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  • 1.
    Agåker, Marcus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Käämbre, Tanel
    Glover, Chris
    Schmitt, Thorsten
    Mattesini, Maurizio
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Resonant inelastic soft x-ray scattering at double core excitations in solid LiCl2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 73, no 24, article id 245111Article in journal (Refereed)
    Abstract [en]

    Inelastic soft x-ray scattering in LiCl, resonantly enhanced at states with two Li 1s vacancies, is investigated. States in which both excited electrons are localized during the double core hole lifetime, in which one of the electrons delocalize, as well as triply excited states in which the double core excitation is accompanied by a valence-to-conduction band excitation, contribute to the scattering. The angular momentum symmetry of the involved states and the vibronic coupling during the scattering process are reflected in the angular anisotropy. The effect on the local electronic structure of multiple core holes is theoretically studied by means of supercell band calculations.

  • 2.
    Agåker, Marcus
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II. Physics IV.
    Söderström, Johan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II. Physics IV.
    Käämbre, Tanel
    Glover, C
    Gridneva, L
    Department of Physics and Materials Science, Physics II. Physics IV.
    Schmitt, Thorsten
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II. Physics IV.
    Augustsson, Andreas
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II. Physics IV.
    Mattesini, M
    Ahuja, Rajeev
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II. Physics IV.
    Rubensson, Jan-Erik
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II. Physics IV.
    Resonant inelastic soft X-ray scattering at hollow lithium states in solid LiCl2004In: Physical Review Letters, Vol. 93Article in journal (Refereed)
  • 3. Alagia, M
    et al.
    Coreno, M
    Farrokhpour, H
    Franceschi, P
    Mihelič, A
    Moise, A
    Omidyan, R
    Prince, K C
    Richter, R
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Stranges, S
    Tabrizchi, M
    Åœitnik, M
    Angular effects in autoionization of 3 P doubly excited states in He2009In: Journal of Physics: Conference Series, Vol. 194, no 2Article in journal (Refereed)
    Abstract [en]

    The first members of dipole allowed 3 P o doubly excited series in helium have been observed in resonant photoexcitation of 1 s 2 s 3 S e metastable atoms. A good agreement measured relative photoionization cross sections is achieved when theory includes the radiation damping and, also important, the effects of spin-orbit multiplet splitting on electron angular distribution.

  • 4. Alagia, M.
    et al.
    Coreno, M.
    Farrokhpour, H.
    Franceschi, P.
    Mihelič, A.
    Moise, A.
    Omidyan, R.
    Prince, K.C.
    Richter, R.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Stranges, S.
    Tabrizchi, M.
    Žitnik, M.
    Excitation of 1S and 3S Metastable Helium Atoms to Doubly Excited States2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, no 15, p. 153001-Article in journal (Refereed)
    Abstract [en]

    We present spectra of triplet and singlet metastable helium atoms resonantly photoexcited to doubly excited states. The first members of three dipole-allowed 1,3Po series have been observed and their relative photoionization cross sections determined, both in the triplet (from 1s2s 3Se) and singlet (from 1s2s 1Se) manifolds. The intensity ratios are drastically different with respect to transitions from the ground state. When radiation damping is included the results for the singlets are in agreement with theory, while for triplets spin-orbit interaction must also be taken into account.

  • 5. Alagia, M
    et al.
    Richter, R
    Stranges, S
    Agåker, Marcus
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II.
    Ström, Magnus
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II.
    Söderström, Johan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II.
    Såthe, Conny
    Department of Physics and Materials Science, Physics II.
    Feifel, Raimund
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II.
    Sorensen, Stacey
    de Fanis, A
    Ueda, K
    Fink, R
    Rubensson, Jan-Erik
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II.
    Core level ionization dynamics in small molecules studied by x-ray-emission threshold-electron coincidence spectroscopy2005In: Physical Review A, Vol. 71, no 1Article in journal (Refereed)
  • 6. 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.

  • 7. Ehara, M.
    et al.
    Tamaki, R.
    Nakatsuji, H.
    Lucchese, R. R.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Tanaka, T.
    Hoshino, M.
    Kitajima, M.
    Tanaka, H.
    Fanis, A. De
    Ueda, K.
    Vibrationally resolved nitrogen K-shell photoelectron spectra of the dinitrogen oxide molecule: Experiment and theory2007In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 438, no 1–3, p. 14-19Article in journal (Refereed)
  • 8. Guo, J. -H
    et al.
    Kastanov, S.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Glans, P. -A
    West, M.
    Learmonth, T.
    Chiou, J. -W
    Luo, Y.
    Nordgren, J.
    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)
  • 9.
    Jana, Somnath
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Terschlüsen, Joachim A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Stefanuik, Robert
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Plogmaker, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. MAX VI Lab, Lund, Sweden..
    Troisi, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Malik, Rameez S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Svanqvist, Mathias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Swedish Def Res Agcy, FOI, SE-14725 Tumba, Sweden..
    Knut, Ronny
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    A setup for element specific magnetization dynamics using the transverse magneto-optic Kerr effect in the energy range of 30-72 eV2017In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 88, no 3, article id 033113Article in journal (Refereed)
    Abstract [en]

    In this paper, we present a spectrometer that is designed for element-specific and time-resolved transverse magneto-optic Kerr effect experiments at the high-harmonic generation pump-probe facility High Energy Laser Induced Overtone Source (HELIOS) laboratory. HELIOS delivers photons with energies between 30 eV and 72 eV with an overall time resolution of less than 40 fs. The spectrometer is based on a Rowland-circle geometry and allows for simultaneous measurements of all magnetic transition-metal elements. The setup also features easy sample transfer and alignment, and it combines high photon throughput, optimized data acquisition, and a fast switching of the magnetic field at the sample. The spectrometer performance is demonstrated by measuring the ultrafast demagnetization of permalloy. Our data are, for all practical purposes, identical to what have been reported in the earlier high-order harmonic generation work of a similar sample by Mathias et al. [Proc. Natl. Acad. Sci. U.S.A. 109, 4792-4797 (2012)], however, obtained within 15% of the acquisition time compared to their study. Furthermore, our data show a shift of the demagnetization curve of Ni relative to Fe, which has previously been interpreted as a delay of the Ni demagnetization to that of Fe [S. Mathias et al., Proc. Natl. Acad. Sci. U. S. A. 109, 4792-4797 (2012)].

  • 10. Kimberg, V.
    et al.
    Lindblad, A.
    Söderström, J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Travnikova, O.
    Nicolas, C.
    Sun, Y. P.
    Gel’mukhanov, F.
    Kosugi, N.
    Miron, C.
    Single-Molecule X-Ray Interferometry: Controlling Coupled Electron-Nuclear Quantum Dynamics and Imaging Molecular Potentials by Ultrahigh-Resolution Resonant Photoemission and Ab Initio Calculations2013In: Physical Review X, ISSN 2160-3308, E-ISSN 2160-3308, Vol. 3, no 1, p. 011017-Article in journal (Refereed)
  • 11. Lindblad, A
    et al.
    Kimberg, V
    Söderström, J
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Nicolas, C
    Travnikova, O
    Kosugi, N
    Gel’mukhanov, F
    Miron, C
    Vibrational scattering anisotropy in O 2 - €”dynamics beyond the Born-Oppenheimer approximation2012In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 14, p. 113018-Article in journal (Refereed)
    Abstract [en]

    Born–Oppenheimer and Franck–Condon approximations are two major concepts in the interpretation of electronic excitations and modeling of spectroscopic data in the gas and condensed phases. We report large variations of the anisotropy parameter ( β ) for the fully resolved vibrational sub-states of the X 2 Π g electronic ground state of O + 2 populated by participator resonant Auger decay following excitations of K-shell electrons into the σ ☆ resonance by monochromatic x-rays. Decay spectra for light polarization directions parallel and perpendicular to the electron detection axis recorded at four different excitation energies in the vicinity of the O1s → σ ☆ transition are presented. Breakdown of the Born–Oppenheimer approximation is for the first time selectively observed for the lower vibrational sub-states, where two quantum paths—resonant and direct—leading to the same final cationic state exist. The higher vibrational sub-states can only be populated by resonant photoemission; hence no interference between these channels can occur.

  • 12. Lindblad, A.
    et al.
    Soderstrom, J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Nicolas, C.
    Robert, E.
    Miron, C.
    A multi purpose source chamber at the PLEIADES beamline at SOLEIL for spectroscopic studies of isolated species: Cold molecules, clusters, and nanoparticles2013In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 84, no 11, p. 113105 (11 pp.)-113105 (11 pp.)Article in journal (Refereed)
  • 13.
    Lindblad, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Kimberg, V.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Nicolas, C.
    Travnikova, O.
    Kosugi, N.
    Gel'mukhanov, F.
    Miron, C.
    Vibrational scattering anisotropy in O-2-dynamics beyond the Born-Oppenheimer approximation2012In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 14, p. 113018-Article in journal (Refereed)
    Abstract [en]

    Born-Oppenheimer and Franck-Condon approximations are two major concepts in the interpretation of electronic excitations and modeling of spectroscopic data in the gas and condensed phases. We report large variations of the anisotropy parameter (beta) for the fully resolved vibrational sub-states of the X-2 Pi(g) electronic ground state of O-2(+) populated by participator resonant Auger decay following excitations of K-shell electrons into the sigma(star) resonance by monochromatic x-rays. Decay spectra for light polarization directions parallel and perpendicular to the electron detection axis recorded at four different excitation energies in the vicinity of the O 1s -> sigma(star) transition are presented. Breakdown of the Born-Oppenheimer approximation is for the first time selectively observed for the lower vibrational sub-states, where two quantum paths-resonant and direct-leading to the same final cationic state exist. The higher vibrational sub-states can only be populated by resonant photoemission; hence no interference between these channels can occur.

  • 14. Lucchese, Robert
    et al.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Tanaka, Takahiro
    Hoshino, Masaki
    Kitajima, Masashi
    Tanaka, Hiroshi
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Ueda, Kiyoshi
    Vibrationally resolved partial cross sections and asymmetry parameters for nitrogen K-shell photoionization of the N2O molecule2007In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 76, no 1, p. 012506-Article in journal (Refereed)
    Abstract [en]

    We have measured the vibrationally resolved partial cross sections σ(v1,v2,v3) and asymmetry parameters β(v1,v2,v3) for Nc and Nt K-shell photoionization of the N2O molecule in the σ* shape resonance region above the Nt and Nc K-shell ionization thresholds. Nc K-shell photoionization of the N2O molecule predominantly causes the excitation of the quasisymmetric vibrations (v1), whereas Nt K-shell photoionization causes both quasisymmetric and quasiantisymmetric vibrations (v1 and v3) to be excited. The shape resonance energy in the Nc K-shell photoionization increases with an increase in v1. The β(v1,0,0) curves for the Nc K-shell photoionization exhibit maxima at energies close to the shape resonance energies for the individual values of v1. The shape resonance energy in the Nt K-shell photoionization decreases with an increase in v1 and slightly increases with an increase in v3. The β(v1,0,0) curves show a significant state dependence in the region of the shape resonance, with the curves shifting to lower energy as v1 increases. The vibrational state dependence of the cross sections σ(v1,v2,v3) and asymmetry parameters β(v1,v2,v3) are well reproduced by the theoretical calculations using the multichannel Schwinger configuration interaction (MCSCI) method, including both the Nc and Nt ion states.

  • 15.
    Martensson, Nils
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Soderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Svensson, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Travnikova, O.
    Patanen, M.
    Miron, C.
    Saethre, L. J.
    Borve, K. J.
    Thomas, T. D.
    Kas, J. J.
    Vila, F. D.
    Rehr, J. J.
    On the relation between X-ray Photoelectron Spectroscopy and XAFS2013In: 15th International Conference On X-Ray Absorption Fine Structure (XAFS15), 2013Conference paper (Refereed)
    Abstract [en]

    XAFS and X-ray Photoelectron Spectroscopy (XPS) are element specific techniques used in a great variety of research fields. The near edge regime of XAFS provides information on the unoccupied electronic states of a system. For the detailed interpretation of the XAFS results, input from XPS is crucial. The combination of the two techniques is also the basis for the so called core-hole clock technique. One of the important aspects of photoelectron spectroscopy is its chemical sensitivity and that one can obtain detailed information about the composition of a sample. We have for a series of carbon based model molecules carefully investigated the relationship between core level photoelectron intensities and stoichiometry. We find strong EXAFS-like modulations of the core ionization cross sections as function of photon energy and that the intensities at high photon energies converge towards values that do not correspond to the stoichiometric ratios. The photoelectron intensities are dependent on the local molecular structure around the ionized atoms. These effects are well described by molecular calculations using multiple scattering theory and by considering the effects due to monopole shake-up and shake-off as well as to intramolecular inelastic scattering processes.

  • 16.
    Ottosson, Niklas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Cwiklik, L.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Öhrwall, G.
    Jungwirth, P.
    Increased Propensity of I-aq(-) for the Water Surface in Non-neutral Solutions: Implications for the Interfacial Behavior of H3Oaq+ and OHaq-2011In: The Journal of Physical Chemistry Letters, ISSN 1948-7185, Vol. 2, no 9, p. 972-976Article in journal (Refereed)
    Abstract [en]

    By a combination of surface-sensitive photoelectron spectroscopy and molecular dynamics simulations, we characterize the surface propensity of the iodide anion in aqueous solutions at acidic, neutral, and basic conditions (pH = 1, 6.8 and 13). In both experiments and simulations, an increased surface concentration of I- is found in non-neutral solutions. We interpret these findings in terms of I- surface coadsorption with hydronium at low pH and "salting out" of iodide by hydroxide from the bulk solution to the surface at high pH. The present study is thus in accord with the picture of a weak surface adsorption of hydronium and surface depletion of hydroxide, being in sharp contradiction with the interpretation of electrophoretic and titration measurements in terms of strong surface enrichment of OH-.

  • 17.
    Ottosson, Niklas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Romanova, Anastasia O.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Öhrwall, Gunnar
    Fedorov, Maxim V.
    Molecular Sinkers: X-ray Photoemission and Atomistic Simulations of Benzoic Acid and Benzoate at the Aqueous Solution/Vapor Interface2012In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 116, no 43, p. 13017-13023Article in journal (Refereed)
    Abstract [en]

    In this work we, for the first time, provide a detailed microscopic picture of the behavior of benzoic acid at the aqueous solution/vapor interface in its neutral as well as in its dissociated form (benzoate). This is achieved through a combination of highly surface-sensitive X-ray photoelectron spectroscopy experiments and fully atomistic molecular simulations. We show that drastic changes occur in the interface behavior of the neutral acid upon release of the proton. The benzoic acid molecules are found to be strongly adsorbed in the interface layer with the planes of the aromatic rings oriented almost parallel to the water surface. In contrast, in the benzoate form the carboxylate group shows a sinker-like behavior while the aromatic ring acts as a buoy, oriented nearly perpendicular to the surface. Furthermore, a significant fraction of the molecular ions move from the interface layer into the bulk of the solution. We rationalize these findings in terms of the very different hydration properties of benzoic acid's carboxylic group in the two charge states. The molecule has an amphiphilic nature and the deprotonation thus changes the hydrophobic/hydrophilic balance between the nonpolar aromatic and the polar carboxylic parts of the molecule. That, consequently, leads to a pronounced reorientation of the molecule at the interface.

  • 18.
    Ottosson, Niklas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Wernersson, Erik
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Pokapanich, Wandared
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Kaufmann, Susanna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Svensson, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Persson, Ingmar
    Öhrwall, Gunnar
    Björnehom, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    The Protonation State of Small Carboxylic Acids at the Water Surface from Photoelectron Spectroscopy2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 26, p. 12261-12267Article in journal (Refereed)
    Abstract [en]

    We report highly surface sensitive core-level photoelectron spectra of small carboxylic acids (formic, acetic and butyric acid) and their respective carboxylate conjugate base forms (formate, acetate and butyrate) in aqueous solution. The relative surface affinity of the carboxylic acids and carboxylates is obtained by monitoring their respective C1s signal intensities from a solution in which their bulk concentrations are equal. All the acids are found to be enriched at the surface relative to the corresponding carboxylates. By monitoring the PE signals of acetic acid and acetate as a function of total concentration, we find that the protonation of acetic acid is nearly complete in the interface layer. This is in agreement with literature surface tension data, from which it is inferred that the acids are enriched at the surface while (sodium) formate and acetate, but not butyrate, are depleted. For butyric acid, we conclude that the carboxylate form co-exist with the acid in the interface layer. The free energy cost of replacing an adsorbed butyric acid molecule with a butyrate ion at 1.0 M concentration is estimated to be >2.2 kBT. By comparing concentration dependent surface excess data with the evolution of the corresponding photoemission signals it is furthermore possible to draw conclusions about how the distribution of molecules that contribute to the excess is altered with bulk concentration.

  • 19. Patanen, M.
    et al.
    Travnikova, O.
    Zahl, M. G.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Decleva, P.
    Thomas, T. D.
    Svensson, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Børve, K. J.
    Saethre, L. J.
    Miron, C.
    Laboratory-frame electron angular distributions: Probing the chemical environment through intramolecular electron scattering2013In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 87, no 6, p. 063420-Article in journal (Refereed)
    Abstract [en]

    Carbon 1s photoelectron asymmetry parameters beta for the chlorinated and the methyl carbon atom of CH3CH2Cl, CH3CHCl2, and CH3CCl3 have been measured using synchrotron radiation in the 340-600 eV energy range. We provide experimental evidence that the intramolecular scattering strongly affects beta values, even far from the ionization threshold. The results are in agreement with B-spline density functional theory calculations, making it possible to single out the behavior of the various continuum partial waves. We conclude that the intramolecular scattering makes electron angular distributions sensitive to the chemical environment, even in isolated gas phase molecules.

  • 20.
    Plogmaker, Stefan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Terschlüsen, Joachim A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Kerbs, N.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Svanqvist, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Forsberg, J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Cappel, Ute B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    HELIOS-A laboratory based on high-order harmonic generation of extreme ultraviolet photons for time-resolved spectroscopy2015In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 86, no 12, article id 123107Article in journal (Refereed)
    Abstract [en]

    In this paper, we present the HELIOS (High Energy Laser Induced Overtone Source) laboratory, an in-house high-order harmonic generation facility which generates extreme ultraviolet (XUV) photon pulses in the range of 15-70 eV with monochromatized XUV pulse lengths below 35 fs. HELIOS is a source for time-resolved pump-probe/two-color spectroscopy in the sub-50 fs range, which can be operated at 5 kHz or 10 kHz. An optical parametric amplifier is available for pump-probe experiments with wavelengths ranging from 240 nm to 20 000 nm. The produced XUV radiation is monochromatized by a grating in the so-called off-plane mount. Together with overall design parameters, first monochromatized spectra are shown with an intensity of 2 . 10(10) photons/s (at 5 kHz) in the 29th harmonic, after the monochromator. The XUV pulse duration is measured to be <25 fs after monochromatization.

  • 21.
    Pokapanich, Wandared
    et al.
    Division of Physics, Faculty of Science, Nakhon Phanom University.
    Ottosson, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Öhrwall, Gunnar
    MAX-lab, Lund UniVersity.
    No signature of contact ion pairs in the K 2p Auger spectra of highlyconcentrated potassium halide solutions2014In: ScienceAsia, ISSN 1513-1874, Vol. 40, no 4, p. 290-294Article in journal (Refereed)
    Abstract [en]

    Possible ion pair formation in highly concentrated aqueous potassium halide solutions (fluoride,chloride, and bromide) has been investigated by applied Auger electron spectroscopy. The potassiumAuger spectra exhibit features at high kinetic energy, which are related to final states withvacancies on the potassium ion and a neighboring water molecule. The potassium ion could possiblyassociate with a halide ion as well, giving rise to additional final states with a vacancy onthe halide instead of a water molecule which should give rise to separable spectral features. Thenecessity of close proximity of the ions for such decays to occur would be strong evidence thatcontact ions pairs are present in the solution, but no features related to final states involving theanion could be observed in this work.

  • 22. Prisle, N. L.
    et al.
    Ottosson, N.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Ohrwall, G.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Dal Maso, M.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Surface/bulk partitioning and acid/base speciation of aqueous decanoate: direct observations and atmospheric implications2012In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 12, no 24, p. 12227-12242Article in journal (Refereed)
    Abstract [en]

    Dilute aqueous solutions of the atmospheric organic surfactant sodium decanoate have been studied using surface sensitive X-ray photoelectron spectroscopy combined with synchrotron radiation. We studied the decanoate/decanoic acid speciation and preferential adsorption at the vapor-liquid interface, and the responses to mixing in solution with some of the most common atmospheric inorganic ions, Na+, NH4+, Cl-, and SO42-. We observe little or no influence of Na+, Cl-, or SO42- ions, on neither the relative speciation nor the individual adsorption properties of decanoate and decanoic acid. In particular, no significant salting-out effect due to common Na+ cations of the organic and inorganic salts was observed for these solutions. On the other hand, mixing with NH4+ cations resulted in a pronounced surface enhancement of decanoic acid, which is attributed to surface specific acid-base chemistry. These changes in surface/bulk partitioning and surface speciation may significantly affect properties of aqueous droplets containing decanoate/decanoic acid, and potential implications for several processes critical to the climate effects of atmospheric aerosols are discussed.

  • 23.
    Rubensson, Jan-Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Binggeli, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Gråsjö, Johan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Andersson, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Sathe, C.
    Hennies, F.
    Bisogni, V.
    Huang, Y.
    Olalde, P.
    Schmitt, T.
    Strocov, V. N.
    Fohlisch, A.
    Kennedy, B.
    Pietzsch, A.
    Rydberg-Resolved Resonant Inelastic Soft X-Ray Scattering: Dynamics at Core Ionization Thresholds2015In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 114, no 13, article id 133001Article in journal (Refereed)
    Abstract [en]

    Resonant inelastic x-ray scattering spectra excited in the immediate vicinity of the core-level ionization thresholds of N-2 have been recorded. Final states of well-resolved symmetry-selected Rydberg series converging to valence-level ionization thresholds with vibrational excitations are observed. The results are well described by a quasi-two-step model which assumes that the excited electron is unaffected by the radiative decay. This threshold dynamics simplifies the interpretation of resonant inelastic x-ray scattering spectra considerably and facilitates characterization of low-energy excited final states in molecular systems.

  • 24.
    Stefanuik, Robert
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Knut, Ronny
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Jana, Somnath
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Terschlüsen, Joachim A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Developments and enhancements to the HELIOS pump probe system2018In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 224, p. 33-37Article in journal (Refereed)
    Abstract [en]

    In this progress report we describe several design improvements that have been implemented at the HELIOS laboratory, as well as presenting the output characteristics that have been measured as a result. The main focus will be on the redesign of the gas cell, which has enhanced the photon flux of the XUV probe beam. Also, a frequency trippler utilizing sum frequency generation has been installed at the end of the pump line, which increases the photon flux available for both 3.1 eV (400 nm) and 4.66 eV (266 nm) applications without significant increment in the pulse width of the pump.

  • 25.
    Ström, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Såthe, Conny
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Agåker, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Stranges, Stefano
    Richter, Robert
    Alagia, Michele
    Gorczyca, Tom
    Robicheaux, Francis
    Magnetic-field induced enhancement in the fluorescence yield spectrum of doubly excited states in helium2006In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 97, no 25, p. 253002-Article in journal (Refereed)
    Abstract [en]

    An influence of static magnetic fields on the fluorescence yield spectrum of He in the vicinity of the N=2 thresholds has been observed. The experimental results are in excellent agreement with predictions based on multichannel quantum defect theory, and it is demonstrated that the Rydberg electron ℓ mixing due to the diamagnetic interaction is essential for the description of the observed fluorescence yield intensity enhancement.

  • 26.
    Såthe, Conny
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II.
    Ström, Magnus
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II.
    Agåker, Marcus
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II.
    Söderström, Johan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II.
    Rubensson, Jan-Erik
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II.
    Richter, R
    Alagia, M
    Stranges, S
    Gorczyca, T W
    Robicheaux, F
    Double excitations of helium in weak static electric fields2006In: Physical Review Letters, Vol. 96, no 4Article in journal (Refereed)
  • 27.
    Söderström, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Agåker, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Richter, Robert
    Alagia, Michele
    Stranges, Stefano
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Oxygen K Edge X-ray-Emission-Threshold-Electron Coincidence Spectrum of CO22007In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 76, no 2, p. 022505-Article in journal (Refereed)
    Abstract [en]

    The oxygen K -edge x-ray-emission-threshold-electron coincidence spectrum of CO2 is presented. A two-step model, describing the result as a threshold-photoelectron spectrum free from post-collision interaction effects, predicts the salient features of the measured spectrum. Small discrepancies from the predictions are discussed in terms of threshold ionization dynamics.

  • 28.
    Söderström, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Agåker, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Zimina, Anna
    Feifel, Raimund
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Eisebitt, Stefan
    Follath, Rolf
    Reichardt, Gerd
    Schwarzkopf, Olaf
    Eberhardt, Wolfgang
    Mihelic, Andrej
    Zitnik, Matjaz
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Radiative decay spectra of selected doubly excited states in helium2008In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 77, no 1, p. 012513-Article in journal (Refereed)
    Abstract [en]

    Radiative decay spectra of doubly excited states in He have been measured after selective excitation with monochromatized synchrotron radiation. The decay spectra are in excellent agreement with predictions based on calculations.

  • 29.
    Söderström, Johan
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics II.
    Alagia, M
    Richter, R
    Stranges, S
    Agåker, Marcus
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics II.
    Ström, Magnus
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics II.
    Sorensen, Stacey
    Rubensson, Jan-Erik
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Physics II.
    X-ray-emission-threshold-electron coincidence spectroscopy2004In: Journal of Electron Spectroscopy and Related Phenomena, Vol. 141, no 2-3, p. 161-170Article in journal (Refereed)
  • 30.
    Söderström, Johan
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Gråsjö, Johan
    Medicinska vetenskapsområdet, Faculty of Pharmacy, Department of Pharmacy.
    Kashtanov, S
    Bergström, Christel
    Medicinska vetenskapsområdet, Faculty of Pharmacy, Department of Pharmacy.
    Agåker, Marcus
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Schmitt, Thorsten
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Augustsson, Andreas
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Duda, Laurent
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Guo, Jinghua
    Nordgren, Joseph
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Luo, Yi
    Artursson, Per
    Medicinska vetenskapsområdet, Faculty of Pharmacy, Department of Pharmacy.
    Rubensson, Jan-Erik
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    X-ray yield and selectively excited X-ray emission spectra of atenolol and nadolol.2005In: J Electr Spectr, Vol. 144-147, p. 283-285Article in journal (Refereed)
  • 31.
    Söderström, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Grum-Grzhimailo, Alexei N.
    Travnikova, Oksana
    Nicolas, Christophe
    Svensson, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Miron, Catalin
    Angle-resolved electron spectroscopy of the resonant Auger decay in xenon with meV energy resolution2011In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 13, p. 073014-Article in journal (Refereed)
    Abstract [en]

    The angle-resolved resonant Auger spectrum of Xe is investigated with a record high meV energy resolution in the kinetic energy region of 34.45-39.20 eV at hv = 65.110 eV, corresponding to the resonant excitation of the Auger Xe* 4d(5/2)(-1)6p state. New lines have been observed and assigned in the spectra. The results of previous measurements concerning energies, intensities and angular distribution asymmetry parameters have been refined, complemented and, for some of the lines, corrected.

  • 32.
    Söderström, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Travnikova, O.
    Patanen, M.
    Miron, C.
    Saethre, L. J.
    Borve, K. J.
    Rehr, J. J.
    Kas, J. J.
    Vila, F. D.
    Thomas, T. D.
    Svensson, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Nonstoichiometric Intensities in Core Photoelectron Spectroscopy2012In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 108, no 19, p. 193005-Article in journal (Refereed)
    Abstract [en]

    X-ray photoemission spectroscopy is used in a great variety of research fields; one observable is the sample's stoichiometry. The stoichiometry can be deduced based on the expectation that the ionization cross sections for innershell orbitals are independent of the molecular composition. Here we used chlorine-substituted ethanes in the gas phase to investigate the apparent carbon stoichiometry. We observe a nonstoichiometric ratio for a wide range of photon energies, the ratio exhibits x-ray-absorption fine structure spectroscopy (EXAFS)-like oscillations and hundreds of eV above the C1s ionization approaches a value far from 1. These effects can be accounted for by considering the scattering of the outgoing photoelectron, which we model by multiple-scattering EXAFS calculations, and by considering the effects of losses due to monopole shakeup and shakeoff and to intramolecular inelastic scattering processes.

  • 33.
    Söderström, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Ottosson, Niklas
    Pokapanich, Wandared
    Öhrwall, Gunnar
    Björneholm, Olle
    Functionalized nanoparticles in aqueous surroundings probed by X-ray photoelectron spectroscopy2011In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 184, no 7, p. 375-378Article in journal (Refereed)
  • 34.
    Söderström, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Ottosson, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Pokapanich, Wandared
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Öhrwall, Gunnar
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Functionalized nanoparticles in aqueous surroundings probed by X-ray photoelectron spectroscopy2011In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 184, no 7, p. 375-378Article in journal (Refereed)
    Abstract [en]

    In this paper we present the first core-level photoelectron spectroscopic study of solid nanoparticles in liquid water. The particles are SiO(2)-based with an average diameter of 70 nm and functionalized with carboxylic groups. Despite that the sample is very dilute, we show that it is possible to obtain reasonable photoemission signal containing chemical information about both the ligands and the outermost parts of the SiO(2)-based core of the nanoparticles. We argue that this is due to a significant enrichment of the dispersed particles at the liquid/vapor interface. This proof-of-principle study expands the field of X-ray photoelectron spectroscopy by adding a new, wide and important class of systems that can be studied.

  • 35. Travnikova, Oksana
    et al.
    Borve, Knut J.
    Patanen, Minna
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Miron, Catalin
    Saethre, Leif J.
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Svensson, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    The ESCA molecule-Historical remarks and new results2012In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 185, no 8-9, p. 191-197Article in journal (Refereed)
    Abstract [en]

    The C is photoelectron spectrum of ethyl trifluoroacetate (CF3-CO-O-CH2-CH3), also known as the 'ESCA molecule', is the most illustrative showcase of chemical shifts in photoelectron spectroscopy. The binding energies of the four carbon atoms of this molecule spread over more than 8 eV with energy separations ranging from 1.7 to 3.1 eV owing to different chemical environments and hence different charge states of these atoms. The paper discusses history and importance of this spectrum in the field of photoelectron spectroscopy starting from the time of invention of the ESCA technique. The main focus of the paper is a 'revisit' of this spectrum using the most modern experimental and computational tools. Large geometrical changes, different for each ionization site, and the presence of two conformers of ethyl trifluoroacetate influence the spectral lineshapes of all four C 1s lines. These effects are carefully modeled by theory and investigated in the experimental spectrum.

  • 36. Travnikova, Oksana
    et al.
    Liu, Ji-Cai
    Lindblad, Andreas
    Nicolas, Christophe
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Kimberg, Victor
    Gel’mukhanov, Faris
    Miron, Catalin
    Circularly Polarized X Rays: Another Probe of Ultrafast Molecular Decay Dynamics2010In: Phys. Rev. Lett., Vol. 105, no 23Article in journal (Refereed)
  • 37. Tremsin, A. S.
    et al.
    Siegmund, O. H. W.
    Hull, J. S.
    Vallerga, J. V.
    McPhate, J. B.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Chiou, J. W.
    Guo, J.
    Hussain, Z.
    High Resolution Photon Counting Detection System for Advanced Inelastic X-Ray Scattering Studies2006In: 2006 IEEE Nuclear Science Symposium Conference Record, 2006, Vol. 2, p. 735-739Conference paper (Refereed)
  • 38.
    Werner, Josephina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Wernersson, Erik
    Ekholm, Victor
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Ottosson, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Ohrwall, Gunnar
    Heyda, Jan
    Persson, Ingmar
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Jungwirth, Pavel
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Surface Behavior of Hydrated Guanidinium and Ammonium Ions: A Comparative Study by Photoelectron Spectroscopy and Molecular Dynamics2014In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 118, no 25, p. 7119-7127Article in journal (Refereed)
    Abstract [en]

    Through the combination of surface sensitive photoelectron spectroscopy and molecular dynamics simulation, the relative surface propensities of guanidinium and ammonium ions in aqueous solution are characterized. The fact that the N Is binding energies differ between these two species was exploited to monitor their relative surface concentration through their respective photoemission intensities. Aqueous solutions of ammonium and guanidinium chloride, and mixtures of these salts, have been studied in a wide concentration range, and it is found that the guanidinium ion has a greater propensity to reside at the aqueous surface than the ammonium ion. A large portion of the relative excess of guanidinium ions in the surface region of the mixed solutions can be explained by replacement of ammonium ions by guanidinium ions in the surface region in combination with a strong salting-out effect of guanidinium by ammonium ions at increased concentrations. This interpretation is supported by molecular dynamics simulations, which reproduce the experimental trends very well. The simulations suggest that the relatively higher surface propensity of guanidinium compared with ammonium ions is due to the ease of dehydration of the faces of the almost planar guanidinium ion, which allows it to approach the water-vapor interface oriented parallel to it.

1 - 38 of 38
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