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  • 1. Aartsen, M. G.
    et al.
    Botner, Olga
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Burgman, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Hallgren, Allan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Pérez de los Heros, Carlos
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Zoecklein, M.
    Efficient propagation of systematic uncertainties from calibration to analysis with the SnowStorm method in IceCube2019In: Journal of Cosmology and Astroparticle Physics, E-ISSN 1475-7516, no 10, article id 048Article in journal (Refereed)
    Abstract [en]

    Efficient treatment of systematic uncertainties that depend on a large number of nuisance parameters is a persistent difficulty in particle physics and astrophysics experiments. Where low-level effects are not amenable to simple parameterization or re-weighting, analyses often rely on discrete simulation sets to quantify the effects of nuisance parameters on key analysis observables. Such methods may become computationally untenable for analyses requiring high statistics Monte Carlo with a large number of nuisance degrees of freedom, especially in cases where these degrees of freedom parameterize the shape of a continuous distribution. In this paper we present a method for treating systematic uncertainties in a computationally efficient and comprehensive manner using a single simulation set with multiple and continuously varied nuisance parameters. This method is demonstrated for the case of the depth-dependent effective dust distribution within the IceCube Neutrino Telescope.

  • 2.
    Gopakumar, Geethanjali
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Muchova, E
    Department of Physical Chemistry, University of Chemistry and Technology, Technick ́a 5, Prague 6, 166 28, Czech Republic.
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Center for Free-Electron Laser Science, DESY, Notkestrasse 85, DE-22607 Hamburg, Germany.
    Malerz, S
    Molecular Physics Department, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany.
    Trinter, F
    Molecular Physics Department, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany.
    Öhrwall, G
    MAX IV Laboratory, Lund University, Box 118, SE-22100 Lund, Sweden.
    Lipparini, F
    Department of Chemistry and Industrial Chemistry, University of Pisa, Via Giuseppe Moruzzi 13, 56124 Pisa, Italy.
    Menucci, B
    Department of Chemistry and Industrial Chemistry, University of Pisa, Via Giuseppe Moruzzi 13, 56124 Pisa, Italy.
    Ceolin, D
    Synchrotron SOLEIL, L’Orme des Merisiers Saint-Aubin, BP 48 91192 Gif-sur-Yvette Cedex, Paris, France.
    Caleman, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Center for Free-Electron Laser Science, DESY, Notkestrasse 85, DE-22607 Hamburg, Germany.
    Wilkinson, I
    Department of Locally-Sensitive Time-Resolved Spectroscopy, Helmholtz-Zentrum Berlin fur Materialien und Energie, 14109 Berlin, Germany.
    Winter, B
    Molecular Physics Department, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany.
    Slavicek, P
    Department of Physical Chemistry, University of Chemistry and Technology, Technick ́a 5, Prague 6, 166 28, Czech Republic.
    Hergenhahn, U
    Molecular Physics Department, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Probing Aqueous Ions with Non-local Auger Relaxation2022In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 24, no 15, p. 8661-8671Article in journal (Refereed)
    Abstract [en]

    The decay of core holes is often regarded as a local process, but in some systems, it involves the autoionization of neighbouring atoms or molecules. Here, we explore such non-local autoionization (Intermolecular Coulombic Decay, ICD) of surrounding molecules upon 1s ionization of aqueous-phase Na+, Mg2+ and Al3+ ions. The three ions are isoelectronic but differ in the strength of the ion-water interactions which is manifested in experimental Auger electron spectra by varying intensities. While for strongly interacting Mg2+ and Al3+ the non-local decay is observed, for weakly bound Na+ no signal was measured. Combined with theoretical simulations we provide a microscopic understanding of the non-local decay processes. We assigned the ICD to decay processes ending with two-hole states delocalized between the central ion and neighbouring water. The ICD process is also shown to be highly selective with respect to water molecular orbitals. The ICD lifetime was estimated to be around 40 fs for Mg and 20 fs for Al. Auger spectroscopy thus represents a novel tool for exploring molecules in the liquid phase, providing simultaneously structural and electronic information.   

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  • 3.
    Gopakumar, Geethanjali
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Svensson, Pamela
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Grånäs, Oscar
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Schwob, Lucas
    Deutsch Elektronen Synchrotron DESY, DE-22607 Hamburg, Germany..
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Saak, Clara-Magdalena
    Univ Vienna, Dept Phys Chem, A-1090 Vienna, Austria..
    Timm, Martin
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, DE-12489 Berlin, Germany.;Tech Univ Berlin, Inst Opt & Atomare Phys, DE-10623 Berlin, Germany..
    Buelow, Christine
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, DE-12489 Berlin, Germany.;Albert Ludwigs Univ Freiburg, Phys Inst, DE-79104 Freiburg, Germany..
    Kubin, Markus
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, DE-12489 Berlin, Germany..
    Zamudio-Bayer, Vicente
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, DE-12489 Berlin, Germany..
    Lau, J. Tobias
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, DE-12489 Berlin, Germany.;Albert Ludwigs Univ Freiburg, Phys Inst, DE-79104 Freiburg, Germany..
    von Issendorff, Bernd
    Albert Ludwigs Univ Freiburg, Phys Inst, DE-79104 Freiburg, Germany..
    Abid, Abdul Rahman
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Univ Oulu, Fac Sci, Nano & Mol Syst Res Unit, Oulu 90570, Finland..
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Danielsson, Emma
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Koerfer, Ebba
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Caleman, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Deutsch Elektronen Synchrotron DESY, Ctr Free Electron Laser Sci, DE-22607 Hamburg, Germany..
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, DE-12489 Berlin, Germany.;Lund Univ, Dept Phys, SE-22100 Lund, Sweden.;Uppsala Univ, Dept Chem, Angstrom Lab, SE-75121 Uppsala, Sweden..
    X-ray Induced Fragmentation of Protonated Cystine2022In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 126, no 9, p. 1496-1503Article in journal (Refereed)
    Abstract [en]

    We demonstrate site-specific X-ray induced fragmentation across the sulfur L-edge of protonated cystine, the dimer of the amino acid cysteine. Ion yield NEXAFS were performed in the gas phase using electrospray ionization (ESI) in combination with an ion trap. The interpretation of the sulfur Ledge NEXAFS spectrum is supported by Restricted Open-Shell Configuration Interaction (ROCIS) calculations. The fragmentation pathway of triply charged cystine ions was modeled by Molecular Dynamics (MD) simulations. We have deduced a possible pathway of fragmentation upon excitation and ionization of S 2p electrons. The disulfide bridge breaks for resonant excitation at lower photon energies but remains intact upon higher energy resonant excitation and upon ionization of S 2p. The larger fragments initially formed subsequently break into smaller fragments.

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  • 4.
    Gopakumar, Geethanjali
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Svensson, Pamela H.W.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Grånäs, Oscar
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Schwob, L
    Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, DE-22607 Hamburg, Germany.
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Saak, Clara-Magdalena
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Timm, M
    Abteilung für Hochempfindliche Röntgenspektroskopie, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, DE-12489 Berlin, Germany; nstitut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstrasse 36, DE-10623 Berlin, Germany.
    Bülow, C
    Abteilung für Hochempfindliche Röntgenspektroskopie, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, DE-12489 Berlin, Germany; Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Strasse 3, DE-79104 Freiburg, Germany.
    Kubin, M
    Abteilung für Hochempfindliche Röntgenspektroskopie, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, DE-12489 Berlin, Germany.
    Zamudio-Bayer, V
    Abteilung für Hochempfindliche Röntgenspektroskopie, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, DE-12489 Berlin, Germany.
    Lau, J-T
    Abteilung für Hochempfindliche Röntgenspektroskopie, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, DE-12489 Berlin, Germany; Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Strasse 3, DE-79104 Freiburg, Germany.
    von Issendorff, B
    Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Strasse 3, DE-79104 Freiburg, Germany.
    Abid, Abdul Rahman
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics. Nano and Molecular Systems Research Unit, Faculty of Science, University of Oulu, P. O. Box 3000, Finland.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Danielsson, E
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Koerfer, E
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Caleman, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics. Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, DE-22607 Hamburg, Germany.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Department of Physics, Lund University, Box 118, SE-22100 Lund, Sweden; Abteilung für Hochempfindliche Röntgenspektroskopie, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, DE-12489 Berlin, Germany.
    X-ray Induced Fragmentation of Protonated CystineManuscript (preprint) (Other academic)
    Abstract [en]

    Protein structure determination using high-intensity X-ray sources induces damage in the protein. Disulfide bridges, formed between two cysteine amino acid residues stabilize the protein structure. Owing to the higher absorption cross-section of sulfur for X-ray photons, and a large number of electrons released from sulfur atoms, these disulfide bridges are hot spots for a higher level of noise in structural studies. But it is yet to be understood how exactly the damage occurs through the interaction of the disulfide bridges with photons. Here we study the fragmentation of protonated cystine in the gas phase, which is the dimer of cysteine, by irradiation with X-rays across the sulfur L-edge using an electrospray ionization source (ESI) in combination with an ion trap. This is complemented with the calculation of the sulfur NEXAFS spectrum on the level of Restricted Open-Shell Configuration Interaction (ROCIS) and Density Functional Theory (DFT) calculations for molecular orbital visualization as well as Molecular Dynamics (MD) simulations for the fragmentation of triply charged cystine ions. We have deduced a possible pathway of fragmentation upon excitation and ionization of S 2p electrons by combining the experiments and simulations. The disulfide bridge breaks for resonant excitation at lower energies but remains intact upon higher energy resonant excitation and upon ionization of S 2p. The larger fragments formed subsequently break into smaller fragments. 

  • 5.
    Gopakumar, Geethanjali
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Saak, Clara-Magdalena
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Öhrwall, Gunnar
    MAX IV Laboratory, Lund University, PO Box 118, SE-22100 Lund, Sweden.
    Naves de Brito, Arnaldo
    University of Campinas, Campinas, SP, Brazil.
    Costa Rizuti da Rocha, Tulio
    Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM), Sao Paulo, Brazil.
    Nicolas, Christophe
    Synchrotron SOLEIL, Gif-sur-Yvette, France.
    Caleman, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics. Center for Free-Electron Laser Science, DESY, Notkestrasse 85, DE-22607 Hamburg, Germany.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    The Surface Composition of Amino Acid - Halide Salt Solutions is pH-Dependent2022In: Environmental Science: Atmospheres, no 3Article in journal (Refereed)
    Abstract [en]

    In atmospheric aerosol particles, the chemical surface composition governs both heterogeneous chemical reactions with gas-phase species and the ability to act as nuclei for cloud droplets. The pH in aerosol droplets is expected to affect these properties, but it is very challenging to measure the pH in individual droplets, precluding the investigation of its influence on the particle's surface composition. In this work, we use photoelectron spectroscopy to explore how the surface composition of aqueous solutions containing inorganic salt and amino acids changes as a function of pH. We observe a change by a factor of 4-5 of the relative distribution of inorganic ions at the surface of a liquid water jet, as a function of solution pH and type of amino acid in the solution. The driving forces for the surface enhancement or depletion are ion pairing and the formation of charged layers close to the aqueous surface. Our findings apply to any aqueous interface at which organic species with charged functional groups are present.

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  • 6. Gopakumar, Geethanjali
    et al.
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics. Center for Free-Electron Laser Science, DESY, Notkestrasse 85, DE-22607 Hamburg, Germany.
    Öhrwall, G
    MAX IV Laboratory, Fotongatan 2, 221 00 Lund, Sweden.
    Malerz, S
    Molecular Physics Department, Fritz Haber Institute of the Max Planck Society, Faradayweg 4, 14195 Berlin, Germany.
    Ceolin, D
    Trinter, F
    Molecular Physics Department, Fritz Haber Institute of the Max Planck Society, Faradayweg 4, 14195 Berlin, Germany.
    Chatzigeorgiou, Evanthia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Winter, B
    Molecular Physics Department, Fritz Haber Institute of the Max Planck Society, Faradayweg 4, 14195 Berlin, Germany.
    Caleman, Carl
    Center for Free-Electron Laser Science, DESY, Notkestrasse 85, DE-22607 Hamburg, Germany.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    X-ray-induced attosecond ion-water electron dynamics of aqueous ionsManuscript (preprint) (Other academic)
    Abstract [en]

    The foundation of many physical and chemical processes is the transfer of charge from one entity to another. In many cases, the charge transfer is mediated by electron transfer and due to the comparatively low mass of electrons, these processes tend to take place within a few femtoseconds or several attoseconds. We investigate the charge transfer from Na+, Mg2+ and Al3+ in an aqueous environment to neighbouring water molecules. In order to achieve this, we use the core-hole clock method and Auger spectroscopy upon 1s ionization of the respective ions. The charge transfer times range from several 100 as below the 1s ionization threshold to only 20 as far above the 1s ionization. The decrease in charge transfer times as a function of the photon energy seems to be continuous. Despite the ions being isoelectronic in our study, we nd differences in their charge transfer behaviour.

  • 7.
    Gopakumar, Geethanjali
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics. Center for Free-Electron Laser Science, DESY, Notkestrasse 85, DE-22607 Hamburg, Germany.
    Öhrwall, I
    MAX IV Laboratory, Fotongatan 2, 221 00 Lund, Sweden.
    Malerz, S
    olecular Physics Department, Fritz Haber Institute of the Max Planck Society, Faradayweg 4, 14195 Berlin, Germany.
    Ceolin, D
    Synchrotron SOLEIL, L’Orme des Merisiers Saint-Aubin, BP 48 91192 Gif-sur-Yvette Cedex, Paris, France.
    Trinter, F
    olecular Physics Department, Fritz Haber Institute of the Max Planck Society, Faradayweg 4, 14195 Berlin, Germany.
    Winter, B
    olecular Physics Department, Fritz Haber Institute of the Max Planck Society, Faradayweg 4, 14195 Berlin, Germany.
    Caleman, Carl
    Center for Free-Electron Laser Science, DESY, Notkestrasse 85, DE-22607 Hamburg, German.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Non-local decay of highly charged aqueous inorganic ions produced by Auger decayManuscript (preprint) (Other academic)
    Abstract [en]

    High-Z atoms are more important for biological radiation damage by photons than their low abundance due to their higher photoionization cross-section. Using the inorganic Mg 2+ and Al3+ ions in water as model systems, we have studied decay processes following deep core-level ionization. Local Auger decay rapidly produces highly charged Mg 4+and Al5+ ions, the decay of which must involve non-local processes involving the surrounding water, such as electron transfer mediated decay (ETMD). Using electron spectroscopy we observe two distinct ETMD decay steps for Al, corresponding to decay from Al5+ to Al4+, and then from Al4+ to Al3+. The ETMD energetics is discussed using both a simple model and calculations. Contrary to expectations, we do not observe any ETMD for Mg, and possible reasons for this are discussed.

  • 8.
    Hans, Andreas
    et al.
    Univ Kassel, Inst Phys, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Univ Kassel, CINSaT, Heinrich Plett Str 40, D-34132 Kassel, Germany.
    Ozga, Christian
    Univ Kassel, Inst Phys, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Univ Kassel, CINSaT, Heinrich Plett Str 40, D-34132 Kassel, Germany.
    Seidel, Robert
    Helmholtz Zentrum Berlin Mat & Energie Methods Ma, Albert Einstein Str 15, D-12489 Berlin, Germany.
    Schmidt, Philipp
    Univ Kassel, Inst Phys, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Univ Kassel, CINSaT, Heinrich Plett Str 40, D-34132 Kassel, Germany.
    Ueltzhoeffer, Timo
    Univ Kassel, Inst Phys, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Univ Kassel, CINSaT, Heinrich Plett Str 40, D-34132 Kassel, Germany.
    Holzapfel, Xaver
    Univ Kassel, Inst Phys, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Univ Kassel, CINSaT, Heinrich Plett Str 40, D-34132 Kassel, Germany.
    Pohl, Marvin N.
    Fritz Haber Inst, Dept Mol Phys, D-14195 Berlin, Germany.
    Wenzel, Philip
    Univ Kassel, Inst Phys, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Univ Kassel, CINSaT, Heinrich Plett Str 40, D-34132 Kassel, Germany.
    Reiss, Philipp
    Univ Kassel, Inst Phys, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Univ Kassel, CINSaT, Heinrich Plett Str 40, D-34132 Kassel, Germany.
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Aziz, Emad F.
    Helmholtz Zentrum Berlin Mat & Energie Methods Ma, Albert Einstein Str 15, D-12489 Berlin, Germany.
    Ehresmann, Arno
    Univ Kassel, Inst Phys, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Univ Kassel, CINSaT, Heinrich Plett Str 40, D-34132 Kassel, Germany.
    Slavicek, Petr
    Univ Chem & Technol, Dept Phys Chem, Tech 5, Prague 16628, Czech Republic.
    Winter, Bernd
    Fritz Haber Inst, Dept Mol Phys, D-14195 Berlin, Germany.
    Knie, Andre
    Univ Kassel, Inst Phys, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Univ Kassel, CINSaT, Heinrich Plett Str 40, D-34132 Kassel, Germany.
    Soft X-ray induced ultraviolet fluorescence emission from bulk and interface of a liquid water microjet2017In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 875, article id UNSP 042008Article in journal (Refereed)
    Abstract [en]

    Tremendous progress has been made in the research on the structure and dynamics of liquids due to the development of advanced experimental techniques such as liquid microjets, enabling investigations on volatile samples in ultrahigh vacuum environments. The spectroscopy of charged particles, e.g. photoelectron or Auger electron spectroscopy on liquids, is an established field by now. Here, we report on the successful application of a fluorescence spectrometer to measure optical emission spectra from liquids irradiated with soft X-ray synchrotron radiation.

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  • 9.
    Hans, Andreas
    et al.
    Univ Kassel, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Ctr Interdisciplinary Nanostruct Sci & Technol CI, Heinrich Plett Str 40, D-34132 Kassel, Germany..
    Ozga, Christian
    Univ Kassel, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Ctr Interdisciplinary Nanostruct Sci & Technol CI, Heinrich Plett Str 40, D-34132 Kassel, Germany..
    Seidel, Robert
    Helmholtz Zentrum Berlin Mat & Energie, Methods Mat Dev, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Schmidt, Philipp
    Univ Kassel, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Ctr Interdisciplinary Nanostruct Sci & Technol CI, Heinrich Plett Str 40, D-34132 Kassel, Germany..
    Ueltzhoeffer, Timo
    Univ Kassel, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Ctr Interdisciplinary Nanostruct Sci & Technol CI, Heinrich Plett Str 40, D-34132 Kassel, Germany..
    Holzapfel, Xaver
    Univ Kassel, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Ctr Interdisciplinary Nanostruct Sci & Technol CI, Heinrich Plett Str 40, D-34132 Kassel, Germany..
    Wenzel, Philip
    Univ Kassel, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Ctr Interdisciplinary Nanostruct Sci & Technol CI, Heinrich Plett Str 40, D-34132 Kassel, Germany..
    Reiss, Philipp
    Univ Kassel, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Ctr Interdisciplinary Nanostruct Sci & Technol CI, Heinrich Plett Str 40, D-34132 Kassel, Germany..
    Pohl, Marvin N.
    Helmholtz Zentrum Berlin Mat & Energie, Methods Mat Dev, Albert Einstein Str 15, D-12489 Berlin, Germany.;Free Univ Berlin, Dept Phys, Arnimallee 14, D-14195 Berlin, Germany.;Max Planck Gesell, Fritz Haber Inst, Faradayweg 4-6, D-14195 Berlin, Germany..
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Aziz, Emad F.
    Helmholtz Zentrum Berlin Mat & Energie, Methods Mat Dev, Albert Einstein Str 15, D-12489 Berlin, Germany.;Free Univ Berlin, Dept Phys, Arnimallee 14, D-14195 Berlin, Germany.;Monash Univ, Sch Chem, Clayton Campus, Clayton, Vic 3800, Australia..
    Ehresmann, Arno
    Univ Kassel, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Ctr Interdisciplinary Nanostruct Sci & Technol CI, Heinrich Plett Str 40, D-34132 Kassel, Germany..
    Slavicek, Petr
    Univ Chem & Technol Prague, Dept Phys Chem, Tech 5, Prague 16628, Czech Republic..
    Winter, Bernd
    Helmholtz Zentrum Berlin Mat & Energie, Methods Mat Dev, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Knie, Andre
    Univ Kassel, Heinrich Plett Str 40, D-34132 Kassel, Germany.;Ctr Interdisciplinary Nanostruct Sci & Technol CI, Heinrich Plett Str 40, D-34132 Kassel, Germany..
    Optical Fluorescence Detected from X-ray Irradiated Liquid Water2017In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 121, no 10, p. 2326-2330Article in journal (Refereed)
    Abstract [en]

    Despite its importance, the structure and dynamics of liquid water are still poorly understood in many apsects. Here, we report on the observation of optical fluorescence upon soft X-ray irradiation of liquid water. Detection of spectrally resolved fluorescence was achieved by a combination of the liquid microjet technique and fluorescence spectroscopy. We observe a genuine liquid-phase fluorescence manifested by a broad emission band in the 170-340 nm (4-7 eV) photon wavelength range. In addition, another narrower emission near 300 nm can be assigned to the fluorescence of OH (A state) in the gas phase, the emitting species being formed by Auger electrons escaping from liquid water. We argue that the newly observed broad-band emission of liquid water is relevant in search of extraterrestrial life, and we also envision the observed electron-ejection mechanism to find application for exploring solutes at liquid vapor interfaces.

  • 10.
    Kaiser, L.
    et al.
    Goethe Univ, Inst Kernphys, Max von Laue Str 1, D-60438 Frankfurt, Germany..
    Fehre, K.
    Univ Kassel, Inst Phys, Heinrich Plett Str 40, D-34142 Kassel, Germany.;Univ Kassel, CINSaT, Heinrich Plett Str 40, D-34142 Kassel, Germany.;Southern Fed Univ, Inst Phys, Rostov Na Donu 344090, Russia..
    Novikovskiy, N. M.
    Goethe Univ, Inst Kernphys, Max von Laue Str 1, D-60438 Frankfurt, Germany..
    Stindl, J.
    Goethe Univ, Inst Kernphys, Max von Laue Str 1, D-60438 Frankfurt, Germany..
    Tsitsonis, D.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Gopakumar, Geethanjali
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Deutsch Elektronen Synchrotron DESY, Notkestr 85, D-22763 Hamburg, Germany..
    Unger, Isaak
    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.
    Bjorneholm, O.
    Goethe Univ, Inst Kernphys, Max von Laue Str 1, D-60438 Frankfurt, Germany..
    Schoeffler, M.
    Goethe Univ, Inst Kernphys, Max von Laue Str 1, D-60438 Frankfurt, Germany..
    Jahnke, T.
    Goethe Univ, Inst Kernphys, Max von Laue Str 1, D-60438 Frankfurt, Germany..
    Doerner, R.
    Goethe Univ, Inst Kernphys, Max von Laue Str 1, D-60438 Frankfurt, Germany..
    Trinter, F.
    Goethe Univ, Inst Kernphys, Max von Laue Str 1, D-60438 Frankfurt, Germany.;Deutsch Elektronen Synchrotron DESY, Notkestr 85, D-22763 Hamburg, Germany.;Fritz Haber Inst Max Planck Gesell, Mol Phys, Faradayweg 4-6, D-14195 Berlin, Germany..
    Demekhin, Ph, V
    Univ Kassel, Inst Phys, Heinrich Plett Str 40, D-34142 Kassel, Germany.;Univ Kassel, CINSaT, Heinrich Plett Str 40, D-34142 Kassel, Germany..
    Angular emission distribution of O 1s photoelectrons of uniaxially oriented methanol2020In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 53, no 19, article id 194002Article in journal (Refereed)
    Abstract [en]

    The angular distribution of O 1s photoelectrons emitted from uniaxially oriented methanol is studied experimentally and theoretically. We employed circularly polarized photons of an energy ofh nu= 550 eV for our investigations. We measured the three-dimensional photoelectron angular distributions of methanol, with the CH3-OH axis oriented in the polarization plane, by means of cold target recoil ion momentum spectroscopy. The experimental results are interpreted by single active electron calculations performed with the single center method. A comparative theoretical study of the respective molecular-frame angular distributions of O 1s photoelectrons of CO, performed for the same photoelectron kinetic energy and for a set of different internuclear distances, allows for disentangling the role of internuclear distance and the hydrogen atoms of methanol as compared to carbon monoxide.

  • 11.
    Leroux, Juliette
    et al.
    Univ Caen Normandie, CIMAP, CEA, CNRS,ENSICAEN, F-14050 Caen, France.;Deutsch Elektronen Synchrotron DESY, Hamburg, Germany..
    Kotobi, Amir
    Deutsch Elektronen Synchrotron DESY, Hamburg, Germany.;Helmholtz Zentrum Hereon, Inst Surface Sci, D-21502 Geesthacht, Germany..
    Hirsch, Konstantin
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindliche Rontgenspekt, D-12489 Berlin, Germany..
    Lau, Tobias
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindliche Rontgenspekt, D-12489 Berlin, Germany..
    Ortiz-Mahecha, Carlos
    Hamburg Univ Technol, Inst Polymers & Composites, D-21073 Hamburg, Germany..
    Maksimov, Dmitrii
    Max Planck Inst Struct & Dynam Matter, D-22761 Hamburg, Germany..
    Meissner, Robert
    Helmholtz Zentrum Hereon, Inst Surface Sci, D-21502 Geesthacht, Germany.;Hamburg Univ Technol, Inst Polymers & Composites, D-21073 Hamburg, Germany..
    Oostenrijk, Bart
    Hamburg Ctr Ultrafast Imaging, Hamburg, Germany..
    Rossi, Mariana
    Max Planck Inst Struct & Dynam Matter, D-22761 Hamburg, Germany..
    Schubert, Kaja
    Deutsch Elektronen Synchrotron DESY, Hamburg, Germany..
    Timm, Martin
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindliche Rontgenspekt, D-12489 Berlin, Germany..
    Trinter, Florian
    Goethe Univ Frankfurt Main, Inst Kernphys, D-60438 Frankfurt, Germany.;Max Planck Gesell, Fritz Haber Inst, Mol Phys, D-14195 Berlin, Germany..
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Zamudio-Bayer, Vicente
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindliche Rontgenspekt, D-12489 Berlin, Germany..
    Schwob, Lucas
    Deutsch Elektronen Synchrotron DESY, Hamburg, Germany..
    Bari, Sadia
    Deutsch Elektronen Synchrotron DESY, Hamburg, Germany.;Hamburg Ctr Ultrafast Imaging, Hamburg, Germany.;Univ Groningen, Zernike Inst Adv Mat, NL-9747 AG Groningen, Netherlands..
    Mapping the electronic transitions of protonation sites in peptides using soft X-ray action spectroscopy2023In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 25, no 37, p. 25603-25618Article in journal (Refereed)
    Abstract [en]

    Near-edge X-ray absorption mass spectrometry (NEXAMS) around the nitrogen and oxygen K-edges was employed on gas-phase peptides to probe the electronic transitions related to their protonation sites, namely at basic side chains, the N-terminus and the amide oxygen. The experimental results are supported by replica exchange molecular dynamics and density-functional theory and restricted open-shell configuration with single calculations to attribute the transitions responsible for the experimentally observed resonances. We studied five tailor-made glycine-based pentapeptides, where we identified the signature of the protonation site of N-terminal proline, histidine, lysine and arginine, at 406 eV, corresponding to N 1s & RARR; & sigma;*(NHx+) (x = 2 or 3) transitions, depending on the peptides. We compared the spectra of pentaglycine and triglycine to evaluate the sensitivity of NEXAMS to protomers. Separate resonances have been identified to distinguish two protomers in triglycine, the protonation site at the N-terminus at 406 eV and the protonation site at the amide oxygen characterized by a transition at 403.1 eV.

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  • 12.
    Patanen, Minna
    et al.
    Univ Oulu, Fac Sci, Nano & Mol Syst Res Unit, OB 3000, Oulu 90014, Finland..
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics. DESY, Notkestr 85, D-22763 Hamburg, Germany..
    Saak, Clara-Magdalena
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics. Univ Vienna, Dept Phys Chem, Wahringer Str 42, A-1090 Vienna, Austria..
    Gopakumar, Geethanjali
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Lexelius, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Salter, Matthew
    Stockholm Univ, Dept Environm Sci, S-10691 Stockholm, Sweden.;Bolin Ctr Climate Res, S-10691 Stockholm, Sweden..
    Zieger, Paul
    Stockholm Univ, Dept Environm Sci, S-10691 Stockholm, Sweden.;Bolin Ctr Climate Res, S-10691 Stockholm, Sweden..
    Surface composition of size-selected sea salt particles under the influence of organic acids studied in situ using synchrotron radiation X-ray photoelectron spectroscopy2022In: Environmental Science: Atmospheres, E-ISSN 2634-3606, Vol. 2, no 5, p. 1032-1040Article in journal (Refereed)
    Abstract [en]

    Sea spray aerosols play a key role in the climate system by scattering solar radiation and by serving as cloud condensation nuclei. Despite their importance, the impact of sea spray aerosols on global climate remains highly uncertain. One of the key knowledge gaps in our understanding of sea spray aerosol is the chemical composition of the particle surface, important for various atmospheric chemical processes, as a function of size and bulk composition. Here, we have applied X-ray photoelectron spectroscopy (XPS) to determine the surface composition of both pure inorganic sea salt aerosols and sea salt aerosols spiked with an amino acid (phenylalanine) and a straight chain fatty acid (octanoic acid). Importantly, the use of a differential mobility analyser allowed size-selection of 150, 250 and 350 nm monodisperse aerosol particles for comparison to polydisperse aerosol particles. We observed enrichment of magnesium at the particle surfaces relative to chloride in all aerosols tested, across all particle sizes. Interestingly, the magnitude of this enrichment was dependent on the type of organic present in the solution as well as the particle size. Our results suggest that the observed enrichment in magnesium is an inorganic effect which can be either enhanced or diminished by the addition of organic substances.

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  • 13.
    Ponzi, Aurora
    et al.
    Rudjer Boskovic Inst, Div Phys Chem, Zagreb 10000, Croatia..
    Rosa, Marta
    Univ Padua, Dept Chem Sci, I-35122 Padua, Italy..
    Kladnik, Gregor
    Univ Ljubljana, Dept Phys, Ljubljana 1000, Slovenia.;CNR, Lab TASC, IOM, I-34149 Trieste, Italy..
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Ciavardini, Alessandra
    CER ERIC, I-34149 Trieste, Italy..
    Di Nardi, Lorys
    Sapienza Univ Rome, Dept Chem, I-00185 Rome, Italy..
    Viola, Elisa
    Sapienza Univ Rome, Dept Chem, I-00185 Rome, Italy..
    Nicolas, Christophe
    Synchrotron SOLEIL, F-91192 Paris, France..
    Doslic, Nada
    Rudjer Boskovic Inst, Div Phys Chem, Zagreb 10000, Croatia..
    Goldoni, Andrea
    Elettra Synchrotron, Micro & Nano Carbon Lab, I-34149 Trieste, Italy..
    Lanzilotto, Valeria
    CNR, Lab TASC, IOM, I-34149 Trieste, Italy.;Sapienza Univ Rome, Dept Chem, I-00185 Rome, Italy.;Elettra Synchrotron, Micro & Nano Carbon Lab, I-34149 Trieste, Italy.;Univ Trieste, Dept Chem & Pharmaceut Sci, I-34127 Trieste, Italy..
    Inequivalent Solvation Effects on the N 1s Levels of Self-Associated Melamine Molecules in Aqueous Solution2023In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 127, no 13, p. 3016-3025Article in journal (Refereed)
    Abstract [en]

    This work shows how the N 1s photoemission (PE) spectrum of self-associated melamine molecules in aqueous solution has been successfully rationalized using an integrated computational approach encompassing classical metadynamics simulations and quantum calculations based on density functional theory (DFT). The first approach allowed us to describe interacting melamine molecules in explicit waters and to identify dimeric configurations based on π–π and/or H-bonding interactions. Then, N 1s binding energies (BEs) and PE spectra were computed at the DFT level for all structures both in the gas phase and in an implicit solvent. While pure π-stacked dimers show gas-phase PE spectra almost identical to that of the monomer, those of the H-bonded dimers are sensibly affected by NH···NH or NH···NC interactions. Interestingly, the solvation suppresses all of the non-equivalences due to the H-bonds yielding similar PE spectra for all dimers, matching very well our measurements.

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  • 14.
    Saak, Clara-Magdalena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Clemens, Richter
    Leibniz Institute of surface engineering (IOM).
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Caleman, Carl
    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, Molecular and Condensed Matter Physics.
    Hergenhahn, Uwe
    Fritz Haber Institute.
    Specific probing of the hydrogen bonding network in aqueous mixtures of glycerol and dimethyl sulfoxideManuscript (preprint) (Other academic)
  • 15.
    Saak, Clara-Magdalena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Richter, Clemens
    Leibniz Institute of Surface Engineering (IOM).
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Mucke, Melanie
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Nicolas, Christophe
    Synchrotron SOLEIL.
    Hergenhahn, Uwe
    Fritz Haber Institute.
    Caleman, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Huttula, Marko
    Oulu University.
    Patanen, Minna
    Oulu University.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Probing the Hydrogen-Bond Strength of Solvent Clusters using Proton DynamicsManuscript (preprint) (Other academic)
  • 16.
    Saak, Clara-Magdalena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Richter, Clemens
    Leibniz Inst Surface Engn IOM, Permoserstr 15, D-04318 Leipzig, Germany.
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Mucke, Melanie
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Nicolas, Christophe
    Orme Merisiers, Synchrotron SOLEIL, BP 48, F-91192 Gif Sur Yvette, France.
    Hergenhahn, Uwe
    Leibniz Inst Surface Engn IOM, Permoserstr 15, D-04318 Leipzig, Germany;Fritz Haber Inst Max Planck Gesell, Faradayweg 4-6, D-14195 Berlin, Germany;Max Planck Inst Plasma Phys, D-17491 Greifswald, Germany.
    Caleman, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. DESY, Ctr Free Electron Laser Sci, Notkestr 85, D-22607 Hamburg, Germany.
    Huttula, Marko
    Univ Oulu, Nano & Mol Syst Res Unit, Fac Sci, POB 3000, Oulu 90014, Finland.
    Patanen, Minna
    Univ Oulu, Nano & Mol Syst Res Unit, Fac Sci, POB 3000, Oulu 90014, Finland.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Proton dynamics in molecular solvent clusters as an indicator for hydrogen bond network strength in confined geometries2020In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 22, no 6, p. 3264-3272Article in journal (Refereed)
    Abstract [en]

    Hydrogen bonding leads to the formation of strong, extended intermolecular networks in molecular liquids such as water. However, it is less well-known how robust the network is to environments in which surface formation or confinement effects become prominent, such as in clusters or droplets. Such systems provide a useful way to probe the robustness of the network, since the degree of confinement can be tuned by altering the cluster size, changing both the surface-to-volume ratio and the radius of curvature. To explore the formation of hydrogen bond networks in confined geometries, here we present O 1s Auger spectra of small and large clusters of water, methanol, and dimethyl ether, as well as their deuterated equivalents. The Auger spectra of the clusters and the corresponding macroscopic liquids are compared and evaluated for an isotope effect, which is due to proton dynamics within the lifetime of the core hole (proton-transfer-mediated charge-separation, PTM-CS), and can be linked to the formation of a hydrogen bond network in the system. An isotope effect is observed in water and methanol but not for dimethyl ether, which cannot donate a hydrogen bond at its oxygen site. The isotope effect, and therefore the strength of the hydrogen bond network, is more pronounced in water than in methanol. Its value depends on the average size of the cluster, indicating that confinement effects change proton dynamics in the core ionised excited state.

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  • 17.
    Saak, Clara-Magdalena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Caleman, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron, DE-22607 Hamburg, Germany.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Site-specific X-ray induced dynamics in liquid methanol2019In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 28, p. 15478-15486Article in journal (Refereed)
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  • 18.
    Saak, Clara-Magdalena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Gopakumar, Geethanjali
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Caleman, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. DESY, Ctr Free Electron Laser Sci, DE-22607 Hamburg, Germany..
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Temperature Dependence of X-ray-Induced Auger Processes in Liquid Water2020In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 11, no 7, p. 2497-2501Article in journal (Refereed)
    Abstract [en]

    Auger spectroscopy has previously been used to study changes in the hydrogen bond network in liquid water, but to the best of our knowledge it has not been used to track such changes as a function of temperature. We show Auger spectroscopy to reflect the weakening of the hydrogen bond network upon heating. This shows that the radiation response of water, i.e., the relative propensity of the different processes occurring after radiation exposure, including femtosecond proton dynamics, depends on the temperature of the system. This proof-of-principle study further demonstrates the suitability of the technique to help elucidate information on the intermolecular structure of liquids such as water, opening the door to further temperature-dependent studies.

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  • 19.
    Silva, Jose Luis
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Matias, Tiago A.
    Franco, Leandro R.
    Damas, Giane
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Costa, Luciano T.
    Toledo, Kalil C. F
    Rocha, Tulio C. R.
    de Brito, Arnaldo N.
    Saak, Clara-Magdalena
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Coutinho, Kaline
    Araki, Koiti
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Araujo, Carlos Moyses
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    X‑ray Photoelectron Fingerprints of High-Valence Ruthenium−Oxo Complexes along the Oxidation Reaction Pathway in an Aqueous Environment2019In: The Journal of Physical Chemistry Letters, Vol. 10, no 24, p. 7636-7643Article in journal (Refereed)
    Abstract [en]

    Recent advances in operando-synchrotron-based X-ray techniques are making it possible to address fundamental questions related to complex proton-coupled electron transfer reactions, for instance, the electrocatalytic water splitting process. However, it is still a grand challenge to assess the ability of the different techniques to characterize the relevant intermediates, with minimal interference on the reaction mechanism. To this end, we have developed a novel methodology employing X-ray photoelectron spectroscopy (XPS) in connection with the liquid-jet approach to probe the electrochemical properties of a model electrocatalyst, [RuII(bpy)2(py)-(OH2)]2+, in an aqueous environment. There is a unique fingerprint of the extremely important higher-valence ruthenium−oxo species in the XPS spectra along the oxidation reaction pathway. Furthermore, a sequential method combining quantum mechanics and molecular mechanics is used to illuminate the underlying physical chemistry of such systems. This study provides the basis for the future development of in-operando XPS techniques for water oxidation reactions.

  • 20.
    Svensson, Pamela
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Schwob, Lucas
    Deutsch Elektronen Synchrotron DESY, Notke str 85, D-22607 Hamburg, Germany..
    Grånäs, Oscar
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Timneanu, Nicusor
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Vieli, Anna-Lydia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Zamudio-Bayer, Vicente
    Helmholtz Zent Berlin Materialien & Energie, Abt Hochempfindl Rontgenspektroskopie, D-12489 Berlin, Germany..
    Timm, Martin
    Helmholtz Zent Berlin Materialien & Energie, Abt Hochempfindl Rontgenspektroskopie, D-12489 Berlin, Germany..
    Hirsch, Konstantin
    Helmholtz Zent Berlin Materialien & Energie, Abt Hochempfindl Rontgenspektroskopie, D-12489 Berlin, Germany..
    Caleman, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics. DESY, Ctr Free Electron Laser Sci, D-22607 Hamburg, Germany..
    Berholts, Marta
    Univ Tartu, Inst Phys, W Ostwald 1, EE-50411 Tartu, Estonia..
    Heavy element incorporation in nitroimidazole radiosensitizers: molecular-level insights into fragmentation dynamics2024In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 26, no 2, p. 770-779Article in journal (Refereed)
    Abstract [en]

    The present study investigates the photofragmentation behavior of iodine-enhanced nitroimidazole-based radiosensitizer model compounds in their protonated form using near-edge X-ray absorption mass spectrometry and quantum mechanical calculations. These molecules possess dual functionality: improved photoabsorption capabilities and the ability to generate species that are relevant to cancer sensitization upon photofragmentation. Four samples were investigated by scanning the generated fragments in the energy regions around C 1s, N 1s, O 1s, and I 3d-edges with a particular focus on NO2+ production. The experimental summed ion yield spectra are explained using the theoretical near-edge X-ray absorption fine structure spectrum based on density functional theory. Born-Oppenheimer-based molecular dynamics simulations were performed to investigate the fragmentation processes.

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  • 21.
    Unger, Isaak
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Saak, Clara-Magdalena
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Salter, Matthew
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Stockholm Univ, Dept Environm Sci & Analyt Chem, SE-10691 Stockholm, Sweden;Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden.
    Zieger, Paul
    Stockholm Univ, Dept Environm Sci & Analyt Chem, SE-10691 Stockholm, Sweden;Bolin Ctr Climate Res, SE-10691 Stockholm, Sweden.
    Patanen, Minna
    Univ Oulu, Fac Sci, Nano & Mol Syst Res Unit, POB 8000, FI-90570 Oulu, Finland.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Influence of Organic Acids on the Surface Composition of Sea Spray Aerosol2020In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 124, no 2, p. 422-429Article in journal (Refereed)
    Abstract [en]

    Recent studies on sea spray aerosol indicate an enrichment of Ca2+ in small particles, which are often thought to originate from the very surface of a water body when bubbles burst. One model to explain this observation is the formation of ion pairs between Ca2+(aq) and surface-active organic species. In this study, we have used X-ray photoelectron spectroscopy to probe aqueous salt solutions and artificial sea spray aerosol to study whether ion pairing in the liquid environment also affects the surface composition of dry aerosol. Carboxylic acids were added to the sample solutions to mimic some of the organic compounds present in natural seawater. Our results show that the formation of a core-shell structure governs the surface composition of the aerosol. The core-shell structure contrasts previous observations of the dry sea spray aerosol on substrates. As such, this may indicate that substrates can impact the morphology of the dried aerosol.

  • 22.
    Unger, Isaak
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Helmholtz Zentrum Berlin Mat & Energie, Inst Methods Mat Dev, Albert Einstein Str 15, D-12489 Berlin, Germany.
    Seidel, Robert
    Helmholtz Zentrum Berlin Mat & Energie, Inst Methods Mat Dev, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Thürmer, Stephan
    Helmholtz Zentrum Berlin Mat & Energie, Inst Methods Mat Dev, Albert Einstein Str 15, D-12489 Berlin, Germany.;Kyoto Univ, Dept Chem, Sakyo Ku, Kyoto 6068502, Japan..
    Pohl, Marvin N.
    Helmholtz Zentrum Berlin Mat & Energie, Inst Methods Mat Dev, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Aziz, Emad F.
    Helmholtz Zentrum Berlin Mat & Energie, Inst Methods Mat Dev, Albert Einstein Str 15, D-12489 Berlin, Germany.;Free Univ Berlin, Dept Phys, Arnimallee 14, D-14159 Berlin, Germany.;Monash Univ, Sch Chem, Clayton, Vic 3800, Australia..
    Cederbaum, Lorenz S.
    Heidelberg Univ, Phys Chem Inst, Theoret Chem, Neuenheimer Feld 229, D-69120 Heidelberg, Germany..
    Muchova, Eva
    Univ Chem & Technol, Dept Phys Chem, Tech 5, Prague 16628, Czech Republic..
    Slavicek, Petr
    Univ Chem & Technol, Dept Phys Chem, Tech 5, Prague 16628, Czech Republic..
    Winter, Bernd
    Helmholtz Zentrum Berlin Mat & Energie, Inst Methods Mat Dev, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Kryzhevoi, Nikolai V.
    Heidelberg Univ, Phys Chem Inst, Theoret Chem, Neuenheimer Feld 229, D-69120 Heidelberg, Germany..
    Observation of electron-transfer-mediated decay in aqueous solution2017In: Nature Chemistry, ISSN 1755-4330, E-ISSN 1755-4349, Vol. 9, no 7, p. 708-714Article in journal (Refereed)
    Abstract [en]

    Photoionization is at the heart of X-ray photoelectron spectroscopy (XPS), which gives access to important information on a sample's local chemical environment. Local and non-local electronic decay after photoionization-in which the refilling of core holes results in electron emission from either the initially ionized species or a neighbour, respectively-have been well studied. However, electron-transfer-mediated decay (ETMD), which involves the refilling of a core hole by an electron from a neighbouring species, has not yet been observed in condensed phase. Here we report the experimental observation of ETMD in an aqueous LiCl solution by detecting characteristic secondary low-energy electrons using liquid-microjet soft XPS. Experimental results are interpreted using molecular dynamics and high-level ab initio calculations. We show that both solvent molecules and counterions participate in the ETMD processes, and different ion associations have distinctive spectral fingerprints. Furthermore, ETMD spectra are sensitive to coordination numbers, ion-solvent distances and solvent arrangement.

  • 23.
    Werner, Josephina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Department of Molecular Sciences, Swedish University of Agricultural Sciences, Box 7015, SE-750 07 Uppsala, Sweden.
    Persson, Ingmar
    Department of Molecular Sciences, Swedish University of Agricultural Sciences, Box 7015, SE-750 07 Uppsala, Sweden.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Kawecki, Delphine
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Saak, Clara-Magdalena
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Walz, Marie-Madeleine
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Ekholm, Victor
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Unger, Isaak
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Valtl, Corina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Caleman, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron, Notkestraße 85, DE-22607 Hamburg, Germany.
    Öhrwall, Gunnar
    MAX IV Laboratory, Lund University, Box 118, SE-22100 Lund, Sweden.
    Prisle, Nonne L.
    Univ Oulu, Nano & Mol Syst Res Unit, Fac Sci, Box 3000, FI-90014 Oulu, Finland;Univ Helsinki, Div Atmospher Sci, Dept Phys, Box 64, FI-00014 Helsinki, Finland.
    Shifted Equilibria of Organic Acids and Bases in the Aqueous Surface Region2018In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 36, p. 23281-23293Article in journal (Refereed)
    Abstract [en]

    Acid-base equilibria of carboxylic acids and alkyl amines in the aqueous surface region were studied using surface-sensitive X-ray photoelectron spectroscopy and molecular dynamics simulations. Solutions of these organic compounds were examined as a function of pH, concentration and chain length to investigate the distribution of acid and base form in the surface region as compared to the aqueous bulk. Results from these experiments show that the neutral forms of the studied acid-base pairs are strongly enriched in the aqueous surface region. Moreover, we show that for species with at least four carbon atoms in their alkyl-chain, their charged forms are also found to be abundant in the surface region. Using a combination of XPS and MD results, a model is proposed that effectively describes the surface composition. Resulting absolute surface concentration estimations show clearly that the total organic mole fractions in the surface region change drastically as a function of solution pH. The origin of the observed surface phenomena, hydronium/hydroxide concentrations in the aqueous surface region and why standard chemical equations, used to describe equilibria in dilute bulk solution are not valid in the aqueous surface region, are discussed in detail. The reported results are of considerable importance especially for the detailed understanding of properties of small aqueous droplets that can be found in the atmosphere.

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