Bio


Anders Nilsson interests covers the application of synchrotron radiation to studies of surfaces and in liquids with a focus on studies catalytic processes in fuel cells, photoelectrochemical decomposition of water, CO2 reduction, chemical bonding on surfaces, structure of liquid water and aqueous solutions, interfacial processes of relevance to molecular environmental science and ultrafast processes on surfaces and in water.

Academic Appointments


  • Professor Emeritus, Photon Science Directorate

Honors & Awards


  • The Liljevalls Award for Young Scientist, Uppsala University (1988)
  • Ångström Award for Outstanding PhD thesis, Uppsala University (1990)
  • The Lindbomska Award for Outstanding PhD thesis, Royal Academy of Science, Stockholm, Sweden (1991)
  • The Royal Oscars Award for Important Contributions in Science, Uppsala University (1994)
  • The Shirley Award for Excellent Research using Soft X-rays, Lawrence Berkeley National Laboratory (1998)
  • Fellow of the Institute of Physics, London, UK (2004)
  • Special Award on the article on water as one of the top 10 breakthroughs of the year, Foundation for Strategic Research in Sweden (2005)
  • Humboldt Senior Research Award, Alexander von Humboldt-Stiftung/Foundation, Germany (2009)

2021-22 Courses


All Publications


  • On the chemical state of Co oxide electrocatalysts during alkaline water splitting. Physical chemistry chemical physics Friebel, D., Bajdich, M., Yeo, B. S., Louie, M. W., Miller, D. J., Sanchez Casalongue, H., Mbuga, F., Weng, T., Nordlund, D., Sokaras, D., Alonso-Mori, R., Bell, A. T., Nilsson, A. 2013; 15 (40): 17460-17467

    Abstract

    Resonant inelastic X-ray scattering and high-resolution X-ray absorption spectroscopy were used to identify the chemical state of a Co electrocatalyst in situ during the oxygen evolution reaction. After anodic electrodeposition onto Au(111) from a Co(2+)-containing electrolyte, the chemical environment of Co can be identified to be almost identical to CoOOH. With increasing potentials, a subtle increase of the Co oxidation state is observed, indicating a non-stoichiometric composition of the working OER catalyst containing a small fraction of Co(4+) sites. In order to confirm this interpretation, we used density functional theory with a Hubbard-U correction approach to compute X-ray absorption spectra of model compounds, which agree well with the experimental spectra. In situ monitoring of catalyst local structure and bonding is essential in the development of structure-activity relationships that can guide the discovery of efficient and earth abundant water splitting catalysts.

    View details for DOI 10.1039/c3cp52981a

    View details for PubMedID 24026021

  • On the chemical state of Co oxide electrocatalysts during alkaline water splitting. Physical chemistry chemical physics Friebel, D., Bajdich, M., Yeo, B. S., Louie, M. W., Miller, D. J., Sanchez Casalongue, H., Mbuga, F., Weng, T., Nordlund, D., Sokaras, D., Alonso-Mori, R., Bell, A. T., Nilsson, A. 2013; 15 (40): 17460-17467

    Abstract

    Resonant inelastic X-ray scattering and high-resolution X-ray absorption spectroscopy were used to identify the chemical state of a Co electrocatalyst in situ during the oxygen evolution reaction. After anodic electrodeposition onto Au(111) from a Co(2+)-containing electrolyte, the chemical environment of Co can be identified to be almost identical to CoOOH. With increasing potentials, a subtle increase of the Co oxidation state is observed, indicating a non-stoichiometric composition of the working OER catalyst containing a small fraction of Co(4+) sites. In order to confirm this interpretation, we used density functional theory with a Hubbard-U correction approach to compute X-ray absorption spectra of model compounds, which agree well with the experimental spectra. In situ monitoring of catalyst local structure and bonding is essential in the development of structure-activity relationships that can guide the discovery of efficient and earth abundant water splitting catalysts.

    View details for DOI 10.1039/c3cp52981a

    View details for PubMedID 24026021

  • Interlayer Carbon Bond Formation Induced by Hydrogen Adsorption in Few-Layer Supported Graphene PHYSICAL REVIEW LETTERS Rajasekaran, S., Abild-Pedersen, F., Ogasawara, H., Nilsson, A., Kaya, S. 2013; 111 (8)

    Abstract

    We report on the hydrogen adsorption induced phase transition of a few layer graphene (1 to 4 layers) to a diamondlike structure on Pt(111) based on core level x-ray spectroscopy, temperature programed desorption, infrared spectroscopy, and density functional theory total energy calculations. The surface adsorption of hydrogen induces a hybridization change of carbon from the sp^{2} to the sp^{3} bond symmetry, which propagates through the graphene layers, resulting in interlayer carbon bond formation. The structure is stabilized through the termination of interfacial sp^{3} carbon atoms by the substrate. The structural transformation occurs as a consequence of high adsorption energy.

    View details for DOI 10.1103/PhysRevLett.111.085503

    View details for Web of Science ID 000323388200016

    View details for PubMedID 24010453

  • Stability of Pt-Modified Cu(111) in the Presence of Oxygen and Its Implication on the Overall Electronic Structure JOURNAL OF PHYSICAL CHEMISTRY C Oberg, H., Anniyev, T., Vojvodic, A., Kaya, S., Ogasawara, H., Friebel, D., Miller, D. J., Nordlund, D., Bergmann, U., Ljungberg, M. P., Abild-Pedersen, F., Nilsson, A., Pettersson, L. G. 2013; 117 (32): 16371-16380

    View details for DOI 10.1021/jp400486r

    View details for Web of Science ID 000323301100012

  • Unique water-water coordination tailored by a metal surface JOURNAL OF CHEMICAL PHYSICS Schiros, T., Andersson, K. J., MacNaughton, J., Gladh, J., Matsuda, A., Ostrom, H., Takahashi, O., Pettersson, L. G., Nilsson, A., Ogasawara, H. 2013; 138 (23)

    Abstract

    At low coverage of water on Cu(110), substrate-mediated electrostatics lead to zigzagging chains along [001] as observed with STM [T. Yamada, S. Tamamori, H. Okuyama, and T. Aruga, "Anisotropic water chain growth on Cu(110) observed with scanning tunneling microscopy" Phys. Rev. Lett. 96, 036105 (2006)]. Using x-ray absorption spectroscopy we find an anomalous low-energy resonance at ~533.1 eV which, based on density functional theory spectrum simulations, we assign to an unexpected configuration of water units whose uncoordinated O-H bonds directly face those of their neighbors; this interaction repeats over trough sites with enhanced electron density and is analogous to the case of a hydrated electron.

    View details for DOI 10.1063/1.4809680

    View details for Web of Science ID 000321012400033

    View details for PubMedID 23802977

  • Resonant inelastic X-ray scattering of liquid water JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Nilsson, A., Tokushima, T., Horikawa, Y., Harada, Y., Ljungberg, M. P., Shin, S., Pettersson, L. G. 2013; 188: 84-100
  • Identification of the electronic structure differences between polar isostructural FeO and CoO films by core-level soft x-ray spectroscopy PHYSICAL REVIEW B Kaya, S., Anniyev, T., Ogasawara, H., Nilsson, A. 2013; 87 (20)
  • Selective Ultrafast Probing of Transient Hot Chemisorbed and Precursor States of CO on Ru(0001) PHYSICAL REVIEW LETTERS Beye, M., Anniyev, T., Coffee, R., Dell'Angela, M., Foehlisch, A., Gladh, J., Katayama, T., Kaya, S., Krupin, O., Mogelhoj, A., Nilsson, A., Nordlund, D., Norskov, J. K., Oberg, H., Ogasawara, H., Pettersson, L. G., Schlotter, W. F., Sellberg, J. A., Sorgenfrei, F., Turner, J. J., Wolf, M., Wurth, W., Ostrom, H. 2013; 110 (18)

    Abstract

    We have studied the femtosecond dynamics following optical laser excitation of CO adsorbed on a Ru surface by monitoring changes in the occupied and unoccupied electronic structure using ultrafast soft x-ray absorption and emission. We recently reported [M. Dell'Angela et al. Science 339, 1302 (2013)] a phonon-mediated transition into a weakly adsorbed precursor state occurring on a time scale of >2 ps prior to desorption. Here we focus on processes within the first picosecond after laser excitation and show that the metal-adsorbate coordination is initially increased due to hot-electron-driven vibrational excitations. This process is faster than, but occurs in parallel with, the transition into the precursor state. With resonant x-ray emission spectroscopy, we probe each of these states selectively and determine the respective transient populations depending on optical laser fluence. Ab initio molecular dynamics simulations of CO adsorbed on Ru(0001) were performed at 1500 and 3000 K providing insight into the desorption process.

    View details for DOI 10.1103/PhysRevLett.110.186101

    View details for Web of Science ID 000319019300011

    View details for PubMedID 23683223

  • Ambient-pressure photoelectron spectroscopy for heterogeneous catalysis and electrochemistry Conference on Oprando IV - Recent Developments and Future Perspectives in Spectroscopy of Working Catalysts Kaya, S., Ogasawara, H., Naeslund, L., Forsell, J., Casalongue, H. S., Miller, D. J., Nilsson, A. ELSEVIER SCIENCE BV. 2013: 101–105
  • Solvation structures of protons and hydroxide ions in water. journal of chemical physics Chen, C., Huang, C., Waluyo, I., Nordlund, D., Weng, T., Sokaras, D., Weiss, T., Bergmann, U., Pettersson, L. G., Nilsson, A. 2013; 138 (15): 154506-?

    Abstract

    X-ray Raman spectroscopy (XRS) combined with small-angle x-ray scattering (SAXS) were used to study aqueous solutions of HCl and NaOH. Hydrated structures of H(+) and OH(-) are not simple mirror images of each other. While both ions have been shown to strengthen local hydrogen bonds in the hydration shell as indicated by XRS, SAXS suggests that H(+) and OH(-) have qualitatively different long-range effects. The SAXS structure factor of HCl (aq) closely resembles that of pure water, while NaOH (aq) behaves similar to NaF (aq). We propose that protons only locally enhance hydrogen bonds while hydroxide ions induce tetrahedrality in the overall hydrogen bond network of water.

    View details for DOI 10.1063/1.4801512

    View details for PubMedID 23614429

  • Comment on "Using Photoelectron Spectroscopy and Quantum Mechanics to Determine d-Band Energies of Metals for Catalytic Applications" JOURNAL OF PHYSICAL CHEMISTRY C Abild-Pedersen, F., Nilsson, A., Norskov, J. K. 2013; 117 (13): 6914-6915

    View details for DOI 10.1021/jp312595p

    View details for Web of Science ID 000317317600050

  • Ultrafast soft X-ray emission spectroscopy of surface adsorbates using an X-ray free electron laser JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Katayama, T., Anniyev, T., Beye, M., Coffee, R., Dell'Angela, M., Foehlisch, A., Gladh, J., Kaya, S., Krupin, O., Nilsson, A., Nordlund, D., Schlotter, W. F., Sellberg, J. A., Sorgenfrei, F., Turner, J. J., Wurth, W., Ostrom, H., Ogasawara, H. 2013; 187: 9-14
  • Real-Time Observation of Surface Bond Breaking with an X-ray Laser SCIENCE Dell'Angela, M., Anniyev, T., Beye, M., Coffee, R., Foehlisch, A., Gladh, J., Katayama, T., Kaya, S., Krupin, O., LaRue, J., Mogelhoj, A., Nordlund, D., Norskov, J. K., Oberg, H., Ogasawara, H., Ostrom, H., Pettersson, L. G., Schlotter, W. F., Sellberg, J. A., Sorgenfrei, F., Turner, J. J., Wolf, M., Wurth, W., Nilsson, A. 2013; 339 (6125): 1302-1305

    Abstract

    We used the Linac Coherent Light Source free-electron x-ray laser to probe the electronic structure of CO molecules as their chemisorption state on Ru(0001) changes upon exciting the substrate by using a femtosecond optical laser pulse. We observed electronic structure changes that are consistent with a weakening of the CO interaction with the substrate but without notable desorption. A large fraction of the molecules (30%) was trapped in a transient precursor state that would precede desorption. We calculated the free energy of the molecule as a function of the desorption reaction coordinate using density functional theory, including van der Waals interactions. Two distinct adsorption wells-chemisorbed and precursor state separated by an entropy barrier-explain the anomalously high prefactors often observed in desorption of molecules from metals.

    View details for DOI 10.1126/science.1231711

    View details for Web of Science ID 000316053400033

  • Real-time observation of surface bond breaking with an x-ray laser. Science Dell'Angela, M., Anniyev, T., Beye, M., Coffee, R., Föhlisch, A., Gladh, J., Katayama, T., Kaya, S., Krupin, O., LaRue, J., Møgelhøj, A., Nordlund, D., Nørskov, J. K., Oberg, H., Ogasawara, H., Oström, H., Pettersson, L. G., Schlotter, W. F., Sellberg, J. A., Sorgenfrei, F., Turner, J. J., Wolf, M., Wurth, W., Nilsson, A. 2013; 339 (6125): 1302-1305

    Abstract

    We used the Linac Coherent Light Source free-electron x-ray laser to probe the electronic structure of CO molecules as their chemisorption state on Ru(0001) changes upon exciting the substrate by using a femtosecond optical laser pulse. We observed electronic structure changes that are consistent with a weakening of the CO interaction with the substrate but without notable desorption. A large fraction of the molecules (30%) was trapped in a transient precursor state that would precede desorption. We calculated the free energy of the molecule as a function of the desorption reaction coordinate using density functional theory, including van der Waals interactions. Two distinct adsorption wells-chemisorbed and precursor state separated by an entropy barrier-explain the anomalously high prefactors often observed in desorption of molecules from metals.

    View details for DOI 10.1126/science.1231711

    View details for PubMedID 23493709

  • Benchmark oxygen-oxygen pair-distribution function of ambient water from x-ray diffraction measurements with a wide Q-range JOURNAL OF CHEMICAL PHYSICS Skinner, L. B., Huang, C., Schlesinger, D., Pettersson, L. G., Nilsson, A., Benmore, C. J. 2013; 138 (7)

    Abstract

    Four recent x-ray diffraction measurements of ambient liquid water are reviewed here. Each of these measurements represents a significant development of the x-ray diffraction technique applied to the study of liquid water. Sources of uncertainty from statistical noise, Q-range, Compton scattering, and self-scattering are discussed. The oxygen-hydrogen contribution to the measured x-ray scattering pattern was subtracted using literature data to yield an experimental determination, with error bars, of the oxygen-oxygen pair-distribution function, g(OO)(r), which essentially describes the distribution of molecular centers. The extended Q-range and low statistical noise of these measurements has significantly reduced truncation effects and related errors in the g(OO)(r) functions obtained. From these measurements and error analysis, the position and height of the nearest neighbor maximum in g(OO)(r) were found to be 2.80(1) Å and 2.57(5) respectively. Numerical data for the coherent differential x-ray scattering cross-section I(X)(Q), the oxygen-oxygen structure factor S(OO)(Q), and the derived g(OO)(r) are provided as benchmarks for calibrating force-fields for water.

    View details for DOI 10.1063/1.4790861

    View details for Web of Science ID 000315263500038

    View details for PubMedID 23445023

  • X-ray Photoemission and Density Functional Theory Study of the Interaction of Water Vapor with the Fe3O4(001) Surface at Near-Ambient Conditions JOURNAL OF PHYSICAL CHEMISTRY C Kendelewicz, T., Kaya, S., Newberg, J. T., Bluhm, H., Mulakaluri, N., Moritz, W., Scheffler, M., Nilsson, A., Pentcheva, R., Brown, G. E. 2013; 117 (6): 2719-2733

    View details for DOI 10.1021/jp3078024

    View details for Web of Science ID 000315181800040

  • Highly Compressed Two-Dimensional Form of Water at Ambient Conditions SCIENTIFIC REPORTS Kaya, S., Schlesinger, D., Yamamoto, S., Newberg, J. T., Bluhm, H., Ogasawara, H., Kendelewicz, T., Brown, G. E., Pettersson, L. G., Nilsson, A. 2013; 3

    Abstract

    The structure of thin-film water on a BaF(2)(111) surface under ambient conditions was studied using x-ray absorption spectroscopy from ambient to supercooled temperatures at relative humidity up to 95%. No hexagonal ice-like structure was observed in spite of the expected templating effect of the lattice-matched (111) surface. The oxygen K-edge x-ray absorption spectrum of liquid thin-film water on BaF(2) exhibits, at all temperatures, a strong resemblance to that of high-density phases for which the observed spectroscopic features correlate linearly with the density. Surprisingly, the highly compressed, high-density thin-film liquid water is found to be stable from ambient (300 K) to supercooled (259 K) temperatures, although a lower-density liquid would be expected at supercooled conditions. Molecular dynamics simulations indicate that the first layer water on BaF(2)(111) is indeed in a unique local structure that resembles high-density water, with a strongly collapsed second coordination shell.

    View details for DOI 10.1038/srep01074

    View details for Web of Science ID 000313551300002

    View details for PubMedID 23323216

    View details for PubMedCentralID PMC3545261

  • The Electronic States of Rhenium Bipyridyl Electrocatalysts for CO2 Reduction as Revealed by X-ray Absorption Spectroscopy and Computational Quantum Chemistry ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Benson, E. E., Sampson, M. D., Grice, K. A., Smieja, J. M., Froehlich, J. D., Friebel, D., Keith, J. A., Carter, E. A., Nilsson, A., Kubiak, C. P. 2013; 52 (18): 4841-4844

    View details for DOI 10.1002/anie.201209911

    View details for Web of Science ID 000318107400018

    View details for PubMedID 23526656

  • Fluctuations in ambient water Annual Meeting of the European-Molecular-Liquids-Group (EMLG)/Japanese-Molecular-Liquids-Group (JMLG) Nilsson, A., Huang, C., Pettersson, L. G. ELSEVIER SCIENCE BV. 2012: 2–16
  • Electrochemical Oxidation of Size-Selected Pt Nanoparticles Studied Using in Situ High-Energy-Resolution X-ray Absorption Spectroscopy ACS CATALYSIS Merte, L. R., Behafarid, F., Miller, D. J., Friebel, D., Cho, S., Mbuga, F., Sokaras, D., Alonso-Mori, R., Weng, T., Nordlund, D., Nilsson, A., Cuenya, B. R. 2012; 2 (11): 2371-2376

    View details for DOI 10.1021/cs300494f

    View details for Web of Science ID 000310723900018

  • Reversible graphene-metal contact through hydrogenation PHYSICAL REVIEW B Rajasekaran, S., Kaya, S., Abild-Pedersen, F., Anniyev, T., Yang, F., Stacchiola, D., Ogasawara, H., Nilsson, A. 2012; 86 (7)
  • Balance of Nanostructure and Bimetallic Interactions in Pt Model Fuel Cell Catalysts: In Situ XAS and DFT Study JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Friebel, D., Viswanathan, V., Miller, D. J., Anniyev, T., Ogasawara, H., Larsen, A. H., O'Grady, C. P., Norskov, J. K., Nilsson, A. 2012; 134 (23): 9664-9671

    Abstract

    We have studied the effect of nanostructuring in Pt monolayer model electrocatalysts on a Rh(111) single-crystal substrate on the adsorption strength of chemisorbed species. In situ high energy resolution fluorescence detection X-ray absorption spectroscopy at the Pt L(3) edge reveals characteristic changes of the shape and intensity of the "white-line" due to chemisorption of atomic hydrogen (H(ad)) at low potentials and oxygen-containing species (O/OH(ad)) at high potentials. On a uniform, two-dimensional Pt monolayer grown by Pt evaporation in ultrahigh vacuum, we observe a significant destabilization of both H(ad) and O/OH(ad) due to strain and ligand effects induced by the underlying Rh(111) substrate. When Pt is deposited via a wet-chemical route, by contrast, three-dimensional Pt islands are formed. In this case, strain and Rh ligand effects are balanced with higher local thickness of the Pt islands as well as higher defect density, shifting H and OH adsorption energies back toward pure Pt. Using density functional theory, we calculate O adsorption energies and corresponding local ORR activities for fcc 3-fold hollow sites with various local geometries that are present in the three-dimensional Pt islands.

    View details for DOI 10.1021/ja3003765

    View details for Web of Science ID 000305107800025

    View details for PubMedID 22616917

  • The soft x-ray instrument for materials studies at the linac coherent light source x-ray free-electron laser REVIEW OF SCIENTIFIC INSTRUMENTS Schlotter, W. F., Turner, J. J., Rowen, M., Heimann, P., Holmes, M., Krupin, O., Messerschmidt, M., Moeller, S., Krzywinski, J., Soufli, R., Fernandez-Perea, M., Kelez, N., Lee, S., Coffee, R., Hays, G., Beye, M., Gerken, N., Sorgenfrei, F., Hau-Riege, S., Juha, L., Chalupsky, J., Hajkova, V., Mancuso, A. P., Singer, A., Yefanov, O., Vartanyants, I. A., Cadenazzi, G., Abbey, B., Nugent, K. A., Sinn, H., Luening, J., Schaffert, S., Eisebitt, S., Lee, W., Scherz, A., Nilsson, A. R., Wurth, W. 2012; 83 (4)

    Abstract

    The soft x-ray materials science instrument is the second operational beamline at the linac coherent light source x-ray free electron laser. The instrument operates with a photon energy range of 480-2000 eV and features a grating monochromator as well as bendable refocusing mirrors. A broad range of experimental stations may be installed to study diverse scientific topics such as: ultrafast chemistry, surface science, highly correlated electron systems, matter under extreme conditions, and laboratory astrophysics. Preliminary commissioning results are presented including the first soft x-ray single-shot energy spectrum from a free electron laser.

    View details for DOI 10.1063/1.3698294

    View details for Web of Science ID 000303415300008

    View details for PubMedID 22559515

  • Microscopic probing of the size dependence in hydrophobic solvation JOURNAL OF CHEMICAL PHYSICS Huang, N., Schlesinger, D., Nordlund, D., Huang, C., Tyliszczak, T., Weiss, T. M., Acremann, Y., Pettersson, L. G., Nilsson, A. 2012; 136 (7)

    Abstract

    We report small angle x-ray scattering data demonstrating the direct experimental microscopic observation of the small-to-large crossover behavior of hydrophobic effects in hydrophobic solvation. By increasing the side chain length of amphiphilic tetraalkyl-ammonium (C(n)H(2n+1))(4)N(+) (R(4)N(+)) cations in aqueous solution we observe diffraction peaks indicating association between cations at a solute size between 4.4 and 5 Å, which show temperature dependence dominated by hydrophobic attraction. Using O K-edge x-ray absorption we show that small solutes affect hydrogen bonding in water similar to a temperature decrease, while large solutes affect water similar to a temperature increase. Molecular dynamics simulations support, and provide further insight into, the origin of the experimental observations.

    View details for DOI 10.1063/1.3684893

    View details for Web of Science ID 000300551000021

    View details for PubMedID 22360248

  • Polarization dependent resonant x-ray emission spectroscopy of D2O and H2O water: Assignment of the local molecular orbital symmetry JOURNAL OF CHEMICAL PHYSICS Tokushima, T., Horikawa, Y., Arai, H., Harada, Y., Takahashi, O., Pettersson, L. G., Nilsson, A., Shin, S. 2012; 136 (4)

    Abstract

    The polarization dependence of the split two peaks in the lone-pair region in the x-ray emission spectra has been determined at several different excitation energies for both D(2)O and H(2)O water. In contrast to predictions based on a narrow range of local water structures where the two peaks would be of different molecular orbital symmetry and arise from, respectively, intact and dissociated molecules, we show that the two peaks in the lone-pair region are both of lone-pair 1b(1) orbital symmetry. The results support the interpretation that the two peaks appear due to fluctuations between two distinct different main structural environments.

    View details for DOI 10.1063/1.3678443

    View details for Web of Science ID 000299793700051

    View details for PubMedID 22299901

  • X-ray emission spectroscopy and density functional study of CO/Fe(100) JOURNAL OF CHEMICAL PHYSICS Gladh, J., Oberg, H., Li, J., Ljungberg, M. P., Matsuda, A., Ogasawara, H., Nilsson, A., Pettersson, L. G., Ostrom, H. 2012; 136 (3)

    Abstract

    We report x-ray emission and absorption spectroscopy studies of the electronic structure of the predissociative α(3) phase of CO bound at hollow sites of Fe(100) as well as of the on-top bound species in the high-coverage α(1) phase. The analysis is supported by density functional calculations of structures and spectra. The bonding of "lying down" CO in the hollow site is well described in terms of π to π∗ charge transfer made possible through bonding interaction also at the oxygen in the minority spin-channel. The on-top CO in the mixed, high-coverage α(1) phase is found to be tilted due to adsorbate-adsorbate interaction, but still with bonding mainly characteristic of "vertical" on-top adsorbed CO similar to other transition-metal surfaces.

    View details for DOI 10.1063/1.3675834

    View details for Web of Science ID 000299387700038

    View details for PubMedID 22280772

  • Probing substrate effects in the carbon-projected band structure of graphene on Pt(111) through resonant inelastic x-ray scattering PHYSICAL REVIEW B Rajasekaran, S., Kaya, S., Anniyev, T., Ogasawara, H., Nilsson, A. 2012; 85 (4)
  • Tuning the Metal-Adsorbate Chemical Bond through the Ligand Effect on Platinum Subsurface Alloys ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Anniyev, T., Kaya, S., Rajasekaran, S., Ogasawara, H., Nordlund, D., Nilsson, A. 2012; 51 (31): 7724-7728

    Abstract

    Scratching beneath the surface: Pt-M(3d)-Pt(111) (M(3d) = Co, Ni) bimetallic subsurface alloys have been designed to show the ligand effect tunes reactivity in oxygen and hydrogen adsorption systems. The platinum-oxygen bond order was investigated by oxygen atom projection in the occupied and unoccupied space using X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS).

    View details for DOI 10.1002/anie.201201068

    View details for Web of Science ID 000306757900018

    View details for PubMedID 22711521

  • Ab Initio van der Waals Interactions in Simulations of Water Alter Structure from Mainly Tetrahedral to High-Density-Like JOURNAL OF PHYSICAL CHEMISTRY B Mogelhoj, A., Kelkkanen, A. K., Wikfedt, K. T., Schiotz, J., Mortensen, J. J., Pettersson, L. G., Lundqvist, B. I., Jacobsen, K. W., Nilsson, A., Norskov, J. K. 2011; 115 (48): 14149-14160

    Abstract

    The structure of liquid water at ambient conditions is studied in ab initio molecular dynamics simulations in the NVE ensemble using van der Waals (vdW) density-functional theory, i.e., using the new exchange-correlation functionals optPBE-vdW and vdW-DF2, where the latter has softer nonlocal correlation terms. Inclusion of the more isotropic vdW interactions counteracts highly directional hydrogen bonds, which are enhanced by standard functionals. This brings about a softening of the microscopic structure of water, as seen from the broadening of angular distribution functions and, in particular, from the much lower and broader first peak in the oxygen-oxygen pair-correlation function (PCF) and loss of structure in the outer hydration shells. Inclusion of vdW interactions is shown to shift the balance of resulting structures from open tetrahedral to more close-packed. The resulting O-O PCF shows some resemblance with experiment for high-density water (Soper, A. K. and Ricci, M. A. Phys. Rev. Lett. 2000, 84, 2881), but not directly with experiment for ambient water. Considering the accuracy of the new functionals for interaction energies, we investigate whether the simulation protocol could cause the deviation. An O-O PCF consisting of a linear combination of 70% from vdW-DF2 and 30% from low-density liquid water, as extrapolated from experiments, reproduces near-quantitatively the experimental O-O PCF for ambient water. This suggests the possibility that the new functionals may be reliable and that instead larger-scale simulations in the NPT ensemble, where the density is allowed to fluctuate in accordance with proposals for supercooled water, could resolve the apparent discrepancy with the measured PCF.

    View details for DOI 10.1021/jp2040345

    View details for Web of Science ID 000297446200020

    View details for PubMedID 21806000

  • Perspective on the structure of liquid water CHEMICAL PHYSICS Nilsson, A., Pettersson, L. G. 2011; 389 (1-3): 1-34
  • Oxidation of Pt(111) under Near-Ambient Conditions PHYSICAL REVIEW LETTERS Miller, D. J., Oberg, H., Kaya, S., Casalongue, H. S., Friebel, D., Anniyev, T., Ogasawara, H., Bluhm, H., Pettersson, L. G., Nilsson, A. 2011; 107 (19)

    Abstract

    The oxidation of Pt(111) at near-ambient O2 pressures has been followed in situ using x-ray photoelectron spectroscopy (XPS) and ex situ using x-ray absorption spectroscopy (XAS). Polarization-dependent XAS signatures at the O K edge reveal significant temperature- and pressure-dependent changes of the Pt-O interaction. Oxide growth commences via a PtO-like surface oxide that coexists with chemisorbed oxygen, while an ultrathin α-PtO2 trilayer is identified as the precursor to bulk oxidation. These results have important implications for understanding the chemical state of Pt in catalysis.

    View details for DOI 10.1103/PhysRevLett.107.195502

    View details for Web of Science ID 000297006700011

    View details for PubMedID 22181624

  • X-ray Raman scattering provides evidence for interfacial acetonitrile-water dipole interactions in aqueous solutions JOURNAL OF CHEMICAL PHYSICS Huang, N., Nordlund, D., Huang, C., Bergmann, U., Weiss, T. M., Pettersson, L. G., Nilsson, A. 2011; 135 (16)

    Abstract

    Aqueous solutions of acetonitrile (MeCN) have been studied with oxygen K-edge x-ray Raman scattering (XRS) which is found to be sensitive to the interaction between water and MeCN. The changes in the XRS spectra can be attributed to water directly interacting with MeCN and are reproduced by density functional theory calculations on small clusters of water and MeCN. The dominant structural arrangement features dipole interaction instead of H-bonds between the two species as revealed by the XRS spectra combined with spectrum calculations. Small-angle x-ray scattering shows the largest heterogeneity for a MeCN to water ratio of 0.4 in agreement with earlier small-angle neutron scattering data.

    View details for DOI 10.1063/1.3655468

    View details for Web of Science ID 000296521200033

    View details for PubMedID 22047254

    View details for PubMedCentralID PMC3298555

  • Increased fraction of low-density structures in aqueous solutions of fluoride JOURNAL OF CHEMICAL PHYSICS Waluyo, I., Huang, C., Nordlund, D., Weiss, T. M., Pettersson, L. G., Nilsson, A. 2011; 134 (22)

    Abstract

    X-ray absorption spectroscopy (XAS) and small angle x-ray scattering (SAXS) were utilized to study the effect of fluoride (F(-)) anion in aqueous solutions. XAS spectra show that F(-) increases the number of strong H-bonds, likely between F(-) and water in the first hydration shell. SAXS data show a low-Q scattering intensity increase similar to the effect of a temperature decrease, suggesting an enhanced anomalous scattering behavior in F(-) solutions. Quantitative analysis revealed that fluoride solutions have larger correlation lengths than chloride solutions with the same cations but shorter compared to pure water. This is interpreted as an increased fraction of tetrahedral low-density structures in the solutions due to the presence of the F(-) ions, which act as nucleation centers replacing water in the H-bonding network and forming stronger H-bonds, but the presence of the cations restricts the extension of strong H-bonds.

    View details for DOI 10.1063/1.3597606

    View details for Web of Science ID 000291660200025

    View details for PubMedID 21682525

    View details for PubMedCentralID PMC3188619

  • Enhanced small-angle scattering connected to the Widom line in simulations of supercooled water JOURNAL OF CHEMICAL PHYSICS Wikfeldt, K. T., Huang, C., Nilsson, A., Pettersson, L. G. 2011; 134 (21)

    Abstract

    We present extensive simulations on the TIP4P∕2005 water model showing significantly enhanced small-angle scattering (SAS) in the supercooled regime. The SAS is related to the presence of a Widom line (T(W)) characterized by maxima in thermodynamic response functions and Ornstein-Zernike correlation length. Recent experimental small-angle x-ray scattering data [Huang et al., J. Chem. Phys. 133, 134504 (2010)] are excellently reproduced, albeit with an increasing temperature offset at lower temperatures. Assuming the same origin of the SAS in experiment and model this suggests the existence of a Widom line also in real supercooled water. Simulations performed at 1000 bar show an increased abruptness of a crossover from dominating high-density (HDL) to dominating low-density (LDL) liquid and strongly enhanced SAS associated with crossing T(W), consistent with a recent determination of the critical pressure of TIP4P∕2005 at 1350 bar. Furthermore, good agreement with experimental isothermal compressibilities at 1000, 1500, and 2000 bar shows that the high pressure supercooled thermodynamic behavior of water is well described by TIP4P∕2005. Analysis of the tetrahedrality parameter Q reveals that the HDL-LDL structural transition is very sharp at 1000 bar, and that structural fluctuations become strongly coupled to density fluctuations upon approaching T(W). Furthermore, the tetrahedrality distribution becomes bimodal at ambient temperatures, an observation that possibly provides a link between HDL-LDL fluctuations and the structural bimodality in liquid water indicated by x-ray spectroscopic techniques. Computed x-ray absorption spectra are indeed found to show sensitivity to the tetrahedrality parameter.

    View details for DOI 10.1063/1.3594545

    View details for Web of Science ID 000291402700030

    View details for PubMedID 21663366

  • Hydrogen Spillover in Pt-Single-Walled Carbon Nanotube Composites: Formation of Stable C-H Bonds JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Bhowmick, R., Rajasekaran, S., Friebel, D., Beasley, C., Jiao, L., Ogasawara, H., Dai, H., Clemens, B., Nilsson, A. 2011; 133 (14): 5580-5586

    Abstract

    Using in situ electrical conductivity and ex situ X-ray photoelectron spectroscopy (XPS) measurements, we have examined how the hydrogen uptake of single-walled carbon nanotubes (SWNTs) is influenced by the addition of Pt nanoparticles. The conductivity of platinum-sputtered single-walled carbon nanotubes (Pt-SWNTs) during molecular hydrogen exposure decreased more rapidly than that of the corresponding pure SWNTs, which supports a hydrogenation mechanism facilitated by "spillover" of dissociated hydrogen from the Pt nanoparticles. C 1s XPS spectra indicate that the Pt-SWNTs store hydrogen by means of chemisorption, that is, covalent C-H bond formation: molecular hydrogen charging at elevated pressure (8.27 bar) and room temperature yielded Pt-SWNTs with up to 16 ± 1.5 at. % sp(3)-hybridized carbon atoms, which corresponds to a hydrogen-storage capacity of 1.2 wt % (excluding the weight of Pt nanoparticles). Pt-SWNTs prepared by the Langmuir-Blodgett (LB) technique exhibited the highest Pt/SWNT ratio and also the best hydrogen uptake.

    View details for DOI 10.1021/ja200403m

    View details for Web of Science ID 000289829100060

    View details for PubMedID 21428292

  • The structure of water in the hydration shell of cations from x-ray Raman and small angle x-ray scattering measurements JOURNAL OF CHEMICAL PHYSICS Waluyo, I., Huang, C., Nordlund, D., Bergmann, U., Weiss, T. M., Pettersson, L. G., Nilsson, A. 2011; 134 (6)

    Abstract

    X-ray Raman scattering (XRS) spectroscopy and small angle x-ray scattering (SAXS) are used to study water in aqueous solutions of NaCl, MgCl(2), and AlCl(3) with the particular aim to provide information about the structure of the hydration shells of the cations. The XRS spectra show that Na(+) weakens the hydrogen bonds of water molecules in its vicinity, similar to the effect of increased temperature and pressure. Mg(2+) and Al(3+), on the other hand, cause the formation of short and strong hydrogen bonds between the surrounding water molecules. The SAXS data show that Mg(2+) and Al(3+) form tightly bound hydration shells that give a large density contrast in the scattering data. From the form factors extracted from the SAXS data, we found that Mg(2+) and Al(3+) have, respectively, an equivalent of one and one and a half stable hydration shells that appear as a density contrast. In addition, we estimated that the density of water in the hydration shells of Mg(2+) and Al(3+) is, respectively, ∼61% and ∼71% higher than in bulk water.

    View details for DOI 10.1063/1.3533958

    View details for Web of Science ID 000287327400058

    View details for PubMedID 21322711

    View details for PubMedCentralID PMC3188634

  • Vibrational interference effects in x-ray emission of a model water dimer: Implications for the interpretation of the liquid spectrum JOURNAL OF CHEMICAL PHYSICS Ljungberg, M. P., Pettersson, L. G., Nilsson, A. 2011; 134 (4)

    Abstract

    We apply the Kramers-Heisenberg formula to a model water dimer to discuss vibrational interference in the x-ray emission spectrum of the donor molecule for which the core-ionized potential energy surface is dissociative but bounded by the accepting molecule. A long core-hole lifetime leads to decay from Zundel-like, fully delocalized vibrational states in the intermediate potential without involvement of a specific dissociated component. Comparison is made to a model with an unbound intermediate state allowing dissociation to infinity which gives a sharp, fully dissociated feature, and a broad molecular peak at long core-hole life time. The implications of the vibrational interference effect on the liquid water spectrum are discussed and it is proposed that this mainly gives rise to an isotope-dependent asymmetrical broadening of the lone pair peak.

    View details for DOI 10.1063/1.3533956

    View details for Web of Science ID 000286897600079

    View details for PubMedID 21280754

  • Formation of hydroxyl and water layers on MgO films studied with ambient pressure XPS SURFACE SCIENCE Newberg, J. T., Starr, D. E., Yamamoto, S., Kaya, S., Kendelewicz, T., Mysak, E. R., Porsgaard, S., Salmeron, M. B., Brown, G. E., Nilsson, A., Bluhm, H. 2011; 605 (1-2): 89-94
  • Degradation of Bimetallic Model Electrocatalysts: An In Situ X-Ray Absorption Spectroscopy Study ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Friebel, D., Miller, D. J., Nordlund, D., Ogasawara, H., Nilsson, A. 2011; 50 (43): 10190-10192

    View details for DOI 10.1002/anie.201101620

    View details for Web of Science ID 000296274700025

    View details for PubMedID 21755581

  • Wide-angle X-ray diffraction and molecular dynamics study of medium-range order in ambient and hot water PHYSICAL CHEMISTRY CHEMICAL PHYSICS Huang, C., Wikfeldt, K. T., Nordlund, D., Bergmann, U., McQueen, T., Sellberg, J., Pettersson, L. G., Nilsson, A. 2011; 13 (44): 19997-20007

    Abstract

    We have developed wide-angle X-ray diffraction measurements with high energy-resolution and accuracy to study water structure at three different temperatures (7, 25 and 66 °C) under normal pressure. Using a spherically curved Ge crystal an energy resolution better than 15 eV has been achieved which eliminates influence from Compton scattering. The high quality of the data allows for a reliable Fourier transform of the experimental data resolving shell structure out to ~12 Å, i.e. 5 hydration shells. Large-scale molecular dynamics (MD) simulations using the TIP4P/2005 force-field reproduce excellently the experimental shell-structure in the range 4-12 Å although less agreement is seen for the first peak in the intermolecular pair-correlation function (PCF). The Shiratani-Sasai Local Structure Index [J. Chem. Phys. 104, 7671 (1996)] identifies a tetrahedral minority giving the intermediate-range oscillations in the O-O PCF and a disordered majority providing a more featureless background in this range. The current study supports the proposal that the structure of liquid water, even at high temperatures, can be described in terms of a two-state fluctuation model involving local structures related to the high-density and low-density forms of liquid water postulated in the liquid-liquid phase transition hypothesis.

    View details for DOI 10.1039/c1cp22804h

    View details for Web of Science ID 000296383100038

    View details for PubMedID 22009343

  • Spatially inhomogeneous bimodal inherent structure of simulated liquid water PHYSICAL CHEMISTRY CHEMICAL PHYSICS Wikfeldt, K. T., Nilsson, A., Pettersson, L. G. 2011; 13 (44): 19918-19924

    Abstract

    In the supercooled regime at elevated pressure two forms of liquid water, high-density (HDL) and low-density (LDL), have been proposed to be separated by a coexistence line ending at a critical point, but a connection to water at ambient conditions has been lacking. Here we perform large-scale molecular dynamics simulations and demonstrate that the underlying potential energy surface gives a strictly bimodal characterization of the molecules at all temperatures and pressures, including the biologically and technologically important ambient regime, as spatially inhomogeneous either LDL- or HDL-like with a 3 : 1 predominance for HDL under ambient conditions. The Widom line in the supercooled regime, where maximal structural fluctuations take place, coincides with a 1 : 1 distribution. Although our results are based on molecular dynamics force-field simulations the close agreement with recent analyses of experimental X-ray spectroscopy and scattering data indicates a unified description also of real liquid water covering supercooled to ambient conditions.

    View details for DOI 10.1039/c1cp22076d

    View details for Web of Science ID 000296383100029

    View details for PubMedID 21915406

  • In situ X-ray probing reveals fingerprints of surface platinum oxide PHYSICAL CHEMISTRY CHEMICAL PHYSICS Friebel, D., Miller, D. J., O'Grady, C. P., Anniyev, T., Bargar, J., Bergmann, U., Ogasawara, H., Wikfeldt, K. T., Pettersson, L. G., Nilsson, A. 2011; 13 (1): 262-266

    Abstract

    In situ X-ray absorption spectroscopy (XAS) at the Pt L(3) edge is a useful probe for Pt-O interactions at polymer electrolyte membrane fuel cell (PEMFC) cathodes. We show that XAS using the high energy resolution fluorescence detection (HERFD) mode, applied to a well-defined monolayer Pt/Rh(111) sample where the bulk penetrating hard X-rays probe only surface Pt atoms, provides a unique sensitivity to structure and chemical bonding at the Pt-electrolyte interface. Ab initio multiple-scattering calculations using the FEFF code and complementary extended X-ray absorption fine structure (EXAFS) results indicate that the commonly observed large increase of the white-line at high electrochemical potentials on PEMFC cathodes originates from platinum oxide formation, whereas previously proposed chemisorbed oxygen-containing species merely give rise to subtle spectral changes.

    View details for DOI 10.1039/c0cp01434f

    View details for Web of Science ID 000285099800030

    View details for PubMedID 21063617

  • Low O-2 dissociation barrier on Pt(111) due to adsorbate-adsorbate interactions JOURNAL OF CHEMICAL PHYSICS Miller, D. J., Oberg, H., Naslund, L., Anniyev, T., Ogasawara, H., Pettersson, L. G., Nilsson, A. 2010; 133 (22)

    Abstract

    O(2) dissociation on Pt(111) has been followed at low and saturation coverage using temperature-programmed x-ray photoelectron spectroscopy and simulated with mean-field kinetic modeling, yielding dissociation (E(a)) and desorption (E(d)) barriers of 0.32 and 0.36 eV, respectively. Density functional theory calculations show that E(a) is strongly influenced by the O-O interatomic potential in the atomic final state: of the supercells considered, that which maximizes attractive third-nearest-neighbor interactions in the atomic final state yields both the lowest computed dissociation barrier (0.24 eV) and the best agreement with experiment. It is proposed that the effect of adsorbate-adsorbate interactions must be considered when modeling catalytic processes involving dissociative steps.

    View details for DOI 10.1063/1.3512618

    View details for Web of Science ID 000285477800016

    View details for PubMedID 21171690

  • Semiclassical description of nuclear dynamics in x-ray emission of water PHYSICAL REVIEW B Ljungberg, M. P., Nilsson, A., Pettersson, L. G. 2010; 82 (24)
  • Direct Interaction of Water Ice with Hydrophobic Methyl-Terminated Si(111) JOURNAL OF PHYSICAL CHEMISTRY C Waluyo, I., Ogasawara, H., Kawai, M., Nilsson, A., Yamada, T. 2010; 114 (44): 19004-19008

    View details for DOI 10.1021/jp106944d

    View details for Web of Science ID 000283703500034

  • X-RAY SPECTROSCOPY Transferring electrons to water (vol 2, pg 800, 2010) NATURE CHEMISTRY Nilsson, A. 2010; 2 (11): 913-913
  • Increasing correlation length in bulk supercooled H2O, D2O, and NaCl solution determined from small angle x-ray scattering JOURNAL OF CHEMICAL PHYSICS Huang, C., Weiss, T. M., Nordlund, D., Wikfeldt, K. T., Pettersson, L. G., Nilsson, A. 2010; 133 (13)

    Abstract

    Using small angle x-ray scattering, we find that the correlation length of bulk liquid water shows a steep increase as temperature decreases at subzero temperatures (supercooling) and that it can, similar to the thermodynamic response functions, be fitted to a power law. This indicates that the anomalous properties of water are attributable to fluctuations between low- and high-density regions with rapidly growing average size upon supercooling. The substitution of H(2)O with D(2)O, as well as the addition of NaCl salt, leads to substantial changes of the power law behavior of the correlation length. Our results are consistent with the proposed existence of a liquid-liquid critical point in the deeply supercooled region but do not exclude a singularity-free model.

    View details for DOI 10.1063/1.3495974

    View details for Web of Science ID 000282699800030

    View details for PubMedID 20942543

    View details for PubMedCentralID PMC2966487

  • Transferring electrons to water (vol 2, pg 800, 2010) NATURE CHEMISTRY Nilsson, A. 2010; 2 (10)
  • X-RAY SPECTROSCOPY Transferring electrons to water NATURE CHEMISTRY Nilsson, A. 2010; 2 (10): 800-802

    View details for DOI 10.1038/nchem.807

    View details for Web of Science ID 000282091300004

    View details for PubMedID 20861888

  • Cooperativity in Surface Bonding and Hydrogen Bonding of Water and Hydroxyl at Metal Surfaces JOURNAL OF PHYSICAL CHEMISTRY C Schiros, T., Ogasawara, H., Naslund, L., Andersson, K. J., Ren, J., Meng, S., Karlberg, G. S., Odelius, M., Nilsson, A., Pettersson, L. G. 2010; 114 (22): 10240-10248

    View details for DOI 10.1021/jp101855v

    View details for Web of Science ID 000278301200022

  • Lattice-strain control of the activity in dealloyed core-shell fuel cell catalysts NATURE CHEMISTRY Strasser, P., Koh, S., Anniyev, T., Greeley, J., More, K., Yu, C., Liu, Z., Kaya, S., Nordlund, D., Ogasawara, H., Toney, M. F., Nilsson, A. 2010; 2 (6): 454-460

    Abstract

    Electrocatalysis will play a key role in future energy conversion and storage technologies, such as water electrolysers, fuel cells and metal-air batteries. Molecular interactions between chemical reactants and the catalytic surface control the activity and efficiency, and hence need to be optimized; however, generalized experimental strategies to do so are scarce. Here we show how lattice strain can be used experimentally to tune the catalytic activity of dealloyed bimetallic nanoparticles for the oxygen-reduction reaction, a key barrier to the application of fuel cells and metal-air batteries. We demonstrate the core-shell structure of the catalyst and clarify the mechanistic origin of its activity. The platinum-rich shell exhibits compressive strain, which results in a shift of the electronic band structure of platinum and weakening chemisorption of oxygenated species. We combine synthesis, measurements and an understanding of strain from theory to generate a reactivity-strain relationship that provides guidelines for tuning electrocatalytic activity.

    View details for DOI 10.1038/NCHEM.623

    View details for Web of Science ID 000277926800012

    View details for PubMedID 20489713

  • Reply to Soper et al.: Fluctuations in water around a bimodal distribution of local hydrogen-bonded structural motifs PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Huang, C., Wikfeldt, K. T., Tokushima, T., Nordlund, D., Harada, Y., Bergmann, U., Niebuhr, M., Weiss, T. M., Horikawa, Y., Leetmaa, M., Ljungberg, M. P., Takahashi, O., Lenz, A., Ojamae, L., Lyubartsev, A. P., Shin, S., Pettersson, L. G., Nilsson, A. 2010; 107 (12): E45-E45
  • Oxygen-oxygen correlations in liquid water: Addressing the discrepancy between diffraction and extended x-ray absorption fine-structure using a novel multiple-data set fitting technique JOURNAL OF CHEMICAL PHYSICS Wikfeldt, K. T., Leetmaa, M., Mace, A., Nilsson, A., Pettersson, L. G. 2010; 132 (10)

    Abstract

    The first peak of the oxygen-oxygen pair-correlation function (O-O PCF) is a critical measure of the first coordination-shell distances in liquid water. Recently, a discrepancy has been uncovered between diffraction and extended x-ray absorption fine-structure (EXAFS) regarding the height and position of this peak, where EXAFS gives a considerably more well-defined peak at a shorter distance compared to the diffraction results. This discrepancy is here investigated through a novel multiple-data set structure modeling technique, SpecSwap-RMC, based on the reverse Monte Carlo (RMC) method. Fitting simultaneously to both EXAFS and a diffraction-based O-O PCF shows that even though the reported EXAFS results disagree with diffraction, the two techniques can be reconciled by taking into account a strong contribution from the photoelectron scattering focusing effect in EXAFS originating from nearly linear hydrogen bonds. This many-body contribution, which is usually neglected in RMC modeling of EXAFS data, is included in the fits by precomputing and storing EXAFS signals from real-space multiple-scattering calculations on a large number of unique water clusters. On the other hand, fitting also the O-O PCF from diffraction is seen to enhance the amount of structural disorder in the joint fit. Thus, both structures containing nearly linear hydrogen bonds and local structural disorder are important to reproduce diffraction and EXAFS simultaneously. This work also illustrates a few of many possible uses of the SpecSwap-RMC method in modeling disordered materials, particularly for fitting computationally demanding techniques and combining multiple data sets.

    View details for DOI 10.1063/1.3330752

    View details for Web of Science ID 000275589700038

    View details for PubMedID 20232977

  • The role of substrate electrons in the wetting of a metal surface JOURNAL OF CHEMICAL PHYSICS Schiros, T., Takahashi, O., Andersson, K. J., Ostrom, H., Pettersson, L. G., Nilsson, A., Ogasawara, H. 2010; 132 (9)

    Abstract

    We address how the electronic and geometric structures of metal surfaces determine water-metal bonding by affecting the balance between Pauli repulsion and electrostatic attraction. We show how the rigid d-electrons and the softer s-electrons utilize different mechanisms for the redistribution of charge that enables surface wetting. On open d-shell Pt(111), the ligand field of water alters the distribution of metal d-electrons to reduce the repulsion. The closed-shell Cu d(10) configuration of isostructural Cu(111), however, does not afford this mechanism, resulting in a hydrophobic surface and three-dimensional ice cluster formation. On the geometrically corrugated Cu(110) surface, however, charge depletion involving the mobile sp-electrons at atomic rows reduces the exchange repulsion sufficiently such that formation of a two-dimensional wetting layer is still favored in spite of the d(10) electronic configuration.

    View details for DOI 10.1063/1.3292681

    View details for Web of Science ID 000275245400025

    View details for PubMedID 20210405

  • Preface to special issue on inner-shell spectroscopies applied to water and hydrogen bonds Preface JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Nilsson, A., Guo, J. 2010; 177 (2-3): 59-59
  • Theoretical approximations to X-ray absorption spectroscopy of liquid water and ice JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Leetmaa, M., Ljungberg, M. P., Lyubartsev, A., Nilsson, A., Pettersson, L. G. 2010; 177 (2-3): 135-157
  • Chemical bonding of water to metal surfaces studied with core-level spectroscopies JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Schiros, T., Andersson, K. J., Pettersson, L. G., Nilsson, A., Ogasawara, H. 2010; 177 (2-3): 85-98
  • X-ray absorption spectroscopy and X-ray Raman scattering of water and ice; an experimental view JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Nilsson, A., Nordlund, D., Waluyo, I., Huang, N., Ogasawara, H., Kaya, S., Bergmann, U., Naeslund, L., Ostrom, H., Wernet, P., Andersson, K. J., Schiros, T., Pettersson, L. G. 2010; 177 (2-3): 99-129
  • High resolution X-ray emission spectroscopy of water and its assignment based on two structural motifs JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Tokushima, T., Harada, Y., Horikawa, Y., Takahashi, O., Senba, Y., Ohashi, H., Pettersson, L. G., Nilsson, A., Shin, S. 2010; 177 (2-3): 192-205
  • Water Adsorption on alpha-Fe2O3(0001) at near Ambient Conditions JOURNAL OF PHYSICAL CHEMISTRY C Yamamoto, S., Kendelewicz, T., Newberg, J. T., Ketteler, G., Starr, D. E., Mysak, E. R., Andersson, K. J., Ogasawara, H., Bluhm, H., Salmeron, M., Brown, G. E., Nilsson, A. 2010; 114 (5): 2256-2266

    View details for DOI 10.1021/jp909876t

    View details for Web of Science ID 000274269700040

  • Peroxide-like intermediate observed at hydrogen rich condition on Pt(111) after interaction with oxygen PHYSICAL CHEMISTRY CHEMICAL PHYSICS MacNaughton, J. B., Naslund, L., Anniyev, T., Ogasawara, H., Nilsson, A. 2010; 12 (21): 5712-5716

    Abstract

    Hydrogen peroxide has been found to form as a byproduct during fuel cell operation, which is linked to the degradation of the ion exchange membrane resulting in a shorter lifetime of the fuel cell. Using O 1s X-ray photoelectron spectroscopy and X-ray absorption spectroscopy we investigated the molecular oxygen adsorption on hydrogenated Pt(111) and found that adsorbed hydrogen promotes the formation of a hydrogen peroxide-like intermediate. Polarization dependent X-ray absorption spectroscopy reveals that the O-O molecular axis is close to parallel and the OH group is perpendicular to the surface.

    View details for DOI 10.1039/b926409b

    View details for Web of Science ID 000277926500022

    View details for PubMedID 20386804

  • Complementarity between high-energy photoelectron and L-edge spectroscopy for probing the electronic structure of 5d transition metal catalysts PHYSICAL CHEMISTRY CHEMICAL PHYSICS Anniyev, T., Ogasawara, H., Ljungberg, M. P., Wikfeldt, K. T., MacNaughton, J. B., Naslund, L., Bergmann, U., Koh, S., Strasser, P., Pettersson, L. G., Nilsson, A. 2010; 12 (21): 5694-5700

    Abstract

    We demonstrate the successful use of hard X-ray photoelectron spectroscopy (HAXPES) for selectively probing the platinum partial d-density of states (DOS) in a Pt-Cu nanoparticle catalyst which shows activity superior to pure Pt towards the oxygen-reduction reaction (ORR). The information about occupied Pt d-band states was complemented by Pt L(2)-edge X-ray absorption near-edge spectroscopy (XANES), which probes unoccupied valence states. We found a significant electronic perturbation of the Pt projected d-DOS which was narrowed and shifted to higher binding energy compared to pure platinum. The effect of this electronic structure perturbation on the chemical properties of the nanoparticle surface is discussed in terms of the d-band model. We have thereby demonstrated that the combination of L-edge spectroscopy and HAXPES allows for an experimental derivation of the valence electronic structure in an element-specific way for 5d metal catalysts.

    View details for DOI 10.1039/b926414k

    View details for Web of Science ID 000277926500019

    View details for PubMedID 20442966

  • Sensitivity of x-ray absorption spectroscopy to hydrogen bond topology PHYSICAL REVIEW B Nordlund, D., Ogasawara, H., Andersson, K. J., Tatarkhanov, M., Salmeron, M., Pettersson, L. G., Nilsson, A. 2009; 80 (23)
  • The inhomogeneous structure of water at ambient conditions PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Huang, C., Wikfeldt, K. T., Tokushima, T., Nordlund, D., Harada, Y., Bergmann, U., Niebuhr, M., Weiss, T. M., Horikawa, Y., Leetmaa, M., Ljungberg, M. P., Takahashi, O., Lenz, A., Ojamae, L., Lyubartsev, A. P., Shin, S., Pettersson, L. G., Nilsson, A. 2009; 106 (36): 15214-15218

    Abstract

    Small-angle X-ray scattering (SAXS) is used to demonstrate the presence of density fluctuations in ambient water on a physical length-scale of approximately 1 nm; this is retained with decreasing temperature while the magnitude is enhanced. In contrast, the magnitude of fluctuations in a normal liquid, such as CCl(4), exhibits no enhancement with decreasing temperature, as is also the case for water from molecular dynamics simulations under ambient conditions. Based on X-ray emission spectroscopy and X-ray Raman scattering data we propose that the density difference contrast in SAXS is due to fluctuations between tetrahedral-like and hydrogen-bond distorted structures related to, respectively, low and high density water. We combine our experimental observations to propose a model of water as a temperature-dependent, fluctuating equilibrium between the two types of local structures driven by incommensurate requirements for minimizing enthalpy (strong near-tetrahedral hydrogen-bonds) and maximizing entropy (nondirectional H-bonds and disorder). The present results provide experimental evidence that the extreme differences anticipated in the hydrogen-bonding environment in the deeply supercooled regime surprisingly remain in bulk water even at conditions ranging from ambient up to close to the boiling point.

    View details for DOI 10.1073/pnas.0904743106

    View details for Web of Science ID 000269632400025

    View details for PubMedID 19706484

    View details for PubMedCentralID PMC2741230

  • Assessing the electric-field approximation to IR and Raman spectra of dilute HOD in D2O JOURNAL OF CHEMICAL PHYSICS Ljungberg, M. P., Lyubartsev, A. P., Nilsson, A., Pettersson, L. G. 2009; 131 (3)

    Abstract

    We analyze the validity of the commonly used electric-field (E-field) approximation to vibrational OH stretch Raman spectra of dilute HOD in D(2)O by computing the OH stretch frequency of all molecules in several different structure models, each containing around 2000 molecules. The calculations are done at the B3LYP level using clusters containing 32 molecules centered around the molecule for which the frequencies are calculated; the large cluster size is required due to significant nonlocal contributions influencing the computed frequencies. The vibrational frequencies are determined using a six-point potential optimized discrete variable representation. Raman and infrared intensities are furthermore computed to generate the spectra. We find that a quadratic fit of E-field versus frequency gives a reasonable representation of the calculated distribution of frequencies. However, the mapping depends significantly on the structural model and is thus not universal. Anharmonic couplings are calculated for several optimized clusters showing a general trend to compress the computed frequency distributions, which is in agreement with dynamical simulations (motional narrowing).

    View details for DOI 10.1063/1.3154144

    View details for Web of Science ID 000268206800035

    View details for PubMedID 19624203

  • Increased fraction of weakened hydrogen bonds of water in aerosol OT reverse micelles JOURNAL OF CHEMICAL PHYSICS Waluyo, I., Nordlund, D., Bergmann, U., Pettersson, L. G., Nilsson, A. 2009; 131 (3)

    Abstract

    Water in aerosol OT reverse micelles has been extensively studied as a model system for nanoconfined water. Results from previous vibrational studies suggest that water confined this way has slower dynamics compared to bulk water; however, the effects on the hydrogen bonding network are unclear. From our study of the structure of water hydrogen bonding using x-ray Raman spectroscopy, we found an increased fraction of weakened hydrogen bonds upon confinement, similar to the effect seen in temperature increase and NaCl solvation, as evidenced by the changes in specific spectral features.

    View details for DOI 10.1063/1.3184764

    View details for Web of Science ID 000268206800003

    View details for PubMedID 19624171

  • On the Range of Water Structure Models Compatible with X-ray and Neutron Diffraction Data JOURNAL OF PHYSICAL CHEMISTRY B Wikfeldt, K. T., Leetmaa, M., Ljungberg, M. P., Nilsson, A., Pettersson, L. G. 2009; 113 (18): 6246-6255

    Abstract

    We use the reverse Monte Carlo (RMC) method to critically evaluate the structural information content of diffraction data on bulk water by fitting simultaneously or separately to X-ray and neutron data; the O-H and H-H, but not the O-O, pair-correlation functions (PCFs) are well-described by the neutron data alone. Enforcing at the same time different H-bonding constraints, we generate four topologically different structure models of liquid water, including a simple mixture model, that all equally well reproduce the diffraction data. Although earlier work [Leetmaa, M.; et al. J. Chem. Phys. 2008, 129, 084502] has focused on tetrahedrality in the H-bond network in liquid water, we show here that, even for the O-O-O three-body correlation, tetrahedrality is not strictly defined by the data. We analyze how well two popular MD models (TIP4P-pol2 and SPC/E) reproduce the neutron data in q-space and find differences in important aspects from the experiment. From the RMC fits, we obtain pair-correlation functions (PCFs) that are in optimal agreement with the diffraction data but still show a surprisingly strong variability both in position and height of the first intermolecular (H-bonding) O-H peak. We conclude that, although diffraction data impose important constraints on the range of possible water structures, additional data are needed to narrow the range of possible structure models.

    View details for DOI 10.1021/jp9007619

    View details for Web of Science ID 000265687500010

    View details for PubMedID 19358575

  • NO2 Adsorption on Ag(100) Supported MgO(100) Thin Films: Controlling the Adsorption State with Film Thickness JOURNAL OF PHYSICAL CHEMISTRY C Starr, D. E., Weis, C., Yamamoto, S., Nilsson, A., Bluhm, H. 2009; 113 (17): 7355-7363

    View details for DOI 10.1021/jp900410v

    View details for Web of Science ID 000265529700067

  • Energetics of C-H Bonds Formed at Single-Walled Carbon Nanotubes NANO LETTERS Nikitin, A., Zhang, Z., Nilsson, A. 2009; 9 (4): 1301-1306

    Abstract

    We have calculated the adsorption energies for different hydrogen dimers adsorbed at the surface of zigzag single-walled carbon nanotubes (SWCNs) (n,0) (for n = 6-28) to identify the range of nanotube structural parameters that provide optimal adsorption energetics. We determined that, for H(2) gas in equilibrium with adsorbed hydrogen dimers, under normal conditions, carbon nanotubes with diameters in the range of 0.77 +/- 0.19 nm have a minimum energy overhead for hydrogen release and uptake in the hydrogen storage process. Most interestingly, we also found that the adsorption energies of hydrogen are correlated to the modulations of the nanotube density of states, because of the quantum confinement of electrons along the circumference of the SWCN. This effect is discussed from the perspective of chemical bond formation and is related to the valence to conduction band excitation energy.

    View details for DOI 10.1021/nl802727h

    View details for Web of Science ID 000265030000004

    View details for PubMedID 19281256

  • Water growth on metals and oxides: binding, dissociation and role of hydroxyl groups FARADAY DISCUSSIONS Salmeron, M., Bluhm, H., Tatarkhanov, N., Ketteler, G., Shimizu, T. K., Mugarza, A., Deng, X., Herranz, T., Yamamoto, S., Nilsson, A. 2009; 141: 221-229

    Abstract

    We discuss the role of the presence of dangling H-bonds from water or from surface hydroxyl species on the wetting behavior of surfaces. Using scanning tunneling and atomic force microscopies and photoelectron spectroscopy, we have examined a variety of surfaces, including mica, oxides and pure metals. We find that in all cases, the availability of free, dangling H-bonds at the surface is crucial for the subsequent growth of wetting water films. In the case of mica, electrostatic forces and H-bonding to surface O atoms determine the water orientation in the first layer and also in subsequent layers with a strong influence in its wetting characteristics. In the case of oxides like TiO2, Cu2O, SiO2 and Al2O3, surface hydroxyls form readily on defects upon exposure to water vapor and help nucleate the subsequent growth of molecular water films. On pure metals, such as Pt, Pd and Ru, the structure of the first water layer and whether or not it exhibits dangling H-bonds is again crucial. Dangling H-bonds are provided by molecules with their plane oriented vertically, or by OH groups formed by the partial dissociation of water. By tying the two H atoms of the water molecules into strong H-bonds with pre-adsorbed O on Ru can also quench the wettability of the surface.

    View details for DOI 10.1039/b806516k

    View details for Web of Science ID 000265964800014

    View details for PubMedID 19227359

  • Probing the hydrogen-bond network of water via time-resolved soft X-ray spectroscopy PHYSICAL CHEMISTRY CHEMICAL PHYSICS Huse, N., Wen, H., Nordlund, D., Szilagyi, E., Daranciang, D., Miller, T. A., Nilsson, A., Schoenlein, R. W., Lindenberg, A. M. 2009; 11 (20): 3951-3957

    Abstract

    We report time-resolved studies of hydrogen bonding in liquid H(2)O, in response to direct excitation of the O-H stretch mode at 3 mum, probed via soft X-ray absorption spectroscopy at the oxygen K-edge. This approach employs a newly developed nanofluidic cell for transient soft X-ray spectroscopy in the liquid phase. Distinct changes in the near-edge spectral region (XANES) are observed, and are indicative of a transient temperature rise of 10 K following transient laser excitation and rapid thermalization of vibrational energy. The rapid heating occurs at constant volume and the associated increase in internal pressure, estimated to be 8 MPa, is manifested by distinct spectral changes that differ from those induced by temperature alone. We conclude that the near-edge spectral shape of the oxygen K-edge is a sensitive probe of internal pressure, opening new possibilities for testing the validity of water models and providing new insight into the nature of hydrogen bonding in water.

    View details for DOI 10.1039/b822210j

    View details for Web of Science ID 000266065400018

    View details for PubMedID 19440624

  • The structure of mixed H2O-OH monolayer films on Ru(0001) JOURNAL OF CHEMICAL PHYSICS Tatarkhanov, M., Fomin, E., Salmeron, M., Andersson, K., Ogasawara, H., Pettersson, L. G., Nilsson, A., Cerda, J. I. 2008; 129 (15)

    Abstract

    Scanning tunneling microscopy (STM) and x-ray absorption spectroscopy (XAS) have been used to study the structures produced by water on Ru(0001) at temperatures above 140 K. It was found that while undissociated water layers are metastable below 140 K, heating above this temperature produces drastic transformations, whereby a fraction of the water molecules partially dissociate and form mixed H(2)O-OH structures. X-ray photoelectron spectroscopy and XAS revealed the presence of hydroxyl groups with their O-H bond essentially parallel to the surface. STM images show that the mixed H(2)O-OH structures consist of long narrow stripes aligned with the three crystallographic directions perpendicular to the close-packed atomic rows of the Ru(0001) substrate. The internal structure of the stripes is a honeycomb network of H-bonded water and hydroxyl species. We found that the metastable low temperature molecular phase can also be converted to a mixed H(2)O-OH phase through excitation by the tunneling electrons when their energy is 0.5 eV or higher above the Fermi level. Structural models based on the STM images were used for density functional theory optimizations of the stripe geometry. The optimized geometry was then utilized to calculate STM images for comparison with the experiment.

    View details for DOI 10.1063/1.2988903

    View details for Web of Science ID 000260280600009

    View details for PubMedID 19045178

  • Diffraction and IR/Raman data do not prove tetrahedral water JOURNAL OF CHEMICAL PHYSICS Leetmaa, M., Wikfeldt, K. T., Ljungberg, M. P., Odelius, M., Swenson, J., Nilsson, A., Pettersson, L. G. 2008; 129 (8)

    Abstract

    We use the reverse Monte Carlo modeling technique to fit two extreme structure models for water to available x-ray and neutron diffraction data in q space as well as to the electric field distribution as a representation of the OH stretch Raman spectrum of dilue HOD in D(2)O; the internal geometries were fitted to a quantum distribution. Forcing the fit to maximize the number of hydrogen (H) bonds results in a tetrahedral model with 74% double H-bond donors (DD) and 21% single donors (SD). Maximizing instead the number of SD species gives 81% SD and 18% DD, while still reproducing the experimental data and losing only 0.7-1.8 kJ/mole interaction energy. By decomposing the simulated Raman spectrum we can relate the models to the observed ultrafast frequency shifts in recent pump-probe measurements. Within the tetrahedral DD structure model the assumed connection between spectrum position and H-bonding indicates ultrafast dynamics in terms of breaking and reforming H bonds while in the strongly distorted model the observed frequency shifts do not necessarily imply H-bond changes. Both pictures are equally valid based on present diffraction and vibrational experimental data. There is thus no strict proof of tetrahedral water based on these data. We also note that the tetrahedral structure model must, to fit diffraction data, be less structured than most models obtained from molecular dynamics simulations.

    View details for DOI 10.1063/1.2968550

    View details for Web of Science ID 000259008900022

    View details for PubMedID 19044830

  • High resolution X-ray emission spectroscopy of liquid water: The observation of two structural motifs CHEMICAL PHYSICS LETTERS Tokushima, T., Harada, Y., Takahashi, O., Senba, Y., Ohashi, H., Pettersson, L. G., Nilsson, A., Shin, S. 2008; 460 (4-6): 387-400
  • Electronic structure effects in liquid water studied by photoelectron spectroscopy and density functional theory CHEMICAL PHYSICS LETTERS Nordlund, D., Odelius, M., Bluhm, H., Ogasawara, H., Pettersson, L. G., Nilsson, A. 2008; 460 (1-3): 86-92
  • C-H bond formation at the graphite surface studied with core level spectroscopy SURFACE SCIENCE Nikitin, A., Naeslund, L., Zhang, Z., Nilsson, A. 2008; 602 (14): 2575-2580
  • Comment on "Isotope and Temperature Effects in Liquid Water Probed by X-ray Absorption and Resonant X-ray Emission Spectroscopy" PHYSICAL REVIEW LETTERS Pettersson, L. G., Tokushima, T., Harada, Y., Takahashi, O., Shin, S., Nilsson, A. 2008; 100 (24)
  • Spectroscopic evidence for the formation of 3-D crystallites during isothermal heating of amorphous ice on Pt(111) SURFACE SCIENCE Waluyo, I., Nordlund, D., Naeslund, L., Ogasawara, H., Pettersson, L. G., Nilsson, A. 2008; 602 (11): 2004-2008
  • In situ x-ray photoelectron spectroscopy studies of water on metals and oxides at ambient conditions JOURNAL OF PHYSICS-CONDENSED MATTER Yamamoto, S., Bluhm, H., Andersson, K., Ketteler, G., Ogasawara, H., Salmeron, M., Nilsson, A. 2008; 20 (18)
  • Autocatalytic water dissociation on Cu(110) at near ambient conditions JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Andersson, K., Ketteler, G., Bluhm, H., Yamamoto, S., Ogasawara, H., Pettersson, L. G., Salmeron, M., Nilsson, A. 2008; 130 (9): 2793-2797

    Abstract

    Autocatalytic dissociation of water on the Cu(110) metal surface is demonstrated on the basis of X-ray photoelectron spectroscopy studies carried out in situ under near ambient conditions of water vapor pressure (1 Torr) and temperature (275-520 K). The autocatalytic reaction is explained as the result of the strong hydrogen-bond in the H2O-OH complex of the dissociated final state, which lowers the water dissociation barrier according to the Brønsted-Evans-Polanyi relations. A simple chemical bonding picture is presented which predicts autocatalytic water dissociation to be a general phenomenon on metal surfaces.

    View details for DOI 10.1021/ja073727x

    View details for Web of Science ID 000253549800039

    View details for PubMedID 18257559

  • Nearest-neighbor oxygen distances in liquid water and ice observed by x-ray Raman based extended x-ray absorption fine structure (vol 127, art no 174504, 2007) JOURNAL OF CHEMICAL PHYSICS Bergmann, U., Di Cicco, A., Wernet, P., Principi, E., Glatzel, P., Nilsson, A. 2008; 128 (8)

    View details for DOI 10.1063/1.2828190

    View details for Web of Science ID 000254047200063

  • Double Role of Water in the Fuel Cell Oxygen Reduction Reaction 8th Symposium on Proton Exchange Membrane Fuel Cells Ogasawara, H., Naeslund, L., MacNaughton, J. B., Anniyev, T., Nilsson, A. ELECTROCHEMICAL SOCIETY INC. 2008: 1385–94

    View details for DOI 10.1149/1.2981979

    View details for Web of Science ID 000271859300142

  • Hydrogen storage in carbon nanotubes through the formation of stable C-H bonds NANO LETTERS Nikitin, A., Li, X., Zhang, Z., Ogasawara, H., Dai, H., Nilsson, A. 2008; 8 (1): 162-167

    Abstract

    To determine if carbon-based materials can be used for hydrogen storage, we have studied hydrogen chemisorption in single-walled carbon nanotubes. Using atomic hydrogen as the hydrogenation agent, we demonstrated that maximal degree of nanotube hydrogenation depends on the nanotube diameter, and for the diameter values around 2.0 nm nanotube-hydrogen complexes with close to 100% hydrogenation exist and are stable at room temperature. This means that specific carbon nanotubes can have a hydrogen storage capacity of more than 7 wt % through the formation of reversible C-H bonds.

    View details for DOI 10.1021/nl072325k

    View details for Web of Science ID 000252257700029

    View details for PubMedID 18088150

  • Geometrical characterization of adenine and guanine on Cu(110) by NEXAFS, XPS, and DFT calculation SURFACE SCIENCE Furukawa, M., Yamada, T., Katano, S., Kawai, M., Ogasawara, H., Nilsson, A. 2007; 601 (23): 5433-5440
  • Probing the electron delocalization in liquid water and ice at attosecond time scales PHYSICAL REVIEW LETTERS Nordlund, D., Ogasawara, H., Bluhm, H., Takahashi, O., Odelius, M., Nagasono, M., Pettersson, L. G., Nilsson, A. 2007; 99 (21)

    Abstract

    We determine electron delocalization rates in liquid water and ice using core-hole decay spectroscopy. The hydrogen-bonded network delocalizes the electrons in less than 500 as. Broken or weak hydrogen bonds--in the liquid or at the surface of ice--provide states where the electron remains localized longer than 20 fs. These asymmetrically bonded water species provide electron traps, acting as a strong precursor channel to the hydrated electron.

    View details for DOI 10.1103/PhysRevLett.99.217406

    View details for Web of Science ID 000251107500062

    View details for PubMedID 18233257

  • Nearest-neighbor oxygen distances in liquid water and ice observed by x-ray Raman based extended x-ray absorption fine structure JOURNAL OF CHEMICAL PHYSICS Bergmann, U., Di Cicco, A., Wernet, P., Principi, E., Glatzel, P., Nilsson, A. 2007; 127 (17)

    Abstract

    We report the nearest-neighbor oxygen-oxygen radial distribution function (NN O-O RDF) of room temperature liquid water and polycrystalline ice Ih (-16.8 degrees C) obtained by x-ray Raman based extended x-ray absorption fine structure (EXAFS) spectroscopy. The spectra of the two systems were taken under identical experimental conditions using the same procedures to obtain the NN O-O RDFs. This protocol ensured a measurement of the relative distance distribution with very small systematic errors. The NN O-O RDF of water is found to be more asymmetric (tail extending to longer distances) with longer average distance (2.81 A for water and 2.76 A for ice) but a slightly shorter peak position (2.70 A for water and 2.71 A for ice). The refinement also showed a small but significant contribution from the linear O-H-O multiple scattering signal. The high sensitivity to short range distances of the EXAFS probe will set further restrictions to the range of possible models of liquid water.

    View details for DOI 10.1063/1.2784123

    View details for Web of Science ID 000250787300026

    View details for PubMedID 17994824

  • Structure and bonding of the water-hydroxyl mixed phase on Pt(111) JOURNAL OF PHYSICAL CHEMISTRY C Schiros, T., Naslund, L., Andersson, K., Gyllenpalm, J., Karlberg, G. S., Odelius, M., Ogasawara, H., Pettersson, L. G., Nilsson, A. 2007; 111 (41): 15003-15012

    View details for DOI 10.1021/jp073405f

    View details for Web of Science ID 000250142300013

  • Geometric and electronic structure of methane adsorbed on a Pt surface JOURNAL OF CHEMICAL PHYSICS Ostrom, H., Ogasawara, H., Naslund, L., Andersson, K., Pettersson, L. G., Nilsson, A. 2007; 127 (14)

    Abstract

    The electronic structure of methane adsorbed on Pt(977) is investigated using angle-resolved x-ray absorption spectroscopy (XAS) in combination with density functional theory spectrum calculations. XAS, which probes the unoccupied states atom specifically, shows the appearance of the symmetry-forbidden gas-phase lowest unoccupied molecular orbital due to s-p rehybridization. In addition new adsorption-induced states appear just above the Fermi level. A systematic investigation, where computed XA spectra are compared with the experiment, indicates elongation of the C-H bond pointing toward the surface to 1.18+/-0.05 A. The bond elongation arises due to mixing between bonding and antibonding C-H orbitals. Computed charge density difference plots show that no covalent chemical bond is formed between the adsorbate and substrate upon adsorption. The changes in electronic structure arise in order to minimize the Pauli repulsion by polarizing charge away from the surface toward the carbon atom of the methane molecule.

    View details for DOI 10.1063/1.2781470

    View details for Web of Science ID 000250140800044

    View details for PubMedID 17935418

  • Bridging the pressure gap in water and hydroxyl chemistry on metal surfaces: The Cu(110) case JOURNAL OF PHYSICAL CHEMISTRY C Andersson, K., Ketteler, G., Bluhm, H., Yamamoto, S., Ogasawara, H., Pettersson, L. G., Salmeron, M., Nilsson, A. 2007; 111 (39): 14493-14499

    View details for DOI 10.1021/jp073681u

    View details for Web of Science ID 000249838300032

  • Dynamical core-hole screening in the x-ray absorption spectra of hydrogenated carbon nanotubes and graphene PHYSICAL REVIEW B Wessely, O., Katsnelson, M. I., Nilsson, A., Nikitin, A., Ogasawara, H., Odelius, M., Sanyal, B., Eriksson, O. 2007; 76 (16)
  • Isotope effects in liquid water probed by x-ray Raman spectroscopy PHYSICAL REVIEW B Bergmann, U., Nordlund, D., Wernet, P., Odelius, M., Pettersson, L. G., Nilsson, A. 2007; 76 (2)
  • The nature of water nucleation sites on TiO2(110) surfaces revealed by ambient pressure X-ray photoelectron spectroscopy JOURNAL OF PHYSICAL CHEMISTRY C Ketteler, G., Yamamoto, S., Bluhm, H., Andersson, K., Starr, D. E., Ogletree, D. F., Ogasawara, H., Nilsson, A., Salmeron, M. 2007; 111 (23): 8278-8282

    View details for DOI 10.1021/jp068606i

    View details for Web of Science ID 000247034200024

  • Hydroxyl-induced wetting of metals by water at near-ambient conditions JOURNAL OF PHYSICAL CHEMISTRY C Yamamoto, S., Andersson, K., Bluhm, H., Ketteler, G., Starr, D. E., Schiros, T., Ogasawara, H., Pettersson, L. G., Salmeron, M., Nilsson, A. 2007; 111 (22): 7848-7850

    View details for DOI 10.1021/jp0731654

    View details for Web of Science ID 000246842400003

  • Recent advances in surface, interface, and environmental geochemistry 12th International Symposium on Water-Rock Interaction (WRI-12) Brown, G. E., Kendelewicz, T., Trainor, T. P., Tanwar, K. S., Chaka, A. M., Eng, P. J., Yamamoto, S., Nilsson, A., Bluhm, H., Starr, D. E., Salmeron, M., Catalano, J. G., Yoon, T. H., Benzerara, K., Morin, G., Ona-Nguema, G., Juillot, F., Cances, B., Farges, F., CALAS, G. TAYLOR & FRANCIS LTD. 2007: 3–11
  • Are recent water models obtained by fitting diffraction data consistent with infrared/Raman and x-ray absorption spectra? JOURNAL OF CHEMICAL PHYSICS Leetmaa, M., Ljungberg, M., Ogasawara, H., Odelius, M., Naslund, L., Nilsson, A., Pettersson, L. G. 2006; 125 (24)

    Abstract

    X-ray absorption (XA) spectra have been computed based on water structures obtained from a recent fit to x-ray and neutron diffraction data using models ranging from symmetrical to asymmetrical local coordination of the water molecules [A. K. Soper, J. Phys.: Condens. Matter 17, S3273 (2005)]. It is found that both the obtained symmetric and asymmetric structural models of water give similar looking XA spectra, which do not match the experiment. The fitted models both contain unphysical structures that are allowed by the diffraction data, where, e.g., hydrogen-hydrogen interactions may occur. A modification to the asymmetric model, in which the non-hydrogen-bonded OH intramolecular distance is allowed to become shorter while the bonded OH distance becomes longer, improves the situation somewhat, but the overall agreement is still unsatisfactory. The electric field (E-field) distributions and infrared (IR) spectra are also calculated using two established theoretical approaches, which, however, show significant discrepancies in their predictions for the asymmetric structural models. Both approaches predict the Raman spectrum of the symmetric model fitted to the diffraction data to be significantly blueshifted compared to experiment. At the moment no water model exists that can equally well describe IR/Raman, x-ray absorption spectroscopy, and diffraction data.

    View details for DOI 10.1063/1.2408419

    View details for Web of Science ID 000243158000027

    View details for PubMedID 17199358

  • Structure of water adsorbed on the open Cu(110) surface: H-up, H-down, or both? CHEMICAL PHYSICS LETTERS Schiros, T., Haq, S., Ogasawara, H., Takahashi, O., Ostrom, H., Andersson, K., Pettersson, L. G., Hodgson, A., Nilsson, A. 2006; 429 (4-6): 415-419
  • Correlation of hydrogen bond lengths and angles in liquid water based on Compton scattering JOURNAL OF CHEMICAL PHYSICS Hakala, M., Nygard, K., Manninen, S., Huotari, S., Buslaps, T., Nilsson, A., Pettersson, L. G., Hamalainen, K. 2006; 125 (8)

    Abstract

    The temperature-dependent hydrogen-bond geometry in liquid water is studied by x-ray Compton scattering using synchrotron radiation combined with density functional theory analysis. Systematic changes, related to the weakening of hydrogen bonding, are observed in the shape of the Compton profile upon increasing the temperature. Using model calculations and published distribution functions of hydrogen-bond geometries obtained from a NMR study we find a significant correlation between the hydrogen-bond length and angle. This imposes a new constraint on the possible local structure distributions in liquid water. In particular, the angular distortions of the short hydrogen bonds are significantly restricted.

    View details for DOI 10.1063/1.2273627

    View details for Web of Science ID 000240237000036

    View details for PubMedID 16965026

  • The local structure of protonated water from x-ray absorption and density functional theory JOURNAL OF CHEMICAL PHYSICS Cavalleri, M., Naslund, L., Edwards, D. C., Wernet, P., Ogasawara, H., Myneni, S., Ojamae, L., Odelius, M., Nilsson, A., Pettersson, L. G. 2006; 124 (19)

    Abstract

    We present a combined x-ray absorption spectroscopy/computational study of water in hydrochloric acid (HCl) solutions of varying concentration to address the structure and bonding of excess protons and their effect on the hydrogen bonding network in liquid water. Intensity variations and energy shifts indicate changes in the hydrogen bonding structure in water as well as the local structure of the protonated complex as a function of the concentration of protons. In particular, in highly acidic solutions we find a dominance of the Eigen form, H(3)O(+), while the proton is less localized to a specific water under less acidic conditions.

    View details for DOI 10.1063/1.2199828

    View details for Web of Science ID 000237683200031

    View details for PubMedID 16729826

  • Physisorption-induced C-H bond elongation in methane PHYSICAL REVIEW LETTERS Ostrom, H., Ogasawara, H., Naslund, L. A., Pettersson, L. G., Nilsson, A. 2006; 96 (14)

    Abstract

    Physisorption of methane to a Pt surface was studied by x-ray absorption spectroscopy in combination with density functional theory spectrum calculations. The experiment shows new electronic states appearing upon physisorption. We find that these states are due to orbital mixing causing charge polarization as a means to minimize Pauli repulsion. The results can be explained by elongation of 1 C-H bond by 0.09 A in the physisorbed state even though no covalent chemical bond is formed.

    View details for DOI 10.1103/PhysRevLett.96.146104

    View details for Web of Science ID 000236797200049

    View details for PubMedID 16712100

  • Bonding in metal-carbonyls: A comparison with experiment and calculations on adsorbed CO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM Nyberg, M., Foehlisch, A., Triguero, L., Bassan, A., Nilsson, A., Pettersson, L. G. 2006; 762 (1-3): 123-132
  • Auger decay calculations with core-hole excited-state molecular-dynamics simulations of water JOURNAL OF CHEMICAL PHYSICS Takahashi, O., Odelius, M., Nordlund, D., Nilsson, A., Bluhm, H., Pettersson, L. G. 2006; 124 (6)

    Abstract

    We report a new theoretical procedure for calculating Auger decay transition rates including effects of core-hole excited-state dynamics. Our procedure was applied to the normal and first resonant Auger processes of gas-phase water and compared to high-resolution experiments. In the normal Auger decay, calculated Auger spectra were found to be insensitive to the dynamics, while the repulsive character of the first resonant core-excited state makes the first resonantly excited Auger decay spectra depend strongly on the dynamics. The ultrafast dissociation of water upon O(1s)-->4a(1) excitation was analyzed and found to be very sensitive to initial vibrational distortions in the ground state which furthermore affect the excitation energy. Our calculated spectra reproduce the experimental Auger spectra except for the Franck-Condon vibrational structure which is not included in the procedure. We found that the Auger decay of OH and O fragments contributes to the total intensity, and that the contribution from these fragments increases with increasing excitation energy.

    View details for DOI 10.1063/1.2166234

    View details for Web of Science ID 000235309400019

    View details for PubMedID 16483207

  • Soft X-ray microscopy and spectroscopy at the molecular environmental science beamline at the Advanced Light Source JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Bluhm, H., Andersson, K., Araki, T., Benzerara, K., Brown, G. E., Dynes, J. J., Ghosal, S., Gilles, M. K., Hansen, H. C., Hemminger, J. C., Hitchcock, A. P., Ketteler, G., Kilcoyne, A. L., Kneedler, E., Lawrence, J. R., Leppard, G. G., Majzlan, J., Mun, B. S., Myneni, S. C., Nilsson, A., Ogasawara, H., Ogletree, D. F., Pecher, K., Salmeron, M., Shuh, D. K., Tonner, B., Tyliszczak, T., Warwick, T., Yoon, T. H. 2006; 150 (2-3): 86-104
  • X-ray absorption spectrum of liquid water from molecular dynamics simulations: Asymmetric model PHYSICAL REVIEW B Odelius, M., Cavalleri, M., Nilsson, A., Pettersson, L. G. 2006; 73 (2)
  • Hydrogenation of single-walled carbon nanotubes PHYSICAL REVIEW LETTERS Nikitin, A., Ogasawara, H., Mann, D., Denecke, R., Zhang, Z., Dai, H., Cho, K., Nilsson, A. 2005; 95 (22)

    Abstract

    Towards the development of a useful mechanism for hydrogen storage, we have studied the hydrogenation of single-walled carbon nanotubes with atomic hydrogen using core-level photoelectron spectroscopy and x-ray absorption spectroscopy. We find that atomic hydrogen creates C-H bonds with the carbon atoms in the nanotube walls, and such C-H bonds can be completely broken by heating to 600 degrees C. We demonstrate approximately 65 +/- 15 at % hydrogenation of carbon atoms in the single-walled carbon nanotubes, which is equivalent to 5.1 +/- 1.2 wt % hydrogen capacity. We also show that the hydrogenation is a reversible process.

    View details for DOI 10.1103/PhysRevLett.95.225507

    View details for Web of Science ID 000233458500040

    View details for PubMedID 16384236

  • Spectroscopic characterization of microscopic hydrogen-bonding disparities in supercritical water JOURNAL OF CHEMICAL PHYSICS Wernet, P., Testemale, D., Hazemann, J. L., Argoud, R., Glatzel, P., Pettersson, L. G., Nilsson, A., Bergmann, U. 2005; 123 (15)

    Abstract

    The local hydrogen-bonding environment in supercritical water (380 degrees C, 300 bars, density 0.54 gcm3) was studied by x-ray Raman scattering at the oxygen K edge. The spectra are compared to those of the gas phase, liquid surface, bulk liquid, and bulk ice, as well as to calculated spectra. The experimental model systems are used to assign spectral features and to quantify specific local hydrogen-bonding situations in supercritical water. The first coordination shell of the molecules is characterized in more detail with the aid of the calculations. Our analysis suggests that approximately 65% of the molecules in supercritical water are hydrogen bonded in configurations that are distinctly different from those in liquid water and ice. In contrast to liquid water the bonded molecules in supercritical water have four intact hydrogen bonds and in contrast to ice large variations of bond angles and distances are observed. The remaining approximately 35% of the molecules exhibit two free O-H bonds and are thus either not involved in hydrogen bonding at all or have one or two hydrogen bonds on the oxygen side. We determine an average O-O distance of 3.1+/-0.1 A in supercritical water for the H bonded molecules at the conditions studied here. This and the corresponding hydrogen bond lengths are shown to agree with neutron- and x-ray-diffraction data at similar conditions. Our results on the local hydrogen-bonding environment with mainly two disparate hydrogen-bonding configurations are consistent with an extended structural model of supercritical water as a heterogeneous system with small patches of bonded molecules in various tetrahedral configurations and surrounding nonbonded gas-phase-like molecules.

    View details for DOI 10.1063/1.2064867

    View details for Web of Science ID 000232697900025

    View details for PubMedID 16252958

  • X-ray absorption spectroscopy measurements of liquid water JOURNAL OF PHYSICAL CHEMISTRY B Naslund, L. A., Luning, J., Ufuktepe, Y., Ogasawara, H., Wernet, P., Bergmann, U., Pettersson, L. G., Nilsson, A. 2005; 109 (28): 13835-13839

    Abstract

    Recent studies, based on X-ray absorption spectroscopy (XAS) and X-ray Raman scattering (XRS), have shown that the hydrogen bond network in liquid water consists mainly of water molecules with only two strong hydrogen bonds. Since this result is controversial, it is important to demonstrate the reliability of the experimental data, which is the purpose of this paper. Here we compare X-ray absorption spectra of liquid water recorded with five very different techniques sensitive to the local environment of the absorbing molecule. Overall, the spectra obtained with photon detection show a very close similarity and even the observable minor differences can be understood. The comparison demonstrates that XAS and XRS can indeed be applied reliably to study the local bonding of the water molecule and thus to reveal the hydrogen bond situation in bulk water.

    View details for DOI 10.1021/jp052046q

    View details for Web of Science ID 000230526800058

    View details for PubMedID 16852732

  • X-ray absorption spectroscopy study of the hydrogen bond network in the bulk water of aqueous solutions JOURNAL OF PHYSICAL CHEMISTRY A Naslund, L. A., Edwards, D. C., Wernet, P., Bergmann, U., Ogasawara, H., Pettersson, L. G., Myneni, S., Nilsson, A. 2005; 109 (27): 5995-6002

    Abstract

    We utilized X-ray absorption spectroscopy (XAS) and X-ray Raman scattering (XRS) in order to study the ion solvation effect on the bulk hydrogen bonding structure of water. The fine structures in the X-ray absorption spectra are sensitive to the local environment of the probed water molecule related to the hydrogen bond length and angles. By varying the concentration of ions, we can distinguish between contributions from water in the bulk and in the first solvation sphere. We show that the hydrogen bond network in bulk water, in terms of forming and breaking hydrogen bonds as detected by XAS/XRS, remains unchanged, and only the water molecules in the close vicinity to the ions are affected.

    View details for DOI 10.1021/jp050413s

    View details for Web of Science ID 000230468100005

    View details for PubMedID 16833935

  • Molecularly intact and dissociative adsorption of water on clean Cu(110): A comparison with the water/Ru(001) system SURFACE SCIENCE Andersson, K., Gomez, A., Glover, C., Nordlund, D., Ostrom, H., Schiros, T., Takahashi, O., Ogasawara, H., Pettersson, L. G., Nilsson, A. 2005; 585 (3): L183-L189
  • Ultrafast core-hole-induced dynamics in water probed by x-ray emission spectroscopy PHYSICAL REVIEW LETTERS Odelius, M., Ogasawara, H., Nordlund, D., Fuchs, O., Weinhardt, L., Maier, F., Umbach, E., Heske, C., Zubavichus, Y., Grunze, M., Denlinger, J. D., Pettersson, L. G., Nilsson, A. 2005; 94 (22)

    Abstract

    The isotope effect and excitation-energy dependence have been measured in the oxygen K-edge x-ray emission spectrum (XES). The use of XES to monitor core decay processes provides information about molecular dynamics (MD) on an ultrafast time scale through the O1s lifetime of a few femtoseconds. Different nuclear masses give rise to differences in the dynamics and the observed isotope effect in XES is direct evidence of the importance of such processes. MD simulations show that even the excitation-energy dependence in the XES is mainly related to differences in core-excited-state dynamics.

    View details for DOI 10.1103/PhysRevLett.94.227401

    View details for Web of Science ID 000229700800069

    View details for PubMedID 16090436

  • X-ray absorption spectroscopy of liquid methanol microjets: Bulk electronic structure and hydrogen bonding network JOURNAL OF PHYSICAL CHEMISTRY B Wilson, K. R., Cavalleri, M., Rude, B. S., Schaller, R. D., Catalano, T., Nilsson, A., Saykally, R. J., Pettersson, L. G. 2005; 109 (20): 10194-10203

    Abstract

    We have measured the X-ray absorption (XA) spectrum of liquid (298 K) methanol at the oxygen and carbon K edges. The 4a(1) orbital at the O K edge exhibits a pronounced sensitivity to the formation of intermolecular hydrogen bonds, with significant differences observed between the vapor and bulk spectra, whereas the C K edge reveals only subtle corresponding spectral changes. Comparison with DFT computed spectra of model methanol clusters indicates that the bulk liquid comprises long chains (n > 6) and rings of hydrogen-bonded monomers.

    View details for DOI 10.1021/jp049278u

    View details for Web of Science ID 000229296600047

    View details for PubMedID 16852236

  • Comment on "Energetics of hydrogen bond network rearrangements in liquid water". Science Nilsson, A., Wernet, P., Nordlund, D., Bergmann, U., Cavalleri, M., Odelius, M., Ogasawara, H., Näslund, L., Hirsch, T. K., Ojamäe, L., Glatzel, P., Pettersson, L. G. 2005; 308 (5723): 793-?

    View details for PubMedID 15879194

  • Comment on "Energetics of hydrogen bond network: Rearrangements in liquid water" SCIENCE Nilsson, A., Wernet, P., Nordlund, D., Bergmann, U., Cavalleri, M., Odelius, M., Ogasawara, H., Naslund, L. A., Hirsch, T. K., Ojamae, L., Glatzel, P., Pettersson, L. G. 2005; 308 (5723): 793A-793A
  • The hydrogen bond in ice probed by soft x-ray spectroscopy and density functional theory JOURNAL OF CHEMICAL PHYSICS Nilsson, A., Ogasawara, H., Cavalleri, M., Nordlund, D., Nyberg, M., Wernet, P., Pettersson, L. G. 2005; 122 (15)

    Abstract

    We combine photoelectron and x-ray absorption spectroscopy with density functional theory to derive a molecular orbital picture of the hydrogen bond in ice. We find that the hydrogen bond involves donation and back-donation of charge between the oxygen lone pair and the O-H antibonding orbitals on neighboring molecules. Together with internal s-p rehybridization this minimizes the repulsive charge overlap of the connecting oxygen and hydrogen atoms, which is essential for a strong attractive electrostatic interaction. Our joint experimental and theoretical results demonstrate that an electrostatic model based on only charge induction from the surrounding medium fails to properly describe the internal charge redistributions upon hydrogen bonding.

    View details for DOI 10.1063/1.1879752

    View details for Web of Science ID 000229185400029

    View details for PubMedID 15945643

  • The electronic structure effect in heterogeneous catalysis CATALYSIS LETTERS Nilsson, A., Pettersson, L. G., Hammer, B., Bligaard, T., Christensen, C. H., Norskov, J. K. 2005; 100 (3-4): 111-114
  • Half or full core hole in density functional theory X-ray absorption spectrum calculations of water? PHYSICAL CHEMISTRY CHEMICAL PHYSICS Cavalleri, M., Odelius, M., Nordlund, D., Nilsson, A., Pettersson, L. G. 2005; 7 (15): 2854-2858

    Abstract

    We analyze the performance of two different core-hole potentials in the theoretical modeling of XAS of ice, liquid and gas phase water; the use of a full core-hole (FCH) in the calculations, as suggested by Hetenyi et al. [B. Hetenyi, F. De Angelis, P. Giamozzi and R. Car, J. Chem. Phys., 2004, 120(18), 8632], gives poor agreement with experiment in terms of intensity distribution as well as transition energies, while the half core hole (HCH) potential, in the case of water, provides a better compromise between initial and final state effects, leading to good agreement with the experimental data.

    View details for DOI 10.1039/b505723j

    View details for Web of Science ID 000230596900019

    View details for PubMedID 16189603

  • Role of water in electron-initiated processes and radical chemistry: Issues and scientific advances CHEMICAL REVIEWS Garrett, B. C., Dixon, D. A., Camaioni, D. M., CHIPMAN, D. M., Johnson, M. A., Jonah, C. D., Kimmel, G. A., Miller, J. H., Rescigno, T. N., Rossky, P. J., Xantheas, S. S., Colson, S. D., Laufer, A. H., Ray, D., Barbara, P. F., Bartels, D. M., BECKER, K. H., Bowen, H., Bradforth, S. E., Carmichael, I., Coe, J. V., Corrales, L. R., Cowin, J. P., Dupuis, M., Eisenthal, K. B., Franz, J. A., Gutowski, M. S., Jordan, K. D., Kay, B. D., LaVerne, J. A., Lymar, S. V., Madey, T. E., McCurdy, C. W., Meisel, D., Mukamel, S., Nilsson, A. R., Orlando, T. M., Petrik, N. G., Pimblott, S. M., Rustad, J. R., Schenter, G. K., Singer, S. J., Tokmakoff, A., Wang, L. S., Wittig, C., ZWIER, T. S. 2005; 105 (1): 355-389

    View details for DOI 10.1021/cr030453x

    View details for Web of Science ID 000226297100009

    View details for PubMedID 15720157

  • X-ray absorption spectra of water within a plane-wave Car-Parrinello molecular dynamics framework JOURNAL OF CHEMICAL PHYSICS Cavalleri, M., Odelius, M., Nilsson, A., Pettersson, L. G. 2004; 121 (20): 10065-10075

    Abstract

    We describe the implementation of a simple technique to simulate core-level spectra within the Car-Parrinello plane-waves molecular dynamics framework. The x-ray absorption (XA) spectra are generated using the transition potential technique with the effect of the core hole included through a specifically developed pseudopotential for the core-excited atom. Despite the lack of 1s core orbitals in the pseudopotential treatment, the required transition moments are accurately calculated without reconstruction of the all-electron orbitals. The method is applied to the oxygen XA spectra of water in its various aggregation states, but it is transferable to any first-row element. The computed spectra are compared favorably with the results from all-electron cluster calculations, as well as with experimental data. The periodicity of the plane-wave technique improves the description of condensed phases. The molecular dynamics simulation enables in principle a proper treatment of thermal effects and dynamical averaging in complex systems.

    View details for DOI 10.1063/1.1807821

    View details for Web of Science ID 000225042700033

    View details for PubMedID 15549881

  • Water dissociation on Ru(001): An activated process PHYSICAL REVIEW LETTERS Andersson, K., Nikitin, A., Pettersson, L. G., Nilsson, A., Ogasawara, H. 2004; 93 (19)

    Abstract

    It is shown using x-ray photoelectron spectroscopy that water is adsorbed either nondissociatively or partially dissociatively on Ru(001) under ultrahigh vacuum conditions. We found an activated dissociation process with a barrier slightly larger than that of desorption. A difference in dissociation barriers is found between H2O and D2O that explains the anomalous isotope effects in the thermal desorption. Previous theoretical and experimental disagreements can be rationalized based on electron or x-ray beam-induced dissociation of the water overlayer and an earlier underestimation of the dissociation barrier.

    View details for DOI 10.1103/PhysRevLett.93.196101

    View details for Web of Science ID 000224924900042

    View details for PubMedID 15600853

  • Experimental and theoretical characterization of the structure of defects at the pyrite FeS2(100) surface PHYSICAL REVIEW B Andersson, K., Nyberg, M., Ogasawara, H., Nordlund, D., Kendelewicz, T., Doyle, C. S., Brown, G. E., Pettersson, L. G., Nilsson, A. 2004; 70 (19)
  • Ultrafast molecular dissociation of water in ice PHYSICAL REVIEW LETTERS Brena, B., Nordlund, D., Odelius, M., Ogasawara, H., Nilsson, A., Pettersson, L. G. 2004; 93 (14)

    Abstract

    Using x-ray emission and photoemission spectroscopies to measure the occupied valence levels in a thin crystalline ice film, we resolve the ionization-induced dissociation of water in ice on a femtosecond time scale. Isotope substitution confirms proton transfer during the core-hole lifetime in spite of the nonresonant excitation. Through ab initio molecular dynamics on the core-ionized state, the dissociation and spectrum evolution are followed at femtosecond intervals. The theoretical simulations confirm the experimental analysis and allow for a detailed study of the dissociative reaction path.

    View details for DOI 10.1103/PhysRevLett.93.148302

    View details for Web of Science ID 000224211900080

    View details for PubMedID 15524849

  • Chemical bonding on surfaces probed by X-ray emission spectroscopy and density functional theory SURFACE SCIENCE REPORTS Nilsson, A., Pettersson, L. G. 2004; 55 (2-5): 49-167
  • Geometric structure and chemical bonding of acetylene adsorbed on Cu(110) SURFACE SCIENCE Ostrom, H., Nordlund, D., Ogasawara, H., Weiss, K., Triguero, L., Pettersson, L. G., Nilsson, A. 2004; 565 (2-3): 206-222
  • X-ray emission spectroscopy of (2 root 3x2 root 3)R30 degrees CO/Ru(0001): Comparison to c(2x2) CO/Ni(100) and c(2x2)CO/Cu(100) JOURNAL OF CHEMICAL PHYSICS Fohlisch, A., Wurth, W., Stichler, M., Keller, C., Nilsson, A. 2004; 121 (10): 4848-4852

    Abstract

    The atom specific electronic structure of (2 square root of 3 x 2 square root of 3)R30 degrees CO on hcp Ru(0001) has been determined with resonantly excited x-ray emission spectroscopy. We find that the general features of the local adsorbate electronic structure are similar to the situation of CO adsorbed on the fcc metals Ni(100) and Cu(100). The interpretation of the surface chemical bond of (2 square root of 3 x 2 square root of 3)R30 degrees CO/Ru(0001) based on the direct application of the local, allylic model from on-top adsorption on the fcc(100) surfaces Ni(100) and Cu(100) explains many aspects of the surface chemical bond. However, also nonlocal contributions like adsorbate-adsorbate interaction and the deviation from upright on-top adsorption on the Ru(0001) surface influence observables like the heat of adsorption and the Me-CO bond strength.

    View details for DOI 10.1063/1.1778380

    View details for Web of Science ID 000223494500048

    View details for PubMedID 15332920

  • Surface structure of thin ice films CHEMICAL PHYSICS LETTERS Nordlund, D., Ogasawara, H., Wernet, P., Nyberg, M., Odelius, M., Pettersson, L. G., Nilsson, A. 2004; 395 (1-3): 161-165
  • Compton profiles for water and mixed water-neon clusters: A measure of coordination PHYSICAL REVIEW B Hakala, M., Huotari, S., Hamalainen, K., Manninen, S., Wernet, P., Nilsson, A., Pettersson, L. G. 2004; 70 (12)
  • Ethylene on Cu(110) and Ni(110): electronic structure and bonding derived from X-ray spectroscopy and theory SURFACE SCIENCE Ostrom, H., Fohlisch, A., Nyberg, M., Weinelt, M., Heske, C., Pettersson, L. G., Nilsson, A. 2004; 559 (2-3): 85-99
  • The structure of the first coordination shell in liquid water SCIENCE Wernet, P., Nordlund, D., Bergmann, U., Cavalleri, M., Odelius, M., Ogasawara, H., Naslund, L. A., Hirsch, T. K., Ojamae, L., Glatzel, P., Pettersson, L. G., Nilsson, A. 2004; 304 (5673): 995-999

    Abstract

    X-ray absorption spectroscopy and x-ray Raman scattering were used to probe the molecular arrangement in the first coordination shell of liquid water. The local structure is characterized by comparison with bulk and surface of ordinary hexagonal ice Ih and with calculated spectra. Most molecules in liquid water are in two hydrogen-bonded configurations with one strong donor and one strong acceptor hydrogen bond in contrast to the four hydrogen-bonded tetrahedral structure in ice. Upon heating from 25 degrees C to 90 degrees C, 5 to 10% of the molecules change from tetrahedral environments to two hydrogen-bonded configurations. Our findings are consistent with neutron and x-ray diffraction data, and combining the results sets a strong limit for possible local structure distributions in liquid water. Serious discrepancies with structures based on current molecular dynamics simulations are observed.

    View details for DOI 10.1126/science.1096205

    View details for Web of Science ID 000221383300044

    View details for PubMedID 15060287

  • Hydrogen bonding between adsorbed deprotonated glycine molecules on Cu(110) JOURNAL OF CHEMICAL PHYSICS Nyberg, M., Odelius, M., Nilsson, A., Pettersson, L. G. 2003; 119 (23): 12577-12585

    View details for DOI 10.1063/1.1625640

    View details for Web of Science ID 000186970000061

  • Direct evidence of orbital mixing between water and solvated transition-metal ions: An oxygen 1s XAS and DFT study of aqueous systems JOURNAL OF PHYSICAL CHEMISTRY A Naslund, L. A., Cavalleri, M., Ogasawara, H., Nilsson, A., Pettersson, L. G., Wernet, P., Edwards, D. C., Sandstrom, M., Myneni, S. 2003; 107 (35): 6869-6876

    View details for DOI 10.1021/jp034296h

    View details for Web of Science ID 000185034600016

  • Bonding of saturated hydrocarbons to metal surfaces PHYSICAL REVIEW LETTERS Ostrom, H., Triguero, L., Nyberg, M., Ogasawara, H., Pettersson, L. G., Nilsson, A. 2003; 91 (4)

    Abstract

    The adsorption of octane on Cu(110) was studied by x-ray absorption and x-ray emission spectroscopy, in combination with spectrum calculations in the framework of density functional theory, as a model system for alkane adsorption on transition metals. Significant electron sharing between the adsorbate and metal surface and involvement of both bonding and antibonding C-H molecular orbitals in the molecule-metal bond was found. The calculations were extended to the case of octane adsorbed on Ni(110), and the position of the metal d band was found to be important for the bonding. The results were generalized to show that this is important for the efficiency as an alkane dehydrogenation catalyst.

    View details for DOI 10.1103/PhysRevLett.91.046102

    View details for Web of Science ID 000184372300033

    View details for PubMedID 12906678

  • X-ray fluorescence spectra of metals excited below threshold PHYSICAL REVIEW B Magnuson, M., Rubensson, J. E., Fohlisch, A., Wassdahl, N., Nilsson, A., Magnuson, M. 2003; 68 (4)
  • Geometrical characterization of pyrimidine base molecules adsorbed on Cu(110) surfaces: XPS and NEXAFS studies 7th International Conference on Nanometer-Scale Science and Technology (NANO-7)/21st European Conference on Surface Science (ECOSS-21) Furukawa, M., Fujisawa, H., KATANO, S., Ogasawara, H., Kim, Y., Komeda, T., Nilsson, A., Kawai, M. ELSEVIER SCIENCE BV. 2003: 261–266
  • Orbital rehybridization in n-octane adsorbed on Cu(110) JOURNAL OF CHEMICAL PHYSICS Ostrom, H., Triguero, L., Weiss, K., Ogasawara, H., Garnier, M. G., Nordlund, D., Nyberg, M., Pettersson, L. G., Nilsson, A. 2003; 118 (8): 3782-3789

    View details for DOI 10.1063/1.1539866

    View details for Web of Science ID 000180803800041

  • XPS and XAS investigation of condensed and adsorbed n-octane on a Cu(110) surface JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Weiss, K., Ostrom, H., Triguero, L., Ogasawara, H., Garnier, M. G., Pettersson, L. G., Nilsson, A. 2003; 128 (2-3): 179-191
  • Structure and bonding of water on Pt(111) PHYSICAL REVIEW LETTERS Ogasawara, H., Brena, B., Nordlund, D., Nyberg, M., Pelmenschikov, A., Pettersson, L. G., Nilsson, A. 2002; 89 (27)

    Abstract

    We address the adsorption of water on Pt(111) using x-ray absorption, x-ray emission, and x-ray photoelectron spectroscopy along with calculations in the framework of density functional theory. Using the direct relationship between the electronic structure and adsorbate geometry, we show that in the first layer all the molecules bind directly to the surface and to each other through the in-layer H bonds without dissociation, creating a nearly flat overlayer. The water molecules are adsorbed through alternating metal-oxygen (M-O) and metal-hydrogen (M-HO) bonds.

    View details for DOI 10.1103/PhysRevLett.89.276102

    View details for Web of Science ID 000179949600037

    View details for PubMedID 12513221

  • The interpretation of X-ray absorption spectra of water and ice CHEMICAL PHYSICS LETTERS Cavalleri, M., Ogasawara, H., Pettersson, L. G., Nilsson, A. 2002; 364 (3-4): 363-370
  • Applications of core level spectroscopy to adsorbates JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Nilsson, A. 2002; 126 (1-3): 3-42
  • X-ray Raman spectroscopy at the oxygen K edge of water and ice: Implications on local structure models PHYSICAL REVIEW B Bergmann, U., Wernet, P., Glatzel, P., Cavalleri, M., Pettersson, L. G., Nilsson, A., Cramer, S. P. 2002; 66 (9)
  • Probing surface states of Cu/Ni thin films using x-ray absorption spectroscopy PHYSICAL REVIEW B Karis, O., Magnuson, M., Wiell, T., Weinelt, M., Wassdahl, N., Nilsson, A., Martensson, N., Holmstrom, E., Niklasson, A. M., Eriksson, O., Johansson, B. 2001; 63 (11)
  • Electronic structure effects from hydrogen bonding in the liquid phase and in chemisorption: an integrated theory and experimental effort 11th International Conference on X-ray Absorption Fine Structure (XAFS XI) Pettersson, L. G., Nilsson, A., Myneni, S., Luo, Y., Nyberg, M., Cavalleri, M., Ojamae, L., Naslund, L. A., Ogasawara, H., Odelius, M., Pelmenschikov, A. WILEY-BLACKWELL. 2001: 136–140

    Abstract

    A closely integrated theoretical and experimental effort to understand chemical bonding using X-ray spectroscopic probes is presented. Theoretical techniques to simulate XAS (X-ray absorption spectroscopy), XES (X-ray emission spectroscopy), RIXS (resonant inelastic X-ray scattering) and XPS (X-ray photoelectron spectroscopy) spectra have been developed and implemented within a density functional theory (DFT) framework. In combination with new experimental techniques, such as high-resolution XAS on liquid water under ambient conditions and XES on complicated surface adsorbates, new insight into e.g. hydrogen-bonded systems is obtained. For the (3x2) overlayer structure of glycine/Cu(110), earlier work has been extended to include adsorbate-adsorbate interactions. Structures are optimized for large cluster models and for periodic boundary conditions. It is found that specific features in the spectra arise from hydrogen-bonding interactions, which thus have important effects at the molecular-orbital level. XAS on liquid water shows a pronounced pre-edge feature with significant intensity, while the spectrum of ice shows only little intensity in this region. Theoretical spectrum calculations, based on instantaneous structures obtained from molecular-dynamics (MD) simulations, show that the pre-edge feature in the liquid is caused by water molecules with unsaturated hydrogen bonding. Some aspects of the theoretical simulations will be briefly discussed.

    View details for Web of Science ID 000167298100019

    View details for PubMedID 11512711

  • Crystal-field splitting in coadsorbate systems: c(2X2) CO/K/Ni(100) PHYSICAL REVIEW B Hasselstrom, J., Fohlisch, A., Denecke, R., Nilsson, A., de Groot, F. M. 2000; 62 (16): 11192-11196
  • Ground-state interpretation of x-ray emission spectroscopy on adsorbates: CO adsorbed on Cu(100) PHYSICAL REVIEW B Fohlisch, A., Hasselstrom, J., Bennich, P., Wassdahl, N., Karis, O., Nilsson, A., Triguero, L., Nyberg, M., Pettersson, L. G. 2000; 61 (23): 16229-16240
  • The bonding of simple carboxylic acids on Cu(110) JOURNAL OF CHEMICAL PHYSICS Karis, O., Hasselstrom, J., Wassdahl, N., Weinelt, M., Nilsson, A., Nyberg, M., Pettersson, L. G., Stohr, J., Samant, M. G. 2000; 112 (18): 8146-8155
  • The electronic structure and surface chemistry of glycine adsorbed on Cu(110) JOURNAL OF CHEMICAL PHYSICS Nyberg, M., Hasselstrom, J., Karis, O., Wassdahl, N., Weinelt, M., Nilsson, A., Pettersson, L. G. 2000; 112 (12): 5420-5427
  • Nature of the ns-derived states for an isolated alkali atom on a surface SURFACE SCIENCE Sandell, A., Bruhwiler, P. A., Nilsson, A., Bennich, P., Rudolf, P., Martensson, N. 1999; 429 (1-3): 309-319
  • Ammonia adsorbed on Cu(110): An angle resolved x-ray spectroscopic and ab initio study JOURNAL OF CHEMICAL PHYSICS Hasselstrom, J., Fohlisch, A., Karis, O., Wassdahl, N., Weinelt, M., Nilsson, A., Nyberg, M., Pettersson, L. G., Stohr, J. 1999; 110 (10): 4880-4890
  • Resonant soft-x-ray emission spectroscopy of surface adsorbates: Theory, computations, and measurements of ethylene and benzene on Cu(110) PHYSICAL REVIEW B Triguero, L., Luo, Y., Pettersson, L. G., Agren, H., Vaterlein, P., Weinelt, M., Fohlisch, A., Hasselstrom, J., Karis, O., Nilsson, A. 1999; 59 (7): 5189-5200
  • Imaging properties of beam line optics for undulator based third generation synchrotron facilities REVIEW OF SCIENTIFIC INSTRUMENTS Sundin, S., Bassler, M., Deneche, R., Weiss, M., Vaterlein, P. 1999; 70 (1): 14-17
  • Beyond the chemical shift: Vibrationally resolved core-level photoelectron spectra of adsorbed CO PHYSICAL REVIEW LETTERS Fohlisch, A., Wassdahl, N., Hasselstrom, J., Karis, O., Menzel, D., Martensson, N., Nilsson, A. 1998; 81 (8): 1730-1733
  • The adsorption structure of glycine adsorbed on Cu(110); comparison with formate and acetate/Cu(110) SURFACE SCIENCE Hasselstrom, J., Karis, O., Weinelt, M., Wassdahl, N., Nilsson, A., Nyberg, M., Pettersson, L. G., Samant, M. G., Stohr, J. 1998; 407 (1-3): 221-236
  • Local probing of the surface chemical bond using X-ray emission spectroscopy International Workshop on Resonant Inelastic Soft X-Ray Scattering (RIXS) Nilsson, A., Wassdahl, N., Weinelt, M., Karis, O., Wiell, T., Bennich, P., Hasselstrom, J., Fohlisch, A., Stohr, J., Samant, M. SPRINGER. 1997: 147–54
  • Coherent and incoherent processes in resonant photoemission International Workshop on Resonant Inelastic Soft X-Ray Scattering (RIXS) Martensson, N., Weinelt, M., Karis, O., Magnuson, M., Wassdahl, N., Nilsson, A., Stohr, J., Samant, M. SPRINGER. 1997: 159–67
  • Bonding of an isolated K atom to a surface: Experiment and theory PHYSICAL REVIEW LETTERS Sandell, A., Hjortstam, O., Nilsson, A., Bruhwiler, P. A., Eriksson, O., Bennich, P., Rudolf, P., Wills, J. M., Johansson, B., Martensson, N. 1997; 78 (26): 4994-4997
  • An atom-specific look at the surface chemical bond PHYSICAL REVIEW LETTERS Nilsson, A., Weinelt, M., Wiell, T., Bennich, P., Karis, O., Wassdahl, N., Stohr, J., Samant, M. G. 1997; 78 (14): 2847-2850
  • INITIAL AND FINAL-STATE RULES IN X-RAY SPECTROSCOPIES OF ADSORBATES 8th International Conference on X-Ray Absorption Fine Structure (XAFS VIII) Nilsson, A., Martensson, N. ELSEVIER SCIENCE BV. 1995: 19–22
  • A VERY HIGH-RESOLUTION ELECTRON SPECTROMETER JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Martensson, N., Baltzer, P., Bruhwiler, P. A., Forsell, J. O., Nilsson, A., Stenborg, A., WANNBERG, B. 1994; 70 (2): 117-128
  • THE INNER VALENCE REGION OF CO ADSORBED ON PD(100) JOURNAL OF PHYSICS-CONDENSED MATTER Sandell, A., Bjorneholm, O., Andersen, J. N., Nilsson, A., Zdansky, E. O., Hernnas, B., Karlsson, U. O., Nyholm, R., Martensson, N. 1994; 6 (49): 10659-10668
  • VIBRATIONALLY AND ORIENTATIONALLY SELECTIVE PROBING OF INTRAMOLECULAR POTENTIALS IN PHYSISORBED MOLECULES PHYSICAL REVIEW LETTERS Bjorneholm, O., TILLBORG, H., Nilsson, A., Martensson, N., Agren, H., LIEGENER, C. M. 1994; 73 (19): 2551-2554
  • CHEMISORPTION OF CO ON CU(100), AG(110) AND AU(110) SURFACE SCIENCE Sandell, A., Bennich, P., Nilsson, A., Hernnas, B., Bjorneholm, O., Martensson, N. 1994; 310 (1-3): 16-26
  • CO-INDUCED REVERSIBLE SURFACE TO BULK TRANSFORMATION OF CARBIDIC CARBON ON NI(100) SURFACE SCIENCE Zdansky, E. O., Nilsson, A., Martensson, N. 1994; 310 (1-3): L583-L588
  • IMAGE-LIKE SCREENING MECHANISMS FOR WEAKLY ADSORBED ATOMS PHYSICAL REVIEW LETTERS Sandell, A., Nilsson, A., Bennich, P., Martensson, N. 1994; 72 (16): 2604-2607
  • PHOTOEMISSION, AUTOIONIZATION, AND X-RAY-ABSORPTION SPECTROSCOPY OF ULTRATHIN-FILM C60 ON AU(110) PHYSICAL REVIEW B Maxwell, A. J., Bruhwiler, P. A., Nilsson, A., Martensson, N., Rudolf, P. 1994; 49 (15): 10717-10725
  • LOCAL PROBING OF ADSORBATE ELECTRONIC-STRUCTURE USING SOFT-X-RAY EMISSION - ATOMIC NITROGEN ON NI(100) AND CU(100) SURFACE SCIENCE Wiell, T., TILLBORG, H., Nilsson, A., Wassdahl, N., Martensson, N., Nordgren, J. 1994; 304 (3): L451-L455
  • ON THE GROWTH OF NI ON CU(100) SURFACE SCIENCE Hernnas, B., KAROLEWSKI, M., TILLBORG, H., Nilsson, A., Martensson, N. 1994; 302 (1-2): 64-72
  • VIBRATIONALLY SELECTIVE AUTOIONIZATION OF PHYSISORBED MOLECULAR NITROGEN PHYSICAL REVIEW B Bjorneholm, O., Nilsson, A., Sandell, A., Hernnas, B., Martensson, N. 1994; 49 (3): 2001-2004
  • CORE-HOLE DECAY STUDIES OF O/NI(100) C(2X2) PHYSICAL REVIEW B Sandell, A., Nilsson, A., Bjorneholm, O., TILLBORG, H., Martensson, N. 1993; 48 (15): 11347-11351
  • DISTINCTION BETWEEN DIFFERENT ADSORPTION STATES - CHEMISORBED AND PHYSISORBED AR SURFACE SCIENCE Nilsson, A., Bjorneholm, O., Hernnas, B., Sandell, A., Martensson, N. 1993; 293 (1-2): L835-L840
  • FINAL-STATE EFFECTS IN SURFACE CORE-LEVEL SHIFTS PHYSICAL REVIEW B Nilsson, A., Stenborg, A., TILLBORG, H., Gunnelin, K., Martensson, N. 1993; 47 (20): 13590-13593
  • CORE-LEVEL SPECTROSCOPY OF PHYSISORBED MOLECULES ON GRAPHITE 8TH INTERNATIONAL CONF ON SOLID SURFACES ( ICSS-8 ) / 12TH INTERNATIONAL VACUUM CONGRESS ( IVC-12 ) Nilsson, A., Bjorneholm, O., TILLBORG, H., Hernnas, B., GUEST, R. J., Sandell, A., Palmer, R. E., Martensson, N. ELSEVIER SCIENCE BV. 1993: 758–769
  • SHAKE-UP AND SHAKE-OFF STRUCTURES IN CORE-LEVEL PHOTOEMISSION SPECTRA FROM ADSORBATES JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA TILLBORG, H., Nilsson, A., Martensson, N. 1993; 62 (1-2): 73-93
  • ADSORPTION-SITE-DEPENDENT X-RAY-ABSORPTION SPECTROSCOPY - CO/H,H2/NI(100) PHYSICAL REVIEW B TILLBORG, H., Nilsson, A., Martensson, N., Andersen, J. N. 1993; 47 (3): 1699-1702
  • HIGHER EXCITED-STATES IN X-RAY-ABSORPTION SPECTRA OF ADSORBATES PHYSICAL REVIEW B Bjorneholm, O., Nilsson, A., Zdansky, E. O., Sandell, A., TILLBORG, H., Andersen, J. N., Martensson, N. 1993; 47 (4): 2308-2319
  • SOFT-X-RAY EMISSION STUDIES OF ADSORBATES PHYSICAL REVIEW LETTERS Wassdahl, N., Nilsson, A., Wiell, T., TILLBORG, H., Duda, L. C., Guo, J. H., Martensson, N., Nordgren, J., Andersen, J. N., Nyholm, R. 1992; 69 (5): 812-815
  • STUDIES OF THE CO-H,H2-NI(100) SYSTEM USING PHOTOELECTRON-SPECTROSCOPY SURFACE SCIENCE TILLBORG, H., Nilsson, A., Martensson, N. 1992; 273 (1-2): 47-60
  • O/CU(100) STUDIED BY CORE LEVEL SPECTROSCOPY 12TH EUROPEAN CONF ON SURFACE SCIENCE ( ECOSS-12 ) TILLBORG, H., Nilsson, A., Hernnas, B., Martensson, N. ELSEVIER SCIENCE BV. 1992: 300–304
  • NEXAFS STUDY OF MOLECULAR-ORIENTATION IN PHYSISORBED OXYGEN ON GRAPHITE 12TH EUROPEAN CONF ON SURFACE SCIENCE ( ECOSS-12 ) GUEST, R. J., Nilsson, A., Bjorneholm, O., Hernnas, B., Sandell, A., Palmer, R. E., Martensson, N. ELSEVIER SCIENCE BV. 1992: 432–437
  • DETERMINATION OF TIME SCALES FOR CHARGE-TRANSFER SCREENING IN PHYSISORBED MOLECULES PHYSICAL REVIEW LETTERS Bjorneholm, O., Nilsson, A., Sandell, A., Hernnas, B., Martensson, N. 1992; 68 (12): 1892-1895
  • ORIENTATION-DEPENDENT FINAL-STATE EFFECTS IN PHOTOELECTRON-SPECTRA OF PHYSISORBED MOLECULES PHYSICAL REVIEW LETTERS Nilsson, A., Palmer, R. E., TILLBORG, H., Hernnas, B., GUEST, R. J., Martensson, N. 1992; 68 (7): 982-985
  • AUTOIONIZATION OF ADSORBATES 2ND INTERNATIONAL WORKSHOP ON AUGER SPECTROSCOPY AND ELECTRONIC STRUCTURE ( IWASES-II ) Bjorneholm, O., Sandell, A., Nilsson, A., Martensson, N., Andersen, J. N. IOP PUBLISHING LTD. 1992: 217–225
  • ADSORPTION OF NO ON NI(100) 11TH EUROPEAN CONF ON SURFACE SCIENCE ( ECOSS-11 ) Sandell, A., Nilsson, A., Martensson, N. ELSEVIER SCIENCE BV. 1991: 971–978
  • LYING DOWN NO ON NI(100) SURFACE SCIENCE Sandell, A., Nilsson, A., Martensson, N. 1991; 241 (1-2): L1-L5
  • VIBRATIONAL MOTION AND GEOMETRICAL STRUCTURE IN ADSORBED CO STUDIED BY CORE LEVEL PHOTOELECTRON-SPECTROSCOPY 6TH INTERNATIONAL CONF ON VIBRATIONS AT SURFACES 1990 ANTONSSON, H., Nilsson, A., Martensson, N., Panas, I., Siegbahn, P. E. ELSEVIER SCIENCE BV. 1990: 601–613
  • RESONANT PHOTOEMISSION AT CORE-LEVEL SHAKE-UP THRESHOLDS - VALENCE-BAND SATELLITES IN NICKEL PHYSICAL REVIEW B Bjorneholm, O., Andersen, J. N., Wigren, C., Nilsson, A., Nyholm, R., Martensson, N. 1990; 41 (15): 10408-10412
  • VIBRATIONAL BROADENING IN CORE-LEVEL SPECTRA FROM ADSORBATES - C, N, AND O ON NI(100) PHYSICAL REVIEW LETTERS Nilsson, A., Martensson, N. 1989; 63 (14): 1483-1486
  • VALENCE CHANGES AND CORE-LEVEL SHIFTS OF SM ADSORBED ON MO(110) PHYSICAL REVIEW B Stenborg, A., Bjorneholm, O., Nilsson, A., Martensson, N., Andersen, J. N., Wigren, C. 1989; 40 (9): 5916-5923
  • VALENCE-TRANSITION-INDUCED 5X5 SURFACE RECONSTRUCTION OF SM(0001) PHYSICAL REVIEW LETTERS Stenborg, A., Andersen, J. N., Bjorneholm, O., Nilsson, A., Martensson, N. 1989; 63 (2): 187-190
  • XPS AND TSD RESULTS ON THE ADSORPTION OF CO ON THE YB/NI(100) SYSTEM SURFACE SCIENCE Andersen, J. N., Onsgaard, J., ZDANSKY, E., Nilsson, A., Martensson, N. 1989; 217 (1-2): 127-139
  • VIBRATIONAL EFFECTS AND SITE DEPENDENT SHIFTS IN CORE LEVEL SPECTRA FROM ADSORBATES - CO/NI(100) SOLID STATE COMMUNICATIONS Nilsson, A., Martensson, N. 1989; 70 (10): 923-926
  • COVERAGE DEPENDENT CORE LEVEL SHIFTS FOR ELECTROPOSITIVE METALS ADSORBED ON METALS - YB ON MO(110) SURFACE SCIENCE Stenborg, A., Bjorneholm, O., Nilsson, A., Martensson, N., Andersen, J. N., Wigren, C. 1989; 211 (1-3): 470-480
  • VIBRATIONAL EFFECTS IN CORE LEVEL SPECTRA FROM ADSORBATES SURFACE SCIENCE Martensson, N., Nilsson, A. 1989; 211 (1-3): 303-313
  • CORE-LEVEL BINDING-ENERGY SHIFTS DURING METAL ADSORPTION AND COMPOUND FORMATION - YB/NI(100) PHYSICAL REVIEW B Nilsson, A., Eriksson, B., Martensson, N., Andersen, J. N., Onsgaard, J. 1988; 38 (15): 10357-10370
  • QUANTITATIVE STUDIES OF METAL-METAL ADHESION AND INTERFACE SEGREGATION ENERGIES USING PHOTOELECTRON-SPECTROSCOPY PHYSICAL REVIEW LETTERS Martensson, N., Stenborg, A., Bjorneholm, O., Nilsson, A., Andersen, J. N. 1988; 60 (17): 1731-1734
  • SOME STRUCTURAL ASPECTS OF THE YB/NI(100) INTERFACE SURFACE SCIENCE Andersen, J. N., Onsgaard, J., Nilsson, A., Eriksson, B., ZDANSKY, E., Martensson, N. 1987; 189: 399-404
  • GROWTH AND PROPERTIES OF CU ON NI(100) SURFACE SCIENCE Nilsson, A., Morris, M. A., Chadwick, D. 1985; 152 (APR): 247-253
  • SURFACE CORE LEVEL SHIFTS AND ENERGIES OF SEGREGATION IN LA AND YB SYSTEMS SURFACE SCIENCE Nilsson, A., Martensson, N., Hedman, J., Eriksson, B., Bergman, R., GELIUS, U. 1985; 162 (1-3): 51-58