualization of macromolecular interactions and the understanding of their molecular and biochemical functions. The fundamental question of whether three-dimensional structures of all proteins and all functional annotations can be determined using X-ray crystallography is investigated. A first-of-its-kind large-scale analysis of crystallization propensity for all proteins encoded in 1953 fully sequenced genomes was performed. It is shown that current X-ray crystallographic knowhow combined with homology modeling can provide structures for 25% of modeling families (protein clusters for which structural models can be obtained through homology modeling), with at least one structural model produced for each Gene Ontology functional annotation. The coverage varies between superkingdoms, with 19% for eukaryotes, 35% for bacteria and 49% for archaea, and with those of viruses following the coverage values of their hosts. It is shown that the crystallization propensities of proteomes from the taxonomic superkingdoms are distinct. The use of knowledge-based target selection is shown to substantially increase the ability to produce X-ray structures. It is demonstrated that the human proteome has one of the highest attainable coverage values among eukaryotes, and GPCR membrane proteins suitable for X-ray structure determination were determined

  12. Study on Coloration Mechanism of Chinese Ancient Ceramics by X-ray Absorption Near-edge Structure

    Science.gov (United States)

    Peng, Y. H.; Xie, Z.; He, J. F.; Liu, Q. H.; Pan, Z. Y.; Cheng, W. R.; Wei, S. Q.

    2013-04-01

    The Fe K-edge X-ray absorption near-edge structure (XANES) spectra of a series of ceramic shards were measured by fluorescence mode to reveal the color-generating techniques of Chinese porcelain. The analysis disclosed relationships among the chemical form of the iron, the firing conditions and the colors of the ceramics. The results indicate that the coloration for different ceramics depend on the valence states of iron as the main color element in glaze and the proportion of Fe2+ and Fe3+ was attributed to the baking technology. The findings provide important information for archaeologist on the coloration researches.

  13. Precision mechanical structure of an ultra-high-resolution spectrometer for inelastic X-ray scattering instrument

    Science.gov (United States)

    Shu, Deming; Shvydko, Yuri; Stoupin, Stanislav A.; Khachatryan, Ruben; Goetze, Kurt A.; Roberts, Timothy

    2015-04-14

    A method and an ultrahigh-resolution spectrometer including a precision mechanical structure for positioning inelastic X-ray scattering optics are provided. The spectrometer includes an X-ray monochromator and an X-ray analyzer, each including X-ray optics of a collimating (C) crystal, a pair of dispersing (D) element crystals, anomalous transmission filter (F) and a wavelength (W) selector crystal. A respective precision mechanical structure is provided with the X-ray monochromator and the X-ray analyzer. The precision mechanical structure includes a base plate, such as an aluminum base plate; positioning stages for D-crystal alignment; positioning stages with an incline sensor for C/F/W-crystal alignment, and the positioning stages including flexure-based high-stiffness structure.

  14. X-ray absorption fine structure spectroscopic determination of plutonium speciation at the Rocky Flats Environmental Technology Site

    International Nuclear Information System (INIS)

    Lezama-pacheco, Juan S.; Conradson, Steven D.; Clark, David L.

    2008-01-01

    X-ray Absorption Fine Structure spectroscopy was used to probe the speciation of the ppm level Pu in thirteen soil and concrete samples from the Rocky Flats Environmental Technology Site in support of the site remediation effort that has been successfully completed since these measurements. In addition to X-ray Absorption Near Edge Spectra, two of the samples yielded Extended X-ray Absorption Fine Structure spectra that could be analyzed by curve-fits. Most of these spectra exhibited features consistent with PU(IV), and more specificaJly, PuO 2+x -type speciation. Two were ambiguous, possibly indicating that Pu that was originally present in a different form was transforming into PuO 2+x , and one was interpreted as demonstrating the presence of an unusual Pu(VI) compound, consistent with its source being spills from a PUREX purification line onto a concrete floor and the resultant extreme conditions. These experimental results therefore validated models that predicted that insoluble PuO 2+x would be the most stable form of Pu in equilibrium with air and water even when the source terms were most likely Pu metal with organic compounds or a Pu fire. A corollary of these models' predictions and other in situ observations is therefore that the minimal transport of Pu that occurred on the site was via the resuspension and mobilization of colloidal particles. Under these conditions, the small amounts of diffusely distributed Pu that were left on the site after its remediation pose only a negligible hazard.

  15. Addressing source-induced structural vibrations in an interventional X-ray system

    NARCIS (Netherlands)

    Van Pinxteren, J.A.W.; Vermeulen, J.P.M.B.; van Loon, R.J.A.; van Schothorst, G.; Billington, D.; Phillips, D.

    2017-01-01

    Interventional radiology is a medical discipline, in which imaging equipment is used to diagnose and treat diseases throughout the human body. Dedicated systems, based on X-ray, computed tomography and ultrasound technology, allow for 2D and 3D imaging of (contrast enhanced) physical structures.

  16. Structural investigation of bistrifluron using x-ray crystallography, NMR spectroscopy, and molecular modeling

    CERN Document Server

    Moon, J K; Rhee, S K; Kim, G B; Yun, H S; Chung, B J; Lee, S S; Lim, Y H

    2002-01-01

    A new insecticide, bistrifluron acts as an inhibitor of insect development and interferes with the cuticle formation of insects. Since it shows low acute oral and dermal toxicities, it can be one of potent insecticides. Based on X-ray crystallography, NMR spectroscopy and molecular modeling, the structural studies of bistrifluron have been carried out.

  17. Analysis of stresses and strains in the materials with limiting structure using x-ray

    International Nuclear Information System (INIS)

    Imafuku, Muneyuki

    2010-01-01

    This review outlines the principle of analysis and the measuring instruments using X-ray for the stresses and strains in the materials with limiting structure. Further the several experimental examples are shown. This method is expected to be useful widely for the characterization evaluation, the reliability insurance, and the development of materials. (M.H.)

  18. The x-ray structure and MNDO calculations of a-terthienyl: a model for polythiophenes

    NARCIS (Netherlands)

    Bolhuis, van F.; Wynberg, H.; Havinga, E.E.; Meijer, E.W.; Staring, E.G.J.

    1989-01-01

    The x-ray structure of a-terthienyl reveals 2 identical, crystallog.-independent mols. in the unit cell. Neighboring thiophene moieties in a-terthienyl are placed antiparallel, while the mol. is almost planar, with torsional angles between the rings of about 6-9 Deg. MNDO calcns. of a-terthienyl

  19. Extended X-ray absorption fine structure investigation of nitrogen stabilized expanded austenite

    DEFF Research Database (Denmark)

    Oddershede, Jette; Christiansen, Thomas; Ståhl, Kenny

    2010-01-01

    As-delivered austenitic stainless steel and nitrogen stabilized expanded austenite, both fully nitrided and denitrided (in H2), were investigated with Cr, Fe and Ni extended X-ray absorption fine structure. The data shows pronounced short-range ordering of Cr and N. For the denitrided specimen...

  20. Grating-based X-ray tomography of 3D food structures

    DEFF Research Database (Denmark)

    Miklos, Rikke; Nielsen, Mikkel Schou; Einarsdottir, Hildur

    2016-01-01

    A novel grating based X-ray phase-contrast tomographic method has been used to study how partly substitution of meat proteins with two different types of soy proteins affect the structure of the formed protein gel in meat emulsions. The measurements were performed at the Swiss synchrotron radiati...

  1. Depth profiling of marker layers using x-ray waveguide structures

    International Nuclear Information System (INIS)

    Gupta, Ajay; Rajput, Parasmani; Saraiya, Amit; Reddy, V. R.; Gupta, Mukul; Bernstorff, Sigrid; Amenitsch, H.

    2005-01-01

    It is demonstrated that x-ray waveguide structures can be used for depth profiling of a marker layer inside the guiding layer with an accuracy of better than 0.2 nm. A combination of x-ray fluorescence and x-ray reflectivity measurements can provide detailed information about the structure of the guiding layer. The position and thickness of the marker layer affect different aspects of the angle-dependent x-ray fluorescence pattern, thus making it possible to determine the structure of the marker layer in an unambiguous manner. As an example, effects of swift heavy ion irradiation on a Si/M/Si trilayer (M=Fe, W), forming the cavity of the waveguide structure, have been studied. It is found that in accordance with the prediction of thermal spike model, Fe is much more sensitive to swift heavy ion induced modifications as compared to W, even in thin film form. However, a clear evidence of movement of the Fe marker layer towards the surface is observed after irradiation, which cannot be understood in terms of the thermal spike model alone

  2. Depth profiling of marker layers using x-ray waveguide structures

    Science.gov (United States)

    Gupta, Ajay; Rajput, Parasmani; Saraiya, Amit; Reddy, V. R.; Gupta, Mukul; Bernstorff, Sigrid; Amenitsch, H.

    2005-08-01

    It is demonstrated that x-ray waveguide structures can be used for depth profiling of a marker layer inside the guiding layer with an accuracy of better than 0.2 nm. A combination of x-ray fluorescence and x-ray reflectivity measurements can provide detailed information about the structure of the guiding layer. The position and thickness of the marker layer affect different aspects of the angle-dependent x-ray fluorescence pattern, thus making it possible to determine the structure of the marker layer in an unambiguous manner. As an example, effects of swift heavy ion irradiation on a Si/M/Si trilayer ( M=Fe , W), forming the cavity of the waveguide structure, have been studied. It is found that in accordance with the prediction of thermal spike model, Fe is much more sensitive to swift heavy ion induced modifications as compared to W, even in thin film form. However, a clear evidence of movement of the Fe marker layer towards the surface is observed after irradiation, which cannot be understood in terms of the thermal spike model alone.

  3. The 1s x-ray absorption pre-edge structures in transition metal oxides

    NARCIS (Netherlands)

    de Groot, Frank|info:eu-repo/dai/nl/08747610X; Vanko, Gyoergy; Glatzel, Pieter

    2009-01-01

    We develop a general procedure to analyse the pre-edges in 1s x-ray absorption near edge structure (XANES) of transition metal oxides and coordination complexes. Transition metal coordination complexes can be described from a local model with one metal ion. The 1s 3d quadrupole transitions are

  4. Stigmasterol from Eichhornia crassipes (water hyacinth) : Isolation, characterization and X-ray structure

    Digital Repository Service at National Institute of Oceanography (India)

    Singh, K.S.; Sawant, S.G.; PrabhaDevi; Kaminsky, W.

    >H48O by combination of NMR and mass spectroscopic data The sterol was fully characterized by FTIR,NMR(1H13C) and mass spectral data Solid state structure of the sterol was determined by single crystal X-Ray diffraction...

  5. Total chemical synthesis and X-ray structure of kaliotoxin by racemic protein crystallography.

    Science.gov (United States)

    Pentelute, Brad L; Mandal, Kalyaneswar; Gates, Zachary P; Sawaya, Michael R; Yeates, Todd O; Kent, Stephen B H

    2010-11-21

    Here we report the total synthesis of kaliotoxin by 'one pot' native chemical ligation of three synthetic peptides. A racemic mixture of D- and L-kaliotoxin synthetic protein molecules gave crystals in the centrosymmetric space group P1 that diffracted to atomic-resolution (0.95 Å), enabling the X-ray structure of kaliotoxin to be determined by direct methods.

  6. Dark-field X-ray microscopy for multiscale structural characterization

    DEFF Research Database (Denmark)

    Simons, Hugh; King, A.; Ludwig, W.

    2015-01-01

    of the interactions between crystalline elements is a key step towards the formulation and validation of multiscale models that account for the entire heterogeneity of a material. Furthermore, dark-field X-ray microscopy is well suited to applied topics, where the structural evolution of internal nanoscale elements...

  7. THE X-RAY STRUCTURE AND THE 13 C NMR DATA OF ...

    African Journals Online (AJOL)

    The alkaloids pellitorine and chelerythrine acetonate were isolated from the stem bark of Zanthoxylum davyi together with methyl octadecyl ketone, lupeol and hesperidin. The alkaloid skimmianie was isolated from the leaves. The X-Ray structure of chelerythrine acetonate was also determined. Key Words: Zanthoxylum ...

  8. Controlled agglomeration of Tb-doped Y2O3 nanocrystals studied by x-ray absorption fine structure, x-ray excited luminescence, and photoluminescence

    International Nuclear Information System (INIS)

    Soo, Y.L.; Huang, S.W.; Kao, Y.H.; Chhabra, V.; Kulkarni, B.; Veliadis, J.V.; Bhargava, R.N.

    1999-01-01

    Local environment surrounding Y atoms in Y 2 O 3 :Tb nanocrystals under various heat treatment conditions has been investigated by using the extended x-ray absorption fine structure (EXAFS) technique. X-ray excited luminescence (XEL) with the incident x-ray energy near Y K edge and Tb L edges has also been measured to investigate the mechanisms of x-ray-to-visible down conversion in these doped nanoparticles. The observed changes in EXAFS, XEL, and photoluminescent data can be explained on the basis of increased average size of the nanoparticles as confirmed by transmission electron microscopy studies. Our results thus demonstrate that the doped nanoparticles can agglomerate to a controllable degree by varying the heat treatment temperature. At higher temperatures, the local environment surrounding Y atoms in the nanoparticles is found to become similar to that in bulk Y 2 O 3 while the XEL output still shows the characteristics of nanocrystals. These results indicate that appropriate heat treatment can afford an effective means to control the intensity and signal-to-background ratio of green luminescence output of these doped nanocrystal phosphors, potentially useful for some device applications. copyright 1999 American Institute of Physics

  9. Characterization of atmospheric aerosols using Synchroton radiation total reflection X-ray fluorescence and Fe K-edge total reflection X-ray fluorescence-X-ray absorption near-edge structure

    Energy Technology Data Exchange (ETDEWEB)

    Fittschen, U.E.A. [Department of Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg (Germany)], E-mail: ursula.fittschen@chemie.uni-hamburg.de; Meirer, F. [Atominstitut, Vienna University of Technology, Stadionallee 2, 1020 Wien (Austria)], E-mail: fmeirer@ati.ac.at; Streli, C. [Atominstitut, Vienna University of Technology, Stadionallee 2, 1020 Wien (Austria)], E-mail: streli@ati.ac.at; Wobrauschek, P. [Atominstitut, Vienna University of Technology, Stadionallee 2, 1020 Wien (Austria)], E-mail: wobi@ati.ac.at; Thiele, J. [Department of Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg (Germany)], E-mail: Julian.Thiele@gmx.de; Falkenberg, G. [Hamburger Synchrotronstrahlungslabor at Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22603 Hamburg (Germany)], E-mail: falkenbe@mail.desy.de; Pepponi, G. [ITC-irst, Via Sommarive 18, 38050 Povo (Trento) (Italy)], E-mail: pepponi@itc.it

    2008-12-15

    In this study a new procedure using Synchrotron total reflection X-ray fluorescence (SR-TXRF) to characterize elemental amounts in atmospheric aerosols down to particle sizes of 0.015 um is presented. The procedure was thoroughly evaluated regarding bounce off effects and blank values. Additionally the potential of total reflection X-ray fluorescence-X-ray absorption near edge structure (SR-TXRF-XANES) for speciation of FeII/III down to amounts of 34 pg in aerosols which were collected for 1 h is shown. The aerosols were collected in the city of Hamburg with a low pressure Berner impactor on Si carriers covered with silicone over time periods of 60 and 20 min each. The particles were collected in four and ten size fractions of 10.0-8.0 {mu}m, 8.0-2.0 {mu}m, 2.0-0.13 {mu}m 0.13-0.015 {mu}m (aerodynamic particle size) and 15-30 nm, 30-60 nm, 60-130 nm, 130-250 nm, 250-500 nm, 0.5-1 {mu}m, 1-2 {mu}m, 2-4 {mu}m, 4-8 {mu}m, 8-16 {mu}m. Prior to the sampling 'bounce off' effects on Silicone and Vaseline coated Si carriers were studied with total reflection X-ray fluorescence. According to the results silicone coated carriers were chosen for the analysis. Additionally, blank levels originating from the sampling device and the calibration procedure were studied. Blank levels of Fe corresponded to 1-10% of Fe in the aerosol samples. Blank levels stemming from the internal standard were found to be negligible. The results from the Synchroton radiation total reflection X-ray fluorescence analysis of the aerosols showed that 20 min of sampling time gave still enough sample material for elemental determination of most elements. For the determination of the oxidation state of Fe in the aerosols different Fe salts were prepared as a reference from suspensions in isopropanol. The results from the Fe K-edge Synchroton radiation total reflection X-ray fluorescence-X-ray absorption near-edge structure analysis of the aerosol samples showed that mainly Fe(III) was present in

  10. Characterization of atmospheric aerosols using Synchroton radiation total reflection X-ray fluorescence and Fe K-edge total reflection X-ray fluorescence-X-ray absorption near-edge structure

    International Nuclear Information System (INIS)

    Fittschen, U.E.A.; Meirer, F.; Streli, C.; Wobrauschek, P.; Thiele, J.; Falkenberg, G.; Pepponi, G.

    2008-01-01

    In this study a new procedure using Synchrotron total reflection X-ray fluorescence (SR-TXRF) to characterize elemental amounts in atmospheric aerosols down to particle sizes of 0.015 um is presented. The procedure was thoroughly evaluated regarding bounce off effects and blank values. Additionally the potential of total reflection X-ray fluorescence-X-ray absorption near edge structure (SR-TXRF-XANES) for speciation of FeII/III down to amounts of 34 pg in aerosols which were collected for 1 h is shown. The aerosols were collected in the city of Hamburg with a low pressure Berner impactor on Si carriers covered with silicone over time periods of 60 and 20 min each. The particles were collected in four and ten size fractions of 10.0-8.0 μm, 8.0-2.0 μm, 2.0-0.13 μm 0.13-0.015 μm (aerodynamic particle size) and 15-30 nm, 30-60 nm, 60-130 nm, 130-250 nm, 250-500 nm, 0.5-1 μm, 1-2 μm, 2-4 μm, 4-8 μm, 8-16 μm. Prior to the sampling 'bounce off' effects on Silicone and Vaseline coated Si carriers were studied with total reflection X-ray fluorescence. According to the results silicone coated carriers were chosen for the analysis. Additionally, blank levels originating from the sampling device and the calibration procedure were studied. Blank levels of Fe corresponded to 1-10% of Fe in the aerosol samples. Blank levels stemming from the internal standard were found to be negligible. The results from the Synchroton radiation total reflection X-ray fluorescence analysis of the aerosols showed that 20 min of sampling time gave still enough sample material for elemental determination of most elements. For the determination of the oxidation state of Fe in the aerosols different Fe salts were prepared as a reference from suspensions in isopropanol. The results from the Fe K-edge Synchroton radiation total reflection X-ray fluorescence-X-ray absorption near-edge structure analysis of the aerosol samples showed that mainly Fe(III) was present in all particle size fractions

  11. Local moments and electronic correlations in Fe-based Heusler alloys: Kα x-ray emission spectra measurements

    International Nuclear Information System (INIS)

    Svyazhin, Artem; Kurmaev, Ernst; Shreder, Elena; Shamin, Sergey; Sahle, Christoph J.

    2016-01-01

    Heusler alloys are a property-rich class of materials, intensively investigated today from both theoretical and real-world application points of view. In this paper, we attempt to shed light on the role of electronic correlations in the Fe_2MeAl group (where Me represents all 3d elements from Ti to Ni) of Heusler alloys. For this purpose, we have investigated the local moments of iron by means of the x-ray emission spectroscopy technique. To obtain numerical values of local moments, the Kα-FWHM method has been employed for the first time. In every compound of the group, the presence of a local moment on the Fe atom was detected. As has been revealed, the values of these moments are temperature-independent, pointing to an insufficiency of a pure itinerant approach to magnetism in these alloys. We also comprehensively compare the usage of Kβ main lines and Kα spectra as tools for the probing of local moments and point out the significant advantages of the latter. - Highlights: • Local spin moments of iron in Fe_2MeAl (Me = Ti … Ni) Heusler alloys were investigated by means of x-ray emission spectroscopy. • Independence of the local moments from temperature confirms their localized nature. • A local moment value of iron in Fe_2MeAl raises with the atomic number of element Me. • The applicability of the Kα x-ray emission line for extracting local moment values of 3d elements was established.

  12. Estimation of identification limit for a small-type OSL dosimeter on the medical images by measurement of X-ray spectra

    OpenAIRE

    Takegami, Kazuki ; Hayashi, Hiroaki; Okino, Hiroki; Kimoto, Natsumi ; Maehata, Itsumi ; Kanazawa, Yuki ; Okazaki, Tohru ; Hashizume, Takuya ; Kobayashi, Ikuo 

    2016-01-01

    Our aim in this study is to derive an identification limit on a dosimeter for not disturbing a medical image when patients wear a small-type optically stimulated luminescence (OSL) dosimeter on their bodies during X-ray diagnostic imaging. For evaluation of the detection limit based on an analysis of X-ray spectra, we propose a new quantitative identification method. We performed experiments for which we used diagnostic X-ray equipment, a soft-tissue-equivalent phantom (1–20 cm), and a CdTe X...

  13. Structure analysis of InN film using extended X-ray absorption fine structure method

    Energy Technology Data Exchange (ETDEWEB)

    Miyajima, T.; Kobayashi, T.; Hirata, S. [Core Technology Development Center, Core Technology and Network Company, Sony Corporation, 4-14-1 Asahi-cho, Atsugi, Kanagawa 243-0014 (Japan); Kudo, Y.; Liu, K.L. [Technology Solutions Center, Sony Corporation, 4-16-1 Okata, Atsugi, Kanagawa 243-0021 (Japan); Uruga, T.; Honma, T. [Japan Synchrotron Radiation Research Institute, Mikazuki-cho, Hyogo 679-5198 (Japan); Saito, Y.; Hori, M.; Nanishi, Y. [Department of Photonics, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, Shiga 525-8577 (Japan)

    2002-12-01

    We investigated the local atomic structure around In atoms of MBE-grown InN which has a direct bandgap energy of 0.8 eV, using extended X-ray absorption fine structure (EXAFS) oscillation of In K-edge. The signals from the first-nearest neighbor atoms (N) and second-nearest atoms (In) from In atoms were clearly observed and the atomic bond length of In-N and In-In was estimated to be d{sub In-N}=0.215 nm and d{sub In-In}=0.353 nm, respectively. The In-N bond length of d{sub In-In}=0.353 nm was closed to the a-axis lattice constant of a=0.3536 nm, which was determined using X-ray diffraction measurements. The obtained local atomic structure agreed with the calculated ideal structure. We conclude, therefore, that the InN film with a bandgap energy of 0.8 eV has a high structural symmetry in the range of a few A around In atoms. (Abstract Copyright [2002], Wiley Periodicals, Inc.)

  14. Structure analysis of InN film using extended X-ray absorption fine structure method

    International Nuclear Information System (INIS)

    Miyajima, T.; Kobayashi, T.; Hirata, S.; Kudo, Y.; Liu, K.L.; Uruga, T.; Honma, T.; Saito, Y.; Hori, M.; Nanishi, Y.

    2002-01-01

    We investigated the local atomic structure around In atoms of MBE-grown InN which has a direct bandgap energy of 0.8 eV, using extended X-ray absorption fine structure (EXAFS) oscillation of In K-edge. The signals from the first-nearest neighbor atoms (N) and second-nearest atoms (In) from In atoms were clearly observed and the atomic bond length of In-N and In-In was estimated to be d In-N =0.215 nm and d In-In =0.353 nm, respectively. The In-N bond length of d In-In =0.353 nm was closed to the a-axis lattice constant of a=0.3536 nm, which was determined using X-ray diffraction measurements. The obtained local atomic structure agreed with the calculated ideal structure. We conclude, therefore, that the InN film with a bandgap energy of 0.8 eV has a high structural symmetry in the range of a few A around In atoms. (Abstract Copyright [2002], Wiley Periodicals, Inc.)

  15. Spatially resolved x-ray laser spectra and demonstration of gain in nickel-like systems

    Energy Technology Data Exchange (ETDEWEB)

    Whelan, D.A.; Keane, C.J.; MacGowan, B.J.; Matthews, D.L.; Trebes, J.E.; Eckart, M.J.

    1987-09-25

    A recent series of experiments have provided spatially resolved near field images of several candidate x-ray lasing transition in neon-like, nickel-like, and hydrogen-like ions from laser-produced plasmas. From these time-gated, spatially, and spectrally resolved measurements the source size for the J = 0 - 1 and the J = 2 - 1 transitions in Ne-like selenium have been determined. Source regions as small as 50 ..mu..m have been observed on transitions with gain-length products >9. In addition, we have obtained the first experimental evidence for the amplification of spontaneous emission in the nickel-like ions of europium and ytterbium. Gains of order 1 cm/sup -1/ and gain-length products of up to 3.8 are observed on the J = 0 - 1, 4d-4p transitions in Eu + 35 at 65.26 and 71.00 A. Analogous transitions in Yb = +42 have been identified and some evidence for ASE has been observed. 7 refs., 11 figs.

  16. Spatially resolved X-ray laser spectra and demonstration of gain in nickel-like systems

    International Nuclear Information System (INIS)

    Whelan, D.A.; Keane, C.J.; MacGowan, B.J.; Matthews, D.L.; Trebes, J.E.; Eckart, M.J.

    1987-01-01

    A recent series of experiments have provided spatially resolved near field images of several candidate x-ray lasing transition in neon-like, nickel-like, and hydrogen-like ions from laser-produced plasmas. From these time-gated, spatially, and spectrally resolved measurements the source size for the J=0-1 and the J=2-1 transitions in Ne-like selenium have been determined. Source regions as small as 50 μm have been observed on transitions with gain-length products >9. In addition, the authors have obtained the first experimental evidence for the amplification of spontaneous emission in the nickel-like ions of europium and ytterbium. Gains of order 1 cm/sup -1/ and gain-length products of up to 3.8 are observed on the J=0-1,4d-4p transitions in Eu/sup +35/ at 65.83 and 71.00A. Analogous transitions in Yb/sup +42/ have been identified and some evidence for ASE has been observed

  17. Study of X-Ray and $\\gamma$-Ray Spectra from Antiprotonic Atoms at the Slowly Extracted Antiproton Beam of LEAR

    CERN Multimedia

    2002-01-01

    This experiment will study the X-ray spectra of antiprotonic atoms and the $\\gamma$ spectra of residual nuclei after the antiproton absorption. We intend to begin with measurements on selected isotopically pure targets. Strong interaction effects, the antiproton absorption and the atomic cascade are analysed through the measurement of energies, lineshapes, relative and absolute intensities of all observable lines. The experiments are continued to determine st in resolved fine structure levels and in different isotopes of the same element. Coincidence techniques may be applied. All components of the experimental set-up are already existing from previous experiments and we could begin the measurements with any slowly extracted beam of low energy at LEAR.

  18. Local electronic and geometrical structures of hydrogen-bonded complexes studied by soft X-ray spectroscopy

    International Nuclear Information System (INIS)

    Luo, Y.

    2004-01-01

    Full text: The hydrogen bond is one of the most important forms of intermolecular interactions. It occurs in all-important components of life. However, the electronic structures of hydrogen-bonded complexes in liquid phases have long been difficult to determine due to the lack of proper experimental techniques. In this talk, a recent joint theoretical and experimental effort to understand hydrogen bonding in liquid water and alcohol/water mixtures using synchrotron radiation based soft-X-ray spectroscopy will be presented. The complexity of the liquid systems has made it impossible to interpret the spectra with physical intuition alone. Theoretical simulations have thus played an essential role in understanding the spectra and providing valuable insights on the local geometrical and electronic structures of these liquids. Our study sheds light on a 40-year controversy over what kinds of molecular structures are formed in pure liquid methanol. It also suggests an explanation for the well-known puzzle of why alcohol and water do not mix completely: the system must balance nature's tendency toward greater disorder (entropy) with the molecules' tendency to form hydrogen bonds. The observation of electron sharing and broken hydrogen bonding local structures in liquid water will be presented. The possible use of X-ray spectroscopy to determinate the local arrangements of hydrogen-bonded nanostructures will also been discussed

  19. Electronic structure and X-ray spectroscopic properties of YbNi{sub 2}P{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Shcherba, I.D., E-mail: ishcherba@gmail.com [Institute of Technology, University of Pedagogy, Podchorazych 2, 30-084 Krakow (Poland); Lviv National University by Ivan Franko, Lviv (Ukraine); Bekenov, L.V.; Antonov, V.N. [Institute for Metal Physics, 36 Vernadsky Street, 03142 Kiev (Ukraine); Noga, H. [Institute of Technology, University of Pedagogy, Podchorazych 2, 30-084 Krakow (Poland); Uskokovic, D. [Institute of Technical Sciences, SASA, Belgrade (Serbia); Zhak, O.; Kovalska, M.V. [Lviv National University by Ivan Franko, Lviv (Ukraine)

    2016-10-15

    Highlights: • We present new experimental and theoretical data for YbNi{sub 2}P{sub 2}. • The presence of divalent and trivalent Yb ion found in YbNi{sub 2}P{sub 2}. • The calculation show good agreement with the experimental measurements. - Abstract: X-ray absorption spectrum at the Yb L{sub 3} edge and X-ray emission spectra of Ni and P at the K and L{sub 2,3} edges have been studied experimentally and theoretically in the mixed valent compound YbNi{sub 2}P{sub 2} with ThCr{sub 2}Si{sub 2} type crystal structure. The electronic structure of YbNi{sub 2}P{sub 2} is investigated using the fully relativistic Dirac linear muffin-tin orbital (LMTO) band-structure method. The effect of the spin–orbit (SO) interaction and Coulomb repulsion U on the electronic structure of YbNi{sub 2}P{sub 2} is examined in the frame of the LSDA + SO + U method. The core-hole effect in the final states as well as the effect of the electric quadrupole E{sub 2} transitions have been investigated. A good agreement between the theory and the experiment was found. Both the trivalent and the divalent Yb ions in YbNi{sub 2}P{sub 2} are reflected in the experimentally measured Yb L{sub 3} X-ray absorption spectrum simultaneously. We found that the best agreement between the experimental spectrum and sum of the theoretically calculated Yb{sup 2+} and Yb{sup 3+} spectra is achieved with 73% ytterbium ions in 2+ state and 27% ions in 3+ state.

  20. XMM-Newton Survey of Local O VII Absorption Lines in the Spectra of Galactic X-Ray Sources

    Science.gov (United States)

    Luo, Yang; Fang, Taotao; Ma, Renyi

    2018-04-01

    The detection of highly ionized metal absorption lines in the X-ray spectra of the Galactic X-ray binaries (XRBs) implies the distribution of hot gas along the sightline toward the background sources. However, the origin of this hot gas is still unclear: it can arise in the hot interstellar medium (ISM), or is intrinsic to the XRBs. In this paper, we present an XMM-Newton survey of the O VII absorption lines in the spectra of Galactic XRBs. A total of 33 XRBs were selected, with 29 low-mass XRBs and 4 high-mass XRBs. At a more than 3σ threshold, O VII absorption line was detected in 16 targets, among which 4 were newly discovered in this work. The average line equivalent width is centered around ∼20 mÅ. Additionally, we do not find strong correlations between the O VII EWs and the Galactic neutral absorption N H, the Galactic coordinates, or the distance of background targets. Such non-correlation may suggest contamination of the circumstellar material, or a lack of constraints on the line Doppler-b parameter. We also find that regardless of the direction of the XRBs, the O VII absorption lines are always detected when the flux of the background XRBs reaches a certain level, suggesting a uniform distribution of this hot gas. We estimate a ratio of 0.004–0.4 between the hot and neutral phases of the ISM. This is the second paper in the series following Fang et al. (2015), in which we focused on the local O VII absorption lines detected in the background AGN spectra. Detailed modeling of the hot ISM distribution will be investigated in a future paper.

  1. X-ray Reflected Spectra from Accretion Disk Models. III. A Complete Grid of Ionized Reflection Calculations

    Science.gov (United States)

    Garcia, J.; Dauser, T.; Reynolds, C. S.; Kallman, T. R.; McClintock, J. E.; Wilms, J.; Ekmann, W.

    2013-01-01

    We present a new and complete library of synthetic spectra for modeling the component of emission that is reflected from an illuminated accretion disk. The spectra were computed using an updated version of our code xillver that incorporates new routines and a richer atomic data base. We offer in the form of a table model an extensive grid of reflection models that cover a wide range of parameters. Each individual model is characterized by the photon index Gamma of the illuminating radiation, the ionization parameter zeta at the surface of the disk (i.e., the ratio of the X-ray flux to the gas density), and the iron abundance A(sub Fe) relative to the solar value. The ranges of the parameters covered are: 1.2 <= Gamma <= 3.4, 1 <= zeta <= 104, and 0.5 <= A(sub Fe) <= 10. These ranges capture the physical conditions typically inferred from observations of active galactic nuclei, and also stellar-mass black holes in the hard state. This library is intended for use when the thermal disk flux is faint compared to the incident power-law flux. The models are expected to provide an accurate description of the Fe K emission line, which is the crucial spectral feature used to measure black hole spin. A total of 720 reflection spectra are provided in a single FITS file suitable for the analysis of X-ray observations via the atable model in xspec. Detailed comparisons with previous reflection models illustrate the improvements incorporated in this version of xillver.

  2. The spectra of the standard x-ray qualities used in STUK's Radiation Metrology Laboratory

    International Nuclear Information System (INIS)

    Tapiovaara, T.; Tapiovaara, M.; Siiskonen, T.; Hakanen, A.

    2008-02-01

    This report presents the fluence spectra of the standard x-radiation qualities used in the Radiation Dosimetry Laboratory of Radiation and Nuclear Safety Authority (STUK). The spectra were measured in August 2007. The radiation qualities characterised in the report are the ISO Narrow spectrum series (ISO N10-N200, ISO 4037-1:1996) and both of the RQR-spectrum series specified by the IEC (IEC 1267:1994 and IEC 61267:2005). The measurements were made using a high purity Ge-detector and the measured pulse height spectra were corrected to fluence spectra. Spectral characteristics were computed from the spectral data and compared to the requirements in the standards and to the values given in the quality manual of the laboratory. (orig.)

  3. Calculation of Absorbed Glandular Dose using a FORTRAN Program Based on Monte Carlo X-ray Spectra in Mammography

    Directory of Open Access Journals (Sweden)

    Ali Asghar Mowlavi

    2011-03-01

    Full Text Available Introduction: Average glandular dose calculation in mammography with Mo-Rh target-filter and dose calculation for different situations is accurate and fast. Material and Methods: In this research, first of all, x-ray spectra of a Mo target bombarded by a 28 keV electron beam with and without a Rh filter were calculated using the MCNP code. Then, we used the Sobol-Wu parameters to write a FORTRAN code to calculate average glandular dose. Results: Average glandular dose variation was calculated against the voltage of the mammographic x-ray tube for d = 5 cm, HVL= 0.35 mm Al, and different value of g. Also, the results related to average glandular absorbed dose variation per unit roentgen radiation against the glandular fraction of breast tissue for kV = 28 and HVL = 0.400 mmAl and different values of d are presented. Finally, average glandular dose against d for g = 60% and three values of kV (23, 27, 35 kV with corresponding HVLs have been calculated. Discussion and Conclusion: The absorbed dose computational program is accurate, complete, fast and user friendly. This program can be used for optimization of exposure dose in mammography. Also, the results of this research are in good agreement with the computational results of others.

  4. Thermal expansion behavior study of Co nanowire array with in situ x-ray diffraction and x-ray absorption fine structure techniques

    Science.gov (United States)

    Mo, Guang; Cai, Quan; Jiang, Longsheng; Wang, Wei; Zhang, Kunhao; Cheng, Weidong; Xing, Xueqing; Chen, Zhongjun; Wu, Zhonghua

    2008-10-01

    In situ x-ray diffraction and x-ray absorption fine structure techniques were used to study the structural change of ordered Co nanowire array with temperature. The results show that the Co nanowires are polycrystalline with hexagonal close packed structure without phase change up until 700 °C. A nonlinear thermal expansion behavior has been found and can be well described by a quadratic equation with the first-order thermal expansion coefficient of 4.3×10-6/°C and the second-order thermal expansion coefficient of 5.9×10-9/°C. The mechanism of this nonlinear thermal expansion behavior is discussed.

  5. Water structure as a function of temperature from X-ray scatteringexperiments and ab initio molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Hura, Greg; Russo, Daniela; Glaeser, Robert M.; Head-Gordon,Teresa; Krack, Matthias; Parrinello, Michele

    2003-03-01

    We present high-quality X-ray scattering experiments on pure water taken over a temperature range of 2 to 77 C using a synchrotron beam line at the advanced light source (ALS) at Lawrence Berkeley National Laboratory. The ALS X-ray scattering intensities are qualitatively different in trend of maximum intensity over this temperature range compared to older X-ray experiments. While the common procedure is to report both the intensity curve and radial distribution function(s), the proper extraction of the real-space pair correlation functions from the experimental scattering is very difficult due to uncertainty introduced in the experimental corrections, the proper weighting of OO, OH, and HH contributions, and numerical problems of Fourier transforming truncated data in Q-space. Instead, we consider the direct calculation of X-ray scattering spectra using electron densities derived from density functional theory based on real-space configurations generated with classical water models. The simulation of the experimental intensity is therefore definitive for determining radial distribution functions over a smaller Q-range. We find that the TIP4P, TIP5P and polarizable TIP4P-Pol2 water models, with DFT-LDA densities, show very good agreement with the experimental intensities, and TIP4P-Pol2 in particular shows quantitative agreement over the full temperature range. The resulting radial distribution functions from TIP4P-Pol2 provide the current best benchmarks for real-space water structure over the biologically relevant temperature range studied here.

  6. Water structure as a function of temperature from X-ray scattering experiments and ab initio molecular dynamics

    International Nuclear Information System (INIS)

    Hura, Greg; Russo, Daniela; Glaeser, Robert M.; Head-Gordon, Teresa; Krack, Matthias; Parrinello, Michele

    2003-01-01

    We present high-quality X-ray scattering experiments on pure water taken over a temperature range of 2 to 77 C using a synchrotron beam line at the advanced light source (ALS) at Lawrence Berkeley National Laboratory. The ALS X-ray scattering intensities are qualitatively different in trend of maximum intensity over this temperature range compared to older X-ray experiments. While the common procedure is to report both the intensity curve and radial distribution function(s), the proper extraction of the real-space pair correlation functions from the experimental scattering is very difficult due to uncertainty introduced in the experimental corrections, the proper weighting of OO, OH, and HH contributions, and numerical problems of Fourier transforming truncated data in Q-space. Instead, we consider the direct calculation of X-ray scattering spectra using electron densities derived from density functional theory based on real-space configurations generated with classical water models. The simulation of the experimental intensity is therefore definitive for determining radial distribution functions over a smaller Q-range. We find that the TIP4P, TIP5P and polarizable TIP4P-Pol2 water models, with DFT-LDA densities, show very good agreement with the experimental intensities, and TIP4P-Pol2 in particular shows quantitative agreement over the full temperature range. The resulting radial distribution functions from TIP4P-Pol2 provide the current best benchmarks for real-space water structure over the biologically relevant temperature range studied here

  7. Accurate quasiparticle calculation of x-ray photoelectron spectra of solids.

    Science.gov (United States)

    Aoki, Tsubasa; Ohno, Kaoru

    2018-05-31

    It has been highly desired to provide an accurate and reliable method to calculate core electron binding energies (CEBEs) of crystals and to understand the final state screening effect on a core hole in high resolution x-ray photoelectron spectroscopy (XPS), because the ΔSCF method cannot be simply used for bulk systems. We propose to use the quasiparticle calculation based on many-body perturbation theory for this problem. In this study, CEBEs of band-gapped crystals, silicon, diamond, β-SiC, BN, and AlP, are investigated by means of the GW approximation (GWA) using the full ω integration and compared with the preexisting XPS data. The screening effect on a deep core hole is also investigated in detail by evaluating the relaxation energy (RE) from the core and valence contributions separately. Calculated results show that not only the valence electrons but also the core electrons have an important contribution to the RE, and the GWA have a tendency to underestimate CEBEs due to the excess RE. This underestimation can be improved by introducing the self-screening correction to the GWA. The resulting C1s, B1s, N1s, Si2p, and Al2p CEBEs are in excellent agreement with the experiments within 1 eV absolute error range. The present self-screening corrected GW approach has the capability to achieve the highly accurate prediction of CEBEs without any empirical parameter for band-gapped crystals, and provide a more reliable theoretical approach than the conventional ΔSCF-DFT method.

  8. Accurate quasiparticle calculation of x-ray photoelectron spectra of solids

    Science.gov (United States)

    Aoki, Tsubasa; Ohno, Kaoru

    2018-05-01

    It has been highly desired to provide an accurate and reliable method to calculate core electron binding energies (CEBEs) of crystals and to understand the final state screening effect on a core hole in high resolution x-ray photoelectron spectroscopy (XPS), because the ΔSCF method cannot be simply used for bulk systems. We propose to use the quasiparticle calculation based on many-body perturbation theory for this problem. In this study, CEBEs of band-gapped crystals, silicon, diamond, β-SiC, BN, and AlP, are investigated by means of the GW approximation (GWA) using the full ω integration and compared with the preexisting XPS data. The screening effect on a deep core hole is also investigated in detail by evaluating the relaxation energy (RE) from the core and valence contributions separately. Calculated results show that not only the valence electrons but also the core electrons have an important contribution to the RE, and the GWA have a tendency to underestimate CEBEs due to the excess RE. This underestimation can be improved by introducing the self-screening correction to the GWA. The resulting C1s, B1s, N1s, Si2p, and Al2p CEBEs are in excellent agreement with the experiments within 1 eV absolute error range. The present self-screening corrected GW approach has the capability to achieve the highly accurate prediction of CEBEs without any empirical parameter for band-gapped crystals, and provide a more reliable theoretical approach than the conventional ΔSCF-DFT method.

  9. A Monte Carlo study of the energy spectra and transmission characteristics of scattered radiation from x-ray computed tomography.

    Science.gov (United States)

    Platten, David John

    2014-06-01

    Existing data used to calculate the barrier transmission of scattered radiation from computed tomography (CT) are based on primary beam CT energy spectra. This study uses the EGSnrc Monte Carlo system and Epp user code to determine the energy spectra of CT scatter from four different primary CT beams passing through an ICRP 110 male reference phantom. Each scatter spectrum was used as a broad-beam x-ray source in transmission simulations through seventeen thicknesses of lead (0.00-3.50 mm). A fit of transmission data to lead thickness was performed to obtain α, β and γ parameters for each spectrum. The mean energy of the scatter spectra were up to 12.3 keV lower than that of the primary spectrum. For 120 kVp scatter beams the transmission through lead was at least 50% less than predicted by existing data for thicknesses of 1.5 mm and greater; at least 30% less transmission was seen for 140 kVp scatter beams. This work has shown that the mean energy and half-value layer of CT scatter spectra are lower than those of the corresponding primary beam. The transmission of CT scatter radiation through lead is lower than that calculated with currently available data. Using the data from this work will result in less lead shielding being required for CT scanner installations.

  10. Electronic structure of molecules of substituted benzenes by x-ray spectroscopy. I. Nitrobenzene

    International Nuclear Information System (INIS)

    Yumatov, V.D.; Murakhtanov, V.V.; Salakhutdinov, N.F.; Okotrub, A.V.; Mazalov, L.N.; Logunova, L.G.; Koptyug, V.A.; Furin, G.G.

    1988-01-01

    The electronic structure of the nitrobenzene molecule has been studied by x-ray spectroscopy with the aid of quantum-chemical calculations. The structure of the molecular orbitals of nitrobenzene has been compared with the structure of benzene and nitrogen dioxide. It has been shown in the framework of a fragment-by-fragment analysis that the interaction of the highest occupied π orbitals of the benzene ring and the nitro group is weak

  11. Atomic structure of large angle grain boundaries determined by quantitative X-ray diffraction techniques

    International Nuclear Information System (INIS)

    Fitzsimmons, M.R.; Sass, S.L.

    1988-01-01

    Quantitative X-ray diffraction techniques have been used to determine the atomic structure of the Σ = 5 and 13 [001] twist boundaries in Au with a resolution of 0.09 Angstrom or better. The reciprocal lattices of these boundaries were mapped out using synchrotron radiation. The atomic structures were obtained by testing model structures against the intensity observations with a chi square analysis. The boundary structure were modeled using polyhedra, including octahedra, special configurations of tetrahedra and Archimedian anti-prisms, interwoven together by the boundary symmetry. The results of this work point to the possibility of obtaining general rules for grain boundary structure based on X-ray diffraction observations that give the atomic positions with high resolution

  12. Pollen structure visualization using high-resolution laboratory-based hard X-ray tomography.

    Science.gov (United States)

    Li, Qiong; Gluch, Jürgen; Krüger, Peter; Gall, Martin; Neinhuis, Christoph; Zschech, Ehrenfried

    2016-10-14

    A laboratory-based X-ray microscope is used to investigate the 3D structure of unstained whole pollen grains. For the first time, high-resolution laboratory-based hard X-ray microscopy is applied to study pollen grains. Based on the efficient acquisition of statistically relevant information-rich images using Zernike phase contrast, both surface- and internal structures of pine pollen - including exine, intine and cellular structures - are clearly visualized. The specific volumes of these structures are calculated from the tomographic data. The systematic three-dimensional study of pollen grains provides morphological and structural information about taxonomic characters that are essential in palynology. Such studies have a direct impact on disciplines such as forestry, agriculture, horticulture, plant breeding and biodiversity. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. DMSO-Water Clustering in Solution Observed in Soft X-ray Spectra.

    Science.gov (United States)

    Engel, Nicholas; Atak, Kaan; Lange, Kathrin M; Gotz, Malte; Soldatov, Mikhail; Golnak, Ronny; Suljoti, Edlira; Rubensson, Jan-Erik; Aziz, Emad F

    2012-12-20

    The significant deviation from the ideality of dimethyl sulfoxide (DMSO)/water mixtures can be addressed based on the change of the local molecular orbitals of each solvent upon mixing. Oxygen K-edge absorption and emission spectra of DMSO/water solutions were measured using the liquid microjet technique. The spectra demonstrate that the hydrogen bond network in liquid water is already influenced at small DMSO concentrations, and at the molar fraction xDMSO = 0.43 we find strong evidence of DMSO-water clustering reflected by the influence on the occupied molecular orbitals.

  14. The x-ray emission spectra of multicharged xenon ions in a gas puff laser-produced plasma

    Energy Technology Data Exchange (ETDEWEB)

    Skobelev, I.Yu.; Dyakin, V.M.; Faenov, A.Ya. [Multicharged Ion Spectra Data Center, VNIIFTRI, Mendeleevo (Russian Federation); Bartnik, A.; Fiedorowicz, H.; Jarocki, R.; Kostecki, J.; Szczurek, M. [Institute of Optoelectronics, Military University of Technology, Warsaw (Poland); Biemont, E. [Institut de Physique Nucleaire Experimentale, Universite de Liege, Liege (Belgium); Astrophysique et Spectroscopie, Universite de Mons-Hainaut, Mons (Belgium); Quinet, P. [Astrophysique et Spectroscopie, Universite de Mons-Hainaut, Mons (Belgium); Nilsen, J. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Behar, E.; Doron, R.; Mandelbaum, P.; Schwob, J.L. [Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem (Israel)

    1999-01-14

    Emission spectra of multicharged xenon ions produced by a laser gas puff are observed with high spectral resolution in the 8.5-9.5 and 17-19 A wavelength ranges. Three different theoretical methods are employed to obtain 3l-n'l'(n' = 4 to 10) wavelengths and Einstein coefficients for Ni-like Xe{sup 26+}. For the 3d-4p transitions, very good agreement is found between the experimental wavelengths and the various theoretical wavelengths. These accurate energy level measurements can be useful for studying the Ni-like xenon x-ray laser scheme. On the other hand, several intense spectral lines could not be identified as 3l-n'l' lines of Ni-like xenon, despite the very good agreement between the wavelengths and Einstein coefficients calculated for these transitions using the three different methods. (author)

  15. Resonant inelastic x-ray scattering on iso-C2H2Cl2 around the chlorine K-edge: Structural and dynamical aspects

    International Nuclear Information System (INIS)

    Kawerk, Elie; Carniato, Stéphane; Journel, Loïc; Marchenko, Tatiana; Simon, Marc; Piancastelli, Maria Novella; Žitnik, Matjaž; Bučar, Klemen; Bohnic, Rok

    2014-01-01

    We report a theoretical and experimental study of the high resolution resonant K α X-ray emission lines around the chlorine K-edge in gas phase 1,1-dichloroethylene. With the help of ab initio electronic structure calculations and cross section evaluation, we interpret the lowest lying peak in the X-ray absorption and emission spectra. The behavior of the K α emission lines with respect to frequency detuning highlights the existence of femtosecond nuclear dynamics on the dissociative Potential Energy Surface of the first K-shell core-excited state

  16. Resonant inelastic x-ray scattering on iso-C2H2Cl2 around the chlorine K-edge: Structural and dynamical aspects

    Science.gov (United States)

    Kawerk, Elie; Carniato, Stéphane; Journel, Loïc; Marchenko, Tatiana; Piancastelli, Maria Novella; Žitnik, Matjaž; Bučar, Klemen; Bohnic, Rok; Kavčič, Matjaž; Céolin, Denis; Khoury, Antonio; Simon, Marc

    2014-10-01

    We report a theoretical and experimental study of the high resolution resonant Kα X-ray emission lines around the chlorine K-edge in gas phase 1,1-dichloroethylene. With the help of ab initio electronic structure calculations and cross section evaluation, we interpret the lowest lying peak in the X-ray absorption and emission spectra. The behavior of the Kα emission lines with respect to frequency detuning highlights the existence of femtosecond nuclear dynamics on the dissociative Potential Energy Surface of the first K-shell core-excited state.

  17. Resonant inelastic x-ray scattering on iso-C₂H₂Cl₂ around the chlorine K-edge: structural and dynamical aspects.

    Science.gov (United States)

    Kawerk, Elie; Carniato, Stéphane; Journel, Loïc; Marchenko, Tatiana; Piancastelli, Maria Novella; Žitnik, Matjaž; Bučar, Klemen; Bohnic, Rok; Kavčič, Matjaž; Céolin, Denis; Khoury, Antonio; Simon, Marc

    2014-10-14

    We report a theoretical and experimental study of the high resolution resonant K(α) X-ray emission lines around the chlorine K-edge in gas phase 1,1-dichloroethylene. With the help of ab initio electronic structure calculations and cross section evaluation, we interpret the lowest lying peak in the X-ray absorption and emission spectra. The behavior of the K(α) emission lines with respect to frequency detuning highlights the existence of femtosecond nuclear dynamics on the dissociative Potential Energy Surface of the first K-shell core-excited state.

  18. Dual-energy X-ray absorptiometry for the simultaneous determination of Density and Moisture Content in Porous Structural Materials

    DEFF Research Database (Denmark)

    Hansen, Kurt Kielsgaard; Jensen, Signe Kamp; Gerward, Leif

    1999-01-01

    The paper describes the dual-energy x-ray equipment, which consists of a x-ray source, filters and a detector. The x-ray beam can be moved automatically in two dimensions relative to a fixed specimen. The purpose of the equipment is to measure simultaneously the density and moisture content...... in porous materials relevant for the building industry. The theory of dual-energy x-ray absorptiometry (DEXA) is presented. DEXA results on two combinations of aluminium and acrylic plastic are compared with corresponding values calculated from the geometry of the experimental setup. The results from the x......-ray measurements show good agreement with results from the two standard materials which imitate water in a porous material. On this background the dual-energy x-ray absorptiometry measurement principle can be used on porous structural materials....

  19. Investigation of the antiprotonic X-ray spectra of the isotopes 6Li, 7Li and 40Ca

    International Nuclear Information System (INIS)

    Barth, H.

    1987-04-01

    With the commissioning of the Low-Energy Antiproton Ring (LEAR) at CERN in Geneva a high intensity, high purity antiproton beam became available, enabling precision measurements of antiprotonic X-ray spectra to be carried out. Besides informations about properties of the elementary particle antiproton itself, as for example its mass and its magnetic moment, such measurements provide informations about the strong-interaction potential between antiproton and nucleus at very low energies, which, in turn, can be derived from the elementary antinucleon-nucleon interaction by using microscopic models. This work investigates the antiprotonic X-ray spectra of the isotopes 6 Li, 7 Li and 40 Ca. The data were taken during the experiment PS176 at LEAR. The strong interaction between antiproton and nucleus leads to an energy shift ε and an absorption width Γ of the lower level of the last observable transition and also to intensity reductions, which can be converted to an absorption width for the upper level. For the isotopes 6 Li, 7 Li and 40 Ca the following results were obtained: 6 Li: ε(2p)=(-215±25) eV, Γ(2p)=(660±170) eV and Γ(3d)=(135±16) meV, 7 Li ε(2p)=(-265±20) eV, Γ(2p)=(690±170) eV and Γ(3d)=(129±13) meV, 40 Ca: ε(4f)=(-1060±130) eV, Γ(4f)=(3670±600) eV and Γ(5g)=(34.9±3.3) eV. The results are in fair agreement with theoretical calculations, at the same time showing up the limits of present understanding of antiproton-nucleus interaction. Particularly the spin-orbit part of the strong interaction seems to play a nonnegligible role. (orig.) [de

  20. Soft X-Ray Spectra from High Current Nitrogen Z-Pinch Discharge

    Czech Academy of Sciences Publication Activity Database

    Vrba, Pavel; Vrbová, M.; Nevrkla, M.; Jančárek, A.

    2016-01-01

    Roč. 3, č. 1 (2016), s. 48 ISSN 2336-2626. [SPPT 2016 - 27th Symposium on Plasma Physics and Technology/27./. Prague, 20.06.2016-23.06.2016] Institutional support: RVO:61389021 Keywords : Capillary discharge * recombination pumping * pinch dynamics * evolution of spectra emission * computer modelling Subject RIV: BH - Optics, Masers, Lasers www.plasmaconference.cz

  1. Electronic structure study of Co doped CeO2 nanoparticles using X-ray absorption fine structure spectroscopy

    International Nuclear Information System (INIS)

    Kumar, Shalendra; Gautam, Sanjeev; Song, T.K.; Chae, Keun Hwa; Jang, K.W.; Kim, S.S.

    2014-01-01

    Highlights: • The electronic structural of Co–CeO 2 nanoparticles is investigated using XAFS. • Ce M 5,4 , Ce L 3 and O K edge NEXAFS reveal that the Ce-ions are in +4 valence state. • The NEXAFS spectrum performed at Co L3,2-edge confirms Co-ion in 2+ state. • The EXAFS analysis also show that Co ions are occupying Ce position in doped CeO 2 . • The distances between Ce–O and Ce–Ce/Co in all shells decreases with Co doping. - Abstract: We investigated the electronic structure of well characterized Co doped CeO 2 nanoparticles using X-ray absorption fine structure (XAFS) spectroscopy. Near edge X-ray absorption fine structure (NEXAFS) spectra at Ce M 5,4 , Ce L 3 and O K-edge conclude that the Ce-ions are in +4 valence state in pure as well as in Co doped CeO 2 nanoparticles. The local structure around Ce-atom in Co doped CeO 2 nanoparticles was also determined using extended X-ray absorption fine structure (EXAFS) spectroscopy at Ce L 3 edge. The EXAFS analysis suggest that the inter-atomic distance of Ce–O, Ce–Ce/Co decreases with Co doping, which indicate a contraction of the lattice. The decease in Ce–O distance also reflect that there is a formation of oxygen vacancies in CeO 2 matrix. The Debye–Waller factor also shows the consistent behaviour for all the coordination shells. The atomic multiplet calculations for Co L 3,2 -edge was performed to determine the valence state, symmetry and field splitting, which reflect that Co-ions are in 2+ state and substituted at Ce-site with crystal field splitting of 10Dq=-0.57eV. The XAFS measurements reveal that the Co-ions occupy the Ce position in the CeO 2 host matrix and create a oxygen vacancy

  2. 3D observation of the solidified structures by x-ray micro computerized tomography

    International Nuclear Information System (INIS)

    Yasuda, Hideyuki; Ohnaka, Itsuo; Tsuchiyama, Akira; Nakano, Tsukasa; Uesugi, Kentaro

    2003-01-01

    The high flux density of the monochromatized and well-collimated X-ray and the high-resolution detector provide a new 3D observation tool for microstructures of metallic alloys and ceramics. The X-ray micro computerized tomography in BL47XU of SPring-8 (SP-μCT) was applied to observe microstructures produced through the eutectic reaction for Sn-based alloys and an Al 2 O 3 -Y 2 O 3 oxide system. The constituent phases in the eutectic structures were three-dimensionally identified, in which the lamellar spacing ranged from several to 10 μm. Since the 3D structure of the unidirectionally solidified specimens contains history of the eutectic structure formation, the 3D structure obtained by SP-μCT gives useful information to consider the microstructure evolution. (author)

  3. Electronic structure of Pt-Co cathode catalysts in membrane electrolyte assembly observed by X-ray absorption fine structure spectroscopy with different probing depth

    International Nuclear Information System (INIS)

    Kobayashi, M.; Hidai, S.; Niwa, H.; Harada, Y.; Oshima, M.; Ofuchi, H.; Nakamori, Y.; Aoki, T.

    2010-01-01

    Electronic structures of Pt-Co cathode and Pt-Ru anode catalysts in membrane electrolyte assemblies (MEAs) for polymer electrolyte fuel cell have been investigated using X-ray absorption near edge structure (XANES) spectroscopy, and the changes of electronic structures accompanied with degradation have been observed by comparison between spectra obtained by fluorescence-yield (FY) and conversion-electron-yield (CEY) methods, probing depths of which are several hundreds μm and ∼100 nm, respectively. The Co K XANES spectra of the as-fabricated MEA show that the Co atoms in the cathode are metallic and oxidized Co ions exist at the interface between the cathode and electrolyte. The spectra of the long-time operated MEA suggest that the oxidation of Co makes progress with degradation of the cathode catalysts. In contrast to the Co K XANES spectra, the line shape of the Ru K XANES spectra is unchanged even after the long-time operation.

  4. Three dimensional analysis of coelacanth body structure by computer graphics and X-ray CT images

    International Nuclear Information System (INIS)

    Suzuki, Naoki; Hamada, Takashi.

    1990-01-01

    Three dimensional imaging processes were applied for the structural and functional analyses of the modern coelacanth (Latimeria chalumnae). Visualization of the obtained images is performed with computer graphics on the basis of serial images by an X-ray CT scanning method. Reconstruction of three dimensional images of the body structure of coelacanth using the volume rendering and surface rendering methods provides us various information about external and internal shapes of this exquisite fish. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  6. Conformation and orientation effects in the x-ray photoelectron spectra of organic polymers

    International Nuclear Information System (INIS)

    Beamson, G.

    2001-01-01

    Conformation and orientation effects in the XPS spectra of organic polymers are small but can be observed with modem high performance equipment. This paper discusses some of the experimental factors that should be considered when attempting to detect such effects, and describes several recent studies which illustrate the subtle phenomena that can now be observed. Conformation effects, revealed by melting semicrystalline polymer samples in the analysis chamber of an XPS spectrometer, are reported for the valence band and C 1s spectra of nylon 12 and poly(ethylene adipate), and for the valence band spectrum of poly(ethylene succinate). For nylon 12 the changes in the C 2s region of the valence band spectrum are interpreted in terms of disordering of the planar zig-zag conformation of the (CH 2 ) 11 segments of the polymer chain. Pendant group surface orientation effects, detected by angle resolved XPS (with emission angles as low as 5 deg. relative to the sample surface), are reported for poly(2-chloroethyl methacrylate) (PCEMA), poly(lauryl methacrylate) (PLMA) and poly(2-hydroxyethyl methacrylate) (PHEMA). For PCEMA and PLMA the uppermost surfaces are enriched with -CH 2 CH 2 Cl and -(CH 2 ) 11 CH 3 pendant groups respectively, whereas for PHEMA the data suggest relatively few -CH 2 CH 2 OH pendant groups at the surface. The C 1s and Cl 2p spectra of PCEMA reveal surface core level binding energy shifts of - +0.2 eV, and the Cl L 23 M 23 M 23 spectrum a surface Auger kinetic energy shift of ∼ -0.6. The C 1s spectra of PLMA and PHEMA also reveal surface core level shifts and for PLMA this is interpreted in terms of a disordered and open arrangement of the -(CH 2 ) 11 CH 3 pendant groups at the polymer surface. (author)

  7. Magnetic and structural properties of Fe/Pd multilayers studied by magnetic x-ray dichroism and x-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Mini, S.M.; Fullerton, E.E.; Sowers, C.H.; Fontaine, A.; Pizzini, S.; Bommannavar, A.S.; Traverse, A.; Baudelet, F.

    1994-12-01

    The results of magnetic circular x-ray dichroism (MCXD) measurements and extended x-ray absorption fine structure measurements (EXAFS) of the Fe K-edges of textured Fe(110)/Pd(111) multilayers are reported. The EXAFS results indicates that the iron in the system goes from bcc to a more densely packed system as the thickness of the iron layer is decreased. The magnetic properties were measured by SQUID magnetometry from 5-350 K. For all the samples, the saturation magnetization was significantly enhanced over the bulk values indicating the interface Pd atoms are polarized by the Fe layer. The enhancement corresponds to a moment of ∼2.5μ B per interface Pd atom

  8. Carbon X-ray absorption spectra of fluoroethenes and acetone: a study at the coupled cluster, density functional, and static-exchange levels of theory.

    Science.gov (United States)

    Fransson, Thomas; Coriani, Sonia; Christiansen, Ove; Norman, Patrick

    2013-03-28

    Near carbon K-edge X-ray absorption fine structure spectra of a series of fluorine-substituted ethenes and acetone have been studied using coupled cluster and density functional theory (DFT) polarization propagator methods, as well as the static-exchange (STEX) approach. With the complex polarization propagator (CPP) implemented in coupled cluster theory, relaxation effects following the excitation of core electrons are accounted for in terms of electron correlation, enabling a systematic convergence of these effects with respect to electron excitations in the cluster operator. Coupled cluster results have been used as benchmarks for the assessment of propagator methods in DFT as well as the state-specific static-exchange approach. Calculations on ethene and 1,1-difluoroethene illustrate the possibility of using nonrelativistic coupled cluster singles and doubles (CCSD) with additional effects of electron correlation and relativity added as scalar shifts in energetics. It has been demonstrated that CPP spectra obtained with coupled cluster singles and approximate doubles (CC2), CCSD, and DFT (with a Coulomb attenuated exchange-correlation functional) yield excellent predictions of chemical shifts for vinylfluoride, 1,1-difluoroethene, trifluoroethene, as well as good spectral features for acetone in the case of CCSD and DFT. Following this, CPP-DFT is considered to be a viable option for the calculation of X-ray absorption spectra of larger π-conjugated systems, and CC2 is deemed applicable for chemical shifts but not for studies of fine structure features. The CCSD method as well as the more approximate CC2 method are shown to yield spectral features relating to π∗-resonances in good agreement with experiment, not only for the aforementioned molecules but also for ethene, cis-1,2-difluoroethene, and tetrafluoroethene. The STEX approach is shown to underestimate π∗-peak separations due to spectral compressions, a characteristic which is inherent to this

  9. Evaluation of transmitted spectra of megavoltage X rays through concrete using Monte Carlo simulation

    International Nuclear Information System (INIS)

    Cordeiro, Thaiana de Paula Vieira; Silva, Ademir Xavier da

    2010-01-01

    With the improvement of technology in radiotherapic centers, medical linear accelerators are largely replacing Cobalt-60 teletherapy units. In most of the cases, the same room that, before, was used to place a 60 Co teletherapy unit is reused to install, in replacement, a linear accelerator. When the room physical space can not be changed, high - density concrete is employed to provide shielding against the primary, scatter and leakage radiation. This work presents a study based on Monte Carlo simulations of transmission of some clinical photon spectra (of 10, 15 and 25 MV accelerators) through concrete of two different densities. Concrete walls of thickness 1.0, 1.5 and 2.0 m were irradiated with 30 cm x 30 cm primary beam spectra. The results show that the thickness of the barrier decreases up to approximately 35%, when barite (high - density concrete) is used instead of ordinary concrete. The average energies of primary and transmitted beam spectra were also calculated. (author)

  10. Evaluation of transmitted spectra of megavoltage X rays through concrete using Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Cordeiro, Thaiana de Paula Vieira; Silva, Ademir Xavier da, E-mail: tcordeiro@con.ufrj.b, E-mail: Ademir@con.ufrj.b [Coordenacao dos Programas de Pos-Graduacao de Engenharia (COPPE/UFRJ), RJ (Brazil). Programa de Engenharia Nuclear

    2010-07-01

    With the improvement of technology in radiotherapic centers, medical linear accelerators are largely replacing Cobalt-60 teletherapy units. In most of the cases, the same room that, before, was used to place a {sup 60}Co teletherapy unit is reused to install, in replacement, a linear accelerator. When the room physical space can not be changed, high - density concrete is employed to provide shielding against the primary, scatter and leakage radiation. This work presents a study based on Monte Carlo simulations of transmission of some clinical photon spectra (of 10, 15 and 25 MV accelerators) through concrete of two different densities. Concrete walls of thickness 1.0, 1.5 and 2.0 m were irradiated with 30 cm x 30 cm primary beam spectra. The results show that the thickness of the barrier decreases up to approximately 35%, when barite (high - density concrete) is used instead of ordinary concrete. The average energies of primary and transmitted beam spectra were also calculated. (author)

  11. Synchrotron x-ray methods in studies of thin organic film structure

    International Nuclear Information System (INIS)

    Gentle, I.

    2002-01-01

    Full text: In recent years, the study of the structures of organic films as thin as a single monolayer has been revolutionized by methods that take advantage of the characteristics of synchrotron radiation. In particular, the methods of grazing incidence X-ray diffraction (GIXD) and X-ray reflectivity have led to a number of valuable insights into structural aspects of thin films at molecular resolution. Our group has been studying films formed at the air/water interface as insoluble monolayers and subsequently transferred to solid substrates using either the vertical (Langmuir-Blodgett) or horizontal (Langmuir-Schaeffer) methods. The main aim of these experiments is to exert control over film structure in the direction parallel to the substrate surface. This is highly desirable in order to design devices that exploit the optical and electrooptical properties of functional materials, but is difficult to do. By varying the chemical structure of the film materials and controlling deposition conditions a degree of control is possible, but only using synchrotron methods can it be easily verified. We have also developed a novel method of rapidly collecting data from GIXD measurements by the application of area detection (imaging plates), which has made possible measurements of dynamic processes such as in-situ annealing. Such measurements are not possible using traditional scanning methods. One area of current interest is films composed of porphyrins as functional materials, either alone or as mixed films with fatty acids. We have been investigating ways of assembling porphyrins in such a way as to overcome the tendency to aggregate, and to produce patterning and ordered structures in the plane of the interface. Examples will be given of how film composition and deposition method affects the final structure, and of how X-ray methods can be used to elucidate both the structures and the mechanisms. Copyright (2002) Australian X-ray Analytical Association Inc

  12. Structural dissection of human metapneumovirus phosphoprotein using small angle x-ray scattering.

    Science.gov (United States)

    Renner, Max; Paesen, Guido C; Grison, Claire M; Granier, Sébastien; Grimes, Jonathan M; Leyrat, Cédric

    2017-11-01

    The phosphoprotein (P) is the main and essential cofactor of the RNA polymerase (L) of non-segmented, negative-strand RNA viruses. P positions the viral polymerase onto its nucleoprotein-RNA template and acts as a chaperone of the nucleoprotein (N), thereby preventing nonspecific encapsidation of cellular RNAs. The phosphoprotein of human metapneumovirus (HMPV) forms homotetramers composed of a stable oligomerization domain (P core ) flanked by large intrinsically disordered regions (IDRs). Here we combined x-ray crystallography of P core with small angle x-ray scattering (SAXS)-based ensemble modeling of the full-length P protein and several of its fragments to provide a structural description of P that captures its dynamic character, and highlights the presence of varyingly stable structural elements within the IDRs. We discuss the implications of the structural properties of HMPV P for the assembly and functioning of the viral transcription/replication machinery.

  13. Structure of liposome encapsulating proteins characterized by X-ray scattering and shell-modeling

    International Nuclear Information System (INIS)

    Hirai, Mitsuhiro; Kimura, Ryota; Takeuchi, Kazuki; Hagiwara, Yoshihiko; Kawai-Hirai, Rika; Ohta, Noboru; Igarashi, Noriyuki; Shimuzu, Nobutaka

    2013-01-01

    Wide-angle X-ray scattering data using a third-generation synchrotron radiation source are presented. Lipid liposomes are promising drug delivery systems because they have superior curative effects owing to their high adaptability to a living body. Lipid liposomes encapsulating proteins were constructed and the structures examined using synchrotron radiation small- and wide-angle X-ray scattering (SR-SWAXS). The liposomes were prepared by a sequential combination of natural swelling, ultrasonic dispersion, freeze-throw, extrusion and spin-filtration. The liposomes were composed of acidic glycosphingolipid (ganglioside), cholesterol and phospholipids. By using shell-modeling methods, the asymmetric bilayer structure of the liposome and the encapsulation efficiency of proteins were determined. As well as other analytical techniques, SR-SWAXS and shell-modeling methods are shown to be a powerful tool for characterizing in situ structures of lipid liposomes as an important candidate of drug delivery systems

  14. Probing the graphite band structure with resonant soft-x-ray fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Carlisle, J.A.; Shirley, E.L.; Hudson, E.A. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    Soft x-ray fluorescence (SXF) spectroscopy using synchrotron radiation offers several advantages over surface sensitive spectroscopies for probing the electronic structure of complex multi-elemental materials. Due to the long mean free path of photons in solids ({approximately}1000 {angstrom}), SXF is a bulk-sensitive probe. Also, since core levels are involved in absorption and emission, SXF is both element- and angular-momentum-selective. SXF measures the local partial density of states (DOS) projected onto each constituent element of the material. The chief limitation of SXF has been the low fluorescence yield for photon emission, particularly for light elements. However, third generation light sources, such as the Advanced Light Source (ALS), offer the high brightness that makes high-resolution SXF experiments practical. In the following the authors utilize this high brightness to demonstrate the capability of SXF to probe the band structure of a polycrystalline sample. In SXF, a valence emission spectrum results from transitions from valence band states to the core hole produced by the incident photons. In the non-resonant energy regime, the excitation energy is far above the core binding energy, and the absorption and emission events are uncoupled. The fluorescence spectrum resembles emission spectra acquired using energetic electrons, and is insensitive to the incident photon`s energy. In the resonant excitation energy regime, core electrons are excited by photons to unoccupied states just above the Fermi level (EF). The absorption and emission events are coupled, and this coupling manifests itself in several ways, depending in part on the localization of the empty electronic states in the material. Here the authors report spectral measurements from highly oriented pyrolytic graphite.

  15. Nonequilibrium effects and structure of X-ray lines in tokamak plasma

    Science.gov (United States)

    Gontis, V. G.; Lisitsa, V. S.

    1986-02-01

    The sensitivity of X-ray spectra to a number of typical non-equilibrium effects occurring in modern tokamaks is examined. Experimental data from the T-10 and ST Tokamaks are cited to illustrate the degree of deviation from coronal equilibrium. The analysis exploits recent atomic data for radiation and autoionization line widths; standard semiempirical formulas are used to calculate the rates of collision processes. Ion diffusion and impurity distribution by degrees of ionization are investigated. The sensitivity of K radiation to electron nonequilibrium and ion charge exchange is examined.

  16. Application- and patient size-dependent optimization of x-ray spectra for CT

    International Nuclear Information System (INIS)

    Kalender, Willi A.; Deak, Paul; Kellermeier, Markus; Straten, Marcel van; Vollmar, Sabrina V.

    2009-01-01

    Although x-ray computed tomography (CT) has been in clinical use for over 3 decades, spectral optimization has not been a topic of great concern; high voltages around 120 kV have been in use since the beginning of CT. It is the purpose of this study to analyze, in a rigorous manner, the energies at which the patient dose necessary to provide a given contrast-to-noise ratio (CNR) for various diagnostic tasks can be minimized. The authors used cylindrical water phantoms and quasianthropomorphic phantoms of the thorax and the abdomen with inserts of 13 mm diameter mimicking soft tissue, bone, and iodine for simulations and measurements. To provide clearly defined contrasts, these inserts were made of solid water with a 1% difference in density (DD) to represent an energy-independent soft-tissue contrast of 10 Hounsfield units (HU), calcium hydroxyapatite (Ca) representing bone, and iodine (I) representing the typical contrast medium. To evaluate CT of the thorax, an adult thorax phantom (300x200 mm 2 ) plus extension rings up to a size of 460x300 mm 2 to mimic different patient cross sections were used. For CT of the abdomen, we used a phantom of 360x200 mm 2 and an extension ring of 460x300 mm 2 . The CT scanner that the authors used was a SOMATOM Definition (Siemens Healthcare, Forchheim, Germany) at 80, 100, 120, and 140 kV. Further voltage settings of 60, 75, 90, and 105 kV were available in an experimental mode. The authors determined contrast for the density difference, calcium, and iodine, and noise and 3D dose distributions for the available voltages by measurements. Additional voltage values and monoenergetic sources were evaluated by simulations. The dose-weighted contrast-to-noise ratio (CNRD) was used as the parameter for optimization. Simulations and measurements were in good agreement with respect to absolute values and trends regarding the dependence on energy for the parameters investigated. For soft-tissue imaging, the standard settings of 120-140 k

  17. DXRaySMCS. First user friendly interface developed for prediction of diagnostic radiology X-ray spectra produced by Monte Carlo (MCNP-4C) simulation in Iran

    International Nuclear Information System (INIS)

    Bahreyni Toossi, M.T.; Zare, H.; Moradi Faradanbe, H.

    2008-01-01

    An accurate knowledge of the output energy spectra of an x-ray tube is essential in many areas of radiological studies. It forms the basis of almost all image quality simulations and enable system designers to predict patient dose more accurately. Many radiological physics problems that can be solved by Monte Carlo simulation methods require an x-ray spectra as input data. Computer simulation of x-ray spectra is one of the most important tools for investigation of patient dose and image quality in diagnostic radiology systems. In this work the general purpose Monte Carlo N-particle radiation transport computer code (MCNP-4C) was used for the simulation of x-ray spectra in diagnostic radiology, Electron's path in the target was followed until it's energy was reduced to 10 keV. A user friendly interface named 'Diagnostic X-ray Spectra by Monte Carlo Simulation (DXRaySMCS)' was developed to facilitate the application of MCNP-4C code for diagnostic radiology spectrum prediction. The program provides a user friendly interface for modifying the MCNP input file, launching the MCNP program to simulate electron and photon transport and processing the MCNP output file to yield a summary of the results (Relative Photon Number per Energy Bin). In this article the development and characteristics of DXRaySMCS are outlined. As part of the validation process, out put spectra for 46 diagnostic radiology system settings produced by DXRaySMCS were compared with the corresponding IPEM78. Generally, there is a good agreement between the two sets of spectra. No statistically significant differences have been observed between IPEM78 reported spectra and the simulated spectra generated in this study. (author)

  18. The structural analysis of zinc borate glass by laboratory EXAFS and X-ray diffraction measurements

    International Nuclear Information System (INIS)

    Kajinami, Akihiko; Harada, Yasushi; Inoue, Shinsuke; Deki, Shigehito; Umesaki, Norimasa

    1999-01-01

    The structure of zinc borate glass has been investigated by laboratory EXAFS and X-ray diffraction measurement as preliminary investigations for the detailed study in SPring-8. The zinc borate glass was prepared in the range from 40 to 65 mol% of zinc oxide content. The X-ray diffraction was measured by horizontal θ-θ goniometer with 60 kV and 300 mA output of Mo target. The EXAFS of zinc borate glass was measured by laboratory EXAFS system with 20 kV, 100 mA output of Mo target for the K absorption edge of zinc atom. From the X-ray diffraction and the EXAFS measurements, it is found that the zinc ion is surrounded by four oxygen atoms and formed a tetrahedral structure whose (Zn-O) distance is about 2 A and that the structure is unchanged with the zinc oxide content. The diffraction data show that the neighboring structure of boron atom transforms from BO 4 tetrahedra to BO 3 tetragonal planar structure with increasing of the zinc oxide content. (author)

  19. Local 3d Electronic Structures of Co-Based Complexes with Medicinal Molecules Probed by Soft X-ray Absorption

    Science.gov (United States)

    Yamagami, Kohei; Fujiwara, Hidenori; Imada, Shin; Kadono, Toshiharu; Yamanaka, Keisuke; Muro, Takayuki; Tanaka, Arata; Itai, Takuma; Yoshinari, Nobuto; Konno, Takumi; Sekiyama, Akira

    2017-07-01

    We have examined the local 3d electronic structures of Co-Au multinuclear complexes with the medicinal molecules d-penicillaminate (d-pen) [Co{Au(PPh3)(d-pen)}2]ClO4 and [Co3{Au3(tdme)(d-pen)3}2] by Co L2,3-edge soft X-ray absorption (XAS) spectroscopy, where PPh3 denotes triphenylphosphine and tdme stands for 1,1,1-tris[(diphenylphosphino)methyl]ethane. The Co L2,3-edge XAS spectra indicate the localized ionic 3d electronic states in both materials. The experimental spectra are well explained by spectral simulation for a localized Co ion under ligand fields with the full multiplet theory, which verifies that the ions are in the low-spin Co3+ state in the former compound and in the high-spin Co2+ state in the latter.

  20. Integrative structural modeling with small angle X-ray scattering profiles

    Directory of Open Access Journals (Sweden)

    Schneidman-Duhovny Dina

    2012-07-01

    Full Text Available Abstract Recent technological advances enabled high-throughput collection of Small Angle X-ray Scattering (SAXS profiles of biological macromolecules. Thus, computational methods for integrating SAXS profiles into structural modeling are needed more than ever. Here, we review specifically the use of SAXS profiles for the structural modeling of proteins, nucleic acids, and their complexes. First, the approaches for computing theoretical SAXS profiles from structures are presented. Second, computational methods for predicting protein structures, dynamics of proteins in solution, and assembly structures are covered. Third, we discuss the use of SAXS profiles in integrative structure modeling approaches that depend simultaneously on several data types.

  1. X-ray refractive index: A tool to determine the average composition in multilayer structures

    International Nuclear Information System (INIS)

    Miceli, P.F.; Neumann, D.A.; Zabel, H.

    1986-01-01

    We present a novel and simple method to determine the average composition of multilayers and superlattices by measuring the x-ray refractive index. Since these modulated structures exhibit Bragg reflections at small angles, by using a triple axis x-ray spectrometer we have accurately determined the peak shifts due to refraction in GaAs/Al/sub x/Ga/sub 1-x/As and Nb/Ta superlattices. Knowledge of the refractive index provides the average fractional composition of the periodic structure since the refractive index is a superposition of the refractive indices of the atomic constituents. We also present a critical discussion of the method and compare the values of the average fractional composition obtained in this manner to the values obtained from the lattice parameter change in the GaAs/Al/sub x/Ga/sub 1-x/As superlattices due to the Al

  2. Structured photocathodes for improved high-energy x-ray efficiency in streak cameras

    Energy Technology Data Exchange (ETDEWEB)

    Opachich, Y. P., E-mail: opachiyp@nv.doe.gov; Huffman, E.; Koch, J. A. [National Security Technologies, LLC, Livermore, California 94551 (United States); Bell, P. M.; Bradley, D. K.; Hatch, B.; Landen, O. L.; MacPhee, A. G.; Nagel, S. R. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Chen, N.; Gopal, A.; Udin, S. [Nanoshift LLC, Emeryville, California 94608 (United States); Feng, J. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Hilsabeck, T. J. [General Atomics, San Diego, California 92121 (United States)

    2016-11-15

    We have designed and fabricated a structured streak camera photocathode to provide enhanced efficiency for high energy X-rays (1–12 keV). This gold coated photocathode was tested in a streak camera and compared side by side against a conventional flat thin film photocathode. Results show that the measured electron yield enhancement at energies ranging from 1 to 10 keV scales well with predictions, and that the total enhancement can be more than 3×. The spatial resolution of the streak camera does not show degradation in the structured region. We predict that the temporal resolution of the detector will also not be affected as it is currently dominated by the slit width. This demonstration with Au motivates exploration of comparable enhancements with CsI and may revolutionize X-ray streak camera photocathode design.

  3. X-ray diffuse scattering effects from Coulomb-type defects in multilayered structures

    International Nuclear Information System (INIS)

    Olikhovskii, S.I.; Molodkin, V.B.; Skakunova, E.S.; Kislovskii, E.N.; Fodchuk, I.M.

    2009-01-01

    The theoretical X-ray diffraction model starting from Takagi-Taupin equation has been developed for the description of coherent and diffuse components of the rocking curve (RC) measured from the multilayered crystal structure with randomly distributed Coulomb-type defects in all the layers and substrate. The model describes both diffuse scattering (DS) intensity distribution and influence of DS on attenuation and angular redistribution of the coherent X-ray scattering intensity. By analyzing the total measured RC with using the proposed diffraction model, the chemical compositions, strains, and characteristics of dislocation loops in layers and substrate of the multilayered structure with InGaAsN/GaAs single quantum well have been determined. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  4. Soft x-ray measurement of internal tearing mode structure in a reversed-field pinch

    International Nuclear Information System (INIS)

    Chartas, G.; Hokin, S.

    1991-01-01

    The structure of internally resonant tearing modes has been studied in the Madison Symmetric Torus reversed-field pinch with a soft x-ray detector system consisting of an imaging array at one toroidal location and several detectors at different toroidal locations. The toroidal mode numbers of m = 1 structures are in the range n = -5, -6, -7. The modes propagate with phase velocity v = 1--6 x 10 6 cm/s, larger than the diamagnetic drift velocity v d ∼ 5 x 10 5 cm/s. Phase locking between modes with different n in manifested as a beating of soft x-ray signals which is found to be strongest near the resonant surfaces of the modes (r/a = 0.1 -- 0.5). 15 refs., 5 figs

  5. Structural characterization of oxidized allotaxially grown CoSi2 layers by x-ray scattering

    International Nuclear Information System (INIS)

    Kaendler, I. D.; Seeck, O. H.; Schlomka, J.-P.; Tolan, M.; Press, W.; Stettner, J.; Kappius, L.; Dieker, C.; Mantl, S.

    2000-01-01

    A series of buried CoSi 2 layers prepared by a modified molecular beam epitaxy process (allotaxy) and a subsequent wet-oxidation process was investigated by x-ray scattering. The oxidation time which determines the depth in which the CoSi 2 layers are located within the Si substrates has been varied during the preparation. The electron density profiles and the structure of the interfaces were extracted from specular reflectivity and diffuse scattering measurements. Crystal truncation rod investigations yielded the structure on an atomic level (crystalline quality). It turns out that the roughness of the CoSi 2 layers increases drastically with increasing oxidation time, i.e., with increasing depth of the buried layers. Furthermore, the x-ray data reveal that the oxidation growth process is diffusion limited. (c) 2000 American Institute of Physics

  6. Structural and microstructural characterization of U3Si2 nuclear fuel using X-ray diffraction

    International Nuclear Information System (INIS)

    Ichikawa, Rodrigo U.; Garcia, Rafael H.L.; Silva, Andre S.B. da; Saliba-Silva, Adonis M.; Lima, Nelson B.; Martinez, Luis G.; Turrillas, Xavier

    2017-01-01

    In this work, two uranium silicide powdered samples, containing 67% and 42 mol% of Si, were analyzed using X-ray diffraction (named as 67 Si and 42 Si). For structural characterization, Rietveld refinement was used to estimate cell parameters, volume fraction (weight percent) of crystalline phases and atomic positions. For the main phases, X-ray line profile analysis (XLPA) was used to estimate mean crystallite sizes and micro strains. The 67 Si sample presents higher content of USi 2( tetragonal) and the 42 Si sample presents higher content of U 3 Si 2 (tetragonal) as identified and calculated from the XRD profiles. Overall there are no appreciable structural changes and the parameters refined are in good accordance with the ones reported in the literature. Mean crystallite sizes determined by XLPA revealed small crystallites of the order of 10 1 nm and low micro strain for all samples. (author)

  7. Single crystal X-ray structure of the artists' pigment zinc yellow

    Science.gov (United States)

    Simonsen, Kim Pilkjær; Christiansen, Marie Bitsch; Vinum, Morten Gotthold; Sanyova, Jana; Bendix, Jesper

    2017-08-01

    The artists' pigment zinc yellow is in general described as a complex potassium zinc chromate with the empirical formula 4ZnCrO4·K2O·3H2O. Even though the pigment has been in use since the second half of the 19th century also in large-scale industrial applications, the exact structure had hitherto been unknown. In this work, zinc yellow was synthesised by precipitation from an aqueous solution of zinc nitrate and potassium chromate under both neutral and basic conditions, and the products were compared with the pigment used in industrial paints. Analyses by Raman microscopy (MRS), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and powder X-ray diffraction (PXRD), showed that the synthesised products and the industrial pigment were identical. Single-crystal X-ray crystallography determined the structure of zinc yellow as KZn2(CrO4)2(H2O)(OH) or as KZn2(CrO4)2(H3O2) emphasizing the μ-H3O2- moiety. Notably, the zinc yellow is isostructural to the recently structurally characterized cadmium analog and both belong to the natrochalcite structure type.

  8. Structural shielding of medical X-ray rooms for diagnostic installations

    International Nuclear Information System (INIS)

    Rabitsch, H.

    1979-06-01

    In Part I (RIG 8), the various design procedures for shielding against X-rays are discussed and compared. In particular, this comparison is carried out between the shielding obtained conforming to the Austrian Regulations for Radiation Protection and that obtained from the DIN-standard DIN 6812; this latter includes the various operating conditions of diagnostic installations up to 150 kV. Several examples for particular structural shielding components in medical radiation rooms are given. (author)

  9. Structural transformation of compressed solid Ar: An x-ray diffraction study to 114 GPa

    International Nuclear Information System (INIS)

    Errandonea, D.; Boehler, R.; Japel, S.; Mezouar, M.; Benedetti, L. R.

    2006-01-01

    Room temperature angle-dispersive x-ray diffraction measurements on solid Ar up to 114 GPa reveal evidence of a structural phase transformation after stress relaxation by laser heating. Beyond 49.6 GPa, Ar exhibits the coexistence of fcc and hcp phases with an increasing hcp/fcc ratio, similar to the observation made recently on krypton and xenon. From the present results, we estimate the fcc-to-hcp transition to be completed at 300 GPa

  10. Total reflection X-ray fluorescence analysis with synchrotron radiation monochromatized by multilayer structures

    International Nuclear Information System (INIS)

    Rieder, R.; Wobrauschek, P.; Ladisich, W.; Streli, C.; Aiginger, H.; Garbe, S.; Gaul, G.; Knoechel, A.; Lechtenberg, F.

    1995-01-01

    To achieve lowest detection limits in total reflection X-ray fluorescence analysis (TXRF) synchrotron radiation has been monochromatized by a multilayer structure to obtain a relative broad energy band compared to Bragg single crystals for an efficient excitation. The energy has been set to 14 keV, 17.5 keV, 31 keV and about 55 keV. Detection limits of 20 fg and 150 fg have been achieved for Sr and Cd, respectively. ((orig.))

  11. Precise material identification method based on a photon counting technique with correction of the beam hardening effect in X-ray spectra

    International Nuclear Information System (INIS)

    Kimoto, Natsumi; Hayashi, Hiroaki; Asahara, Takashi; Mihara, Yoshiki; Kanazawa, Yuki; Yamakawa, Tsutomu; Yamamoto, Shuichiro; Yamasaki, Masashi; Okada, Masahiro

    2017-01-01

    The aim of our study is to develop a novel material identification method based on a photon counting technique, in which the incident and penetrating X-ray spectra are analyzed. Dividing a 40 kV X-ray spectra into two energy regions, the corresponding linear attenuation coefficients are derived. We can identify the materials precisely using the relationship between atomic number and linear attenuation coefficient through the correction of the beam hardening effect of the X-ray spectra. - Highlights: • We propose a precise material identification method to be used as a photon counting system. • Beam hardening correction is important, even when the analysis is applied to the short energy regions in the X-ray spectrum. • Experiments using a single probe-type CdTe detector were performed, and Monte Carlo simulation was also carried out. • We described the applicability of our method for clinical diagnostic X-ray imaging in the near future.

  12. Electrokinetic detection for X-ray spectra of weakly interacting liquids: n-decane and n-nonane

    International Nuclear Information System (INIS)

    Lam, Royce K.; Smith, Jacob W.; Sheardy, Alex T.; Rizzuto, Anthony M.; Saykally, Richard J.; Shih, Orion; Prendergast, David

    2014-01-01

    The introduction of liquid microjets into soft X-ray absorption spectroscopy enabled the windowless study of liquids by this powerful atom-selective high vacuum methodology. However, weakly interacting liquids produce large vapor backgrounds that strongly perturb the liquid signal. Consequently, solvents (e.g., hydrocarbons, ethers, ketones, etc.) and solutions of central importance in chemistry and biology have been inaccessible by this technology. Here we describe a new detection method, upstream detection, which greatly reduces the vapor phase contribution to the X-ray absorption signal while retaining important advantages of liquid microjet sample introduction (e.g., minimal radiation damage). The effectiveness of the upstream detection method is demonstrated in this first study of room temperature liquid hydrocarbons: n-nonane and n-decane. Good agreement with first principles’ calculations indicates that the eXcited electron and Core Hole theory adequately describes the subtle interactions in these liquids that perturb the electronic structure of the unoccupied states probed in core-level experiments

  13. Electrokinetic detection for X-ray spectra of weakly interacting liquids: n-decane and n-nonane

    Science.gov (United States)

    Lam, Royce K.; Shih, Orion; Smith, Jacob W.; Sheardy, Alex T.; Rizzuto, Anthony M.; Prendergast, David; Saykally, Richard J.

    2014-06-01

    The introduction of liquid microjets into soft X-ray absorption spectroscopy enabled the windowless study of liquids by this powerful atom-selective high vacuum methodology. However, weakly interacting liquids produce large vapor backgrounds that strongly perturb the liquid signal. Consequently, solvents (e.g., hydrocarbons, ethers, ketones, etc.) and solutions of central importance in chemistry and biology have been inaccessible by this technology. Here we describe a new detection method, upstream detection, which greatly reduces the vapor phase contribution to the X-ray absorption signal while retaining important advantages of liquid microjet sample introduction (e.g., minimal radiation damage). The effectiveness of the upstream detection method is demonstrated in this first study of room temperature liquid hydrocarbons: n-nonane and n-decane. Good agreement with first principles' calculations indicates that the eXcited electron and Core Hole theory adequately describes the subtle interactions in these liquids that perturb the electronic structure of the unoccupied states probed in core-level experiments.

  14. Microwave imaging of a solar limb flare - Comparison of spectra and spatial geometry with hard X-rays

    Science.gov (United States)

    Schmahl, E. J.; Kundu, M. R.; Dennis, B. R.

    1985-01-01

    A solar limb flare was mapped using the Very Large Array (VLA) together with hard X-ray (HXR) spectral and spatial observations of the Solar Maximum Mission satellite. Microwave flux records from 2.8 to 19.6 GHz were instrumental in determining the burst spectrum, which has a maximum at 10 GHz. The flux spectrum and area of the burst sources were used to determine the number of electrons producing gyrosynchrotron emission, magnetic field strength, and the energy distribution of gyrosynchrotron-emitting electrons. Applying the thick target model to the HXR spectrum, the number of high energy electrons responsible for the X-ray bursts was found to be 10 to the 36th, and the electron energy distribution was approximately E exp -5, significantly different from the parameters derived from the microwave observations. The HXR imaging observations exhibit some similiarities in size and structure o the first two burst sources mapped with the VLA. However, during the initial burst, the HXR source was single and lower in the corona than the double 6 cm source. The observations are explained in terms of a single loop with an isotropic high-energy electron distribution which produced the microwaves, and a larger beamed component which produced the HXR at the feet of the loop.

  15. Electrokinetic detection for X-ray spectra of weakly interacting liquids: n-decane and n-nonane

    Energy Technology Data Exchange (ETDEWEB)

    Lam, Royce K.; Smith, Jacob W.; Sheardy, Alex T.; Rizzuto, Anthony M.; Saykally, Richard J., E-mail: saykally@berkeley.edu [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Shih, Orion [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Prendergast, David [Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2014-06-21

    The introduction of liquid microjets into soft X-ray absorption spectroscopy enabled the windowless study of liquids by this powerful atom-selective high vacuum methodology. However, weakly interacting liquids produce large vapor backgrounds that strongly perturb the liquid signal. Consequently, solvents (e.g., hydrocarbons, ethers, ketones, etc.) and solutions of central importance in chemistry and biology have been inaccessible by this technology. Here we describe a new detection method, upstream detection, which greatly reduces the vapor phase contribution to the X-ray absorption signal while retaining important advantages of liquid microjet sample introduction (e.g., minimal radiation damage). The effectiveness of the upstream detection method is demonstrated in this first study of room temperature liquid hydrocarbons: n-nonane and n-decane. Good agreement with first principles’ calculations indicates that the eXcited electron and Core Hole theory adequately describes the subtle interactions in these liquids that perturb the electronic structure of the unoccupied states probed in core-level experiments.

  16. Study of the argyrophil structures of thymus connective tissue after exposure to X-rays

    International Nuclear Information System (INIS)

    Beletskij, V.K.; Beletskaya, L.V.; Akademiya Meditsinskikh Nauk SSSR, Moscow. Inst. Ehpidemiologii i Mikrobiologii)

    1980-01-01

    Studied are argyrophil structures of thymus connective tissue - histiocytes (appendiculate macrophages) and reticuline fibers after the bulk of lymphoid cells has migrated from the organ due to irradiation of animals with X-rays. 10 intact and 16 experimental guinea pigs subjected to the whole-body irradiation with X-rays in the dose of 1000-3000 rad have been used for investigations. It is shown that argyrophil stroma elements of thymus connective tissue, histiocytes and reticular cells, are rather resistant to X-rays and preserve their argyrophily property in the irradiation with high doses, as well as the epithelial cells of the organ. Paraplastic structures in irradiated animals are expressed more completely being demasked as a result of lymphocyte migration and death. The expressed hypertrophy and proliferation of reticular cells and appendiculate macrophages are probably the response to the alternative process in the organ tissues caused by irradiation. A close structural connection of reticular and epithelial tissues on the territory of both layers of thymus sections is noted

  17. Structural Modification of Cobalt Catalysts: Effect of Wetting Studied by X-Ray and Infrared Techniques

    Directory of Open Access Journals (Sweden)

    Khodakov A.

    1999-07-01

    Full Text Available The effect of wetting on the structure and localisation of cobalt species on various supports (Al2O3, SiO2, TiO2, HZSM-5 zeolite was studied using X-ray diffraction, Fourier transform infrared spectroscopy with CO as a molecular probe, X-ray photoelectron spectroscopy and extended X-ray absorption fine structure analysis. Aqueous impregnation to incipient wetness of reduced and passivated cobalt catalysts results, even in the absence of any promoter, in a considerable decrease in the concentration of Co crystalline phases and modifies the surface sites. The decrease in the concentration of Co3O4 crystallites was especially pronounced on silica supported catalysts prepared via impregnation of cobalt and on a mixture of Co3O4 and HZSM-5 zeolite. Saturation with water of the passivated Co/SiO2 sample results in an amorphous solid with a local structure close to that of Co2SiO4. For Co/Al2O3 and Co/TiO2 catalysts, the effect of wetting on the concentration of Co3O4 crystalline phase was considerably smaller.

  18. Predicting X-ray diffuse scattering from translation–libration–screw structural ensembles

    International Nuclear Information System (INIS)

    Van Benschoten, Andrew H.; Afonine, Pavel V.; Terwilliger, Thomas C.; Wall, Michael E.; Jackson, Colin J.; Sauter, Nicholas K.; Adams, Paul D.; Urzhumtsev, Alexandre; Fraser, James S.

    2015-01-01

    A method of simulating X-ray diffuse scattering from multi-model PDB files is presented. Despite similar agreement with Bragg data, different translation–libration–screw refinement strategies produce unique diffuse intensity patterns. Identifying the intramolecular motions of proteins and nucleic acids is a major challenge in macromolecular X-ray crystallography. Because Bragg diffraction describes the average positional distribution of crystalline atoms with imperfect precision, the resulting electron density can be compatible with multiple models of motion. Diffuse X-ray scattering can reduce this degeneracy by reporting on correlated atomic displacements. Although recent technological advances are increasing the potential to accurately measure diffuse scattering, computational modeling and validation tools are still needed to quantify the agreement between experimental data and different parameterizations of crystalline disorder. A new tool, phenix.diffuse, addresses this need by employing Guinier’s equation to calculate diffuse scattering from Protein Data Bank (PDB)-formatted structural ensembles. As an example case, phenix.diffuse is applied to translation–libration–screw (TLS) refinement, which models rigid-body displacement for segments of the macromolecule. To enable the calculation of diffuse scattering from TLS-refined structures, phenix.tls-as-xyz builds multi-model PDB files that sample the underlying T, L and S tensors. In the glycerophosphodiesterase GpdQ, alternative TLS-group partitioning and different motional correlations between groups yield markedly dissimilar diffuse scattering maps with distinct implications for molecular mechanism and allostery. These methods demonstrate how, in principle, X-ray diffuse scattering could extend macromolecular structural refinement, validation and analysis

  19. Predicting X-ray diffuse scattering from translation–libration–screw structural ensembles

    Energy Technology Data Exchange (ETDEWEB)

    Van Benschoten, Andrew H. [University of California San Francisco, San Francisco, CA 94158 (United States); Afonine, Pavel V. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Terwilliger, Thomas C.; Wall, Michael E. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Jackson, Colin J. [Australian National University, Canberra, ACT 2601 (Australia); Sauter, Nicholas K. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Adams, Paul D. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); University of California Berkeley, Berkeley, CA 94720 (United States); Urzhumtsev, Alexandre [Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS–INSERM–UdS, 1 Rue Laurent Fries, BP 10142, 67404 Illkirch (France); Université de Lorraine, BP 239, 54506 Vandoeuvre-les-Nancy (France); Fraser, James S., E-mail: james.fraser@ucsf.edu [University of California San Francisco, San Francisco, CA 94158 (United States)

    2015-07-28

    A method of simulating X-ray diffuse scattering from multi-model PDB files is presented. Despite similar agreement with Bragg data, different translation–libration–screw refinement strategies produce unique diffuse intensity patterns. Identifying the intramolecular motions of proteins and nucleic acids is a major challenge in macromolecular X-ray crystallography. Because Bragg diffraction describes the average positional distribution of crystalline atoms with imperfect precision, the resulting electron density can be compatible with multiple models of motion. Diffuse X-ray scattering can reduce this degeneracy by reporting on correlated atomic displacements. Although recent technological advances are increasing the potential to accurately measure diffuse scattering, computational modeling and validation tools are still needed to quantify the agreement between experimental data and different parameterizations of crystalline disorder. A new tool, phenix.diffuse, addresses this need by employing Guinier’s equation to calculate diffuse scattering from Protein Data Bank (PDB)-formatted structural ensembles. As an example case, phenix.diffuse is applied to translation–libration–screw (TLS) refinement, which models rigid-body displacement for segments of the macromolecule. To enable the calculation of diffuse scattering from TLS-refined structures, phenix.tls-as-xyz builds multi-model PDB files that sample the underlying T, L and S tensors. In the glycerophosphodiesterase GpdQ, alternative TLS-group partitioning and different motional correlations between groups yield markedly dissimilar diffuse scattering maps with distinct implications for molecular mechanism and allostery. These methods demonstrate how, in principle, X-ray diffuse scattering could extend macromolecular structural refinement, validation and analysis.

  20. Transmission X-ray scattering as a probe for complex liquid-surface structures

    Energy Technology Data Exchange (ETDEWEB)

    Fukuto, Masafumi; Yang, Lin; Nykypanchuk, Dmytro; Kuzmenko, Ivan

    2016-01-28

    The need for functional materials calls for increasing complexity in self-assembly systems. As a result, the ability to probe both local structure and heterogeneities, such as phase-coexistence and domain morphologies, has become increasingly important to controlling self-assembly processes, including those at liquid surfaces. The traditional X-ray scattering methods for liquid surfaces, such as specular reflectivity and grazing-incidence diffraction, are not well suited to spatially resolving lateral heterogeneities due to large illuminated footprint. A possible alternative approach is to use scanning transmission X-ray scattering to simultaneously probe local intermolecular structures and heterogeneous domain morphologies on liquid surfaces. To test the feasibility of this approach, transmission small- and wide-angle X-ray scattering (TSAXS/TWAXS) studies of Langmuir films formed on water meniscus against a vertically immersed hydrophilic Si substrate were recently carried out. First-order diffraction rings were observed in TSAXS patterns from a monolayer of hexagonally packed gold nanoparticles and in TWAXS patterns from a monolayer of fluorinated fatty acids, both as a Langmuir monolayer on water meniscus and as a Langmuir–Blodgett monolayer on the substrate. The patterns taken at multiple spots have been analyzed to extract the shape of the meniscus surface and the ordered-monolayer coverage as a function of spot position. These results, together with continual improvement in the brightness and spot size of X-ray beams available at synchrotron facilities, support the possibility of using scanning-probe TSAXS/TWAXS to characterize heterogeneous structures at liquid surfaces.

  1. PREFACE: Structure and dynamics determined by neutron and x-ray scattering Structure and dynamics determined by neutron and x-ray scattering

    Science.gov (United States)

    Müller-Buschbaum, Peter

    2011-06-01

    Neutron and x-ray scattering have emerged as powerful methods for the determination of structure and dynamics. Driven by emerging new, powerful neutron and synchrotron radiation sources, the continuous development of new instrumentation and novel scattering techniques gives rise to exciting possibilities. For example, in situ observations become possible via a high neutron or x-ray flux at the sample and, as a consequence, morphological transitions with small time constants can be detected. This special issue covers a broad range of different materials from soft to hard condensed matter. Hence, different material classes such as colloids, polymers, alloys, oxides and metals are addressed. The issue is dedicated to the 60th birthday of Professor Winfried Petry, scientific director of the Research Neutron Source Heinz Maier-Leibnitz (FRM-II), Germany, advisor at the physics department for the Bayerische Elite-Akademie, chair person of the Arbeitsgemeinschaft Metall- und Materialphysik of the German Physical Society (DPG) and a member of the professional council of the German Science Foundation (Deutsche Forschungsgemeinschaft, DFG). We would like to acknowledge and thank all contributors for their submissions, which made this special issue possible in the first place. Moreover, we would like to thank the staff at IOP Publishing for helping us with the administrative aspects and for coordinating the refereeing process, and Valeria Lauter for the beautiful cover artwork. Finally, to the readers, we hope that you find this special issue a valuable resource that provides insights into the present possibilities of neutron and x-ray scattering as powerful tools for the investigation of structure and dynamics. Structure and dynamics determined by neutron and x-ray scattering contents In situ studies of mass transport in liquid alloys by means of neutron radiography F Kargl, M Engelhardt, F Yang, H Weis, P Schmakat, B Schillinger, A Griesche and A Meyer Magnetic spin

  2. X-ray photoemission electron microscopy, a tool for the investigation of complex magnetic structures

    International Nuclear Information System (INIS)

    Scholl, Andreas; Ohldag, Hendrik; Nolting, Frithjof; Stohr, Joachim; Padmore, Howard A.

    2001-01-01

    X-ray Photoemission Electron Microscopy unites the chemical specificity and magnetic sensitivity of soft x-ray absorption techniques with the high spatial resolution of electron microscopy. The discussed instrument possesses a spatial resolution of better than 50 nm and is located at a bending magnet beamline at the Advanced Light Source, providing linearly and circularly polarized radiation between 250 and 1300 eV. We will present examples which demonstrate the power of this technique applied to problems in the field of thin film magnetism. The chemical and elemental specificity is of particular importance for the study of magnetic exchange coupling because it allows separating the signal of the different layers and interfaces in complex multi-layered structures

  3. Template assisted self-assembly of iron oxide nanoparticles: An x-ray structural analysis

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, D. [Department of Physics, Ruhr-University Bochum, 44780 Bochum (Germany); Institut fuer Optik und Atomare Physik, Technische Universitaet Berlin, Strasse des 17. Juni 135, 10623 Berlin (Germany); Zabel, H. [Department of Physics, Ruhr-University Bochum, 44780 Bochum (Germany); Ulyanov, S. V. [St.-Petersburg State University, Ul' yanovskaya ul.1, Petrodvorets, St.-Petersburg 198904 (Russian Federation); St.-Petersburg University of Commerce and Economics, St.-Petersburg 194018 (Russian Federation); Romanov, V. P. [St.-Petersburg State University, Ul' yanovskaya ul.1, Petrodvorets, St.-Petersburg 198904 (Russian Federation); Uzdin, V. M. [St.-Petersburg State University, Ul' yanovskaya ul.1, Petrodvorets, St.-Petersburg 198904 (Russian Federation); St.-Petersburg National Research University of Information Technologies, Mechanics and Optics, 49, Kronverkskij, St.-Petersburg 197101 (Russian Federation)

    2014-02-07

    We have fabricated by e-beam lithography periodic arrays of rectangular shaped trenches of different widths into Si substrates. The trenches were filled with iron oxide nanoparticles, 20 nm in diameter, by spin-coating them onto the Si substrate. The trenches have the purpose to assist the self-assembly of the iron oxide nanoparticles. Using x-ray scattering techniques, we have analyzed the structure factor of the trenches before and after filling in order to determine the filling factor. We present a theoretical analysis of the x-ray scattering function within the distorted-wave Born approximation and we present a quantitative comparison between theory and experiment.

  4. Template assisted self-assembly of iron oxide nanoparticles: An x-ray structural analysis

    International Nuclear Information System (INIS)

    Mishra, D.; Zabel, H.; Ulyanov, S. V.; Romanov, V. P.; Uzdin, V. M.

    2014-01-01

    We have fabricated by e-beam lithography periodic arrays of rectangular shaped trenches of different widths into Si substrates. The trenches were filled with iron oxide nanoparticles, 20 nm in diameter, by spin-coating them onto the Si substrate. The trenches have the purpose to assist the self-assembly of the iron oxide nanoparticles. Using x-ray scattering techniques, we have analyzed the structure factor of the trenches before and after filling in order to determine the filling factor. We present a theoretical analysis of the x-ray scattering function within the distorted-wave Born approximation and we present a quantitative comparison between theory and experiment

  5. Determining biological fine structure by differential absorption of soft x-rays

    International Nuclear Information System (INIS)

    Panessa-Warren, B.J.; Warren, J.B.

    1979-06-01

    The use of soft x-ray contact microscopy in examining histochemically treated human tissue embedded in plastic and exposed as unstained thin sections is demonstrated. When our preliminary data revealed that we could clearly image not only the histochemical reaction product, but the unstained biological fine structure of the surrounding tissues, we decided to test our hypothesis further and see if we could image unstained biological molecular aggregates as well. For this part of the investigation, we chose to examine hydrated proteoglycan aggregates. Proteoglycans are an essential component of the organic matrix of cartilage, and play a primary role in the retention and maintenance of extracellular water. To avoid any artifacts due to the introduction of exogeneous materials, and examine the proteoglycan aggregates in their hydrated, natural configuration, we made contact x-ray images of isolated proteoglycan aggregates in water

  6. Structure of Se-rich As-Se glasses by high-resolution x-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Golovchak, R.; Kovalskiy, A.; Miller, A. C.; Jain, H.; Shpotyuk, O.

    2007-01-01

    To establish the validity of various proposed structural models, we have investigated the structure of the binary As x Se 100-x chalcogenide glass family (x≤40) by high-resolution x-ray photoelectron spectroscopy. From the composition dependence of the valence band, the contributions to the density of states from the 4p lone pair electrons of Se and the 4p bonding states and 4s electrons of Se and As are identified in the top part of the band. The analysis of Se 3d and As 3d core-level spectra supports the so-called chain crossing model for the atomic structure of Se-rich As x Se 100-x bulk glasses. The results also indicate small deviations (∼3-8%) from this model, especially for glass compositions with short Se chains (25 40 Se 60 and of Se-Se-Se fragments in a glass with composition x=30 is established

  7. Si K EDGE STRUCTURE AND VARIABILITY IN GALACTIC X-RAY BINARIES

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, Norbert S.; Corrales, Lia; Canizares, Claude R. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2016-08-10

    We survey the Si K edge structure in various absorbed Galactic low-mass X-ray binaries (LMXBs) to study states of silicon in the inter- and circum-stellar medium. The bulk of these LMXBs lie toward the Galactic bulge region and all have column densities above 10{sup 22} cm{sup −2}. The observations were performed using the Chandra High Energy Transmission Grating Spectrometer. The Si K edge in all sources appears at an energy value of 1844 ± 0.001 eV. The edge exhibits significant substructure that can be described by a near edge absorption feature at 1849 ± 0.002 eV and a far edge absorption feature at 1865 ± 0.002 eV. Both of these absorption features appear variable with equivalent widths up to several mÅ. We can describe the edge structure using several components: multiple edge functions, near edge absorption excesses from silicates in dust form, signatures from X-ray scattering optical depths, and a variable warm absorber from ionized atomic silicon. The measured optical depths of the edges indicate much higher values than expected from atomic silicon cross sections and interstellar medium abundances, and they appear consistent with predictions from silicate X-ray absorption and scattering. A comparison with models also indicates a preference for larger dust grain sizes. In many cases, we identify Si xiii resonance absorption and determine ionization parameters between log ξ = 1.8 and 2.8 and turbulent velocities between 300 and 1000 km s{sup −1}. This places the warm absorber in close vicinity of the X-ray binaries. In some data, we observe a weak edge at 1.840 keV, potentially from a lesser contribution of neutral atomic silicon.

  8. Local hydrated structure of an Fe2+/Fe3+ aqueous solution: an investigation using a combination of molecular dynamics and X-ray absorption fine structure methods

    International Nuclear Information System (INIS)

    Ye Qing; Zhou Jing; Zhao Haifeng; Chen Xing; Chu Wangsheng; Zheng Xusheng; Marcelli, Augusto; Wu Ziyu

    2013-01-01

    The hydrated shell of both Fe 2+ and Fe 3+ aqueous solutions are investigated by using the molecular dynamics (MD) and X-ray absorption structure (XAS) methods. The MD simulations show that the first hydrated shells of both Fe 2+ and Fe 3+ are characterized by a regular octahedron with an Fe-O distance of 2.08Å for Fe 2+ and 1.96Å for Fe 3+ , and rule out the occurrence of a Jahn-Teller distortion in the hydrated shell of an Fe 2+ aqueous solution. The corresponding X-ray absorption near edge fine structure (XANES) calculation successfully reproduces all features in the XANES spectra in Fe 2+ and Fe 3+ aqueous solution. A feature that is located at energy 1 eV higher than the white line (WL) in an Fe 3+ aqueous solution may be assigned to the contribution of the charge transfer. (authors)

  9. Enabling liquid solvent structure analysis using hard x-ray absorption spectroscopy with a transferrable microfluidic reactor

    Science.gov (United States)

    Zheng, Jian; Zhang, Wei; Wang, Feng; Yu, Xiao-Ying

    2018-05-01

    In this paper, a vacuum compatible microfluidic device, system for analysis at the liquid vacuum interface, is integrated to hard x-ray absorption spectroscopy to obtain the local structure of K3[Fe(CN)6] in aqueous solutions with three concentrations of 0.5 M, 0.05 M, and 0.005 M. The solutions were sealed in a microchannel 500 µm wide and 300 µm deep in a portable microfluidic device. The Fe K-edge x-ray absorption spectra indicate a presence of Fe(III) in the complex in water, with an octahedral geometry coordinated with 6 C atoms in the first shell with a distance of ~1.92 Å and 6 N atoms in the second shell with a distance of ~3.10 Å. Varying the concentration has no observable influence on the structure of K3[Fe(CN)6]. Our results demonstrate the feasibility of using microfluidic based liquid cells in large synchrotron facilities. Using portable microfludic reactors provides a viable approach to enable multifaceted measurements of liquids in the future.

  10. Enabling liquid solvent structure analysis using hard x-ray absorption spectroscopy with a transferrable microfluidic reactor

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Jian; Zhang, Wei; Wang, Feng; Yu, Xiao-Ying

    2018-04-11

    In this paper, a vacuum compatible microfluidic device, System for Analysis at the Liquid Vacuum Interface (SALVI), is integrated to hard x-ray absorption spectroscopy (XAS) to obtain the local structure of K3[Fe(CN)6] in aqueous solutions with three concentrations of 0.5 M, 0.05 M, and 0.005 M. The solutions were sealed in a microchannel of 500 μm wide and 300 µm deep in a portable microfluidic device. The Fe K-edge x-ray absorption spectra show that the complex in water is Fe(III). The complex is present with octahedral geometry coordinated with 6 C atoms in the first shell with a distance of ~1.92 Å and 6 N atoms in the second shell with a distance of ~3.10 Å. Varying the concentration has no observable influence on the structure of K3[Fe(CN)6]. Our results demonstrate the feasibility of using microfluidic based liquid cells in large synchrotron facilities and it is a viable approach to enable multifaceted measurements of liquids in the future.

  11. Monopeptide versus Monopeptoid: Insights on Structure and Hydration of Aqueous Alanine and Sarcosine via X-ray Absorption Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Uejio, Janel S.; Schwartz, Craig P.; Duffin, Andrew M.; England, Alice; Prendergast, David; Saykally, Richard J.

    2009-11-19

    Despite the obvious significance, the aqueous interactions of peptides remain incompletely understood. Their synthetic analogues called peptoids (poly-N-substituted glycines), have recently emerged as a promising biomimetic material, particularly due to their robust secondary structure and resistance to denaturation. We describe comparative near-edge x-ray absorption fine structure (NEXAFS) spectroscopy studies of aqueous sarcosine, the simplest peptoid, and alanine, its peptide isomer, interpreted by density functional theory calculations. The sarcosine nitrogen K-edge spectrum is blue-shifted with respect to that of alanine, in agreement with our calculations; we conclude that this shift results primarily from the methyl group substitution on the nitrogen of sarcosine. Our calculations indicate that the nitrogen K-edge spectrum of alanine differs significantly between dehydrated and hydrated scenarios, while that of the sarcosine zwitterion is less affected by hydration. In contrast, the computed sarcosine spectrum is greatly impacted by conformational variations, while the alanine spectrum is not. This relates to a predicted solvent dependence for alanine, as compared to sarcosine. Additionally, we show the theoretical nitrogen K-edge spectra to be sensitive to the degree of hydration, indicating that experimental X-ray spectroscopy may be able to distinguish between bulk and partial hydration, such as found in confined environments near proteins and in reverse micelles.

  12. Energetic electron processes fluorescence effects for structured nanoparticles X-ray analysis and nuclear medicine applications

    Energy Technology Data Exchange (ETDEWEB)

    Taborda, A.; Desbrée, A. [Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PRP-HOM/SDI/LEDI, BP-17, 31, Avenue de la Division Leclerc, 92262 Fontenay-aux-Roses (France); Carvalho, A. [IEQUALTECS, Lda, Rua Dr. Francisco Sá Carneiro, 36, 2500-065 S. Gregório CLD (Portugal); Chaves, P.C. [C" 2TN, Campus Tecnológico e Nuclear, Instituto Superior Técnico, Universidade de Lisboa, EN10 km 139.7, 2685-066 Bobadela LRS (Portugal); Reis, M.A., E-mail: mareis@ctn.tecnico.ulisboa.pt [IEQUALTECS, Lda, Rua Dr. Francisco Sá Carneiro, 36, 2500-065 S. Gregório CLD (Portugal); C" 2TN, Campus Tecnológico e Nuclear, Instituto Superior Técnico, Universidade de Lisboa, EN10 km 139.7, 2685-066 Bobadela LRS (Portugal)

    2016-08-15

    Superparamagnetic iron oxide (SPIO) nanoparticles are widely used as contrast agents for nuclear magnetic resonance imaging (MRI), and can be modified for improved imaging or to become tissue-specific or even protein-specific. The knowledge of their detailed elemental composition characterisation and potential use in nuclear medicine applications, is, therefore, an important issue. X-ray fluorescence techniques such as particle induced X-ray emission (PIXE) or X-ray fluorescence spectrometry (XRF), can be used for elemental characterisation even in problematic situations where very little sample volume is available. Still, the fluorescence coefficient of Fe is such that, during the decay of the inner-shell ionised atomic structure, keV Auger electrons are produced in excess to X-rays. Since cross-sections for ionisation induced by keV electrons, for low atomic number atoms, are of the order of 10{sup 3} barn, care should be taken to account for possible fluorescence effects caused by Auger electrons, which may lead to the wrong quantification of elements having atomic number lower than the atomic number of Fe. Furthermore, the same electron processes will occur in iron oxide nanoparticles containing {sup 57}Co, which may be used for nuclear medicine therapy purposes. In the present work, simple approximation algorithms are proposed for the quantitative description of radiative and non-radiative processes associated with Auger electrons cascades. The effects on analytical processes and nuclear medicine applications are quantified for the case of iron oxide nanoparticles, by calculating both electron fluorescence emissions and energy deposition on cell tissues where the nanoparticles may be embedded.

  13. Synthesis, X-ray crystal structure and optical properties research of novel diphenyl sulfone-based bis-pyrazoline derivatives

    International Nuclear Information System (INIS)

    Gong Zhongliang; Zheng Liangwen; Zhao Baoxiang

    2012-01-01

    A series of novel bis-pyrazoline derivatives were synthesized by the reaction of chalcone and (sulfonylbis(3,1-phenylene))bis(hydrazine) in 20–34% yields. The structures of the compounds were determined by IR, 1 H NMR, HRMS spectra, and a representative compound 3b was confirmed based on the X-ray crystallographic analysis. Absorption and fluorescence spectra of these compounds in dichloromethane solution were investigated. The results showed that the emission maxima varied from 415 to 444 nm mainly depending on C3 substituents of pyrazoline moiety. The compounds had higher quantum yields, when C3 substituent was an electron-withdrawing p-chlorophenyl group. Moreover, absorption spectra and emission spectra exhibited a blue-shift and a red-shift with increasing the polarity of solvents, respectively. Fluorescent molecules happened to collide with each other and resulted in quench of the fluorescence when the concentration increased over to 10 −5 M. - Highlights: ► A series of novel diphenyl sulfone-based bis-pyrazoline derivatives were designed and synthesized. ► Their UV–vis absorption and fluorescence emission spectra were investigated. ► The relationship of substituents and the optical properties were discussed. ► With increasing the solvent polarity, fluorescence emission displayed a red-shift and fluorescence quantum yields decreased. ► Fluorescence was quenched when the concentration increased over to 10 −5 M.

  14. Electronic structure and optical properties of CdS{sub x}Se{sub 1−x} solid solution nanostructures from X-ray absorption near edge structure, X-ray excited optical luminescence, and density functional theory investigations

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, M. W. [DESY (Deutsches Elektronen-Synchrotron), FS-PEX, Notkestrasse 85, 22607 Hamburg (Germany); Yiu, Y. M., E-mail: yyiu@uwo.ca; Sham, T. K. [Department of Chemistry, University of Western Ontario, London, ON N6A5B7 (Canada); Ward, M. J. [Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, NY 14853 (United States); Liu, L. [Institute of Functional Nano and Soft Materials (FUNSOM) and Soochow University-Western University Center for Synchrotron Radiation Research, Soochow University, Suzhou, Jiangsu, 215123 (China); Hu, Y. [Canadian Light Source, University of Saskatchewan, Saskatoon, SK S7N2V3 (Canada); Zapien, J. A. [Center Of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR (China); Liu, Yingkai [Institute of Physics and Electronic Information, Yunnan Normal University, Kunming, Yunnan, 650500 (China)

    2014-11-21

    The electronic structure and optical properties of a series of iso-electronic and iso-structural CdS{sub x}Se{sub 1−x} solid solution nanostructures have been investigated using X-ray absorption near edge structure, extended X-ray absorption fine structure, and X-ray excited optical luminescence at various absorption edges of Cd, S, and Se. It is found that the system exhibits compositions, with variable local structure in-between that of CdS and CdSe accompanied by tunable optical band gap between that of CdS and CdSe. Theoretical calculation using density functional theory has been carried out to elucidate the observations. It is also found that luminescence induced by X-ray excitation shows new optical channels not observed previously with laser excitation. The implications of these observations are discussed.

  15. Anomalous scattering, transport, and spatial distribution of X-ray fluorescence at the exit of polycapillary structures

    Energy Technology Data Exchange (ETDEWEB)

    Mazuritskiy, M. I., E-mail: mazurmik@gmail.com; Lerer, A. M.; Makhno, P. V. [Southern Federal University (Russian Federation)

    2016-12-15

    The angular distribution of the X-ray intensity at the exit of microchannel plates at grazing incidence of monochromatic radiation on the walls of microcapillaries has been investigated. The angles and energies of the primary radiation quanta at which the synchrotron beam excites X-ray fluorescence propagating inside polycapillary structures have been determined. The angular dependences of the intensity distribution of X-rays transmitted through the microcapillaries have been studied theoretically and experimentally for energies corresponding to the region of anomalous dispersion near the L{sub 2,3} absorption edges of silicon. The propagation of waves in hollow polycapillary waveguides, the excitation of X-ray fluorescence, and the X-ray diffraction at the exit of microchannel plates have been modeled mathematically. The mathematical model takes into account the presence of a transition layer on the microchannel surface.

  16. Silicon Σ13(5 0 1) grain boundary interface structure determined by bicrystal Bragg rod X-ray scattering

    International Nuclear Information System (INIS)

    Howes, P.B.; Rhead, S.; Roy, M.; Nicklin, C.L.; Rawle, J.L.; Norris, C.A.

    2013-01-01

    The atomic structure of the silicon Σ13(5 0 1) symmetric tilt grain boundary interface has been determined using Bragg rod X-ray scattering. In contrast to conventional structural studies of grain boundary structure using transmission electron microscopy, this approach allows the non-destructive measurement of macroscopic samples. The interface was found to have a single structure that is fully fourfold coordinated. X-ray diffraction data were measured at Beamline I07 at the Diamond Light Source

  17. X-ray structure analyses of biological molecules and particles in Japan. A brief history and future prospect

    International Nuclear Information System (INIS)

    Nakasako, Masayoshi; Yamamoto, Masaki

    2015-01-01

    In Japan, X-ray structure analyses of molecules and particles from biology started in the 1970s. The structure analysis methods have been developed through the innovation of various techniques in advance, and have contributed for understanding the elementary and microscopic processes in life. Here we summarize briefly the history of X-ray structure analyses for structural biology in Japan and think about the prospect. (author)

  18. Providing x-rays

    International Nuclear Information System (INIS)

    Mallozzi, P.J.; Epstein, H.M.

    1985-01-01

    This invention provides an apparatus for providing x-rays to an object that may be in an ordinary environment such as air at approximately atmospheric pressure. The apparatus comprises: means (typically a laser beam) for directing energy onto a target to produce x-rays of a selected spectrum and intensity at the target; a fluid-tight enclosure around the target; means for maintaining the pressure in the first enclosure substantially below atmospheric pressure; a fluid-tight second enclosure adjoining the first enclosure, the common wall portion having an opening large enough to permit x-rays to pass through but small enough to allow the pressure reducing means to evacuate gas from the first enclosure at least as fast as it enters through the opening; the second enclosure filled with a gas that is highly transparent to x-rays; the wall of the second enclosure to which the x-rays travel having a portion that is highly transparent to x-rays (usually a beryllium or plastic foil), so that the object to which the x-rays are to be provided may be located outside the second enclosure and adjacent thereto and thus receive the x-rays substantially unimpeded by air or other intervening matter. The apparatus is particularly suited to obtaining EXAFS (extended x-ray fine structure spectroscopy) data on a material

  19. Electronic structure simulation of chromium aluminum oxynitride by discrete variational-X{alpha} method and X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Youngmin; Chang, Hyunju; Lee, Jae Do [Korea Research Inst. of Chemical Technology, Taejon (Korea); Kim, Eunah; No, Kwangsoo [Korea Advanced Inst. of Science and Technology, Taejon (Korea)

    2002-09-01

    We use a first-principles discrete variational (DV)-X{alpha} method to investigate the electronic structure of chromium aluminum oxynitride. When nitrogen is substituted for oxygen in the Cr-Al-O system, the N2p level appears in the energy range between O2p and Cr3d levels. Consequently, the valence band of chromium aluminum oxynitride becomes broader and the band gap becomes smaller than that of chromium aluminum oxide, which is consistent with the photoelectron spectra for the valence band using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). We expect that this valence band structure of chromium aluminum oxynitride will modify the transmittance slope which is a requirement for photomask application. (author)

  20. Structural relaxation in the dynamics of glycerol: a joint visible, UV and x-ray inelastic scattering study

    International Nuclear Information System (INIS)

    Giugni, A; Cunsolo, A

    2006-01-01

    We describe an experimental study of the dynamic structure factor of liquid glycerol performed by complementary inelastic techniques such as Brillouin visible, ultraviolet and x-ray scattering. The spectra have been collected as a function of both temperature and momentum transfer. The relevant hypersonic parameters are evaluated from the spectral lineshape analysis modelling the data with a simple hydrodynamic profile. The study of their frequency dependence allows us to observe the occurrence of an active structural relaxation and to measure the related timescale. We also find signatures of further relaxation processes occurring below the accessible frequency window. As a result, the dynamic window traditionally probed in spectroscopic experiments is greatly extended and partially bridges the gap between MHz and THz techniques