WorldWideScience

Sample records for absorption edge shifts

  1. Chemical shift of Mn and Cr K-edges in X-ray absorption

    Indian Academy of Sciences (India)

    ... Lecture Workshops · Refresher Courses · Symposia · Live Streaming. Home; Journals; Bulletin of Materials Science; Volume 36; Issue 6. Chemical shift of Mn and Cr K-edges in X-ray absorption spectroscopy with synchrotron radiation. D Joseph A K Yadav S N Jha D Bhattacharyya. Volume 36 Issue 6 November 2013 pp ...

  2. Origin of the chemical shift in X-ray absorption near-edge spectroscopy at the Mn K-Edge in manganese oxide compounds

    NARCIS (Netherlands)

    de Vries, AH; Hozoi, L.; Broer, R.

    2003-01-01

    The absorption edge in Mn K-edge X-ray absorption spectra of manganese oxide compounds shows a shift of several electronvolts in going from MnO through LaMnO3 to CaMnO3. On the other hand, in X-ray photoelectron spectra much smaller shifts are observed. To identify the mechanisms that cause the

  3. Chemical shift of U L3 edges in different uranium compounds obtained by X-ray absorption spectroscopy with synchrotron radiation

    International Nuclear Information System (INIS)

    Joseph, D.; Jha, S.N.; Nayak, C.; Bhattacharyya, D.; Babu, P. Venu

    2014-01-01

    Uranium L 3 X-ray absorption edge was measured in various compounds containing uranium in U 4+ , U 5+ and U 5+ oxidation states. The measurements have been carried out at the Energy Dispersive EXAFS beamline (BL-08) at INDUS-2 synchrotron radiation source at RRCAT, Indore. Energy shifts of ∼ 2-3 eV were observed for U L 3 edge in the U-compounds compared to their value in elemental U. The different chemical shifts observed for the compounds having the same oxidation state of the cation but different anions or ligands show the effect of different chemical environments surrounding the cations in determining their X-ray absorption edges in the above compounds. The above chemical effect has been quantitatively described by determining the effective charges on U cation in the above compounds. (author)

  4. Doping and bond length contributions to Mn K-edge shift in La1 ...

    Indian Academy of Sciences (India)

    ... corresponds to the shift in the center of gravity of the unoccupied Mn 4-band contributing to the Mn K-absorption edge region. This correspondence is then used to separate the doping and size contributions to the edge shift due to variation in the number of electrons in valence band and Mn-O bond lengths, respectively, ...

  5. Chemical shift of U L3 edges in different uranium compounds ...

    Indian Academy of Sciences (India)

    Administrator

    by X-ray absorption spectroscopy with synchrotron radiation. D JOSEPH†, C NAYAK††, ... Bhabha Atomic Research Centre, Mumbai 400 085, India. MS received 28 .... As has been discussed in the 'Introduction' section, the above edge shift ...

  6. Fundamental absorption edge of CdP2 single crystals

    International Nuclear Information System (INIS)

    Bondar', G.I.; Koval', V.S.; Kurik, M.V.

    1986-01-01

    Fundamental absorption edge of tetragonal CdP 2 crystals is investigated within the temperature range of 4.2-293 K. The crystals are grown by the Bridgman methods and resublimation methods and possess different degree of perfection and purity. In perfect CdP 2 crystals with small concentration of impurities in the region of K > 20 cm -1 the shape of the absorption edge spectrum is described by the Urbach rule. The Urbach rule parameters are defined. The electron-phonon interaction is shown to be the determinant at K > 20 cm -1 and the direct vertical transition is observed. A slight additional absorption with maximum at 2.163 eV within the range of K -1 and at T ≤ 50 is associated with transition from shallow acceptor level to the conduction zone. The impurity leads to the shift of the fundamental absorption edge to the long-wavelength side and diffusion of electrons on impurities is resulted

  7. The P K-near edge absorption spectra of phosphates

    Science.gov (United States)

    Franke, R.; Hormes, J.

    1995-12-01

    The X-ray absorption near edge structure (XANES) at the P K-edge in several orthophosphates with various cations, in condensed, and in substituted sodium phosphates have been measured using synchrotron radiation from the ELSA storage ring at the University of Bonn. The measured spectra demonstrate that chemical changes beyond the PO 4- tetrahedra are reflected by energy shifts of the pre-edge and continuum resonances, by the presence of characteristic shoulders and new peaks and by differences in the intensity of the white line. We discuss the energy differences between the white line positions and the corresponding P ls binding energies as a measure of half of the energy gap. The corresponding values correlate with the valence of the cations and the intensity of the white lines. The energy positions of the continuum resonances are discussed on the basis of an empirical bond-length correlation supporting a 1/ r2 - dependence.

  8. Absorption-Edge-Modulated Transmission Spectra for Water Contaminant Monitoring

    Science.gov (United States)

    2016-03-31

    Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6390--16-9675 Absorption- Edge -Modulated Transmission Spectra for Water Contaminant...ABSTRACT c. THIS PAGE 18. NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Absorption- Edge -Modulated Transmission Spectra for Water Contaminant Monitoring...contaminants, within a volume of sampled solution, requires sufficient sensitivity. The present study examines the sensitivity of absorption- edge

  9. Determination of the separation between the soft X-ray K-emission and K-absorption edges in beryllium metal from self-absorption studies

    International Nuclear Information System (INIS)

    Crisp, R.S.

    1979-01-01

    Recent theoretical studies have aroused interest in the phonon broadening of the soft X-ray emission and absorption edges and the shift between them. Using a self-absorption technique a separation of about 0.2 eV is shown to exist between the edges in Be metal. This shift explains the very small self-absorption effects previously observed in Be by Crisp (1977). (Auth.)

  10. Determination of the separation between the soft X-ray K-emission and K-absorption edges in beryllium metal from self-absorption studies

    International Nuclear Information System (INIS)

    Crisp, R.S.

    1979-01-01

    Recent theoretical studies have aroused interest in the phonon broadening of the soft X-ray emission and absorption edges and the shift between them. Using a self-absorption technique a separation of about 0.2 eV is shown to exist between the edges in Be metal. This shift explains the very small self-absorption effects previously observed in Be. (Auth.)

  11. Attenuation studies near K-absorption edges using Compton ...

    Indian Academy of Sciences (India)

    The results are consistent with theoretical values derived from the XCOM package. Keywords. Photon interaction; 241Am; gamma ray attenuation; Compton scattering; absorption edge; rare earth elements. PACS Nos 32.80.-t; 32.90.+a. 1. Introduction. Photon interaction studies at energies around the absorption edge have ...

  12. Hopping absorption edge in silicon inversion layers

    International Nuclear Information System (INIS)

    Kostadinov, I.Z.

    1983-09-01

    The low frequency gap observed in the absorption spectrum of silicon inversion layers is related to the AC variable range hopping. The frequency dependence of the absorption coefficient is calculated. (author)

  13. 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.

  14. X-ray K-absorption edge of zirconium in some perovskite type zirconates

    Energy Technology Data Exchange (ETDEWEB)

    Chougule, B K; Patil, R N [Shivaji Univ., Kolhapur (India). Dept. of Physics

    1979-01-01

    The chemical shifts in the X-ray K-absorption edges of zirconium in the zirconates of calcium, strontium, barium and lead and zirconium oxide have been investigated employing a 400 mm bent crystal X-ray spectrograph. It has been found that the discontinuity shifts towards the high energy side with respect to that in the pure metal and that the chemical shift depends upon the size of the next nearest cation. The larger the size of the cation, smaller is the chemical shift. Dependence of the shift on the crystal structure and the packing factor of the perovskite is also reported.

  15. Studies on absorption coefficient near edge of multi elements

    International Nuclear Information System (INIS)

    Eisa, M.H.; Shen, H.; Yao, H.Y.; Mi, Y.; Zhou, Z.Y.; Hu, T.D.; Xie, Y.N.

    2005-01-01

    X-ray absorption near edge structure (XANES) was used to study the near edge mass-absorption coefficients of seven elements, such as, Ti, V, Fe, Co, Ni, Cu and Zn. It is well known that, on the near edge absorption of element, when incident X-ray a few eV change can make the absorption coefficient an order magnitude alteration. So that, there are only a few points mass-absorption coefficient at the near edge absorption and that always average value in published table. Our results showed a wide range of data, the total measured data of mass-absorption coefficient of the seven elements was about 505. The investigation confirmed that XANES is useful technique for multi-element absorption coefficient measurement. Details of experimental methods and results are given and discussed. The experimental work has been performed at Beijing Synchrotron Radiation Facility. The measured values were compared with the published data. Good agreement between experimental results and published data is obtained

  16. Studies on absorption coefficient near edge of multi elements

    Science.gov (United States)

    Eisa, M. H.; Shen, H.; Yao, H. Y.; Mi, Y.; Zhou, Z. Y.; Hu, T. D.; Xie, Y. N.

    2005-12-01

    X-ray absorption near edge structure (XANES) was used to study the near edge mass-absorption coefficients of seven elements, such as, Ti, V, Fe, Co, Ni, Cu and Zn. It is well known that, on the near edge absorption of element, when incident X-ray a few eV change can make the absorption coefficient an order magnitude alteration. So that, there are only a few points mass-absorption coefficient at the near edge absorption and that always average value in published table. Our results showed a wide range of data, the total measured data of mass-absorption coefficient of the seven elements was about 505. The investigation confirmed that XANES is useful technique for multi-element absorption coefficient measurement. Details of experimental methods and results are given and discussed. The experimental work has been performed at Beijing Synchrotron Radiation Facility. The measured values were compared with the published data. Good agreement between experimental results and published data is obtained.

  17. Red photoluminescence and band edge shift from ZnO thin films

    International Nuclear Information System (INIS)

    Marotti, Ricardo E.; Badan, Juan A.; Quagliata, Eduardo; Dalchiele, Enrique A.

    2007-01-01

    The red photoluminescence (PL) band (peaked between 610 and 640 nm) from electrochemically deposited ZnO thin films is studied. The absorption coefficient is obtained from diffuse reflectance measurements. The absorption band edge depends on deposition conditions. The PL peak follows the shift of the band edge. A similar correlation appears when cooling down to 20 K. This suggests that PL is due to a transition from an intrinsic shallow state to an intrinsic deep state. Comparing against ZnO samples showing green PL, the shallow nature of the state is confirmed

  18. Fundamental absorption edge of NiO nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, V.I., E-mail: visokolov@imp.uran.ru [Institute of Metal Physics, Ural Branch of RAS, S. Kovalevskaya Street 18, 620990 Yekaterinburg (Russian Federation); Druzhinin, A.V. [Institute of Metal Physics, Ural Branch of RAS, S. Kovalevskaya Street 18, 620990 Yekaterinburg (Russian Federation); Kim, G.A. [Institute of Organic Synthesis Ural Branch of RAS, S. Kovalevskaya Street 20, 620990 Yekaterinburg (Russian Federation); Gruzdev, N.B.; Yermakov, A.Ye.; Uimin, M.A.; Byzov, I.V.; Shchegoleva, N.N.; Vykhodets, V.B.; Kurennykh, T.E. [Institute of Metal Physics, Ural Branch of RAS, S. Kovalevskaya Street 18, 620990 Yekaterinburg (Russian Federation)

    2013-12-01

    NiO nanocrystals with the average size of 5, 10 and 25 nm were synthesized by gas-condensation method. The well-defined increase of the optical density D near the fundamental absorption edge of NiO nanocrystals in the range of 3.5–4.0 eV observed after the annealing in air is caused by the oxygen content growth. It is the direct experimental evidence of the fact that p—d charge transfer transitions form the fundamental absorption edge.

  19. Fundamental absorption edge of NiO nanocrystals

    International Nuclear Information System (INIS)

    Sokolov, V.I.; Druzhinin, A.V.; Kim, G.A.; Gruzdev, N.B.; Yermakov, A.Ye.; Uimin, M.A.; Byzov, I.V.; Shchegoleva, N.N.; Vykhodets, V.B.; Kurennykh, T.E.

    2013-01-01

    NiO nanocrystals with the average size of 5, 10 and 25 nm were synthesized by gas-condensation method. The well-defined increase of the optical density D near the fundamental absorption edge of NiO nanocrystals in the range of 3.5–4.0 eV observed after the annealing in air is caused by the oxygen content growth. It is the direct experimental evidence of the fact that p—d charge transfer transitions form the fundamental absorption edge

  20. Fundamental optical absorption edge in MnGa2Te4 single crystals

    International Nuclear Information System (INIS)

    Medvedkin, G.A.; Rud, Yu.V.; Tairov, M.A.

    1988-01-01

    A study is made of the optical properties of oriented MnGa 2 Te 4 crystals in the region of the fundamental absorption edge. The energy gap width for the temperatures 77, 300, and 370 K is determined to be E G = 1.635, 1.52, and 1.50 eV. The spectral response α(ℎω/2π) is found to follow Urbach's rule thoughout the temperature range studied, the slope of the absorption edge remaining constant (α = 10 2 cm -1 ). Crystal annealing with subsequent rapid cooling results in a shift of the absorption edge longward by 25 meV with the exponential form of α(ℎω/2π) prevailing over the range T = 77 to 370 K. An analysis shows the optical absorption in the region of the fundamental edge to be a sum of the effects coming from the density-of-states tails, local scattering centers associated with a high vacancy concentration, and electron-phonon interaction. Optical linear dichroism of the absorption edge of MnGa 2 Te 4 single crystals with pseudotetragonal structure is revealed and studied. The single crystals are established to be optically uniaxial, their optical transmission dichroism being negative. It is shown that the minimal direct optical transitions in MnGa 2 Te 4 are allowed in the E parallel c polarization in the temperature range 77 to 370 K, the crystal-field splitting of the valence band increasing with temperature. (author)

  1. Nuclear safeguards applications of energy-dispersive absorption edge densitometry

    International Nuclear Information System (INIS)

    Russo, P.A.; Hsue, S.T.; Langner, D.G.; Sprinkle, J.K. Jr.

    1980-01-01

    The principles and techniques of absorption edge densitometry in the energy-dispersive mode are summarized as they apply to the nondestructive assay of special nuclear materials. Five existing field instruments, designed for special nuclear materials accounting measurements, are described. Results of the testing of these instruments as well as recent laboratory results are used to define the capabilities of the technique for special nuclear materials accounting. Possibilities for future applications are reviewed. 14 figures

  2. Study of X-ray L2 absorption edges of Gd, Dy, Ho and Er in metals and compounds

    International Nuclear Information System (INIS)

    Agarwal, B.K.; Agarwal, B.R.K.

    1978-01-01

    The positions and shapes of L2 X-ray absorption edges of Gd, Dy, Ho and Er have been studied in metals and in oxides and chlorides, using a forty centimetre bent mica crystal spectrograph. It has been found that the L2 edge shifts towards the high energy side in the compounds and that the chemical shift ΔE depends on the degree of covalency involved. The white line structure at the edge has been analysed in terms of transitions of L2 shell electron to optical nd (n >= 5) states. (author)

  3. The influence of coordination geometry and valency on the K-edge absorption near edge spectra of selected chromium compounds

    International Nuclear Information System (INIS)

    Pantelouris, A.; Modrow, H.; Pantelouris, M.; Hormes, J.; Reinen, D.

    2004-01-01

    X-ray absorption spectra at the chromium K-edge are reported for a number of selected chromium compounds of known chemical structure. The spectra were obtained with use of synchrotron radiation available at the ELectron Stretcher Accelerator ELSA in Bonn. The compounds studied include the tetrahedrally coordinated compounds Ca 2 Ge 0.8 Cr 0.2 O 4 , Ba 2 Ge 0.1 Cr 0.9 O 4 , Sr 2 CrO 4 , Ca 2 (PO 4 ) x (CrO 4 ) 1-x Cl (x=0.25,0.5), Ca 5 (CrO 4 ) 3 Cl, CrO 3 , the octahedrally coordinated compounds Cr(II)-acetate, CrCl 3 , CrF 3 , Cr 2 O 3 , KCr(SO 4 ) 2 · 12H 2 O, CrO 2 and cubic coordinated metallic chromium. In these compounds chromium exhibits a wide range of formal oxidation states (0 to VI). The absorption features in the near edge region are shown to be characteristic of the spatial environment of the absorbing atom. The occurrence of a single pre-edge line easily allows one to distinguish between tetrahedral and octahedral coordination geometry, whereas the energy position of the absorption edge is found to be very sensitive to the valency of the excited chromium atom. Calculations of the ionisation potential of Cr in different oxidation states using the non-relativistic Hartree-Fock method (Froese-Fischer) confirm that the ionisation limit shifts to higher energy with increasing Cr valency. More detailed information on the electronic structure of the different compounds is gained by real-space full multiple scattering calculations using the FEFF8 code

  4. The influence of coordination geometry and valency on the K-edge absorption near edge spectra of selected chromium compounds

    Energy Technology Data Exchange (ETDEWEB)

    Pantelouris, A.; Modrow, H.; Pantelouris, M.; Hormes, J.; Reinen, D

    2004-05-10

    X-ray absorption spectra at the chromium K-edge are reported for a number of selected chromium compounds of known chemical structure. The spectra were obtained with use of synchrotron radiation available at the ELectron Stretcher Accelerator ELSA in Bonn. The compounds studied include the tetrahedrally coordinated compounds Ca{sub 2}Ge{sub 0.8}Cr{sub 0.2}O{sub 4}, Ba{sub 2}Ge{sub 0.1}Cr{sub 0.9}O{sub 4}, Sr{sub 2}CrO{sub 4}, Ca{sub 2}(PO{sub 4}){sub x}(CrO{sub 4}){sub 1-x}Cl (x=0.25,0.5), Ca{sub 5}(CrO{sub 4}){sub 3}Cl, CrO{sub 3}, the octahedrally coordinated compounds Cr(II)-acetate, CrCl{sub 3}, CrF{sub 3}, Cr{sub 2}O{sub 3}, KCr(SO{sub 4}){sub 2} {center_dot} 12H{sub 2}O, CrO{sub 2} and cubic coordinated metallic chromium. In these compounds chromium exhibits a wide range of formal oxidation states (0 to VI). The absorption features in the near edge region are shown to be characteristic of the spatial environment of the absorbing atom. The occurrence of a single pre-edge line easily allows one to distinguish between tetrahedral and octahedral coordination geometry, whereas the energy position of the absorption edge is found to be very sensitive to the valency of the excited chromium atom. Calculations of the ionisation potential of Cr in different oxidation states using the non-relativistic Hartree-Fock method (Froese-Fischer) confirm that the ionisation limit shifts to higher energy with increasing Cr valency. More detailed information on the electronic structure of the different compounds is gained by real-space full multiple scattering calculations using the FEFF8 code.

  5. The influence of coordination geometry and valency on the K-edge absorption near edge spectra of selected chromium compounds

    Science.gov (United States)

    Pantelouris, A.; Modrow, H.; Pantelouris, M.; Hormes, J.; Reinen, D.

    2004-05-01

    X-ray absorption spectra at the chromium K-edge are reported for a number of selected chromium compounds of known chemical structure. The spectra were obtained with use of synchrotron radiation available at the ELectron Stretcher Accelerator ELSA in Bonn. The compounds studied include the tetrahedrally coordinated compounds Ca 2Ge 0.8Cr 0.2O 4, Ba 2Ge 0.1Cr 0.9O 4, Sr 2CrO 4, Ca 2(PO 4) x(CrO 4) 1- xCl ( x=0.25,0.5), Ca 5(CrO 4) 3Cl, CrO 3, the octahedrally coordinated compounds Cr(II)-acetate, CrCl 3, CrF 3, Cr 2O 3, KCr(SO 4) 2 · 12H 2O, CrO 2 and cubic coordinated metallic chromium. In these compounds chromium exhibits a wide range of formal oxidation states (0 to VI). The absorption features in the near edge region are shown to be characteristic of the spatial environment of the absorbing atom. The occurrence of a single pre-edge line easily allows one to distinguish between tetrahedral and octahedral coordination geometry, whereas the energy position of the absorption edge is found to be very sensitive to the valency of the excited chromium atom. Calculations of the ionisation potential of Cr in different oxidation states using the non-relativistic Hartree-Fock method (Froese-Fischer) confirm that the ionisation limit shifts to higher energy with increasing Cr valency. More detailed information on the electronic structure of the different compounds is gained by real-space full multiple scattering calculations using the FEFF8 code.

  6. Resonance absorption of ICRF wave in edge plasma

    International Nuclear Information System (INIS)

    Sugihara, Ryo; Yamanaka, Kaoru.

    1987-07-01

    An edge plasma is shown to significantly absorb ICRF wave when a resonant triplet, a cutoff-resonance-cutoff triplet, is constructed in the evanescent region. Two-ion-component plasmas in a torus are considered though the plasmas are modeled by a slab in which the density changes linearly along the x-axis. The resonance is a perpendicular-ion-cyclotron resonance, i.e., an Alfven resonance, and is formed when the applied frequency ω is smaller than the local cyclotron frequency, at the edge of the antenna side, of the lighter species of ions. Roughly the absorption rate A b is given by M 2 for M 2 >> S 2 and S 4 for S 2 >> M 2 where M = k y l and S ≅ k z l and l is a scale length of the order of the plasma minor radius and k y and k z are the perpendicular and the parallel components of the wave vector. It is noted that the both quantities, M and S, readily become of the order of unity. Since A b is not very sensitive to the density ratio of the two ion species, a few percent of impurities may cause a significant absorption. As the mass ratio of the two ion species comes close to unity the triplet forms readily. Therefore a D-T plasma seems to suffer more easily this kind of resonance absorption than a D-H plasma. (author)

  7. Blue shift of the plasma edge of a ferromagnetic semimetal

    International Nuclear Information System (INIS)

    Wachter, P.; Bommeli, F.; Degiorgi, L.; Burlet, P.; Bourdarot, F.

    1998-01-01

    Full text: In general rare earth pnictides are semimetals and antiferromagnets. Only some nitrides are quoted as ferri or ferromagnetic. However, it has been shown when prepared stoichiometrically and in single crystalline form the free carrier concentration is only in the percent per cation range, thus they are typical low carrier systems. Under these conditions the nitrides are all canted antiferromagnets and metamagnets, i.e. they show Abstract only. The full magnetic moment only with an applied magnetic field. However, when prepared as single crystals but with excess of the rare earths they become spontaneously ferromagnets due to the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in addition to the superexchange mechanisms. On such ferromagnetic compositions of TbN and GdN and also in EuB 6 a new magneto-optic effect has been discovered, a spontaneous blue shift of the plasma edge upon magnetic order. The plasma edge is measured with optical reflectivity and it depends on the free carrier concentration. In other words the free carrier concentration increases upon ferromagnetic order. This effect can be understood with the spontaneous exchange splitting of mainly the 5d conduction band, lowering the bottom of the spin up 5d band, thus increasing the indirect overlap with the valence p band of the anions and thus enhancing the carrier concentration. This blue shift of the plasma edge follows a spin correlation function. An external magnetic field applied near TC enhances the blue shift since the magnetization is not yet saturated. For T→0 a magnetic field has no effect since the magnetization is spontaneously saturated

  8. Nonlinear refraction at the absorption edge in InAs.

    Science.gov (United States)

    Poole, C D; Garmire, E

    1984-08-01

    The results of measurements of nonlinear refraction at the absorption edge in InAs between 68 and 90 K taken with an HF laser are compared with those of a band-gap resonant model in which the contribution of the light-hole band is included and found to account for more than 40% of the observed nonlinear refraction. A generalized expression for the nonlinear index is derived by using the complete Fermi-Dirac distribution function. Good agreement between theory and experiment is obtained, with no free parameters.

  9. Red shift of near band edge emission in cerium implanted GaN

    International Nuclear Information System (INIS)

    Majid, Abdul; Ali, Akbar

    2009-01-01

    Rare earth (RE) doping in GaN is a promising technology to control the optical properties. However, there are no reports on doping of cerium (Ce) into GaN, which is a very unique RE element. In this paper, we performed photoluminescence (PL) and optical transmission measurements on Ce-doped GaN for the first time. A significant red shift of about 120 meV was observed in the PL peak position of the donor bound excitons. This red shift of near band emission was corroborated by the red shift of the absorption edge related to GaN in the optical transmission measurements. This observation is attributed to the band gap narrowing in GaN heavily doped with Ce. The activation energy of the Ce-related shallow donor is found to be 21.9 meV in GaN.

  10. Red shift of near band edge emission in cerium implanted GaN

    Energy Technology Data Exchange (ETDEWEB)

    Majid, Abdul; Ali, Akbar, E-mail: abdulmajid40@yahoo.co, E-mail: akbar@qau.edu.p [Advance Materials Physics Laboratory, Physics Department, Quaid-i-Azam University, Islamabad (Pakistan)

    2009-02-21

    Rare earth (RE) doping in GaN is a promising technology to control the optical properties. However, there are no reports on doping of cerium (Ce) into GaN, which is a very unique RE element. In this paper, we performed photoluminescence (PL) and optical transmission measurements on Ce-doped GaN for the first time. A significant red shift of about 120 meV was observed in the PL peak position of the donor bound excitons. This red shift of near band emission was corroborated by the red shift of the absorption edge related to GaN in the optical transmission measurements. This observation is attributed to the band gap narrowing in GaN heavily doped with Ce. The activation energy of the Ce-related shallow donor is found to be 21.9 meV in GaN.

  11. Sulfur K-edge absorption spectroscopy on selected biological systems

    International Nuclear Information System (INIS)

    Lichtenberg, Henning

    2008-07-01

    Sulfur is an essential element in organisms. In this thesis investigations of sulfur compounds in selected biological systems by XANES (X-ray Absorption Near Edge Structure) spectroscopy are reported. XANES spectroscopy at the sulfur K-edge provides an excellent tool to gain information about the local environments of sulfur atoms in intact biological samples - no extraction processes are required. Spatially resolved measurements using a Kirkpatrick-Baez mirror focusing system were carried out to investigate the infection of wheat leaves by rust fungi. The results give information about changes in the sulfur metabolism of the host induced by the parasite and about the extension of the infection into visibly uninfected plant tissue. Furthermore, XANES spectra of microbial mats from sulfidic caves were measured. These mats are dominated by microbial groups involved in cycling sulfur. Additionally, the influence of sulfate deprivation and H 2 S exposure on sulfur compounds in onion was investigated. To gain an insight into the thermal degradation of organic material the influence of roasting of sulfur compounds in coffee beans was studied. (orig.)

  12. 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

  13. Enhancement of broadband optical absorption in photovoltaic devices by band-edge effect of photonic crystals.

    Science.gov (United States)

    Tanaka, Yoshinori; Kawamoto, Yosuke; Fujita, Masayuki; Noda, Susumu

    2013-08-26

    We numerically investigate broadband optical absorption enhancement in thin, 400-nm thick microcrystalline silicon (µc-Si) photovoltaic devices by photonic crystals (PCs). We realize absorption enhancement by coupling the light from the free space to the large area resonant modes at the photonic band-edge induced by the photonic crystals. We show that multiple photonic band-edge modes can be produced by higher order modes in the vertical direction of the Si photovoltaic layer, which can enhance the absorption on multiple wavelengths. Moreover, we reveal that the photonic superlattice structure can produce more photonic band-edge modes that lead to further optical absorption. The absorption average in wavelengths of 500-1000 nm weighted to the solar spectrum (AM 1.5) increases almost twice: from 33% without photonic crystal to 58% with a 4 × 4 period superlattice photonic crystal; our result outperforms the Lambertian textured structure.

  14. Femtosecond Near Edge X-ray Absorption Measurement of the VO2 Phase Transition

    International Nuclear Information System (INIS)

    Cavalleri, A.; Chong, H.H.W.; Fourmaux, S.; Glover, T.E.; Heimann, P.A; Kieffer, J.C.; Padmore, H.A.; Schoenlein, R.W.

    2004-01-01

    The authors measure the insulator-to-metal transition in VO 2 using femtosecond Near-Edge X-ray Absorption. Sliced pulses of synchrotron radiation are used to detect the photo-induced dynamics at the 516-eV Vanadium L 3 edge

  15. 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

  16. F K-edge soft X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Sugimura, Tetsuro; Kawai, Jun; Maeda, Kuniko; Fukushima, Akiko; Shin, S.; Motoyama, Muneyuki; Nakajima Tsuyoshi

    2001-01-01

    We measured F X-ray absorption spectra of various fluorine compounds using a synchrotron radiation at KEK-PF. The absorption spectra were measured using X-ray fluorescence yield (XFY) and total electron yield (TEY) methods. Change of the spectral shape has a relation to the metal-fluorine bond distance. By comparing with the experimental spectrum and calculated spectrum, F 2p state density is divined into up and down states. (author)

  17. Edge effects in phase-shifting masks for 0.25-µm lithography

    Science.gov (United States)

    Wong, Alfred K. K.; Neureuther, Andrew R.

    1993-03-01

    The impact on image quality of scattering from phase-shifter edges and of interactions between phase-shifter and chrome edges is assessed using rigorous electromagnetic simulation. Effects of edge taper in phase-shift masks, spacing between phase-shifter and chrome edges, small outrigger features with a trench phase-shifter, and of the repair of phase defects by etching to 360 degree(s) are considered. Near field distributions and diffraction efficiencies are examined and images are compared with more approximate results from the commonly used Hopkins' theory of imaging.

  18. Probing ultrafast ππ*/nπ* internal conversion in organic chromophores via K-edge resonant absorption

    DEFF Research Database (Denmark)

    Wolf, T. J. A.; Myhre, Rolf H.; Cryan, J. P.

    2017-01-01

    -edge soft X-ray absorption spectroscopy. As a hole forms in the n orbital during ππ*/nπ* internal conversion, the absorption spectrum at the heteroatom K-edge exhibits an additional resonance. We demonstrate the concept using the nucleobase thymine at the oxygen K-edge, and unambiguously show that ππ...

  19. X-ray speckle contrast variation at a sample-specific absorption edges

    International Nuclear Information System (INIS)

    Retsch, C. C.; Wang, Y.; Frigo, S. P.; Stephenson, G. B.; McNulty, I.

    2000-01-01

    The authors measured static x-ray speckle contrast variation with the incident photon energy across sample-specific absorption edges. They propose that the variation depends strongly on the spectral response function of the monochromator. Speckle techniques have been introduced to the x-ray regime during recent years. Most of these experiments, however, were done at photon energies above 5 keV. They are working on this technique in the 1 to 4 keV range, an energy range that includes many important x-ray absorption edges, e.g., in Al, Si, P, S, the rare-earths, and others. To their knowledge, the effect of absorption edges on speckle contrast has not yet been studied. In this paper, they present their initial measurements and understanding of the observed phenomena

  20. Edge physics of the quantum spin Hall insulator from a quantum dot excited by optical absorption.

    Science.gov (United States)

    Vasseur, Romain; Moore, Joel E

    2014-04-11

    The gapless edge modes of the quantum spin Hall insulator form a helical liquid in which the direction of motion along the edge is determined by the spin orientation of the electrons. In order to probe the Luttinger liquid physics of these edge states and their interaction with a magnetic (Kondo) impurity, we consider a setup where the helical liquid is tunnel coupled to a semiconductor quantum dot that is excited by optical absorption, thereby inducing an effective quantum quench of the tunneling. At low energy, the absorption spectrum is dominated by a power-law singularity. The corresponding exponent is directly related to the interaction strength (Luttinger parameter) and can be computed exactly using boundary conformal field theory thanks to the unique nature of the quantum spin Hall edge.

  1. Two-photon spectroscopy study of edge absorption peculiarities in oxygen-octahedric ferroelectrics

    International Nuclear Information System (INIS)

    Shablaev, S.I.; Danishevskij, A.M.; Subashiev, V.K.

    1984-01-01

    Two-photon absorption (TPA) spectra of ferroelectric crystals with BaTiO 3 , KTaO 3 and SrTiO 3 perovskite strUcture Were obtained. The detailed investigation of temperature dependence of edge spectrum regions was conducted and on the basis of their analysis the indirect character of edge absorption was concluded for all mentioned crystals. TPA spectra of BaTiO 3 and KTaO 3 are characterized by the regions corresponding to one indirect edge TPA spectra of SrTiO 3 - to two indirect edges. The corresponding inter-zone gaps were determined for all investigated crystals, the energy of phonons, participating in indirect two photon transitions, inter-zone gaps, corresponding to direct transitions were determined as well

  2. Interferometric measurement of lines shift in flames in connection with interpretation of lined absorption method in atomic absorption spectroscopy

    International Nuclear Information System (INIS)

    L'vov, B.V.; Polzik, L.K.; Katskov, D.A.; Kruglikova, L.P.

    1975-01-01

    This paper is concerned with interferometric measuring of the line shift in flames in the view of interpretation of absorption lines in the atomic absorption spectroscopy. The newly measured line shifts were compared to the known data on Lorentz broadening of the same lines obtained by methods free of the systematic errors. The resonant lines of the alkaline earth elements (Sr, Ca, Ba) were investigated. To reduce self-absorption in the flame the solutions with minimum concentrations of the elements were used. The computation scheme includes the spectrometer apparatus width and line broadening due to the self-absorption. Formulae are given for computing the values studied. Good agreement was observed between the computed and experimental results. Error analysis was performed. It was concluded that any line shifts in the hydrocarbons were correctly taken into an account in the absolute computations of absorption

  3. Measurement of the effective atomic numbers of compounds with cerium near to the absorption edge

    International Nuclear Information System (INIS)

    Polat, Recep; Icelli, Orhan

    2010-01-01

    In order to measure atomic, molecular and electronic cross-section; the effective atomic number, density of electron and absorption jump factor, we have first measured μ t values of compounds which are determined by mixture rule using transmission method. In order to measure experimentally the effective atomic number within absorption jump factors of compounds with Ce, the X-ray source used Am-241 whose gamma rays were stopped at secondary source (Sm), thus producing Kα and Kβ X-ray emission. The most crucial finding in this study is that measurement of the effective atomic number is not appropriate near to the absorption edge and the effective atomic number is affected by near to the absorption edge. The results obtained have been compared with theoretical values.

  4. 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.

  5. X-ray absorption near edge spectroscopy at the Mn K-edge in highly homogeneous GaMnN diluted magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Sancho-Juan, O.; Cantarero, A.; Garro, N.; Cros, A. [Materials Science Institute, University of Valencia, PO Box 22085, 46071 Valencia (Spain); Martinez-Criado, G.; Salome, M.; Susini, J. [ESRF, Polygone Scientifique Louis Neel, 6 rue Jules Horowitz, 38000 Grenoble (France); Olguin, D. [Dept. de Fisica, CINVESTAV-IPN, 07300 Mexico D.F. (Mexico); Dhar, S.; Ploog, K. [Paul Drude Institute, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2006-06-15

    We have studied by X-ray absorption spectroscopy the local environment of Mn in highly homogeneous Ga{sub 1-x}Mn{sub x}N (0.06edges. In this report, we focus our attention to the X-ray absorption near edge spectroscopy (XANES) results. The comparison of the XANES spectra corresponding to the Ga and Mn edges indicates that Mn is substitutional to Ga in all samples studied. The XANES spectra measured at the Mn absorption edge shows in the near-edge region a double peak and a shoulder below the absorption edge and the main absorption peak after the edge, separated around 15 eV above the pre-edge structure. We have compared the position of the edge with that of MnO (Mn{sup 2+}) and Mn{sub 2}O{sub 3} (Mn{sup 3+}). All samples studied present the same Mn oxidation state, 2{sup +}. In order to interprete the near-edge structure, we have performed ab initio calculations with a 2 x 2 x 1supercell ({proportional_to}6% Mn) using the full potential linear augmented plane wave method as implemented in the Wien2k code. The calculations show the appearance of Mn anti-bonding t{sub 2g} bands, which are responsible for the pre-edge absorption. The shoulder and main absorption peaks are due to transitions from the valence band 1s-states of Mn to the p-contributions of the conduction bands. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Enhanced electroabsorption in strained-layer InxGa1-xAs-InP quantum wells via absorption edge merging

    International Nuclear Information System (INIS)

    Gomatam, B.N.; Anderson, N.G.

    1990-01-01

    Optoelectronic modulators are useful for optical communications, optical computing and other applications which require the electronic control of guided light. Considerable research has recently been devoted to multiple quantum well (MQW) modulators which use an electroabsorption effect unique to quantum wells: the quantum confined Stark effect (QCSE). Voltage controlled optical modulation can be achieved by Stark-shifting the absorption edge above and below the incident photon energy. This paper reports that, to obtain increased optical on-off ratios at decreased drive voltages, the authors are investigating a novel approach which exploits characteristics of MQWs under biaxial tension. The light hole band edge lies at a higher energy than the heavy hole band edge in these structures, which is opposite the case for unstrained or biaxially compressed structures. Since the absorption edge associated with the heavy holes decreases more rapidly with applied field than that for the light holes, merging of the two edges can be expected at some value of the applied field. This effect here called absorption edge merging (AEM), can be expected to give rise to a significant improvement in modulator design. We have theoretically investigated the AEM effect in In x Ga 1-x As/InP quantum well structures with x x Ga 1-x As quantum wells are under tension in such structures, hence the required light hole up band configuration can be achieved

  7. Low Z elements (Mg, Al, and Si) K-edge X-ray absorption spectroscopy in minerals and disordered systems

    International Nuclear Information System (INIS)

    Ildefonse, P.; Calas, G.; Flank, A.M.; Lagarde, P.

    1995-01-01

    Soft X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy have been performed at the Mg-, Al- and Si-K edges in order to establish the ability of this spectroscopy to derive structural information in disordered solids such as glasses and gels. Mg- and Al-K XANES are good structural probes to determine the coordination state of these elements in important minerals, glasses and gels. In a CaO-MgO-2SiO 2 glass Mg XANES spectra differ from that found in the crystalline equivalent, with a significant shift of the edge maxima to lower energy, consistent with a CN lower than 6. Mg-EXAFS on the same sample are in agreement and indicate the presence of 5-coordinated Mg with Mg-O distances of 2.01 A. In aluminosilicate gels, Al-K XANES has been used to investigate the [4]Al/Al total ratios. These ratios increase as the Al/Si ratios decrease. Aluminosilicate and ferric-silicate gels were studied by using Si-K edge XANES. XANES spectra differ significantly among the samples studied. Aluminosilicate gels with Al/Si=1 present a different Al and Si local environment from that known in clay minerals with the same Al/Si ratio. The gel-to-mineral transformation thus implies a dissolution-recrystallization mechanism. On the contrary, ferric-silicate gel presents a Si local environment close to that found in nontronite which may be formed by a long range ordering of the initial gels. (orig.)

  8. Low Z elements (Mg, Al, and Si) K-edge X-ray absorption spectroscopy in minerals and disordered systems

    Science.gov (United States)

    Ildefonse, Ph.; Calas, G.; Flank, A. M.; Lagarde, P.

    1995-05-01

    Soft X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy have been performed at the Mg-, Al- and Si-K edges in order to establish the ability of this spectroscopy to derive structural information in disordered solids such as glasses and gels. Mg- and Al-K XANES are good structural probes to determine the coordination state of these elements in important minerals, glasses and gels. In a CaOsbnd MgOsbnd 2SiO2 glass Mg XANES spectra differ from that found in the crystalline equivalent, with a significant shift of the edge maxima to lower energy, consistent with a CN lower than 6. Mg-EXAFS on the same sample are in agreement and indicate the presence of 5-coordinated Mg with Mgsbnd O distances of 2.01Å. In aluminosilicate gels, Alsbnd K XANES has been used to investigate the [4]Al/Altotal ratios. These ratios increase as the Al/Si ratios decrease. Aluminosilicate and ferric-silicate gels were studied by using Sisbnd K edge XANES. XANES spectra differ significantly among the samples studied. Aluminosilicate gels with Al/Si= 1 present a different Al and Si local environment from that known in clay minerals with the same Al/Si ratio. The gel-to-mineral transformation thus implies a dissolution-recrystallization mechanism. On the contrary, ferric-silicate gel presents a Si local environment close to that found in nontronite which may be formed by a long range ordering of the initial gels.

  9. Simulated big sagebrush regeneration supports predicted changes at the trailing and leading edges of distribution shifts

    Science.gov (United States)

    Schlaepfer, Daniel R.; Taylor, Kyle A.; Pennington, Victoria E.; Nelson, Kellen N.; Martin, Trace E.; Rottler, Caitlin M.; Lauenroth, William K.; Bradford, John B.

    2015-01-01

    Many semi-arid plant communities in western North America are dominated by big sagebrush. These ecosystems are being reduced in extent and quality due to economic development, invasive species, and climate change. These pervasive modifications have generated concern about the long-term viability of sagebrush habitat and sagebrush-obligate wildlife species (notably greater sage-grouse), highlighting the need for better understanding of the future big sagebrush distribution, particularly at the species' range margins. These leading and trailing edges of potential climate-driven sagebrush distribution shifts are likely to be areas most sensitive to climate change. We used a process-based regeneration model for big sagebrush, which simulates potential germination and seedling survival in response to climatic and edaphic conditions and tested expectations about current and future regeneration responses at trailing and leading edges that were previously identified using traditional species distribution models. Our results confirmed expectations of increased probability of regeneration at the leading edge and decreased probability of regeneration at the trailing edge below current levels. Our simulations indicated that soil water dynamics at the leading edge became more similar to the typical seasonal ecohydrological conditions observed within the current range of big sagebrush ecosystems. At the trailing edge, an increased winter and spring dryness represented a departure from conditions typically supportive of big sagebrush. Our results highlighted that minimum and maximum daily temperatures as well as soil water recharge and summer dry periods are important constraints for big sagebrush regeneration. Overall, our results confirmed previous predictions, i.e., we see consistent changes in areas identified as trailing and leading edges; however, we also identified potential local refugia within the trailing edge, mostly at sites at higher elevation. Decreasing

  10. The dispersion of the refractive index of semiconductors at the edge of their intrinsic absorption

    International Nuclear Information System (INIS)

    Kudykina, T.A.; Lisitsa, M.P.

    1986-01-01

    The authors discuss the frequency dependence of the refractive index of various semiconductors near the edge of their intrinsic absorption in both theory and experiment. Beginning with random phase approximation, equations are presented which include all possible excitations and result in values for the width of the forbidden energy gap, the oscillator strengths, and spectral functions for the absorption coefficients. Data are presented for the following materials: CdS, CdSe, CdTe, GaSb, InP, GaAs, ZnTe, PbTe, InAs, InSb, and ZnSe

  11. A high resolution x-ray fluorescence spectrometer for near edge absorption studies

    International Nuclear Information System (INIS)

    Stojanoff, V.; Hamalainen, K.; Siddons, D.P.; Hastings, J.B.; Berman, L.E.; Cramer, S.; Smith, G.

    1991-01-01

    A high resolution fluorescence spectrometer using a Johann geometry in a back scattering arrangement was developed. The spectrometer, with a resolution of 0.3 eV at 6.5 keV, combined with an incident beam, with a resolution of 0.7 eV, form the basis of a high resolution instrument for measuring x-ray absorption spectra. The advantages of the instrument are illustrated with the near edge absorption spectrum of dysprosium nitrate. 10 refs., 4 figs

  12. Identifying anthropogenic uranium compounds using soft X-ray near-edge absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ward, Jesse D.; Bowden, Mark; Tom Resch, C.; Eiden, Gregory C.; Pemmaraju, C. D.; Prendergast, David; Duffin, Andrew M.

    2017-01-01

    Uranium ores mined for industrial use are typically acid-leached to produce yellowcake and then converted into uranium halides for enrichment and purification. These anthropogenic chemical forms of uranium are distinct from their mineral counterparts. The purpose of this study is to use soft X-ray absorption spectroscopy to characterize several common anthropogenic uranium compounds important to the nuclear fuel cycle. Non-destructive chemical analyses of these compounds is important for process and environmental monitoring and X-ray absorption techniques have several advantages in this regard, including element-specificity, chemical sensitivity, and high spectral resolution. Oxygen K-edge spectra were collected for uranyl nitrate, uranyl fluoride, and uranyl chloride, and fluorine K-edge spectra were collected for uranyl fluoride and uranium tetrafluoride. Interpretation of the data is aided by comparisons to calculated spectra. These compounds have unique spectral signatures that can be used to identify unknown samples.

  13. X-ray absorption near-edge spectroscopic study of nickel catalysts

    International Nuclear Information System (INIS)

    Soldatov, Alexander V.; Smolentsev, Grigory; Kravtsova, Antonina; Yalovega, Galina; Feiters, Martin C.; Metselaar, Gerald A.; Joly, Yves

    2006-01-01

    Ni-isocyanide and Ni-acac complexes have been studied by X-ray absorption spectroscopy. Theoretical analysis has been done using self-consistent full multiple scattering (MS) approach within both muffin-tin (MT) model of the potential and non-MT finite deference method. For the isocyanide complex, it was shown that MS theoretical spectra reproduce all structural details of the X-ray absorption near-edge structure (XANES), but also that it is important to consider the non-MT effects in the potential for a correct simulation of the shape of the pre-edge structures. The contribution of a non-constant potential in the interstitial regions is extremely important for the interpretation of the XANES of Ni(acac) 2

  14. Determination of uranium in bench test by L_Ⅲ-absorption edge method

    International Nuclear Information System (INIS)

    Song You; Zheng Weiming; Liu Guijiao; Chen Chen

    2014-01-01

    By independent research L_Ⅲ--absorption edge densimeter, an analytical method for uranium sample with the concentration from 20 g/L to 200 g/L was developed. The fitting area for uranium measurement was determined through experiment. The left fitting area was 1659-1856 channel, and the right one was 2063-2280 channel. The uranium L_Ⅲ--absorption edge was at 1995 channel. The results show that the influence of HNO_3 concentration lower than 9 mol/L, Al and Fe concentration lower than 10 g/L was negligibly small. The uranium measurement precision is better than 0.5%, and the instrument stability is good. Some samples in bench test of uranium recovery were determined. The results are satisfactory. (authors)

  15. X-ray absorption near-edge spectroscopy of plutonium solid species

    International Nuclear Information System (INIS)

    Kropf, A. J.

    1998-01-01

    We present XANES at the L III edge for four plutonium solid phases: Pu(III)F 3 , Pu(IV)O 2 , NaPu(V)O 2 CO 3 , and Ba 3 Pu(VI)O 6 . These correspond to the four important oxidation states in the process chemistry and environmental chemistry of plutonium. By a fitting method that uses an arc tangent function and gaussian curves, it was possible to reproducibly determine the edge energy and distinguish among the four oxidation states. These data demonstrate a 1.85 ± 0.20 eV shift per oxidation state

  16. White line structure in the x-ray Lsub(III) absorption edge of holmium

    International Nuclear Information System (INIS)

    Agarwal, B.K.; Agarwal, B.R.K.

    1978-01-01

    The white line at the Ho Lsub(III) absorption edge has been recorded in Ho metal, Ho 2 O 3 and HoCl 3 . The white line structure in Ho 2 O 3 has been analysed by regarding it as due to the transition into bound states of the Lsub(III) excited ion. The extended fine structure has been used to obtain information on the bond lengths in the compounds. (author)

  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. Influence of Two Photon Absorption on Soliton Self-Frequency Shift

    DEFF Research Database (Denmark)

    Steffensen, Henrik; Rottwitt, Karsten; Jepsen, Peter Uhd

    2011-01-01

    The creation of mid-infrared supercontinua necessitates the use of soft-glass fibers. However, some materials, like chalcogenide, have a substantial two photon absorption. We introduce a model for soliton self-frequency shift that successfully includes this effect.......The creation of mid-infrared supercontinua necessitates the use of soft-glass fibers. However, some materials, like chalcogenide, have a substantial two photon absorption. We introduce a model for soliton self-frequency shift that successfully includes this effect....

  19. Communication: Systematic shifts of the lowest unoccupied molecular orbital peak in x-ray absorption for a series of 3d metal porphyrins

    DEFF Research Database (Denmark)

    García Lastra, Juan Maria; Cook, P. L.; Himpsel, F. J.

    2010-01-01

    Porphyrins are widely used as dye molecules in solar cells. Knowing the energies of their frontier orbitals is crucial for optimizing the energy level structure of solar cells. We use near edge x-ray absorption fine structure (NEXAFS) spectroscopy to obtain the energy of the lowest unoccupied...... molecular orbital (LUMO) with respect to the N-1s core level of the molecule. A systematic energy shift of the N-1s to LUMO transition is found along a series of 3d metal octaethylporphyrins and explained by density functional theory. It is mainly due to a shift of the N-1s level rather than a shift...

  20. Mammographic x-ray unit kilovoltage test tool based on k-edge absorption effect.

    Science.gov (United States)

    Napolitano, Mary E; Trueblood, Jon H; Hertel, Nolan E; David, George

    2002-09-01

    A simple tool to determine the peak kilovoltage (kVp) of a mammographic x-ray unit has been designed. Tool design is based on comparing the effect of k-edge discontinuity of the attenuation coefficient for a series of element filters. Compatibility with the mammography accreditation phantom (MAP) to obtain a single quality control film is a second design objective. When the attenuation of a series of sequential elements is studied simultaneously, differences in the absorption characteristics due to the k-edge discontinuities are more evident. Specifically, when the incident photon energy is higher than the k-edge energy of a number of the elements and lower than the remainder, an inflection may be seen in the resulting attenuation data. The maximum energy of the incident photon spectra may be determined based on this inflection point for a series of element filters. Monte Carlo photon transport analysis was used to estimate the photon transmission probabilities for each of the sequential k-edge filter elements. The photon transmission corresponds directly to optical density recorded on mammographic x-ray film. To observe the inflection, the element filters chosen must have k-edge energies that span a range greater than the expected range of the end point energies to be determined. For the design, incident x-ray spectra ranging from 25 to 40 kVp were assumed to be from a molybdenum target. Over this range, the k-edge energy changes by approximately 1.5 keV between sequential elements. For this design 21 elements spanning an energy range from 20 to 50 keV were chosen. Optimum filter element thicknesses were calculated to maximize attenuation differences at the k-edge while maintaining optical densities between 0.10 and 3.00. Calculated relative transmission data show that the kVp could be determined to within +/-1 kV. To obtain experimental data, a phantom was constructed containing 21 different elements placed in an acrylic holder. MAP images were used to determine

  1. Mammographic x-ray unit kilovoltage test tool based on k-edge absorption effect

    International Nuclear Information System (INIS)

    Napolitano, Mary E.; Trueblood, Jon H.; Hertel, Nolan E.; David, George

    2002-01-01

    A simple tool to determine the peak kilovoltage (kVp) of a mammographic x-ray unit has been designed. Tool design is based on comparing the effect of k-edge discontinuity of the attenuation coefficient for a series of element filters. Compatibility with the mammography accreditation phantom (MAP) to obtain a single quality control film is a second design objective. When the attenuation of a series of sequential elements is studied simultaneously, differences in the absorption characteristics due to the k-edge discontinuities are more evident. Specifically, when the incident photon energy is higher than the k-edge energy of a number of the elements and lower than the remainder, an inflection may be seen in the resulting attenuation data. The maximum energy of the incident photon spectra may be determined based on this inflection point for a series of element filters. Monte Carlo photon transport analysis was used to estimate the photon transmission probabilities for each of the sequential k-edge filter elements. The photon transmission corresponds directly to optical density recorded on mammographic x-ray film. To observe the inflection, the element filters chosen must have k-edge energies that span a range greater than the expected range of the end point energies to be determined. For the design, incident x-ray spectra ranging from 25 to 40 kVp were assumed to be from a molybdenum target. Over this range, the k-edge energy changes by approximately 1.5 keV between sequential elements. For this design 21 elements spanning an energy range from 20 to 50 keV were chosen. Optimum filter element thicknesses were calculated to maximize attenuation differences at the k-edge while maintaining optical densities between 0.10 and 3.00. Calculated relative transmission data show that the kVp could be determined to within ±1 kV. To obtain experimental data, a phantom was constructed containing 21 different elements placed in an acrylic holder. MAP images were used to determine

  2. Sulfur K-edge X-ray absorption spectroscopy and time-dependent density functional theory of arsenic dithiocarbamates.

    Science.gov (United States)

    Donahue, Courtney M; Pacheco, Juan S Lezama; Keith, Jason M; Daly, Scott R

    2014-06-28

    S K-edge X-ray absorption spectroscopy (XAS) and time-dependent density functional theory (TDDFT) calculations were performed on a series of As[S2CNR2]3 complexes, where R2 = Et2, (CH2)5 and Ph2, to determine how dithiocarbamate substituents attached to N affect As[S2CNR2]3 electronic structure. Complimentary [PPh4][S2CNR2] salts were also studied to compare dithiocarbamate bonding in the absence of As. The XAS results indicate that changing the orientation of the alkyl substituents from trans to cis (R2 = Et2vs. (CH2)5) yields subtle variations whereas differences associated with a change from alkyl to aryl are much more pronounced. For example, despite the differences in As 4p mixing, the first features in the S K-edge XAS spectra of [PPh4][S2CNPh2] and As[S2CNPh2]3 were both shifted by 0.3 eV compared to their alkyl-substituted derivatives. DFT calculations revealed that the unique shift observed for [PPh4][S2CNPh2] is due to phenyl-induced splitting of the π* orbitals delocalized over N, C and S. A similar phenomenon accounts for the shift observed for As[S2CNPh2]3, but the presence of two unique S environments (As-S and As···S) prevented reliable analysis of As-S covalency from the XAS data. In the absence of experimental values, DFT calculations revealed a decrease in As-S orbital mixing in As[S2CNPh2]3 that stems from a redistribution of electron density to S atoms participating in weaker As···S interactions. Simulated spectra obtained from TDDFT calculations reproduce the experimental differences in the S K-edge XAS data, which suggests that the theory is accurately modeling the experimental differences in As-S orbital mixing. The results highlight how S K-edge XAS and DFT can be used cooperatively to understand the electronic structure of low symmetry coordination complexes containing S atoms in different chemical environments.

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

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, W. [Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027 (China); Chu, W.S.; Yang, F.F.; Yu, M.J.; Chen, D.L.; Guo, X.Y. [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Zhou, D.W.; Shi, N. [Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027 (China); Marcelli, A. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, P.O. Box 13, Frascati 00044 (Italy); Niu, L.W.; Teng, M.K. [Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027 (China); Gong, W.M. [Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101 (China); Benfatto, M. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, P.O. Box 13, Frascati 00044 (Italy); Wu, Z.Y. [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, P.O. Box 13, Frascati 00044 (Italy)], E-mail: wuzy@ihep.ac.cn

    2007-09-21

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

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

    International Nuclear Information System (INIS)

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

    2007-01-01

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

  5. Mass attenuation coefficient of chromium and manganese compounds around absorption edge.

    Science.gov (United States)

    Sharanabasappa; Kaginelli, S B; Kerur, B R; Anilkumar, S; Hanumaiah, B

    2009-01-01

    The total mass attenuation coefficient for Potassium dichromate, Potassium chromate and Manganese acetate compounds are measured at different photon energies 5.895, 6.404, 6.490, 7.058, 8.041 and 14.390 keV using Fe-55, Co-57 and 241Am source with Copper target, radioactive sources. The photon intensity is analyzed using a high resolution HPGe detector system coupled to MCA under good geometrical arrangement. The obtained values of mass attenuation coefficient values are compared with theoretical values. This study suggests that measured mass attenuation coefficient values at and near absorption edges differ from the theoretical value by about 5-28%.

  6. Measurement of mass attenuation coefficients around the K absorption edge by parametric X-rays

    International Nuclear Information System (INIS)

    Tamura, Masaya; Akimoto, Tadashi; Aoki, Yohei; Ikeda, Jiro; Sato, Koichi; Fujita, Fumiyuki; Homma, Akira; Sawamura, Teruko; Narita, Masakuni

    2002-01-01

    When electrons at relativistic velocities pass through a crystal plate, such as silicon, photons are emitted around the Bragg angle for X-ray diffraction. This phenomenon is called parametric X-ray radiation (PXR). The monochromaticity and directivity of PXR are adequate and the energy can be changed continuously by rotating the crystal. This study measured the mass attenuation coefficient around the K-shell absorption edge of Nb, Zr and Mo as a PXR application of monochromatic hard X-ray radiation sources

  7. Measurement of mass attenuation coefficients around the K absorption edge by parametric X-rays

    CERN Document Server

    Tamura, M; Aoki, Y; Ikeda, J; Sato, K; Fujita, F; Homma, A; Sawamura, T; Narita, M

    2002-01-01

    When electrons at relativistic velocities pass through a crystal plate, such as silicon, photons are emitted around the Bragg angle for X-ray diffraction. This phenomenon is called parametric X-ray radiation (PXR). The monochromaticity and directivity of PXR are adequate and the energy can be changed continuously by rotating the crystal. This study measured the mass attenuation coefficient around the K-shell absorption edge of Nb, Zr and Mo as a PXR application of monochromatic hard X-ray radiation sources.

  8. 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.

  9. Edge-promoting reconstruction of absorption and diffusivity in optical tomography

    International Nuclear Information System (INIS)

    Hannukainen, A; Hyvönen, N; Majander, H; Harhanen, L

    2016-01-01

    In optical tomography a physical body is illuminated with near-infrared light and the resulting outward photon flux is measured at the object boundary. The goal is to reconstruct internal optical properties of the body, such as absorption and diffusivity. In this work, it is assumed that the imaged object is composed of an approximately homogeneous background with clearly distinguishable embedded inhomogeneities. An algorithm for finding the maximum a posteriori estimate for the absorption and diffusion coefficients is introduced assuming an edge-preferring prior and an additive Gaussian measurement noise model. The method is based on iteratively combining a lagged diffusivity step and a linearization of the measurement model of diffuse optical tomography with priorconditioned LSQR. The performance of the reconstruction technique is tested via three-dimensional numerical experiments with simulated data. (paper)

  10. Genesis of Co/SiO2 catalysts : XAS study at the cobalt L-III,L- II absorption edges

    NARCIS (Netherlands)

    Bazin, D.; Kovacs, I.; Guczi, L.; Parent, P.; Laffon, C.; De Groot, F.; Ducreux, O.; Lynch, J.

    2000-01-01

    Silica-supported cobalt catalysts have been investigated by soft X-ray absorption techniques. Soft X-ray absorption spectra were collected at the Co LII,III edge during in situ reduction of calcined samples in a stream of hydrogen in the temperature range between 300 and 650°C. Using reference

  11. Diaryl-substituted norbornadienes with red-shifted absorption for molecular solar thermal energy storage.

    Science.gov (United States)

    Gray, Victor; Lennartson, Anders; Ratanalert, Phasin; Börjesson, Karl; Moth-Poulsen, Kasper

    2014-05-25

    Red-shifting the absorption of norbornadienes (NBDs), into the visible region, enables the photo-isomerization of NBDs to quadricyclanes (QCs) to be driven by sunlight. This is necessary in order to utilize the NBD-QC system for molecular solar thermal (MOST) energy storage. Reported here is a study on five diaryl-substituted norbornadienes. The introduced aryl-groups induce a significant red-shift of the UV/vis absorption spectrum of the norbornadienes, and device experiments using a solar-simulator set-up demonstrate the potential use of these compounds for MOST energy storage.

  12. Optical band-edge absorption of oxide compound SnO2

    International Nuclear Information System (INIS)

    Roman, L.S.; Valaski, R.; Canestraro, C.D.; Magalhaes, E.C.S.; Persson, C.; Ahuja, R.; Silva, E.F. da; Pepe, I.; Silva, A. Ferreira da

    2006-01-01

    Tin oxide (SnO 2 ) is an important oxide for efficient dielectrics, catalysis, sensor devices, electrodes and transparent conducting coating oxide technologies. SnO 2 thin film is widely used in glass applications due to its low infra-red heat emissivity. In this work, the SnO 2 electronic band-edge structure and optical properties are studied employing a first-principle and fully relativistic full-potential linearized augmented plane wave (FPLAPW) method within the local density approximation (LDA). The optical band-edge absorption α(ω) of intrinsic SnO 2 is investigated experimentally by transmission spectroscopy measurements and their roughness in the light of the atomic force microscopy (AFM) measurements. The sample films were prepared by spray pyrolysis deposition method onto glass substrate considering different thickness layers. We found for SnO 2 qualitatively good agreement of the calculated optical band-gap energy as well as the optical absorption with the experimental results

  13. Pressure and solvent shifts of charge transfer absorption band of iodine complexes

    International Nuclear Information System (INIS)

    Sawamura, Seiji; Taniguchi, Yoshihiro; Suzuki, Keizo

    1979-01-01

    Absorption spectra of the CT band of I 2 complexes were observed in several nonpolar solvents at 1 bar, and in heptane up to 4400 bar. All solvent shifts were red with an increase in (n 2 - 1)/(2n 2 + 1), the refractive index (n) function of solvents, consistent with the solvent shift theory. On the other hand pressure caused a variety of shifts, that is, red shifts in benzene-, toluene-, and mesitylene-I 2 complexes, an inversion shift from red to blue in HMB-I 2 complex, and blue shifts in Et 3 N-, n-Pr 3 N-, and n-Bu 3 N-I 2 complexes, though increase in pressure invariably raises the (n 2 - 1)/(2n 2 + 1) value of solvent. The pressure shifts of I 2 complexes seem to be interpreted by a sum of two effects. One is the increased polarity of the solvent, which causes a red shift. The other is the decrease in the bond distance between a donor and an acceptor, which contributes to a blue shift in a strong CT complex and to a red shift in a week one. The pressure and solvent shifts of I 2 complexes were compared with those of π-donor-TCNE complexes. (author)

  14. Influence of two-photon absorption on soliton self-frequency shift

    DEFF Research Database (Denmark)

    Steffensen, Henrik; Agger, Christian; Bang, Ole

    2012-01-01

    In this paper we develop an analytical model for the soliton self-frequency shift, which includes second- and thirdorder dispersion, self-steepening, the full Raman term, and, for the first time to our best knowledge, the effect of two-photon absorption (TPA). We show that TPA can have a signific...

  15. Shifted knife-edge aperture digital in-line holography for fluid velocimetry.

    Science.gov (United States)

    Palero, Virginia; Lobera, Julia; Andrés, Nieves; Arroyo, M Pilar

    2014-06-01

    We describe a digital holography technique that, with the simplicity of an in-line configuration, produces holograms where the real and virtual images are completely separated, as in an off-axis configuration. An in-line setup, in which the object is imaged near the sensor, is modified by placing a shifted knife-edge aperture that blocks half the frequency spectrum at the focal plane of the imaging lens. This simple modification of the in-line holographic configuration allows discriminating the virtual and real images. As a fluid velocimetry technique, the use of this aperture removes the minimum defocusing distance requisite and reduces the out-of-plane velocity measurement errors of classical in-line holography. Results with different test objects are shown.

  16. K-edge x-ray-absorption spectroscopy of laser-generated Kr+ and Kr2+

    International Nuclear Information System (INIS)

    Southworth, S. H.; Arms, D. A.; Dufresne, E. M.; Dunford, R. W.; Ederer, D. L.; Hoehr, C.; Kanter, E. P.; Kraessig, B.; Landahl, E. C.; Peterson, E. R.; Rudati, J.; Santra, R.; Walko, D. A.; Young, L.

    2007-01-01

    Tunable, polarized, microfocused x-ray pulses were used to record x-ray absorption spectra across the K edges of Kr + and Kr 2+ produced by laser ionization of Kr. Prominent 1s→4p and 5p excitations are observed below the 1s ionization thresholds in accord with calculated transition energies and probabilities. Due to alignment of 4p hole states in the laser-ionization process, the Kr + 1s→4p cross section varies with respect to the angle between the laser and x-ray polarization vectors. This effect is used to determine the Kr + 4p 3/2 and 4p 1/2 quantum state populations, and these are compared with results of an adiabatic strong-field ionization theory that includes spin-orbit coupling

  17. Attenuation studies near K-absorption edges using Compton scattered 241Am gamma rays

    International Nuclear Information System (INIS)

    Abdullah, K.K.; Ramachandran, N.; Karunakaran Nair, K.; Babu, B.R.S.; Joseph, Antony; Thomas, Rajive; Varier, K.M.

    2008-01-01

    We have carried out photon attenuation measurements at several energies in the range from 49.38 keV to 57.96 keV around the K-absorption edges of the rare earth elements Sm, Eu, Gd, Tb, Dy and Er using 59.54 keV gamma rays from 241 Am source after Compton scattering from an aluminium target. Pellets of oxides of the rare earth elements were chosen as mixture absorbers in these investigations. A narrow beam good geometry set-up was used for the attenuation measurements. The scattered gamma rays were detected by an HPGe detector. The results are consistent with theoretical values derived from the XCOM package. (author)

  18. Luminescence properties of KCl:Ag{sup -} crystals excited near the fundamental absorption edge

    Energy Technology Data Exchange (ETDEWEB)

    Kawai, Taketoshi, E-mail: buri@p.s.osakafu-u.ac.jp [Department of Physical Science, Graduate School of Science, Osaka Prefecture University, Gakuen-cho 1-1, Naka-ku, Sakai, Osaka 599-8531 (Japan); Hirai, Takeshi [Department of Physical Science, Faculty of Science and Engineering, Ritsumeikan University, Noji Higashi 1-1-1, Kusatsu, Shiga 525-8577 (Japan)

    2012-02-15

    Luminescence properties of KCl single crystals doped with Ag{sup -} centers have been investigated under various excitation energies around the fundamental absorption edge at low temperatures. Under the excitation at 6.89 eV, which is lower than the intrinsic exciton energy by 0.87 eV, the A Prime luminescence band due to the intraionic transition in the Ag{sup -} ion is dominantly observed at 2.91 eV. On the other hand, the excitation at 6.66 eV induces a broad luminescence band at 2.60 eV in addition to the A Prime luminescence band. From the comparison with the localized excitons in KCl:I crystals, the 2.60 eV luminescence band is attributed to the two-center type localized exciton related with the Ag{sup -} ion. The adiabatic potential energy surfaces of the excited states in the Ag{sup -} center and the localized exciton in KCl:Ag{sup -} are discussed. - Highlights: Black-Right-Pointing-Pointer We study the luminescence properties of KCl single crystals doped with Ag{sup -} ions. Black-Right-Pointing-Pointer The excitation around the absorption edge induces a broad luminescence at 2.60 eV. Black-Right-Pointing-Pointer The 2.60 eV luminescence is attributed to the exciton localized at the Ag{sup -} ion. Black-Right-Pointing-Pointer The localized exciton has the two-center type configuration of the relaxed exciton.

  19. Constraining Primordial Black Holes with the EDGES 21-cm Absorption Signal arXiv

    CERN Document Server

    Hektor, Andi; Marzola, Luca; Raidal, Martti; Vaskonen, Ville; Veermäe, Hardi

    The EDGES experiment has recently measured an anomalous global 21-cm spectrum due to hydrogen absorptions at redshifts of about $z\\sim 17$. Model independently, the unusually low temperature of baryons probed by this observable sets strong constraints on any physical process that transfers energy into the baryonic environment at such redshifts. Here we make use of the 21-cm spectrum to derive bounds on the energy injection due to a possible population of ${\\cal O}(1-100) M_\\odot$ primordial black holes, which induce a wide spectrum of radiation during the accretion of the surrounding gas. After calculating the total radiative intensity of a primordial black hole population, we estimate the amount of heat and ionisations produced in the baryonic gas and compute the resulting thermal history of the Universe with a modified version of RECFAST code. Finally, by imposing that the temperature of the gas at $z\\sim 17$ does not exceed the indications of EDGES, we constrain the possible abundance of primordial black h...

  20. Surface modification study of borate materials from B K-edge X-ray absorption spectroscopy

    Science.gov (United States)

    Kasrai, Masoud; Fleet, Michael E.; Muthupari, Swaminathan; Li, D.; Bancroft, G. M.

    The B K-edge X-ray absorption near-edge structure (XANES) spectra of two borates with tetrahedrally-coordinated B [[4]B; natural danburite (CaB2Si2O8) and synthetic boron phosphate (BPO4)] have been recorded in total electron yield (TEY) and fluorescence yield (FY) modes to investigate the surface and bulk structure of these materials. The TEY XANES measurement shows that danburite is susceptible to surface damage involving conversion of [4]B sites to [3]B sites by reaction with moisture and/or mechanical abrasion (grinding, polishing, etc.). The bulk of the mineral is essentially unaffected. Commercial boron phosphate powder exhibits more extensive surface and bulk damage, which increases with air exposure but is recovered on heating at 650°C. In contrast to ELNES, the XANES technique is not affected by beam damage and when collected in the FY mode is capable of yielding meaningful information on the coordination and intermediate-range structure of B in borate and borosilicate materials.

  1. Parameters Influencing Sulfur Speciation in Environmental Samples Using Sulfur K-Edge X-Ray Absorption Near-Edge Structure

    Directory of Open Access Journals (Sweden)

    Siwatt Pongpiachan

    2012-01-01

    Full Text Available This paper aims to enhance the credibility of applying the sulfur K-edge XANES spectroscopy as an innovative “fingerprint” for characterizing environmental samples. The sensitivities of sulfur K-edge XANES spectra of ten sulfur compound standards detected by two different detectors, namely, Lytle detector (LyD and Germanium detector (GeD, were studied and compared. Further investigation on “self-absorption” effect revealed that the maximum sensitivities of sulfur K-edge XANES spectra were achieved when diluting sulfur compound standards with boron nitride (BN at the mixing ratio of 0.1%. The “particle-size” effect on sulfur K-edge XANES spectrum sensitivities was examined by comparing signal-to-noise ratios of total suspended particles (TSP and particulate matter of less than 10 millionths of a meter (PM10 collected at three major cities of Thailand. The analytical results have demonstrated that the signal-to-noise ratios of sulfur K-edge XANES spectra were positively correlated with sulfate content in aerosols and negatively connected with particle sizes. The combination of hierarchical cluster analysis (HCA and principal component analysis (PCA has proved that sulfur K-edge XANES spectrum can be used to characterize German terrestrial soils and Andaman coastal sediments. In addition, this study highlighted the capability of sulfur K-edge XANES spectra as an innovative “fingerprint” to distinguish tsunami backwash deposits (TBD from typical marine sediments (TMS.

  2. Measurement of X-ray attenuation coefficients around K-absorption edges using Fe Kα X-rays

    International Nuclear Information System (INIS)

    Kerur, B.R.; Thontadarya, S.R.; Hanumaiah, B.

    1993-01-01

    The x-ray mass attenuation coefficients were measured around the K-absorption edges of elements in the range 16 ≤ Z ≤ 30 using Fe Kα x-rays of energy 6.400 keV, which is the weighted average energy of Kα 1 and Kα 2 x-ray components from the 57 Co radioactive source. Kβ x-rays were almost eliminated by the differential absorption technique. The small difference in energy between Kα 1 and Kα 2 , 13 eV, was shown to be inconsequential by comparing the measured and theoretical values of μ/ρ for standard materials such as Al, Cu, Mo and Ta. The effect of fine structure of the K-absorption edge on μ/ρ was elucidated by using the compounds of elements in the range 16 ≤ X ≤ 30, containing one element with its K-absorption edge energy (E k ) close to the incident photon energy (E x ). The results clearly indicate the validity of the theoretical mixture rule for all those compounds whose K edge is far away from the incident energy but show deviations of as much as 10% for the manganese compound whose K edge is 140 eV above E x and about 12% for the chromium compound whose K edge is 410 eV below E x . These deviations are attributed to the possible influence of resonance Raman scattering when the incident photon energy E x is less than the edge and to the influence of EXAFS when E x is more than the edge energy. (Author)

  3. Stress Analysis of an Edge-Cracked Plate by using Photoelastic Fringe Phase Shifting Method

    International Nuclear Information System (INIS)

    Baek, Tae Hyun; Kim, Myung Soo; Cho, Sung Ho

    2000-01-01

    The method of photoelasticity allows one to obtain principal stress differences and principal stress directions in a photoelastic model. In the classical approach, the photoelastic parameters are measured manually point by point. The previous methods require much time and skill in the identification and measurement of photoelastic data. Fringe phase shifting method has been recently developed and widely used to measure and analyze fringe data in photo-mechanics. This paper presents the test results of photoelastic fringe phase shifting technique for the stress analysis of a circular disk under compression and an edge-cracked plate subjected to tensile load. The technique used here requires four phase stepped photoelastic images obtained from a circular polariscope by rotating the analyzer at 0 .deg. ,45 .deg. ,90 .deg. ,and 135 .deg. . Experimental results are compared with those or FEM. Good agreement between the results can be observed. However, some error may be included if the technique is used to general direction which is not parallel to isoclinic fringe

  4. 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.

  5. Evaluation of bulk and surfaces absorption edge energy of sol-gel-dip-coating SnO2 thin films

    Directory of Open Access Journals (Sweden)

    Emerson Aparecido Floriano

    2010-12-01

    Full Text Available The absorption edge and the bandgap transition of sol-gel-dip-coating SnO2 thin films, deposited on quartz substrates, are evaluated from optical absorption data and temperature dependent photoconductivity spectra. Structural properties of these films help the interpretation of bandgap transition nature, since the obtained nanosized dimensions of crystallites are determinant on dominant growth direction and, thus, absorption energy. Electronic properties of the bulk and (110 and (101 surfaces are also presented, calculated by means of density functional theory applied to periodic calculations at B3LYP hybrid functional level. Experimentally obtained absorption edge is compared to the calculated energy band diagrams of bulk and (110 and (101 surfaces. The overall calculated electronic properties in conjunction with structural and electro-optical experimental data suggest that the nature of the bandgap transition is related to a combined effect of bulk and (101 surface, which presents direct bandgap transition.

  6. A new term 'Jzeff' derived from measured total attenuation coefficients of photons near the absorption edges of some compounds

    International Nuclear Information System (INIS)

    Polat, Recep; Icelli, Orhan

    2010-01-01

    In order to determine the effect of XAFS (X-ray absorption fine structure) on J zeff , we have measured μ/ρ values of compounds, which are determined by the mixture rule or the independent atomic model. Also, we want to obtain both XAFS effect and non-applicability or applicability of mixture rule. The most crucial finding in this study is that measurement of the effective atomic number is not appropriate near the absorption edge and the effective atomic number is affected by near the absorption edge. The results obtained have been compared with theoretical values. Also, the objective of this study is to show that there is a term 'J zeff ' between effective atomic numbers and absorption jump factor.

  7. Arsenic K-edge X-ray absorption near-edge spectroscopy to determine oxidation states of arsenic of a coastal aquifer–aquitard system

    International Nuclear Information System (INIS)

    Wang, Ya; Jiao, Jiu Jimmy; Zhu, Sanyuan; Li, Yiliang

    2013-01-01

    Determination of oxidation states of solid-phase arsenic in bulk sediments is a valuable step in the evaluation of its bioavailability and environmental fate in deposits, but is difficult when the sediments have low arsenic contents and heterogeneous distribution of arsenic species. As K-edge X-ray absorption near-edge spectroscopy (XANES) was used to determine quantitatively the oxidation states of arsenic in sediments collected from different depths of boreholes in the Pearl River Delta, China, where the highest aquatic arsenic concentration is 161.4 μg/L, but the highest solid arsenic content only 39.6 mg/kg. The results demonstrated that XANES is efficient in determining arsenic oxidation states of the sediments with low arsenic contents and multiple arsenic species. The study on the high-resolution vertical variations of arsenic oxidation states also indicated that these states are influenced strongly by groundwater activities. With the help of geochemical data, solid arsenic speciation, toxicity and availability were further discussed. -- Highlights: •XANES is efficient in determining arsenic oxidation states of the bulk sediments. •Distribution of arsenic oxidation states is consistent with geochemical conditions. •Arsenic oxidation states are influenced strongly by groundwater activities. -- As K-edge X-ray absorption near-edge spectroscopy is efficient in determining arsenic oxidation states of the bulk sediments with low arsenic contents and heterogeneous distribution of arsenic species

  8. A study of the Nb3Ge system by Ge K-edge extended x-ray absorption fine structure and x-ray absorption near-edge structure spectroscopy

    International Nuclear Information System (INIS)

    Saini, N L; Filippi, M; Wu Ziyu; Oyanagi, H; Ihara, H; Iyo, A; Agrestini, S; Bianconi, A

    2002-01-01

    The local structure of Nb 3 Ge intermetallic superconductor has been studied by Ge K-edge absorption spectroscopy. Extended x-ray absorption fine structure (EXAFS) experiments show two Ge-Nb distances. In addition to the crystallographic distance of ∼2.87 A, there exists a second Ge-Nb distance, shorter than the first by ∼0.2 A, assigned to a phase with short-range symmetry related to local displacements in the Nb-Nb chains. The x-ray absorption near-edge structure (XANES) spectrum has been simulated by full multiple-scattering calculations considering the local displacements determined by the EXAFS analysis. The XANES spectrum has been well reproduced by considering a cluster of 99 atoms within a radius of about 7 A from the central Ge atom and introducing determined local displacements

  9. X-ray reflectivity of cobalt and titanium in the vicinity of the Lsub(2,3) absorption edges

    International Nuclear Information System (INIS)

    Bremer, J.; Kaihola, L.; Keski-Kuha, R.

    1980-01-01

    X-ray reflectivity across cobalt and titanium Lsub(2,3) absorption edges was measured as a function of energy by means of continuous radiation from a tungsten anode in a grating spectrometer. The real and imaginary parts of the refractive index were obtained from the absorption curves and an exact Kramers-Kronig analysis. A measured fine structure in the reflected intensities was interpreted as an effect of white lines in the absorption spectra. The x-ray intensity was calculated as a function of energy by means of the Fresnel formula. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-11-27

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

  11. Active control of an edge-mode-based plasmon-induced absorption sensor.

    Science.gov (United States)

    Li, Yong; Su, Yi; Lin, Qi; Zhai, Xiang; Wang, Ling-Ling

    2018-04-01

    We investigate the formation and evolution of plasmon-induced absorption (PIA) effect in a three-dimensional graphene waveguide structure. The PIA window is formed by near-field coupling of the graphene edge mode, the extremely destructive interference between the radiative mode and sub-radiative mode of graphene nanoribbons. The resonance intensity has a significant dependence on the coupling distance between the graphene nanoribbons. At the same time, it is particularly sensitive to the refractive index of the environment, which is promising for sensing devices. In addition, the resonant wavelength can be actively controlled by changing the Fermi energy of graphene. Moreover, it can be seen that the group time delay of the PIA window reaches -0.28   ps , which is a good candidate for ultrafast light application. Finally, additional graphene nanoribbons can also form a double-channel PIA window. Our work may provide an excellent platform for controlling the optical transmission of highly integrated plasmonic components.

  12. Calculation of optical and K pre-edge absorption spectra for ferrous iron of distorted sites in oxide crystals

    Science.gov (United States)

    Vercamer, Vincent; Hunault, Myrtille O. J. Y.; Lelong, Gérald; Haverkort, Maurits W.; Calas, Georges; Arai, Yusuke; Hijiya, Hiroyuki; Paulatto, Lorenzo; Brouder, Christian; Arrio, Marie-Anne; Juhin, Amélie

    2016-12-01

    Advanced semiempirical calculations have been performed to compute simultaneously optical absorption and K pre-edge x-ray absorption spectra of Fe2 + in four distinct site symmetries found in minerals. The four symmetries, i.e., a distorted octahedron, a distorted tetrahedron, a square planar site, and a trigonal bipyramidal site, are representative of the Fe2 + sites found in crystals and glasses. A particular attention has been paid to the definition of the p -d hybridization Hamiltonian which occurs for noncentrosymmetric symmetries in order to account for electric dipole transitions. For the different sites under study, an excellent agreement between calculations and experiments was found for both optical and x-ray absorption spectra, in particular in terms of relative intensities and energy positions of electronic transitions. To our knowledge, these are the first calculations of optical absorption spectra on Fe2 + placed in such diverse site symmetries, including centrosymmetric sites. The proposed theoretical model should help to interpret the features of both the optical absorption and the K pre-edge absorption spectra of 3 d transition metal ions and to go beyond the usual fingerprint interpretation.

  13. Photoabsorption of the molecular IH cation at the iodine 3 d absorption edge

    Science.gov (United States)

    Klumpp, Stephan; Guda, Alexander A.; Schubert, Kaja; Mertens, Karolin; Hellhund, Jonas; Müller, Alfred; Schippers, Stefan; Bari, Sadia; Martins, Michael

    2018-03-01

    Yields of atomic iodine Iq + (q ≥2 ) fragments resulting from photoexcitation and photoionization of the target ions IH+ and I+ have been measured in the photon-energy range 610-680 eV, which comprises the thresholds for iodine 3 d ionization. The measured ion-yield spectra show two strong and broad resonance features due to the excitation of the 3 d3 /2 ,5 /2 electrons into ɛ f states rather similar for both parent ions. In the 3 d pre-edge range, excitations into (n p π ) -like orbitals and into an additional σ* orbital are found for IH+, which have been identified by comparison of the atomic I+ and molecular IH+ data and with the help of (time-dependent) density functional theory (DFT) and atomic Hartree-Fock calculations. The (5 p π ) orbital is almost atomlike, whereas all other resonances of the IH+ primary ion show a more pronounced molecular character, which is deduced from the chemical shifts of the resonances and the theoretical analysis.

  14. Understanding the shrinkage of optical absorption edges of nanostructured Cd-Zn sulphide films for photothermal applications

    Energy Technology Data Exchange (ETDEWEB)

    Hossain, Md. Sohrab [Department of Physics, Jahangirnagar University, Savar, Dhaka 1342 (Bangladesh); Kabir, Humayun [Department of Physics, Jahangirnagar University, Savar, Dhaka 1342 (Bangladesh); School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Rahman, M. Mahbubur, E-mail: M.Rahman@Murdoch.edu.au [Department of Physics, Jahangirnagar University, Savar, Dhaka 1342 (Bangladesh); Surface Analysis and Materials Engineering Research Group, School of Engineering & Information Technology, Murdoch University, Perth, Western Australia 6150 (Australia); Hasan, Kamrul [Department of Chemistry, College of Sciences, University of Sharjah, P.O. Box 27272, Sharjah (United Arab Emirates); Bashar, Muhammad Shahriar; Rahman, Mashudur [Institute of Fuel and Research Development, Bangladesh Council for Scientific and Industrial Research, Dhanmondi, Dhaka (Bangladesh); Gafur, Md. Abdul [Pilot Plant and Process Development Center, Bangladesh Council for Scientific and Industrial Research, Dhanmondi, Dhaka (Bangladesh); Islam, Shariful [Department of Physics, Comilla University, Comilla (Bangladesh); Amri, Amun [Department of Chemical Engineering, Universitas Riau, Pekanbaru (Indonesia); Jiang, Zhong-Tao [Surface Analysis and Materials Engineering Research Group, School of Engineering & Information Technology, Murdoch University, Perth, Western Australia 6150 (Australia); Altarawneh, Mohammednoor; Dlugogorski, Bogdan Z. [School of Engineering & Information Technology, Murdoch University, Murdoch, WA 6150 (Australia)

    2017-01-15

    Highlights: • Cd-Zn sulphide films synthesized via chemical bath deposition technique. • Nanocrystalline phase of Cd-Zn sulphide films were seen in XRD studies. • Nanocrystalline structures of the films were also confirmed by the SEM. • The band gap of these films is a combination of composition and size. • E{sub U} and σ studies ascribed the shrinkage of absorption edges around the optical band-gaps. - Abstract: In this article Cd-Zn sulphide thin films deposited onto soda lime glass substrates via chemical bath deposition (CBD) technique were investigated for photovoltaic applications. The synthesized films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet visible (UV–vis) spectroscopic methodologies. A higher degree of crystallinity of the films was attained with the increase of film thicknesses. SEM micrographs exhibited a partial crystalline structure with a particulate appearance surrounded by the amorphous grain boundaries. The optical absorbance and absorption coefficient of the films were also enhanced significantly with the increase in film thicknesses. Optical band-gap analysis indicated a monotonic decrease in direct and indirect band-gaps with the increase of thicknesses of the films. The presence of direct and indirect transitional energies due to the exponential falling edges of the absorption curves may either be due to the lack of long-range order or to the existence of defects in the films. The declination of the optical absorption edges was also confirmed via Urbach energy and steepness parameters studies.

  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. 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.

  17. 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

  18. Experimental investigation on electron cyclotron absorption at down-shifted frequency in the PLT tokamak

    International Nuclear Information System (INIS)

    Mazzucato, E.; Fidone, I.; Cavallo, A.; von Goeler, S.; Hsuan, H.

    1986-05-01

    The absorption of 60 GHz electron cyclotron waves, with the extraordinary mode and an oblique angle of propagation, has been investigated in the PLT tokamak in the regime of down-shifted frequencies. The production of energetic electrons, with energies of up to 300 to 400 keV, peaks at values of toroidal field (approx. =29 kG) for which the wave frequency is significantly smaller than the electron cyclotron frequency in the whole plasma region. The observations are consistent with the predictions of the relativistic theory of electron cyclotron damping at down-shifted frequency. Existing rf sources make this process a viable method for assisting the current ramp-up, and for heating the plasma of present large tokamaks

  19. 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...

  20. Study of non-validity of mixture rule near K-absorption edges by X-ray spectrometric technique

    International Nuclear Information System (INIS)

    Sharanabasappa; Chitralekha, A.; Kerur, B.R.; Anilkumar, S.

    2012-01-01

    X-ray spectrometric technique has been described to determine the X-ray mass attenuation coefficient, μ/ρ, of X-rays employing HPGe X-ray detector and radioactive sources. The photon intensity is measured by gating the channel of the spectrometer at FWHM/photo peak. Using the technique the 'best value' values of μ/ρ were obtained for those thicknesses which lie in the transmission (T) range 0.5 ≥ T ≥ 0.02. Total attenuation cross sections for other elements and lead compounds were measured at photon energies from 17 to 88 keV to study the Bragg's additivity law near the absorption edge of the lead. The measured values of mass attenuation coefficient values are compared with theoretical values obtained using Winxcom (programme). This study suggests that measured mass attenuation coefficient values at and near absorption edges differ from the theoretical value by about 17-23%. (author)

  1. Calculations of Energy Shift of the Conduction Band-Edge in Doped and Compensated GaP

    OpenAIRE

    Endo, Tamio; Itoh, Nobuhiko; Okino, Yasushi; 遠藤, 民生; 伊藤, 伸彦; 沖野, 祥[他

    1989-01-01

    The energy shifts of the parabolic conduction band-edge at 77 and 300K with doping the Te-donor in GaP were calculated in the nondegenerate system for the two cases ; unintentional and intentional compensations, using the two models proposed by Hwang abd by Mahan. The total parabolic shift △EM(△EH), and the contributions of the exchangeinteraction △μex(△Ee) and of the Coulomb interaction △μed(△Ec) calculated by the Mahan's model (Hwang's model), increase with increasing donor concentration in...

  2. Investigation into short-range order, electric conductivity and optical absorption edge of indium selenide thin amorphous films

    International Nuclear Information System (INIS)

    Bilyj, M.N.; Didyk, G.V.; Stetsiv, Ya.I.; Yurechko, R.Ya.

    1980-01-01

    Thin amorphous films of InSe have been obtained by the method of discrete vacuum evaporation of about 10 -2 Pa. The short-range order is investigated according to the radial distribution curves. The temperature and film thickness are shown to affect the character of conductivity. The width of the forbidden band determined by the fundamental absorption edge is found to depend on the time of film annealing

  3. Sulfur K-edge X-ray absorption spectroscopy as an experimental probe for S-nitroso proteins

    International Nuclear Information System (INIS)

    Szilagyi, Robert K.; Schwab, David E.

    2005-01-01

    X-ray absorption spectroscopy at the sulfur K-edge (2.4-2.6 keV) provides a sensitive and specific technique to identify S-nitroso compounds, which have significance in nitric oxide-based cell signaling. Unique spectral features clearly distinguish the S-nitroso-form of a cysteine residue from the sulfhydryl-form or from a methionine thioether. Comparison of the sulfur K-edge spectra of thiolate, thiol, thioether, and S-nitroso thiolate compounds indicates high sensitivity of energy positions and intensities of XAS pre-edge features as determined by the electronic environment of the sulfur absorber. A new experimental setup is being developed for reaching the in vivo concentration range of S-nitroso thiol levels in biological samples

  4. Small fluorescence-activating and absorption-shifting tag for tunable protein imaging in vivo.

    Science.gov (United States)

    Plamont, Marie-Aude; Billon-Denis, Emmanuelle; Maurin, Sylvie; Gauron, Carole; Pimenta, Frederico M; Specht, Christian G; Shi, Jian; Quérard, Jérôme; Pan, Buyan; Rossignol, Julien; Moncoq, Karine; Morellet, Nelly; Volovitch, Michel; Lescop, Ewen; Chen, Yong; Triller, Antoine; Vriz, Sophie; Le Saux, Thomas; Jullien, Ludovic; Gautier, Arnaud

    2016-01-19

    This paper presents Yellow Fluorescence-Activating and absorption-Shifting Tag (Y-FAST), a small monomeric protein tag, half as large as the green fluorescent protein, enabling fluorescent labeling of proteins in a reversible and specific manner through the reversible binding and activation of a cell-permeant and nontoxic fluorogenic ligand (a so-called fluorogen). A unique fluorogen activation mechanism based on two spectroscopic changes, increase of fluorescence quantum yield and absorption red shift, provides high labeling selectivity. Y-FAST was engineered from the 14-kDa photoactive yellow protein by directed evolution using yeast display and fluorescence-activated cell sorting. Y-FAST is as bright as common fluorescent proteins, exhibits good photostability, and allows the efficient labeling of proteins in various organelles and hosts. Upon fluorogen binding, fluorescence appears instantaneously, allowing monitoring of rapid processes in near real time. Y-FAST distinguishes itself from other tagging systems because the fluorogen binding is highly dynamic and fully reversible, which enables rapid labeling and unlabeling of proteins by addition and withdrawal of the fluorogen, opening new exciting prospects for the development of multiplexing imaging protocols based on sequential labeling.

  5. Infrared study of the absorption edge of β-InN films grown on GaN/MgO structures

    Science.gov (United States)

    Pérez-Caro, M.; Rodríguez, A. G.; Vidal, M. A.; Navarro-Contreras, H.

    2010-07-01

    Infrared optical studies were carried out in a group of cubic InN samples grown by gas source molecular beam epitaxy on MgO (001) substrates. Room temperature (RT) reflectance and low-temperature (LT) transmittance measurements were performed by using fast Fourier transform infrared spectrometry. Reflectance fittings allowed to establish that β-InN films have large free-carrier concentrations present (>1019 cm-3), a result that is corroborated by Hall effect measurements. Each sample explored exhibited a different optical absorption edge. The Varshni parameters that describe adequately the optical absorption edge responses with temperature are obtained for the set of samples studied. The observed temperatures changes, from LT to RT, are the lowest reported for III-V semiconductor binary compounds. The temperature coefficient of the conduction band depends on the strength of the electron-phonon interaction (e-ph-i), as well as on the thermal expansion. It has been predicted that cubic InN has one of the smallest e-ph-i of all III-V compounds, which is corroborated by these results. The variation in values of absorption edges is clearly consistent with the Burstein-Moss and band renormalization effects, produced by high free electron concentrations. It is shown that the conduction band in β-InN, analogous to wurtzite InN, follows a nonparabolic behavior.

  6. Infrared study of the absorption edge of β-InN films grown on GaN/MgO structures

    International Nuclear Information System (INIS)

    Perez-Caro, M.; Rodriguez, A. G.; Vidal, M. A.; Navarro-Contreras, H.

    2010-01-01

    Infrared optical studies were carried out in a group of cubic InN samples grown by gas source molecular beam epitaxy on MgO (001) substrates. Room temperature (RT) reflectance and low-temperature (LT) transmittance measurements were performed by using fast Fourier transform infrared spectrometry. Reflectance fittings allowed to establish that β-InN films have large free-carrier concentrations present (>10 19 cm -3 ), a result that is corroborated by Hall effect measurements. Each sample explored exhibited a different optical absorption edge. The Varshni parameters that describe adequately the optical absorption edge responses with temperature are obtained for the set of samples studied. The observed temperatures changes, from LT to RT, are the lowest reported for III-V semiconductor binary compounds. The temperature coefficient of the conduction band depends on the strength of the electron-phonon interaction (e-ph-i), as well as on the thermal expansion. It has been predicted that cubic InN has one of the smallest e-ph-i of all III-V compounds, which is corroborated by these results. The variation in values of absorption edges is clearly consistent with the Burstein-Moss and band renormalization effects, produced by high free electron concentrations. It is shown that the conduction band in β-InN, analogous to wurtzite InN, follows a nonparabolic behavior.

  7. Chemical shift of Mn and Cr K-edges in X-ray absorption ...

    Indian Academy of Sciences (India)

    particularly on Mn and Cr compounds (Ghatikar et al 1977;. Padalia and Nayak 1977; ... conventional X-ray sources and hence may lack reliability. 2. Experimental ..... with the result obtained by Hinge et al (2011) for Cu com- pounds and is ... Chem. 84 2200. Nietubyc R, Sobczak E and Attenkofer K E 2001 J. Alloys Compd.

  8. Quantitative uranium speciation with U M{sub 4,5}-edge HERFD absorption spectra

    Energy Technology Data Exchange (ETDEWEB)

    Kvashnina, Kristina O.; Rossberg, Andre [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Molecular Structures

    2017-06-01

    This report gives a brief description of the quantitative uranium speciation performed by iterative transformation factor analysis (ITFA) of High Energy Resolution X-ray Fluorescence Detection (HERFD) data collected at the M{sub 4,5} edge.

  9. Quantifying the blue shift in the light absorption of small gold nanoparticles

    International Nuclear Information System (INIS)

    Tsekov, Roumen; Georgiev, Peter; Simeonova, Silviya; Balashev, Konstantin

    2017-01-01

    The dependence of the surface plasmons resonance (SPR) frequency on the size of gold nanoparticles (GNPs) is experimentally studied. The measured data for the SPR frequency by UV-Vis spectroscopy and GNPs diameter by Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM) are collected in the course of classical citrate GNPs synthesis. The relationship between the GNPs size and the blue shift of the light absorption is presented. They are fitted by an equation with a single free parameter, the dielectric permittivity of the surrounding media. Thus, the refractive index of the surrounding media is determined, which characterizes the GNPs surface shell. Key words: Gold nanoparticles (GNPs), Surface plasmon resonance (SPR), Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM)

  10. The dressed atom as binary phase modulator: towards attojoule/edge optical phase-shift keying.

    Science.gov (United States)

    Kerckhoff, Joseph; Armen, Michael A; Pavlichin, Dmitri S; Mabuchi, Hideo

    2011-03-28

    We use a single 133Cs atom strongly coupled to an optical resonator to induce random binary phase modulation of a near infra-red, ∼ 500 pW laser beam, with each modulation edge caused by the dissipation of a single photon (≈ 0.23 aJ) by the atom. While our ability to deterministically induce phase edges with an additional optical control beam is limited thus far, theoretical analysis of an analogous, solid-state system indicates that efficient external control should be achievable in demonstrated nanophotonic systems.

  11. Study of the L2,3 edges of 3d transition metals by X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Akguel, G.; Aksoy, F.; Bozduman, A.; Ozkendir, O.M.; Ufuktepe, Y.; Luening, J.

    2008-01-01

    In the soft X-rays energy region, near edge X-ray absorption fine structure (NEXAFS) spectra are generally recorded by monitoring yield signals of secondary particles. These secondary particles, electrons or fluorescence photons, follow from the decay of the core hole excited in the primary absorption process. In general the yield signals are, to a good approximation, proportional to the absorption coefficient. However, in several applications it would be desirable to measure the absorption coefficient quantitatively. To derive the absorption coefficient quantitatively from a yield spectrum, one needs to know the escape depth of the emitted electrons (λ e ) of the applied yield technique in the material of interest. Since this quantity is difficult to calculate, it is unknown for most materials. In this paper we present the first results of our systematic investigation of the total electron-yield (TEY) escape depth of the 3d transition metals (Fe, Co and Cu). In addition our results gave important information on the variation of the TEY escape depth with the filling of the 3d band

  12. Study of the L2,3 Edges of 3d Transition Metals By X-Ray Absorption Spectroscopy

    International Nuclear Information System (INIS)

    Akgul, G.; Aksoy, F.; Bozduman, A.; Ozkendir, O.M.; Ufuktepe, Y.; Luning, J.

    2008-01-01

    In the soft X-rays energy region, near edge X-ray absorption fine structure (NEXAFS) spectra are generally recorded by monitoring yield signals of secondary particles. These secondary particles, electrons or fluorescence photons, follow from the decay of the core hole excited in the primary absorption process. In general the yield signals are, to a good approximation, proportional to the absorption coefficient. However, in several applications it would be desirable to measure the absorption coefficient quantitatively. To derive the absorption coefficient quantitatively from a yield spectrum, one needs to know the escape depth of the emitted electrons (λ e ) of the applied yield technique in the material of interest. Since this quantity is difficult to calculate, it is unknown for most materials. In this paper we present the first results of our systematic investigation of the total electron-yield (TEY) escape depth of the 3d transition metals (Fe, Co and Cu). In addition our results gave important information on the variation of the TEY escape depth with the filling of the 3d band.

  13. Grazing exit versus grazing incidence geometry for x-ray absorption near edge structure analysis of arsenic traces

    International Nuclear Information System (INIS)

    Meirer, F.; Streli, C.; Wobrauschek, P.; Zoeger, N.; Pepponi, G.

    2009-01-01

    In the presented study the grazing exit x-ray fluorescence was tested for its applicability to x-ray absorption near edge structure analysis of arsenic in droplet samples. The experimental results have been compared to the findings of former analyses of the same samples using a grazing incidence (GI) setup to compare the performance of both geometries. Furthermore, the investigations were accomplished to gain a better understanding of the so called self-absorption effect, which was observed and investigated in previous studies using a GI geometry. It was suggested that a normal incidence-grazing-exit geometry would not suffer from self-absorption effects in x-ray absorption fine structure (XAFS) analysis due to the minimized path length of the incident beam through the sample. The results proved this assumption and in turn confirmed the occurrence of the self-absorption effect for GI geometry. Due to its lower sensitivity it is difficult to apply the GE geometry to XAFS analysis of trace amounts (few nanograms) of samples but the technique is well suited for the analysis of small amounts of concentrated samples

  14. White lines at the Lsub(I), Lsub(II), and Lsub(III) absorption edges of some rare earth compounds

    Energy Technology Data Exchange (ETDEWEB)

    Garg, K B; Sharma, B K; Jain, D C [Rajasthan Univ., Jaipur (India). Dept. of Physics; Sinha, A I.P. [Banasthali Vidyapeeth (India). Dept. of Chemistry

    1980-11-01

    The paper reports the appearance of white lines (WLS) at all the three L-absorption edges of the sulfur coordinated thiosalicylic acid compounds of Sm, Tb, and Dy. The profiles of the observed WLS are presented and discussed.

  15. In situ time-resolved X-ray near-edge absorption spectroscopy of selenite reduction by siderite

    International Nuclear Information System (INIS)

    Badaut, V.; Schlegel, M.L.; Descostes, M.; Moutiers, G.

    2012-01-01

    The reduction oxidation-reaction between aqueous selenite (SeO 3 2- ) and siderite (FeCO 3 (s)) was monitored by in situ, time-resolved X-ray absorption near-edge structure (XANES) spectroscopy at the selenium K edge in a controlled electrochemical environment. Spectral evolutions showed that more than 60% of selenite was reduced at the siderite surface after 20 h of experiment, at which time the reaction was still incomplete. Fitting of XANES spectra by linear combination of reference spectra showed that selenite reaction with siderite is essentially a two-step process, selenite ions being immobilized on siderite surface prior to their reduction. A kinetic model of the reduction step is proposed, allowing to identify the specific contribution of surface reduction. These results have strong implications for the retention of selenite by corrosion products in nuclear waste repositories and in a larger extent for the fate of selenium in the environment. (authors)

  16. Electronic Structure from Iron L-edge Spectroscopy : An Example of Spin Transition Evidenced by Soft X-ray Absorption Spectroscopy

    NARCIS (Netherlands)

    Cartier dit Moulin, Ch.; Flank, A.M.; Rudolf, P.; Chen, C.T.

    1993-01-01

    Soft X-ray Absorption Spectroscopy at the transition metal L2,3 edges provides information about the 3d unoccupied states by dipole allowed transitions. We have recorded iron L2,3 edges in order to follow the reversible thermal spin interconversion (S=2 S=0) of the Fe(II)(o-phenantroline)2(NCS)2.

  17. Determination of shift in energy of band edges and band gap of ZnSe spherical quantum dot

    Science.gov (United States)

    Siboh, Dutem; Kalita, Pradip Kumar; Sarma, Jayanta Kumar; Nath, Nayan Mani

    2018-04-01

    We have determined the quantum confinement induced shifts in energy of band edges and band gap with respect to size of ZnSe spherical quantum dot employing an effective confinement potential model developed in our earlier communication "arXiv:1705.10343". We have also performed phenomenological analysis of our theoretical results in comparison with available experimental data and observe a very good agreement in this regard. Phenomenological success achieved in this regard confirms validity of the confining potential model as well as signifies the capability and applicability of the ansatz for the effective confining potential to have reasonable information in the study of real nano-structured spherical systems.

  18. Influence of defects on the absorption edge of InN thin films: The band gap value

    Science.gov (United States)

    Thakur, J. S.; Danylyuk, Y. V.; Haddad, D.; Naik, V. M.; Naik, R.; Auner, G. W.

    2007-07-01

    We investigate the optical-absorption spectra of InN thin films whose electron density varies from ˜1017tõ1021cm-3 . The low-density films are grown by molecular-beam-epitaxy deposition while highly degenerate films are grown by plasma-source molecular-beam epitaxy. The optical-absorption edge is found to increase from 0.61to1.90eV as the carrier density of the films is increased from low to high density. Since films are polycrystalline and contain various types of defects, we discuss the band gap values by studying the influence of electron degeneracy, electron-electron, electron-ionized impurities, and electron-LO-phonon interaction self-energies on the spectral absorption coefficients of these films. The quasiparticle self-energies of the valence and conduction bands are calculated using dielectric screening within the random-phase approximation. Using one-particle Green’s function analysis, we self-consistently determine the chemical potential for films by coupling equations for the chemical potential and the single-particle scattering rate calculated within the effective-mass approximation for the electron scatterings from ionized impurities and LO phonons. By subtracting the influence of self-energies and chemical potential from the optical-absorption edge energy, we estimate the intrinsic band gap values for the films. We also determine the variations in the calculated band gap values due to the variations in the electron effective mass and static dielectric constant. For the lowest-density film, the estimated band gap energy is ˜0.59eV , while for the highest-density film, it varies from ˜0.60tõ0.68eV depending on the values of electron effective mass and dielectric constant.

  19. X-Ray K Absorption Edge Structures of Ligand Chlorine Ion in Some Cobalt Coordination Compounds

    Science.gov (United States)

    Obashi, Masayoshi; Matsukawa, Tokuo

    1983-03-01

    The X-ray Cl K absorption spectra in [Co(NH3)6]Cl3, [Co(NH3)5Cl]Cl2, trans-[Co(NH3)4Cl2]Cl and Cs2[CoCl4] are measured with a high-resolution vacuum two-crystal spectrometer. The spectra, except that of [Co(NH3)6]Cl3, show an extremely narrow absorption line at the absorption threshold. The result is interpreted on the basis of molecular orbital theory and it is proposed that the intensity of these narrow absorption lines depends on the chemical state between the cobalt and ligand chlorine ions. The narrow absorption line may well be attributed to transitions of the Cl 1s electron into the eg* antibonding orbitals having partially the 3p character of chlorine in [Co(NH3)5Cl]Cl2 and trans-[Co(NH3)4Cl2]Cl. In Cs2[CoCl4] it may be ascribed to the Cl 1s-t2* transitions.

  20. Effect of exciton polaritons of absorption edge of GaTe

    International Nuclear Information System (INIS)

    Kurbatov, L.N.; Dirochka, A.I.; Sosin, V.A.

    1979-01-01

    The experimental results, pointing to the dependence of spectral and integral coefficients of exciton absorption as well as to the exciton relaxation parameter γsub(0) over the exciton zone on the sample thickness, are presented. It is tried to explain the inverse dependences of absorption intensity in the maximum of αsub(max) and γsub(0) exciton line within the limits of polariton theory. The values of polariton free path length in GaTe at various temperatures, as well as the volume γsub(vol.) and surface γsub(surf.) parameters of exciton relaxation over the exciton zone are discussed

  1. Local shifts in floral biotic interactions in habitat edges and their effect on quantity and quality of plant offspring

    Science.gov (United States)

    Fenu, Giuseppe; Bernardo, Liliana

    2017-01-01

    Abstract Spatial shifts in insect fauna due to ecological heterogeneity can severely constrain plant reproduction. Nonetheless, data showing effects of insect visit patterns and intensity of mutualistic and/or antagonistic plant–insect interactions on plant reproduction over structured ecological gradients remain scarce. We investigated how changes in flower-visitor abundance, identity and behaviour over a forest-open habitat gradient affect plant biotic interactions, and quantitative and qualitative fitness in the edge-specialist Dianthus balbisii. Composition and behaviour of the insects visiting flowers of D. balbisii strongly varied over the study gradient, influencing strength and patterns of plant biotic interactions (i.e. herbivory and pollination likelihood). Seed set comparison in free- and manually pollinated flowers suggested spatial variations in the extent of quantitative pollen limitation, which appeared more pronounced at the gradient extremes. Such variations were congruent to patterns of flower visit and plant biotic interactions. The analyses on seed and seedling viability evidenced that spatial variation in amount and type of pollinators, and frequency of herbivory affected qualitative fitness of D. balbisii by influencing selfing and outcrossing rates. Our work emphasizes the role of plant biotic interactions as a fine-scale mediator of plant fitness in ecotones, highlighting that optimal plant reproduction can take place into a restricted interval of the ecological gradients occurring at forest edges. Reducing the habitat complexity typical of such transition contexts can threat edge-adapted plants. PMID:28775831

  2. Physical properties of the interstellar medium using high-resolution Chandra spectra: O K-edge absorption

    Energy Technology Data Exchange (ETDEWEB)

    Gatuzz, E.; Mendoza, C. [Centro de Física, Instituto Venezolano de Investigaciones Científicas (IVIC), P.O. Box 20632, Caracas 1020A (Venezuela, Bolivarian Republic of); García, J. [Harvard-Smithsonian Center for Astrophysics, MS-6, 60 Garden Street, Cambridge, MA 02138 (United States); Kallman, T. R. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bautista, M. A.; Gorczyca, T. W., E-mail: egatuzz@ivic.gob.ve, E-mail: claudio@ivic.gob.ve, E-mail: javier@head.cfa.harvard.edu, E-mail: manuel.bautista@wmich.edu, E-mail: thomas.gorczyca@wmich.edu, E-mail: timothy.r.kallman@nasa.gov [Department of Physics, Western Michigan University, Kalamazoo, MI 49008 (United States)

    2014-08-01

    Chandra high-resolution spectra toward eight low-mass Galactic binaries have been analyzed with a photoionization model that is capable of determining the physical state of the interstellar medium. Particular attention is given to the accuracy of the atomic data. Hydrogen column densities are derived with a broadband fit that takes into account pileup effects, and in general are in good agreement with previous results. The dominant features in the oxygen-edge region are O I and O II Kα absorption lines whose simultaneous fits lead to average values of the ionization parameter of log ξ = –2.90 and oxygen abundance of A{sub O} = 0.70. The latter is given relative to the standard by Grevesse and Sauval, but rescaling with the revision by Asplund et al. would lead to an average abundance value fairly close to solar. The low average oxygen column density (N{sub O} = 9.2 × 10{sup 17} cm{sup –2}) suggests a correlation with the low ionization parameters, the latter also being in evidence in the column density ratios N(O II)/N(O I) and N(O III)/N(O I) that are estimated to be less than 0.1. We do not find conclusive evidence for absorption by any other compound but atomic oxygen in our oxygen-edge region analysis.

  3. Manganese L-edge X-ray absorption spectroscopy of manganese catalase from Lactobacillus plantarum and mixed valence manganese complexes

    Energy Technology Data Exchange (ETDEWEB)

    Grush, M.M.; Chen, J.; George, S.J. [Univ. of California, Davis, CA (United States)] [and others

    1996-01-10

    The first Mn L-edge absorption spectra of a Mn metalloprotein are presented in this paper. Both reduced and superoxidized Mn catalase have been examined by fluorescence-detected soft X-ray absorption spectroscopy, and their Mn L-edge spectra are dramatically different. The spectrum of reduced Mn(II)Mn(II) catalase has been interpreted by ligand field atomic multiplet calculations and by comparison to model compound spectra. The analysis finds a 10 Dq value of nearly 1.1 eV, consistent with coordination by predominately nitrogen and oxygen donor ligands. For interpretation of mixed valence Mn spectra, an empirical simulation procedure based on the addition of homovalent model compound spectra has been developed and was tested on a variety of Mn complexes and superoxidized Mn catalase. This routine was also used to determine the oxidation state composition of the Mn in [Ba{sub 8}Na{sub 2}ClMn{sub 16}(OH){sub 8}(CO{sub 3}){sub 4}L{sub 8}] .53 H{sub 2}O (L=1,3-diamino-2-hydroxypropane-N,N,N`N`-tetraacetic acid). 27 refs., 6 figs.

  4. Experimental and theoretical study of X-ray absorption around the chlorine L edge in vinyl chloride

    International Nuclear Information System (INIS)

    Kawerk, Elie; Carniato, Stéphane; Iwayama, Hiroshi; Shigemasa, Eiji; Piancastelli, Maria Novella; Wassaf, Joseph; Khoury, Antonio; Simon, Marc

    2013-01-01

    Highlights: ► We measured the X-ray absorption spectrum of C 2 H 3 Cl around the chlorine L edge. ► Ab-initio calculations of the spectrum shed light on eventual electronic resonances. ► Vibrational substructures for particular core excited states are considered. ► The potential energy surfaces of the core excited electronic states are evaluated. ► Sharp or narrow spectral bands are associated to bound or dissociative surfaces. -- Abstract: We present a combined experimental and theoretical study of the high-resolution chlorine L edge X-ray absorption spectrum in gas-phase vinyl chloride (C 2 H 3 Cl). With the help of ab-initio calculations, we interpret the experimental spectrum and attribute each band to its corresponding electronic transitions terminating at states characterized by an either binding or dissociative potential energy surface (PES). Vibrational substructures in some specific core-excited electronic states are taken into account

  5. Experimental and theoretical study of X-ray absorption around the chlorine L edge in vinyl chloride

    Energy Technology Data Exchange (ETDEWEB)

    Kawerk, Elie, E-mail: elie.kawerk@etu.upmc.fr [Université Pierre et Marie Curie, Laboratoire de Chimie Physique-Matière et Rayonnement, UMR 7614, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Université Libanaise, Faculté des Sciences II Fanar, Laboratoire de Physique Appliquée, 90656 Jdeidet el Metn (Lebanon); Carniato, Stéphane [Université Pierre et Marie Curie, Laboratoire de Chimie Physique-Matière et Rayonnement, UMR 7614, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Iwayama, Hiroshi; Shigemasa, Eiji [Ultraviolet Synchrotron Orbital Radiation Facility, Institute for Molecular Science, Okazaki 444-8585 (Japan); Piancastelli, Maria Novella [Université Pierre et Marie Curie, Laboratoire de Chimie Physique-Matière et Rayonnement, UMR 7614, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Wassaf, Joseph; Khoury, Antonio [Université Libanaise, Faculté des Sciences II Fanar, Laboratoire de Physique Appliquée, 90656 Jdeidet el Metn (Lebanon); Simon, Marc [Université Pierre et Marie Curie, Laboratoire de Chimie Physique-Matière et Rayonnement, UMR 7614, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France)

    2013-02-15

    Highlights: ► We measured the X-ray absorption spectrum of C{sub 2}H{sub 3}Cl around the chlorine L edge. ► Ab-initio calculations of the spectrum shed light on eventual electronic resonances. ► Vibrational substructures for particular core excited states are considered. ► The potential energy surfaces of the core excited electronic states are evaluated. ► Sharp or narrow spectral bands are associated to bound or dissociative surfaces. -- Abstract: We present a combined experimental and theoretical study of the high-resolution chlorine L edge X-ray absorption spectrum in gas-phase vinyl chloride (C{sub 2}H{sub 3}Cl). With the help of ab-initio calculations, we interpret the experimental spectrum and attribute each band to its corresponding electronic transitions terminating at states characterized by an either binding or dissociative potential energy surface (PES). Vibrational substructures in some specific core-excited electronic states are taken into account.

  6. X-ray absorption near-edge structure of GaN with high Mn concentration grown on SiC

    International Nuclear Information System (INIS)

    Sancho-Juan, O; Cantarero, A; Garro, N; Cros, A; Martinez-Criado, G; Salome, M; Susini, J; Olguin, D; Dhar, S

    2009-01-01

    By means of x-ray absorption near-edge structure (XANES) several Ga 1-x Mn x N (0.03 2 ↑ band localized in the gap region, and the corresponding anti-bonding state t 2 ↓, which seem to be responsible for the double structure which appears at the pre-edge absorption region. The shoulders and main absorption peak of the XANES spectra are attributed to transitions from the Mn(1s) band to the conduction bands, which are partially dipole allowed because of the Mn(4p) contribution to these bands.

  7. Oxygen K-edge absorption spectra of small molecules in the gas phase

    Energy Technology Data Exchange (ETDEWEB)

    Yang, B.X.; Kirz, J.; Sham, T.K.

    1986-01-01

    The absorption spectra of O/sub 2/, CO, CO/sub 2/ and OCS have been recorded in a transmission mode in the energy region from 500 to 950 eV. Recent observation of EXAFS in these molecules is confirmed in this study. 7 refs., 3 figs.

  8. Oxygen K-edge absorption spectra of small molecules in the gas phase

    International Nuclear Information System (INIS)

    Yang, B.X.; Kirz, J.; Sham, T.K.

    1986-01-01

    The absorption spectra of O 2 , CO, CO 2 and OCS have been recorded in a transmission mode in the energy region from 500 to 950 eV. Recent observation of EXAFS in these molecules is confirmed in this study. 7 refs., 3 figs

  9. High-resolution molybdenum K-edge X-ray absorption spectroscopy analyzed with time-dependent density functional theory.

    Science.gov (United States)

    Lima, Frederico A; Bjornsson, Ragnar; Weyhermüller, Thomas; Chandrasekaran, Perumalreddy; Glatzel, Pieter; Neese, Frank; DeBeer, Serena

    2013-12-28

    X-ray absorption spectroscopy (XAS) is a widely used experimental technique capable of selectively probing the local structure around an absorbing atomic species in molecules and materials. When applied to heavy elements, however, the quantitative interpretation can be challenging due to the intrinsic spectral broadening arising from the decrease in the core-hole lifetime. In this work we have used high-energy resolution fluorescence detected XAS (HERFD-XAS) to investigate a series of molybdenum complexes. The sharper spectral features obtained by HERFD-XAS measurements enable a clear assignment of the features present in the pre-edge region. Time-dependent density functional theory (TDDFT) has been previously shown to predict K-pre-edge XAS spectra of first row transition metal compounds with a reasonable degree of accuracy. Here we extend this approach to molybdenum K-edge HERFD-XAS and present the necessary calibration. Modern pure and hybrid functionals are utilized and relativistic effects are accounted for using either the Zeroth Order Regular Approximation (ZORA) or the second order Douglas-Kroll-Hess (DKH2) scalar relativistic approximations. We have found that both the predicted energies and intensities are in excellent agreement with experiment, independent of the functional used. The model chosen to account for relativistic effects also has little impact on the calculated spectra. This study provides an important calibration set for future applications of molybdenum HERFD-XAS to complex catalytic systems.

  10. The fundamental absorption edge in MnIn{sub 2}Se{sub 4} layer semi-magnetic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Rincón, C., E-mail: crincon@ula.ve [Centro de Estudios de Semiconductores, Departamento de Física, Facultad de Ciencias, Universidad de Los Andes, Mérida (Venezuela, Bolivarian Republic of); Torrres, T.E. [Laboratorio de Magnetismo, Departamento de Física, Facultad de Ciencias, Universidad de Los Andes, Mérida (Venezuela, Bolivarian Republic of); Instituto de Nanociencia de Aragón, Laboratorio de Microscopías Avanzadas, Universidad de Zaragoza 50009, Zaragoza (Spain); Departamento de Física de la Materia Condensada, Facultad de Ciencias, Universidad de Zaragoza 50009, Zaragoza, Spain. (Spain); Sagredo, V. [Laboratorio de Magnetismo, Departamento de Física, Facultad de Ciencias, Universidad de Los Andes, Mérida (Venezuela, Bolivarian Republic of); Jiménez-Sandoval, Sergio J.; Mares-Jacinto, E. [CINVESTAV Querétaro, Libramiento Norponiente N° 2000, Frac. Real de Juriquilla, Querétaro, Qro. 76230 (Mexico)

    2015-11-15

    From the study of the optical absorption coefficient and photoluminescence spectra of the layer semi-magnetic semiconductor MnIn{sub 2}Se{sub 4} the nature of its fundamental absorption edge is established. It is found that the lowest-energy-gap of this compound is allowed-indirect between parabolic bands that vary from about 1.55–1.43 eV in the temperature range from 10 K to room temperature. In addition, two allowed direct band-to-band transitions beginning at 1.72 and 1.85 eV at 295 K, and at 1.82 and 1.96 eV at 10 K which are related to optical absorption processes between the uppermost Γ{sub 4}(z) and the middle Γ{sub 5}(x) valence bands and the conduction band respectively, are observed in the high energy range. It is also found that the crystal field splitting parameter (Δ{sub cf}) of MnIn{sub 2}Se{sub 4} is of about 0.15 eV nearly independent of the temperature. At energies around 2.2 eV a photoluminescence band related to internal transitions between d-excited levels of Mn{sup +2} ion to its {sup 6}A{sub 1} ground state is also observed in spectra.

  11. Modification of the Absorption Edge of GaAs Arising from Hot-Electron Effects

    DEFF Research Database (Denmark)

    McGroddy, J. C.; Christensen, Ove

    1973-01-01

    We have observed a large enhancement of the electric-field-induced optical absorption arising from hot-electron effects in n-type GaAs at 77 K. The magnitude and field dependence of the enhancement can be approximately accounted for by a theory attributing the effect to broadening of the final...... states of the optical transitions by interaction with the nonequilibrium optical phonons produced by the hot electrons....

  12. Measurement of edge residual stresses in glass by the phase-shifting method

    Science.gov (United States)

    Ajovalasit, A.; Petrucci, G.; Scafidi, M.

    2011-05-01

    Control and measurement of residual stress in glass is of great importance in the industrial field. Since glass is a birefringent material, the residual stress analysis is based mainly on the photoelastic method. This paper considers two methods of automated analysis of membrane residual stress in glass sheets, based on the phase-shifting concept in monochromatic light. In particular these methods are the automated versions of goniometric compensation methods of Tardy and Sénarmont. The proposed methods can effectively replace manual methods of compensation (goniometric compensation of Tardy and Sénarmont, Babinet and Babinet-Soleil compensators) provided by current standards on the analysis of residual stresses in glasses.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    The work presents the X-ray absorption fine structure (XAFS) technique for measuring the X-ray mass attenuation coefficient of nickel metal foil in the X-ray energy range of 8271.2–8849.4 eV using scanning XAFS beam line (BL-09) at Indus-2 synchrotron radiation source facility, Raja Ramanna Centre for Advanced Technology (RRCAT) at Indore, India. The result represents the X-ray mass attenuation coefficient data for 0.02 mm thick Ni metal foil in the XAFS region of Ni K-edge. However, the results are compared to theoretical values using X-COM. There is a maximum deviation which is found exactly near the K-edge jump and decreases as we move away from the absorption edge. Oscillatory structure appears just above the observed absorption edge i.e., 8348.7 eV and is confined to around 250 eV above the edge. - Highlights: • Mass attenuation coefficient measurements of nickel using synchrotron radiation. • The measurements were taken exactly near the Ni K-edge at an energy step of 1 eV. • A maximum deviation is found near the K-edge

  14. The dispersion surface of X-rays very near the absorption edge

    International Nuclear Information System (INIS)

    Fukamachi, T.; Negishi, R.; Kawamura, T.

    1995-01-01

    To discuss the X-ray dynamical diffraction when the imaginary part of the X-ray polarizability is larger than the real part, the dispersion surface is studied as a function of the ratio between the real and the imaginary parts of the polarizability. The dispersion surface in the Laue case when the real part is zero has a similar form to that in the Bragg case when the imaginary part is zero. The relations between the dispersion surface and the diffracted intensity are studied in some special cases. The abnormal absorption and the abnormal transmission effect are related to the features of the dispersion surface. (orig.)

  15. Edge-promoting reconstruction of absorption and diffusivity in optical tomography

    DEFF Research Database (Denmark)

    Hannukainen, A.; Harhanen, Lauri Oskari; Hyvönen, N.

    2015-01-01

    In optical tomography a physical body is illuminated with near-infrared light and the resulting outward photon flux is measured at the object boundary. The goal is to reconstruct internal optical properties of the body, such as absorption and diffusivity. In this work, it is assumed that the imaged...... measurement noise model. The method is based on iteratively combining a lagged diffusivity step and a linearization of the measurement model of diffuse optical tomography with priorconditioned LSQR. The performance of the reconstruction technique is tested via three-dimensional numerical experiments...

  16. Resonant photoemission of La and Yb at the 3d absorption edge

    CERN Document Server

    Lagarde, P; Ogasawara, H; Kotani, A

    2003-01-01

    Resonant photoemission and resonant Auger experiments at the 3d threshold are presented for La and Yb over a binding energy domain which extends up to the 4p levels. These experimental results are well explained by calculations in the framework of full-multiplet Hartree-Fock theory with an atomic model. Strong participator and spectator Auger transitions are observed without ordinary Auger transition, indicating that the 4f wavefunction is well localized in the intermediate state even in the case of La. The 4d sub 3 sub / sub 2 and 4d sub 5 sub / sub 2 branching ratio of the 4d resonant photoemission of La at the M sub 4 and M sub 5 edges is observed experimentally and analyzed theoretically. The difference in the resonant processes behavior for La and Yb is discussed based upon the different 4f occupation number.

  17. Sulfur K-edge absorption spectroscopy on selected biological systems; Schwefel-K-Kanten-Absorptionsspektroskopie an ausgewaehlten biologischen Systemen

    Energy Technology Data Exchange (ETDEWEB)

    Lichtenberg, Henning

    2008-07-15

    Sulfur is an essential element in organisms. In this thesis investigations of sulfur compounds in selected biological systems by XANES (X-ray Absorption Near Edge Structure) spectroscopy are reported. XANES spectroscopy at the sulfur K-edge provides an excellent tool to gain information about the local environments of sulfur atoms in intact biological samples - no extraction processes are required. Spatially resolved measurements using a Kirkpatrick-Baez mirror focusing system were carried out to investigate the infection of wheat leaves by rust fungi. The results give information about changes in the sulfur metabolism of the host induced by the parasite and about the extension of the infection into visibly uninfected plant tissue. Furthermore, XANES spectra of microbial mats from sulfidic caves were measured. These mats are dominated by microbial groups involved in cycling sulfur. Additionally, the influence of sulfate deprivation and H{sub 2}S exposure on sulfur compounds in onion was investigated. To gain an insight into the thermal degradation of organic material the influence of roasting of sulfur compounds in coffee beans was studied. (orig.)

  18. X-Ray Absorption in Carbon Ions Near the K-Edge

    Science.gov (United States)

    Hasoglu, M. F.; Abdel-Naby, Sh. A.; Nikolic, D.; Gorczyca, T. W.; McLaughlin, B. M.

    2007-06-01

    K-shell photoabsorption calculations are important for determining the elemental abundances of the interstellar medium (ISM) from observed X-ray absorption spectra. Previously, we performed reliable K-shell photoabsorption calculations for oxygen [1-3] and neon [4,5] ions. We have executed detailed R-matrix calculations for carbon ions, including Auger broadening, by using an optical potential, and relaxation effects, by using pseudoorbitals with the necessary pseudoresonance elimination. This work was funded by NASA's Astronomy Physics Research and Analysis (APRA) and Solar and Heliospheric Physics (SHP) Supporting Research and Technology (SR&T) programs. References: [1] T. W. Gorczyca and B. M. McLaughlin. J Phys. B. 33 L859 (2000) [2] A. M. Juett, et al., Astrophys. J. 612, 308 (2004) [3] J. Garcia et al., Astrophys. J. Supp. S. 158, 68 (2005) [4] T. W. Gorczyca., Phys. Rev. A. 61, 024702 (2000) [5] A. M. Juett, et al., Astrophys. J. 648, 1066 (2006)

  19. Calculation of near-edge x-ray-absorption fine structure at finite temperatures: Spectral signatures of hydrogen bond breaking in liquid water

    International Nuclear Information System (INIS)

    Hetenyi, Balazs; De Angelis, Filippo; Giannozzi, Paolo; Car, Roberto

    2004-01-01

    We calculate the near-edge x-ray-absorption fine structure of H 2 O in the gas, hexagonal ice, and liquid phases using heuristic density-functional based methods. We present a detailed comparison of our results with experiment. The differences between the ice and water spectra can be rationalized in terms of the breaking of hydrogen bonds around the absorbing molecule. In particular the increase in the pre-edge absorption feature from ice to water is shown to be due to the breaking of a donor hydrogen bond. We also find that in water approximately 19% of hydrogen bonds are broken

  20. 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.

  1. Lattice positions of Sn in Cu2ZnSnS4 nanoparticles and thin films studied by synchrotron X-ray absorption near edge structure analysis

    Science.gov (United States)

    Zillner, E.; Paul, A.; Jutimoosik, J.; Chandarak, S.; Monnor, T.; Rujirawat, S.; Yimnirun, R.; Lin, X. Z.; Ennaoui, A.; Dittrich, Th.; Lux-Steiner, M.

    2013-06-01

    Lattice positions of Sn in kesterite Cu2ZnSnS4 and Cu2SnS3 nanoparticles and thin films were investigated by XANES (x-ray absorption near edge structure) analysis at the S K-edge. XANES spectra were analyzed by comparison with simulations taking into account anti-site defects and vacancies. Annealing of Cu2ZnSnS4 nanoparticle thin films led to a decrease of Sn at its native and defect sites. The results show that XANES analysis at the S K-edge is a sensitive tool for the investigation of defect sites, being critical in kesterite thin film solar cells.

  2. In Situ Solid-State Reactions Monitored by X-ray Absorption Spectroscopy: Temperature-Induced Proton Transfer Leads to Chemical Shifts.

    Science.gov (United States)

    Stevens, Joanna S; Walczak, Monika; Jaye, Cherno; Fischer, Daniel A

    2016-10-24

    The dramatic colour and phase alteration with the solid-state, temperature-dependent reaction between squaric acid and 4,4'-bipyridine has been probed in situ with X-ray absorption spectroscopy. The electronic and chemical sensitivity to the local atomic environment through chemical shifts in the near-edge X-ray absorption fine structure (NEXAFS) revealed proton transfer from the acid to the bipyridine base through the change in nitrogen protonation state in the high-temperature form. Direct detection of proton transfer coupled with structural analysis elucidates the nature of the solid-state process, with intermolecular proton transfer occurring along an acid-base chain followed by a domino effect to the subsequent acid-base chains, leading to the rapid migration along the length of the crystal. NEXAFS thereby conveys the ability to monitor the nature of solid-state chemical reactions in situ, without the need for a priori information or long-range order. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Debris of potassium–magnesium silicate glass generated by femtosecond laser-induced ablation in air: An analysis by near edge X-ray absorption spectroscopy, micro Raman and energy dispersive X-ray spectroscopy

    International Nuclear Information System (INIS)

    Grehn, M.; Seuthe, T.; Reinhardt, F.; Höfner, M.; Griga, N.; Eberstein, M.; Bonse, J.

    2014-01-01

    The redeposited material (debris) resulting from ablation of a potassium–magnesium silicate glass upon scanning femtosecond laser pulse irradiation (130 fs, 800 nm) in air environment is investigated by means of three complementary surface analytical methods. Changes in the electronic band structure of the glass constituent Magnesium (Mg) were identified by X-ray Absorption Near Edge Structure spectroscopy (XANES) using synchrotron radiation. An up-shift of ≈0.8 eV of a specific Magnesium K-edge absorption peak in the spectrum of the redeposited material along with a significant change in its leading edge position was detected. In contrast, the surface left after laser ablation exhibits a downshift of the peak position by ≈0.9 eV. Both observations may be related to a change of the Mg coordinative state of the laser modified/redeposited glass material. The presence of carbon in the debris is revealed by micro Raman spectroscopy (μ-RS) and was confirmed by energy dispersive X-ray spectroscopy (EDX). These observations are attributed to structural changes and chemical reactions taking place during the ablation process.

  4. Islanding and strain-induced shifts in the infrared absorption peaks of cubic boron nitride thin films

    International Nuclear Information System (INIS)

    Fahy, S.; Taylor, C.A. II and; Clarke, R.

    1997-01-01

    Experimental and theoretical investigations of the infrared-active, polarization-dependent phonon frequencies of cubic boron nitride films have been performed in light of recent claims that large frequency shifts during initial nucleation are the result of strain caused by highly nonequilibrium growth conditions. We show that the formation of small, separate grains of cubic boron nitride during the initial growth leads to a frequency shift in the infrared-active transverse-optic mode, polarized normal to the substrate, which is opposite in sign and twice the magnitude of the shift for modes polarized parallel to the substrate. In contrast, film strain causes a frequency shift in the mode polarized normal to the substrate, which is much smaller in magnitude than the frequency shift for modes polarized parallel to the substrate. Normal and off-normal incidence absorption measurements, performed at different stages of nucleation and growth, show that large frequency shifts in the transverse-optic-phonon modes during the initial stage of growth are not compatible with the expected effects of strain, but are in large part due to nucleation of small isolated cubic BN grains which coalesce to form a uniform layer. Numerical results from a simple model of island nucleation and growth are in good agreement with experimental results. copyright 1997 The American Physical Society

  5. Electrosynthesis of ZnO nanorods and nanotowers: Morphology and X-ray Absorption Near Edge Spectroscopy studies

    Science.gov (United States)

    Sigircik, Gokmen; Erken, Ozge; Tuken, Tunc; Gumus, Cebrail; Ozkendir, Osman M.; Ufuktepe, Yuksel

    2015-06-01

    Deposition mechanism of nano-structured ZnO films has been investigated in the absence and presence of chloride ions from aqueous solution. The resulting opto-electronic properties were interpreted extensively, using X-ray diffraction (XRD), X-ray Absorption Near Edge Spectroscopy (XANES), field emission scanning electron microscopy (FE-SEM), UV-Visible spectroscopy and four probe techniques. The ZnO deposition is mass transport controlled process and the interaction of chloride ions with the surface has great influence on diffusion kinetics, considering the substantial species (Zn2+ and OH-) involved in the construction of ZnO film. This effect does not change major lattice parameters, as shown with detailed analysis of XRD data. However, the texture coefficient (Tc) (0 0 2) value is higher in presence of chloride ions containing synthesis solution which gave vertically aligned, well defined and uniformly dispersed nanorods structure. The calculated Eg values are in the range 3.28-3.41 eV and 3.22-3.31 eV for ZnO nanorods and nanotowers synthesized at different deposition periods, respectively. Furthermore, the charge mobility values regarding the deposition periods were measured to be in the ranges from 130.4 to 449.2 cm2 V-1 s-1 and 126.2 to 204.7 cm2 V-1 s-1 for nanorods and nanotowers, respectively. From XANES results, it was shown that the Zn K-edge spectrum is dominated by the transition of Zn 1s core electrons into the unoccupied Zn 4p states of the conduction band. Comparing the rod and tower nano-structured ZnO thin films, the excitation behavior of valence band electrons is different. Moreover, the density states of Zn 4p are higher for ZnO nanorods.

  6. Anomalous x-ray attenuation coefficients around the absorption edges using Mn Ksub(α) and Cu Ksub(α) x-rays

    International Nuclear Information System (INIS)

    Kerur, B.R.; Thontadarya, S.R.; Hanumaiah, B.

    1994-01-01

    The x-ray attenuation coefficients for three elements and for eight compounds are determined, adopting the method developed by employing a proportional counter, with a view to study the effect of fine structure on the mass attenuation coefficient values using Mn K α and Cu K α x-rays derived from K x-ray emitters, 55 Fe and 65 Zn radioactive sources, by a differential absorption technique. It is experimentally established that a small difference in energy between K α1 and K α2 (11 eV in the case of Mn K α and 24 eV in the case of the Cu K α x-ray) is inconsequential by comparing the measured and theoretical values of μ/ρ for standard elements, aluminium, copper and tantalum. The effect of fine structure on μ/ρ values is studied using the compounds containing one element with its absorption edge close to the incident photon energy. Results obtained in the present investigation show the nonvalidity of the mixture rule above the edge and also below the edge, ranging from about 600 eV below the edge to about 1500 eV about the edge. The contribution of resonance Raman scattering to the attenuation coefficient and indications to the presence of pre-edge structure similar to EXAFS are discussed. (author)

  7. [Chlorine speciation and concentration in cultivated soil in the northeastern China studied by X-ray absorption near edge structure].

    Science.gov (United States)

    Li, Jing; Lang, Chun-Yan; Ma, Ling-Ling; Xu, Dian-Dou; Zheng, Lei; Lu, Yu-Nanz; Cui Li-Rui; Zhang, Xiao-Meng

    2014-10-01

    A procedure has been proposed to determine chlorine speciation and concentration in soil with X-ray absorption near edge structure (XANES), and this method was applied to study the cultivated soil (bog, dark brown and black cultivated soil) in the Northeastern China. Qualitative analysis was carried out by least-squares fitting of sample spectra with standard spectra of three model compounds (NaCl, 3-chloropropionic acid, chlorophenol red). Linear correlation between the absolute fluorescence intensity of a series of NaCl standards and the Cl concentration was used as quantification standard for measuring the total Cl concentration in samples. The detection limits,relative standard deviation (RSD), recoveries were 2 mg · kg(-1), 0%-5% and 77%-133%, respectively. The average concentration of total Cl was 19 mg · kg(-1). The average relative content was as high as 61% of organochlorine with the concentration of 1-2 times as high as the concentration of inorganic chloride. The distribution trend of the total Cl, inorganic chloride and organic chlorine in different types of soil was: bog arable soil > dark brown soil > black soil. In conclusion, XANES is a reliable method to nondestructively characterize the speciation and concentration of chlorine in soil, which would provide some basic data for the future study of the chlorine's biogeochemical transformations.

  8. Analysis of sulfidic linkages formed in natural rubber latex medical gloves by using X-ray absorption near edge structure

    Science.gov (United States)

    Chankrachang, M.; Limphirat, W.; Yongyingsakthavorn, P.; Nontakaew, U.; Tohsan, A.

    2017-09-01

    A study of sulfidic linkages formed in natural rubber (NR) latex medical gloves by using X-ray Absorption Near Edge Structure (XANES) is presented in this paper. The NR latex compound was prepared by using prevulcanization method, that is, it was prevulcanized at room temperature for 24 hrs before utilization. After the 24 hrs of prevulcanization, the latex film samples were obtained by dipping process. The dipped films were subjected to vulcanize at 110°C for 5 to 25 min. It was observed that after the compound was prevulcanized for 24 hrs, polysulfidic linkages were mainly formed in the sample. It was however found that after curing at 110°C for 5-25 min, the polysulfidic linkages are tended to change into disulfide linkages. Especially, in the case of 25 minutes cured sample, disulfide linkages are found to be the main linkages. In term of tensile strength, it was observed that when cure time increased from 5 - 10 min, tensile strengths were also increased. But when the cure time of the film is 25 minutes, tensile strength was slightly dropped. The dropped of tensile strength when cure time is longer than 10 minutes can be ascribed to a degradation of polysulfidic and disulfidic linkages during curing. Therefore, by using XANES analysis, it was found to be very useful to understand the cure characteristic, thus it can be very helpful to optimize cure time and tensile properties of the product.

  9. 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.

  10. Refractive index of ternary and quaternary compound semiconductors below the fundamental absorption edge: Linear and nonlinear effects

    International Nuclear Information System (INIS)

    Jensen, B.; Torabi, A.

    1985-01-01

    The index of refraction n is calculated as a function of frequency and mole fraction x for the following compounds: Hg/sub l-x/Cd/sub x/Te, Al/sub x/Ga/sub l-x/As, and In/sub l-x/Ga/sub x/As/sub y/P/sub l-y/ lattice matched to InP. Lattice matching of In/sub l-x/Ga/sub x/As/sub y/P/sub l-y/ to InP requires that x = 0.466 y. The theoretical result for the refractive index is obtained from a quantum mechanical calculation of the dielectric constant of a compound semiconductor. It is given in terms of the basic material parameters of band gap energy, effective electron mass m/sub n/, effective heavy hole mass m/sub rho/, spin orbit splitting energy, lattice constant, and carrier concentration n/sub e/ or rho for n-type or rho-type materials, respectively. If these quantities are known as functions of mole fraction x, there are no adjustable parameters involved. A negative change in the refractive index near the fundamental absorption edge is predicted on passing radiation through a crystal if the change in carrier concentration of the initially unoccupied conduction band is assumed proportional to internal intensity I. Comparison of theory with experimental data is given

  11. Temperature dependent evolution of the local electronic structure of atmospheric plasma treated carbon nanotubes: Near edge x-ray absorption fine structure study

    International Nuclear Information System (INIS)

    Roy, S. S.; Papakonstantinou, P.; Okpalugo, T. I. T.; Murphy, H.

    2006-01-01

    Near edge x-ray absorption fine structure (NEXAFS) spectroscopy has been employed to obtain the temperature dependent evolution of the electronic structure of acid treated carbon nanotubes, which were further modified by dielectric barrier discharge plasma processing in an ammonia atmosphere. The NEXAFS studies were performed from room temperature up to 900 deg. C. The presence of oxygen and nitrogen containing functional groups was observed in C K edge, N K edge, and O K edge NEXAFS spectra of the multiwalled carbon nanotubes. The N K edge spectra revealed three types of π* features, the source of which was decisively identified by their temperature dependent evolution. It was established that these features are attributed to pyridinelike, NO, and graphitelike structures, respectively. The O K edge indicated that both carbonyl (C=O), π*(CO), and ether C-O-C, σ*(CO), functionalities were present. Upon heating in a vacuum to 900 deg. C the π*(CO) resonances disappeared while the σ*(CO) resonances were still present confirming their higher thermal stability. Heating did not produce a significant change in the π* feature of the C K edge spectrum indicating that the tabular structure of the nanotubes is essentially preserved following the thermal decomposition of the functional groups on the nanotube surface

  12. X-ray absorption near-edge structure of GaN with high Mn concentration grown on SiC

    Science.gov (United States)

    Sancho-Juan, O.; Cantarero, A.; Garro, N.; Cros, A.; Martínez-Criado, G.; Salomé, M.; Susini, J.; Olguín, D.; Dhar, S.

    2009-07-01

    By means of x-ray absorption near-edge structure (XANES) several Ga1-xMnxN (0.03edges. All samples studied present a similar Mn ionization state, very close to 2+, and tetrahedral coordination. In order to interpret the near-edge structure, we have performed ab initio calculations using the full potential linear augmented plane wave method as implemented in the Wien2k code. The calculations show the appearance of a Mn bonding \\mathrm {t_{2}}\\uparrow band localized in the gap region, and the corresponding anti-bonding state \\mathrm {t_{2}}\\downarrow , which seem to be responsible for the double structure which appears at the pre-edge absorption region. The shoulders and main absorption peak of the XANES spectra are attributed to transitions from the Mn(1s) band to the conduction bands, which are partially dipole allowed because of the Mn(4p) contribution to these bands.

  13. X-ray absorption near-edge structure of GaN with high Mn concentration grown on SiC

    Energy Technology Data Exchange (ETDEWEB)

    Sancho-Juan, O; Cantarero, A; Garro, N; Cros, A [Materials Science Institute, University of Valencia, PO Box 22085, E46071 Valencia (Spain); Martinez-Criado, G; Salome, M; Susini, J [European Synchrotron Radiation Facility, 6 rue Jules Horowitz, 38043 Grenoble (France); Olguin, D [Dept. de Fisica, CINVESTAV-IPN, 07300 Mexico D F (Mexico); Dhar, S [Experimentalphysik, Universitaet Duisburg-Essen, Lotharstrasse 1, 47057 Duisburg (Germany)

    2009-07-22

    By means of x-ray absorption near-edge structure (XANES) several Ga{sub 1-x}Mn{sub x}N (0.03edges. All samples studied present a similar Mn ionization state, very close to 2+, and tetrahedral coordination. In order to interpret the near-edge structure, we have performed ab initio calculations using the full potential linear augmented plane wave method as implemented in the Wien2k code. The calculations show the appearance of a Mn bonding t{sub 2}arrow up band localized in the gap region, and the corresponding anti-bonding state t{sub 2}arrow down, which seem to be responsible for the double structure which appears at the pre-edge absorption region. The shoulders and main absorption peak of the XANES spectra are attributed to transitions from the Mn(1s) band to the conduction bands, which are partially dipole allowed because of the Mn(4p) contribution to these bands.

  14. Room temperature ferromagnetism and absorption red-shift in nitrogen-doped TiO2 nanoparticles

    International Nuclear Information System (INIS)

    Gómez-Polo, C.; Larumbe, S.; Monge, M.

    2014-01-01

    Highlights: • N-doped TiO 2 anatase nanoparticles were obtained by sol–gel. • The nanoparticle size, controlled by the N doping, determines lattice parameters. • Correlation between room temperature ferromagnetism and absorption red-shift. • Oxygen vacancies reinforce both phenomena. • Metal transition impurities contribute to the room temperature ferromagnetism. - Abstract: In this work, room-temperature ferromagnetism and the red-shift of the optical absorption is analyzed in nitrogen doped TiO 2 semiconductor nanoparticles. The nanoparticles were synthesized by the sol–gel method using urea as the nitrogen source. Titanium Tetraisopropoxide (TTIP) was employed as the alkoxyde precursor and dissolved in ethanol. The as prepared gels were dried and calcined in air at 300 °C. Additionally, post-annealing treatments under vacuum atmosphere were performed to modify the oxygen stoichiometry of the samples. The anatase lattice parameters, analyzed by means of powder X-ray diffractometry, depend on the nanometer grain size of the nanoparticles (increase and decrease, respectively, of the tetragonal a and c lattice parameters with respect to the bulk values). The diffuse reflectance ultraviolet–visible (UV–Vis) absorbance spectra show a clear red-shift as consequence of the nitrogen and the occurrence of intragap energy levels. The samples display ferromagnetic features at room temperature that are reinforced with the nitrogen content and after the post annealings in vacuum. The results indicate a clear correlation between the room temperature ferromagnetism and the shift of the absorbance spectrum. In both phenomena, oxygen vacancies (either induced by the nitrogen doping or by the post vacuum annealings) play a dominant role. However, we conclude the existence of very low concentration of diluted transition metal impurities that determine the room ferromagnetic response (bound magnetic polaron BMP model). The contraction of the c soft axis of the

  15. Room temperature ferromagnetism and absorption red-shift in nitrogen-doped TiO{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Gómez-Polo, C., E-mail: gpolo@unavarra.es [Departamento de Física, Universidad Pública de Navarra, Campus de Arrosadia, 31006 Pamplona (Spain); Larumbe, S. [Departamento de Física, Universidad Pública de Navarra, Campus de Arrosadia, 31006 Pamplona (Spain); Monge, M. [Departamento de Química, Universidad de la Rioja, Centro de Investigación en Síntesis Química (CISQ), Complejo Científico Tecnológico, 26006 Logroño (Spain)

    2014-11-05

    Highlights: • N-doped TiO{sub 2} anatase nanoparticles were obtained by sol–gel. • The nanoparticle size, controlled by the N doping, determines lattice parameters. • Correlation between room temperature ferromagnetism and absorption red-shift. • Oxygen vacancies reinforce both phenomena. • Metal transition impurities contribute to the room temperature ferromagnetism. - Abstract: In this work, room-temperature ferromagnetism and the red-shift of the optical absorption is analyzed in nitrogen doped TiO{sub 2} semiconductor nanoparticles. The nanoparticles were synthesized by the sol–gel method using urea as the nitrogen source. Titanium Tetraisopropoxide (TTIP) was employed as the alkoxyde precursor and dissolved in ethanol. The as prepared gels were dried and calcined in air at 300 °C. Additionally, post-annealing treatments under vacuum atmosphere were performed to modify the oxygen stoichiometry of the samples. The anatase lattice parameters, analyzed by means of powder X-ray diffractometry, depend on the nanometer grain size of the nanoparticles (increase and decrease, respectively, of the tetragonal a and c lattice parameters with respect to the bulk values). The diffuse reflectance ultraviolet–visible (UV–Vis) absorbance spectra show a clear red-shift as consequence of the nitrogen and the occurrence of intragap energy levels. The samples display ferromagnetic features at room temperature that are reinforced with the nitrogen content and after the post annealings in vacuum. The results indicate a clear correlation between the room temperature ferromagnetism and the shift of the absorbance spectrum. In both phenomena, oxygen vacancies (either induced by the nitrogen doping or by the post vacuum annealings) play a dominant role. However, we conclude the existence of very low concentration of diluted transition metal impurities that determine the room ferromagnetic response (bound magnetic polaron BMP model). The contraction of the c soft axis

  16. Electrosynthesis of ZnO nanorods and nanotowers: Morphology and X-ray Absorption Near Edge Spectroscopy studies

    Energy Technology Data Exchange (ETDEWEB)

    Sigircik, Gokmen, E-mail: gsigircik@cu.edu.tr [Chemistry Department, University of Cukurova, 01330 Adana (Turkey); Erken, Ozge [Department of Physics, Faculty Science and Letters, Adiyaman University, 02040 Adiyaman (Turkey); Tuken, Tunc [Chemistry Department, University of Cukurova, 01330 Adana (Turkey); Gumus, Cebrail [Physics Department, University of Cukurova, 01330 Adana (Turkey); Ozkendir, Osman M. [Department of Energy Systems Engineering Tarsus Technology Faculty, Mersin University, 33400 Tarsus (Turkey); Ufuktepe, Yuksel [Physics Department, University of Cukurova, 01330 Adana (Turkey)

    2015-06-15

    Highlights: • Deposition mechanism of nano-structured ZnO films has been investigated in the absence and presence of chloride ions from aqueous solution. • Uniform and well-defined ZnO nano-towers and rods have been obtained via electrochemical deposition. • The presence of chloride ions altered the nucleation rate of ZnO particles on ITO substrates and resulting crystallographic properties. • Comparing the rod and tower nano-structured ZnO thin films, the excitation behavior of valance band electrons is different. - Abstract: Deposition mechanism of nano-structured ZnO films has been investigated in the absence and presence of chloride ions from aqueous solution. The resulting opto-electronic properties were interpreted extensively, using X-ray diffraction (XRD), X-ray Absorption Near Edge Spectroscopy (XANES), field emission scanning electron microscopy (FE-SEM), UV-Visible spectroscopy and four probe techniques. The ZnO deposition is mass transport controlled process and the interaction of chloride ions with the surface has great influence on diffusion kinetics, considering the substantial species (Zn{sup 2+} and OH{sup −}) involved in the construction of ZnO film. This effect does not change major lattice parameters, as shown with detailed analysis of XRD data. However, the texture coefficient (T{sub c}) (0 0 2) value is higher in presence of chloride ions containing synthesis solution which gave vertically aligned, well defined and uniformly dispersed nanorods structure. The calculated E{sub g} values are in the range 3.28–3.41 eV and 3.22–3.31 eV for ZnO nanorods and nanotowers synthesized at different deposition periods, respectively. Furthermore, the charge mobility values regarding the deposition periods were measured to be in the ranges from 130.4 to 449.2 cm{sup 2} V{sup −1} s{sup −1} and 126.2 to 204.7 cm{sup 2} V{sup −1} s{sup −1} for nanorods and nanotowers, respectively. From XANES results, it was shown that the Zn K-edge

  17. Electrosynthesis of ZnO nanorods and nanotowers: Morphology and X-ray Absorption Near Edge Spectroscopy studies

    International Nuclear Information System (INIS)

    Sigircik, Gokmen; Erken, Ozge; Tuken, Tunc; Gumus, Cebrail; Ozkendir, Osman M.; Ufuktepe, Yuksel

    2015-01-01

    Highlights: • Deposition mechanism of nano-structured ZnO films has been investigated in the absence and presence of chloride ions from aqueous solution. • Uniform and well-defined ZnO nano-towers and rods have been obtained via electrochemical deposition. • The presence of chloride ions altered the nucleation rate of ZnO particles on ITO substrates and resulting crystallographic properties. • Comparing the rod and tower nano-structured ZnO thin films, the excitation behavior of valance band electrons is different. - Abstract: Deposition mechanism of nano-structured ZnO films has been investigated in the absence and presence of chloride ions from aqueous solution. The resulting opto-electronic properties were interpreted extensively, using X-ray diffraction (XRD), X-ray Absorption Near Edge Spectroscopy (XANES), field emission scanning electron microscopy (FE-SEM), UV-Visible spectroscopy and four probe techniques. The ZnO deposition is mass transport controlled process and the interaction of chloride ions with the surface has great influence on diffusion kinetics, considering the substantial species (Zn 2+ and OH − ) involved in the construction of ZnO film. This effect does not change major lattice parameters, as shown with detailed analysis of XRD data. However, the texture coefficient (T c ) (0 0 2) value is higher in presence of chloride ions containing synthesis solution which gave vertically aligned, well defined and uniformly dispersed nanorods structure. The calculated E g values are in the range 3.28–3.41 eV and 3.22–3.31 eV for ZnO nanorods and nanotowers synthesized at different deposition periods, respectively. Furthermore, the charge mobility values regarding the deposition periods were measured to be in the ranges from 130.4 to 449.2 cm 2 V −1 s −1 and 126.2 to 204.7 cm 2 V −1 s −1 for nanorods and nanotowers, respectively. From XANES results, it was shown that the Zn K-edge spectrum is dominated by the transition of Zn 1s core

  18. Structural Disorder in Colloidal InAs and CdSe Nanocrystals Observed by X-Ray Absorption Near-Edge Spectroscopy

    International Nuclear Information System (INIS)

    Hamad, K.S.; Hamad, K.S.; Roth, R.; Roth, R.; Rockenberger, J.; Rockenberger, J.; Alivisatos, A.P.; Alivisatos, A.P.; Buuren, T. van

    1999-01-01

    We report the observation of size dependent structural disorder by x-ray absorption near-edge spectroscopy (XANES) in InAs and CdSe nanocrystals 17 - 80 Angstrom in diameter. XANES of the In and Cd M 4,5 edges yields features that are sharp for the bulk solid but broaden considerably as the size of the particle decreases. FEFF7 multiple-scattering simulations reproduce the size dependent broadening of the spectra if a bulklike surface reconstruction of a spherical nanocrystal model is included. This illustrates that XANES is sensitive to the structure of the entire nanocrystal including the surface. copyright 1999 The American Physical Society

  19. Influence of Reduced Graphene Oxide on Effective Absorption Bandwidth Shift of Hybrid Absorbers.

    Science.gov (United States)

    Ameer, Shahid; Gul, Iftikhar Hussain

    2016-01-01

    The magnetic nanoparticle composite NiFe2O4 has traditionally been studied for high-frequency microwave absorption with marginal performance towards low-frequency radar bands (particularly L and S bands). Here, NiFe2O4 nanoparticles and nanohybrids using large-diameter graphene oxide (GO) sheets are prepared via solvothermal synthesis for low-frequency wide bandwidth shielding (L and S radar bands). The synthesized materials were characterized using XRD, SEM, FTIR and microwave magneto dielectric spectroscopy. The dimension of these solvothermally synthesized pristine particles and hybrids lies within 30-58 nm. Microwave magneto-dielectric spectroscopy was performed in the low-frequency region in the 1 MHz-3 GHz spectrum. The as-synthesized pristine nanoparticles and hybrids were found to be highly absorbing for microwaves throughout the L and S radar bands (graphene sheet coupling shows application of these materials with absorption bandwidth which is tailored such that these could be used for low frequency. Previously, these were used for high frequency absorptions (typically > 4 GHz) with limited selective bandwidth.

  20. Fundamental absorption edge in CuIn5Se8 and CuGa3Se5 single crystals

    International Nuclear Information System (INIS)

    Leon, M.; Merino, J.M.; Levcenko, S.; Nateprov, A.; Tezlevan, V.; Arushanov, E.; Syrbu, N.N.

    2006-01-01

    Optical absorption spectra of CuIn 5 Se 8 and CuGa 3 Se 5 single crystals have been investigated. The energy gap E g for CuIn 5 Se 8 (CuGa 3 Se 5 ) was found to be varied from 1.27(1.79) to 1.21(1.71) eV in the temperature range between 10 and 300 K. The temperature dependence of E g was studied by means of the Einstein model and the Paessler model. The Einstein temperature {222(267)K}, the Debye temperature {310(380)K}, a dimensionless constant related to the electron-phonon coupling {1.62(2.65)} as well as an effective energy {20 (24) meV} and a cut-off phonon energy {35(39) meV} have been estimated for CuIn 5 Se 8 (CuGa 3 Se 5 ). It was also found that the major contribution of phonons to the shift of E g versus temperature in CuIn 5 Se 8 (CuGa 3 Se 5 ) is mainly from optical phonons. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  1. Resonant photoelectron spectroscopy at the Mo 4p→4d absorption edge in MoS2

    International Nuclear Information System (INIS)

    Lince, J.R.; Didziulis, S.V.; Yarmoff, J.A.

    1991-01-01

    A systematic study has been conducted of the resonant behavior of the valence-band photoelectron spectrum of MoS 2 for hν=26--70 eV, spanning the Mo 4p→4d transition region. A broad Fano-like resonance appears at ∼42 eV in the constant-initial-state (CIS) intensity plot of the d z 2 peak near the valence-band maximum [∼2 eV binding energy (BE)], confirming its predominantly Mo 4d character. A second shoulder on the higher-hν side of the maximum in the d z 2 CIS intensity plot is suggested to result from transitions to unoccupied states in the 5sp band ∼10 eV above E F , by comparison with a partial-yield spectrum and previous inverse-photoemission data. The region of the valence band in the range 3--4.5-eV BE also exhibits resonant behavior, indicating Mo 4d character, although somewhat less than for the d z 2 peak. The 5--7-eV BE range does not exhibit resonance behavior at the Mo 4p edge and, therefore, contains negligible Mo 4d character. A feature at ∼30 eV in the CIS intensity plot for the 5--7-eV BE range could not be definitively assigned in this study, but may be due to a resonance between direct photoemission and a process involving absorption and autoionization of electronic states that contain Mo 5s and 5p character

  2. Simulation of Near-Edge X-ray Absorption Fine Structure with Time-Dependent Equation-of-Motion Coupled-Cluster Theory.

    Science.gov (United States)

    Nascimento, Daniel R; DePrince, A Eugene

    2017-07-06

    An explicitly time-dependent (TD) approach to equation-of-motion (EOM) coupled-cluster theory with single and double excitations (CCSD) is implemented for simulating near-edge X-ray absorption fine structure in molecular systems. The TD-EOM-CCSD absorption line shape function is given by the Fourier transform of the CCSD dipole autocorrelation function. We represent this transform by its Padé approximant, which provides converged spectra in much shorter simulation times than are required by the Fourier form. The result is a powerful framework for the blackbox simulation of broadband absorption spectra. K-edge X-ray absorption spectra for carbon, nitrogen, and oxygen in several small molecules are obtained from the real part of the absorption line shape function and are compared with experiment. The computed and experimentally obtained spectra are in good agreement; the mean unsigned error in the predicted peak positions is only 1.2 eV. We also explore the spectral signatures of protonation in these molecules.

  3. Simulating Ru L3-edge X-ray absorption spectroscopy with time-dependent density functional theory: model complexes and electron localization in mixed-valence metal dimers.

    Science.gov (United States)

    Van Kuiken, Benjamin E; Valiev, Marat; Daifuku, Stephanie L; Bannan, Caitlin; Strader, Matthew L; Cho, Hana; Huse, Nils; Schoenlein, Robert W; Govind, Niranjan; Khalil, Munira

    2013-05-30

    Ruthenium L3-edge X-ray absorption (XA) spectroscopy probes unoccupied 4d orbitals of the metal atom and is increasingly being used to investigate the local electronic structure in ground and excited electronic states of Ru complexes. The simultaneous development of computational tools for simulating Ru L3-edge spectra is crucial for interpreting the spectral features at a molecular level. This study demonstrates that time-dependent density functional theory (TDDFT) is a viable and predictive tool for simulating ruthenium L3-edge XA spectroscopy. We systematically investigate the effects of exchange correlation functional and implicit and explicit solvent interactions on a series of Ru(II) and Ru(III) complexes in their ground and electronic excited states. The TDDFT simulations reproduce all of the experimentally observed features in Ru L3-edge XA spectra within the experimental resolution (0.4 eV). Our simulations identify ligand-specific charge transfer features in complicated Ru L3-edge spectra of [Ru(CN)6](4-) and Ru(II) polypyridyl complexes illustrating the advantage of using TDDFT in complex systems. We conclude that the B3LYP functional most accurately predicts the transition energies of charge transfer features in these systems. We use our TDDFT approach to simulate experimental Ru L3-edge XA spectra of transition metal mixed-valence dimers of the form [(NC)5M(II)-CN-Ru(III)(NH3)5](-) (where M = Fe or Ru) dissolved in water. Our study determines the spectral signatures of electron delocalization in Ru L3-edge XA spectra. We find that the inclusion of explicit solvent molecules is necessary for reproducing the spectral features and the experimentally determined valencies in these mixed-valence complexes. This study validates the use of TDDFT for simulating Ru 2p excitations using popular quantum chemistry codes and providing a powerful interpretive tool for equilibrium and ultrafast Ru L3-edge XA spectroscopy.

  4. Influence of Reduced Graphene Oxide on Effective Absorption Bandwidth Shift of Hybrid Absorbers.

    Directory of Open Access Journals (Sweden)

    Shahid Ameer

    Full Text Available The magnetic nanoparticle composite NiFe2O4 has traditionally been studied for high-frequency microwave absorption with marginal performance towards low-frequency radar bands (particularly L and S bands. Here, NiFe2O4 nanoparticles and nanohybrids using large-diameter graphene oxide (GO sheets are prepared via solvothermal synthesis for low-frequency wide bandwidth shielding (L and S radar bands. The synthesized materials were characterized using XRD, SEM, FTIR and microwave magneto dielectric spectroscopy. The dimension of these solvothermally synthesized pristine particles and hybrids lies within 30-58 nm. Microwave magneto-dielectric spectroscopy was performed in the low-frequency region in the 1 MHz-3 GHz spectrum. The as-synthesized pristine nanoparticles and hybrids were found to be highly absorbing for microwaves throughout the L and S radar bands ( 4 GHz with limited selective bandwidth.

  5. Near-edge X-ray absorption fine structure studies of Cr{sub 1−x}M{sub x}N coatings

    Energy Technology Data Exchange (ETDEWEB)

    Mahbubur Rahman, M. [School of Engineering and Information Technology, Murdoch University, Murdoch, WA 6150 (Australia); Department of Physics, Jahangirnagar University, Savar, Dhaka 1342 (Bangladesh); Duan, Alex [School of Chemistry, The University of Melbourne, Parkville, VIC 3010 (Australia); Jiang, Zhong-Tao, E-mail: Z.Jiang@murdoch.edu.au [School of Engineering and Information Technology, Murdoch University, Murdoch, WA 6150 (Australia); Xie, Zonghan [School of Mechanical Engineering, University of Adelaide, SA 5005 (Australia); School of Engineering, Edith Cowan University, WA 6027 (Australia); Wu, Alex [School of Chemistry, The University of Melbourne, Parkville, VIC 3010 (Australia); Amri, Amun [Department of Chemical Engineering, Riau University, Pekanbaru (Indonesia); Cowie, Bruce [Australian Synchrotron, 800 Blackburn Rd., Clayton, VIC 3168 (Australia); Yin, Chun-Yang [Chemical and Analytical Sciences, Murdoch University, Murdoch, WA 6150 (Australia)

    2013-11-25

    Highlights: •Al or Si is doped on CrN and AlN coatings using magnetron sputtering system. •NEXAFS analysis is conducted to measure the Al and Si K-edges, and chromium L-edge. •Structural evolution of CrN matrix with addition of Al or Si element is investigated. -- Abstract: Cr{sub 1−x}M{sub x}N coatings, with doping concentrations (Si or Al) varying from 14.3 to 28.5 at.%, were prepared on AISI M2 tool steel substrates using a TEER UDP 650/4 closed field unbalanced magnetron sputtering system. Near-edge X-ray absorption fine structure (NEXAFS) characterization was carried out to measure the aluminum and silicon K-edges, as well as chromium L-edge, in the coatings. Two soft X-ray techniques, Auger electron yield (AEY) and total fluorescence yield (TFY), were employed to investigate the surface and inner structural properties of the materials in order to understand the structural evolution of CrN matrix with addition of Al (or Si) elements. Investigations on the local bonding states and grain boundaries of the coatings, using NEXAFS technique, provide significant information which facilitates understanding of the local electronic structure of the atoms and shed light on the origins of the high mechanical strength and oxidation resistance of these technologically important coatings.

  6. Cell thickness of UV absorption by the cell: relation to UV action spectrum shift in mammalian cells in culture

    International Nuclear Information System (INIS)

    Sakharov, V.H.; Voronkova, L.N.; Blokhin, A.V.

    1985-01-01

    By means of reconstruction of series half - thin transverse sections the three - dimensional morphometry of SPEV cells for a series of their specific states in culture is performed: for exponential growth in a monolayer, in a merged monolayer, in the mitosis phase, for giant cells and suspension cells. In the monolayer the cell thickness in its central part depended mainly on the nucleus thickness and in average changed but slightly despite a wide range of changes in volumes of nuclei and cells and their density in culture. The cell thickness has noticeably increased in mitosis. For the above states of cells UV radiation absorption spectra are determined. It is shown that a certain shift of action spectrus of death of mammalian cells as compared with that for bacterial cell can be a seguence of selfshielding and not differences in the nature of active chromophores

  7. X-Ray Absorption Near-Edge Structure (XANES) of Calcium L3,2 Edges of Various Calcium Compounds and X-Ray Excited Optical Luminescence (XEOL) Studies of Luminescent Calcium Compounds

    International Nuclear Information System (INIS)

    Ko, J. Y. Peter; Zhou Xingtai; Sham, T.-K.; Heigl, Franziskus; Regier, Tom; Blyth, Robert

    2007-01-01

    X-ray absorption at calcium L3,2 edges of various calcium compounds were measured using a high resolution Spherical Grating Monochromator (SGM) at the Canadian Light Source (CLS). We observe that each compound has its unique fine structure of L3,2 edges. This uniqueness is due to differences in local structure of compounds. We also performed (X-ray Excited Optical Luminescence) XEOL of selected luminescent calcium compounds to investigate their optical properties. XEOL is a photon-in-photon-out technique in which the optical luminescence that is excited by tunable x-rays from a synchrotron light source is monitored. Depending on excitation energy of the x-ray, relative intensities of luminescence peaks vary. Recent findings of the results will be presented here

  8. Shifts in Plant Assemblages Reduce the Richness of Galling Insects Across Edge-Affected Habitats in the Atlantic Forest.

    Science.gov (United States)

    Souza, Danielle G; Santos, Jean C; Oliveira, Marcondes A; Tabarelli, Marcelo

    2016-10-01

    Impacts of habitat loss and fragmentation on specialist herbivores have been rarely addressed. Here we examine the structure of plant and galling insect assemblages in a fragmented landscape of the Atlantic forest to verify a potential impoverishment of these assemblages mediated by edge effects. Saplings and galling insects were recorded once within a 0.1-ha area at habitat level, covering forest interior stands, forest edges, and small fragments. A total of 1,769 saplings from 219 tree species were recorded across all three habitats, with differences in terms of sapling abundance and species richness. Additionally, edge-affected habitats exhibited reduced richness of both host-plant and galling insects at plot and habitat spatial scale. Attack levels also differed among forest types at habitat spatial scale (21.1% of attacked stems in forest interior, 12.4% in small fragments but only 8.5% in forest edges). Plot ordination resulted in three clearly segregated clusters: one formed by forest interior, one by small fragments, and another formed by edge plots. Finally, the indicator species analysis identified seven and one indicator plant species in forest interior and edge-affected habitats, respectively. Consequently, edge effects lead to formation of distinct taxonomic groups and also an impoverished assemblage of plants and galling insects at multiple spatial scales. The results of the present study indicate that fragmentation-related changes in plant assemblages can have a cascade effects on specialist herbivores. Accordingly, hyperfragmented landscapes may not be able to retain an expressive portion of tropical biodiversity. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  9. Order-disorder in olivine minerals by synchrotron X-ray absorption near-edge structure (Xane) spectroscopy at the Mg, Fe and Ca K edges

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Z.; Marcelli, A.; Cibin, G. [Istituto Nazionale di Fisica Nucleare, Frascati, RM (Italy). Laboratori Nazionali di Frascati; Mottana, A. [Istituto Nazionale di Fisica Nucleare, Frascati, RM (Italy). Laboratori Nazionali di Frascati; Rome Univ. Roma Tre, Rome (Italy). Dipt. di Scienze Geologiche; Paris, E.; Giuli, G [INFM, Camerino Univ., Camerino, MC (Italy). Dipt. di Scienze della Terra

    1999-07-01

    In this paper, are presented new, high-resolution experimental spectra at the Mg and Fe K edges for the two Fe-Mg end members F o and F a, and for three other olivines. Two are the Ca end members of the family, namely monticellite (Mtc: CaMgSiO4) and kirschsteinite (Krs: CaFeSiO4). The main purpose of this work is to investigate the effects of Mg, Fe, and Ca partition in the Pbnm (or {alpha}) olivine structure on the electronic properties, as well as the relationships that exist between chemical substitutions and features occurring in Xanes spectra. One wants to explore the relationships that intervene between LRO, as determined by XRD, and SRO, as determined by Xanes, on the endmembers and on a well-known intermediate member as well, and deduce from it a model for the behavior of the entire olivine solid-solution system.

  10. Order-disorder in olivine minerals by synchrotron X-ray absorption near-edge structure (Xane) spectroscopy at the Mg, Fe and Ca K edges

    International Nuclear Information System (INIS)

    Wu, Z.; Marcelli, A.; Cibin, G.; Mottana, A.; Rome Univ. Roma Tre, Rome; Paris, E.; Giuli, G.

    1999-01-01

    In this paper, are presented new, high-resolution experimental spectra at the Mg and Fe K edges for the two Fe-Mg endmembers F o and F a, and for three other olivines. Two are the Ca endmembers of the family, namely monticellite (Mtc: CaMgSiO4) and kirschsteinite (Krs: CaFeSiO4). The main purpose of this work is to investigate the effects of Mg, Fe, and Ca partition in the Pbnm (or α) olivine structure on the electronic properties, as well as the relationships that exist between chemical substitutions and features occurring in Xanes spectra. One wants to explore the relationships that intervene between LRO, as determined by XRD, and SRO, as determined by Xanes, on the endmembers and on a well-known intermediate member as well, and deduce from it a model for the behavior of the entire olivine solid-solution system

  11. The interaction of copper ions with Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli: an X-ray absorption near-edge structure (XANES) spectroscopy study.

    Science.gov (United States)

    Zanzen, Ulrike; Bovenkamp-Langlois, Lisa; Klysubun, Wantana; Hormes, Josef; Prange, Alexander

    2018-04-01

    The antimicrobial properties of copper ions have been known for a long time. However, the exact mechanism of action of the transition metal on microorganisms has long been unclear. X-ray absorption near-edge structure (XANES) spectroscopy at the Cu K edge allows the determination of copper speciation in Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa that have been treated with Cu(II) and Cu(I) solutions. The death/inactivation of the bacteria was observed using plate counting and light microscopy. The Cu K-XANES spectra of the two Gram-negative bacteria are different than those of the Gram-positive strain. The results clearly show that the Cu + -S bond contributes to the antibacterial activity of copper, as in the case of silver. The detailed evaluation of the differentiated absorption spectra shows that Cu + (not Cu 2+ ) is the dominant ion that binds to the bacteria. Because Cu + is not the most common copper ion, copper is not as effective an antibacterial agent as silver, whose common valency is actually + 1. Any reaction of copper with phosphorus from the bacteria can be excluded after the evaluation of the absorption spectra.

  12. Unexpected covalency from actinide 5f orbital interactions (An = Th, U, Np, Pu) determined from chlorine K-edge X-ray absorption spectroscopy and electronic structure theory

    International Nuclear Information System (INIS)

    Clark, D.L.; Batista, E.R.; Boland, K.S.

    2010-01-01

    We have employed Cl K-edge XAS and multiple levels of sophisticated electronic structure calculations on a series of simple octahedral light actinide (Th, U, Np, Pu) chloride salts, AnCl 6 n- in order to assess the relative roles of the valence 5f and 6d orbitals in chemical bonding. Chlorine K-edge X-ray absorption spectroscopy on AnCl 6 n- (An = Th, U, Np, Pu) systems indicates the presence of covalent interactions between both Cl 3p and An 5f and 6d orbitals, with the relative contributions changing across the series. Electronic structure calculations indicate the predominant covalent interactions are expected to occur through An-Cl bonding via t 1u and t 2u interactions with the An 5f orbitals, and through t 2g and e g interactions with An 6d orbitals. For the Cl K-edge data therefore, we expect bound state transitions from Cl 1s → e g (σ), t 2g (π), and t 1u (σ + π) orbitals. Qualitatively, the Cl K-edge data fulfills these expectations

  13. Surface structure of alpha-Fe sub 2 O sub 3 nanocrystal observed by O K-edge X-ray absorption spectroscopy

    CERN Document Server

    Zhang, J; Ibrahim, K; Abbas, M I; Ju, X

    2003-01-01

    X-ray absorption near edge structure (XANES) spectra is used as a probe of surface structure of alpha-Fe sub 2 O sub 3 nanocrystal, prepared by sol-gel method. We present O K-edge XANES of alpha-Fe sub 2 O sub 3 in nanocrystal and bulk by total electron yield at the photoemission station of Beijing Synchrotron Radiation Facility. The spectrum of alpha-Fe sub 2 O sub 3 shows a splitting of the pre-edge structure, which is interpreted as two subsets of Fe 3d t sub 2 sub g and e sub g orbitals in oxygen octahedral (O sub h) crystal field, and is also sensitive to long-range order effects. However, no distinguishable splitting of the pre-edge peak of nanocrystal alpha-Fe sub 2 O sub 3 is observed. This suggests that there exists the distorted octahedral coordination around Fe sites and also the long-range disorder due to the surface as compared with bulk alpha-Fe sub 2 O sub 3.

  14. Electronic structure of Cr doped Fe3O4 thin films by X-ray absorption near-edge structure spectroscopy

    Science.gov (United States)

    Chen, Chi-Liang; Dong, Chung-Li; Asokan, Kandasami; Chern, G.; Chang, C. L.

    2018-04-01

    Present study reports the electronic structures of Cr doped Fe3O4 (Fe3-xCrxO4 (0 ≤ x ≤ 3) grown on MgO (100) substrates in the form of thin films fabricated by a plasma-oxygen assisted Molecular Beam Epitaxy (MBE). X-ray absorption near-edge structure (XANES) spectra at Cr & Fe L-, and O K-edges were used to understand the electronic structure: changes in the bonding nature, valence states, and site occupancies. Cr doping in Fe3O4 results in the change of charge transfer, crystal structure, and selective occupation of ions in octahedral and tetrahedral sites. Such change modifies the electrical and magnetic properties due to the covalency of Cr ions. The physical and chemical properties of ferrites are strongly dependent on the lattice site, ion size of dopant, and magnetic nature present at different structural symmetry of the spinel structure.

  15. X-ray absorption near edge structure study on Acutolysin-C, a zinc-metalloproteinase from Agkistrodon acutus venom: Insight into the acid-inactive mechanism

    International Nuclear Information System (INIS)

    Zhao Wei; Chu Wangsheng; Li Shujun; Liu Yiwei; Gao Bin; Niu Liwen; Teng Maikun; Benfatto, Maurizio; Hu Tiandou; Wu Ziyu

    2007-01-01

    Acutolysin-C, a snake-venom zinc metalloproteinase, displays a distinct pH-dependent proteolytic activity, which has been tentatively assigned to a structural change of the zinc-containing catalytic center. In this work we compare X-ray absorption near-edge structure (XANES) experimental spectra at the Zn K-edge and theoretical calculations of solutions at different pH values. The experimental data show clear differences confirmed by a best fit using the MXAN procedure. The results show that, when pH decreases from pH 8.0 to pH 3.0, the zinc-coordinating catalytic water molecule moves far from the Glu143 residue that is considered to play an essential role in the proteolytic process. Data suggests that this is the possible mechanism that deactivates the metalloproteinase

  16. The origin of luminescence from di[4-(4-diphenylaminophenyl)phenyl]sulfone (DAPSF), a blue light emitter: an X-ray excited optical luminescence (XEOL) and X-ray absorption near edge structure (XANES) study.

    Science.gov (United States)

    Zhang, Duo; Zhang, Hui; Zhang, Xiaohong; Sham, Tsun-Kong; Hu, Yongfeng; Sun, Xuhui

    2016-03-07

    The electronic structure and optical properties of di[4-(4-diphenylaminophenyl)phenyl]sulfone (denoted as DAPSF), a highly efficient fluorophor, have been investigated using X-ray excited optical luminescence (XEOL) and X-ray absorption near edge structure (XANES) spectroscopy at excitation energies across the C, N, O K-edges and the sulfur K-edge. The results indicate that the blue luminescence is mainly related to the sulfur functional group.

  17. Mn L2,3-edge X-ray absorption spectroscopic studies on charge-discharge mechanism of Li2MnO3

    International Nuclear Information System (INIS)

    Kubobuchi, Kei; Mogi, Masato; Imai, Hideto; Ikeno, Hidekazu; Tanaka, Isao; Mizoguchi, Teruyasu

    2014-01-01

    The redox reaction of Mn in Li 2 MnO 3 was studied by X-ray absorption spectroscopy and ab initio multiplet calculation. Associated with the de-intercalation of Li-ion, small but clear spectral changes were observed in Mn-L 2,3 X-ray absorption near edge structure (XANES). The systematic ab initio multiplet calculations of Mn-L 2,3 XANES revealed that the spectral changes in the experiment could not simply be ascribed to the change of the valency from Mn 4+ to Mn 5+ but can be explained well by the changes of local atomic structures around Mn 4+ due to the Li de-intercalation. Our results suggest that the electronic state of oxygen should change during charging in Li 2 MnO 3

  18. 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.

  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. K- and L-edge X-ray absorption spectrum calculations of closed-shell carbon, silicon, germanium, and sulfur compounds using damped four-component density functional response theory.

    Science.gov (United States)

    Fransson, Thomas; Burdakova, Daria; Norman, Patrick

    2016-05-21

    X-ray absorption spectra of carbon, silicon, germanium, and sulfur compounds have been investigated by means of damped four-component density functional response theory. It is demonstrated that a reliable description of relativistic effects is obtained at both K- and L-edges. Notably, an excellent agreement with experimental results is obtained for L2,3-spectra-with spin-orbit effects well accounted for-also in cases when the experimental intensity ratio deviates from the statistical one of 2 : 1. The theoretical results are consistent with calculations using standard response theory as well as recently reported real-time propagation methods in time-dependent density functional theory, and the virtues of different approaches are discussed. As compared to silane and silicon tetrachloride, an anomalous error in the absolute energy is reported for the L2,3-spectrum of silicon tetrafluoride, amounting to an additional spectral shift of ∼1 eV. This anomaly is also observed for other exchange-correlation functionals, but it is seen neither at other silicon edges nor at the carbon K-edge of fluorine derivatives of ethene. Considering the series of molecules SiH4-XFX with X = 1, 2, 3, 4, a gradual divergence from interpolated experimental ionization potentials is observed at the level of Kohn-Sham density functional theory (DFT), and to a smaller extent with the use of Hartree-Fock. This anomalous error is thus attributed partly to difficulties in correctly emulating the electronic structure effects imposed by the very electronegative fluorines, and partly due to inconsistencies in the spurious electron self-repulsion in DFT. Substitution with one, or possibly two, fluorine atoms is estimated to yield small enough errors to allow for reliable interpretations and predictions of L2,3-spectra of more complex and extended silicon-based systems.

  1. Predicting the Shifts of Absorption Maxima of Azulene Derivatives Using Molecular Modeling and ZINDO CI Calculations of UV-Vis Spectra

    Science.gov (United States)

    Patalinghug, Wyona C.; Chang, Maharlika; Solis, Joanne

    2007-01-01

    The deep blue color of azulene is drastically changed by the addition of substituents such as CH[subscript 3], F, or CHO. Computational semiempirical methods using ZINDO CI are used to model azulene and azulene derivatives and to calculate their UV-vis spectra. The calculated spectra are used to show the trends in absorption band shifts upon…

  2. Modeling L2,3-Edge X-ray Absorption Spectroscopy with Real-Time Exact Two-Component Relativistic Time-Dependent Density Functional Theory.

    Science.gov (United States)

    Kasper, Joseph M; Lestrange, Patrick J; Stetina, Torin F; Li, Xiaosong

    2018-04-10

    X-ray absorption spectroscopy is a powerful technique to probe local electronic and nuclear structure. There has been extensive theoretical work modeling K-edge spectra from first principles. However, modeling L-edge spectra directly with density functional theory poses a unique challenge requiring further study. Spin-orbit coupling must be included in the model, and a noncollinear density functional theory is required. Using the real-time exact two-component method, we are able to variationally include one-electron spin-orbit coupling terms when calculating the absorption spectrum. The abilities of different basis sets and density functionals to model spectra for both closed- and open-shell systems are investigated using SiCl 4 and three transition metal complexes, TiCl 4 , CrO 2 Cl 2 , and [FeCl 6 ] 3- . Although we are working in the real-time framework, individual molecular orbital transitions can still be recovered by projecting the density onto the ground state molecular orbital space and separating contributions to the time evolving dipole moment.

  3. The radiation effects of aspergillus oryzae spores with soft x-rays near the K shell absorption edges of C, N, O elements from synchrotron radiation

    International Nuclear Information System (INIS)

    Chen Liang; Jiang Shiping; Wan Libiao; Ma Xiaodong; Li Meifang

    2007-01-01

    The dose deposition of different parts of Aspergillus oryzae spores were analyzed with soft X-ray energies near the K-shell absorption edges of C, N, O elements (4.4nm, 3.2nm and 2.3nm), respectively. At the same time, the spores were irradiated with the three wavelengths of soft X-rays on the soft X-ray microscopy from synchrotron radiation at NSRL, and the survivals were compared. The theoretical analyses showed that the deposition doses of different parts of the spore were varying with X-ray energies because of the effects of C, N, O K-shell absorption edges and elemental contents of the different parts of spore. The experimental studies proved three wavelengths of soft X-rays all had high killing abilities. Among these, 2.3nm wavelength X-rays had higher radiation damage to spore than that of 3.2nm, 4.4nm. (authors)

  4. Lithium-modulated conduction band edge shifts and charge-transfer dynamics in dye-sensitized solar cells based on a dicyanamide ionic liquid.

    Science.gov (United States)

    Bai, Yu; Zhang, Jing; Wang, Yinghui; Zhang, Min; Wang, Peng

    2011-04-19

    Lithium ions are known for their potent function in modulating the energy alignment at the oxide semiconductor/dye/electrolyte interface in dye-sensitized solar cells (DSCs), offering the opportunity to control the associated multichannel charge-transfer dynamics. Herein, by optimizing the lithium iodide content in 1-ethyl-3-methylimidazolium dicyanamide-based ionic liquid electrolytes, we present a solvent-free DSC displaying an impressive 8.4% efficiency at 100 mW cm(-2) AM1.5G conditions. We further scrutinize the origins of evident impacts of lithium ions upon current density-voltage characteristics as well as photocurrent action spectra of DSCs based thereon. It is found that, along with a gradual increase of the lithium content in ionic liquid electrolytes, a consecutive diminishment of the open-circuit photovoltage arises, primarily owing to a noticeable downward movement of the titania conduction band edge. The conduction band edge displacement away from vacuum also assists the formation of a more favorable energy offset at the titania/dye interface, and thereby leads to a faster electron injection rate and a higher exciton dissociation yield as implied by transient emission measurements. We also notice that the adverse influence of the titania conduction band edge downward shift arising from lithium addition upon photovoltage is partly compensated by a concomitant suppression of the triiodide involving interfacial charge recombination. © 2011 American Chemical Society

  5. Silicon K-edge XANES spectra of silicate minerals

    Science.gov (United States)

    Li, Dien; Bancroft, G. M.; Fleet, M. E.; Feng, X. H.

    1995-03-01

    Silicon K-edge x-ray absorption near-edge structure (XANES) spectra of a selection of silicate and aluminosilicate minerals have been measured using synchrotron radiation (SR). The spectra are qualitatively interpreted based on MO calculation of the tetrahedral SiO{4/4-}cluster. The Si K-edge generally shifts to higher energy with increased polymerization of silicates by about 1.3 eV, but with considerable overlap for silicates of different polymerization types. The substitution of Al for Si shifts the Si K-edge to lower energy. The chemical shift of Si K-edge is also sensitive to cations in more distant atom shells; for example, the Si K-edge shifts to lower energy with the substitution of Al for Mg in octahedral sites. The shifts of the Si K-edge show weak correlation with average Si-O bond distance (dSi-O), Si-O bond valence (sSi-O) and distortion of SiO4 tetrahedra, due to the crystal structure complexity of silicate minerals and multiple factors effecting the x-ray absorption processes.

  6. Phase transition in LiVO2 studied by near-edge x-ray-absorption spectroscopy

    NARCIS (Netherlands)

    Pen, HF; Tjeng, LH; Pellegrin, E; deGroot, FMF; Sawatzky, GA; vanVeenendaal, MA; Chen, CT

    1997-01-01

    We present temperature-dependent V-2p and O-1s x-ray-absorption spectra of LiVO2. The aim of this study is to monitor changes in electronic structure on going through the phase transition. The spectral changes turn out to be very small: the V-3d-O-2p hybridization does not change considerably, and

  7. Characterization of local chemistry and disorder in synthetic and natural α-Al2O3 materials by X-ray absorption near edge structure spectroscopy

    International Nuclear Information System (INIS)

    Mottana, A.; Murata, T.

    1997-11-01

    X-ray absorption fine spectra at the Al K-edge were measured experimentally on and calculated theoretically via the multiple-scattering formalism for a chemically pure and physically perfect synthetic α-Al 2 O 3 (α-alumina), a natural 'ruby/sapphire' (corundum) and a series of artificial 'corundum' produced for technical purposes and used as geochemical standards. The Al K-edge spectra differ despite of the identical coordination (short-range arrangement) assumed by O around Al, and vary slightly in relation to the slightly different chemistries of the materials (substitutional defects) as well as on account of the location taken by foreign atoms in the structural lattices (positional defects). A quantitative treatment of the observed changes is made in terms of short-range modification of the coordination polyhedron and of medium- to long-range modifications in the overall structure; both of them induced by substitutions. In some technical 'corundums', the impurities of admixed 'β-alumina', where Al is both in four- and six-fold coordination, produce another small but detectable effect on Al K-edges. Therefore, XAFS spectroscopy proves its potentials for both measuring a light element such as Al, and detecting minor coordination changes and substitutions (ca. 1∼3 wt.% as oxide) of the absorber by dilute other atoms, at least under favorable conditions as those occurring in this system are

  8. A combined DFT and restricted open-shell configuration interaction method including spin-orbit coupling: Application to transition metal L-edge X-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Roemelt, Michael; Maganas, Dimitrios; Neese, Frank [Max-Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Muelheim an der Ruhr (Germany); DeBeer, Serena [Max-Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Muelheim an der Ruhr (Germany); Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853 (United States)

    2013-05-28

    A novel restricted-open-shell configuration interaction with singles (ROCIS) approach for the calculation of transition metal L-edge X-ray absorption spectra is introduced. In this method, one first calculates the ground state and a number of excited states of the non-relativistic Hamiltonian. By construction, the total spin is a good quantum number in each of these states. For a ground state with total spin S excited states with spin S Prime = S, S - 1, and S + 1 are constructed. Using Wigner-Eckart algebra, all magnetic sublevels with M{sub S}= S, Horizontal-Ellipsis , -S for each multiplet of spin S are obtained. The spin-orbit operator is represented by a mean-field approximation to the full Breit-Pauli spin-orbit operator and is diagonalized over this N-particle basis. This is equivalent to a quasi-degenerate treatment of the spin-orbit interaction to all orders. Importantly, the excitation space spans all of the molecular multiplets that arise from the atomic Russell-Saunders terms. Hence, the method represents a rigorous first-principles approach to the complicated low-symmetry molecular multiplet problem met in L-edge X-ray absorption spectroscopy. In order to gain computational efficiency, as well as additional accuracy, the excitation space is restricted to single excitations and the configuration interaction matrix is slightly parameterized in order to account for dynamic correlation effects in an average way. To this end, it is advantageous to employ Kohn-Sham rather than Hartree-Fock orbitals thus defining the density functional theory/ROCIS method. However, the method can also be used in an entirely non-empirical fashion. Only three global empirical parameters are introduced and have been determined here for future application of the method to any system containing any transition metal. The three parameters were carefully calibrated using the L-edge X-ray absorption spectroscopy spectra of a test set of coordination complexes containing first row

  9. Ge L{sub 3}-edge x-ray absorption near-edge structure study of structural changes accompanying conductivity drift in the amorphous phase of Ge{sub 2}Sb{sub 2}Te{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Mitrofanov, K. V. [Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8562 (Japan); Kolobov, A. V., E-mail: a.kolobov@aist.go.jp; Fons, P. [Nanoelectronics Research Institute and Green Nanoelectronics Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8562, Japan and Synchrotron Radiation Research Institute (JASRI), SPring-8, 1-1-1, Kouto, Sayo, Hyogo 679-5198 (Japan); Wang, X.; Tominaga, J. [Nanoelectronics Research Institute and Green Nanoelectronics Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8562 (Japan); Tamenori, Y.; Uruga, T. [Synchrotron Radiation Research Institute (JASRI), SPring-8, 1-1-1, Kouto, Sayo, Hyogo 679-5198 (Japan); Ciocchini, N.; Ielmini, D. [DEIB - Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano (Italy)

    2014-05-07

    A gradual uncontrollable increase in the resistivity of the amorphous phase of phase-change alloys, such as Ge{sub 2}Sb{sub 2}Te{sub 5}, known as drift, is a serious technological issue for application of phase-change memory. While it has been proposed that drift is related to structural relaxation, no direct structural results have been reported so far. Here, we report the results of Ge L{sub 3}-edge x-ray absorption measurements that suggest that the drift in electrical conductivity is associated with the gradual conversion of tetrahedrally coordinated Ge sites into pyramidal sites, while the system still remains in the amorphous phase. Based on electronic configuration arguments, we propose that during this process, which is governed by the existence of lone-pair electrons, the concentration of free carriers in the system decreases resulting in an increase in resistance despite the structural relaxation towards the crystalline phase.

  10. Structural study of glasses in the binary system NaPO{sub 3}-MoO{sub 3} by X-ray absorption spectroscopy at the Mo K and L{sub 3} edges

    Energy Technology Data Exchange (ETDEWEB)

    Poirier, Gael, E-mail: gael@unifal-mg.edu.br [Department of Science and Technology, UNIFAL-MG, Rua Corumba 72, CEP 37701-100, Pocos de Caldas, MG (Brazil); Cassanjes, Fabia C. [Department of Science and Technology, UNIFAL-MG, Rua Corumba 72, CEP 37701-100, Pocos de Caldas, MG (Brazil)

    2010-04-15

    Glasses were prepared in the binary system (100 - x)NaPO{sub 3}-xMoO{sub 3} with x varying from 0 to 50 mol%. An increase in the MoO{sub 3} concentration promotes a strong absorption in the visible and near infrared attributed to Mo reduction during glass synthesis. X-ray absorption measurements were performed at the Mo K and L{sub 3} edges to investigate both the coordination number and oxidation state of Mo in these glasses. The evolution of the pre-peak observed at the K edge suggests that Mo atoms are six-fold coordinated in these glasses. This hypothesis was confirmed by data obtained at the Mo-L{sub 3}-absorption edge. Since the final electronic states at the L{sub 3}-absorption edge are mostly orbitals of d-character which are splitted by the ligand field, the amplitude of the d-orbital splitting could be estimated and the related coordination number of Mo obtained. Finally, the oxidation state of Mo could be related with a change of the white line intensity at the Mo-L{sub 3} edge. These results confirm that the optical absorption in the visible is due to Mo reduction and that transparent samples prepared by slow cooling contain less reduced Mo species.

  11. 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

  12. 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

  13. M-edge x-ray absorption spectroscopy: A new tool for dilute mixed-valent materials

    International Nuclear Information System (INIS)

    Kaindl, G.; Brewer, W.D.; Kalkowski, G.; Holtzberg, F.

    1983-01-01

    The valence of Tm compounds is derived from M/sub V/ x-ray absorption spectra recorded by total electron yield under ultra-high-vacuum conditions. For mixed-valent systems the spectra are superpositions of Tm 3+ (three lines) and Tm 2+ (one line) components, providing accurate mean valence values even in highly dilute systems, such as Tm/sub x/Y/sub 1-x/Se, which agree well with those from lattice constant systematics. A surface valence change on TmS(100) is identified as an initial-state effect

  14. X-ray diffraction and X-ray K absorption near edge studies of copper (II) complexes with amino acids

    Science.gov (United States)

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

    2017-05-01

    Synthesis of copper (II) complexes [CuL1L2X].nH2O, where n=1, 2,3 (X=Cl,Br,NO3) (L1is 2,2’-bipyridine and L2 is L-tyrosine) by the chemical root method. The XRD data for the samples have been recorded. EXAFS spectra have also been recorded at the K-edge of Cu using the dispersive beam line BL-8 at 2.5 Gev Indus-2 Synchrotron radiation source at RRCAT, Indore, India. XRD and EXAFS data have been analysed using the computer software. X-ray diffraction studies of all complexes indicate their crystalline nature. Lattice parameter, bond length, particle size have been determined from XRD data.

  15. Damage to adenosine-triphosphate induced by monochromatic X rays around the K shell absorption edge of phosphorus

    International Nuclear Information System (INIS)

    Watanabe, Ritsuko; Ishikawa, Mitsuo; Takakura, Kaoru; Kobayashi, Katsumi

    1992-01-01

    Adenosine-triphosphate (ATP) is well known to have an important role in the energy metabolism in biological systems. The purpose of this study is to clarify the radiation effects on ATP specific to inner shell ionization. ATP, in concentrated aqueous solution, was irradiated with monochromatic X rays having energies of the resonance absorption peak of the phosphorus K shell, 2.153 keV, and slightly below and above the peak, 2.145 keV and 2.160 keV, selected from synchrotron radiation. Adenine, Adenosine 5'monophosphate (5'AMP) and Adenosine 5'diphosphate (5'ADP) were obtained as radioproducts by the method of high performance liquid chromatography (HPLC). G values of these products were calculated on the basis of the absorbed energy. When the ATP solution of 0.282 mol/l was irradiated with 2.160 keV X rays which can ionize the K shell of phosphorus, G values of Adenine, 5'AMP and 5'ADP were estimated to be 1.4, 0.40 and 0.46, respectively. These values were respectively 1.3, 2.9 and 3.8 times higher than those obtained upon irradiation with 2.146 keV X rays which cannot ionize the K shell of phosphorus. These energy dependent enhancements may reflect the difference in energy absorption processes, especially the Auger cascade in phosphorus may be suspected to play an important role in these enhancements

  16. Identification of isomers in the gas phase and as adsorbates by near-edge X-ray absorption fine structure spectroscopy: Cis- and trans-stilbene

    International Nuclear Information System (INIS)

    Püttner, Ralph; Schmidt-Weber, Philipp; Kampen, Thorsten; Kolczewski, Christine; Hermann, Klaus; Horn, Karsten

    2017-01-01

    Highlights: • NEXAFS spectra of the cis- and trans-isomer of stilbene reveal distinct differences by which the isomers can be distinguished. • DFT calculations using the transition potential approach assign specific transitions that are different in the two isomers. • On Si(100), these differences in NEXAFS are also observed, suggesting that their conformations survive in the bonding situation. • NEXAFS is thus shown to be a sensitive tool to distinguish isomers in adsorbed species. - Abstract: Near-edge x-ray absorption fine structure spectra of the cis- and trans-isomers of stilbene in the gas phase reveal clear differences, which are analyzed by results from density-functional theory calculations using the transition potential approach. The differences between the two species also occur in stilbene adsorbed on Si(100), opening the way towards studying structural changes in molecules in different surface environments, and configurational switching in organic molecules on surfaces in particular.

  17. Investigation of Pb species in soils, celery and duckweed by synchrotron radiation X-ray absorption near-edge structure spectrometry

    Science.gov (United States)

    Luo, Liqiang; Shen, Yating; Liu, Jian; Zeng, Yuan

    2016-08-01

    The Pb species play a key role in its translocation in biogeochemical cycles. Soils, sediments and plants were collected from farmlands around Pb mines, and the Pb species in them was identified by X-ray absorption near-edge structure spectrometry. In soils, Pb5(PO4)3Cl and Pb3(PO4)2 were detected, and in sediments, Pb-fulvic acids (FAs) complex was identified. A Pb complex with FA fragments was also detected in celery samples. We found that (1) different Pb species were present in soils and sediments; (2) the Pb species in celery, which was grown in sediments, was different from the species present in duckweed, which grew in water; and (3) a Pb-FA-like compound was present in celery roots. The newly identified Pb species, the Pb-FA-like compound, may play a key role in Pb tolerance and translocation within plants.

  18. Multi-edge X-ray absorption spectroscopy study of road dust samples from a traffic area of Venice using stoichiometric and environmental references

    Science.gov (United States)

    Valotto, Gabrio; Cattaruzza, Elti; Bardelli, Fabrizio

    2017-02-01

    The appropriate selection of representative pure compounds to be used as reference is a crucial step for successful analysis of X-ray absorption near edge spectroscopy (XANES) data, and it is often not a trivial task. This is particularly true when complex environmental matrices are investigated, being their elemental speciation a priori unknown. In this paper, an investigation on the speciation of Cu, Zn, and Sb based on the use of conventional (stoichiometric compounds) and non-conventional (environmental samples or relevant certified materials) references is explored. This method can be useful in when the effectiveness of XANES analysis is limited because of the difficulty in obtaining a set of references sufficiently representative of the investigated samples. Road dust samples collected along the bridge connecting Venice to the mainland were used to show the potentialities and the limits of this approach.

  19. Identification of isomers in the gas phase and as adsorbates by near-edge X-ray absorption fine structure spectroscopy: Cis- and trans-stilbene

    Energy Technology Data Exchange (ETDEWEB)

    Püttner, Ralph [Department of Physics, Freie Universität Berlin, 14195 Berlin (Germany); Schmidt-Weber, Philipp [Fritz Haber Institute of the Max Planck Society, 14195 Berlin (Germany); Kampen, Thorsten [SPECS Surface Nano Analysis GmbH, 13355 Berlin (Germany); Kolczewski, Christine [Deutsches Museum München, 80538 Munich (Germany); Hermann, Klaus [Fritz Haber Institute of the Max Planck Society, 14195 Berlin (Germany); Horn, Karsten, E-mail: horn@fhi-berlin.mpg.de [Fritz Haber Institute of the Max Planck Society, 14195 Berlin (Germany)

    2017-02-15

    Highlights: • NEXAFS spectra of the cis- and trans-isomer of stilbene reveal distinct differences by which the isomers can be distinguished. • DFT calculations using the transition potential approach assign specific transitions that are different in the two isomers. • On Si(100), these differences in NEXAFS are also observed, suggesting that their conformations survive in the bonding situation. • NEXAFS is thus shown to be a sensitive tool to distinguish isomers in adsorbed species. - Abstract: Near-edge x-ray absorption fine structure spectra of the cis- and trans-isomers of stilbene in the gas phase reveal clear differences, which are analyzed by results from density-functional theory calculations using the transition potential approach. The differences between the two species also occur in stilbene adsorbed on Si(100), opening the way towards studying structural changes in molecules in different surface environments, and configurational switching in organic molecules on surfaces in particular.

  20. Simulation and evaluation of the absorption edge subtraction technique in energy-resolved X-ray radiography applied to the cultural heritage studies

    International Nuclear Information System (INIS)

    Leyva Pernia, Diana; Cabal Rodriguez, Ana E.; Pinnera Hernandez, Ibrahin; Leyva Fabelo, Antonio; Abreu Alfonso, Yamiel; Espen, Piet Van

    2011-01-01

    In this work the mathematical simulation of photon transport in the matter was used to evaluate the potentials of a new energy-resolved X-ray radiography system. The system is intended for investigations of cultural heritage object, mainly painting. The radiographic system uses polychromatic radiation from an X-ray tube and measures the spectrum transmitted through the object with an energy-dispersive X-ray detector on a pixel-by-pixel basis. Manipulation of the data-set obtained allows constructing images with enhanced contrast for certain elements. Here the use of the absorption edge subtraction technique was emphasized. The simulated results were in good agreement with the experimental data.(author)

  1. Near-Edge X-ray Absorption Fine Structure Studies of Electrospun Poly(dimethylsiloxane)/Poly (methyl methacrylate)/Multiwall Carbon Nanotube Composites

    Science.gov (United States)

    Winter, A. Douglas; Larios, Eduardo; Alamgir, Faisal M.; Jaye, Cherno; Fischer, Daniel; Campo, Eva M.

    2014-01-01

    This work describes the near conduction band edge structure of electrospun mats of MWCNT-PDMS-PMMA by near edge X-Ray absorption fine structure (NEXAFS) spectroscopy. Effects of adding nanofillers of different sizes were addressed. Despite observed morphological variations and inhomogeneous carbon nanotube distribution, spun mats appeared homogeneous under NEXAFS analysis. Spectra revealed differences in emissions from glancing and normal spectra; which may evidence phase separation within the bulk of the micron-size fibers. Further, dichroic ratios show polymer chains did not align, even in the presence of nanofillers. Addition of nanofillers affected emissions in the C-H, C=O and C-C regimes, suggesting their involvement in interfacial matrix-carbon nanotube bonding. Spectral differences at glancing angles between pristine and composite mats suggest that geometric conformational configurations are taking place between polymeric chains and carbon nanotubes. These differences appear to be carbon nanotube-dimension dependent, and are promoted upon room temperature mixing and shear flow during electrospinning. CH-π bonding between polymer chains and graphitic walls, as well as H-bonds between impurities in the as-grown CNTs and polymer pendant groups are proposed bonding mechanisms promoting matrix conformation. PMID:24308286

  2. Predicting Near Edge X-ray Absorption Spectra with the Spin-Free Exact-Two-Component Hamiltonian and Orthogonality Constrained Density Functional Theory.

    Science.gov (United States)

    Verma, Prakash; Derricotte, Wallace D; Evangelista, Francesco A

    2016-01-12

    Orthogonality constrained density functional theory (OCDFT) provides near-edge X-ray absorption (NEXAS) spectra of first-row elements within one electronvolt from experimental values. However, with increasing atomic number, scalar relativistic effects become the dominant source of error in a nonrelativistic OCDFT treatment of core-valence excitations. In this work we report a novel implementation of the spin-free exact-two-component (X2C) one-electron treatment of scalar relativistic effects and its combination with a recently developed OCDFT approach to compute a manifold of core-valence excited states. The inclusion of scalar relativistic effects in OCDFT reduces the mean absolute error of second-row elements core-valence excitations from 10.3 to 2.3 eV. For all the excitations considered, the results from X2C calculations are also found to be in excellent agreement with those from low-order spin-free Douglas-Kroll-Hess relativistic Hamiltonians. The X2C-OCDFT NEXAS spectra of three organotitanium complexes (TiCl4, TiCpCl3, TiCp2Cl2) are in very good agreement with unshifted experimental results and show a maximum absolute error of 5-6 eV. In addition, a decomposition of the total transition dipole moment into partial atomic contributions is proposed and applied to analyze the nature of the Ti pre-edge transitions in the three organotitanium complexes.

  3. Temperature-Induced Large Broadening and Blue Shift in the Electronic Band Structure and Optical Absorption of Methylammonium Lead Iodide Perovskite.

    Science.gov (United States)

    Yang, Jia-Yue; Hu, Ming

    2017-08-17

    The power conversion efficiency of hybrid halide perovskite solar cells is profoundly influenced by the operating temperature. Here we investigate the temperature influence on the electronic band structure and optical absorption of cubic CH 3 NH 3 PbI 3 from first-principles by accounting for both the electron-phonon interaction and thermal expansion. Within the framework of density functional perturbation theory, the electron-phonon coupling induces slightly enlarged band gap and strongly broadened electronic relaxation time as temperature increases. The large broadening effect is mainly due to the presence of cation organic atoms. Consequently, the temperature-dependent absorption peak exhibits blue-shift position, decreased amplitude, and broadened width. This work uncovers the atomistic origin of temperature influence on the optical absorption of cubic CH 3 NH 3 PbI 3 and can provide guidance to design high-performance hybrid halide perovskite solar cells at different operating temperatures.

  4. UV-Photochemistry of the Disulfide Bond: Evolution of Early Photoproducts from Picosecond X-ray Absorption Spectroscopy at the Sulfur K-Edge.

    Science.gov (United States)

    Ochmann, Miguel; Hussain, Abid; von Ahnen, Inga; Cordones, Amy A; Hong, Kiryong; Lee, Jae Hyuk; Ma, Rory; Adamczyk, Katrin; Kim, Tae Kyu; Schoenlein, Robert W; Vendrell, Oriol; Huse, Nils

    2018-05-30

    We have investigated dimethyl disulfide as the basic moiety for understanding the photochemistry of disulfide bonds, which are central to a broad range of biochemical processes. Picosecond time-resolved X-ray absorption spectroscopy at the sulfur K-edge provides unique element-specific insight into the photochemistry of the disulfide bond initiated by 267 nm femtosecond pulses. We observe a broad but distinct transient induced absorption spectrum which recovers on at least two time scales in the nanosecond range. We employed RASSCF electronic structure calculations to simulate the sulfur-1s transitions of multiple possible chemical species, and identified the methylthiyl and methylperthiyl radicals as the primary reaction products. In addition, we identify disulfur and the CH 2 S thione as the secondary reaction products of the perthiyl radical that are most likely to explain the observed spectral and kinetic signatures of our experiment. Our study underscores the importance of elemental specificity and the potential of time-resolved X-ray spectroscopy to identify short-lived reaction products in complex reaction schemes that underlie the rich photochemistry of disulfide systems.

  5. Ca 3d unoccupied states in Bi2Sr2CaCu2O8 investigated by Ca L2,3 x-ray-absorption near-edge structure

    International Nuclear Information System (INIS)

    Borg, A.; King, P.L.; Pianetta, P.; Lindau, I.; Mitzi, D.B.; Kapitulnik, A.; Soldatov, A.V.; Della Longa, S.; Bianconi, A.

    1992-01-01

    The high-resolution Ca L 2,3 x-ray-absorption near-edge-structure (XANES) spectrum of a Bi 2 Sr 2 CaCu 2 O 8 single crystal has been measured by use of a magnetic-projection x-ray microscope probing a surface area of 200x200 μm 2 . The Ca L 2,3 XANES spectrum is analyzed by performing a multiple-scattering XANES calculation in real space and comparing the results with the spectrum of CaF 2 . Good agreement between the calculated and experimental crystal-field splitting Δ f of the Ca 3d final states is found and the splitting is shown to be smaller by 0.5 eV than in the initial state. The Ca 3d partial density of states is found to be close to the Fermi level in the initial state. The Ca-O(in plane) distance is shown to be a critical parameter associated with the shift of the Ca 3d states relative to the Fermi level; in particular, we have studied the effect of the out-of-plane dimpling mode of the in-plane oxygen atoms O(in plane) that will move the Ca 3d states on or off the Fermi level. This mode can therefore play a role in modulating the charge transfer between the two CuO 2 planes separated by the Ca ions

  6. Ca 3d unoccupied states in Bi2Sr2CaCu2O8 investigated by Ca L2,3 x-ray-absorption near-edge structure

    Energy Technology Data Exchange (ETDEWEB)

    Borg, A; King, P L; Pianetta, P; Lindau, I; Mitzi, D B

    1992-01-01

    The high-resolution Ca L(2,3) x-ray-absorption near-edge-structure (XANES) spectrum of a Bi2Sr2CaCu2O8 single crystal has been measured by use of a magnetic-projection x-ray microscope probing a surface area of 200x200 micrometers square. The Ca L(2,3) XANES spectrum is analyzed by performing a multiple-scattering XANES calculation in real space and comparing the results with the spectrum of CaF2. Good agreement between the calculated and experimental crystal-field splitting Delta f of the Ca 3d final states is found and the splitting is shown to be smaller by 0.5 eV than in the initial state. The Ca 3d partial density of states is found to be close to the Fermi level in the initial state. The Ca-O (in plane) distance is shown to be a critical parameter associated with the shift of the Ca 3d states relative to the Fermi level; in particular, the authors have studied the effect of the out-of-plane dimpling mode of the in-plane oxygen atoms O(in plane) that will move the Ca 3d states on or off the Fermi level. This mode can therefore play a role in modulating the charge transfer between the two CuO2 planes separated by the Ca ions.

  7. Structural evidence for the sorption of Ni(II) atoms on the edges of montmorillonite clay minerals: a polarized X-ray absorption fine structure study

    Science.gov (United States)

    Dähn, Rainer; Scheidegger, André M.; Manceau, Alain; Schlegel, Michel L.; Baeyens, Bart; Bradbury, Michael H.; Chateigner, Daniel

    The nature of surface complexes formed on Ni uptake onto montmorillonite (a dioctahedral smectite) has been investigated over an extended time period by polarized extended X-ray absorption fine structure (P-EXAFS) spectroscopy. Self-supporting films of Ni-sorbed montmorillonite were prepared by contacting Ni and montmorillonite at pH 7.2, high ionic strength (0.3 M NaClO 4), and low Ni concentration ([Ni] initial = 19.9 μM) for 14- and 360-d reaction time. The resulting Ni concentration on the clay varied from 4 to 7 μmol/g. Quantitative texture analysis indicates that the montmorillonite particles were well orientated with respect to the plane of the film. The full width at half maximum of the orientation distribution of the c* axes of individual clay platelets about the normal to the film plane was 44.3° (14-d reaction time) and 47.1° (360-d reaction time). These values were used to correct the coordination numbers determined by P-EXAFS for texture effects. Ni K-edge P-EXAFS spectra were recorded at angles between the incident beam and the film normal equal to 10, 35, 55, and 80°. Spectral analysis led to the identification of three nearest cationic subshells containing 2.0 ± 0.5 Al at 3.0 Å and 2.0 ± 0.5 Si at 3.12 Å and 4.0 ± 0.5 Si at 3.26 Å. These distances are characteristic of edge-sharing linkages between Al and Ni octahedra and of corner-sharing linkages between Ni octahedra and Si tetrahedra, as in clay structures. The angular dependence of the Ni-Al and Ni-Si contributions indicates that Ni-Al pairs are oriented parallel to the film plane, whereas Ni-Si pairs are not. The study reveals the formation of Ni inner-sphere mononuclear surface complexes located at the edges of montmorillonite platelets and thus that heavy metals binding to edge sites is a possible sorption mechanism for dioctahedral smectites. Data analysis further suggests that either the number of neighboring Al atoms slightly increases from 1.6 to 2 or that the structural order

  8. Distribution of solute atoms in β- and spinel Si6-zAlzOzN8-z by Al K-edge x-ray absorption near-edge structure

    International Nuclear Information System (INIS)

    Tatsumi, Kazuyoshi; Mizoguchi, Teruyasu; Yoshioka, Satoru; Tanaka, Isao; Yamamoto, Tomoyuki; Suga, Takeo; Sekine, Toshimori

    2005-01-01

    Local environments of solutes in β- and spinel Si 6-z Al z O z N 8-z are investigated by means of Al K x-ray absorption near-edge structure. The experimental spectra are found to be the same throughout the wide solubility range. This suggests that the local environments of Al are independent of the solute concentration. First-principles band-structure calculations are systematically made to interpret the experimental spectra. Effect of a core hole was included into the calculation. Theoretical spectra were obtained using variety of different model structures constructed by a set of plane-wave pseudopotentials calculations in our previous study [K. Tatsumi, I. Tanaka, H. Adachi, and M. Yoshiya, Phys. Rev. B 66, 165210 (2002)]. The numbers of models were 51 and 45 for both β and spinel, respectively. They are classified and averaged according to the local atomic structure of Al solutes. The combination of experimental spectra and theoretical results can unambiguously lead to the conclusion that Al atoms are preferentially coordinated by O atoms in both β and spinel phases. This is consistent with the conclusion obtained by the first-principles total-energy calculations. In the spinel phase, Al atoms are found to be located preferentially at the octahedral cationic site. This agrees with the conclusion in a recent report on the nuclear magnetic resonance experiment

  9. Probing the influence of X-rays on aqueous copper solutions using time-resolved in situ combined video/X-ray absorption near-edge/ultraviolet-visible spectroscopy

    NARCIS (Netherlands)

    Mesu, J. Gerbrand; Beale, Andrew M.; de Groot, Frank M. F.; Weckhuysen, Bert M.

    2006-01-01

    Time-resolved in situ video monitoring and ultraviolet-visible spectroscopy in combination with X-ray absorption near-edge spectroscopy (XANES) have been used for the first time in a combined manner to study the effect of synchrotron radiation on a series of homogeneous aqueous copper solutions in a

  10. X-ray absorption near-edge structure of hexagonal ternary phases in sputter-deposited TiAlN films

    Energy Technology Data Exchange (ETDEWEB)

    Gago, R., E-mail: rgago@icmm.csic.es [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, E-28049 Madrid (Spain); Soldera, F. [Department of Materials Science and Engineering, Saarland University, D-66123 Saarbruecken (Germany); Hübner, R.; Lehmann, J.; Munnik, F. [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden (Germany); Vázquez, L. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, E-28049 Madrid (Spain); Redondo-Cubero, A. [Instituto Tecnológico e Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, 2686-953 Sacavém (Portugal); Endrino, J.L. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, E-28049 Madrid (Spain); Abengoa Research S.L., c/Energía Solar 1, Palmas Altas, E-41014 Seville (Spain)

    2013-06-05

    Highlights: ► Growth of ternary TiAlN films with nearly single-phase wurzite structure. ► Soft X-rays XANES measurements of ternary TiAlN films with wurzite structure. ► Identification of ternary TiAlN hexagonal phases by XANES. ► Correlation of XANES measurements with reported theoretical calculations. -- Abstract: Titanium aluminium nitride (TiAlN) coatings have been grown by reactive (Ar/N{sub 2}) direct-current magnetron sputtering from a Ti{sub 50}Al{sub 50} compound target. The film composition has been quantified by ion beam analysis showing the formation of Al-rich nitrides (Ti/Al ∼ 0.3), with stoichiometric films for N{sub 2} contents in the gas mixture equal or above ∼25%. The surface morphology of the films has been imaged by atomic force microscopy, showing very smooth surfaces with roughness values below 2 nm. X-ray and electron diffraction patterns reveal that the films are nanocrystalline with a wurzite (w) structure of lattice parameters larger (∼2.5%) than those for w-AlN. The lattice expansion correlates with the Ti/Al ratio in stoichiometric films, which suggests the incorporation of Ti into w-AlN. The atomic environments around Ti, Al and N sites have been extracted from the X-ray absorption near-edge structure (XANES) by recording the Ti2p, Al1s and N1s edges, respectively. The analysis of the XANES spectral lineshape and comparison with reported theoretical calculations confirm the formation of a ternary hexagonal phase.

  11. Tetrahalide complexes of the [U(NR)2]2+ ion: synthesis, theory, and chlorine K-edge X-ray absorption spectroscopy.

    Science.gov (United States)

    Spencer, Liam P; Yang, Ping; Minasian, Stefan G; Jilek, Robert E; Batista, Enrique R; Boland, Kevin S; Boncella, James M; Conradson, Steven D; Clark, David L; Hayton, Trevor W; Kozimor, Stosh A; Martin, Richard L; MacInnes, Molly M; Olson, Angela C; Scott, Brian L; Shuh, David K; Wilkerson, Marianne P

    2013-02-13

    Synthetic routes to salts containing uranium bis-imido tetrahalide anions [U(NR)(2)X(4)](2-) (X = Cl(-), Br(-)) and non-coordinating NEt(4)(+) and PPh(4)(+) countercations are reported. In general, these compounds can be prepared from U(NR)(2)I(2)(THF)(x) (x = 2 and R = (t)Bu, Ph; x = 3 and R = Me) upon addition of excess halide. In addition to providing stable coordination complexes with Cl(-), the [U(NMe)(2)](2+) cation also reacts with Br(-) to form stable [NEt(4)](2)[U(NMe)(2)Br(4)] complexes. These materials were used as a platform to compare electronic structure and bonding in [U(NR)(2)](2+) with [UO(2)](2+). Specifically, Cl K-edge X-ray absorption spectroscopy (XAS) and both ground-state and time-dependent hybrid density functional theory (DFT and TDDFT) were used to probe U-Cl bonding interactions in [PPh(4)](2)[U(N(t)Bu)(2)Cl(4)] and [PPh(4)](2)[UO(2)Cl(4)]. The DFT and XAS results show the total amount of Cl 3p character mixed with the U 5f orbitals was roughly 7-10% per U-Cl bond for both compounds, which shows that moving from oxo to imido has little effect on orbital mixing between the U 5f and equatorial Cl 3p orbitals. The results are presented in the context of recent Cl K-edge XAS and DFT studies on other hexavalent uranium chloride systems with fewer oxo or imido ligands.

  12. Water-vapor absorption line measurements in the 940-nm band by using a Raman-shifted dye laser

    Science.gov (United States)

    Chu, Zhiping; Wilkerson, Thomas D.; Singh, Upendra N.

    1993-01-01

    We report water-vapor absorption line measurements that are made by using the first Stokes radiation (930-982 nm) with HWHM 0.015/cm generated by a narrow-linewidth, tunable dye laser. Forty-five absorption line strengths are measured with an uncertainty of 6 percent and among them are fourteen strong lines that are compared with previous measurements for the assessment of spectral purity of the light source. Thirty air-broadened linewidths are measured with 8 percent uncertainty at ambient atmospheric pressure with an average of 0.101/cm. The lines are selected for the purpose of temperature-sensitive or temperature-insensitive lidar measurements. Results for these line strengths and linewidths are corrected for broadband radiation and finite laser linewidth broadening effects and compared with the high-resolution transmission molecular absorption.

  13. Test and evaluation of the in-line plutonium solution K-absorption-edge densitometer at the Savannah River Plant. Phase I. Off-line testing results

    International Nuclear Information System (INIS)

    Smith, H.A. Jr.; Marks, T.; Johnson, S.S.

    1982-04-01

    An in-line, plutonium-solution, K-edge absorption densitometer has been developed at Los Alamos and is currently undergoing test and evaluation at the Savannah River Plant (SRP). The first phase of the test and evaluation (off-line instrument calibration and solution assays) was completed, and preparations are under way to install the instrument in-line, as soon as process schedules permit. Calibration data in the design concentration range of 25 to 40 g Pu/L demonstrate routine achievement of densitometry assay precisions of 0.5% or better in 40 min. Plutonium assays at concentrations outside the calibration range were investigated in an effort to define better the limitations of the instrument and address other possible assay situations at SRP. Densitometry precisions obtained for 40-min assays range from 3% to 5 g Pu/L down to 0.4% at 70 g Pu/L. At higher plutonium concentrations, the precision deteriorated due to increasing gamma-ray absorption by the solution. In addition, with actinide concentrations above approximately 100 g/L, the assay accuracy also suffered because of enhanced small-angle scattering effects in the large sample cell. Measurements on mixed U/Pu solutions demonstrated the feasibility of accurate plutonium assays with correction for the large uranium matrix contributions being determined from the measurement data. The 239 240 Pu weight fractions and 241 Pu/ 239 Pu and 238 Pu/ 239 Pu isotopic ratios can be determined. In a mockup of the in-line solution plumbing system, all assay sequences, error conditions, and interlock criteria were exercised and verified to be working properly

  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. Remarkable optical red shift and extremely high optical absorption coefficient of V-Ga co-doped TiO2

    Science.gov (United States)

    Deng, Quanrong; Han, Xiaoping; Gao, Yun; Shao, Guosheng

    2012-07-01

    A first attempt has been made to study the effect of codoping of transition metal and sp metal on the electronic structure and associated optical properties of TiO2, through V-Ga codoped thin films. V-Ga codoped rutile TiO2 films were fabricated on fused quartz substrates using pulsed laser ablation, followed by heat treatment at high temperatures. Gigantic redshift in the optical absorption edge was observed in V-Ga co-doped TiO2 materials, from UV to infrared region with high absorption coefficient. Through combined structural characterization and theoretical modeling, this is attributed to the p-d hybridization between the two metals. This leads to additional energy bands to overlap with the minimum of the conduction band, leading to remarkably narrowed band gap free of mid-gap states. The direct-gap of the co-doped phase is key to the remarkably high optical absorption coefficient of the coped titania.

  16. Chlorine levels and species in fine and size resolved atmospheric particles by X-ray absorption near-edge structure spectroscopy analysis in Beijing, China.

    Science.gov (United States)

    Ouyang, Jie; Yang, Guo-Sheng; Ma, Ling-Ling; Luo, Min; Zheng, Lei; Huo, Qing; Zhao, Yi-Dong; Hu, Tian-Dou; Cai, Zhen-Feng; Xu, Dian-Dou

    2018-04-01

    An understanding of the species of chlorine is crucial in the metropolis-Beijing, which is suffering serious haze pollution with high frequency. Particulate Matters (PMs) with five different sizes were collected in Beijing from July 2009 to March 2016, and characterized non-destructively by X-ray absorption near edge structure spectroscopy. PM 2.5 contributed for the major PMs mass in spring and summer, PM 0.5-1.0 and PM 1.0-2.5 contributed for the major PMs mass in autumn and winter. The concentrations of the three chlorine species were in the order of inorganic chlorine (Cl inorg ) > aliphatic chlorine (Cl ali ) > aromatic chlorine (Cl aro ), indicating that Cl inorg constituted the primary chlorine fraction and less toxic Cl ali constituted the primary total organic chlorine (Cl ali  + Cl aro , abbreviated as Cl org ) in the PMs in Beijing. In addition, these three chlorine species exhibited identical seasonal variation in PM 2.5 : winter > autumn > spring > summer. Wet precipitation is an important factor to result in the lower mass concentrations of these three chlorine species in summer. The temporal variations of both size resolved PM mass concentrations and chlorine species concentrations suggested that the air pollution prevention and control in Beijing has just won initial success. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. 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.

  18. Structural evolution of fluorinated graphene upon molten-alkali treatment probed by X-ray absorption near-edge structure spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Xianqing, E-mail: lxq@gxu.edu.cn [Guangxi Colleges and Universities Key Laboratory of Novel Energy Materials and Related Technology, College of Physics Science and Technology, Guangxi University, Nanning 530004 (China); Guangxi Collaborative Innovation Center of Structure and Property for New Energy and Materials, School of Material Science and Engineering, Guilin University of Electronic Technology, Guilin 541004 (China); Pan, Deyou; Lao, Ming; Liang, Shuiying [Guangxi Colleges and Universities Key Laboratory of Novel Energy Materials and Related Technology, College of Physics Science and Technology, Guangxi University, Nanning 530004 (China); Huang, Dan; Zhou, Wenzheng; Guo, Jin [Guangxi Colleges and Universities Key Laboratory of Novel Energy Materials and Related Technology, College of Physics Science and Technology, Guangxi University, Nanning 530004 (China); Guangxi Collaborative Innovation Center of Structure and Property for New Energy and Materials, School of Material Science and Engineering, Guilin University of Electronic Technology, Guilin 541004 (China)

    2017-05-15

    Highlights: • Structural evolution of FG during the molten-alkali treatment was studied. • XANES results reveal the transformation of surface functional groups of HFG. • The local and electronic structure of HFG can be tuned by varying the alkali-FG ratio. - Abstract: The structural evolution of fluorinated graphene (FG) nanosheets upon molten-alkali treatment has been systematically investigated utilizing X-ray absorption near-edge structure (XANES) spectroscopy. It is found that the hydroxyl groups can progressively displace fluorine atoms to form covalent bonds to the graphene sheets under designed molten-alkali condition. The XANES spectra also reveal the formation of epoxide groups through intramolecular dehydration of neighbouring hydroxyl groups after substitution reaction. At high alkali-FG weight ratio, the restoration of the π-conjugated structure in graphene sheets can be observed due to the gradual decomposition of epoxide groups. Our experimental results indicate that the surface chemistry and electronic structure of hydroxyl-functionalized FG (HFG) can be readily tuned by varying the ratio of reactants.

  19. The aquatic hyphomycete Heliscus lugdunensis protects its hyphae tip cells from cadmium: A micro X-ray fluorescence and X-ray absorption near edge structure spectroscopy study

    Science.gov (United States)

    Isaure, Marie-Pierre; Leyh, Benjamin; Salomé, Murielle; Krauss, Gerd-Joachim; Schaumlöffel, Dirk; Dobritzsch, Dirk

    2017-11-01

    Aquatic fungi can be used to evaluate the functioning of natural ecosystems. Heliscus lugdunensis is an early colonizer of allochthone leafs. Since this aquatic hyphomycete is able to develop in metal contaminated habitats and tolerates cadmium, it appears to be a good candidate to investigate adaptation to metal pollution. This study aimed at examining the sequestration of Cd in the hyphae of H. lugdunensis, and particularly the role of the tip cells. For that, H. lugdunensis growth was evaluated under various Cd concentrations, and a combination of synchrotron micro X-ray fluorescence and X-ray absorption near edge structure spectroscopy was carried out to determine the compartments of Cd accumulation and the Cd chemical species, respectively. Results showed that the hyphal tip cells were depleted in Cd, and that the metal was stored in older cells. Cd was mainly associated with sulfur ligands and to a lesser extent bound to phosphates and carboxyl/hydroxyl groups from cell wall and/or organic acids. Finally, the aquatic fungus was able to maintain the tip cell as a functional system, thus allowing the colonization of contaminated environments.

  20. X-ray absorption study at the Mg and O K edges of ultrathin MgO epilayers on Ag(001)

    International Nuclear Information System (INIS)

    Luches, P.; D'Addato, S.; Valeri, S.; Groppo, E.; Prestipino, C.; Lamberti, C.; Boscherini, F.

    2004-01-01

    We determined the local atomic structure of MgO epilayers on Ag(001) by means of polarization-dependent x-ray absorption spectroscopy measurements at the Mg and O K edges. A quantitative analysis of the data in the extended energy range has been performed using multiple scattering simulations. We found that, even in the ultrathin limit, the local structure of the films is rocksalt and we obtained a quantitative evaluation of the average in-plane and out-of-plane film strain at the different thicknesses investigated. An in-plane compressive strain, due to lattice mismatch with the Ag substrate, is clearly present for the 3 ML film. The out-of-plane lattice constant is found to be expanded, in agreement with the expected behavior for a tetragonal distortion of the unit cell. This growth-induced strain is gradually released with increasing thickness and it is almost completely relaxed at 20 ML. Any significant intermixing with the Ag substrate can be ruled out. An expansion of the interplanar distance at the MgO-Ag interface is detected and its sign and magnitude are found to be in agreement with recent ab initio simulations. This work provides previously unavailable input for modeling the physical properties of the system and supports the hypothesis that the different electronic properties of MgO films on Ag(001) are not related to structural or compositional differences at the ultrathin limit

  1. In situ X-ray near-edge absorption spectroscopy investigation of the state of charge of all-vanadium redox flow batteries.

    Science.gov (United States)

    Jia, Chuankun; Liu, Qi; Sun, Cheng-Jun; Yang, Fan; Ren, Yang; Heald, Steve M; Liu, Yadong; Li, Zhe-Fei; Lu, Wenquan; Xie, Jian

    2014-10-22

    Synchrotron-based in situ X-ray near-edge absorption spectroscopy (XANES) has been used to study the valence state evolution of the vanadium ion for both the catholyte and anolyte in all-vanadium redox flow batteries (VRB) under realistic cycling conditions. The results indicate that, when using the widely used charge-discharge profile during the first charge process (charging the VRB cell to 1.65 V under a constant current mode), the vanadium ion valence did not reach V(V) in the catholyte and did not reach V(II) in the anolyte. Consequently, the state of charge (SOC) for the VRB cell was only 82%, far below the desired 100% SOC. Thus, such incompletely charged mix electrolytes results in not only wasting the electrolytes but also decreasing the cell performance in the following cycles. On the basis of our study, we proposed a new charge-discharge profile (first charged at a constant current mode up to 1.65 V and then continuously charged at a constant voltage mode until the capacity was close to the theoretical value) for the first charge process that achieved 100% SOC after the initial charge process. Utilizing this new charge-discharge profile, the theoretical charge capacity and the full utilization of electrolytes has been achieved, thus having a significant impact on the cost reduction of the electrolytes in VRB.

  2. Study of apical oxygen atoms in a spin-ladder cuprate compound by X-ray absorption spectroscopy near the Cu K edge

    Energy Technology Data Exchange (ETDEWEB)

    Hatterer, C.J.; Eustache, B.; Collin, L.; Beuran, C.F.; Partiot, C.; Germain, P.; Xu, X.Z.; Lagues, M. [CNRS, Paris (France). Surfaces et Supraconducteurs; Michalowicz, A. [Laboratoire de Physique des Milieux Desordonnes, Universite Paris XII Val-de-Marne, 61 avenue du general de Gaulle, 94010, Creteil Cedex (France)]|[LURE, Universite Paris Sud, 91405, Orsay Cedex (France); Moscovici, J. [Laboratoire de Physique des Milieux Desordonnes, Universite Paris XII Val-de-Marne, 61 avenue du general de Gaulle, 94010, Creteil Cedex (France); Deville Cavellin, C. [CNRS, Paris (France). Surfaces et Supraconducteurs]|[Laboratoire d`Electronique, Universite Paris XII Val-de-Marne, 61 av. du general de Gaulle, 94010, Creteil Cedex (France); Traverse, A. [LURE, Universite Paris Sud, 91405, Orsay Cedex (France)

    1997-04-01

    The structure of high-T{sub c} superconducting cuprate compounds is based on CuO{sub 2} planes alternating with blocks that behave as charge reservoirs. The apical oxygen atoms which belong to these reservoirs are suspected to play a role in the mechanism of superconductivity. It thus seems necessary to measure the amount of apical oxygen atoms in various compounds, as a function of the superconducting properties. Polarisation dependent X-ray absorption spectroscopy (XAS) measurements were performed near the Cu K-edge on three types of phases. We collected information about the neighbourhood of the copper atom in the cuprate planes and in the direction perpendicular to these planes. Two of these phases have well known structures: Bi2212 in which copper atoms are on a pyramidal site and infinite layer phase, a square planar cuprate without apical oxygen. We used the obtained results as reference data to study a new copper-rich phase related to the spin-ladder series. (orig.)

  3. Comparative Investigation of Guided Fuzzy Clustering and Mean Shift Clustering for Edge Detection in Electrical Resistivity Tomography Images of Mineral Deposits

    Science.gov (United States)

    Ward, Wil; Wilkinson, Paul; Chambers, Jon; Bai, Li

    2014-05-01

    Geophysical surveying using electrical resistivity tomography (ERT) can be used as a rapid non-intrusive method to investigate mineral deposits [1]. One of the key challenges with this approach is to find a robust automated method to assess and characterise deposits on the basis of an ERT image. Recent research applying edge detection techniques has yielded a framework that can successfully locate geological interfaces in ERT images using a minimal assumption data clustering technique, the guided fuzzy clustering method (gfcm) [2]. Non-parametric clustering techniques are statistically grounded methods of image segmentation that do not require any assumptions about the distribution of data under investigation. This study is a comparison of two such methods to assess geological structure based on the resistivity images. In addition to gfcm, a method called mean-shift clustering [3] is investigated with comparisons directed at accuracy, computational expense, and degree of user interaction. Neither approach requires the number of clusters as input (a common parameter and often impractical), rather they are based on a similar theory that data can be clustered based on peaks in the probability density function (pdf) of the data. Each local maximum in these functions represents the modal value of a particular population corresponding to a cluster and as such the data are assigned based on their relationships to these model values. The two methods differ in that gfcm approximates the pdf using kernel density estimation and identifies population means, assigning cluster membership probabilities to each resistivity value in the model based on its distance from the distribution averages. Whereas, in mean-shift clustering, the density function is not calculated, but a gradient ascent method creates a vector that leads each datum towards high density distributions iteratively using weighted kernels to calculate locally dense regions. The only parameter needed in both methods

  4. Determination of Scattering and Absorption Coefficients for Plasma-Sprayed Yttria-Stabilized Zirconia Thermal Barrier Coatings at Elevated Temperatures

    Science.gov (United States)

    Eldridge, Jeffrey I.; Spuckler, Charles M.; Markham, James R.

    2009-01-01

    The temperature dependence of the scattering and absorption coefficients for a set of freestanding plasma-sprayed 8 wt% yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs) was determined at temperatures up to 1360 C in a wavelength range from 1.2 micrometers up to the 8YSZ absorption edge. The scattering and absorption coefficients were determined by fitting the directional-hemispherical reflectance and transmittance values calculated by a four-flux Kubelka Munk method to the experimentally measured hemispherical-directional reflectance and transmittance values obtained for five 8YSZ thicknesses. The scattering coefficient exhibited a continuous decrease with increasing wavelength and showed no significant temperature dependence. The scattering is primarily attributed to the relatively temperature-insensitive refractive index mismatch between the 8YSZ and its internal voids. The absorption coefficient was very low (less than 1 per centimeter) at wavelengths between 2 micrometers and the absorption edge and showed a definite temperature dependence that consisted of a shift of the absorption edge to shorter wavelengths and an increase in the weak absorption below the absorption edge with increasing temperature. The shift in the absorption edge with temperature is attributed to strongly temperature-dependent multiphonon absorption. While TBC hemispherical transmittance beyond the absorption edge can be predicted by a simple exponential decrease with thickness, below the absorption edge, typical TBC thicknesses are well below the thickness range where a simple exponential decrease in hemispherical transmittance with TBC thickness is expected. [Correction added after online publication August 11, 2009: "edge to a shorter wavelengths" has been updated as edge to shorter wavelengths."

  5. Carbon K-edge X-ray absorption spectroscopy and time-dependent density functional theory examination of metal-carbon bonding in metallocene dichlorides.

    Science.gov (United States)

    Minasian, Stefan G; Keith, Jason M; Batista, Enrique R; Boland, Kevin S; Kozimor, Stosh A; Martin, Richard L; Shuh, David K; Tyliszczak, Tolek; Vernon, Louis J

    2013-10-02

    Metal-carbon covalence in (C5H5)2MCl2 (M = Ti, Zr, Hf) has been evaluated using carbon K-edge X-ray absorption spectroscopy (XAS) as well as ground-state and time-dependent hybrid density functional theory (DFT and TDDFT). Differences in orbital mixing were determined experimentally using transmission XAS of thin crystalline material with a scanning transmission X-ray microscope (STXM). Moving down the periodic table (Ti to Hf) has a marked effect on the experimental transition intensities associated with the low-lying antibonding 1a1* and 1b2* orbitals. The peak intensities, which are directly related to the M-(C5H5) orbital mixing coefficients, increase from 0.08(1) and 0.26(3) for (C5H5)2TiCl2 to 0.31(3) and 0.75(8) for (C5H5)2ZrCl2, and finally to 0.54(5) and 0.83(8) for (C5H5)2HfCl2. The experimental trend toward increased peak intensity for transitions associated with 1a1* and 1b2* orbitals agrees with the calculated TDDFT oscillator strengths [0.10 and 0.21, (C5H5)2TiCl2; 0.21 and 0.73, (C5H5)2ZrCl2; 0.35 and 0.69, (C5H5)2HfCl2] and with the amount of C 2p character obtained from the Mulliken populations for the antibonding 1a1* and 1b2* orbitals [8.2 and 23.4%, (C5H5)2TiCl2; 15.3 and 39.7%, (C5H5)2ZrCl2; 20.1 and 50.9%, (C5H5)2HfCl2]. The excellent agreement between experiment, theory, and recent Cl K-edge XAS and DFT measurements shows that C 2p orbital mixing is enhanced for the diffuse Hf (5d) and Zr (4d) atomic orbitals in relation to the more localized Ti (3d) orbitals. These results provide insight into how changes in M-Cl orbital mixing within the metallocene wedge are correlated with periodic trends in covalent bonding between the metal and the cyclopentadienide ancillary ligands.

  6. Investigation of the electronic structure of high-temperature superconductors and related transition metal oxides with near-edge x-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Gerhold, S.

    2001-01-01

    The unoccupied electronic structure and its orbital character has been studied with polarization-dependent near-edge x-ray absorption spectroscopy (NEXAFS) for selected high-temperature superconductors (HTSC) and related transition metal oxides. Although YBa 2 Cu 3 O 7-δ (Y-123) is arguably the best-investigated HTSC a conclusive NEXAFS study on how partial substitution of Cu by other transition metals affects the electronic structure has sorely been missing. The study presented here on a series of well characterized YBa 2 Cu 3-x Fe x O y single crystals shows that the cause for T c suppression is not at all magnetic pair breaking but charge carrier depletion, primarily in the chains; effects from disorder cannot be excluded. Annealing at high oxygen pressure increases along with oxygen content both the hole concentration and T c . Fe 3d-O 2p-derived states contribute prominently to the spectra for all polarizations a few eV above E F . Iron prefers a trivalent state in Y-123; upon reduction a spin transition can be observed. As YBa 2 Cu 3-x Fe x O y single crystals cannot be detwinned it is very difficult to distinguish between contributions from planes and chains to the spectra. In this situation thin films grown with a reduced degree of twinning ('twin-poor') allow more detailed investigations. An extended self-absorption correction was developed for fluorescence yield NEXAFS on epitactical HTSC thin films. Its application to twin-poor Y-123 thin films demonstrates that (apart from the effect of residual twins) the spectral information is equivalent to that of detwinned single crystals for a range of optimum film thicknesses, and this in turn allows to augment the NEXAFS study of YBa 2 Cu 3-x Fe x O y with spectra for corresponding twin-poor thin films. The system Ca 2-x (Sr,La) x RuO 4 is structurally related to the HTSCs; the development of its unoccupied electronic structure with x was investigated in this work, with emphasis on the metal

  7. Effect of geometric nanostructures on the absorption edges of 1-D and 2-D TiO₂ fabricated by atomic layer deposition.

    Science.gov (United States)

    Chang, Yung-Huang; Liu, Chien-Min; Cheng, Hsyi-En; Chen, Chih

    2013-05-01

    2-Dimensional (2-D) TiO2 thin films and 1-dimensional (1-D) TiO2 nanotube arrays were fabricated on Si and quartz substrates using atomic layer deposition (ALD) with an anodic aluminum oxide (AAO) template at 400 °C. The film thickness and the tube wall thickness can be precisely controlled using the ALD approach. The intensities of the absorption spectra were enhanced by an increase in the thickness of the TiO2 thin film and tube walls. A blue-shift was observed for a decrease in the 1-D and 2-D TiO2 nanostructure thicknesses, indicating a change in the energy band gap with the change in the size of the TiO2 nanostructures. Indirect and direct interband transitions were used to investigate the change in the energy band gap. The results indicate that both quantum confinement and interband transitions should be considered when the sizes of 1-D and 2-D TiO2 nanostructures are less than 10 nm.

  8. Speciation of copper and zinc in size-fractionated atmospheric particulate matter using total reflection mode X-ray absorption near-edge structure spectrometry

    International Nuclear Information System (INIS)

    Osan, Janos; Meirer, Florian; Groma, Veronika; Toeroek, Szabina; Ingerle, Dieter; Streli, Christina; Pepponi, Giancarlo

    2010-01-01

    The health effects of aerosol depend on the size distribution and the chemical composition of the particles. Heavy metals of anthropogenic origin are bound to the fine aerosol fraction (PM 2.5 ). The composition and speciation of aerosol particles can be variable in time, due to the time-dependence of anthropogenic sources as well as meteorological conditions. Synchrotron-radiation total reflection X-ray fluorescence (SR-TXRF) provides very high sensitivity for characterization of atmospheric particulate matter. X-ray absorption near-edge structure (XANES) spectrometry in conjunction with TXRF detection can deliver speciation information on heavy metals in aerosol particles collected directly on the reflector surface. The suitability of TXRF-XANES for copper and zinc speciation in size-fractionated atmospheric particulate matter from a short sampling period is presented. For high size resolution analysis, atmospheric aerosol particles were collected at different urban and rural locations using a 7-stage May cascade impactor having adapted for sampling on Si wafers. The thin stripe geometry formed by the particulate matter deposited on the May-impactor plates is ideally suited to SR-TXRF. Capabilities of the combination of the May-impactor sampling and TXRF-XANES measurements at HASYLAB Beamline L to Cu and Zn speciation in size-fractionated atmospheric particulate matter are demonstrated. Information on Cu and Zn speciation could be performed for elemental concentrations as low as 140 pg/m 3 . The Cu and Zn speciation in the different size fraction was found to be very distinctive for samples of different origin. Zn and Cu chemical state typical for soils was detected only in the largest particles studied (2-4 μm fraction). The fine particles, however, contained the metals of interest in the sulfate and nitrate forms.

  9. K- and L-edge X-ray Absorption Spectroscopy (XAS) and Resonant Inelastic X-ray Scattering (RIXS) Determination of Differential Orbital Covalency (DOC) of Transition Metal Sites.

    Science.gov (United States)

    Baker, Michael L; Mara, Michael W; Yan, James J; Hodgson, Keith O; Hedman, Britt; Solomon, Edward I

    2017-08-15

    Continual advancements in the development of synchrotron radiation sources have resulted in X-ray based spectroscopic techniques capable of probing the electronic and structural properties of numerous systems. This review gives an overview of the application of metal K-edge and L-edge X-ray absorption spectroscopy (XAS), as well as K resonant inelastic X-ray scattering (RIXS), to the study of electronic structure in transition metal sites with emphasis on experimentally quantifying 3d orbital covalency. The specific sensitivities of K-edge XAS, L-edge XAS, and RIXS are discussed emphasizing the complementary nature of the methods. L-edge XAS and RIXS are sensitive to mixing between 3d orbitals and ligand valence orbitals, and to the differential orbital covalency (DOC), that is, the difference in the covalencies for different symmetry sets of the d orbitals. Both L-edge XAS and RIXS are highly sensitive to and enable separation of and donor bonding and back bonding contributions to bonding. Applying ligand field multiplet simulations, including charge transfer via valence bond configuration interactions, DOC can be obtained for direct comparison with density functional theory calculations and to understand chemical trends. The application of RIXS as a probe of frontier molecular orbitals in a heme enzyme demonstrates the potential of this method for the study of metal sites in highly covalent coordination sites in bioinorganic chemistry.

  10. Influence of 4-tert-butylpyridine/guanidinium thiocyanate co-additives on band edge shift and recombination of dye-sensitized solar cells: experimental and theoretical aspects

    International Nuclear Information System (INIS)

    Wang, Yuqiao; Lu, Jing; Yin, Jie; Lü, Gang; Cui, Yingmin; Wang, Shasha; Deng, Shengyuan; Shan, Dan; Tao, Hailiang; Sun, Yueming

    2015-01-01

    Graphical Abstract: The frontier orbitals between 4-tert-butylpyridine and TiO 2 are sufficiently overlapped to induce the negative shift of Fermi energy, increasing the open-circuit voltage. The guanidinium cations can be tightly absorbed on TiO 2 surface to form a passivated layer, depressing the recombination rate and improving the short-circuit photocurrent. The photovoltaic performance might be as a result of a synergistic effect of co-additives due to the competitive effect between volume and electrostatic effect. - Highlights: • The frontier orbitals between 4-tert-butylpyridine and TiO 2 are sufficiently overlapped to induce the negative shift of Fermi energy, increasing the open-circuit voltage. • The guanidinium cations can be tightly absorbed on TiO 2 surface by electrostatic attraction to form a passivated layer, depressing the recombination rate and improving the short-circuit photocurrent. • The photovoltaic performance might be as a result of a synergistic effect of co-additives due to the competitive effect between volume and electrostatic effect. - ABSTRACT: The co-additives of 4-tert-butylpyridine (TBP) and guanidinium thiocyanate (GuSCN) in electrolytes can prominently affect the photovoltaic behavior of dye-sensitized solar cell (DSSC) due to their advantages fitting with energy levels and charge transfer. Mott-Schottky analysis is used to quantify the TiO 2 band edge movement to clarify the change of open-circuit voltage. The corresponding kinetic investigations are carried out using cyclic voltammetry, electrochemical impedance spectroscopy, intensity modulated photocurrent/photovoltage spectroscopy and charge extraction. Theoretically, the density functional theory (DFT) method is performed to explore the details of the adsorption, including the interacting energy, Fermi energy and frontier orbitals properties. The results show that the frontier orbitals between TBP and TiO 2 are sufficiently overlapped to induce the negative shift of

  11. Simulating Ru L 3 -Edge X-ray Absorption Spectroscopy with Time-Dependent Density Functional Theory: Model Complexes and Electron Localization in Mixed-Valence Metal Dimers

    Energy Technology Data Exchange (ETDEWEB)

    Van Kuiken, Benjamin E.; Valiev, Marat; Daifuku, Stephanie L.; Bannan, Caitlin; Strader, Matthew L.; Cho, Hana; Huse, Nils; Schoenlein, Robert W.; Govind, Niranjan; Khalil, Munira

    2013-05-30

    Ruthenium L3-edge X-ray absorption (XA) spectroscopy probes unoccupied 4d orbitals of the metal atom and is increasingly being used to investigate the local electronic structure in ground and excited electronic states of Ru complexes. The simultaneous development of computational tools for simulating Ru L3-edge spectra is crucial for interpreting the spectral features at a molecular level. This study demonstrates that time-dependent density functional theory (TDDFT) is a viable and predictive tool for simulating ruthenium L3-edge XA spectroscopy. We systematically investigate the effects of exchange correlation functional and implicit and explicit solvent interactions on a series of RuII and RuIII complexes in their ground and electronic excited states. The TDDFT simulations reproduce all of the experimentally observed features in Ru L3-edge XA spectra within the experimental resolution (0.4 eV). Our simulations identify ligand-specific charge transfer features in complicated Ru L3-edge spectra of [Ru(CN)6]4- and RuII polypyridyl complexes illustrating the advantage of using TDDFT in complex systems. We conclude that the B3LYP functional most accurately predicts the transition energies of charge transfer features in these systems. We use our TDDFT approach to simulate experimental Ru L3-edge XA spectra of transition metal mixed-valence dimers of the form [(NC)5MII-CN-RuIII(NH3)5] (where M = Fe or Ru) dissolved in water. Our study determines the spectral signatures of electron delocalization in Ru L3-edge XA spectra. We find that the inclusion of explicit solvent molecules is necessary for reproducing the spectral features and the experimentally determined valencies in these mixed-valence complexes. This study validates the use of TDDFT for simulating Ru 2p excitations using popular quantum chemistry codes and providing a powerful interpretive tool for equilibrium and ultrafast Ru L3-edge XA spectroscopy.

  12. X-ray absorption edges and E.X.A.F.S.: application to the study of electronic and atomic structures of titanium and vanadium carbides TiC(1-x) and VC(1-x)

    International Nuclear Information System (INIS)

    Moisy-Maurice, Virginie.

    1980-09-01

    This text presents a systematic study of the X-ray absorption fine structures evolution, at the K edge of titanium, with vacancy concentration in TiC(1-x). The absorption edges are situated in the 50 eV following the coefficient discontinuity: from the evaluation of their general aspect, it is deduced that the positive charge of titanium atoms decreases when vacancy concentration increases in TiC(1-x). This allowed us to determine the best band structure calculation model. The interpretation of EXAFS spectra (modulation of the absorption coefficient until 1500 eV above the edge) gives indications about the local atomic structure. Here, the contraction of the average titanium-carbon interatomic distances compared to the distances between crystallographic sites is of the order of the experimental resolution 0.02 A for Ti C(0.8). The study of the damping of the spectra in terms of Debye-Waller factors gave an evaluation of the relative static atomic mean square displacements between first neighbours. Last, it has been established that the disordering of vacancies in the order-disorder transition of V 8 C 7 is an atomic scale phenomenon [fr

  13. Use of X-ray absorption near edge structure (XANES) to identify physisorption and chemisorption of phosphate onto ferrihydrite-modified diatomite.

    Science.gov (United States)

    Xiong, Wenhui; Peng, Jian; Hu, Yongfeng

    2012-02-15

    This paper presents a novel technique integrating bulk-sensitive and surface-sensitive XANES methods to distinguish between physisorption and chemisorption for phosphate adsorption onto ferrihydrite-modified diatomite (FHMD). XANES P K-edge, L-edge, and Fe M-edge spectra were obtained for reference samples (K(2)HPO(4) and FePO(4)·2H(2)O) and test samples (phosphate adsorbed onto FHMD (FHMD-Ps) and Si-containing ferrihydrite (FHYD-Ps)). A resolvable pre-edge peak in the P K-edge spectra of FHMD-Ps and FHYD-Ps provided direct evidence for the formation of P-O-Fe(III) coordination and the occurrence of chemisorption. The resemblance between the P L-edge spectra of K(2)HPO(4) and FHMD-Ps and the marked difference between the spectra of FHMD-Ps and FePO(4)·2H(2)O indicated the intact existence of the adsorbate and the adsorbent. The similarity between Fe M-edge spectra of FHMD and FHMD-Ps and the difference between the spectra of FHMD-Ps and FePO(4)·2H(2)O confirmed the findings from P L-edge analyses. Therefore, chemisorption and physisorption coexisted during phosphate adsorption onto FHMD. Phosphate chemisorption occurred in the deeper zone of FHMD (from 50 nm to 5 μm); whereas physisorption occurred in the zone of FHMD shallower than 50 nm since the probing depth of XANES P K-edge method is 5 μm and that of P L-edge and Fe M-edge methods is 50 nm. Copyright © 2011 Elsevier Inc. All rights reserved.

  14. Frequency up-shift in the stimulated thermal scattering under two-photon absorption in liquids and colloids of metal nanoparticles

    Science.gov (United States)

    Smetanin, I. V.; Erokhin, A. I.; Baranov, A. N.

    2018-07-01

    We report the results of the experimental and theoretical study of stimulated temperature scattering in toluene and hexane solutions of Ag-nanoparticles, as well as in pure toluene in the two-photon absorption regime. A four-wave mixing scheme with two counter-propagating pump waves of the same frequency is utilised to demonstrate the lasing effect and the amplification of the backscattered anti-Stokes signal. For the first time, we have measured anti-Stokes spectral shifts which turn out to appreciably exceed the Rayleigh line widths in those liquids. It is shown that the amplification effect is provided predominantly by thermally induced coherent polarisation oscillations, while the dynamic interference temperature grating causes the formation of a self-induced optical cavity inside the interaction region.

  15. Blue shift in optical absorption, magnetism and light-induced superparamagnetism in γ-Fe{sub 2}O{sub 3} nanoparticles formed in dendrimer

    Energy Technology Data Exchange (ETDEWEB)

    Domracheva, Natalia E., E-mail: ndomracheva@gmail.com; Vorobeva, Valerya E. [Zavoisky Kazan Physical-Technical Institute (Russian Federation); Gruzdev, Matvey S. [Institute of Solution Chemistry (Russian Federation); Pyataev, Andrew V. [Kazan Federal University (Russian Federation)

    2015-02-15

    We are presenting the investigation of the optical, magnetic, and photoinduced superparamagnetic properties of single-domain γ-Fe{sub 2}O{sub 3} nanoparticles (NPs) with diameters of about 2.5 nm formed in second-generation poly(propylene imine) dendrimer. The optical absorption studies indicated direct allowed transition with the band gap (4.5 eV), which is blue shift with respect to the value of the bulk material. Low-temperature blocking of the NPs magnetic moments at 18 K is determined by SQUID measurements. The influence of pulsed laser irradiation on the superparamagnetic properties of γ-Fe{sub 2}O{sub 3} NPs was studied by EPR spectroscopy. It has been shown that irradiation of the sample held in vacuo and cooled in zero magnetic field to 6.9 K leads to the appearance of a new EPR signal, which decays immediately after the irradiation is stopped. The appearance and disappearance of this new signal can be repeated many times at 6.9 K when we turn on/turn off the laser. We suppose that the generation of conduction band electrons by irradiation into the band gap of the γ-Fe{sub 2}O{sub 3} changes the superparamagnetic properties of NPs. Graphical Abstract: Features of the behavior of single-domain γ-Fe{sub 2}O{sub 3} nanoparticles formed in dendrimer were found by UV-Vis and EPR spectroscopy: “blue” shift in optical absorption, a significant increase in the band gap width and variation of superparamagnetic properties under light irradiation.

  16. Characterization of Functionalized Self-Assembled Monolayers and Surface-Attached Interlocking Molecules Using Near-Edge X-ray Absorption Fine Structure Spectroscopy

    International Nuclear Information System (INIS)

    Willey, T; Willey, T

    2004-01-01

    Quantitative knowledge of the fundamental structure and substrate binding, as well as the direct measurement of conformational changes, are essential to the development of self-assembled monolayers (SAMs) and surface-attached interlocking molecules, catenanes and rotaxanes. These monolayers are vital to development of nano-mechanical, molecular electronic, and biological/chemical sensor applications. This dissertation investigates properties of functionalized SAMs in sulfur-gold based adsorbed molecular monolayers using quantitative spectroscopic techniques including near-edge x-ray absorption fine structure spectroscopy (NEXAFS) and x-ray photoelectron spectroscopy (XPS). The stability of the gold-thiolate interface is addressed. A simple model SAM consisting of dodecanethiol adsorbed on Au(111) degrades significantly in less than 24 hours under ambient laboratory air. S 2p and O 1s XPS show the gold-bound thiolates oxidize to sulfinates and sulfonates. A reduction of organic material on the surface and a decrease in order are observed as the layer degrades. The effect of the carboxyl vs. carboxylate functionalization on SAM structure is investigated. Carboxyl-terminated layers consisting of long alkyl-chain thiols vs. thioctic acid with short, sterically separated, alkyl groups are compared and contrasted. NEXAFS shows a conformational change, or chemical switchability, with carboxyl groups tilted over and carboxylate endgroups more upright. Surface-attached loops and simple surface-attached rotaxanes are quantitatively characterized, and preparation conditions that lead to desired films are outlined. A dithiol is often insufficient to form a molecular species bound at each end to the substrate, while a structurally related disulfide-containing polymer yields surface-attached loops. Similarly, spectroscopic techniques show the successful production of a simple, surface-attached rotaxane that requires a ''molecular riveting'' step to hold the mechanically attached

  17. Study of oxidation states of the transition metals in a series of Prussian blue analogs using x-ray absorption near edge structure (XANES) spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Adak, S. [Department of Physics, New Mexico State University, Las Cruces, NM, 88003 (United States); Hartl, M., E-mail: monika.hartl@esss.se [European Spallation Source ESS AB, 22100, Lund (Sweden); Manuel Lujan Jr. Neutron Scattering Center (LANSCE-LC), Los Alamos National Laboratory, Los Alamos, NM, 87545 (United States); Daemen, L. [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN, 37830 (United States); Manuel Lujan Jr. Neutron Scattering Center (LANSCE-LC), Los Alamos National Laboratory, Los Alamos, NM, 87545 (United States); Fohtung, E.; Nakotte, H. [Department of Physics, New Mexico State University, Las Cruces, NM, 88003 (United States)

    2017-01-15

    Highlights: • Systematic XANES measurements on Prussian blue analogs shows oxidation state of transition metals. • Cobal-iron bimetallic hexacyanometallates show unexpected oxidation states. • Iron(II) ions in hexacyanometallates(III) show varying spin state depending on their bond to the “N” end or “C” end of the cyanide ligand. • Thermal expansion coefficients have been linked to the XANES results. - Abstract: There have been renewed interests in metal-organic framework classes of materials such as Prussian blue analogues (PBAs) due to their potential usage in energy storage applications. In particular, due to their high surface areas, controllable structures and excellent electrochemical properties, PBAs such as hexacyanometalates M{sup II}{sub 3}[A{sup III}(CN){sub 6}]{sub 2*}nH{sub 2}O (M = Mn, Fe, Co, Ni, Cu, Zn; A = Co, Fe, Cr; n = no. of water molecules present), M{sup II}{sub 2}[Fe{sup II}(CN){sub 6}]{sub 2*}nH{sub 2}O (M = Mn, Co, Ni, Cu, Zn) and mixed hexacyanometalates(III) (Fe{sub 1-x}Co{sub x}){sub 3}[B{sup III}(CN){sub 6}]{sub 2}·nH{sub 2}O (x = 0.25, 0.5, 0.75; B = Co, Fe) could have possible usage as a new class of cathode and even anode materials for rechargeable batteries. Detailed knowledge of the oxidation states of the transition metals in PBAs is required to improve efficiency and durability of such devices. Furthermore, a link between the thermal expansion observed in these materials and the oxidation state of the transition metal is of interest to synthesize materials with a desired thermal expansion behavior, Here we demonstrate the use of Synchrotron based X-ray absorption near-edge structure (XANES) spectra to identify transition metal oxidation states. Our analysis reveals the presence of divalent, trivalent and/or mixed valence transition metals in the materials as well as high-spin and low-spin complexes.

  18. Studies of nitride- and oxide-based materials as absorptive shifters for embedded attenuated phase-shifting mask in 193 nm

    Science.gov (United States)

    Lin, Cheng-ming; Chang, Keh-wen; Lee, Ming-der; Loong, Wen-An

    1999-07-01

    Abstract-Five materials which are PdSixOy, CrAlxOy, SiNx, TiSixNy, and TiSixOyNz as absorptive shifters for attenuated phase-shifting mask in 193 nm wavelength lithography are presented. PdSixOy films were deposited by dual e-gun evaporation. CrAlxOy, TiSixNy and TiSixOyNz films were formed by plasma sputtering and SiNx films were formed with LPCVD. All of these materials are shown to be capable of achieving 4 percent - 15 percent transmittance in 193 nm with thickness that produce a 180 degrees phase shift. Under BCl3:Cl2 equals 14:70 sccm; chamber pressure 5 mtorr and RF power 1900W, the dry etching selectivity of TiSixNy over DQN positive resist and fused silica, were found to be 2:1 and 4,8:1 respectively. An embedded layer TiSixNy with 0.5 micrometers line/space was successfully patterned.

  19. Theoretical modeling of deuteration-induced shifts of the 0-0 bands in absorption spectra of selected aromatic amines: the role of the double-well potential.

    Science.gov (United States)

    Andrzejak, Marcin; Kolek, Przemysław

    2013-12-05

    The harmonic approximation fails for inversion of the NH2 group in the ground state of aromatic amines as this vibration is characterized by a symmetric double-well potential with relatively small energy barrier. In such cases, the standard harmonic vibrational analysis is inapplicable: the inversion frequency calculated for the bottom of the potential well is strongly overestimated, while it attains imaginary values for the planar conformation of the molecule. The model calculations are discussed taking explicitly into account the presence of the double-well potential. The study is initially focused on reproduction of the deuteration-induced shifts of the 0-0 absorption band for anthranilic acid. The (incorrect) harmonic frequency of the NH2 inversion is replaced by a better one, obtained from numerical calculations employing a simple, quartic-quadratic model for the double-well potential, which is parametrized using just the harmonic frequency of the inversion and the height of the energy barrier. This operation brings theoretical results to qualitative agreement with experiment. A still better match is achieved with a modified version of the model that accounts for mixing of the NH2 inversion mode with other normal modes while retaining the initial simplicity of one-dimensional approach. The corrected results show surprisingly good accuracy, with deviations of the calculated shifts from the experimental values reduced to less than 5 cm(-1). In order to test the performance of the model for systems with higher energy barrier for the NH2 inversion, we have measured the LIF excitation spectra of three different amminobenzonitriles. Partial assignment of the 0-0 bands has been achieved based on their relative intensities for samples with different isotopic exchange ratios. Calculated shifts are in excellent agreement with experimental values for the identified bands. Theoretical predictions are used to complete the assignment of the 0-0 bands in the spectra of the

  20. X-ray absorption spectroscopy of soybean lipoxygenase-1 : Influence of lipid hydroperoxide activation and lyophilization on the structure of the non-heme iron active site

    NARCIS (Netherlands)

    Vliegenthart, J.F.G.; Heijdt, L.M. van der; Feiters, M.C.; Navaratnam, S.; Nolting, H.-F.; Hermes, C.; Veldink, G.A.

    1992-01-01

    X-ray absorption spectra at the Fe K-edge of the non-heme iron site in Fe(II) as well as Fe(III) soybean lipoxygenase-1, in frozen solution or lyophilized, are presented; the latter spectra were obtained by incubation of the Fe(II) enzyme with its product hydroperoxide. An edge shift of about 23 eV

  1. Pressure Swing Absorption Device and Process for Separating CO{sub 2} from Shifted Syngas and its Capture for Subsequent Storage

    Energy Technology Data Exchange (ETDEWEB)

    Sirkar, Kamalesh; Jie, Xingming; Chau, John; Obuskovic, Gordana

    2013-03-31

    Using the ionic liquid (IL) 1-butyl-3-methylimidazolium dicyanamide ([bmim][DCA]) as the absorbent on the shell side of a membrane module containing either a porous hydrophobized ceramic tubule or porous hydrophobized polyether ether ketone (PEEK) hollow fiber membranes, studies for CO{sub 2} removal from hot simulated pre-combustion shifted syngas were carried out by a novel pressure swing membrane absorption (PSMAB) process. Helium was used as a surrogate for H{sub 2} in a simulated shifted syngas with CO{sub 2} around 40% (dry gas basis). In this cyclic separation process, the membrane module was used to achieve non-dispersive gas absorption from a high-pressure feed gas (689-1724 kPag; 100-250 psig) at temperatures between 25-1000C into a stationary absorbent liquid on the module shell side during a certain part of the cycle followed by among other cycle steps controlled desorption of the absorbed gases from the liquid in the rest of the cycle. Two product streams were obtained, one He-rich and the other CO{sub 2}-rich. Addition of polyamidoamine (PAMAM) dendrimer of generation 0 to IL [bmim][DCA] improved the system performance at higher temperatures. The solubilities of CO{sub 2} and He were determined in the ionic liquid with or without the dendrimer in solution as well as in the presence or absence of moisture; polyethylene glycol (PEG) 400 was also studied as a replacement for the IL. The solubility selectivity of the ionic liquid containing the dendrimer for CO{sub 2} over helium was considerably larger than that for the pure ionic liquid. The solubility of CO{sub 2} and CO{sub 2}-He solubility selectivity of PEG 400 and a solution of the dendrimer in PEG 400 were higher than the corresponding ones in the IL, [bmim][DCA]. A mathematical model was developed to describe the PSMAB process; a numerical solution of the governing equations described successfully the observed performance of the PSMAB process for the pure ionic liquid-based system.

  2. A measuring method of photo-electric cross section. Application to high-Z elements between 40 keV and 220 keV. Measurement of K absorption edge energy of Au, Th, U, Pu

    International Nuclear Information System (INIS)

    Chartier, J.-L.

    1977-09-01

    This study first describes a bent crystal monochromator developed for the production of monochromatic beams in a continuous energy range from 30 to 250 keV; it is completed by a metrological application of the device (determination of K absorption edge energy of Au, Th, U, Pu). A method and the associated experimental procedure were developed to measure the photo-electric cross section for high-Z elements; the results are presented with a relative uncertainty ranging between 3 and 6%. Finally, the experimental values are compared with values calculated from theories using self-consistent potential models [fr

  3. Mn L{sub 2,3}-edge X-ray absorption spectroscopic studies on charge-discharge mechanism of Li{sub 2}MnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kubobuchi, Kei, E-mail: kubobuchi@nissan-arc.co.jp [NISSAN ARC Ltd., 1 Natsushima, Yokosuka 237-0061 (Japan); Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505, Japan. (Japan); Mogi, Masato; Imai, Hideto [NISSAN ARC Ltd., 1 Natsushima, Yokosuka 237-0061 (Japan); Ikeno, Hidekazu [Osaka Prefecture University, 1-2 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8570 (Japan); Tanaka, Isao [Department of Materials Science and Engineering, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501 (Japan); Mizoguchi, Teruyasu, E-mail: teru@iis.u-tokyo.ac.jp [Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505, Japan. (Japan)

    2014-02-03

    The redox reaction of Mn in Li{sub 2}MnO{sub 3} was studied by X-ray absorption spectroscopy and ab initio multiplet calculation. Associated with the de-intercalation of Li-ion, small but clear spectral changes were observed in Mn-L{sub 2,3} X-ray absorption near edge structure (XANES). The systematic ab initio multiplet calculations of Mn-L{sub 2,3} XANES revealed that the spectral changes in the experiment could not simply be ascribed to the change of the valency from Mn{sup 4+} to Mn{sup 5+} but can be explained well by the changes of local atomic structures around Mn{sup 4+} due to the Li de-intercalation. Our results suggest that the electronic state of oxygen should change during charging in Li{sub 2}MnO{sub 3}.

  4. Estimation of ground and excited state dipole moment of laser dyes C504T and C521T using solvatochromic shifts of absorption and fluorescence spectra.

    Science.gov (United States)

    Basavaraja, Jana; Suresh Kumar, H M; Inamdar, S R; Wari, M N

    2016-02-05

    The absorption and fluorescence spectra of laser dyes: coumarin 504T (C504T) and coumarin 521T (C521T) have been recorded at room temperature in a series of non-polar and polar solvents. The spectra of these dyes showed bathochromic shift with increasing in solvent polarity indicating the involvement of π→π⁎ transition. Kamlet-Taft and Catalan solvent parameters were used to analyze the effect of solvents on C504T and C521T molecules. The study reveals that both general solute-solvent interactions and specific interactions are operative in these two systems. The ground state dipole moment was estimated using Guggenheim's method and also by quantum mechanical calculations. The solvatochromic data were used to determine the excited state dipole moment (μ(e)). It is observed that dipole moment value of excited state (μ(e)) is higher than that of the ground state in both the laser dyes indicating that these dyes are more polar in nature in the excited state than in the ground state. Copyright © 2015. Published by Elsevier B.V.

  5. X-ray absorption spectroscopic studies of the blue copper site: Metal and ligand K-edge studies to probe the origin of the EPR hyperfine splitting in plastocyanin

    International Nuclear Information System (INIS)

    Shadle, S.E.; Penner-Hahn, J.E.; Schugar, H.J.; Hedman, B.; Hodgson, K.O.; Solomon, E.I.

    1993-01-01

    X-ray absorption spectra for the oxidized blue copper protein plastocyanin and several Cu(II) model complexes have been measured at both the Cu K-edge and the ligand K-edges (Cl and S) in order to elucidate the source of the small parallel hyperfine splitting in the EPR spectra of blue copper centers. Assignment and analysis of a feature in the Cu K-edge X-ray absorption spectrum at ∼8,987 eV as the Cu 1s → 4p + ligand-to-metal charge-transfer shakedown transition has allowed for quantitation of 4p mixing into the ground-state wave function as reflected in the 1s →3d (+4p) intensity at ∼8,979 eV. The results show that distorted tetrahedral (D 2d )CuCl 4 2- is characterized by z mixing, while plastocyanin has only Cu 4p xy mixing. Thus, the small parallel hyperfine splitting in the EPR spectra of D 2d CuCl 4 2- and of oxidized plastocyanin cannot be explained by 12% 4p z mixing into the 3d x 2 -y 2 orbital as had been previously postulated. Data collected at the Cl K-edge for CuCl 4 2- show that the intensity of the ligand pre-edge feature at ∼2,820 eV reflects the degree of covalency between the metal half-occupied orbital and the ligands. The data show that D 2d CuCl 4 2- is not unusually covalent. The source of the small parallel splitting in the EPR of D 2d CuCl 4 2- is discussed. Experiments at the S K-edge (∼2,470 eV) show that plastocyanin is characterized by a highly covalent Cu-S(cysteine) bond relative to the cupric-thiolate model complex [Cu(tet b)(o-SC 6 H 4 CO 2 )]·H 2 O. The XAS results demonstrate that the small parallel hyperfine splitting in the EPR spectra of blue copper sites reflects the high degree of covalency of the copper-thiolate bond. 34 refs., 12 figs., 3 tabs

  6. Diurnal Variation and Spatial Distribution Effects on Sulfur Speciation in Aerosol Samples as Assessed by X-Ray Absorption Near-Edge Structure (XANES

    Directory of Open Access Journals (Sweden)

    Siwatt Pongpiachan

    2012-01-01

    Full Text Available This paper focuses on providing new results relating to the impacts of Diurnal variation, Vertical distribution, and Emission source on sulfur K-edge XANES spectrum of aerosol samples. All aerosol samples used in the diurnal variation experiment were preserved using anoxic preservation stainless cylinders (APSCs and pressure-controlled glove boxes (PCGBs, which were specially designed to prevent oxidation of the sulfur states in PM10. Further investigation of sulfur K-edge XANES spectra revealed that PM10 samples were dominated by S(VI, even when preserved in anoxic conditions. The “Emission source effect” on the sulfur oxidation state of PM10 was examined by comparing sulfur K-edge XANES spectra collected from various emission sources in southern Thailand, while “Vertical distribution effects” on the sulfur oxidation state of PM10 were made with samples collected from three different altitudes from rooftops of the highest buildings in three major cities in Thailand. The analytical results have demonstrated that neither “Emission source” nor “Vertical distribution” appreciably contribute to the characteristic fingerprint of sulfur K-edge XANES spectrum in PM10.

  7. Climate Change and Genetic Structure of Leading Edge and Rear End Populations in a Northwards Shifting Marine Fish Species, the Corkwing Wrasse (Symphodus melops).

    Science.gov (United States)

    Knutsen, Halvor; Jorde, Per Erik; Gonzalez, Enrique Blanco; Robalo, Joana; Albretsen, Jon; Almada, Vitor

    2013-01-01

    One mechanism by which marine organisms may respond to climate shifts is range shifts. The corkwing wrasse (Symphodus melops) is a temperate fish species, inhabiting the coasts of Europe, that show strong indications of current as well as historical (ice-age) range shifts towards the north. Nine neutral microsatellite DNA markers were screened to study genetic signatures and spatial population structure over the entire geographic and thermal gradient of the species from Portugal to Norway. A major genetic break (F ST  = 0.159 average among pairs) was identified between Scandinavian and more southern populations, with a marked reduction (30% or more) in levels of genetic variability in Scandinavia. The break is probably related to bottleneck(s) associated with post-glacial colonization of the Scandinavian coasts, and indicates a lack of present gene flow across the North Sea. The lack of gene flow can most likely be attributed to the species' need for rocky substrate for nesting and a relatively short pelagic larval phase, limiting dispersal by ocean currents. These findings demonstrate that long-distance dispersal may be severely limited in the corkwing wrasse, and that successful range-shifts following present climate change may be problematic for this and other species with limited dispersal abilities, even in the seemingly continuous marine environment.

  8. X-ray absorption near-edge structure in alpha-quartz and stishovite: Ab initio calculation with core - hole interaction

    International Nuclear Information System (INIS)

    Mo, Shang-Di; Ching, W. Y.

    2001-01-01

    Ab initio calculation of the XANSE/ELNES spectra for α quartz and stishovite were carried out using a large-supercell approach that includes the electron - core - hole interaction. Excellent agreements with experimental spectra were obtained for Si - K, Si - L 2,3 , and O - K edges. The usual interpretation using orbital-resolved local density of states in the conduction band is unsatisfactory. [copyright] 2001 American Institute of Physics

  9. Temperature-dependent optical absorption of SrTiO3

    International Nuclear Information System (INIS)

    Kok, Dirk J.; Irmscher, Klaus; Naumann, Martin; Guguschev, Christo; Galazka, Zbigniew; Uecker, Reinhard

    2015-01-01

    The optical absorption edge and near infrared absorption of SrTiO 3 were measured at temperatures from 4 to 1703 K. The absorption edge decreases from 3.25 eV at 4 K to 1.8 eV at 1703 K and is extrapolated to approximately 1.2 eV at the melting point (2350 K). The transmission in the near IR decreases rapidly above 1400 K because of free carrier absorption and is about 50% of the room temperature value at 1673 K. The free carriers are generated by thermal excitation of electrons over the band gap and the formation of charged vacancies. The observed temperature-dependent infrared absorption can be well reproduced by a calculation based on simple models for the intrinsic free carrier concentration and the free carrier absorption coefficient. The measured red shift of the optical absorption edge and the rising free carrier absorption strongly narrow the spectral range of transmission and impede radiative heat transport through the crystal. These effects have to be considered in high temperature applications of SrTiO 3 -based devices, as the number of free carriers rises considerably, and in bulk crystal growth to avoid growth instabilities. Temperature dependent optical absorption edge of SrTiO 3 , measured, fitted, and extrapolated to the melting point. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Doped holes in edge-shared CuO.sub.2./sub. chains and the dynamic spectral weght transfer in X-ray absorption spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Hu, Z.; Drechsler, S.L.; Málek, Jiří; Rosner, H.; Neudert, R.; Knupper, M.; Golden, M. S.; Fink, J.; Karpinski, J.; Kaindl, G.

    2002-01-01

    Roč. 59, č. 1 (2002), s. 135-141 ISSN 0295-5075 Institutional research plan: CEZ:AV0Z1010914 Keywords : X-ray absorption spectra * strongly correlated electron systems * heavy fermions * many-electron systems Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.360, year: 2002

  11. [Effect of Long-Term Fertilization on Organic Nitrogen Functional Groups in Black Soil as Revealed by Synchrotron-Based X-Ray Absorption Near-Edge Structure Spectroscopy].

    Science.gov (United States)

    Li, Hui; Gao, Qiang; Wang, Shuai; Zhu, Ping; Zhang, Jin-jing; Zhao, Yi-dong

    2015-07-01

    Nitrogen (N) is a common limiting nutrient in crop production. The N content of soil has been used as an important soil fertility index. Organic N is the major form of N in soil. In most agricultural surface soils, more than 90% of total N occurs in organic forms. Therefore, understanding the compositional characteristics of soil organic N functional groups can provide the scientific basis for formulating the reasonable farmland management strategies. Synchrotron radiation soft X-ray absorption near-edge structure (N K-edge XANES) spectroscopy is the most powerful tool to characterize in situ organic N functional groups compositions in soil. However, to our most knowledge, no studies have been conducted to examine the organic N functional groups compositions of soil using N K-edge XANES spectroscopy under long-term fertilization practices. Based on a long-term field experiment (started in 1990) in a black soil (Gongzhuling, Northeast China), we investigated the differences in organic N functional groups compositions in bulk soil and clay-size soil fraction among fertilization patterns using synchrotron-based N K- edge XANES spectroscopy. Composite soil samples (0-20 cm) were collected in 2008. The present study included six treatments: farmland fallow (FALL), no-fertilization control (CK), chemical nitrogen, phosphorus, and potassium fertilization (NPK), NPK in combination with organic manure (NPKM), 1.5 times of NPKM (1.5 NPKM), and NPK in combination with maize straw (NPKS). The results showed that N K-edge XANES spectra of all the treatments under study exhibited characteristic absorption peaks in the ranges of 401.2-401.6 and 402.7-403.1 eV, which were assigned as amides/amine-N and pyrrole-N, respectively. These characteristic absorption peaks were more obvious in clay-size soil fraction than in bulk soil. The results obtained from the semi-quantitative analysis of N K-edge XANES spectra indicated that the relative proportion of amides/amine-N was the highest

  12. Molecular design of TiO2 for gigantic red shift via sublattice substitution.

    Science.gov (United States)

    Shao, Guosheng; Deng, Quanrong; Wan, Lin; Guo, Meilan; Xia, Xiaohong; Gao, Yun

    2010-11-01

    The effects of 3d transition metal doping in TiO2 phases have been simulated in detail. The results of modelling indicate that Mn has the biggest potential among 3d transition metals, for the reduction of energy gap and the introduction of effective intermediate bands to allow multi-band optical absorption. On the basis of theoretical formulation, we have incorporated considerable amount of Mn in nano-crystalline TiO2 materials. Mn doped samples demonstrate significant red shift in the optical absorption edge, with a secondary absorption edge corresponding to theoretically predicted intermediate bands/states. The gigantic red shift achievable in Mn-doped TiO2 is expected to extend the useful TiO2 functionalities well beyond the UV threshold via the optical absorption of both visible and infrared photon irradiance.

  13. In situ analysis of the Zn(S,O) buffer layer preparation for chalcopyrite solar cells by Zn L-edge X-ray absorption spectroscopy.

    Science.gov (United States)

    Lauermann, Iver; Kropp, Timo; Vottier, Damien; Ennaoui, Ahmed; Eberhardt, Wolfgang; Aziz, Emad F

    2009-02-23

    Bridging the gap between high-vacuum soft X-ray absorption spectroscopy and real systems under ambient conditions probes chemical reactions in situ during deposition and annealing processes. The origin of highly efficient buffer layers in Zn(S,O) is the complex formation between Zn(2+) and the S=C group of thiourea (see schematic), which allows ligand-to-metal and metal-to-ligand charge transfer (LMCT and MLCT).

  14. Determination of the photoeffect cross section and the K- absorption edge energy of Dy, Ta, Pt and Au atoms using Bremsstrahlung

    International Nuclear Information System (INIS)

    Garcia-Alvarez, J. A.; Lopez-Pino, N.; Diaz Rizo, O.; Corrales, Y.; Padilla-Cabal, F.; Perez-Liva, M.; D' Alessandro, K.; Maidana, N. L.

    2011-01-01

    An experiment to determine the K-shell photoelectric cross-section (CS) of Dy, Ta, Pt and Au atoms was implemented at the Nuclear Analytical Laboratory (LAN) of the InSTEC. Bremsstrahlung photons, produced by 90 Sr- 90 Y beta particles hitting a thin Ni converter, were used to irradiate the foils target of the elements under study. A HPGe detector, coupled to standard nuclear instrumentation, collected the incident and transmitted spectra. A sharp decrease in intensity at the K-shell binding energy was observed in the transmitted spectra. The photon beam divergence effects were corrected with a calibration curve calculated by means of Monte Carlo simulations (MCNPX 2.6). In order to establish accurately the CS at the K-edge energy, the obtained data was processed by two methods: fitting the total CS to a sigmoidal function, as well as the CS branches around the K edge to the empirical law σ=(A/E) n . The results were compared with experimental and theoretical values showing the best agreement when the thinner foils were used. (Author)

  15. Absorption measurement s in InSe single crystal under an applied electric field

    International Nuclear Information System (INIS)

    Ates, A.; Guerbulak, B.; Guer, E.; Yildirim, T.; Yildirim, M.

    2002-01-01

    InSe single crystal was grown by Bridgman-Stockberger method. Electric field effect on the absorption measurements have been investigated as a function of temperature in InSe single crystal. The absorption edge shifted towards longer wavelengths and decreased of intensity in absorption spectra under an electric field. Using absorption measurements, Urbach energy was calculated under an electric field. Applied electric field caused a increasing in the Urbach energy. At 10 K and 320 K, the first exciton energies were calculated as 1.350 and 1.311 eV for zero voltage and 1.334 and 1.301 eV for electric field respectively

  16. Fe K-Edge X-ray absorption near-edge spectroscopy (XANES) and X-ray diffraction (XRD) analyses of LiFePO4 and its base materials

    Science.gov (United States)

    Latif, C.; Negara, V. S. I.; Wongtepa, W.; Thamatkeng, P.; Zainuri, M.; Pratapa, S.

    2018-03-01

    XANES analysis has been performed with the aim of knowing the Fe oxidation state in a synthesized LiFePO4 and its base materials. XANES measurements were performed at SLRI on energy around Fe K-edge. An XRD analysis has also been performed with the aim of knowing the phase composition, lattice parameters and crystallite size of the LiFePO4 as well as the base materials. From the XRD analysis, it was found that the dominating phase in the iron sand sample was Fe3O4 and the only phase found after calcination was LiFePO4. The latter phase exhibited crystallite size of 100 nm and lattice parameters a = 10.169916 Å, b = 5.919674 Å, c = 4.627893 Å. Qualitative analysis of XANES data revealed that the oxidation number of Fe in the sample before calcination was greater than that after calcination and Fe in the natural iron sand, indicated by the E0 values of 7129.2 eV, 7120.6 eV and 7124.4 eV respectively.

  17. Theory and X-ray Absorption Spectroscopy for Aluminum Coordination Complexes – Al K-Edge Studies of Charge and Bonding in (BDI)Al, (BDI)AlR2, and (BDI)AlX2 Complexes.

    Science.gov (United States)

    Altman, Alison B; Pemmaraju, C D; Camp, Clément; Arnold, John; Minasian, Stefan G; Prendergast, David; Shuh, David K; Tyliszczak, Tolek

    2015-08-19

    Polarized aluminum K-edge X-ray absorption near edge structure (XANES) spectroscopy and first-principles calculations were used to probe electronic structure in a series of (BDI)Al, (BDI)AlX2, and (BDI)AlR2 coordination compounds (X = F, Cl, I; R = H, Me; BDI = 2,6-diisopropylphenyl-β-diketiminate). Spectral interpretations were guided by examination of the calculated transition energies and polarization-dependent oscillator strengths, which agreed well with the XANES spectroscopy measurements. Pre-edge features were assigned to transitions associated with the Al 3p orbitals involved in metal-ligand bonding. Qualitative trends in Al 1s core energy and valence orbital occupation were established through a systematic comparison of excited states derived from Al 3p orbitals with similar symmetries in a molecular orbital framework. These trends suggested that the higher transition energies observed for (BDI)AlX2 systems with more electronegative X(1-) ligands could be ascribed to a decrease in electron density around the aluminum atom, which causes an increase in the attractive potential of the Al nucleus and concomitant increase in the binding energy of the Al 1s core orbitals. For (BDI)Al and (BDI)AlH2 the experimental Al K-edge XANES spectra and spectra calculated using the eXcited electron and Core-Hole (XCH) approach had nearly identical energies for transitions to final state orbitals of similar composition and symmetry. These results implied that the charge distributions about the aluminum atoms in (BDI)Al and (BDI)AlH2 are similar relative to the (BDI)AlX2 and (BDI)AlMe2 compounds, despite having different formal oxidation states of +1 and +3, respectively. However, (BDI)Al was unique in that it exhibited a low-energy feature that was attributed to transitions into a low-lying p-orbital of b1 symmetry that is localized on Al and orthogonal to the (BDI)Al plane. The presence of this low-energy unoccupied molecular orbital on electron-rich (BDI)Al distinguishes

  18. Using solution- and solid-state S K-edge X-ray absorption spectroscopy with density functional theory to evaluate M-S bonding for MS4(2-) (M = Cr, Mo, W) dianions.

    Science.gov (United States)

    Olson, Angela C; Keith, Jason M; Batista, Enrique R; Boland, Kevin S; Daly, Scott R; Kozimor, Stosh A; MacInnes, Molly M; Martin, Richard L; Scott, Brian L

    2014-12-14

    Herein, we have evaluated relative changes in M-S electronic structure and orbital mixing in Group 6 MS4(2-) dianions using solid- and solution-phase S K-edge X-ray absorption spectroscopy (XAS; M = Mo, W), as well as density functional theory (DFT; M = Cr, Mo, W) and time-dependent density functional theory (TDDFT) calculations. To facilitate comparison with solution measurements (conducted in acetonitrile), theoretical models included gas-phase calculations as well as those that incorporated an acetonitrile dielectric, the latter of which provided better agreement with experiment. Two pre-edge features arising from S 1s → e* and t electron excitations were observed in the S K-edge XAS spectra and were reasonably assigned as (1)A1 → (1)T2 transitions. For MoS4(2-), both solution-phase pre-edge peak intensities were consistent with results from the solid-state spectra. For WS4(2-), solution- and solid-state pre-edge peak intensities for transitions involving e* were equivalent, while transitions involving the t orbitals were less intense in solution. Experimental and computational results have been presented in comparison to recent analyses of MO4(2-) dianions, which allowed M-S and M-O orbital mixing to be evaluated as the principle quantum number (n) for the metal valence d orbitals increased (3d, 4d, 5d). Overall, the M-E (E = O, S) analyses revealed distinct trends in orbital mixing. For example, as the Group 6 triad was descended, e* (π*) orbital mixing remained constant in the M-S bonds, but increased appreciably for M-O interactions. For the t orbitals (σ* + π*), mixing decreased slightly for M-S bonding and increased only slightly for the M-O interactions. These results suggested that the metal and ligand valence orbital energies and radial extensions delicately influenced the orbital compositions for isoelectronic ME4(2-) (E = O, S) dianions.

  19. Surface and in-depth characterization of lithium-ion battery cathodes at different cycle states using confocal micro-X-ray fluorescence-X-ray absorption near edge structure analysis

    International Nuclear Information System (INIS)

    Menzel, Magnus; Schlifke, Annalena; Falk, Mareike; Janek, Jürgen; Fröba, Michael; Fittschen, Ursula Elisabeth Adriane

    2013-01-01

    The cathode material LiNi 0.5 Mn 1.5 O 4 for lithium-ion batteries has been studied with confocal micro-X-ray fluorescence (CMXRF) combined with X-ray absorption near edge structure (XANES) at the Mn-K edge and the Ni-K edge. This technique allows for a non-destructive, spatially resolved (x, y and z) investigation of the oxidation states of surface areas and to some extent of deeper layers of the electrode. Until now CMXRF-XANES has been applied to a limited number of applications, mainly geo-science. Here, we introduce this technique to material science applications and show its performance to study a part of a working system. A novel mesoporous LiNi 0.5 Mn 1.5 O 4 material was cycled (charged and discharged) to investigate the effects on the oxidation states at the cathode/electrolyte interface. With this approach the degradation of Mn 3+ to Mn 4+ only observable at the surface of the electrode could be directly shown. The spatially resolved non-destructive analysis provides knowledge helpful for further understanding of deterioration and the development of high voltage battery materials, because of its nondestructive nature it will be also suitable to monitor processes during battery cycling. - Highlights: • The potential of confocal micro-XRF-XANES for spatial resolved species analysis in a part of a working system is shown. • The spatial resolution enables differentiation of the oxidized interface from deeper layers. • With the analytical technique confocal micro-XRF-XANES 3D in-situ analyses of working systems are feasible. • The multidimensional and nondestructive analysis of Li-ion battery cathodes is shown. • The analysis will allow for a deeper understanding of processes at interfaces in battery science and others

  20. Surface and in-depth characterization of lithium-ion battery cathodes at different cycle states using confocal micro-X-ray fluorescence-X-ray absorption near edge structure analysis

    Energy Technology Data Exchange (ETDEWEB)

    Menzel, Magnus; Schlifke, Annalena [Institut für Anorganische und Angewandte Chemie, Universität Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg (Germany); Falk, Mareike; Janek, Jürgen [Physikalisch-Chemisches Institut, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 58, 35392 Gießen (Germany); Fröba, Michael, E-mail: froeba@chemie.uni-hamburg.de [Institut für Anorganische und Angewandte Chemie, Universität Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg (Germany); Fittschen, Ursula Elisabeth Adriane, E-mail: ursula.fittschen@chemie.uni-hamburg.de [Institut für Anorganische und Angewandte Chemie, Universität Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg (Germany)

    2013-07-01

    The cathode material LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} for lithium-ion batteries has been studied with confocal micro-X-ray fluorescence (CMXRF) combined with X-ray absorption near edge structure (XANES) at the Mn-K edge and the Ni-K edge. This technique allows for a non-destructive, spatially resolved (x, y and z) investigation of the oxidation states of surface areas and to some extent of deeper layers of the electrode. Until now CMXRF-XANES has been applied to a limited number of applications, mainly geo-science. Here, we introduce this technique to material science applications and show its performance to study a part of a working system. A novel mesoporous LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} material was cycled (charged and discharged) to investigate the effects on the oxidation states at the cathode/electrolyte interface. With this approach the degradation of Mn{sup 3+} to Mn{sup 4+} only observable at the surface of the electrode could be directly shown. The spatially resolved non-destructive analysis provides knowledge helpful for further understanding of deterioration and the development of high voltage battery materials, because of its nondestructive nature it will be also suitable to monitor processes during battery cycling. - Highlights: • The potential of confocal micro-XRF-XANES for spatial resolved species analysis in a part of a working system is shown. • The spatial resolution enables differentiation of the oxidized interface from deeper layers. • With the analytical technique confocal micro-XRF-XANES 3D in-situ analyses of working systems are feasible. • The multidimensional and nondestructive analysis of Li-ion battery cathodes is shown. • The analysis will allow for a deeper understanding of processes at interfaces in battery science and others.

  1. Excitation of half-integer up-shifted decay channel and quasi-mode in plasma edge for high power electron Bernstein wave heating scenario

    Directory of Open Access Journals (Sweden)

    M. Ali Asgarian

    2018-04-01

    Full Text Available Electron Bernstein waves (EBW consist of promising tools in driving localized off-axis current needed for sustained operation as well as effective selective heating scenarios in advanced over dense fusion plasmas like spherical tori and stellarators by applying high power radio frequency waves within the range of Megawatts. Here some serious non-linear effects like parametric decay modes are highly expect-able which have been extensively studied theoretically and experimentally. In general, the decay of an EBW depends on the ratio of the incident frequency and electron cyclotron frequency. At ratios less than two, parametric decay leads to a lower hybrid wave (or an ion Bernstein wave and EBWs at a lower frequency. For ratios more than two, the daughter waves constitute either an electron cyclotron quasi-mode and another EBW or an ion wave and EBW. However, in contrast with these decay patterns, the excitation of an unusual up-shifted frequency decay channel for the ratio less than two is demonstrated in this study which is totally different as to its generation and persistence. It is shown that this mode varies from the conventional parametric decay channels which necessarily satisfy the matching conditions in frequency and wave-vector. Moreover, the excitation of some less-known local non-propagating quasi-modes (virtual modes through weak-turbulence theory and their contributions to energy leakage from conversion process leading the reduction in conversion efficiency is assessed.

  2. Excitation of half-integer up-shifted decay channel and quasi-mode in plasma edge for high power electron Bernstein wave heating scenario

    Science.gov (United States)

    Ali Asgarian, M.; Abbasi, M.

    2018-04-01

    Electron Bernstein waves (EBW) consist of promising tools in driving localized off-axis current needed for sustained operation as well as effective selective heating scenarios in advanced over dense fusion plasmas like spherical tori and stellarators by applying high power radio frequency waves within the range of Megawatts. Here some serious non-linear effects like parametric decay modes are highly expect-able which have been extensively studied theoretically and experimentally. In general, the decay of an EBW depends on the ratio of the incident frequency and electron cyclotron frequency. At ratios less than two, parametric decay leads to a lower hybrid wave (or an ion Bernstein wave) and EBWs at a lower frequency. For ratios more than two, the daughter waves constitute either an electron cyclotron quasi-mode and another EBW or an ion wave and EBW. However, in contrast with these decay patterns, the excitation of an unusual up-shifted frequency decay channel for the ratio less than two is demonstrated in this study which is totally different as to its generation and persistence. It is shown that this mode varies from the conventional parametric decay channels which necessarily satisfy the matching conditions in frequency and wave-vector. Moreover, the excitation of some less-known local non-propagating quasi-modes (virtual modes) through weak-turbulence theory and their contributions to energy leakage from conversion process leading the reduction in conversion efficiency is assessed.

  3. Theoretical and experimental study of high-magnetic-field XMCD spectra at the L2,3 absorption edges of mixed-valence rare-earth compounds

    International Nuclear Information System (INIS)

    Kotani, Akio; Matsuda, Yasuhiro H; Nojiri, Hiroyuki

    2009-01-01

    X-ray magnetic circular dichroism(XMCD) spectra at the L 2,3 edges of mixed-valence rare-earth compounds in high magnetic fields are studied both theoretically and experimentally. The theoretical study is based on a new framework proposed recently by Kotani. The Zeeman splitting of 4f states, the mixed-valence character of 4f states, and the 4f-5d exchange interaction are incorporated into a single impurity Anderson model. New XMCD experiments in high magnetic fields up to 40 T are carried out for the mixed-valence compounds EuNi 2 (Si 0.18 Ge 0.82 ) 2 and YbInCu 4 by using a miniature pulsed magnet, which was developed recently by Matsuda et al. The XMCD data are taken at 5 K by transmission measurements for incident X-rays with ± helicities at BL39XU in SPring-8. After giving a survey on recent developments in the theory of XMCD spectra for mixed-valence Ce and Yb compounds, we calculate the XMCD spectra of YbInCu 4 at the field-induced valence transition around 32 T by applying the recent theoretical framework and by newly introducing at 32 T a discontinuous change in the Yb 4f level and that in the hybridization strength between the Yb 4f and conduction electrons. The calculated results are compared with the experimental ones.

  4. Detection of metal stress in boreal forest species using the 0.67-micron chlorophyll absorption band

    Science.gov (United States)

    Singhroy, Vernon H.; Kruse, Fred A.

    1991-01-01

    Several recent studies have shown that a shift of the red-edge inflection near 0.70 micron in vegetation reflectance spectra is an indicator of metal stress, partially attributable to changes in chlorophyll concentration. This 'red-edge shift', however, is difficult to detect and has been reported both toward longer (red) and shorter (blue) wavelengths. Our work demonstrates that direct measurement of the depth and width of the chlorophyll absorption band at 0.67 micron using digital feature extraction and absorption band characterization procedures developed for the analysis of mineral spectra is a more consistent indicator of metal stress. Additionally, the magnitude of these parameters is generally greater than that of the red edge shift and thus should be more amenable to detection and mapping using field and aircraft spectrometers.

  5. Randic and Schultz molecular topological indices and their correlation with some X-ray absorption parameters

    International Nuclear Information System (INIS)

    Khatri, Sunil; Kekre, Pravin A; Mishra, Ashutosh

    2016-01-01

    The properties of a molecular system are affected by the topology of molecule. Therefore many studies have been made where the various physic-chemical properties are correlated with the topological indices. These studies have shown a very good correlation demonstrating the utility of the graph theoretical approach. It is, therefore, very natural to expect that the various physical properties obtained by the X-ray absorption spectra may also show correlation with the topological indices. Some complexes were used to establish correlation between topological indices and some X-ray absorption parameters like chemical shift. The chemical shift is on the higher energy side of the metal edge in these complexes. The result obtained in these studies shows that the topological indices of organic molecule acting as a legands can be used for estimating edge shift theoretically. (paper)

  6. Arsenate reduction and methylation in the cells of Trichoderma asperellum SM-12F1, Penicillium janthinellum SM-12F4, and Fusarium oxysporum CZ-8F1 investigated with X-ray absorption near edge structure

    International Nuclear Information System (INIS)

    Su, S.M.; Zeng, X.B.; Li, L.F.; Duan, R.; Bai, L.Y.; Li, A.G.; Wang, J.; Jiang, S.

    2012-01-01

    Highlights: ► Three fungal strains are capable of As(V) reduction and methylation. ► As(V) reduction might be more easily processed than the methylation in fungal cells. ► As sequestration and speciation transformation might be the detoxification processes. - Abstract: Synchrotron radiation-based X-ray absorption near edge structure (XANES) was introduced to directly analysis chemical species of arsenic (As) in the cells of Trichoderma asperellum SM-12F1, Penicillium janthinellum SM-12F4, and Fusarium oxysporum CZ-8F1 capable of As accumulation and volatilisation. After exposure to As(V) of 500 mg L −1 for 15 days, a total of 60.5% and 65.3% of the accumulated As in the cells of T. asperellum SM-12F1 and P. janthinellum SM-12F4, respectively, was As(III), followed by 31.3% and 32.4% DMA (dimethylarsinic acid), 8.3% and 2.3% MMA (monomethylarsonic acid), respectively. However, for F. oxysporum CZ-8F1, 54.5% of the accumulated As was As(III), followed by 37.8% MMA and 7.7% As(V). The reduction and methylation of As(V) formed As(III), MMA, and DMA as the primacy products, and the reduction of As(V) might be more easily processed than the methylation. These results will help to understanding the mechanisms of As detoxification and its future application in bioremediation.

  7. Cluster model calculation for X-ray magnetic circular dichroism at rare-earth (R) L sub 2 sub , sub 3 absorption edges in R sub 2 Fe sub 1 sub 4 B

    CERN Document Server

    Asakura, K; Harada, I; Ogasawara, H; Fukui, K; Kotani, A

    2002-01-01

    X-ray magnetic circular dichroism (MCD) at the L sub 2 sub , sub 3 absorption edges for the entire series of rare-earth (RE) elements in R sub 2 Fe sub 1 sub 4 B (R=RE) is studied based on a cluster model including 10 RE and 16 Fe atoms. The cluster model takes into account band effects of RE 5d states, to which the electric dipole transition occurs from the core 2p states, as well as spin polarization of the 5d states due to the interatomic hybridization with the spin polarized Fe 3d states. We also take into account spin and orbital polarization of the 5d states due to the 5d-4f intra-atomic exchange interaction, and the 2p to 4f quadrupole transition. The calculated results are in satisfactory agreement with experimental ones, suggesting that the cluster model calculation provides a new method to calculate quantitatively MCD spectra of RE systems with complicated atomic arrangements. (author)

  8. Chemical kinetics of Cs species in an alkali-activated municipal solid waste incineration fly ash and pyrophyllite-based system using Cs K-edge in situ X-ray absorption fine structure analysis

    Science.gov (United States)

    Shiota, Kenji; Nakamura, Takafumi; Takaoka, Masaki; Nitta, Kiyofumi; Oshita, Kazuyuki; Fujimori, Takashi; Ina, Toshiaki

    2017-05-01

    We conducted in situ X-ray absorption fine structure (in situ XAFS) analysis at the Cs K-edge to investigate the chemical kinetics of Cs species during reaction in an alkali-activated municipal solid waste incineration fly ash (MSWIFA) and pyrophyllite-based system. Understanding the kinetics of Cs is essential to the design of appropriate conditions for Cs stabilization. In situ XAFS analysis of four pastes, prepared from NaOHaq, sodium silicate solution, pyrophyllite, and MSWIFA with the addition of CsCl, was conducted in custom-built reaction cells at four curing temperatures (room temperature, 60 °C, 80 °C, 105 °C) for approximately 34 h. The results indicated that the change in Cs species during reaction at room temperature was small, while changes at higher temperatures were faster and more extreme, with the fastest conversion to pollucite occurring at 105 °C. Further analysis using a leaching test and a simple reaction model for Cs species during reaction showed that the pollucite formation rate was dependent on the curing temperature and had a significant negative correlation with Cs leaching. The activation energy of pollucite formation was estimated to be 31.5 kJ/mol. These results revealed that an important change in the chemical state of Cs occurs during reaction in the system.

  9. Edge Matters

    DEFF Research Database (Denmark)

    Earon, Ofri

    2013-01-01

    of this container is to separate inside from outside and to protect and provide privacy, psychological as well as physical (Venturi, 1966). But, if dwelling phenomenon takes place both inside and outside the private house – why is the urban house an enclosed box? What is the differentiation between inside...... and outside the contemporary urban house? And what is the interplay between them? The research argues for re-thinking the edge zone between inside and outside the urban house. Therefore, although, residential buildings in the city are the objects of study, the focal point here is the edge zone along...... the building. The research explores and develops the architectural characteristics of correlations between the resident, the singular unit, the building and the given location at the edge zone. It approaches the edge zone of the urban house as a platform for dynamic interactions between these behaviours...

  10. 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

  11. Pressure shift coefficient measurements in an RF discharge for Ar 4s[3/2]2—5p[3/2]3 transition with the help of diodelaser absorption spectroscopy

    Science.gov (United States)

    Chernyshov, A. K.; Mikheyev, P. A.; Lunev, N. N.; Azyazov, V. N.

    2018-04-01

    Optically pumped all-rare-gas laser (OPRGL) with unique properties were recently proposed with a possibility to obtain the laser power on the order of hundreds of Watts from a cubic centimeter. To provide high laser efficiency, the pumping radiation has to match the absorption spectrum of the rare gas metastables. To meet this condition a reliable diagnostics of the key parameters of the active medium is required and knowledge of the broadening and shift coefficients for corresponding transitions of rare gases is necessary. In this paper, the diode-laser absorption spectroscopy was employed to determine the pressure shift coefficient for 811.5 nm Ar line. The value of obtained coefficient in pure argon reduced to 300 K is -(2.1 ± 0.1) × 10-10 s-1cm3. In the course of the study the pressure broadening coefficient was also evaluated and found to be (2.4 ± 0.5) × 10-10 s-1cm3.

  12. Robust time-shifted spoke pulse design in the presence of large B0 variations with simultaneous reduction of through-plane dephasing, B1+ effects, and the specific absorption rate using parallel transmission.

    Science.gov (United States)

    Guérin, Bastien; Stockmann, Jason P; Baboli, Mehran; Torrado-Carvajal, Angel; Stenger, Andrew V; Wald, Lawrence L

    2016-08-01

    To design parallel transmission spokes pulses with time-shifted profiles for joint mitigation of intensity variations due to B1+ effects, signal loss due to through-plane dephasing, and the specific absorption rate (SAR) at 7T. We derived a slice-averaged small tip angle (SA-STA) approximation of the magnetization signal at echo time that depends on the B1+ transmit profiles, the through-slice B0 gradient and the amplitude and time-shifts of the spoke waveforms. We minimize a magnitude least-squares objective based on this signal equation using a fast interior-point approach with analytical expressions of the Jacobian and Hessian. Our algorithm runs in less than three minutes for the design of two-spoke pulses subject to hundreds of local SAR constraints. On a B0/B1+ head phantom, joint optimization of the channel-dependent time-shifts and spoke amplitudes allowed signal recovery in high-B0 regions at no increase of SAR. Although the method creates uniform magnetization profiles (ie, uniform intensity), the flip angle varies across the image, which makes it ill-suited to T1-weighted applications. The SA-STA approach presented in this study is best suited to T2*-weighted applications with long echo times that require signal recovery around high B0 regions. Magn Reson Med 76:540-554, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

  13. Water absorption lines, 931-961 nm - Selected intensities, N2-collision-broadening coefficients, self-broadening coefficients, and pressure shifts in air

    Science.gov (United States)

    Giver, L. P.; Gentry, B.; Schwemmer, G.; Wilkerson, T. D.

    1982-01-01

    Intensities were measured for 97 lines of H2O vapor between 932 and 961 nm. The lines were selected for their potential usefulness for remote laser measurements of H2O vapor in the earth's atmosphere. The spectra were obtained with several different H2O vapor abundances and N2 broadening gas pressures; the spectral resolution was 0.046/cm FWHM. Measured H2O line intensities range from 7 x 10 to the -25th to 7 x 10 to the -22nd/cm per (molecules/sq cm). H2O self-broadening coefficients were measured for 13 of these strongest lines; the mean value was 0.5/cm per atm. N2-collision-broadening coefficients were measured for 73 lines, and the average was 0.11 cm per atm HWHM. Pressure shifts in air were determined for a sample of six lines between 948 and 950 nm; these lines shift to lower frequency by an amount comparable to 0.1 of the collision-broadened widths measured in air or N2. The measured intensities of many lines of 300-000 band are much larger than expected from prior computations, in some cases by over an order of magnitude. Coriolis interactions with the stronger 201-000 band appear to be the primary cause of the enhancement of these line intensities.

  14. Arsenate reduction and methylation in the cells of Trichoderma asperellum SM-12F1, Penicillium janthinellum SM-12F4, and Fusarium oxysporum CZ-8F1 investigated with X-ray absorption near edge structure

    Energy Technology Data Exchange (ETDEWEB)

    Su, S.M., E-mail: shimingsu@163.com [Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-Environment, Ministry of Agriculture, Beijing (China); Zeng, X.B., E-mail: zengxb@ieda.org.cn [Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-Environment, Ministry of Agriculture, Beijing (China); Li, L.F.; Duan, R.; Bai, L.Y. [Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-Environment, Ministry of Agriculture, Beijing (China); Li, A.G.; Wang, J.; Jiang, S. [Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai (China)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer Three fungal strains are capable of As(V) reduction and methylation. Black-Right-Pointing-Pointer As(V) reduction might be more easily processed than the methylation in fungal cells. Black-Right-Pointing-Pointer As sequestration and speciation transformation might be the detoxification processes. - Abstract: Synchrotron radiation-based X-ray absorption near edge structure (XANES) was introduced to directly analysis chemical species of arsenic (As) in the cells of Trichoderma asperellum SM-12F1, Penicillium janthinellum SM-12F4, and Fusarium oxysporum CZ-8F1 capable of As accumulation and volatilisation. After exposure to As(V) of 500 mg L{sup -1} for 15 days, a total of 60.5% and 65.3% of the accumulated As in the cells of T. asperellum SM-12F1 and P. janthinellum SM-12F4, respectively, was As(III), followed by 31.3% and 32.4% DMA (dimethylarsinic acid), 8.3% and 2.3% MMA (monomethylarsonic acid), respectively. However, for F. oxysporum CZ-8F1, 54.5% of the accumulated As was As(III), followed by 37.8% MMA and 7.7% As(V). The reduction and methylation of As(V) formed As(III), MMA, and DMA as the primacy products, and the reduction of As(V) might be more easily processed than the methylation. These results will help to understanding the mechanisms of As detoxification and its future application in bioremediation.

  15. Thin Film Structure of Tetraceno(2,3-B)thiophene Characterized By Grazing Incidence X-Ray Scattering And Near-Edge X-Ray Absorption Fine Structure Analysis

    International Nuclear Information System (INIS)

    Yuan, Q.; Mannsfeld, S.C.B.; Tang, M.L.; Toney, M.F.; Luening, J.; Bao, Z.A.

    2008-01-01

    Understanding the structure-property relationship for organic semiconductors is crucial in rational molecular design and organic thin film process control. Charge carrier transport in organic field-effect transistors predominantly occurs in a few semiconductor layers close to the interface in contact with the dielectric layer, and the transport properties depend sensitively on the precise molecular packing. Therefore, a better understanding of the impact of molecular packing and thin film morphology in the first few monolayers above the dielectric layer on charge transport is needed to improve the transistor performance. In this Article, we show that the detailed molecular packing in thin organic semiconductor films can be solved through a combination of grazing incidence X-ray diffraction (GIXD), near-edge X-ray absorption spectra fine structure (NEXAFS) spectroscopy, energy minimization packing calculations, and structure refinement of the diffraction data. We solve the thin film structure for 2 and 20 nm thick films of tetraceno(2,3-b)thiophene and detect only a single phase for these thicknesses. The GIXD yields accurate unit cell dimensions, while the precise molecular arrangement in the unit cell was found from the energy minimization and structure refinement; the NEXAFS yields a consistent molecular tilt. For the 20 nm film, the unit cell is triclinic with a = 5.96 A, b = 7.71 A, c = 15.16 A, alpha = 97.30 degrees, beta = 95.63 degrees, gamma = 90 degrees; there are two molecules per unit cell with herringbone packing (49-59 degree angle) and tilted about 7 degrees from the substrate normal. The thin film structure is significantly different from the bulk single-crystal structure, indicating the importance of characterizing thin film to correlate with thin film device performance. The results are compared to the corresponding data for the chemically similar and widely used pentacene. Possible effects of the observed thin film structure and morphology on

  16. Electric field influence on exciton absorption of Er doped and undoped InSe single crystals

    International Nuclear Information System (INIS)

    Guerbulak, B; Kundakci, M; Ates, A; Yildirim, M

    2007-01-01

    Undoped InSe and Er doped InSe (InSe:Er) single crystals were grown by using the Stockbarger method. Ingots had no cracks and voids on the surface. The absorption measurements were carried out in InSe and InSe:Er samples for U=0 and U=30 V in the temperature range 10-320 K with a step of 10 K. Electric field effects on excitons are observed in InSe and InSe:Er single crystals. The absorption edge shifted towards longer wavelengths and decreased intensity in absorption spectra under an electric field E≅5.9 kV cm -1 . The applied electric field caused a shifting and a decreasing of intensity in the absorption spectra. The shifting of the absorption edge can be explained on the basis of the Franz-Keldysh effect (FKE) or thermal heating of the sample under the electric field. At 10 and 320 K, the first exciton energies for InSe were calculated as 1.336 and 1.291 eV for zero voltage and 1.331 and 1.280 eV for electric field and InSe:Er as 1.329 and 1.251 eV for zero voltage and 1.318 and 1.248 eV for electric field, respectively

  17. Time-Resolved K-shell Photoabsorption Edge Measurement in a Strongly Coupled Matter Driven by Laser-converted Radiation

    Science.gov (United States)

    Zhao, Yang; Yang, Jia-Min; Zhang, Ji-Yan; Yang, Guo-Hong; Xiong, Gang; Wei, Min-Xi; Song, Tian-Ming; Zhang, Zhi-Yu

    2013-06-01

    A time-resolved K edge absorption measurement of warm dense KCl was performed on Shenguang II laser facility. The x-ray radiation driven shocks were adopted to take colliding shocks compression. By using Dog bone hohlraum the CH/KCl/CH sample was shielded from the laser hitting point to suppress the M band preheating and enhance the compressibility. Thus, an unexplored and extreme region of the plasma state with the maximum 5 times solid density and temperature lower than 3 eV (with coupling constant Γii around 100) was first obtained. The photoabsorption spectra of chlorine near the K-shell edge have been measured with a crystal spectrometer using a short x-ray backlighter. The K edge red shift up to 11.7 eV and broadening of 15.2 eV were obtained for the maximum compression. The electron temperature, inferred by Fermi-Dirac fit of the measured K-edge broadening, was consistent with the hydrodynamic predictions. The comparison of the K edge shift with a plasma model, in which the ionization effect, continuum lowering and partial degeneracy are considered, shows that more improvements are desired to describe in details the variation of K edge shift. This work might extend future study of WDM in extreme conditions of high compression.

  18. Defects and the optical absorption in nanocrystalline ZnO

    International Nuclear Information System (INIS)

    Dutta, Sreetama; Chattopadhyay, Sanjay; Sutradhar, Manas; Sarkar, Anindya; Chakrabarti, Mahuya; Sanyal, Dirtha; Jana, Debnarayan

    2007-01-01

    The correlation between the structural and optical properties of mechanically milled high purity ZnO powder is reported in the present work. Reduction of average grain size and enhancement of strain as a result of milling have been estimated from the broadening of x-ray powder diffraction patterns. After milling, the optical bandgap, revealed from absorption spectroscopy, has been red-shifted and the width of the localized states, calculated from the analysis of the Urbach tail below the absorption edge, has been extended more and more into the bandgap. Moreover, the band tailing parameter is seen to vary exponentially with the inverse of the grain size. Finally, the positron annihilation technique has been employed to identify the nature of defects present (or generated due to milling) in the system and thereby to correlate the defect mediated modification of optical absorption in ZnO

  19. Defects and the optical absorption in nanocrystalline ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Sreetama [Department of Physics, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Chattopadhyay, Sanjay [Department of Physics, Taki Government College, Taki 743429 (India); Sutradhar, Manas [Department of Chemistry, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Sarkar, Anindya [Department of Physics, Bangabasi Morning College, 19 Rajkumar Chakraborty Sarani, Kolkata 700 009 (India); Chakrabarti, Mahuya [Variable Energy Cyclotron Centre, 1/AF, Bidhannagar, Kolkata 700 064 (India); Sanyal, Dirtha [Variable Energy Cyclotron Centre, 1/AF, Bidhannagar, Kolkata 700 064 (India); Jana, Debnarayan [Department of Physics, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009 (India)

    2007-06-13

    The correlation between the structural and optical properties of mechanically milled high purity ZnO powder is reported in the present work. Reduction of average grain size and enhancement of strain as a result of milling have been estimated from the broadening of x-ray powder diffraction patterns. After milling, the optical bandgap, revealed from absorption spectroscopy, has been red-shifted and the width of the localized states, calculated from the analysis of the Urbach tail below the absorption edge, has been extended more and more into the bandgap. Moreover, the band tailing parameter is seen to vary exponentially with the inverse of the grain size. Finally, the positron annihilation technique has been employed to identify the nature of defects present (or generated due to milling) in the system and thereby to correlate the defect mediated modification of optical absorption in ZnO.

  20. Edge Detection,

    Science.gov (United States)

    1985-09-01

    PROJECT. T ASK0 Artificial Inteligence Laboratory AREA It WORK UNIT NUMBERS V 545 Technology Square ( Cambridge, HA 02139 I I* CONTOOL1LIN@4OFFICE NAME...ARD-A1t62 62 EDGE DETECTION(U) NASSACNUSETTS INST OF TECH CAMBRIDGE 1/1 ARTIFICIAL INTELLIGENCE LAB E C HILDRETH SEP 85 AI-M-8 N99SI4-8S-C-6595...used to carry out this analysis. cce~iO a N) ’.~" D LI’BL. P p ------------ Sj. t i MASSACHUSETTS INSTITUTE OF TECHNOLOGY i ARTIFICIAL INTELLIGENCE

  1. Shift Colors

    Science.gov (United States)

    Publications & News Shift Colors Pages default Sign In NPC Logo Banner : Shift Colors Search Navy Personnel Command > Reference Library > Publications & News > Shift Colors Top Link Bar Navy Personnel Library Expand Reference Library Quick Launch Shift Colors Shift Colors Archives Mailing Address How to

  2. Infrared absorption in pseudobinary InSb1-xBix compounds

    International Nuclear Information System (INIS)

    El-Den, M.B.; Mina, N.K.; Samy, A.M.; El-Mously, M.K.

    1988-08-01

    The group III-V pseudobinary InSb 1-x Bi x compounds, with x = 0, 0.2 and 0.04, were prepared in thin ribbon forms (30 μ) by splat cooling in air. The optical absorption α(λ) was measured in the wavelength range from 4 to 15 μm. The optical energy gap E opt. , was calculated for the three compounds. A shift of the absorption edge towards longer wavelengths with increasing Bi content was observed. (author). 7 refs, 4 figs

  3. Living edge

    DEFF Research Database (Denmark)

    Earon, Ofri

    2014-01-01

    was originally introduced to enhance indoor qualities including light and view. Throughout the paper, it is argued that these ecological motives have grown to architectural and urban dimensions. The paper analyzes the characteristics and potentials of these dimensions and their interconnections. The paper...... on the ground level, but there is a lack of recognition in the significance of communicative characters as well at the higher part of the edge. The city’s planning approach is “Consider urban life before urban space. Consider urban space before buildings” This urban strategy neglects the possible architectural...... contribution to the street atmosphere and its effect on urban life. Bay balcony has been a common architectural element in Copenhagen’s residential buildings, since the end of the twenties. It is a domestic border with an architectural thickness combining window, door, windowsill and balcony. The bay balcony...

  4. UV-VIS absorption spectra of molten AgCl and AgBr and of their mixtures with group I and II halide salts

    Energy Technology Data Exchange (ETDEWEB)

    Greening, Giorgio G.W. [Technische Universitaet Darmstadt (Germany). Eduard-Zintl-Institut fuer Anorganische und Physikalische Chemie

    2015-07-01

    The UV-VIS absorption spectra of (Ag{sub 1-X}[Li-Cs, Ba]{sub X})Cl and of (Ag{sub 1-X}[Na, K, Cs]{sub X})Br at 823 K at the concentrations X=0.0, 0.1, 0.2 have been measured. The findings show that on adding the respective halides to molten silver chloride and silver bromide, shifts of the fundamental absorption edge to shorter wavelengths result. A correlation between the observed shifts and the expansion of the silver sub-lattice is found, which is valid for both silver halide systems studied in this work.

  5. Subgap absorption in conjugated polymers

    Energy Technology Data Exchange (ETDEWEB)

    Sinclair, M.; Seager, C.H. (Sandia National Labs., Albuquerque, NM (USA)); McBranch, D.; Heeger, A.J. (California Univ., Santa Barbara, CA (USA)); Baker, G.L. (Bell Communications Research, Inc., Red Bank, NJ (USA))

    1991-01-01

    Along with X{sup (3)}, the magnitude of the optical absorption in the transparent window below the principal absorption edge is an important parameter which will ultimately determine the utility of conjugated polymers in active integrated optical devices. With an absorptance sensitivity of < 10{sup {minus}5}, Photothermal Deflection Spectroscopy (PDS) is ideal for determining the absorption coefficients of thin films of transparent'' materials. We have used PDS to measure the optical absorption spectra of the conjugated polymers poly(1,4-phenylene-vinylene) (and derivitives) and polydiacetylene-4BCMU in the spectral region from 0.55 eV to 3 eV. Our spectra show that the shape of the absorption edge varies considerably from polymer to polymer, with polydiacetylene-4BCMU having the steepest absorption edge. The minimum absorption coefficients measured varied somewhat with sample age and quality, but were typically in the range 1 cm{sup {minus}1} to 10 cm{sup {minus}1}. In the region below 1 eV, overtones of C-H stretching modes were observed, indicating that further improvements in transparency in this spectral region might be achieved via deuteration of fluorination. 11 refs., 4 figs.

  6. 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.

  7. Using Synchrotron-based X-ray Absorption Spectrometry to Identify the Arsenic Chemical Forms in Mine Waste Materials

    International Nuclear Information System (INIS)

    Matanitobua, Vitukawalu P.; Noller, Barry N.; Chiswell, Barry; Ng, Jack C.; Bruce, Scott L.; Huang, Daphne; Riley, Mark; Harris, Hugh H.

    2007-01-01

    X-ray Absorption Near Edge Spectroscopy (XANES) gives arsenic form directly in the solid phase and has lower detection limits than extraction techniques. An important and common application of XANES is to use the shift of the edge position to determine the valence state. XANES speciation analysis is based on fitting linear combinations of known spectra from model compounds to determine the ratios of valence states and/or phases present. As(V)/As(III) ratios were determined for various Australian mine waste samples and dispersed mine waste samples from river/creek sediments in Vatukoula, Fiji

  8. Subgap Absorption in Conjugated Polymers

    Science.gov (United States)

    Sinclair, M.; Seager, C. H.; McBranch, D.; Heeger, A. J; Baker, G. L.

    1991-01-01

    Along with X{sup (3)}, the magnitude of the optical absorption in the transparent window below the principal absorption edge is an important parameter which will ultimately determine the utility of conjugated polymers in active integrated optical devices. With an absorptance sensitivity of materials. We have used PDS to measure the optical absorption spectra of the conjugated polymers poly(1,4-phenylene-vinylene) (and derivitives) and polydiacetylene-4BCMU in the spectral region from 0.55 eV to 3 eV. Our spectra show that the shape of the absorption edge varies considerably from polymer to polymer, with polydiacetylene-4BCMU having the steepest absorption edge. The minimum absorption coefficients measured varied somewhat with sample age and quality, but were typically in the range 1 cm{sup {minus}1} to 10 cm{sup {minus}1}. In the region below 1 eV, overtones of C-H stretching modes were observed, indicating that further improvements in transparency in this spectral region might be achieved via deuteration of fluorination.

  9. Estimation of edge electron temperature profiles via forward modelling of the electron cyclotron radiation transport at ASDEX Upgrade

    International Nuclear Information System (INIS)

    Rathgeber, S K; Barrera, L; Eich, T; Fischer, R; Suttrop, W; Wolfrum, E; Nold, B; Willensdorfer, M

    2013-01-01

    We present a method to obtain reliable edge profiles of the electron temperature by forward modelling of the electron cyclotron radiation transport. While for the core of ASDEX Upgrade plasmas, straightforward analysis of electron cyclotron intensity measurements based on the optically thick plasma approximation is usually justified, reasonable analysis of the steep and optically thin plasma edge needs to consider broadened emission and absorption profiles and radiation transport processes. This is carried out in the framework of integrated data analysis which applies Bayesian probability theory for joint analysis of the electron density and temperature with data of different interdependent and complementary diagnostics. By this means, electron cyclotron radiation intensity delivers highly spatially resolved electron temperature data for the plasma edge. In H-mode, the edge gradient of the electron temperature can be several times higher than the one of the radiation temperature. Furthermore, we are able to reproduce the ‘shine-through’ peak—the observation of increased radiation temperatures at frequencies resonant in the optically thin scrape-off layer. This phenomenon is caused by strongly down-shifted radiation of Maxwellian tail electrons located in the H-mode edge region and, therefore, contains valuable information about the electron temperature edge gradient. (paper)

  10. Shifting Attention

    Science.gov (United States)

    Ingram, Jenni

    2014-01-01

    This article examines the shifts in attention and focus as one teacher introduces and explains an image that represents the processes involved in a numeric problem that his students have been working on. This paper takes a micro-analytic approach to examine how the focus of attention shifts through what the teacher and students do and say in the…

  11. High-resolution three-dimensional imaging of a depleted CMOS sensor using an edge Transient Current Technique based on the Two Photon Absorption process (TPA-eTCT)

    CERN Document Server

    García, Marcos Fernández; Echeverría, Richard Jaramillo; Moll, Michael; Santos, Raúl Montero; Moya, David; Pinto, Rogelio Palomo; Vila, Iván

    2016-01-01

    For the first time, the deep n-well (DNW) depletion space of a High Voltage CMOS sensor has been characterized using a Transient Current Technique based on the simultaneous absorption of two photons. This novel approach has allowed to resolve the DNW implant boundaries and therefore to accurately determine the real depleted volume and the effective doping concentration of the substrate. The unprecedented spatial resolution of this new method comes from the fact that measurable free carrier generation in two photon mode only occurs in a micrometric scale voxel around the focus of the beam. Real three-dimensional spatial resolution is achieved by scanning the beam focus within the sample.

  12. High-resolution three-dimensional imaging of a depleted CMOS sensor using an edge Transient Current Technique based on the Two Photon Absorption process (TPA-eTCT)

    Energy Technology Data Exchange (ETDEWEB)

    García, Marcos Fernández; Sánchez, Javier González; Echeverría, Richard Jaramillo [Instituto de Física de Cantabria (CSIC-UC), Avda. los Castros s/n, E-39005 Santander (Spain); Moll, Michael [CERN, Organisation europénne pour la recherche nucléaire, CH-1211 Genéve 23 (Switzerland); Santos, Raúl Montero [SGIker Laser Facility, UPV/EHU, Sarriena, s/n - 48940 Leioa-Bizkaia (Spain); Moya, David [Instituto de Física de Cantabria (CSIC-UC), Avda. los Castros s/n, E-39005 Santander (Spain); Pinto, Rogelio Palomo [Departamento de Ingeniería Electrónica, Escuela Superior de Ingenieros Universidad de Sevilla (Spain); Vila, Iván [Instituto de Física de Cantabria (CSIC-UC), Avda. los Castros s/n, E-39005 Santander (Spain)

    2017-02-11

    For the first time, the deep n-well (DNW) depletion space of a High Voltage CMOS sensor has been characterized using a Transient Current Technique based on the simultaneous absorption of two photons. This novel approach has allowed to resolve the DNW implant boundaries and therefore to accurately determine the real depleted volume and the effective doping concentration of the substrate. The unprecedented spatial resolution of this new method comes from the fact that measurable free carrier generation in two photon mode only occurs in a micrometric scale voxel around the focus of the beam. Real three-dimensional spatial resolution is achieved by scanning the beam focus within the sample.

  13. Natural and artificial spectral edges in exoplanets

    Science.gov (United States)

    Lingam, Manasvi; Loeb, Abraham

    2017-09-01

    Technological civilizations may rely upon large-scale photovoltaic arrays to harness energy from their host star. Photovoltaic materials, such as silicon, possess distinctive spectral features, including an 'artificial edge' that is characteristically shifted in wavelength shortwards of the 'red edge' of vegetation. Future observations of reflected light from exoplanets would be able to detect both natural and artificial edges photometrically, if a significant fraction of the planet's surface is covered by vegetation or photovoltaic arrays, respectively. The stellar energy thus tapped can be utilized for terraforming activities by transferring heat and light from the day side to the night side on tidally locked exoplanets, thereby producing detectable artefacts.

  14. Calcium absorption

    International Nuclear Information System (INIS)

    Carlmark, B.; Reizenstein, P.; Dudley, R.A.

    1976-01-01

    The methods most commonly used to measure the absorption and retention of orally administered calcium are reviewed. Nearly all make use of calcium radioisotopes. The magnitude of calcium absorption and retention depends upon the chemical form and amount of calcium administered, and the clinical and nutritional status of the subject; these influences are briefly surveyed. (author)

  15. Absorption studies

    International Nuclear Information System (INIS)

    Ganatra, R.D.

    1992-01-01

    Absorption studies were once quite popular but hardly anyone does them these days. It is easier to estimate the blood level of the nutrient directly by radioimmunoassay (RIA). However, the information obtained by estimating the blood levels of the nutrients is not the same that can be obtained from the absorption studies. Absorption studies are primarily done to find out whether some of the essential nutrients are absorbed from the gut or not and if they are absorbed, to determine how much is being absorbed. In the advanced countries, these tests were mostly done to detect pernicious anaemia where vitamin B 12 is not absorbed because of the lack of the intrinsic factor in the stomach. In the tropical countries, ''malabsorption syndrome'' is quire common. In this condition, several nutrients like fat, folic acid and vitamin B 12 are not absorbed. It is possible to study absorption of these nutrients by radioisotopic absorption studies

  16. Studies of selected transuranium and lanthanide tri-iodides under pressure using absorption spectrophotometry

    International Nuclear Information System (INIS)

    Haire, R.G.; Young, J.P.; Peterson, J.R.; Tennessee Univ., Knoxville; Benedict, U.

    1987-01-01

    The anhydrous tri-iodides of plutonium, americium and curium under pressure have been investigated using absorption spectrophotometry. These initial studies on plutonium and curium tri-iodides together with the published data for americium tri-iodide show that the rhombohedral form of these compounds (BiI 3 -type structure) can be converted to the orthorhombic form (PuBr 3 -type structure) by applying pressure at room temperature. Absorption spectrophotometry can often differentiate between two crystallographic forms of a material and has been used in the present high-pressure studies to monitor the effects of pressure on the tri-iodides. A complication in these studies of the tri-iodides is a significant shift of their absorption edges with pressure from the near UV to the visible spectral region. With curium tri-iodide this shift causes interference with the major f-f absorption peaks and precludes identification by absorption spectrophotometry of the high pressure phase of CmI 3 . (orig.)

  17. Chemical shift imaging: a review

    International Nuclear Information System (INIS)

    Brateman, L.

    1986-01-01

    Chemical shift is the phenomenon that is seen when an isotope possessing a nuclear magnetic dipole moment resonates at a spectrum of resonance frequencies in a given magnetic field. These resonance frequencies, or chemical shifts, depend on the chemical environments of particular nuclei. Mapping the spatial distribution of nuclei associated with a particular chemical shift (e.g., hydrogen nuclei associated with water molecules or with lipid groups) is called chemical shift imaging. Several techniques of proton chemical shift imaging that have been applied in vivo are presented, and their clinical findings are reported and summarized. Acquiring high-resolution spectra for large numbers of volume elements in two or three dimensions may be prohibitive because of time constraints, but other methods of imaging lipid of water distributions (i.e., selective excitation, selective saturation, or variations in conventional magnetic resonance imaging pulse sequences) can provide chemical shift information. These techniques require less time, but they lack spectral information. Since fat deposition seen by chemical shift imaging may not be demonstrated by conventional magnetic resonance imaging, certain applications of chemical shift imaging, such as in the determination of fatty liver disease, have greater diagnostic utility than conventional magnetic resonance imaging. Furthermore, edge artifacts caused by chemical shift effects can be eliminated by certain selective methods of data acquisition employed in chemical shift imaging

  18. Local versus global electronic properties of chalcopyrite alloys: X-ray absorption spectroscopy and ab initio calculations

    Energy Technology Data Exchange (ETDEWEB)

    Sarmiento-Pérez, Rafael; Botti, Silvana, E-mail: silvana.botti@univ-lyon1.fr [Institut Lumière Matière and ETSF, UMR5306 Université Lyon 1-CNRS, Université de Lyon, F-69622 Villeurbanne Cedex (France); Schnohr, Claudia S., E-mail: c.schnohr@uni-jena.de [Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Lauermann, Iver [Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner Platz 1, 14109 Berlin (Germany); Rubio, Angel [Nano-Bio Spectroscopy Group and ETSF Scientific Development Centre, Departamento de Física de Materiales, Centro de Física de Materiales CSIC-MPC and DIPC, Universidad del País Vasco UPV/EHU, Avenida de Tolosa 72, E-20018 San Sebastián (Spain); Fritz Haber Institute, Max Planck Society, Faradayweg 4-6, 14195 Berlin (Germany); Johnson, Benjamin, E-mail: benjamin.johnson@alumni.tu-berlin.de [Fritz Haber Institute, Max Planck Society, Faradayweg 4-6, 14195 Berlin (Germany)

    2014-09-07

    Element-specific unoccupied electronic states of Cu(In, Ga)S{sub 2} were studied as a function of the In/Ga ratio by combining X-ray absorption spectroscopy with density functional theory calculations. The S absorption edge shifts with changing In/Ga ratio as expected from the variation of the band gap. In contrast, the cation edge positions are largely independent of composition despite the changing band gap. This unexpected behavior is well reproduced by our calculations and originates from the dependence of the electronic states on the local atomic environment. The changing band gap arises from a changing spatial average of these localized states with changing alloy composition.

  19. Folate absorption

    International Nuclear Information System (INIS)

    Baker, S.J.

    1976-01-01

    Folate is the generic term given to numerous compounds of pteroic acid with glutamic acid. Knowledge of absorption is limited because of the complexities introduced by the variety of compounds and because of the inadequacy of investigational methods. Two assay methods are in use, namely microbiological and radioactive. Techniques used to study absorption include measurement of urinary excretion, serum concentration, faecal excretion, intestinal perfusion, and haematological response. It is probably necessary to test absorption of both pteroylmonoglutamic acid and one or more polyglutamates, and such tests would be facilitated by availability of synthesized compounds labelled with radioactive tracers at specifically selected sites. (author)

  20. Stability of edge states and edge magnetism in graphene nanoribbons

    OpenAIRE

    Kunstmann, Jens; Özdoğan, Cem; Quandt, Alexander; Fehske, Holger

    2010-01-01

    We critically discuss the stability of edge states and edge magnetism in zigzag edge graphene nanoribbons (ZGNRs). We point out that magnetic edge states might not exist in real systems, and show that there are at least three very natural mechanisms - edge reconstruction, edge passivation, and edge closure - which dramatically reduce the effect of edge states in ZGNRs or even totally eliminate them. Even if systems with magnetic edge states could be made, the intrinsic magnetism would not be ...

  1. Nanoindentation near the edge

    Science.gov (United States)

    J.E. Jakes; C.R. Frihart; J.F. Beecher; R.J. Moon; P.J. Resto; Z.H. Melgarejo; O.M. Saurez; H. Baumgart; A.A. Elmustafa; D.S. Stone

    2009-01-01

    Whenever a nanoindent is placed near an edge, such as the free edge of the specimen or heterophase interface intersecting the surface, the elastic discontinuity associated with the edge produces artifacts in the load-depth data. Unless properly handled in the data analysis, the artifacts can produce spurious results that obscure any real trends in properties as...

  2. Influence of the core-hole effect on optical properties of magnesium oxide (MgO) near the Mg L-edge region.

    Science.gov (United States)

    Sinha, Mangalika; Modi, Mohammed H; Ghosh, Haranath; Yadav, P K; Gupta, R K

    2018-05-01

    The influence of the core-hole effect on optical properties of magnesium oxide (MgO) is established through experimental determination of optical constants and first-principles density functional theory studies. Optical constants (δ and β) of MgO thin film are measured in the spectral region 40-300 eV using reflectance spectroscopy techniques at the Indus-1 synchrotron radiation source. The obtained optical constants show strong core exciton features near the Mg L-edge region, causing significant mismatch with Henke's tabulated values. On comparing the experimentally obtained optical constants with Henke's tabulated values, an edge shift of ∼3.0 eV is also observed. Distinct evidence of effects of core exciton on optical constants (δ and β) in the near Mg L-edge absorption spectra are confirmed through first-principles simulations.

  3. Market shifting

    Energy Technology Data Exchange (ETDEWEB)

    Forst, Michael

    2013-11-01

    After years of oversupply and artificially low module pricing, market analysts believe that the solar industry will begin to stabilize by 2017. While the market activities are shifting from Europe to the Asia Pacific region and the United States, the solar shakeout continues to be in full swing including solar cell and module manufacturing. (orig.)

  4. Tough Shift

    DEFF Research Database (Denmark)

    Brewer, Robert S.; Verdezoto, Nervo; Holst, Thomas

    2015-01-01

    people to change their behavior at home. Leveraging prior research on encouraging reductions in residential energy use through game play, we introduce ShareBuddy: a casual mobile game intended to encourage players not only to reduce, but also to shift their electricity use. We conducted two field studies...... real-world resource use into a game....

  5. C-C bond unsaturation degree in monosubstituted ferrocenes for molecular electronics investigated by a combined near-edge x-ray absorption fine structure, x-ray photoemission spectroscopy, and density functional theory approach

    International Nuclear Information System (INIS)

    Boccia, A.; Lanzilotto, V.; Marrani, A. G.; Zanoni, R.; Stranges, S.; Alagia, M.; Fronzoni, G.; Decleva, P.

    2012-01-01

    We present the results of an experimental and theoretical investigation of monosubstituted ethyl-, vinyl-, and ethynyl-ferrocene (EtFC, VFC, and EFC) free molecules, obtained by means of synchrotron-radiation based C 1s photoabsorption (NEXAFS) and photoemission (C 1s XPS) spectroscopies, and density functional theory (DFT) calculations. Such a combined study is aimed at elucidating the role played by the C-C bond unsaturation degree of the substituent on the electronic structure of the ferrocene derivatives. Such substituents are required for molecular chemical anchoring onto relevant surfaces when ferrocenes are used for molecular electronics hybrid devices. The high resolution C 1s NEXAFS spectra exhibit distinctive features that depend on the degree of unsaturation of the hydrocarbon substituent. The theoretical approach to consider the NEXAFS spectrum made of three parts allowed to disentangle the specific contribution of the substituent group to the experimental spectrum as a function of its unsaturation degree. C 1s IEs were derived from the experimental data analysis based on the DFT calculated IE values for the different carbon atoms of the substituent and cyclopentadienyl (Cp) rings. Distinctive trends of chemical shifts were observed for the substituent carbon atoms and the substituted atom of the Cp ring along the series of ferrocenes. The calculated IE pattern was rationalized in terms of initial and final state effects influencing the IE value, with special regard to the different mechanism of electron conjugation between the Cp ring and the substituent, namely the σ/π hyperconjugation in EtFC and the π-conjugation in VFC and EFC.

  6. An edge pedestal model

    International Nuclear Information System (INIS)

    Stacev, W.M.

    2001-01-01

    A new model for calculation of the gradient scale lengths in the edge pedestal region and of the edge transport barrier width in H-mode tokamak plasmas will be described. Model problem calculations which demonstrate the promise of this model for predicting experimental pedestal properties will be discussed. The density and Prague gradient scale lengths (L) in the edge are calculated from the particle and ion and electron energy radial transport equations, making use of (presumed) known particle and energy fluxes flowing across the edge transport barrier from the core into the SOL and of edge transport coefficients. The average values of the particle and heat fluxes in the edge transport barrier are calculated in terms of the fluxes crossing into the SOL and the atomic physics reaction rates (ionisation, charge-exchange, elastic scattering, impurity radiation) in the edge by integrating the respective transport equations from the pedestal to the separatrix. An important implication of this model is that the pedestal gradient scale lengths depend not just on local pedestal platers properties but also on particle and energy fluxes from the core plasma and on recycling neutral fluxes that penetrate into the plasma edge, both of which in turn depend on the pedestal properties. The MHD edge pressure gradient constraint α≤ α C is used to determine the pressure width of the edge transport barrier, Δ TB = Δ TB (α c ). Three different models for the MHD edge pressure gradient constraint have been investigated: (1) nominal ideal ballooning mode theory, (2) ballooning mode theory taking into account the edge geometry and shear to access He second stability region; and pedestal β-limit theory when the ballooning modes are stabilised by diamagnetic effects. A series of calculations have been made for a DIII-D model problem. The calculated gradient scale lengths and edge transport barrier widths are of the magnitude of values observed experimentally, and certain trends

  7. Spatially resolved sulfur K-edge XANES spectroscopy of wheat leaves infected by Puccinia triticina

    International Nuclear Information System (INIS)

    Lichtenberg, H; Prange, A; Hormes, J; Steiner, U; Oerke, E-C

    2009-01-01

    In this study, wheat leaves infected with brown rust, a plant disease of serious economic concern caused by the fungus Puccinia triticina, were investigated using spatially resolved XANES (X-ray Absorption Near Edge Structure) spectroscopy at the sulfur K-absorption edge.

  8. Spatially resolved sulfur K-edge XANES spectroscopy of wheat leaves infected by Puccinia triticina

    Energy Technology Data Exchange (ETDEWEB)

    Lichtenberg, H; Prange, A; Hormes, J [CAMD, Louisiana State University, 6980 Jefferson Hwy, Baton Rouge, LA 70806 (United States); Steiner, U; Oerke, E-C, E-mail: lichtenberg@lsu.ed [INRES-Phytomedicine, University of Bonn, Nussallee 9, 53115 Bonn (Germany)

    2009-11-15

    In this study, wheat leaves infected with brown rust, a plant disease of serious economic concern caused by the fungus Puccinia triticina, were investigated using spatially resolved XANES (X-ray Absorption Near Edge Structure) spectroscopy at the sulfur K-absorption edge.

  9. Detailed tabulation of atomic form factors, photoelectric absorption and scattering cross section, and mass attenuation coefficients in the vicinity of absorption edges in the soft X-ray (Z=30-36, Z=60-89, E=0.1 keV-10 keV), addressing convergence issues of earlier work

    International Nuclear Information System (INIS)

    Chantler, C.T.

    2000-01-01

    Reliable knowledge of the complex x-ray form factor [Re(f ) ] and the photoelectric attenuation coefficient (σ PE ) is required for crystallography, medical diagnosis, radiation safety, and XAFS studies. Discrepancies between currently used theoretical approaches of 200% exist for numerous elements from 1 to 3 keV x-ray energies. The key discrepancies are due to the smoothing of edge structure, the use of nonrelativistic wave functions, and the lack of appropriate convergence of wave functions. This paper addresses these key discrepancies and derives new theoretical results of substantially higher accuracy in near-edge soft x-ray regions. The high-energy limitations of the current approach are also illustrated. The energy range covered is 0.1 to 10 keV. The associated figures and tabulation demonstrate the current comparison with alternate theory and with available experimental data. In general, experimental data are not sufficiently accurate to establish the errors and inadequacies of theory at this level. However, the best experimental data and the observed experimental structure as a function of energy are strong indicators of the validity of the current approach. New developments in experimental measurement hold great promise in making critical comparisons with theory in the near future

  10. Effects of heat treatment on optical absorption properties of Ni-P/AAO nano-array composite structure

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yi-Fan; Wang, Feng-Hua; Guo, Dong-Lai; Huang, Sheng-You; Zou, Xian-Wu [Wuhan University, Department of Physics, Wuhan (China); Sang, Jian-Ping [Wuhan University, Department of Physics, Wuhan (China); Jianghan University, Department of Physics, Wuhan (China)

    2009-11-15

    Ni-P/AAO nano-array composite structure assemblies with Ni and P grown in the pores of anodic aluminum oxide (AAO) membranes were prepared by electroless deposition. The results of SEM, TEM and SAED show that as-deposited Ni-P nanowires have an amorphous structure and a few nanocrystallites form after annealing. The optical absorption spectra reveal that, as the annealing temperature increases, the absorption band edge of the Ni-P/AAO composite structure is obviously blue shifted, which is attributed to a decrease of the internal pressure after heat treatment. Meanwhile, the annealed Ni-P/AAO nano-array composite structure exhibits the absorption behavior of a direct band gap semiconductor. Details of this behavior are discussed together with the implications for potential device applications. (orig.)

  11. X-ray absorption in atomic potassium

    International Nuclear Information System (INIS)

    Gomilsek, Jana Padeznik; Kodre, Alojz; Arcon, Iztok; Nemanic, Vincenc

    2008-01-01

    A new high-temperature absorption cell for potassium vapor is described. X-ray absorption coefficient of atomic potassium is determined in the energy interval of 600 eV above the K edge where thresholds for simultaneous excitations of 1s and outer electrons, down to [1s2p] excitation, appear. The result represents also the atomic absorption background for XAFS (X-ray absorption fine structure) structure analysis. The K ionization energy in the potassium vapor is determined and compared with theoretical data and with the value for the metal

  12. Narrative absorption

    DEFF Research Database (Denmark)

    Narrative Absorption brings together research from the social sciences and Humanities to solve a number of mysteries: Most of us will have had those moments, of being totally absorbed in a book, a movie, or computer game. Typically we do not have any idea about how we ended up in such a state. No...

  13. Temperature dependence of the soft-x-ray emission edges of simple metals

    International Nuclear Information System (INIS)

    Tagle, J.A.; Arakawa, E.T.; Callcott, T.A.

    1980-01-01

    The widths and energy positions of the M/sub 2,3/-emission edge of potassium, K-emission edge of beryllium, and L/sub 2,3/-emission edges of aluminum and magnesium have been measured for temperatures between 80 and 600 0 K. All band edges broaden (ΔGAMMA) and shift in energy (ΔE) with increasing temperatures for these materials. Similar results were reported earlier for the Li K-emission edge and Na L/sub 2,3/ edge. Lattice-relaxation processes and the phonon core-hole interaction are the dominant mechanisms affecting the core-level widths and the experimentally observed edge widths. The edge shifts are found to be proportional to the thermal expansion of the lattice, and are discussed in terms of the electron energy-level shifts which occur as the lattice dilates

  14. X-ray absorption and emission studies of diamond nanoparticles

    International Nuclear Information System (INIS)

    Van Buuren, T.; Willey, T.; Raty, J.Y.; Galli, G.; Terminello, L.J.; Bostedt, C.

    2004-01-01

    Full text: A new family of carbon nanopaticles produced in detonations, are found to have a core of diamond with a coating fullerene- like carbon. X-ray diffraction and TEM show that the nanodiamond powder is crystalline and approximately 4 nm in diameter. These nano-sized diamonds do not display the characteristic property of other group IV nanoparticles: a strong widening of the energy gap between the conduction and valence bands owing to quantum-confinement effects. For nano-sized diamond with a size distribution of 4 nm, there is no shift of the band energies relative to bulk diamond. Although the C1s core exciton feature clearly observed in the K-edge absorption edge of bulk diamond is shifted and broadening due to increased overlap of the excited electron with the core holein the small particle. Also the depth of the second gap in the nanodiamond spectra is shallower than that of bulk diamond. A feature at lower energy in the X-ray absorption spectra that is not present in the bulk samples is consistent with a fullerene like surface reconstruction. By exposing the diamond nanoparticles to an Argon /Oxygen plasma then annealing in a UHV environment we have obtained a hydrogen free surface. The nanodiamonds processed in this manner show an increase fullerene type contribution in the carbon x-ray absorption pre-edge. High spatial resolution EELS measurements of the empty states of a single nanodiamond particle acquired with a ld emission TEM also show the core of the particle is bulk diamond like where as the surface has a fullerene like structure. Standard density-functional calculations on clusters in which the diamond surface bonds are terminated with hydrogen atoms, show that the bandgap begins to increase above the bulk value only for clusters smaller than 1 nm. Surface hydrogen atoms are found to be about as close as they do in molecular hydrogen and can escape as H 2 , forcing the respective carbon atoms to rearrange. A series of such rearrangements can

  15. Fluid Shifts

    Science.gov (United States)

    Stenger, M. B.; Hargens, A. R.; Dulchavsky, S. A.; Arbeille, P.; Danielson, R. W.; Ebert, D. J.; Garcia, K. M.; Johnston, S. L.; Laurie, S. S.; Lee, S. M. C.; hide

    2017-01-01

    Introduction. NASA's Human Research Program is focused on addressing health risks associated with long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but now more than 50 percent of ISS astronauts have experienced more profound, chronic changes with objective structural findings such as optic disc edema, globe flattening and choroidal folds. These structural and functional changes are referred to as the visual impairment and intracranial pressure (VIIP) syndrome. Development of VIIP symptoms may be related to elevated intracranial pressure (ICP) secondary to spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight and to determine if a relation exists with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as any VIIP-related effects of those shifts, are predicted by the crewmember's pre-flight status and responses to acute hemodynamic manipulations, specifically posture changes and lower body negative pressure. Methods. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, and calcaneus tissue thickness (by ultrasound); (3) vascular dimensions by ultrasound (jugular veins, cerebral and carotid arteries, vertebral arteries and veins, portal vein); (4) vascular dynamics by MRI (head/neck blood flow, cerebrospinal fluid

  16. Intrinsic defect oriented visible region absorption in zinc oxide films

    Science.gov (United States)

    Rakhesh, V.; Shankar, Balakrishnan

    2018-05-01

    Zinc Oxide films were deposited on the glass substrate using vacuum arc sputtering technology. Films were prepared in oxygen ambience for 10mA and 15 mA deposition current separately. The UV-Visible spectroscopy of the samples showed that both samples possess sharp absorption near 3.5eV which is the characteristic band gap absorption energy of ZnO films. The absorption coefficient were calculated for the samples and the (αℎϑ)2 vs energy plot is drawn. The plot suggested that in addition to the sharp band edge absorption, the sample prepared at 10mA deposition current showed sharp absorption edge near 1.51eV and that at 15 mA showed absorption edge near 1.47eV. This refers to the presence of an intrinsic defect level which is likely to be deep in the band gap.

  17. Absorptive products

    International Nuclear Information System (INIS)

    Assarsson, P.G.; King, P.A.

    1976-01-01

    Applications for hydrophile gels produced by the radiation induced cross-linking in aqueous solution of polyethylene oxide and starch, as described in Norwegian patent 133501 (INIS RN 281494), such as sanitary napkins (diapers) and sanitary towels, are discussed. The process itself is also discussed and results, expressed as the percentage of insoluble gel and its absorptive capacity for saline solution as functions of the ratio of polyethylene oxide to starch and the radiation dose, are presented. (JIW)

  18. Donor-related optical absorption spectra in GaAs-(Ga,Al)As quantum wells: hydrostatic pressure effects

    International Nuclear Information System (INIS)

    Lopez, S.Y.; Duque, C.A.; Porras-Montenegro, N.

    2004-01-01

    Full text: Donor-related optical-absorption spectra for GaAs-(Ga,Al)As quantum wells under hydrostatic pressure are investigated. A variational procedure in the e effective-mass approximation is used in order to obtain binding energies and wave functions. As a general feature, we observe that the binding energy increases with the pressure and with the decreasing of the width of the well. The pressure-related Γ-X crossover has been taken into account in the whole calculation. For the low-pressure regime we observe a linear binding energy behavior, whereas for high pressure the main effect associated with the height of the barrier is the bending of the binding energy curves towards smaller values. Two special structures in the density of impurity states and in the donor-related optical-absorption spectra are observed: an edge associated with transitions involving impurities at the center of the well and a peak associated with transitions related to impurities at the edges of the quantum well. Also, we observe shifts to higher energies of the density of impurity states as a function of the binding energy, as well as changes in the intensity with a red shift of the absorption effect with the hydrostatic pressure. (author)

  19. Sulfur K-edge X-ray absorption spectroscopy and density functional theory calculations on monooxo Mo(IV) and bisoxo Mo(VI) bis-dithiolenes: insights into the mechanism of oxo transfer in sulfite oxidase and its relation to the mechanism of DMSO reductase.

    Science.gov (United States)

    Ha, Yang; Tenderholt, Adam L; Holm, Richard H; Hedman, Britt; Hodgson, Keith O; Solomon, Edward I

    2014-06-25

    Sulfur K-edge X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations have been used to determine the electronic structures of two complexes [Mo(IV)O(bdt)2](2-) and [Mo(VI)O2(bdt)2](2-) (bdt = benzene-1,2-dithiolate(2-)) that relate to the reduced and oxidized forms of sulfite oxidase (SO). These are compared with those of previously studied dimethyl sulfoxide reductase (DMSOr) models. DFT calculations supported by the data are extended to evaluate the reaction coordinate for oxo transfer to a phosphite ester substrate. Three possible transition states are found with the one at lowest energy, stabilized by a P-S interaction, in good agreement with experimental kinetics data. Comparison of both oxo transfer reactions shows that in DMSOr, where the oxo is transferred from the substrate to the metal ion, the oxo transfer induces electron transfer, while in SO, where the oxo transfer is from the metal site to the substrate, the electron transfer initiates oxo transfer. This difference in reactivity is related to the difference in frontier molecular orbitals (FMO) of the metal-oxo and substrate-oxo bonds. Finally, these experimentally related calculations are extended to oxo transfer by sulfite oxidase. The presence of only one dithiolene at the enzyme active site selectively activates the equatorial oxo for transfer, and allows facile structural reorganization during turnover.

  20. Determinação de diagramas de bandas de energia e da borda de absorção em SnO2, depositado via sol-gel, sobre quartzo Determination of the band energy diagram and absorption fundamental edge in SnO2, deposited via sol-gel, on quartz

    Directory of Open Access Journals (Sweden)

    E. A. Floriano

    2009-03-01

    Full Text Available Propriedades ópticas e estruturais de filmes finos de SnO2, depositados sobre substratos de quartzo, são apresentadas. Os filmes são preparados pela técnica de molhamento via sol-gel. Uma avaliação das propriedades eletrônicas do cristal (bulk e das superfícies (110 e (101 do material é também efetuada, através de cálculos baseados em um método mecânico-quântico que utiliza a Teoria do Funcional da Densidade (DFT em conjunto com o funcional hibrido B3LYP. A borda fundamental de absorção, obtida experimentalmente, é então comparada com os diagramas de bandas de energia do bulk e superfícies (110 e (101, calculadas.Optical and structural properties of SnO2 thin films, deposited on quartz substrates, are presented. Films are prepared by the sol-gel-dip-coating technique. An evaluation of the electronic properties of bulk and surfaces (110 and (101 of the material is also carried out, through calculation based on a quantum-mechanical method using the Density Functional Theory (DFT in conjunction with the hybrid functional B3LYP. The absorption fundamental edge, experimentally obtained, is compared to the calculated band energy diagram of bulk and surfaces (110 and (101.

  1. Goos-Haenchen shift in complex crystals

    Energy Technology Data Exchange (ETDEWEB)

    Longhi, Stefano; Della Valle, Giuseppe; Staliunas, Kestutis [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy); Departament de Fisica i Enginyeria Nuclear, Instituci Catalana de Recerca i Estudis Avanats (ICREA), Universitat Politcnica de Catalunya, Colom 11, E-08222 Terrassa, Barcelona (Spain)

    2011-10-15

    The Goos-Haenchen (GH) effect for wave scattering from complex PT-symmetric periodic potentials (complex crystals) is theoretically investigated, with specific reference to optical GH shift in photonic crystal slabs with a sinusoidal periodic modulation of both real and imaginary parts of the dielectric constant. The analysis highlights some distinct and rather unique features as compared to the GH shift found in ordinary crystals. In particular, as opposed to GH shift in ordinary crystals, which is large at the band gap edges, in complex crystals the GH shift can be large inside the reflection (amplification) band and becomes extremely large as the PT symmetry-breaking threshold is approached.

  2. Theoretical and experimental investigation of optical absorption anisotropy in β-Ga2O3.

    Science.gov (United States)

    Ricci, F; Boschi, F; Baraldi, A; Filippetti, A; Higashiwaki, M; Kuramata, A; Fiorentini, V; Fornari, R

    2016-06-08

    The question of optical bandgap anisotropy in the monoclinic semiconductor β-Ga2O3 was revisited by combining accurate optical absorption measurements with theoretical analysis, performed using different advanced computation methods. As expected, the bandgap edge of bulk β-Ga2O3 was found to be a function of light polarization and crystal orientation, with the lowest onset occurring at polarization in the ac crystal plane around 4.5-4.6 eV; polarization along b unambiguously shifts the onset up by 0.2 eV. The theoretical analysis clearly indicates that the shift in the b onset is due to a suppression of the transition matrix elements of the three top valence bands at Γ point.

  3. Optically Unraveling the Edge Chirality-Dependent Band Structure and Plasmon Damping in Graphene Edges.

    Science.gov (United States)

    Duan, Jiahua; Chen, Runkun; Cheng, Yuan; Yang, Tianzhong; Zhai, Feng; Dai, Qing; Chen, Jianing

    2018-05-01

    The nontrivial topological origin and pseudospinorial character of electron wavefunctions make edge states possess unusual electronic properties. Twenty years ago, the tight-binding model calculation predicted that zigzag termination of 2D sheets of carbon atoms have peculiar edge states, which show potential application in spintronics and modern information technologies. Although scanning probe microscopy is employed to capture this phenomenon, the experimental demonstration of its optical response remains challenging. Here, the propagating graphene plasmon provides an edge-selective polaritonic probe to directly detect and control the electronic edge state at ambient condition. Compared with armchair, the edge-band structure in the bandgap gives rise to additional optical absorption and strongly absorbed rim at zigzag edge. Furthermore, the optical conductivity is reconstructed and the anisotropic plasmon damping in graphene systems is revealed. The reported approach paves the way for detecting edge-specific phenomena in other van der Waals materials and topological insulators. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. 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.

  5. Edge effects in composites

    International Nuclear Information System (INIS)

    Guz, A.N.; Kokhanenko, Yu.V.

    1995-01-01

    In the present article we survey papers on edge effects investigated by the rigorous approach. We interpret edge effects as stressed states created in a composite as a result of zones in which the stresses exhibit a rapidly changing behavior in comparison with the slow variation of the stresses outside such zones. Here the range of the edge effect is defined as the distance from the point of its inception to the boundary of the edge zone in a given direction. The transition of the stresses to the slowly varying state is determined within prescribed error limits. The size and configuration of the edge zone depends on the tolerated error. Clearly, the main difficulty associated with the rigorous approach is finding solutions of the elasticity problems. The finite-difference approach is suggested for the approximate solution of these problems. In light of the comparative time consumption of the finite-difference approach, it is best directed at certain classes of problems rather than at particular individual problems. Not too many papers on the investigation of edge effects by the rigorous approach have been published to date. Below, following in their footsteps, we formulate edge effect problems in composites, determine classes of problems, and investigate edge effects in composite materials and structural elements using them in Cartesian (planar and three-dimensional problems) and cylindrical (axisymmetric problems) coordinate frames. We note that the division of approaches to the study of edge effects into qualitative (nonrigorous) and quantitative (rigorous) reflects the authors own point of view. Of course, other schemes of classification of the approaches to the investigation of the regions of rapidly varying states in composites are possible

  6. Edge colouring by total labellings

    DEFF Research Database (Denmark)

    Brandt, Stephan; Rautenbach, D.; Stiebitz, M.

    2010-01-01

    We introduce the concept of an edge-colouring total k-labelling. This is a labelling of the vertices and the edges of a graph G with labels 1, 2, ..., k such that the weights of the edges define a proper edge colouring of G. Here the weight of an edge is the sum of its label and the labels of its...

  7. Adobe Edge Quickstart Guide

    CERN Document Server

    Labrecque, Joseph

    2012-01-01

    Adobe Edge Quickstart Guide is a practical guide on creating engaging content for the Web with Adobe's newest HTML5 tool. By taking a chapter-by-chapter look at each major aspect of Adobe Edge, the book lets you digest the available features in small, easily understandable chunks, allowing you to start using Adobe Edge for your web design needs immediately. If you are interested in creating engaging motion and interactive compositions using web standards with professional tooling, then this book is for you. Those with a background in Flash Professional wanting to get started quickly with Adobe

  8. Mortality after percutaneous edge-to-edge mitral valve repair: a contemporary review.

    Science.gov (United States)

    Kortlandt, Friso A; de Beenhouwer, Thomas; Swaans, Martin J; Post, Marco C; van der Heyden, Jan A S; Eefting, Frank D; Rensing, Benno J W M

    2016-04-01

    Percutaneous edge-to-edge mitral valve (MV) repair is a relatively new treatment option for mitral regurgitation (MR). After the feasibility and safety having been proved in low-surgical-risk patients, the use of this procedure has shifted more to the treatment of high-risk patients. With the absence of randomized controlled trials (RCT) for this particular subgroup, observational studies try to add evidence to the safety aspect of this procedure. These also provide short- and mid-term mortality figures. Several mortality predictors have been identified, which may help the optimal selection of patients who will benefit most from this technique. In this article we provide an overview of the literature about mortality and its predictors in patients treated with the percutaneous edge-to-edge device.

  9. Shifting Sugars and Shifting Paradigms

    Science.gov (United States)

    Siegal, Mark L.

    2015-01-01

    No organism lives in a constant environment. Based on classical studies in molecular biology, many have viewed microbes as following strict rules for shifting their metabolic activities when prevailing conditions change. For example, students learn that the bacterium Escherichia coli makes proteins for digesting lactose only when lactose is available and glucose, a better sugar, is not. However, recent studies, including three PLOS Biology papers examining sugar utilization in the budding yeast Saccharomyces cerevisiae, show that considerable heterogeneity in response to complex environments exists within and between populations. These results join similar recent results in other organisms that suggest that microbial populations anticipate predictable environmental changes and hedge their bets against unpredictable ones. The classical view therefore represents but one special case in a range of evolutionary adaptations to environmental changes that all organisms face. PMID:25688600

  10. Shifting sugars and shifting paradigms.

    Directory of Open Access Journals (Sweden)

    Mark L Siegal

    2015-02-01

    Full Text Available No organism lives in a constant environment. Based on classical studies in molecular biology, many have viewed microbes as following strict rules for shifting their metabolic activities when prevailing conditions change. For example, students learn that the bacterium Escherichia coli makes proteins for digesting lactose only when lactose is available and glucose, a better sugar, is not. However, recent studies, including three PLOS Biology papers examining sugar utilization in the budding yeast Saccharomyces cerevisiae, show that considerable heterogeneity in response to complex environments exists within and between populations. These results join similar recent results in other organisms that suggest that microbial populations anticipate predictable environmental changes and hedge their bets against unpredictable ones. The classical view therefore represents but one special case in a range of evolutionary adaptations to environmental changes that all organisms face.

  11. Adobe Edge Preview 3

    CERN Document Server

    Grover, Chris

    2011-01-01

    Want to use an Adobe tool to design animated web graphics that work on iPhone and iPad? You've come to the right book. Adobe Edge Preview 3: The Missing Manual shows you how to build HTML5 graphics using simple visual tools. No programming experience? No problem. Adobe Edge writes the underlying code for you. With this eBook, you'll be designing great-looking web elements in no time. Get to know the workspace. Learn how Adobe Edge Preview 3 performs its magic.Create and import graphics. Make drawings with Edge's tools, or use art you designed in other programs.Work with text. Build menus, lab

  12. Pavement edge treatment.

    Science.gov (United States)

    2013-01-01

    Four projects were built over two construction seasons using special devices attached to the paving machine that produces a 30 slope on the outside pavement edge instead of the near vertical drop-off common with conventional paving equipment. This ...

  13. Edge Simulation Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Krasheninnikov, Sergei I. [Univ. of California, San Diego, CA (United States); Angus, Justin [Univ. of California, San Diego, CA (United States); Lee, Wonjae [Univ. of California, San Diego, CA (United States)

    2018-01-05

    The goal of the Edge Simulation Laboratory (ESL) multi-institutional project is to advance scientific understanding of the edge plasma region of magnetic fusion devices via a coordinated effort utilizing modern computing resources, advanced algorithms, and ongoing theoretical development. The UCSD team was involved in the development of the COGENT code for kinetic studies across a magnetic separatrix. This work included a kinetic treatment of electrons and multiple ion species (impurities) and accurate collision operators.

  14. Fluorescence and absorption spectroscopy for warm dense matter studies and ICF plasma diagnostics

    Science.gov (United States)

    Hansen, S. B.; Harding, E. C.; Knapp, P. F.; Gomez, M. R.; Nagayama, T.; Bailey, J. E.

    2018-05-01

    The burning core of an inertial confinement fusion (ICF) plasma produces bright x-rays at stagnation that can directly diagnose core conditions essential for comparison to simulations and understanding fusion yields. These x-rays also backlight the surrounding shell of warm, dense matter, whose properties are critical to understanding the efficacy of the inertial confinement and global morphology. We show that the absorption and fluorescence spectra of mid-Z impurities or dopants in the warm dense shell can reveal the optical depth, temperature, and density of the shell and help constrain models of warm, dense matter. This is illustrated by the example of a high-resolution spectrum collected from an ICF plasma with a beryllium shell containing native iron impurities. Analysis of the iron K-edge provides model-independent diagnostics of the shell density (2.3 × 1024 e/cm3) and temperature (10 eV), while a 12-eV red shift in Kβ and 5-eV blue shift in the K-edge discriminate among models of warm dense matter: Both shifts are well described by a self-consistent field model based on density functional theory but are not fully consistent with isolated-atom models using ad-hoc density effects.

  15. Edge and core dynamics in harness

    International Nuclear Information System (INIS)

    Ball, R.

    2007-01-01

    , which has an asymptotically stable periodic solution (u(t), x(t)) = (cos(ωt + θ), sin(ωt + θ)), where ω s is the sawtooth frequency and θ is an arbitrary phase shift. There is a spontaneous reversal of shear flow before the dynamics can settle onto a limit cycle in the negative shear flow domain. We see that a periodic power input can suppress this reversal. In further work to be presented it is shown that inductive and MHD coupling can also modulate the edge dynamics, and examples are given of sawtooth-controlled ELMs and confinement transitions. (author)

  16. Electron temperature and pressure at the edge of ASDEX Upgrade plasmas. Estimation via electron cyclotron radiation and investigations on the effect of magnetic perturbations

    International Nuclear Information System (INIS)

    Rathgeber, Sylvia K.

    2013-01-01

    Understanding and control of the plasma edge behaviour are essential for the success of ITER and future fusion plants. This requires the availability of suitable methods for assessing the edge parameters and reliable techniques to handle edge phenomena, e.g. to mitigate 'Edge Localized Modes' (ELMs) - a potentially harmful plasma edge instability. This thesis introduces a new method for the estimation of accurate edge electron temperature profiles by forward modelling of the electron cyclotron radiation transport and demonstrates its successful application to investigate the impact of Magnetic Perturbation (MP) fields used for ELM mitigation on the edge kinetic data. While for ASDEX Upgrade bulk plasmas, straightforward analysis of the measured electron cyclotron intensity spectrum based on the optically thick plasma approximation is usually justified, reasonable analysis of the steep and optically thin edge region relies on full treatment of the radiation transport considering broadened emission and absorption profiles. This is realized in the framework of integrated data analysis which applies Bayesian probability theory for joint analysis of the electron density and temperature with data of different independent and complementary diagnostics. The method reveals that in regimes with improved confinement ('High-confinement modes' (H-modes)) the edge gradient of the electron temperature can be several times higher than that of the radiation temperature. Furthermore, the model is able to reproduce the 'shine-through' peak - the observation of increased radiation temperatures at frequencies with cold resonance outside the confined plasma region. This phenomenon is caused by strongly down-shifted radiation of Maxwellian tail electrons located in the H-mode edge region and, therefore, contains valuable information about the electron temperature edge gradient. The accurate knowledge about the edge profiles and gradients of the electron temperature and - including the

  17. The Edge supersonic transport

    Science.gov (United States)

    Agosta, Roxana; Bilbija, Dushan; Deutsch, Marc; Gallant, David; Rose, Don; Shreve, Gene; Smario, David; Suffredini, Brian

    1992-01-01

    As intercontinental business and tourism volumes continue their rapid expansion, the need to reduce travel times becomes increasingly acute. The Edge Supersonic Transport Aircraft is designed to meet this demand by the year 2015. With a maximum range of 5750 nm, a payload of 294 passengers and a cruising speed of M = 2.4, The Edge will cut current international flight durations in half, while maintaining competitive first class, business class, and economy class comfort levels. Moreover, this transport will render a minimal impact upon the environment, and will meet all Federal Aviation Administration Part 36, Stage III noise requirements. The cornerstone of The Edge's superior flight performance is its aerodynamically efficient, dual-configuration design incorporating variable-geometry wingtips. This arrangement combines the benefits of a high aspect ratio wing at takeoff and low cruising speeds with the high performance of an arrow-wing in supersonic cruise. And while the structural weight concerns relating to swinging wingtips are substantial, The Edge looks to ever-advancing material technologies to further increase its viability. Heeding well the lessons of the past, The Edge design holds economic feasibility as its primary focus. Therefore, in addition to its inherently superior aerodynamic performance, The Edge uses a lightweight, largely windowless configuration, relying on a synthetic vision system for outside viewing by both pilot and passengers. Additionally, a fly-by-light flight control system is incorporated to address aircraft supersonic cruise instability. The Edge will be produced at an estimated volume of 400 aircraft and will be offered to airlines in 2015 at $167 million per transport (1992 dollars).

  18. Properties on the edge: graphene edge energies, edge stresses, edge warping, and the Wulff shape of graphene flakes

    International Nuclear Information System (INIS)

    Branicio, Paulo S; Jhon, Mark H; Gan, Chee Kwan; Srolovitz, David J

    2011-01-01

    It has been shown that the broken bonds of an unreconstructed graphene edge generate compressive edge stresses leading to edge warping. Here, we investigate edge energies and edge stresses of graphene nanoribbons with arbitrary orientations from armchair to zigzag, considering both flat and warped edge shapes in the presence and absence of hydrogen. We use the second generation reactive empirical bond order potential to calculate the edge energies and stresses for clean and hydrogenated edges. Using these energies, we perform a Wulff construction to determine the equilibrium shapes of flat graphene flakes as a function of hydrogen chemical potential. While edge stresses for clean, flat edges are compressive, they become tensile if allowed to warp. Conversely, we find that edge energies change little (∼1%) with edge warping. Hydrogenation of the edges virtually eliminates both the edge energy and edge stresses. For warped edges an approximately linear relationship is found between amplitudes and wavelengths. The equilibrium shape of a graphene flake is determined by the value of the hydrogen chemical potential. For very small (and large) values of it the flakes have a nearly hexagonal (dodecagon) shape with zigzag oriented edges, while for intermediate values graphene flakes are found with complex shapes

  19. Theoretical Mn K-edge XANES for Li2MnO3: DFT + U study

    International Nuclear Information System (INIS)

    Tamura, Tomoyuki; Ohwaki, Tsukuru; Ito, Atsushi; Ohsawa, Yasuhiko; Kobayashi, Ryo; Ogata, Shuji

    2012-01-01

    Spectral features of Mn K-edge x-ray absorption near-edge structure (XANES) for Li 2 MnO 3 were calculated using the first-principles full projector augmented wave method with the general gradient approximation plus U method. We demonstrated that the U parameter affects the spectral features in the pre-edge region while it does not affect those in the major absorption region. From the comparison with the experimental spectra and those of reference compounds, we showed that the spectral features of Mn K-edge XANES and the differences in the valence state can be reproduced well. (paper)

  20. Theory of edge radiation

    Energy Technology Data Exchange (ETDEWEB)

    Geloni, G.; Kocharyan, V.; Saldin, E.; Schneidmiller, E.; Yurkov, M.

    2008-08-15

    We formulate a complete theory of Edge Radiation based on a novel method relying on Fourier Optics techniques. Similar types of radiation like Transition UndulatorRadiation are addressed in the framework of the same formalism. Special attention is payed in discussing the validity of approximations upon which the theory is built. Our study makes consistent use of both similarity techniques and comparisons with numerical results from simulation. We discuss both near and far zone. Physical understanding of many asymptotes is discussed. Based on the solution of the field equation with a tensor Green's function technique, we also discuss an analytical model to describe the presence of a vacuum chamber. In particular, explicit calculations for a circular vacuum chamber are reported. Finally, we consider the use of Edge Radiation as a tool for electron beam diagnostics. We discuss Coherent Edge Radiation, Extraction of Edge Radiation by a mirror, and other issues becoming important at high electron energy and long radiation wavelength. Based on this work we also study the impact of Edge Radiation on XFEL setups and we discuss recent results. (orig.)

  1. K-edge Radiography and applications to Cultural Heritage

    OpenAIRE

    Albertin, Fauzia

    2011-01-01

    The present work of thesis is focused on application of X-ray K-edge technique to paintings. This technique allows one to achieve a topographic map of a pigment on the whole surface of the painting. The digital acquisition of radiographic images by using monochromatic X-ray beams allows to take advantage of the sharp rise of X-ray absorption coefficient of the elements, the K-edge discontinuity. Working at different energies, bracketing the K-edge peak, allows recognition ...

  2. Atomic absorption spectrophotometer

    International Nuclear Information System (INIS)

    Stockdale, T. J.

    1985-01-01

    In atomic absorption spectrophotometer, a reference path may be provided for radiation which excludes the flame. This radiation provides a signal from a detector which varies only with the instrumental drift produced by variations in the radiation source brightness and by variations in detector gain. The signal can be used to compensate for drift in other signals received through a sample path including the flame. In the present invention, radiation passes through the sample path continuously during measurement, and only through the reference path between sample measurements. Movable mirrors shift the radiation between the paths upon externally applied commands. Conveniently, the reference path measurement is made while the flame is stabilized during the change between samples. The reference path measurements are stored and used to correct for drift

  3. Sn-L3 EDGE and Fe K edge XANES spectra of the surface layer of ancient Chinese black mirror Heiqigu

    International Nuclear Information System (INIS)

    Gaowei Mengjia; Liu Yuzhen; Chu Wangsheng; Wu Ziyu; Wang Changsui

    2009-01-01

    The Chinese ancient black mirror known as Heiqigu was studied by x-ray-absorption near-edge structure spectroscopy and results were reported. The Sn-L 3 edge and Fe K edge spectra further confirmed the Schottky-type defect model in the Heiqigu surface system. And it was suggested that the surface layer of the mirror was a combined structure of oxidation of Sn(IV) and Sn(II). (authors)

  4. High Speed Edge Detection

    Science.gov (United States)

    Prokop, Norman F (Inventor)

    2016-01-01

    Analog circuits for detecting edges in pixel arrays are disclosed. A comparator may be configured to receive an all pass signal and a low pass signal for a pixel intensity in an array of pixels. A latch may be configured to receive a counter signal and a latching signal from the comparator. The comparator may be configured to send the latching signal to the latch when the all pass signal is below the low pass signal minus an offset. The latch may be configured to hold a last negative edge location when the latching signal is received from the comparator.

  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. The Inner Urban Edge

    Science.gov (United States)

    Ferebee, Ann; Carpenter, Edward K.

    1974-01-01

    In this article, renewal of the inner urban edge is discussed. Norfolk (Virginia) is attempting to blur the difference between old and new neighbor hoods through zoning and architectural controls. Cincinnati (Ohio) is developing an environmentally sound hillside design. Reading (Pennsylvania) is utilizing old railyards for greenbelts of hiking and…

  7. Swords with Blunt Edges

    Science.gov (United States)

    Popham, W. James

    2004-01-01

    Many U.S. educators now wonder whether they're teachers or targets. This mentality stems from the specter of their school being sanctioned for failing the state accountability tests mandated under No Child Left Behind (NCLB). According to this author, most of those tests are like blunt-edged swords: They function badly in two directions. While…

  8. Infrared absorption in PbTe single crystals

    International Nuclear Information System (INIS)

    Kudykina, T.A.

    1982-01-01

    A group-theoretical analysis is conducted to select rules for optical transitions between bands in PbTe single crystals. It is shown that transitions between valence bands which are near a forbidden band are also forbidden. The extra absorption observed in p-PbTe and p-Pbsub(1-x)Snsub(x)Te in the region between the self-absorption edge and the free-carrier absorption edge is probably connected with transitions between one of valence bands and the p-state of the impurity

  9. Absorption and scattering effects by silver nanoparticles near the interface of organic/inorganic semiconductor tandem films

    International Nuclear Information System (INIS)

    Nemes, Coleen T.; Vijapurapu, Divya K.; Petoukhoff, Christopher E.; Cheung, Gary Z.; O’Carroll, Deirdre M.

    2013-01-01

    We experimentally and theoretically characterize back-scattering and extinction of Ag nanoparticle (AgNP) arrays on both Si wafer substrates and optically-thick Ag substrates with and without organic poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methyl ester (P3HT:PCBM) bulk-heterojunction thin film coatings. A strong red-shift in back-scattered light wavelength occurs from AgNP arrays on Si as a function of increasing mean nanoparticle diameter (ranging from 30 to 90 nm). Back-scattering from the AgNP array is notably quenched in the wavelength range of strong P3HT absorption when the organic layer is applied. However, back-scattering is enhanced to a degree relative to the uncoated AgNP array on Si at wavelengths greater than the absorption band edge of P3HT. For comparison, the optical properties of AgNPs on an optically-thick Ag substrate are reported with and without P3HT:PCBM thin film coatings. On the reflective Ag substrates, a significant enhancement (by a factor of 7.5) and red-shift of back-scattered light occurred upon coating of the AgNPs with the P3HT:PCBM layer. Additionally, red-edge extinction was enhanced in the P3HT:PCBM layer with the presence of the AgNPs compared to the planar case. Theoretical electromagnetic simulations were carried out to help validate and explain the scattering and extinction changes observed in experiment. Both increasing nanoparticle size and an increasing degree of contact with the Si substrate (i.e., effective index of the nanoparticle environment) are shown to play a role in increasing back- and forward-scattering intensity and wavelength, and in increasing absorption enhancements in both the organic and Si layers. AgNPs placed at the P3HT:PCBM/Si interface give rise to absorption increases in P3HT of up to 18 %, and only enhance Si absorption at wavelengths longer than the absorption band edge of P3HT (by almost 90 % in the 660–1,200 nm wavelength range). These results provide insight into how metal

  10. Near edge x-ray spectroscopy theory

    International Nuclear Information System (INIS)

    1994-01-01

    We propose to develop a quantitative theory of x-ray spectroscopies in the near edge region, within about 100 eV of threshold. These spectroscopies include XAFS (X-ray absorption fine structure), photoelectron diffraction (PD), and diffraction anomalous fine structure (DAFS), all of which are important tools for structural studies using synchrotron radiation x-ray sources. Of primary importance in these studies are many-body effects, such as the photoelectron self-energy, and inelastic losses. A better understanding of these quantities is needed to obtain theories without adjustable parameters. We propose both analytical and numerical calculations, the latter based on our x-ray spectroscopy codes FEFF

  11. Information theoretic analysis of canny edge detection in visual communication

    Science.gov (United States)

    Jiang, Bo; Rahman, Zia-ur

    2011-06-01

    In general edge detection evaluation, the edge detectors are examined, analyzed, and compared either visually or with a metric for specific an application. This analysis is usually independent of the characteristics of the image-gathering, transmission and display processes that do impact the quality of the acquired image and thus, the resulting edge image. We propose a new information theoretic analysis of edge detection that unites the different components of the visual communication channel and assesses edge detection algorithms in an integrated manner based on Shannon's information theory. The edge detection algorithm here is considered to achieve high performance only if the information rate from the scene to the edge approaches the maximum possible. Thus, by setting initial conditions of the visual communication system as constant, different edge detection algorithms could be evaluated. This analysis is normally limited to linear shift-invariant filters so in order to examine the Canny edge operator in our proposed system, we need to estimate its "power spectral density" (PSD). Since the Canny operator is non-linear and shift variant, we perform the estimation for a set of different system environment conditions using simulations. In our paper we will first introduce the PSD of the Canny operator for a range of system parameters. Then, using the estimated PSD, we will assess the Canny operator using information theoretic analysis. The information-theoretic metric is also used to compare the performance of the Canny operator with other edge-detection operators. This also provides a simple tool for selecting appropriate edgedetection algorithms based on system parameters, and for adjusting their parameters to maximize information throughput.

  12. Network Unfolding Map by Vertex-Edge Dynamics Modeling.

    Science.gov (United States)

    Verri, Filipe Alves Neto; Urio, Paulo Roberto; Zhao, Liang

    2018-02-01

    The emergence of collective dynamics in neural networks is a mechanism of the animal and human brain for information processing. In this paper, we develop a computational technique using distributed processing elements in a complex network, which are called particles, to solve semisupervised learning problems. Three actions govern the particles' dynamics: generation, walking, and absorption. Labeled vertices generate new particles that compete against rival particles for edge domination. Active particles randomly walk in the network until they are absorbed by either a rival vertex or an edge currently dominated by rival particles. The result from the model evolution consists of sets of edges arranged by the label dominance. Each set tends to form a connected subnetwork to represent a data class. Although the intrinsic dynamics of the model is a stochastic one, we prove that there exists a deterministic version with largely reduced computational complexity; specifically, with linear growth. Furthermore, the edge domination process corresponds to an unfolding map in such way that edges "stretch" and "shrink" according to the vertex-edge dynamics. Consequently, the unfolding effect summarizes the relevant relationships between vertices and the uncovered data classes. The proposed model captures important details of connectivity patterns over the vertex-edge dynamics evolution, in contrast to the previous approaches, which focused on only vertex or only edge dynamics. Computer simulations reveal that the new model can identify nonlinear features in both real and artificial data, including boundaries between distinct classes and overlapping structures of data.

  13. 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.

  14. Changes in forest productivity across Alaska consistent with biome shift

    Science.gov (United States)

    Peter S.A. Beck; Glenn P. Juday; Claire Alix; Valerie A. Barber; Stephen E. Winslow; Emily E. Sousa; Patricia Heiser; James D. Herriges; Scott J. Goetz

    2011-01-01

    Global vegetation models predict that boreal forests are particularly sensitive to a biome shift during the 21st century. This shift would manifest itself first at the biome's margins, with evergreen forest expanding into current tundra while being replaced by grasslands or temperate forest at the biome's southern edge. We evaluated changes in forest...

  15. ICRF edge modeling

    International Nuclear Information System (INIS)

    1991-01-01

    This report describes the technical progress for the DOE sponsored grant, ''ICRF Edge Modeling.'' An emphasis is placed on the progress since the Technical Progress Report (January 10, 1990) was submitted to the Department of Energy. The design of ICRF antennas for C-Mod and TFTR was investigated during this period. In addition, quasilinear models for electron heating were refined and applied to the design of ICRF antennas. The relevant professional activities sponsored by this grant are given. 4 refs., 11 figs

  16. ICRF edge modeling studies

    Energy Technology Data Exchange (ETDEWEB)

    Lehrman, I.S. (Grumman Corp. Research Center, Princeton, NJ (USA)); Colestock, P.L. (Princeton Univ., NJ (USA). Plasma Physics Lab.)

    1990-04-01

    Theoretical models have been developed, and are currently being refined, to explain the edge plasma-antenna interaction that occurs during ICRF heating. The periodic structure of a Faraday shielded antenna is found to result in strong ponderomotive force in the vicinity of the antenna. A fluid model, which incorporates the ponderomotive force, shows an increase in transport to the Faraday shield. A kinetic model shows that the strong antenna near fields act to increase the energy of deuterons which strike the shield, thereby increasing the sputtering of shield material. Estimates of edge impurity harmonic heating show no significant heating for either in or out-of-phase antenna operation. Additionally, a particle model for electrons near the shield shows that heating results from the parallel electric field associated with the fast wave. A quasilinear model for edge electron heating is presented and compared to the particle calculations. The models' predictions are shown to be consistent with measurements of enhanced transport. (orig.).

  17. Properties of aqueous nitrate and nitrite from x-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Jacob W.; Lam, Royce K.; 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 [National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China); Rizzuto, Anthony M. [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Prendergast, David [The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2015-08-28

    Nitrate and nitrite ions are of considerable interest, both for their widespread use in commercial and research contexts and because of their central role in the global nitrogen cycle. The chemistry of atmospheric aerosols, wherein nitrate is abundant, has been found to depend on the interfacial behavior of ionic species. The interfacial behavior of ions is determined largely by their hydration properties; consequently, the study of the hydration and interfacial behavior of nitrate and nitrite comprises a significant field of study. In this work, we describe the study of aqueous solutions of sodium nitrate and nitrite via X-ray absorption spectroscopy (XAS), interpreted in light of first-principles density functional theory electronic structure calculations. Experimental and calculated spectra of the nitrogen K-edge XA spectra of bulk solutions exhibit a large 3.7 eV shift between the XA spectra of nitrate and nitrite resulting from greater stabilization of the nitrogen 1s energy level in nitrate. A similar shift is not observed in the oxygen K-edge XA spectra of NO{sub 3}{sup −} and NO{sub 2}{sup −}. The hydration properties of nitrate and nitrite are found to be similar, with both anions exhibiting a similar propensity towards ion pairing.

  18. Examination of the Measurement of Absorption Using the Reverberant Room Method for Highly Absorptive Acoustic Foam

    Science.gov (United States)

    Hughes, William O.; McNelis, Anne M.; Chris Nottoli; Eric Wolfram

    2015-01-01

    The absorption coefficient for material specimens are needed to quantify the expected acoustic performance of that material in its actual usage and environment. The ASTM C423-09a standard, "Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberant Room Method" is often used to measure the absorption coefficient of material test specimens. This method has its basics in the Sabine formula. Although widely used, the interpretation of these measurements are a topic of interest. For example, in certain cases the measured Sabine absorption coefficients are greater than 1.0 for highly absorptive materials. This is often attributed to the diffraction edge effect phenomenon. An investigative test program to measure the absorption properties of highly absorbent melamine foam has been performed at the Riverbank Acoustical Laboratories. This paper will present and discuss the test results relating to the effect of the test materials' surface area, thickness and edge sealing conditions. A follow-on paper is envisioned that will present and discuss the results relating to the spacing between multiple piece specimens, and the mounting condition of the test specimen.

  19. Smoothness in Binomial Edge Ideals

    Directory of Open Access Journals (Sweden)

    Hamid Damadi

    2016-06-01

    Full Text Available In this paper we study some geometric properties of the algebraic set associated to the binomial edge ideal of a graph. We study the singularity and smoothness of the algebraic set associated to the binomial edge ideal of a graph. Some of these algebraic sets are irreducible and some of them are reducible. If every irreducible component of the algebraic set is smooth we call the graph an edge smooth graph, otherwise it is called an edge singular graph. We show that complete graphs are edge smooth and introduce two conditions such that the graph G is edge singular if and only if it satisfies these conditions. Then, it is shown that cycles and most of trees are edge singular. In addition, it is proved that complete bipartite graphs are edge smooth.

  20. The Edge Detectors Suitable for Retinal OCT Image Segmentation

    Directory of Open Access Journals (Sweden)

    Su Luo

    2017-01-01

    Full Text Available Retinal layer thickness measurement offers important information for reliable diagnosis of retinal diseases and for the evaluation of disease development and medical treatment responses. This task critically depends on the accurate edge detection of the retinal layers in OCT images. Here, we intended to search for the most suitable edge detectors for the retinal OCT image segmentation task. The three most promising edge detection algorithms were identified in the related literature: Canny edge detector, the two-pass method, and the EdgeFlow technique. The quantitative evaluation results show that the two-pass method outperforms consistently the Canny detector and the EdgeFlow technique in delineating the retinal layer boundaries in the OCT images. In addition, the mean localization deviation metrics show that the two-pass method caused the smallest edge shifting problem. These findings suggest that the two-pass method is the best among the three algorithms for detecting retinal layer boundaries. The overall better performance of Canny and two-pass methods over EdgeFlow technique implies that the OCT images contain more intensity gradient information than texture changes along the retinal layer boundaries. The results will guide our future efforts in the quantitative analysis of retinal OCT images for the effective use of OCT technologies in the field of ophthalmology.

  1. Modification of tokamak edge turbulence using feedback

    International Nuclear Information System (INIS)

    Richards, B.; Uckan, T.; Wootton, A.J.; Carreras, B.A.; Bengtson, R.D.; Hurwitz, P.; Li, G.X.; Lin, H.; Rowan, W.L.; Tsui, H.Y.W.; Sen, A.K.; Uglum, J.

    1994-01-01

    Using active feedback, the turbulent fluctuation levels have been reduced by as much as a factor of 2 in the edge of the Texas Experimental Tokamak (TEXT) [K. W. Gentle, Nucl. Fusion Technol. 1, 479 (1981)]. A probe system was used to drive a suppressor wave in the TEXT limiter shadow. A decrease in the local turbulence-induced particle flux has been seen, but a global change in the particle transport at the present time has not been observed. By changing the phase shift and gain of the feedback network, the amplitude of the turbulence was increased by a factor of 10

  2. XUV Absorption by Solid Density Aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Iglesias, C A

    2009-09-21

    An inverse bremsstrahlung model for plasmas and simple metals that approximates the cold, solid Al experimental data below the L-edge is applied to matter conditions relevant to XUV laser applications. The model involves an all-order calculation using a semi-analytical effective electron-ion interaction. The predicted increases in XUV absorption with rising temperature occur via two effects: increased availability of final states from reduced electron degeneracy and a stronger electron-ion interaction from reduced screening. Discrepancies in the temperature dependence as well as other details between the present approach and a recently proposed absorption model are discussed.

  3. Hydrogen production by absorption enhanced water gas shift (AEWGS)

    Energy Technology Data Exchange (ETDEWEB)

    Escobedo Bretado, Miguel A. [Facultad de Ciencias Quimicas, Universidad Juarez del Estado de Durango, Ave. Veterinaria s/n, Circuito Universitario, Durango 34120 (Mexico); Departamento de Quimica de Materiales, Centro de Investigacion en Materiales Avanzados, S.C. Miguel de Cervantes 120, Chihuahua, Chih. 31109 (Mexico); Delgado Vigil, Manuel D.; Gutierrez, Jesus Salinas; Lopez Ortiz, Alejandro; Collins-Martinez, Virginia [Departamento de Quimica de Materiales, Centro de Investigacion en Materiales Avanzados, S.C. Miguel de Cervantes 120, Chihuahua, Chih. 31109 (Mexico)

    2010-11-15

    AEWGS is a reaction that combines the WGS reaction and CO{sub 2} capture by a solid absorbent to produce high purity H{sub 2} from synthesis gas in one single step at 600-800 C. This reactor system, if homogeneous, would not require a catalyst. However, previous research on this concept was not conclusive, since a steel reactor was used and reactor walls were suspected to act as catalyst. Therefore, there is a need to address this issue and to select and evaluate suitable CO{sub 2} absorbents for this concept. AEWGS was studied using a quartz-made fixed-bed reactor at; SV = 3000 h{sup -1}, feed; 5% CO, 15% H{sub 2}O, balance He-N{sub 2} at 600 C, 1 atm. CO{sub 2} absorbents tested were CaO*MgO, and Na{sub 2}ZrO{sub 3}. Empty quartz-reactor tests leaded to conclude that a catalyst is needed for the WGS at temperatures of interest. A 97% H{sub 2} product was obtained with calcined dolomite suggesting this last to act as a WGS catalyst. (author)

  4. Competing edge networks

    Science.gov (United States)

    Parsons, Mark; Grindrod, Peter

    2012-06-01

    We introduce a model for a pair of nonlinear evolving networks, defined over a common set of vertices, subject to edgewise competition. Each network may grow new edges spontaneously or through triad closure. Both networks inhibit the other's growth and encourage the other's demise. These nonlinear stochastic competition equations yield to a mean field analysis resulting in a nonlinear deterministic system. There may be multiple equilibria; and bifurcations of different types are shown to occur within a reduced parameter space. This situation models competitive communication networks such as BlackBerry Messenger displacing SMS; or instant messaging displacing emails.

  5. [The photoluminescence and absorption properties of Co/AAO nano-array composites].

    Science.gov (United States)

    Li, Shou-Yi; Wang, Cheng-Wei; Li, Yan; Wang, Jian; Ma, Bao-Hong

    2008-03-01

    Ordered Co/AAO nano-array structures were fabricated by alternating current (AC) electrodeposition method within the cylindrical pores of anodic aluminum oxide (AAO) template prepared in oxalic acid electrolyte. The photoluminescence (PL) emission and photoabsorption of AAO templates and Co/AAO nano-array structures were investigated respectively. The results show that a marked photoluminescence band of AAO membranes occurs in the wavelength range of 350-550 nm and their PL peak position is at 395 nm. And with the increase in the deposition amount of Co nanoparticles, the PL intensity of Co/AAO nano-array structures decreases gradually, and their peak positions of the PL are invariable (395 nm). Meanwhile the absorption edges of Co/AAO show a larger redshift, and the largest shift from the near ultraviolet to the infrared exceeds 380 nm. The above phenomena caused by Co nano-particles in Co/AAO composite were analyzed.

  6. Band gap engineering of tandem structured CIGS compound absorption layer fabricated by sputtering and selenization

    Energy Technology Data Exchange (ETDEWEB)

    Kang, San; Sharma, Rahul; Sim, Jae-Kwan [Semiconductor Materials Processing Laboratory, School of Advanced Materials Engineering, College of Engineering, Research Center for Advanced Materials Development (RCAMD), Chonbuk National University, Deokjin-dong 664-14, Jeonju 561-756 (Korea, Republic of); Lee, Cheul-Ro, E-mail: crlee7@jbnu.ac.kr [Semiconductor Materials Processing Laboratory, School of Advanced Materials Engineering, College of Engineering, Research Center for Advanced Materials Development (RCAMD), Chonbuk National University, Deokjin-dong 664-14, Jeonju 561-756 (Korea, Republic of)

    2013-06-25

    Highlights: ► Systematic band gap engineering to fabricate tandem Cu(In,Ga)Se{sub 2} absorption layers. ► XRD shows prominent (1 1 2) reflection shift for attributed CIS, CIGS, and CGS phases. ► Optical transmittance and reflectance spectrum are improved towards infrared region. ► The Cu/In + Ga and Ga/In + Ga effect is matched with highest efficient solar cell. ► Tandem CIS/CIGS/CGS layer, the band gap is increased from 1.15 to 2.06 eV. -- Abstract: Band gap engineering was executed to fabricate a multi-junction stacked i.e. tandem Cu(In,Ga)Se{sub 2} (CIGS) absorption layer. The CIGS absorption layers consist of multi-junction stacked CIS/CIGS/CGS thin films from bottom to top with increasing band gap. Tandem CIGS layers were fabricated by using three precursor of CuIn, In/CuGa/In, and CuGa onto the Mo coated soda-lime glass (SLG) by the sequential sputtering of CuIn, CuGa, and In targets. The CIG precursors were converted into CIGS absorption thin film by selenization process. From the X-ray diffraction (XRD) pattern of CIS/CIGS/CGS tandem layer, with the prominent peak shift for (1 1 2) reflections was attributed to the individual CIS, CIGS, and CGS phases at 26.76°, 27.15°, and 27.65° diffraction angles, respectively. The morphologies and atomic (at%) composition uniformity onto the surface and along the depth were extensively analyzed with field effect scanning electron microscope (FESEM) attached energy dispersive spectroscopy (EDS) and secondary ion mass spectroscopy (SIMS). The optical properties such as transmittance, reflectance and absorbance were found to improve in the infrared region for all the tandem CIGS layers. Near the fundamental absorption edge, the absorption coefficient was approached to 10{sup 5} cm{sup −1} for CIS/CIGS/CGS tandem layer. The straight-line behavior indicates that the films have a direct band gap. The band gap was found to increase from 1.15 to 1.74 eV with the Ga-grading along the depth of individual CIS, CIGS

  7. Band gap engineering of tandem structured CIGS compound absorption layer fabricated by sputtering and selenization

    International Nuclear Information System (INIS)

    Kang, San; Sharma, Rahul; Sim, Jae-Kwan; Lee, Cheul-Ro

    2013-01-01

    Highlights: ► Systematic band gap engineering to fabricate tandem Cu(In,Ga)Se 2 absorption layers. ► XRD shows prominent (1 1 2) reflection shift for attributed CIS, CIGS, and CGS phases. ► Optical transmittance and reflectance spectrum are improved towards infrared region. ► The Cu/In + Ga and Ga/In + Ga effect is matched with highest efficient solar cell. ► Tandem CIS/CIGS/CGS layer, the band gap is increased from 1.15 to 2.06 eV. -- Abstract: Band gap engineering was executed to fabricate a multi-junction stacked i.e. tandem Cu(In,Ga)Se 2 (CIGS) absorption layer. The CIGS absorption layers consist of multi-junction stacked CIS/CIGS/CGS thin films from bottom to top with increasing band gap. Tandem CIGS layers were fabricated by using three precursor of CuIn, In/CuGa/In, and CuGa onto the Mo coated soda-lime glass (SLG) by the sequential sputtering of CuIn, CuGa, and In targets. The CIG precursors were converted into CIGS absorption thin film by selenization process. From the X-ray diffraction (XRD) pattern of CIS/CIGS/CGS tandem layer, with the prominent peak shift for (1 1 2) reflections was attributed to the individual CIS, CIGS, and CGS phases at 26.76°, 27.15°, and 27.65° diffraction angles, respectively. The morphologies and atomic (at%) composition uniformity onto the surface and along the depth were extensively analyzed with field effect scanning electron microscope (FESEM) attached energy dispersive spectroscopy (EDS) and secondary ion mass spectroscopy (SIMS). The optical properties such as transmittance, reflectance and absorbance were found to improve in the infrared region for all the tandem CIGS layers. Near the fundamental absorption edge, the absorption coefficient was approached to 10 5 cm −1 for CIS/CIGS/CGS tandem layer. The straight-line behavior indicates that the films have a direct band gap. The band gap was found to increase from 1.15 to 1.74 eV with the Ga-grading along the depth of individual CIS, CIGS, and CGS thin films

  8. Low scatter edge blackening compounds for refractive optical elements

    International Nuclear Information System (INIS)

    Lewis, I.T.; Telkamp, A.R.; Ledebuhr, A.G.

    1989-01-01

    This paper reports on low scatter edge blackening compounds for refractive optical elements. Perkin-Elmer's Applied Optics Operation recently delivered several prototype wide-field-of-view (WFOV), F/2.8, 250 mm efl, near diffraction limited, concentric lenses toLawrence Livermore National Laboratory (LLNL). In these lenses, special attention was paid to reducing stray light to allow viewing of very dim objects. Because of the very large FOV, the use of a long baffle to eliminate direct illumination of lens edges was not practical. With the existing relatively short baffle design, one-bounce stray light paths off the element edges are possible. The scattering off the inside edges thus had to be kept to an absolute minimum. While common means for blackening the edges of optical elements are easy to apply and quite cost effective for normal lens assemblies, their blackening effect is limited by the Fresnel reflection due to the index of refraction mismatch at the glass boundary. At high angles of incidence, total internal reflection (TIR) might occur ruining the effect of the blackening process. An index-match absorbing medium applied to the edges of such elements is the most effective approach for reducing the amount of undesired light reflection or scattered off these edges. The presence of such a medium provides an extended path outside the glass boundary in which an absorptive non-scattering dye can be used to eliminate light that might otherwise have propagated to the focal plane

  9. Si K-edge XANES study of SiOxCyHz amorphous polymeric materials

    International Nuclear Information System (INIS)

    Chaboy, J.; Barranco, A.; Yanguas-Gil, A.; Yubero, F.; Gonzalez-Elipe, A. R.

    2007-01-01

    This work reports on x-ray absorption spectroscopy study at the Si K edge of several amorphous SiO x C y H z polymers prepared by plasma-enhanced chemical-vapor deposition with different C/O ratios. SiO 2 and SiC have been used as reference materials. The comparison of the experimental Si K-edge x-ray absorption near-edge structure spectra with theoretical computations based on multiple scattering theory has allowed us to monitor the modification of the local coordination around Si as a function of the overall C/O ratio in this kind of materials

  10. Degenerate band edge laser

    Science.gov (United States)

    Veysi, Mehdi; Othman, Mohamed A. K.; Figotin, Alexander; Capolino, Filippo

    2018-05-01

    We propose a class of lasers based on a fourth-order exceptional point of degeneracy (EPD) referred to as the degenerate band edge (DBE). EPDs have been found in parity-time-symmetric photonic structures that require loss and/or gain; here we show that the DBE is a different kind of EPD since it occurs in periodic structures that are lossless and gainless. Because of this property, a small level of gain is sufficient to induce single-frequency lasing based on a synchronous operation of four degenerate Floquet-Bloch eigenwaves. This lasing scheme constitutes a light-matter interaction mechanism that leads also to a unique scaling law of the laser threshold with the inverse of the fifth power of the laser-cavity length. The DBE laser has the lowest lasing threshold in comparison to a regular band edge laser and to a conventional laser in cavities with the same loaded quality (Q ) factor and length. In particular, even without mirror reflectors the DBE laser exhibits a lasing threshold which is an order of magnitude lower than that of a uniform cavity laser of the same length and with very high mirror reflectivity. Importantly, this novel DBE lasing regime enforces mode selectivity and coherent single-frequency operation even for pumping rates well beyond the lasing threshold, in contrast to the multifrequency nature of conventional uniform cavity lasers.

  11. Galactic absorption line coronae

    International Nuclear Information System (INIS)

    Bregman, J.N.

    1981-01-01

    We have investigated whether gaseous coronae around galaxies rise to the absorption systems seen in quasar spectra. In our model, gas originally located in the disk is heated to the million degree range and rises to surround the galaxy; the gas remains bound to the galaxy. Optically thin radiative cooling drives a thermal instability in the hot gas which causes cool clouds (T 4 K) to condense out of the corona. These clouds, which follow ballistic trajectories back to the disk, are the absorption sites. A two-dimensional hydrodynamic code with radiative cooling was used to study the dynamics and thermodynamics of the corona as well as the position rate at which clouds form. Coupled to the code is a galaxy with two mass components, a disk (approx.10 11 M/sub sun/) and a dark halo (approx.10 12 M/sub sun/). In a model where the temperature at the base of the corona (in the disk) is 3 x 10 6 K, absorbing gas of column density NL> or approx. =10 18 cm 2 extends radially to 100 kpc (face-on orientation) and vertically to 60 Kpc (edge-on orientation). The total mass of gas required here (coronal plus cloud gas) is 1.4 x 10 10 M/sub sun/, while the minimum supernova heating rate is one supernova per 27 years. In two other models (base coronal temperatures of 0.50 x 10 6 K and 1 x 10 6 K), coronal gas rises from an extended gaseous disk (in the previous model, the gas comes from a typical gaseous disk approximately 15 kpc in extent). Here, column densities of 10 19 cm -2 out to a radius of 70 kpc (face-on orientation) are achieved with a total gas mass of 1.7 x 10 9 M/sub direct-product/ and 2.0 x 10 9 M/sub sun/ and minimum heating rates of approximately one supernova per 170 years and one supernova per 60 years

  12. A heuristic approach to edge detection in on-line portal imaging

    International Nuclear Information System (INIS)

    McGee, Kiaran P.; Schultheiss, Timothy E.; Martin, Eric E.

    1995-01-01

    Purpose: Portal field edge detection is an essential component of several postprocessing techniques used in on-line portal imaging, including field shape verification, selective contrast enhancement, and treatment setup error detection. Currently edge detection of successive fractions in a multifraction portal image series involves the repetitive application of the same algorithm. As the number of changes in the field is small compared to the total number of fractions, standard edge detection algorithms essentially recalculate the same field shape numerous times. A heuristic approach to portal edge detection has been developed that takes advantage of the relatively few changes in the portal field shape throughout a fractionation series. Methods and Materials: The routine applies a standard edge detection routine to calculate an initial field edge and saves the edge information. Subsequent fractions are processed by applying an edge detection operator over a small region about each point of the previously defined contour, to determine any shifts in the field shape in the new image. Failure of this edge check indicates that a significant change in the field edge has occurred, and the original edge detection routine is applied to the image. Otherwise the modified edge contour is used to define the new edge. Results: Two hundred and eighty-one portal images collected from an electronic portal imaging device were processed by the edge detection routine. The algorithm accurately calculated each portal field edge, as well as reducing processing time in subsequent fractions of an individual portal field by a factor of up to 14. Conclusions: The heuristic edge detection routine is an accurate and fast method for calculating portal field edges and determining field edge setup errors

  13. Ultra-violet and visible absorption characterization of explosives by differential reflectometry.

    Science.gov (United States)

    Dubroca, Thierry; Moyant, Kyle; Hummel, Rolf E

    2013-03-15

    This study presents some optical properties of TNT (2,4,6-trinitrotoluene), RDX, HMX and tetryl, specifically their absorption spectra as a function of concentration in various solvents in the ultraviolet and visible portion of the electromagnetic spectrum. We utilize a standoff explosives detection method, called differential reflectometry (DR). TNT was diluted in six different solvents (acetone, acetonitrile, ethanol, ethyl acetate, methanol, and toluene), which allowed for a direct comparison of absorption features over a wide range of concentrations. A line-shape analysis was adopted with great accuracy (R(2)>0.99) to model the absorption features of TNT in differential reflectivity spectra. We observed a blue shift in the pertinent absorption band with decreasing TNT concentration for all solvents. Moreover, using this technique, it was found that for all utilized solvents the concentration of TNT as well as of RDX, HMX, and tetryl, measured as a function of the transition wavelength of the ultra-violet absorption edge in differential reflectivity spectra shows three distinct regions. A model is presented to explain this behavior which is based on intermolecular hydrogen bonding of explosives molecules with themselves (or lack thereof) at different concentrations. Other intermolecular forces such as dipole-dipole interactions, London dispersion forces and π-stacking contribute to slight variations in the resulting spectra, which were determined to be rather insignificant in comparison to hydrogen bonding. The results are aimed towards a better understanding of the DR spectra of explosives energetic materials. Copyright © 2012 Elsevier B.V. All rights reserved.

  14. Full-waveform data for building roof step edge localization

    Science.gov (United States)

    Słota, Małgorzata

    2015-08-01

    Airborne laser scanning data perfectly represent flat or gently sloped areas; to date, however, accurate breakline detection is the main drawback of this technique. This issue becomes particularly important in the case of modeling buildings, where accuracy higher than the footprint size is often required. This article covers several issues related to full-waveform data registered on building step edges. First, the full-waveform data simulator was developed and presented in this paper. Second, this article provides a full description of the changes in echo amplitude, echo width and returned power caused by the presence of edges within the laser footprint. Additionally, two important properties of step edge echoes, peak shift and echo asymmetry, were noted and described. It was shown that these properties lead to incorrect echo positioning along the laser center line and can significantly reduce the edge points' accuracy. For these reasons and because all points are aligned with the center of the beam, regardless of the actual target position within the beam footprint, we can state that step edge points require geometric corrections. This article presents a novel algorithm for the refinement of step edge points. The main distinguishing advantage of the developed algorithm is the fact that none of the additional data, such as emitted signal parameters, beam divergence, approximate edge geometry or scanning settings, are required. The proposed algorithm works only on georeferenced profiles of reflected laser energy. Another major advantage is the simplicity of the calculation, allowing for very efficient data processing. Additionally, the developed method of point correction allows for the accurate determination of points lying on edges and edge point densification. For this reason, fully automatic localization of building roof step edges based on LiDAR full-waveform data with higher accuracy than the size of the lidar footprint is feasible.

  15. Sound absorption and transmission through flexible micro-perforated panels backed by an air layer and a thin plate.

    Science.gov (United States)

    Bravo, Teresa; Maury, Cédric; Pinhède, Cédric

    2012-05-01

    This paper describes theoretical and experimental investigations into the sound absorption and transmission properties of micro-perforated panels (MPP) backed by an air cavity and a thin plate. A fully coupled modal approach is proposed to calculate the absorption coefficient and the transmission loss of finite-sized micro-perforated panels-cavity-panel (MPPCP) partitions with conservative boundary conditions. It is validated against infinite partition models and experimental data. A practical methodology is proposed using collocated pressure-velocity sensors to evaluate in an anechoic environment the transmission and absorption properties of conventional MPPCPs. Results show under which conditions edge scattering effects should be accounted for at low frequencies. Coupled mode analysis is also performed and analytical approximations are derived from the resonance frequencies and mode shapes of a flexible MPPCP. It is found that the Helmholtz-type resonance frequency is deduced from the one associated to the rigidly backed MPPCP absorber shifted up by the mass-air mass resonance of the flexible non-perforated double-panel. Moreover, it is shown analytically and experimentally that the absorption mechanisms at the resonances are governed by a large air-frame relative velocity over the MPP surface, with either in-phase or out-of-phase relationships, depending on the MPPCP parameters.

  16. Cheating on the edge.

    Directory of Open Access Journals (Sweden)

    Lee Alan Dugatkin

    2008-07-01

    Full Text Available We present the results of an individual agent-based model of antibiotic resistance in bacteria. Our model examines antibiotic resistance when two strategies exist: "producers"--who secrete a substance that breaks down antibiotics--and nonproducers ("cheats" who do not secrete, or carry the machinery associated with secretion. The model allows for populations of up to 10,000, in which bacteria are affected by their nearest neighbors, and we assume cheaters die when there are no producers in their neighborhood. Each of 10,000 slots on our grid (a torus could be occupied by a producer or a nonproducer, or could (temporarily be unoccupied. The most surprising and dramatic result we uncovered is that when producers and nonproducers coexist at equilibrium, nonproducers are almost always found on the edges of clusters of producers.

  17. Challenges in edge modeling

    International Nuclear Information System (INIS)

    Schneider, R.

    2007-01-01

    Fluid models like B2, UEDGE or EDGE2D are the working horses for scrape-off layer physics, both for design and experimental support. The concept of a numerical tokamak, aiming at a predictive code for ITER, triggers the need to re-assess the available tools and their necessary extensions. These additional physics issues will be summarized from a personal point-of-view. Depending on the specific problem, several complexity levels of scrape-off layer models will be needed. Therefore, a hierarchy of tools is necessary, which will be discussed. Furthermore, the experience existing in other scientific fields with multi-scale problems and modeling should be used. Here, the coupling of different length and time scales are in particular of interest for fusion problems. (author)

  18. Edge remap for solids

    Energy Technology Data Exchange (ETDEWEB)

    Kamm, James R.; Love, Edward; Robinson, Allen C; Young, Joseph G.; Ridzal, Denis

    2013-12-01

    We review the edge element formulation for describing the kinematics of hyperelastic solids. This approach is used to frame the problem of remapping the inverse deformation gradient for Arbitrary Lagrangian-Eulerian (ALE) simulations of solid dynamics. For hyperelastic materials, the stress state is completely determined by the deformation gradient, so remapping this quantity effectively updates the stress state of the material. A method, inspired by the constrained transport remap in electromagnetics, is reviewed, according to which the zero-curl constraint on the inverse deformation gradient is implicitly satisfied. Open issues related to the accuracy of this approach are identified. An optimization-based approach is implemented to enforce positivity of the determinant of the deformation gradient. The efficacy of this approach is illustrated with numerical examples.

  19. Playing on the edge

    DEFF Research Database (Denmark)

    Cermak-Sassenrath, Daniel

    2018-01-01

    and specific ways. For instance, gambling for money, party and drinking games, professional play and show sports, art installations, violent and military propaganda computer games, pervasive/mobile gaming, live-action role playing, festivals, performances, and games such as Ghosting and Planking. It is argued......Everything gets more interesting, challenging, or intense the closer it gets to the edge, and so does play. How edgy can play become and still be play? Based on Huizinga’s notion of play, this chapter discusses how a wide range of playful activities pushes the boundaries of play in different...... that in concert with a number of characteristics that mark an activity as play, play is essentially a subjective perspective and individual decision of the player. Huizinga calls this attitude the play spirit, which informs a player’s actions and is in turn sustained by them. Edgy digital or mobile games do...

  20. Competing edge networks

    International Nuclear Information System (INIS)

    Parsons, Mark; Grindrod, Peter

    2012-01-01

    We introduce a model for a pair of nonlinear evolving networks, defined over a common set of vertices, subject to edgewise competition. Each network may grow new edges spontaneously or through triad closure. Both networks inhibit the other's growth and encourage the other's demise. These nonlinear stochastic competition equations yield to a mean field analysis resulting in a nonlinear deterministic system. There may be multiple equilibria; and bifurcations of different types are shown to occur within a reduced parameter space. This situation models competitive communication networks such as BlackBerry Messenger displacing SMS; or instant messaging displacing emails. -- Highlights: ► A model for edgewise-competing evolving network pairs is introduced. ► Defined competition equations yield to a mean field analysis. ► Multiple equilibrium states and different bifurcation types can occur. ► The system is sensitive to sparse initial conditions and near unstable equilibriums.

  1. Urbach tails in the absorption spectra of semiconducting molybdenum-borate glasses

    International Nuclear Information System (INIS)

    Jamel Basha Adlan, M.; Wan Yusri Wan Yusuff; Tan, C.W.; Yam, F.K.

    1991-01-01

    The absorption curve of many amorphous compound semiconductors may be divided into three regions: (1) the high absorption region (α(w)≥10 4 cm -1 ), (2) an exponential region (1cm -1 ≤(w)≤10 4 cm -1 ) which obeys Urbach's rule and (3) a weak absorption tail (α(w)≤1cm -1 ). In this paper we will present the absorption edge of binary Molybdenum-Borate glasses at the exponential region of the spectra

  2. Spectral stability of shifted states on star graphs

    Science.gov (United States)

    Kairzhan, Adilbek; Pelinovsky, Dmitry E.

    2018-03-01

    We consider the nonlinear Schrödinger (NLS) equation with the subcritical power nonlinearity on a star graph consisting of N edges and a single vertex under generalized Kirchhoff boundary conditions. The stationary NLS equation may admit a family of solitary waves parameterized by a translational parameter, which we call the shifted states. The two main examples include (i) the star graph with even N under the classical Kirchhoff boundary conditions and (ii) the star graph with one incoming edge and N  -  1 outgoing edges under a single constraint on coefficients of the generalized Kirchhoff boundary conditions. We obtain the general counting results on the Morse index of the shifted states and apply them to the two examples. In the case of (i), we prove that the shifted states with even N ≥slant 4 are saddle points of the action functional which are spectrally unstable under the NLS flow. In the case of (ii), we prove that the shifted states with the monotone profiles in the N  -  1 edges are spectrally stable, whereas the shifted states with non-monotone profiles in the N  -  1 edges are spectrally unstable, the two families intersect at the half-soliton states which are spectrally stable but nonlinearly unstable under the NLS flow. Since the NLS equation on a star graph with shifted states can be reduced to the homogeneous NLS equation on an infinite line, the spectral instability of shifted states is due to the perturbations breaking this reduction. We give a simple argument suggesting that the spectrally stable shifted states in the case of (ii) are nonlinearly unstable under the NLS flow due to the perturbations breaking the reduction to the homogeneous NLS equation.

  3. D-xylose absorption

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/003606.htm D-xylose absorption To use the sharing features on this page, please enable JavaScript. D-xylose absorption is a laboratory test to determine ...

  4. Micropatch Antenna Phase Shifting

    National Research Council Canada - National Science Library

    Thursby, Michael

    2000-01-01

    .... We have been looking at the ability of embedded element to adjust the phase shift seen by the element with the goal of being able to remove the phase shifting devices from the antenna and replace...

  5. Micropatch Antenna Phase Shifting

    National Research Council Canada - National Science Library

    Thursby, Michael

    1999-01-01

    .... We have been looking at the ability of embedded element to adjust the phase shift seen by the element wit the goal of being able to remove the phase shifting devices from the antenna and replace...

  6. Cutting Edge Localisation in an Edge Profile Milling Head

    NARCIS (Netherlands)

    Fernandez Robles, Laura; Azzopardi, George; Alegre, Enrique; Petkov, Nicolai

    2015-01-01

    Wear evaluation of cutting tools is a key issue for prolonging their lifetime and ensuring high quality of products. In this paper, we present a method for the effective localisation of cutting edges of inserts in digital images of an edge profile milling head. We introduce a new image data set of

  7. Gold analysis by the gamma absorption technique

    International Nuclear Information System (INIS)

    Kurtoglu, Arzu; Tugrul, A.B.

    2003-01-01

    Gold (Au) analyses are generally performed using destructive techniques. In this study, the Gamma Absorption Technique has been employed for gold analysis. A series of different gold alloys of known gold content were analysed and a calibration curve was obtained. This curve was then used for the analysis of unknown samples. Gold analyses can be made non-destructively, easily and quickly by the gamma absorption technique. The mass attenuation coefficients of the alloys were measured around the K-shell absorption edge of Au. Theoretical mass attenuation coefficient values were obtained using the WinXCom program and comparison of the experimental results with the theoretical values showed generally good and acceptable agreement

  8. Absorption and excretion tests

    International Nuclear Information System (INIS)

    Berberich, R.

    1988-01-01

    The absorption and excretion of radiopharmaceuticals is still of interest in diagnostic investigations of nuclear medicine. In this paper the most common methods of measuring absorption and excretion are described. The performance of the different tests and their standard values are discussed. More over the basic possibilities of measuring absorption and excretion including the needed measurement equipments are presented. (orig.) [de

  9. OpenShift Workshop

    CERN Multimedia

    CERN. Geneva; Rodriguez Peon, Alberto

    2017-01-01

    Workshop to introduce developers to the OpenShift platform available at CERN. Several use cases will be shown, including deploying an existing application into OpenShift. We expect attendees to realize about OpenShift features and general architecture of the service.

  10. Multiple scattering approach to X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Benfatto, M.; Wu Ziyu

    2003-01-01

    In this paper authors present the state of the art of the theoretical background needed for analyzing X-ray absorption spectra in the whole energy range. The multiple-scattering (MS) theory is presented in detail with some applications on real systems. Authors also describe recent progress in performing geometrical fitting of the XANES (X-ray absorption near-edge structure) energy region and beyond using a full multiple-scattering approach

  11. Flap Side Edge Liners for Airframe Noise Reduction

    Science.gov (United States)

    Jones, Michael G. (Inventor); Khorrami, Mehdi R. (Inventor); Choudhari, Meelan M. (Inventor); Howerton, Brian M. (Inventor)

    2014-01-01

    One or more acoustic liners comprising internal chambers or passageways that absorb energy from a noise source on the aircraft are disclosed. The acoustic liners may be positioned at the ends of flaps of an aircraft wing to provide broadband noise absorption and/or dampen the noise producing unsteady flow features, and to reduce the amount of noise generated due to unsteady flow at the inboard and/or outboard end edges of a flap.

  12. Edge instabilities of topological superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Hofmann, Johannes S. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg (Germany); Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany); Assaad, Fakher F. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg (Germany); Schnyder, Andreas P. [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany)

    2016-07-01

    Nodal topological superconductors display zero-energy Majorana flat bands at generic edges. The flatness of these edge bands, which is protected by time-reversal and translation symmetry, gives rise to an extensive ground state degeneracy and a diverging density of states. Therefore, even arbitrarily weak interactions lead to an instability of the flat-band edge states towards time-reversal and translation-symmetry broken phases, which lift the ground-state degeneracy. Here, we employ Monte Carlo simulations combined with mean-field considerations to examine the instabilities of the flat-band edge states of d{sub xy}-wave superconductors. We find that attractive interactions induce a complex s-wave pairing instability together with a density wave instability. Repulsive interactions, on the other hand, lead to ferromagnetism mixed with spin-triplet pairing at the edge. We discuss the implications of our findings for experiments on cuprate high-temperature superconductors.

  13. Calcium absorption and achlorhydria

    International Nuclear Information System (INIS)

    Recker, R.R.

    1985-01-01

    Defective absorption of calcium has been thought to exist in patients with achlorhydria. The author compared absorption of calcium in its carbonate form with that in a pH-adjusted citrate form in a group of 11 fasting patients with achlorhydria and in 9 fasting normal subjects. Fractional calcium absorption was measured by a modified double-isotope procedure with 0.25 g of calcium used as the carrier. Mean calcium absorption (+/- S.D.) in the patients with achlorhydria was 0.452 +/- 0.125 for citrate and 0.042 +/- 0.021 for carbonate (P less than 0.0001). Fractional calcium absorption in the normal subjects was 0.243 +/- 0.049 for citrate and 0.225 +/- 0.108 for carbonate (not significant). Absorption of calcium from carbonate in patients with achlorhydria was significantly lower than in the normal subjects and was lower than absorption from citrate in either group; absorption from citrate in those with achlorhydria was significantly higher than in the normal subjects, as well as higher than absorption from carbonate in either group. Administration of calcium carbonate as part of a normal breakfast resulted in completely normal absorption in the achlorhydric subjects. These results indicate that calcium absorption from carbonate is impaired in achlorhydria under fasting conditions. Since achlorhydria is common in older persons, calcium carbonate may not be the ideal dietary supplement

  14. Hydrogen bonding interaction of small acetaldehyde clusters studied with core-electron excitation spectroscopy in the oxygen K-edge region

    Science.gov (United States)

    Tabayashi, K.; Chohda, M.; Yamanaka, T.; Tsutsumi, Y.; Takahashi, O.; Yoshida, H.; Taniguchi, M.

    2010-06-01

    In order to examine inner-shell electron excitation spectra of molecular clusters with strong multipole interactions, excitation spectra and time-of-flight (TOF) fragment-mass spectra of small acetaldehyde (AA) clusters have been studied under the beam conditions. The TOF spectra at the oxygen K-edge region showed an intense growth of the protonated clusters, MnH+ (M=CH3CHO) in the cluster beams. "cluster-specific" excitation spectra could be generated by monitoring partial-ion-yields of the protonated clusters. The most intense band of O1s→π*CO was found to shift to a higher energy by 0.15 eV relative to the monomer band upon clusterization. X-ray absorption spectra (XAS) were also calculated for the representative dimer configurations using a computer modelling program based on the density functional theory. The XAS prediction for the most stable (non-planar) configuration was found to give a close comparison with the cluster-band shift observed. The band shift was interpreted as being due to the HOMO-LUMO interaction within the complex where a contribution of vibrationally blue-shifting hydrogen bonding could be identified.

  15. Edge computing technologies for Internet of Things: a primer

    Directory of Open Access Journals (Sweden)

    Yuan Ai

    2018-04-01

    Full Text Available With the rapid development of mobile internet and Internet of Things applications, the conventional centralized cloud computing is encountering severe challenges, such as high latency, low Spectral Efficiency (SE, and non-adaptive machine type of communication. Motivated to solve these challenges, a new technology is driving a trend that shifts the function of centralized cloud computing to edge devices of networks. Several edge computing technologies originating from different backgrounds to decrease latency, improve SE, and support the massive machine type of communication have been emerging. This paper comprehensively presents a tutorial on three typical edge computing technologies, namely mobile edge computing, cloudlets, and fog computing. In particular, the standardization efforts, principles, architectures, and applications of these three technologies are summarized and compared. From the viewpoint of radio access network, the differences between mobile edge computing and fog computing are highlighted, and the characteristics of fog computing-based radio access network are discussed. Finally, open issues and future research directions are identified as well. Keywords: Internet of Things (IoT, Mobile edge computing, Cloudlets, Fog computing

  16. [Study on lead absorption in pumpkin by atomic absorption spectrophotometry].

    Science.gov (United States)

    Li, Zhen-Xia; Sun, Yong-Dong; Chen, Bi-Hua; Li, Xin-Zheng

    2008-07-01

    A study was carried out on the characteristic of lead absorption in pumpkin via atomic absorption spectrophotometer. The results showed that lead absorption amount in pumpkin increased with time, but the absorption rate decreased with time; And the lead absorption amount reached the peak in pH 7. Lead and cadmium have similar characteristic of absorption in pumpkin.

  17. Optical absorption of BaF2 crystals with different prehistory when irradiated by high-energy electrons

    International Nuclear Information System (INIS)

    Chinkov, E P; Stepanov, S A; Shtan'ko, V F; Ivanova, T S

    2016-01-01

    The spectra of stable optical absorption of BaF 2 crystals containing uncontrollable impurities after irradiation with 3 MeV electrons are studied at room temperature. The dependence of the efficiency of stable color accumulation in the region of emerging crossluminescence on the absorption coefficients measured near the fundamental absorption edge in unirradiated crystals of various prehistory is traced. (paper)

  18. K-edge resonant x-ray magnetic scattering from a transition-metal oxide: NiO

    DEFF Research Database (Denmark)

    Hill, J.P.; Kao, C.C.; McMorrow, D.F.

    1997-01-01

    We report the observation of resonant x-ray magnetic scattering in the vicinity of the Ni K edge in the antiferromagnet NiO. An approximately twofold increase in the scattering is observed as the incident photon energy is tuned through a pre-edge feature in the absorption spectrum, associated...

  19. Characterization of the Electronic Structure of Silicon Nanoparticles Using X-ray Absorption and Emission

    Energy Technology Data Exchange (ETDEWEB)

    Vaverka, April Susan Montoya [Univ.of California, Davis, CA (United States)

    2008-01-01

    Resolving open questions regarding transport in nanostructures can have a huge impact on a broad range of future technologies such as light harvesting for energy. Silicon has potential to be used in many of these applications. Understanding how the band edges of nanostructures move as a function of size, surface termination and assembly is of fundamental importance in understanding the transport properties of these materials. In this thesis work I have investigated the change in the electronic structure of silicon nanoparticle assemblies as the surface termination is changed. Nanoparticles are synthesized using a thermal evaporation technique and sizes are determined using atomic force microscopy (AFM). By passivating the particles with molecules containing alcohol groups we are able to modify the size dependent band edge shifts. Both the valence and conduction bands are measured using synchrotron based x-ray absorption spectroscopy (XAS) and soft x-ray fluorescence (SXF) techniques. Particles synthesized via recrystallization of amorphous silicon/SiO2 multilayers of thicknesses below 10 nm are also investigated using the synchrotron techniques. These samples also show quantum confinement effects but the electronic structure is different from those synthesized via evaporation methods. The total bandgap is determined for all samples measured. The origins of these differences in the electronic structures are discussed.

  20. The edge of space time

    International Nuclear Information System (INIS)

    Hawking, S.

    1993-01-01

    What happened at the beginning of the expansion of the universe. Did space time have an edge at the Big Bang. The answer is that, if the boundary conditions of the universe are that it has no boundary, time ceases to be well-defined in the very early universe as the direction ''north'' ceases to be well defined at the North Pole of the Earth. The quantity that we measure as time has a beginning but that does not mean spacetime has an edge, just as the surface of the Earth does not have an edge at the North Pole. 8 figs

  1. Choice Shifts in Groups

    OpenAIRE

    Kfir Eliaz; Debraj Ray

    2004-01-01

    The phenomenon of "choice shifts" in group decision-making is fairly ubiquitous in the social psychology literature. Faced with a choice between a ``safe" and ``risky" decision, group members appear to move to one extreme or the other, relative to the choices each member might have made on her own. Both risky and cautious shifts have been identified in different situations. This paper demonstrates that from an individual decision-making perspective, choice shifts may be viewed as a systematic...

  2. Reduction of airfoil trailing edge noise by trailing edge blowing

    International Nuclear Information System (INIS)

    Gerhard, T; Carolus, T; Erbslöh, S

    2014-01-01

    The paper deals with airfoil trailing edge noise and its reduction by trailing edge blowing. A Somers S834 airfoil section which originally was designed for small wind turbines is investigated. To mimic realistic Reynolds numbers the boundary layer is tripped on pressure and suction side. The chordwise position of the blowing slot is varied. The acoustic sources, i.e. the unsteady flow quantities in the turbulent boundary layer in the vicinity of the trailing edge, are quantified for the airfoil without and with trailing edge blowing by means of a large eddy simulation and complementary measurements. Eventually the far field airfoil noise is measured by a two-microphone filtering and correlation and a 40 microphone array technique. Both, LES-prediction and measurements showed that a suitable blowing jet on the airfoil suction side is able to reduce significantly the turbulence intensity and the induced surface pressure fluctuations in the trailing edge region. As a consequence, trailing edge noise associated with a spectral hump around 500 Hz could be reduced by 3 dB. For that a jet velocity of 50% of the free field velocity was sufficient. The most favourable slot position was at 90% chord length

  3. Absorption heat pumps

    International Nuclear Information System (INIS)

    Formigoni, C.

    1998-01-01

    A brief description of the difference between a compression and an absorption heat pump is made, and the reasons why absorption systems have spread lately are given. Studies and projects recently started in the field of absorption heat pumps, as well as criteria usually followed in project development are described. An outline (performance targets, basic components) of a project on a water/air absorption heat pump, running on natural gas or LPG, is given. The project was developed by the Robur Group as an evolution of a water absorption refrigerator operating with a water/ammonia solution, which has been on the market for a long time and recently innovated. Finally, a list of the main energy and cost advantages deriving from the use of absorption heat pumps is made [it

  4. Implementing OpenShift

    CERN Document Server

    Miller, Adam

    2013-01-01

    A standard tutorial-based approach to using OpenShift and deploying custom or pre-built web applications to the OpenShift Online cloud.This book is for software developers and DevOps alike who are interested in learning how to use the OpenShift Platform-as-a-Service for developing and deploying applications, how the environment works on the back end, and how to deploy their very own open source Platform-as-a-Service based on the upstream OpenShift Origin project.

  5. Insomnia in shift work.

    Science.gov (United States)

    Vallières, Annie; Azaiez, Aïda; Moreau, Vincent; LeBlanc, Mélanie; Morin, Charles M

    2014-12-01

    Shift work disorder involves insomnia and/or excessive sleepiness associated with the work schedule. The present study examined the impact of insomnia on the perceived physical and psychological health of adults working on night and rotating shift schedules compared to day workers. A total of 418 adults (51% women, mean age 41.4 years), including 51 night workers, 158 rotating shift workers, and 209 day workers were selected from an epidemiological study. An algorithm was used to classify each participant of the two groups (working night or rotating shifts) according to the presence or absence of insomnia symptoms. Each of these individuals was paired with a day worker according to gender, age, and income. Participants completed several questionnaires measuring sleep, health, and psychological variables. Night and rotating shift workers with insomnia presented a sleep profile similar to that of day workers with insomnia. Sleep time was more strongly related to insomnia than to shift work per se. Participants with insomnia in the three groups complained of anxiety, depression, and fatigue, and reported consuming equal amounts of sleep-aid medication. Insomnia also contributed to chronic pain and otorhinolaryngology problems, especially among rotating shift workers. Work productivity and absenteeism were more strongly related to insomnia. The present study highlights insomnia as an important component of the sleep difficulties experienced by shift workers. Insomnia may exacerbate certain physical and mental health problems of shift workers, and impair their quality of life. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Nanoscale Phase Separation and Lattice Complexity in VO2: The Metal–Insulator Transition Investigated by XANES via Auger Electron Yield at the Vanadium L23-Edge and Resonant Photoemission

    Directory of Open Access Journals (Sweden)

    Augusto Marcelli

    2017-12-01

    Full Text Available Among transition metal oxides, VO2 is a particularly interesting and challenging correlated electron material where an insulator to metal transition (MIT occurs near room temperature. Here we investigate a 16 nm thick strained vanadium dioxide film, trying to clarify the dynamic behavior of the insulator/metal transition. We measured (resonant photoemission below and above the MIT transition temperature, focusing on heating and cooling effects at the vanadium L23-edge using X-ray Absorption Near-Edge Structure (XANES. The vanadium L23-edges probe the transitions from the 2p core level to final unoccupied states with 3d orbital symmetry above the Fermi level. The dynamics of the 3d unoccupied states both at the L3- and at the L2-edge are in agreement with the hysteretic behavior of this thin film. In the first stage of the cooling, the 3d unoccupied states do not change while the transition in the insulating phase appears below 60 °C. Finally, Resonant Photoemission Spectra (ResPES point out a shift of the Fermi level of ~0.75 eV, which can be correlated to the dynamics of the 3d// orbitals, the electron–electron correlation, and the stability of the metallic state.

  7. Lifshitz Tails for the Interband Light Absorption Coefficient

    Indian Academy of Sciences (India)

    In this paper we consider the interband light absorption coefficient (ILAC) for various models. We show that at the lower and upper edges of the spectrum the Lifshitz tails behaviour of the density of states implies similar behaviour for the ILAC at appropriate energies. The Lifshitz tails property is also exhibited at some points ...

  8. Improved edge charge exchange recombination spectroscopy in DIII-D.

    Science.gov (United States)

    Chrystal, C; Burrell, K H; Grierson, B A; Haskey, S R; Groebner, R J; Kaplan, D H; Briesemeister, A

    2016-11-01

    The charge exchange recombination spectroscopy diagnostic on the DIII-D tokamak has been upgraded with the addition of more high radial resolution view chords near the edge of the plasma (r/a > 0.8). The additional views are diagnosed with the same number of spectrometers by placing fiber optics side-by-side at the spectrometer entrance with a precise separation that avoids wavelength shifted crosstalk without the use of bandpass filters. The new views improve measurement of edge impurity parameters in steep gradient, H-mode plasmas with many different shapes. The number of edge view chords with 8 mm radial separation has increased from 16 to 38. New fused silica fibers have improved light throughput and clarify the observation of non-Gaussian spectra that suggest the ion distribution function can be non-Maxwellian in low collisionality plasmas.

  9. Characterization of selective binding of alkali cations with carboxylate by x-ray absorption spectroscopy of liquid microjets

    Energy Technology Data Exchange (ETDEWEB)

    Saykally, Richard J; Uejio, Janel S.; Schwartz, Craig P.; Duffin, Andrew M.; Drisdell, Walter S.; Cohen, Ronald C.; Saykally, Richard J.

    2008-01-08

    We describe an approach for characterizing selective binding between oppositely charged ionic functional groups under biologically relevant conditions. Relative shifts in K-shell x-ray absorption spectra of aqueous cations and carboxylate anions indicate the corresponding binding strengths via perturbations of carbonyl antibonding orbitals. XAS spectra measured for aqueous formate and acetate solutions containing lithium, sodium, and potassium cations reveal monotonically stronger binding of the lighter metals, supporting recent results from simulations and other experiments. The carbon K-edge spectra of the acetate carbonyl feature centered near 290 eV clearly indicate a preferential interaction of sodium versus potassium, which was less apparent with formate. These results are in accord with the Law of Matching Water Affinities, relating relative hydration strengths of ions to their respective tendencies to form contact ion pairs. Density functional theory calculations of K-shell spectra support the experimental findings.

  10. Characterization of selective binding of alkali cations with carboxylate by x-ray absorption spectroscopy of liquid microjets

    International Nuclear Information System (INIS)

    Saykally, Richard J; Uejio, Janel S.; Schwartz, Craig P.; Duffin, Andrew M.; Drisdell, Walter S.; Cohen, Ronald C.; Saykally, Richard J.

    2008-01-01

    We describe an approach for characterizing selective binding between oppositely charged ionic functional groups under biologically relevant conditions. Relative shifts in K-shell x-ray absorption spectra of aqueous cations and carboxylate anions indicate the corresponding binding strengths via perturbations of carbonyl antibonding orbitals. XAS spectra measured for aqueous formate and acetate solutions containing lithium, sodium, and potassium cations reveal monotonically stronger binding of the lighter metals, supporting recent results from simulations and other experiments. The carbon K-edge spectra of the acetate carbonyl feature centered near 290 eV clearly indicate a preferential interaction of sodium versus potassium, which was less apparent with formate. These results are in accord with the Law of Matching Water Affinities, relating relative hydration strengths of ions to their respective tendencies to form contact ion pairs. Density functional theory calculations of K-shell spectra support the experimental findings

  11. Excited State s-cis Rotamers Produced by Extreme Red Edge Excitation of all-trans-1,4-Diphenyl-1,3-butadiene

    DEFF Research Database (Denmark)

    Wallace-Williams, Stacie E.; Møller, Søren; Goldbeck, Robert A.

    1993-01-01

    with the wavelength independence observed for the excited singlet-state absorption and fluorescence emission spectra of 1,5-diphenyl-2,3,4,6,7,8- hexahydronaphthalene and for the fluorescence emission spectra of 1,4diphenyl-1,3-cyclopentadiene, s-trans and s-cis structural analogs of DPB, respectively. The spectral...... changes in DPB can be explained in terms of an excitation wavelength-dependent production of s-cis and s-trans rotamer populations in the excited state. The DPB fluorescence emission spectrum was resolved into s-cis and s-trans components. The vibronic structure of the s-cis fluorescence spectrum...... is similar to that of s-trans, but the band origin is red-shifted and there is a slightly larger amplitude on the red edge. The excited-state absorption spectrum of s-cis DPB appears to be red-shifted relative to that of s-trans DPB as well....

  12. Diffraction at a Straight Edge

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 20; Issue 5. Diffraction at a Straight Edge: A Gem from Sommerfeld's Work in Classical Physics. Rajaram Nityananda. General Article Volume 20 Issue 5 May 2015 pp 389-400 ...

  13. DAVs: Red Edge and Outbursts

    Science.gov (United States)

    Luan, Jing

    2018-04-01

    As established by ground based surveys, white dwarfs with hydrogen atmospheres pulsate as they cool across the temperature range, 12500Kred edge is a two-decade old puzzle. Recently, Kepler discovered a number of cool DAVs exhibiting sporadic outbursts separated by days, each lasting several hours, and releasing \\sim 10^{33}-10^{34} {erg}. We provide quantitative explanations for both the red edge and the outbursts. The minimal frequency for overstable modes rises abruptly near the red edge. Although high frequency overstable modes exist below the red edge, their photometric amplitudes are generally too small to be detected by ground based observations. Nevertheless, these overstable parent modes can manifest themselves through nonlinear mode couplings to damped daughter modes which generate limit cycles giving rise to photometric outbursts.

  14. Edge Fracture in Complex Fluids.

    Science.gov (United States)

    Hemingway, Ewan J; Kusumaatmaja, Halim; Fielding, Suzanne M

    2017-07-14

    We study theoretically the edge fracture instability in sheared complex fluids, by means of linear stability analysis and direct nonlinear simulations. We derive an exact analytical expression for the onset of edge fracture in terms of the shear-rate derivative of the fluid's second normal stress difference, the shear-rate derivative of the shear stress, the jump in shear stress across the interface between the fluid and the outside medium (usually air), the surface tension of that interface, and the rheometer gap size. We provide a full mechanistic understanding of the edge fracture instability, carefully validated against our simulations. These findings, which are robust with respect to choice of rheological constitutive model, also suggest a possible route to mitigating edge fracture, potentially allowing experimentalists to achieve and accurately measure flows stronger than hitherto possible.

  15. Lateral shifting in one dimensional chiral photonic crystal

    International Nuclear Information System (INIS)

    You Yuan; Chen Changyuan

    2012-01-01

    We report the lateral shifts of the transmitted waves in a one dimensional chiral photonic crystal by using the stationary-phase approach. It is revealed that two kinds of lateral shifts are observed due to the existence of cross coupling in chiral materials, which is different from what has been observed in previous non-chiral photonic crystals. Unlike the chiral slab, the positions of lateral shift peaks are closely related to the band edges of band gap characteristics of periodic structure and lateral shifts can be positive as well as negative. Besides, the lateral shifts show a strong dependence on the chiral factor, which varies the lateral shift peaks in both magnitudes and positions. These features are desirable for future device applications.

  16. Lateral shifting in one dimensional chiral photonic crystal

    Energy Technology Data Exchange (ETDEWEB)

    You Yuan, E-mail: yctcyouyuan@163.com [School of Physics and Electronics, Yancheng Teachers University, Yancheng, 224002 Jiangsu (China); Chen Changyuan [School of Physics and Electronics, Yancheng Teachers University, Yancheng, 224002 Jiangsu (China)

    2012-07-01

    We report the lateral shifts of the transmitted waves in a one dimensional chiral photonic crystal by using the stationary-phase approach. It is revealed that two kinds of lateral shifts are observed due to the existence of cross coupling in chiral materials, which is different from what has been observed in previous non-chiral photonic crystals. Unlike the chiral slab, the positions of lateral shift peaks are closely related to the band edges of band gap characteristics of periodic structure and lateral shifts can be positive as well as negative. Besides, the lateral shifts show a strong dependence on the chiral factor, which varies the lateral shift peaks in both magnitudes and positions. These features are desirable for future device applications.

  17. Material Discrimination Based on K-edge Characteristics

    Directory of Open Access Journals (Sweden)

    Peng He

    2013-01-01

    Full Text Available Spectral/multienergy CT employing the state-of-the-art energy-discriminative photon-counting detector can identify absorption features in the multiple ranges of photon energies and has the potential to distinguish different materials based on K-edge characteristics. K-edge characteristics involve the sudden attenuation increase in the attenuation profile of a relatively high atomic number material. Hence, spectral CT can utilize material K-edge characteristics (sudden attenuation increase to capture images in available energy bins (levels/windows to distinguish different material components. In this paper, we propose an imaging model based on K-edge characteristics for maximum material discrimination with spectral CT. The wider the energy bin width is, the lower the noise level is, but the poorer the reconstructed image contrast is. Here, we introduce the contrast-to-noise ratio (CNR criterion to optimize the energy bin width after the K-edge jump for the maximum CNR. In the simulation, we analyze the reconstructed image quality in different energy bins and demonstrate that our proposed optimization approach can maximize CNR between target region and background region in reconstructed image.

  18. 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.

  19. Feedback control of edge turbulence in a tokamak

    International Nuclear Information System (INIS)

    Kan, Zhai; Yi-zhi, Wen; Chang-xuan, Yu; Wan-dong, Liu; Chao, Wang; Ge, Zhuang; Kan, Zhai; Zhi-Zhan, Yu

    1997-01-01

    An experiment on feedback control of edge turbulence has been undertaken on the KT-5C tokamak. The results indicate that the edge turbulence could be suppressed or enhanced depending on the phase shift of the feedback network. In a typical case of 90 degree phase shift feedback, the turbulence amplitudes of both T e and n e were reduced by about 25% when the gain of the feedback network was 15. Correspondingly the radial particle flux decreased to about 75% level of the background. Through bispectral analysis it is found that there exists a substantial nonlinear coupling between various modes comprised in edge turbulence, especially in the frequency range from about 10 kHz to 100 kHz, which contains the large part of the edge turbulence energy in KT-5C tokamak. In particular, by actively controlling the turbulence amplitude using feedback, a direct experimental evidence of the link between the nonlinear wave-wave coupling over the whole spectrum in turbulence, the saturated turbulence amplitude, and the radial particle flux was provided. copyright 1997 The American Physical Society

  20. Edge of polar cap patches

    Science.gov (United States)

    Hosokawa, K.; Taguchi, S.; Ogawa, Y.

    2016-04-01

    On the night of 4 December 2013, a sequence of polar cap patches was captured by an all-sky airglow imager (ASI) in Longyearbyen, Norway (78.1°N, 15.5°E). The 630.0 nm airglow images from the ASI of 4 second exposure time, oversampled the emission of natural lifetime (with quenching) of at least ˜30 sec, introduce no observational blurring effects. By using such high-quality ASI images, we succeeded in visualizing an asymmetry in the gradients between the leading/trailing edges of the patches in a 2-D fashion. The gradient in the leading edge was found to be 2-3 times steeper than that in the trailing edge. We also identified fingerlike structures, appearing only along the trailing edge of the patches, whose horizontal scale size ranged from 55 to 210 km. These fingers are considered to be manifestations of plasma structuring through the gradient-drift instability (GDI), which is known to occur only along the trailing edge of patches. That is, the current 2-D observations visualized, for the first time, how GDI stirs the patch plasma and such a mixing process makes the trailing edge more gradual. This result strongly implies a close connection between the GDI-driven plasma stirring and the asymmetry in the large-scale shape of patches and then suggests that the fingerlike structures can be used as markers to estimate the fine-scale structure in the plasma flow within patches.

  1. A cutting-edge solution for 1µm laser metal processing

    Science.gov (United States)

    Baumbach, N.; Kühl, P.; Karam, J.; Jonkers, J.; Villarreal-Saucedo, F.; Reyes, M.

    2017-02-01

    The recent 1μm-laser cutting market is dominated by fiber and disk lasers due to their excellent beam quality of below 4mm*mrad. Teradiode's 4kW direct diode laser source achieves similar beam quality while having a different beam shape and shorter wavelengths which are known for higher absorption rates at the inclined front of the cutting keyhole. Research projects, such as the HALO Project, have additionally shown that polarized radiation and beams with shapes different from the typical LG00 lead to improved cut quality for ferrous and non-ferrous metals. [1] Diode laser have the inherent property of not being sensitive to back reflection which brings advantages in cutting high-reflective materials. The II-VI HIGHYAG laser cutting head BIMO-FSC offers the unique feature of machine controlled and continuous adjustment of both the focus diameter and the focus position. This feature is proven to be beneficial for cutting and piercing with high speed and small hole diameters. In addition, the optics are designed for lowest focus shift. As a leading laser processing head manufacturer, II-VI HIGHYAG qualified its BIMO-FSC MZ (M=magnification, Z=focus position) cutting head for Teradiode's 4kW direct diode laser source to offer a cutting-edge solution for highpower laser cutting. Combining the magnification ability of the cutting head with this laser source, customers experience strong advantages in cutting metals in broad thickness ranges. Thicknesses up to 25mm mild steel can easily be cut with excellent edge quality. Furthermore, a new optical setup equivalent to an axicon with a variable axicon angle is demonstrated which generates variable sized ring spots. The setup provides new degrees of freedom to tailor the energy distribution for even higher productivity and quality.

  2. Shifted Independent Component Analysis

    DEFF Research Database (Denmark)

    Mørup, Morten; Madsen, Kristoffer Hougaard; Hansen, Lars Kai

    2007-01-01

    Delayed mixing is a problem of theoretical interest and practical importance, e.g., in speech processing, bio-medical signal analysis and financial data modelling. Most previous analyses have been based on models with integer shifts, i.e., shifts by a number of samples, and have often been carried...

  3. Homogeneous bilateral block shifts

    Indian Academy of Sciences (India)

    Douglas class were classified in [3]; they are unilateral block shifts of arbitrary block size (i.e. dim H(n) can be anything). However, no examples of irreducible homogeneous bilateral block shifts of block size larger than 1 were known until now.

  4. OpenShift cookbook

    CERN Document Server

    Gulati, Shekhar

    2014-01-01

    If you are a web application developer who wants to use the OpenShift platform to host your next big idea but are looking for guidance on how to achieve this, then this book is the first step you need to take. This is a very accessible cookbook where no previous knowledge of OpenShift is needed.

  5. Ion charge-state production and photoionization near the K edge in argon and potassium

    International Nuclear Information System (INIS)

    Berry, H.G.; Azuma, Y.; Cowan, P.L.; Gemmell, D.S.; LeBrun, T.; Amusia, M.Y.

    1994-01-01

    We have measured the time-of-flight charge distributions of ions of argon and potassium following x-ray absorption at energies near their respective K edges. We confirm previously observed enhancements of the higher charge states at energies up to 100 eV below the K edge in argon. The measurements confirm recent calculations suggesting excitation of a virtual 1s state in this energy range

  6. Josephson shift registers

    International Nuclear Information System (INIS)

    Przybysz, J.X.

    1989-01-01

    This paper gives a review of Josephson shift register circuits that were designed, fabricated, or tested, with emphasis on work in the 1980s. Operating speed is most important, since it often limits system performance. Older designs used square-wave clocks, but most modern designs use offset sine waves, with either two or three phases. Operating margins and gate bias uniformity are key concerns. The fastest measured Josephson shift register operated at 2.3 GHz, which compares well with a GaAs shift register that consumes 250 times more power. The difficulties of high-speed testing have prevented many Josephson shift registers from being operated at their highest speeds. Computer simulations suggest that 30-GHz operation is possible with current Nb/Al 2 O 3 /Nb technology. Junctions with critical current densities near 10 kA/cm 2 would make 100-GHz shift registers feasible

  7. Solar absorption surface panel

    Science.gov (United States)

    Santala, Teuvo J.

    1978-01-01

    A composite metal of aluminum and nickel is used to form an economical solar absorption surface for a collector plate wherein an intermetallic compound of the aluminum and nickel provides a surface morphology with high absorptance and relatively low infrared emittance along with good durability.

  8. Nutrition and magnesium absorption

    NARCIS (Netherlands)

    Brink, E.J.

    1992-01-01

    The influence of various nutrients present in dairy products and soybean-based products on absorption of magnesium has been investigated. The studies demonstrate that soybean protein versus casein lowers apparent magnesium absorption in rats through its phytate component. However, true

  9. Zeeman atomic absorption spectroscopy

    International Nuclear Information System (INIS)

    Loos-Vollebregt, M.T.C. de.

    1980-01-01

    A new method of background correction in atomic absorption spectroscopy has recently been introduced, based on the Zeeman splitting of spectral lines in a magnetic field. A theoretical analysis of the background correction capability observed in such instruments is presented. A Zeeman atomic absorption spectrometer utilizing a 50 Hz sine wave modulated magnetic field is described. (Auth.)

  10. X-ray absorption spectroscopy of PbMoO 4 single crystals

    Indian Academy of Sciences (India)

    X-ray absorption spectra of PbMoO4 (LMO) crystals have been investigated for the first time in literature. The measurements have been carried out at Mo absorption edge at the dispersive EXAFS beamline (BL-8) of INDUS-2 Synchrotron facility at Indore, India. The optics of the beamline was set to obtain a band of 2000 eV ...

  11. Optical absorption and Faraday rotation in spin doped Cd1-xHgxSe : Mn crystals

    NARCIS (Netherlands)

    Savchuk, AI; Paranchich, SY; Paranchich, LD; Romanyuk, OS; Andriychuk, MD; Nikitin, PI; Tomlinson, RD; Hill, AE; Pilkington, RD

    1998-01-01

    Optical absorption spectra and the Faraday effect in crystals of Cd1-xHgxSe : Mn have been studied. The studied samples have been characterized abrupt absorption edge and transparency region with high transmission coefficient. The measured values of Verdet constant were considerably larger than in

  12. Determination of Cr(VI) in wood specimen: A XANES study at the Cr K edge

    International Nuclear Information System (INIS)

    Strub, E.; Plarre, R.; Radtke, M.; Reinholz, U.; Riesemeier, H.; Schoknecht, U.; Urban, K.; Juengel, P.

    2008-01-01

    The content of chromium in different oxidation states in chromium-treated wood was studied with XANES (X-ray absorption near-edge structure) measurements at the Cr K absorption edge. It could be shown that wood samples treated with Cr(VI) (pine and beech) did still contain a measurable content of Cr(VI) after four weeks conditioning. If such wood samples were heat exposed for 2 h with 135 deg. C prior conditioning, Cr(VI) was no longer detected by XANES, indicating a complete reduction to chromium (III)

  13. 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

  14. [Road Extraction in Remote Sensing Images Based on Spectral and Edge Analysis].

    Science.gov (United States)

    Zhao, Wen-zhi; Luo, Li-qun; Guo, Zhou; Yue, Jun; Yu, Xue-ying; Liu, Hui; Wei, Jing

    2015-10-01

    Roads are typically man-made objects in urban areas. Road extraction from high-resolution images has important applications for urban planning and transportation development. However, due to the confusion of spectral characteristic, it is difficult to distinguish roads from other objects by merely using traditional classification methods that mainly depend on spectral information. Edge is an important feature for the identification of linear objects (e. g. , roads). The distribution patterns of edges vary greatly among different objects. It is crucial to merge edge statistical information into spectral ones. In this study, a new method that combines spectral information and edge statistical features has been proposed. First, edge detection is conducted by using self-adaptive mean-shift algorithm on the panchromatic band, which can greatly reduce pseudo-edges and noise effects. Then, edge statistical features are obtained from the edge statistical model, which measures the length and angle distribution of edges. Finally, by integrating the spectral and edge statistical features, SVM algorithm is used to classify the image and roads are ultimately extracted. A series of experiments are conducted and the results show that the overall accuracy of proposed method is 93% comparing with only 78% overall accuracy of the traditional. The results demonstrate that the proposed method is efficient and valuable for road extraction, especially on high-resolution images.

  15. Numerical study of surface plasmon enhanced nonlinear absorption and refraction.

    Science.gov (United States)

    Kohlgraf-Owens, Dana C; Kik, Pieter G

    2008-07-07

    Maxwell Garnett effective medium theory is used to study the influence of silver nanoparticle induced field enhancement on the nonlinear response of a Kerr-type nonlinear host. We show that the composite nonlinear absorption coefficient, beta(c), can be enhanced relative to the host nonlinear absorption coefficient near the surface plasmon resonance of silver nanoparticles. This enhancement is not due to a resonant enhancement of the host nonlinear absorption, but rather due to a phase shifted enhancement of the host nonlinear refractive response. The enhancement occurs at the expense of introducing linear absorption, alpha(c), which leads to an overall reduced figure of merit beta(c)/alpha(c) for nonlinear absorption. For thin (< 1 microm) composites, the use of surface plasmons is found to result in an increased nonlinear absorption response compared to that of the host material.

  16. Optical absorption of carbon-gold core-shell nanoparticles

    Science.gov (United States)

    Wang, Zhaolong; Quan, Xiaojun; Zhang, Zhuomin; Cheng, Ping

    2018-01-01

    In order to enhance the solar thermal energy conversion efficiency, we propose to use carbon-gold core-shell nanoparticles dispersed in liquid water. This work demonstrates theoretically that an absorbing carbon (C) core enclosed in a plasmonic gold (Au) nanoshell can enhance the absorption peak while broadening the absorption band; giving rise to a much higher solar absorption than most previously studied core-shell combinations. The exact Mie solution is used to evaluate the absorption efficiency factor of spherical nanoparticles in the wavelength region from 300 nm to 1100 nm as well as the electric field and power dissipation profiles inside the nanoparticles at specified wavelengths (mostly at the localized surface plasmon resonance wavelength). The field enhancement by the localized plasmons at the gold surfaces boosts the absorption of the carbon particle, resulting in a redshift of the absorption peak with increased peak height and bandwidth. In addition to spherical nanoparticles, we use the finite-difference time-domain method to calculate the absorption of cubic core-shell nanoparticles. Even stronger enhancement can be achieved with cubic C-Au core-shell structures due to the localized plasmonic resonances at the sharp edges of the Au shell. The solar absorption efficiency factor can exceed 1.5 in the spherical case and reach 2.3 in the cubic case with a shell thickness of 10 nm. Such broadband absorption enhancement is in great demand for solar thermal applications including steam generation.

  17. Mercury's shifting, rolling past

    OpenAIRE

    Trulove, Susan

    2008-01-01

    Patterns of scalloped-edged cliffs or lobate scarps on Mercury's surface are thrust faults that are consistent with the planet shrinking and cooling with time. However, compression occurred in the planet's early history and Mariner 10 images revealed decades ago that lobate scarps are among the youngest features on Mercury. Why don't we find more evidence of older compressive features?

  18. Resonance-shifting luminescent solar concentrators

    Energy Technology Data Exchange (ETDEWEB)

    Giebink, Noel Christopher; Wiederrecht, Gary P.; Wasielewski, Michael R.

    2018-01-23

    An optical system and method to overcome luminescent solar concentrator inefficiencies by resonance-shifting, in which sharply directed emission from a bi-layer cavity into a glass substrate returns to interact with the cavity off-resonance at each subsequent reflection, significantly reducing reabsorption loss en route to the edges. In one embodiment, the system comprises a luminescent solar concentrator comprising a transparent substrate, a luminescent film having a variable thickness; and a low refractive index layer disposed between the transparent substrate and the luminescent film.

  19. Protected Edge Modes without Symmetry

    Directory of Open Access Journals (Sweden)

    Michael Levin

    2013-05-01

    Full Text Available We discuss the question of when a gapped two-dimensional electron system without any symmetry has a protected gapless edge mode. While it is well known that systems with a nonzero thermal Hall conductance, K_{H}≠0, support such modes, here we show that robust modes can also occur when K_{H}=0—if the system has quasiparticles with fractional statistics. We show that some types of fractional statistics are compatible with a gapped edge, while others are fundamentally incompatible. More generally, we give a criterion for when an electron system with Abelian statistics and K_{H}=0 can support a gapped edge: We show that a gapped edge is possible if and only if there exists a subset of quasiparticle types M such that (1 all the quasiparticles in M have trivial mutual statistics, and (2 every quasiparticle that is not in M has nontrivial mutual statistics with at least one quasiparticle in M. We derive this criterion using three different approaches: a microscopic analysis of the edge, a general argument based on braiding statistics, and finally a conformal field theory approach that uses constraints from modular invariance. We also discuss the analogous result for two-dimensional boson systems.

  20. Image reconstruction for x-ray K-edge imaging with a photon counting detector

    Science.gov (United States)

    Meng, Bo; Cong, Wenxiang; Xi, Yan; Wang, Ge

    2014-09-01

    Contrast agents with high-Z elements have K-absorption edges which significantly change X-ray attenuation coefficients. The K-edge characteristics is different for various kinds of contrast agents, which offers opportunities for material decomposition in biomedical applications. In this paper, we propose a new K-edge imaging method, which not only quantifies a distribution of a contrast agent but also provides an optimized contrast ratio. Our numerical simulation tests demonstrate the feasibility and merits of the proposed methodology.

  1. Plutonium isotopic assay of reprocessing product solutions in the KfK K-edge densitometer

    International Nuclear Information System (INIS)

    Eberle, H.; Ottmar, H.; Matussek, P.

    1985-04-01

    The KfK K-edge densiometer, designed for accurate element concentration measurements using the technique of X-ray absorptiometry at the K absorption edge, provides as an additional option the possibility to determine the isotopic composition of freshly separated plutonium from an gamma-spectrometric analysis of its self-radiation. This report describes the underlying methodology and experimental procedures for the isotopic analysis in the K-edge densitometer. The paper also presents and discusses the experimental results so far obtained from routine measurements on reprocessing product solutions. (orig.)

  2. Optical absorption in SrC4H4O6·3H2O crystals

    International Nuclear Information System (INIS)

    Arora, S.K.; Patel, Vipul; Kothari, Anjana; Chudasama, Bhupendra

    2004-01-01

    Study of optical absorption in the gel-grown strontium tartrate trihydrate (STT) single crystals measured in UV-vis range at room temperature reveals transitions involving absorption and emission of phonons. Based on the theory of interband optical absorptions, the electronic transition near the fundamental absorption edge is analysed. Some feeble disorder in the crystal is conceived to be present. The analysis carried out hereunder leads to estimation of energy of the lattice phonons involved

  3. Quasar Absorption Studies

    Science.gov (United States)

    Mushotzky, Richard (Technical Monitor); Elvis, Martin

    2004-01-01

    The aim of the proposal is to investigate the absorption properties of a sample of inter-mediate redshift quasars. The main goals of the project are: Measure the redshift and the column density of the X-ray absorbers; test the correlation between absorption and redshift suggested by ROSAT and ASCA data; constrain the absorber ionization status and metallicity; constrain the absorber dust content and composition through the comparison between the amount of X-ray absorption and optical dust extinction. Unanticipated low energy cut-offs where discovered in ROSAT spectra of quasars and confirmed by ASCA, BeppoSAX and Chandra. In most cases it was not possible to constrain adequately the redshift of the absorber from the X-ray data alone. Two possibilities remain open: a) absorption at the quasar redshift; and b) intervening absorption. The evidences in favour of intrinsic absorption are all indirect. Sensitive XMM observations can discriminate between these different scenarios. If the absorption is at the quasar redshift we can study whether the quasar environment evolves with the Cosmic time.

  4. Analytical theory for the nuclear level shift of hadronic atoms

    International Nuclear Information System (INIS)

    Kudryavtsev, A.E.; Lisin, V.I.; Popov, V.S.

    1982-01-01

    The spectrum problem in the Coulomb potential distorted at small distances is considered. Nuclear shifts of 3-levels in p anti p and Σ - p atoms are calculated. The probabilities of radiative transitions from p-states to the shifted s-states in hadronic atom are also given. It is shown that the reconstruction of atomic levels switches to oscillation regime when absorption increases. The limits of applicability of the perturbation theory in terms of the scattering length for different values of absorption is discussed. An exactly solvable model, Coulomb plus Yamaguchi potential, is considered

  5. Particle-in-a-box model of exciton absorption and electroabsorption in conjugated polymers

    Science.gov (United States)

    Pedersen, Thomas G.

    2000-12-01

    The recently proposed particle-in-a-box model of one-dimensional excitons in conjugated polymers is applied in calculations of optical absorption and electroabsorption spectra. It is demonstrated that for polymers of long conjugation length a superposition of single exciton resonances produces a line shape characterized by a square-root singularity in agreement with experimental spectra near the absorption edge. The effects of finite conjugation length on both absorption and electroabsorption spectra are analyzed.

  6. Uranium absorption study pile

    International Nuclear Information System (INIS)

    Raievski, V.; Sautiez, B.

    1959-01-01

    The report describes a pile designed to measure the absorption of fuel slugs. The pile is of graphite and comprises a central section composed of uranium rods in a regular lattice. RaBe sources and BF 3 counters are situated on either side of the center. A given uranium charge is compared with a specimen charge of about 560 kg, and the difference in absorption between the two noted. The sensitivity of the equipment will detect absorption variations of about a few ppm boron (10 -6 boron per gr. of uranium) or better. (author) [fr

  7. Total photon absorption

    International Nuclear Information System (INIS)

    Carlos, P.

    1985-06-01

    The present discussion is limited to a presentation of the most recent total photonuclear absorption experiments performed with real photons at intermediate energy, and more precisely in the region of nucleon resonances. The main sources of real photons are briefly reviewed and the experimental procedures used for total photonuclear absorption cross section measurements. The main results obtained below 140 MeV photon energy as well as above 2 GeV are recalled. The experimental study of total photonuclear absorption in the nuclear resonance region (140 MeV< E<2 GeV) is still at its beginning and some results are presented

  8. Nurses' shift reports

    DEFF Research Database (Denmark)

    Buus, Niels; Hoeck, Bente; Hamilton, Bridget Elizabeth

    2017-01-01

    AIMS AND OBJECTIVES: To identify reporting practices that feature in studies of nurses' shift reports across diverse nursing specialities. The objectives were to perform an exhaustive systematic literature search and to critically review the quality and findings of qualitative field studies...... of nurses' shift reports. BACKGROUND: Nurses' shift reports are routine occurrences in healthcare organisations that are viewed as crucial for patient outcomes, patient safety and continuity of care. Studies of communication between nurses attend primarily to 1:1 communication and analyse the adequacy...... and accuracy of patient information and feature handovers at the bedside. Still, verbal reports between groups of nurses about patients are commonplace. Shift reports are obvious sites for studying the situated accomplishment of professional nursing at the group level. This review is focused exclusively...

  9. Shift Verification and Validation

    Energy Technology Data Exchange (ETDEWEB)

    Pandya, Tara M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Evans, Thomas M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Davidson, Gregory G [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Johnson, Seth R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Godfrey, Andrew T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-09-07

    This documentation outlines the verification and validation of Shift for the Consortium for Advanced Simulation of Light Water Reactors (CASL). Five main types of problems were used for validation: small criticality benchmark problems; full-core reactor benchmarks for light water reactors; fixed-source coupled neutron-photon dosimetry benchmarks; depletion/burnup benchmarks; and full-core reactor performance benchmarks. We compared Shift results to measured data and other simulated Monte Carlo radiation transport code results, and found very good agreement in a variety of comparison measures. These include prediction of critical eigenvalue, radial and axial pin power distributions, rod worth, leakage spectra, and nuclide inventories over a burn cycle. Based on this validation of Shift, we are confident in Shift to provide reference results for CASL benchmarking.

  10. All-graphene edge contacts

    DEFF Research Database (Denmark)

    Jacobsen, Kåre Wedel; Falkenberg, Jesper Toft; Papior, Nick Rübner

    2016-01-01

    Using ab-initio methods we investigate the possibility of three-terminalgraphene "T-junction" devices and show that these all-graphene edge contactsare energetically feasible when the 1D interface itself is free from foreignatoms. We examine the energetics of various junction structures as a func......Using ab-initio methods we investigate the possibility of three-terminalgraphene "T-junction" devices and show that these all-graphene edge contactsare energetically feasible when the 1D interface itself is free from foreignatoms. We examine the energetics of various junction structures...... to be in therange of 1-10 kΩμm which is comparable to the best contact resistance reportedfor edge-contacted graphene-metal contacts. We conclude that conductingall-carbon T-junctions should be feasible....

  11. Molecular Electronic Shift Registers

    Science.gov (United States)

    Beratan, David N.; Onuchic, Jose N.

    1990-01-01

    Molecular-scale shift registers eventually constructed as parts of high-density integrated memory circuits. In principle, variety of organic molecules makes possible large number of different configurations and modes of operation for such shift-register devices. Several classes of devices and implementations in some specific types of molecules proposed. All based on transfer of electrons or holes along chains of repeating molecular units.

  12. Improving color constancy by photometric edge weighting

    NARCIS (Netherlands)

    Gijsenij, A.; Gevers, T.; van de Weijer, J.

    2012-01-01

    Edge-based color constancy methods make use of image derivatives to estimate the illuminant. However, different edge types exist in real-world images, such as material, shadow, and highlight edges. These different edge types may have a distinctive influence on the performance of the illuminant

  13. The knife-edge chamber

    International Nuclear Information System (INIS)

    Barasch, E.F.; Bowcock, T.J.V.; Drew, M.M.; Elliott, S.M.; Lee, B.; McIntyre, P.M.; Pang, Y.; Popovic, M.; Smith, D.D.

    1990-01-01

    In this paper the design for a new technology for particle track detectors is described. Using standard IC fabrication techniques, a pattern of microscopic knife edges and field-shaping electrodes can be fabricated on a silicon substrate. The knife-edge chamber uniquely offers attractive performance for the track chambers required for SSC detectors, for which no present technology is yet satisfactory. Its features include: excellent radiation hardness (10 Mrad), excellent spatial resolution (∼20 μm), short drift time (20 ns), and large pulse height (1 mV)

  14. Identifying the perfect absorption of metamaterial absorbers

    Science.gov (United States)

    Duan, G.; Schalch, J.; Zhao, X.; Zhang, J.; Averitt, R. D.; Zhang, X.

    2018-01-01

    We present a detailed analysis of the conditions that result in unity absorption in metamaterial absorbers to guide the design and optimization of this important class of functional electromagnetic composites. Multilayer absorbers consisting of a metamaterial layer, dielectric spacer, and ground plane are specifically considered. Using interference theory, the dielectric spacer thickness and resonant frequency for unity absorption can be numerically determined from the functional dependence of the relative phase shift of the total reflection. Further, using transmission line theory in combination with interference theory we obtain analytical expressions for the unity absorption resonance frequency and corresponding spacer layer thickness in terms of the bare resonant frequency of the metamaterial layer and metallic and dielectric losses within the absorber structure. These simple expressions reveal a redshift of the unity absorption frequency with increasing loss that, in turn, necessitates an increase in the thickness of the dielectric spacer. The results of our analysis are experimentally confirmed by performing reflection-based terahertz time-domain spectroscopy on fabricated absorber structures covering a range of dielectric spacer thicknesses with careful control of the loss accomplished through water absorption in a semiporous polyimide dielectric spacer. Our findings can be widely applied to guide the design and optimization of the metamaterial absorbers and sensors.

  15. Preposition stranding versus pied-piping: Negative Shift of prepositional complements in dialects of Faroese

    Directory of Open Access Journals (Sweden)

    Eva Engels

    2009-01-01

             These asymmetries will be accounted for within Fox and Pesetsky's (2003, 2005 cyclic linearization model, which requires non-string-vacuous movement to proceed through the left edge of Spell-out domains, deriving cross-linguistic variation as to Negative Shift from differences in the availability of these left-edge positions. Thereby, pied-piping is considered a last resort strategy, possible only if the prepositional complement cannot undergo Negative Shift on its own due to the unavailability of the relevant left-edge position.

  16. Absorption heat pump system

    Science.gov (United States)

    Grossman, G.

    1982-06-16

    The efficiency of an absorption heat pump system is improved by conducting liquid from a second stage evaporator thereof to an auxiliary heat exchanger positioned downstream of a primary heat exchanger in the desorber of the system.

  17. Zeeman atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Hadeishi, T.; McLaughlin, R.

    1978-08-01

    The design and development of a Zeeman atomic absorption spectrometer for trace element analysis are described. An instruction manual is included which details the operation, adjustment, and maintenance. Specifications and circuit diagrams are given

  18. Absorption by Spinning Dust: A Contaminant for High-redshift 21 cm Observations

    Science.gov (United States)

    Draine, B. T.; Miralda-Escudé, Jordi

    2018-05-01

    Spinning dust grains in front of the bright Galactic synchrotron background can produce a weak absorption signal that could affect measurements of high-redshift 21 cm absorption. At frequencies near 80 MHz where the Experiment to Detect the Global EoR Signature (EDGES) has reported 21 cm absorption at z≈ 17, absorption could be produced by interstellar nanoparticles with radii a≈ 50 \\mathringA in the cold interstellar medium (ISM), with rotational temperature T ≈ 50 K. Atmospheric aerosols could contribute additional absorption. The strength of the absorption depends on the abundance of such grains and on their dipole moments, which are uncertain. The breadth of the absorption spectrum of spinning dust limits its possible impact on measurement of a relatively narrow 21 cm absorption feature.

  19. Extended x-ray absorption fine structure study of MnFeP0.56Si0.44 compound

    International Nuclear Information System (INIS)

    Li Ying-Jie; Haschaolu W; Wurentuya; Song Zhi-Qiang; Ou Zhi-Qiang; Tegus O; Nakai Ikuo

    2015-01-01

    The MnFeP 0.56 Si 0.44 compound is investigated by x-ray diffraction, magnetic measurements, and x-ray absorption fine structure spectroscopy. It crystallizes in Fe 2 P-type structure with the lattice parameters a = b = 5.9823(0) Å and c = 3.4551(1) Å and undergoes a first-order phase transition at the Curie temperature of 255 K. The Fe K edge and Mn K edge x-ray absorption fine structure spectra show that Mn atoms mainly reside at 3g sites, while 3f sites are occupied by Fe atoms. The distances between the absorbing Fe atom and the first and second nearest neighbor Fe atoms in a 3f-layer shift from 2.65 Å and 4.01 Å in the ferromagnetic state to 2.61 Å and 3.96 Å in the paramagnetic phase. On the other hand, the distance between the 3g-layer and 3f-layer changes a little as 2.66 Å–2.73 Å below the Curie temperature and 2.68 Å–2.75 Å above it. (paper)

  20. Extension to Low Energies (<7keV) of High Pressure X-Ray Absorption Spectroscopy

    International Nuclear Information System (INIS)

    Itie, J.-P.; Flank, A.-M.; Lagarde, P.; Idir, M.; Polian, A.; Couzinet, B.

    2007-01-01

    High pressure x-ray absorption has been performed down to 3.6 keV, thanks to the new LUCIA beamline (SLS, PSI) and to the use of perforated diamonds or Be gasket. Various experimental geometries are proposed, depending on the energy of the edge and on the concentration of the studied element. A few examples will be presented: BaTiO3 at the titanium K edge, Zn0.95 Mn0.05O at the manganese K edge, KCl at the potassium K edge

  1. Revisiting Absorptive Capacity

    DEFF Research Database (Denmark)

    de Araújo, Ana Luiza Lara; Ulhøi, John Parm; Lettl, Christopher

    Absorptive capacity has mostly been perceived as a 'passive' outcome of R&D investments. Recently, however, a growing interest into its 'proactive' potentials has emerged. This paper taps into this development and proposes a dynamic model for conceptualizing the determinants of the complementary...... learning processes of absorptive capacity, which comprise combinative and adaptive capabilities. Drawing on survey data (n=169), the study concludes that combinative capabilities primarily enhance transformative and exploratory learning processes, while adaptive capabilities strengthen all three learning...

  2. Comment on resonant absorption

    International Nuclear Information System (INIS)

    Hammerling, P.

    1977-01-01

    An average over angles of incidence of the usual resonant absorption function is presented. This form is appropriate under experimental conditions where the angles of incidence vary greatly and in an unknown manner. For comparison a lens-ellipsoidal mirror illumination system with a known longitudinal aberration is considered. In the latter example the angles of incidence are readily obtained and the resulting resonance absorption function evaluated. The associated fields are calculated in a similar fashion. (author)

  3. Optical absorption measurement system

    International Nuclear Information System (INIS)

    Draggoo, V.G.; Morton, R.G.; Sawicki, R.H.; Bissinger, H.D.

    1989-01-01

    This patent describes a non-intrusive method for measuring the temperature rise of optical elements under high laser power optical loading to determine the absorption coefficient. The method comprises irradiating the optical element with a high average power laser beam, viewing the optical element with an infrared camera to determine the temperature across the optical element and calculating the absorption of the optical element from the temperature

  4. Absorption band Q model for the earth

    International Nuclear Information System (INIS)

    Anderson, D.L.; Given, J.W.

    1982-01-01

    Body wave, surface wave, and normal mode data are used to place constraints on the frequency dependence of Q in the mantle. With a simple absorption band model it is possible to satisfy the shear sensitive data over a broad frequency range. The quality factor Q/sub s/(ω) is proportional to ω/sup α/ in the band and to ω and ω -1 at higher and lower frequencies, respectively, as appropriate for a relaxation mechanism with a spectrum of relaxation time. The parameters of the band are Q(min) = 80, α = 0.15, and width, 5 decades. The center of the band varies from 10 1 seconds in the upper mantle, to 1.6 x 10 3 seconds in the lower mantle. The shift of the band with depth is consistent with the expected effects of temperature, pressure and stress. High Q, regions of the mantle are attributed to a shift of the absorption band to longer periods. To satisfy the gravest fundamental spheroidal modes and the ScS data, the absorption band must shift back into the short-period seismic band at the base of the mantle. This may be due to a high temperature gradient or high shear stresses. A preliminary attempt is also made to specify bulk dissipation in the mantle and core. Specific features of the absorption band model are low Q in the body wave band at both the top and the base of the mantle, low Q for long-period body waves in the outer core, an inner core Q 2 that increases with period, and low Q/sub p//Q/sub s/ at short periods in the middle mantel. The short-period Q/sub s/ increases rapidly at 400 km and is relatively constant from this depth to 2400 km. The deformational Q of the earth at a period of 14 months is predicted to be 463

  5. Absorption of ultraviolet radiation by antarctic phytoplankton

    Energy Technology Data Exchange (ETDEWEB)

    Vernet, M.; Mitchell, B.G. (Univ. of California-San Diego, La Jolla (United States))

    1990-01-09

    Antarctic phytoplankton contain UV-absorbing compounds that may block damaging radiation. Compounds that absorb from 320-340 nm were observed in spectral absorption of both particulates and in methanol extracts of the particulates. The decrease in the total concentration of these UV compounds with respect to chlorophyll a, as measured by the ratio of in vitro absorption at 335 nm to absorption at 665 nm is variable and decreases with depth. We observed up to 5-fold decrease in this ratio for samples within the physically mixes surface layer. The absorption of UV radiation in methanol extracts, which peaks from 320 to 340 nm, may be composed of several compounds. Shifts in peak absorption with depth (for example, from 331 nm at surface to 321 nm at 75 m), may be interpreted as a change in composition. Ratios of protective yellow xanthophylls (diadinoxanthin + diatoxanthin) to photosynthetic fucoxanthin-like pigments have highest values in surface waters. As these pigments also absorb in the near UV, their function might extend to protection as well as utilization of UV radiation for photosynthesis. We document strong absorption in the UV from 320-330 nm for Antarctic marine particulates. Below this region of the solar energy spectrum, absolute energy levels of incident radiation drop off dramatically. Only wavelengths shorter than about 320 nm will be significantly enhanced due to ozone depletion. If the absorption we observed serves a protective role for phytoplankton photosynthesis, it appears the peak band is in the region where solar energy increases rapidly, and not in the region where depletion would cause significant variations in absolute flux.

  6. Comparison of iodine K-edge subtraction and fluorescence subtraction imaging in an animal system

    International Nuclear Information System (INIS)

    Zhang, H.; Zhu, Y.; Bewer, B.; Zhang, L.; Korbas, M.; Pickering, I.J.; George, G.N.; Gupta, M.; Chapman, D.

    2008-01-01

    K-Edge Subtraction (KES) utilizes the discontinuity in the X-ray absorption across the absorption edge of the selected contrast element and creates an image of the projected density of the contrast element from two images acquired just above and below the K-edge of the contrast element. KES has proved to be powerful in coronary angiography, micro-angiography, bronchography, and lymphatic imaging. X-ray fluorescence imaging is a successful technique for the detection of dilute quantities of elements in specimens. However, its application at high X-ray energies (e.g. at the iodine K-edge) is complicated by significant Compton background, which may enter the energy window set for the contrast material's fluorescent X-rays. Inspired by KES, Fluorescence Subtraction Imaging (FSI) is a technique for high-energy (>20 keV) fluorescence imaging using two different incident beam energies just above and below the absorption edge of a contrast element (e.g. iodine). The below-edge image can be assumed as a 'background' image, which includes Compton scatter and fluorescence from other elements. The above-edge image will contain nearly identical spectral content as the below-edge image but will contain the additional fluorescence of the contrast element. This imaging method is especially promising with thick objects with dilute contrast materials, significant Compton background, and/or competing fluorescence lines from other materials. A quality factor is developed to facilitate the comparison. The theoretical value of the quality factor sets the upper limit that an imaging method can achieve when the noise is Poisson limited. The measured value of this factor makes two or more imaging methods comparable. Using the Hard X-ray Micro-Analysis (HXMA) beamline at the Canadian Light Source (CLS), the techniques of FSI and KES were critically compared, with reference to radiation dose, image acquisition time, resolution, signal-to-noise ratios, and quality factor

  7. At the edge of intonation

    DEFF Research Database (Denmark)

    Niebuhr, Oliver

    2012-01-01

    The paper is concerned with the 'edge of intonation' in a twofold sense. It focuses on utterance-final F0 movements and crosses the traditional segment-prosody divide by investigating the interplay of F0 and voiceless fricatives in speech production. An experiment was performed for German with four...

  8. Capillary Sharp Inner Edge Manufacturing

    Czech Academy of Sciences Publication Activity Database

    Hošek, Jan; Studenovský, K.; Najdek, D.

    2009-01-01

    Roč. 19, č. 35 (2009), s. 19-25 ISSN 1584-5982. [MECAHITECH 09 /1./. Bukurešť, 08.10.2009-09.10.2009] R&D Projects: GA AV ČR IAA200760905 Institutional research plan: CEZ:AV0Z20760514 Keywords : capillary * edge * manufacturing Subject RIV: JR - Other Machinery

  9. Development of edge effects around experimental ecosystem hotspots is affected by edge density and matrix type

    Science.gov (United States)

    Ecological edge effects are sensitive to landscape context. In particular, edge effects can be altered by matrix type and by the presence of other nearby edges. We experimentally altered patch configurations in an African savanna to determine how edge density and matrix type influence edge effect de...

  10. Piecing together the fragments: Elucidating edge effects on forest carbon dynamics

    Science.gov (United States)

    Hutyra, L.; Smith, I. A.; Reinmann, A.; Marrs, J.; Thompson, J.

    2017-12-01

    Forest fragmentation is pervasive throughout the world's forests, impacting growing conditions and carbon dynamics through edge effects that produce gradients in microclimate, biogeochemistry, and stand structure. Despite the majority of the world's forests being biome, but current forest carbon accounting methods and ecosystem models largely do not include edge effects, highlighting an important gap in our understanding of the terrestrial carbon cycle. Characterizing the role of forest fragmentation in regional and global biogeochemical cycles necessitates advancing our understanding of how shifts in microenvironment at the forest edge interact with local prevailing drivers of global change and limitations to microbial activity and forest growth. This study synthesizes the literature related to edge effects and the carbon cycle, considering how fragmentation affects the growing conditions of the world's remaining forests based on risks and opportunities for forests near the edge.

  11. Control of Surface and Edge Oxidation on Phosphorene.

    Science.gov (United States)

    Kuntz, Kaci L; Wells, Rebekah A; Hu, Jun; Yang, Teng; Dong, Baojuan; Guo, Huaihong; Woomer, Adam H; Druffel, Daniel L; Alabanza, Anginelle; Tománek, David; Warren, Scott C

    2017-03-15

    Phosphorene is emerging as an important two-dimensional semiconductor, but controlling the surface chemistry of phosphorene remains a significant challenge. Here, we show that controlled oxidation of phosphorene determines the composition and spatial distribution of the resulting oxide. We used X-ray photoemission spectroscopy to measure the binding energy shifts that accompany oxidation. We interpreted these spectra by calculating the binding energy shift for 24 likely bonding configurations, including phosphorus oxides and hydroxides located on the basal surface or edges of flakes. After brief exposure to high-purity oxygen or high-purity water vapor at room temperature, we observed phosphorus in the +1 and +2 oxidation states; longer exposures led to a large population of phosphorus in the +3 oxidation state. To provide insight into the spatial distribution of the oxide, transmission electron microscopy was performed at several stages during the oxidation. We found crucial differences between oxygen and water oxidants: while pure oxygen produced an oxide layer on the van der Waals surface, water oxidized the material at pre-existing defects such as edges or steps. We propose a mechanism based on the thermodynamics of electron transfer to interpret these observations. This work opens a route to functionalize the basal surface or edges of two-dimensional (2D) black phosphorus through site-selective chemical reactions and presents the opportunity to explore the synthesis of 2D phosphorene oxide by oxidation.

  12. Influence of near-edge processes in the elemental analysis using X

    Indian Academy of Sciences (India)

    The near-edge processes, such as X-ray absorption fine structure (XAFS) andresonant ... away from the shell/subshell ionization thresholds of the attenuator element. ... The influence of XAFS to the attenuation coefficient depends upon the ...

  13. Edge-injective and edge-surjective vertex labellings

    DEFF Research Database (Denmark)

    Brandt, Stephan; Rautenbach, D.; Regen, F.

    2010-01-01

    For a graph G = (V, E) we consider vertex-k-labellings f : V → {1,2, ,k} for which the induced edge weighting w : E → {2, 3,., 2k} with w(uv) = f(u) + f(v) is injective or surjective or both. We study the relation between these labellings and the number theoretic notions of an additive basis and ...

  14. Optimization of transition-edge calorimeter performance

    International Nuclear Information System (INIS)

    Ullom, J.N.; Beall, J.A.; Doriese, W.B.; Duncan, W.D.; Ferreira, L.; Hilton, G.C.; Irwin, K.D.; O'Neil, G.C.; Reintsema, C.D.; Vale, L.R.; Zink, B.L.

    2006-01-01

    Calorimeters that exploit the superconducting-to-normal transition are used to detect individual photons from near-infrared to γ-ray wavelengths. Across this wide range, absorption efficiency, speed, and energy resolution are key performance parameters. Here, we describe recent improvements in the resolution of X-ray and γ-ray transition-edge sensors (TESs). Using the measured dependencies of the high-frequency unexplained noise in TESs, we have optimized the design of our TES X-ray sensors and achieved FWHM energy resolutions of 2.4 eV at 5.9 keV in Constellation-X style sensors and ∼2.9 eV at 5.9 keV in larger sensors suitable for materials analysis. We have also achieved a FWHM energy resolution of 42 eV at 103 keV in a TES calorimeter optimized for the detection of hard X-rays and γ-rays

  15. Generalized Multi-Edge Analysis for K-Edge Densitometry

    International Nuclear Information System (INIS)

    Collins, M.

    1998-01-01

    In K-edge densitometry (KED), a continuous-energy x-ray beam is transmitted through a liquid sample. The actinide content of the sample can be measured through analysis of the transmitted portion of the x-ray beam. Traditional methods for KED analysis allow the simultaneous calculation of, at most, two actinide concentrations. A generalized multi-edge KED analytical method is presented, allowing up to six actinide concentrations to be calculated simultaneously. Applications of this method for hybrid KED/x-ray fluorescence (HKED) systems are discussed. Current HKED systems require the operator to know the approximate actinide content of each sample, and manually select the proper analysis mode. The new multi-edge KED technique allows rapid identification of the major actinide components in a sample, independent of actinide content. The proper HKED analysis mode can be selected automatically, without requiring sample content information from the user. Automatic HKED analysis would be especially useful in an analytical laboratory setting, where samples with truly unknown characteristics are encountered. Because this technique requires no hardware modifications, several facilities that use HKED may eventually benefit from this approach

  16. Vitamin A absorption

    International Nuclear Information System (INIS)

    Baker, S.J.

    1976-01-01

    Investigation of the absorption of vitamin A and related substances is complicated by the multiplicity of forms in which they occur in the diet and by the possibility that they may be subject to different mechanisms of absorption. Present knowledge of these mechanisms is inadequate, especially in the case of carotenoids. Numerous tests of absorption have been developed. The most common has been the biochemical measurement of the rise in plasma vitamin A after an oral dose of retinol or retinyl ester, but standardization is inadequate. Radioisotope tests based upon assay of serum or faecal activity following oral administration of tritiated vitamin A derivaties hold considerable promise, but again standardization is inadequate. From investigations hitherto performed it is known that absorption of vitamin A is influenced by several diseases, although as yet the consistency of results and the correlation with other tests of intestinal function have often been poor. However, the test of vitamin A absorption is nevertheless of clinical importance as a specialized measure of intestinal function. (author)

  17. Red shifts of the Eg(1) Raman mode of nanocrystalline TiO2:Er monoliths grown by sol-gel process

    Science.gov (United States)

    Palomino-Merino, R.; Trejo-Garcia, P.; Portillo-Moreno, O.; Jiménez-Sandoval, S.; Tomás, S. A.; Zelaya-Angel, O.; Lozada-Morales, R.; Castaño, V. M.

    2015-08-01

    Nanocrystalline monoliths of Er doped TiO2 were prepared by the sol-gel technique, by controlling the Er-doping levels into the TiO2 precursor solution. As-prepared and annealed in air samples showed the anatase TiO2 phase. The average diameter of the nanoparticles ranged from 19 to 2.6 nm as the nominal concentration of Er varies from 0% to 7%, as revealed by EDS analysis in an electron microscope. Photo Acoustic Spectroscopy (PAS) allowed calculate the forbidden band gap, evidencing an absorption edge at around 300 nm, attributed to TiO2 and evidence of electronic transitions or Er3+. The Raman spectra, corresponding to the anatase phase, show the main phonon mode Eg(1) band position at 144 cm-1 with a red shift for the annealing samples.

  18. Absorption of surface acoustic waves by topological insulator thin films

    International Nuclear Information System (INIS)

    Li, L. L.; Xu, W.

    2014-01-01

    We present a theoretical study on the absorption of the surface acoustic waves (SAWs) by Dirac electrons in topological insulator (TI) thin films (TITFs). We find that due to momentum and energy conservation laws, the absorption of the SAWs in TITFs can only be achieved via intra-band electronic transitions. The strong absorption can be observed up to sub-terahertz frequencies. With increasing temperature, the absorption intensity increases significantly and the cut-off frequency is blue-shifted. More interestingly, we find that the absorption of the SAWs by the TITFs can be markedly enhanced by the tunable subgap in the Dirac energy spectrum of the TI surface states. Such a subgap is absent in conventional two-dimensional electron gases (2DEGs) and in the gapless Dirac 2DEG such as graphene. This study is pertinent to the exploration of the acoustic properties of TIs and to potential application of TIs as tunable SAW devices working at hypersonic frequencies

  19. On the Dynamics of Edge-core Coupling

    Energy Technology Data Exchange (ETDEWEB)

    Hahm,T.S.; Diamond, P.H.; Lin, Z.; Rewoldt, G.; Gurcan, O.; Ethier, S.

    2005-08-26

    One of the nagging, unresolved questions in fusion theory is concerned with the extent of the edge. Gyrokinetic particle simulations of toroidal ion temperature gradient (ITG) turbulence spreading using the Gyrokinetic Toroidal Code (GTC) [Z. Lin et al., Science 281, 1835 (1998)] and its related dynamical model have been extended to a system with radially varying ion temperature gradient, in order to study the inward spreading of edge turbulence toward the core plasma. Due to such spreading, the turbulence intensity in the core region is significantly enhanced over the value obtained from simulations of the core region only, and the precise boundary of the edge region is blurred. Even when the core gradient is within the Dimits shift regime (i.e., dominated by self-generated zonal flows which reduce the transport to a negligible value), a significant level of turbulence can penetrate to the core due to spreading from the edge. The scaling of the turbulent front propagation speed is closer to the prediction from a nonlinear diffusion model than from one based on linear toroidal coupling.

  20. Mapping Catalytically Relevant Edge Electronic States of MoS2

    Science.gov (United States)

    2018-01-01

    Molybdenum disulfide (MoS2) is a semiconducting transition metal dichalcogenide that is known to be a catalyst for both the hydrogen evolution reaction (HER) as well as for hydro-desulfurization (HDS) of sulfur-rich hydrocarbon fuels. Specifically, the edges of MoS2 nanostructures are known to be far more catalytically active as compared to unmodified basal planes. However, in the absence of the precise details of the geometric and electronic structure of the active catalytic sites, a rational means of modulating edge reactivity remain to be developed. Here we demonstrate using first-principles calculations, X-ray absorption spectroscopy, as well as scanning transmission X-ray microscopy (STXM) imaging that edge corrugations yield distinctive spectroscopic signatures corresponding to increased localization of hybrid Mo 4d states. Independent spectroscopic signatures of such edge states are identified at both the S L2,3 and S K-edges with distinctive spatial localization of such states observed in S L2,3-edge STXM imaging. The presence of such low-energy hybrid states at the edge of the conduction band is seen to correlate with substantially enhanced electrocatalytic activity in terms of a lower Tafel slope and higher exchange current density. These results elucidate the nature of the edge electronic structure and provide a clear framework for its rational manipulation to enhance catalytic activity. PMID:29721532

  1. Interaction of ICRF power and edge plasma in Tore Supra ergodic divertor configuration

    International Nuclear Information System (INIS)

    Nguyen, F.; Grosman, A.; Basiuk, V.; Fraboulet, D.; Beaumont, B.; Becoulet, A.; Ghendrih, Ph.; Ladurelle, L.; Meslin, B.

    2000-01-01

    The coupling of ICRF power to plasma is a crucial problem in Tore Supra for high power and long pulse operations and depends greatly on the edge parameters, in particular on the edge density. Conversely, the behaviour of the bulk plasma is related to the edge conditions and the injection of RF power also induces major modifications on the edge plasma. Moreover, the Ergodic Divertor (ED) of Tore Supra imposes a complex configuration at the edge due to the presence of the magnetic perturbation. Several diagnostics are available to study the interaction of ICRF power with the edge plasma: Langmuir probes on the ED modules, infra red (IR) cameras, charge exchange neutral analysers. In minority heating scheme, the edge density is very sensitive to any perturbation in the high recycling regime which is always found in the ED configuration for relevant plasma parameters. Partially detached regimes, with or without inhomogeneities of density and temperature induced by the flux tubes of the laminar layer, are obtained for high resistance coupling values. The coupling is then not very robust and feedback control or antenna automatic matching techniques are developed. In fast wave electron heating scheme with ED, various fast wave absorption mechanisms (minority heating, Mode Conversion, Alfven resonance) are present at the plasma edge due to the large size of the plasma. The ICRF coupling is difficult due to the low fast wave direct electron damping, even with high hydrogen minority scheme. An increase of the injected ICRF power could improve this situation

  2. Direct and Versatile Synthesis of Red-Shifted Azobenzenes

    NARCIS (Netherlands)

    Hansen, Mickel J.; Lerch, Michael M.; Szymanski, Wiktor; Feringa, Ben L.

    2016-01-01

    A straightforward synthesis of azobenzenes with bathochromically-shifted absorption bands is presented. It employs an ortho-lithiation of aromatic substrates, followed by a coupling reaction with aryldiazonium salts. The products are obtained with good to excellent yields after simple purification.

  3. Operando Soft X-ray Absorption Spectroscopic Study on a Solid Oxide Fuel Cell Cathode during Electrochemical Oxygen Reduction.

    Science.gov (United States)

    Nakamura, Takashi; Oike, Ryo; Kimura, Yuta; Tamenori, Yusuke; Kawada, Tatsuya; Amezawa, Koji

    2017-05-09

    An operando soft X-ray absorption spectroscopic technique, which enabled the analysis of the electronic structures of the electrode materials at elevated temperature in a controlled atmosphere and electrochemical polarization, was established and its availability was demonstrated by investigating the electronic structural changes of an La 2 NiO 4+δ dense-film electrode during an electrochemical oxygen reduction reaction. Clear O K-edge and Ni L-edge X-ray absorption spectra could be obtained below 773 K under an atmospheric pressure of 100 ppm O 2 /He, 0.1 % O 2 /He, and 1 % O 2 /He gas mixtures. Considerable spectral changes were observed in the O K-edge X-ray absorption spectra upon changing the PO2 and application of electrical potential, whereas only small spectral changes were observed in Ni L-edge X-ray absorption spectra. A pre-edge peak of the O K-edge X-ray absorption spectra, which reflects the unoccupied partial density of states of Ni 3d-O 2p hybridization, increased or decreased with cathodic or anodic polarization, respectively. The electronic structural changes of the outermost orbital of the electrode material due to electrochemical polarization were successfully confirmed by the operando X-ray absorption spectroscopic technique developed in this study. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Mechanical spectral shift reactor

    International Nuclear Information System (INIS)

    Sherwood, D.G.; Wilson, J.F.; Salton, R.B.; Fensterer, H.F.

    1981-01-01

    A mechanical spectral shift reactor comprises apparatus for inserting and withdrawing water displacer elements from the reactor core for selectively changing the water-moderator volume in the core thereby changing the reactivity of the core. The apparatus includes drivemechanisms for moving the displacer elements relative to the core and guide mechanisms for guiding the displayer rods through the reactor vessel

  5. Mechanical spectral shift reactor

    International Nuclear Information System (INIS)

    Sherwood, D.G.; Wilson, J.F.; Salton, R.B.; Fensterer, H.F.

    1982-01-01

    A mechanical spectral shift reactor comprises apparatus for inserting and withdrawing water displacer elements from the reactor core for selectively changing the water-moderator volume in the core thereby changing the reactivity of the core. The apparatus includes drive mechanisms for moving the displacer elements relative to the core and guide mechanisms for guiding the displacer rods through the reactor vessel. (author)

  6. Edge imaging in intense beams

    Directory of Open Access Journals (Sweden)

    S. Bernal

    2002-06-01

    Full Text Available The appearance of rings of charge observed near the edge of beams from high-perveance guns is described with a simple ray tracing technique inspired by the particle-core model. We illustrate the technique, which has no analog in light optics, with examples from experiments employing solenoid focusing of an electron beam. The rings of charge result from the combined effects of external focusing and space-charge forces acting on paraxial fringe particles with relatively large initial transverse velocities. The model is independent of the physical mechanisms responsible for the fringe particles. Furthermore, the focal length for edge imaging in a uniform focusing channel is derived using a linearized trajectory equation for the motion of fringe particles. Counterintuitively, the focal length decreases as the beam current increases.

  7. Time evolution of absorption process in nonlinear metallic photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Mahi R.; Hatef, Ali [Department of Physics and Astronomy, University of Western Ontario, London (Canada)

    2009-05-15

    The time evolution of the absorption coefficient in metallic photonic crystals has been studied numerically. These crystals are made from metallic spheres which are arranged periodically in air. The refractive index of the metallic spheres depends on the plasma frequency. Probe and pump fields are applied to monitor the absorption process. Ensembles of three-level particles are embedded in the crystal. Nanoparticles are interacting with the metallic crystals via the electron-photon interaction. It is found that when the resonance states lie away from the band edges system goes to transparent state. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Multiple scattering theory of X-ray absorption. A review

    International Nuclear Information System (INIS)

    Fonda, L.

    1991-11-01

    We review the basic elements of the theory of X-ray absorption using the tools provided by the theory of multiple scattering. A momentum space approach of clear physical insight is used where the final formulas expressing EXAFS and XANES, i.e. the structures appearing in the absorption coefficient above the edge of a deep core level threshold, are given in terms of eigenstates of the photoelectron momentum. A simple graphic representation is given for the multiple scattering function. (author). 38 refs, 4 figs, 1 tab

  9. Substitution behavior of x(Na0.5K0.5)NbO3-(1 - x)BaTiO3 ceramics for multilayer ceramic capacitors by a near edge x-ray absorption fine structure analysis

    Science.gov (United States)

    Ha, Jooyeon; Ryu, Jiseung; Lee, Heesoo

    2014-06-01

    The doping effect of (Na0.5K0.5)NbO3 (NKN) as alternatives for rare-earth elements on the electrical properties of BaTiO3 has been investigated, in terms of their substitution behavior. The dielectric constant of a specimen with x = 0.05 was about 79% higher than that of pure BaTiO3, and the temperature coefficient of capacitance was satisfied by the X7R specification. The specimen with x = 0.05 showed the lowest tetragonality among the four compositions and had a fine grain size of x-ray absorption fine structure spectroscopy, the practical substitution behavior was defined by the change in Ti 3d orbital states. The energy separation of the Ti 3d orbitals was more apparent with the specimen of x = 0.05, which is related to the donor level from the donor substitution of Nb5+ ion for Ti-sites. Therefore, the simultaneous substitution of Na+/K+ and Nb5+ ions into BaTiO3 can improve dielectric properties, based on the charge-transfer process.

  10. Nonreference Medical Image Edge Map Measure

    Directory of Open Access Journals (Sweden)

    Karen Panetta

    2014-01-01

    Full Text Available Edge detection is a key step in medical image processing. It is widely used to extract features, perform segmentation, and further assist in diagnosis. A poor quality edge map can result in false alarms and misses in cancer detection algorithms. Therefore, it is necessary to have a reliable edge measure to assist in selecting the optimal edge map. Existing reference based edge measures require a ground truth edge map to evaluate the similarity between the generated edge map and the ground truth. However, the ground truth images are not available for medical images. Therefore, a nonreference edge measure is ideal for medical image processing applications. In this paper, a nonreference reconstruction based edge map evaluation (NREM is proposed. The theoretical basis is that a good edge map keeps the structure and details of the original image thus would yield a good reconstructed image. The NREM is based on comparing the similarity between the reconstructed image with the original image using this concept. The edge measure is used for selecting the optimal edge detection algorithm and optimal parameters for the algorithm. Experimental results show that the quantitative evaluations given by the edge measure have good correlations with human visual analysis.

  11. Gyrosheath near the tokamak edge

    International Nuclear Information System (INIS)

    Hazeltine, R.D.; Xiao, H.; Valanju, P.M.

    1993-03-01

    A new model for the structure of the radial electric field profile in the edge during the H-mode is proposed. Charge separation caused by the difference between electron and ion gyromotion, or more importantly in a tokamak, the banana motion (halo effect) can self-consistently produce an electric dipole moment that causes the sheared radial electric field. The calculated results based on the model are consistent with D-III D and TEXTOR experimental results

  12. Calculation of relativistic and isotope shifts in Mg I

    International Nuclear Information System (INIS)

    Berengut, J.C.; Flambaum, V.V.; Kozlov, M.G.

    2005-01-01

    We present an ab initio method of calculation of the isotope and relativistic shifts in atoms with a few valence electrons. It is based on an energy calculation involving the combination of the configuration-interaction method and many-body perturbation theory. This work is motivated by analyses of quasar absorption spectra that suggest that the fine-structure constant α was smaller at an early epoch. Relativistic shifts are needed to measure this variation of α, while isotope shifts are needed to resolve systematic effects in this study. The isotope shifts can also be used to measure isotopic abundances in gas clouds in the early universe, which are needed to study nuclear reactions in stars and supernovae and test models of chemical evolution. This paper shows that the isotope shift in magnesium can be calculated to very high precision using our method

  13. Knife-edge seal for vacuum bagging

    Science.gov (United States)

    Rauschl, J. A.

    1980-01-01

    Cam actuated clamps pinch bagging material between long knife edge (mounted to clamps) and high temperature rubber cushion bonded to baseplate. No adhesive, tape, or sealing groove is needed to seal edge of bagging sheet against base plate.

  14. Environmental Dataset Gateway (EDG) REST Interface

    Data.gov (United States)

    U.S. Environmental Protection Agency — Use the Environmental Dataset Gateway (EDG) to find and access EPA's environmental resources. Many options are available for easily reusing EDG content in other...

  15. Organizing on the Edge: Appreciation and Critique

    National Research Council Canada - National Science Library

    Scott, W. R

    2006-01-01

    .... Hayes, "Power to the Edge: Command, Control in the Information Age" (2003). The author places the "edge" perspective in the broader context of organizational studies, noting both its strengths and limitations...

  16. Edge effect on weevils and spiders

    Directory of Open Access Journals (Sweden)

    R. Horváth

    2002-05-01

    Full Text Available The edge effect on weevils and spiders was tested along oak forest – meadow transects using sweep-net samples at the Síkfökút Project in Hungary. For spiders the species richness was significantly higher in the forest edge than either in the meadow or the forest interior. For weevils the species richness of the forest edge was higher than that of the meadow, but the difference was not statistically significant whereas the species richness of the forest interior was significantly lower than that of the forest edge and the meadow. The composition of the spider assemblage of the edge was more similar to the forest, while the composition of weevils in the edge was more similar to the meadow. Our results based on two invertebrate groups operating on different trophic levels suggest that there is a significant edge effect for the studied taxa resulting in higher species richness in the edge.

  17. Modelling absorption and photoluminescence of TPD

    Energy Technology Data Exchange (ETDEWEB)

    Vragovic, Igor [Dpto. de Fisica Aplicada and Inst. Universitario de Materiales de Alicante, Universidad de Alicante, E-03080 Alicante (Spain)], E-mail: igor.vragovic@ua.es; Calzado, Eva M.; Diaz Garcia, Maria A.; Himcinschi, C. [Max-Planck-Institut fuer Mikrostrukturphysik, D-06120 Halle (Germany); Gisslen, L.; Scholz, R. [Walter Schottky Institut, Technische Universitaet Muenchen, D-85748 Garching (Germany)

    2008-05-15

    We analyse the optical spectra of N,N{sup '}-diphenyl-N,N{sup '}-bis(3-methyl-phenyl)-(1,1{sup '}-biphenyl)-4,4{sup '}-diamine (TPD) doped polystyrene films. The aim of the present paper is to give a microscopic interpretation of the significant Stokes shift between absorption and photoluminescence, which makes this material suitable for stimulated emission. The optimized geometric structures and energies of a neutral TPD monomer in ground and excited states are obtained by ab initio calculations using Hartree-Fock and density functional theory. The results indicate that the second distinct peak observed in absorption may arise either from a group of higher electronic transitions of the monomer or from the lowest optical transitions of a TPD dimer.

  18. Modelling absorption and photoluminescence of TPD

    International Nuclear Information System (INIS)

    Vragovic, Igor; Calzado, Eva M.; Diaz Garcia, Maria A.; Himcinschi, C.; Gisslen, L.; Scholz, R.

    2008-01-01

    We analyse the optical spectra of N,N ' -diphenyl-N,N ' -bis(3-methyl-phenyl)-(1,1 ' -biphenyl)-4,4 ' -diamine (TPD) doped polystyrene films. The aim of the present paper is to give a microscopic interpretation of the significant Stokes shift between absorption and photoluminescence, which makes this material suitable for stimulated emission. The optimized geometric structures and energies of a neutral TPD monomer in ground and excited states are obtained by ab initio calculations using Hartree-Fock and density functional theory. The results indicate that the second distinct peak observed in absorption may arise either from a group of higher electronic transitions of the monomer or from the lowest optical transitions of a TPD dimer

  19. Neutron resonance absorption theory

    International Nuclear Information System (INIS)

    Reuss, P.

    1991-11-01

    After some recalls on the physics of neutron resonance absorption during their slowing down, this paper presents the main features of the theoretical developments performed by the french school of reactor physics: the effective reaction rate method so called Livolant-Jeanpierre theory, the generalizations carried out by the author, and the probability table method [fr

  20. Noble gas absorption process

    International Nuclear Information System (INIS)

    Thomas, J.W.

    1975-01-01

    A method of removing a noble gas from air comprising the use of activated carbon filters in stages in which absorption and desorption steps in succession are conducted in order to increase the capacity of the filters is described. (U.S.)