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  • 1.
    Brena, Barbara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Palmgren, P
    Nilson, K
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Yu, Shun
    Hennies, F
    Agnarsson, B
    Onsten, A
    Månsson, M
    Göthelid, M
    InSb-TiOPc interfaces: Band alignment, ordering and structure dependent HOMO splitting2009In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 603, no 20, p. 3160-3169Article in journal (Refereed)
    Abstract [en]

    Thin films of titanyl phthalocyanine (TiOPc) have been adsorbed on InSb(1 1 1) (3 x 3) and InSb(1 0 0) c(8 x 2) surfaces and studied with respect to their electronic structure using photoemission (PES), density functional theory (DFT) and scanning tunneling microscopy (STM). The interface chemical interaction is weak in both cases; no adsorbate induced surface band bending is observed and the energy level alignment across the interface is determined by the original position of the substrate Fermi level and the charge neutrality level of the molecule. Room temperature adsorption results in disordered films on both surfaces. The behaviors after annealing are different; on InSb(1 0 0) well-ordered molecular chains form along and on top of the In-rows, whereas on (1 1 1) no long range order is observed. The disorder leads to intermolecular interactions between the titanyl group and neighboring benzene rings leading to a split of TiOPc HOMO (highest occupied molecular orbital) by as much as 0.8 eV. (C) 2009 Elsevier B.V. All rights reserved.

  • 2.
    Gråsjö, Johan
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Andersson, Egil
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Forsberg, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Aziz, Emad F.
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Johansson, Christian
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Nordgren, Joseph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Duda, Laurent
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Andersson, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Hennies, Franz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Hansson, Per
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Electronic structure of water molecules confined in a micelle lattice2009In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 113, no 24, p. 8201-8205Article in journal (Refereed)
    Abstract [en]

    Oxygen K absorption and emission spectra of water molecules confined in dodecyltrimethyl ammonium chloride micelle structures are presented. The local electronic structure of the water molecules is found to be dramatically different from the electronic structure of water molecules in the gas-phase as well as in liquid water. Hybridization with states of the ions in the surrounding ions is directly observed, and evidence for stabilization of the water molecules relative to molecules in bulk water is found.

  • 3.
    Gråsjö, Johan
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Andersson, Egil
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Forsberg, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Duda, Laurent
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Henke, Ev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Pokapanich, Wandared
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Andersson, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Pietsch, Annette
    Hennies, Franz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Jan-Erik, Rubensson
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Local Electronic Structure of Functional Groups in Glycine As Anion, Zwitterion, and Cation in Aqueous Solution2009In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 113, no 49, p. 16002-16006Article in journal (Refereed)
    Abstract [en]

    Nitrogen and oxygen K emission spectra of glycine in the form of  anions, zwitterions, and cations in aqueous solution are presented. It  is shown that protonation has a dramatic influence on the local   electronic structure and that the functional groups give a distinct  spectral fingerprint.

     

  • 4. Hennies, F
    et al.
    Bao, Z
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Travnikova, O
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Piancastelli, M. N.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Structure and Bonding of Ethylene Oxide on Si(100)2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 36, p. 16077-16082Article in journal (Refereed)
    Abstract [en]

    The bonding configuration and electronic structure of ethylene oxide adsorbed on Si(100)-(2 x 1) is investigated with fully polarization resolved X-ray absorption spectroscopy as well as with core level and valence band photoemission spectroscopy. Ethylene oxide is found to adsorb via a ring-opening reaction, where the molecule forms a five-membered ring together with the silicon surface dimer atoms inserting between a carbon and the oxygen atom. In the resulting geometry, the molecule is tilted out of the surface plane.

  • 5. Hennies, F
    et al.
    Bao, Z
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Travnikova, O
    Piancastelli, M. N
    The Bonding of Chemisorbed Ethylene Oxide on Si (100) SurfaceManuscript (Other academic)
  • 6. Hennies, F.
    et al.
    Polyutov, S.
    Minkov, I.
    Pietzsch, A.
    Nagasono, M.
    Agren, H.
    Triguero, L.
    Piancastelli, Maria Novella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics V.
    Wurth, W.
    Gel'mukhanov, F.
    Foehlisch, A.
    Dynamic interpretation of resonant x-ray Raman scattering: Ethylene and benzene2007In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 76, no 3, p. 032505-Article in journal (Refereed)
    Abstract [en]

    We present a dynamic interpretation of resonant x-ray Raman scattering where vibrationally selective excitation into molecular resonances has been employed in comparison with excitation into higher lying continuum states for condensed ethylene and benzene as molecular model systems. In order to describe the purely vibrational spectral loss features and coupled electronic and vibrational losses the one-step theory for resonant soft x-ray scattering is applied, taking multiple vibrational modes and vibronic coupling into account. The scattering profile is found to be strongly excitation energy dependent and to reflect the intermediate states dynamics of the scattering process. In particular, the purely vibrational loss features allow one to map the electronic ground state potential energy surface in light of the excited state dynamics. Our study of ethylene and benzene underlines the necessity of an explicit description of the coupled electronic and vibrational loss features for the assignment of spectral features observed in resonant x-ray Raman scattering at polyatomic systems, which can be done in both a time independent and a time dependent picture. The possibility to probe ground state vibrational properties opens a perspective to future applications of this photon-in-photon-out spectroscopy.

  • 7.
    Hennies, Franz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Pietzsch, Annette
    Berglund, Martin
    Föhlisch, Alexander
    Schmitt, Thorsten
    Strocov, Vladimir
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Andersson, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Resonant Inelastic Scattering Spectra of Free Molecules with Vibrational Resolution2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 104, no 19, p. 193002-Article in journal (Refereed)
    Abstract [en]

    Inelastic x-ray scattering spectra excited at the 1s(-1) pi* resonance of gas phase O-2 have been recorded with an overall energy resolution that allows for well-resolved vibrational progressions. The nuclear wave packet dynamics in the intermediate state is reflected in vibrational excitations of the electronic ground state, and by fine-tuning the excitation energy the dissociation dynamics in the predissociative B' (3) Pi(g) final state is controlled.

  • 8.
    Mårtensson, Nils
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Preobrajenski, A. B.
    Hennies, F.
    Bonding and dynamics of surface systems probed by soft X-rays2009In: The European Physical Journal - Special Topics, ISSN 1951-6355, Vol. 169, no 1, p. 133-140Article, review/survey (Refereed)
    Abstract [en]

    We review some aspects of the investigation of surface systems with soft X-rays. Examples are presented, showing how core level spectroscopies provide detailed information on the structure, bonding and chemistry of adsorbates and thin layers on surfaces. Core level spectroscopies employed at high brilliance synchrotron light sources allow furthermore access to electron dynamics in the attosecond domain, as we demonstrate for the core hole clock method.

  • 9.
    Nilson, Katharina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Palmgren, Pål
    Åhlund, John
    Schiessling, Joachim
    Göthelid, Emmanuelle
    Hennies, Franz
    Göthelid, Mats
    Mårtensson, Nils
    Puglia, Carla
    Characterization of Metal-free Phthalocyanine adsorbed on Al(110)Manuscript (Other academic)
  • 10.
    Nilson, Katharina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Åhlund, John
    Schiessling, Joachim
    Palmgren, Pål
    Brena, Barbara
    Göthelid, Emmanuelle
    Hennies, Franz
    Rudolf, Petra
    Göthelid, Mats
    Mårtensson, Nils
    Potassium doped H2Pc films: alkali induced electronic and geometrical modificationsManuscript (Other academic)
  • 11.
    Nilson, Katharina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Åhlund, John
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Shariati, Masumeh-Nina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Schiessling, Joachim
    Palmgren, Pål
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Göthelid, Emmanuelle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Hennies, Franz
    Huismans, Y
    Evangelista, F
    Rudolf, Petra
    Göthelid, Mats
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Potassium-intercalated H2Pc films: Alkali-induced electronic and geometrical modifications2012In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 137, no 4, p. 044708-Article in journal (Refereed)
    Abstract [en]

    X-ray spectroscopy studies of potassium intercalated metal-free phthalocyanine multilayers adsorbed on Al(110) have been undertaken. Photoelectron spectroscopy measurements show the presence of several charge states of the molecules upon K intercalation, due to a charge transfer from the alkali. In addition, the comparison of valence band photoemission spectra with the density functional theory calculations of the density of states of the H2Pc anion indicates a filling of the formerly lowest unoccupied molecular orbital by charge transfer from the alkali. This is further confirmed by x-ray absorption spectroscopy (XAS) studies, which show a decreased density of unoccupied states. XAS measurements in different experimental geometries reveal that the molecules in the pristine film are standing upright on the surface or are only slightly tilted away from the surface normal but upon K intercalation, the molecular orientation is changed in that the tilt angle of the molecules increases.

  • 12. Palmgren, P.
    et al.
    Nilson, K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Yu, S.
    Hennies, F.
    Angot, T.
    Nlebedim, C. I.
    Layet, J. -M.
    Le Lay, G.
    Goethlid, M.
    Strong interactions in dye-sensitized interfaces2008In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, no 15, p. 5972-5977Article in journal (Refereed)
    Abstract [en]

    Phthalocyanines (Pcs) are capable of converting sunlight into electric energy when adsorbed on TiO2 in a dye-sensitized solar cell. Of special interest in this type of cell is the energy level alignment as well as how molecules adsorb on the surface as it determines the output of the cell. We investigated the FePc-TiO2(110) interface using scanning tunneling microscopy, synchrotron-based photoelectron spectroscopy, and X-ray absorption spectroscopy. We found a strong coupling of the first-layer FePc to the substrate resulting in an alteration of the electronic structure and charge transfer from the molecules. The FePc in the second layer is not severely affected by the bonding to the surface and has bulk-like electronic properties. The growth of FePc thin films proceeds in a layer plus island mode, and the molecular plane is parallel to the surface. The energy level alignment at the interface is determined, and the lowest unoccupied molecular orbital is found above the conduction band minimum of the oxide substrate.

  • 13. Palmgren, P.
    et al.
    Yu, S.
    Hennies, F.
    Nilson, K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Akermark, B.
    Gothelid, M.
    Changing adsorption mode of FePc on TiO2(110) by surface modification with bipyridine2008In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 129, no 7, p. 074707-Article in journal (Refereed)
    Abstract [en]

    Surface modification of reactive oxide substrates to obtain a less strongly interacting template for dye adsorption may be a way to enhance performance in dye-sensitized solar cells. In this work, we have investigated the electronic and structural properties of 4,4(')-bipyridine (bipy) as modifier adsorbed on the TiO2(110) surface. The modified surface is then coated with iron phthalocyanine (FePc) and the properties of this heterostructure are investigated with synchrotron based photoelectron spectroscopy, x-ray absorption spectroscopy, and scanning tunneling microscopy. We find that a saturated monolayer consisting of standing bipy molecules with one nitrogen atom pointing outward is formed on the oxide surface. FePc adsorb in molecular chains along the [001] direction on top of bipy and ordered in a tilted arrangement with adjacent molecules partially overlapping. Already from the first layer, the electronic properties of FePc resemble those of multilayer films. FePc alone is oxidized on the TiO2(110) surface, but preadsorbed bipy prevents this reaction. The energy level lineup at the interface is clarified.

  • 14.
    Piancastelli, Maria Novella
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Bao, Zhuo
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Hennies, F.
    Travnikova, Oksana
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Céolin, Denis
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Kampen, T.
    Horn, K.
    Electronic and Geometric Structure of Methyl Oxirane Adsorbed on Si (100) 2 × 12007In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 254, no 1, p. 108-112Article in journal (Refereed)
    Abstract [en]

    Electronic and geometric properties of the adsorbate–substrate complex formed upon adsorption of methyl oxirane on Si(1 0 0)2 × 1 at room temperature is reported, obtained with synchrotron radiation-induced valence and core-level photoemission. A ring-opening reaction is demonstrated to occur, followed by a five-membered ring formation involving two of the Si surface atoms bound to a surface dimer. Core-level photoemission spectra support the ring-opening reaction and the SiO and SiC bond formation, while from the valence spectra a more extended molecular fragmentation can be ruled out. We discuss the most likely geometry of the five-membered ring.

  • 15.
    Pietzsch, A.
    et al.
    MAX-lab, Lund University, Box 118, S-221 00 Lund, Sweden.
    Sun, Y. -P
    Department of Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, S-106 91 Stockholm, Sweden.
    Hennies, Franz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Rinkevicius, Z.
    Department of Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, S-106 91 Stockholm, Sweden.
    Karlsson, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Schmitt, T.
    Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
    Strocov, V. N.
    Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
    Andersson, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Kennedy, B.
    MAX-lab, Lund University, Box 118, S-221 00 Lund, Sweden.
    Schlappa, J.
    Institute for Methods and Instrumentation in Synchrotron Radiation Research G-I2, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
    Foehlisch, A.
    Institute for Methods and Instrumentation in Synchrotron Radiation Research G-I2, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Gel'mukhanov, F.
    Department of Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, S-106 91 Stockholm, Sweden.
    Spatial Quantum Beats in Vibrational Resonant Inelastic Soft X-Ray Scattering at Dissociating States in Oxygen2011In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 106, no 15, p. 153004-1-153004-4Article in journal (Refereed)
    Abstract [en]

    Resonant inelastic soft x-ray scattering (RIXS) spectra excited at the 1 sigma(g) -> 3 sigma(u) resonance in gas-phase O-2 show excitations due to the nuclear degrees of freedom with up to 35 well-resolved discrete vibronic states and a continuum due to the kinetic energy distribution of the separated atoms. The RIXS profile demonstrates spatial quantum beats caused by two interfering wave packets with different momenta as the atoms separate. Thomson scattering strongly affects both the spectral profile and the scattering anisotropy.

  • 16.
    Rubensson, J. E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Hennies, F.
    Werme, L. O.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Karnland, O.
    Soft X-ray Spectroscopic Characterization of Montmorillonite2009In: / [ed] Hyatt NC; Pickett DA; Rebak RB, 2009, Vol. 1124, p. 257-261Conference paper (Refereed)
    Abstract [en]

    Soft X-ray spectroscopy was applied to study a calcium bentonite from the Kutch area in India. We recorded the X-ray absorption spectra from the L-edge of calcium, silicon, and aluminum, and from K-edge of oxygen. The Ca absorption spectrum shows a quasi-atomic behavior, while the Si spectrum closely simulates the absorption spectrum of a pure silicon oxide The O K spectrum shows a pre-peak, which is absent in the spectra of both the pure, bulk aluminum and silicon oxides. The At L spectrum is complex and shows almost no resemblance to the absorption spectrum of aluminum oxides. The chemical state of the At atoms (in octahedral coordination) must, thus, be quite different from what is common in the oxides. The obtained data show that soft X-ray spectroscopy is a promising technique for studying clay minerals. It is capable of supplying unique information that is complementary to information accessible using other techniques; especially, it can be used to determine the local electronic structure at various atomic sites in the complex samples.

  • 17.
    Rubensson, Jan-Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Pietzsch, Annette
    Hennies, Franz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Vibrationally resolved resonant inelastic soft X-ray scattering spectra of free molecules2012In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 185, no 8-9, p. 294-300Article in journal (Refereed)
    Abstract [en]

    The brilliance of modern synchrotron radiation sources and capabilities of new instrumentation facilitate molecular resonant inelastic soft X-ray scattering with high spectral quality. Especially, energy resolution of vibrational fine structure allows for a detailed analysis, providing information about the dynamic coupling between nuclear and electronic degrees of freedom. After a brief historical account and a short qualitative comparison between the radiative and non-radiative decay channels we review the recent results for the oxygen molecule. Nuclear wavepacket dynamics in bound and unbound states is studied, and in the latter case spatial quantum beats are observed as the dissociation proceeds via two different electronic states. A new internal spin-coupling conservation rule is established, whereas a commonly accepted selection rule based on orbital symmetry is violated.

  • 18. Sun, Y. -P
    et al.
    Hennies, Franz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Pietzsch, A.
    Kennedy, B.
    Schmitt, T.
    Strocov, V. N.
    Andersson, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Berglund, M.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Aidas, K.
    Gel'mukhanov, F.
    Odelius, M.
    Foehlisch, A.
    Intramolecular soft modes and intermolecular interactions in liquid acetone2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 13, p. 132202-Article in journal (Refereed)
    Abstract [en]

    Resonant inelastic x-ray scattering spectra excited at the O1s(-1)pi* resonance of liquid acetone are presented. Scattering to the electronic ground state shows a resolved vibrational progression where the dominant contribution is due to the C-O stretching mode, thus demonstrating a unique sensitivity of the method to the local potential energy surface in complex molecular systems. For scattering to electronically excited states, soft vibrational modes and, to a smaller extent, intermolecular interactions give a broadening, which blurs the vibrational fine structure. It is predicted that environmental broadening is dominant in aqueous acetone.

  • 19. Sun, Y-P
    et al.
    Pietzsch, A.
    Hennies, Franz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Rinkevicius, Z.
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Schmitt, T.
    Strocov, V. N.
    Andersson, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Kennedy, B.
    Schlappa, J.
    Föhlisch, A.
    Gel'mukhanov, F.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Internal symmetry and selection rules in resonant inelastic soft x-ray scattering2011In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 44, no 16, p. 161002-Article in journal (Refereed)
    Abstract [en]

    Resonant inelastic soft x-ray scattering spectra excited at the dissociative 1 sigma(g) -> 3 sigma(u) resonance in gas-phase O(2) are presented and discussed in terms of state-of-the-art molecular theory. A new selection rule due to internal spin coupling is established, facilitating a deep analysis of the valence excited final states. Furthermore, it is found that a commonly accepted symmetry selection rule due to orbital parity breaks down, as the core hole and excited electron swap parity, thereby opening the symmetry forbidden 3 sigma(g) decay channel.

  • 20. Yu, Shun
    et al.
    Ahmadi, Sarch
    Palmgren, Pål
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Hennies, Franz
    Zuleta, Marcelo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Gothelid, Mats
    Modification of charge transfer and energy level alignment at organic/TiO2 interfaces2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 31, p. 13765-13771Article in journal (Refereed)
    Abstract [en]

    Adsorption of titanyl phthalocyanine (TiOPc) on rutile TiO2(110) modified by a set of pyridine derivatives (2,2'-bipyridine, 4,4'-bipyridine, and 4-tert-butyl pyridine) has been investigated using synchrotron radiation based X-ray photoelectron spectroscopy (XPS). For the unmodified TiOPc/TiO2 system, a strong charge transfer is observed from the first layer TiOPc into the substrate, which leads to a molecular layer at the interface with a depleted highest occupied molecular orbital (HOMO). However, precovering the TiO2 surface with a saturated pyridine monolayer effectively reduce this process and leave the TiOPc in a less perturbed molecular state. Furthermore, the TiOPc HOMO and core levels are observed at different binding energies ranging by 0.3 eV on the three pyridine monolayers, which is ascribed to differences in surface potentials set up by the different pyridine/TiO2 systems.

  • 21. Yu, Shun
    et al.
    Ahmadi, Sareh
    Sun, Chenghua
    Schulte, Karina
    Pietzsch, Annette
    Hennies, Franz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Zuleta, Marcelo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Göthelid, Mats
    Crystallization-Induced Charge-Transfer Change in TiOPc Thin Films Revealed by Resonant Photoemission Spectroscopy2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 30, p. 14969-14977Article in journal (Refereed)
    Abstract [en]

    Organic semiconductors usually demonstrate crystal structure dependent electronic properties, and through precise control of film structure, the performance of novel organic electronic devices can be greatly improved. Understanding the crystal structure dependent charge-transfer mechanism thus becomes critical. In this work, we have prepared amorphous titanyl phthalocyanine films by vacuum molecular beam evaporation and have further crystallized them through vacuum annealing. In the crystalline phase, an excited electron is rapidly transferred into neighboring molecules; while in the amorphous phase, it is mainly localized and recombines with the core hole as revealed by resonant photoemission spectroscopy (RPES). The fast electron transfer time is determined to be around 16 fs in the crystalline film, which is in good agreement with the charge-transfer hopping time estimated from the best device performance reported. The crystallized film shows more p-type characteristics than the amorphous with all the energy levels shifting toward the vacuum level. However, the greatly improved charge transfer is assigned to the molecular orbital coupling rather than this shift. From density functional theory and RPES, we specify the contribution of two differently coordinated nitrogen atoms (N2c and N3c) to the experimental results and illustrate that the N3c related orbital has experienced a dramatic change, which is keenly related to the improved charge transfer.

  • 22. Yu, Shun
    et al.
    Ahmadi, Sareh
    Zuleta, Marcelo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Tian, Haining
    Schulte, Karina
    Pietzsch, Annette
    Hennies, Franz
    Weissenrieder, Jonas
    Yang, Xichuan
    Göthelid, Mats
    Adsorption geometry, molecular interaction, and charge transfer of triphenylamine-based dye on rutile TiO2(110)2010In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 133, no 22, p. 224704-Article in journal (Refereed)
    Abstract [en]

    The fast development of new organic sensitizers leads to the need for a better understanding of the complexity and significance of their adsorption processes on TiO2 surfaces. We have investigated a prototype of the triphenylamine-cyanoacrylic acid (donor-acceptor) on rutile TiO2 (110) surface with special attention on the monolayer region. This molecule belongs to the type of dye, some of which so far has delivered the record efficiency of 10%-10.3% for pure organic sensitizers [W. Zeng, Y. Cao, Y. Bai, Y. Wang, Y. Shi, M. Zhang, F. Wang, C. Pan, and P. Wang, Chem. Mater. 22, 1915 (2010)]. The molecular configuration of this dye on the TiO2 surface was found to vary with coverage and adopt gradually an upright geometry, as determined from near edge x-ray absorption fine structure spectroscopy. Due to the molecular interaction within the increasingly dense packed layer, the molecular electronic structure changes systematically: all energy levels shift to higher binding energies, as shown by photoelectron spectroscopy. Furthermore, the investigation of charge delocalization within the molecule was carried out by means of resonant photoelectron spectroscopy. A fast delocalization (similar to 1.8 fs) occurs at the donor part while a competing process between delocalization and localization takes place at the acceptor part. This depicts the "push-pull" concept in donor-acceptor molecular system in time scale.

  • 23.
    Århammar, Cecilia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Pietzsch, Annette
    MAX-lab, Lunds universitet, Lund.
    Bock, Nicolas
    Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
    Holmström, Erik
    Instituto di Fisica, Universidad Austral de Chile, Valdivia, Chile.
    Araujo, Carlos Moyses
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Gråsjö, Johan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Zhao, Shuxi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Green, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Peery, T
    Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
    Hennies, Franz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Amerioun, Shahrad
    Sandvik Tooling, R and D, Stockholm.
    Foehlisch, Alexander
    Insitute for Methods and Instrumentation in Synchrotron Radiation Research G-12, Helmhotz-Zentrum Berlin für Materialien und Energie, Berlin, Tyskland.
    Schlappa, Justine
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Schmitt, Thorsten
    Swiss Light Source, Paul Scherrer Institut, Villigen, Schweiz.
    Strocov, Vladimir N
    Swiss Light Source, Paul Scherrer Institut, Villigen, Schweiz.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wallace, Duane C
    Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Unveiling the complex electronic structure of amorphous metal oxides2011In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 108, no 16, p. 6355-6360Article in journal (Refereed)
    Abstract [en]

    Amorphous materials represent a large and important emerging area of material's science. Amorphous oxides are key technological oxides in applications such as a gate dielectric in Complementary metal-oxide semiconductor devices and in Silicon-Oxide-Nitride-Oxide-Silicon and TANOS (TaN-Al2O3-Si3N4-SiO2-Silicon) flash memories. These technologies are required for the high packing density of today's integrated circuits. Therefore the investigation of defect states in these structures is crucial. In this work we present X-ray synchrotron measurements, with an energy resolution which is about 5-10 times higher than is attainable with standard spectrometers, of amorphous alumina. We demonstrate that our experimental results are in agreement with calculated spectra of amorphous alumina which we have generated by stochastic quenching. This first principles method, which we have recently developed, is found to be superior to molecular dynamics in simulating the rapid gas to solid transition that takes place as this material is deposited for thin film applications. We detect and analyze in detail states in the band gap that originate from oxygen pairs. Similar states were previously found in amorphous alumina by other spectroscopic methods and were assigned to oxygen vacancies claimed to act mutually as electron and hole traps. The oxygen pairs which we probe in this work act as hole traps only and will influence the information retention in electronic devices. In amorphous silica oxygen pairs have already been found, thus they may be a feature which is characteristic also of other amorphous metal oxides.

1 - 23 of 23
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