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  • 1
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    The character of doped holes in La1.9Sr0.1CuO4: polarization-dependent x-ray fluorescence study at the O K edge (2000)
    Institute of Physics
    Details
    Publication Date: 2000-06-27
    Print ISSN: 0953-8984
    Electronic ISSN: 1361-648X
    Topics: Physics
    Published by Institute of Physics
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  • 2
    Electronic Resource
    Electronic Resource
    A photoion–photoelectron coincidence study of Arn (n=2–4) (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2995-3003 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photoion–photoelectron coincidence (PIPECO) spectra for Ar+n (n=2–4) in the wavelength region of 750–875 A(ring) have been measured at different nozzle stagnation pressures. The ionization energies (IE) for the ground Ar+2[I(1/2)u] and Ar+3[I(1/2)u] states are determined to be 14.518±0.017 eV (854±1 A(ring)) and 14.350±0.033 eV (864±2 A(ring)), in agreement with the findings of previous photoionization experiments. The IE for Ar+2[II(1/2)u] is found to be (approximately-less-than)15.83 eV (783 A(ring)). The observation of the Ar+2[II(1/2)u] PIPECO band supports the interpretation that Ar+2[II(1/2)u] is metastable with a lifetime longer than 47 μs, a value in accord with the calculated radiative lifetime of 90.9 μs for the II(1/2)u →I(1/2)g transition. The PIPECO spectrum for Ar+2 is dominated by autoionization structure similar to that resolved in the photoionization efficiency spectrum for Ar+2, indicating that a significant fraction of electrons produced by these autoionizing states are slow electrons with near-zero kinetic energies. Evidence is found that metastable Ar+3 and Ar+4 ions formed by photoionization of Ar3 and Ar4 at energies above the Ar+2[I(1/2)u]+Ar(1S0) and Ar+3[I(1/2)u]+Ar(1S0) dissociation limits may live longer than 58 and 66 μs, respectively. We suggest that the formation of Ar+3 in metastable electronic states may be responsible for the long dissociation lifetimes of Ar+3 observed in this experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455901
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  • 3
    Electronic Resource
    Electronic Resource
    A photoion–photoelectron coincidence study of (CO)2 and (CO)3 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 6026-6033 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photoion–photoelectron coincidence (PIPECO) spectra for (CO)+2 in the wavelength region of 620–990 A(ring) have been obtained at different nozzle stagnation pressures (P0). The ionization energy for (CO)2 to CO+(X˜)⋅CO is determined to be (approximately-less-than)12.73±0.05 eV (974±4 A(ring)), indicating that CO+(X˜)⋅CO is bound by more than 1.29 eV. The PIPECO measurements also provide evidence that CO+(A˜,B˜)⋅CO are bound with dissociation energies 〉0.3 eV. At P0≤200 Torr and a nozzle temperature (T) of 120 K, nozzle expansion conditions which minimize the formation of (CO)n (n≥3), the intensities for the CO+(A˜,B˜)⋅CO PIPECO bands are found to be negligibly small compared to that for the CO+(X˜)⋅CO PIPECO band. This observation supports the conclusion that the excited CO+(A˜,B˜)⋅CO ions are dissociative, with dissociation lifetimes〈42 μs. This conclusion is contrary to that of the preliminary study which is based on the PIPECO spectrum for (CO)+2 measured at P0=350 Torr and T=120 K. Assuming that the radiative lifetimes of CO+(A˜ or B˜) and CO+(A˜ or B˜)⋅CO are identical, we estimate that the dissociation lifetimes for CO+(A˜)⋅CO and CO+(B˜)⋅CO are (approximately-less-than)4 μs and (approximately-less-than)50 ns, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456368
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  • 4
    Electronic Resource
    Electronic Resource
    End station for polarization and excitation energy selective soft x-ray fluorescence spectroscopy : Proceedings of the 5th international conference on synchrotron radiation instrumentation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1561-1563 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An end station for soft x-ray fluorescence spectroscopy has been constructed, which includes an experiment chamber, rotatable 90° under ultrahigh vacuum conditions around the incoming synchrotron radiation beam, which is provided with a high-resolution soft x-ray spectrometer. A manipulator allowing three axes of rotation, three directions of translation, as well as LN2 cooling and resistive heating is mounted to the chamber and serves as the sample holder. Samples can be transferred under vacuum between the experiment chamber and two other chambers, one for sample preparation and another for introducing new samples and for sample storage. The end station has been used at two different synchrotron radiation laboratories (beamline BW3) at HASYLAB in Hamburg and at ALS (beamline 7.0) in Berkeley. Polarization-dependent and angular resolved, selectively excited x-ray emission studies have been made on ordered as well as nonordered systems, e.g., high-Tc superconducting systems, diamond, fullerenes, and molecular ices. The experimental system will be presented along with some recent scientific results. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145908
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  • 5
    Electronic Resource
    Electronic Resource
    First results from the SpectroMicroscopy Beamline at the Advanced Light Source : Proceedings of the 5th international conference on synchrotron radiation instrumentation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1342-1345 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The SpectroMicroscopy Facility at the Advanced Light Source is based on a high brightness, high-resolution beamline, and includes a collection of projects designed to exploit the unique characteristics of the soft x-ray beam. The beamline itself is comprised of a 5-m long, 5-cm-period undulator, a spherical-grating monochromator with water-cooled gratings. Adaptive optics refocus the monochromatic beam to two "microfocus'' experimental stations with spot sizes less than 50 μm diameter and a third "nanofocus'' station uses a zone-plate lens to further demagnify the microfocus spot. Experimental stations include an "ultraESCA'' spectrometer for small-area spectroscopy and photoelectron diffraction, a scanning transmission x-ray microscope, and photoelectron microscopes. Commissioning experiments of microscopic actinide photoemission, surface-core-level photoelectron diffraction, and high-resolution soft x-ray fluorescence demonstrate dramatic improvements in sensitivity due to the high brightness and small focus of the beamline. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145969
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  • 6
    Electronic Resource
    Electronic Resource
    High-pressure granulites in the Sanggan area, North China craton: metamorphic evolution, P–T paths and geotectonic significance (2002)
    Oxford, UK : Blackwell Science Inc
    Journal of metamorphic geology 20 (2002), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: High-pressure basic granulites are widely distributed as enclaves and sheet-like blocks in the Huaian TTG gneiss terrane in the Sanggan area of the Central Zone of the North China craton. Four stages of the metamorphic history have been recognised in mineral assemblages based on inclusion, exsolution and reaction textures integrated with garnet zonation patterns as revealed by compositional maps and compositional profiles. The P–T conditions for each metamorphic stage were obtained using thermodynamically and experimentally calibrated geothermobarometers. The low-Ca core of growth-zoned garnet, along with inclusion minerals, defines a prograde assemblage (M1) of garnet + clinopyroxene + plagioclase + quartz, yielding 700 °C and 10 kbar. The peak of metamorphism at about 750–870 °C and 11–14.5 kbar (M2) is defined by high-Ca domains in garnet interiors and inclusion minerals of clinopyroxene, plagioclase and quartz. Kelyphites or coronas of orthopyroxene + plagioclase ± magnetite around garnet porphyroblasts indicate garnet breakdown reactions (M3) at conditions around 770–830 °C and 8.5–10.5 kbar. Garnet exsolution lamellae in clinopyroxene and kelyphites of amphibole + plagioclase around garnet formed during the cooling process at about 500–650 °C and 5.5–8 kbar (M4). These results help define a sequential P–T path containing prograde, near-isothermal decompression (ITD) and near-isobaric cooling (IBC) stages.The clockwise hybrid ITD and IBC P–T paths of the HP granulites in the Sanggan area imply a model of thickening followed by extension in a collisional environment. Furthermore, the relatively high-pressures (6–14.5 kbar) of the four metamorphic stages and the geometry of the P–T paths suggest that the HP granulites, together with their host Huaian TTG gneisses, represent the lower plate in a crust thickened during collision. The corresponding upper-plate might be the tectonically overlying Khondalite series, which was subjected to medium- to low-pressure (MP/LP: 7–4 kbar) granulite facies metamorphism with a clockwise P–T path including an ITD segment. Both the HP and the MP/LP granulite facies events occurred contemporaneously at c. 1.90–1.85 Ga in a collisional environment created by the assembly process of the North China craton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1525-1314.2002.00401.x
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  • 7
    Electronic Resource
    Electronic Resource
    A photoion–photoelectron coincidence study of (CO)2 (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4098-4099 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photoion–photoelectron coincidence (PIPECO) spectrum for (CO)+2 has been measured in the wavelength region of ∼600–1 000 A(ring). The lower limits for the bond dissociation energies of CO+ (X˜)⋅CO, CO+ (A˜)⋅CO, and CO+ (B˜)⋅CO are determined to be 29.8, 17, and 16 kcal/mol, respectively. Evidence supporting the existence of long-lived (CO)+2 states with dissociation lifetimes 〉40 μs at energies above the CO+ (X˜,v=0)+CO asymptote is found. The dissociative lifetimes of CO+ (A˜)⋅CO and CO+(B˜)⋅CO are estimated to be longer than 4 μs and 50 ns, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453814
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  • 8
    Electronic Resource
    Electronic Resource
    The electronic structure of polyaniline and doped phases studied by soft x-ray absorption and emission spectroscopies (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 4756-4761 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic structure of the conjugated polymer, polyaniline, has been studied by resonant and nonresonant soft x-ray emission spectroscopy using synchrotron radiation for the excitation. The measurements were made on polyaniline and a few doped (protonated) phases for both the carbon and nitrogen contents. The resonant x-ray emission spectra show depletion of the π electron bands due to the selective excitation which enhances the effect of symmetry selection rules. The valence band structures in the x-ray emission spectra attributed to the π bands show unambiguous changes of the electronic structure upon protonation. By comparing to x-ray absorption measurements, the chemical bonding and electronic configuration is characterized. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479238
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  • 9
    Electronic Resource
    Electronic Resource
    Resonant and nonresonant x-ray scattering spectra of some poly(phenylenevinylene)s (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 5990-5996 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic structure of some poly(phenylenevinylene)s have been investigated by resonant and nonresonant x-ray inelastic scattering spectroscopies. The nonresonant as well as all resonant spectra for each polymer demonstrate benzene-like features, indicating a local character of the x-ray emission in which the phenyl ring acts as a building block. Theoretical simulations of x-ray energies and intensities taking the repeat unit as a model molecule of the polymer agree with the experimental spectra fairly well. The edges of the occupied bands have been identified in the nonresonant spectra of each polymer. By subtracting the emission energy of the highest occupied molecular orbital in the nonresonant spectrum from the core excitation energy in the resonant spectrum an alternative way to determine the optical band gap is obtained. As for free benzene the outer π band in the polymer spectra show a depletion of the emission going from the nonresonant to the resonant x-ray emission spectra. It is demonstrated that this transition, which is strictly symmetry forbidden for free benzene, becomes effectively forbidden in the polymer case as a result of strong interference effects, and it is argued that this is the general case for resonant x-ray emission of conjugated polymers as far as the frozen orbital approximation holds. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476011
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  • 10
    Electronic Resource
    Electronic Resource
    Electronic structure of La"2"-"xSr"xCuO"4 studied by resonant soft x-ray fluorescence spectroscopy
    Amsterdam : Elsevier
    Journal of Physics and Chemistry of Solids 54 (1993), S. 1203-1206 
    Details
    ISSN: 0022-3697
    Keywords: High Tc Superconductor ; La"2"-"xSr"xCuO"4 ; Soft X-ray Fluorescence ; Tunable Monochromatized Synchrotron Radiation
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0022-3697(93)90167-P
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