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Sample records for absorption spectroscopy cu

  1. Studies of Y-Ba-Cu-O single crystals by x-ray absorption spectroscopy

    SciTech Connect

    Krol, A.; Ming, Z.H.; Kao, Y.H.; Nuecker, N.; Roth, G.; Fink, J.; Smith, G.C.; Erband, A.; Mueller-Vogt, G.; Karpinski, J.; Kaldis, E.; Schoenmann, K.

    1992-02-01

    The symmetry and density of unoccupied states of YBa{sub 2}Cu{sub 3}O{sub 7} YBa{sub 2}Cu{sub 4}O{sub 8} have been investigated by orientation dependent x-ray absorption spectroscopy on the O 1s edge using a bulk-sensitive fluorescence-yield-detection method. It has been found that the O 2p holes are distributed equally between the CuO{sub 2} planes and CuO chains and that the partial density of unoccupied O 2p states in the CuO{sub 2} planes are identical in both systems investigated. The upper Hubbard band has been observed in the planes but not in the chains in both systems. 18 refs.

  2. Spectroscopy of CuN in the Near Infrared by Intracavity Laser Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    O'Brien, Leah C.; Womack, Kaitlin A.; O'Brien, James J.

    2012-06-01

    Transitions with red-degraded bandheads have been identified at 13005, 12963, 12957, and 12948 cm-1. One P and one R branch are identified in each transition. We have tentatively assigned these transitions as absorption from the X 3Σ- ground state of CuN. Rotational analyses of these bands are in progress, and results will be presented. A strong perturbation is observed in one of the excited states. The electronic structure of CuN will be discussed and compared with predicted electronic states from theoretical calculations. The gas phase CuN molecules were produced using a copper hollow cathode in a plasma discharge.

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

    SciTech Connect

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

    2004-06-04

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

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

  5. Atomic Resolution Mapping of the Excited-State Electronic Structure of Cu2O with Time-Resolved X-Ray Absorption Spectroscopy

    SciTech Connect

    Hillyard, Patrick B.; Kuchibhatla, Satyanarayana V N T; Glover, T. E.; Hertlein, M. P.; Huse, N.; Nachimuthu, Ponnusamy; Saraf, Laxmikant V.; Thevuthasan, Suntharampillai; Gaffney, Kelly J.

    2009-09-29

    We have used time-resolved soft x-ray spectroscopy to investigate the electronic structure of optically excited cuprous oxide at the O K-edge and the Cu L3-edge. The 400 nm optical excitation shifts the Cu and O absorptions to lower energy, but does not change the integrated x-ray absorption significantly for either edge. The constant integrated x-ray absorption cross-section indicates that that the conduction band and valence band edges have very similar Cu 3d and O 2p orbital contributions. The 2.1 eV optical band gap of Cu2O significantly exceeds the one eV shift in the Cu L3- and O K-edges absorption edges induced by optical excitation, demonstrating the importance of core-hole excitonic effects and valence electron screening in the x-ray absorption process.

  6. Atomic resolution mapping of the excited-state electronic structure of Cu2O with time-resolved x-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Hillyard, P. W.; Kuchibhatla, S. V. N. T.; Glover, T. E.; Hertlein, M. P.; Huse, N.; Nachimuthu, P.; Saraf, L. V.; Thevuthasan, S.; Gaffney, K. J.

    2009-09-01

    We have used time-resolved soft x-ray spectroscopy to investigate the electronic structure of optically excited cuprous oxide at the OK edge and the CuL3 edge. The 400 nm optical excitation shifts the Cu and O absorptions to lower energy, but does not change the integrated x-ray absorption significantly for either edge. The constant integrated x-ray absorption cross-section indicates that the conduction-band and valence-band edges have very similar Cu3d and O2p orbital contributions. The 2.1 eV optical band gap of Cu2O significantly exceeds the one eV shift in the CuL3 - and OK -edges absorption edges induced by optical excitation, demonstrating the importance of core-hole excitonic effects and valence electron screening in the x-ray absorption process.

  7. Atomic resolution mapping of the excited-state electronic structure of Cu2O with time-resolved x-ray absorption spectroscopy

    SciTech Connect

    Hillyard, P. W.; Kuchibhatla, S. V. N. T.; Glover, T. E.; Hertlein, M. P.; Huse, Nils; Nachimuthu, P.; Saraf, L. V.; Thevuthasan, S.; Gaffney, K. J.

    2010-05-02

    We have used time-resolved soft x-ray spectroscopy to investigate the electronic structure of optically excited cuprous oxide at the O K-edge and the Cu L3-edge. The 400 nm optical excitation shifts the Cu and O absorptions to lower energy, but does not change the integrated x-ray absorption significantly for either edge. The constant integrated x-ray absorption cross-section indicates that the conduction-band and valence-band edges have very similar Cu 3d and O 2p orbital contributions. The 2.1 eV optical band gap of Cu2O significantly exceeds the one eV shift in the Cu L3- and O K-edges absorption edges induced by optical excitation, demonstrating the importance of core-hole excitonic effects and valence electron screening in the x-ray absorption process.

  8. Conduction-band electronic states of YbInCu{sub 4} studied by photoemission and soft x-ray absorption spectroscopies

    SciTech Connect

    Utsumi, Yuki; Kurihara, Hidenao; Maso, Hiroyuki; Tobimatsu, Komei; Sato, Hitoshi; Shimada, Kenya; Namatame, Hirofumi; Hiraoka, Koichi; Kojima, Kenichi; Ohkochi, Takuo; Fujimori, Shin-ichi; Takeda, Yukiharu; Saitoh, Yuji; Mimura, Kojiro; Ueda, Shigenori; Yamashita, Yoshiyuki; Yoshikawa, Hideki; Kobayashi, Keisuke; Oguchi, Tamio; Taniguchi, Masaki

    2011-09-15

    We have studied conduction-band (CB) electronic states of a typical valence-transition compound YbInCu{sub 4} by means of temperature-dependent hard x-ray photoemission spectroscopy (HX-PES) of the Cu 2p{sub 3/2} and In 3d{sub 5/2} core states taken at h{nu}=5.95 keV, soft x-ray absorption spectroscopy (XAS) of the Cu 2p{sub 3/2} core absorption region around h{nu}{approx}935 eV, and soft x-ray photoemission spectroscopy (SX-PES) of the valence band at the Cu 2p{sub 3/2} absorption edge of h{nu}=933.0 eV. With decreasing temperature below the valence transition at T{sub V}=42 K, we have found that (1) the Cu 2p{sub 3/2} and In 3d{sub 5/2} peaks in the HX-PES spectra exhibit the energy shift toward the lower binding-energy side by {approx}40 and {approx}30 meV, respectively, (2) an energy position of the Cu 2p{sub 3/2} main absorption peak in the XAS spectrum is shifted toward higher photon-energy side by {approx}100 meV, with an appearance of a shoulder structure below the Cu 2p{sub 3/2} main absorption peak, and (3) an intensity of the Cu L{sub 3}VV Auger spectrum is abruptly enhanced. These experimental results suggest that the Fermi level of the CB-derived density of states is shifted toward the lower binding-energy side. We have described the valence transition in YbInCu{sub 4} in terms of the charge transfer from the CB to Yb 4f states.

  9. Fe-heme structure in Cu, Zn superoxide dismutase from Haemophilus ducreyi by X-ray absorption spectroscopy.

    PubMed

    D'Angelo, Paola; Zitolo, Andrea; Pacello, Francesca; Mancini, Giordano; Proux, Olivier; Hazemann, Jean Louis; Desideri, Alessandro; Battistoni, Andrea

    2010-06-01

    We have carried out an X-ray Absorption Spectroscopy (XAS) study of ferric, ferrous, CO- and NO-bound Haemophilus ducreyi Cu,ZnSOD (HdSOD) in solution to investigate the structural modifications induced by the binding of small gaseous ligands to heme in this enzyme. The combined analysis of EXAFS and XANES data has allowed us to characterize the local structure around the Fe-heme with 0.02A accuracy, revealing a heterogeneity in the distances between iron and the two histidine ligands which was not evident in the X-ray crystal structure. In addition, we have shown that the metal oxidation state does not influence the Fe-heme coordination environment, whereas the presence of the CO and NO ligands induces local structural rearrangements in the enzyme which are very similar to those already observed in other hexa-coordinated heme proteins, such as neuroglobin.

  10. Local atomic structure investigation of AlFeCuCrMgx (0.5, 1, 1.7) high entropy alloys: X-ray absorption spectroscopy study

    NASA Astrophysics Data System (ADS)

    Maulik, Ornov; Patra, N.; Bhattacharyya, D.; Jha, S. N.; Kumar, Vinod

    2017-02-01

    The present paper reports local atomic structure investigation of novel AlFeCuCrMgx (x=0.5, 1, 1.7) high entropy alloys (HEAs) produced by mechanical alloying using Fe, Cr and Cu K-edge X-ray absorption near edge spectroscopy (XANES) and extended x-ray absorption fine structure (EXAFS) spectroscopy. XANES spectra measured at Fe and Cr K-edges resemble that of the respective pure metal foils, while the spectrum measured at Cu K-edge manifests the presence of some other phases in the as-milled alloys. The radial distribution functions (RDFs) obtained from Fourier transformation of EXAFS spectra support the formation of disordered BCC structure.

  11. An X-ray absorption spectroscopy investigation of the local atomic structure in Cu-Ni-Si alloy after severe plastic deformation and ageing

    NASA Astrophysics Data System (ADS)

    Azzeddine, H.; Harfouche, M.; Hennet, L.; Thiaudiere, D.; Kawasaki, M.; Bradai, D.; Langdon, T. G.

    2015-08-01

    The local atomic structure of Cu-Ni-Si alloy after severe plastic deformation (SPD) processing and the decomposition of supersaturated solid solution upon annealing were investigated by means of X-ray absorption spectroscopy. The coordination number and interatomic distances were obtained by analyzing experimental extend X-ray absorption fine structure data collected at the Ni K-edge. Results indicate that the environment of Ni atoms in Cu-Ni-Si alloy is strongly influenced by the deformation process. Moreover, ageing at 973 K affects strongly the atomic structure around the Ni atoms in Cu-Ni-Si deformed by equal channel angular pressing and high pressure torsion. This influence is discussed in terms of changes and decomposition features of the Cu-Ni-Si solid solution.

  12. A quantitative description of the ground-state wave function of Cu(A) by X-ray absorption spectroscopy: comparison to plastocyanin and relevance to electron transfer.

    PubMed

    DeBeer George, S; Metz, M; Szilagyi, R K; Wang, H; Cramer, S P; Lu, Y; Tolman, W B; Hedman, B; Hodgson, K O; Solomon, E I

    2001-06-20

    To evaluate the importance of the electronic structure of Cu(A) to its electron-transfer (ET) function, a quantitative description of the ground-state wave function of the mixed-valence (MV) binuclear Cu(A) center engineered into Pseudomonas aeruginosa azurin has been developed, using a combination of S K-edge and Cu L-edge X-ray absorption spectroscopies (XAS). Parallel descriptions have been developed for a binuclear thiolate-bridged MV reference model complex ([(L(i)(PrdacoS)Cu)(2)](+)) and a homovalent (II,II) analogue ([L(i)(Pr2tacnS)Cu)(2)](2+), where L(i)(PrdacoS) and L(i)(Pr2tacnS) are macrocyclic ligands with attached thiolates that bridge the Cu ions. Previous studies have qualitatively defined the ground-state wave function of Cu(A) in terms of ligand field effects on the orbital orientation and the presence of a metal--metal bond. The studies presented here provide further evidence for a direct Cu--Cu interaction and, importantly, experimentally quantify the covalency of the ground-state wave function. The experimental results are further supported by DFT calculations. The nature of the ground-state wave function of Cu(A) is compared to that of the well-defined blue copper site in plastocyanin, and the importance of this wave function to the lower reorganization energy and ET function of Cu(A) is discussed. This wave function incorporates anisotropic covalency into the intra- and intermolecular ET pathways in cytochrome c oxidase. Thus, the high covalency of the Cys--Cu bond allows a path through this ligand to become competitive with a shorter His path in the intramolecular ET from Cu(A) to heme a and is particularly important for activating the intermolecular ET path from heme c to Cu(A).

  13. Probing CuI in Homogeneous Catalysis using High-Energy-Resolution Fluorescence-Detected X-ray Absorption Spectroscopy

    PubMed Central

    Walroth, Richard C.; Uebler, Jacob W. H.

    2015-01-01

    Metal-to-ligand charge transfer excitations in CuI X-ray absorption spectra are introduced as spectroscopic handles for the characterization of species in homogeneous catalytic reaction mixtures. Analysis is supported by correlation of a spectral library to calculations and to complementary spectroscopic parameters. PMID:25994112

  14. Soliton absorption spectroscopy

    PubMed Central

    Kalashnikov, V. L.; Sorokin, E.

    2010-01-01

    We analyze optical soliton propagation in the presence of weak absorption lines with much narrower linewidths as compared to the soliton spectrum width using the novel perturbation analysis technique based on an integral representation in the spectral domain. The stable soliton acquires spectral modulation that follows the associated index of refraction of the absorber. The model can be applied to ordinary soliton propagation and to an absorber inside a passively modelocked laser. In the latter case, a comparison with water vapor absorption in a femtosecond Cr:ZnSe laser yields a very good agreement with experiment. Compared to the conventional absorption measurement in a cell of the same length, the signal is increased by an order of magnitude. The obtained analytical expressions allow further improving of the sensitivity and spectroscopic accuracy making the soliton absorption spectroscopy a promising novel measurement technique. PMID:21151755

  15. Resonant photoemission and absorption spectroscopy of the Cu{sub x}TiSe{sub 2} compound

    SciTech Connect

    Shkvarin, A. S. Yarmoshenko, Yu. M.; Skorikov, N. A.; Titov, A. A.; Titov, A. N.

    2012-02-15

    Single crystals of the Cu{sub x}TiSe{sub 2} compound with x = 0.05, 0.09, and 0.33 have been grown. Resonance photoelectron Cu 3p-3d and 2d-3d spectra of the valence bands, the spectra of the core levels, and the L absorption spectra for titanium and copper have been obtained. It is shown that the degree of oxidation of titanium atoms is +4 and the state of copper atoms is close to the state of free copper ions. It is found that the spectra of the valence bands obtained under the Cu 3p and 2p resonance conditions radically differ. For the spectra in the Cu 2p excitation regime, several bands corresponding to different decay channels of the excited state are observed. According to calculations of the density of states, the 3d states of copper are filled incompletely; the occupancy of the 3d band of copper is 9.5 electrons per atom.

  16. Relic Neutrino Absorption Spectroscopy

    SciTech Connect

    Eberle, b

    2004-01-28

    Resonant annihilation of extremely high-energy cosmic neutrinos on big-bang relic anti-neutrinos (and vice versa) into Z-bosons leads to sizable absorption dips in the neutrino flux to be observed at Earth. The high-energy edges of these dips are fixed, via the resonance energies, by the neutrino masses alone. Their depths are determined by the cosmic neutrino background density, by the cosmological parameters determining the expansion rate of the universe, and by the large redshift history of the cosmic neutrino sources. We investigate the possibility of determining the existence of the cosmic neutrino background within the next decade from a measurement of these absorption dips in the neutrino flux. As a by-product, we study the prospects to infer the absolute neutrino mass scale. We find that, with the presently planned neutrino detectors (ANITA, Auger, EUSO, OWL, RICE, and SalSA) operating in the relevant energy regime above 10{sup 21} eV, relic neutrino absorption spectroscopy becomes a realistic possibility. It requires, however, the existence of extremely powerful neutrino sources, which should be opaque to nucleons and high-energy photons to evade present constraints. Furthermore, the neutrino mass spectrum must be quasi-degenerate to optimize the dip, which implies m{sub {nu}} 0.1 eV for the lightest neutrino. With a second generation of neutrino detectors, these demanding requirements can be relaxed considerably.

  17. Skeletal Ru/Cu catalysts prepared from crystalline and quasicrystalline ternary alloy precursors: characterization by X-ray absorption spectroscopy and CO oxidation.

    PubMed

    Highfield, James; Liu, Tao; Loo, Yook Si; Grushko, Benjamin; Borgna, Armando

    2009-02-28

    The Ru/Cu system is of historical significance in catalysis. The early development and application of X-ray absorption spectroscopy (XAS) led to the original 'bimetallic cluster" concept for highly-immiscible systems. This work explores alkali leaching of Al-based ternary crystalline and quasicrystalline precursors as a potential route to bulk Ru/Cu alloys. Single-phase ternary alloys at 3 trial compositions; Al(71)Ru(22)Cu(7), Al(70.5)Ru(17)Cu(12.5), and Al(70)Ru(10)Cu(20), were prepared by arc melting of the pure metal components. After leaching, the bimetallic residues were characterized principally by transmission XAS, "as-leached" and after annealing in H(2) (and passivation) in a thermobalance. XRD and BET revealed a nanocrystalline product with a native structure of hexagonal Ru. XPS surface analysis of Ru(22)Cu(7) and Ru(17)Cu(12.5) found only slight enrichment by Cu in the as-leached forms, with little change upon annealing. Ru(10)Cu(20) was highly segregated as-leached. XANES data showed preferential oxidation of Cu in Ru(22)Cu(7), implying that it exists as an encapsulating layer. TG data supports this view since it does not show the distinct two-stage O(2) uptake characteristic of skeletal Ru. Cu K-edge EXAFS data for Ru(22)Cu(7) were unique in showing a high proportion of Ru neighbours. The spacing, d(CuRu) = 2.65 A, was that expected from a hypothetical (ideal) solid solution at this composition, but this is unlikely in such a bulk-immiscible system and Ru K-edge EXAFS failed to confirm bulk alloying. Furthermore its invariance under annealing was more indicative of an interfacial bond between bulk components, although partial alloying with retention of local order cannot entirely be ruled out. The XAS and XPS data were reconciled in a model involving surface and bulk segregation, Cu being present at both the grain exterior and in ultra-fine internal pores. This structure can be considered as the 3-dimensional analogue of the classical type

  18. In-plane polarization dependence of (Bi,Pb)2Sr2CaCu2O8+δ single crystals studied by X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Ghafari, A.; Ariffin, A. K.; Janowitz, C.; Dwelk, H.; Krapf, A.; Manzke, R.

    2014-06-01

    The effects of in-plane polarization change on the determination of the hole density of weakly under-doped (Bi, Pb)-2212 single crystals has been studied by x-ray absorption spectroscopy (XAS). The XAS signal at the CuL3 edge (925-940 eV) and O K edge (525 eV to 539 eV) were recorded under continuous rotation of the CuO2 plane from 0° to 180° with a minimum increment of 1.8°, yielding experimentally an in-plane polarization dependence for the absorption signals at the respective threshold. From that the in-plane angular dependence of the hole density (nH(φ) could be determined. Fermi's golden rule was then used for the evaluation of the in-plane polarization dependence showing the expected polarization independence in disaccord to the experimental observations. Possible scenarios to solve this issue are discussed. Our results propose that polarization dependence could be due to inhomogeneous distribution of holes in the CuO2 planes which is also supported by models. Second, the role of out of plane orbitals has to be taken into account for interpretation.

  19. Adsorption kinetics and intermolecular interactions of CO adsorbed on Cu(100) by transient laser reflection-absorption spectroscopy

    SciTech Connect

    Borguet, E.; Dai, H.L.

    1993-12-31

    IR and visible transient laser spectroscopic techniques have been developed to probe adsorption/desorption kinetics and intermolecular interactions of the CO/Cu(100) system. Vibrational spectroscopy, in general, can provide information about the nature of species adsorbed on surfaces e.g. chemical identity, site, orientation and concentration. In the presence of a few percent of CO adsorbed at step/defect sites, the spectra of the CO adsorbed on the terrace sites are greatly perturbed through dynamic-dipole coupling. This perturbation depends strongly on the intermolecular distance and the short-range order of the adsorbates. An analysis of this dynamic-dipole coupling reveals that the local arrangement of adsorbates is dominant by repulsive nearest-neighbor interactions. Successful modeling of the observed lineshapes allows the populations at each site to be determined at all coverages. The authors have also observed non-resonant adsorbate induced changes in both the IR and visible reflectance for a number of different adsorbates. This provides a simple and sensitive optical means of studying adsorption and desorption kinetics.

  20. Direct measurement of Urbach tail and gap state absorption in CuGaSe2 thin films by photothermal deflection spectroscopy and the constant photocurrent method

    NASA Astrophysics Data System (ADS)

    Meeder, A.; Marron, D. Fuertes; Rumberg, A.; Lux-Steiner, M. Ch.; Chu, V.; Conde, J. P.

    2002-09-01

    The applicability of photothermal deflection spectroscopy (PDS) and the constant photocurrent method (CPM) to chemical vapor deposited and physical vapor deposited CuGaSe2 (CGSe) thin films is investigated. Process dependent variations in direct band-gap energies, Urbach tail widths, bulk and surface defect densities of the films are given as a function of composition. Differences in the PDS and CPM absorption spectra of more than one order of magnitude are found. Using the standard a-Si theory of PDS and CPM analysis, a two-layer system consisting of a defect-rich near-surface layer and a less defective bulk layer is found in device-quality films. Optical improvements due to the Ga+Se annealing step as a second stage of the growth process result in a reduced bulk defect density while the near-surface defect density remains unchanged.

  1. X-ray Absorption Spectroscopy

    SciTech Connect

    Yano, Junko; Yachandra, Vittal K.

    2009-07-09

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

  2. The Long-Term Fate of Cu2+, Zn2+, and Pb2+ Adsorption Complexes at the Calcite Surface: An X-ray Absorption Spectroscopy Study

    SciTech Connect

    Elzinga,E.; Rouff, A.; Reeder, R.

    2006-01-01

    In this study, the speciation of Zn{sup 2+}, Pb{sup 2+}, and Cu{sup 2+} ions sorbed at the calcite surface was monitored during a 2.5-year reaction period, using extended X-ray absorption spectroscopy to characterize metal speciation on the molecular scale. Experiments were performed using pre-equilibrated calcite-water suspensions of pH 8.3, at metal concentrations below the solubility of metal hydroxide and carbonate precipitates, and at constant metal surface loadings. The EXAFS results indicate that all three metals remained coordinated at the calcite surface as inner-sphere adsorption complexes during the 2.5-year ageing period, with no evidence to suggest slow formation of dilute metal-calcite solid solutions under the reaction conditions employed. All three divalent metals were found to form non-octahedral complexes upon coordination to the calcite surface, with Zn{sup 2+} adsorbing as a tetrahedral complex, Cu{sup 2+} as a Jahn-Teller distorted octahedral complex, and Pb{sup 2+} coordinating as a trigonal- or square-pyramidal surface complex. The non-octahedral configurations of these surface complexes may have hindered metal transfer from the calcite surface into the bulk, where Ca{sup 2+} is in octahedral coordination with respect to first-shell O. The use of pre-equilibrated calcite suspensions, with no net calcite dissolution or precipitation, likely prevented metal incorporation into the lattice as a result of surface recrystallization. The results from this study imply that ageing alone does not increase the stability of Zn{sup 2+}, Pb{sup 2+}, and Cu{sup 2+} partitioning to calcite if equilibrium with the solution is maintained during reaction; under these conditions, these metals are likely to remain available for exchange even after extended sorption times.

  3. Redox chemistry of a binary transition metal oxide (AB 2 O 4 ): a study of the Cu 2+ /Cu 0 and Fe 3+ /Fe 0 interconversions observed upon lithiation in a CuFe 2 O 4 battery using X-ray absorption spectroscopy

    DOE PAGES

    Cama, Christina A.; Pelliccione, Christopher J.; Brady, Alexander B.; ...

    2016-06-06

    Copper ferrite, CuFe2 O 4, is a promising candidate for application as a high energy electrode material in lithium based batteries. Mechanistic insight on the electrochemical reduction and oxidation processes was gained through the first X-ray absorption spectroscopic study of lithiation and delithiation of CuFe2 O 4. A phase pure tetragonal CuFe2 O 4 material was prepared and characterized using laboratory and synchrotron X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. We used ex situ X-ray absorption spectroscopy (XAS) measurements to study the battery redox processes at the Fe and Cu K-edges, using X-ray absorption near-edge structure (XANES), extended X-raymore » absorption fine structure (EXAFS), and transmission X-ray microscopy (TXM) spectroscopies. EXAFS analysis showed upon discharge, an initial conversion of 50% of the copper(II) to copper metal positioned outside of the spinel structure, followed by a migration of tetrahedral iron(III) cations to octahedral positions previously occupied by copper(II). Then, upon charging to 3.5 V, the copper metal remained in the metallic state, while iron metal oxidation to iron(III) was achieved. Our results provide new mechanistic insight regarding the evolution of the local coordination environments at the iron and copper centers upon discharging and charging.« less

  4. Redox chemistry of a binary transition metal oxide (AB 2 O 4 ): a study of the Cu 2+ /Cu 0 and Fe 3+ /Fe 0 interconversions observed upon lithiation in a CuFe 2 O 4 battery using X-ray absorption spectroscopy

    SciTech Connect

    Cama, Christina A.; Pelliccione, Christopher J.; Brady, Alexander B.; Li, Jing; Stach, Eric A.; Wang, Jiajun; Wang, Jun; Takeuchi, Esther S.; Takeuchi, Kenneth J.; Marschilok, Amy C.

    2016-06-06

    Copper ferrite, CuFe2 O 4, is a promising candidate for application as a high energy electrode material in lithium based batteries. Mechanistic insight on the electrochemical reduction and oxidation processes was gained through the first X-ray absorption spectroscopic study of lithiation and delithiation of CuFe2 O 4. A phase pure tetragonal CuFe2 O 4 material was prepared and characterized using laboratory and synchrotron X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. We used ex situ X-ray absorption spectroscopy (XAS) measurements to study the battery redox processes at the Fe and Cu K-edges, using X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and transmission X-ray microscopy (TXM) spectroscopies. EXAFS analysis showed upon discharge, an initial conversion of 50% of the copper(II) to copper metal positioned outside of the spinel structure, followed by a migration of tetrahedral iron(III) cations to octahedral positions previously occupied by copper(II). Then, upon charging to 3.5 V, the copper metal remained in the metallic state, while iron metal oxidation to iron(III) was achieved. Our results provide new mechanistic insight regarding the evolution of the local coordination environments at the iron and copper centers upon discharging and charging.

  5. Mechanistic Study of CO 2 Photoreduction with H 2 O on Cu/TiO 2 Nanocomposites by in Situ X-ray Absorption and Infrared Spectroscopies

    SciTech Connect

    Liu, Lianjun; Zhao, Cunyu; Miller, Jeffrey T.; Li, Ying

    2016-12-15

    Cu/TiO2 composites are extensively studied for photocatalytic reduction of CO2 with H2O, but the roles of Cu species (Cu2+, Cu+, or Cu0) is not well understood, and the photocatalyst deactivation mechanism is seldom addressed. In this work, we have employed in situ techniques, i.e., X-ray absorption spectroscopy (XAS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), to explore the surface chemistry of Cu/TiO2 composites under CO2 photoreduction environment. We found that the air-calcined Cu/TiO2 (Cu/Ti(air)) surface was dominated by isolated Cu2+ sites, while the one post-treated with H2 at 200 °C (Cu/Ti(H2)) was rich in Cu+ and oxygen vacancy (VO). Cu/Ti(H2) showed more than 50% higher activity than Cu/Ti(air) for CO2 photoreduction to CO, mainly resulting from the synergy of Cu+, OH groups, and VO that could scavenge holes to enhance electron transfer, provide CO2 adsorption sites, and facilitate the activation and conversion of the adsorbed CO2 (HCO3– and CO2–). Meanwhile, the consumption of OH groups and Cu+ active sites by holes may result in the deactivation of Cu/Ti(H2). Moreover, in situ XAS results directly demonstrated that (1) the photoinduced oxidation of Cu+ to Cu2+ changed the surrounding environments of Cu by increasing the coordination number; (2) thermal treatment by H2 could not fully recover the OH and Cu+ sites to their original states; and (3) adding hole scavengers (e.g., methanol) maintained or even increased the more active Cu+ species from the photoreduction of Cu2+, thus leading to a higher and more stable CO2 reduction activity. Findings in this work and the application of in situ XAS technique will help develop a more efficient photocatalyst for CO2 photoreduction and advance the understanding of the reaction mechanism and surface chemistry.

  6. Bioacoustic Absorption Spectroscopy

    DTIC Science & Technology

    2016-06-07

    seas in co-operation with fisheries biologists. The first planned experiment will be in the seas off California in co-operation with the Southwest... Fisheries Science Center of NOAA’s National Marine Fisheries Service. These experiments will be designed to investigate the “signatures” of the two major...formulating environmental adaptation strategies for tactical sonars. Fisheries applications: These results suggest that bioacoustic absorptivity can be used to

  7. Self-Supported Copper Oxide Electrocatalyst for Water Oxidation at Low Overpotential and Confirmation of Its Robustness by Cu K-edge X-ray Absorption Spectroscopy

    SciTech Connect

    Liu, Xiang; Cui, Shengsheng; Sun, Zijun; Ren, Yang; Zhang, Xiaoyi; Du, Pingwu

    2016-01-21

    Developing efficient water oxidation catalysts made of earth-abundant elements is a demanding challenge that should be met to fulfill the promise of water splitting for clean energy. Herein we report an annealing approach to synthesize binder-free, self-supported heterogeneous copper oxide (CuO) on conductive electrodes for oxygen evolution reaction (OER), producing electrodes with excellent electrocatalytic properties such as high efficiency, low overpotential, and good stability. The catalysts were grown in situ on fluorine-doped tin oxide (FTO) by electrodeposition from a simple Cu(II) salt solution, followed by annealing at a high temperature. Under optimal conditions, the CuO-based OER catalyst shows an onset potential of <0.58 V (vs Ag/AgCl) in 1.0 M KOH at pH 13.6. From the Tafel plot, the required overpotentials for current densities of 0.1 and 1.0 mA/cm2 are only 360 and 430 mV, respectively. The structure and the presence of a CuO motif in the catalyst have been identified by high-energy X-ray diffraction (HE-XRD), Cu K-edge X-ray absorption (XAS) spectra including X-ray absorption near-edge structure (XANES), and extended X-ray absorption fine structure (EXAFS). To the best of our knowledge, this represents the best catalytic activity for CuO-based OER catalysts to date.

  8. Cu K-edge X-ray Absorption Spectroscopy Reveals Differential Copper Coordimation Within Amyloid-beta Oligomers Compared to Amyloid-beta Monomers

    SciTech Connect

    J Shearer; P Callan; T Tran; V Szalai

    2011-12-31

    The fatal neurodegenerative disorder Alzheimer's disease (AD) has been linked to the formation of soluble neurotoxic oligomers of amyloid-{beta} (A{beta}) peptides. These peptides have high affinities for copper cations. Despite their potential importance in AD neurodegeneration few studies have focused on probing the Cu{sup 2+/1+} coordination environment within A{beta} oligomers. Herein we present a Cu K-edge X-ray absorption spectroscopic study probing the copper-coordination environment within oligomers of A{beta}(42) (sequence: DAEFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVVIA). We find that the Cu{sup 2+} cation is contained within a square planar mixed N/O ligand environment within A{beta}(42) oligomers, which is similar to the copper coordination environment of the monomeric forms of {l_brace}Cu{sup II}A{beta}(40){r_brace} and {l_brace}Cu{sup II}A{beta}(16){r_brace}. Reduction of the Cu{sup 2+} cation within the A{beta}(42) oligomers to Cu{sup 1+} yields a highly dioxygen sensitive copper-species that contains Cu{sup 1+} in a tetrahedral coordination geometry. This can be contrasted with monomers of {l_brace}Cu{sup I}A{beta}(40){r_brace} and {l_brace}Cu{sup I}A{beta}(16){r_brace}, which contain copper in a dioxygen inert linear bis-histidine ligand environment [Shearer and Szalai, J. Am. Chem. Soc., 2008, 130, 17826]. The biological implications of these findings are discussed.

  9. Local structure study of (In{sub 0.95−x}Fe{sub x}Cu{sub 0.05}){sub 2}O{sub 3} thin films using x-ray absorption spectroscopy

    SciTech Connect

    Ren, Yuan; Xing, Yaya; Ma, Guanxiong; Wang, Shiqi; An, Yukai Liu, Jiwen; Zhao, Xingliang

    2015-07-15

    The (In{sub 0.95−x}Fe{sub x}Cu{sub 0.05}){sub 2}O{sub 3} (x = 0.06, 0.08, 0.15, and 0.20) films prepared by RF-magnetron sputtering were investigated by the combination of x-ray absorption spectroscopy (XAS) at Fe, Cu, and O K-edge. Although the Fe and O K-edge XAS spectra show that the Fe atoms substitute for the In sites of In{sub 2}O{sub 3} lattice for all the films, the Cu K-edge XAS spectra reveal that the codoped Cu atoms are separated to form the Cu metal clusters. After being annealed in air, the Fe atoms are still substitutionally incorporated into the In{sub 2}O{sub 3} lattice, while the Cu atoms form the CuO secondary phases. With the increase of Fe concentration, the bond length R{sub Fe-O} shortens and the Debye–Waller factor σ{sup 2}{sub Fe-O} increases in the first coordination shell of Fe, which are attributed to the relaxation of oxygen environment around the substitutional Fe ions. The forming of Cu relating secondary phases in the films is due to high ionization energy of Cu atoms, leading that the Cu atoms are energetically much harder to be oxidized to substitute for the In sites of In{sub 2}O{sub 3} lattice than Fe atoms. These results provide new experimental guidance in the preparation of the codoped In{sub 2}O{sub 3} based dilute magnetic oxides.

  10. Microwave absorption of electroplated NiFeCu/Cu multilayers deposited directly on Si (100) substrates

    NASA Astrophysics Data System (ADS)

    Silva, B. G.; Gonzalez-Chavez, D. E.; Filho, J. Gomes; Sommer, R. L.

    2016-12-01

    We study the magnetic properties and broadband microwave absorption of electroplated NiFeCu/Cu multilayered thin films deposited directly on Si (100) substrates. We produced samples with 20 nm thick NiFeCu layers and Cu layer thickness tCu in the range 0-2.8 nm. Structural properties were studied by grazing incidence X-ray diffraction (GIXRD), while the composition and morphological aspects were studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). GIXRD confirmed the cubic face centered FCC phase of NiFeCu with all diffraction peaks drifting toward lower angles with tCu. SEM images show the appearance of Cu islands instead of continuous Cu layers. A minimum coercive field of 1.4 Oe is obtained for tCu = 1.0 nm, while the ferromagnetic resonance linewidth exhibited 200 Oe constant values for tCu between 0.7 and 2.1 nm. The effective magnetization increases with tCu, possibly associated to the increase on Fe content as observed by EDX. The effective dynamic anisotropy behavior with tCu seems to be associated to the island structure observed in the films.

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

    PubMed

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

    2017-01-25

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

  12. Determination of Cd, Co, Cu, Mn, Ni, Pb, and Zn by Inductively Coupled Plasma Mass Spectroscopy or Flame Atomic Absorption Spectrometry after On-line Preconcentration and Solvent Extraction by Flow Injection System

    PubMed

    Bortoli; Gerotto; Marchiori; Mariconti; Palonta; Troncon

    1996-11-01

    The concentrations of Cd, Co, Cu, Mn, Ni, Pb, and Zn in natural and sea waters are too low to be directly determined with by flame atomic absorption spectrometry (FAAS) or graphite furnace atomic absorption spectrometry (GFAAS). Specific sample preparations are requested that make possible the determination of these analytes by preconcentration or extraction. These techniques are affected by severe problems of sample contamination. In this work Cd, Co, Cu, Mn, Ni, Pb, and Zn were determined by inductively coupled plasma mass spectroscopy (ICP-MS) or by atomic absorption spectrometry, in fresh and seawater samples, after on-line preconcentration and following solvent elution with a flow injection system. Bonded silica with octadecyl functional group C18, packed in a microcolumn of 100-μl capacity, was used to collect diethyldithiocarbamate complexes of the heavy metals in aqueous solutions. The metals are complexed with a chelating agent, adsorbed on the C18 column, and eluted with methanol directly in the flow injection system. The methanolic stream can be addressed to FAAS for direct determination of Cu, Ni, and Zn, or collected in a vial for successive analysis by GFAAS. The eluted samples can be also dried in a vacuum container and restored to a little volume with concentrated HNO3 and Milli-Q water for analysis by ICP-MS or GFAAS.

  13. Absorption Spectroscopy in Homogeneous and Micellar Solutions.

    ERIC Educational Resources Information Center

    Shah, S. Sadiq; Henscheid, Leonard G.

    1983-01-01

    Describes an experiment which has helped physical chemistry students learn principles of absorption spectroscopy, the effect of solvent polarity on absorption spectra, and some micellar chemistry. Background information and experimental procedures are provided. (JN)

  14. Atomic absorption spectroscopy in ion channel screening.

    PubMed

    Stankovich, Larisa; Wicks, David; Despotovski, Sasko; Liang, Dong

    2004-10-01

    This article examines the utility of atomic absorption spectroscopy, in conjunction with cold flux assays, to ion channel screening. The multiplicity of ion channels that can be interrogated using cold flux assays and atomic absorption spectroscopy is summarized. The importance of atomic absorption spectroscopy as a screening tool is further elaborated upon by providing examples of the relevance of ion channels to various physiological processes and targeted diseases.

  15. X-ray absorption spectroscopy of detwinned Pr{sub x}Y{sub 1{minus}x}Ba{sub 2}Cu{sub 3}O{sub 7{minus}y} single crystals: Electronic structure and hole distribution

    SciTech Connect

    Merz, M.; Nuecker, N.; Pellegrin, E.; Schweiss, P.; Schuppler, S.; Kielwein, M.; Knupfer, M.; Golden, M.S.; Fink, J.; Chen, C.T.; Chakarian, V.; Idzerda, Y.U.; Erb, A.

    1997-04-01

    Substituting Y in orthorhombic (Y,R)Ba{sub 2}Cu{sub 3}O{sub 7} by any rare-earth element R has generally little effect on the superconducting properties. For R=Pr, however, superconductivity is completely suppressed. To understand this effect we have studied the unoccupied electronic structure of Pr{sub x}Y{sub 1{minus}x}Ba{sub 2}Cu{sub 3}O{sub 7{minus}y} (x=0.0, 0.4, 0.8) using polarization-dependent O 1s near-edge x-ray absorption spectroscopy of detwinned single crystals. We identify the hole states in the CuO{sub 2} planes and the CuO{sub 3} chains and give estimates of the relative contributions of the O 2p{sub x}, O 2p{sub y}, and O 2p{sub z} orbitals to these states. Along with the comparison of oxygen-rich (y{approx}0.1) to the oxygen-depleted materials (y{approx}0.9), this allows a test of the current theoretical explanations for the Pr-induced suppression of superconductivity. While we can rule out models involving hole filling or charge transfer between the planes and the chains, our data are consistent with approaches based on Pr 4f{endash}O 2p{sub {pi}} hybridization. {copyright} {ital 1997} {ital The American Physical Society}

  16. [Digestion-flame atomic absorption spectroscopy].

    PubMed

    Xu, Liang; Hu, Jian-Guo; Liu, Rui-Ping; Wang, Zhi-Min; Narenhua

    2008-01-01

    A microwave digestion-flame atomic absorption spectroscopy (FAAS) method was developed for the determination of metal elements Na, Zn, Cu, Fe, Mn, Ca and Mg in Mongolian patents. The instrument parameters for the determination were optimized, and the appropriate digestion solvent was selected. The recovery of the method was between 95.8% and 104.3%, and the RSD was between 1.6% and 4.2%. The accuracy and precision of the method was tested by comparing the values obtained from the determination of the standard sample, bush twigs and leaves (GSV-1) by this method with the reference values of GSV-1. The determination results were found to be basically consistent with the reference values. The microwave digestion technique was applied to process the samples, and the experimental results showed that compared to the traditional wet method, the present method has the merits of simplicity, saving agents, rapidness, and non-polluting. The method was accurate and reliable, and could be used to determine the contents of seven kinds of metal elements in mongolian patents.

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

    SciTech Connect

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

    2009-05-28

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

  18. Laser ionization and spectroscopy of Cu in superfluid helium nanodroplets

    PubMed Central

    Lindebner, Friedrich; Kautsch, Andreas; Koch, Markus; Ernst, Wolfgang E.

    2014-01-01

    Mass and optical spectroscopic methods are used for the analysis of copper (Cu) atoms and clusters doped to helium nanodroplets (HeN). A two-color resonant two-photon ionization scheme is applied to study the Cu 2P1/2,3/2∘←2S1/2 ground state transition. The absorption is strongly broadened for Cu atoms submerged inside helium nanodroplets and a comparison with computed literature values is provided. An observed ejection of the dopant from the droplet is triggered upon excitation, populating energetically lower states. The formation of Cun clusters up to Cu7 inside helium nanodroplets was observed by means of electron impact ionization mass spectroscopy. PMID:25844053

  19. Unusual Cu(I)/Ag(I) coordination of Escherichia coli CusF as revealed by atomic resolution crystallography and X-ray absorption spectroscopy

    PubMed Central

    Loftin, Isabell R.; Franke, Sylvia; Blackburn, Ninian J.; McEvoy, Megan M.

    2007-01-01

    Elevated levels of copper or silver ions in the environment are an immediate threat to many organisms. Escherichia coli is able to resist the toxic effects of these ions through strictly limiting intracellular levels of Cu(I) and Ag(I). The CusCFBA system is one system in E. coli responsible for copper/silver tolerance. A key component of this system is the periplasmic copper/silver-binding protein, CusF. Here the X-ray structure and XAS data on the CusF–Ag(I) and CusF–Cu(I) complexes, respectively, are reported. In the CusF–Ag(I) structure, Ag(I) is coordinated by two methionines and a histidine, with a nearby tryptophan capping the metal site. EXAFS measurements on the CusF–Cu(I) complex show a similar environment for Cu(I). The arrangement of ligands effectively sequesters the metal from its periplasmic environment and thus may play a role in protecting the cell from the toxic ion. PMID:17893365

  20. Cavity Enhanced Ultrafast Transient Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Allison, Thomas K.; Reber, Melanie Roberts; Chen, Yuning

    2015-06-01

    Ultrafast spectroscopy on gas phase systems is typically restricted to techniques involving photoionization, whereas solution phase experiments utilize the detection of light. At Stony Brook, we are developing new techniques for performing femtosecond time-resolved spectroscopy using frequency combs and high-finesse optical resonators. A large detection sensitivity enhancement over traditional methods enables the extension of all-optical ultrafast spectroscopies, such as broad-band transient absorption spectroscopy (TAS) and 2D spectroscopy, to dilute gas phase samples produced in molecular beams. Here, gas phase data can be directly compared to solution phase data. Initial demonstration experiments are focusing on the photodissociation of iodine in small neutral argon clusters, where cluster size strongly influences the effects solvent-caging and geminate recombination. I will discuss these initial results, our high power home-built Yb:fiber laser systems, and also extensions of the methods to the mid-IR to study the vibrational dynamics of hydrogen bonded clusters.

  1. Triplet absorption spectroscopy and electromagnetically induced transparency

    NASA Astrophysics Data System (ADS)

    Ghafoor, F.; Nazmitdinov, R. G.

    2016-09-01

    Coherence phenomena in a four-level atomic system, cyclically driven by three coherent fields, are investigated thoroughly at zero and weak magnetic fields. Each strongly interacting atomic state is converted to a triplet due to a dynamical Stark effect. Two dark lines with a Fano-like profile arise in the triplet absorption spectrum with anomalous dispersions. We provide conditions to control the widths of the transparency windows by means of the relative phase of the driving fields and the intensity of the microwave field, which closes the optical system loop. The effect of Doppler broadening on the results of the triplet absorption spectroscopy is analysed in detail.

  2. Determination of copper, zinc and iron in broncho-alveolar lavages by atomic absorption spectroscopy.

    PubMed

    Harlyk, C; Mccourt, J; Bordin, G; Rodriguez, A R; van der Eeckhout, A

    1997-11-01

    Concentrations of Zn, Cu and Fe were measured in 157 broncho-alveolar lavages (BAL), before and after centrifugation, collected at the Leuven University Hospital (Belgium). Zn was measured by flame-atomic absorption spectroscopy, using direct calibration, while Cu and Fe were determined by electrothermal atomic absorption spectroscopy, using the method of standard additions. For Fe only 56 samples were measured. Most of the studied elements are present in the liquid phase (supernatant). About 90% of Cu concentrations lie between 0 and 15 micrograms/kg, while 90% of Zn concentrations are lower than 230 micrograms/kg, with 30% between 30 and 70 micrograms/kg, and 50% between 100 and 200 micrograms/kg. There seems to be a reverse relationship between Cu and Zn levels with high Cu going along with low Zn and vice versa.

  3. Methane overtone absorption by intracavity laser spectroscopy

    NASA Technical Reports Server (NTRS)

    Obrien, James J.

    1990-01-01

    Interpretation of planetary methane (CH4) visible-near IR spectra, used to develop models of planetary atmospheres, has been hampered by a lack of suitable laboratory spectroscopic data. The particular CH4 spectral bands are due to intrinsically weak, high overtone-combination transitions too complex for classical spectroscopic analysis. The traditional multipass cell approach to measuring spectra of weakly absorbing species is insufficiently sensitive to yield reliable results for some of the weakest CH4 absorption features and is difficult to apply at the temperatures of the planetary environments. A time modulated form of intracavity laser spectroscopy (ILS), has been shown to provide effective absorption pathlengths of 100 to 200 km with sample cells less than 1 m long. The optical physics governing this technique and the experimental parameters important for obtaining reliable, quantitative results are now well understood. Quantitative data for CH4 absorption obtained by ILS have been reported recently. Illustrative ILS data for CH4 absorption in the 619.7 nm and 681.9 nm bands are presented. New ILS facilities at UM-St. Louis will be used to measure CH4 absorption in the 700 to 1000 nm region under conditions appropriate to the planetary atmospheres.

  4. Investigation of short-range structural order in Zr69.5Cu12Ni11Al7.5 and Zr41.5Ti41.5Ni17 glasses, using X-ray absorption spectroscopy and ab initio molecular dynamics simulations.

    PubMed

    Lahiri, Debdutta; Sharma, Surinder M; Verma, Ashok K; Vishwanadh, B; Dey, G K; Schumacher, Gerhard; Scherb, Tobias; Riesemeier, Heinrich; Reinholz, Uwe; Radtke, Martin; Banerjee, S

    2014-11-01

    Short-range order has been investigated in Zr69.5Cu12Ni11Al7.5 and Zr41.5Ti41.5Ni17 metallic glasses using X-ray absorption spectroscopy and ab initio molecular dynamics simulations. While both of these alloys are good glass formers, there is a difference in their glass-forming abilities (Zr41.5Ti41.5Ni17 > Zr69.5Cu12Ni11Al7.5). This difference is explained by inciting the relative importance of strong chemical order, icosahedral content, cluster symmetry and configuration diversity.

  5. UV laser long-path absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Dorn, Hans-Peter; Brauers, Theo; Neuroth, Rudolf

    1994-01-01

    Long path Differential Optical Absorption Spectroscopy (DOAS) using a picosecond UV laser as a light source was developed in our institute. Tropospheric OH radicals are measured by their rotational absorption lines around 308 nm. The spectra are obtained using a high resolution spectrograph. The detection system has been improved over the formerly used optomechanical scanning device by application of a photodiode array which increased the observed spectral range by a factor of 6 and which utilizes the light much more effectively leading to a considerable reduction of the measurement time. This technique provides direct measurements of OH because the signal is given by the product of the absorption coefficient and the OH concentration along the light path according to Lambert-Beers law. No calibration is needed. Since the integrated absorption coefficient is well known the accuracy of the measurement essentially depends on the extent to which the OH absorption pattern can be detected in the spectra. No interference by self generated OH radicals in the detection lightpath has been observed. The large bandwidth (greater than 0.15 nm) and the high spectral resolution (1.5 pm) allows absolute determination of interferences by other trace gas absorptions. The measurement error is directly accessible from the absorption-signal to baseline-noise ratio in the spectra. The applicability of the method strongly depends on visibility. Elevated concentrations of aerosols lead to considerable attenuation of the laser light which reduces the S/N-ratio. In the moderately polluted air of Julich, where we performed a number of OH measurement spectra. In addition absorption features of unidentified species were frequently detected. A quantitative deconvolution even of the known species is not easy to achieve and can leave residual structures in the spectra. Thus interferences usually increase the noise and deteriorate the OH detection sensitivity. Using diode arrays for sensitive

  6. Remote laser evaporative molecular absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Hughes, Gary B.; Lubin, Philip; Cohen, Alexander; Madajian, Jonathan; Kulkarni, Neeraj; Zhang, Qicheng; Griswold, Janelle; Brashears, Travis

    2016-09-01

    We describe a novel method for probing bulk molecular and atomic composition of solid targets from a distant vantage. A laser is used to melt and vaporize a spot on the target. With sufficient flux, the spot temperature rises rapidly, and evaporation of surface materials occurs. The melted spot creates a high-temperature blackbody source, and ejected material creates a plume of surface materials in front of the spot. Molecular and atomic absorption occurs as the blackbody radiation passes through the ejected plume. Bulk molecular and atomic composition of the surface material is investigated by using a spectrometer to view the heated spot through the ejected plume. The proposed method is distinct from current stand-off approaches to composition analysis, such as Laser-Induced Breakdown Spectroscopy (LIBS), which atomizes and ionizes target material and observes emission spectra to determine bulk atomic composition. Initial simulations of absorption profiles with laser heating show great promise for Remote Laser-Evaporative Molecular Absorption (R-LEMA) spectroscopy. The method is well-suited for exploration of cold solar system targets—asteroids, comets, planets, moons—such as from a spacecraft orbiting the target. Spatial composition maps could be created by scanning the surface. Applying the beam to a single spot continuously produces a borehole or trench, and shallow subsurface composition profiling is possible. This paper describes system concepts for implementing the proposed method to probe the bulk molecular composition of an asteroid from an orbiting spacecraft, including laser array, photovoltaic power, heating and ablation, plume characteristics, absorption, spectrometry and data management.

  7. In vivo absorption spectroscopy for absolute measurement.

    PubMed

    Furukawa, Hiromitsu; Fukuda, Takashi

    2012-10-01

    In in vivo spectroscopy, there are differences between individual subjects in parameters such as tissue scattering and sample concentration. We propose a method that can provide the absolute value of a particular substance concentration, independent of these individual differences. Thus, it is not necessary to use the typical statistical calibration curve, which assumes an average level of scattering and an averaged concentration over individual subjects. This method is expected to greatly reduce the difficulties encountered during in vivo measurements. As an example, for in vivo absorption spectroscopy, the method was applied to the reflectance measurement in retinal vessels to monitor their oxygen saturation levels. This method was then validated by applying it to the tissue phantom under a variety of absorbance values and scattering efficiencies.

  8. Atmospheric Measurements by Cavity Enhanced Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Yi, Hongming; Wu, Tao; Coeur-Tourneur, Cécile; Fertein, Eric; Gao, Xiaoming; Zhao, Weixiong; Zhang, Weijun; Chen, Weidong

    2015-04-01

    Since the last decade, atmospheric environmental monitoring has benefited from the development of novel spectroscopic measurement techniques owing to the significant breakthroughs in photonic technology from the UV to the infrared spectral domain [1]. In this presentation, we will overview our recent development and applications of cavity enhanced absorption spectroscopy techniques for in situ optical monitoring of chemically reactive atmospheric species (such as HONO, NO3, NO2, N2O5) in intensive campaigns [2] and/or in smog chamber studies [3]. These field deployments demonstrated that modern photonic technologies (newly emergent light sources combined with high sensitivity spectroscopic techniques) can provide a useful tool to improve our understanding of tropospheric chemical processes which affect climate, air quality, and the spread of pollution. Experimental detail and preliminary results will be presented. Acknowledgements. The financial support from the French Agence Nationale de la Recherche (ANR) under the NexCILAS (ANR-11-NS09-0002) and the CaPPA (ANR-10-LABX-005) contracts is acknowledged. References [1] X. Cui, C. Lengignon, T. Wu, W. Zhao, G. Wysocki, E. Fertein, C. Coeur, A. Cassez,L. Croisé, W. Chen, et al., "Photonic Sensing of the Atmosphere by absorption spectroscopy", J. Quant. Spectrosc. Rad. Transfer 113 (2012) 1300-1316 [2] T. Wu, Q. Zha, W. Chen, Z. XU, T. Wang, X. He, "Development and deployment of a cavity enhanced UV-LED spectrometer for measurements of atmospheric HONO and NO2 in Hong Kong", Atmos. Environ. 95 (2014) 544-551 [3] T. Wu, C. Coeur-Tourneur, G. Dhont,A. Cassez, E. Fertein, X. He, W. Chen,"Application of IBBCEAS to kinetic study of NO3 radical formation from O3 + NO2 reaction in an atmospheric simulation chamber", J. Quant. Spectrosc. Rad. Transfer 133 (2014)199-205

  9. Highly sensitive detection using Herriott cell for laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhao, Chongyi; Song, Guangming; Du, Yang; Zhao, Xiaojun; Wang, Wenju; Zhong, Liujun; Hu, Mai

    2016-11-01

    The tunable diode laser absorption spectroscopy combined with the long absorption path technique is a significant method to detect harmful gas. The long optical path could come true by Herriott cell reducing the size of the spectrometers. A 15 cm long Herriott cell with 28.8 m optical absorption path after 96 times reflection was designed that enhanced detection sensitivity of absorption spectroscopy. According to the theory data of calculation, Herriott cell is analyzed and simulated by softwares Matlab and Lighttools.

  10. Double point contact single molecule absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Howard, John Brooks

    Our primary objective with the presentation of this thesis is to utilize superconducting transport through microscopic objects to both excite and analyze the vibrational degrees of freedom of various molecules of a biological nature. The technique stems from a Josephson junction's ability to generate radiation that falls in the terahertz gap (≈ 10 THz) and consequently can be used to excite vibrational modes of simple and complex molecules. Analysis of the change in IV characteristics coupled with the differential conductance dIdV allows determination of both the absorption spectra and the vibrational modes of biological molecules. Presented here are both the theoretical foundations of superconductivity relevant to our experimental technique and the fabrication process of our samples. Comparisons between our technique and that of other absorption spectroscopy techniques are included as a means of providing a reference upon which to judge the merits of our novel procedure. This technique is meant to improve not only our understanding of the vibrational degrees of freedom of useful biological molecules, but also these molecule's structural, electronic and mechanical properties.

  11. Precision Saturated Absorption Spectroscopy of H3+

    NASA Astrophysics Data System (ADS)

    Guan, Yu-chan; Liao, Yi-Chieh; Chang, Yung-Hsiang; Peng, Jin-Long; Shy, Jow-Tsong

    2016-06-01

    In our previous work on the Lamb dips of the νb{2} fundamental band of H3+, the saturated absorption spectrum was obtained by the third-derivative spectroscopy using frequency modulation [1]. However, the frequency modulation also causes error in absolute frequency determination. To solve this problem, we have built an offset-locking system to lock the OPO pump frequency to an iodine-stabilized Nd:YAG laser. With this modification, we are able to scan the OPO idler frequency precisely and obtain the profile of the Lamb dips. Double modulation (amplitude modulation of the idler power and concentration modulation of the ion) is employed to subtract the interference fringes of the signal and increase the signal-to-noise ratio effectively. To Determine the absolute frequency of the idler wave, the pump wave is offset locked on the R(56) 32-0 a10 hyperfine component of 127I2, and the signal wave is locked on a GPS disciplined fiber optical frequency comb (OFC). All references and lock systems have absolute frequency accuracy better than 10 kHz. Here, we demonstrate its performance by measuring one transition of methane and sixteen transitions of H3+. This instrument could pave the way for the high-resolution spectroscopy of a variety of molecular ions. [1] H.-C. Chen, C.-Y. Hsiao, J.-L. Peng, T. Amano, and J.-T. Shy, Phys. Rev. Lett. 109, 263002 (2012).

  12. Transient absorption spectroscopy of laser shocked explosives

    SciTech Connect

    Mcgrane, Shawn D; Dang, Nhan C; Whitley, Von H; Bolome, Cindy A; Moore, D S

    2010-01-01

    Transient absorption spectra from 390-890 nm of laser shocked RDX, PETN, sapphire, and polyvinylnitrate (PVN) at sub-nanosecond time scales are reported. RDX shows a nearly linear increase in absorption with time after shock at {approx}23 GPa. PETN is similar, but with smaller total absorption. A broad visible absorption in sapphire begins nearly immediately upon shock loading but does not build over time. PVN exhibits thin film interference in the absorption spectra along with increased absorption with time. The absorptions in RDX and PETN are suggested to originate in chemical reactions happening on picosecond time scales at these shock stresses, although further diagnostics are required to prove this interpretation.

  13. Analysis of the absorption layer of CIGS solar cell by laser-induced breakdown spectroscopy.

    PubMed

    Lee, Seok H; Shim, Hee S; Kim, Chan K; Yoo, Jong H; Russo, Richard E; Jeong, Sungho

    2012-03-01

    Laser induced breakdown spectroscopy (LIBS) was applied for the elemental analysis of the thin copper indium gallium diselenide (CuIn(1-x)Ga(x)Se(2) [CIGS]) absorption layer deposited on Mo-coated soda-lime glass by the co-evaporation technique. The optimal laser and detection parameters for LIBS measurement of the CIGS absorption layer (1.23 μm) were investigated. The calibration results of Ga/In ratio with respect to the concentration ratios measured by x-ray fluorescence and inductively coupled plasma optical emission spectroscopy showed good linearity.

  14. Applications of absorption spectroscopy using quantum cascade lasers.

    PubMed

    Zhang, Lizhu; Tian, Guang; Li, Jingsong; Yu, Benli

    2014-01-01

    Infrared laser absorption spectroscopy (LAS) is a promising modern technique for sensing trace gases with high sensitivity, selectivity, and high time resolution. Mid-infrared quantum cascade lasers, operating in a pulsed or continuous wave mode, have potential as spectroscopic sources because of their narrow linewidths, single mode operation, tunability, high output power, reliability, low power consumption, and compactness. This paper reviews some important developments in modern laser absorption spectroscopy based on the use of quantum cascade laser (QCL) sources. Among the various laser spectroscopic methods, this review is focused on selected absorption spectroscopy applications of QCLs, with particular emphasis on molecular spectroscopy, industrial process control, combustion diagnostics, and medical breath analysis.

  15. Characterization of the Cu(Π) and Zn(Π) binding to the Amyloid-β short peptides by both the Extended X-ray Absorption Fine Structure and the Synchrotron Radiation Circular Dichroism spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Zhiyin; Sun, Shuaishuai; Xu, Jianhua; Zhang, Jing; Huang, Yan; Zhang, Bingbing; Tao, Ye

    2013-04-01

    Alzheimer's disease (AD) is a progressive and devastating neurodegenerative pathology, clinically characterized by dementia, cognitive impairment, personality disorders and memory loss. It is generally accepted that, misfolding of Aβ peptides is the key element in pathogenesis and the secondary structure of Aβ can be changed to major β-strand with reasons unknown yet. Many studies have shown that the misfolding may be linked with some biometals, mainly copper and zinc ions. To characterize interactions of Aβ and metal ions, we utilized both the extended X-ray fine structure spectroscopy (EXAFS) and the synchrotron radiation circular dichroism spectroscopy (SRCD). Aβ (13-22), Aβ (13-21), Aβ (E22G) and Aβ(HH-AA) were selected to study the mechanism of copper and zinc binding to Aβ. We found that Cu interaction with H13 and H14 residues led to the disappearance of the PPΠ, while the Cu binding E22 residue caused a remarkable conformation change to β-sheet enrichment. The Zn ion, in contrast, made little effect on the conformation and it coordinated to only one histidine (H residue) or not.

  16. UV-VIS absorption spectroscopy: Lambert-Beer reloaded.

    PubMed

    Mäntele, Werner; Deniz, Erhan

    2017-02-15

    UV-VIS absorption spectroscopy is used in almost every spectroscopy laboratory for routine analysis or research. All spectroscopists rely on the Lambert-Beer Law but many of them are less aware of its limitations. This tutorial discusses typical problems in routine spectroscopy that come along with technical limitations or careless selection of experimental parameters. Simple rules are provided to avoid these problems.

  17. UV-VIS absorption spectroscopy: Lambert-Beer reloaded

    NASA Astrophysics Data System (ADS)

    Mäntele, Werner; Deniz, Erhan

    2017-02-01

    UV-VIS absorption spectroscopy is used in almost every spectroscopy laboratory for routine analysis or research. All spectroscopists rely on the Lambert-Beer Law but many of them are less aware of its limitations. This tutorial discusses typical problems in routine spectroscopy that come along with technical limitations or careless selection of experimental parameters. Simple rules are provided to avoid these problems.

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

    PubMed

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

    2009-12-15

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

  19. The saturable absorption and reverse saturable absorption properties of Cu doped zinc oxide thin films

    NASA Astrophysics Data System (ADS)

    Yao, Cheng-Bao; Wen, Xin; Li, Qiang-Hua; Yan, Xiao-Yan; Li, Jin; Zhang, Ke-Xin; Sun, Wen-Jun; Bai, Li-Na; Yang, Shou-Bin

    2017-03-01

    We present the structure and nonlinear absorption (NLA) properties of Cu-doped ZnO (CZO) films prepared by magnetron sputtering. The films were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that the CZO films can maintain a wurtzite structure. Furthermore, the open-aperture (OA) Z-scan measurements of the film were carried out by nanosecond laser pulse. A transition from saturable absorption (SA) to reverse saturable absorption (RSA) was observed as the excitation intensity increasing. With good excellent nonlinear optical coefficient, the samples were expected to be the potential applications in optical devices.

  20. Soft x-ray absorption spectroscopy studies of doped Pr-containing cuprates

    NASA Astrophysics Data System (ADS)

    Chen, J. M.; Liu, S. J.; Chang, C. F.; Lin, J.-Y.; Gou, Y. S.; Yang, H. D.

    2003-01-01

    Using high-resolution O K-edge x-ray absorption near-edge-structure (XANES) spectroscopy, unoccupied states of the YxPr1-xBa2Cu3O7 (x=0 1) thin films and polycrystalline Pr1-xCaxBa2Cu3O7 (x=0 0.3) as well as R0.8Pr0.2Ba2Cu3O7 samples (R=Tm, Dy, Gd, and Sm) are investigated. In YxPr1-xBa2Cu3O7, hole numbers in the CuO2 planes decrease significantly with increasing Pr doping level. Hole carriers generated via Ca doping in Pr1-xCaxBa2Cu3O7 are directed predominantly into both the Zhang-Rice and Fehrenbacher-Rice (FR) states, while those in the CuO3 ribbons remain almost unchanged with Ca substitution. In R0.8Pr0.2Ba2Cu3O7, the hole content in the CuO2 planes decreases monotonically with increasing ionic size of the R3+ ions, confirming the hole depletion effect based on the Pr 4f O 2p hybridization. We demonstrate the spectroscopic evidence of the existence of the FR states. The present XANES results provide a deeper understanding of the nature of hybridization and the origin of the ionic size effect.

  1. The determination of aluminum, copper, iron, and lead in glycol formulations by atomic absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Initial screening tests and the results obtained in developing procedures to determine Al, Cu, Fe, and Pb in glycol formulations are described. Atomic absorption completion was selected for Cu, Fe and Pb, and after comparison with emission spectroscopy, was selected for Al also. Before completion, carbon, iron, and lead are extracted with diethyl dithio carbamate (DDC) into methyl isobutyl ketone (MIBK). Aluminum was also extracted into MIBK using 8-hydroxyquinoline as a chelating agent. As little as 0.02 mg/l carbon and 0.06 mg/l lead or iron may be determined in glycol formulations. As little as 0.3 mg/l aluminum may be determined.

  2. Ultrafast transient absorption spectroscopy: principles and application to photosynthetic systems.

    PubMed

    Berera, Rudi; van Grondelle, Rienk; Kennis, John T M

    2009-01-01

    The photophysical and photochemical reactions, after light absorption by a photosynthetic pigment-protein complex, are among the fastest events in biology, taking place on timescales ranging from tens of femtoseconds to a few nanoseconds. The advent of ultrafast laser systems that produce pulses with femtosecond duration opened up a new area of research and enabled investigation of these photophysical and photochemical reactions in real time. Here, we provide a basic description of the ultrafast transient absorption technique, the laser and wavelength-conversion equipment, the transient absorption setup, and the collection of transient absorption data. Recent applications of ultrafast transient absorption spectroscopy on systems with increasing degree of complexity, from biomimetic light-harvesting systems to natural light-harvesting antennas, are presented. In particular, we will discuss, in this educational review, how a molecular understanding of the light-harvesting and photoprotective functions of carotenoids in photosynthesis is accomplished through the application of ultrafast transient absorption spectroscopy.

  3. Photoelectron and X-ray Absorption Spectroscopy Of Pu

    SciTech Connect

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

    2003-11-12

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

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

    SciTech Connect

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

    2008-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

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

  6. Assessment of Aided Phytostabilization of Copper-Contaminated Soil by X-ray Absorption Spectroscopy and Chemical Extractions

    SciTech Connect

    J Kumpiene; M Mench; C Bes; J Fitts

    2011-12-31

    Field plots were established at a timber treatment site to evaluate remediation of Cu contaminated topsoils with aided phytostabilization. Soil containing 2600 mg kg{sup -1} Cu was amended with a combination of 5 wt% compost and 2 wt% iron grit, and vegetated. Sequential extraction was combined with extended X-ray absorption fine structure (EXAFS) spectroscopy to correlate changes in Cu distribution across five fractions with changes in the predominant Cu compounds two years after treatment in parallel treated and untreated field plots. Exchangeable Cu dominated untreated soil, most likely as Cu(II) species non-specifically bound to natural organic matter. The EXAFS spectroscopic results are consistent with the sequential extraction results, which show a major shift in Cu distribution as a result of soil treatment to the fraction bound to poorly crystalline Fe oxyhydroxides forming binuclear inner-sphere complexes.

  7. Nearedge Absorption Spectroscopy of Interplanetary Dust Particles

    SciTech Connect

    Brennan, S.; Luening, K.; Pianetta, P.; Bradley, J.; Graham, G.; Westphal, A.; Snead, C.; Dominguez, G.; /SLAC, SSRL

    2006-10-25

    Interplanetary Dust Particles (IDPs) are derived from primitive Solar System bodies like asteroids and comets. Studies of IDPs provide a window onto the origins of the solar system and presolar interstellar environments. We are using Total Reflection X-ray Fluorescence (TXRF) techniques developed for the measurement of the cleanliness of silicon wafer surfaces to analyze these particles with high detection sensitivity. In addition to elemental analysis of the particles, we have collected X-ray Absorption Near-Edge spectra in a grazing incidence geometry at the Fe and Ni absorption edges for particles placed on a silicon wafer substrate. We find that the iron is dominated by Fe{sub 2}O{sub 3}.

  8. Electronic and optical properties of Cu, CuO and Cu2O studied by electron spectroscopy

    NASA Astrophysics Data System (ADS)

    Tahir, Dahlang; Tougaard, Sven

    2012-05-01

    The electronic and optical properties of Cu, CuO and Cu2O were studied by x-ray photoelectron spectroscopy (XPS) and reflection electron energy-loss spectroscopy (REELS). We report detailed Cu 2p, Cu LVV, O 1s and O KLL spectra which are in good agreement with previous results. REELS spectra, recorded for primary energies in the range from 150 to 2000 eV, were corrected for multiple inelastically scattered electrons to determine the effective inelastic scattering cross section. The dielectric functions and optical properties were determined by comparing the experimental inelastic electron scattering cross section with a simulated cross section calculated within the semi-classical dielectric response model in which the only input is Im(-1/ɛ) by using the QUEELS-ɛ(k,ω)-REELS software package. By Kramers-Kronig transformation of the determined Im(-1/ɛ), the real and imaginary parts (ɛ1 and ɛ2) of the dielectric function, and the refractive index n and extinction coefficient k were determined for Cu, CuO, and Cu2O in the 0-100 eV energy range. Observed differences between Cu, CuO and Cu2O are mainly due to modifications of the 3d and O 2p electron configurations.

  9. Optoacoustic spectroscopy and its application to molecular and particle absorption

    NASA Astrophysics Data System (ADS)

    Trees, Charles C.; Voss, Kenneth J.

    1990-09-01

    Light absorption in the ocean has been the least studied optical property because of the difficulties in making accurate measurements. With the previously used techniques, large differences have been reported for the specific absorption coefficient of phytoplankton (cultures and natural assemblages). It is difficult to determine if the diversity in these values are methodological or a function of actual variations in absorption. With the renewed interest and activity in optoacoustic spectroscopy (OAS), which accurately measures absorption, some of these discrepancies should be resolved. In this method, as molecules and particles absorb light from a modulated source, they thermally expand and contract, thereby generating acoustic waves, at the modulation frequency, which are detected by a hydrophone. Optoacoustic spectroscopy is ideally suited for measuring dissolved organic material and particle absorptions because of its high sensitivity (105m1) and the egligible effect of scattered light. In this paper the instrumental design for an optoacoustic spectrophotometer (OAS), which pecifically measures phytoplankton absorption (420-S5Onm), is described. The spectral absorption of dissolved organic material and a phytoplankton culture is presented. OAS holds promise in being able to measure absorption without use of either filtration or concentration techniques.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  11. Molecular shock response of explosives: electronic absorption spectroscopy

    SciTech Connect

    Mcgrne, Shawn D; Moore, David S; Whitley, Von H; Bolme, Cindy A; Eakins, Daniel E

    2009-01-01

    Electronic absorption spectroscopy in the range 400-800 nm was coupled to ultrafast laser generated shocks to begin addressing the question of the extent to which electronic excitations are involved in shock induced reactions. Data are presented on shocked polymethylmethacrylate (PMMA) thin films and single crystal pentaerythritol tetranitrate (PETN). Shocked PMMA exhibited thin film interference effects from the shock front. Shocked PETN exhibited interference from the shock front as well as broadband increased absorption. Relation to shock initiation hypotheses and the need for time dependent absorption data (future experiments) is briefly discussed.

  12. Molecular Shock Response of Explosives: Electronic Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    McGrane, S. D.; Moore, D. S.; Whitley, V. H.; Bolme, C. A.; Eakins, D. E.

    2009-12-01

    Electronic absorption spectroscopy in the range 400-800 nm was coupled to ultrafast laser generated shocks to begin addressing the extent to which electronic excitations are involved in shock induced reactions. Data are presented on shocked polymethylmethacrylate (PMMA) thin films and single crystal pentaerythritol tetranitrate (PETN). Shocked PMMA exhibited thin film interference effects from the shock front. Shocked PETN exhibited interference as well as broadband increased absorption. Relation to shock initiation and the need for time dependent absorption (future experiments) is briefly discussed.

  13. Absorption and Emission Spectroscopy of a Lasing Material: Ruby

    ERIC Educational Resources Information Center

    Esposti, C. Degli; Bizzocchi, L.

    2007-01-01

    Ruby is a crystalline material, which comes very expensive and is of great significance, as it helped in the creation of first laser. An experiment to determine the absorption and emission spectroscopy, in addition to the determination of the room-temperature lifetime of the substance is being described.

  14. Atomic Absorption Spectroscopy. The Present and the Future.

    ERIC Educational Resources Information Center

    Slavin, Walter

    1982-01-01

    The status of current techniques and methods of atomic absorption (AA) spectroscopy (flame, hybrid, and furnace AA) is discussed, including limitations. Technological opportunities and how they may be used in AA are also discussed, focusing on automation, microprocessors, continuum AA, hybrid analyses, and others. (Author/JN)

  15. Visualizing the Solute Vaporization Interference in Flame Atomic Absorption Spectroscopy

    ERIC Educational Resources Information Center

    Dockery, Christopher R.; Blew, Michael J.; Goode, Scott R.

    2008-01-01

    Every day, tens of thousands of chemists use analytical atomic spectroscopy in their work, often without knowledge of possible interferences. We present a unique approach to study these interferences by using modern response surface methods to visualize an interference in which aluminum depresses the calcium atomic absorption signal. Calcium…

  16. [Burner head with high sensitivity in atomic absorption spectroscopy].

    PubMed

    Feng, X; Yang, Y

    1998-12-01

    This paper presents a burner head with gas-sample separate entrance and double access, which is used for atomic absorption spectroscopy. According to comparison and detection, the device can improve sensitivity by a factor of 1 to 5. In the meantime it has properties of high stability and resistance to interference.

  17. Developing a Transdisciplinary Teaching Implement for Atomic Absorption Spectroscopy

    ERIC Educational Resources Information Center

    Drew, John

    2008-01-01

    In this article I explain why I wrote the set of teaching notes on Atomic Absorption Spectroscopy (AAS) and why they look the way they do. The notes were intended as a student reference to question, highlight and write over as much as they wish during an initial practical demonstration of the threshold concept being introduced, in this case…

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  19. Polarization-enhanced absorption spectroscopy for laser stabilization.

    PubMed

    Kunz, Paul D; Heavner, Thomas P; Jefferts, Steven R

    2013-11-20

    We demonstrate a variation of pump-probe spectroscopy that is particularly useful for laser frequency stabilization. The polarization-enhanced absorption spectroscopy (POLEAS) signal provides a significant improvement in signal-to-noise ratio over saturated absorption spectroscopy (SAS) for the important and commonly used atomic cycling transitions. The improvements can directly increase the short-term stability of a laser frequency lock, given sufficient servo loop bandwidth. The long-term stability of the POLEAS method, which is limited by environmental sensitivities, is comparable to that of SAS. The POLEAS signal is automatically Doppler-free, without requiring a separate Doppler subtraction beam, and lends itself to straightforward compact packaging. Finally, by increasing the amplitude of the desired (cycling) peak, while reducing the amplitude of all other peaks in the manifold, the POLEAS method eases the implementation of laser auto-locking schemes.

  20. Construction of CuS Nanoflakes Vertically Aligned on Magnetically Decorated Graphene and Their Enhanced Microwave Absorption Properties.

    PubMed

    Liu, Panbo; Huang, Ying; Yan, Jing; Yang, Yiwen; Zhao, Yang

    2016-03-02

    Hybrid nanocomposites with enhanced microwave absorption properties have been designed by growing CuS nanoflakes on magnetically decorated graphene, and the effect of special nanostructures on microwave absorption properties has been investigated. The structure of the nanocomposites was characterized by Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), N2 adsorption-desorption, and vibrating sample magnetometer (VSM). The influence of cetyltrimethylammonium bromide (CTAB) on the morphology of CuS nanoflakes was also investigated. A possible formation process of the nanocomposites and the mechanism of microwave absorption were explained in detail. As an absorber, the nanocomposites with a filler loading of 20 wt % exhibited enhanced microwave absorption properties due to the special nanostructures, extra void space, and synergistic effect. The maximum reflection loss can reach -54.5 dB at 11.4 GHz, and the absorption bandwidths exceeding -10 dB are 4.5 GHz with a thickness of 2.5 mm, which can be adjusted by the thickness. The results indicate that the hybrid nanocomposites with enhanced microwave absorption properties and lightweight have a promising future in decreasing electromagnetic wave irradiation.

  1. [Cu and Pb absorption and tolerance of Agrostis stolonifera and Festuca arundinacea].

    PubMed

    Wang, Yan; Xin, Shi-Gang; Ma, Lian-Ju; Dai, Bao-Qing; Yu, Long; Wang, Lan-Lan

    2007-03-01

    This paper studied the seed germination rate, chlorophyll content, net photosynthetic rate, SOD activity, and Cu and Pb absorption of Agrostis stolonifera and Festuca arundinacea under Cu and Pb pollution. The results showed that Cu and Pb pollution had a significant effect on the seed germination rate of F. arundinacea. The chlorophyll content of F. arundinacea decreased dramatically under Pb and Cu-Pb pollution, while decreased slightly under Cu pollution. No significant effect of Cu and Pb was observed on the chlorophyll content of A. stolonifera. The SOD activity of A. stolonifera increased under 350 mg Cu x kg(-1) and all test concentrations of Pb, while that of F. arundinacea only increased under 700 mg Pb x kg(-1) and 350 mg Cu x kg(-1) + 1100 mg Pb x kg(-1). The net photosynthetic rate of F. arundinacea decreased more under Pb pollution than under Cu pollution, but that of A. stolonifera all decreased under Cu or Pb pollution. It was suggested that A. stolonifera was more tolerant in physiological characteristics to Cu and Pb pollution than F. arundinacea, while F. arundinacea was more tolerant to Cu than to Pb. The Cu absorption amount of F. arundinacea was relatively large, but did not increase with increasing Cu pollution. A. stolonifera had a high absorption ability of Pb, and the absorbed Pb amount was increased with increasing Pb pollution. A. stolonifera and F. arundinace could be the potential phytoremediation plants for Pb and Cu-polluted soil, respectively.

  2. In situ X-ray Absorption Spectroscopic Investigation of the Electrochemical Conversion Reactions of CuF2-MoO3 Nanocomposite

    SciTech Connect

    A Mansour; F Badway; W Yoon; K Chung; G Amatucci

    2011-12-31

    We have used X-ray absorption spectroscopy at the Cu K-edge to investigate the electrochemical conversion reaction of 20 nm size 85 wt% CuF{sub 2}-15 wt% MoO{sub 3} nanocomposite under in situ conditions. The nanocomposite was prepared by high energy milling. Upon discharge, the lithiation reaction with the nanocomposite resulted in the formation of nanophase metallic Cu, which is consistent with the conversion of CuF{sub 2} into Cu and LiF. Based on XANES and Fourier transforms of EXAFS spectra, we show that the discharge process proceeded via the formation of highly dispersed Cu particles. Based on the coordination number of the first shell of Cu, the average size of the Cu particles was estimated to be in the 1-3 nm range in the fully discharged state.

  3. Analyte-induced spectral filtering in femtosecond transient absorption spectroscopy

    DOE PAGES

    Abraham, Baxter; Nieto-Pescador, Jesus; Gundlach, Lars

    2017-03-06

    Here, we discuss the influence of spectral filtering by samples in femtosecond transient absorption measurements. Commercial instruments for transient absorption spectroscopy (TA) have become increasingly available to scientists in recent years and TA is becoming an established technique to measure the dynamics of photoexcited systems. Furthermore, we show that absorption of the excitation pulse by the sample can severely alter the spectrum and consequently the temporal pulse shape. This “spectral self-filtering” effect can lead to systematic errors and misinterpretation of data, most notably in concentration dependent measurements. Finally, the combination of narrow absorption peaks in the sample with ultrafast broadbandmore » excitation pulses is especially prone to this effect.« less

  4. Communication: XUV transient absorption spectroscopy of iodomethane and iodobenzene photodissociation.

    PubMed

    Drescher, L; Galbraith, M C E; Reitsma, G; Dura, J; Zhavoronkov, N; Patchkovskii, S; Vrakking, M J J; Mikosch, J

    2016-07-07

    Time-resolved extreme ultraviolet (XUV) transient absorption spectroscopy of iodomethane and iodobenzene photodissociation at the iodine pre-N4,5 edge is presented, using femtosecond UV pump pulses and XUV probe pulses from high harmonic generation. For both molecules the molecular core-to-valence absorption lines fade immediately, within the pump-probe time-resolution. Absorption lines converging to the atomic iodine product emerge promptly in CH3I but are time-delayed in C6H5I. We attribute this delay to the initial π → σ(*) excitation in iodobenzene, which is distant from the iodine reporter atom. We measure a continuous shift in energy of the emerging atomic absorption lines in CH3I, attributed to relaxation of the excited valence shell. An independent particle model is used to rationalize the observed experimental findings.

  5. Communication: XUV transient absorption spectroscopy of iodomethane and iodobenzene photodissociation

    NASA Astrophysics Data System (ADS)

    Drescher, L.; Galbraith, M. C. E.; Reitsma, G.; Dura, J.; Zhavoronkov, N.; Patchkovskii, S.; Vrakking, M. J. J.; Mikosch, J.

    2016-07-01

    Time-resolved extreme ultraviolet (XUV) transient absorption spectroscopy of iodomethane and iodobenzene photodissociation at the iodine pre-N4,5 edge is presented, using femtosecond UV pump pulses and XUV probe pulses from high harmonic generation. For both molecules the molecular core-to-valence absorption lines fade immediately, within the pump-probe time-resolution. Absorption lines converging to the atomic iodine product emerge promptly in CH3I but are time-delayed in C6H5I. We attribute this delay to the initial π → σ* excitation in iodobenzene, which is distant from the iodine reporter atom. We measure a continuous shift in energy of the emerging atomic absorption lines in CH3I, attributed to relaxation of the excited valence shell. An independent particle model is used to rationalize the observed experimental findings.

  6. Estimation of molar absorptivities and pigment sizes for eumelanin and pheomelanin using femtosecond transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Piletic, Ivan R.; Matthews, Thomas E.; Warren, Warren S.

    2009-11-01

    Fundamental optical and structural properties of melanins are not well understood due to their poor solubility characteristics and the chemical disorder present during biomolecular synthesis. We apply nonlinear transient absorption spectroscopy to quantify molar absorptivities for eumelanin and pheomelanin and thereby get an estimate for their average pigment sizes. We determine that pheomelanin exhibits a larger molar absorptivity at near IR wavelengths (750nm), which may be extended to shorter wavelengths. Using the molar absorptivities, we estimate that melanin pigments contain ˜46 and 28 monomer units for eumelanin and pheomelanin, respectively. This is considerably larger than the oligomeric species that have been recently proposed to account for the absorption spectrum of eumelanin and illustrates that larger pigments comprise a significant fraction of the pigment distribution.

  7. Estimation of molar absorptivities and pigment sizes for eumelanin and pheomelanin using femtosecond transient absorption spectroscopy.

    PubMed

    Piletic, Ivan R; Matthews, Thomas E; Warren, Warren S

    2009-11-14

    Fundamental optical and structural properties of melanins are not well understood due to their poor solubility characteristics and the chemical disorder present during biomolecular synthesis. We apply nonlinear transient absorption spectroscopy to quantify molar absorptivities for eumelanin and pheomelanin and thereby get an estimate for their average pigment sizes. We determine that pheomelanin exhibits a larger molar absorptivity at near IR wavelengths (750 nm), which may be extended to shorter wavelengths. Using the molar absorptivities, we estimate that melanin pigments contain approximately 46 and 28 monomer units for eumelanin and pheomelanin, respectively. This is considerably larger than the oligomeric species that have been recently proposed to account for the absorption spectrum of eumelanin and illustrates that larger pigments comprise a significant fraction of the pigment distribution.

  8. Sequence and symmetry of hole injection in YBa 2Cu 3O 6+x in situ and ex situ experiments on powders and single crystals using X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Tolentino, H.; Baudelet, F.; Fontaine, A.; Gourieux, T.; Krill, G.; Henry, J. Y.; Rossat-Mignod, J.

    1992-03-01

    Very accurate XAS in situ and ex situ measurements at the Cu K-edge on powders and single crystals of YBa 2Cu 3O 6+ x have been carried out using the time-resolved dispersive spectrometer at LURE-DCI. The whole range of oxygen content has been investigated and the x-dependence of the amount of Cu(I) has been evaluated at room and at high temperatures (from 400 to 750°C). Owing to the balance of charges, we derived the amount of the oxygen 2p holes. The sequence of injection was separated into steps, associated with three oxygen bands of distinct symmetries and with the well-known steps in the superconducting behavior.

  9. Determination of heavy metals in solid emission and immission samples using atomic absorption spectroscopy

    SciTech Connect

    Fara, M.; Novak, F.

    1995-12-01

    Both flame and electrothermal methods of atomic absorption spectroscopy (AAS) have been applied to the determination of Al, As, Be, Ca, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, TI, Se, V and Zn in emission and emission (deposition) samples decomposed in open PTFE test-tubes by individual fuming-off hydrofluoric, perchloroic and nitric acid. An alternative hydride technique was also used for As and Se determination and Hg was determined using a self-contained AAS analyzer. A graphite platform proved good to overcome non-spectral interferences in AAS-ETA. Methods developed were verified by reference materials (inc. NBS 1633a).

  10. [Measurement of trace elements in blood serum by atomic absorption spectroscopy with electrothermal atomization].

    PubMed

    Rogul'skiĭ, Iu V; Danil'chenko, S N; Lushpa, A P; Sukhodub, L F

    1997-09-01

    Describes a method for measuring trace elements Cr, Mn, Co, Fe, Cu, Zn, and Mo in the blood serum using non-flame atomization (KAC 120.1 complex). Optimal conditions for preparing the samples were defined, temperature regimens for analysis of each element selected, and original software permitting automated assays created. The method permits analysis making use of the minimal samples: 0.1 ml per 10 parallel measurements, which is 100 times less than needed for atomic absorption spectroscopy with flame atomization of liquid samples. Metrological characteristics of the method are assessed.

  11. Infrared absorption spectroscopy and chemical kinetics of free radicals

    SciTech Connect

    Curl, R.F.; Glass, G.P.

    1993-12-01

    This research is directed at the detection, monitoring, and study of chemical kinetic behavior by infrared absorption spectroscopy of small free radical species thought to be important intermediates in combustion. During the last year, infrared kinetic spectroscopy using excimer laser flash photolysis and color-center laser probing has been employed to study the high resolution spectrum of HCCN, the rate constant of the reaction between ethynyl (C{sub 2}H) radical and H{sub 2} in the temperature region between 295 and 875 K, and the recombination rate of propargyl (CH{sub 2}CCH) at room temperature.

  12. Determining copper and lead binding in Larrea tridentata through chemical modification and X-ray absorption spectroscopy

    SciTech Connect

    Polette, L.; Gardea-Torresdey, J.L.; Chianelli, R.; Pickering, I.J.; George, G.N.

    1997-12-31

    Metal contamination in soils has become a widespread problem. Emerging technologies, such as phytoremediation, may offer low cost cleanup methods. The authors have identified a desert plant, Larrea tridentata (creosote bush), which naturally grows and uptakes copper and lead from a contaminated area near a smelting operation. They determined, through chemical modification of carboxyl groups with methanol, that these functional groups may be responsible for a portion of copper(II) binding. In contrast, lead binding was minimally affected by modification of carboxyl groups. X-ray absorption spectroscopy studies conducted at Stanford Synchrotron Radiation Laboratory (SSRL) further support copper binding to oxygen-coordinated ligands and also imply that the binding is not solely due to phytochelatins. The EXAFS data indicate the presence of both Cu-O and Cu-S back scatters, no short Cu-Cu interactions, but with significant Cu-Cu back scattering at 3.7 {angstrom} (unlike phytochelatins with predominantly Cu-S coordination and short Cu-Cu interactions at 2.7 {angstrom}). Cu EXAFS of roots and leaves also vary depending on the level of heavy metal contamination in the environment from which the various creosote samples were obtained. In contrast, Pb XANES data of roots and leaves of creosote collected from different contaminated sites indicate no difference in valence states or ligand coordination.

  13. Absorption/emission spectroscopy and applications using shock tubes

    NASA Astrophysics Data System (ADS)

    Sulzmann, K. G. P.

    1988-09-01

    A historical overview is presented about the important contributions made by Penner, his co-workers, and his students to the application of shock-tube techniques for quantitative emission and absorption spectroscopy and its applications to chemical kinetics studies in high-temperature gases. The discussions address critical aspects related to valid determinations of quantitative spectroscopic data and chemical rate parameters and stress the requirements for uniformly heated gas samples, temperature determinations, gas-mixture preparations, selection of useful spectral intervals, verification of LTE conditions, time resolutions for concentration histories, uniqueness of kinetic measurements, as well as accuracies and reproducibilities of measurement results.The potential of absorption spectroscopy by molecule and/or radical resonance radiation and by laser transmission techniques is highlighted for kinetic studies in mixtures with very small reactant concentrations.Besides the work by the honoree and his school, the references include books, monographs and key articles related to the subjects discussed.

  14. Screened coulomb hybrid DFT investigation of band gap and optical absorption predictions of CuVO3, CuNbO3 and Cu5Ta11O30 materials.

    PubMed

    Harb, Moussab; Masih, Dilshad; Takanabe, Kazuhiro

    2014-09-14

    We present a joint theoretical and experimental investigation of the optoelectronic properties of CuVO3, CuNbO3 and Cu5Ta11O30 materials for potential photocatalytic and solar cell applications. In addition to the experimental results obtained by powder X-ray diffraction and UV-Vis spectroscopy of the materials synthesized under flowing N2 gas at atmospheric pressure via solid-state reactions, the electronic structure and the UV-Vis optical absorption coefficient of these compounds are predicted with high accuracy using advanced first-principles quantum methods based on DFT (including the perturbation theory approach DFPT) within the screened coulomb hybrid HSE06 exchange-correlation formalism. The calculated density of states are found to be in agreement with the UV-Vis diffuse reflectance spectra, predicting a small indirect band gap of 1.4 eV for CuVO3, a direct band gap of 2.6 eV for CuNbO3, and an indirect (direct) band gap of 2.1 (2.6) eV for Cu5Ta11O30. It is confirmed that the Cu(I)-based multi-metal oxides possess a strong contribution of filled Cu(I) states in the valence band and of empty d(0) metal states in the conduction band. Interestingly, CuVO3 with its predicted small indirect band gap of 1.4 eV shows the highest absorption coefficient in the visible range with a broad absorption edge extending to 886 nm. This novel result offers a great opportunity for this material to be an excellent candidate for solar cell applications.

  15. Label free detection of phospholipids by infrared absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Ahmed, Tahsin; Foster, Erick; Vigil, Genevieve; Khan, Aamir A.; Bohn, Paul; Howard, Scott S.

    2014-08-01

    We present our study on compact, label-free dissolved lipid sensing by combining capillary electrophoresis separation in a PDMS microfluidic chip online with mid-infrared (MIR) absorption spectroscopy for biomarker detection. On-chip capillary electrophoresis is used to separate the biomarkers without introducing any extrinsic contrast agent, which reduces both cost and complexity. The label free biomarker detection could be done by interrogating separated biomarkers in the channel by MIR absorption spectroscopy. Phospholipids biomarkers of degenerative neurological, kidney, and bone diseases are detectable using this label free technique. These phospholipids exhibit strong absorption resonances in the MIR and are present in biofluids including urine, blood plasma, and cerebrospinal fluid. MIR spectroscopy of a 12-carbon chain phosphatidic acid (PA) (1,2-dilauroyl-snglycero- 3-phosphate (sodium salt)) dissolved in N-methylformamide, exhibits a strong amide peak near wavenumber 1660 cm-1 (wavelength 6 μm), arising from the phosphate headgroup vibrations within a low-loss window of the solvent. PA has a similar structure to many important phospholipids molecules like phosphatidylcholine (PC), phosphatidylinositol (PI), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and phosphatidylserine (PS), making it an ideal molecule for initial proof-of-concept studies. This newly proposed detection technique can lead us to minimal sample preparation and is capable of identifying several biomarkers from the same sample simultaneously.

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

    PubMed

    Meibohm, Jan; Schreck, Simon; Wernet, Philippe

    2014-10-01

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

  17. Atmospheric and environmental sensing by photonic absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, W.; Wu, T.; Zhao, W.; Wysocki, G.; Cui, X.; Lengignon, C.; Maamary, R.; Fertein, E.; Coeur, C.; Cassez, A.; Wang, Y.; Zhang, W.; Gao, X.; Liu, W.; Dong, F.; Zha, G.; Zheng, Xu; Wang, T.

    2013-01-01

    Chemically reactive short-lived species play a crucial role in tropospheric processes affecting regional air quality and global climate change. Contrary to long-lived species (such as greenhouse gases), fast, accurate and precise monitoring changes in concentration of atmospheric short-lived species represents a real challenge due to their short life time (~1 s for OH radical) and very low concentration in the atmosphere (down to 106 molecules/cm3, corresponding to 0.1 pptv at standard temperature and pressure). We report on our recent progress in instrumentation developments for spectroscopic sensing of trace reactive species. Modern photonic sources such as quantum cascade laser (QCL), distributed feedback (DFB) diode laser, light emitting diode (LED), difference-frequency generation (DFG) parametric source are implemented in conjunction with highsensitivity spectroscopic measurement techniques for : (1) nitrous acid (HONO) monitoring by QCL-based long optical pathlength absorption spectroscopy and LED-based IBBCEAS (incoherent broadband cavity-enhanced absorption spectroscopy); (2) DFB laser-based hydroxyl free radical (OH) detection using WM-OA-ICOS (wavelength modulation off-axis integrated cavity output spectroscopy) and FRS (Faraday rotation spectroscopy), respectively; (3) nitrate radical (NO3) and nitrogen dioxide (NO2) simultaneous measurements with IBBCEAS approach. Applications in field observation and in smog chamber study will be presented.

  18. Use of absorption spectroscopy for refined petroleum product discrimination

    NASA Astrophysics Data System (ADS)

    Short, Michael

    1991-07-01

    On-line discrimination between arbitrary petroleum products is necessary for optimal control of petroleum refinery and pipeline operation and process control involving petroleum distillates. There are a number of techniques by which petroleum products can be distinguished from one another. Among these, optical measurements offer fast, non-intrusive, real-time characterization. The application examined here involves optically monitoring the interface between dissimilar batches of fluids in a gasoline pipeline. After examination of near- infrared and mid-infrared absorption spectroscopy and Raman spectroscopy, Fourier transform mid-infrared (FTIR) spectroscopy was chosen as the best candidate for implementation. On- line FTIR data is presented, verifying the applicability of the technique for batch interface detection.

  19. Time-resolved X-ray Absorption Spectroscopy for Electron Transport Study in Warm Dense Gold

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Won; Bae, Leejin; Engelhorn, Kyle; Heimann, Philip; Ping, Yuan; Barbrel, Ben; Fernandez, Amalia; Beckwith, Martha Anne; Cho, Byoung-Ick; GIST Team; IBS Team; LBNL Collaboration; SLAC Collaboration; LLNL Collaboration

    2015-11-01

    The warm dense Matter represents states of which the temperature is comparable to Fermi energy and ions are strongly coupled. One of the experimental techniques to create such state in the laboratory condition is the isochoric heating of thin metal foil with femtosecond laser pulses. This concept largely relies on the ballistic transport of electrons near the Fermi-level, which were mainly studied for the metals in ambient conditions. However, they were barely investigated in warm dense conditions. We present a time-resolved x-ray absorption spectroscopy measured for the Au/Cu dual layered sample. The front Au layer was isochorically heated with a femtosecond laser pulse, and the x-ray absorption changes around L-edge of Cu, which was attached on the backside of Au, was measured with a picosecond resolution. Time delays between the heating of the `front surface' of Au layer and the alternation of x-ray spectrum of Cu attached on the `rear surface' of Au indicate the energetic electron transport mechanism through Au in the warm dense conditions. IBS (IBS-R012-D1) and the NRF (No. 2013R1A1A1007084) of Korea.

  20. Wear-metal analysis in engine oil by microwave digestion and atomic absorption spectroscopy. Final report, August 1987-January 1988

    SciTech Connect

    Muse, W.T.

    1990-05-01

    Digestion procedures are described for the analysis of wear metals in National Bureau of Standards (NBS) oil samples by a closed vessel microwave digestion system. Samples were analyzed by flame atomic absorption spectroscopy. Recoveries of Al, Fe, Ni, Cu, and Pb in the 300-ppm NBS oil ranged from 98 to 103% with standard deviations from 3 to 14%. This method serves as a relatively quick matrix destruction technique for the quantitation of metals in oil.

  1. APPLICATION OF ABSORPTION SPECTROSCOPY TO ACTINIDE PROCESS ANALYSIS AND MONITORING

    SciTech Connect

    Lascola, R.; Sharma, V.

    2010-06-03

    The characteristic strong colors of aqueous actinide solutions form the basis of analytical techniques for actinides based on absorption spectroscopy. Colorimetric measurements of samples from processing activities have been used for at least half a century. This seemingly mature technology has been recently revitalized by developments in chemometric data analysis. Where reliable measurements could formerly only be obtained under well-defined conditions, modern methods are robust with respect to variations in acidity, concentration of complexants and spectral interferents, and temperature. This paper describes two examples of the use of process absorption spectroscopy for Pu analysis at the Savannah River Site, in Aiken, SC. In one example, custom optical filters allow accurate colorimetric measurements of Pu in a stream with rapid nitric acid variation. The second example demonstrates simultaneous measurement of Pu and U by chemometric treatment of absorption spectra. The paper concludes with a description of the use of these analyzers to supplement existing technologies in nuclear materials monitoring in processing, reprocessing, and storage facilities.

  2. Polarization-controlled optimal scatter suppression in transient absorption spectroscopy

    PubMed Central

    Malý, Pavel; Ravensbergen, Janneke; Kennis, John T. M.; van Grondelle, Rienk; Croce, Roberta; Mančal, Tomáš; van Oort, Bart

    2017-01-01

    Ultrafast transient absorption spectroscopy is a powerful technique to study fast photo-induced processes, such as electron, proton and energy transfer, isomerization and molecular dynamics, in a diverse range of samples, including solid state materials and proteins. Many such experiments suffer from signal distortion by scattered excitation light, in particular close to the excitation (pump) frequency. Scattered light can be effectively suppressed by a polarizer oriented perpendicular to the excitation polarization and positioned behind the sample in the optical path of the probe beam. However, this introduces anisotropic polarization contributions into the recorded signal. We present an approach based on setting specific polarizations of the pump and probe pulses, combined with a polarizer behind the sample. Together, this controls the signal-to-scatter ratio (SSR), while maintaining isotropic signal. We present SSR for the full range of polarizations and analytically derive the optimal configuration at angles of 40.5° between probe and pump and of 66.9° between polarizer and pump polarizations. This improves SSR by (or compared to polarizer parallel to probe). The calculations are validated by transient absorption experiments on the common fluorescent dye Rhodamine B. This approach provides a simple method to considerably improve the SSR in transient absorption spectroscopy. PMID:28262765

  3. Polarization-controlled optimal scatter suppression in transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Malý, Pavel; Ravensbergen, Janneke; Kennis, John T. M.; van Grondelle, Rienk; Croce, Roberta; Mančal, Tomáš; van Oort, Bart

    2017-03-01

    Ultrafast transient absorption spectroscopy is a powerful technique to study fast photo-induced processes, such as electron, proton and energy transfer, isomerization and molecular dynamics, in a diverse range of samples, including solid state materials and proteins. Many such experiments suffer from signal distortion by scattered excitation light, in particular close to the excitation (pump) frequency. Scattered light can be effectively suppressed by a polarizer oriented perpendicular to the excitation polarization and positioned behind the sample in the optical path of the probe beam. However, this introduces anisotropic polarization contributions into the recorded signal. We present an approach based on setting specific polarizations of the pump and probe pulses, combined with a polarizer behind the sample. Together, this controls the signal-to-scatter ratio (SSR), while maintaining isotropic signal. We present SSR for the full range of polarizations and analytically derive the optimal configuration at angles of 40.5° between probe and pump and of 66.9° between polarizer and pump polarizations. This improves SSR by (or compared to polarizer parallel to probe). The calculations are validated by transient absorption experiments on the common fluorescent dye Rhodamine B. This approach provides a simple method to considerably improve the SSR in transient absorption spectroscopy.

  4. Pathlength Determination for Gas in Scattering Media Absorption Spectroscopy

    PubMed Central

    Mei, Liang; Somesfalean, Gabriel; Svanberg, Sune

    2014-01-01

    Gas in scattering media absorption spectroscopy (GASMAS) has been extensively studied and applied during recent years in, e.g., food packaging, human sinus monitoring, gas diffusion studies, and pharmaceutical tablet characterization. The focus has been on the evaluation of the gas absorption pathlength in porous media, which a priori is unknown due to heavy light scattering. In this paper, three different approaches are summarized. One possibility is to simultaneously monitor another gas with known concentration (e.g., water vapor), the pathlength of which can then be obtained and used for the target gas (e.g., oxygen) to retrieve its concentration. The second approach is to measure the mean optical pathlength or physical pathlength with other methods, including time-of-flight spectroscopy, frequency-modulated light scattering interferometry and the frequency domain photon migration method. By utilizing these methods, an average concentration can be obtained and the porosities of the material are studied. The last method retrieves the gas concentration without knowing its pathlength by analyzing the gas absorption line shape, which depends upon the concentration of buffer gases due to intermolecular collisions. The pathlength enhancement effect due to multiple scattering enables also the use of porous media as multipass gas cells for trace gas monitoring. All these efforts open up a multitude of different applications for the GASMAS technique. PMID:24573311

  5. Controlled growth of Cu-Ni nanowires and nanospheres for enhanced microwave absorption properties

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoxia; Dong, Lifeng; Zhang, Baoqin; Yu, Mingxun; Liu, Jingquan

    2016-03-01

    Copper is a good dielectric loss material but has low stability, whereas nickel is a good magnetic loss material and is corrosion resistant but with low conductivity, therefore Cu-Ni hybrid nanostructures have synergistic advantages as microwave absorption (MA) materials. Different Cu/Ni molar ratios of bimetallic nanowires (Cu13@Ni7, Cu5@Ni5 and Cu7@Ni13) and nanospheres (Cu13@Ni7, Cu5@Ni5 and Cu1@Ni3) have been successfully synthesized via facile reduction of hydrazine under similar reaction conditions, and the morphology can be easily tuned by varying the feed ratio or the complexing agent. Apart from the concentrations of Cu2+ and Ni2+, the reduction parameters are similar for all samples to confirm the effects of the Cu/Ni molar ratio and morphology on MA properties. Ni is incorporated into the Cu-Ni nanomaterials as a shell over the Cu core at low temperature, as proved by XRD, SEM, TEM and XPS. Through the complex relative permittivity and permeability, reflection loss was evaluated, which revealed that the MA capacity greatly depended on the Cu/Ni molar ratio and morphology. For Cu@Ni nanowires, as the molar ratio of Ni shell increased the MA properties decreased accordingly. However, for Cu@Ni nanospheres, the opposite trend was found, that is, as the molar ratio of the Ni shell increased the MA properties increased.

  6. Diagnostic potential of cosmic-neutrino absorption spectroscopy

    SciTech Connect

    Barenboim, Gabriela; Requejo, Olga Mena; Quigg, Chris

    2005-04-15

    Annihilation of extremely energetic cosmic neutrinos on the relic-neutrino background can give rise to absorption lines at energies corresponding to formation of the electroweak gauge boson Z{sup 0}. The positions of the absorption dips are set by the masses of the relic neutrinos. Suitably intense sources of extremely energetic (10{sup 21}-10{sup 25}-eV) cosmic neutrinos might therefore enable the determination of the absolute neutrino masses and the flavor composition of the mass eigenstates. Several factors--other than neutrino mass and composition--distort the absorption lines, however. We analyze the influence of the time evolution of the relic-neutrino density and the consequences of neutrino decay. We consider the sensitivity of the line shape to the age and character of extremely energetic neutrino sources, and to the thermal history of the Universe, reflected in the expansion rate. We take into account Fermi motion arising from the thermal distribution of the relic-neutrino gas. We also note the implications of Dirac vs. Majorana relics, and briefly consider unconventional neutrino histories. We ask what kinds of external information would enhance the potential of cosmic-neutrino absorption spectroscopy, and estimate the sensitivity required to make the technique a reality.

  7. Diagnostic potential of cosmic-neutrino absorption spectroscopy

    SciTech Connect

    Barenboim, Gabriela; Mena Requejo, Olga; Quigg, Chris; /Fermilab

    2004-12-01

    Annihilation of extremely energetic cosmic neutrinos on the relic-neutrino background can give rise to absorption lines at energies corresponding to formation of the electroweak gauge boson Z{sup 0}. The positions of the absorption dips are set by the masses of the relic neutrinos. Suitably intense sources of extremely energetic (10{sup 21} - 10{sup 25}-eV) cosmic neutrinos might therefore enable the determination of the absolute neutrino masses and the flavor composition of the mass eigenstates. Several factors--other than neutrino mass and composition--distort the absorption lines, however. We analyze the influence of the time-evolution of the relic-neutrino density and the consequences of neutrino decay. We consider the sensitivity of the lineshape to the age and character of extremely energetic neutrino sources, and to the thermal history of the Universe, reflected in the expansion rate. We take into account Fermi motion arising from the thermal distribution of the relic-neutrino gas. We also note the implications of Dirac vs. Majorana relics, and briefly consider unconventional neutrino histories. We ask what kinds of external information would enhance the potential of cosmic-neutrino absorption spectroscopy, and estimate the sensitivity required to make the technique a reality.

  8. Principles and calibration of collinear photofragmentation and atomic absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Sorvajärvi, Tapio; Toivonen, Juha

    2014-06-01

    The kinetics of signal formation in collinear photofragmentation and atomic absorption spectroscopy (CPFAAS) are discussed, and theoretical equations describing the relation between the concentration of the target molecule and the detected atomic absorption in case of pure and impure samples are derived. The validity of the equation for pure samples is studied experimentally by comparing measured target molecule concentrations to concentrations determined using two other independent techniques. Our study shows that CPFAAS is capable of measuring target molecule concentrations from parts per billion (ppb) to hundreds of parts per million (ppm) in microsecond timescale. Moreover, the possibility to extend the dynamic range to cover eight orders of magnitude with a proper selection of fragmentation light source is discussed. The maximum deviation between the CPFAAS technique and a reference measurement technique is found to be less than 5 %. In this study, potassium chloride vapor and atomic potassium are used as a target molecule and a probed atom, respectively.

  9. The determination of vanadium in brines by atomic absorption spectroscopy

    USGS Publications Warehouse

    Crump-Wiesner, Hans J.; Feltz, H.R.; Purdy, W.C.

    1971-01-01

    A standard addition method is described for the determination of vanadium in brines by atomic absorption spectroscopy with a nitrous oxide-acetylene flame. Sample pH is adjusted to 1.0 with concentrated hydrochloric acid and the vanadium is directly extracted with 5% cupferron in methyl isobutyl ketone (MIBK). The ketone layer is then aspirated into the flame and the recorded absorption values are plotted as a function of the concentration of the added metal. As little as 2.5 ??g l-1 of vanadium can be detected under the conditions of the procedure. Tungsten and tin interfere when present in excess of 5 and 10 ??g ml-1, respectively. The concentrations of the two interfering ions normally found in brines are well below interference levels. ?? 1971.

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

    PubMed

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

    2012-06-21

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

  11. Quantitative analysis of immobilized metalloenzymes by atomic absorption spectroscopy.

    PubMed

    Opwis, Klaus; Knittel, Dierk; Schollmeyer, Eckhard

    2004-12-01

    A new, sensitive assay for the quantitative determination of immobilized metal containing enzymes has been developed using atomic absorption spectroscopy (AAS). In contrast with conventionally used indirect methods the described quantitative AAS assay for metalloenzymes allows more exact analyses, because the carrier material with the enzyme is investigated directly. As an example, the validity and reliability of the method was examined by fixing the iron-containing enzyme catalase on cotton fabrics using different immobilization techniques. Sample preparation was carried out by dissolving the loaded fabrics in sulfuric acid before oxidising the residues with hydrogen peroxide. The iron concentrations were determined by flame atomic absorption spectrometry after calibration of the spectrometer with solutions of the free enzyme at different concentrations.

  12. Fingerprints of polycyclic aromatic hydrocarbons (PAHs) in infrared absorption spectroscopy.

    PubMed

    Tommasini, Matteo; Lucotti, Andrea; Alfè, Michela; Ciajolo, Anna; Zerbi, Giuseppe

    2016-01-05

    We have analyzed a set of 51 PAHs whose structures have been hypothesized from mass spectrometry data collected on samples extracted from carbon particles of combustion origin. We have obtained relationships between infrared absorption signals in the fingerprint region (mid-IR) and the chemical structures of PAHs, thus proving the potential of IR spectroscopy for the characterization of the molecular structure of aromatic combustion products. The results obtained here for the spectroscopic characterization of PAHs can be also of interest in Materials Science and Astrophysics.

  13. X-ray Absorption Spectroscopic and Computational Investigation of a Possible S···S Interaction in the [Cu3S2]3+ Core

    PubMed Central

    Sarangi, Ritimukta; Yang, Lei; Winikoff, Stuart G.; Gagliardi, Laura; Cramer, Christopher J.; Tolman, William B.; Solomon, Edward I.

    2011-01-01

    The electronic structure of the [Cu3S2]3+ core of [(LCu)3(S)2]3+ (L = N,N,N′,N′-tetramethyl-2R,3R-cyclohexanediamine) is investigated using a combination of Cu and S K-edge X-ray absorption spectroscopy and calculations at the density functional and multireference second-order perturbation levels of theory. The results show that the [Cu3S2]3+ core is best described as having all copper centers close to, but more oxidized than, Cu2+, while the charge on the S2 fragment is between that of a sulfide (S2−) and a subsulfide (S23−) species. The [Cu3S2]3+ core thus is different from a previously described, analogous [Cu3O2]3+ core, which has a localized [(Cu3+Cu2+Cu2+)(O2−)2]3+ electronic structure. The difference in electronic structure between the two analogues is attributed to increased covalent overlap between the Cu 3d and S 3p orbitals and the increased radial distribution function of the S 3p orbital (relative to O 2p). These features result in donation of electron density from the S-S σ* to the Cu and result in some bonding interaction between the two S atoms at ~ 2.69 Å in [Cu3S2]3+, stabilizing a delocalized S=1 ground state. PMID:21923178

  14. Low-Dimensional Water on Ru(0001)Model System for X-ray Absorption Spectroscopy Studies of Liquid Water

    SciTech Connect

    Nordlund, D

    2012-02-14

    We present an x-ray absorption spectroscopy results for fully broken to a complete H-bond network of water molecules on Ru(0001) by varying the morphology from isolated water molecules via two-dimensional clusters to a fully covered monolayer as probed by scanning tunneling microscopy. The sensitivity of x-ray absorption to the symmetry of H-bonding is further elucidated for the amino (-NH{sub 2}) group in glycine adsorbed on Cu(110) where the E-vector is parallel either to the NH donating an H-bond or to the non-H-bonded NH. The results give further evidence for the interpretation of the various spectral features of liquid water and for the general applicability of x-ray absorption spectroscopy to analyze H-bonded systems.

  15. Nondestructive Determination of Cu Residue in Orange Peel by Laser Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Hu, Huiqin; Huang, Lin; Liu, Muhua; Chen, Tianbing; Yang, Ping; Yao, Mingyin

    2015-08-01

    Laser induced breakdown spectroscopy (LIBS) is an emerging tool with rapid, nondestructive, green characteristics in qualitative or quantitative analyses of composition in materials. But LIBS has its shortcomings in detect limit and sensitivity. In this work, heavy metal Cu in Gannan Navel Orange, which is one of famous fruits from Jiangxi of China, was analyzed. In view of LIBS's limit, it is difficult to determinate heavy metals in natural fruits. In this work, nine orange samples were pretreated in 50-500 μg/mL Cu solution, respectively. Another one orange sample was chosen as a control group without any pollution treatment. Previous researchers observed that the content of heavy metals is much higher in peel than in pulp. So, the content in pulp can be reflected by detecting peel. The real concentrations of Cu in peels were acquired by atomic absorption spectrophotometer (AAS). A calibration model of Cu I 324.7 and Cu I 327.4 was constructed between LIBS intensity and AAS concentration by six samples. The correlation coefficient of the two models is also 0.95. All of the samples were used to verify the accuracy of the model. The results show that the relative error (RE) between predicted and real concentration is less than 6.5%, and Cu I 324.7 line has smaller RE than Cu I 327.4. The analysis demonstrated that different characteristic lines decided different accuracy. The results prove the feasibility of detecting heavy metals in fruits by LIBS. But the results are limited in treated samples. The next work will focus on direct analysis of heavy metals in natural fruits without any pretreatment. This work is helpful to explore the distribution of heavy metals between pulp and peel. supported by National Natural Science Foundation of China (No. 31460419) and Major Project of Science and Technology of Jiangxi, China (No. 20143ACB21013)

  16. Monitoring PVD metal vapors using laser absorption spectroscopy

    SciTech Connect

    Braun, D.G.; Anklam, T.M.; Berzins, L.V.; Hagans, K.G.

    1994-04-01

    Laser absorption spectroscopy (LAS) has been used by the Atomic Vapor Laser Isotope Separation (AVLIS) program for over 10 years to monitor the co-vaporization of uranium and iron in its separators. During that time, LAS has proven to be an accurate and reliable method to monitor both the density and composition of the vapor. It has distinct advantages over other rate monitors, in that it is completely non-obtrusive to the vaporization process and its accuracy is unaffected by the duration of the run. Additionally, the LAS diagnostic has been incorporated into a very successful process control system. LAS requires only a line of sight through the vacuum chamber, as all hardware is external to the vessel. The laser is swept in frequency through an absorption line of interest. In the process a baseline is established, and the line integrated density is determined from the absorption profile. The measurement requires no hardware calibration. Through a proper choice of the atomic transition, a wide range of elements and densities have been monitored (e.g. nickel, iron, cerium and gadolinium). A great deal of information about the vapor plume can be obtained from the measured absorption profiles. By monitoring different species at the same location, the composition of the vapor is measured in real time. By measuring the same density at different locations, the spatial profile of the vapor plume is determined. The shape of the absorption profile is used to obtain the flow speed of the vapor. Finally, all of the above information is used evaluate the total vaporization rate.

  17. Mid-infrared absorption spectroscopy using quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Haibach, Fred; Erlich, Adam; Deutsch, Erik

    2011-06-01

    Block Engineering has developed an absorption spectroscopy system based on widely tunable Quantum Cascade Lasers (QCL). The QCL spectrometer rapidly cycles through a user-selected range in the mid-infrared spectrum, between 6 to 12 μm (1667 to 833 cm-1), to detect and identify substances on surfaces based on their absorption characteristics from a standoff distance of up to 2 feet with an eye-safe laser. It can also analyze vapors and liquids in a single device. For military applications, the QCL spectrometer has demonstrated trace explosive, chemical warfare agent (CWA), and toxic industrial chemical (TIC) detection and analysis. The QCL's higher power density enables measurements from diffuse and highly absorbing materials and substrates. Other advantages over Fourier Transform Infrared (FTIR) spectroscopy include portability, ruggedness, rapid analysis, and the ability to function from a distance through free space or a fiber optic probe. This paper will discuss the basic technology behind the system and the empirical data on various safety and security applications.

  18. Azimuthal Doppler shift of absorption spectrum in optical vortex laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Yoshimura, Shinji; Aramaki, Mitsutoshi; Ozawa, Naoya; Terasaka, Kenichiro; Tanaka, Masayoshi; Nagaoka, Kenichi; Morisaki, Tomohiro

    2016-10-01

    Laser spectroscopy is a powerful diagnostic tool for measuring the mean flow velocity of plasma particles. We have been developing a new laser spectroscopy method utilizing an optical vortex beam, which has helical phase fronts corresponding to the phase change in the azimuthal direction. Because of this phase change, a Doppler effect is experienced even by an atom crossing the beam vertically. The additional azimuthal Doppler shift is proportional to the topological charge of optical vortex and is inversely proportional to the distance from the beam axis in which the beam intensity is vanished by destructive interference or the phase singularity. In order to detect the azimuthal Doppler shift, we have performed a laser absorption spectroscopy experiment with the linear ECR plasma device HYPER-I. Since the azimuthal Doppler shift depends on a position in the beam cross section, the absorption spectra at various positions were reconstructed from the transmitted beam intensity measured by a beam profiler. We have observed a clear spatial dependence of the Doppler shift, which qualitatively agreed with theory. Detailed experimental results, as well as remaining issues and future prospect, will be discussed at the meeting. This study was partially supported by JAPS KAKENHI Grand Numbers 15K05365 and 25287152.

  19. Femtosecond transient absorption spectroscopy of silanized silicon quantum dots

    NASA Astrophysics Data System (ADS)

    Kuntermann, Volker; Cimpean, Carla; Brehm, Georg; Sauer, Guido; Kryschi, Carola; Wiggers, Hartmut

    2008-03-01

    Excitonic properties of colloidal silicon quantum dots (Si qdots) with mean sizes of 4nm were examined using stationary and time-resolved optical spectroscopy. Chemically stable silicon oxide shells were prepared by controlled surface oxidation and silanization of HF-etched Si qdots. The ultrafast relaxation dynamics of photogenerated excitons in Si qdot colloids were studied on the picosecond time scale from 0.3psto2.3ns using femtosecond-resolved transient absorption spectroscopy. The time evolution of the transient absorption spectra of the Si qdots excited with a 150fs pump pulse at 390nm was observed to consist of decays of various absorption transitions of photoexcited electrons in the conduction band which overlap with both the photoluminescence and the photobleaching of the valence band population density. Gaussian deconvolution of the spectroscopic data allowed for disentangling various carrier relaxation processes involving electron-phonon and phonon-phonon scatterings or arising from surface-state trapping. The initial energy and momentum relaxation of hot carriers was observed to take place via scattering by optical phonons within 0.6ps . Exciton capturing by surface states forming shallow traps in the amorphous SiOx shell was found to occur with a time constant of 4ps , whereas deeper traps presumably localized in the Si-SiOx interface gave rise to exciton trapping processes with time constants of 110 and 180ps . Electron transfer from initially populated, higher-lying surface states to the conduction band of Si qdots (>2nm) was observed to take place within 400 or 700fs .

  20. Precision atomic beam density characterization by diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Oxley, Paul; Wihbey, Joseph

    2016-09-01

    We provide experimental and theoretical details of a simple technique to determine absolute line-of-sight integrated atomic beam densities based on resonant laser absorption. In our experiments, a thermal lithium beam is chopped on and off while the frequency of a laser crossing the beam at right angles is scanned slowly across the resonance transition. A lock-in amplifier detects the laser absorption signal at the chop frequency from which the atomic density is determined. The accuracy of our experimental method is confirmed using the related technique of wavelength modulation spectroscopy. For beams which absorb of order 1% of the incident laser light, our measurements allow the beam density to be determined to an accuracy better than 5% and with a precision of 3% on a time scale of order 1 s. Fractional absorptions of order 10-5 are detectable on a one-minute time scale when we employ a double laser beam technique which limits laser intensity noise. For a lithium beam with a thickness of 9 mm, we have measured atomic densities as low as 5 × 104 atoms cm-3. The simplicity of our technique and the details we provide should allow our method to be easily implemented in most atomic or molecular beam apparatuses.

  1. Optical re-injection in cavity-enhanced absorption spectroscopy

    PubMed Central

    Leen, J. Brian; O’Keefe, Anthony

    2014-01-01

    Non-mode-matched cavity-enhanced absorption spectrometry (e.g., cavity ringdown spectroscopy and integrated cavity output spectroscopy) is commonly used for the ultrasensitive detection of trace gases. These techniques are attractive for their simplicity and robustness, but their performance may be limited by the reflection of light from the front mirror and the resulting low optical transmission. Although this low transmitted power can sometimes be overcome with higher power lasers and lower noise detectors (e.g., in the near-infrared), many regimes exist where the available light intensity or photodetector sensitivity limits instrument performance (e.g., in the mid-infrared). In this article, we describe a method of repeatedly re-injecting light reflected off the front mirror of the optical cavity to boost the cavity's circulating power and deliver more light to the photodetector and thus increase the signal-to-noise ratio of the absorption measurement. We model and experimentally demonstrate the method's performance using off-axis cavity ringdown spectroscopy (OA-CRDS) with a broadly tunable external cavity quantum cascade laser. The power coupled through the cavity to the detector is increased by a factor of 22.5. The cavity loss is measured with a precision of 2 × 10−10 cm−1/\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$\\sqrt {{\\rm Hz;}}$\\end{document} Hz ; an increase of 12 times over the standard off-axis configuration without reinjection and comparable to the best reported sensitivities in the mid-infrared. Finally, the re-injected CRDS system is used to measure the spectrum of several volatile organic compounds, demonstrating the improved ability to resolve weakly absorbing spectroscopic features. PMID:25273701

  2. Optical re-injection in cavity-enhanced absorption spectroscopy

    SciTech Connect

    Leen, J. Brian O’Keefe, Anthony

    2014-09-15

    Non-mode-matched cavity-enhanced absorption spectrometry (e.g., cavity ringdown spectroscopy and integrated cavity output spectroscopy) is commonly used for the ultrasensitive detection of trace gases. These techniques are attractive for their simplicity and robustness, but their performance may be limited by the reflection of light from the front mirror and the resulting low optical transmission. Although this low transmitted power can sometimes be overcome with higher power lasers and lower noise detectors (e.g., in the near-infrared), many regimes exist where the available light intensity or photodetector sensitivity limits instrument performance (e.g., in the mid-infrared). In this article, we describe a method of repeatedly re-injecting light reflected off the front mirror of the optical cavity to boost the cavity's circulating power and deliver more light to the photodetector and thus increase the signal-to-noise ratio of the absorption measurement. We model and experimentally demonstrate the method's performance using off-axis cavity ringdown spectroscopy (OA-CRDS) with a broadly tunable external cavity quantum cascade laser. The power coupled through the cavity to the detector is increased by a factor of 22.5. The cavity loss is measured with a precision of 2 × 10{sup −10} cm{sup −1}/√(Hz;) an increase of 12 times over the standard off-axis configuration without reinjection and comparable to the best reported sensitivities in the mid-infrared. Finally, the re-injected CRDS system is used to measure the spectrum of several volatile organic compounds, demonstrating the improved ability to resolve weakly absorbing spectroscopic features.

  3. Optical re-injection in cavity-enhanced absorption spectroscopy.

    PubMed

    Leen, J Brian; O'Keefe, Anthony

    2014-09-01

    Non-mode-matched cavity-enhanced absorption spectrometry (e.g., cavity ringdown spectroscopy and integrated cavity output spectroscopy) is commonly used for the ultrasensitive detection of trace gases. These techniques are attractive for their simplicity and robustness, but their performance may be limited by the reflection of light from the front mirror and the resulting low optical transmission. Although this low transmitted power can sometimes be overcome with higher power lasers and lower noise detectors (e.g., in the near-infrared), many regimes exist where the available light intensity or photodetector sensitivity limits instrument performance (e.g., in the mid-infrared). In this article, we describe a method of repeatedly re-injecting light reflected off the front mirror of the optical cavity to boost the cavity's circulating power and deliver more light to the photodetector and thus increase the signal-to-noise ratio of the absorption measurement. We model and experimentally demonstrate the method's performance using off-axis cavity ringdown spectroscopy (OA-CRDS) with a broadly tunable external cavity quantum cascade laser. The power coupled through the cavity to the detector is increased by a factor of 22.5. The cavity loss is measured with a precision of 2 × 10(-10) cm(-1)/√Hz; an increase of 12 times over the standard off-axis configuration without reinjection and comparable to the best reported sensitivities in the mid-infrared. Finally, the re-injected CRDS system is used to measure the spectrum of several volatile organic compounds, demonstrating the improved ability to resolve weakly absorbing spectroscopic features.

  4. Optical absorption and scattering spectroscopies of single nano-objects.

    PubMed

    Crut, Aurélien; Maioli, Paolo; Del Fatti, Natalia; Vallée, Fabrice

    2014-06-07

    Developments of optical detection and spectroscopy methods for single nano-objects are key advances for applications and fundamental understanding of the novel properties exhibited by nanosize systems. These methods are reviewed, focusing on far-field optical approaches based on light absorption and elastic scattering. The principles of the main linear and nonlinear methods are described and experimental results are illustrated in the case of metal nanoparticles, stressing the key role played by the object environment, such as the presence of a substrate, bound surface molecules or other nano-objects. Special attention is devoted to quantitative methods and correlation of the measured optical spectra of a nano-object with its morphology, characterized either optically or by electron microscopy, as this permits precise comparison with theoretical models. Application of these methods to optical detection and spectroscopy for single semiconductor nanowires and carbon nanotubes is also presented. Extension to ultrafast nonlinear extinction or scattering spectroscopies of single nano-objects is finally discussed in the context of investigation of their nonlinear optical response and their electronic, acoustic and thermal properties.

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

    PubMed

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

    2006-04-17

    Thermal immobilization of copper contaminant in a copper-containing solid material collected from local copper smelting and foundry area is investigated in the present work. X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) are employed for copper speciation. XAS results indicate that cupric hydroxide is the major copper species in the solid material dried at 105 degrees C. After being subjected to a 500 degrees C thermal process, cupric hydroxide still remains as the main copper species, but some Cu(II) is chemically reduced to Cu(I). More cupric hydroxide is progressively converted to Cu(I) as the sample was heated at 1100 degrees C than that heated at 500 degrees C. The sample heated at 500 degrees C is in its original powder form. However, thermal treatment at 1100 degrees C transforms the powder into a hardened granule-like form that is much bigger in size and difficult to be ground into powders. The sample is sintered with the sparingly soluble cuprous oxide and elemental copper being encapsulated inside. Toxicity characteristic leaching procedure (TCLP) results depict that amount of copper leached from the sample (containing 133,000 mg copper kg-1) heated at 1100 degrees C for 2 h is considerably minor, being 367 mg copper kg-1.

  6. EPR and optical absorption study of Cu2+ doped lithium sulphate monohydrate (LSMH) single crystals

    NASA Astrophysics Data System (ADS)

    Sheela, K. Juliet; Krishnan, S. Radha; Shanmugam, V. M.; Subramanian, P.

    2016-05-01

    EPR study of Cu2+ doped NLO active Lithium Sulphate monohydrate (Li2SO4.H2O) single crystals were grown successfully by slow evaporation method at room temperature. The principal values of g and A tensors indicate existence of orthorhombic symmetry around the Cu2+ ion. From the direction cosines of g and A tensors, the locations of Cu2+ in the lattice have been identified as interstitial site. Optical absorption confirms the rhombic symmetry and ground state wave function of the Cu2+ ion in a lattice as dx2-y2.

  7. Elemental characterisation of melanin in feathers via synchrotron X-ray imaging and absorption spectroscopy

    PubMed Central

    Edwards, Nicholas P.; van Veelen, Arjen; Anné, Jennifer; Manning, Phillip L.; Bergmann, Uwe; Sellers, William I.; Egerton, Victoria M.; Sokaras, Dimosthenis; Alonso-Mori, Roberto; Wakamatsu, Kazumasa; Ito, Shosuke; Wogelius, Roy A.

    2016-01-01

    Melanin is a critical component of biological systems, but the exact chemistry of melanin is still imprecisely known. This is partly due to melanin’s complex heterogeneous nature and partly because many studies use synthetic analogues and/or pigments extracted from their natural biological setting, which may display important differences from endogenous pigments. Here we demonstrate how synchrotron X-ray analyses can non-destructively characterise the elements associated with melanin pigment in situ within extant feathers. Elemental imaging shows that the distributions of Ca, Cu and Zn are almost exclusively controlled by melanin pigment distribution. X-ray absorption spectroscopy demonstrates that the atomic coordination of zinc and sulfur is different within eumelanised regions compared to pheomelanised regions. This not only impacts our fundamental understanding of pigmentation in extant organisms but also provides a significant contribution to the evidence-based colour palette available for reconstructing the appearance of fossil organisms. PMID:27658854

  8. Elemental characterisation of melanin in feathers via synchrotron X-ray imaging and absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Edwards, Nicholas P.; van Veelen, Arjen; Anné, Jennifer; Manning, Phillip L.; Bergmann, Uwe; Sellers, William I.; Egerton, Victoria M.; Sokaras, Dimosthenis; Alonso-Mori, Roberto; Wakamatsu, Kazumasa; Ito, Shosuke; Wogelius, Roy A.

    2016-09-01

    Melanin is a critical component of biological systems, but the exact chemistry of melanin is still imprecisely known. This is partly due to melanin’s complex heterogeneous nature and partly because many studies use synthetic analogues and/or pigments extracted from their natural biological setting, which may display important differences from endogenous pigments. Here we demonstrate how synchrotron X-ray analyses can non-destructively characterise the elements associated with melanin pigment in situ within extant feathers. Elemental imaging shows that the distributions of Ca, Cu and Zn are almost exclusively controlled by melanin pigment distribution. X-ray absorption spectroscopy demonstrates that the atomic coordination of zinc and sulfur is different within eumelanised regions compared to pheomelanised regions. This not only impacts our fundamental understanding of pigmentation in extant organisms but also provides a significant contribution to the evidence-based colour palette available for reconstructing the appearance of fossil organisms.

  9. Atomic Absorption Spectroscopy, Atomic Emission Spectroscopy, and Inductively Coupled Plasma-Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Miller, Dennis D.; Rutzke, Michael A.

    Atomic spectroscopy has played a major role in the development of our current database for mineral nutrients and toxicants in foods. When atomic absorption spectrometers became widely available in the 1960s, the development of atomic absorption spectroscopy (AAS) methods for accurately measuring trace amounts of mineral elements in biological samples paved the way for unprecedented advances in fields as diverse as food analysis, nutrition, biochemistry, and toxicology (1). The application of plasmas as excitation sources for atomic emission spectroscopy (AES) led to the commercial availability of instruments for inductively coupled plasma - atomic emission spectroscopy (ICP-AES) beginning in the late 1970s. This instrument has further enhanced our ability to measure the mineral composition of foods and other materials rapidly, accurately, and precisely. More recently, plasmas have been joined with mass spectrometers (MS) to form inductively coupled plasma-mass spectrometer ICP-MS instruments that are capable of measuring mineral elements with extremely low detection limits. These three instrumental methods have largely replaced traditional wet chemistry methods for mineral analysis of foods, although traditional methods for calcium, chloride, iron, and phosphorus remain in use today (see Chap. 12).

  10. Investigating Actinide Molecular Adducts From Absorption Edge Spectroscopy

    SciTech Connect

    Den Auwer, C.; Conradson, S.D.; Guilbaud, P.; Moisy, P.; Mustre de Leon, J.; Simoni, E.; /SLAC, SSRL

    2006-10-27

    Although Absorption Edge Spectroscopy has been widely applied to the speciation of actinide elements, specifically at the L{sub III} edge, understanding and interpretation of actinide edge spectra are not complete. In that sense, semi-quantitative analysis is scarce. In this paper, different aspects of edge simulation are presented, including semi-quantitative approaches. Comparison is made between various actinyl (U, Np) aquo or hydroxy compounds. An excursion into transition metal osmium chemistry allows us to compare the structurally related osmyl and uranyl hydroxides. The edge shape and characteristic features are discussed within the multiple scattering picture and the role of the first coordination sphere as well as contributions from the water solvent are described.

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

    SciTech Connect

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

    2012-08-15

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

  12. Terahertz absorption spectroscopy of protein-containing reverse micellar solution

    NASA Astrophysics Data System (ADS)

    Murakami, H.; Toyota, Y.; Nishi, T.; Nashima, S.

    2012-01-01

    Terahertz time-domain spectroscopy has been carried out for AOT/isooctane reverse micellar solution with myoglobin at the water-to-surfactant molar ratios ( w0) of 0.2 and 4.4. The amplitude of the absorption spectrum increases with increasing the protein concentration at w0 = 0.2, whereas it decreases at w0 = 4.4. The molar extinction coefficients of the protein-filled reverse micelle, and the constituents, i.e., myoglobin, water, and AOT, have been derived by use of the structural parameters of the micellar solution. The experimental results are interpreted in terms of hydration onto the protein and surfactant in the reverse micelle.

  13. High Resolution Absorption Spectroscopy using Externally Dispersed Interferometry

    SciTech Connect

    Edelstein, J; Erskine, D J

    2005-07-06

    We describe the use of Externally Dispersed Interferometry (EDI) for high-resolution absorption spectroscopy. By adding a small fixed-delay interferometer to a dispersive spectrograph, a precise fiducial grid in wavelength is created over the entire spectrograph bandwidth. The fiducial grid interacts with narrow spectral features in the input spectrum to create a moire pattern. EDI uses the moire pattern to obtain new information about the spectra that is otherwise unavailable, thereby improving spectrograph performance. We describe the theory and practice of EDI instruments and demonstrate improvements in the spectral resolution of conventional spectrographs by a factor of 2 to 6. The improvement of spectral resolution offered by EDI can benefit space instruments by reducing spectrograph size or increasing instantaneous bandwidth.

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

    PubMed Central

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

    2016-01-01

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

  15. La Saturated Absorption Spectroscopy for Applications in Quantum Information

    NASA Astrophysics Data System (ADS)

    Becker, Patrick; Donoghue, Liz; Dungan, Kristina; Liu, Jackie; Olmschenk, Steven

    2015-05-01

    Quantum information may revolutionize computation and communication by utilizing quantum systems based on matter quantum bits and entangled light. Ions are excellent candidates for quantum bits as they can be well-isolated from unwanted external influences by trapping and laser cooling. Doubly-ionized lanthanum in particular shows promise for use in quantum information as it has infrared transitions in the telecom band, with low attenuation in standard optical fiber, potentially allowing for long distance information transfer. However, the hyperfine splittings of the lowest energy levels, required for laser cooling, have not been measured. We present progress and recent results towards measuring the hyperfine splittings of these levels in lanthanum by saturated absorption spectroscopy with a hollow cathode lamp. This research is supported by the Army Research Office, Research Corporation for Science Advancement, and Denison University.

  16. Antimony quantification in Leishmania by electrothermal atomic absorption spectroscopy.

    PubMed

    Roberts, W L; Rainey, P M

    1993-05-15

    Tri- and pentavalent antimony were quantified in Leishmania mexicana pifanoi amastigotes and promastigotes by atomic absorption spectroscopy with electrothermal atomization. Leishmania grown in axenic culture were treated with either potassium antimony tartrate [Sb(III)] or sodium stibogluconate [Sb(V)]. The parasites were collected, digested with nitric acid, and subjected to atomic absorption spectroscopy. The method was linear from 0 to 7 ng of antimony. The interassay coefficients of variation were 9.6 and 5.7% (N = 5) for 0.52 and 3.7-ng samples of leishmanial antimony, respectively. The limit of detection was 95 pg of antimony. The assay was used to characterize Sb(III) and Sb(V) influx and efflux kinetics. Influx rates were determined at antimony concentrations that produced a 50% inhibition of growth (IC50). The influx rates of Sb(V) into amastigotes and promastigotes were 4.8 and 12 pg/million cells/h, respectively, at 200 micrograms antimony/ml. The influx rate of Sb(III) into amastigotes was 41 pg/million cells/h at 20 micrograms antimony/ml. Influx of Sb(III) into promastigotes at 1 microgram antimony/ml was rapid and reached a plateau of 175 pg/million cells in 2 h. Efflux of Sb(III) and Sb(V) from amastigotes and promastigotes exhibited biphasic kinetics. The initial (alpha) half-life of Sb(V) efflux was less than 4 min and that of Sb(III) was 1-2 h. The apparent terminal (beta) half-lives ranged from 7 to 14 h.

  17. Absorption and emission spectroscopy in natural and synthetic corundum

    NASA Astrophysics Data System (ADS)

    Spinolo, G.; Palanza, V.; Ledonne, A.; Paleari, A.

    2009-04-01

    sapphires absorption spectra. In conclusion, both for metamorphic, synthetic and magmatic sapphires we reached a quite complete interpretation of the spectroscopic data in terms of "non interacting impurity ions". Orange, purple and green sapphires absorption spectra may also be discussed in terms of such interpretative approach. References Fontana I, LeDonne A, Palanza V, Binetti S and Spinolo G (2008) Optical spectroscopy study of type 1 natural and synthetic sapphires. J. Phys:Condens.Matter 20:125228-125232

  18. X-ray absorption edge spectroscopy of Co(II)-binding sites of copper- and zinc-containing proteins.

    PubMed

    Desideri, A; Comin, F; Morpurgo, L; Cocco, D; Calabrese, L; Mondovi, B; Maret, W; Rotilio, G

    1981-10-28

    X-ray absorption near-edge spectroscopy (XANES) of Co(II) in three derivatives of superoxide dismutase, namely [Cu(II)-Co(II)], [Cu(I)-Co(II)] and [...-Co(II)], suggests a tetrahedral coordination of the metal for all compounds. Significant differences, detected in the spectrum of the [Cu(II)-Co(II)] derivative as compared to the other species, indicate that a conformational change and/or a different charge of the imidazole bridging the two metal sites in superoxide dismutase occur in coincidence with the change of copper valence. The XANES spectra of the cobalt derivatives of alcohol dehydrogenase, carbonic anhydrase and stellacyanin show features that can be accounted for by an increasing degree of covalency in the metal first sphere of coordination, in the following order: alcohol dehydrogenase greater than stellacyanin greater than superoxide dismutase greater than or equal to carbonic anhydrase.

  19. Non-destructive plant health sensing using absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Bledsoe, Jim; Manukian, Ara; Pearce, Michael; Weiss, Lee

    1988-01-01

    The sensor group of the 1988 EGM 4001 class, working on NASA's Controlled Ecological Life Support Systems (CELSS) project, investigated many different plant health indicators and the technologies used to test them. The project selected by the group was to measure chlorophyll levels using absorption spectroscopy. The spectrometer measures the amount of chlorophyll in a leaf by measuring the intensity of light of a specific wavelength that is passed through a leaf. The three wavelengths of light being used corresponded to the near-IR absorption peaks of chlorophyll a, chlorophyll b, and chlorophyll-free structures. Experimentation showed that the sensor is indeed measuring levels of chlorophyll a and b and their changes before the human eye can see any changes. The detector clamp causes little damage to the leaf and will give fairly accurate readings on similar locations on a leaf, freeing the clamp from having to remain on the same spot of a leaf for all measurements. External light affects the readings only slightly so that measurements may be taken in light or dark environments. Future designs and experimentation will concentrate on reducing the size of the sensor and adapting it to a wider range of plants.

  20. Laser absorption spectroscopy system for vaporization process characterization and control

    SciTech Connect

    Galkowski, J.; Hagans, K.

    1993-09-07

    In support of the Lawrence Livermore National Laboratory`s (LLNL`s) Uranium Atomic Vapor Laser Isotope Separation (U-AVLIS) Program, a laser atomic absorption spectroscopy (LAS) system has been developed. This multi-laser system is capable of simultaneously measuring the line densities of {sup 238}U ground and metastable states, {sup 235}U ground and metastable states, iron, and ions at up to nine locations within the separator vessel. Supporting enrichment experiments that last over one hundred hours, this laser spectroscopy system is employed to diagnose and optimize separator system performance, control the electron beam vaporizer and metal feed systems, and provide physics data for the validation of computer models. As a tool for spectroscopic research, vapor plume characterization, vapor deposition monitoring, and vaporizer development, LLNL`s LAS laboratory with its six argon-ion-pumped ring dye lasers and recently added Ti:Sapphire and external-cavity diode-lasers has capabilities far beyond the requirements of its primary mission.

  1. Optical Absorption and Photo-Thermal Conversion Properties of CuO/H2O Nanofluids.

    PubMed

    Wang, Liangang; Wu, Mingyan; Wu, Daxiong; Zhang, Canying; Zhu, Qunzhi; Zhu, Haitao

    2015-04-01

    Stable CuO/H2O nanofluids were synthesized in a wet chemical method. Optical absorption property of CuO/H2O nanofluids was investigated with hemispheric transmission spectrum in the wavelength range from 200 nm to 2500 nm. Photo-thermal conversion property of the CuO/H2O nanofluids was studied with an evaluation system equipped with an AUT-FSL semiconductor/solid state laser. The results indicate that CuO/H2O nanofluids have strong absorption in visible light region where water has little absorption. Under the irradiation of laser beam with a wavelength of 635 nm and a power of 0.015 W, the temperature of CuO/H2O nanofluids with 1.0% mass fraction increased by 5.6 °C within 40 seconds. Furthermore, the temperature elevation of CuO/H2O nanofluids was proved to increase with increasing mass fractions. On the contrast, water showed little temperature elevation under the identical conditions. The present work shows that the CuO/H2O nanofluids have high potential in the application as working fluids for solar utilization purpose.

  2. Impurity mediated large three photon absorption in ZnS:Cu nanophosphors

    NASA Astrophysics Data System (ADS)

    Sreeja, R.; Sridharan, Kishore; Philip, Reji; Jayaraj, M. K.

    2014-03-01

    Copper doped ZnS nanophosphors with the cubic zinc blende (Sphalerite) structure have been prepared through the wet chemical route in aqueous media. The ZnS:Cu nanoparticles display a widening in the band gap with increase in Cu dopant concentration. The observed green photoluminescence (PL) in ZnS:Cu originates from the transition between the conduction band and the copper acceptor levels. The open aperture Z-scan traces of the ZnS:Cu nanoparticles embedded in PVA matrix, excited at 800 nm using 100 fs laser pulses, show an optical limiting type nonlinearity which is attributed to three photon absorption. An increase in the value of the three photon absorption coefficient is observed with increase in the Cu doping concentration. The increase in the density of intermediate defect levels plays a significant role in the enhancement of three photon absorption in Cu doped ZnS. These studies reveal that Cu doped ZnS nanoparticles in polymer matrices are potential candidates for ultra fast optical limiting applications.

  3. Comparison of absorption, fluorescence, and polarization spectroscopy of atomic rubidium

    NASA Astrophysics Data System (ADS)

    Ashman, Seth; Stifler, Cayla; Romero, Joaquin

    2015-05-01

    An ongoing spectroscopic investigation of atomic rubidium utilizes a two-photon, single-laser excitation process. Transitions accessible with our tunable laser include 5P1 / 2F' <-- 5S1 / 2 F and 5P3 / 2F' <-- 5S1 / 2 F . The laser is split into a pump and probe beam to allow for Doppler-free measurements of transitions between hyperfine levels. The pump and probe beams are overlapped in a counter-propagating geometry and the laser frequency scans over a transition. Absorption, fluorescence and polarization spectroscopy techniques are applied to this basic experimental setup. The temperature of the vapor cell and the power of the pump and probe beams have been varied to explore line broadening effects and signal-to-noise of each technique. This humble setup will hopefully grow into a more robust experimental arrangement in which double resonance, two-laser excitations are used to explore hyperfine state changing collisions between rubidium atoms and noble gas atoms. Rb-noble gas collisions can transfer population between hyperfine levels, such as 5P3 / 2 (F' = 3) <-- Collision 5P3 / 2 (F ' = 2) , and the probe beam couples 7S1 / 2 (F'' = 2) <-- 5P3 / 2 (F' = 3) . Polarization spectroscopy signal depends on the rate of population transfer due to the collision as well as maintaining the orientation created by the pump laser. Fluorescence spectroscopy relies only on transfer of population due to the collision. Comparison of these techniques yields information regarding the change of the magnetic sublevels, mF, during hyperfine state changing collisions.

  4. Self-calibration wavelength modulation spectroscopy for acetylene detection based on tunable diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Huang, Qin-Bin; Xu, Xue-Mei; Li, Chen-Jing; Ding, Yi-Peng; Cao, Can; Yin, Lin-Zi; Ding, Jia-Feng

    2016-11-01

    The expressions of the second harmonic (2f) signal are derived on the basis of absorption spectral and lock-in theories. A parametric study indicates that the phase shift between the intensity and wavelength modulation makes a great contribution to the 2f signal. A self-calibration wavelength modulation spectroscopy (WMS) method based on tunable diode laser absorption spectroscopy (TDLAS) is applied, combining the advantages of ambient pressure, temperature suppression, and phase-shift influences elimination. Species concentration is retrieved simultaneously from selected 2f signal pairs of measured and reference WMS-2f spectra. The absorption line of acetylene (C2H2) at 1530.36 nm near-infrared is selected to detect C2H2 concentrations in the range of 0-400 ppmv. System sensitivity, detection precision and limit are markedly improved, demonstrating that the self-calibration method has better detecting performance than the conventional WMS. Project supported by the National Natural Science Foundation of China (Grant Nos. 61172047, 61502538, and 61501525).

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

    NASA Astrophysics Data System (ADS)

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

    2007-09-01

    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.

  6. Soft X-Ray Spectroscopy of Glycyl-Glycine Adsorbed on Cu(110) Surface

    NASA Astrophysics Data System (ADS)

    Feyer, V.; Plekan, O.; Lyamayev, V.; Skala, T.; Prince, K. C.; Chab, V.; Tsud, N.; Matolin, V.; Carravetta, V.

    2010-06-01

    Studies of the interaction between organic compounds and surfaces are motivated by their application as bio sensors, and their relevance to biocompatibility of implants and the origin of life. In the present work interaction of the simplest peptide, glycyl-glycine, with the Cu surface has been studied. Multilayer, monolayer and sub-monolayer films of this dipeptide on the clean and oxygen modified Cu(110) surface were prepared by thermal evaporation in high vacuum. The techniques used were soft X-ray photoelectron spectroscopy, near edge X-ray absorption fine structure spectroscopy and density functional theory calculations. By comparing the experimental and theoretical spectra, detailed models of the electronic structure and adsorption geometry for each coverage have been proposed, which are in good agreement with the theoretical calculations. The carboxylic acid group of glycyl-glycine loses hydrogen and the molecule is coordinated via the carboxylate oxygen atoms to the surface. At low coverage the amino group bonds to the surface via a hydrogen atom, while at higher coverage the bonding is via the nitrogen lone pair. The peptide group is not involved in the bonding to the surface.

  7. X-ray absorption spectroscopy proves the trigonal-planar sulfur-only coordination of copper(I) with high-affinity tripodal pseudopeptides.

    PubMed

    Jullien, Anne-Solène; Gateau, Christelle; Kieffer, Isabelle; Testemale, Denis; Delangle, Pascale

    2013-09-03

    A series of tripodal ligands L derived from nitrilotriacetic acid (NTA) and extended by three converging metal-binding cysteine chains were previously found to bind selectively copper(I) both in vitro and in vivo. The ligands L(1) (ester) and L(2) (amide) were demonstrated to form copper(I) species with very high affinities, close to that reported for the metal-sequestering metallothioneins (MTs; log K(Cu-MT) ≈ 19). Here, an in-depth study by Cu K-edge X-ray absorption spectroscopy (XAS) was performed to completely characterize the copper(I) coordination sphere in the complexes, previously evidenced by other physicochemical analyses. The X-ray absorption near-edge structure (XANES) spectra shed light on the equilibrium between a mononuclear complex and a cluster for both L(1) (ester) and L(2) (amide). The exclusive symmetric CuS3 geometry adopted in the mononuclear complexes (Cu-S ≈ 2.23 Å) was clearly demonstrated by extended X-ray absorption fine structure (EXAFS) analyses. The EXAFS analyses also proved that the clusters are organized on a symmetric CuS3 core (Cu-S ≈ 2.26 Å) and interact with three nearby copper atoms (Cu---Cu ≈ 2.7 Å), consistent with the Cu6S9-type clusters previously characterized by pulsed gradient spin echo NMR spectroscopy. XAS data obtained for other architectures based on the NTA template (L(3) acid, L(4) without a functionalized carbonyl group, etc.) demonstrated the formation of polymetallic species only, which evidence the necessity of the proximal ester or amide group to stabilize the CuS3 mononuclear species. Finally, XAS was demonstrated to be a powerful method to quantify the equilibrium between the two copper(I) environments evidenced with L(1) and L(2) at different copper concentrations and to determine the equilibrium constants between these two complexes.

  8. Determination of Aluminum Concentration in Seawater by Colorimetry and Atomic Absorption Spectroscopy.

    DTIC Science & Technology

    1972-11-30

    this was also high. 5 . ,Irj ~ - • lri*; llo. TALLE 2 ATOMIC ABSORPTION SPECTROSCOPY DETEPIJINATION OF ALUMINU1 CONCENTRATIO11 OF SEAWATER OCEAN...Concentration in Seawater by Colorimetr-y and Atomic Absorption Spectroscopy Charles A. Greene, Jr. and Everett N. Jones Ocean Science Department T14

  9. Absorption and emission spectroscopy of individual semiconductor nanostructures

    NASA Astrophysics Data System (ADS)

    McDonald, Matthew P.

    The advent of controllable synthetic methods for the production of semiconductor nanostructures has led to their use in a host of applications, including light-emitting diodes, field effect transistors, sensors, and even television displays. This is, in part, due to the size, shape, and morphologically dependent optical and electrical properties that make this class of materials extremely customizable; wire-, rod- and sphere-shaped nanocrystals are readily synthesized through common wet chemical methods. Most notably, confining the physical dimension of the nanostructure to a size below its Bohr radius (aB) results in quantum confinement effects that increase its optical energy gap. Not only the size, but the shape of a particle can be exploited to tailor its optical and electrical properties. For example, confined CdSe quantum dots (QDs) and nanowires (NWs) of equivalent diameter possess significantly different optical gaps. This phenomenon has been ascribed to electrostatic contributions arising from dielectric screening effects that are more pronounced in an elongated (wire-like) morphology. Semiconducting nanostructures have thus received significant attention over the past two decades. However, surprisingly little work has been done to elucidate their basic photophysics on a single particle basis. What has been done has generally been accomplished through emission-based measurements, and thus does not fully capture the full breadth of these intriguing systems. What is therefore needed then are absorption-based studies that probe the size and shape dependent evolution of nanostructure photophysics. This thesis summarizes the single particle absorption spectroscopy that we have carried out to fill this knowledge gap. Specifically, the diameter-dependent progression of one-dimensional (1D) excitonic states in CdSe NWs has been revealed. This is followed by a study that focuses on the polarization selection rules of 1D excitons within single CdSe NWs. Finally

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  11. The Fe-Cu Metastable Nano-scale Compound for Enhanced Absorption in the UV-Vis and NIR Ranges

    NASA Astrophysics Data System (ADS)

    Alami, Abdul Hai; Abed, Jehad; Almheiri, Meera; Alketbi, Afra

    2015-12-01

    This paper investigates the synthesis, microstructural characterization, electrical and optical, and thermal testing of Fe-Cu metastable alloy system for selective solar absorption applications. The system is produced by mechanical alloying using high-energy ball milling while monitoring its crystallographic morphology via X-ray diffraction from the initial as-is mixture up to the one produced after 8 hours milling time. The resulting homogeneous, metastable microstructure is examined by scanning electron microscopy and energy dispersive X-ray spectroscopy to verify the sought result of efficient inter-diffusion of elements. Optical spectroscopy results exhibit up to 81 pct enhanced absorption in the UV-Vis-NIR wavelength range with increased milling time from the as-is compound to the one obtained after 8 hours, while the trends of absorptivity curves had clear correlations with microstructural evolution. The impedance measurement of the resulting compound shows an increase in the resistance up to 120 Ω, compared with zero for the as-is starting mixture, which is a useful observation for many applications.

  12. Decay Heat Measurements Using Total Absorption Gamma-ray Spectroscopy

    NASA Astrophysics Data System (ADS)

    Rice, S.; Valencia, E.; Algora, A.; Taín, J. L.; Regan, P. H.; Podolyák, Z.; Agramunt, J.; Gelletly, W.; Nichols, A. L.

    2012-09-01

    A knowledge of the decay heat emitted by thermal neutron-irradiated nuclear fuel is an important factor in ensuring safe reactor design and operation, spent fuel removal from the core, and subsequent storage prior to and after reprocessing, and waste disposal. Decay heat can be readily calculated from the nuclear decay properties of the fission products, actinides and their decay products as generated within the irradiated fuel. Much of the information comes from experiments performed with HPGe detectors, which often underestimate the beta feeding to states at high excitation energies. This inability to detect high-energy gamma emissions effectively results in the derivation of decay schemes that suffer from the pandemonium effect, although such a serious problem can be avoided through application of total absorption γ-ray spectroscopy (TAS). The beta decay of key radionuclei produced as a consequence of the neutron-induced fission of 235U and 239Pu are being re-assessed by means of this spectroscopic technique. A brief synopsis is given of the Valencia-Surrey (BaF2) TAS detector, and their method of operation, calibration and spectral analysis.

  13. Femtosecond XUV transient absorption spectroscopy of small organic molecules

    NASA Astrophysics Data System (ADS)

    Lackner, Florian; Chatterley, Adam S.; Neumark, Daniel M.; Leone, Stephen R.; Gessner, Oliver

    2015-05-01

    High-order harmonic generation has evolved as a powerful method for the generation of femtosecond XUV pulses with table-top laser systems. Femtosecond XUV transient absorption spectroscopy is an emerging application of these novel light sources for the investigation of molecular dynamics. Recording time-dependent XUV induced core-to-valence transitions traces a molecular response to an initial perturbation with IR, VIS or UV laser pulses from the perspective of distinct atomic sites. Preliminary results for sulfur and selenium containing organic molecules, such as thiophene (C4H4S) and selenophene(C4H4Se), are presented. While molecular orbital dynamics in thiophene will be monitored at the sulfur 2p edge around 165 eV, experiments at the Se 3d (57 eV) and Se 3p (163 eV) edges of selenophene will provide insight about the impact of specific inner-shell transitions within the same atom on the spectroscopic fingerprint of similar dynamics. The method's element-specificity and sensitivity to local valance electronic structures will be exploited to monitor the photo-induced opening of the aromatic rings at the S-C and Se-C bonds, thereby shining new light on the primary steps of photochemical reaction pathways in organic compounds.

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

    SciTech Connect

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

    1993-06-01

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

  15. Intracavity Dye-Laser Absorption Spectroscopy (IDLAS) for application to planetary molecules

    NASA Technical Reports Server (NTRS)

    Lang, Todd M.; Allen, John E., Jr.

    1990-01-01

    Time-resolved, quasi-continuous wave, intracavity dye-laser absorption spectroscopy is applied to the investigation of absolute absorption coefficients for vibrational-rotational overtone bands of water at visible wavelengths. Emphasis is placed on critical factors affecting detection sensitivity and data analysis. Typical generation-time dependent absorption spectra are given.

  16. Optical spectroscopy reveals transition of CuInS2/ZnS to CuxZn1-xInS2/ZnS:Cu alloyed quantum dots with resultant double-defect luminescence

    NASA Astrophysics Data System (ADS)

    Yan, Ruolin; Zhang, Wenxia; Wu, Wenhui; Dong, Xingmin; Wang, Qiqi; Fan, Jiyang

    2016-12-01

    The structure and luminescence mechanisms of the CuInS2 quantum dots (QDs) after epitaxial growth of ZnS shell are in debate. The light absorption/emission spectroscopy reveals that after ZnS shell growth the cation diffusion at the CuInS2/ZnS interface results in formation of the alloyed CuxZn1- xInS2/ZnS:Cu QDs. These core/shell QDs exhibit dual-color photoluminescence with abnormal blue shift with decreasing excitation photon energy. The results show that the green and orange emissions originate separately from defects in the core and the shell. The absorption tail of the ZnS QDs turns from Urbach to Halperin-Lax type after Cu doping.

  17. Low absorption vitreous carbon reactors for operando XAS: a case study on Cu/Zeolites for selective catalytic reduction of NO(x) by NH3.

    PubMed

    Kispersky, Vincent F; Kropf, A Jeremy; Ribeiro, Fabio H; Miller, Jeffrey T

    2012-02-21

    We describe the use of vitreous carbon as an improved reactor material for an operando X-ray absorption spectroscopy (XAS) plug-flow reactor. These tubes significantly broaden the operating range for operando experiments. Using selective catalytic reduction (SCR) of NO(x) by NH(3) on Cu/Zeolites (SSZ-13, SAPO-34 and ZSM-5) as an example reaction, we illustrate the high-quality XAS data achievable with these reactors. The operando experiments showed that in Standard SCR conditions of 300 ppm NO, 300 ppm NH(3), 5% O(2), 5% H(2)O, 5% CO(2) and balance He at 200 °C, the Cu was a mixture of Cu(I) and Cu(II) oxidation states. XANES and EXAFS fitting found the percent of Cu(I) to be 15%, 45% and 65% for SSZ-13, SAPO-34 and ZSM-5, respectively. For Standard SCR, the catalytic rates per mole of Cu for Cu/SSZ-13 and Cu/SAPO-34 were about one third of the rate per mole of Cu on Cu/ZSM-5. Based on the apparent lack of correlation of rate with the presence of Cu(I), we propose that the reaction occurs via a redox cycle of Cu(I) and Cu(II). Cu(I) was not found in in situ SCR experiments on Cu/Zeolites under the same conditions, demonstrating a possible pitfall of in situ measurements. A Cu/SiO(2) catalyst, reduced in H(2) at 300 °C, was also used to demonstrate the reactor's operando capabilities using a bending magnet beamline. Analysis of the EXAFS data showed the Cu/SiO(2) catalyst to be in a partially reduced Cu metal-Cu(I) state. In addition to improvements in data quality, the reactors are superior in temperature, stability, strength and ease of use compared to previously proposed borosilicate glass, polyimide tubing, beryllium and capillary reactors. The solid carbon tubes are non-porous, machinable, can be operated at high pressure (tested at 25 bar), are inert, have high material purity and high X-ray transmittance.

  18. Methanogenic activity tests by Infrared Tunable Diode Laser Absorption Spectroscopy.

    PubMed

    Martinez-Cruz, Karla; Sepulveda-Jauregui, Armando; Escobar-Orozco, Nayeli; Thalasso, Frederic

    2012-10-01

    Methanogenic activity (MA) tests are commonly carried out to estimate the capability of anaerobic biomass to treat effluents, to evaluate anaerobic activity in bioreactors or natural ecosystems, or to quantify inhibitory effects on methanogenic activity. These activity tests are usually based on the measurement of the volume of biogas produced by volumetric, pressure increase or gas chromatography (GC) methods. In this study, we present an alternative method for non-invasive measurement of methane produced during activity tests in closed vials, based on Infrared Tunable Diode Laser Absorption Spectroscopy (MA-TDLAS). This new method was tested during model acetoclastic and hydrogenotrophic methanogenic activity tests and was compared to a more traditional method based on gas chromatography. From the results obtained, the CH(4) detection limit of the method was estimated to 60 ppm and the minimum measurable methane production rate was estimated to 1.09(.)10(-3) mg l(-1) h(-1), which is below CH(4) production rate usually reported in both anaerobic reactors and natural ecosystems. Additionally to sensitivity, the method has several potential interests compared to more traditional methods among which short measurements time allowing the measurement of a large number of MA test vials, non-invasive measurements avoiding leakage or external interferences and similar cost to GC based methods. It is concluded that MA-TDLAS is a promising method that could be of interest not only in the field of anaerobic digestion but also, in the field of environmental ecology where CH(4) production rates are usually very low.

  19. An EPR and optical absorption study of Cu(2+) doped in disodium malonate trihydrate single crystal.

    PubMed

    Yarbaşi, Zeynep; Karabulut, Bünyamin; Karabulut, Abdulhalik

    2009-03-01

    Single crystals and powder electron paramagnetic resonance (EPR) studies of Cu(2+)-doped disodium malonate trihydrate [C(3)H(2)O(4)Na(2).3H(2)O] have been carried out at room temperature. The angular variation of the disodium malonate trihydrate single crystal have shown that two different Cu(2+) complexes are located in different chemical environments, and each environment contains one magnetically inequivalent Cu(2+) sites in distinct orientations occupying substitutional positions in the lattice and show very high angular dependence. The principal values of the g and the hyperfine tensors were determined and were found to be in agreement with the literature values. Crystal field around the Cu(2+) ion is nearly rhombic. The optical absorption studies show two bands at 603nm (16584cm(-1)) and 890nm (11236cm(-1)) which confirm the rhombic symmetry. The crystals field parameters and than the wave function are determined.

  20. An EPR and optical absorption study of Cu 2+ doped in disodium malonate trihydrate single crystal

    NASA Astrophysics Data System (ADS)

    Yarbaşı, Zeynep; Karabulut, Bünyamin; Karabulut, Abdulhalik

    2009-03-01

    Single crystals and powder electron paramagnetic resonance (EPR) studies of Cu 2+-doped disodium malonate trihydrate [C 3H 2O 4Na 2·3H 2O] have been carried out at room temperature. The angular variation of the disodium malonate trihydrate single crystal have shown that two different Cu 2+ complexes are located in different chemical environments, and each environment contains one magnetically inequivalent Cu 2+ sites in distinct orientations occupying substitutional positions in the lattice and show very high angular dependence. The principal values of the g and the hyperfine tensors were determined and were found to be in agreement with the literature values. Crystal field around the Cu 2+ ion is nearly rhombic. The optical absorption studies show two bands at 603 nm (16584 cm -1) and 890 nm (11236 cm -1) which confirm the rhombic symmetry. The crystals field parameters and than the wave function are determined.

  1. Cu2ZnSnS4 absorption layers with controlled phase purity.

    PubMed

    Su, Chia-Ying; Chiu, Chiu-Yen; Ting, Jyh-Ming

    2015-03-24

    We report the synthesis and characterization of Cu2ZnSnS4 (CZTS) with controlled phase purity. The precursor was first prepared using sequential electrodeposition of Cu, Zn, and Sn in different orders. The Cu/(Sn+Zn) ratio in each stacking order was also varied. The precursor was subjected to annealing at 200°C and sulfurization at 500°C in a 5%-H2S/Ar atmosphere for the formation of CZTS. The phase evolutions during the electrodeposition and annealing stages, and the final phase formation at the sulfurization stage were examined using both x-ray diffractometry and Raman spectroscopy, both of which are shown to be complimentary tools for phase identification. Detailed growth path is therefore reported. We also demonstrate by controlling the stacking order and the Cu/(Sn+Zn) ratio, CZTS with a phase purity as high as 93% is obtained.

  2. Cu2ZnSnS4 absorption layers with controlled phase purity

    PubMed Central

    Su, Chia-Ying; -Yen Chiu, Chiu; Ting, Jyh-Ming

    2015-01-01

    We report the synthesis and characterization of Cu2ZnSnS4 (CZTS) with controlled phase purity. The precursor was first prepared using sequential electrodeposition of Cu, Zn, and Sn in different orders. The Cu/(Sn+Zn) ratio in each stacking order was also varied. The precursor was subjected to annealing at 200°C and sulfurization at 500°C in a 5%-H2S/Ar atmosphere for the formation of CZTS. The phase evolutions during the electrodeposition and annealing stages, and the final phase formation at the sulfurization stage were examined using both x-ray diffractometry and Raman spectroscopy, both of which are shown to be complimentary tools for phase identification. Detailed growth path is therefore reported. We also demonstrate by controlling the stacking order and the Cu/(Sn+Zn) ratio, CZTS with a phase purity as high as 93% is obtained. PMID:25801219

  3. Monitoring spacecraft atmosphere contaminants by laser absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Steinfeld, J. I.

    1975-01-01

    Data were obtained which will provide a test of the accuracy of the differential absorption method for trace contaminant detection in many-component gas mixtures. The necessary accurate absorption coefficient determinations were carried out for several gases; acetonitrile, 1,2-dichloroethane, Freon-113, furan, methyl ethyl ketone, and t-butyl alcohol. The absorption coefficients are displayed graphically. An opto-acoustic method was tested for measuring absorbance, similar to the system described by Dewey.

  4. Resonant X-Ray Scattering and Absorption for the Global and Local Structures of Cu-modified Metallothioneins in Solution

    PubMed Central

    Li, Meiyi; Huang, Yu-Shan; Jeng, U-Ser; Hsu, I-Jui; Sermon Wu, YewChung; Lai, Ying-Huang; Su, Chiu-Hun; Lee, Jyh-Fu; Wang, Yu; Chang, Chia-Ching

    2009-01-01

    Abstract With Cd and Zn metal ions removed from the native rabbit-liver metallothionein upon unfolding, Cu-modified metallothioneins (Cu-MTs) were obtained during refolding in solutions containing CuI or CuII ions. X-ray absorption near-edge spectroscopic results confirm the respectively assigned oxidation states of the copper ions in CuI-MT and CuII-MT. Global and local structures of the Cu-MTs were subsequently characterized by anomalous small-angle x-ray scattering (ASAXS) and extended x-ray absorption fine structure. Energy-dependent ASAXS results indicate that the morphology of CuII-MT resembles that of the native MT, whereas CuI-MT forms oligomers with a higher copper content. Both dummy-residue simulation and model-shape fitting of the ASAXS data reveal consistently rodlike morphology for CuII-MT. Clearly identified Cu-S, Cu-O, and Cu-Cu contributions in the extended x-ray absorption fine structure analysis indicate that both CuI and CuII ions are bonded with O and S atoms of nearby amino acids in a four-coordination environment, forming metal clusters smaller than metal thiolate clusters in the native MT. It is demonstrated that a combination of resonant x-ray scattering and x-ray absorption can be particularly useful in revealing complementary global and local structures of metalloproteins due to the atom specific characteristics of the two techniques. PMID:19619476

  5. Studies of cavity enhanced absorption spectroscopy for weak absorption gas measurements

    NASA Astrophysics Data System (ADS)

    Li, Liucheng; Duo, Liping; Gong, Deyu; Ma, Yanhua; Zhang, Zhiguo; Wang, Yuanhu; Zhou, Dongjian; Jin, Yuqi

    2017-01-01

    In order to determine the concentrations of trace amount metastable species in chemical lasers, an off-axis cavity enhanced absorption spectrometer for the detection of weak absorption gases has been built with a noise equivalent absorption sensitivity of 1.6x10-8 cm-1. The absorption spectrum of trace amount gaseous ammonia and water vapor was obtained with a spectral resolution of about 78 MHz. A multiple-line absorption spectroscopic method to determine the temperature of gaseous ammonia has been developed by use of multiple lines of ammonia molecule absorption spectrum.

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

    SciTech Connect

    Sarmiento-Pérez, Rafael; Botti, Silvana; Schnohr, Claudia S.; Lauermann, Iver; Rubio, Angel; Johnson, Benjamin

    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.

  7. Transition from exo- to endo- Cu absorption in CuSin clusters: A Genetic Algorithms Density Functional Theory (DFT) Study

    PubMed Central

    Oña, Ofelia B.; Ferraro, Marta B.; Facelli, Julio C.

    2010-01-01

    The characterization and prediction of the structures of metal silicon clusters is important for nanotechnology research because these clusters can be used as building blocks for nano devices, integrated circuits and solar cells. Several authors have postulated that there is a transition between exo to endo absorption of Cu in Sin clusters and showed that for n larger than 9 it is possible to find endohedral clusters. Unfortunately, no global searchers have confirmed this observation, which is based on local optimizations of plausible structures. Here we use parallel Genetic Algorithms (GA), as implemented in our MGAC software, directly coupled with DFT energy calculations to show that the global search of CuSin cluster structures does not find endohedral clusters for n < 8 but finds them for n ≥ 10. PMID:21785526

  8. First principles absorption spectra of Cu{sub n} (n = 2 - 20) clusters.

    SciTech Connect

    Baishya, K.; Idrobo, J. C.; Ogut, S.; Yang, M.; Jackson, K. A.; Jellinek, J.

    2011-06-17

    Optical absorption spectra for the computed ground state structures of copper clusters (Cu{sub n}, n = 2-20) are investigated from first principles using time-dependent density functional theory in the adiabatic local density approximation (TDLDA). The results are compared with available experimental data, existing calculations, and with results from our previous computations on silver and gold clusters. The main effects of d electrons on the absorption spectra, quenching the oscillator strengths, and getting directly involved in low-energy excitations increase in going from Ag{sub n} to Au{sub n} to Cu{sub n} due to the increase in the hybridization of the occupied, yet shallow, d orbitals and the partially occupied s orbitals. We predict that while Cu nanoparticles of spherical or moderately ellipsoidal shape do not exhibit Mie (surface plasmon) resonances, unlike the case for Ag and Au, extremely prolate or oblate Cu nanoparticles with eccentricities near unity should give rise to Mie resonances in the lower end of the visible range and in the infrared. This tunable resonance predicted by the classical Mie-Gans theory is reproduced with remarkable accuracy by our TDLDA computations on hypothetical Cu clusters in the form of zigzag chains with as few as 6 to 20 atoms.

  9. Catalysts at work: From integral to spatially resolved X-ray absorption spectroscopy

    SciTech Connect

    Grunwaldt, Jan-Dierk; Kimmerle, Bertram; Baiker, Alfons; Boye, Pit; Schroer, Christian G.; Glatzel, Pieter; Borca, Camelia N.; Beckmann, Felix

    2009-09-25

    Spectroscopic studies on heterogeneous catalysts have mostly been done in an integral mode. However, in many cases spatial variations in catalyst structure can occur, e.g. during impregnation of pre-shaped particles, during reaction in a catalytic reactor, or in microstructured reactors as the present overview shows. Therefore, spatially resolved molecular information on a microscale is required for a comprehensive understanding of theses systems, partly in ex situ studies, partly under stationary reaction conditions and in some cases even under dynamic reaction conditions. Among the different available techniques, X-ray absorption spectroscopy (XAS) is a well-suited tool for this purpose as the different selected examples highlight. Two different techniques, scanning and full-field X-ray microscopy/tomography, are described and compared. At first, the tomographic structure of impregnated alumina pellets is presented using full-field transmission microtomography and compared to the results obtained with a scanning X-ray microbeam technique to analyse the catalyst bed inside a catalytic quartz glass reactor. On the other hand, by using XAS in scanning microtomography, the structure and the distribution of Cu(0), Cu(I), Cu(II) species in a Cu/ZnO catalyst loaded in a quartz capillary microreactor could be reconstructed quantitatively on a virtual section through the reactor. An illustrating example for spatially resolved XAS under reaction conditions is the partial oxidation of methane over noble metal-based catalysts. In order to obtain spectroscopic information on the spatial variation of the oxidation state of the catalyst inside the reactor XAS spectra were recorded by scanning with a micro-focussed beam along the catalyst bed. Alternatively, full-field transmission imaging was used to efficiently determine the distribution of the oxidation state of a catalyst inside a reactor under reaction conditions. The new technical approaches together with quantitative data

  10. The rotational spectrum of CuCCH(X̃  1Σ+): a Fourier transform microwave discharge assisted laser ablation spectroscopy and millimeter/submillimeter study.

    PubMed

    Sun, M; Halfen, D T; Min, J; Harris, B; Clouthier, D J; Ziurys, L M

    2010-11-07

    The pure rotational spectrum of CuCCH in its ground electronic state (X̃  (1)Σ(+)) has been measured in the frequency range of 7-305 GHz using Fourier transform microwave (FTMW) and direct absorption millimeter/submillimeter methods. This work is the first spectroscopic study of CuCCH, a model system for copper acetylides. The molecule was synthesized using a new technique, discharge assisted laser ablation spectroscopy (DALAS). Four to five rotational transitions were measured for this species in six isotopologues ((63)CuCCH, (65)CuCCH, (63)Cu(13)CCH, (63)CuC(13)CH, (63)Cu(13)C(13)CH, and (63)CuCCD); hyperfine interactions arising from the copper nucleus were resolved, as well as smaller splittings in CuCCD due to deuterium quadrupole coupling. Five rotational transitions were also recorded in the millimeter region for (63)CuCCH and (65)CuCCH, using a Broida oven source. The combined FTMW and millimeter spectra were analyzed with an effective Hamiltonian, and rotational, electric quadrupole (Cu and D) and copper nuclear spin-rotation constants were determined. From the rotational constants, an r(m)(2) structure for CuCCH was established, with r(Cu-C) = 1.8177(6) Å, r(C-C) = 1.2174(6) Å, and r(C-H) = 1.046(2) Å. The geometry suggests that CuCCH is primarily a covalent species with the copper atom singly bonded to the C≡C-H moiety. The copper quadrupole constant indicates that the bonding orbital of this atom may be sp hybridized. The DALAS technique promises to be fruitful in the study of other small, metal-containing molecules of chemical interest.

  11. X-ray absorption study of the ferromagnetic Cu moment at the YBa2Cu3O7/La2 /3Ca1 /3MnO3 interface and variation of its exchange interaction with the Mn moment

    NASA Astrophysics Data System (ADS)

    Sen, K.; Perret, E.; Alberca, A.; Uribe-Laverde, M. A.; Marozau, I.; Yazdi-Rizi, M.; Mallett, B. P. P.; Marsik, P.; Piamonteze, C.; Khaydukov, Y.; Döbeli, M.; Keller, T.; Biškup, N.; Varela, M.; Vašátko, J.; Munzar, D.; Bernhard, C.

    2016-05-01

    With x-ray absorption spectroscopy and polarized neutron reflectometry we studied how the magnetic proximity effect at the interface between the cuprate high-TC superconductor YBa2Cu3O7 (YBCO) and the ferromagnet La2 /3Ca1 /3MnO3 (LCMO) is related to the electronic and magnetic properties of the LCMO layers. In particular, we explored how the magnitude of the ferromagnetic Cu moment on the YBCO side depends on the strength of the antiferromagnetic (AF) exchange coupling with the Mn moment on the LCMO side. We found that the Cu moment remains sizable if the AF coupling with the Mn moments is strongly reduced or even entirely suppressed. The ferromagnetic order of the Cu moments thus seems to be intrinsic to the interfacial CuO2 planes and related to a weakly ferromagnetic intraplanar exchange interaction. The latter is discussed in terms of the partial occupation of the Cu 3 d3 z2-r2 orbitals, which occurs in the context of the so-called orbital reconstruction of the interfacial Cu ions.

  12. Aerosol particle absorption spectroscopy by photothermal modulation of Mie scattered light

    SciTech Connect

    Campillo, A.J.; Dodge, C.J.; Lin, H.B.

    1981-09-15

    Absorption spectroscopy of suspended submicron-sized aqueous ammonium-sulfate aerosol droplets has been performed by employing a CO/sub 2/ laser to photothermally modulate visible Mie scattered light. (AIP)

  13. Determination of tin in poly(vinyl chloride) by atomic-absorption spectroscopy.

    PubMed

    Anwar, J; Marr, I L

    1982-10-01

    A simple procedure is described for the determination of tin in PVC by atomic-absorption spectroscopy with an air-hydrogen flame, after wet digestion of the sample with sulphuric acid and hydrogen peroxide.

  14. Infrared absorption spectroscopic and DFT calculation studies on the adsorption structures of nitromethane on the single crystals of Cu and Ag

    NASA Astrophysics Data System (ADS)

    Itoh, K.; Iwa, A.; Uriu, Y.; Kadokura, K.

    2008-07-01

    The adsorption structures of nitromethane on Ag(1 1 0), Ag(1 1 1), Cu(1 1 0) and Cu(1 1 1) at 80 K were studied by using infrared reflection absorption spectroscopy (IRAS) and non-local density functional theory (DFT) calculation performed on nitromethane/Cu(1 1 0) and nitromethane/Cu(1 1 1) cluster models. Upon increasing exposure levels, the adsorbate on each substrate exhibits discrete spectral changes, characterizing sub-monolayer and/or monolayer, amorphous and multilayer (crystalline) states. The DFT calculation successively simulated the IRA spectra of nitromethane on the copper substrates, suggesting that nitromethane adsorbs on Cu(1 1 0) through an on-top coordination with one of the oxygen atom of the NO 2 group to the Cu atom and that nitromethane adsorbs on Cu(1 1 1) through a bridging coordination of the oxygen atom. In both states nitromethane takes an eclipsed form with the molecular plane perpendicular to the substrates surface and the hydrogen atom pointing to the surface in the molecular plane plays an important role in stabilizing the adsorption states in addition to the coordination interaction.

  15. Characterization of compounds derived from copper-oxamate and imidazolium by X-ray absorption and vibrational spectroscopies.

    PubMed

    do Nascimento, Gustavo M; do Pim, Walace D; Reis, Daniella O; Simões, Tatiana R G; Pradie, Noriberto A; Stumpf, Humberto O

    2015-05-05

    In this work, compounds derived from copper-oxamate anions (ortho, meta, and para)-phenylenebis (oxamate) and imidazolium cations (1-butyl-3-methylimidazolium) were synthesized. The compounds were characterized by Raman and FTIR spectroscopies and the band assignments were supported by DFT calculations. Strong IR bands from 1610 to 1700cm(-1) dominated the spectra of the complex and can be assigned to νCO vibrations of the [Cu(opba)](2-) anions by the comparison with the DFT data. In opposition to the FTIR spectra, the main vibrational bands in the Raman spectra are observed in the 1350-1600cm(-1) range. All bands in this region are associated to the modified benzene vibrations of the copper-phenylenebis(oxamate) anions. X-ray absorption near edge (XANES) at different energies (NK and Cu L2,3 edges) was also used to probe the interionic interactions. XANES data show that anion-cation interaction in the Cu-oxamate-imidazolium changes the electronic structure around the CuN sites in the oxamate anion.

  16. Optical spectroscopy of the Triangular Lattice Antiferromagnets CuCrO2 and α-CaCr2O4

    NASA Astrophysics Data System (ADS)

    Schmidt, Michael; Wang, Zhe; Mayr, F.; Toth, S.; Lake, B.; Islam, A. T. M. N.; Tsurkan, V.; Loidl, A.; Deisenhofer, J.

    2012-02-01

    We will compare and discuss our results obtained by optical spectroscopy on CuCrO2 and α-CaCr2O4. While CuCrO2 is famous for its multiferroicity [1], in α-CaCr2O4 a polarization can only be observed under the application of electric or magnetic field, despite having a closely related structure [2]. At near infrared and visible light frequencies we observe Cr^3+ crystal field absorptions and below TN excitons and exciton-magnon-transitions appear. The width of these exciton-magnon transitions is analyzed with respect to the existence of Z2 vortices as proposed by Kojima et al. [3]. [4pt] [1] S. Seki et al., Phys. Rev. Lett. 101, 067240 (2008)[0pt] [2] K. Singh et al., Phys. Rev. B 84, 064129 (2011)[0pt] [3] N. Kojima et al., J. Phys. Soc. Jpn. 62, 4137 (1993)

  17. Direct and quantitative photothermal absorption spectroscopy of individual particulates

    SciTech Connect

    Tong, Jonathan K.; Hsu, Wei-Chun; Eon Han, Sang; Burg, Brian R.; Chen, Gang; Zheng, Ruiting; Shen, Sheng

    2013-12-23

    Photonic structures can exhibit significant absorption enhancement when an object's length scale is comparable to or smaller than the wavelength of light. This property has enabled photonic structures to be an integral component in many applications such as solar cells, light emitting diodes, and photothermal therapy. To characterize this enhancement at the single particulate level, conventional methods have consisted of indirect or qualitative approaches which are often limited to certain sample types. To overcome these limitations, we used a bilayer cantilever to directly and quantitatively measure the spectral absorption efficiency of a single silicon microwire in the visible wavelength range. We demonstrate an absorption enhancement on a per unit volume basis compared to a thin film, which shows good agreement with Mie theory calculations. This approach offers a quantitative approach for broadband absorption measurements on a wide range of photonic structures of different geometric and material compositions.

  18. VUV absorption spectroscopy of bacterial spores and DNA components

    NASA Astrophysics Data System (ADS)

    Fiebrandt, Marcel; Lackmann, Jan-Wilm; Raguse, Marina; Moeller, Ralf; Awakowicz, Peter; Stapelmann, Katharina

    2017-01-01

    Low-pressure plasmas can be used to inactivate bacterial spores and sterilize goods for medical and pharmaceutical applications. A crucial factor are damages induced by UV and VUV radiation emitted by the plasma. To analyze inactivation processes and protection strategies of spores, absorption spectra of two B. subtilis strains are measured. The results indicate, that the inner and outer coat of the spore significantly contribute to the absorption of UV-C and also of the VUV, protecting the spore against radiation based damages. As the sample preparation can significantly influence the absorption spectra due to salt residues, the cleaning procedure and sample deposition is tested for its reproducibility by measuring DNA oligomers and pUC18 plasmid DNA. The measurements are compared and discussed with results from the literature, showing a strong decrease of the salt content enabling the detection of absorption structures in the samples.

  19. In situ Gas Temperature Measurements by UV-Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Fateev, A.; Clausen, S.

    2009-02-01

    The absorption spectrum of the NO A2Σ+ ← X2Πγ-system can be used for in situ evaluation of gas temperature. Experiments were performed with a newly developed atmospheric-pressure high-temperature flow gas cell at highly uniform and stable gas temperatures over a 0.533 m path in the range from 23 °C to 1,500 °C. The gas temperature was evaluated (1) from the analysis of the structure of selected NO high-resolution γ-absorption bands and (2) from the analysis of vibrational distribution in the NO γ-absorption system in the (211-238) nm spectral range. The accuracy of both methods is discussed. Validation of the classical Lambert-Beer law has been demonstrated at NO concentrations up to 500 ppm and gas temperatures up to 1,500 °C over an optical absorption path length of 0.533 m.

  20. Structure and spectroscopy of CuH prepared via borohydride reduction

    PubMed Central

    Bennett, Elliot L.; Wilson, Thomas; Murphy, Patrick J.; Refson, Keith; Hannon, Alex C.; Imberti, Silvia; Callear, Samantha K.; Chass, Gregory A.; Parker, Stewart F.

    2015-01-01

    Copper(I) hydride (cuprous hydride, CuH) was the first binary metal hydride to be discovered (in 1844) and is singular in that it is synthesized in solution, at ambient temperature. There are several synthetic paths to CuH, one of which involves reduction of an aqueous solution of CuSO4·5H2O by borohydride ions. The product from this procedure has not been extensively characterized. Using a combination of diffraction methods (X-ray and neutron) and inelastic neutron scattering spectroscopy, we show that the CuH from the borohydride route has the same bulk structure as CuH produced by other routes. Our work shows that the product consists of a core of CuH with a shell of water and that this may be largely replaced by ethanol. This offers the possibility of modifying the properties of CuH produced by aqueous routes. PMID:26634717

  1. The use of CNDO in spectroscopy. XV. Two photon absorption

    NASA Astrophysics Data System (ADS)

    Marchese, Francis T.; Seliskar, C. J.; Jaffé, H. H.

    1980-04-01

    Two-photon absorptivities have been calculated within the CNDO/S-CI molecular orbital framework of Del Bene and Jaffé utilizing the second order time dependent perturbation equations of Göppert-Mayer and polarization methods of McClain. Good agreement is found between this theory and experiment for transition energies, symmetries, and two-photon absorptivities for the following molecules: biphenyl, terphenyl, 2,2'-difluorobiphenyl, 2,2'-bipyridyl, phenanthrene, and the isoelectronic series: fluorene, carbazole, dibenzofuran.

  2. Characterization of Metalloproteins by High-throughput X-ray Absorption Spectroscopy

    SciTech Connect

    W Shi; M Punta; J Bohon; J Sauder; R DMello; M Sullivan; J Toomey; D Abel; M Lippi; et al.

    2011-12-31

    High-throughput X-ray absorption spectroscopy was used to measure transition metal content based on quantitative detection of X-ray fluorescence signals for 3879 purified proteins from several hundred different protein families generated by the New York SGX Research Center for Structural Genomics. Approximately 9% of the proteins analyzed showed the presence of transition metal atoms (Zn, Cu, Ni, Co, Fe, or Mn) in stoichiometric amounts. The method is highly automated and highly reliable based on comparison of the results to crystal structure data derived from the same protein set. To leverage the experimental metalloprotein annotations, we used a sequence-based de novo prediction method, MetalDetector, to identify Cys and His residues that bind to transition metals for the redundancy reduced subset of 2411 sequences sharing <70% sequence identity and having at least one His or Cys. As the HT-XAS identifies metal type and protein binding, while the bioinformatics analysis identifies metal-binding residues, the results were combined to identify putative metal-binding sites in the proteins and their associated families. We explored the combination of this data with homology models to generate detailed structure models of metal-binding sites for representative proteins. Finally, we used extended X-ray absorption fine structure data from two of the purified Zn metalloproteins to validate predicted metalloprotein binding site structures. This combination of experimental and bioinformatics approaches provides comprehensive active site analysis on the genome scale for metalloproteins as a class, revealing new insights into metalloprotein structure and function.

  3. Trace gas absorption spectroscopy using laser difference-frequency spectrometer for environmental application

    NASA Technical Reports Server (NTRS)

    Chen, W.; Cazier, F.; Boucher, D.; Tittel, F. K.; Davies, P. B.

    2001-01-01

    A widely tunable infrared spectrometer based on difference frequency generation (DFG) has been developed for organic trace gas detection by laser absorption spectroscopy. On-line measurements of concentration of various hydrocarbons, such as acetylene, benzene, and ethylene, were investigated using high-resolution DFG trace gas spectroscopy for highly sensitive detection.

  4. Optical absorption of small copper clusters in neon: Cu(n), (n = 1-9).

    PubMed

    Lecoultre, S; Rydlo, A; Félix, C; Buttet, J; Gilb, S; Harbich, W

    2011-02-21

    We present optical absorption spectra in the UV-visible range (1.6 eV < ℏω < 5.5 eV) of mass selected neutral copper clusters Cu(n)(n = 1-9) embedded in a solid neon matrix at 7 K. The atom and the dimer have already been measured in neon matrices, while the absorption spectra for sizes between Cu(3) and Cu(9) are entirely (n = 6-9) or in great part new. They show a higher complexity and a larger number of transitions distributed over the whole energy range compared to similar sizes of silver clusters. The experimental spectra are compared to the time dependent density functional theory (TD-DFT) implemented in the TURBOMOLE package. The analysis indicates that for energies larger than 3 eV the transitions are mainly issued from d-type states; however, the TD-DFT scheme does not reproduce well the detailed structure of the absorption spectra. Below 3 eV the agreement for transitions issued from s-type states is better.

  5. High-Resolution Absorption Spectroscopy of NO2

    DTIC Science & Technology

    1987-08-31

    identify by block number) FIELD GROUP SUB-GROUP Atmospheric propagation, Laser spectroscopy, Nitrogen dioxide , Spectroscopy 19. RACT (Continue on reverse if...pulsed dye laser having a 0.05-A"-bandwidth (FWHM). This represents an improvement of at least a factor of three over the resolution employed in...concise interpretation of the observed features has yet to be made. Actual state-to-state assignments in the visible and near UV have been possible only

  6. Method and apparatus for aerosol particle absorption spectroscopy

    DOEpatents

    Campillo, Anthony J.; Lin, Horn-Bond

    1983-11-15

    A method and apparatus for determining the absorption spectra, and other properties, of aerosol particles. A heating beam source provides a beam of electromagnetic energy which is scanned through the region of the spectrum which is of interest. Particles exposed to the heating beam which have absorption bands within the band width of the heating beam absorb energy from the beam. The particles are also illuminated by light of a wave length such that the light is scattered by the particles. The absorption spectra of the particles can thus be determined from an analysis of the scattered light since the absorption of energy by the particles will affect the way the light is scattered. Preferably the heating beam is modulated to simplify the analysis of the scattered light. In one embodiment the heating beam is intensity modulated so that the scattered light will also be intensity modulated when the particles absorb energy. In another embodiment the heating beam passes through an interferometer and the scattered light reflects the Fourier Transform of the absorption spectra.

  7. Review on VUV to MIR absorption spectroscopy of atmospheric pressure plasma jets

    NASA Astrophysics Data System (ADS)

    Reuter, Stephan; Santos Sousa, Joao; Stancu, Gabi Daniel; Hubertus van Helden, Jean-Pierre

    2015-10-01

    Absorption spectroscopy (AS) represents a reliable method for the characterization of cold atmospheric pressure plasma jets. The method’s simplicity stands out in comparison to competing diagnostic techniques. AS is an in situ, non-invasive technique giving absolute densities, free of calibration procedures, which other diagnostics, such as laser-induced fluorescence or optical emission spectroscopy, have to rely on. Ground state densities can be determined without the knowledge of the influence of collisional quenching. Therefore, absolute densities determined by absorption spectroscopy can be taken as calibration for other methods. In this paper, fundamentals of absorption spectroscopy are presented as an entrance to the topic. In the second part of the manuscript, a review of AS performed on cold atmospheric pressure plasma jets, as they are used e.g. in the field of plasma medicine, is presented. The focus is set on special techniques overcoming not only the drawback of spectrally overlapping absorbing species, but also the line-of-sight densities that AS usually provides or the necessity of sufficiently long absorption lengths. Where references are not available for measurements on cold atmospheric pressure plasma jets, other plasma sources including low-pressure plasmas are taken as an example to give suggestions for possible approaches. The final part is a table summarizing examples of absorption spectroscopic measurements on cold atmospheric pressure plasma jets. With this, the paper provides a ‘best practice’ guideline and gives a compendium of works by groups performing absorption spectroscopy on cold atmospheric pressure plasma jets.

  8. Direct and quantitative broadband absorptance spectroscopy with multilayer cantilever probes

    DOEpatents

    Hsu, Wei-Chun; Tong, Jonathan Kien-Kwok; Liao, Bolin; Chen, Gang

    2015-04-21

    A system for measuring the absorption spectrum of a sample is provided that includes a broadband light source that produces broadband light defined within a range of an absorptance spectrum. An interferometer modulates the intensity of the broadband light source for a range of modulation frequencies. A bi-layer cantilever probe arm is thermally connected to a sample arm having at most two layers of materials. The broadband light modulated by the interferometer is directed towards the sample and absorbed by the sample and converted into heat, which causes a temperature rise and bending of the bi-layer cantilever probe arm. A detector mechanism measures and records the deflection of the probe arm so as to obtain the absorptance spectrum of the sample.

  9. [The Research for Trace Ammonia Escape Monitoring System Based on Tunable Diode Laser Absorption Spectroscopy].

    PubMed

    Zhang, Li-fang; Wang, Fei; Yu, Li-bin; Yan, Jian-hua; Cen, Ke-fa

    2015-06-01

    In order to on-line measure the trace ammonia slip of the commercial power plant in the future, this research seeks to measure the trace ammonia by using tunable diode laser absorption spectroscopy under ambient temperature and pressure, and at different temperatures, and the measuring temperature is about 650 K in the power plant. In recent years lasers have become commercially available in the near-infrared where the transitions are much stronger, and ammonia's spectroscopy is pretty complicated and the overlapping lines are difficult to resolve. A group of ammonia transitions near 4 433.5 cm(-1) in the v2 +v3 combination band have been thoroughly selected for detecting lower concentration by analyzing its absorption characteristic and considering other absorption interference in combustion gases where H2O and CO2 mole fraction are very large. To illustrate the potential for NH3 concentration measurements, predictions for NH3, H2O and CO2 are simultaneously simulated, NH3 absorption lines near 4 433.5 cm(-1) wavelength meet weaker H2O absorption than the commercial NH3 lines, and there is almost no CO2 absorption, all the parameters are based on the HITRAN database, and an improved detection limit was obtained for interference-free NH3 monitoring, this 2.25 μm band has line strengths several times larger than absorption lines in the 1.53 μm band which was often used by NH3 sensors for emission monitoring and analyzing. The measurement system was developed with a new Herriott cell and a heated gas cell realizing fast absorption measurements of high resolution, and combined with direct absorption and wavelenguh modulation based on tunable diode laser absorption spectroscopy at different temperatures. The lorentzian line shape is dominant at ambient temperature and pressure, and the estimated detectivity is approximately 0.225 x 10(-6) (SNR = 1) for the directed absorption spectroscopy, assuming a noise-equivalent absorbance of 1 x 10(-4). The heated cell

  10. Time-resolved pump-probe spectroscopy of intraband absorption by a semiconductor nanorod

    NASA Astrophysics Data System (ADS)

    Leonov, Mikhail Y.; Rukhlenko, Ivan D.; Baranov, Alexander V.; Fedorov, Anatoly V.

    2013-09-01

    We develop a theory of time-resolved pump-probe optical spectroscopy of intraband absorption of a probe pulse inside an anisotropic semiconductor nanorod. The absorption is preceded by the absorption of the pump pulse resonant to an interband transition. It is assumed that the resonantly exited states of the nanorod are interrelated via the relaxation induced by their interaction with a bath. We reveal the conditions for which the absorption of the probe's pulse is governed by a simple formula regardless of the pulse's shape. This formula is useful for the analysis of the experimental data containing information on the relaxation parameters of the nanorod's electronic subsystem.

  11. High covalence in CuSO4 and the radicalization of sulfate: an X-ray absorption and density functional study.

    PubMed

    Szilagyi, Robert K; Frank, Patrick; DeBeer George, Serena; Hedman, Britt; Hodgson, Keith O

    2004-12-27

    Sulfur K-edge X-ray absorption spectroscopy (XAS) of anhydrous CuSO(4) reveals a well-resolved preedge transition feature at 2478.8 eV that has no counterpart in the XAS spectra of anhydrous ZnSO(4) or copper sulfate pentahydrate. Similar but weaker preedge features occur in the sulfur K-edge XAS spectra of [Cu(itao)SO(4)] (2478.4 eV) and [Cu[(CH(3))(6)tren]SO(4)] (2477.7 eV). Preedge features in the XAS spectra of transition metal ligands are generally attributed to covalent delocalization of a metal d-orbital hole into a ligand-based orbital. Copper L-edge XAS of CuSO(4) revealed that 56% of the Cu(II) 3d hole is delocalized onto the sulfate ligand. Hybrid density functional calculations on the two most realistic models of the covalent delocalization pathways in CuSO(4) indicate about 50% electron delocalization onto the sulfate oxygen-based 2p orbitals; however, at most 14% of that can be found on sulfate sulfur. Both experimental and computational results indicated that the high covalence of anhydrous CuSO(4) has made sulfate more like the radical monoanion, inducing an extensive mixing and redistribution of sulfur 3p-based unoccupied orbitals to lower energy in comparison to sulfate in ZnSO(4). It is this redistribution, rather than a direct covalent interaction between Cu(II) and sulfur, that is the origin of the observed sulfur XAS preedge feature. From pseudo-Voigt fits to the CuSO(4) sulfur K-edge XAS spectrum, a ground-state 3p character of 6% was quantified for the orbital contributing to the preedge transition, in reasonable agreement with the DFT calculation. Similar XAS fits indicated 2% sulfur 3p character for the preedge transition orbitals in [Cu(itao)SO(4)] and [Cu[(CH(3))(6)tren]SO(4)]. The covalent radicalization of ligands similar to sulfate, with consequent energy redistribution of the virtual orbitals, represents a new mechanism for the induction of ligand preedge XAS features. The high covalence of the Cu sites in CuSO(4) was found to be

  12. Studies of Arctic Middle Atmosphere Chemistry using Infrared Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Lindenmaier, Rodica

    The objective of this Ph.D. project is to investigate Arctic middle atmosphere chemistry using solar infrared absorption spectroscopy. These measurements were made at the Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka, Nunavut, which is operated by the Canadian Network for the Detection of Atmospheric Change (CANDAC). This research is part of the CANDAC/PEARL Arctic Middle Atmosphere Chemistry theme and aims to improve our understanding of the processes controlling the stratospheric ozone budget using measurements of the concentrations of stratospheric constituents. The instrument, a Bruker IFS 125HR Fourier transform infrared (FTIR) spectrometer, has been specifically designed for high-resolution measurements over a broad spectral range and has been used to measure reactive species, source gases, reservoirs, and dynamical tracers at PEARL since August 2006. The first part of this research focuses on the optimization of ozone retrievals, for which 22 microwindows were studied and compared. The spectral region from 1000 to 1005 cm-1 was found to be the most sensitive in both the stratosphere and troposphere, giving the highest number of independent pieces of information and the smallest total error for retrievals at Eureka. Similar studies were performed in coordination with the Network for the Detection of Atmospheric Composition Change for nine other species, with the goal of improving and harmonizing the retrieval parameters among all Infrared Working Group sites. Previous satellite validation exercises have identified the highly variable polar conditions of the spring period to be a challenge. In this work, comparisons between the 125HR and ACE-FTS (Atmospheric Chemistry Experiment-Fourier transform spectrometer) from 2007 to 2010 have been used to develop strict criteria that allow the ground and satellite-based instruments to be confidently compared. After applying these criteria, the differences between the two instruments were generally

  13. Resonant interaction between two Cu quantum wells investigated by angle-resolved photoemission spectroscopy

    NASA Astrophysics Data System (ADS)

    Wu, Y. Z.; Won, C.; Rotenberg, E.; Zhao, H. W.; Xue, Qi-Kun; Kim, W.; Owens, T. L.; Smith, N. V.; Qiu, Z. Q.

    2006-03-01

    Double quantum wells (QWs) of Cu thin films were investigated using angle-resolved photoemission spectroscopy. The thickness ratio of the two Cu QW films was chosen to be 1:1 and 2:1 to purposely group the QW states of the two Cu films into degenerate and nondegenerate states. The energy spectra of the valence band show that only the degenerate QW states interact resonantly to split each degenerate state into two separate states. Furthermore, by investigating the interaction of two Cu films across a Ni/Cu [14 monolayer (ML)]/Ni QW, we show clearly that resonant splitting occurs at the quantized energy levels of the middle 14 ML Cu QW film.

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

    NASA Astrophysics Data System (ADS)

    Pauli, Mark Daniel

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

  15. Ultrafast Extreme Ultraviolet Absorption Spectroscopy of Methylammonium Lead Iodide Perovskite

    NASA Astrophysics Data System (ADS)

    Verkamp, Max A.; Lin, Ming-Fu; Ryland, Elizabeth S.; Vura-Weis, Josh

    2016-06-01

    Methylammonium lead iodide (perovskite) is a leading candidate for use in next-generation solar cell devices. However, the photophysics responsible for its strong photovoltaic qualities are not fully understood. Ultrafast extreme ultraviolet (XUV) absorption was used to investigate electron and hole dynamics in perovskite by observing transitions from a common inner-shell level (I 4d) to the valence and conduction bands. Ultrashort (30 fs) pulses of XUV radiation with a broad spectrum (40-70 eV) were generated via high-harmonic generation using a tabletop instrument. Transient absorption measurements with visible pump and XUV probe directly observed the relaxation of charge carriers in perovskite after above-band excitation in the femtosecond and picosecond time ranges.

  16. Mapping of the Local Interstellar Medium using Absorption Line Spectroscopy

    NASA Astrophysics Data System (ADS)

    Penprase, Bryan Edward

    2017-01-01

    Using the Yale SMARTS 1.5-meter telescope at CTIO and the CHIRON spectrograph, we have developed a program for mapping the local interstellar medium using a sample of over 200 newly observed B stars previously unobserved using Na I absorption lines. This sample includes stars that extend out to map beyond the local bubble to 500 pc. The sample has been observed using high resolution absorption lines, and when combined with previously observed stars with Na I and Ca II data provides a more complete picture of the local ISM than previous surveys. The distances to the stars using the new GAIA database also allows for more accurate determination of distances to features in the lcoal ISM, and new maps of the structure of the ISM hav been prepared with the data.

  17. Magnetic dipole moments of {sup 58}Cu and {sup 59}Cu by in-source laser spectroscopy

    SciTech Connect

    Stone, N. J.; Koester, U.; Stone, J. Rikovska; Fedorov, D. V.; Fedoseyev, V. N.; Flanagan, K. T.; Hass, M.; Lakshmi, S.

    2008-06-15

    Online measurements of the magnetic dipole moments and isotope shifts of {sup 58}Cu and {sup 59}Cu by the in-source laser spectroscopy method are reported. The results for the magnetic moments are {mu} ({sup 58}Cu) =+0.52(8) {mu}{sub N},{mu}({sup 59}Cu) =+1.84(3) {mu}{sub N} and for the isotope shifts {delta}{nu}{sup 59,65}=1.72(22) GHz and {delta}{nu}{sup 58,65}=1.99(30) GHz in the transition from the 3d{sup 10}4s {sup 2}S{sub 1/2} ground state to the 3d{sup 10}4p {sup 2}P{sub 1/2} state in Cu I. The magnetic moment of {sup 58}Cu is discussed in the context of the strength of the subshell closure at {sup 56}Ni, additivity rules and large-scale shell model calculations.

  18. Direct and Quantitative Photothermal Absorption Spectroscopy of Individual Particulates

    DTIC Science & Technology

    2013-01-01

    photovoltaics and photo detectors.17,22,23 To predict the absorptive properties of an individual silicon microwire, the well-established Mie theory was... silicon microwire is frequency limiting .43 It was also observed that vibration, thermal drift, and electrical noise were significant below 100 Hz. In...NOTES 14. ABSTRACT 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT Same as Report (SAR) 18. NUMBER OF PAGES 7

  19. Aerosol particle microphotography and glare-spot absorption spectroscopy.

    PubMed

    Arnold, S; Holler, S; Li, J H; Serpengüzel, A; Auffermann, W F; Hill, S C

    1995-04-01

    The relative intensities of glare spots in the image of an electrodynamically trapped aerosol droplet are measured experimentally with an aerosol particle microscope and calculated theoretically. The theoretical calculations are in good agreement with these experiments and indicate that the intensities of these spots are extremely sensitive to the imaginary part of the refractive index. Experimentally, we obtain the molecular absorption spectrum of an impurity within a droplet by recording the spectrum of an individual glare spot produced by broadband illumination.

  20. Characterization of compounds derived from copper-oxamate and imidazolium by X-ray absorption and vibrational spectroscopies

    NASA Astrophysics Data System (ADS)

    do Nascimento, Gustavo M.; do Pim, Walace D.; Reis, Daniella O.; Simões, Tatiana R. G.; Pradie, Noriberto A.; Stumpf, Humberto O.

    2015-05-01

    In this work, compounds derived from copper-oxamate anions (ortho, meta, and para)-phenylenebis (oxamate) and imidazolium cations (1-butyl-3-methylimidazolium) were synthesized. The compounds were characterized by Raman and FTIR spectroscopies and the band assignments were supported by DFT calculations. Strong IR bands from 1610 to 1700 cm-1 dominated the spectra of the complex and can be assigned to νCdbnd O vibrations of the [Cu(opba)]2- anions by the comparison with the DFT data. In opposition to the FTIR spectra, the main vibrational bands in the Raman spectra are observed in the 1350-1600 cm-1 range. All bands in this region are associated to the modified benzene vibrations of the copper-phenylenebis(oxamate) anions. X-ray absorption near edge (XANES) at different energies (NK and Cu L2,3 edges) was also used to probe the interionic interactions. XANES data show that anion-cation interaction in the Cu-oxamate-imidazolium changes the electronic structure around the sbnd Cusbnd Nsbnd sites in the oxamate anion.

  1. [Determination of trace elements in Lophatherum gracile brongn from different habitat by microwave digestion-atomic absorption spectroscopy].

    PubMed

    Yuan, Ke; Xue, Yue-Qin; Gui, Ren-Yi; Sun, Su-Qin; Yin, Ming-Wen

    2010-03-01

    A method of microwave digestion technique was proposed to determine the content of Zn, Fe, Cu, Mn, K, Ca, Mg, Ni, Cd, Pb, Cr, Co, Al, Se and As in Lophatherum gracile brongn of different habitat by atomic absorption spectroscopy. The RSD of the method was between 1.23% and 3.32%, and the recovery rates obtained by standard addition method were between 95.8% and 104.20%. The results of the study indicate that the proposed method has the advantages of simplicity, speediness and sensitivity. It is suitable for the determination of the contents of metal elements in Lophatherum gracile brongn. The experimental results also indicated that different areas' Lophantherum gracile brongn had different trace elements content. The content of trace elements K, Mg, Ca, Fe and Mn beneficial to the human body was rich. The content of the heavy metal trace element Pb in Lophantherum gracile brongn of Hunan province was slightly high. The content of the heavy metal trace element Cu in Lophantherum gracile brongn of Guangdong province and Anhui province is also slightly higher. Beside, the contents of harmful trace heavy metal elements Cd, Cu, Cr, Pb and As in Lophatherum gracile brongn of different habitat are all lower than the limits of Chinese Pharmacopoeia and Green Trade Standard for Importing and Exporting Medicinal Plant and Preparation and National Food Sanitation Standard. These determination results provided the scientific data for further discussing the relationship between the content of trace elements in Lophantherum gracile brongn and the medicine efficacy.

  2. Carbohydrate-based switch-on molecular sensor for Cu(II) in buffer: absorption and fluorescence study of the selective recognition of Cu(II) ions by galactosyl derivatives in HEPES buffer.

    PubMed

    Singhal, Nitin Kumar; Ramanujam, Balaji; Mariappanadar, Vairamani; Rao, Chebrolu Pulla

    2006-08-03

    [graph: see text] 1-(Beta-D-galactopyranosyl-1'-deoxy-1'-iminomethyl)-2-hydroxynaphthalene (L1), possessing an ONO binding core, was found to be selective for Cu2+ ions in N-[2-hydroxyethyl]piperazine-N'-[2-ethanesulfonic acid] buffer, at concentrations < or = 580 ppb, at physiological pH by eliciting switch-on behavior, whereas the other ions, viz., Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Ni2+, Zn2+, and Cd2+, caused no significant change in the fluorescence. Whereas the binding characteristics were ascertained by absorption spectroscopy, the species formed were shown by Q-TOF ES MS.

  3. X-Ray Absorption Spectroscopy Of Thin Foils Irradiated By An Ultra-short Laser Pulse

    SciTech Connect

    Renaudin, P.; Blancard, C.; Cosse, P.; Faussurier, G.; Lecherbourg, L.; Audebert, P.; Bastiani-Ceccotti, S.; Geindre, J.-P.; Shepherd, R.

    2007-08-02

    Point-projection K-shell absorption spectroscopy has been used to measure absorption spectra of transient plasma created by an ultra-short laser pulse. The 1s-2p and 1s-3p absorption lines of weakly ionized aluminum and the 2p-3d absorption lines of bromine were measured over an extended range of densities in a low-temperature regime. Independent plasma characterization was obtained using frequency domain interferometry diagnostic (FDI) that allows the interpretation of the absorption spectra in terms of spectral opacities. Assuming local thermodynamic equilibrium, spectral opacity calculations have been performed using the density and temperature inferred from the FDI diagnostic to compare to the measured absorption spectra. A good agreement is obtained when non-equilibrium effects due to non-stationary atomic physics are negligible at the x-ray probe time.

  4. X-Ray Absorption Spectroscopy Of Thin Foils Irradiated By An Ultra-short Laser Pulse

    NASA Astrophysics Data System (ADS)

    Renaudin, P.; Lecherbourg, L.; Blancard, C.; Cossé, P.; Faussurier, G.; Audebert, P.; Bastiani-Ceccotti, S.; Geindre, J.-P.; Shepherd, R.

    2007-08-01

    Point-projection K-shell absorption spectroscopy has been used to measure absorption spectra of transient plasma created by an ultra-short laser pulse. The 1s-2p and 1s-3p absorption lines of weakly ionized aluminum and the 2p-3d absorption lines of bromine were measured over an extended range of densities in a low-temperature regime. Independent plasma characterization was obtained using frequency domain interferometry diagnostic (FDI) that allows the interpretation of the absorption spectra in terms of spectral opacities. Assuming local thermodynamic equilibrium, spectral opacity calculations have been performed using the density and temperature inferred from the FDI diagnostic to compare to the measured absorption spectra. A good agreement is obtained when non-equilibrium effects due to non-stationary atomic physics are negligible at the x-ray probe time.

  5. [Determination of Cu, Zn and Fe in Huaiyao by suspension sampling-flame atomic absorption spectrometry].

    PubMed

    Wei, Wei; Qu, Ling-bo; Li, Jian-jun; Li, Yan-hong

    2002-10-01

    A new method--suspension sampling technique was applied to flame atomic absorption spectrometry and was successfully used to determine Cu, Zn, Fe in Huaiyao. Then studied the choice of suspension agent and elimination of chemical interference. The huaiyao sample was suspended in agar sol, and injected into air-acetylene flame by using standard addition method to determine Cu, Zn, Fe. Determined results were consistent with those obtained by HNO3 + H2SO4 + HClO4 method. The t-test showed that no obvious difference was found between the two methods. Displacement of HNO3 + H2SO4 + HClO4 method by suspension sampling method for the sample pretreatment is possible. This method is convenient, rapid and accurate.

  6. Non-coincident multi-wavelength emission absorption spectroscopy

    SciTech Connect

    Baumann, L.E.

    1995-02-01

    An analysis is presented of the effect of noncoincident sampling on the measurement of atomic number density and temperature by multiwavelength emission absorption. The assumption is made that the two signals, emission and transmitted lamp, are time resolved but not coincident. The analysis demonstrates the validity of averages of such measurements despite fluctuations in temperature and optical depth. At potassium-seeded MHD conditions, the fluctuations introduce additional uncertainty into measurements of potassium atom number density and temperature but do not significantly bias the average results. Experimental measurements in the CFFF aerodynamic duct with coincident and noncoincident sampling support the analysis.

  7. Absorption spectroscopy of a laboratory photoionized plasma experiment at Z

    SciTech Connect

    Hall, I. M.; Durmaz, T.; Mancini, R. C.; Bailey, J. E.; Rochau, G. A.; Golovkin, I. E.; MacFarlane, J. J.

    2014-03-15

    The Z facility at the Sandia National Laboratories is the most energetic terrestrial source of X-rays and provides an opportunity to produce photoionized plasmas in a relatively well characterised radiation environment. We use detailed atomic-kinetic and spectral simulations to analyze the absorption spectra of a photoionized neon plasma driven by the x-ray flux from a z-pinch. The broadband x-ray flux both photoionizes and backlights the plasma. In particular, we focus on extracting the charge state distribution of the plasma and the characteristics of the radiation field driving the plasma in order to estimate the ionisation parameter.

  8. A GAS TEMPERATURE PROFILE BY INFRARED EMISSION-ABSORPTION SPECTROSCOPY

    NASA Technical Reports Server (NTRS)

    Buchele, D. R.

    1994-01-01

    This computer program calculates the temperature profile of a flame or hot gas. Emphasis is on profiles found in jet engine or rocket engine exhaust streams containing water vapor or carbon dioxide as radiating gases. The temperature profile is assumed to be axisymmetric with a functional form controlled by two variable parameters. The parameters are calculated using measurements of gas radiation at two wavelengths in the infrared spectrum. Infrared emission and absorption measurements at two or more wavelengths provide a method of determining a gas temperature profile along a path through the gas by using a radiation source and receiver located outside the gas stream being measured. This permits simplified spectral scanning of a jet or rocket engine exhaust stream with the instrumentation outside the exhaust gas stream. This program provides an iterative-cyclic computation in which an initial assumed temperature profile is altered in shape until the computed emission and absorption agree, within specified limits, with the actual instrument measurements of emission and absorption. Temperature determination by experimental measurements of emission and absorption at two or more wavelengths is also provided by this program. Additionally, the program provides a technique for selecting the wavelengths to be used for determining the temperature profiles prior to the beginning of the experiment. By using this program feature, the experimenter has a higher probability of selecting wavelengths which will result in accurate temperature profile measurements. This program provides the user with a technique for determining whether this program will be sufficiently accurate for his particular application, as well as providing a means of finding the solution. The input to the program consists of four types of data: (1) computer program control constants, (2) measurements of gas radiance and transmittance at selected wavelengths, (3) tabulations from the literature of gas

  9. Monitoring of monochlorophenols adsorbed on metal (Cu and Zn) supported pumice by infrared spectroscopy.

    PubMed

    Bardakçi, Belgin

    2009-01-01

    The adsorption of monochlorophenols (o-, m-, p-chlorophenol) on pumice, Zn/pumice and Cu/pumice has been studied through Fourier Transform Infrared (FTIR) Spectroscopy in transmission mode. The data show that after Zn and Cu were supported on pumice, the adsorption of 4-chlorophenol is characterized by the bands at 1591, 1494, 1092 and 824 cm(-1). Adsorption process occurred via metal cations on the surface of pumice. Metal oxides on pumice can mediate binding of p-chlorophenol.

  10. X-Ray Absorption Spectroscopy of Uranium Dioxide

    SciTech Connect

    Tobin, J G

    2010-12-10

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

  11. The exciton absorption spectrum of thin CuPb3Br7 superionic conductor films

    NASA Astrophysics Data System (ADS)

    Yunakova, O. N.; Yunakov, N. N.; Kovalenko, E. N.; Kovalenko, V. V.

    2016-09-01

    A study of the absorption spectrum of thin CuPb2Br7 films in the 2-6 eV spectral and 90-500 K temperature ranges. It is shown that the exciton spectrum of the compound is associated with transitions in the lead ion. The temperature dependence of the spectral position and half-width of the low-frequency exciton band contains features associated with phase transitions γ → β (Tc1 = 159 K) and β → α (Tc2 = 434 K) and the disordering of the cation sublattice of the compound in the transition to the superionic state.

  12. Electronic structure differences between H(2)-, Fe-, Co-, and Cu-phthalocyanine highly oriented thin films observed using NEXAFS spectroscopy.

    PubMed

    Willey, T M; Bagge-Hansen, M; Lee, J R I; Call, R; Landt, L; van Buuren, T; Colesniuc, C; Monton, C; Valmianski, I; Schuller, Ivan K

    2013-07-21

    Phthalocyanines, a class of macrocyclic, square planar molecules, are extensively studied as semiconductor materials for chemical sensors, dye-sensitized solar cells, and other applications. In this study, we use angular dependent near-edge x-ray absorption fine structure (NEXAFS) spectroscopy as a quantitative probe of the orientation and electronic structure of H2-, Fe-, Co-, and Cu-phthalocyanine molecular thin films. NEXAFS measurements at both the carbon and nitrogen K-edges reveal that phthalocyanine films deposited on sapphire have upright molecular orientations, while films up to 50 nm thick deposited on gold substrates contain prostrate molecules. Although great similarity is observed in the carbon and nitrogen K-edge NEXAFS spectra recorded for the films composed of prostrate molecules, the H2-phthalocyanine exhibits the cleanest angular dependence due to its purely out-of-plane π* resonances at the absorption onset. In contrast, organometallic-phthalocyanine nitrogen K-edges have a small in-plane resonance superimposed on this π* region that is due to a transition into molecular orbitals interacting with the 3dx(2)-y(2) empty state. NEXAFS spectra recorded at the metal L-edges for the prostrate films reveal dramatic variations in the angular dependence of specific resonances for the Cu-phthalocyanines compared with the Fe-, and Co-phthalocyanines. The Cu L3,2 edge exhibits a strong in-plane resonance, attributed to its b1g empty state with dx(2)-y(2) character at the Cu center. Conversely, the Fe- and Co- phthalocyanine L3,2 edges have strong out-of-plane resonances; these are attributed to transitions into not only b1g (dz(2)) but also eg states with dxz and dyz character at the metal center.

  13. Quasi zero-background tunable diode laser absorption spectroscopy employing a balanced Michelson interferometer.

    PubMed

    Guan, Zuguang; Lewander, Märta; Svanberg, Sune

    2008-12-22

    Tunable diode laser spectroscopy (TDLS) normally observes small fractional absorptive reductions in the light flux. We show, that instead a signal increase on a zero background can be obtained. A Michelson interferometer, which is initially balanced out in destructive interference, is perturbed by gas absorption in one of its arms. Both theoretical analysis and experimental demonstration show that the proposed zero-background TDLS can improve the achievable signal-to-noise ratio.

  14. Calibration of effective optical path length for hollow-waveguide based gas cell using absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Lin; Du, Zhenhui; Li, Jinyi

    2016-10-01

    The Hollow Waveguide (HWG) has emerged as a novel tool to transmit laser power. Owing to its long Effective Optical Path Length (EOPL) within a relatively small volume, it is suitable for the application as a gas cell in concentration measurement by using laser spectroscopy. The measurement of effective optical path length for a hollow waveguide, which possesses the physical length of 284.0 cm, by using Tunable Diode Laser Absorption Spectroscopy (TDLAS) was demonstrated. Carbon dioxide was used as a sample gas for a hollow waveguide calibration. A 2004 nm Distributed Feed-Back (DFB) laser was used as the light source to cover a CO2 line near 2003 nm, which was selected as the target line in the measurement. The reference direct absorption spectroscopy signal was obtained by delivering CO2 into a reference cell possessing a length of 29.4 cm. Then the effective optical path length of HWG was calculated by least-squares fitting the measured absorption signal to the reference absorption signal. The measured EOPL of HWG was 282.8 cm and the repeatability error of effective optical path length was calculated as 0.08 cm. A detection limit of 0.057 cm (with integral time 5 s) characterized by the Allan variance, was derived. The effective optical path length is obtained as the significant parameter to calculate the concentration of gases and it is of great importance to precise measurement of absorption spectroscopy.

  15. Study of atomic clusters in neutron irradiated reactor pressure vessel surveillance samples by extended X-ray absorption fine structure spectroscopy

    NASA Astrophysics Data System (ADS)

    Cammelli, S.; Degueldre, C.; Kuri, G.; Bertsch, J.; Lützenkirchen-Hecht, D.; Frahm, R.

    2009-03-01

    Copper and nickel impurities in nuclear reactor pressure vessel (RPV) steel can form nano-clusters, which have a strong impact on the ductile-brittle transition temperature of the material. Thus, for control purposes and simulation of long irradiation times, surveillance samples are submitted to enhanced neutron irradiation. In this work, surveillance samples from a Swiss nuclear power plant were investigated by extended X-ray absorption fine structure spectroscopy (EXAFS). The density of Cu and Ni atoms determined in the first and second shells around the absorber is affected by the irradiation and temperature. The comparison of the EXAFS data at Cu and Ni K-edges shows that these elements reside in arrangements similar to bcc Fe. However, the EXAFS analysis reveals local irradiation damage in the form of vacancy fractions, which can be determined with a precision of ∼5%. There are indications that the formation of Cu and Ni clusters differs significantly.

  16. Near-infrared absorption spectroscopy of interstellar hydrocarbon grains

    NASA Technical Reports Server (NTRS)

    Pendleton, Y. J.; Sandford, S. A.; Allamandola, L. J.; Tielens, A. G. G. M.; Sellgren, K.

    1994-01-01

    We present new 3600 - 2700/cm (2.8 - 3.7 micrometer) spectra of objects whose extinction is dominated by dust in the diffuse interstellar medium. The observations presented here augment an ongoing study of the organic component of the diffuse interstellar medium. These spectra contain a broad feature centered near 3300/cm (3.0 micrometers) and/or a feature with a more complex profile near 2950/cm (3.4 micrometers), the latter of which is attributed to saturated aliphatic hydrocarbons in interstellar grains and is the primary interest of this paper. As in our earlier work, the similarity of the absorption bands near 2950/cm (3.4 micrometers) along different lines of sight and the correlation of these features with interstellar extinction reveal that the carrier of this band lies in the dust in the diffuse interstellar medium (DISM). At least 2.5% of the cosmic carbon in the local interstellar medium and 4% toward the Galactic center is tied up in the carrier of the 2950/cm (3.4 micrometer) band. The spectral structure of the diffuse dust hydrocarbon C-H stretch absorption features is reasonably similar to UV photolyzed laboratory ice residues and is quite similar to the carbonaceous component of the Murchison meteorite. The similarity between the DISM and the meteoritic spectrum suggests that some of the interstellar material originally incorporated into the solar nebula may have survived relatively untouched in primitive solar system bodies. Comparisons of the DISM spectrum to hydrogenated amorphous carbon and quenched carbonaceous composite are also presented. The A(sub V)/tau ratio for the 2950/cm (3.4 micrometer) feature is lower toward the Galactic center than toward sources in the local solar neighborhood (approximately 150 for the Galactic center sources vs. approximately 250 for the local ISM sources). A similar trend has been observed previously for silicates in the diffuse medium by Roche & Aitken, suggesting that (1) the silicate and carbonaceous

  17. Atomic structure of PtCu nanoparticles in PtCu/C catalysts from EXAFS spectroscopy data

    NASA Astrophysics Data System (ADS)

    Srabionyan, V. V.; Pryadchenko, V. V.; Kurzin, A. A.; Belenov, S. V.; Avakyan, L. A.; Guterman, V. E.; Bugaev, L. A.

    2016-04-01

    Deposited electrocatalysts with different distributions of components in PtCu bimetallic nanoparticles involved in their composition were synthesized by simultaneous and sequential reduction of Cu(2+) and Pt(IV) in a carbon suspension. The dependence of the atomic structure of PtCu nanoparticles on the synthesis conditions and the degree of influence of post-treatment was established from analysis of the changes in Fourier transforms of the experimental Pt and Cu EXAFS spectra, as well as the structural parameters obtained by their fitting before and after the treatment of the materials in an acid solution. A technique was proposed for visualizing the atomic structure of synthesized bimetallic nanoparticles. This technique made it possible to determine the character of the distribution of the components over the nanoparticle volume in accordance with the component composition and local atomic structure parameters determined from EXAFS spectroscopy and to obtain the visualization of the distribution of the components in PtCu nanoparticles synthesized by the aforementioned methods.

  18. Total absorption spectroscopy of N = 51 nucleus 85Se

    NASA Astrophysics Data System (ADS)

    Goetz, K. C.; Grzywacz, R. K.; Rykaczewski, K. P.; Karny, M.; Fialkowska, A.; Wolinska-Cichocka, M.; Rasco, B. C.; Zganjar, E. F.; Johnson, J. W.; Gross, C. J.

    2014-09-01

    An experimental campaign utilizing the Modular Total Absorption Spectrometer (MTAS) was conducted at the HRIBF facility in January of 2012. The campaign studied 22 isotopes, many of which were identified as the highest priority for decay heat analysis during a nuclear fuel cycle, see the report by the OECD-IAEA Nuclear Energy Agency in 2007. The case of 85Se will be discussed. 85Se is a Z = 34, N = 51 nucleus with the valence neutron located in the positive parity sd single particle state. Therefore, its decay properties are determined by interplay between first forbidden decays of the valence neutron and Gamow-Teller decay of a 78Ni core. Analysis of the data obtained during the January 2012 run indicates a significant increase of the beta strength function when compared with previous measurements, see Ref..

  19. Monitoring spacecraft atmosphere contaminants by laser absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Steinfeld, J. I.

    1976-01-01

    Laser-based spectrophotometric methods which have been proposed for the detection of trace concentrations of gaseous contaminants include Raman backscattering (LIDAR) and passive radiometry (LOPAIR). Remote sensing techniques using laser spectrometry are presented and in particular a simple long-path laser absorption method (LOLA), which is capable of resolving complex mixtures of closely related trace contaminants at ppm levels is discussed. A number of species were selected for study which are representative of those most likely to accumulate in closed environments, such as submarines or long-duration manned space flights. Computer programs were developed which will permit a real-time analysis of the monitored atmosphere. Estimates of the dynamic range of this monitoring technique for various system configurations, and comparison with other methods of analysis, are given.

  20. VUV Absorption Spectroscopy of Planetary Molecules at Low Temperature

    NASA Astrophysics Data System (ADS)

    Jolly, A.; Benilan, Y.; Ferradaz, T.; Fray, N.; Schwell, M.

    2005-08-01

    A critical review of the available absorption coefficient in the vacuum ultraviolet domain (100-200 nm) has lead us to undertake new measurements at the Berlin synchrotron facility (BESSY). Many of the molecules detected in planetary atmospheres and in particular those which need to be synthesized in the laboratory, have never been measured at low temperature. The first molecules that we have studied are HCN, HC3N and C2N2. New absorption coefficients have been obtained including first spectra at low temperature (220 K). The effect of the temperature on the spectra can then be discussed in view of the application to the much colder atmosphere of Titan. The nitriles studied here play an important role in the chemistry taking place in Titan's atmosphere and are believed to be responsible for the formation of Titan's aerosols. From our measurements, we have calculated the photodissociation rates for each molecule which are essential to include in any photochemical model. This is true for Titan but also for cometary and interstellar medium models. To describe the formation of a solid phase, the models also need to include photodissociation rates for larger molecules which have not been detected yet. This will now be possible for HC5N since the first spectra of this molecule has been obtained by our team. Furthermore, the first stellar occultation measurement of Titan's atmosphere by the UV spectrometer (UVIS) on board the CASSINI spacecraft has permitted the detection of species not observed before in this wavelength domain. But it has also shown a lack of experimental data in this domain. So far, the model is not able to reproduce the observed spectral feature. C4H2 is the molecule that should explain some of the observed feature but absolute cross sections are missing. We will present our latest experimental measurements on this molecule.

  1. Difference Between Far-Infrared Photoconductivity Spectroscopy and Absorption Spectroscopy: Theoretical Evidence of the Electron Reservoir Mechanism

    NASA Astrophysics Data System (ADS)

    Toyoda, Tadashi; Fujita, Maho; Uchida, Tomohisa; Hiraiwa, Nobuyoshi; Fukuda, Taturo; Koizumi, Hideki; Zhang, Chao

    2013-08-01

    The intriguing difference between far-infrared photoconductivity spectroscopy and absorption spectroscopy in the measurement of the magnetoplasmon frequency in GaAs quantum wells reported by Holland et al. [Phys. Rev. Lett. 93, 186804 (2004)] remains unexplained to date. This Letter provides a consistent mechanism to solve this puzzle. The mechanism is based on the electron reservoir model for the integer quantum Hall effect in graphene [Phys. Lett. A 376, 616 (2012)]. We predict sharp kinks to appear in the magnetic induction dependence of the magnetoplasmon frequency at very low temperatures such as 14 mK in the same GaAs quantum well sample used by Holland et al..

  2. Time-Resolved Broadband Cavity-Enhanced Absorption Spectroscopy behind Shock Waves.

    PubMed

    Matsugi, Akira; Shiina, Hiroumi; Oguchi, Tatsuo; Takahashi, Kazuo

    2016-04-07

    A fast and sensitive broadband absorption technique for measurements of high-temperature chemical kinetics and spectroscopy has been developed by applying broadband cavity-enhanced absorption spectroscopy (BBCEAS) in a shock tube. The developed method has effective absorption path lengths of 60-200 cm, or cavity enhancement factors of 12-40, over a wavelength range of 280-420 nm, and is capable of simultaneously recording absorption time profiles over an ∼32 nm spectral bandpass in a single experiment with temporal and spectral resolutions of 5 μs and 2 nm, respectively. The accuracy of the kinetic and spectroscopic measurements was examined by investigating high-temperature reactions and absorption spectra of formaldehyde behind reflected shock waves using 1,3,5-trioxane as a precursor. The rate constants obtained for the thermal decomposition reactions of 1,3,5-trioxane (to three formaldehyde molecules) and formaldehyde (to HCO + H) agreed well with the literature data. High-temperature absorption cross sections of formaldehyde between 280 and 410 nm have been determined at the post-reflected-shock temperatures of 955, 1265, and 1708 K. The results demonstrate the applicability of the BBCEAS technique to time- and wavelength-resolved sensitive absorption measurements at high temperatures.

  3. [High-order derivative spectroscopy of infrared absorption spectra of the reaction centers from Rhodobacter sphaeroides].

    PubMed

    2005-01-01

    The infrared absorption spectra of reduced and chemically oxidized reaction center preparations from the purple bacterium Rhodobacter sphaeroides were investigated by means of high-order derivative spectroscopy. The model Gaussian band with a maximum at 810 nm and a half-band of 15 nm found in the absorption spectrum of the reduced reaction center preparation is eliminated after the oxidation of photoactive bacteriochlorophyll dimer (P). This band was related to the absorption of the P(+)y excitonic band of P. On the basis of experimental results, it was concluded that the bleaching of the P(+)y absorption band at 810 nm in the oxidized reaction center preparations gives the main contribution to the blue shift of the 800 nm absorption band of Rb. sphaeroides reaction centers.

  4. Rapid analysis with transversely heated graphite furnace atomic absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Zhang; Carnrick, Glen; Slavin, Walter

    1993-09-01

    A new graphite furnace instrument using a transversely heated furnace tube with a longitudinal Zeeman correction system has been specifically designed to provide more nearly stabilized temperature platform furnace (STPF) conditions than previous furnace systems. Because there are no cold ends on this furnace tube on which to condense analyte and matrix materials, the vapor phase interferences are expected to be smaller. Also, the cooldown step can be avoided, thus saving time. This instrument permits the delivery of sample into a furnace already heated. The delivery rate of the autosampler can be slowed. These opportunities make it feasible for the sample to be dry on the platform by the time the delivery is complete. Several elements of environmental significance were chosen for test: As, Pb, Se, Tl, Cd, Cu, Cr and V. In almost all of these situations, the analyte was fully recovered without using a matrix modifier or a pyrolysis step. However, As and Pb in urine and As in sediment required a modifier and pyrolysis step for accurate results. A new fast furnace protocol was developed to accommodate use of a matrix modifier and this new protocol was successful for Pb and As in these matrices. All the procedures required less than 1 min total cycle times and produced results in agreement with certified values. This is in contrast with conventional methods which require 2-3 min per firing. These results confirm that graphite furnace methods can be accomplished with a throughput greater than 60 determinations per hour, and eventually, it may be possible to increase this rate beyond 100 determinations per hour.

  5. Enhanced photosensitivity of InGaZnO-TFT with a CuPc light absorption layer

    NASA Astrophysics Data System (ADS)

    Li, Jun; Zhou, Fan; Lin, Hua-Ping; Zhu, Wen-Qing; Zhang, Jian-Hua; Jiang, Xue-Yin; Zhang, Zhi-Lin

    2012-04-01

    A copper phthalocyanine (CuPc) organic semiconductor is capped onto an amorphous indium-gallium-zinc-oxide (InGaZnO) thin film transistor (TFT) to enhance the photosensitivity of InGaZnO-TFT. The CuPc organic semiconductor is served as a light absorption layer and forms a p-n junction with the InGaZnO film. After 60 s white light illumination, light responsivity (R) of InGaZnO-TFT with a CuPc light absorption layer reaches a value of 148.5 A/W at a gate-source voltage (VGS) of 20 V, which is much larger than that (31.2 A/W) of the conventional InGaZnO-TFT. The results are attributed to the following mechanism. First, a CuPc layer is employed as the light absorption layer. Second, CuPc/InGaZnO p-n junction enables the injection of electron into InGaZnO film. Our results indicate that using CuPc as light absorption layer is an effective approach to improve the photosensitivity of InGaZnO-TFT.

  6. Observation of confinement effects through liner and nonlinear absorption spectroscopy in cuprous oxide

    NASA Astrophysics Data System (ADS)

    Sekhar, H.; Rakesh Kumar, Y.; Narayana Rao, D.

    2015-02-01

    Cuprous oxide nano clusters, micro cubes and micro particles were successfully synthesized by reducing copper (II) salt with ascorbic acid in the presence of sodium hydroxide via a co-precipitation method. The X-ray diffraction studies revealed the formation of pure single phase cubic. Raman spectrum shows the inevitable presence of CuO on the surface of the Cu2O powders which may have an impact on the stability of the phase. Transmission electron microscopy (TEM) data revealed that the morphology evolves from nanoclusters to micro cubes and micro particles by increasing the concentration of NaOH. Linear optical measurements show that the absorption peak maximum shifts towards red with changing morphology from nano clusters to micro cubes and micro particles. The nonlinear optical properties were studied using open aperture Z-scan technique with 532 nm, 6 ns laser pulses. Samples exhibited saturable as well as reverse saturable absorption. The results show that the transition from SA to RSA is ascribed to excited-state absorption (ESA) induced by two-photon absorption (TPA) process. Due to confinement effects (enhanced band gap) we observed enhanced nonlinear absorption coefficient (βeff) in the case of nano-clusters compared to their micro-cubes and micro-particles.

  7. Uv Spectroscopy on Gas Phase Cu(I)-BIPYRIDYL Complexes

    NASA Astrophysics Data System (ADS)

    Xu, Shuang; Christopher, Casey; Weber, J. Mathias

    2015-06-01

    Transition metal complexes with bipyridine ligands are of great interest in metal-organic chemistry, since they are prototypes for many applications in photochemistry and homogeneous catalysis. Under-coordinated bipyridyl complexes are elusive species in the condensed phase, and the ligand-induced changes in electronic structure are of fundamental interest. We present UV photodissociation spectra of mass-selected monocationic copper(I)-bipyridyl complexes [bpy-Cu-L]+ with different ligands (L = H2O, D2, N2, MeOH, Cl). Complexes were prepared via electrospray ionization of copper/bipyridine solutions followed by accumulation and buffer gas cooling in a cryogenic Paul trap. In addition, we show spectra of similar species based on copper oxide, [bpy-CuO-L]+.

  8. Cu spectroscopy from a z-pinch plasma

    NASA Astrophysics Data System (ADS)

    Dasgupta, Arati; Clark, Robert W.; Ouart, Nicholas D.; Giuliani, John L.

    2014-11-01

    Recent improvements in diagnostic techniques at the Sandia Laboratories Z accelerator have facilitated the production of very detailed x-ray spectral data in the range of 1-20 keV. The high energy density plasma produced in a z-pinch is inherently in non-local thermodynamic equilibrium (NLTE). We therefore employ a NLTE collisional equilibrium model in a 1D radiation-magnetohydrodynamics code to simulate the dynamics of the pinch and to generate synthetic emission spectra. We will discuss the effects on radiation spectra and the yields of using simplifying assumptions in the atomic model and/or the radiation transport. X-ray emission from moderately high atomic number plasmas such as Fe and Cu wire array implosions often include substantial 2p-1s K-α radiation. In a z-pinch plasma, K-shell vacancies can be produced by e-beams, hot electrons at the tail of a Maxwellian and also by photopumping from energetic photons emitted near the pinch axis. In the Z-1975 Cu wire implosion, K-α lines from various ionization stages of Cu as well as from minor constituents including Ni, Fe and Cr are observed. We have calculated K-α production within a full simulation of a Cu implosion, including contributions from energetic electrons and photons. Photo-pumped K-α emission can be distinguished from that produced by e-beams; K-shell vacancies will be produced near the axis for a beam, and near the outer edge of the plasma for energetic photons. Spectroscopic modeling of these K-α lines as well as K- and L-shell emission from valence electrons can provide quantitative diagnostics of plasma parameters. This methodology can also be used to investigate K-α emission from other laboratory experiments such as EBIT and astrophysical plasmas.

  9. [Near infrared Cavity enhanced absorption spectroscopy study of NO2O].

    PubMed

    Wu, Zhi-wei; Dong, Yan-ting; Zhou, Wei-dong

    2014-08-01

    Using a tunable near infrared external cavity diode laser and a 650 mm long high finesse optical cavity consisting of two highly reflective (R=99.97% at 6561.39 cm(-1)) plan-concave mirrors of curvature radius approximately 1000 mm, a cavity enhanced absorption spectroscopy (CEAS) system was made. The absorption spectra centered at 6561.39 cm(-1) of pure N2O gas and gas mixtures of N2O and N2 were recorded. According to the absorption of N2O at 6561.39 cm(-1) in the cavity, the measured effective absorption path was about 1460 km. The spectra line intensity and line-width of N2O centered at 6561.39 cm(-1) were carefully studied. The relationship between the line-width of absorption spectra and the gas pressure was derived. The pressure broadening parameter of N2 gas for NO2O line centered at 6 561. 39 cm(-1) was deduced and given a value of approximately (0.114 +/- 0.004) cm(-1) x atm(-1). The possibility to detect trace N2O gas in mixture using this CEAS system was investigated. By recording the ab- sorption spectra of N2O gas mixtures at different concentration, the relationship between the line intensity and gas concentration was derived. The minimum detectable absorption was found to be 2.34 x 10(-7) cm(-1) using this cavity enhanced absorption spectroscopy system. And te measurement precision in terms of relative standard deviation (RSD) for N2O is approximately 1.73%, indicating the possibility of using the cavity enhanced absorption spectroscopy system for micro gas N2O analysis in the future.

  10. Status of the X-Ray Absorption Spectroscopy (XAS) Beamline at the Australian Synchrotron

    NASA Astrophysics Data System (ADS)

    Glover, C.; McKinlay, J.; Clift, M.; Barg, B.; Boldeman, J.; Ridgway, M.; Foran, G.; Garret, R.; Lay, P.; Broadbent, A.

    2007-02-01

    We present herein the current status of the X-ray Absorption Spectroscopy (XAS) Beamline at the 3 GeV Australian Synchrotron. The optical design and performance, details of the insertion device (Wiggler), end station capabilities and construction and commissioning timeline are given.

  11. Synchrotron radiation based Mössbauer absorption spectroscopy of various nuclides

    NASA Astrophysics Data System (ADS)

    Masuda, Ryo; Kobayashi, Yasuhiro; Kitao, Shinji; Kurokuzu, Masayuki; Saito, Makina; Yoda, Yoshitaka; Mitsui, Takaya; Seto, Makoto

    2016-12-01

    Synchrotron-radiation (SR) based Mössbauer absorption spectroscopy of various nuclides is reviewed. The details of the measuring system and analysis method are described. Especially, the following two advantages of the current system are described: the detection of internal conversion electrons and the close distance between the energy standard scatterer and the detector. Both of these advantages yield the enhancement of the counting rate and reduction of the measuring time. Furthermore, SR-based Mössbauer absorption spectroscopy of 40K, 151Eu, and 174Yb is introduced to show the wide applicability of this method. In addition to these three nuclides, SR-based Mössbauer absorption spectroscopy of 61Ni, 73Ge, 119Sn, 125Te, 127I, 149Sm, and 189Os has been performed. We continue to develop the method to increase available nuclides and to increase its ease of use. The complementary relation between the time-domain method using SR, such as nuclear forward scattering and the energy-domain methods such as SR-based Mössbauer absorption spectroscopy is also noted.

  12. Circuit Board Analysis for Lead by Atomic Absorption Spectroscopy in a Course for Nonscience Majors

    ERIC Educational Resources Information Center

    Weidenhammer, Jeffrey D.

    2007-01-01

    A circuit board analysis of the atomic absorption spectroscopy, which is used to measure lead content in a course for nonscience majors, is being presented. The experiment can also be used to explain the potential environmental hazards of unsafe disposal of various used electronic equipments.

  13. DETERMINING BERYLLIUM IN DRINKING WATER BY GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROSCOPY

    EPA Science Inventory

    A direct graphite furnace atomic absorption spectroscopy method for the analysis of beryllium in drinking water has been derived from a method for determining beryllium in urine. Ammonium phosphomolybdate and ascorbic acid were employed as matrix modifiers. The matrix modifiers s...

  14. Attosecond Transient Absorption Spectroscopy of doubly-excited states in helium

    NASA Astrophysics Data System (ADS)

    Argenti, Luca; Ott, Christian; Pfeifer, Thomas; Martín, Fernando

    2014-04-01

    Theoretical calculations of the XUV attosecond transient absorption spectrum (ATAS) of helium in the doubly-excited state region reproduce recent high-precision measurements, reveal novel means of controlling the dynamics of transiently-bound electronic wavepackets in intense laser fields, and indicates a possible extension of 2D-spectroscopies to the XUV range.

  15. Determination of sub microgram amounts of selenium in rocks by atomic-absorption spectroscopy.

    PubMed

    Golembeski, T

    1975-06-01

    Atomic-absorption spectroscopy was used to determine trace amounts of selenium accurately in U.S. Geological Survey standard rocks, GSP-1, W-1 and BCR-1. The results obtained were compared with those obtained by neutron-activation analysis and excellent agreement was found; in addition, the selenium:sulphur ratio was calculated and agreed with results obtained by other workers.

  16. Absorption and Scattering Coefficients: A Biophysical-Chemistry Experiment Using Reflectance Spectroscopy

    ERIC Educational Resources Information Center

    Cordon, Gabriela B.; Lagorio, M. Gabriela

    2007-01-01

    A biophysical-chemistry experiment, based on the reflectance spectroscopy for calculating the absorption and scattering coefficients of leaves is described. The results show that different plants species exhibit different values for both the coefficients because of their different pigment composition.

  17. LISA: the Italian CRG beamline for x-ray Absorption Spectroscopy at ESRF

    NASA Astrophysics Data System (ADS)

    d'Acapito, F.; Trapananti, A.; Puri, A.

    2016-05-01

    LISA is the acronym of Linea Italiana per la Spettroscopia di Assorbimento di raggi X (Italian beamline for X-ray Absorption Spectroscopy) and is the upgrade of the former GILDA beamline installed on the BM08 bending magnet port of European Synchrotron Radiation Facility (ESRF). Within this contribution a full description of the project is provided.

  18. Toward omnidirectional light absorption by plasmonic effect for high-efficiency flexible nonvacuum Cu(In,Ga)Se2 thin film solar cells.

    PubMed

    Chen, Shih-Chen; Chen, Yi-Ju; Chen, Wei Ting; Yen, Yu-Ting; Kao, Tsung Sheng; Chuang, Tsung-Yeh; Liao, Yu-Kuang; Wu, Kaung-Hsiung; Yabushita, Atsushi; Hsieh, Tung-Po; Charlton, Martin D B; Tsai, Din Ping; Kuo, Hao-Chung; Chueh, Yu-Lun

    2014-09-23

    We have successfully demonstrated a great advantage of plasmonic Au nanoparticles for efficient enhancement of Cu(In,Ga)Se2(CIGS) flexible photovoltaic devices. The incorporation of Au NPs can eliminate obstacles in the way of developing ink-printing CIGS flexible thin film photovoltaics (TFPV), such as poor absorption at wavelengths in the high intensity region of solar spectrum, and that occurs significantly at large incident angle of solar irradiation. The enhancement of external quantum efficiency and photocurrent have been systematically analyzed via the calculated electromagnetic field distribution. Finally, the major benefits of the localized surface plasmon resonances (LSPR) in visible wavelength have been investigated by ultrabroadband pump-probe spectroscopy, providing a solid evidence on the strong absorption and reduction of surface recombination that increases electron-hole generation and improves the carrier transportation in the vicinity of pn-juction.

  19. Flash-induced absorption spectroscopy studies of copper interaction with photosystem II in higher plants.

    PubMed

    Schröder, W P; Arellano, J B; Bittner, T; Barón, M; Eckert, H J; Renger, G

    1994-12-30

    Measurements of flash-induced absorption changes at 325, 436, and 830 nm and of oxygen evolution were performed in order to analyze in detail the inhibition of photosystem II (PS II) by Cu(II) in PS II membrane fragments from spinach. (a) The kinetics of P680+ reduction become markedly slower in the presence of 100 microM CuSO4. (b) The CuSO4-induced kinetics of P680+ reduction are dominated by a 140-160-microsecond decay. (c) The extent of these 140-160-microsecond kinetics, normalized to the overall decay, remains virtually unaffected by addition of the exogenous PS II donor, NH2OH. (d) In thoroughly dark-adapted samples the CuSO4-induced 140-160-microsecond kinetics are already observed after the first flash and remain unchanged by a train of excitation flashes. (e) The extent of P680+ and QA- formation under repetitive flash excitation is not diminished by addition of 100 microM CuSO4. (f) The induction of microsecond kinetics of P680+ reduction at the expense of ns kinetics and the inhibition of the saturation rate of oxygen evolution exhibit the same dependence on CuSO4 concentration. (g) CuSO4 also transforms the 10-20-microsecond reduction of P680+ by TyrZ in Tris-washed PS II membrane fragments into 140-160-microsecond kinetics without any effect on the extent of flash-induced P680+ formation. These results unambiguously show that Cu(II) does not affect the charge separation (P680+QA-), but instead specifically modifies TyrZ and/or its micro environment so that the electron transfer to P680+ becomes blocked.

  20. X-ray absorption spectroscopy on the basis of hybrid X-pinch radiation

    SciTech Connect

    Tilikin, I. N. Shelkovenko, T. A.; Pikuz, S. A.; Knapp, P. F.; Hammer, D. A.

    2015-07-15

    Results of experiments on X-ray absorption spectroscopy carried out at the BIN (270 kA, 100 ns) and XP (450 kA, 45 ns) facilities are presented. Continuum radiation of a Mo hybrid X-pinch was used as probing radiation, against which absorption lines of the plasma of exploded Al wires placed in the return current circuit of a hybrid X-pinch, as well as in a two- and four-wire array, were observed. The experiments have demonstrated that the radiation of a hybrid X-pinch hot spot can be used as probing radiation for X-ray absorption spectroscopy and that, in many parameters, such a source surpasses those on the basis of laser-produced plasma. The plasma parameters in arrays made of two and four Al wires were studied experimentally.

  1. Spectrum sensing of trace C(2)H(2) detection in differential optical absorption spectroscopy technique.

    PubMed

    Chen, Xi; Dong, Xiaopeng

    2014-09-10

    An improved algorithm for trace C(2)H(2) detection is presented in this paper. The trace concentration is accurately calculated by focusing on the absorption spectrum from the frequency domain perspective. The advantage of the absorption spectroscopy frequency domain algorithm is its anti-interference capability. First, the influence of the background noise on the minimum detectable concentration is greatly reduced. Second, the time-consuming preprocess of spectra calibration in the differential optical absorption spectroscopy technique is skipped. Experimental results showed the detection limit of 50 ppm is achieved at a lightpath length of 0.2 m. This algorithm can be used in real-time spectrum analysis with high accuracy.

  2. X-ray absorption spectroscopy on the basis of hybrid X-pinch radiation

    NASA Astrophysics Data System (ADS)

    Tilikin, I. N.; Shelkovenko, T. A.; Pikuz, S. A.; Knapp, P. F.; Hammer, D. A.

    2015-07-01

    Results of experiments on X-ray absorption spectroscopy carried out at the BIN (270 kA, 100 ns) and XP (450 kA, 45 ns) facilities are presented. Continuum radiation of a Mo hybrid X-pinch was used as probing radiation, against which absorption lines of the plasma of exploded Al wires placed in the return current circuit of a hybrid X-pinch, as well as in a two- and four-wire array, were observed. The experiments have demonstrated that the radiation of a hybrid X-pinch hot spot can be used as probing radiation for X-ray absorption spectroscopy and that, in many parameters, such a source surpasses those on the basis of laser-produced plasma. The plasma parameters in arrays made of two and four Al wires were studied experimentally.

  3. Photodissociation spectroscopy of the anionic copper nitrate association complex Cu(NO3)3(-).

    PubMed

    Kaufman, Sydney H; Weber, J Mathias

    2014-10-16

    We report the UV photodissociation spectrum of mass-selected Cu(NO3)(3)(-) ions at photon energies between 3.0 and 5.6 eV. Upon photon absorption, Cu(NO3)(3)(-) undergoes reductive dissociation losing neutral NO3 and resulting in the formation of Cu(NO3)(2)(-). The experimental results are discussed and interpreted with the aid of quantum-chemical calculations. The parent ion is calculated to have C2 symmetry with a strongly distorted octahedral coordination around the Cu ion. Time-dependent density functional theory is used to describe the accessible electronic transitions, which can be characterized as ligand-to-metal charge transfer transitions from the nitrate ligands to the copper ion.

  4. Reduced Graphene Oxide-Cu0.5Ni0.5Fe2O4-Polyaniline Nanocomposite: Preparation, Characterization and Microwave Absorption Properties

    NASA Astrophysics Data System (ADS)

    Dat, Tran Quang; Ha, Nguyen Tran; Hung, Do Quoc

    2017-02-01

    Reduced graphene oxide-Cu0.5Ni0.5Fe2O4-polyaniline nanocomposite (RGO-CNF-PANI) was synthesized by a three-step method. The morphology, structure and magnetic properties of composite samples were characterized by scanning electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy (RAMAN) and vibrating sample magnetometer. It was found that reduced graphene oxide was exfoliated and decorated homogeneously with ferrite nanoparticles having diameters between 11 nm and 21 nm. The polyaniline was coated by an in situ chemical oxidation polymerization. The measurement of magnetic properties found the remanence (Mr) and coercive field (Hc) were near zero, indicating that the obtained material was superparamagnetic. The microwave measurements found that the nanocomposite exhibited a good absorption property with the optimum matching thickness of 3 mm in the frequency of 8-12 GHz. The value of the maximum RL was -40.7 dB at 9.8 GHz.

  5. [Influence of silver/silicon dioxide on infrared absorption spectroscopy of sodium nitrate].

    PubMed

    Yang, Shi-Ling; Yue, Li; Jia, Zhi-Jun

    2014-09-01

    Quickly detecting of ocean nutrient was one important task in marine pollution monitoring. We discovered the application of surface-enhanced infrared absorption spectroscopy in the detection of ocean nutrient through researching the evaporation of sodium nitrate solution. The silicon dioxide (SiO2) with highly dispersion was prepared by Stober method, The silver/silica (Ag/SiO2) composite materials were prepared by mixing ammonia solution and silicon dioxide aqueous solution. Three kinds of composite materials with different surface morphology were fabricated through optimizing the experimental parameter and changing the experimental process. The surface morphology, crystal orientation and surface plasmon resonance were investigated by means of the scanning electronic microscope (SEM), X-ray diffraction (XRD), UV-Visible absorption spectrum and infrared ab- sorption spectroscopy. The SEM images showed that the sample A was purified SiO2, sample B and sample C were mixture of silver nanoparticle and silicon dioxide, while sample D was completed nanoshell structure. The absorption spectroscopy showed that there was surface plasmon resonance in the UV-visible region, while there was possibility of surface plasmon resonance in the Infrared absorption region. The effect of Ag/SiO2 composite material on the infrared absorption spectra of sodium nitrite solution was investigated through systematically analyzing the infrared absorption spectroscopy of sodium nitrate solution during its evaporation, i. e. the peak integration area of nitrate and the peak integration area of water molecule. The experimental results show that the integration area of nitrate was enhanced greatly during the evaporation process while the integration area of water molecule decreased continuously. The integration area of nitrate comes from the anti-symmetric stretch vibration and the enhancement of the vibration is attributed to the interface effect of Ag/SiO2 which is consistent with Jensen T

  6. Pharmaceutical applications of separation of absorption and scattering in near-infrared spectroscopy (NIRS).

    PubMed

    Shi, Zhenqi; Anderson, Carl A

    2010-12-01

    The number of near-infrared (NIR) spectroscopic applications in the pharmaceutical sciences has grown significantly in the last decade. Despite its widespread application, the fundamental interaction between NIR radiation and pharmaceutical materials is often not mechanistically well understood. Separation of absorption and scattering in near-infrared spectroscopy (NIRS) is intended to extract absorption and scattering spectra (i.e., absorption and reduced scattering coefficients) from reflectance/transmittance NIR measurements. The purpose of the separation is twofold: (1) to enhance the understanding of the individual roles played by absorption and scattering in NIRS and (2) to apply the separated absorption and scattering spectra for practical spectroscopic analyses. This review paper surveys the multiple techniques reported to date on the separation of NIR absorption and scattering within pharmaceutical applications, focusing on the instrumentations, mathematical approaches used to separate absorption and scattering and related pharmaceutical applications. This literature review is expected to enhance the understanding and thereby the utility of NIRS in pharmaceutical science. Further, the measurement and subsequent understanding of the separation of absorption and scattering is expected to increase not only the number of NIRS applications, but also their robustness.

  7. Determination of Calcium in Cereal with Flame Atomic Absorption Spectroscopy: An Experiment for a Quantitative Methods of Analysis Course

    ERIC Educational Resources Information Center

    Bazzi, Ali; Kreuz, Bette; Fischer, Jeffrey

    2004-01-01

    An experiment for determination of calcium in cereal using two-increment standard addition method in conjunction with flame atomic absorption spectroscopy (FAAS) is demonstrated. The experiment is intended to introduce students to the principles of atomic absorption spectroscopy giving them hands on experience using quantitative methods of…

  8. Structural Investigations of CuO-B2O3-Bi2O3 Glasses by Means of EPR and Ft-Ir Spectroscopies

    NASA Astrophysics Data System (ADS)

    Ardelean, I.; Cora, Simona; Ciceo-Lucacel, Raluca

    EPR and FT-IR spectroscopy have been used to investigate the B2O3-Bi2O3 glass matrix containing CuO in order to obtain more information about the local structure of these glasses. The EPR absorption spectra revealed the presence in the glass structure of the Cu2+ ions in axially distorted octahedral environments. No superexchange interaction of Cu2+ was detected. In the samples with x≥5 mol%, mixed valence states of copper ions were revealed. The FT-IR measurements indicate the presence in the glass structure of the distorted [BiO6] polyhedra, tri- and tetra-borate units (BO3, BO4) and its dependence by the copper content.

  9. Recovery of acetylene absorption line profile basing on tunable diode laser spectroscopy with intensity modulation and photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Li; Thursby, Graham; Stewart, George; Arsad, Norhana; Uttamchandani, Deepak; Culshaw, Brian; Wang, Yiding

    2010-04-01

    A novel and direct absorption line recovery technique based on tunable diode laser spectroscopy with intensity modulation is presented. Photoacoustic spectroscopy is applied for high sensitivity, zero background and efficient acoustic enhancement at a low modulation frequency. A micro-electromechanical systems (MEMS) mirror driven by an electrothermal actuator is used for generating laser intensity modulation (without wavelength modulation) through the external reflection. The MEMS mirror with 10μm thick structure material layer and 100nm thick gold coating is formed as a circular mirror of 2mm diameter attached to an electrothermal actuator and is fabricated on a chip that is wire-bonded and placed on a PCB holder. Low modulation frequency is adopted (since the resonant frequencies of the photoacoustic gas cell and the electrothermal actuator are different) and intrinsic high signal amplitude characteristics in low frequency region achieved from measured frequency responses for the MEMS mirror and the gas cell. Based on the property of photoacoustic spectroscopy and Beer's law that detectable sensitivity is a function of input laser intensity in the case of constant gas concentration and laser path length, a Keopsys erbium doped fibre amplifier (EDFA) with opto-communication C band and high output power up to 1W is chosen to increase the laser power. High modulation depth is achieved through adjusting the MEMS mirror's reflection position and driving voltage. In order to scan through the target gas absorption line, the temperature swept method is adopted for the tunable distributed feed-back (DFB) diode laser working at 1535nm that accesses the near-infrared vibration-rotation spectrum of acetylene. The profile of acetylene P17 absorption line at 1535.39nm is recovered ideally for ~100 parts-per-million (ppm) acetylene balanced by nitrogen. The experimental signal to noise ratio (SNR) of absorption line recovery for 500mW laser power was ~80 and hence the

  10. Photocarrier dynamics in anatase TiO{sub 2} investigated by pump-probe absorption spectroscopy

    SciTech Connect

    Matsuzaki, H. E-mail: okamotoh@k.u-tokyo.ac.jp; Matsui, Y.; Uchida, R.; Yada, H.; Terashige, T.; Li, B.-S.; Sawa, A.; Kawasaki, M.; Tokura, Y.; Okamoto, H. E-mail: okamotoh@k.u-tokyo.ac.jp

    2014-02-07

    The dynamics of photogenerated electrons and holes in undoped anatase TiO{sub 2} were studied by femtosecond absorption spectroscopy from the visible to mid-infrared region (0.1–2.0 eV). The transient absorption spectra exhibited clear metallic responses, which were well reproduced by a simple Drude model. No mid-gap absorptions originating from photocarrier localization were observed. The reduced optical mass of the photocarriers obtained from the Drude-model analysis is comparable to theoretically expected one. These results demonstrate that both photogenerated holes and electrons act as mobile carriers in anatase TiO{sub 2}. We also discuss scattering and recombination dynamics of photogenerated electrons and holes on the basis of the time dependence of absorption changes.

  11. Ultrafast carrier dynamics of titanic acid nanotubes investigated by transient absorption spectroscopy.

    PubMed

    Wang, Li; Zhao, Hui; Pan, Lin Yun; Weng, Yu Xiang; Nakato, Yoshihiro; Tamai, Naoto

    2010-12-01

    Carrier dynamics of titanic acid nanotubes (phase of H2Ti2O5.H2O) deposited on a quartz plate was examined by visible/near-IR transient absorption spectroscopy with an ultraviolet excitation. The carrier dynamics of titanic acid nanotubes follows the fast trapping process which attributed to the intrinsic tubular structure, the relaxation of shallow trapped carriers and the recombination as a second-order kinetic process. Transient absorption of titanic acid nanotubes was dominated by the absorption of surface-trapped holes in visible region around 500 nm, which was proved by the faster decay dynamics in the presence of polyvinyl alcohol as a hole-scavenger. However, the slow relaxation of free carriers was much more pronounced in the TiO2 single crystals, as compared with the transient absorption spectra of titanic acid nanotubes under the similar excitation.

  12. Minute Concentration Measurements of Simple Hydrocarbon Species Using Supercontinuum Laser Absorption Spectroscopy.

    PubMed

    Yoo, Jihyung; Traina, Nicholas; Halloran, Michael; Lee, Tonghun

    2016-06-01

    Minute concentration measurements of simple hydrocarbon gases are demonstrated using near-infrared supercontinuum laser absorption spectroscopy. Absorption-based gas sensors, particularly when combined with optical fiber components, can significantly enhance diagnostic capabilities to unprecedented levels. However, these diagnostic techniques are subject to limitations under certain gas sensing applications where interference and harsh conditions dominate. Supercontinuum laser absorption spectroscopy is a novel laser-based diagnostic technique that can exceed the above-mentioned limitations and provide accurate and quantitative concentration measurement of simple hydrocarbon species while maintaining compatibility with telecommunications-grade optical fiber components. Supercontinuum radiation generated using a highly nonlinear photonic crystal fiber is used to probe rovibrational absorption bands of four hydrocarbon species using full-spectral absorption diagnostics. Absorption spectra of methane (CH4), acetylene (C2H2), and ethylene (C2H4) were measured in the near-infrared spectrum at various pressures and concentrations to determine the accuracy and feasibility of the diagnostic strategy. Absorption spectra of propane (C3H8) were subsequently probed between 1650 nm and 1700 nm, to demonstrate the applicability of the strategy. Measurements agreed very well with simulated spectra generated using the HITRAN database as well as with previous experimental results. Absorption spectra of CH4, C2H2, and C2H4 were then analyzed to determine their respective measurement accuracy and detection limit. Concentration measurements integrated from experimental results were in very good agreement with independent concentration measurements. Calculated detection limits of CH4, C2H2, and C2H4 at room temperature and atmospheric pressure are 0.1%, 0.09%, and 0.17%, respectively.

  13. Determining Concentrations and Temperatures in Semiconductor Manufacturing Plasmas via Submillimeter Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Helal, Yaser H.; Neese, Christopher F.; De Lucia, Frank C.; Ewing, Paul R.; Agarwal, Ankur; Craver, Barry; Stout, Phillip J.; Armacost, Michael D.

    2016-06-01

    Plasmas used in the manufacturing processes of semiconductors are similar in pressure and temperature to plasmas used in studying the spectroscopy of astrophysical species. Likewise, the developed technology in submillimeter absorption spectroscopy can be used for the study of industrial plasmas and for monitoring manufacturing processes. An advantage of submillimeter absorption spectroscopy is that it can be used to determine absolute concentrations and temperatures of plasma species without the need for intrusive probes. A continuous wave, 500 - 750 GHz absorption spectrometer was developed for the purpose of being used as a remote sensor of gas and plasma species. An important part of this work was the optical design to match the geometry of existing plasma reactors in the manufacturing industry. A software fitting routine was developed to simultaneously fit for the background and absorption signal, solving for concentration, rotational temperature, and translational temperature. Examples of measurements made on inductively coupled plasmas will be demonstrated. We would like to thank the Texas Analog Center of Excellence/Semiconductor Research Corporation (TxACE/SRC) and Applied Materials for their support of this work.

  14. Absorption spectroscopy at the ultimate quantum limit from single-photon states

    NASA Astrophysics Data System (ADS)

    Whittaker, R.; Erven, C.; Neville, A.; Berry, M.; O’Brien, J. L.; Cable, H.; Matthews, J. C. F.

    2017-02-01

    Absorption spectroscopy is routinely used to characterise chemical and biological samples. For the state-of-the-art in laser absorption spectroscopy, precision is theoretically limited by shot-noise due to the fundamental Poisson-distribution of photon number in laser radiation. In practice, the shot-noise limit can only be achieved when all other sources of noise are eliminated. Here, we use wavelength-correlated and tuneable photon pairs to demonstrate how absorption spectroscopy can be performed with precision beyond the shot-noise limit and near the ultimate quantum limit by using the optimal probe for absorption measurement—single photons. We present a practically realisable scheme, which we characterise both the precision and accuracy of by measuring the response of a control feature. We demonstrate that the technique can successfully probe liquid samples and using two spectrally similar types of haemoglobin we show that obtaining a given precision in resolution requires fewer heralded single probe photons compared to using an idealised laser.

  15. Rapid, Time-Division Multiplexed, Direct Absorption- and Wavelength Modulation-Spectroscopy

    PubMed Central

    Klein, Alexander; Witzel, Oliver; Ebert, Volker

    2014-01-01

    We present a tunable diode laser spectrometer with a novel, rapid time multiplexed direct absorption- and wavelength modulation-spectroscopy operation mode. The new technique allows enhancing the precision and dynamic range of a tunable diode laser absorption spectrometer without sacrificing accuracy. The spectroscopic technique combines the benefits of absolute concentration measurements using calibration-free direct tunable diode laser absorption spectroscopy (dTDLAS) with the enhanced noise rejection of wavelength modulation spectroscopy (WMS). In this work we demonstrate for the first time a 125 Hz time division multiplexed (TDM-dTDLAS-WMS) spectroscopic scheme by alternating the modulation of a DFB-laser between a triangle-ramp (dTDLAS) and an additional 20 kHz sinusoidal modulation (WMS). The absolute concentration measurement via the dTDLAS-technique allows one to simultaneously calibrate the normalized 2f/1f-signal of the WMS-technique. A dTDLAS/WMS-spectrometer at 1.37 μm for H2O detection was built for experimental validation of the multiplexing scheme over a concentration range from 50 to 3000 ppmV (0.1 MPa, 293 K). A precision of 190 ppbV was achieved with an absorption length of 12.7 cm and an averaging time of two seconds. Our results show a five-fold improvement in precision over the entire concentration range and a significantly decreased averaging time of the spectrometer. PMID:25405508

  16. X-ray absorption near-edge structure of selenium in the Cu-In-Se system

    NASA Astrophysics Data System (ADS)

    Wolska, A.; Bacewicz, R.; Filipowicz, J.; Attenkofer, K.

    2001-05-01

    The x-ray absorption near edge structure (XANES) of selenium is investigated in the crystals with compositions from the pseudobinary cut line Cu2Se-In2Se3. This includes CuInSe2, indium-rich ternary compounds (Cu2In4Se7, CuIn3Se5, CuIn5Se8, CuIn7Se11) and α-In2Se3. The absorption at the K and L3/L2 edges of selenium has been measured using synchrotron radiation. Two theoretical approaches are used to the interpretation of the experimental data: the band structure calculation and the real-space multiple-scattering (RSMS) method. In the first one, the angular momentum projected densities of states at Se sites are calculated for CuInSe2 and α-In2Se3 for the energies up to 17 eV above the conduction band minimum by the LMTO-ASA method. The RSMS approach represented by the FEFF8 code is used to calculate the XANES spectra for the phases with tetragonal symmetry. Clusters up to 160 atoms are used in the calculations. The influence of different structural factors on the selenium XANES is studied.

  17. High sensitivity ultra-broad-band absorption spectroscopy of inductively coupled chlorine plasma

    NASA Astrophysics Data System (ADS)

    Marinov, Daniil; Foucher, Mickaël; Campbell, Ewen; Brouard, Mark; Chabert, Pascal; Booth, Jean-Paul

    2016-06-01

    We propose a method to measure the densities of vibrationally excited Cl2(v) molecules in levels up to v  =  3 in pure chlorine inductively coupled plasmas (ICPs). The absorption continuum of Cl2 in the 250-450 nm spectral range is deconvoluted into the individual components originating from the different vibrational levels of the ground state, using a set of ab initio absorption cross sections. It is shown that gas heating at constant pressure is the major depletion mechanism of the Cl2 feedstock in the plasma. In these line-integrated absorption measurements, the absorption by the hot (and therefore rarefied) Cl2 gas in the reactor centre is masked by the cooler (and therefore denser) Cl2 near the walls. These radial gradients in temperature and density make it difficult to assess the degree of vibrational excitation in the centre of the reactor. The observed line-averaged vibrational distributions, when analyzed taking into account the radial temperature gradient, suggest that vibrational and translational degrees of freedom in the plasma are close to local equilibrium. This can be explained by efficient vibrational-translational (VT) relaxation between Cl2 and Cl atoms. Besides the Cl2(v) absorption band, a weak continuum absorption is observed at shorter wavelengths, and is attributed to photodetachment of Cl- negative ions. Thus, line-integrated densities of negative ions in chlorine plasmas can be directly measured using broad-band absorption spectroscopy.

  18. Evaluation of ammonia absorption coefficients by photoacoustic spectroscopy for detection of ammonia levels in human breath

    NASA Astrophysics Data System (ADS)

    Dumitras, D. C.; Dutu, D. C.; Matei, C.; Cernat, R.; Banita, S.; Patachia, M.; Bratu, A. M.; Petrus, M.; Popa, C.

    2011-04-01

    Photoacoustic spectroscopy represents a powerful technique for measuring extremely low absorptions independent of the path length and offers a degree of parameter control that cannot be attained by other methods. We report precise measurements of the ammonia absorption coefficients at the CO2 laser wavelengths by using a photoacoustic (PA) cell in an extracavity configuration and we compare our results with other values reported in the literature. Ammonia presents a clear fingerprint spectrum and high absorption strengths in the CO2 wavelengths region. Because more than 250 molecular gases of environmental concern for atmospheric, industrial, medical, military, and scientific spheres exhibit strong absorption bands in the region 9.2-10.8 μm, we have chosen a frequency tunable CO2 laser. In the present work, ammonia absorption coefficients were measured at both branches of the CO2 laser lines by using a calibrated mixture of 10 ppm NH3 in N2. We found the maximum absorption in the 9 μm region, at 9R(30) line of the CO2 laser. One of the applications based on the ammonia absorption coefficients is used to measure the ammonia levels in exhaled human breath. This can be used to determine the exact time necessary at every session for an optimal degree of dialysis at patients with end-stage renal disease.

  19. Direct and combined methods for the determination of chromium, copper, and nickel in honey by electrothermal atomic absorption spectroscopy.

    PubMed

    Rodríguez García, J C; Barciela García, J; Herrero Latorre, C; García Martín, S; Peña Crecente, R M

    2005-08-24

    In the present work, direct methods for the determination of chromium, copper, and nickel in honey by electrothermal atomic absorption spectroscopy were developed using experimental design as an optimization tool. Once the optimum conditions for the individual methods were established, a direct method for the combined determination of the three elements was optimized using the response surface tool. Palladium was used as chemical modifier in all cases. Honey was diluted in water, hydrogen peroxide, and nitric acid. Triton X-100 was added to minimize the matrix effect and the viscosity of the sample. The RSD (better than 10%) and the analytical recovery (98-103%) were acceptable for all of the developed methods. Calibration graphs were used in the four methods to determine the concentration of the analytes in the sample. The detection limits of the combined method (0.21, 0.35, and 0.37 microg L(-)(1) for Cr, Cu, and Ni, respectively) were similar to those obtained for the individual methods (LOD = 0.17, 0.21, 0.33 microg L(-)(1) for Cr, Cu, and Ni, respectively). The direct-combined proposed method has been applied to the determination of chromium, copper, and nickel content in representative honey samples from Galicia (northwestern Spain). The concentrations found in the analyzed samples were in the range of (5.75 +/- 0.64)-(26.4 +/- 0.38) ng g(-)(1) of Cr, (79 +/- 7.8)-(2049 +/- 80) ng g(-)(1) of Cu, and (12.6 +/- 1.36)-(172 +/- 6.88) ng g(-)(1) of Ni.

  20. EPR and optical absorption studies of Cu{sup 2+} ions in alkaline earth alumino borate glasses

    SciTech Connect

    Ramesh Kumar, V.; Rao, J.L. . E-mail: jlrao46@yahoo.co.in; Gopal, N.O.

    2005-08-11

    Electron paramagnetic resonance (EPR) and optical absorption spectra of Cu{sup 2+} ions in alkaline earth alumino borate glasses doped with different concentrations of CuO have been studied. The EPR spectra of all the glasses exhibit the resonance signals, characteristic of Cu{sup 2+} ions present in axially elongated octahedral sites. The number of spins participating in the resonance has been calculated as a function of temperature for calcium alumino borate (CaAB) glass doped with 0.1 mol% of CuO. From the EPR data, the paramagnetic susceptibility ({chi}) was calculated at different temperatures (T) and from the 1/{chi}-T graph, the Curie temperature of the glass has been evaluated. The optical absorption spectra of all the glasses show a single broad band, which has been assigned to the {sup 2}B{sub 1g} {yields} {sup 2}B{sub 2g} transition of the Cu{sup 2+} ions. The variation in the intensity of optical absorption with the ionic radius of the alkaline earth ion has been explained based on the Coulombic forces. By correlating the EPR and optical absorption spectral data, the nature of the in-plane {sigma} bonding between Cu{sup 2+} ion and the ligands is estimated. From the fundamental ultraviolet absorption edges of the glasses, the optical energy gap (E {sub opt}) and the Urbach energy ({delta}E) are evaluated. The variation in E {sub opt} and {delta}E is explained based on the number of defect centers in the glass.

  1. Influence of temperature and turbidity on water COD detection by UV absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhou, Kun-peng; Bi, Wei-hong; Zhang, Qi-hang; Fu, Xing-hu; Wu, Guo-qing

    2016-11-01

    Ultraviolet (UV) absorption spectroscopy is used to detect the concentration of water chemical oxygen demand (COD). The UV absorption spectra of COD solutions are analyzed qualitatively and quantitatively. The partial least square (PLS) algorithm is used to model COD solution and the modeling results are compared. The influence of environmental temperature and turbidity is analyzed. These results show that the influence of temperature on the predicted value can be ignored. However, the change of turbidity can affect the detection results of UV spectra, and the COD detection error can be effectively compensated by establishing the single-element regression model.

  2. Thin-film absorption coefficients by attenuated-total-reflection spectroscopy.

    PubMed

    Holm, R T; Palik, E D

    1978-02-01

    The application of attenuated-total-reflection spectroscopy to the measurement of the absorption coefficient of thin films is presented. For low absorption the sensitivity of ATR is discussed in terms of the concept of an effective thickness. Both the case in which the refractive index of the film is higher and the case in which it is lower than that of the ATR trapezoid are considered. Experimental ATR data for antireflection-coating materials for laser windows is analyzed and compared with calorimetric data.

  3. Assignment of benzodiazepine UV absorption spectra by the use of photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Khvostenko, O. G.; Tzeplin, E. E.; Lomakin, G. S.

    2002-04-01

    Correlations between singlet transition energies and energy gaps of corresponding pairs of occupied and unoccupied molecular orbitals were revealed in a series of benzodiazepines. The occupied orbital energies were taken from the photoelectron spectra of the compound investigated, the unoccupied ones were obtained from MNDO/d calculations, and the singlet energies were taken from the UV absorption spectra. The correspondence of the singlet transitions to certain molecular orbitals was established using MNDO/d calculations and comparing between UV and photoelectron spectra. It has been concluded that photoelectron spectroscopy can be applied for interpretation of UV absorption spectra of various compounds on the basis of similar correlations.

  4. Interactions of hypericin with a model mutagen - Acridine orange analyzed by light absorption and fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Pietrzak, Monika; Szabelski, Mariusz; Kasparek, Adam; Wieczorek, Zbigniew

    2017-02-01

    The present study was designed to estimate the ability of hypericin to interact with a model mutagen - acridine orange. The hetero-association of hypericin and acridine orange was investigated with absorption and fluorescence spectroscopy methods in aqueous solution of DMSO. The data indicate that hypericin forms complexes with acridine orange and that the association constants are relatively high and depend on DMSO concentration. The absorption spectra of the hypericin - acridine orange complexes were examined as well. Owing to its ability to interact with flat aromatic compounds, hypericin may potentially be used as an interceptor molecule.

  5. Molecular scale shock response: electronic absorption spectroscopy of laser shocked explosives

    NASA Astrophysics Data System (ADS)

    McGrane, Shawn; Whitley, Von; Moore, David; Bolme, Cindy; Eakins, Daniel

    2009-06-01

    Single shot spectroscopies are being employed to answer questions fundamental to shock initiation of explosives. The goals are to: 1) determine the extent to which electronic excitations are, or are not, involved in shock induced reactions, 2) test the multiphonon up-pumping hypothesis in explosives, and 3) provide data on the initial evolution of temperature and chemistry following the shock loading of explosives on scales amenable to comparison to molecular dynamics simulations. The data presented in this talk are focused on answering the first question. Recent experimental results measuring the time history of ultraviolet/visible absorption spectroscopy of laser shocked explosive thin films and single crystals will be discussed.

  6. Enhanced microwave absorption properties of CTAB assisted Pr-Cu substituted nanomaterial

    NASA Astrophysics Data System (ADS)

    Sadiq, Imran; Naseem, Shahzad; Riaz, Saira; Khan, Hasan M.; Ashiq, Muhammad Naeem; Hussain, S. Sajjad; Rana, Mazhar

    2016-09-01

    In this study, the rare earth Pr3+and divalent Cu2+ elements substituted Sr1-xPrxMn2Fe16-yCuyO27 (x=0, 0.02, 0.06, 0.1 and y=0, 0.1, 0.3, 0.5) W-type hexagonal ferrites were prepared by Sol-Gel method. TGA and DSC analysis of as prepared material was carried out to confirm the temperature at which required phase can be obtained. The XRD patterns exhibit the single phase for all the samples and the lattice parameters were changed with the additives. The absorption bands at wave number 636 and 554 cm-1 in FTIR spectrum indicate the stretching vibration of metal-oxygen ions which also ratifies the single phase for the prepared material. Microstructural analysis confirms the agglomeration of nanograins which leads to formation of platelet like structure which cause in the enhancement of the microwave absorption properties of material. The minimum reflection loss of -59.8 dB at 9.34 GHz frequency was observed makes the prepared material good candidate to be used in super high frequency application. The attenuation constant and reflectivity results are also in good agreement with minimum reflection losses results.

  7. Submillimeter Absorption Spectroscopy in Semiconductor Manufacturing Plasmas and Comparison to Theoretical Models

    NASA Astrophysics Data System (ADS)

    Helal, Yaser H.; Neese, Christopher F.; De Lucia, Frank C.; Ewing, Paul R.; Agarwal, Ankur; Craver, Barry; Stout, Phillip J.; Armacost, Michael D.

    2015-06-01

    Plasmas used in the semiconductor manufacturing industry are of a similar nature to the environments often created for submillimeter spectroscopic study of astrophysical species. At the low operating pressures of these plasmas, submillimeter absorption spectroscopy is a method capable of measuring the abundances and temperatures of molecules, radicals, and ions without disturbing any of the properties of the plasma. These measurements provide details and insight into the interactions and reactions occurring within the plasma and their implications for semiconductor manufacturing processes. A continuous wave, 500 to 750 GHz, absorption spectrometer was designed and used to make measurements of species in semiconductor processing plasmas. Comparisons with expectations from theoretical plasma models provide a basis for validating and improving these models, which is a complex and difficult science itself. Furthermore, these comparisons are an evaluation for the use of submillimeter spectroscopy as a diagnostic tool in manufacturing processes.

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

    SciTech Connect

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

    2014-10-15

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

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

    PubMed

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

    2014-10-01

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

  10. Infrared Absorption in Partially Disordered K2CuCl4·2H2O-TYPE Compounds

    NASA Astrophysics Data System (ADS)

    Grado-Caffaro, M. A.; Grado-Caffaro, M.

    An approximate relationship for the coefficient of optical absorption valid, in principle, for the infrared range, corresponding to K2CuCl4·2H2O-type compounds is derived from a model for electronic density of states. These compounds are assumed to be partially disordered from the point of view of the general theory of solids.

  11. Undistorted X-ray Absorption Spectroscopy Using s-Core-Orbital Emissions.

    PubMed

    Golnak, Ronny; Xiao, Jie; Atak, Kaan; Unger, Isaak; Seidel, Robert; Winter, Bernd; Aziz, Emad F

    2016-05-12

    Detection of secondary emissions, fluorescence yield (FY), or electron yield (EY), originating from the relaxation processes upon X-ray resonant absorption has been widely adopted for X-ray absorption spectroscopy (XAS) measurements when the primary absorption process cannot be probed directly in transmission mode. Various spectral distortion effects inherent in the relaxation processes and in the subsequent transportation of emitted particles (electron or photon) through the sample, however, undermine the proportionality of the emission signals to the X-ray absorption coefficient. In the present study, multiple radiative (FY) and nonradiative (EY) decay channels have been experimentally investigated on a model system, FeCl3 aqueous solution, at the excitation energy of the Fe L-edge. The systematic comparisons between the experimental spectra taken from various decay channels, as well as the comparison with the theoretically simulated Fe L-edge XA spectrum that involves only the absorption process, indicate that the detection of the Fe 3s → 2p partial fluorescence yield (PFY) gives rise to the true Fe L-edge XA spectrum. The two key characteristics generalized from this particular decay channel-zero orbital angular momentum (i.e., s orbital) and core-level emission-set a guideline for obtaining undistorted X-ray absorption spectra in the future.

  12. Progress in Applying Tunable Diode Laser Absorption Spectroscopy to Scramjet Isolators and Combustors

    DTIC Science & Technology

    2010-05-01

    AFRL-RZ-WP-TP-2010-2146 PROGRESS IN APPLYING TUNABLE DIODE LASER ABSORPTION SPECTROSCOPY TO SCRAMJET ISOLATORS AND COMBUSTORS Michael S... COMBUSTORS 5a. CONTRACT NUMBER IN HOUSE 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) Michael S. Brown, Skip Williams...paths -- scramjet engines in particular. In this report we summarize our progress in applying TDLAS to scramjet isolators and combustors . 15

  13. X-ray absorption spectroscopy beyond the core-hole lifetime

    SciTech Connect

    Haemaelaeinen, K.; Hastings, J.B.; Siddons, D.P.; Berman, L.

    1992-01-01

    A new technique to overcome the core-hole lifetime broadening in x-ray absorption spectroscopy is presented. It utilizes a high resolution fluorescence spectrometer which can be used to analyze the fluorescence photon energy with better resolution than the natural lifetime width. Furthermore, the high resolution spectrometer can also be used to select the final state in the fluorescence process which can offer spin selectivity even without long range magnetic order in the sample.

  14. X-ray absorption spectroscopy beyond the core-hole lifetime

    SciTech Connect

    Haemaelaeinen, K.; Hastings, J.B.; Siddons, D.P.; Berman, L.

    1992-10-01

    A new technique to overcome the core-hole lifetime broadening in x-ray absorption spectroscopy is presented. It utilizes a high resolution fluorescence spectrometer which can be used to analyze the fluorescence photon energy with better resolution than the natural lifetime width. Furthermore, the high resolution spectrometer can also be used to select the final state in the fluorescence process which can offer spin selectivity even without long range magnetic order in the sample.

  15. Conformational study of the chromophore of C-phycocyanin by resonance raman and electronic absorption spectroscopy.

    NASA Astrophysics Data System (ADS)

    Margulies, L.; Toporowicz, M.

    1988-05-01

    The conformation of the chromophore of C-phycocyanin (PC) was investigated by using electronic absorption and resonance Raman spectroscopy, and theoretical calculations. Using an A-dihydrobilindione as model compound, the syn, syn, syn conformation was established for the isolated chromophore in solution. For the native PC, the best results were obtained by considering the syn, syn, anti conformation, although the possibility of having a syn, anti, anti conformation could not be excluded.

  16. Capturing Transient Electronic and Molecular Structures in Liquids by Picosecond X-Ray Absorption Spectroscopy

    SciTech Connect

    Gawelda, W.; Pham, V. T.; El Nahhas, A.; Kaiser, M.; Zaushitsyn, Y.; Bressler, C.; Chergui, M.; Johnson, S. L.; Grolimund, D.; Abela, R.; Hauser, A.

    2007-02-02

    We describe an advanced setup for time-resolved x-ray absorption fine structure (XAFS) Spectroscopy with picosecond temporal resolution. It combines an intense femtosecond laser source synchronized to the x-ray pulses delivered into the microXAS beamline of the Swiss Light Source (SLS). The setup is applied to measure the short-lived high-spin geometric structure of photoexcited aqueous Fe(bpy)3 at room temperature.

  17. Intracavity Laser Absorption Spectroscopy of Platinum Nitride in the Near Infrared

    NASA Astrophysics Data System (ADS)

    O'Brien, Leah C.; Womack, Kaitlin A.; O'Brien, James J.; Whittemore, Sean

    2013-06-01

    The (2,0) band of the A^{2}Σ^{-} - X^{2}Π_{1/2} electronic transition of PtN has been recorded using intracavity laser absorption spectroscopy. Transitions from ^{194}PtN, ^{195}PtN, and ^{196}PtN isotopologues are observed, as well as the nuclear hyperfine splitting due to ^{195}Pt with I=1/2. The results of the analysis will be presented and compared with ab initio calculations.

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

    SciTech Connect

    Paesler, M.; Sayers, D.

    1988-12-01

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

  19. Application of microemulsions in determination of chromium naphthenate in gasoline by flame atomic absorption spectroscopy.

    PubMed

    Du, B; Wei, Q; Wang, S; Yu, W

    1997-10-01

    A new method using microemulsified samples is presented. It is for the determination of chromium naphthenate in gasoline by flame absorption spectroscopy. The method has the advantage of simplicity, speed and the use of aqueous standards for calibration instead of organic standards. Coexistent elements do not disturb the determination. Results obtained by this method were better than those obtained by other methods for the same samples.

  20. Nile blue shows its true colors in gas-phase absorption and luminescence ion spectroscopy

    NASA Astrophysics Data System (ADS)

    Stockett, M. H.; Houmøller, J.; Brøndsted Nielsen, S.

    2016-09-01

    Nile blue is used extensively in biology as a histological stain and fluorescent probe. Its absorption and emission spectra are strongly solvent dependent, with variations larger than 100 nm. The molecule is charged due to an iminium group, and it is therefore an obvious target for gas-phase ion spectroscopy. Here we report the absorption and emission spectra of the mass-selected bare ions isolated in vacuo, and based on our results we revisit the interpretation of solution-phase spectra. An accelerator mass spectrometer was used for absorption spectroscopy where the absorption is represented by the yield of photofragment ions versus excitation wavelength (action spectroscopy). The luminescence experiments were done with a newly built ion trap setup equipped with an electrospray ion source, and some details on the mass selection technique will be given which have not been described before. In vacuo, the absorption and emission maxima are at 580 ± 10 nm and 628 ± 1 nm. These values are somewhat blue-shifted relative to those obtained in most solvents; however, they are much further to the red than those in some of the most non-polar solvents. Furthermore, the Stokes shift in the gas phase (1300 cm-1) is much smaller than that in these non-polar solvents but similar to that in polar ones. An explanation based on charge localization by solvent dipoles, or by counterions in some non-polar solvents, can fully account for these findings. Hence in the case of ions, it is nontrivial to establish intrinsic electronic transition energies from solvatochromic shifts alone.

  1. Communication: Near edge x-ray absorption fine structure spectroscopy of aqueous adenosine triphosphate at the carbon and nitrogen K-edges.

    PubMed

    Kelly, Daniel N; Schwartz, Craig P; Uejio, Janel S; Duffin, Andrew M; England, Alice H; Saykally, Richard J

    2010-09-14

    Near edge x-ray absorption fine structure (NEXAFS) spectroscopy at the nitrogen and carbon K-edges was used to study the hydration of adenosine triphosphate in liquid microjets. The total electron yield spectra were recorded as a function of concentration, pH, and the presence of sodium, magnesium, and copper ions (Na(+)/Mg(2+)/Cu(2+)). Significant spectral changes were observed upon protonation of the adenine ring, but not under conditions that promote π-stacking, such as high concentration or presence of Mg(2+), indicating that NEXAFS is insensitive to the phenomenon. Intramolecular inner-sphere association of Cu(2+) did create observable broadening of the nitrogen spectrum, whereas outer-sphere association with Mg(2+) did not.

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

    SciTech Connect

    Citron, Robert; Kropf, A.J.

    2008-01-01

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

  3. Supercontinuum high-speed cavity-enhanced absorption spectroscopy for sensitive multispecies detection.

    PubMed

    Werblinski, Thomas; Lämmlein, Bastian; Huber, Franz J T; Zigan, Lars; Will, Stefan

    2016-05-15

    Cavity-enhanced absorption spectroscopy is promising for many applications requiring a very high concentration sensitivity but often accompanied by low temporal resolution. In this Letter, we demonstrate a broadband cavity-enhanced absorption spectrometer capable of detection rates of up to 50 kHz, based on a spatially coherent supercontinuum (SC) light source and an in-house-built, high-speed near-infrared spectrograph. The SC spectrometer allows for the simultaneous quantitative detection of CO2, C2H2, and H2O within a spectral range from 1420 to 1570 nm. Using cavity mirrors with a specified reflectivity of R=98.0±0.3% a minimal spectrally averaged absorption coefficient of αmin=1·10-5  cm-1 can be detected at a repetition rate of 50 kHz.

  4. Gas trace detection with cavity enhanced absorption spectroscopy: a review of its process in the field

    NASA Astrophysics Data System (ADS)

    Liu, Siqi; Luo, Zhifu; Tan, Zhongqi; Long, Xingwu

    2016-11-01

    Cavity-enhanced absorption spectroscopy (CEAS) is a technology in which the intracavity absorption is deduced from the intensity of light transmitted by the high finesse optical cavity. Then the samples' parameters, such as their species, concentration and absorption cross section, would be detection. It was first proposed and demonstrated by Engeln R. [1] and O'Keefe[2] in 1998. This technology has extraordinary detection sensitivity, high resolution and good practicability, so it is used in many fields , such as clinical medicine, gas detection and basic physics research. In this paper, we focus on the use of gas trace detection, including the advance of CEAS over the past twenty years, the newest research progresses, and the prediction of this technology's development direction in the future.

  5. Photodissociation Structural Dynamics of TrirutheniumDodecacarbonyl Investigated by X-ray Transient Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Harpham, Michael R.; Stickrath, Andrew, B.; Zhang, Xiaoyi,; Huang, Jier; Mara, Michael W.; Chen, Lin X.; Liu, Di-Jia

    2013-10-01

    The molecular and electronic structures of the transient intermediates generated from the photolysis of trirutheniumdodecacarbonyl, Ru3(CO)12, by ultrafast UV (351 nm) laser excitation were investigated using X-ray transient absorption (XTA) spectroscopy. The electronic configuration change and nuclear rearrangement after the dissociation of carbonyls were observed at ruthenium K-edge X-ray absorption near edge structure and X-ray absorption fine structure spectra. Analysis of XTA data, acquired after 100, 200, and 400 ps and 300 ns time delay following the photoexcitation, identified the presence of three intermediate species with Ru3(CO)10 being the most dominating one. The results set an example of applying XTA in capturing both transient electronic and nuclear configurations in metal clusters simulating catalysts in chemical reactions.

  6. Absorption spectroscopy setup for determination of whole human blood and blood-derived materials spectral characteristics

    NASA Astrophysics Data System (ADS)

    Wróbel, M. S.; Gnyba, M.; Milewska, D.; Mitura, K.; Karpienko, K.

    2015-09-01

    A dedicated absorption spectroscopy system was set up using tungsten-halogen broadband source, optical fibers, sample holder, and a commercial spectrometer with CCD array. Analysis of noise present in the setup was carried out. Data processing was applied to the absorption spectra to reduce spectral noise, and improve the quality of the spectra and to remove the baseline level. The absorption spectra were measured for whole blood samples, separated components: plasma, saline, washed erythrocytes in saline and human whole blood with biomarkers - biocompatible nanodiamonds (ND). Blood samples had been derived from a number of healthy donors. The results prove a correct setup arrangement, with adequate preprocessing of the data. The results of blood-ND mixtures measurements show no toxic effect on blood cells, which proves the NDs as a potential biocompatible biomarkers.

  7. Electronic structure of warm dense copper studied by ultrafast x-ray absorption spectroscopy.

    PubMed

    Cho, B I; Engelhorn, K; Correa, A A; Ogitsu, T; Weber, C P; Lee, H J; Feng, J; Ni, P A; Ping, Y; Nelson, A J; Prendergast, D; Lee, R W; Falcone, R W; Heimann, P A

    2011-04-22

    We use time-resolved x-ray absorption spectroscopy to investigate the unoccupied electronic density of states of warm dense copper that is produced isochorically through the absorption of an ultrafast optical pulse. The temperature of the superheated electron-hole plasma, which ranges from 4000 to 10 000 K, was determined by comparing the measured x-ray absorption spectrum with a simulation. The electronic structure of warm dense copper is adequately described with the high temperature electronic density of state calculated by the density functional theory. The dynamics of the electron temperature is consistent with a two-temperature model, while a temperature-dependent electron-phonon coupling parameter is necessary.

  8. Deep ultraviolet Raman spectroscopy: A resonance-absorption trade-off illustrated by diluted liquid benzene

    NASA Astrophysics Data System (ADS)

    Chadwick, C. T.; Willitsford, A. H.; Philbrick, C. R.; Hallen, H. D.

    2015-12-01

    The magnitude of resonance Raman intensity, in terms of the real signal level measured on-resonance compared to the signal level measured off-resonance for the same sample, is investigated using a tunable laser source. Resonance Raman enhancements, occurring as the excitation energy is tuned through ultraviolet absorption lines, are used to examine the 1332 cm-1 vibrational mode of diamond and the 992 cm-1 ring-breathing mode of benzene. Competition between the wavelength dependent optical absorption and the magnitude of the resonance enhancement is studied using measured signal levels as a function of wavelength. Two system applications are identified where the resonance Raman significantly increases the real signal levels despite the presence of strong absorption: characterization of trace species in laser remote sensing and spectroscopy of the few molecules in the tiny working volumes of near-field optical microscopy.

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

    PubMed

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

    2011-10-01

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

  10. Sensitive and rapid laser diagnostic for shock tube kinetics studies using cavity-enhanced absorption spectroscopy.

    PubMed

    Sun, Kai; Wang, Shengkai; Sur, Ritobrata; Chao, Xing; Jeffries, Jay B; Hanson, Ronald K

    2014-04-21

    We report the first application of cavity-enhanced absorption spectroscopy (CEAS) using a coherent light source for sensitive and rapid gaseous species time-history measurements in a shock tube. Off-axis alignment and fast scanning of the laser wavelength were used to minimize coupling noise in a low-finesse cavity. An absorption gain factor of 83 with a measurement time resolution of 20 µs was demonstrated for C2H2 detection using a near-infrared transition near 1537 nm, corresponding to a noise-equivalent detection limit of 20 ppm at 296 K and 76 ppm at 906 K at 50 kHz. This substantial gain in signal, relative to conventional single-pass absorption, will enable ultra-sensitive species detection in shock tube kinetics studies, particularly useful for measurements of minor species and for studies of dilute reactive systems.

  11. Picosecond and femtosecond X-ray absorption spectroscopy of molecular systems.

    PubMed

    Chergui, Majed

    2010-03-01

    The need to visualize molecular structure in the course of a chemical reaction, a phase transformation or a biological function has been a dream of scientists for decades. The development of time-resolved X-ray and electron-based methods is making this true. X-ray absorption spectroscopy is ideal for the study of structural dynamics in liquids, because it can be implemented in amorphous media. Furthermore, it is chemically selective. Using X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) in laser pump/X-ray probe experiments allows the retrieval of the local geometric structure of the system under study, but also the underlying photoinduced electronic structure changes that drive the structural dynamics. Recent developments in picosecond and femtosecond X-ray absorption spectroscopy applied to molecular systems in solution are reviewed: examples on ultrafast photoinduced processes such as intramolecular electron transfer, low-to-high spin change, and bond formation are presented.

  12. Mid-infrared laser absorption spectroscopy of NO2 at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Sur, Ritobrata; Peng, Wen Yu; Strand, Christopher; Mitchell Spearrin, R.; Jeffries, Jay B.; Hanson, Ronald K.; Bekal, Anish; Halder, Purbasha; Poonacha, Samhitha P.; Vartak, Sameer; Sridharan, Arun K.

    2017-01-01

    A mid-infrared quantum cascade laser absorption sensor was developed for in-situ detection of NO2 in high-temperature gas environments. A cluster of spin-split transitions near 1599.9 cm-1 from the ν3 absorption band of NO2 was selected due to the strength of these transitions and the low spectral interference from water vapor within this region. Temperature- and species-dependent collisional broadening parameters of ten neighboring NO2 transitions with Ar, O2, N2, CO2 and H2O were measured and reported. The spectral model was validated through comparisons with direct absorption spectroscopy measurements of NO2 seeded in various bath gases. The performance of the scanned wavelength modulation spectroscopy (WMS)-based sensor was demonstrated in a combustion exhaust stream seeded with varying flow rates of NO2, achieving reliable detection of 1.45 and 1.6 ppm NO2 by mole at 600 K and 800 K, respectively, with a measurement uncertainty of ±11%. 2σ noise levels of 360 ppb and 760 ppb were observed at 600 K and 800 K, respectively, in an absorption path length of 1.79 m.

  13. Wafer-scale metasurface for total power absorption, local field enhancement and single molecule Raman spectroscopy.

    PubMed

    Wang, Dongxing; Zhu, Wenqi; Best, Michael D; Camden, Jon P; Crozier, Kenneth B

    2013-10-04

    The ability to detect molecules at low concentrations is highly desired for applications that range from basic science to healthcare. Considerable interest also exists for ultrathin materials with high optical absorption, e.g. for microbolometers and thermal emitters. Metal nanostructures present opportunities to achieve both purposes. Metal nanoparticles can generate gigantic field enhancements, sufficient for the Raman spectroscopy of single molecules. Thin layers containing metal nanostructures ("metasurfaces") can achieve near-total power absorption at visible and near-infrared wavelengths. Thus far, however, both aims (i.e. single molecule Raman and total power absorption) have only been achieved using metal nanostructures produced by techniques (high resolution lithography or colloidal synthesis) that are complex and/or difficult to implement over large areas. Here, we demonstrate a metasurface that achieves the near-perfect absorption of visible-wavelength light and enables the Raman spectroscopy of single molecules. Our metasurface is fabricated using thin film depositions, and is of unprecedented (wafer-scale) extent.

  14. Nanoscale infrared absorption spectroscopy of individual nanoparticles enabled by scattering-type near-field microscopy.

    PubMed

    Stiegler, Johannes M; Abate, Yohannes; Cvitkovic, Antonija; Romanyuk, Yaroslav E; Huber, Andreas J; Leone, Stephen R; Hillenbrand, Rainer

    2011-08-23

    Infrared absorption spectroscopy is a powerful and widely used tool for analyzing the chemical composition and structure of materials. Because of the diffraction limit, however, it cannot be applied for studying individual nanostructures. Here we demonstrate that the phase contrast in substrate-enhanced scattering-type scanning near-field optical microscopy (s-SNOM) provides a map of the infrared absorption spectrum of individual nanoparticles with nanometer-scale spatial resolution. We succeeded in the chemical identification of silicon nitride nanoislands with heights well below 10 nm, by infrared near-field fingerprint spectroscopy of the Si-N stretching bond. Employing a novel theoretical model, we show that the near-field phase spectra of small particles correlate well with their far-field absorption spectra. On the other hand, the spectral near-field contrast does not scale with the volume of the particles. We find a nearly linear scaling law, which we can attribute to the near-field coupling between the near-field probe and the substrate. Our results provide fundamental insights into the spectral near-field contrast of nanoparticles and clearly demonstrate the capability of s-SNOM for nanoscale chemical mapping based on local infrared absorption.

  15. Formation of M-C≡C-Cl (m = ag or Cu) and Characterization by Rotational Spectroscopy

    NASA Astrophysics Data System (ADS)

    Zaleski, Daniel P.; Tew, David Peter; Walker, Nick; Legon, Anthony

    2015-06-01

    The new linear molecule Ag-C≡C-Cl has been detected and characterized by means of rotational spectroscopy. It was synthesized by laser ablation of a slver rod in the presence of a gaseous sample containing a low concentration of CCl4 in argon, cooled to a rotational temperature approaching 2 K through supersonic expansion and analyzed by chirped pulse Fourier transform microwave spectroscopy. Substitution coordinates are available for the silver and chlorine positions and will be compared to ab initio calculations at the CCSD(T)/aug-cc-pV5Z level of theory. The Ag-13C≡13C-Cl isotopologue was also observed using a similar gas mixture containing 13CCl4. The Cu analogue Cu-C≡C-Cl was similarly identified and characterized.

  16. Synthesis and characterization of Cu(In, Ga)Se2 absorption/scattering layers by electrodeposition method

    NASA Astrophysics Data System (ADS)

    Jeong, Soochang; Choi, Hyonkwang; Hwang, Junghwan; Park, Juntae; Im, Ki Hong; Jung, Yongil; Jeon, Minhyon

    2013-11-01

    We propose a Cu(In, Ga)Se2 double absorption layer structure with both absorption and scattering effects. We synthesized CIGS absorption layers by electro-deposition using different electrical potentials. Structural properties were characterized by x-ray diffraction and field-emission scanning electron microscopy. Optical properties were measured using UV/VIS spectrometry. Grain size and surface roughness were controlled by manipulation of the electrical potential. From these results, the currently typical, single CIGS absorption layer, was replaced with two CIGS layers: a top CIGS layer of smaller grain size and a bottom CIGS layer of larger grain size. We found that the larger-grain CIGS layer provides better scattering effect, so that the CIGS double layer structure provides enhanced light absorption performance in visible light. By applying this new CIGS double layer structure, it is expected that conversion efficiency will be increased.

  17. Microwave Spectroscopy and Structure Determination of H_2S-MI (M=Cu,Ag,Au)

    NASA Astrophysics Data System (ADS)

    Medcraft, Chris; Legon, Anthony; Walker, Nick

    2016-06-01

    A series of hydrogen sulphide-metal iodide complexes (H_2S-MI, M=Cu, Ag and Au) have been measured via chirped pulse Fourier transform microwave spectroscopy between 7.5-18 GHz. The complexes were generated in a supersonic expansion via laser ablation of the metal and decomposition of CF_3I. Experimental structures were obtained by least squares fitting of structural parameters to the rotational constants of deuterium and metal (63Cu / 65Cu and 107Ag / 109Ag) isotopologues. Interestingly K-1=1 transitions were observed in the spectra containing D_2S, these were not observed in previous studies of similar molecules (H_2S-MCl). This allowed for the determination of an extra rotational constant and, consequently, extra structural information could be obtained. The structures are compared to high level coupled cluster theory calculations.

  18. Stark spectroscopy of CuPc organic semiconductor with a submicron metal-electrode grating

    NASA Astrophysics Data System (ADS)

    Blinov, L. M.; Lazarev, V. V.; Yudin, S. G.; Palto, S. P.

    2016-02-01

    The optical and electro-optical properties of organic copper phthalocyanine semiconductor (α- CuPc) have been investigated by Stark (electroabsorption) spectroscopy using a metal electrode grating with a submicron (0.88 μm) interelectrode distance. Differences between dipole moments (Δμ) and polarizabilities (Δα) in the excited and ground states of α-CuPc are measured for a nanoscale semiconductor film. It is concluded that the extremely high values of Δμ and Δα are in principle not parameters of individual α-CuPc molecules: they are determined by exciton effects specifically in the polycrystalline medium with a characteristic morphology of hyperfine films, which depends on the structure of the samples and their fabrication technology.

  19. An x-ray absorption near edge structure spectroscopy study of metal coordination in Co(II)-substituted Carcinus maenas hemocyanin.

    PubMed Central

    Della Longa, S; Bianconi, A; Palladino, L; Simonelli, B; Congiu Castellano, A; Borghi, E; Barteri, M; Beltramini, M; Rocco, G P; Salvato, B

    1993-01-01

    High-resolution x-ray absorption near edge structure spectroscopy was used to characterize the metal sites in three different cobalt-substituted derivatives of Carcinus maenas hemocyanin (Hc), including a mononuclear cobalt, a dinuclear cobalt and a copper-cobalt hybrid derivative. Co(II) model complexes with structures exemplifying octahedral, trigonal bipyramidal, pseudo-tetrahedral, and square planar geometries were also studied. The results provide structural information about the metal binding site(s) in the Co-Hcs that extend earlier results from EPR and optical spectroscopy (Bubacco et al. 1992. Biochemistry. 31: 9294-9303). Experimental spectra were compared to those calculated for atomic clusters of idealized geometry, generated using a multiple scattering approach. The energy of the dipole forbidden 1s-->3d transition and of the absorption edge in the spectra for all cobalt Hc derivatives confirmed the cobaltous oxidation state which rules out the presence of an oxygenated site. Comparisons between data and simulations showed that the mononuclear and dinuclear Co(II) derivatives, as well as the hybrid derivative, contain four-coordinate Co(II) in distorted tetrahedral sites. Although the spectra for Co(II) in dinuclear metal sites more closely resemble the simulated spectrum for a tetrahedral complex than do spectra for the mononuclear derivative, the Co(II) sites in all derivatives are very similar. The Cu K-edge high resolution x-ray absorption near edge structure spectrum of the hybrid Cu-Co-Hc resembles that of deoxy-Hc demonstrating the presence of three-coordinate Cu(I). PMID:8312502

  20. Titanium-silicon oxide film structures for polarization-modulated infrared reflection absorption spectroscopy

    PubMed Central

    Dunlop, Iain E.; Zorn, Stefan; Richter, Gunther; Srot, Vesna; Kelsch, Marion; van Aken, Peter A.; Skoda, Maximilian; Gerlach, Alexander; Spatz, Joachim P.; Schreiber, Frank

    2010-01-01

    We present a titanium-silicon oxide film structure that permits polarization modulated infrared reflection absorption spectroscopy on silicon oxide surfaces. The structure consists of a ~6 nm sputtered silicon oxide film on a ~200 nm sputtered titanium film. Characterization using conventional and scanning transmission electron microscopy, electron energy loss spectroscopy, X-ray photoelectron spectroscopy and X-ray reflectometry is presented. We demonstrate the use of this structure to investigate a selectively protein-resistant self-assembled monolayer (SAM) consisting of silane-anchored, biotin-terminated poly(ethylene glycol) (PEG). PEG-associated IR bands were observed. Measurements of protein-characteristic band intensities showed that this SAM adsorbed streptavidin whereas it repelled bovine serum albumin, as had been expected from its structure. PMID:20418963

  1. [On using tunable diode laser absorption spectroscopy to determine gas fluxes over cropland].

    PubMed

    Tian, Yong-zhi; Liu, Jian-guo; Zhang, Yu-jun; Lu, Yi-huai; He, Ying

    2012-04-01

    Tunable diode laser absorption spectroscopy (TDLAS) is a compact, automated, high precision technique and fit for in-situ or field measurements. Two spectroscopy measurement systems, TDLAS and NDIR (non-dispersive infrared spectroscopy), were used to monitor trace gas emission over cropland at Fengqiu Agricultural Ecology Experimental Station for one month. The fluxes of carbon dioxide were estimated by flux-gradient and eddy covariance method, respectively. A footprint model was developed during experiment. Based on this model, the source areas of TDLAS and NDIR were investigated. The effects of different factors on the flux measurement were also analyzed. The authors concluded that the source areas for the two techniques are discrepant in most of the cases. The source areas increase with path length and detecting height. This result will help the installation of instruments.

  2. High-resolution X-ray absorption spectroscopy of iron carbonyl complexes.

    PubMed

    Atkins, Andrew J; Bauer, Matthias; Jacob, Christoph R

    2015-06-07

    We apply high-energy-resolution fluorescence-detected (HERFD) X-ray absorption near-edge spectroscopy (XANES) to study iron carbonyl complexes. Mono-, bi-, and tri-nuclear carbonyl complexes and pure carbonyl complexes as well as carbonyl complexes containing hydrocarbon ligands are considered. The HERFD-XANES spectra reveal multiple pre-edge peaks with individual signatures for each complex, which could not be detected previously with conventional XANES spectroscopy. These peaks are assigned and analysed with the help of TD-DFT calculations. We demonstrate that the pre-edge peaks can be used to distinguish the different types of iron-iron interactions in carbonyl complexes. This opens up new possibilities for applying HERFD-XANES spectroscopy to probe the electronic structure of iron catalysts.

  3. Determination of zinc in serum, blood, and ultrafiltrate fluid from patients on hemofiltration by graphite furnace/atomic absorption spectroscopy or flow injection analysis/atomic absorption spectroscopy.

    PubMed

    de Blas, O J; Rodriguez, R S; Mendez, J H; Tomero, J A; Gomez, B de L; Gonzalez, S V

    1994-01-01

    Two methods were optimized for the determination of zinc in samples of blood, serum, and ultrafiltrate fluid from patients with chronic renal impairment undergoing hemofiltration. In the first procedure, after acid digestion of the samples, Zn in blood and serum is determined by a system coupled to flow injection analysis and atomic absorption spectroscopy. The method is rapid, automated, simple, needs small amounts of sample, and has acceptable analytical characteristics. The analytical characteristics obtained were as follows: determination range of method, 0.05-2.0 ppm of Zn; precision as coefficient of variation (CV), 5.3%; recovery, 95-105%; and detection limit (DL), 0.02 ppm. The second method is optimized for ultrafiltrate fluid because the sensitivity of the first procedure is not suitable for the levels of Zn (ppb or ng/mL) in these samples. The technique chosen was atomic absorption spectroscopy with electrothermal atomization in a graphite furnace. The analytical characteristics obtained were as follows: determination range of method, 0.3-2.0 ppb Zn; CV, 5.7%; recovery, 93-107%; and DL, 0.12 ppb. The methods were used to determine zinc in samples of blood, serum, and ultrafiltrate fluid from 5 patients with chronic renal impairment undergoing hemofiltration to discover whether there were significant differences in the zinc contents of blood, serum, and ultrafiltrate fluid after the hemofiltration process. An analysis of variance of the experimental data obtained from a randomly selected group of 5 patients showed that zinc concentrations in the ultrafiltrate fluid, venous blood, and venous serum do not vary during hemofiltration (p < 0.05), whereas in arterial blood and serum, the time factor has a significant effect.

  4. Kinetics of the Reaction C2H + O2 from 193 to 350 K Using Laser Flash Kinetic Infrared Absorption Spectroscopy

    NASA Technical Reports Server (NTRS)

    Opansky, Brian J.; Seakins, Paul W.; Pedersen, Jens Olaf P.; Leone, Stephen R.

    1993-01-01

    Rate coefficients for the reaction C2H + O2 are measured from 193 to 350 K by using transient absorption spectroscopy with an infrared color center laser. Ethynyl radicals are produced by pulsed laser photolysis of C2H2 in a temperature variable flow cell and a tunable color center laser probes the transient removal Of C2H ((bar-X(sup 2))Sigma(+))(0,0,0)) in absorption. The rate coefficient has a slight negative temperature dependence over the range 193-350 K which can be expressed as k(O2) = (1.5 +/- 0.3) x 10(exp -11) exp((230 +/- 36)/T) Cu cm/(Molecule.s). The lack of a pressure dependence under our experimental conditions strongly suggests that the HCCOO* complex is short lived with respect to encountering a collision and rapidly dissociates to products without competition from collisional stabilization to HCCOO or collisionally induced dissociation to reactants.

  5. Fluorescence X-ray absorption spectroscopy using a Ge pixel array detector: application to high-temperature superconducting thin-film single crystals.

    PubMed

    Oyanagi, H; Tsukada, A; Naito, M; Saini, N L; Lampert, M O; Gutknecht, D; Dressler, P; Ogawa, S; Kasai, K; Mohamed, S; Fukano, A

    2006-07-01

    A Ge pixel array detector with 100 segments was applied to fluorescence X-ray absorption spectroscopy, probing the local structure of high-temperature superconducting thin-film single crystals (100 nm in thickness). Independent monitoring of pixel signals allows real-time inspection of artifacts owing to substrate diffractions. By optimizing the grazing-incidence angle theta and adjusting the azimuthal angle phi, smooth extended X-ray absorption fine structure (EXAFS) oscillations were obtained for strained (La,Sr)2CuO4 thin-film single crystals grown by molecular beam epitaxy. The results of EXAFS data analysis show that the local structure (CuO6 octahedron) in (La,Sr)2CuO4 thin films grown on LaSrAlO4 and SrTiO3 substrates is uniaxially distorted changing the tetragonality by approximately 5 x 10(-3) in accordance with the crystallographic lattice mismatch. It is demonstrated that the local structure of thin-film single crystals can be probed with high accuracy at low temperature without interference from substrates.

  6. Cavity enhanced ultra-thin aluminum plasmonic resonator for surface enhanced infrared absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Wei, Wei; Jiang, Xiao; Nong, Jinpeng; Chen, Na; Lan, Guilian; Tang, Linlong

    2016-11-01

    Owing to the advantages of natural abundance, low cost, and amenability to manufacturing processes, aluminum has recently been recognized as a highly promising plasmonic material that attracts extensive research interest. Here, we propose a cavity-enhanced ultra-thin plasmonic resonator for surface enhanced infrared absorption spectroscopy. The considered resonator consists of a patterned ultra-thin aluminum grating strips, a dielectric spacer layer and a reflective layer. In such structure, the resonance absorption is enhanced by the cavity formed between the patterned aluminum strips and the reflective layer. It is demonstrated that the spectral features of the resonator can be tuned by adjusting the structural parameters. Furthermore, in order to achieve a deep and broad spectral line shape, the spacer layer thickness should be properly designed to realize the simultaneous resonances for the electric and the magnetic excitations. The enhanced infrared absorption characteristics can be used for infrared sensing of the environment. When the resonator is covered with a molecular layer, the resonator can be used as a surface enhanced infrared absorption substrate to enhance the absorption signal of the molecules. A high enhanced factor of 1.15×105 can be achieved when the resonance wavelength of resonator is adjusted to match the desired vibrational mode of the molecules. Such a cavity-enhanced plasmonic resonator, which is easy for practical fabrication, is expected to have potential applications for infrared sensing with high-performance.

  7. Infrared intracavity laser absorption spectroscopy with a continuous-scan Fourier-transform interferometer.

    PubMed

    Cheng, J; Lin, H; Hu, S; He, S; Zhu, Q; Kachanov, A

    2000-05-01

    High-quality broadband infrared high-resolution spectra were obtained by use of the intracavity laser absorption spectroscopy technique with a Ti:sapphire laser in combination with a continuous-scan Fourier-transform (FT) interferometer. With electronic filtering used to smooth out the fluctuations of the laser power, the absorption of atmospheric water vapor in the range of 12,450-12,700 cm(-1) was recorded at a resolution of 0.05 cm(-1). A signal-to-noise ratio of greater than 300 was observed in this spectrum, corresponding to a minimum detectable absorption of approximately 2 x 10(-9) cm(-1). Comparison with previous measurements by use of a conventional FT technique shows that this method gives absorption spectra with highly accurate line positions along with reasonable line intensities. Investigation of the evolution of intracavity laser absorption spectra with the generation time is also shown to be possible with a continuous-scan FT spectrometer by use of the interleave rapid-scan method.

  8. [Study on removing the lamp spectrum structure in differential optical absorption spectroscopy].

    PubMed

    Qu, Xiao-ying; Li, Yu-jin

    2010-11-01

    Differential optical absorption spectroscopy (DOAS) technique has been used to measure trace gases in the atmosphere by their strongly structured absorption of radiation in the UV and visible spectral range, and nowadays this technique has been widely utilized to measure trace polluted gases in the atmosphere e.g. SO2, NO2, O3, HCHO, etc. However, there exists lamp (xenon lamp or deuteriumlamp) spectrum structure in the measured band (300-700 nm) of the absorption spectra of atmosphere, which badly impacts on precision of retrieving the concentration of trace gases in the atmosphere. People home and abroad generally employ two ways to handle this problem, one is segmenting band retrieving method, another is remedial retrieving method. In the present paper, a new retrieving method to deal with this trouble is introduced. The authors used moving-window average smoothing method to obtain the slow part of the absorption spectra of atmosphere, then achieved the lamp (xenon lamp in the paper) spectrum structure in the measured band of the absorption spectra of atmosphere. The authors analyzed and retrieved the measured spectrum of the atmosphere, and the result is better than the forenamed ways. Chi-square of residuum is 2.995 x 10(-4), and this method was proved to be able to avoid shortcoming of choosing narrowband and disadvantage of discovering the new component of atmosphere in retrieving the concentration of air pollutants and measuring the air pollutants.

  9. A split imaging spectrometer for temporally and spatially resolved titanium absorption spectroscopy

    SciTech Connect

    Hager, J. D. Lanier, N. E.; Kline, J. L.; Flippo, K. A.; Bruns, H. C.; Schneider, M.; Saculla, M.; McCarville, T.

    2014-11-15

    We present a temporally and a spatially resolved spectrometer for titanium x-ray absorption spectroscopy along 2 axial symmetric lines-of-sight. Each line-of-sight of the instrument uses an elliptical crystal to acquire both the 2p and 3p Ti absorption lines on a single, time gated channel of the instrument. The 2 axial symmetric lines-of-sight allow the 2p and 3p absorption features to be measured through the same point in space using both channels of the instrument. The spatially dependent material temperature can be inferred by observing the 2p and the 3p Ti absorption features. The data are recorded on a two strip framing camera with each strip collecting data from a single line-of-sight. The design is compatible for use at both the OMEGA laser and the National Ignition Facility. The spectrometer is intended to measure the material temperature behind a Marshak wave in a radiatively driven SiO{sub 2} foam with a Ti foam tracer. In this configuration, a broad band CsI backlighter will be used for a source and the Ti absorption spectrum measured.

  10. New advances in the use of infrared absorption spectroscopy for the characterization of heterogeneous catalytic reactions.

    PubMed

    Zaera, Francisco

    2014-11-21

    Infrared absorption spectroscopy has proven to be one of the most powerful spectroscopic techniques available for the characterization of catalytic systems. Although the history of IR absorption spectroscopy in catalysis is long, the technique continues to provide key fundamental information about a variety of catalysts and catalytic reactions, and to also offer novel options for the acquisition of new information on both reaction mechanisms and the nature of the solids used as catalysts. In this review, an overview is provided of the main contributions that have been derived from IR absorption spectroscopy studies of catalytic systems, and a discussion is included on new trends and new potential directions of research involving IR in catalysis. We start by briefly describing the power of Fourier-transform IR (FTIR) instruments and the main experimental IR setups available, namely, transmission (TIR), diffuse reflectance (DRIFTS), attenuated total reflection (ATR-IR), and reflection-absorption (RAIRS), for advancing research in catalysis. We then discuss the different environments under which IR characterization of catalysts is carried out, including in situ and operando studies of typical catalytic processes in gas-phase, research with model catalysts in ultrahigh vacuum (UHV) and so-called high-pressure cell instruments, and work involving liquid/solid interfaces. A presentation of the type of information extracted from IR data follows in terms of the identification of adsorbed intermediates, the characterization of the surfaces of the catalysts themselves, the quantitation of IR intensities to extract surface coverages, and the use of probe molecules to identify and titrate specific catalytic sites. Finally, the different options for carrying out kinetic studies with temporal resolution such as rapid-scan FTIR, step-scan FTIR, and the use of tunable lasers or synchrotron sources, and to obtain spatially resolved spectra, by sample rastering or by 2D imaging, are

  11. Cavity ring-down spectroscopy (CRDS) system for measuring atmospheric mercury using differential absorption

    NASA Astrophysics Data System (ADS)

    Pierce, A.; Obrist, D.; Moosmuller, H.; Moore, C.

    2012-04-01

    Atmospheric elemental mercury (Hg0) is a globally pervasive element that can be transported and deposited to remote ecosystems where it poses — particularly in its methylated form — harm to many organisms including humans. Current techniques for measurement of atmospheric Hg0 require several liters of sample air and several minutes for each analysis. Fast-response (i.e., 1 second or faster) measurements would improve our ability to understand and track chemical cycling of mercury in the atmosphere, including high frequency Hg0 fluctuations, sources and sinks, and chemical transformation processes. We present theory, design, challenges, and current results of our new prototype sensor based on cavity ring-down spectroscopy (CRDS) for fast-response measurement of Hg0 mass concentrations. CRDS is a direct absorption technique that implements path-lengths of multiple kilometers in a compact absorption cell using high-reflectivity mirrors, thereby improving sensitivity and reducing sample volume compared to conventional absorption spectroscopy. Our sensor includes a frequency-doubled, dye-laser emitting laser pulses tunable from 215 to 280 nm, pumped by a Q-switched, frequency tripled Nd:YAG laser with a pulse repetition rate of 50 Hz. We present how we successfully perform automated wavelength locking and stabilization of the laser to the peak Hg0 absorption line at 253.65 nm using an external isotopically-enriched mercury (202Hg0) cell. An emphasis of this presentation will be on the implementation of differential absorption measurement whereby measurements are alternated between the peak Hg0 absorption wavelength and a nearby wavelength "off" the absorption line. This can be achieved using a piezo electric tuning element that allows for pulse-by-pulse tuning and detuning of the laser "online" and "offline" of the Hg absorption line, and thereby allows for continuous correction of baseline extinction losses. Unexpected challenges with this approach included

  12. [Second-harmonic detection with tunable diode laser absorption spectroscopy of CO and CO2 at 1.58 microm].

    PubMed

    Tu, Xing-Hua; Liu, Wen-Qing; Zhang, Yu-Jun; Dong, Feng-Zhong; Wang, Min; Wang, Tie-Dong; Wang, Xiao-Mei; Liu, Jian-Guo

    2006-07-01

    Tunable diode laser absorption spectroscopy has been applied in the fields of atmospheric chemistry and monitoring pollutant gases as a new method of measuring trace gases. The technique of remote sensing of CO and CO2 at 760 mm Hg pressure with tunable diode laser absorption spectroscopy in the near-infrared region is introduced. And the relationship between the second-harmonic spectrum of CO2 in Lorentzian line shape and the modulation amplitude is also presented.

  13. Determination of toxic metals in some herbal drugs through atomic absorption spectroscopy.

    PubMed

    Hina, Bushra; Rizwani, Ghazala Hafeez; Naseem, Shahid

    2011-07-01

    This study presents a picture of occurrence of heavy metals (Pb, Cd, Cu, Cr, Co, Fe, Ni, Zn) in some selected valuable herbal drugs (G. glabra, O. bracteatum, V. odorata , F. vulgare, C. cyminum, C. sativum, and Z. officinalis) purchased from three different zones (southern, eastern, and western) of Karachi city using atomic absorption spectrophotometer. Heavy metal concentrations in these drugs were found in the range of: 3.26-30.46 for Pb, 1.6-4.91 for Cd, 0.65-120.21 for Cu, 83.74-433.76 for Zn, 1.61-186.75 for Cr, 0.48-76.97 for Ni, 5.54-77.97 for Co and 65.68-1652.89 µg/g for Fe. Percentage of heavy metals that were found beyond the permissible limits were: 71.4% for Pb, 28.51% for Cd, 14.2% for Cu, and 9.5 % for Cr. Significant difference was noticed for each heavy metal among herbal drugs as well as their zones of collection using two way ANOVA followed by least significant (LSD) test at p<0.05.Purpose of this research is to detect each type of heavy metal contaminant of herbal drugs by environmental pollution, as well as to highlight the health risks associated with the use of such herbal drugs that contain high levels of toxic heavy metals.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  15. UV-Vis Reflection-Absorption Spectroscopy at air-liquid interfaces.

    PubMed

    Rubia-Payá, Carlos; de Miguel, Gustavo; Martín-Romero, María T; Giner-Casares, Juan J; Camacho, Luis

    2015-11-01

    UV-Visible Reflection-Absorption Spectroscopy (UVRAS) technique is reviewed with a general perspective on fundamental and applications. UVRAS is formally identical to IR Reflection-Absorption Spectroscopy (IRRAS), and therefore, the methodology developed for this IR technique can be applied in the UV-visible region. UVRAS can be applied to air-solid, air-liquid or liquid-liquid interfaces. This review focuses on the use of UVRAS for studying Langmuir monolayers. We introduce the theoretical framework for a successful understanding of the UVRAS data, and we illustrate the usage of this data treatment to a previous study from our group comprising an amphiphilic porphyrin. For ultrathin films with a thickness of few nm, UVRAS produces positive or negative bands when p-polarized radiation is used, depending on the incidence angle and the orientation of dipole absorption. UVRAS technique provides highly valuable information on tilt of chromophores at the air-liquid interface, and moreover allows the determination of optical parameters. We propose UVRAS as a powerful technique to investigate the in situ optical properties of Langmuir monolayers.

  16. High-performance dispersive Raman and absorption spectroscopy as tools for drug identification

    NASA Astrophysics Data System (ADS)

    Pawluczyk, Olga; Andrey, Sam; Nogas, Paul; Roy, Andrew; Pawluczyk, Romuald

    2009-02-01

    Due to increasing availability of pharmaceuticals from many sources, a need is growing to quickly and efficiently analyze substances in terms of the consistency and accuracy of their chemical composition. Differences in chemical composition occur at very low concentrations, so that highly sensitive analytical methods become crucial. Recent progress in dispersive spectroscopy with the use of 2-dimensional detector arrays, permits for signal integration along a long (up to 12 mm long) entrance slit of a spectrometer, thereby increasing signal to noise ratio and improving the ability to detect small concentration changes. This is achieved with a non-scanning, non-destructive system. Two different methods using P&P Optica high performance spectrometers were used. High performance optical dispersion Raman and high performance optical absorption spectroscopy were employed to differentiate various acetaminophen-containing drugs, such as Tylenol and other generic brands, which differ in their ingredients. A 785 nm excitation wavelength was used in Raman measurements and strong Raman signals were observed in the spectral range 300-1800 cm-1. Measurements with the absorption spectrometer were performed in the wavelength range 620-1020 nm. Both Raman and absorption techniques used transmission light spectrometers with volume phase holographic gratings and provided sufficient spectral differences, often structural, allowing for drug differentiation.

  17. Time resolved metal line profile by near-ultraviolet tunable diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Vitelaru, C.; de Poucques, L.; Minea, T. M.; Popa, G.

    2011-03-01

    Pulsed systems are extensively used to produce active species such as atoms, radicals, excited states, etc. The tunable diode laser absorption spectroscopy (TD-LAS) is successfully used to quantify the density of absorbing species, but especially for stationary or slow changing systems. The time resolved-direct absorption profile (TR-DAP) measurement method by TD-LAS, with time resolution of μs is proposed here as an extension of the regular use of diode laser absorption spectroscopy. The spectral narrowness of laser diodes, especially in the blue range (˜0.01 pm), combined with the nanosecond fast trigger of the magnetron pulsed plasma and long trace recording on the oscilloscope (period of second scale) permit the detection of the sputtered titanium metal evolution in the afterglow (˜ms). TR-DAP method can follow the time-dependence of the temperature (Doppler profile) and the density (deduced from the absorbance) of any medium and heavy species in a pulsed system.

  18. [Signal analysis and spectrum distortion correction for tunable diode laser absorption spectroscopy system].

    PubMed

    Bao, Wei-Yi; Zhu, Yong; Chen, Jun; Chen, Jun-Qing; Liang, Bo

    2011-04-01

    In the present paper, the signal of a tunable diode laser absorption spectroscopy (TDLAS) trace gas sensing system, which has a wavelength modulation with a wide range of modulation amplitudes, is studied based on Fourier analysis method. Theory explanation of spectrum distortion induced by laser intensity amplitude modulation is given. In order to rectify the spectrum distortion, a method of synchronous amplitude modulation suppression by a variable optical attenuator is proposed. To validate the method, an experimental setup is designed. Absorption spectrum measurement experiments on CO2 gas were carried out. The results show that the residual laser intensity modulation amplitude of the experimental system is reduced to -0.1% of its original value and the spectrum distortion improvement is 92% with the synchronous amplitude modulation suppression. The modulation amplitude of laser intensity can be effectively reduced and the spectrum distortion can be well corrected by using the given correction method and system. By using a variable optical attenuator in the TDLAS (tunable diode laser absorption spectroscopy) system, the dynamic range requirements of photoelectric detector, digital to analog converter, filters and other aspects of the TDLAS system are reduced. This spectrum distortion correction method can be used for online trace gas analyzing in process industry.

  19. Surface arsenic speciation of a drinking-water treatment residual using X-ray absorption spectroscopy.

    PubMed

    Makris, Konstantinos C; Sarkar, Dibyendu; Parsons, Jason G; Datta, Rupali; Gardea-Torresdey, Jorge L

    2007-07-15

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

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

    PubMed

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

    2016-10-14

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

  1. Angle-tunable enhanced infrared reflection absorption spectroscopy via grating-coupled surface plasmon resonance.

    PubMed

    Petefish, Joseph W; Hillier, Andrew C

    2014-03-04

    Surface enhanced infrared absorption (SEIRA) spectroscopy is an attractive method for increasing the prominence of vibrational modes in infrared spectroscopy. To date, the majority of reports associated with SEIRA utilize localized surface plasmon resonance from metal nanoparticles to enhance electromagnetic fields in the region of analytes. Limited work has been performed using propagating surface plasmons as a method for SEIRA excitation. In this report, we demonstrate angle-tunable enhancement of vibrational stretching modes associated with a thin poly(methyl methacrylate) (PMMA) film that is coupled to a silver-coated diffraction grating. Gratings are fabricated using laser interference lithography to achieve precise surface periodicities, which can be used to generate surface plasmons that overlap with specific vibrational modes in the polymer film. Infrared reflection absorption spectra are presented for both bare silver and PMMA-coated silver gratings at a range of angles and polarization states. In addition, spectra were obtained with the grating direction oriented perpendicular and parallel to the infrared source in order to isolate plasmon enhancement effects. Optical simulations using the rigorous coupled-wave analysis method were used to identify the origin of the plasmon-induced enhancement. Angle-dependent absorption measurements achieved signal enhancements of more than 10-times the signal in the absence of the plasmon.

  2. Controlled variation of the information depth by angle dependent soft X-ray emission spectroscopy: A study on polycrystalline Cu(In,Ga)Se 2

    NASA Astrophysics Data System (ADS)

    Mönig, H.; Lauermann, I.; Grimm, A.; Camus, C.; Kaufmann, C. A.; Pistor, P.; Jung, Ch.; Kropp, T.; Lux-Steiner, M. C.; Fischer, Ch.-H.

    2008-12-01

    Angle dependent X-ray emission spectroscopy (AXES) is introduced as a tool for depth dependent composition analysis. A controlled variation of the information depth is demonstrated by changing the geometry from grazing exit to grazing incidence geometry. First results are presented from Cu(In,Ga)Se 2 (CIGSe)-based polycrystalline thin film solar cell bi-layer components. A mathematical model explains changes in relative intensity due to the absorption and emission behavior of thin CdS and Zn(S,O) cover layers. The fact that the presented data can be modelled by ideal bi-layer structures, provides both, proof of concept in general and the proof of applicability to the relatively rough layered structures based on CIGSe. In bare CIGSe a homogeneous distribution of Cu and Ga is found in a depth range between 22 and 470 nm.

  3. Broadband spectroscopy with external cavity quantum cascade lasers beyond conventional absorption measurements.

    PubMed

    Lambrecht, Armin; Pfeifer, Marcel; Konz, Werner; Herbst, Johannes; Axtmann, Felix

    2014-05-07

    Laser spectroscopy is a powerful tool for analyzing small molecules, i.e. in the gas phase. In the mid-infrared spectral region quantum cascade lasers (QCLs) have been established as the most frequently used laser radiation source. Spectroscopy of larger molecules in the gas phase, of complex mixtures, and analysis in the liquid phase requires a broader tuning range and is thus still the domain of Fourier transform infrared (FTIR) spectroscopy. However, the development of tunable external cavity (EC) QCLs is starting to change this situation. The main advantage of QCLs is their high spectral emission power that is enhanced by a factor of 10(4) compared with thermal light sources. Obviously, transmission measurements with EC-QCLs in strongly absorbing samples are feasible, which can hardly be measured by FTIR due to detector noise limitations. We show that the high power of EC-QCLs facilitates spectroscopy beyond simple absorption measurements. Starting from QCL experiments with liquid samples, we show results of fiber evanescent field analysis (FEFA) to detect pesticides in drinking water. FEFA is a special case of attenuated total reflection spectroscopy. Furthermore, powerful CW EC-QCLs enable fast vibrational circular dichroism (VCD) spectroscopy of chiral molecules in the liquid phase - a technique which is very time consuming with standard FTIR equipment. We present results obtained for the chiral compound 1,1'-bi-2-naphthol (BINOL). Finally, powerful CW EC-QCLs enable the application of laser photothermal emission spectroscopy (LPTES). We demonstrate this for a narrowband and broadband absorber in the gas phase. All three techniques have great potential for MIR process analytical applications.

  4. Excited state assisted three-photon absorption based optical limiting in nanocrystalline Cu2Se and FeSe2

    NASA Astrophysics Data System (ADS)

    Anand, Benoy; Molli, Muralikrishna; Aditha, Saikiran; Mimani Rattan, Tanu; Siva Sankara Sai, S.; Kamisetti, Venkataramaniah

    2013-09-01

    Transition metal selenides (FeSe2 and Cu2Se) are synthesized by the hydrothermal co-reduction method. XRD results revealed the crystalline nature of their single phase and the elemental compositions are obtained using EDS. TEM images of the as-prepared samples show the formation of nanorods of 10-20 nm diameter in case of iron selenide and nanoparticles of 10-35 nm diameter in case of copper selenide. The energy bandgap values are calculated using tauc plots obtained from UV-Visible absorption spectra. The open aperture Z-scan measurements carried out using 5 ns pulses at 532 nm revealed that the samples showed excellent optical limiting behavior owing to strong nonlinear absorption (NLA). Through numerical simulations, the mechanism of NLA is found to be effective three-photon absorption which has significant contribution from excited state absorption.

  5. Immersed single-drop microextraction-electrothermal vaporization atomic absorption spectroscopy for the trace determination of mercury in water samples.

    PubMed

    Bagheri, Habib; Naderi, Mehrnoush

    2009-06-15

    A new method based on single-drop microextraction (SDME) combined with electrothermal vaporization atomic absorption spectroscopy (ETV-AAS) was developed for the trace determination of mercury in water samples. A microdrop of m-xylene was applied as the extraction solvent. After extraction, the microdrop was introduced, directly, into a graphite furnace of AAS. Some important extraction parameters such as type of solvent, volume of solvent, sample stirring, ionic strength, sample pH, chelating agent concentration, sample temperature, and extraction time were investigated and optimized. The highest possible microdrop volume of 10 microL, a sampling temperature of 27 degrees C, and use of m-xylene containing dithizone, as complexing agent, are major parameters led to achieve a high enrichment factor of 970. Under the optimized conditions, the detection limit of the method was 0.01 microg L(-1) and the relative standard deviation was 6.1% (n=7). The proposed method has been successfully applied to the determination of Hg in two river water samples. The effects of interfering species such as Pt, Pd, Cu, Au, and Bi, having the tendency to form complexes with dithizone, at two concentration levels of 100 and 1000 microg L(-1) were also studied.

  6. In situ x-ray absorption spectroscopy study of tin anode nanomaterials for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Pelliccione, Christopher J.

    Tin is an attractive alternative to replace traditional carbon based anodes in lithium-ion batteries (LIBs) due to the nearly three-fold increase in theoretical capacity over carbon. However, metallic tin suffers from volumetric expansion of the crystal structure during initial lithium insertion that quickly degrades the material and reduces the performance of the battery. Various techniques have been previously investigated with the goal of suppressing this destructive expansion by incorporating oxygen or a lithium-inactive metal into the tin to provide structural support and mitigate volumetric expansion. These materials show increased capacity retention compared to metallic tin, but still suffer from capacity fading. The nature of these structural degradations must be fully understood to permit engineering of materials that avoid these destructive tendencies and can be considered as viable options for LIBs. In situ X-ray absorption spectroscopy (XAS) measurements were acquired on Sn, SnO2, Sn3O2(OH) 2, Cu6Sn5 and Ni3Sn4 nanoparticle anodes for LIBs. Accompanying the electrochemical characterization conducted on each material, the local atomic structure was modeled as a function of potential during the first charge and also as a function of charged/discharged states for several cycles. The extended X-ray absorption fine structure (EXAFS) theoretical modeling included the first unambiguous observation of Sn-Li coordination numbers and atomic distances in tin-based anode materials. From correlating the electrochemical performance to the EXAFS analysis, the long-term capacity retention of tin-based anodes is dependent on the structural deformations that occur during the first charge. The conversion of oxygen to amorphous Li2O, and the network that it forms, has a dramatic effect on the kinetics of the system and the stability of the local metallic tin structure.

  7. Temperature and multi-species measurements by supercontinuum absorption spectroscopy for IC engine applications.

    PubMed

    Werblinski, Thomas; Engel, Sascha R; Engelbrecht, Rainer; Zigan, Lars; Will, Stefan

    2013-06-03

    The first supercontinuum (SC) absorption spectroscopy measurements showing the feasibility of quantitative temperature evaluation are presented to the best of the authors' knowledge. Temperature and multi-species measurements were carried out at a detection rate of ~2 MHz in a high-temperature flow cell within a temperature range from 450 K to 750 K at 0.22 MPa, representing conditions during the suction and compression stroke in an internal combustion (IC) engine. The broadband SC pulses were temporally dispersed into fast wavelength sweeps, covering the overtone absorption bands 2ν(1), 2ν(3), ν(1) + ν(3) of H2O and 3ν(3) of CO2 in the near-infrared region from 1330 nm to 1500 nm. The temperature information is inferred from the peak ratio of a temperature sensitive (1362.42 nm) and insensitive (1418.91 nm) absorption feature in the ν(1) + ν(3) overtone bands of water. The experimental results are in very good agreement with theoretical intensity ratios calculated from absorption spectra based on HiTran data.

  8. Tunable Diode Laser Atomic Absorption Spectroscopy for Detection of Potassium under Optically Thick Conditions.

    PubMed

    Qu, Zhechao; Steinvall, Erik; Ghorbani, Ramin; Schmidt, Florian M

    2016-04-05

    Potassium (K) is an important element related to ash and fine-particle formation in biomass combustion processes. In situ measurements of gaseous atomic potassium, K(g), using robust optical absorption techniques can provide valuable insight into the K chemistry. However, for typical parts per billion K(g) concentrations in biomass flames and reactor gases, the product of atomic line strength and absorption path length can give rise to such high absorbance that the sample becomes opaque around the transition line center. We present a tunable diode laser atomic absorption spectroscopy (TDLAAS) methodology that enables accurate, calibration-free species quantification even under optically thick conditions, given that Beer-Lambert's law is valid. Analyte concentration and collisional line shape broadening are simultaneously determined by a least-squares fit of simulated to measured absorption profiles. Method validation measurements of K(g) concentrations in saturated potassium hydroxide vapor in the temperature range 950-1200 K showed excellent agreement with equilibrium calculations, and a dynamic range from 40 pptv cm to 40 ppmv cm. The applicability of the compact TDLAAS sensor is demonstrated by real-time detection of K(g) concentrations close to biomass pellets during atmospheric combustion in a laboratory reactor.

  9. Determining crystal phase purity in c-BP through X-ray absorption spectroscopy.

    PubMed

    Huber, S P; Medvedev, V V; Gullikson, E; Padavala, B; Edgar, J H; van de Kruijs, R W E; Bijkerk, F; Prendergast, D

    2017-02-02

    We employ X-ray absorption near-edge spectroscopy at the boron K-edge and the phosphorus L2,3-edge to study the structural properties of cubic boron phosphide (c-BP) samples. The X-ray absorption spectra are modeled from first-principles within the density functional theory framework using the excited electron core-hole (XCH) approach. A simple structural model of a perfect c-BP crystal accurately reproduces the P L2,3-edge, however it fails to describe the broad and gradual onset of the B K-edge. Simulations of the spectroscopic signatures in boron 1s excitations of intrinsic point defects and the hexagonal BP crystal phase show that these additions to the structural model cannot reproduce the broad pre-edge of the experimental spectrum. Calculated formation enthalpies show that, during the growth of c-BP, it is possible that amorphous boron phases can be grown in conjunction with the desired boron phosphide crystalline phase. In combination with experimental and theoretically obtained X-ray absorption spectra of an amorphous boron structure, which have a similar broad absorption onset in the B K-edge spectrum as the cubic boron phosphide samples, we provide evidence for the presence of amorphous boron clusters in the synthesized c-BP samples.

  10. [Concentration retrieving method of SO2 using differential optical absorption spectroscopy based on statistics].

    PubMed

    Liu, Bin; Sun, Chang-Ku; Zhang, Chi; Zhao, Yu-Mei; Liu, Jun-Ping

    2011-01-01

    A concentration retrieving method using statistics is presented, which is applied in differential optical absorption spectroscopy (DOAS) for measuring the concentration of SO2. The method uses the standard deviation of the differential absorption to represents the gas concentration. Principle component analysis (PCA) method is used to process the differential absorption spectrum. In the method, the basis data for the concentration retrieval of SO2 is the combination of the PCA processing result, the correlation coefficient, and the standard deviation of the differential absorption. The method is applied to a continuous emission monitoring system (CEMS) with optical path length of 0.3 m. Its measuring range for SO2 concentration is 0-5 800 mg x m(-3). The nonlinear calibration and the temperature compensation for the system were executed. The full scale error of the retrieving concentration is less than 0.7% FS. And the measuring result is -4.54 mg x m(-3) when the concentration of SO2 is zero.

  11. Diffuse reflectance spectroscopy as a tool to measure the absorption coefficient in skin: system calibration.

    PubMed

    Karsten, A E; Singh, A; Karsten, P A; Braun, M W H

    2013-02-01

    An individualised laser skin treatment may enhance the treatment and reduces risks and side-effects. The optical properties (absorption and scattering coefficients) are important parameters in the propagation of laser light in skin tissue. The differences in the melanin content of different skin phototypes influence the absorption of the light. The absorption coefficient at the treatment wavelength for an individual can be determined by diffuse reflectance spectroscopy, using a probe containing seven fibres. Six of the fibres deliver the light to the measurement site and the central fibre collects the diffused reflected light. This is an in vivo technique, offering benefits for near-real-time results. Such a probe, with an effective wavelength band from 450 to 800 nm, was used to calibrate skin-simulating phantoms consisting of intralipid and ink. The calibration constants were used to calculate the absorption coefficients from the diffuse reflectance measurements of three volunteers (skin phototypes, II, IV and V) for sun-exposed and non-exposed areas on the arm.

  12. An x-ray absorption spectroscopy study of Mo oxidation in Pb at elevated temperatures

    SciTech Connect

    Liu, Shanshan; Olive, Daniel; Terry, Jeff; Segre, Carlo U.

    2009-06-30

    The corrosion of fuel cladding and structural materials by lead and lead-bismuth eutectic in the liquid state at elevated temperatures is an issue that must be considered when designing advanced nuclear systems and high-power spallation neutron targets. In this work, lead corrosion studies of molybdenum were performed to investigate the interaction layer as a function of temperature by X-ray absorption spectroscopy. In situ X-ray absorption measurements on a Mo substrate with a 3-6 {micro}m layer of Pb deposited by thermal evaporation were performed at temperatures up to 900 C and at a 15{sup o} angle to the incident X-rays. The changes in the local atomic structure of the corrosion layer are visible in the difference extended X-ray absorption fine structure and the linear combination fitting of the X-ray absorption near-edge structure to as-deposited molybdenum sample and molybdenum oxide (MoO{sub 2} and MoO{sub 3}) standards. The data are consistent with the appearance of MoO{sub 3} in an intermediate temperature range (650-800 C) and the more stable MoO{sub 2} phase dominating at high and low temperatures.

  13. The analysis of time-resolved optical waveguide absorption spectroscopy based on positive matrix factorization.

    PubMed

    Liu, Ping; Li, Zhu; Li, Bo; Shi, Guolong; Li, Minqiang; Yu, Daoyang; Liu, Jinhuai

    2013-08-01

    Time-resolved optical waveguide absorption spectroscopy (OWAS) makes use of an evanescent field to detect the polarized absorption spectra of sub-monomolecular adlayers. This technique is suitable for the investigation of kinetics at the solid/liquid interface of dyes, pigments, fluorescent molecules, quantum dots, metallic nanoparticles, and proteins with chromophores. In this work, we demonstrate the application of positive matrix factorization (PMF) to analyze time-resolved OWAS for the first time. Meanwhile, PCA is researched to compare with PMF. The absorption/desorption kinetics of Rhodamine 6G (R6G) onto a hydrophilic glass surface and the dynamic process of Meisenheimer complex between Cysteine and TNT are selected as samples to verify experimental system and analytical methods. The results are shown that time-resolved OWAS can well record the absorption/desorption of R6G onto a hydrophilic glass surface and the dynamic formation process of Meisenheimer complexes. The feature of OWAS extracted by PMF is dynamic and consistent with the results analyzed by the traditional function of time/wavelength-absorbance. Moreover, PMF prevents the negative factors from occurring, avoids contradicting physical reality, and makes factors more easily interpretable. Therefore, we believe that PMF will provide a valuable analysis route to allow processing of increasingly large and complex data sets.

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

    SciTech Connect

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

    2017-01-01

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

  15. Measurement of temperature profiles in flames by emission-absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Simmons, F. S.; Arnold, C. B.; Lindquist, G. H.

    1972-01-01

    An investigation was conducted to explore the use of infrared and ultraviolet emission-absorption spectroscopy for determination of temperature profiles in flames. Spectral radiances and absorptances were measured in the 2.7-micron H2O band and the 3064-A OH band in H2/O2 flames for several temperature profiles which were directly measured by a sodium line-reversal technique. The temperature profiles, determined by inversion of the infrared and ultraviolet spectra, showed an average disagreement with line-reversal measurements of 50 K for the infrared and 200 K for the ultraviolet at a temperature of 2600 K. The reasons for these discrepancies are discussed in some detail.

  16. The nature of arsenic in uranium mill tailings by X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Cutler, J. N.; Chen, N.; Jiang, D. T.; Demopoulos, G. P.; Jia, Y.; Rowson, J. W.

    2003-05-01

    In order to understand the evolving world of environmental issues, the ability to characterize and predict the stability and bioavailability of heavy métal contaminants in mine waste is becoming increasingly more important. X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopies were used to characterize a series of synthetic and natural samples associated with mine tailings processing. XANES was shown to be excellent as a tool to rapidly differentiate oxidation states of arsenic within the samples. The EXAFS spectra provided information on the mineralogy of the precipitated raffinate and tailings and showed that these samples are composed of a mixture of amorphous ferric arsenates, adsorbed arsenates and a mixture of other poorly ordered arsenates.

  17. Ablation-initiated Isotope-selective Atomic Absorption Spectroscopy of Lanthanide Elements

    SciTech Connect

    Miyabe, M.; Oba, M.; Iimura, H.; Akaoka, K.; Maruyama, Y.; Wakaida, I.; Watanabe, K.

    2009-03-17

    For remote isotope analysis of low-decontaminated trans-uranium (TRU) fuel, absorption spectroscopy has been applied to a laser-ablated plume of lanthanide elements. To improve isotopic selectivity and detection sensitivity of the ablated species, various experimental conditions were optimized. Isotope-selective absorption spectra were measured by observing the slow component of the plume produced under low-pressure rare-gas ambient. The measured minimum line width of about 0.9 GHz was close to the Doppler width of the Gd atomic transition at room temperature. The relaxation rate of high-lying metastable state was found to be higher than that of the ground state, which suggests that higher analytical sensitivity can be obtained using low-lying state transition. Under helium gas environment, Doppler splitting was caused from particle motion. This effect was considered for optimization for isotope selection and analysis. Some analytical performances of this method were determined under optimum conditions and were discussed.

  18. Differential Optical Absorption Spectroscopy (DOAS) using Targets: SO2 and NO2 Measurements in Montevideo City

    NASA Astrophysics Data System (ADS)

    Louban, Ilia; Píriz, Gustavo; Platt, Ulrich; Frins, Erna

    2008-04-01

    SO2 and NO2 were remotely measured in a main street of Montevideo city using Multiaxis-Differential Optical Absorption Spectroscopy (MAX-DOAS) combined with on-field selected targets. Target-based measurements are the basis of a new experimental procedure called Topographic Target Light scattering-DOAS (TOTAL-DOAS) that provides a well define absorption path to measure the near surface distribution of trace gases in the boundary layer. It combines the measurement principles of the long-path DOAS and zenith-scattered sunlight DOAS, within the near UV and VIS spectral range. We give a general description of the procedure and present first results of the 2006 campaign at Montevideo.

  19. Reflection-absorption infrared spectroscopy of thin films using an external cavity quantum cascade laser

    NASA Astrophysics Data System (ADS)

    Phillips, Mark C.; Craig, Ian M.; Blake, Thomas A.

    2013-01-01

    We present experimental demonstrations using a broadly tunable external cavity quantum cascade laser (ECQCL) to perform Reflection-Absorption InfraRed Spectroscopy (RAIRS) of thin layers and residues on surfaces. The ECQCL compliance voltage was used to measure fluctuations in the ECQCL output power and improve the performance of the RAIRS measurements. Absorption spectra from self-assembled monolayers of a fluorinated alkane thiol and a thiol carboxylic acid were measured and compared with FTIR measurements. RAIRS spectra of the explosive compounds PETN, RDX, and tetryl deposited on gold substrates were also measured. Rapid measurement times and low noise were demonstrated, with <1E-3 absorbance noise for a 10 second measurement time.

  20. Quantifying the effect of finite spectral bandwidth on extinction coefficient of species in laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Singh, Manjeet; Singh, Jaswant; Singh, Baljit; Ghanshyam, C.

    2016-11-01

    The aim of this study is to quantify the finite spectral bandwidth effect on laser absorption spectroscopy for a wide-band laser source. Experimental analysis reveals that the extinction coefficient of an analyte is affected by the bandwidth of the spectral source, which may result in the erroneous conclusions. An approximate mathematical model has been developed for optical intensities having Gaussian line shape, which includes the impact of source's spectral bandwidth in the equation for spectroscopic absorption. This is done by introducing a suitable first order and second order bandwidth approximation in the Beer-Lambert law equation for finite bandwidth case. The derived expressions were validated using spectroscopic analysis with higher SBW on a test sample, Rhodamine B. The concentrations calculated using proposed approximation, were in significant agreement with the true values when compared with those calculated with conventional approach.

  1. Space Launch System Base Heating Test: Tunable Diode Laser Absorption Spectroscopy

    NASA Technical Reports Server (NTRS)

    Parker, Ron; Carr, Zak; MacLean, Mathew; Dufrene, Aaron; Mehta, Manish

    2016-01-01

    This paper describes the Tunable Diode Laser Absorption Spectroscopy (TDLAS) measurement of several water transitions that were interrogated during a hot-fire testing of the Space Launch Systems (SLS) sub-scale vehicle installed in LENS II. The temperature of the recirculating gas flow over the base plate was found to increase with altitude and is consistent with CFD results. It was also observed that the gas above the base plate has significant velocity along the optical path of the sensor at the higher altitudes. The line-by-line analysis of the H2O absorption features must include the effects of the Doppler shift phenomena particularly at high altitude. The TDLAS experimental measurements and the analysis procedure which incorporates the velocity dependent flow will be described.

  2. Reconstruction of an excited-state molecular wave packet with attosecond transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Cheng, Yan; Chini, Michael; Wang, Xiaowei; González-Castrillo, Alberto; Palacios, Alicia; Argenti, Luca; Martín, Fernando; Chang, Zenghu

    2016-08-01

    Attosecond science promises to allow new forms of quantum control in which a broadband isolated attosecond pulse excites a molecular wave packet consisting of a coherent superposition of multiple excited electronic states. This electronic excitation triggers nuclear motion on the molecular manifold of potential energy surfaces and can result in permanent rearrangement of the constituent atoms. Here, we demonstrate attosecond transient absorption spectroscopy (ATAS) as a viable probe of the electronic and nuclear dynamics initiated in excited states of a neutral molecule by a broadband vacuum ultraviolet pulse. Owing to the high spectral and temporal resolution of ATAS, we are able to reconstruct the time evolution of a vibrational wave packet within the excited B'Σ1u+ electronic state of H2 via the laser-perturbed transient absorption spectrum.

  3. Absorption spectroscopy of wire-array plasma at the non-radiative stage

    NASA Astrophysics Data System (ADS)

    Ivanov, V. V.; Hakel, P.; Mancini, R. C.; Wiewior, P.; Durmaz, T.; Anderson, A.; Astanovitskiy, A.; Chalyy, O.; Altemara, S. D.; Papp, D.; McKee, E.; Chittenden, J. P.; Niasse, N.; Shevelko, A. P.

    2010-11-01

    Absorption spectroscopy was applied to 1 MA wire-array Z-pinches. The 50 TW Leopard laser was coupled with the Zebra generator for x-ray backlighting of wire arrays. Wire-array plasmas were investigated at the ablation and implosion stages. Broadband x-ray radiation from a laser produced Sm plasma was used to backlight Al star wire arrays in the range of 7-9 å. Two time-integrated x-ray conical spectrometers recorded reference and main spectra. The backlighting radiation was separated from the powerful Z-pinch x-ray burst by collimators. A comparison of the backlighting radiation spectra that passed through the plasma with reference spectra indicates absorption lines in the range of 8.2-8.4 å. A plasma density profile was simulated with a 3D resistive MHD code. Simulations with atomic kinetics models derived an electron temperature of Al wire-array plasma.

  4. Infrared and near infrared transient absorption spectroscopy of molecular free radicals

    SciTech Connect

    Sears, T.J.; Wu, M.; Hall, G.E.; Chang, B.C.; Hansford, G.; Bloch, J.C.; Field, R.W.

    1993-12-31

    The advantages of absorption spectroscopy at low absorbances include a linear relationship between signal size and number of absorbing molecules, line of sight measurement, and easily interpretable lineshape functions. The main disadvantage is due to the necessity of measuring a small change in light intensity, usually in the presence of a strong background, which limits the sensitivity. In this work, recent results obtained using absorption techniques with continuous wave lasers to measure vibrational and electronic spectra in the mid- and near-infrared of small free radicals are reported. The radical of interest was generated by excimer laser photolysis of a chemically stable precursor molecule and detected by measuring the transient decrease in power of a continuous wave probe laser that traversed the photolyzed volume before being imaged onto a detector.

  5. Time-resolved x-ray absorption spectroscopy with a water window high-harmonic source

    NASA Astrophysics Data System (ADS)

    Pertot, Yoann; Schmidt, Cédric; Matthews, Mary; Chauvet, Adrien; Huppert, Martin; Svoboda, Vit; von Conta, Aaron; Tehlar, Andres; Baykusheva, Denitsa; Wolf, Jean-Pierre; Wörner, Hans Jakob

    2017-01-01

    Time-resolved x-ray absorption spectroscopy (TR-XAS) has so far practically been limited to large-scale facilities, to subpicosecond temporal resolution, and to the condensed phase. We report the realization of TR-XAS with a temporal resolution in the low femtosecond range by developing a tabletop high-harmonic source reaching up to 350 electron volts, thus partially covering the spectral region of 280 to 530 electron volts, where water is transmissive. We used this source to follow previously unexamined light-induced chemical reactions in the lowest electronic states of isolated CF4+ and SF6+ molecules in the gas phase. By probing element-specific core-to-valence transitions at the carbon K-edge or the sulfur L-edges, we characterized their reaction paths and observed the effect of symmetry breaking through the splitting of absorption bands and Rydberg-valence mixing induced by the geometry changes.

  6. Melting of iron determined by X-ray absorption spectroscopy to 100 GPa

    PubMed Central

    Aquilanti, Giuliana; Trapananti, Angela; Karandikar, Amol; Kantor, Innokenty; Marini, Carlo; Mathon, Olivier; Pascarelli, Sakura; Boehler, Reinhard

    2015-01-01

    Temperature, thermal history, and dynamics of Earth rely critically on the knowledge of the melting temperature of iron at the pressure conditions of the inner core boundary (ICB) where the geotherm crosses the melting curve. The literature on this subject is overwhelming, and no consensus has been reached, with a very large disagreement of the order of 2,000 K for the ICB temperature. Here we report new data on the melting temperature of iron in a laser-heated diamond anvil cell to 103 GPa obtained by X-ray absorption spectroscopy, a technique rarely used at such conditions. The modifications of the onset of the absorption spectra are used as a reliable melting criterion regardless of the solid phase from which the solid to liquid transition takes place. Our results show a melting temperature of iron in agreement with most previous studies up to 100 GPa, namely of 3,090 K at 103 GPa. PMID:26371317

  7. Reflection-Absorption Infrared Spectroscopy of Thin Films Using an External Cavity Quantum Cascade Laser

    SciTech Connect

    Phillips, Mark C.; Craig, Ian M.; Blake, Thomas A.

    2013-02-04

    We present experimental demonstrations using a broadly tunable external cavity quantum cascade laser (ECQCL) to perform Reflection-Absorption InfraRed Spectroscopy (RAIRS) of thin layers and residues on surfaces. The ECQCL compliance voltage was used to measure fluctuations in the ECQCL output power and improve the performance of the RAIRS measurements. Absorption spectra from self-assembled monolayers of a fluorinated alkane thiol and a thiol carboxylic acid were measured and compared with FTIR measurements. RAIRS spectra of the explosive compounds PETN, RDX, and tetryl deposited on gold substrates were also measured. Rapid measurement times and low noise were demonstrated, with < 1E-3 absorbance noise for a 10 second measurement time.

  8. Quantitative Determination of Absolute Organohalogen Concentrations in Environmental Samples by X-ray Absorption Spectroscopy

    SciTech Connect

    Leri,A.; Hay, M.; Lanzirotti, A.; Rao, W.; Myneni, S.

    2006-01-01

    An in situ procedure for quantifying total organic and inorganic Cl concentrations in environmental samples based on X-ray absorption near-edge structure (XANES) spectroscopy has been developed. Cl 1s XANES spectra reflect contributions from all Cl species present in a sample, providing a definitive measure of total Cl concentration in chemically heterogeneous samples. Spectral features near the Cl K-absorption edge provide detailed information about the bonding state of Cl, whereas the absolute fluorescence intensity of the spectra is directly proportional to total Cl concentration, allowing for simultaneous determination of Cl speciation and concentration in plant, soil, and natural water samples. Absolute Cl concentrations are obtained from Cl 1s XANES spectra using a series of Cl standards in a matrix of uniform bulk density. With the high sensitivity of synchrotron-based X-ray absorption spectroscopy, Cl concentration can be reliably measured down to the 5-10 ppm range in solid and liquid samples. Referencing the characteristic near-edge features of Cl in various model compounds, we can distinguish between inorganic chloride (Cl{sub inorg}) and organochlorine (Cl{sub org}), as well as between aliphatic Cl{sub org} and aromatic Cl{sub org}, with uncertainties in the range of {approx}6%. In addition, total organic and inorganic Br concentrations in sediment samples are quantified using a combination of Br 1s XANES and X-ray fluorescence (XRF) spectroscopy. Br concentration is detected down to {approx}1 ppm by XRF, and Br 1s XANES spectra allow quantification of the Br{sub inorg} and Br{sub org} fractions. These procedures provide nondestructive, element-specific techniques for quantification of Cl and Br concentrations that preclude extensive sample preparation.

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

    DOE PAGES

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

    2015-03-02

    We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ~106 photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >107 laser pulses, we also presentmore » data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments.« less

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

    PubMed Central

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

    2015-01-01

    We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ∼106 photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >107 laser pulses, we also present data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments. PMID:26798792

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

    SciTech Connect

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

    2015-03-02

    We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ~106 photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >107 laser pulses, we also present data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments.

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

    PubMed

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

    2015-03-01

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

  13. Tunable Diode Laser Absorption Spectroscopy of Metastable Atoms in Dusty Plasmas

    SciTech Connect

    Hoang Tung Do; Hippler, Rainer

    2008-09-07

    Spatial density profile of neon metastable produced in dusty plasma was investigated by means of tunable diode laser absorption spectroscopy. The line averaged measured density drops about 30% with the presence of dust particles. The observations provide evidence for a significant interaction between atoms and powder particles which are important for energy transfer from plasma to particles. The power per unit area absorbed by dust particles due to the collision of metastable atoms with dust particle surface is about some tens of mW/m{sup 2}.

  14. Metal release in metallothioneins induced by nitric oxide: X-ray absorption spectroscopy study.

    PubMed

    Casero, Elena; Martín-Gago, José A; Pariente, Félix; Lorenzo, Encarnación

    2004-12-01

    Metallothioneins (MTs) are low molecular weight proteins that include metal ions in thiolate clusters. The capability of metallothioneins to bind different metals has suggested their use as biosensors for different elements. We study here the interaction of nitric oxide with rat liver MTs by using in situ X-ray absorption spectroscopy techniques. We univocally show that the presence of NO induces the release of Zn atoms from the MT structure to the solution. Zn ions transform in the presence of NO from a tetrahedral four-fold coordinated environment in the MT into a regular octahedral six-fold coordinated state, with interatomic distances compatible with those of Zn solvated in water.

  15. Determination of the melting temperature of palladium nanoparticles by X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Vlasenko, V. G.; Podsukhina, S. S.; Kozinkin, A. V.; Zubavichus, Ya. V.

    2016-02-01

    The anharmonicity parameters of the interatomic potential in ~4-nm palladium nanoparticles deposited on poly(tetra)fluoroethylene microgranules 0.2-0.5 μm in average size were studied by X-ray absorption spectroscopy from an analysis of temperature-dependent EXAFS Pd K edges. The parameters of the interatomic potential obtained were used to calculate melting temperature T melt = 1591 K and Debye temperature ΘD = 257 K of palladium nanoparticles; these temperatures are significantly lower than those in metallic palladium: 277 K and 1825 K, respectively.

  16. Wavelength modulation spectroscopy--digital detection of gas absorption harmonics based on Fourier analysis.

    PubMed

    Mei, Liang; Svanberg, Sune

    2015-03-20

    This work presents a detailed study of the theoretical aspects of the Fourier analysis method, which has been utilized for gas absorption harmonic detection in wavelength modulation spectroscopy (WMS). The lock-in detection of the harmonic signal is accomplished by studying the phase term of the inverse Fourier transform of the Fourier spectrum that corresponds to the harmonic signal. The mathematics and the corresponding simulation results are given for each procedure when applying the Fourier analysis method. The present work provides a detailed view of the WMS technique when applying the Fourier analysis method.

  17. Infrared reflection absorption spectroscopy investigation of carbon nanotube growth on cobalt catalyst surfaces

    NASA Astrophysics Data System (ADS)

    Kimura, Yasuo; Numasawa, Takeru; Nihei, Mizuhisa; Niwano, Michio

    2007-02-01

    To clarify the effect the oxygen has on the carbon nanotube (CNT) growth mechanisms, the authors use infrared absorption spectroscopy for the monitoring of CNT growth on cobalt catalyst surfaces. CNT grew when methanol was used as a reaction gas, while they did not grow when methane was used. The authors observed spectral changes due to the formation of cobalt oxides and methoxides on the cobalt catalyst surfaces only during the growth of CNT. The results indicate that partial oxidation of the cobalt catalyst surface increases the adsorption probability of the reaction gas and ultimately induces growth of CNT.

  18. Intracavity Laser Absorption Spectroscopy of Zirconium Fluoride in the Near Infrared

    NASA Astrophysics Data System (ADS)

    O'Brien, Leah C.; Harms, Jack C.; O'Brien, James J.

    2013-06-01

    A new band of ZrF has been recorded in the near-infrared with rotational resolution using intracavity laser absorption spectroscopy. A red-degraded bandhead is observed at 12527wn, and 2 R-branches and 2 P-branches have been identified. The results of the analysis will be presented. The gas phase ZrF molecules were produced using a zirconium-lined hollow cathode in an argon-based electric discharge with a small amount of SF_{6}.

  19. Quantum Cascade Laser Absorption Spectroscopy as a Plasma Diagnostic Tool: An Overview

    PubMed Central

    Welzel, Stefan; Hempel, Frank; Hübner, Marko; Lang, Norbert; Davies, Paul B.; Röpcke, Jürgen

    2010-01-01

    The recent availability of thermoelectrically cooled pulsed and continuous wave quantum and inter-band cascade lasers in the mid-infrared spectral region has led to significant improvements and new developments in chemical sensing techniques using in-situ laser absorption spectroscopy for plasma diagnostic purposes. The aim of this article is therefore two-fold: (i) to summarize the challenges which arise in the application of quantum cascade lasers in such environments, and, (ii) to provide an overview of recent spectroscopic results (encompassing cavity enhanced methods) obtained in different kinds of plasma used in both research and industry. PMID:22163581

  20. Total Absorption Spectroscopy Study of (92)Rb Decay: A Major Contributor to Reactor Antineutrino Spectrum Shape.

    PubMed

    Zakari-Issoufou, A-A; Fallot, M; Porta, A; Algora, A; Tain, J L; Valencia, E; Rice, S; Bui, V M; Cormon, S; Estienne, M; Agramunt, J; Äystö, J; Bowry, M; Briz, J A; Caballero-Folch, R; Cano-Ott, D; Cucoanes, A; Elomaa, V-V; Eronen, T; Estévez, E; Farrelly, G F; Garcia, A R; Gelletly, W; Gomez-Hornillos, M B; Gorlychev, V; Hakala, J; Jokinen, A; Jordan, M D; Kankainen, A; Karvonen, P; Kolhinen, V S; Kondev, F G; Martinez, T; Mendoza, E; Molina, F; Moore, I; Perez-Cerdán, A B; Podolyák, Zs; Penttilä, H; Regan, P H; Reponen, M; Rissanen, J; Rubio, B; Shiba, T; Sonzogni, A A; Weber, C

    2015-09-04

    The antineutrino spectra measured in recent experiments at reactors are inconsistent with calculations based on the conversion of integral beta spectra recorded at the ILL reactor. (92)Rb makes the dominant contribution to the reactor antineutrino spectrum in the 5-8 MeV range but its decay properties are in question. We have studied (92)Rb decay with total absorption spectroscopy. Previously unobserved beta feeding was seen in the 4.5-5.5 region and the GS to GS feeding was found to be 87.5(25)%. The impact on the reactor antineutrino spectra calculated with the summation method is shown and discussed.

  1. A quality control technique based on UV-VIS absorption spectroscopy for tequila distillery factories

    NASA Astrophysics Data System (ADS)

    Barbosa Garcia, O.; Ramos Ortiz, G.; Maldonado, J. L.; Pichardo Molina, J.; Meneses Nava, M. A.; Landgrave, Enrique; Cervantes, M. J.

    2006-02-01

    A low cost technique based on the UV-VIS absorption spectroscopy is presented for the quality control of the spirit drink known as tequila. It is shown that such spectra offer enough information to discriminate a given spirit drink from a group of bottled commercial tequilas. The technique was applied to white tequilas. Contrary to the reference analytic methods, such as chromatography, for this technique neither special personal training nor sophisticated instrumentations is required. By using hand-held instrumentation this technique can be applied in situ during the production process.

  2. Diffuse-light absorption spectroscopy for beer classification and prediction of alcoholic content

    NASA Astrophysics Data System (ADS)

    Ciaccheri, L.; Samano Baca, E. E.; Russo, M. T.; Ottevaere, H.; Thienpont, H.; Mignani, A. G.

    2012-04-01

    A miscellaneous of 86 beers was characterized by non-destructive, fast and reagent-free optical measurements. Diffuselight absorption spectroscopy performed in the visible and near-infrared bands was used to gather a turbidity-free spectroscopic information. Also, conventional turbidity and refractive index measurements were added for completing the optical characterization. The near-infrared spectra provided a straightforward turbidity-free assessment of the alcoholic strength. Then, the entire optical data set was processed by means of multivariate analysis looking for a beer clustering according to the own character and identity. Good results were achieved, indicating that optical methods can be successfully used for beer authentication.

  3. Multiplexed detection of xylene and trichloroethylene in water by photonic crystal absorption spectroscopy.

    PubMed

    Lai, Wei-Cheng; Chakravarty, Swapnajit; Zou, Yi; Chen, Ray T

    2013-10-01

    We experimentally demonstrate simultaneous selective detection of xylene and trichloroethylene (TCE) using multiplexed photonic crystal waveguides (PCWs) by near-infrared optical absorption spectroscopy on a chip. Based on the slow light effect of photonic crystal structure, the sensitivity of our device is enhanced to 1 ppb (v/v) for xylene and 10 ppb (v/v) for TCE in water. Multiplexing is enabled by multimode interference power splitters and Y-combiners that integrate multiple PCWs on a silicon chip in a silicon-on-insulator platform.

  4. An x-ray absorption spectroscopy study of Cd binding onto a halophilic archaeon

    NASA Astrophysics Data System (ADS)

    Showalter, Allison R.; Szymanowski, Jennifer E. S.; Fein, Jeremy B.; Bunker, Bruce A.

    2016-05-01

    X-ray absorption spectroscopy (XAS) and cadmium (Cd) isotherm experiments determine how Cd adsorbs to the surface of halophilic archaeon Halobacterium noricense. This archaeon, isolated from the Waste Isolation Pilot Plant (WIPP) near Carlsbad, New Mexico could be involved with the transport of toxic metals stored in the transuranic waste in the salt mine. The isotherm experiments show that adsorption is relatively constant across the tolerable pH range for H. noricense. The XAS results indicate that Cd adsorption occurs predominately via a sulfur site, most likely sulfhydryl, with the same site dominating all measured pH values.

  5. Solvation and Deprotonation Dynamics in Reverse Micelles via Broadband Femtoseond Transient Absorption (BFTA) Spectroscopy

    NASA Astrophysics Data System (ADS)

    Cole, Richard

    2009-10-01

    Broadband femtosecond transient absorption (BFTA) spectroscopy is a useful tool in characterizing femtosecond and picosecond physical and chemical dynamics such as solvation, electron transfer, and deprotonation dynamics. This presentation will focus on our most recent results, which utilize BFTA spectroscopy in the ultraviolet-visible (UV-vis) spectral range to probe deprotonation and solvation dynamics in the nanoscopic confinement of reverse micelles. In these studies, pyranine, a `photo-acid', probes both solvation and deprotonation dynamics in reverse micelles formed from cationic (cetyl trimethylammonium bromide, CTAB), anionic (sodium dioctyl sulfosuccinate, AOT), and neutral (polyoxyethylene nonylphenylether, Igepal) surfactants. Dynamic behavior will be discussed in terms of the degree of nanoscopic confinement (micellar size) and the impact of varying interfacial environments.

  6. Revisiting the inelastic electron tunneling spectroscopy of single hydrogen atom adsorbed on the Cu(100) surface

    SciTech Connect

    Jiang, Zhuoling; Wang, Hao; Sanvito, Stefano; Hou, Shimin

    2015-12-21

    Inelastic electron tunneling spectroscopy (IETS) of a single hydrogen atom on the Cu(100) surface in a scanning tunneling microscopy (STM) configuration has been investigated by employing the non-equilibrium Green’s function formalism combined with density functional theory. The electron-vibration interaction is treated at the level of lowest order expansion. Our calculations show that the single peak observed in the previous STM-IETS experiments is dominated by the perpendicular mode of the adsorbed H atom, while the parallel one only makes a negligible contribution even when the STM tip is laterally displaced from the top position of the H atom. This propensity of the IETS is deeply rooted in the symmetry of the vibrational modes and the characteristics of the conduction channel of the Cu-H-Cu tunneling junction, which is mainly composed of the 4s and 4p{sub z} atomic orbitals of the Cu apex atom and the 1s orbital of the adsorbed H atom. These findings are helpful for deepening our understanding of the propensity rules for IETS and promoting IETS as a more popular spectroscopic tool for molecular devices.

  7. Revisiting the inelastic electron tunneling spectroscopy of single hydrogen atom adsorbed on the Cu(100) surface.

    PubMed

    Jiang, Zhuoling; Wang, Hao; Sanvito, Stefano; Hou, Shimin

    2015-12-21

    Inelastic electron tunneling spectroscopy (IETS) of a single hydrogen atom on the Cu(100) surface in a scanning tunneling microscopy (STM) configuration has been investigated by employing the non-equilibrium Green's function formalism combined with density functional theory. The electron-vibration interaction is treated at the level of lowest order expansion. Our calculations show that the single peak observed in the previous STM-IETS experiments is dominated by the perpendicular mode of the adsorbed H atom, while the parallel one only makes a negligible contribution even when the STM tip is laterally displaced from the top position of the H atom. This propensity of the IETS is deeply rooted in the symmetry of the vibrational modes and the characteristics of the conduction channel of the Cu-H-Cu tunneling junction, which is mainly composed of the 4s and 4pz atomic orbitals of the Cu apex atom and the 1s orbital of the adsorbed H atom. These findings are helpful for deepening our understanding of the propensity rules for IETS and promoting IETS as a more popular spectroscopic tool for molecular devices.

  8. A Complete Overhaul of the Electron Energy-Loss Spectroscopy and X-Ray Absorption Spectroscopy Database: eelsdb.eu.

    PubMed

    Ewels, Philip; Sikora, Thierry; Serin, Virginie; Ewels, Chris P; Lajaunie, Luc

    2016-06-01

    The electron energy-loss spectroscopy (EELS) and X-ray absorption spectroscopy (XAS) database has been completely rewritten, with an improved design, user interface, and a number of new tools. The database is accessible at https://eelsdb.eu/ and can now be used without registration. The submission process has been streamlined to encourage spectrum submissions and the new design gives greater emphasis on contributors' original work by highlighting their papers. With numerous new filters and a powerful search function, it is now simple to explore the database of several hundred EELS and XAS spectra. Interactive plots allow spectra to be overlaid, facilitating online comparison. An application-programming interface has been created, allowing external tools and software to easily access the information held within the database. In addition to the database itself, users can post and manage job adverts and read the latest news and events regarding the EELS and XAS communities. In accordance with the ongoing drive toward open access data increasingly demanded by funding bodies, the database will facilitate open access data sharing of EELS and XAS spectra.

  9. Quantitative analysis of Cu and Co adsorbed on fish bones via laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Rezk, R. A.; Galmed, A. H.; Abdelkreem, M.; Ghany, N. A. Abdel; Harith, M. A.

    2016-09-01

    In the present work, laser-induced breakdown spectroscopy (LIBS) has been applied for qualitative and quantitative analysis of heavy metals adsorbed by fish bones. Fish bones were used as a natural and low cost heavy metal sorbent (mainly Cu and Co) from synthetic wastewater. The removal efficiency of the adsorbent was studied as a function of initial metal concentration and pH value. Optimal experimental conditions were evaluated for improving the sensitivity of LIBS technique through parametric dependence studies. Furthermore, calibration curves were constructed based on X-ray fluorescence (XRF) analysis technique, whereas, the limits of detection (LOD) for Cu and Co were calculated. The results were validated by comparing LIBS data with those obtained by XRF spectrometry. The results of the two techniques are strongly correlated which verified the feasibility of using LIBS to detect traces of heavy metals adsorbed from wastewater by fish bones. This study reflects the potential of using LIBS in environmental applications.

  10. Structural changes in a polyelectrolyte multilayer assembly investigated by reflection absorption infrared spectroscopy and sum frequency generation spectroscopy.

    PubMed

    Kett, Peter J N; Casford, Michael T L; Yang, Amanda Y; Lane, Thomas J; Johal, Malkiat S; Davies, Paul B

    2009-02-12

    The structure of polyelectrolyte multilayer films adsorbed onto either a per-protonated or per-deuterated 11-mercaptoundecanoic acid (h-MUA/d-MUA) self assembled monolayer (SAM) on gold was investigated in air using two surface vibrational spectroscopy techniques, namely, reflection absorption infrared spectroscopy (RAIRS) and sum frequency generation (SFG) spectroscopy. Determination of film masses and dissipation values were made using a quartz crystal microbalance with dissipation monitoring (QCM-D). The films, containing alternating layers of the polyanion poly[1-[4-(3-carboxy-4-hydroxyphenylazo) benzenesulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) and the polycation poly(ethylenimine) (PEI) built on the MUA SAM, were formed using the layer-by-layer electrostatic self-assembly method. The SFG spectrum of the SAM itself comprised strong methylene resonances, indicating the presence of gauche defects in the alkyl chains of the acid. The RAIRS spectrum of the SAM also contained strong methylene bands, indicating a degree of orientation of the methylene groups parallel to the surface normal. Changes in the SFG and RAIRS spectra when a PEI layer was adsorbed on the MUA monolayer showed that the expected electrostatic interaction between the polymer and the SAM, probably involving interpenetration of the PEI into the MUA monolayer, caused a straightening of the alkyl chains of the MUA and, consequently, a decrease in the number of gauche defects. When a layer of PAZO was subsequently deposited on the MUA/PEI film, further spectral changes occurred that can be explained by the formation of a complex PEI/PAZO interpenetrated layer. A per-deuterated MUA SAM was used to determine the relative contributions from the adsorbed polyelectrolytes and the MUA monolayer to the RAIRS and SFG spectra. Spectroscopic and adsorbed mass measurements combined showed that as further bilayers were constructed the interpenetration of PAZO into preadsorbed PEI layers was repeated, up to

  11. Soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering spectroscopy below 100 eV: probing first-row transition-metal M-edges in chemical complexes.

    PubMed

    Wang, Hongxin; Young, Anthony T; Guo, Jinghua; Cramer, Stephen P; Friedrich, Stephan; Braun, Artur; Gu, Weiwei

    2013-07-01

    X-ray absorption and scattering spectroscopies involving the 3d transition-metal K- and L-edges have a long history in studying inorganic and bioinorganic molecules. However, there have been very few studies using the M-edges, which are below 100 eV. Synchrotron-based X-ray sources can have higher energy resolution at M-edges. M-edge X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) could therefore provide complementary information to K- and L-edge spectroscopies. In this study, M2,3-edge XAS on several Co, Ni and Cu complexes are measured and their spectral information, such as chemical shifts and covalency effects, are analyzed and discussed. In addition, M2,3-edge RIXS on NiO, NiF2 and two other covalent complexes have been performed and different d-d transition patterns have been observed. Although still preliminary, this work on 3d metal complexes demonstrates the potential to use M-edge XAS and RIXS on more complicated 3d metal complexes in the future. The potential for using high-sensitivity and high-resolution superconducting tunnel junction X-ray detectors below 100 eV is also illustrated and discussed.

  12. Physisorbed H{sub 2}@Cu(100) surface: Potential and spectroscopy

    SciTech Connect

    Bernard, Eddy; Houriez, Céline; Mitrushchenkov, Alexander O.; Guitou, Marie; Chambaud, Gilberte

    2015-02-07

    Using an embedding approach, a 2-D potential energy function has been calculated to describe the physisorption interaction of H{sub 2} with a Cu(100) surface. For this purpose, a cluster model of the system calculated with highly correlated wavefunctions is combined with a periodic Density-Functional-Theory method using van der Waals-DF2 functional. Rotational and vibrational energy levels of physisorbed H{sub 2}, as well as D{sub 2} and HD, are calculated using the 2D embedding corrected potential energy function. The calculated transitions are in a very good agreement with Electron-Energy-Loss-Spectroscopy observations.

  13. Evolution of silver nanoparticles in the rat lung investigated by X-ray absorption spectroscopy

    SciTech Connect

    Davidson, R. Andrew; Anderson, Donald S.; Van Winkle, Laura S.; Pinkerton, Kent E.; Guo, T.

    2014-12-16

    Following a 6-h inhalation exposure to aerosolized 20 and 110 nm diameter silver nanoparticles, lung tissues from rats were investigated with X-ray absorption spectroscopy, which can identify the chemical state of silver species. Lung tissues were processed immediately after sacrifice of the animals at 0, 1, 3, and 7 days post exposure and the samples were stored in an inert and low-temperature environment until measured. We found that it is critical to follow a proper processing, storage and measurement protocol; otherwise only silver oxides are detected after inhalation even for the larger nanoparticles. The results of X-ray absorption spectroscopy measurements taken in air at 85 K suggest that the dominating silver species in all the postexposure lung tissues were metallic silver, not silver oxide, or solvated silver cations. The results further indicate that the silver nanoparticles in the tissues were transformed from the original nanoparticles to other forms of metallic silver nanomaterials and the rate of this transformation depended on the size of the original nanoparticles. Furthermore, we found that 20 nm diameter silver nanoparticles were significantly modified after aerosolization and 6-h inhalation/deposition, whereas larger, 110 nm diameter nanoparticles were largely unchanged. Over the seven-day postexposure period the smaller 20 nm silver nanoparticles underwent less change in the lung tissue than the larger 110 nm silver nanoparticles. In contrast, silica-coated gold nanoparticles did not undergo any modification processes and remained as the initial nanoparticles throughout the 7-day study period.

  14. Peroxy radical detection for airborne atmospheric measurements using absorption spectroscopy of NO2

    NASA Astrophysics Data System (ADS)

    Horstjann, M.; Andrés Hernández, M. D.; Nenakhov, V.; Chrobry, A.; Burrows, J. P.

    2014-05-01

    Development of an airborne instrument for the determination of peroxy radicals (PeRCEAS - peroxy radical chemical enhancement and absorption spectroscopy) is reported. Ambient peroxy radicals (HO2 and RO2, R being an organic chain) are converted to NO2 in a reactor using a chain reaction involving NO and CO. Provided that the amplification factor, called effective chain length (eCL), is known, the concentration of NO2 can be used as a proxy for the peroxy radical concentration in the sampled air. The eCL depends on radical surface losses and must thus be determined experimentally for each individual setup. NO2 is detected by continuous-wave cavity ring-down spectroscopy (cw-CRDS) using an extended cavity diode laser (ECDL) at 408.9 nm. Optical feedback from a V-shaped resonator maximizes transmission and allows for a simple detector setup. CRDS directly yields absorption coefficients, thus providing NO2 concentrations without additional calibration. The optimum 1σ detection limit is 0.3 ppbv at an averaging time of 40 s and an inlet pressure of 300 hPa. Effective chain lengths were determined for HO2 and CH3O2 at different inlet pressures. The 1σ detection limit at an inlet pressure of 300 hPa for HO2 is 3 pptv for an averaging time of 120 s.

  15. X-ray absorption spectroscopy (XAS) of toxic metal mineral transformations by fungi.

    PubMed

    Fomina, Marina; Charnock, John; Bowen, Andrew D; Gadd, Geoffrey M

    2007-02-01

    Fungi can be highly efficient biogeochemical agents and accumulators of soluble and particulate forms of metals. This work aims to understand some of the physico-chemical mechanisms involved in toxic metal transformations focusing on the speciation of metals accumulated by fungi and mycorrhizal associations. The amorphous state or poor crystallinity of metal complexes within biomass and relatively low metal concentrations make the determination of metal speciation in biological systems a challenging problem but this can be overcome by using synchrotron-based element-specific X-ray absorption spectroscopy (XAS) techniques. In this research, we have exposed fungi and ectomycorrhizas to a variety of copper-, zinc- and lead-containing minerals. X-ray absorption spectroscopy studies revealed that oxygen ligands (phosphate, carboxylate) played a major role in toxic metal coordination within the fungal and ectomycorrhizal biomass during the accumulation of mobilized toxic metals. Coordination of toxic metals within biomass depended on the fungal species, initial mineral composition, the nitrogen source, and the physiological state/age of the fungal mycelium.

  16. Adsorption of mercury on lignin: combined surface complexation modeling and X-ray absorption spectroscopy studies.

    PubMed

    Lv, Jitao; Luo, Lei; Zhang, Jing; Christie, Peter; Zhang, Shuzhen

    2012-03-01

    Adsorption of mercury (Hg) on lignin was studied at a range of pH values using a combination of batch adsorption experiments, a surface complexation model (SCM) and synchrotron X-ray absorption spectroscopy (XAS). Surface complexation modeling indicates that three types of acid sites on lignin surfaces, namely aliphatic carboxylic-, aromatic carboxylic- and phenolic-type surface groups, contributed to Hg(II) adsorption. The bond distance and coordination number of Hg(II) adsorption samples at pH 3.0, 4.0 and 5.5 were obtained from extended X-ray absorption fine structure (EXAFS) spectroscopy analysis. The results of SCM and XAS combined reveal that the predominant adsorption species of Hg(II) on lignin changes from HgCl(2)(0) to monodentate complex -C-O-HgCl and then bidentate complex -C-O-Hg-O-C- with increasing pH value from 2.0 to 6.0. The good agreement between SCM and XAS results provides new insight into understanding the mechanisms of Hg(II) adsorption on lignin.

  17. Combined characterization of bovine polyhemoglobin microcapsules by UV-Vis absorption spectroscopy and cyclic voltammetry.

    PubMed

    Knirsch, Marcos Camargo; Dell'Anno, Filippo; Salerno, Marco; Larosa, Claudio; Polakiewicz, Bronislaw; Eggenhöffner, Roberto; Converti, Attilio

    2017-03-01

    Polyhemoglobin produced from pure bovine hemoglobin by reaction with PEG bis(N-succynimidil succinate) as a cross-linking agent was encapsulated in gelatin and dehydrated by freeze-drying. Free carboxyhemoglobin and polyhemoglobin microcapsules were characterized by UV-Vis spectroscopy in the absorption range 450-650 nm and cyclic voltammetry in the voltage range from -0.8 to 0.6 mV to evaluate the ability to break the bond with carbon monoxide and to study the carrier's affinity for oxygen, respectively. SEM used to observe the shape of cross-linked gelatin-polyhemoglobin microparticles showed a regular distribution of globular shapes, with mean size of ~750 nm, which was ascribed to gelatin. Atomic absorption spectroscopy was also performed to detect iron presence in microparticles. Cyclic voltammetry using an Ag-AgCl electrode highlighted characteristic peaks at around -0.6 mV that were attributed to reversible oxygen bonding with iron in oxy-polyhemoglobin structure. These results suggest this technique as a powerful, direct and alternative method to evaluate the extent of hemoglobin oxygenation.

  18. Total Absorption Spectroscopy of the 137Xe, 137I, and 92Rb β-Decays

    NASA Astrophysics Data System (ADS)

    Rasco, B. C.; Fijałkowska, A.; Karny, M.; Rykaczewski, K. P.; Wolińska-Cichocka, M.; Goetz, K. C.; Grzywacz, R. K.; Gross, C. J.; Miernik, K.; Stracener, D.

    2015-10-01

    The NaI(Tl) based Modular Total Absorption Spectrometer (MTAS) was constructed to measure improved β-decay feeding patterns from neutron-rich nuclei. It is difficult to measure β-decay feeding intensities with high precision γ-ray measurements due to the low efficiency of high precision detectors. There are several important applications of improved measurements of β-decay feeding patterns by total absorption spectroscopy; improve understanding of elemental abundances in the universe, help with stockpile stewardship, contribute to understanding of underlying nuclear structure, and improve β-decay feeding measurements to calculate accurately the νe spectra needed to evaluate precisely reactor neutrino measurements. We present β-decay feeding results for two ``priority one'' measurements, 137Xe and 137I, and for 92Rb, which is a large individual contributor to the νe uncertainty of the reactor anomaly. In addition to β- γ decays, 137I has a β-neutron decay channel which is measurable in MTAS. We will demonstrate techniques for analyzing MTAS γ-decay data. We will also describe β and neutron spectroscopy in MTAS. This work was supported by the US DOE by Award No. DE-FG02- 96ER40978 and by US DOE, Office of Nuclear Physics.

  19. Evolution of Silver Nanoparticles in the Rat Lung Investigated by X-ray Absorption Spectroscopy

    PubMed Central

    2015-01-01

    Following a 6-h inhalation exposure to aerosolized 20 and 110 nm diameter silver nanoparticles, lung tissues from rats were investigated with X-ray absorption spectroscopy, which can identify the chemical state of silver species. Lung tissues were processed immediately after sacrifice of the animals at 0, 1, 3, and 7 days post exposure and the samples were stored in an inert and low-temperature environment until measured. We found that it is critical to follow a proper processing, storage and measurement protocol; otherwise only silver oxides are detected after inhalation even for the larger nanoparticles. The results of X-ray absorption spectroscopy measurements taken in air at 85 K suggest that the dominating silver species in all the postexposure lung tissues were metallic silver, not silver oxide, or solvated silver cations. The results further indicate that the silver nanoparticles in the tissues were transformed from the original nanoparticles to other forms of metallic silver nanomaterials and the rate of this transformation depended on the size of the original nanoparticles. We found that 20 nm diameter silver nanoparticles were significantly modified after aerosolization and 6-h inhalation/deposition, whereas larger, 110 nm diameter nanoparticles were largely unchanged. Over the seven-day postexposure period the smaller 20 nm silver nanoparticles underwent less change in the lung tissue than the larger 110 nm silver nanoparticles. In contrast, silica-coated gold nanoparticles did not undergo any modification processes and remained as the initial nanoparticles throughout the 7-day study period. PMID:25517690

  20. Silver in geological fluids from in situ X-ray absorption spectroscopy and first-principles molecular dynamics

    NASA Astrophysics Data System (ADS)

    Pokrovski, Gleb S.; Roux, Jacques; Ferlat, Guillaume; Jonchiere, Romain; Seitsonen, Ari P.; Vuilleumier, Rodolphe; Hazemann, Jean-Louis

    2013-04-01

    The molecular structure and stability of species formed by silver in aqueous saline solutions typical of hydrothermal settings were quantified using in situ X-ray absorption spectroscopy (XAS) measurements, quantum-chemical modeling of near-edge absorption spectra (XANES) and extended fine structure spectra (EXAFS), and first-principles molecular dynamics (FPMD). Results show that in nitrate-bearing acidic solutions to at least 200 °C, silver speciation is dominated by the hydrated Ag+ cation surrounded by 4-6 water molecules in its nearest coordination shell with mean Ag-O distances of 2.32 ± 0.02 Å. In NaCl-bearing acidic aqueous solutions of total Cl concentration from 0.7 to 5.9 mol/kg H2O (m) at temperatures from 200 to 450 °C and pressures to 750 bar, the dominant species are the di-chloride complex AgCl2- with Ag-Cl distances of 2.40 ± 0.02 Å and Cl-Ag-Cl angle of 160 ± 10°, and the tri-chloride complex AgCl32- of a triangular structure and mean Ag-Cl distances of 2.60 ± 0.05 Å. With increasing temperature, the contribution of the tri-chloride species decreases from ˜50% of total dissolved Ag in the most concentrated solution (5.9m Cl) at 200 °C to less than 10-20% at supercritical temperatures for all investigated solutions, so that AgCl2- becomes by far the dominant Ag-bearing species at conditions typical of hydrothermal-magmatic fluids. Both di- and tri-chloride species exhibit outer-sphere interactions with the solvent as shown by the detection, using FPMD modeling, of H2O, Cl-, and Na+ at distances of 3-4 Å from the silver atom. The species fractions derived from XAS and FPMD analyses, and total AgCl(s) solubilities, measured in situ in this work from the absorption edge height of XAS spectra, are in accord with thermodynamic predictions using the stability constants of AgCl2- and AgCl32- from Akinfiev and Zotov (2001) and Zotov et al. (1995), respectively, which are based on extensive previous AgCl(s) solubility measurements. These data

  1. Multinuclear (67Zn, 119Sn and 65Cu) NMR spectroscopy--an ideal technique to probe the cationic ordering in Cu2ZnSnS4 photovoltaic materials.

    PubMed

    Choubrac, Léo; Paris, Michaël; Lafond, Alain; Guillot-Deudon, Catherine; Rocquefelte, Xavier; Jobic, Stéphane

    2013-07-14

    For the very first time, (67)Zn, (119)Sn and (65)Cu NMR investigations have been carried out on Cu2ZnSnS4 derivatives (CZTS) for photovoltaic applications. NMR spectroscopy is shown to be sensitive enough to probe the Cu/Zn disorder within the kesterite structure of the studied compounds. In addition, reference spectra of Cu2ZnSnS4 are provided, and experimental (67)Zn and (65)Cu parameters are compared with ab initio calculations.

  2. Time-resolved postdischarge absolute silicon monoxide density measurement by resonant absorption spectroscopy in a nonthermal atmospheric plasma

    SciTech Connect

    Motret, Olivier; Coursimault, Fabien; Pouvesle, Jean-Michel

    2006-11-01

    In this study we present the technique of resonant absorption spectroscopy diagnostic developed to estimate the density of silicon monoxide (SiO) molecules during the postdischarge of an atmospheric dielectric barrier discharge plasma. The ultraviolet (0,0) rovibrational band of the SiO(A {sup 1}{pi}-X {sup 1}{sigma}{sup +}) electronic transition was investigated. Effective values of absorption coefficient and absorption cross section for the rotational transitions under consideration were calculated. The SiO concentration was estimated by comparison between experimental and computed spectra. The self-absorption in the probe reactor was taken into account in the computed spectra.

  3. Frequency dependence of the absorption component of the magnetic susceptibility in superconducting Y1Ba2Cu3O7

    NASA Astrophysics Data System (ADS)

    Ducharme, S.; Durny, R.; Hautala, J.; Symko, O. G.; Taylor, P. C.

    Measurements of an apparent magnetic-field-dependent absorption (imaginary part of the a.c. magnetic susceptibility) in superconducting Y1Ba2Cu3O7 ceramics and crystals are reported. The absorption, which is observed over a wide range of frequencies but only when the material is below the superconducting transition temperature, is characterized by a narrow (about 30 Gauss FWHM at 6 MHz) peak and a wide (greater than 10 kG) feature, both of which are maximum at zero magnetic field. The absorption strength varies approximately as one over the square root of the frequency. The unusual magnetic-field-dependent peaks in the magnetic susceptibility are inherent in single grains and therefore do not originate from intergrain Josephson currents or multigrain (i.e., percolative) loops. The susceptibility peaks must be due to bulk behavior, interactions at grain surfaces, intragrain current loops, or intragrain Josephson junctions.

  4. Electronic structure measurements of metal-organic solar cell dyes using x-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Johnson, Phillip S.

    The focus of this thesis is twofold: to report the results of X-ray absorption studies of metal-organic dye molecules for dye-sensitized solar cells and to provide a basic training manual on X-ray absorption spectroscopy techniques and data analysis. The purpose of our research on solar cell dyes is to work toward an understanding of the factors influencing the electronic structure of the dye: the choice of the metal, its oxidation state, ligands, and cage structure. First we study the effect of replacing Ru in several common dye structures by Fe. First-principles calculations and X-ray absorption spectroscopy at the C 1s and N 1s edges are combined to investigate transition metal dyes in octahedral and square planar N cages. Octahedral molecules are found to have a downward shift in the N 1s-to-pi* transition energy and an upward shift in C 1s-to-pi* transition energy when Ru is replaced by Fe, explained by an extra transfer of negative charge from Fe to the N ligands compared to Ru. For the square planar molecules, the behavior is more complex because of the influence of axial ligands and oxidation state. Next the crystal field parameters for a series of phthalocyanine and porphyrins dyes are systematically determined using density functional calculations and atomic multiplet calculations with polarization-dependent X-ray absorption spectra. The polarization dependence of the spectra provides information on orbital symmetries which ensures the determination of the crystal field parameters is unique. A uniform downward scaling of the calculated crystal field parameters by 5-30% is found to be necessary to best fit the spectra. This work is a part of the ongoing effort to design and test new solar cell dyes. Replacing the rare metal Ru with abundant metals like Fe would be a significant advance for dye-sensitized solar cells. Understanding the effects of changing the metal centers in these dyes in terms of optical absorption, charge transfer, and electronic

  5. Impact of atmospheric state uncertainties on retrieved XCO2 columns from laser differential absorption spectroscopy measurements

    NASA Astrophysics Data System (ADS)

    Zaccheo, T. Scott; Pernini, Timothy; Snell, Hilary E.; Browell, Edward V.

    2014-01-01

    This work assesses the impact of uncertainties in atmospheric state knowledge on retrievals of carbon dioxide column amounts (XCO2) from laser differential absorption spectroscopy (LAS) measurements. LAS estimates of XCO2 columns are normally derived not only from differential absorption observations but also from measured or prior knowledge of atmospheric state that includes temperature, moisture, and pressure along the viewing path. In the case of global space-based monitoring systems, it is often difficult if not impossible to provide collocated in situ measurements of atmospheric state for all observations, so retrievals often rely on collocated remote-sensed data or values derived from numerical weather prediction (NWP) models to describe the atmospheric state. A radiative transfer-based simulation framework, combined with representative global upper-air observations and matched NWP profiles, was used to assess the impact of model differences on estimates of column CO2 and O2 concentrations. These analyses focus on characterizing these errors for LAS measurements of CO2 in the 1.57-μm region and of O2 in the 1.27-μm region. The results provide a set of signal-to-noise metrics that characterize the errors in retrieved values associated with uncertainties in atmospheric state and provide a method for selecting optimal differential absorption line pairs to minimize the impact of these noise terms.

  6. Initial Results of Optical Vortex Laser Absorption Spectroscopy in the HYPER-I Device

    NASA Astrophysics Data System (ADS)

    Yoshimura, Shinji; Asai, Shoma; Aramaki, Mitsutoshi; Terasaka, Kenichiro; Ozawa, Naoya; Tanaka, Masayoshi; Morisaki, Tomohiro

    2015-11-01

    Optical vortex beams have a potential to make a new Doppler measurement, because not only parallel but perpendicular movement of atoms against the beam axis causes the Doppler shift of their resonant absorption frequency. As the first step of a proof-of-principle experiment, we have performed the optical vortex laser absorption spectroscopy for metastable argon neutrals in an ECR plasma produced in the HYPER-I device at the National Institute for Fusion Science, Japan. An external cavity diode laser (TOPTICA, DL100) of which center wavelength was 696.735 nm in vacuum was used for the light source. The Hermite-Gaussian (HG) beam was converted into the Laguerre-Gaussian (LG) beam (optical vortex) by a computer-generated hologram displayed on the spatial light modulator (Hamamatsu, LCOS-SLM X10468-07). In order to make fast neutral flow across the LG beam, a high speed solenoid valve system was installed on the HYPER-I device. Initial results including the comparison of absorption spectra for HG and LG beams will be presented. This study was supported by NINS young scientists collaboration program for cross-disciplinary study, NIFS collaboration research program (NIFS13KOAP026), and JSPS KAKENHI grant number 15K05365.

  7. Study of acyl group migration by femtosecond transient absorption spectroscopy and computational chemistry.

    PubMed

    Pritchina, Elena A; Gritsan, Nina P; Burdzinski, Gotard T; Platz, Matthew S

    2007-10-25

    The primary photophysical and photochemical processes in the photochemistry of 1-acetoxy-2-methoxyanthraquinone (1a) were studied using femtosecond transient absorption spectroscopy. Excitation of 1a at 270 nm results in the population of a set of highly excited singlet states. Internal conversion to the lowest singlet npi* excited state, followed by an intramolecular vibrational energy redistribution (IVR) process, proceeds with a time constant of 150 +/- 90 fs. The 1npi* excited state undergoes very fast intersystem crossing (ISC, 11 +/- 1 ps) to form the lowest triplet pipi* excited state which contains excess vibrational energy. The vibrational cooling occurs somewhat faster (4 +/- 1 ps) than ISC. The primary photochemical process, migration of acetoxy group, proceeds on the triplet potential energy surface with a time constant of 220 +/- 30 ps. The transient absorption spectra of the lowest singlet and triplet excited states of 1a, as well as the triplet excited state of the product, 9-acetoxy-2-methoxy-1,10-anthraquinone (2a), were detected. The assignments of the transient absorption spectra were supported by time-dependent DFT calculations of the UV-vis spectra of the proposed intermediates. All of the stationary points for acyl group migration on the triplet and ground state singlet potential energy surfaces were localized, and the influence of the acyl group substitution on the rate constants of the photochemical and thermal processes was analyzed.

  8. Identification of Uranyl Minerals Using Oxygen K-Edge X Ray Absorption Spectroscopy

    SciTech Connect

    Ward, Jesse D.; Bowden, Mark E.; Resch, Charles T.; Smith, Steven C.; McNamara, Bruce K.; Buck, Edgar C.; Eiden, Gregory C.; Duffin, Andrew M.

    2016-03-01

    Uranium analysis is consistently needed throughout the fuel cycle, from mining to fuel fabrication to environmental monitoring. Although most of the world’s uranium is immobilized as pitchblende or uraninite, there exists a plethora of secondary uranium minerals, nearly all of which contain the uranyl cation. Analysis of uranyl compounds can provide clues as to a sample’s facility of origin and chemical history. X-ray absorption spectroscopy is one technique that could enhance our ability to identify uranium minerals. Although there is limited chemical information to be gained from the uranium X-ray absorption edges, recent studies have successfully used ligand NEXAFS to study the physical chemistry of various uranium compounds. This study extends the use of ligand NEXAFS to analyze a suite of uranium minerals. We find that major classes of uranyl compounds (carbonate, oxyhydroxide, silicate, and phosphate) exhibit characteristic lineshapes in the oxygen K-edge absorption spectra. As a result, this work establishes a library of reference spectra that can be used to classify unknown uranyl minerals.

  9. Sedimentation field flow fractionation and optical absorption spectroscopy for a quantitative size characterization of silver nanoparticles.

    PubMed

    Contado, Catia; Argazzi, Roberto; Amendola, Vincenzo

    2016-11-04

    Many advanced industrial and biomedical applications that use silver nanoparticles (AgNPs), require that particles are not only nano-sized, but also well dispersed, not aggregated and not agglomerated. This study presents two methods able to give rapidly sizes of monodispersed AgNPs suspensions in the dimensional range of 20-100nm. The first method, based on the application of Mie's theory, determines the particle sizes from the values of the surface plasmon resonance wavelength (SPRMAX), read from the optical absorption spectra, recorded between 190nm and 800nm. The computed sizes were compared with those determined by transmission electron microscopy (TEM) and dynamic light scattering (DLS) and resulted in agreement with the nominal values in a range between 13% (for 20nm NPs) and 1% (for 100nm NPs), The second method is based on the masterly combination of the Sedimentation Field Flow Fractionation (SdFFF - now sold as Centrifugal FFF-CFFF) and the Optical Absorption Spectroscopy (OAS) techniques to accomplish sizes and quantitative particle size distributions for monodispersed, non-aggregated AgNPs suspensions. The SdFFF separation abilities, well exploited to size NPs, greatly benefits from the application of Mie's theory to the UV-vis signal elaboration, producing quantitative mass-based particle size distributions, from which trusted number-sized particle size distributions can be derived. The silver mass distributions were verified and supported by detecting off-line the Ag concentration with the graphite furnace atomic absorption spectrometry (GF-AAS).

  10. The Optical Absorption Coefficient of Bean Seeds Investigated Using Photoacoustic Spectroscopy

    NASA Astrophysics Data System (ADS)

    Sanchez-Hernandez, G.; Hernandez-Aguilar, C.; Dominguez-Pacheco, A.; Cruz-Orea, A.; Perez-Reyes, M. C. J.; Martinez, E. Moreno

    2015-06-01

    A knowledge about seed optical parameters is of great relevance in seed technology practice. Such parameters provide information about its absorption and reflectance, which could be useful for biostimulation processes, by light sources, in early stages of seed germination. In the present research photoacoustic spectroscopy (PAS) and the Rosencwaig and Gersho model were used to determine the optical absorption coefficient () of five varieties of bean seeds ( Phaseolus vulgaris L.), of different productive cycles; the seeds were biostimulated by laser treatment to evaluate the effects of biostimulation pre-sowing. It was found that the bean varieties V1, V2, V4, and V5 were optically opaque in the visible spectrum; in the case of the V3 variety, this sample was optically transparent from 680 nm. The varieties of the studied bean seeds showed significant statistical differences in sizes and also in their optical absorption spectra. The biostimulation effects showed that the seed samples with a higher optical penetration length had a positive biostimulation, in the percentage of germination, obtaining an enhancement of 47 % compared to the control sample. The utility of PAS for the optical characterization of seeds has been demonstrated in this study of the laser biostimulation process of this kind of samples.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  12. The rotational spectrum of CuCCH(X~ 1Σ+): A Fourier transform microwave discharge assisted laser ablation spectroscopy and millimeter/submillimeter study

    NASA Astrophysics Data System (ADS)

    Sun, M.; Halfen, D. T.; Min, J.; Harris, B.; Clouthier, D. J.; Ziurys, L. M.

    2010-11-01

    The pure rotational spectrum of CuCCH in its ground electronic state (X˜ Σ1+) has been measured in the frequency range of 7-305 GHz using Fourier transform microwave (FTMW) and direct absorption millimeter/submillimeter methods. This work is the first spectroscopic study of CuCCH, a model system for copper acetylides. The molecule was synthesized using a new technique, discharge assisted laser ablation spectroscopy (DALAS). Four to five rotational transitions were measured for this species in six isotopologues (C63uCCH, C65uCCH, C63uC13CH, C63uCC13H, C63uC13C13H, and C63uCCD); hyperfine interactions arising from the copper nucleus were resolved, as well as smaller splittings in CuCCD due to deuterium quadrupole coupling. Five rotational transitions were also recorded in the millimeter region for C63uCCH and C65uCCH, using a Broida oven source. The combined FTMW and millimeter spectra were analyzed with an effective Hamiltonian, and rotational, electric quadrupole (Cu and D) and copper nuclear spin-rotation constants were determined. From the rotational constants, an rm(2) structure for CuCCH was established, with rCuC=1.8177(6) Å, rCC=1.2174(6) Å, and rCH=1.046(2) Å. The geometry suggests that CuCCH is primarily a covalent species with the copper atom singly bonded to the CCH moiety. The copper quadrupole constant indicates that the bonding orbital of this atom may be sp hybridized. The DALAS technique promises to be fruitful in the study of other small, metal-containing molecules of chemical interest.

  13. Chemical Modification of Graphene Oxide by Nitrogenation: An X-ray Absorption and Emission Spectroscopy Study

    PubMed Central

    Chuang, Cheng-Hao; Ray, Sekhar C.; Mazumder, Debarati; Sharma, Surbhi; Ganguly, Abhijit; Papakonstantinou, Pagona; Chiou, Jau-Wern; Tsai, Huang-Ming; Shiu, Hung-Wei; Chen, Chia-Hao; Lin, Hong-Ji; Guo, Jinghua; Pong, Way-Faung

    2017-01-01

    Nitrogen-doped graphene oxides (GO:Nx) were synthesized by a partial reduction of graphene oxide (GO) using urea [CO(NH2)2]. Their electronic/bonding structures were investigated using X-ray absorption near-edge structure (XANES), valence-band photoemission spectroscopy (VB-PES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). During GO:Nx synthesis, different nitrogen-bonding species, such as pyrrolic/graphitic-nitrogen, were formed by replacing of oxygen-containing functional groups. At lower N-content (2.7 at%), pyrrolic-N, owing to surface and subsurface diffusion of C, N and NH is deduced from various X-ray spectroscopies. In contrast, at higher N-content (5.0 at%) graphitic nitrogen was formed in which each N-atom trigonally bonds to three distinct sp2-hybridized carbons with substitution of the N-atoms for C atoms in the graphite layer. Upon nitrogen substitution, the total density of state close to Fermi level is increased to raise the valence-band maximum, as revealed by VB-PES spectra, indicating an electron donation from nitrogen, molecular bonding C/N/O coordination or/and lattice structure reorganization in GO:Nx. The well-ordered chemical environments induced by nitrogen dopant are revealed by XANES and RIXS measurements. PMID:28186190

  14. Chemical Modification of Graphene Oxide by Nitrogenation: An X-ray Absorption and Emission Spectroscopy Study.

    PubMed

    Chuang, Cheng-Hao; Ray, Sekhar C; Mazumder, Debarati; Sharma, Surbhi; Ganguly, Abhijit; Papakonstantinou, Pagona; Chiou, Jau-Wern; Tsai, Huang-Ming; Shiu, Hung-Wei; Chen, Chia-Hao; Lin, Hong-Ji; Guo, Jinghua; Pong, Way-Faung

    2017-02-10

    Nitrogen-doped graphene oxides (GO:Nx) were synthesized by a partial reduction of graphene oxide (GO) using urea [CO(NH2)2]. Their electronic/bonding structures were investigated using X-ray absorption near-edge structure (XANES), valence-band photoemission spectroscopy (VB-PES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). During GO:Nx synthesis, different nitrogen-bonding species, such as pyrrolic/graphitic-nitrogen, were formed by replacing of oxygen-containing functional groups. At lower N-content (2.7 at%), pyrrolic-N, owing to surface and subsurface diffusion of C, N and NH is deduced from various X-ray spectroscopies. In contrast, at higher N-content (5.0 at%) graphitic nitrogen was formed in which each N-atom trigonally bonds to three distinct sp(2)-hybridized carbons with substitution of the N-atoms for C atoms in the graphite layer. Upon nitrogen substitution, the total density of state close to Fermi level is increased to raise the valence-band maximum, as revealed by VB-PES spectra, indicating an electron donation from nitrogen, molecular bonding C/N/O coordination or/and lattice structure reorganization in GO:Nx. The well-ordered chemical environments induced by nitrogen dopant are revealed by XANES and RIXS measurements.

  15. Doppler-Free Two-Photon Absorption Spectroscopy of Naphthalene Assisted by AN Optical Frequency Comb

    NASA Astrophysics Data System (ADS)

    Nishiyama, Akiko; Matsuba, Ayumi; Misono, Masatoshi

    2014-06-01

    Optical frequency combs are powerful tools for precise frequency measurements in various wavelength regions. The combs have been applied not only to metrology, but also to molecular spectroscopy. Recently, we studied high resolution spectroscopy of iodine molecule assisted by an optical frequency comb. In the study, the comb was used for frequency calibration of a scanning dye laser. In this study, we developed a frequency calibration scheme with a comb and an acousto-optic modulator to realize more precise frequency measurement in a wide frequency range. And the frequency calibration scheme was applied to Doppler-free two-photon absorption (DFTPA) spectroscopy of naphthalene. Naphthalene is one of the prototypical aromatic molecules, and its detailed structure and dynamics in excited states have been reported. We measured DFTPA spectra of A^1B1u(v4=1) ← X^1A_g(v=0) transition around 298 nm. A part of obtained spectra is shown in the figure. The spectral lines are rotationally resolved and the resolution is about 100 kHz. The horizontal axis was calibrated by the developed frequency calibration system employing the comb. The uncertainties of the calibrated frequencies were determined by the fluctuations of the comb modes which were stabilized to a GPS-disciplined clock. A. Nishiyama, D. Ishikawa, and M. Misono, J. Opt. Soc. Am. B 30, 2107 (2013).

  16. Chemical Modification of Graphene Oxide by Nitrogenation: An X-ray Absorption and Emission Spectroscopy Study

    NASA Astrophysics Data System (ADS)

    Chuang, Cheng-Hao; Ray, Sekhar C.; Mazumder, Debarati; Sharma, Surbhi; Ganguly, Abhijit; Papakonstantinou, Pagona; Chiou, Jau-Wern; Tsai, Huang-Ming; Shiu, Hung-Wei; Chen, Chia-Hao; Lin, Hong-Ji; Guo, Jinghua; Pong, Way-Faung

    2017-02-01

    Nitrogen-doped graphene oxides (GO:Nx) were synthesized by a partial reduction of graphene oxide (GO) using urea [CO(NH2)2]. Their electronic/bonding structures were investigated using X-ray absorption near-edge structure (XANES), valence-band photoemission spectroscopy (VB-PES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). During GO:Nx synthesis, different nitrogen-bonding species, such as pyrrolic/graphitic-nitrogen, were formed by replacing of oxygen-containing functional groups. At lower N-content (2.7 at%), pyrrolic-N, owing to surface and subsurface diffusion of C, N and NH is deduced from various X-ray spectroscopies. In contrast, at higher N-content (5.0 at%) graphitic nitrogen was formed in which each N-atom trigonally bonds to three distinct sp2-hybridized carbons with substitution of the N-atoms for C atoms in the graphite layer. Upon nitrogen substitution, the total density of state close to Fermi level is increased to raise the valence-band maximum, as revealed by VB-PES spectra, indicating an electron donation from nitrogen, molecular bonding C/N/O coordination or/and lattice structure reorganization in GO:Nx. The well-ordered chemical environments induced by nitrogen dopant are revealed by XANES and RIXS measurements.

  17. Determination of metal concentration in fat supplements for swine nutrition by atomic absorption spectroscopy.

    PubMed

    Cocchi, Marina; Faeti, Valerio; Manfredini, Matteo; Manzini, Daniela; Marchetti, Andrea; Sighinolfi, Simona

    2005-01-01

    The presence of some essential and toxic metals in fat supplements for swine diet was investigated. Collected samples represented a relevant production of the Italian industry. In particular, some samples were enriched with antioxidants or waste cooking oils. The method for the determination of Ca, Cu, Cd, Fe, Mg, Mn, Ni, Pb, and Zn in fat samples was developed by means of a certified reference material (CRM 186) and a representative fatty sample (RFS). All samples were digested in closed vessels in a microwave oven and then analyzed by flame atomic absorption or graphite furnace atomic absorption spectrometry. The entire analytical method provided a satisfactory repeatability and reproducibility confirmed by agreement between the experimental recovery data obtained for the CRM 186 sample and, with the method of standard additions, for the RFS material. The samples generally showed a small amount of metals compared with the recommended daily intake for the essential elements. On the other hand, some samples contained a significant concentration, from an analytical point of view, of Cd, Ni, and Pb. Principal component analysis (PCA) was applied to inspect the experimental data obtained from samples analysis. Basically no differences were detected in terms of metal concentration among the fat supplements analyzed.

  18. Suprathermal electron production in laser-irradiated Cu targets characterized by combined methods of x-ray imaging and spectroscopy

    NASA Astrophysics Data System (ADS)

    Renner, O.; Šmíd, M.; Batani, D.; Antonelli, L.

    2016-07-01

    In a series of experiments performed with laser-irradiated planar targets at the PALS laser facility, the generation of suprathermal electrons has been studied at conditions relevant for the development of a shock ignition approach to inertial confinement fusion. A simultaneous application of high-collection-efficiency K-shell imaging with high resolution x-ray spectroscopy offers a novel approach to hot electron diagnosis at non-coated or moderately coated, medium-atomic-number targets, where the contribution of suprathermal-electron-generated, frequency-shifted Kα emission from highly ionized atoms cannot be neglected. Based on experimental data provided by these combined techniques and their interpretation via collisional-radiative atomic codes and Monte Carlo modeling of hot electron energy deposition in heated Cu targets, the fraction of the energy converted to hot electrons at laser intensities  ≈1016 W cm-2 was measured to be at the level of 0.1-0.8%. The higher values of conversion efficiency found for frequency tripled radiation support a theoretical conjecture of enhanced laser energy absorption by a resonance mechanism and its transport to a flow of fast electrons.

  19. Polarized Raman spectroscopy of Cu-poor and Zn-rich single-crystal Cu2ZnSnSe4

    NASA Astrophysics Data System (ADS)

    Nam, Dahyun; Kim, Jungcheol; Lee, Jae-Ung; Nagaoka, Akira; Yoshino, Kenji; Cha, Wonsuk; Kim, Hyunjung; Hwang, In Chul; Yoon, Kyung Byung; Cheong, Hyeonsik

    2014-10-01

    Cu2ZnSnSe4 (CZTSe) is a p-type semiconductor which has been developed as an absorber layer of polycrystalline thin film solar cells. Generally, Cu-poor and Zn-rich compositions tend to give the highest solar conversion efficiencies. Raman spectroscopy has been used to detect secondary phases such as ZnSe and Cu2SnSe3 in CZTSe thin films. However, the fundamental phonon modes in single-crystal CZTSe with a composition matching that of high-efficiency thin film solar cells have not yet been fully understood. We performed polarized Raman measurements on Cu-poor and Zn-rich single-crystal CZTSe and identified 12 peaks, including two low-frequency peaks. By comparing the polarization dependence of the Raman peaks with a group theoretical analysis, we concluded that the crystal structure of CZTSe single-crystal is kesterite and made appropriate peak assignments.

  20. Absorption spectroscopy characterization measurements of a laser-produced Na atomic beam

    SciTech Connect

    Ching, C.H.; Bailey, J.E.; Lake, P.W.; Filuk, A.B.; Adams, R.G.; McKenney, J.

    1997-01-01

    A pulsed Na atomic beam source developed for spectroscopic diagnosis of a high-power ion diode is described. The goal is to produce a {approximately}10{sup 12}-cm{sup {minus}3}-density Na atomic beam that can be injected into the diode acceleration gap to measure electric and magnetic fields from the Stark and Zeeman effects through laser-induced fluorescence or absorption spectroscopy. A {approximately}10 ns full width at half-maximum (FWHM), 1.06 {mu}m, 0.6 J/cm{sup 2} laser incident through a glass slide heats a Na-bearing thin film, creating a plasma that generates a sodium vapor plume. A {approximately}1 {mu}s FWHM dye laser beam tuned to 5890 {Angstrom} is used for absorption measurement of the NaI resonant doublet by viewing parallel to the film surface. The dye laser light is coupled through a fiber to a spectrograph with a time-integrated charge-coupled-device camera. A two-dimensional mapping of the Na vapor density is obtained through absorption measurements at different spatial locations. Time-of-flight and Doppler broadening of the absorption with {approximately}0.1 {Angstrom} spectral resolution indicate that the Na neutral vapor temperature is about 0.5{endash}2 eV. Laser-induced fluorescence from {approximately}1{times}10{sup 12} cm{sup {minus}3} NaI 3s-3p lines observed with a streaked spectrograph provides a signal level sufficient for {approximately}{plus_minus}0.06 {Angstrom} wavelength shift measurements in a mock-up of an ion diode experiment. {copyright} {ital 1997 American Institute of Physics.}

  1. Absorption spectroscopy characterization measurements of a laser-produced Na atomic beam

    SciTech Connect

    Ching, C.H.; Bailey, J.E.; Lake, P.W.; Filuk, A.B.; Adams, R.G.; McKenney, J.

    1996-06-01

    This work describes a pulsed Na atomic beam source developed for spectroscopic diagnosis of a high-power ion diode on the Particle Beam Fusion Accelerator II. The goal is to produce a {approximately} 10{sup 12}-cm{sup {minus}3}-density Na atomic beam that can be injected into the diode acceleration gap to measure electric and magnetic fields from the Stark and Zeeman effects through laser-induced-fluorescence or absorption spectroscopy. A {approximately} 10 ns fwhm, 1.06 {micro}m, 0.6 J/cm{sup 2} laser incident through a glass slide heats a Na-bearing thin film, creating a plasma that generates a sodium vapor plume. A {approximately} 1 {micro}sec fwhm dye laser beam tuned to 5,890 {angstrom} is used for absorption measurement of the Na I resonant doublet by viewing parallel to the film surface. The dye laser light is coupled through a fiber to a spectrograph with a time-integrated CCD camera. A two-dimensional mapping of the Na vapor density is obtained through absorption measurements at different spatial locations. Time-of-flight and Doppler broadening of the absorption with {approximately} 0.1 {angstrom} spectral resolution indicate that the Na neutral vapor temperature is about 0.5 to 2 eV. Laser-induced-fluorescence from {approximately} 1 {times} 10{sup 12}-cm{sup {minus}3} Na I 3s-3p lines observed with a streaked spectrograph provides a signal level sufficient for {approximately} 0.06 {angstrom} wavelength shift measurements in a mock-up of an ion diode experiment.

  2. INTEGRAL FIELD SPECTROSCOPY OF AGN ABSORPTION OUTFLOWS: MRK 509 AND IRAS F04250–5718

    SciTech Connect

    Liu, Guilin; Arav, Nahum; Rupke, David S. N.

    2015-11-15

    Ultraviolet (UV) absorption lines provide abundant spectroscopic information enabling the probe of the physical conditions in active galactic nucleus (AGN) outflows, but the outflow radii (and the energetics consequently) can only be determined indirectly. We present the first direct test of these determinations using integral field unit (IFU) spectroscopy. We have conducted Gemini IFU mapping of the ionized gas nebulae surrounding two AGNs, whose outflow radii have been constrained by UV absorption line analyses. In Mrk 509, we find a quasi-spherical outflow with a radius of 1.2 kpc and a velocity of ∼290 km s{sup −1}, while IRAS F04250–5718 is driving a biconical outflow extending out to 2.9 kpc, with a velocity of ∼580 km s{sup −1} and an opening angle of ∼70°. The derived mass flow rate ∼5 and >1 M{sub ⊙} yr{sup −1}, respectively, and the kinetic luminosity ≳1 × 10{sup 41} erg s{sup −1} for both. Adopting the outflow radii and geometric parameters measured from IFU, absorption line analyses would yield mass flow rates and kinetic luminosities in agreement with the above results within a factor of ∼2. We conclude that the spatial locations, kinematics, and energetics revealed by this IFU emission-line study are consistent with pre-existing UV absorption line analyses, providing a long-awaited direct confirmation of the latter as an effective approach for characterizing outflow properties.

  3. Extreme ultraviolet spectroscopy and modeling of Cu on the SSPX Spheromak and laser plasma 'Sparky'

    SciTech Connect

    Weller, M. E.; Safronova, A. S.; Kantsyrev, V. L.; Safronova, U. I.; Petkov, E. E.; Wilcox, P. G.; Osborne, G. C.; Clementson, J.; Beiersdorfer, P.

    2012-10-15

    Impurities play a critical role in magnetic fusion research. In large quantities, impurities can cool and dilute plasma creating problems for achieving ignition and burn; however in smaller amounts the impurities could provide valuable information about several plasma parameters through the use of spectroscopy. Many impurity ions radiate within the extreme ultraviolet (EUV) range. Here, we report on spectra from the silver flat field spectrometer, which was implemented at the Sustained Spheromak Physics experiment (SSPX) to monitor ion impurity emissions. The chamber within the SSPX was made of Cu, which makes M-shell Cu a prominent impurity signature. The Spect3D spectral analysis code was utilized to identify spectral features in the range of 115-315 A and to more fully understand the plasma conditions. A second set of experiments was carried out on the compact laser-plasma x-ray/EUV facility 'Sparky' at UNR, with Cu flat targets used. The EUV spectra were recorded between 40-300 A and compared with results from SSPX.

  4. Laser absorption spectroscopy using lead salt and quantum cascade tunable lasers

    NASA Astrophysics Data System (ADS)

    Namjou-Khales, Khosrow

    A new class of analytic instruments based on the detection of chemical species through their spectroscopic absorption 'fingerprint' is emerging based on the use of tunable semiconductor lasers as the excitation source. Advantages of this approach include compact device size, in-line measurement capability, and large signal-bandwidth product. To realize these advantages will require the marriage of laser devices with broad tunability in the infrared spectral range with sophisticated signal processing techniques. Currently, commercial devices based on short wavelength telecommunications type lasers exist but there is potential for much more versatile instruments based on longer wavelength operation. This thesis is divided into two parts. In the first part I present a theoretical analysis and experimental characterization of frequency and wavelength modulation spectroscopy using long wavelength infrared tunable lasers. The experimental measurements were carried out using commercially available lead salt lasers and excellent agreement is found between theoretically predicted performance and experimental verification. The lead salt laser has several important drawbacks as a source in practical instrumentation. In the second part of the thesis I report on the use of the quantum cascade (QC) laser for use in sensitive absorption spectroscopy. The QC laser is a new type of tunable device developed at Bell Laboratories. It features broad infrared tunability, single mode distributed feedback operation, and near room temperature lasing. Using the modulation techniques developed originally for the lead salt lasers, the QC laser was used to detect Nsb2O and other small molecules with absorption features near 8 mum wavelength. The noise equivalent absorption for our measurements was 5× 10sp{-5}/sqrt{Hz} which corresponds to a detection limit of ˜0.25 ppm-m/sqrt{Hz} for Nsb2O. The QC laser sensitivity was found to be limited by excess amplitude modulation in the detection

  5. In-situ ultra-sensitive infrared absorption spectroscopy of biomolecule interactions in real time with plasmonic nanoantennas

    PubMed Central

    Adato, Ronen; Altug, Hatice

    2013-01-01

    Infrared absorption spectroscopy is a powerful biochemical analysis tool as it extracts detailed molecular structural information in a label-free fashion. Its molecular specificity renders the technique sensitive to the subtle conformational changes exhibited by proteins in response to a variety of stimuli. Yet, sensitivity limitations and the extremely strong absorption bands of liquid water severely limit infrared spectroscopy in performing kinetic measurements in biomolecules’ native, aqueous environments. Here we demonstrate a plasmonic chip-based technology that overcomes these challenges, enabling the in-situ monitoring of protein and nanoparticle interactions at high sensitivity in real time, even allowing the observation of minute volumes of water displacement during binding events. Our approach leverages the plasmonic enhancement of absorption bands in conjunction with a non-classical form of internal reflection. These features not only expand the reach of infrared spectroscopy to a new class of biological interactions but also additionally enable a unique chip-based technology. PMID:23877168

  6. In-situ ultra-sensitive infrared absorption spectroscopy of biomolecule interactions in real time with plasmonic nanoantennas.

    PubMed

    Adato, Ronen; Altug, Hatice

    2013-01-01

    Infrared absorption spectroscopy is a powerful biochemical analysis tool as it extracts detailed molecular structural information in a label-free fashion. Its molecular specificity renders the technique sensitive to the subtle conformational changes exhibited by proteins in response to a variety of stimuli. Yet, sensitivity limitations and the extremely strong absorption bands of liquid water severely limit infrared spectroscopy in performing kinetic measurements in biomolecules' native, aqueous environments. Here we demonstrate a plasmonic chip-based technology that overcomes these challenges, enabling the in-situ monitoring of protein and nanoparticle interactions at high sensitivity in real time, even allowing the observation of minute volumes of water displacement during binding events. Our approach leverages the plasmonic enhancement of absorption bands in conjunction with a non-classical form of internal reflection. These features not only expand the reach of infrared spectroscopy to a new class of biological interactions but also additionally enable a unique chip-based technology.

  7. (n,m)-Specific Absorption Cross Sections of Single-Walled Carbon Nanotubes Measured by Variance Spectroscopy.

    PubMed

    Sanchez, Stephen R; Bachilo, Sergei M; Kadria-Vili, Yara; Lin, Ching-Wei; Weisman, R Bruce

    2016-11-09

    A new method based on variance spectroscopy has enabled the determination of absolute absorption cross sections for the first electronic transition of 12 (n,m) structural species of semiconducting single-walled carbon nanotubes (SWCNTs). Spectrally resolved measurements of fluorescence variance in dilute bulk samples provided particle number concentrations of specific SWCNT species. These values were converted to carbon concentrations and correlated with resonant components in the absorbance spectrum to deduce (n,m)-specific absorption cross sections (absorptivities) for nanotubes ranging in diameter from 0.69 to 1.03 nm. The measured cross sections per atom tend to vary inversely with nanotube diameter and are slightly greater for structures of mod 1 type than for mod 2. Directly measured and extrapolated values are now available to support quantitative analysis of SWCNT samples through absorption spectroscopy.

  8. Trace and Essential Elements Analysis in Cymbopogon citratus (DC.) Stapf Samples by Graphite Furnace-Atomic Absorption Spectroscopy and Its Health Concern

    PubMed Central

    Anal, Jasha Momo H.

    2014-01-01

    Cymbopogon citratus (DC.) Stapf commonly known as lemon grass is used extensively as green tea and even as herbal tea ingredient across the world. Plants have the ability to uptake metals as nutrient from the soil and its environment which are so essential for their physiological and biochemical growth. Concentrations of these twelve trace elements, namely, Mg, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Mo, As, Cd, and Pb, are analysed by graphite furnace-atomic absorption spectroscopy (GF-AAS) and are compared with the permissible limits of FAO/WHO, ICMR, and NIH, USA, which are found to be within permissible limits. Toxic metals like As, Cd, and Pb, analysed are within the tolerable daily diet limit and at low concentration. PMID:25525430

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Trace and Essential Elements Analysis in Cymbopogon citratus (DC.) Stapf Samples by Graphite Furnace-Atomic Absorption Spectroscopy and Its Health Concern.

    PubMed

    Anal, Jasha Momo H

    2014-01-01

    Cymbopogon citratus (DC.) Stapf commonly known as lemon grass is used extensively as green tea and even as herbal tea ingredient across the world. Plants have the ability to uptake metals as nutrient from the soil and its environment which are so essential for their physiological and biochemical growth. Concentrations of these twelve trace elements, namely, Mg, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Mo, As, Cd, and Pb, are analysed by graphite furnace-atomic absorption spectroscopy (GF-AAS) and are compared with the permissible limits of FAO/WHO, ICMR, and NIH, USA, which are found to be within permissible limits. Toxic metals like As, Cd, and Pb, analysed are within the tolerable daily diet limit and at low concentration.

  11. Application of atomic absorption spectroscopy for detection of multimetal traces in low-voltage electrical marks.

    PubMed

    Jakubeniene, Marija; Zakaras, Algirdas; Minkuviene, Zita Nijole; Benoshys, Alvydas

    2006-08-10

    Application of atomic absorption spectroscopy to detect multimetal traces in injured skin is a promising tool for investigation of fatalities caused by electrocution. The present paper is aimed at testing the reliability of this method for metal traces detection in electric current marks and is focused on study of peculiarities of metal penetration into the skin exposed to a current impact. Bare aluminum wire, tin-lead coated copper multistrand wire, and zinc-plated steel rope were used to make electrical marks on pig skin. It is demonstrated that amount of copper, zinc, lead, and iron may serve as statistically reliable indicators for the type of wire, which caused the electrical mark, in spite of the background content of these metals in the skin without injury. Different penetration rates for different metals contained in the wire inflicting an electrical mark were observed.

  12. Visualizing interfacial charge transfer in dye sensitized nanoparticles using x-ray transient absorption spectroscopy.

    SciTech Connect

    Zhang, X. Y.; Smolentsev, G.; Guo, J.; Attenkofer, K.; Kurtz, C.; Jennings, G.; Lockard, J. V.; Stickrath, A. B.; Chen, L. X.

    2011-01-01

    A molecular level understanding of the structural reorganization accompanying interfacial electron transfer is important for rational design of solar cells. Here we have applied XTA (X-ray transient absorption) spectroscopy to study transient structures in a heterogeneous interfacial system mimicking the charge separation process in dye-sensitized solar cell (DSSC) with Ru(dcbpy){sub 2}(NCS){sub 2} (RuN3) dye adsorbed to TiO{sub 2} nanoparticle surfaces. The results show that the average Ru-NCS bond length reduces by 0.06 {angstrom}, whereas the average Ru-N(dcbpy) bond length remains nearly unchanged after the electron injection. The differences in bond-order change and steric hindrance between two types of ligands are attributed to their structural response in the charge separation. This study extends the application of XTA into optically opaque hybrid interfacial systems relevant to the solar energy conversion.

  13. Electronic topological transition in zinc under pressure: An x-ray absorption spectroscopy study

    SciTech Connect

    Aquilanti, G.; Trapananti, A.; Pascarelli, S.; Minicucci, M.; Principi, E.; Liscio, F.; Twarog, A.

    2007-10-01

    Zinc metal has been studied at high pressure using x-ray absorption spectroscopy. In order to investigate the role of the different degrees of hydrostaticity on the occurrence of structural anomalies following the electronic topological transition, two pressure transmitting media have been used. Results show that the electronic topological transition, if it exists, does not induce an anomaly in the local environment of compressed Zn as a function of hydrostatic pressure and any anomaly must be related to a loss of hydrostaticity of the pressure transmitting medium. The near-edge structures of the spectra, sensitive to variations in the electronic density of states above the Fermi level, do not show any evidence of electronic transition whatever pressure transmitting medium is used.

  14. NO binding kinetics in myoglobin investigated by picosecond Fe K-edge absorption spectroscopy

    PubMed Central

    Silatani, Mahsa; Lima, Frederico A.; Penfold, Thomas J.; Rittmann, Jochen; Reinhard, Marco E.; Rittmann-Frank, Hannelore M.; Borca, Camelia; Grolimund, Daniel; Milne, Christopher J.; Chergui, Majed

    2015-01-01

    Diatomic ligands in hemoproteins and the way they bind to the active center are central to the protein’s function. Using picosecond Fe K-edge X-ray absorption spectroscopy, we probe the NO-heme recombination kinetics with direct sensitivity to the Fe-NO binding after 532-nm photoexcitation of nitrosylmyoglobin (MbNO) in physiological solutions. The transients at 70 and 300 ps are identical, but they deviate from the difference between the static spectra of deoxymyoglobin and MbNO, showing the formation of an intermediate species. We propose the latter to be a six-coordinated domed species that is populated on a timescale of ∼200 ps by recombination with NO ligands. This work shows the feasibility of ultrafast pump–probe X-ray spectroscopic studies of proteins in physiological media, delivering insight into the electronic and geometric structure of the active center. PMID:26438842

  15. X-Ray absorption spectroscopy investigation of 1-alkyl-3-methylimidazolium bromide salts

    SciTech Connect

    D'Angelo, Paola; Zitolo, Andrea; Migliorati, Valentina; Bodo, Enrico; Caminiti, Ruggero; Aquilanti, Giuliana; Hazemann, Jean Louis; Testemale, Denis; Mancini, Giordano

    2011-08-21

    X-ray absorption spectroscopy (XAS) has been used to unveil the bromide ion local coordination structure in 1-alkyl-3-methylimidazolium bromide [C{sub n}mim]Br ionic liquids (ILs) with different alkyl chains. The XAS spectrum of 1-ethyl-3-methylimidazolium bromide has been found to be different from those of the other members of the series, from the butyl to the decyl derivatives, that have all identical XAS spectra. This result indicates that starting from 1-buthyl-3-methylimidazolium bromide the local molecular arrangement around the bromide anion is the same independently from the length of the alkyl chain, and that the imidazolium head groups in the liquid ILs with long alkyl chains assume locally the same orientation as in the [C{sub 4}mim]Br crystal. With this study we show that the XAS technique is an effective direct tool for unveiling the local structural arrangements around selected atoms in ILs.

  16. The Optical Absorption Coefficient of Maize Grains Investigated by Photoacoustic Spectroscopy

    NASA Astrophysics Data System (ADS)

    Rodríguez-Páez, C. L.; Carballo-Carballo, A.; Rico-Molina, R.; Hernández-Aguilar, C.; Domínguez-Pacheco, A.; Cruz-Orea, A.; Moreno-Martínez, E.

    2017-01-01

    In the maize and tortilla industry, it is important to characterize the color of maize ( Zea mays L.) grain, as it is one of the attributes that directly affect the quality of the tortillas consumed by the population. For this reason, the availability of alternative techniques for assessing and improving the quality of grain is valued. Photoacoustic spectroscopy has proven to be a useful tool for characterizing maize grain. So, the objective of the present study was to determine the optical absorption coefficient β of the maize grain used to make tortillas from two regions of Mexico: (a) Valles Altos, 2012-2013 production cycle and (b) Guasave, Sinaloa, 2013-2014 production cycle. Traditional reflectance measurements, physical characteristics of the grain and nutrient content were also calculated. The experimental results show different characteristics for maize grains.

  17. Time-resolved broadband cavity-enhanced absorption spectroscopy for chemical kinetics.

    SciTech Connect

    Sheps, Leonid; Chandler, David W.

    2013-04-01

    Experimental measurements of elementary reaction rate coefficients and product branching ratios are essential to our understanding of many fundamentally important processes in Combustion Chemistry. However, such measurements are often impossible because of a lack of adequate detection techniques. Some of the largest gaps in our knowledge concern some of the most important radical species, because their short lifetimes and low steady-state concentrations make them particularly difficult to detect. To address this challenge, we propose a novel general detection method for gas-phase chemical kinetics: time-resolved broadband cavity-enhanced absorption spectroscopy (TR-BB-CEAS). This all-optical, non-intrusive, multiplexed method enables sensitive direct probing of transient reaction intermediates in a simple, inexpensive, and robust experimental package.

  18. Zinc ligands in the metal hyperaccumulator Thlaspi caerulescens as determined using X-ray absorption spectroscopy

    SciTech Connect

    Salt, D.E.; Prince, R.C.; Baker, A.J.M.; Raskin, I.; Pickering, I.J.

    1999-03-01

    Using the noninvasive technique of X-ray absorption spectroscopy (XAS), the authors have been able to determine the ligand environment of Zn in different tissues of the Zn-hyperaccumulator Thlaspi caerulescens. The majority of intracellular Zn in roots of T. caerulescens was found to be coordinated with histidine. In the xylem sap Zn was found to be transported mainly as the free hydrated Zn{sup 2+} cation with a smaller proportion coordinated with organic acids. In the shoots, Zn coordination occurred mainly via organic acids, with a smaller proportion present as the hydrated cation and coordinated with histidine and the cell wall. Their data suggest that histidine plays an important role in Zn homeostasis in the roots, whereas organic acids are involved in xylem transport and Zn storage in shoots.

  19. Fast transient absorption spectroscopy of the early events in photoexcited chiral benzophenone naphthalene dyads

    NASA Astrophysics Data System (ADS)

    Perez-Ruiz, Raul; Groeneveld, Michiel; van Stokkum, Ivo H. M.; Tormos, Rosa; Williams, René M.; Miranda, Miguel A.

    2006-09-01

    Photoinduced intra-molecular energy transfer in two ketoprofen(KP)-naproxol(NPX) diastereomers proceeds via two pathways. Very fast singlet-triplet energy transfer ( k = 1.2 × 10 11 s -1) from KP to NPX occurs for a small percentage (6%) and the major pathway is triplet-triplet energy transfer ( k ˜ 3 × 10 9 s -1). This was shown with femtosecond transient absorption spectroscopy and global and target analysis. Whereas the NPX triplet decay is strongly stereospecific (ratio of 1.6), the NPX triplet state formation for both dyads is very similar (ratio of 1 for the fast process and 1.2 for the slower process).

  20. The irradiation of ammonia ice studied by near edge x-ray absorption spectroscopy

    SciTech Connect

    Parent, Ph.; Bournel, F.; Lasne, J.; Laffon, C.; Carniato, S.; Lacombe, S.; Strazzulla, G.; Gardonio, S.; Lizzit, S.; Kappler, J.-P.; Joly, L.

    2009-10-21

    A vapor-deposited NH{sub 3} ice film irradiated at 20 K with 150 eV photons has been studied with near-edge x-ray absorption fine structure (NEXAFS) spectroscopy at the nitrogen K-edge. Irradiation leads to the formation of high amounts (12%) of molecular nitrogen N{sub 2}, whose concentration as a function of the absorbed energy has been quantified to 0.13 molecule/eV. The stability of N{sub 2} in solid NH{sub 3} has been also studied, showing that N{sub 2} continuously desorbs between 20 and 95 K from the irradiated ammonia ice film. Weak concentrations (<1%) of other photoproducts are also detected. Our NEXAFS simulations show that these features own to NH{sub 2}, N{sub 2}H{sub 2}, and N{sub 3}{sup -}.

  1. NO binding kinetics in myoglobin investigated by picosecond Fe K-edge absorption spectroscopy.

    PubMed

    Silatani, Mahsa; Lima, Frederico A; Penfold, Thomas J; Rittmann, Jochen; Reinhard, Marco E; Rittmann-Frank, Hannelore M; Borca, Camelia; Grolimund, Daniel; Milne, Christopher J; Chergui, Majed

    2015-10-20

    Diatomic ligands in hemoproteins and the way they bind to the active center are central to the protein's function. Using picosecond Fe K-edge X-ray absorption spectroscopy, we probe the NO-heme recombination kinetics with direct sensitivity to the Fe-NO binding after 532-nm photoexcitation of nitrosylmyoglobin (MbNO) in physiological solutions. The transients at 70 and 300 ps are identical, but they deviate from the difference between the static spectra of deoxymyoglobin and MbNO, showing the formation of an intermediate species. We propose the latter to be a six-coordinated domed species that is populated on a timescale of ∼ 200 ps by recombination with NO ligands. This work shows the feasibility of ultrafast pump-probe X-ray spectroscopic studies of proteins in physiological media, delivering insight into the electronic and geometric structure of the active center.

  2. Biomimetic environment to study E. coli complex I through surface-enhanced IR absorption spectroscopy.

    PubMed

    Kriegel, Sébastien; Uchida, Taro; Osawa, Masatoshi; Friedrich, Thorsten; Hellwig, Petra

    2014-10-14

    In this study complex I was immobilized in a biomimetic environment on a gold layer deposited on an ATR-crystal in order to functionally probe the enzyme against substrates and inhibitors via surface-enhanced IR absorption spectroscopy (SEIRAS) and cyclic voltammetry (CV). To achieve this immobilization, two methods based on the generation of a high affinity self-assembled monolayer (SAM) were probed. The first made use of the affinity of Ni-NTA toward a hexahistidine tag that was genetically engineered onto complex I and the second exploited the affinity of the enzyme toward its natural substrate NADH. Experiments were also performed with complex I reconstituted in lipids. Both approaches have been found to be successful, and electrochemically induced IR difference spectra of complex I were obtained.

  3. Intracavity laser absorption spectroscopy using mid-IR quantum cascade laser

    NASA Astrophysics Data System (ADS)

    Medhi, G.; Muravjov, A. V.; Saxena, H.; Fredricksen, C. J.; Brusentsova, T.; Peale, R. E.; Edwards, O.

    2011-06-01

    Intracavity Laser Absorption Spectroscopy (ICLAS) at IR wavelengths offers an opportunity for spectral sensing with sufficient sensitivity to detect vapors of low vapor pressure compounds such as explosives. Reported here are key enabling technologies for this approach, including multi-mode external-cavity quantum cascade lasers and a scanning Fabry-Perot spectrometer to analyze the laser mode spectrum in the presence of a molecular intracavity absorber. Reported also is the design of a compact integrated data acquisition and control system. Applications include military and commercial sensing for threat compounds, chemical gases, biological aerosols, drugs, and banned or invasive plants or animals, bio-medical breath analysis, and terrestrial or planetary atmosphere science.

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

    SciTech Connect

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

    2001-03-25

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

  5. Detection, identification and mapping of iron anomalies in brain tissue using X-ray absorption spectroscopy

    SciTech Connect

    Mikhaylova, A.; Davidson, M.; Toastmann, H.; Channell, J.E.T.; Guyodo, Y.; Batich, C.; Dobson, J.

    2008-06-16

    This work describes a novel method for the detection, identification and mapping of anomalous iron compounds in mammalian brain tissue using X-ray absorption spectroscopy. We have located and identified individual iron anomalies in an avian tissue model associated with ferritin, biogenic magnetite and haemoglobin with a pixel resolution of less than 5 {micro}m. This technique represents a breakthrough in the study of both intra- and extra-cellular iron compounds in brain tissue. The potential for high-resolution iron mapping using microfocused X-ray beams has direct application to investigations of the location and structural form of iron compounds associated with human neurodegenerative disorders - a problem which has vexed researchers for 50 years.

  6. Performance improvements in temperature reconstructions of 2-D tunable diode laser absorption spectroscopy (TDLAS)

    NASA Astrophysics Data System (ADS)

    Choi, Doo-Won; Jeon, Min-Gyu; Cho, Gyeong-Rae; Kamimoto, Takahiro; Deguchi, Yoshihiro; Doh, Deog-Hee

    2016-02-01

    Performance improvement was attained in data reconstructions of 2-dimensional tunable diode laser absorption spectroscopy (TDLAS). Multiplicative Algebraic Reconstruction Technique (MART) algorithm was adopted for data reconstruction. The data obtained in an experiment for the measurement of temperature and concentration fields of gas flows were used. The measurement theory is based upon the Beer-Lambert law, and the measurement system consists of a tunable laser, collimators, detectors, and an analyzer. Methane was used as a fuel for combustion with air in the Bunsen-type burner. The data used for the reconstruction are from the optical signals of 8-laser beams passed on a cross-section of the methane flame. The performances of MART algorithm in data reconstruction were validated and compared with those obtained by Algebraic Reconstruction Technique (ART) algorithm.

  7. Structural analysis of sulfur in natural rubber using X-ray absorption near-edge spectroscopy.

    PubMed

    Pattanasiriwisawa, Wanwisa; Siritapetawee, Jaruwan; Patarapaiboolchai, Orasa; Klysubun, Wantana

    2008-09-01

    X-ray absorption near-edge spectroscopy (XANES) has been applied to natural rubber in order to study the local environment of sulfur atoms in sulfur crosslinking structures introduced in the vulcanization process. Different types of chemical accelerators in conventional, semi-efficient and efficient vulcanization systems were investigated. The experimental results show the good sensitivity and reproducibility of XANES to characterize the local geometry and electronic environment of the sulfur K-shell under various conditions of vulcanization and non-vulcanization of natural rubber. Several applications of XANES in this study demonstrate an alternative way of identifying sulfur crosslinks in treated natural rubber based on differences in their spectra and oxidation states.

  8. Detection of the transient PNO molecule by infrared laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Bell, I. S.; Hamilton, P. A.; Davies, P. B.

    The PNO molecule has been observed in the gas phase for the first time. Some 200 vibrationrotation transitions were detected in the 1760cm-1 region using infrared diode laser absorption spectroscopy in a long path cell. Most of the lines can be assigned to the (001)←(000) stretching fundamental and (011)←(010) hot band transitions. The fundamental band exhibits a perturbation at high rotational levels which leads to a unique assignment of the rotational numbering. The effective rotational constants determined are in good agreement with ab initio predictions and the band origin, 1756.64586(24)cm-1, is very close to the matrix value. A tentative rotational assignment of the hot band transitions has been made which gives a band origin of 1748.388cm-1.

  9. [Genetic programming used for the measurement of CO concentration based on nondispersive infrared absorption spectroscopy].

    PubMed

    Chen, Jin; Duan, Fa-jie; Tong, Ying; Gao, Qiang

    2011-07-01

    Nondispersive infrared absorption spectroscopy(NDIR) is an important method to measure CO concentration in the air. In the present study, an open-path measurement system and continuous measuring device was developed, and genetic programming was used to establish the calibration model of subjects' light intensity sampling values. Continuous measurements were carried out in 10 different concentration of CO, and 40 sampled data were acquired and analyzed. For validation set, the correlation coefficient was 0.9997. The biggest relative error of validation was 4.00%, and the average relative error was 1.11%. Results show that genetic programming can be a good method for the modeling of gas concentration measurements equipped with NDIR systems.

  10. [Studies on the remote measurement of the emission of formaldehyde by mobile differential optical absorption spectroscopy].

    PubMed

    Wu, Feng-Cheng; Xie, Pin-Hua; Li, Ang; Si, Fu-Qi; Dou, Ke; Liu, Yu; Xu, Jin; Wang, Jie

    2011-11-01

    Formaldehyde (HCHO) is the most abundant carbonyl compounds that play an important role in atmospheric chemistry and photochemical reactions. Formaldehyde is an important indicator of atmospheric reactivity and urban atmospheric aerosol precursors. In the present paper, the emission of formaldehyde from chemical area was measured using the mobile differential optical absorption spectroscopy (DOAS). This instrument uses the zenith scattered sunlight as the light source with successful sampling in the area loop. Vertical column density was retrieved by this system, combined with the meteorological wind field and car speed information, the emission of formaldehyde in the area was estimated. The authors carried out the measuring experiment in one chemical plant in Beijing using this technology. The result showed that the average value of the flux of formaldehyde in this area was 605 kg x h(-1) during the measuring period.

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

    SciTech Connect

    Huang, Chun-Chao; Chang, Shu-Jui; Yang, Chao-Yao; Tseng, Yuan-Chieh; Chou, Hsiung

    2013-12-15

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

  12. Broadband femtosecond transient absorption spectroscopy for a CVD Mo S2 monolayer

    NASA Astrophysics Data System (ADS)

    Aleithan, Shrouq H.; Livshits, Maksim Y.; Khadka, Sudiksha; Rack, Jeffrey J.; Kordesch, Martin E.; Stinaff, Eric

    2016-07-01

    Carrier dynamics in monolayer Mo S2 have been investigated using broadband femtosecond transient absorption spectroscopy (FTAS). A tunable pump pulse was used while a broadband probe pulse revealed ground and excited state carrier dynamics. Interestingly, for pump wavelengths both resonant and nonresonant with the A and B excitons, we observe a broad ground state bleach around 2.9 eV, with decay components similar to A and B. Associating this bleach with the band nesting region between K and Γ in the band structure indicates significant k-space delocalization and overlap among excitonic wave functions identified as A, B, C, and D. Comparison of time dynamics for all features in resonance and nonresonance excitation is consistent with this finding.

  13. Uranium and thorium sorption on minerals studied by x-ray absorption spectroscopy

    SciTech Connect

    Hudson, E.A.; Terminello, L.J.; Viani, B.E.

    1995-12-01

    Several actinide-mineral sorption systems were studied by uranium and thorium L{sub 3}-edge x-ray absorption spectroscopy. A series of layer silicate minerals, including micas, were selected for their systematic variations in surface structure, e.g. degree of permanent negative charge on the basal planes. An expansible layer silicate, vermiculite, was treated to provide several different interlayer spacings, allowing variations in the accessibility of interior cation exchange sites. The finely powdered minerals were exposed to aqueous solutions of uranyl chloride or thorium chloride. Analysis of the EXAFS and XANES spectra indicates the influence of the mineral substrate upon the local structure of the bound actinide species. Trends in the data are interpreted based upon the known variations in mineral structure.

  14. Accurate frequency of the 119 micron methanol laser from tunable far-infrared absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Inguscio, M.; Zink, L. R.; Evenson, K. M.; Jennings, D. A.

    1990-01-01

    High-accuracy absorption spectroscopy of CH3OH in the far infrared is discussed. In addition to 22 transitions in the ground state, the frequency of the (n, tau, J, K), (0, 1, 16, 8) to (0, 2, 15, 7) transition in the nu5 excited vibrational level, which is responsible for the laser emission at 119 microns, was measured. The measured frequency is 2,522,782.57(10) MHz at zero pressure, with a pressure shift of 6.1(32) kHz/Pa (0.805/420/ MHz/torr). An accurate remeasurement of the laser emission frequency has also been performed, and the results are in good agreement.

  15. [Determination of trace selenium in edible fungi with graphite furnace atomic absorption spectroscopy].

    PubMed

    Tie, Mei; Zhang, Wei; Li, Jing; Jing, Kui; Zang, Shu-liang; Li, Hua-wei

    2006-01-01

    In the present article, samples were digested by a quartz high-pressure digestion pot, reducing the loss of selenium in digestion. The content of selenium in edible fungi was determined by using graphite furnace atomic absorption spectroscopy, and the results showed that when the content of selenium in edible fungi was determined by using 1% Ni(NO3)2 as a matrix modifier, ashing temperature of 500 degreed C, and atomization temperature of 2 500 degrees C, and rectifying background by deuterium light, the recovery was in the range of 92.1%-115.5%, the relative standard deviation of the method was 1.28%, and the limit of detection was 15.8 microg x L(-1). The method was suitable for the determination of trace selenium in edible fungi with the advantages of being simple, rapid, sensitive, stable and accurate etc., and the results were satisfactory.

  16. Etalon-induced baseline drift and correction in atom flux sensors based on atomic absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Du, Yingge; Chambers, Scott A.

    2014-10-01

    Atom flux sensors based on atomic absorption (AA) spectroscopy are of significant interest in thin film growth as they can provide unobtrusive, element specific real-time flux sensing and control. The ultimate sensitivity and performance of these sensors are strongly affected by baseline drift. Here we demonstrate that an etalon effect resulting from temperature changes in optical viewport housings is a major source of signal instability, which has not been previously considered, and cannot be corrected using existing methods. We show that small temperature variations in the fused silica viewports can introduce intensity modulations of up to 1.5% which in turn significantly deteriorate AA sensor performance. This undesirable effect can be at least partially eliminated by reducing the size of the beam and tilting the incident light beam off the viewport normal.

  17. Determination of tellurium in geochemical materials by flameless atomic-absorption spectroscopy.

    PubMed

    Sighinolfi, G P; Santos, A M; Martinelli, G

    1979-02-01

    A method is described for the determination of tellurium at nanogram levels in rocks and in other complex materials by the use of flameless atomic-absorption spectroscopy. A very selective organic extraction procedure is applied to avoid matrix interference effects during extraction of Te and the atomization stage in the graphite furnace. Prior separation of iron and other interfering elements is achieved by a combined cupferron-ethyl acetate extraction. Tellerium is extracted from 6M hydrochloric acid with MIBK and stripped into aqueous medium. Pipetting of the aqueous extract into the graphite furnace gives fairly good instrumental reproducibility (2-3% error). Detection limits of about 10 ppM Te for a 0.5-g sample have been achieved with the medium-performance apparatus used. Results for Te in some geochemical reference materials are reported. Indications are given for the determination of Sb and Mo in the same solutions.

  18. Determination of palladium by graphite furnace atomic absorption spectroscopy without matrix matching.

    PubMed

    Jia, X; Wang, T; Wu, J

    2001-05-30

    A graphite furnace atomic absorption spectroscopy method for the analysis of the palladium (Pd) content in bulk pharmaceutical drug substances and their intermediates prepared in aqueous solutions is extended to samples prepared in acetonitrile (ACN) and ACN-water mixtures as well to samples prepared in dimethyl sulfoxide (DMSO) and DMSO-water mixtures. The Pd content in samples solubilized in these solvents can be accurately determined with calibration established with standards prepared in aqueous solutions without matrix matching or using the method of standard additions. The validity of this method is demonstrated by spike recovery studies and by the agreement with results for the same samples prepared in these solvents, in concentrated nitric acid, and prepared by a microwave digestion system.

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

    SciTech Connect

    Pelliccione, CJ; Timofeeva, EV; Katsoudas, JP; Segre, CU

    2014-12-01

    In situ x-ray absorption spectroscopy (XAS) provides element-specific characterization of both crystalline and amorphous phases and enables direct correlations between electrochemical performance and structural characteristics of cathode and anode materials. In situ XAS measurements are very demanding to the design of the experimental setup. We have developed a sample chamber that provides electrical connectivity and inert atmosphere for operating electrochemical cells and also accounts for x-ray interactions with the chamber and cell materials. The design of the sample chamber for in situ measurements is presented along with example XAS spectra from anode materials in operating pouch cells at the Zn and Sn K-edges measured in fluorescence and transmission modes, respectively. (C) 2014 AIP Publishing LLC.

  20. Absolute 1* quantum yields for the ICN A state by diode laser gain versus absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Hess, Wayne P.; Leone, Stephen R.

    1987-01-01

    Absolute I* quantum yields were measured as a function of wavelength for room temperature photodissociation of the ICN A state continuum. The temperature yields are obtained by the technique of time-resolved diode laser gain-versus-absorption spectroscopy. Quantum yields are evaluated at seven wavelengths from 248 to 284 nm. The yield at 266 nm is 66.0 +/- 2% and it falls off to 53.4 +/- 2% and 44.0 +/- 4% at 284 and 248 respectively. The latter values are significantly higher than those obtained by previous workers using infrared fluorescence. Estimates of I* quantum yields obtained from analysis of CN photofragment rotational distributions, as discussed by other workers, are in good agreement with the I* yields. The results are considered in conjunction with recent theoretical and experimental work on the CN rotational distributions and with previous I* yield results.

  1. Infrared Reflection-Absorption Spectroscopy: Principles and Applications to Lipid-Protein Interaction in Langmuir Films

    PubMed Central

    Mendelsohn, Richard; Mao, Guangru; Flach, Carol R.

    2010-01-01

    Infrared reflection-absorption spectroscopy (IRRAS) of lipid/protein monolayer films in situ at the air/water interface provides unique molecular structure and orientation information from the film constituents. The technique is thus well suited for studies of lipid/protein interaction in a physiologically relevant environment. Initially, the nature of the IRRAS experiment is described and the molecular structure information that may be obtained is recapitulated. Subsequently, several types of applications, including the determination of lipid chain conformation and tilt as well as elucidation of protein secondary structure are reviewed. The current article attempts to provide the reader with an understanding of the current capabilities of IRRAS instrumentation and the type of results that have been achieved to date from IRRAS studies of lipids, proteins and lipid/protein films of progressively increasing complexity. Finally, possible extensions of the technology are briefly considered. PMID:20004639

  2. High resolution laser induced fluorescence Doppler velocimetry utilizing saturated absorption spectroscopy

    SciTech Connect

    Aramaki, Mitsutoshi; Ogiwara, Kohei; Etoh, Shuzo; Yoshimura, Shinji; Tanaka, Masayoshi Y.

    2009-05-15

    A high resolution laser induced fluorescence (LIF) system has been developed to measure the flow velocity field of neutral particles in an electron-cyclotron-resonance argon plasma. The flow velocity has been determined by the Doppler shift of the LIF spectrum, which is proportional to the velocity distribution function. Very high accuracy in velocity determination has been achieved by installing a saturated absorption spectroscopy unit into the LIF system, where the absolute value and scale of laser wavelength are determined by using the Lamb dip and the fringes of a Fabry-Perot interferometer. The minimum detectable flow velocity of a newly developed LIF system is {+-}2 m/s, and this performance remains unchanged in a long-time experiment. From the radial measurements of LIF spectra of argon metastable atoms, it is found that there exists an inward flow of neutral particles associated with neutral depletion.

  3. Infrared Absorption Spectroscopy and Chemical Kinetics of Free Radicals, Final Technical Report

    DOE R&D Accomplishments Database

    Curl, Robert F.; Glass, Graham P.

    2004-11-01

    This research was directed at the detection, monitoring, and study of the chemical kinetic behavior by infrared absorption spectroscopy of small free radical species thought to be important intermediates in combustion. Work on the reaction of OH with acetaldehyde has been completed and published and work on the reaction of O({sup 1}D) with CH{sub 4} has been completed and submitted for publication. In the course of our investigation of branching ratios of the reactions of O({sup 1}D) with acetaldehyde and methane, we discovered that hot atom chemistry effects are not negligible at the gas pressures (13 Torr) initially used. Branching ratios of the reaction of O({sup 1}D) with CH{sub 4} have been measured at a tenfold higher He flow and fivefold higher pressure.

  4. Vacancy trapping by solute atoms during quenching in Cu-based dilute alloys studied by positron annihilation spectroscopy

    NASA Astrophysics Data System (ADS)

    Yabuuchi, A.; Yamamoto, Y.; Ohira, J.; Sugita, K.; Mizuno, M.; Araki, H.; Shirai, Y.

    2009-11-01

    Frozen-in vacancies and the recovery have been investigated in some Cu-based dilute alloys by using positron annihilation lifetime spectroscopy. Cu-0.5at%Sb, Cu-0.5at%Sn and Cu-0.5at%In dilute bulk alloys were quenched to ice water from 1223 K. A pure-Cu specimen was also quenched from the same temperature. As a result, no frozen-in vacancies have been detected in as-quenched pure-Cu specimen. On the other hand, as-quenched Cu-0.5at%Sb alloy contained frozen-in thermal equilibrium vacancies with concentration of 3 × 10-5. Furthermore, these frozen-in vacancies in Cu-0.5at%Sb alloy were stable until 473 K, and began to migrate at 523 K. Finally, the Cu-Sb alloy were recovered to the fully annealed state at 823 K. This thermal stability clearly implies some interaction exists between a vacancy and Sb atom and due to the interaction, thermal equilibrium vacancies are trapped by Sb atoms during quenching.

  5. Direct determination of Cu and Zn in fruit juices and bovine milk by thermospray flame furnace atomic absorption spectrometry.

    PubMed

    Nascentes, Clésia C; Arruda, Marco A Z; Nogueira, Ana Rita A; Nóbrega, Joaquim A

    2004-11-15

    In the present work, thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) was employed for Cu and Zn determination in bovine milk and fruit juice samples without any pretreatment. TS-FF-AAS system was optimized and a sample volume of 300mul was injected into the carrier stream (0.014moll(-1) HNO(3) at a flow rate of 0.4mlmin(-1)), and it was introduced into a hot Ni tube. The detection limits obtained for Cu and Zn in aqueous solution were 2.2 and 0.91mugl(-1), respectively, and 3.2mugl(-1) for Cu in a medium containing water-soluble tertiary amines. The relative standard deviations varied from 2.7 to 4.2% (n=12). Sample preparation was carried out by simple dilution in water or in water-soluble tertiary amines medium. Accuracy was checked by performing addition-recovery experiments as well as by using reference materials (whole milk powder, non-fat milk powder, and infant formula). Recoveries varied from 97.7 to 105.3% for Cu and Zn. All results obtained for reference materials were in agreement with certified values at a 95% confidence level.

  6. Site- and phase-selective x-ray absorption spectroscopy based on phase-retrieval calculation

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Tomoya; Fukuda, Katsutoshi; Matsubara, Eiichiro

    2017-03-01

    Understanding the chemical state of a particular element with multiple crystallographic sites and/or phases is essential to unlocking the origin of material properties. To this end, resonant x-ray diffraction spectroscopy (RXDS) achieved through a combination of x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS) techniques can allow for the measurement of diffraction anomalous fine structure (DAFS). This is expected to provide a peerless tool for electronic/local structural analyses of materials with complicated structures thanks to its capability to extract spectroscopic information about a given element at each crystallographic site and/or phase. At present, one of the major challenges for the practical application of RXDS is the rigorous determination of resonant terms from observed DAFS, as this requires somehow determining the phase change in the elastic scattering around the absorption edge from the scattering intensity. This is widely known in the field of XRD as the phase problem. The present review describes the basics of this problem, including the relevant background and theory for DAFS and a guide to a newly-developed phase-retrieval method based on the logarithmic dispersion relation that makes it possible to analyze DAFS without suffering from the intrinsic ambiguities of conventional iterative-fitting. Several matters relating to data collection and correction of RXDS are also covered, with a final emphasis on the great potential of powder-sample-based RXDS (P-RXDS) to be used in various applications relevant to practical materials, including antisite-defect-type electrode materials for lithium-ion batteries.

  7. Study on synchronous detection method of methane and ethane with laser absorption spectroscopy technology

    NASA Astrophysics Data System (ADS)

    He, Ying; Zhang, Yu-jun; You, Kun; Gao, Yan-wei; Chen, Chen; Liu, Jian-guo; Liu, Wen-qing

    2016-10-01

    The main ingredient of mash gas is alkenes, and methane is the most parts of mash gas and ethane is a small portion of it. Fast, accurate, real-time measurement of methane and ethane concentration is an important task for preventing coal mining disaster. In this research, a monitoring system with tunable diode laser absorption spectroscopy (TDLAS) technology has been set up for simultaneous measurement of methane and ethane, and a DFB laser at wavelength of 1.653μm was used as the laser source. The absorption spectroscopy information of methane and ethane, especially the characteristic of the spectrum peak positions and relative intensity were determined by available spectral structures from previous study and available database. Then, the concentration inversion algorithm method based on the spectral resolution and feature extraction was designed for methane and ethane synchronous detection. At last, the continuously experimental results obtained by different concentration of methane and ethane sample gases with the multiple reflection cell and the standard distribution system. In this experiment, the standard distribution system made with the standard gas and two high precision mass flow meters of D07 Sevenstar series whose flow velocity is 1l/min and 5l/min respectively. When the multiple reflection cell work stably, the biggest detection error of methane concentration inversion was 3.7%, and the biggest detection error of ethane was 4.8%. So it is verified that this concentration inversion algorithm works stably and reliably. Thus, this technology could realize the real-time, fast and continuous measurement requirement of mash gas and it will provide the effective technical support to coal mining production in safety for our country.

  8. Evolution of silver nanoparticles in the rat lung investigated by X-ray absorption spectroscopy

    DOE PAGES

    Davidson, R. Andrew; Anderson, Donald S.; Van Winkle, Laura S.; ...

    2014-12-16

    Following a 6-h inhalation exposure to aerosolized 20 and 110 nm diameter silver nanoparticles, lung tissues from rats were investigated with X-ray absorption spectroscopy, which can identify the chemical state of silver species. Lung tissues were processed immediately after sacrifice of the animals at 0, 1, 3, and 7 days post exposure and the samples were stored in an inert and low-temperature environment until measured. We found that it is critical to follow a proper processing, storage and measurement protocol; otherwise only silver oxides are detected after inhalation even for the larger nanoparticles. The results of X-ray absorption spectroscopy measurementsmore » taken in air at 85 K suggest that the dominating silver species in all the postexposure lung tissues were metallic silver, not silver oxide, or solvated silver cations. The results further indicate that the silver nanoparticles in the tissues were transformed from the original nanoparticles to other forms of metallic silver nanomaterials and the rate of this transformation depended on the size of the original nanoparticles. Furthermore, we found that 20 nm diameter silver nanoparticles were significantly modified after aerosolization and 6-h inhalation/deposition, whereas larger, 110 nm diameter nanoparticles were largely unchanged. Over the seven-day postexposure period the smaller 20 nm silver nanoparticles underwent less change in the lung tissue than the larger 110 nm silver nanoparticles. In contrast, silica-coated gold nanoparticles did not undergo any modification processes and remained as the initial nanoparticles throughout the 7-day study period.« less

  9. Ionization and dissociation dynamics of vinyl bromide probed by femtosecond extreme ultraviolet transient absorption spectroscopy.

    PubMed

    Lin, Ming-Fu; Neumark, Daniel M; Gessner, Oliver; Leone, Stephen R

    2014-02-14

    Strong-field induced ionization and dissociation dynamics of vinyl bromide, CH2=CHBr, are probed using femtosecond extreme ultraviolet (XUV) transient absorption spectroscopy. Strong-field ionization is initiated with an intense femtosecond, near infrared (NIR, 775 nm) laser field. Femtosecond XUV pulses covering the photon energy range of 50-72 eV probe the subsequent dynamics by measuring the time-dependent spectroscopic features associated with transitions of the Br (3d) inner-shell electrons to vacancies in molecular and atomic valence orbitals. Spectral signatures are observed for the depletion of neutral C2H3Br, the formation of C2H3Br(+) ions in their ground (X̃) and first excited (Ã) states, the production of C2H3Br(++) ions, and the appearance of neutral Br ((2)P3/2) atoms by dissociative ionization. The formation of free Br ((2)P3/2) atoms occurs on a timescale of 330 ± 150 fs. The ionic à state exhibits a time-dependent XUV absorption energy shift of ∼0.4 eV within the time window of the atomic Br formation. The yield of Br atoms correlates with the yield of parent ions in the à state as a function of NIR peak intensity. The observations suggest that a fraction of vibrationally excited C2H3Br(+) (Ã) ions undergoes intramolecular vibrational energy redistribution followed by the C-Br bond dissociation. The C2H3Br(+) (X̃) products and the majority of the C2H3Br(++) ions are relatively stable due to a deeper potential well and a high dissociation barrier, respectively. The results offer powerful new insights about orbital-specific electronic processes in high field ionization, coupled vibrational relaxation and dissociation dynamics, and the correlation of valence hole-state location and dissociation in polyatomic molecules, all probed simultaneously by ultrafast table-top XUV spectroscopy.

  10. [Dithiobis-succinimidyl propionate on gold island films: surface-enhanced infrared absorption spectroscopy study].

    PubMed

    Guo, Hao; Ding, Li; Zhang, Tian-Jie; Mao, Yan-Li

    2013-05-01

    Dithiobis-succinimidyl propionate (DTSP), an important homobifunctional crosslinker, has been widely used for the covalent immobilization of proteins onto solid supports by amine coupling. In the present study, adsorption of DTSP on vacuum-deposited gold island films was analyzed by means of surface-enhanced infrared absorption spectroscopy (SEIRAS). For the sake of a reliable assignment of the vibrational spectra, IR intensity of the adsorption model of TSP on one gold surface was calculated using density functional theory (DFT) at the Beck' s three-parameter Lee-Yang-Parr (B3LYP) level with the LANL2DZ basis set. SEIRAS and multiple-angle-of-incidence polarization infrared reflection-absorption spectroscopy indicated that TSP is arranged orderly in a tilted fashion with a dihedral angle of 65 degrees between the plane of succinimidyl ring and the gold surface. The binding kinetics revealed that that the time constant of self-assembly of the TSP layer is 220 sec. Furthermore, the coupling process of amino-nitrilotriacetic acid (ANTA) with surface-bound TSP monolayer was monitored in situ by SEIRAS. Three negative bands observed at 1 807, 1 776, and 1 728 cm(-1) respectively provided direct evidence for the reaction of the succinimidyl ester. The appearance of one intense band at 1 566 cm(-1) gave a clear support for the presence of the cross-link between ANTA and TSP. We hope that the results in current investigation will contribute to the better understanding of properties of DTSP and related reactions at the molecular level.

  11. Site- and phase-selective x-ray absorption spectroscopy based on phase-retrieval calculation.

    PubMed

    Kawaguchi, Tomoya; Fukuda, Katsutoshi; Matsubara, Eiichiro

    2017-03-22

    Understanding the chemical state of a particular element with multiple crystallographic sites and/or phases is essential to unlocking the origin of material properties. To this end, resonant x-ray diffraction spectroscopy (RXDS) achieved through a combination of x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS) techniques can allow for the measurement of diffraction anomalous fine structure (DAFS). This is expected to provide a peerless tool for electronic/local structural analyses of materials with complicated structures thanks to its capability to extract spectroscopic information about a given element at each crystallographic site and/or phase. At present, one of the major challenges for the practical application of RXDS is the rigorous determination of resonant terms from observed DAFS, as this requires somehow determining the phase change in the elastic scattering around the absorption edge from the scattering intensity. This is widely known in the field of XRD as the phase problem. The present review describes the basics of this problem, including the relevant background and theory for DAFS and a guide to a newly-developed phase-retrieval method based on the logarithmic dispersion relation that makes it possible to analyze DAFS without suffering from the intrinsic ambiguities of conventional iterative-fitting. Several matters relating to data collection and correction of RXDS are also covered, with a final emphasis on the great potential of powder-sample-based RXDS (P-RXDS) to be used in various applications relevant to practical materials, including antisite-defect-type electrode materials for lithium-ion batteries.

  12. Speciation of zinc in municipal solid waste incineration fly ash after heat treatment: an X-ray absorption spectroscopy study.

    PubMed

    Struis, Rudolf P W J; Ludwig, Christian; Lutz, Harald; Scheidegger, André M

    2004-07-01

    Fly ash is commonly deposited in special landfills as it contains toxic concentrations of heavy metals, such as Zn, Pb, Cd, and Cu. This study was inspired by our efforts to detoxify fly ash from municipal solid waste incineration by thermal treatment to produce secondary raw materials suited for reprocessing. The potential of the thermal treatment was studied by monitoring the evaporation rate of zinc from a certified fly ash (BCR176) during heating between 300 and 950 degrees C under different carrier gas compositions. Samples were quenched at different temperatures for subsequent investigation with X-ray absorption spectroscopy (XAS). The XAS spectra were analyzed using principal component analysis (PCA), target transformation (TT), and linear combination fitting (LCF) to analyze the major Zn compounds in the fly ash as a function of the temperature. The original fly ash comprised about 60% zinc oxides mainly in the form of hydrozincite (Zn5(OH)6(CO3)2) and 40% inerts like willemite (Zn2SiO4) and gahnite (ZnAl2O4) in a weight ratio of about 3:1. At intermediate temperatures (550-750 degrees C) the speciation underlines the competition between indigenous S and Cl with solid zinc oxides to form either volatile ZnCl2 or solid ZnS. ZnS then transformed into volatile species at about 200 degrees C higher temperatures. The inhibiting influence of S was found absent when oxygen was introduced to the inert carrier gas stream or chloride-donating alkali salt was added to the fly ash.

  13. Transient Absorption Spectroscopy of C1 and C2 Criegee Intermediates: UV Spectrum and Reaction Kinetics

    NASA Astrophysics Data System (ADS)

    Smith, M. C.; Chao, W.; Ting, A.; Chang, C. H.; Lin, L. C.; Takahashi, K.; Boering, K. A.; Lin, J. J. M.

    2015-12-01

    Atmospheric production and removal rates of Criegee intermediates produced in alkene ozonolysis must be understood to constrain the importance of these species in VOC oxidation and other processes. To estimate these rates, reliable detection methods and laboratory measurements of the UV absorption spectra and reaction kinetics of Criegee intermediates are needed. Here, transient absorption spectroscopy was used to directly measure the UV spectrum of the C2 Criegee intermediate CH3CHOO in a flow reactor at 295 K. The UV spectrum was scaled to the absolute absorption cross section at 308 nm determined by laser depletion measurements in a molecular beam, resulting in a peak UV cross section of (1.27±0.11) × 10-17 cm2 molecule-1 at 328 nm. This spectrum represents the absorption of the syn and anti conformers of CH3CHOO under near-atmospheric conditions, both of which contribute to CH3CHOO atmospheric removal due to UV photolysis. Transient UV absorption was also used to measure the kinetics of the reaction of the C1 Criegee intermediate CH2OO with water vapor at temperatures from 283 to 324 K. The observed CH2OO decay is quadratic with respect to the H2O concentration, indicating that reaction with water dimer is the primary process affecting CH2OO loss. The rate coefficient for the reaction of CH2OO with water dimer exhibits a strong negative temperature dependence with an Arrhenius activation energy of -8.1±0.6 kcal mol-1. The temperature dependence increases the effective loss rate for CH2OO (relative to 298 K) by a factor of ˜2.5 at 278 K and 70% relative humidity, and decreases the loss rate by a factor of ˜2 at 313 K and 30% humidity, which demonstrates that variations in reaction rate due to temperature differences should be included in estimates of Criegee intermediate removal via reactions with water dimer in the atmosphere.

  14. Probing Multiple Core Samples through the SN 1006 Remnant by UV Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Winkler, P. F.; Long, K. S.; Fesen, R. A.; Hamilton, A. J. S.

    2003-12-01

    Ejecta within young supernova remnants (SNRs) have been widely studied both through the X-ray emission from highly ionized plasma heated by fast shocks and through the optical emission from isolated dense filaments excited by secondary shocks. A full inventory of the ejecta, however, must also include cold, unshocked material within the SNR shell, which can be studied through UV absorption spectroscopy if suitable background ``UV lightbulbs'' can be identified. So far, this technique has been applied only in the remnant of SN 1006, where IUE and HST spectra of the Schweizer-Middleditch (S-M) star have probed a single sight line 3 arcmin from the projected center of the 15 arcmin radius shell (Hamilton et al. 1997, ApJ 481, 838 and references therein). We have identified at least two more background UV sources that enable us to probe additional core samples through the SN 1006 shell, corresponding to the sight lines to each of these sources, using spectra from HST-STIS. A QSO with V = 18.3 and z = 0.337, located 9 arcmin NE of the projected center, shows evidence of broad but asymmetric (primarily red-shifted) absorption in Si II and Si IV lines. There is only marginal evidence for absorption from Fe II at 2382 and 2599 Å with near zero velocity. Only a near-UV spectrum was obtained for a fainter (V = 19.5) QSO at z = 1.026, located within 2 arcmin of the SNR center. This shows strong evidence for broad Fe II absorption with a sharp blue edge at ˜ -3000 km/s and a more gradual red edge extending to > 8000 km/s. These profiles appear similar to those for the S-M star. Two A0 stars are probably more distant than SN 1006 but are located far from the center, within 3 arcmin of the shell rim. Neither appears to show evidence for absorption along the line of sight. These multiple cores through the SNR shell enable us to better map the distribution of ejecta. This research is based on observations with the Hubble Space Telescope and is directly supported through NASA

  15. Observation of nonlinear absorption and visible photoluminescence emission in chemically synthesized Cu2+ doped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Kole, A. K.; Kumbhakar, P.; Chatterjee, U.

    2012-01-01

    Nonlinear optical properties of chemically synthesized ZnS and Cu2+ doped ZnS nanoparticles of average sizes ˜2.5 nm are reported by using open aperture z-scan technique with the Nd:YAG laser second harmonic radiation at 532 nm. Tunable photoluminescence emissions in the visible region due to the increase in concentration of Cu2+ doping in ZnS are observed at room temperature. By analyzing the experimental z-scan data, it is found that three photon absorptions (3PA) are taking place in all the samples. The extracted values of 3PA coefficients of the samples are ˜109 times higher than that of bulk ZnS.

  16. Extending differential optical absorption spectroscopy for limb measurements in the UV

    NASA Astrophysics Data System (ADS)

    Puä·Ä«Te, J.; Kühl, S.; Deutschmann, T.; Platt, U.; Wagner, T.

    2010-05-01

    Methods of UV/VIS absorption spectroscopy to determine the constituents in the Earth's atmosphere from measurements of scattered light are often based on the Beer-Lambert law, like e.g. Differential Optical Absorption Spectroscopy (DOAS). While the Beer-Lambert law is strictly valid for a single light path only, the relation between the optical depth and the concentration of any absorber can be approximated as linear also for scattered light observations at a single wavelength if the absorption is weak. If the light path distribution is approximated not to vary with wavelength, also linearity between the optical depth and the product of the cross-section and the concentration of an absorber can be assumed. These assumptions are widely made for DOAS applications for scattered light observations. For medium and strong absorption of scattered light (e.g. along very long light-paths like in limb geometry) the relation between the optical depth and the concentration of an absorber is no longer linear. In addition, for broad wavelength intervals the differences in the travelled light-paths at different wavelengths become important, especially in the UV, where the probability for scattering increases strongly with decreasing wavelength. However, the DOAS method can be extended to cases with medium to strong absorptions and for broader wavelength intervals by the so called air mass factor modified (or extended) DOAS and the weighting function modified DOAS. These approaches take into account the wavelength dependency of the slant column densities (SCDs), but also require a priori knowledge for the air mass factor or the weighting function from radiative transfer modelling. We describe an approach that considers the fitting results obtained from DOAS, the SCDs, as a function of wavelength and vertical optical depth and expands this function into a Taylor series of both quantities. The Taylor coefficients are then applied as additional fitting parameters in the DOAS analysis

  17. NO2 measurements in Hong Kong using LED based long path differential optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Chan, K. L.; Pöhler, D.; Kuhlmann, G.; Hartl, A.; Platt, U.; Wenig, M. O.

    2012-05-01

    In this study we present the first long term measurements of atmospheric nitrogen dioxide (NO2) using a LED based Long Path Differential Optical Absorption Spectroscopy (LP-DOAS) instrument. This instrument is measuring continuously in Hong Kong since December 2009, first in a setup with a 550 m absorption path and then with a 3820 m path at about 30 m to 50 m above street level. The instrument is using a high power blue light LED with peak intensity at 450 nm coupled into the telescope using a Y-fibre bundle. The LP-DOAS instrument measures NO2 levels in the Kowloon Tong and Mongkok district of Hong Kong and we compare the measurement results to mixing ratios reported by monitoring stations operated by the Hong Kong Environmental Protection Department in that area. Hourly averages of coinciding measurements are in reasonable agreement (R = 0.74). Furthermore, we used the long-term data set to validate the Ozone Monitoring Instrument (OMI) NO2 data product. Monthly averaged LP-DOAS and OMI measurements correlate well (R = 0.84) when comparing the data for the OMI overpass time. We analyzed weekly patterns in both data sets and found that the LP-DOAS detects a clear weekly cycle with a reduction on weekends during rush hour peaks, whereas OMI is not able to observe this weekly cycle due to its fix overpass time (13:30-14:30 LT - local time).

  18. X-ray absorption spectroscopy and EPR studies of oriented spinach thylakoid preparations

    SciTech Connect

    Andrews, J.C. |

    1995-08-01

    In this study, oriented Photosystem II (PS II) particles from spinach chloroplasts are studied with electron paramagnetic resonance (EPR) and x-ray absorption spectroscopy (XAS) to determine more details of the structure of the oxygen evolving complex (OEC). The nature of halide binding to Mn is also studied with Cl K-edge and Mn EXAFS (extended x-ray absorption fine structure) of Mn-Cl model compounds, and with Mn EXAFS of oriented PS II in which Br has replaced Cl. Attention is focused on the following: photosynthesis and the oxygen evolving complex; determination of mosaic spread in oriented photosystem II particles from signal II EPR measurement; oriented EXAFS--studies of PS II in the S{sub 2} state; structural changes in PS II as a result of treatment with ammonia: EPR and XAS studies; studies of halide binding to Mn: Cl K-edge and Mn EXAFS of Mn-Cl model compounds and Mn EXAFS of oriented Br-treated photosystem II.

  19. Photo-induced dynamics in heterocyclic aromatic molecules probed by femtosecond XUV transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Lackner, Florian; Chatterley, Adam S.; Pemmaraju, Chaitanya D.; Neumark, Daniel M.; Leone, Stephen R.; Gessner, Oliver

    2016-05-01

    We report on the ring-opening and dissociation dynamics of strong-field ionized selenophene (C4 H4 Se), studied by transient XUV absorption spectroscopy at the Se 3d edge. The table-top experiments are facilitated by high-order harmonic generation coupled with a gas phase transient XUV absorption setup that is optimized for the study of organic compounds. Employing element-specific core-to-valence transitions, the ultrafast molecular dynamics are monitored from the perspective of the well-localized Se atoms. Spectral features are assigned based on first principles TDDFT calculations for a large manifold of electronic states. We observe signatures of rapidly (~ 35 fs) decaying highly excited molecular cations, the formation of ring-opened products on a 100 fs time scale and, most notably, the elimination of bare Se+ ions in a very rapid multi-step process. A delayed onset of the Se+ ions provides direct evidence that both selenium-carbon bonds are broken within only ~ 130 fs and that a sequential mechanism, presumably an initial ring-opening followed by a subsequent breaking of the second bond, is required to eliminate the atomic fragments.

  20. Molybdenum speciation in uranium mine tailings using X-ray absorption spectroscopy.

    PubMed

    Essilfie-Dughan, Joseph; Pickering, Ingrid J; Hendry, M Jim; George, Graham N; Kotzer, Tom

    2011-01-15

    Uranium (U) mill tailings in northern Saskatchewan, Canada, contain elevated concentrations of molybdenum (Mo). The potential for long-term (>10,000 years) mobilization of Mo from the tailings management facilities to regional groundwater systems is an environmental concern. To assist in characterizing long-term stability, X-ray absorption spectroscopy was used to define the chemical (redox and molecular) speciation of Mo in tailings samples from the Deilmann Tailings Management Facility (DTMF) at the Key Lake operations of Cameco Corporation. Comparison of Mo K near-edge X-ray absorption spectra of tailings samples and reference compounds of known oxidation states indicates Mo exists mainly as molybdate (+6 oxidation state). Principal component analysis of tailings samples spectra followed by linear combination fitting using spectra of reference compounds indicates that various proportions of NiMoO(4) and CaMoO(4) complexes, as well as molybdate adsorbed onto ferrihydrite, are the Mo species present in the U mine tailings. Tailings samples with low Fe/Mo (<708) and high Ni/Mo (>113) molar ratios are dominated by NiMoO(4), whereas those with high Fe/Mo (>708) and low Ni/Mo (<113) molar ratios are dominated by molybdate adsorbed onto ferrihydrite. This suggests that the speciation of Mo in the tailings is dependent in part on the chemistry of the original ore.

  1. [In situ temperature measurement by absorption spectroscopy based on time division multiplexing technology].

    PubMed

    Lou, Nan-zheng; Li, Ning; Weng, Chun-sheng

    2012-05-01

    Tunable diode laser absorption spectroscopy (TDLAS) technology is a kind of high sensitivity, high selectivity of non contacting gas in situ measurement technique. In the present paper, in situ gas temperature measurement of an open environment was achieved by means of direct scanning multiple characteristic lines of H2O and combined with least-squares algorithm. Through the use of HITRAN spectral database, the boundary effect on the gas temperature and concentration measurements was discussed in detail, and results showed that the combination of scanning multiple characteristic lines and least-squares algorithm can effectively reduce the boundary effect on the gas temperature measurements under the open environment. Experiments using time division multiplexing technology to simultaneously scan 7444.36, 7185.60, 7182.95 and 7447.48 cm(-1), the four characteristic H2O lines, the gas temperature of tubular furnace in the range of 573-973 K was measured under different conditions. The maximum temperature difference between absorption spectrum measurement and thermocouple signal was less than 52.4 K, and the maximum relative error of temperature measurement was 6.8%.

  2. An x-ray absorption spectroscopy study of Ni-Mn-Ga shape memory alloys.

    PubMed

    Sathe, V G; Dubey, Aditi; Banik, Soma; Barman, S R; Olivi, L

    2013-01-30

    The austenite to martensite phase transition in Ni-Mn-Ga ferromagnetic shape memory alloys was studied by extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) spectroscopy. The spectra at all the three elements', namely, Mn, Ga and Ni, K-edges in several Ni-Mn-Ga samples (with both Ni and Mn excess) were analyzed at room temperature and low temperatures. The EXAFS analysis suggested a displacement of Mn and Ga atoms in opposite direction with respect to the Ni atoms when the compound transforms from the austenite phase to the martensite phase. The first coordination distances around the Mn and Ga atoms remained undisturbed on transition, while the second and subsequent shells showed dramatic changes indicating the presence of a modulated structure. The Mn rich compounds showed the presence of antisite disorder of Mn and Ga. The XANES results showed remarkable changes in the unoccupied partial density of states corresponding to Mn and Ni, while the electronic structure of Ga remained unperturbed across the martensite transition. The post-edge features in the Mn K-edge XANES spectra changed from a double peak like structure to a flat peak like structure upon phase transition. The study establishes strong correlation between the crystal structure and the unoccupied electronic structure in these shape memory alloys.

  3. X-ray absorption spectroscopy as a probe of dissolved polysulfides in lithium sulfur batteries

    NASA Astrophysics Data System (ADS)

    Pascal, Tod; Prendergast, David

    2015-03-01

    There has been enormous interest lately in lithium sulfur batteries, since they have 5 times the theoretical capacity of lithium ion batteries. Large-scale adoption of this technology has been hampered by numerous shortcomings, chiefly the poor utilization of the active cathode material and rapid capacity fading during cycling. Overcoming these limitations requires methods capable of identifying and quantifying the products of the poorly understood electrochemical reactions. One recent advance has been the use of X-ray absorption spectroscopy (XAS), an element-specific probe of the unoccupied energy levels around an excited atom upon absorption of an X-ray photon, to identify the reaction products and intermediates. In this talk, we'll present first principles molecular dynamics and spectral simulations of dissolved lithium polysulfide species, showing how finite temperature dynamics, molecular geometry, molecular charge state and solvent environment conspire to determine the peak positions and intensity of the XAS. We'll present a spectral analysis of the radical (-1e charge) species, and reveal a unique low energy feature that can be used to identify these species from their more common dianion (-2e charge) counterparts.

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

    NASA Astrophysics Data System (ADS)

    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. Chemical analyses of these compounds are important for process and environmental monitoring. 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. The effect of hydration state on the sample, a potential complication in interpreting oxygen K-edge spectra, is discussed. These compounds have unique spectral signatures that can be used to identify unknown samples.

  5. [Study on Differential Optical Absorption Spectroscopy Data Processing Based on Chirp-Z Transformation].

    PubMed

    Zheng, Hai-ming; Li, Guang-jie; Wu, Hao

    2015-06-01

    Differential optical absorption spectroscopy (DOAS) is a commonly used atmospheric pollution monitoring method. Denoising of monitoring spectral data will improve the inversion accuracy. Fourier transform filtering method is effectively capable of filtering out the noise in the spectral data. But the algorithm itself can introduce errors. In this paper, a chirp-z transform method is put forward. By means of the local thinning of Fourier transform spectrum, it can retain the denoising effect of Fourier transform and compensate the error of the algorithm, which will further improve the inversion accuracy. The paper study on the concentration retrieving of SO2 and NO2. The results show that simple division causes bigger error and is not very stable. Chirp-z transform is proved to be more accurate than Fourier transform. Results of the frequency spectrum analysis show that Fourier transform cannot solve the distortion and weakening problems of characteristic absorption spectrum. Chirp-z transform shows ability in fine refactoring of specific frequency spectrum.

  6. Strontium localization in bone tissue studied by X-ray absorption spectroscopy.

    PubMed

    Frankær, Christian Grundahl; Raffalt, Anders Christer; Stahl, Kenny

    2014-02-01

    Strontium has recently been introduced as a pharmacological agent for the treatment and prevention of osteoporosis. We determined the localization of strontium incorporated into bone matrix from dogs treated with Sr malonate by X-ray absorption spectroscopy. A new approach for analyzing the X-ray absorption spectra resulted in a compositional model and allowed the relative distribution of strontium in the different bone components to be estimated. Approximately 35-45% of the strontium present is incorporated into calcium hydroxyapatite (CaHA) by substitution of some of the calcium ions occupying highly ordered sites, and at least 30% is located at less ordered sites where only the first solvation shell is resolved, suggesting that strontium is surrounded by only oxygen atoms similar to Sr(2+) in solution. Strontium was furthermore shown to be absorbed in collagen in which it obtains a higher structural order than when present in serum but less order than when it is incorporated into CaHA. The total amount of strontium in the samples was determined by inductively coupled plasma mass spectrometry, and the amount of Sr was found to increase with increasing dose levels and treatment periods, whereas the relative distribution of strontium among the different components appears to be independent of treatment period and dose level.

  7. Quantum state-resolved gas/surface reaction dynamics probed by reflection absorption infrared spectroscopy

    SciTech Connect

    Chen Li; Ueta, Hirokazu; Beck, Rainer D.; Bisson, Regis

    2013-05-15

    We report the design and characterization of a new molecular-beam/surface-science apparatus for quantum state-resolved studies of gas/surface reaction dynamics combining optical state-specific reactant preparation in a molecular beam by rapid adiabatic passage with detection of surface-bound reaction products by reflection absorption infrared spectroscopy (RAIRS). RAIRS is a non-invasive infrared spectroscopic detection technique that enables online monitoring of the buildup of reaction products on the target surface during reactant deposition by a molecular beam. The product uptake rate obtained by calibrated RAIRS detection yields the coverage dependent state-resolved reaction probability S({theta}). Furthermore, the infrared absorption spectra of the adsorbed products obtained by the RAIRS technique provide structural information, which help to identify nascent reaction products, investigate reaction pathways, and determine branching ratios for different pathways of a chemisorption reaction. Measurements of the dissociative chemisorption of methane on Pt(111) with this new apparatus are presented to illustrate the utility of RAIRS detection for highly detailed studies of chemical reactions at the gas/surface interface.

  8. Millisecond Kinetics of Nanocrystal Cation Exchange UsingMicrofluidic X-ray Absorption Spectroscopy

    SciTech Connect

    Chan, Emory M.; Marcus, Matthew A.; Fakra, Sirine; Elnaggar,Mariam S.; Mathies, Richard A.; Alivisatos, A. Paul

    2007-05-07

    We describe the use of a flow-focusing microfluidic reactorto measure the kinetics of theCdSe-to-Ag2Se nanocrystal cation exchangereaction using micro-X-ray absorption spectroscopy (mu XAS). The smallmicroreactor dimensions facilitate the millisecond mixing of CdSenanocrystal and Ag+ reactant solutions, and the transposition of thereaction time onto spatial coordinates enables the in situ observation ofthe millisecond reaction with mu XAS. XAS spectra show the progression ofCdSe nanocrystals to Ag2Se over the course of 100 ms without the presenceof long-lived intermediates. These results, along with supporting stoppedflow absorption experiments, suggest that this nanocrystal cationexchange reaction is highly efficient and provide insight into how thereaction progresses in individual particles. This experiment illustratesthe value and potential of in situ microfluidic X-ray synchrotrontechniques for detailed studies of the millisecond structuraltransformations of nanoparticles and other solution-phase reactions inwhich diffusive mixing initiates changes in local bond structures oroxidation states.

  9. Diamond sensors and polycapillary lenses for X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Ravel, B.; Attenkofer, K.; Bohon, J.; Muller, E.; Smedley, J.

    2013-10-01

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

  10. Application of quantum cascade laser absorption spectroscopy to studies of fluorocarbon molecules

    NASA Astrophysics Data System (ADS)

    Welzel, S.; Stepanov, S.; Meichsner, J.; Röpcke, J.

    2009-03-01

    The recent advent of quantum cascade lasers (QCLs) enables room-temperature mid-infrared spectrometer operation which is particularly favourable for industrial process monitoring and control, i.e. the detection of transient and stable molecular species. Conversely, fluorocarbon containing radio-frequency discharges are of special interest for plasma etching and deposition as well as for fundamental studies on gas phase and plasma surface reactions. The application of QCL absorption spectroscopy to such low pressure plasmas is typically hampered by non-linear effects connected with the pulsed mode of the lasers. Nevertheless, adequate calibration can eliminate such effects, especially in the case of complex spectra where single line parameters are not available. In order to facilitate measurements in fluorocarbon plasmas, studies on complex spectra of CF4 and C3F8 at 7.86 μm (1269 - 1275 cm-1) under low pressure conditions have been performed. The intra-pulse mode, i.e. pulses of up to 300 ns, was applied yielding highly resolved spectral scans of ~ 1 cm-1 coverage. Effective absorption cross sections were determined and their temperature dependence was studied in the relevant range up to 400 K and found to be non-negligible.

  11. Quantum state-resolved gas/surface reaction dynamics probed by reflection absorption infrared spectroscopy.

    PubMed

    Chen, Li; Ueta, Hirokazu; Bisson, Régis; Beck, Rainer D

    2013-05-01

    We report the design and characterization of a new molecular-beam/surface-science apparatus for quantum state-resolved studies of gas/surface reaction dynamics combining optical state-specific reactant preparation in a molecular beam by rapid adiabatic passage with detection of surface-bound reaction products by reflection absorption infrared spectroscopy (RAIRS). RAIRS is a non-invasive infrared spectroscopic detection technique that enables online monitoring of the buildup of reaction products on the target surface during reactant deposition by a molecular beam. The product uptake rate obtained by calibrated RAIRS detection yields the coverage dependent state-resolved reaction probability S(θ). Furthermore, the infrared absorption spectra of the adsorbed products obtained by the RAIRS technique provide structural information, which help to identify nascent reaction products, investigate reaction pathways, and determine branching ratios for different pathways of a chemisorption reaction. Measurements of the dissociative chemisorption of methane on Pt(111) with this new apparatus are presented to illustrate the utility of RAIRS detection for highly detailed studies of chemical reactions at the gas/surface interface.

  12. Use of flameless atomic absorption spectroscopy in immune cytolysis for nonradioactive determination of killer cell activity.

    PubMed

    Borella, P; Bargellini, A; Salvioli, S; Cossarizza, A

    1996-02-01

    We describe here a novel method to evaluate natural killer (NK) cytolytic activity by use of flameless atomic absorption spectroscopy (GF-AAS). This technique may be adopted for use in laboratories equipped with electrothermal atomic absorption spectrometers. Nonradioactive Cr as Na2CrO4 was used to label target cells (K562), and cell lysis was evaluated by measuring Cr released after 4 h of incubation with the effectors. We selected 520 micrograms/L as the optimal dose for labeling targets, between 12 and 20 h as the optimal incubation time, and 10(4) cells as the optimal target size. Advantages of this method include: (a) exclusion of radioactive tracer, with no risk for workers; (b) limited costs; (c) high sensitivity and reproducibility; (d) possibility to store samples; and (e) better control of Cr used for labeling cells due to well-determined, fixed Cr concentrations in the range of nontoxic and linear cellular uptake. Comparison with data obtained by conventional 51Cr labeling of targets killed by the same effectors was excellent, yielding comparable results and corroborating the method.

  13. Quantitation of a novel metalloporphyrin drug in plasma by atomic absorption spectroscopy.

    PubMed

    Hoffman, K L; Feng, M R; Rossi, D T

    1999-03-01

    A bioanalytical method to quantify cobalt mesoporphyrin (CoMP), a novel therapeutic agent, in plasma has been developed and validated. The approach involves atomic absorption spectroscopy to determine total cobalt in a sample and a back-calculation of the amount of compound present. Endogenous plasma cobalt concentrations were small ( <0.2 ng/ml(-1) Co in rat plasma) in comparison to the quantitation limit (4.5 ng/ml(-1) Co). The inter-day imprecision of the method was 10.0% relative standard deviation (RSD) and the inter-day bias was +/- 8.0% relative error (RE) over a standard curve range of 4.5- 45.0 ng/ml(-1) Co. Because it quantifies total cobalt, the method cannot differentiate between parent drug and metabolites, but negligible metabolism allows reliable estimates of the actual parent drug concentration. A correlation study between the atomic absorption method and 14C-radiometry demonstrated excellent agreement (r = 0.9868, slope = 1.041 +/- 0.028, intercept = 223.7 +/- 190.0) and further substantiated the accuracy of the methods. Methodology was successfully applied to a pharmacokinetic study of CoMP in rat, with pharmacokinetic parameter estimation. The elimination half-lives, after intra-muscular and subcutaneous administration, were 7.7 and 8.8 days, respectively.

  14. Metamaterial-enhanced vibrational absorption spectroscopy for the detection of protein molecules.

    PubMed

    Bui, Tung S; Dao, Thang D; Dang, Luu H; Vu, Lam D; Ohi, Akihiko; Nabatame, Toshihide; Lee, YoungPak; Nagao, Tadaaki; Hoang, Chung V

    2016-08-24

    From visible to mid-infrared frequencies, molecular sensing has been a major successful application of plasmonics because of the enormous enhancement of the surface electromagnetic nearfield associated with the induced collective motion of surface free carriers excited by the probe light. However, in the lower-energy terahertz (THz) region, sensing by detecting molecular vibrations is still challenging because of low sensitivity, complicated spectral features, and relatively little accumulated knowledge of molecules. Here, we report the use of a micron-scale thin-slab metamaterial (MM) architecture, which functions as an amplifier for enhancing the absorption signal of the THz vibration of an ultrathin adsorbed layer of large organic molecules. We examined bovine serum albumin (BSA) as a prototype large protein molecule and Rhodamine 6G (Rh6G) and 3,3'-diethylthiatricarbocyanine iodide (DTTCI) as examples of small molecules. Among them, our MM significantly magnified only the signal strength of bulky BSA. On the other hand, DTTCI and Rh6G are inactive, as they lack low-frequency vibrational modes in this frequency region. The results obtained here clearly demonstrate the promise of MM-enhanced absorption spectroscopy in the THz region for detection and structural monitoring of large biomolecules such as proteins or pathogenic enzymes.

  15. Metamaterial-enhanced vibrational absorption spectroscopy for the detection of protein molecules

    PubMed Central

    Bui, Tung S.; Dao, Thang D.; Dang, Luu H.; Vu, Lam D.; Ohi, Akihiko; Nabatame, Toshihide; Lee, YoungPak; Nagao, Tadaaki; Hoang, Chung V.

    2016-01-01

    From visible to mid-infrared frequencies, molecular sensing has been a major successful application of plasmonics because of the enormous enhancement of the surface electromagnetic nearfield associated with the induced collective motion of surface free carriers excited by the probe light. However, in the lower-energy terahertz (THz) region, sensing by detecting molecular vibrations is still challenging because of low sensitivity, complicated spectral features, and relatively little accumulated knowledge of molecules. Here, we report the use of a micron-scale thin-slab metamaterial (MM) architecture, which functions as an amplifier for enhancing the absorption signal of the THz vibration of an ultrathin adsorbed layer of large organic molecules. We examined bovine serum albumin (BSA) as a prototype large protein molecule and Rhodamine 6G (Rh6G) and 3,3′-diethylthiatricarbocyanine iodide (DTTCI) as examples of small molecules. Among them, our MM significantly magnified only the signal strength of bulky BSA. On the other hand, DTTCI and Rh6G are inactive, as they lack low-frequency vibrational modes in this frequency region. The results obtained here clearly demonstrate the promise of MM-enhanced absorption spectroscopy in the THz region for detection and structural monitoring of large biomolecules such as proteins or pathogenic enzymes. PMID:27555217

  16. Metamaterial-enhanced vibrational absorption spectroscopy for the detection of protein molecules

    NASA Astrophysics Data System (ADS)

    Bui, Tung S.; Dao, Thang D.; Dang, Luu H.; Vu, Lam D.; Ohi, Akihiko; Nabatame, Toshihide; Lee, Youngpak; Nagao, Tadaaki; Hoang, Chung V.

    2016-08-01

    From visible to mid-infrared frequencies, molecular sensing has been a major successful application of plasmonics because of the enormous enhancement of the surface electromagnetic nearfield associated with the induced collective motion of surface free carriers excited by the probe light. However, in the lower-energy terahertz (THz) region, sensing by detecting molecular vibrations is still challenging because of low sensitivity, complicated spectral features, and relatively little accumulated knowledge of molecules. Here, we report the use of a micron-scale thin-slab metamaterial (MM) architecture, which functions as an amplifier for enhancing the absorption signal of the THz vibration of an ultrathin adsorbed layer of large organic molecules. We examined bovine serum albumin (BSA) as a prototype large protein molecule and Rhodamine 6G (Rh6G) and 3,3‧-diethylthiatricarbocyanine iodide (DTTCI) as examples of small molecules. Among them, our MM significantly magnified only the signal strength of bulky BSA. On the other hand, DTTCI and Rh6G are inactive, as they lack low-frequency vibrational modes in this frequency region. The results obtained here clearly demonstrate the promise of MM-enhanced absorption spectroscopy in the THz region for detection and structural monitoring of large biomolecules such as proteins or pathogenic enzymes.

  17. The use of tunable diode laser absorption spectroscopy for the measurement of flame dynamics

    NASA Astrophysics Data System (ADS)

    Hendricks, A. G.; Vandsburger, U.; Saunders, W. R.; Baumann, W. T.

    2006-01-01

    Tunable diode laser absorption spectroscopy was used to measure temperature fluctuations in acoustically forced laminar and turbulent flames. The absorption of two high-temperature water lines, at 7444.37 cm-1 (v1+v3 bands) and 7185.59 cm-1 (2v1, v1+v3 bands), yielded an instantaneous temperature measurement of the product stream. The instantaneous temperature of the gases was used as an indicator of the energy transferred to the product stream from the combustion process. The frequency response of product gas temperature to velocity perturbations was compared to the frequency response of OH* chemiluminescence, an indicator of the chemical heat release rate. Past measurements of flame dynamics used chemiluminescence as the sole indicator of heat release rate, in effect assuming that the energy input rate from the flame into the acoustic field is dynamically equivalent to the chemical reaction rate. Through the use of TDLAS, the unsteady enthalpy of the gases was measured, which includes the effects of thermal diffusion and heat transfer. The measurements show that the frequency response function of gas temperature differs significantly from the chemiluminescence frequency response.

  18. β-Carotene Revisited by Transient Absorption and Stimulated Raman Spectroscopy.

    PubMed

    Quick, Martin; Kasper, Marc-André; Richter, Celin; Mahrwald, Rainer; Dobryakov, Alexander L; Kovalenko, Sergey A; Ernsting, Nikolaus P

    2015-12-21

    β-Carotene in n-hexane was examined by femtosecond transient absorption and stimulated Raman spectroscopy. Electronic change is separated from vibrational relaxation with the help of band integrals. Overlaid on the decay of S1 excited-state absorption, a picosecond process is found that is absent when the C9 -methyl group is replaced by ethyl or isopropyl. It is attributed to reorganization on the S1 potential energy surface, involving dihedral angles between C6 and C9 . In Raman studies, electronic states S2 or S1 were selected through resonance conditions. We observe a broad vibrational band at 1770 cm(-1) in S2 already. With 200 fs it decays and transforms into the well-known S1 Raman line for an asymmetric C=C stretching mode. Low-frequency activity (<800 cm(-1) ) in S2 and S1 is also seen. A dependence of solvent lines on solute dynamics implies intermolecular coupling between β-carotene and nearby n-hexane molecules.

  19. Shock-tube measurements of excited oxygen atoms using cavity-enhanced absorption spectroscopy.

    PubMed

    Nations, Marcel; Wang, Shengkai; Goldenstein, Christopher S; Sun, Kai; Davidson, David F; Jeffries, Jay B; Hanson, Ronald K

    2015-10-10

    We report the use of cavity-enhanced absorption spectroscopy (CEAS) using two distributed feedback diode lasers near 777.2 and 844.6 nm for sensitive, time-resolved, in situ measurements of excited-state populations of atomic oxygen in a shock tube. Here, a 1% O2/Ar mixture was shock-heated to 5400-8000 K behind reflected shock waves. The combined use of a low-finesse cavity, fast wavelength scanning of the lasers, and an off-axis alignment enabled measurements with 10 μs time response and low cavity noise. The CEAS absorption gain factors of 104 and 142 for the P35←S520 (777.2 nm) and P0,1,23←S310 (844.6 nm) atomic oxygen transitions, respectively, significantly improved the detection sensitivity over conventional single-pass measurements. This work demonstrates the potential of using CEAS to improve shock-tube studies of nonequilibrium electronic-excitation processes at high temperatures.

  20. High-resolution absorption spectroscopy of the OH 2Π3/2 ground state line

    NASA Astrophysics Data System (ADS)

    Wiesemeyer, H.; Güsten, R.; Heyminck, S.; Jacobs, K.; Menten, K. M.; Neufeld, D. A.; Requena-Torres, M. A.; Stutzki, J.

    2012-06-01

    The chemical composition of the interstellar medium is determined by gas phase chemistry, assisted by grain surface reactions, and by shock chemistry. The aim of this study is to measure the abundance of the hydroxyl radical (OH) in diffuse spiral arm clouds as a contribution to our understanding of the underlying network of chemical reactions. Owing to their high critical density, the ground states of light hydrides provide a tool to directly estimate column densities by means of absorption spectroscopy against bright background sources. We observed onboard the SOFIA observatory the 2Π3/2, J = 5/2 ← 3/2 2.5 THz line of ground-state OH in the diffuse clouds of the Carina-Sagittarius spiral arm. OH column densities in the spiral arm clouds along the sightlines to W49N, W51 and G34.26+0.15 were found to be of the order of 1014 cm-2, which corresponds to a fractional abundance of 10-7 to 10-8, which is comparable to that of H2O. The absorption spectra of both species have similar velocity components, and the ratio of the derived H2O to OH column densities ranges from 0.3 to 1.0. In W49N we also detected the corresponding line of 18OH.

  1. Direct determination of Cu, Mn, Pb, and Zn in beer by thermospray flame furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Nascentes, Clésia C.; Kamogawa, Marcos Y.; Fernandes, Kelly G.; Arruda, Marco A. Z.; Nogueira, Ana Rita A.; Nóbrega, Joaquim A.

    2005-06-01

    In this work, thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) was employed for Cu, Mn, Pb, and Zn determination in beer without any sample digestion. The system was optimized and calibration was based on the analyte addition technique. A sample volume of 300 μl was introduced into the hot Ni tube at a flow-rate of 0.4 ml min -1 using 0.14 mol l -1 nitric acid solution or air as carrier. Different Brazilian beers were directly analyzed after ultrasonic degasification. Results were compared with those obtained by graphite furnace atomic absorption spectrometry (GFAAS). The detection limits obtained for Cu, Mn, Pb, and Zn in aqueous solution were 2.2, 18, 1.6, and 0.9 μg l -1, respectively. The relative standard deviations varied from 2.7% to 7.3% ( n=8) for solutions containing the analytes in the 25-50 μg l -1 range. The concentration ranges obtained for analytes in beer samples were: Cu: 38.0-155 μg l -1; Mn: 110-348 μg l -1, Pb: 13.0-32.9 μg l -1, and Zn: 52.7-226 μg l -1. Results obtained by TS-FF-AAS and GFAAS were in agreement at a 95% confidence level. The proposed method is fast and simple, since sample digestion is not required and sensitivity can be improved without using expensive devices. The TS-FF-AAS presented suitable sensitivity for determination of Cu, Mn, Pb, and Zn in the quality control of a brewery.

  2. Probing local structure of pyrochlore lead zinc niobate with synchrotron x-ray absorption spectroscopy technique

    NASA Astrophysics Data System (ADS)

    Kanchiang, Kanokwan; Pramchu, Sittichain; Yimnirun, Rattikorn; Pakawanit, Phakkhananan; Ananta, Supon; Laosiritaworn, Yongyut

    2013-08-01

    Local structure of lead zinc niobate (PZN) ceramic, synthesized via B-site oxide precursor route in atmospheric pressure, was investigated using synchrotron x-ray absorption spectroscopy (XAS) technique. The x-ray absorption near-edge structure (XANES) simulation was first carried out. The XANES simulation results indicate that the PZN ceramic is in pyrochlore phase having Zn2+ substituted on Nb5+ site. Afterwards, the extended x-ray absorption fine structure (EXAFS) analysis was performed to extract the bond length information between Zn2+ and its neighboring atoms. From the EXAFS fitting, the bond length between Zn2+ and Pb2+ in the pyrochlore phase was found to be longer than the previously reported bond length in the perovskite phase. Further, with the radial distribution information of Zn2+'s neighboring atoms, the formation energies along the precursor-to-pyrochlore and precursor-to-perovskite reaction paths were calculated using the density functional theory (DFT). The calculated results show that the formation energy of the perovskite phase is noticeably higher than that of the pyrochlore phase, which is influenced by the presence of energetic Pb2+ lone pair, as the perovskite phase has shorter Zn2+ to Pb2+ bonding. This therefore suggests the steric hindrance of Pb2+ lone pair and the mutual interactions between Pb2+ lone pair and Zn2+ are main causes of the instability of lead zinc niobate in the perovskite structure and confirm the efficacy of XAS and DFT analysis in revealing local structural details of complex pyrochlore materials.

  3. X-ray Absorption Spectroscopy Characterization of Electrochemical Processes in Renewable Energy Storage and Conversion Devices

    SciTech Connect

    Farmand, Maryam

    2013-05-19

    The development of better energy conversion and storage devices, such as fuel cells and batteries, is crucial for reduction of our global carbon footprint and improving the quality of the air we breathe. However, both of these technologies face important challenges. The development of lower cost and better electrode materials, which are more durable and allow more control over the electrochemical reactions occurring at the electrode/electrolyte interface, is perhaps most important for meeting these challenges. Hence, full characterization of the electrochemical processes that occur at the electrodes is vital for intelligent design of more energy efficient electrodes. X-ray absorption spectroscopy (XAS) is a short-range order, element specific technique that can be utilized to probe the processes occurring at operating electrode surfaces, as well for studying the amorphous materials and nano-particles making up the electrodes. It has been increasingly used in recent years to study fuel cell catalysts through application of the and #916; and mgr; XANES technique, in combination with the more traditional X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) techniques. The and #916; and mgr; XANES data analysis technique, previously developed and applied to heterogeneous catalysts and fuel cell electrocatalysts by the GWU group, was extended in this work to provide for the first time space resolved adsorbate coverages on both electrodes of a direct methanol fuel cell. Even more importantly, the and #916; and mgr; technique was applied for the first time to battery relevant materials, where bulk properties such as the oxidation state and local geometry of a cathode are followed.

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

    SciTech Connect

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

    2007-11-27

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

  5. Electronic transitions and fermi edge singularity in polar heterostructures studied by absorption and emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Pandey, S.; Cavalcoli, D.; Minj, A.; Fraboni, B.; Cavallini, A.; Gamarra, P.; Poisson, M. A.

    2012-12-01

    Optically induced electronic transitions in nitride based polar heterostructures have been investigated by absorption and emission spectroscopy. Surface photovoltage (SPV), photocurrent (PC), and photo luminescence spectroscopy have been applied to high quality InAlN/AlN/GaN structures to study the optical properties of two dimensional electron gas. Energy levels within the two dimensional electron gas (2DEG) well at the interface between the GaN and AlN have been directly observed by SPV and PC. Moreover, a strong enhancement of the photoluminescence intensity due to holes recombining with electrons at the Fermi Energy, known as fermi energy singularity, has been observed. These analyses have been carried out on InAlN/AlN/GaN heterojunctions with the InAlN barrier layer having different In content, a parameter which affects the energy levels within the 2DEG well as well as the optical signal intensity. The measured energy values are in a very good agreement with the ones obtained by Schrödinger-Poisson simulations.

  6. Characterising legacy spent nuclear fuel pond materials using microfocus X-ray absorption spectroscopy.

    PubMed

    Bower, W R; Morris, K; Mosselmans, J F W; Thompson, O R; Banford, A W; Law, K; Pattrick, R A D

    2016-11-05

    Analysis of a radioactive, coated concrete core from the decommissioned, spent nuclear fuel cooling pond at the Hunterston-A nuclear site (UK) has provided a unique opportunity to study radionuclides within a real-world system. The core, obtained from a dividing wall and sampled at the fill level of the pond, exhibited radioactivity (dominantly (137)Cs and (90)Sr) heterogeneously distributed across both painted faces. Chemical analysis of the core was undertaken using microfocus spectroscopy at Diamond Light Source, UK. Mapping of Sr across the surface coatings using microfocus X-ray fluorescence (μXRF) combined with X-ray absorption spectroscopy showed that Sr was bound to TiO2 particles in the paint layers, suggesting an association between TiO2 and radiostrontium. Stable Sr and Cs sorption experiments using concrete coupons were also undertaken to assess their interactions with the bulk concrete in case of a breach in the coating layers. μXRF and scanning electron microscopy showed that Sr was immobilized by the cement phases, whilst at the elevated experimental concentrations, Cs was associated with clay minerals in the aggregates. This study provides a crucial insight into poorly understood infrastructural contamination in complex systems and is directly applicable to the UK's nuclear decommissioning efforts.

  7. Towards a standard for the dynamic measurement of pressure based on laser absorption spectroscopy

    PubMed Central

    Douglass, K O; Olson, D A

    2016-01-01

    We describe an approach for creating a standard for the dynamic measurement of pressure based on the measurement of fundamental quantum properties of molecular systems. From the linewidth and intensities of ro-vibrational transitions we plan on making an accurate determination of pressure and temperature. The goal is to achieve an absolute uncertainty for time-varying pressure of 5 % with a measurement rate of 100 kHz, which will in the future serve as a method for the traceable calibration of pressure sensors used in transient processes. To illustrate this concept we have used wavelength modulation spectroscopy (WMS), due to inherent advantages over direct absorption spectroscopy, to perform rapid measurements of carbon dioxide in order to determine the pressure. The system records the full lineshape profile of a single ro-vibrational transition of CO2 at a repetition rate of 4 kHz and with a systematic measurement uncertainty of 12 % for the linewidth measurement. A series of pressures were measured at a rate of 400 Hz (10 averages) and from these measurements the linewidth was determined with a relative uncertainty of about 0.5 % on average. The pressures measured using WMS have an average difference of 0.6 % from the absolute pressure measured with a capacitance diaphragm sensor. PMID:27881884

  8. Hemodynamic measurements in rat brain combining diffuse near-infrared absorption and correlation spectroscopies

    NASA Astrophysics Data System (ADS)

    Yu, Guoqiang; Durduran, Turgut; Furuya, Daisuke; Greenberg, Joel H.; Yodh, Arjun G.

    2002-09-01

    Measurement of concentration, oxygenation, and flow characteristics of blood cells can reveal information about tissue metabolism and functional heterogeneity. An instrument has been built that combines two near-infrared diffuse optical techniques to simultaneously monitor blood flow, blood volume and blood oxygen saturation. Diffuse correlation spectroscopy (DCS) monitors blood flow by measuring the optical phase shifts caused by moving blood cells, while diffuse photon density wave (DPDW) spectroscopy measured tissue absorption and scattering. The modularized design of the instrument provides the instrument great flexibility for trading off the temporal, spectral and spatial resolution by selecting the number of source-detector pairs and wavelengths. The frame acquisition rate of the current instrument is 0.2 Hz with 3l (wavelengths) x 15s (source positions) x 4d (detectors) for DPDW measurement in the frequency domain, and 1λ x 3s; x 9d for DCS. Higher frame acquisition rate could be achieved by reducing the spatial resolution, for example, 2 Hz with 3λ x 1s x 4d for DPDW and 1l x 1s x 9d for DCS. The unique non-contact probe mounted on the back of a camera allows non-contact measurement that avoids potentially altering blood flow. We used this instrument to monitor in vivo the hemodynamic responses in rat brain during KCl induced cortical spreading depression (CSD).

  9. Resonant photoemission and X-ray absorption spectroscopies of lithiated magnetite thin film

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Takashi; Kawamura, Kinya; Namiki, Wataru; Furuichi, Shoto; Takayanagi, Makoto; Minohara, Makoto; Kobayashi, Masaki; Horiba, Koji; Kumigashira, Hiroshi; Terabe, Kazuya; Higuchi, Tohru

    2017-04-01

    Resonant photoemission spectroscopy (RPES) and X-ray absorption spectroscopy (XAS) were used to investigate the effect of lithiation on the electronic structure of Fe3O4 thin film relevant to the operation mechanism of nanoionic devices to enable magnetic property tuning. Comparison of the Fe 2p XAS spectrum for lithiated Fe3O4 (Li-Fe3O4) with that for pristine Fe3O4 clearly demonstrated that the number of Fe2+ ions at octahedral B sites is increased by lithiation. The valence band RPES spectra of Li-Fe3O4 further showed that lithiation increases the density of states near the Fermi level originating Fe2+ ions at octahedral B sites. These findings agree well with the observed decrease in the saturation magnetization in the magnetization-magnetic field (M-H) loop of Li-Fe3O4 thin film, indicating that minority spins (down spins) increase (i.e., total spins decrease) due to lithiation. The variation in the number of Fe2+ ions at B sites is suggested to be an underlying operating mechanism of a nanoionics-based magnetic property tuning device.

  10. Examination of arsenic speciation in sulfidic solutions using X-ray absorption spectroscopy.

    PubMed

    Beak, Douglas G; Wilkin, Richard T; Ford, Robert G; Kelly, Shelly D

    2008-03-01

    Both thioarsenites and thioarsenates have been demonstrated to exist in sulfidic waters, yet there is uncertainty regarding the geochemical conditions that govern the formation of these arsenic species. The purpose of this research was to use advanced spectroscopy techniques, speciation modeling, and chromatography to elucidate the chemical speciation of arsenic in sulfidic solutions initially containing arsenite and sulfide. Results of X-ray absorption spectroscopy (XAS) show that experimental solutions contained mixtures of arsenite and thioarsenites with increasing substitution of sulfur for oxygen on arsenic as the sulfide concentration increased. Experimental samples showed no evidence of polymeric arsenic species, or transformation of thioarsenites to thioarsenates. The arsenic speciation measured using XAS was similar to predictions obtained from a thermodynamic model for arsenic speciation, excluding thioarsenate species in sulfidic systems. Our data cast some doubt on the application of chromatographic methods for determining thioarsenates and thioarsenites (or mixtures) in natural waters in cases where the arsenic oxidation state cannot be independently verified. The same chromatographic peak positions proposed for thioarsenates can be explained bythioarsenite species. Furthermore, sample dilution was shown to change the species distribution and care should be taken to avoid sample dilution prior to chromatographic analysis.

  11. Examination of arsenic speciation in sulfidic solutions using x-ray absorption spectroscopy.

    SciTech Connect

    Beak, D. G.; Wilkin, R. T.; Ford, R. G.; Kelly, S. D.; Biosciences Division; EPA

    2008-03-01

    Both thioarsenites and thioarsenates have been demonstrated to exist in sulfidic waters, yet there is uncertainty regarding the geochemical conditions that govern the formation of these arsenic species. The purpose of this research was to use advanced spectroscopy techniques, speciation modeling, and chromatography to elucidate the chemical speciation of arsenic in sulfidic solutions initially containing arsenite and sulfide. Results of X-ray absorption spectroscopy (XAS) show that experimental solutions contained mixtures of arsenite and thioarsenites with increasing substitution of sulfur for oxygen on arsenic as the sulfide concentration increased. Experimental samples showed no evidence of polymeric arsenic species, or transformation of thioarsenites to thioarsenates. The arsenic speciation measured using XAS was similar to predictions obtained from a thermodynamic model for arsenic speciation, excluding thioarsenate species in sulfidic systems. Our data cast some doubt on the application of chromatographic methods for determining thioarsenates and thioarsenites (or mixtures) in natural waters in cases where the arsenic oxidation state cannot be independently verified. The same chromatographic peak positions proposed for thioarsenates can be explained by thioarsenite species. Furthermore, sample dilution was shown to change the species distribution and care should be taken to avoid sample dilution prior to chromatographic analysis.

  12. Towards a standard for the dynamic measurement of pressure based on laser absorption spectroscopy.

    PubMed

    Douglass, K O; Olson, D A

    2016-06-01

    We describe an approach for creating a standard for the dynamic measurement of pressure based on the measurement of fundamental quantum properties of molecular systems. From the linewidth and intensities of ro-vibrational transitions we plan on making an accurate determination of pressure and temperature. The goal is to achieve an absolute uncertainty for time-varying pressure of 5 % with a measurement rate of 100 kHz, which will in the future serve as a method for the traceable calibration of pressure sensors used in transient processes. To illustrate this concept we have used wavelength modulation spectroscopy (WMS), due to inherent advantages over direct absorption spectroscopy, to perform rapid measurements of carbon dioxide in order to determine the pressure. The system records the full lineshape profile of a single ro-vibrational transition of CO2 at a repetition rate of 4 kHz and with a systematic measurement uncertainty of 12 % for the linewidth measurement. A series of pressures were measured at a rate of 400 Hz (10 averages) and from these measurements the linewidth was determined with a relative uncertainty of about 0.5 % on average. The pressures measured using WMS have an average difference of 0.6 % from the absolute pressure measured with a capacitance diaphragm sensor.

  13. Multipitched Diffraction Gratings for Surface Plasmon Resonance-Enhanced Infrared Reflection Absorption Spectroscopy.

    PubMed

    Petefish, Joseph W; Hillier, Andrew C

    2015-11-03

    We demonstrate the application of metal-coated diffraction gratings possessing multiple simultaneous pitch values for surface enhanced infrared absorption (SEIRA) spectroscopy. SEIRA increases the magnitude of vibrational signals in infrared measurements by one of several mechanisms, most frequently involving the enhanced electric field associated with surface plasmon resonance (SPR). While the majority of SEIRA applications to date have employed nanoparticle-based plasmonic systems, recent advances have shown how various metals and structures lead to similar signal enhancement. Recently, diffraction grating couplers have been demonstrated as a highly tunable platform for SEIRA. Indeed, gratings are an experimentally advantageous platform due to the inherently tunable nature of surface plasmon excitation at these surfaces since both the grating pitch and incident angle can be used to modify the spectral location of the plasmon resonance. In this work, we use laser interference lithography (LIL) to fabricate gratings possessing multiple pitch values by subjecting photoresist-coated glass slides to repetitive exposures at varying orientations. After metal coating, these gratings produced multiple, simultaneous plasmon peaks associated with the multipitched surface, as identified by infrared reflectance measurements. These plasmon peaks could then be coupled to vibrational modes in thin films to provide localized enhancement of infrared signals. We demonstrate the flexibility and tunability of this platform for signal enhancement. It is anticipated that, with further refinement, this approach might be used as a general platform for broadband enhancement of infrared spectroscopy.

  14. Optical absorption and emission spectroscopy studies of ammonia-containing plasmas

    NASA Astrophysics Data System (ADS)

    Kang, S. J.; Donnelly, V. M.

    2007-05-01

    The chemistry of NH3/Ar/He plasmas was investigated, using a combination of ultraviolet (UV) optical absorption spectroscopy (OAS) and optical emission spectroscopy (OES). Absolute NH3 number densities in 1 Torr plasmas were measured by OAS as a function of inductively coupled plasma power and substrate heater temperature (Th). OES and actinometry were used to determine semi-quantitative H-atom density. A 'self-actinometry' method was introduced to measure the absolute number density of N2 that formed following the dissociation of NH3 and secondary reactions. In this approach, small amounts of N2 are added to the NH3-containing plasma, leading to an increase in the N2(C 3 Πu → B 3 Πg) emission intensity. This provides an accurate calibration factor for converting relative N2 emission intensities into absolute number densities. The number densities of NH3 were found to decrease with increasing power and Th, reaching >90% dissociation at 400 W and 900 K. N2 densities increased with power and Th. The majority of dissociated NH3 was converted to N2 (i.e. the total nitrogen content was conserved in the sum of these two species). The major hydrogen-containing species appeared to be H2; however, a substantial amount of H-atoms (comparable to H2) was present at the highest powers.

  15. In-source laser spectroscopy of {sup 75,77,78}Cu: Direct evidence for a change in the quasiparticle energy sequence in {sup 75,77}Cu and an absence of longer-lived isomers in {sup 78}Cu

    SciTech Connect

    Koester, U.; Materna, T.; Stone, N. J.; Stone, J. Rikovska; Flanagan, K. T.; Fedosseev, V. N.; Marsh, B. A.; Kratz, K. L.; Mathieu, L.; Serot, O.; Seliverstov, M. D.; Sjoedin, A. M.

    2011-09-15

    This paper describes measurements on the isotopes {sup 75,77,78}Cu by the technique of in-source laser spectroscopy, at the ISOLDE facility, CERN. The role of this technique is briefly discussed in the context of this and other, higher resolution, methods applied to copper isotopes in the range {sup 57-78}Cu. The data, analyzed in comparison with previous results on the lighter isotopes {sup 59,63}Cu, establish the ground-state nuclear spin of {sup 75,77}Cu as 5/2 and yield their magnetic dipole moments as +1.01(5){mu}{sub N} and +1.61(5){mu}{sub N}, respectively. The results on {sup 78}Cu show no evidence for long-lived isomerism at this mass number and are consistent with a spin in the range 3-6 and moment of 0.0(4) {mu}{sub N}.

  16. Studies of solvent effects on reaction dynamics using ultrafast transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Harris, Don Ahmasi

    Ultrafast transient absorption spectroscopy was used to investigate the solvent dependent reaction dynamics of two prototypical chemical systems: (1) The ring-opening reaction of 1,3-cyclohexadiene, the isolated chromophore in Provitamin D, and (2) The photolysis of various Vitamin B12 cofactors. We investigated the influence of solvent polarity on the ground state conformational relaxation of 1,3,5-cis hexatriene subsequent to the ring opening of 1,3-cyclohexadiene in methanol and 1-propanol solvents. Comparisons to the conformational relaxation in alkane solvents studied earlier demonstrated a surprising influence of solvent polarity on single bond isomerization. Temperature dependent transient absorption measurements were performed on 1,3,5-cis hexatriene in cyclohexane and 1-propanol to determine the effect of solvent polarity on the activation energy barrier for ground state single bond isomerization. These measurements conclude that the polar solvent lowers the energy barrier for single bond isomerization allowing conformational relaxation to proceed faster in alcohol solvents compared to alkane solvents. With no perceived polar transition state for single bond isomerization, this result disagrees with the conventional view of solvation and differentiates the single bond isomerization dynamics of polyenes from alkanes. Transient absorption spectroscopy was also utilized to study the solvent effects in the photolysis of various B12 cofactors in different environments. We investigated the solvent dependent photolysis of adenosylcobalamin, methylcobalamin, and cyanocobalamin in water and ethylene glycol as a function of solvent temperature. In comparing the radical cage escape of adenosylcobalamin and cyanocobalamin, we determined a larger than expected hydrodynamic radii for the diffusing radicals in water compared to ethylene glycol, thus making necessary a revised perspective of solvent interaction with the diffusing radical. In addition, we investigated the

  17. Atomic layer deposition of ultrathin Cu{sub 2}O and subsequent reduction to Cu studied by in situ x-ray photoelectron spectroscopy

    SciTech Connect

    Dhakal, Dileep; Assim, Khaybar; Lang, Heinrich; Bruener, Philipp; Grehl, Thomas; Georgi, Colin; Waechtler, Thomas; Ecke, Ramona; Schulz, Stefan E. Gessner, Thomas

    2016-01-15

    The growth of ultrathin (<5 nm) Ru-doped Cu{sub 2}O films deposited on SiO{sub 2} by atomic layer deposition (ALD) and Cu films by subsequent reduction of the Cu{sub 2}O using HCO{sub 2}H or CO is reported. Ru-doped Cu{sub 2}O has been deposited by a mixture of 16: 99 mol. % of [({sup n}Bu{sub 3}P){sub 2}Cu(acac)] as Cu precursor and 17: 1 mol. % of [Ru(η{sup 5}-C{sub 7}H{sub 11})(η{sup 5}-C{sub 5}H{sub 4}SiMe{sub 3})] as Ru precursor. The catalytic amount of Ru precursor was to support low temperature reduction of Cu{sub 2}O to metallic Cu by formic acid (HCO{sub 2}H) on arbitrary substrate. In situ x-ray photoelectron spectroscopy investigations of the Cu{sub 2}O ALD film indicated nearly 1 at. % of carbon contamination and a phosphorous contamination below the detection limit after sputter cleaning. Systematic investigations of the reduction of Ru-doped Cu{sub 2}O to metallic Cu by HCO{sub 2}H or CO as reducing agents are described. Following the ALD of 3.0 nm Cu{sub 2}O, the ultrathin films are reduced between 100 and 160 °C. The use of HCO{sub 2}H at 110 °C enabled the reduction of around 90% Cu{sub 2}O. HCO{sub 2}H is found to be very effective in the removal of oxygen from Ru-doped Cu{sub 2}O films with 2.5–4.7 nm thickness. In contrast, CO was effective for the removal of oxygen from the Cu{sub 2}O films only below 3.0 nm at 145 °C. Root mean square surface roughness of 0.4 ± 0.1 nm was observed from atomic force microscopy (AFM) investigations after the ALD of Cu{sub 2}O, followed by the subsequent reduction of 3.0 nm Cu{sub 2}O using either HCO{sub 2}H at 110 °C or CO at 145 °C on SiO{sub 2}. Furthermore, ex situ low energy ion scattering and AFM investigations confirmed that the Cu{sub 2}O film after ALD and Cu films after subsequent reduction was continuous on the SiO{sub 2} substrate.

  18. Time-resolved detection of temperature, concentration, and pressure in a shock tube by intracavity absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Fjodorow, Peter; Fikri, Mustapha; Schulz, Christof; Hellmig, Ortwin; Baev, Valery M.

    2016-06-01

    In this paper, we demonstrate the first application of intracavity absorption spectroscopy (ICAS) for monitoring species concentration, total pressure, and temperature in shock-tube experiments. ICAS with a broadband Er3+-doped fiber laser is applied to time-resolved measurements of absorption spectra of shock-heated C2H2. The measurements are performed in a spectral range between 6512 and 6542 cm-1, including many absorption lines of C2H2, with a time resolution of 100 µs and an effective absorption path length of 15 m. Up to 18-times increase of the total pressure and a temperature rise of up to 1200 K have been monitored. Due to the ability of simultaneously recording many absorption lines in a broad spectral range, the presented technique can also be applied to multi-component analysis of transient single-shot processes in reactive gas mixtures in shock tubes, pulse detonation engines, or explosions.

  19. Use of L-edge X-ray absorption spectroscopy to characterize multiple valence states of 3 d transition metals; a new probe for mineralogical and geochemical research

    NASA Astrophysics Data System (ADS)

    Cressey, G.; Henderson, C. M. B.; van der Laan, G.

    1993-07-01

    2 p ( L 2,3) X-ray absorption spectra are presented for a range of minerals to demonstrate the usefulness of L-edge spectroscopy as a symmetry- and valenceselective probe. 2 p XAS provides a sensitive fingerprint of the electronic states of 3 d transition metals and can be applied to phases containing mixtures of such elements. Calculated spectra for 3 d n → 2 p 5 3 d n+1 transitions provide a basis for the interpretation of the measured spectra. Thus, in principle, multiple valence states of a particular 3 d metal can be precisely characterized from a single L-edge spectrum. Examples of vanadium L-edge spectra are presented for a range of minerals; these complex spectra hold information concerning the presence of vanadium in multiple valence states. The Cu L-edge spectrum of sulvanite (Cu3 VS4) indicates the presence of both Cu+ and Cu2+; the V L-edge spectrum of the same sample shows that both V2+ and V5+ are present. Spectral simulations representing mixtures of Fe d 5 and Fe d 6 states are used to quantify Fe3+/ ∑Fe in a spinel, a glass, and an amphibole, all of which contain Fe as a major component. To illustrate the sensitivity of 2 p XAS in a dilute system, the Fe L-edge spectrum of amethyst ( α-SiO2: Fe) has been recorded; this spectrum shows that ˜68% of the Fe in amethyst is Fe2+, and ˜32% is Fe3+. Although previous studies on amethyst using other spectroscopic methods cite evidence for Fe4+, there is no indication in the L-edge spectrum for Fe4+ in amethyst. Comparison of theoretical and experimental spectra not only allows the valence states of 3 d ions to be recognised, but also provides site-symmetry information and crystal field parameters for each ion site.

  20. Sub-bandgap absorption in polymer-fullerene solar cells studied by temperature-dependent external quantum efficiency and absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Presselt, Martin; Herrmann, Felix; Shokhovets, Sviatoslav; Hoppe, Harald; Runge, Erich; Gobsch, Gerhard

    2012-07-01

    We study the sub-bandgap (SBG) absorption in solar cells made of poly(3-hexylthiophene-2,5-diyl) and [6,6]-phenylC61-butyric-acid-methyl-ester by photothermal deflection absorption spectroscopy and measurement of temperature-dependent external-quantum-efficiency (EQE) spectra. Several models for SBG absorption are critically reviewed in view of the EQE results. The latter suggest polaron-related transitions as origin of the Gaussian SBG peak near 1.6 eV. Intermolecular charge transfer (CT) excitations as an explanation cannot completely be ruled out. However, the assumption of CT excitons with large binding energies is difficult to reconcile with the rapid loss of weight of the Gaussian SBG-peak seen in EQE above room temperature.