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| 2. |
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| 3. |
- Triguero, L., et al.
(författare)
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Direct experimental measurement of donation/back-donation in unsaturated hydrocarbon bonding to metals
- 2000
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 122:49, s. 12310-12316
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Tidskriftsartikel (refereegranskat)abstract
- Using resonant and off-resonant X-ray emission spectroscopy, in combination with ground-state density functional calculations, we examine the electronic structure of chemisarbed ethylene and benzene on thr Cu(110) surface to investigate the suitability of the donation/back-donation bonding model given by Dewar(1) and Chart and Duncanson(2) (DCD) for the interaction of unsaturated hydrocarbons with metal surfaces. We give an experimental verification of the DCD model and find donation/back-donation to be twice as large for ethylene as for benzene. In particular, the degree of sigma-pi mixing (rehybridization) is found to correspond to the amount of donation/back-donation, which is put in relation to the aromatic and nonaromatic pi characters of benzene and ethylene, respectively.
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| 4. |
- Weiss, K., et al.
(författare)
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XPS and XAS investigation of condensed and adsorbed n-octane on a Cu(110) surface
- 2003
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Ingår i: Journal of electron spectroscopy and related phenomena. - : Elsevier. - 0368-2048. ; 128:2-3, s. 179-191
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of n-octane adsorbed on Cu(110) is studied by using X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) in combination with cluster model calculations in the framework of density functional theory (DFT). The molecule is found to be well oriented on the surface, which is seen from the high degree of XAS dichroism. Saturated hydrocarbons are commonly considered to physisorb on metals such as Cu(110), but still the C 1s XAS spectra reveal large changes in the electronic structure of the adsorbed octane relative to the free molecule. We find that the XAS resonances corresponding to the molecular Rydberg-valence states are strongly quenched upon adsorption and that there is a significant hybridization of the molecular valence orbitals with the metal bands. In addition to a precise interpretation of the XAS spectra, we present details on the molecular orbital structure of the adsorbed octane molecule. We also discuss shifts in the relative binding energies of the chemically inequivalent carbon atoms in octane upon adsorption, which lead to a narrower XPS spectrum for the adsorbate than the condensed phase spectrum due to the existence of a new relaxation channel.
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| 5. |
- Öström, Henrik, et al.
(författare)
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Bonding of Saturated Hydrocarbons to Metal Surfaces
- 2003
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Ingår i: Physical Review Letters. - : The American Physical Society. - 0031-9007. ; 91:4, s. 046102-
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Tidskriftsartikel (refereegranskat)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.
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| 6. |
- Öström, H., et al.
(författare)
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Orbital rehybridization in n-octane adsorbed on Cu(110)
- 2003
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Ingår i: Journal of Chemical Physics. - : American Institute of Physics. - 0021-9606. ; 118:8, s. 3782-3789
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the local electronic structure of n-octane adsorbed on the Cu(110) surface using symmetry-resolved x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES) in combination with density functional theory (DFT) spectrum calculations. We found new adsorption-induced states in the XE spectra, which we assign to interaction between the bonding CH orbitals and the metal surface. By performing a systematic investigation of the influence of different structural parameters on the XA and XE spectra, we conclude that the molecular geometry is significantly distorted relative to the gas-phase structure. The bonding to the surface leads to a strengthening of the carbon–carbon bonds and a weakening of the carbon–hydrogen bonds, consistent with a rehybridization of the carbons from sp3 to sp2.8. ©2003 American Institute of Physics.
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| 7. |
- Fohlisch, A, et al.
(författare)
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Ground-state interpretation of x-ray emission spectroscopy on adsorbates: CO adsorbed on Cu(100)
- 2000
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Ingår i: PHYSICAL REVIEW B. - : AMERICAN PHYSICAL SOC. - 0163-1829. ; 61:23, s. 16229-16240
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Tidskriftsartikel (refereegranskat)abstract
- The application of resonant inelastic x-ray scattering and resonantly excited x-ray emission to adsorbates has evolved into a powerful technique to investigate the valence electronic structure of adsorbates in an atom-specific and orbital-symmetry-selecti
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| 8. |
- Fohlisch, A, et al.
(författare)
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The bonding of CO to metal surfaces
- 2000
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Ingår i: JOURNAL OF CHEMICAL PHYSICS. - : AMER INST PHYSICS. - 0021-9606. ; 112:4, s. 1946-1958
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Tidskriftsartikel (refereegranskat)abstract
- The atom and symmetry specific properties of x-ray emission spectroscopy have been applied to the investigation of CO adsorbed on Ni(100) and Cu(100) surfaces. In comparison to ab initio electronic structure calculations, obtained in density functional th
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| 9. |
- Hennies, F., et al.
(författare)
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Dynamic interpretation of resonant x-ray Raman scattering : ethylene and benzene
- 2007
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 76:3, s. 032505-
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Tidskriftsartikel (refereegranskat)abstract
- We present a dynamic interpretation of resonant x-ray Raman scattering where vibrationally selective excitation into molecular resonances has been employed in comparison with excitation into higher lying continuum states for condensed ethylene and benzene as molecular model systems. In order to describe the purely vibrational spectral loss features and coupled electronic and vibrational losses the one-step theory for resonant soft x-ray scattering is applied, taking multiple vibrational modes and vibronic coupling into account. The scattering profile is found to be strongly excitation energy dependent and to reflect the intermediate states dynamics of the scattering process. In particular, the purely vibrational loss features allow one to map the electronic ground state potential energy surface in light of the excited state dynamics. Our study of ethylene and benzene underlines the necessity of an explicit description of the coupled electronic and vibrational loss features for the assignment of spectral features observed in resonant x-ray Raman scattering at polyatomic systems, which can be done in both a time independent and a time dependent picture. The possibility to probe ground state vibrational properties opens a perspective to future applications of this photon-in-photon-out spectroscopy.
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| 10. |
- Hennies, F., et al.
(författare)
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Non-Adiabatic effects in Resonant Inelastic x-ray Scattering
- 2005
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 95:16, s. 163002-
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the spectral features of resonant inelastic x-ray scattering of condensed ethylene with vibrational selectivity both experimentally and theoretically. Purely vibrational spectral loss features and coupled electronic and vibrational losses are observed. The one-step theory for resonant soft x-ray scattering is applied, taking multiple vibrational modes and vibronic coupling into account. Our investigation of ethylene underlines that the assignment of spectral features observed in resonant inelastic x-ray scattering of polyatomic systems requires an explicit description of the coupled electronic and vibrational loss features.
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| 11. |
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| 12. |
- Marselle, Melissa R., et al.
(författare)
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Pathways linking biodiversity to human health : A conceptual framework
- 2021
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Ingår i: Environment International. - : Elsevier. - 0160-4120 .- 1873-6750. ; 150
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Forskningsöversikt (refereegranskat)abstract
- Biodiversity is a cornerstone of human health and well-being. However, while evidence of the contributions of nature to human health is rapidly building, research into how biodiversity relates to human health remains limited in important respects. In particular, a better mechanistic understanding of the range of pathways through which biodiversity can influence human health is needed. These pathways relate to both psychological and social processes as well as biophysical processes. Building on evidence from across the natural, social and health sciences, we present a conceptual framework organizing the pathways linking biodiversity to human health. Four domains of pathways?both beneficial as well as harmful?link biodiversity with human health: (i) reducing harm (e.g. provision of medicines, decreasing exposure to air and noise pollution); (ii) restoring capacities (e.g. attention restoration, stress reduction); (iii) building capacities (e.g. promoting physical activity, transcendent experiences); and (iv) causing harm (e.g. dangerous wildlife, zoonotic diseases, allergens). We discuss how to test components of the biodiversity-health framework with available analytical approaches and existing datasets. In a world with accelerating declines in biodiversity, profound land-use change, and an increase in non communicable and zoonotic diseases globally, greater understanding of these pathways can reinforce biodiversity conservation as a strategy for the promotion of health for both people and nature. We conclude by identifying research avenues and recommendations for policy and practice to foster biodiversity-focused public health actions.
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| 13. |
- Nilsson, A, et al.
(författare)
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Probing chemical bonding in adsorbates using X-ray emission spectroscopy
- 2000
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Ingår i: JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA. - : ELSEVIER SCIENCE BV. - 0368-2048. ; 110:1-3, s. 15-39
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Tidskriftsartikel (refereegranskat)abstract
- When a molecule is adsorbed on a metal surface by chemical bonding new electronic states are formed. The direct observation and identification of these states has been an experimental challenge. Their signature is often obscured by bulk substrate states.
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| 14. |
- Triguero, L, et al.
(författare)
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Direct experimental measurement of donation/back-donation in unsaturated hydrocarbon bonding to metals
- 2000
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Ingår i: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. - : AMER CHEMICAL SOC. - 0002-7863. ; 122:49, s. 12310-12316 Language: English
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Tidskriftsartikel (refereegranskat)abstract
- Using resonant and off-resonant X-ray emission spectroscopy, in combination with ground-state density functional calculations, we examine the electronic structure of chemisarbed ethylene and benzene on thr Cu(110) surface to investigate the suitability of
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| 15. |
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| 16. |
- Öström, Henrik, et al.
(författare)
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Geometric structure and chemical bonding of acetylene adsorbed on Cu(110)
- 2004
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 565:2-3, s. 206-222
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Tidskriftsartikel (refereegranskat)abstract
- The chemical bonding and geometric structure of acetylene adsorbed on Cu(I 10) is analyzed using X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) in combination with density functional theory (DFT) total energy geometry optimizations and spectral calculations. XPS reveals two different adsorbed species at liquid nitrogen temperature. The molecular alignment is deduced from angle-resolved XAS, revealing that in one site the molecules are aligned with the C-C axis along the [0 0 1] direction and in the other site with an average angle of 35degrees to the Cu rows. The position of the shape resonance is used to deduce a C-C bond length of 1.35 Angstrom, which is close to the values obtained from the DFT geometry optimizations. XES reveals strong sigma-pi mixing and new occupied states close to the Fermi level, originating from the out-of-plane pi* orbital, which becomes occupied upon adsorption in agreement with the Dewar-Chatt-Duncanson model of the bonding.
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