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  • 1.
    Agåker, Marcus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Andersson, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Englund, Carl-Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Rausch, J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Nordgren, Joseph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Spectroscopy in the vacuum-ultraviolet2011In: Nature Photonics, ISSN 1749-4885, Vol. 5, no 5, p. 248-248Article in journal (Refereed)
  • 2.
    Agåker, Marcus
    et al.
    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.
    Double Core Excitations in Lithium Halides2007In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 4, p. 045112-Article in journal (Refereed)
    Abstract [en]

    Resonant inelastic x-ray scattering spectra of LiF , LiCl , LiBr , and LiI excited in the vicinity of the Li double core hole resonances are presented. All lithium halides show similar phenomenology, including scattering via states where both excited electrons are localized during the scattering process, as well as states where one electron delocalizes. Also transitions that involve additional band excitations are observed. A strong influence of the chemical surrounding is found, and it is discussed in terms of the ionic character of the chemical bond.

  • 3. Andersson, E.
    et al.
    Linusson, P.
    Fritzsche, S.
    Hedin, Lage
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Eland, John H. D.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Karlsson, Leif
    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.
    Feifel, Raimund
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Formation of Kr3+ via core-valence doubly ionized intermediate states2012In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 85, no 3, p. 032502-Article in journal (Refereed)
    Abstract [en]

    The time-of-flight photoelectron-photoion coincidence technique has been used to study single-photon 3d(9)4p(5) core-valence double ionization of Kr and subsequent Auger decay to triply charged states associated with the 4s(2)4p(3) and 4s(1)4p(4) configurations. The photon energy used was h nu = 150 eV. Multiconfiguration Dirac-Fock calculations were performed both for the doubly ionized intermediate states and the triply ionized final states. The intermediate states of Kr2+ are observed between 120 and 125 eV, whereas the final states of Kr3+ are observed between 74- and 120-eV ionization energy. Assignments of all structures are made based on the present numerical results. The calculated Auger rates give a detailed explanation of the relative line strengths observed.

  • 4.
    Andersson, Egil
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Multi-Electron Coincidence Studies of Atoms and Molecules2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns multi-ionization coincidence measurements of atoms and small molecules using a magnetic bottle time-of-flight (TOF) spectrometer designed for multi-electron coincidence studies. Also, a time-of-flight mass spectrometer has been used together with the TOF electron  spectrometer for electron-ion coincidence measurements. The multi-ionization processes have been studied by employing a pulsed discharge lamp in the vacuum ultraviolet spectral region and synchrotron radiation in the soft X-ray region. The designs of the spectrometers are described in some detail, and several timing schemes suitable for the light sources mentioned above are presented.

    Studies have been performed on krypton, molecular oxygen, carbon disulfide and a series of alcohol molecules. For the latter, double ionization spectra have been recorded and new information has been obtained on the dicationic states. A recently found rule-of-thumb  and quantum chemical calculations have been used to quantify the effective distance of the two vacancies in the dications of these molecules.

    For Kr, O2, and CS2, single-photon core-valence spectra have been obtained at the synchrotron radiation facility BESSY II in Berlin and interpreted on the basis of quantum chemical calculations. These spectra show a remarkable similarity to conventional valence photoelectron spectra.

    Spectra of triply charged ions were recorded, also at BESSY II, for Kr and CS2 by measuring, in coincidence, all three electrons ejected. The complex transition channels leading to tricationic states were mapped in substantial detail for Kr. It was found that for 3d-ionized krypton, the tricationic states are dominantly populated by cascade Auger decays via distinct intermediate states whose energies have been determined. The triple ionization spectra of CS2 from the direct double Auger effect via S2p, S2s and C1s hole states contain several resolved features and show selectivity based on the initial charge localisation and on the identity of the initial state.

    List of papers
    1. Multielectron coincidence study of the double Auger decay of 3d-ionized krypton
    Open this publication in new window or tab >>Multielectron coincidence study of the double Auger decay of 3d-ionized krypton
    Show others...
    2010 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 82, no 4, p. 043418-Article in journal (Refereed) Published
    Abstract [en]

    Multielectron coincidence data for triple ionization of krypton have been recorded above the 3d ionization threshold at two photon energies (140 and 150 eV). Three principal transition pathways have been observed, two involving double Auger transitions from Kr+, and one involving single Auger transitions from Kr2+ created by direct single-photon double ionization. The decay of the 3d(9) D-2(5/2,3/2) states in Kr+ has been analyzed in some detail and is found to be strongly dominated by cascade processes where two electrons with well-defined energies are emitted. The decay paths leading to the 4s(2)4p(3) S-4, D-2, and P-2 states of Kr3+ are analyzed and energies of seven intermediate states in Kr2+ are given. A preliminary investigation of the decay paths from Kr+ 3d (9)4p(5)nl shake-up states has also been carried out.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-122568 (URN)10.1103/PhysRevA.82.043418 (DOI)000283114900005 ()
    Available from: 2010-04-14 Created: 2010-04-14 Last updated: 2017-12-12Bibliographically approved
    2. Formation of Kr3+ via core-valence doubly ionized intermediate states
    Open this publication in new window or tab >>Formation of Kr3+ via core-valence doubly ionized intermediate states
    Show others...
    2012 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 85, no 3, p. 032502-Article in journal (Refereed) Published
    Abstract [en]

    The time-of-flight photoelectron-photoion coincidence technique has been used to study single-photon 3d(9)4p(5) core-valence double ionization of Kr and subsequent Auger decay to triply charged states associated with the 4s(2)4p(3) and 4s(1)4p(4) configurations. The photon energy used was h nu = 150 eV. Multiconfiguration Dirac-Fock calculations were performed both for the doubly ionized intermediate states and the triply ionized final states. The intermediate states of Kr2+ are observed between 120 and 125 eV, whereas the final states of Kr3+ are observed between 74- and 120-eV ionization energy. Assignments of all structures are made based on the present numerical results. The calculated Auger rates give a detailed explanation of the relative line strengths observed.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-172032 (URN)10.1103/PhysRevA.85.032502 (DOI)000301104400014 ()
    Available from: 2012-04-02 Created: 2012-04-01 Last updated: 2017-12-07Bibliographically approved
    3. Double photoionization of alcohol molecules
    Open this publication in new window or tab >>Double photoionization of alcohol molecules
    Show others...
    2009 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 80, no 3, p. 032516-Article in journal (Refereed) Published
    Abstract [en]

    The double valence photoionization spectra of methanol, ethanol, and n-propyl alcohol have been recorded using a time-of-flight photoelectron-photoelectron coincidence technique. The spectra show a well-defined onset followed by broad rounded bands. The lowest vertical double ionization energies have been determined for all molecules and are found to be 32.1, 29.6, and 28.2 eV, respectively. These energies have been applied along with single ionization energies from conventional photoelectron spectra to investigate a recently derived rule of thumb for determination of the lowest double ionization energy in molecules. Many-electron ab initio calculations have been performed on the dicationic ground states in good agreement with the experimental values. For methanol, also excited dicationic states have been calculated up to about 40 eV and used for a detailed interpretation of the experimental spectrum.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-114304 (URN)10.1103/PhysRevA.80.032516 (DOI)000270383900088 ()
    Available from: 2010-02-12 Created: 2010-02-12 Last updated: 2017-12-12Bibliographically approved
    4. Single-photon core-valence double ionization of molecular oxygen
    Open this publication in new window or tab >>Single-photon core-valence double ionization of molecular oxygen
    Show others...
    2008 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 78, no 2, p. 023409-Article in journal (Refereed) Published
    Abstract [en]

    Single-photon core-valence double ionization of molecular oxygen has been studied using a magnetic bottle time-of-flight electron coincidence spectrometer. The K-1V-1 double ionization electron spectrum of O-2 is reported and is assigned with the aid of ab initio calculations. A direct comparison of the core-valence double ionization electron spectra with the conventional valence band photoelectron spectrum is made. The lowest core-valence double ionization energy is found to be 571.6 eV and is associated with a (3)Pi dicationic state.

    Keywords
    Autoionization, photoionization, and photodetachment, Oscillator and band strengths, lifetimes, transition moments, and Franck-Condon factors, Electronic excitation and ionization of molecules; intermediate molecular states
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-107900 (URN)10.1103/PhysRevA.78.023409 (DOI)000259263500009 ()
    Note
    Part BAvailable from: 2009-09-01 Created: 2009-08-31 Last updated: 2017-12-13Bibliographically approved
    5. Core-valence double photoionization of the CS2 molecule
    Open this publication in new window or tab >>Core-valence double photoionization of the CS2 molecule
    Show others...
    2010 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 133, no 9, p. 094305-Article in journal (Refereed) Published
    Abstract [en]

    Double photoionization spectra of the CS2 molecule have been recorded using the TOF-PEPECO technique in combination with synchrotron radiation at the photon energies h nu=220, 230, 240, 243, and 362.7 eV. The spectra were recorded in the S 2p and C 1s inner-shell ionization regions and reflect dicationic states formed out of one inner-shell vacancy and one vacancy in the valence region. MCSCF calculations were performed to model the energies of the dicationic states. The spectra associated with a S 2p vacancy are well structured and have been interpreted in some detail by comparison to conventional S 2p and valence photoelectron spectra. The lowest inner-shell-valence dicationic state is observed at the vertical double ionization energy 188.45 eV and is associated with a (2p(3/2))(-1)(2 pi(g))(-1) double vacancy. The spectrum connected to the C 1s vacancy shows a distinct line at 310.8 eV, accompanied by additional broad features at higher double ionization energies. This line is associated with a (C 1s)(-1)(2 pi(g))(-1) double vacancy.

    Keywords
    carbon compounds, inner-shell ionisation, molecule-photon collisions, photoionisation, SCF calculations
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-122570 (URN)10.1063/1.3469812 (DOI)000281742900011 ()
    Available from: 2010-04-20 Created: 2010-04-14 Last updated: 2017-12-12Bibliographically approved
    6. Spectra of the triply charged ion CS[sub 2][sup 3+] and selectivity in molecular Auger effects
    Open this publication in new window or tab >>Spectra of the triply charged ion CS[sub 2][sup 3+] and selectivity in molecular Auger effects
    Show others...
    2010 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 132, no 10, p. 104311-Article in journal (Refereed) Published
    Abstract [en]

    Spectra of triply charged carbon disulphide have been obtained by measuring, in coincidence, all three electrons ejected in its formation by photoionization. Measurements of the CS23+ ion in coincidence with the three electrons identify the energy range where stable trications are formed. A sharp peak in this energy range is identified as the 2Π ground state at 53.1±0.1 eV, which is the lowest electronic state according to ab initio molecular orbital calculations. Triple ionization by the double Auger effect is provisionally divided, on the basis of the pattern of energy sharing between the two Auger electrons into contributions from direct and cascade Auger processes. The spectra from the direct double Auger effect via S 2p, S 2s, and C 1s hole states contain several resolved features and show selectivity based on the initial charge localization and on the identity of the initial state. Triple ionization spectra from single Auger decay of S 2p -based core-valence states CS22+ show retention of the valence holes in this Auger process. Related ion-electron coincidence measurements give the triple ionization yields and the breakdown patterns in triple photoionization at selected photon energies from 90 eV to above the inner shell edges.

    Keywords
    ab initio calculations, Auger effect, carbon compounds, molecule-photon collisions, orbital calculations, photoionisation, positive ions, time of flight spectra
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-121766 (URN)10.1063/1.3352549 (DOI)000275589700025 ()
    Available from: 2010-03-30 Created: 2010-03-30 Last updated: 2017-12-12Bibliographically approved
  • 5.
    Andersson, Egil
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Fritzsche, Stephan
    Linusson, Per
    Hedin, Lage
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Eland, John H. D.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Karlsson, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Feifel, Raimund
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Multielectron coincidence study of the double Auger decay of 3d-ionized krypton2010In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 82, no 4, p. 043418-Article in journal (Refereed)
    Abstract [en]

    Multielectron coincidence data for triple ionization of krypton have been recorded above the 3d ionization threshold at two photon energies (140 and 150 eV). Three principal transition pathways have been observed, two involving double Auger transitions from Kr+, and one involving single Auger transitions from Kr2+ created by direct single-photon double ionization. The decay of the 3d(9) D-2(5/2,3/2) states in Kr+ has been analyzed in some detail and is found to be strongly dominated by cascade processes where two electrons with well-defined energies are emitted. The decay paths leading to the 4s(2)4p(3) S-4, D-2, and P-2 states of Kr3+ are analyzed and energies of seven intermediate states in Kr2+ are given. A preliminary investigation of the decay paths from Kr+ 3d (9)4p(5)nl shake-up states has also been carried out.

  • 6.
    Andersson, Egil
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Niskanen, Johannes
    Hedin, Lage
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Eland, John H. D.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Linusson, Per
    Karlsson, Leif
    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.
    Carravetta, V.
    Ågren, Hans
    Feifel, Raimund
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Core-valence double photoionization of the CS2 molecule2010In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 133, no 9, p. 094305-Article in journal (Refereed)
    Abstract [en]

    Double photoionization spectra of the CS2 molecule have been recorded using the TOF-PEPECO technique in combination with synchrotron radiation at the photon energies h nu=220, 230, 240, 243, and 362.7 eV. The spectra were recorded in the S 2p and C 1s inner-shell ionization regions and reflect dicationic states formed out of one inner-shell vacancy and one vacancy in the valence region. MCSCF calculations were performed to model the energies of the dicationic states. The spectra associated with a S 2p vacancy are well structured and have been interpreted in some detail by comparison to conventional S 2p and valence photoelectron spectra. The lowest inner-shell-valence dicationic state is observed at the vertical double ionization energy 188.45 eV and is associated with a (2p(3/2))(-1)(2 pi(g))(-1) double vacancy. The spectrum connected to the C 1s vacancy shows a distinct line at 310.8 eV, accompanied by additional broad features at higher double ionization energies. This line is associated with a (C 1s)(-1)(2 pi(g))(-1) double vacancy.

  • 7. Atak, Kaan
    et al.
    Engel, Nicholas
    Lange, Kathrin M.
    Golnak, Ronny
    Gotz, Malte
    Soldatov, Mikhail
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Kosugi, Nobuhiro
    Aziz, Emad F.
    The Chemical Bond in Carbonyl and Sulfinyl Groups Studied by Soft X-ray Spectroscopy and ab Initio Calculations2012In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 13, no 13, p. 3106-3111Article in journal (Refereed)
    Abstract [en]

    The polar character of the sulfinyl bond, which determines many of the properties of dimethyl sulfoxide (DMSO), is a result of charge transfer in low-lying π-type orbitals. This characteristic—together with the wide energy gap between the highest occupied and the lowest unoccupied molecular orbitals of this substance—makes DMSO a relatively inert aprotic solvent with strong nucleophilicity and electrophilicity.

  • 8. Aziz, Emad F
    et al.
    Gråsjö, Johan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Forsberg, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Andersson, Egil
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Duda, Laurent
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Zhang, Wenhua
    Yang, Jinglong
    Eisebitt, Stefan
    Bergström, Christel
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Luo, Yi
    Nordgren, Joseph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Eberhardt, Wolfgang
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Photoinduced Formation of N2 Molecules in Ammonium Compounds2007In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 111, no 39, p. 9662-9669Article in journal (Refereed)
    Abstract [en]

    Via fluorescence yield (FY) and resonant inelastic scattering spectroscopy in the soft X-ray range we find that soft X-rays induce formation of N2 molecules in solid NH4Cl and in related compounds. The nitrogen molecules form weak bonds in NH4Cl, so that a substantial fraction of the molecules remains in the sample. From measurements of the FY as a function of exposure and temperature, the rates for the photochemical processes are estimated. At elevated temperatures (363 K), several nitrogen atoms are removed from the sample per incoming photon. At lower temperatures (233 K), the rate is reduced to around 0.02 nitrogen atoms for each incoming photon. Virtually all these atoms form N2 molecules which are bound in the sample. The generality and implications of these results are briefly discussed.

  • 9. Berner, G.
    et al.
    Glawion, S.
    Walde, J.
    Pfaff, F.
    Hollmark, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Duda, Laurent
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Paetel, S.
    Richter, C.
    Mannhart, J.
    Sing, M.
    Claessen, R.
    LaAlO3/SrTiO3 oxide heterostructures studied by resonant inelastic x-ray scattering2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, no 24, p. 241405-Article in journal (Refereed)
    Abstract [en]

    We report the application of resonant inelastic X-ray scattering to explore the nature of the single conducting interface in the oxide heterostructure LaAlO/sub 3//SrTiO/sub 3/. From the Ti 3d crystal-field excitations measured at the Ti L/sub 3/ resonance we not only derive information on the local geometry at the interface but are also able to follow the evolution of the sheet carrier density with the thickness of the LaAlO/sub 3/ overlayer. These findings confirm after calibration to previous hard X-ray photoelectron spectroscopy measurements that the charge density from spectroscopy exceeds the one derived from Hall-effect measurements, indicating the coexistence of itinerant /i and/ localized Ti 3d electrons at the interface. On the other hand, we observe a saturation of the charge-carrier concentration above a LaAlO/sub 3/ thickness of 6 unit cells at ~1*10/sup 14/ cm/sup -2/, well below the canonical value for ideal electronic reconstruction.

  • 10. Berrah, Nora
    et al.
    Fang, Li
    Murphy, Brendan
    Osipov, Timur
    Ueda, Kiyoshi
    Kukk, Edwin
    Feifel, Raimund
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    van der Meulen, Peter
    Salen, Peter
    Schmidt, Henning T.
    Thomas, Richard D.
    Larsson, Mats
    Richter, Robert
    Prince, Kevin C.
    Bozek, John D.
    Bostedt, Christoph
    Wada, Shin-ichi
    Piancastelli, Maria N.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Tashiro, Motomichi
    Ehara, Masahiro
    Double-core-hole spectroscopy for chemical analysis with an intense X-ray femtosecond laser2011In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 108, no 41, p. 16912-16915Article in journal (Refereed)
    Abstract [en]

    Theory predicts that double-core-hole (DCH) spectroscopy can provide a new powerful means of differentiating between similar chemical systems with a sensitivity not hitherto possible. Although DCH ionization on a single site in molecules was recently measured with double-and single-photon absorption, double-core holes with single vacancies on two different sites, allowing unambiguous chemical analysis, have remained elusive. Here we report that direct observation of double-core holes with single vacancies on two different sites produced via sequential two-photon absorption, using short, intense X-ray pulses from the Linac Coherent Light Source free-electron laser and compare it with theoretical modeling. The observation of DCH states, which exhibit a unique signature, and agreement with theory proves the feasibility of the method. Our findings exploit the ultrashort pulse duration of the free-electron laser to eject two core electrons on a time scale comparable to that of Auger decay and demonstrate possible future X-ray control of physical inner-shell processes.

  • 11.
    Duda, Laurent
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Schmitt, Thorsten
    Magnuson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Forsberg, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Olsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Nordgren, Joseph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Okada, K
    Kotani, A
    Resonant inelastic x-ray scattering at the NiO O K-resonance: non-local charge-transfer and double singlet excitations2006In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 96, no 6, p. 067402-Article in journal (Refereed)
  • 12. Ehara, M.
    et al.
    Horikawa, T.
    Fukuda, R.
    Nakatsuji, H.
    Tanaka, T.
    Kato, H.
    Hoshino, M.
    Tanaka, H.
    Feifel, Raimund
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Ueda, K.
    Symmetry and vibrationally resolved absorption spectra near the N K edges of N2O: experiment and theory2011In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 83, no 6, p. 062506-Article in journal (Refereed)
    Abstract [en]

    In this study, angle-resolved energetic-ion yield spectra were measured in the N 1s excitation region of N2O. A Franck-Condon analysis based on ab initio two-dimensional potential energy surfaces of the core-excited Rydberg states, which were calculated by the symmetry-adapted cluster-configuration interaction method, reproduced observed vibrational excitations specific to the individual Rydberg states well and enabled quantitative assignments. Geometric changes in the terminal nitrogen N-t 1s and the central nitrogen N-c 1s excited states with respect to the 3p pi, 3p sigma, and 4s sigma transitions were analyzed. The coupling of these valence and Rydbergs states was examined based on the second moment analysis. Irregular Rydberg-state behavior in the N-c 1s(-1) 4s sigma state was observed.

  • 13. Eland, J. H. D.
    et al.
    Rigby, C. F.
    Andersson, Egil
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Palaudoux, J.
    Andric, L.
    Penent, F.
    Linusson, P.
    Hedin, Lage
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Karlsson, Leif
    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.
    Hikosaka, Y
    Ito, K
    Lablanquie, P
    Feifel, Raimund
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Spectra of the triply charged ion CS[sub 2][sup 3+] and selectivity in molecular Auger effects2010In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 132, no 10, p. 104311-Article in journal (Refereed)
    Abstract [en]

    Spectra of triply charged carbon disulphide have been obtained by measuring, in coincidence, all three electrons ejected in its formation by photoionization. Measurements of the CS23+ ion in coincidence with the three electrons identify the energy range where stable trications are formed. A sharp peak in this energy range is identified as the 2Π ground state at 53.1±0.1 eV, which is the lowest electronic state according to ab initio molecular orbital calculations. Triple ionization by the double Auger effect is provisionally divided, on the basis of the pattern of energy sharing between the two Auger electrons into contributions from direct and cascade Auger processes. The spectra from the direct double Auger effect via S 2p, S 2s, and C 1s hole states contain several resolved features and show selectivity based on the initial charge localization and on the identity of the initial state. Triple ionization spectra from single Auger decay of S 2p -based core-valence states CS22+ show retention of the valence holes in this Auger process. Related ion-electron coincidence measurements give the triple ionization yields and the breakdown patterns in triple photoionization at selected photon energies from 90 eV to above the inner shell edges.

  • 14. Eland, J.H.D
    et al.
    Hochlaf, M.
    Linusson, Per
    Andersson, Egil
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Hedin, Lage
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Feifel, Raimund
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Triple ionization spectra by coincidence measurements of double Auger decay: The case of OCS2010In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 132, no 1, p. 014311-Article in journal (Refereed)
    Abstract [en]

    By combining multiple electron coincidence detection with ionization by synchrotron radiation, we have obtained resolved spectra of the OCS3+ ion created through the double Auger effect. The form of the spectra depends critically on the identity of the atom bearing the initial hole. High and intermediate level electron structure calculations lead to an assignment of the resolved spectrum from ionization via the S 2p hole. From the analysis it appears that the double Auger effect from closed shell molecules favors formation of doublet states over quartet states. Molecular field effects in the double Auger effect are similar to those in the single Auger effect in linear molecules.

  • 15.
    Eland, John H. D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Andric, L.
    Linusson, P.
    Hedin, Lage
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Plogmaker, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Palaudoux, J.
    Penent, F.
    Lablanquie, P.
    Feifel, Raimund
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Triple ionization of CO(2) by valence and inner shell photoionization2011In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 135, no 13, p. 134309-Article in journal (Refereed)
    Abstract [en]

    Spectra of triply ionized CO(2) have been obtained from photoionization of the molecule using soft x-ray synchrotron light and an efficient multi-electron coincidence technique. Although all states of the CO(2)(+++) trication are unstable, the ionization energy for formation of molecular ions at a geometry similar to that of the neutral molecule is determined as 74 +/- 0.5 eV.

  • 16.
    Eland, John H. D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Fink, R. F.
    Linusson, P.
    Hedin, L.
    Plogmaker, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Feifel, R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Single and multiple photoionisation of H(2)S by 40-250 eV photons2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 41, p. 18428-18435Article in journal (Refereed)
    Abstract [en]

    Multi-electron coincidence measurements on photoionisation of H(2)S have been carried out at photon energies from 40 to 250 eV. They quantify molecular field effects on the Auger process in detail and are in good agreement with the existing theory. Spectra of core-valence double ionisation of H(2)S are presented and partially analysed. Auger decays from the core-valence states produce triply charged product spectra with unexplained and surprising intensity distributions. Triple ionisation by the double Auger process from 2p hole states shows little effect of the molecular field splitting, but includes a substantial contribution from cascade processes, some involving dissociation in intermediate states. The onset of triple ionisation at the molecular geometry is determined as 61 +/- 0.5 eV.

  • 17.
    Eland, John H. D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Linusson, P.
    Mucke, Melanie
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Feifel, Raimund
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Homonuclear site-specific photochemistry by an ion-electron multi-coincidence spectroscopy technique2012In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 548, p. 90-94Article in journal (Refereed)
    Abstract [en]

    By combining multi-particle coincidence detection of electrons and ions with ionisation by soft X-ray synchrotron radiation we demonstrate an effective tool for atomic spectroscopy and site-specific photochemistry. Its most novel capability is application to molecular fragmentation after K-shell vacancy production in atoms distinguished only by their chemical environment.

  • 18.
    Eland, John H.D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Tashiro, M.
    Linusson, P.
    Ehara, M.
    Ueda, K.
    Feifel, Raimund
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Double Core Hole Creation and Subsequent Auger Decay in NH3 and CH4 Molecules2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 105, no 21, p. 213005-Article in journal (Refereed)
    Abstract [en]

    Energies of the hollow molecules CH42+ and NH32+ with double vacancies in the 1s shells have been measured using an efficient coincidence technique combined with synchrotron radiation. The energies of these states have been determined accurately by high level electronic structure calculations and can be well understood on the basis of a simple theoretical model. Their major decay pathway, successive Auger emissions, leads first to a new form of triply charged ion with a core hole and two valence vacancies; experimental evidence for such a state is presented with its theoretical interpretation. Preedge 2-hole-1-particle (2h-1p) states at energies below the double core-hole states are located in the same experiments and their decay pathways are also identified.

  • 19. Fang, L.
    et al.
    Osipov, T.
    Murphy, B.
    Juranic, P.
    Berrah, N.
    Kukk, E.
    Ueda, K.
    Feifel, R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    van der Meulen, P.
    Salen, P.
    Schmidt, H.
    Thomas, R.
    Larsson, M.
    Richter, R.
    Prince, K. C.
    Bozek, J. D.
    Bostedt, C.
    Wada, S.
    Piancastelli, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Tashiro, M.
    Ehara, M.
    Tarantelli, F.
    Multiple Ionization and Double Core-hole Production in Molecules using the LCLS X-ray FEL2012In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 388, no 3, p. 032028-Article in journal (Refereed)
    Abstract [en]

    We used the world's first hard x-ray FEL to investigate the response of molecular systems to the ultra-intense, femtosecond x-ray radiation. We report sequential multiphoton ionization, frustrated absorption and double core hole production mechanisms.

  • 20. Farrell, J. P.
    et al.
    McFarland, B. K.
    Berrah, N.
    Bostedt, C.
    Bozek, J.
    Bucksbaum, P. H.
    Coffee, R.
    Cryan, J.
    Fang, L.
    Feifel, R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Gaffney, K.
    Glownia, J.
    Martinez, T.
    Mucke, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Murphy, B.
    Miyabe, S.
    Natan, A.
    Osipov, T.
    Petrovic, V.
    Schorb, S.
    Schultz, T.
    Spector, L.
    Tarantelli, F.
    Tenney, I.
    Wang, S.
    White, W.
    White, J.
    Guehr, M.
    Ultrafast X-ray probe of nucleobase photoprotection2012In: Quantum Electronics and Laser Science Conference: Strong-Field and Short-Wavelength Interactions (QW1F), 2012, p. 6327153-Conference paper (Refereed)
    Abstract [en]

    We will present first results of a UV-pump X-ray-probe study of the photoprotection mechanism of thymine. The experiment used element specific Auger spectroscopy and was carried out at the LCLS.

  • 21.
    Feifel, Raimund
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Piancastelli, Maria Novella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Core-level spectroscopy and dynamics of free molecules2011In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 183, no 1-3, p. 10-28Article in journal (Refereed)
    Abstract [en]

    A review of recent results on spectroscopy and dynamics of free molecules is presented. The experimental research reported here is mainly concerned with processes of core excitation and decay of isolated molecules, primarily investigated by resonant Auger spectroscopy. Several examples are shown concerning the interplay of the timescales of electron decay with nuclear motion involving dissociation processes, the occurrence of interference phenomena and recoil. The capability of such studies to reveal subtle details of the light-matter interaction, of the electronic structure and of the evolution of the short-lived states thus created is enlightened.

  • 22. Freelon, B.
    et al.
    Augustsson, A.
    Guo, J. -H
    Medaglia, P. G.
    Tebano, A.
    Balestrino, G.
    Dong, C. L.
    Chang, C. L.
    Glans, P. A.
    Learmonth, T.
    Smith, K. E.
    Nordgren, Joseph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Hussain, Z.
    Low energy electronic spectroscopy of an infinite-layer cuprate: A resonant inelastic X-ray scattering study of CaCuO22010In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 470, no 3, p. 187-192Article in journal (Refereed)
    Abstract [en]

    We report the results of Oxygen K-edge soft X-ray absorption and emission spectroscopy that was performed on an infinite-layer insulating cuprate thin film CaCuO2 Experimentally obtained spectra arc consistent with local density approximation calculations X-ray absorption spectra show a close resemblance to spectra obtained from homologous single crystal cuprates In addition to d-d excitations. X-ray emission spectra reveal the presence of Zhang-Rice singlet states in the infinite-layer CuO2 planes The question of whether the Zhang-Rice singlet features are masked by the O 2p main-band is addressed. it is possible to quantify the position of the Zhang-Rice singlet using emission intensity profiles X-ray emission is demonstrated as a tool for understanding CuO2 planar electronic correlation in the prototypical infinite-layer The energy difference, 2 0 eV, between the oxygen main-band and the Zhang-Rice singlet band is found to match values obtained theoretically using established planar electronic correlation parameters.

  • 23. Förstel, Marko
    et al.
    Mucke, Melanie
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Anon, Tiberiu
    Lischke, Toralf
    Barth, Silko
    Ulrich, Volker
    Öhrwall, Gunnar
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Hergenhahn, Uwe
    Bradshaw, Alex M.
    Energy band dispersion in photoemission spectra of argon clusters2011In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 184, no 3-6, p. 107-112Article in journal (Refereed)
    Abstract [en]

    Using photoemission we have investigated free argon clusters from a supersonic nozzle expansion in the photon energy range from threshold up to 28 eV. Measurements were performed both at high resolution with a hemispherical electrostatic energy analyser and at lower resolution with a magnetic bottle device. The latter experiments were performed for various mean cluster sizes. In addition to the approximate to 15eV broad 3p-derived valence band seen in previous work, there is a sharper feature at approximate to 15eV binding energy. Surprisingly for non-oriented clusters, this peak shifts smoothly in binding energy over the narrow photon energy range 15.5-17.7 eV, indicating energy band dispersion. The onset of this bulk band-like behaviour could be determined from the cluster size dependence.

  • 24. Gerasimov, G. N.
    et al.
    Krylov, B. E.
    Stasel'Ko, D. I.
    Alekseev, I. V.
    Hallin, R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Arnesen, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Amplifying the VUV radiation of atomic nitrogen in helium, argon, krypton, and xenon2012In: Journal of optical technology (Print), ISSN 1070-9762, E-ISSN 1091-0786, Vol. 79, no 8, p. 462-469Article in journal (Refereed)
    Abstract [en]

    This paper discusses the spectral features of the amplification of narrow-band radiation of atomic nitrogen in the excimeric media of inert gases, including helium, argon, krypton, and xenon. Appreciable short-wavelength shifts (up to 0.026 nm) are detected in the spectra of the amplified radiation relative to the atomic emission lines of nitrogen that initiate this radiation. The observed shifts exceeded the instrumental resolution of the spectrometer that we used, were determined by the composition of the amplifying medium, and were independent of its excitation parameters under the experimental conditions. An explanation of the observed effect is proposed.

  • 25. Glawion, S.
    et al.
    Heidler, J.
    Haverkort, M. W.
    Duda, Laurent C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Schmitt, T.
    Strocov, V. N.
    Monney, C.
    Zhou, K.
    Ruff, A.
    Sing, M.
    Claessen, R.
    Two-Spinon and Orbital Excitations of the Spin-Peierls System TiOCl2011In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 107, no 10, p. 107402-Article in journal (Refereed)
    Abstract [en]

    We combine high-resolution resonant inelastic x-ray scattering with cluster calculations utilizing a recently derived effective magnetic scattering operator to analyze the polarization, excitation energy, and momentum-dependent excitation spectrum of the low-dimensional quantum magnet TiOCl in the range expected for orbital and magnetic excitations (0-2.5 eV). Ti 3d orbital excitations yield complete information on the temperature-dependent crystal-field splitting. In the spin-Peierls phase we observe a dispersive two-spinon excitation and estimate the inter- and intradimer magnetic exchange coupling from a comparison to cluster calculations.

  • 26.
    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.

  • 27. Guo, J. -H
    et al.
    Kastanov, S.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Glans, P. -A
    West, M.
    Learmonth, T.
    Chiou, J. -W
    Luo, Yi
    Nordgren, Joseph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Smith, K.
    Pong, W. -F
    Cheng, H.
    Griffiss, J. M.
    Electronic structure study of the bases in DNA duplexes by in situ photon-in/photon-out soft X-ray spectroscopy2010In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 181, no 2-3, p. 197-201Article in journal (Refereed)
    Abstract [en]

    Understanding protein functionality is of fundamental importance in biochemistry. Soft X-ray transitions, where the core-level vacancies are filled by the valence-orbital electrons, give direct information about the chemical bonding. Soft X-ray absorption and emission study of poly(dG) -poly(dC) in aqueous solutions can elucidate the relation between the structure and functionality of proteins. We report the N K-edge soft X-ray absorption (XAS) and resonant soft X-ray emission spectroscopy (XES) to characterize the electronic structure near the Fermi level of DNA duplexes to specify the charge migration mechanism. Since N atoms are included in only bases in DNA duplexes, the XES spectra excited from N Is to unoccupied states purely extract the electronic orbital features of the bases in DNA. The fact that N atoms in different bonding environments form well-defined structure has been determined. The experimental findings provide the evidence for the charge-hopping and/or charge-transfer effects in understanding of electric conduction in DNA duplexes when electrons pass through the pi* states of DNA bases. (C) 2010 Elsevier B.V. All rights reserved.

  • 28.
    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.

  • 29. Holland, D. M. P.
    et al.
    Potts, A. W.
    Karlsson, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Stener, M.
    Decleva, P.
    A study of the valence shell photoionisation dynamics of pyrimidine and pyrazine2011In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 390, no 1, p. 25-35Article in journal (Refereed)
    Abstract [en]

    The complete valence shell photoelectron spectra of pyrimidine and pyrazine have been recorded with synchrotron radiation and the observed structure has been interpreted with the aid of vertical ionisation energies and relative spectral intensities calculated using time-dependent density functional theory. The theoretical predictions for the single-hole ionic states due to outer valence shell ionisation agree satisfactorily with the experimental results. Ionisation from the inner valence orbitals is strongly influenced by many-body effects and the intensity associated with a particular orbital is spread amongst numerous satellites. Photoelectron angular distributions and partial cross sections have been determined both experimentally and theoretically, and demonstrate that shape resonances affect the valence shell photoionisation dynamics. In addition to shape resonances occurring a few eV above the ionisation threshold, the calculations indicate that many of the orbitals are influenced by shape resonant processes at much higher energies. Some of these higher energy resonances have been confirmed through a comparison between the relevant theoretical and experimental photoelectron asymmetry parameters. The spectral behaviour of asymmetry parameters associated with pi-orbitals has been shown to differ from that of asymmetry parameters associated with sigma-orbitals. These differences provide a means of distinguishing between the two types of orbitals even in heavily congested regions of the photoelectron spectrum suffering from band overlap.

  • 30.
    Hollmark, Håkan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Duda, Laurent-C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Resonant inelastic X-ray scattering and X-ray absorption spectroscopy on the cathode materials LiMnPO4 and LiMn0.9Fe0.1PO4: A comparative study2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 45, p. 20215-20222Article in journal (Refereed)
    Abstract [en]

    We present a study of the charge-state behavior of the Li-ion battery cathode materials LixMnPO4 and LixMn0.9Fe0.1PO4 usingx-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS). A set of six identical battery cathodesfor each material have been cycled and left in different charge states in the range of x=0.2...1.0 before disassembly in an Arglove box. Unexpectedly, we find that the Mn 3d-bands are almost inert to the delithiation process, suggesting that Mn ionsparticipate to a very small extent in the charge compensation process. In LixMn0.9Fe0.1PO4 the Fe 3d-band shows much moreresponse to delithiation than the Mn 3d-band. The O 2p-band hybridizes with the bands of the other ions in LixMnPO4 and LixMn0.9Fe0.1PO4 and thus, indirectly, carries useful information about the effects of delithiation at all ion sites. We conclude,that the redox reactions during lithiation/delithiation of these materials are complex and involve repopulation of charges for allconstituent elements.

  • 31.
    Hollmark, Håkan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Keech, Pete
    Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada.
    Vegelius, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Werme, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Duda, Laurent
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    X-ray absorption spectroscopy on electrochemically oxidized Cu exposed to Na2S2011In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 54, p. 85-89Article in journal (Refereed)
    Abstract [en]

    Copper surfaces have been investigated by X-ray absorption spectroscopy after electrochemical oxidation and subsequent exposure to sulfide solution. Oxide surface layers on bulk copper surfaces were electrochemically grown in anaqueous NaOH solution at two different potentials and the resulting chemical composition was investigated using X-ray absorption spectroscopy. At both potentials the resulting surfaces consisted largely of Cu2O. At the more strongly oxidizing potential, an admixture of Cu2+-containing phases – mostly Cu(OH)2 – was detected. Sulfide exposure of both surfaces was found to completely reduce the surface from Cu2+ to Cu1+ and resulted in the formation of Cu2S with an admixture of Cu2O.

  • 32.
    Hollmark, Håkan M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Duda, Laurent
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Dahbi, Mohammed
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Saadoune, Ismael
    LCME, University Cadi Ayyad, Marrakech, Morocco.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Resonant Soft X-Ray Emission Spectroscopy and X-Ray Absorption Spectroscopy on the Cathode Material LiNi0.65Co0.25Mn0.1O22010In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, no 8, p. A962-A966Article in journal (Refereed)
    Abstract [en]

    We present a study of the charge-state behavior of the Li-ion battery cathode material LixNi(0.65)Co(0.25)Mn(0.1)O(2) as observed by X-ray absorption spectroscopy (XAS) and resonant soft X-ray emission (RSXE). A set of six identical Li//LixNi0.65Co0.25Mn0.1O2 batteries has been cycled and is studied in different states of charge in the range of x = 1.0, ... ,0.2 before disassembly in an Ar glove box. Site and symmetry selective information about the electronic structure of the conduction and valence bands reveals that Ni as well as Co ions participate in the uptake and release of the extra electron charge that the inserted Li ions provide, but the Ni ion is much less than expected. The net amount of charge on the oxygen varies approximately 0.24 charge units in the range of x, and dramatic changes in the hybridization are evident in XAS and in particular in RSXE at the O K edge. We attribute this to a strong screening behavior of the Li ions between the oxide layers. Structural integrity effects limit the extraction of Li ions to a value of about x = 0.2-0.4. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3454739] All rights reserved.

  • 33.
    Hollmark, Håkan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Maher, Kenza
    ECME, FST Marrakech, University Cadi Ayyad, BP549, Av. A. Khattabi, Marrakech, Morocco.
    Saadoune, Ismael
    ECME, FST Marrakech, University Cadi Ayyad, BP549, Av. A. Khattabi, Marrakech, Morocco.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Duda, Laurent-C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Resonant inelastic X-ray scattering and X-ray absorption spectroscopy on the negative electrode material Li0.5Ni0.25TiOPO4 in a Li-ion battery2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 14, p. 6544-6551Article in journal (Refereed)
    Abstract [en]

    We have studied the first lithiation/delithiation cycle of the Li-ion battery electrode material LixNi0.25TiOPO4 applying X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). A set of ten identical LixNi0.25TiOPO4 battery electrodes have been cycled and left in different states of charge in the range of x = 0.5 … 2.5, before disassembly in an Ar filled glove box. We find that Ni-, Ti-, and O-ions are affected simultaneously, rather than sequentially, upon lithiation of the material. In particular, Ni is reduced from Ni2+ to Ni0 but only partially re-oxidized to Ni1+, again, by delithiation. Overall, there is considerable “crosstalk” between the different atomic species and non-linearity in the response of the electronic structure during the lithiation/delithiation process. Fortuitously, the background variation in Ni L-XAS shows to contain valuable information about solid–electrolyte interface (SEI) creation, showing that the SEI is a function of the degree of lithiation.