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  • 1. Bednarska, Joanna
    et al.
    Zalesny, Robert
    Murugan, N. Arul
    Bartkowiak, Wojciech
    Agren, Hans
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Elucidating the Mechanism of Zn2+ Sensing by a Bipyridine Probe Based on Two-Photon Absorption2016Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 120, nr 34, s. 9067-9075Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, we examine, by means of computational methods, the mechanism of Zn2+ sensing by a bipyridine-centered, D-pi-A-pi-D-type-ratiometric molecular probe. According to recently published experimental data [Divya, K. P.; Sreejith, S.; Ashokkumar, P.; Yuzhan, K.; Peng, Q; Maji, S. K.; Tong, Y.; Yu, H.; Zhao, Y.; Ramamurthy, P.; Ajayaghosh, A. A ratiometric fluorescent molecular -probe with enhanced two-photon response upon Zn2+ binding for in vitro and in vivo: bioimaging.= Chem. Sci. 2014, S, 3469-3474], after coordination to zinc ions the -probe exhibits a large enhancement of the two -photon absorption cross section. The goal of our investigation was to elucidate the mechanism behind this phenomenon. For this purpose, linear and nonlinear optical properties of -the unbound (cation-free) and bound probe were calculated, including the influence of solute Solvent interactions, implicitly using a polarizable continuum model and exp-licitely employing the QM/MM approach. Because the results of the calculations indicate that many conformers of the probe are energetically accessible at room temperature in solution and hence contribute to the Signal, structurepteperty relationships were also taken into account. Results of our simulations-demonstrate that the one-photon absorption bands for both the unbound -and bound forms correspond to the bright pi -> pi* transition to the first excited state; which, on the other hand,. exhibits negligible two-photon activity. On the basis of the results of the quadratic respOnse calculations, we put forward-notion that it is the second excited state that gives the strong signal in the experimental nonlinear spectrum. To explain the differenCes in the two-photon absorption activity for the two lowest-lying excited states and nonlinear response enhancement upon binding, we employed the generalized few -state model including the ground, first, and- second excited states. The analysis of the optical channel suggests that the large two-photon response is due to the coordination -induced increase of the, transition- moment from the first to the second excited state.

  • 2. Blum, M.
    et al.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Weinhardt, L.
    Pookpanratana, S.
    Baer, M.
    Zhang, Y.
    Fuchs, O.
    Yang, W.
    Umbach, E.
    Heske, C.
    Ultrafast Proton Dynamics in Aqueous Amino Acid Solutions Studied by Resonant Inelastic Soft X-ray Scattering2012Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 116, nr 46, s. 13757-13764Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Resonant inelastic soft X-ray scattering (RIXS) has been used to study the electronic structure of glycine and lysine in aqueous solution. Upon variation of the pH value of the solution from acidic to basic, major changes of the nitrogen K edge RIXS data are observed for both amino acids, which are associated with the protonation and deprotonation of the amino groups. The experimental results are compared with simulations based on density functional theory, yielding a detailed understanding of the spectral changes, as well as insights into the ultrafast proton dynamics in the intermediate core-excited/ionized state of the RIXS process.

  • 3.
    Cavalleri, M.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Nordlund, D.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Odelius, M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Nilsson, A.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Pettersson, L.G.M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Half or full core hole in density functional theory X-ray absorption spectrum calculations of water?2005Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 7, nr 15, s. 2854-2858Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 4. Chaudhuri, A
    et al.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Jones, R G
    Lee, T-L
    Detlefs, B
    Woodruff, D P
    The structure of the Au(111)/methylthiolate interface: new insights from near-edge x-ray absorption spectroscopy and x-ray standing waves.2009Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 130, nr 12, s. 124708-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The local structure of the Au(111)(√3x√3)R30 degrees-methylthiolate surface phase has been investigated by S K-edge near-edge s-ray absorption fine structure (NEXAFS) both experimentally and theoretically and by experimental normal-incidence x-ray standing waves (NIXSW) at both the C and S atomic sites. NEXAFS shows not only excitation into the intramolecular σ*S-C resonance but also into a σ* S-Au orbital perpendicular to the surface, clearly identifying the local S headgroup site as atop a Au atom. Simulations show that it is not possible, however, to distinguish between the two possible adatom reconstruction models; a single thiolate species atop a hollow-site Au adatom or a dithiolate moiety comprising two thiolate species bonded to a bridge-bonded Au adatom. Within this dithiolate moiety a second σ* S-Au orbital that lies near parallel to the surface has a higher energy that overlaps that of the σ* S-C resonance. The new NIXSW data show the S-C bond to be tilted by 61 degrees relative to the surface normal, with a preferred azimuthal orientation in <211>, corresponding to the intermolecular nearest-neighbor directions. This azimuthal orientation is consistent with the thiolate being atop a hollow-site Au adatom, but not consistent with the originally proposed Au-adatom-dithiolate moiety. However, internal conformational changes within this species could, perhaps, render this model also consistent with the experimental data.

  • 5. Couto, Rafael C.
    et al.
    Cruz, Vinicius V.
    Ertan, Emelie
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Eckert, Sebastian
    Fondell, Mattis
    Dantz, Marcus
    Kennedy, Brian
    Schmitt, Thorsten
    Pietzsch, Annette
    Guimarães, Freddy F.
    Ågren, Hans
    Gel'mukhanov, Faris
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Kimberg, Victor
    Föhlisch, Alexander
    Selective gating to vibrational modes through resonant X-ray scattering2017Inngår i: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 8, artikkel-id 14165Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The dynamics of fragmentation and vibration of molecular systems with a large number of coupled degrees of freedom are key aspects for understanding chemical reactivity and properties. Here we present a resonant inelastic X-ray scattering (RIXS) study to show how it is possible to break down such a complex multidimensional problem into elementary components. Local multimode nuclear wave packets created by X-ray excitation to different core-excited potential energy surfaces (PESs) will act as spatial gates to selectively probe the particular ground-state vibrational modes and, hence, the PES along these modes. We demonstrate this principle by combining ultra-high resolution RIXS measurements for gas-phase water with state-of-the-art simulations.

  • 6. da Cruz, Vinícius Vaz
    et al.
    Gel'mukhanov, Faris
    Eckert, Sebastian
    Iannuzzi, Marcella
    Ertan, Emelie
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Pietzsch, Annette
    Couto, Rafael C.
    Niskanen, Johannes
    Fondell, Mattis
    Dantz, Marcus
    Schmitt, Thorsten
    Lu, Xingye
    McNally, Daniel
    Jay, Raphael M.
    Kimberg, Victor
    Föhlisch, Alexander
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Probing hydrogen bond strength in liquid water by resonant inelastic X-ray scattering2019Inngår i: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, artikkel-id 1013Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Local probes of the electronic ground state are essential for understanding hydrogen bonding in aqueous environments. When tuned to the dissociative core-excited state at the O1s pre-edge of water, resonant inelastic X-ray scattering back to the electronic ground state exhibits a long vibrational progression due to ultrafast nuclear dynamics. We show how the coherent evolution of the OH bonds around the core-excited oxygen provides access to high vibrational levels in liquid water. The OH bonds stretch into the long-range part of the potential energy curve, which makes the X-ray probe more sensitive than infra-red spectroscopy to the local environment. We exploit this property to effectively probe hydrogen bond strength via the distribution of intramolecular OH potentials derived from measurements. In contrast, the dynamical splitting in the spectral feature of the lowest valence-excited state arises from the short-range part of the OH potential curve and is rather insensitive to hydrogen bonding.

  • 7. da Cruz, Vinícius Vaz
    et al.
    Ignatova, Nina
    Couto, Rafael C.
    Fedotov, Daniil A.
    Rehn, Dirk R.
    Savchenko, Viktoriia
    Norman, Patrick
    Ågren, Hans
    Polyutov, Sergey
    Niskanen, Johannes
    Eckert, Sebastian
    Jay, Raphael M.
    Fondell, Mattis
    Schmitt, Thorsten
    Pietzsch, Annette
    Föhlisch, Alexander
    Gel'mukhanov, Faris
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Kimberg, Victor
    Nuclear dynamics in resonant inelastic X-ray scattering and X-ray absorption of methanol2019Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 150, nr 23, artikkel-id 234301Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on a combined theoretical and experimental study of core-excitation spectra of gas and liquid phase methanol as obtained with the use of X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). The electronic transitions are studied with computational methods that include strict and extended second-order algebraic diagrammatic construction [ADC(2) and ADC(2)-x], restricted active space second-order perturbation theory, and time-dependent density functional theory-providing a complete assignment of the near oxygen K-edge XAS. We show that multimode nuclear dynamics is of crucial importance for explaining the available experimental XAS and RIXS spectra. The multimode nuclear motion was considered in a recently developed mixed representation where dissociative states and highly excited vibrational modes are accurately treated with a time-dependent wave packet technique, while the remaining active vibrational modes are described using Franck-Condon amplitudes. Particular attention is paid to the polarization dependence of RIXS and the effects of the isotopic substitution on the RIXS profile in the case of dissociative core-excited states. Our approach predicts the splitting of the 2a RIXS peak to be due to an interplay between molecular and pseudo-atomic features arising in the course of transitions between dissociative core- and valence-excited states. The dynamical nature of the splitting of the 2a peak in RIXS of liquid methanol near pre-edge core excitation is shown. The theoretical results are in good agreement with our liquid phase measurements and gas phase experimental data available from the literature.

  • 8. Eckert, Sebastian
    et al.
    da Cruz, Vinícius Vaz
    Gel'mukhanov, Faris
    Ertan, Emelie
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Ignatova, Nina
    Polyutov, Sergey
    Couto, Rafael C.
    Fondell, Mattis
    Dantz, Marcus
    Kennedy, Brian
    Schmitt, Thorsten
    Pietzsch, Annette
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Föhlisch, Alexander
    One-dimensional cuts through multidimensional potential-energy surfaces by tunable x rays2018Inngår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information, ISSN 2469-9926, E-ISSN 2469-9934, Vol. 97, nr 5, artikkel-id 053410Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The concept of the potential-energy surface (PES) and directional reaction coordinates is the backbone of our description of chemical reaction mechanisms. Although the eigenenergies of the nuclear Hamiltonian uniquely link a PES to its spectrum, this information is in general experimentally inaccessible in large polyatomic systems. This is due to (near) degenerate rovibrational levels across the parameter space of all degrees of freedom, which effectively forms a pseudospectrum given by the centers of gravity of groups of close-lying vibrational levels. We show here that resonant inelastic x-ray scattering (RIXS) constitutes an ideal probe for revealing one-dimensional cuts through the ground-state PES of molecular systems, even far away from the equilibrium geometry, where the independent-mode picture is broken. We strictly link the center of gravity of close-lying vibrational peaks in RIXS to a pseudospectrum which is shown to coincide with the eigenvalues of an effective one-dimensional Hamiltonian along the propagation coordinate of the core-excited wave packet. This concept, combined with directional and site selectivity of the core-excited states, allows us to experimentally extract cuts through the ground-state PES along three complementary directions for the showcase H2O molecule.

  • 9. Eckert, Sebastian
    et al.
    Norell, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Jay, Raphael M.
    Fondell, Mattis
    Mitzner, Rolf
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Föhlisch, Alexander
    T-1 Population as the Driver of Excited-State Proton-Transfer in 2-Thiopyridone2019Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 25, nr 7, s. 1733-1739Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Excited-state proton transfer (ESPT) is a fundamental process in biomolecular photochemistry, but its underlying mediators often evade direct observation. We identify a distinct pathway for ESPT in aqueous 2-thiopyridone, by employing transient N1s X-ray absorption spectroscopy and multi-configurational spectrum simulations. Photoexcitations to the singlet S-2 and S-4 states both relax promptly through intersystem crossing to the triplet T-1 state. The T-1 state, through its rapid population and near nanosecond lifetime, mediates nitrogen site deprotonation by ESPT in a secondary intersystem crossing to the S-0 potential energy surface. This conclusively establishes a dominant ESPT pathway for the system in aqueous solution, which is also compatible with previous measurements in acetonitrile. Thereby, the hitherto open questions of the pathway for ESPT in the compound, including its possible dependence on excitation wavelength and choice of solvent, are resolved.

  • 10. Eckert, Sebastian
    et al.
    Norell, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Miedema, Piter S.
    Beye, Martin
    Fondell, Mattis
    Quevedo, Wilson
    Kennedy, Brian
    Hantschmann, Markus
    Pietzsch, Annette
    Van Kuiken, Benjamin E.
    Ross, Matthew
    Minitti, Michael P.
    Moeller, Stefan P.
    Schlotter, William F.
    Khalil, Munira
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Föhlisch, Alexander
    Ultrafast Independent N-H and N-C Bond Deformation Investigated with Resonant Inelastic X-Ray Scattering2017Inngår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 56, nr 22, s. 6088-6092Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The femtosecond excited-state dynamics following resonant photoexcitation enable the selective deformation of N-H and N-C chemical bonds in 2-thiopyridone in aqueous solution with optical or X-ray pulses. In combination with multiconfigurational quantum-chemical calculations, the orbital-specific electronic structure and its ultrafast dynamics accessed with resonant inelastic X-ray scattering at the N 1s level using synchrotron radiation and the soft X-ray free-electron laser LCLS provide direct evidence for this controlled photoinduced molecular deformation and its ultrashort time-scale.

  • 11. Ekimova, Maria
    et al.
    Kubin, Markus
    Ochmann, Miguel
    Ludwig, Jan
    Huse, Nils
    Wernet, Philippe
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Nibbering, Erik T. J.
    Soft X-ray Spectroscopy of the Amine Group: Hydrogen Bond Motifs in Alkylamine/Alkylammonium Acid-Base Pairs2018Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 122, nr 31, s. 7737-7746Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We use N K-edge absorption spectroscopy to explore the electronic structure of the amine group, one of the most prototypical chemical functionalities playing a key role in acid base chemistry, electron donor-acceptor interactions, and nucleophilic substitution reactions. In this study, we focus on aliphatic amines and make use of the nitrogen is core electron excitations to elucidate the roles of N-H sigma* and N-C sigma* contributions in the unoccupied orbitals. We have measured N K-edge absorption spectra of the ethylamine bases EtxNH3-x (x = 0...3; Et- = C2H5-) and the conjugate positively charged ethylammonium cation acids EtyNH4-y+ (y = 0...4; Et- = C2H5-) dissolved in the protic solvents ethanol and water. Upon consecutive exchange of N-H for ethyl-groups, we observe a spectral shift, a systematic decrease of the N K-edge pre-edge peak, and a major contribution in the post edge region for the ethylamine series. Instead, for the ethylammonium ions, the consecutive exchange of N-H for ethyl groups leads to an apparent reduction of pre-edge and post-edge intensities relative to the main-edge band, without significant frequency shifts. Building on findings from our previously reported study on aqueous ammonia and ammonium ions, we can rationalize these observations by comparing calculated N K-edge absorption spectra of free and hydrogen-bonded clusters. Hydrogen bonding interactions lead only to minor spectral effects in the ethylamine series, but have a large impact in the ethylammonium ion series. Visualization of the unoccupied molecular orbitals shows the consecutive change in molecular orbital character from N-H sigma* to N-C sigma* in these alkylamine/alkylammonium ion series. This can act as a benchmark for future studies on chemically more involved amine compounds.

  • 12. Eriksson, Susanna K.
    et al.
    Hahlin, Maria
    Axnanda, Stephanus
    Crumlin, Ethan
    Wilks, Regan
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Eriksson, Anna I. K.
    Liu, Zhi
    Åhlund, John
    Hagfeldt, Anders
    Starr, David E.
    Bär, Marcus
    Rensmo, Håkan
    Siegbahn, Hans
    In-Situ Probing of H2O Effects on a Ru-Complex Adsorbed on TiO2 Using Ambient Pressure Photoelectron Spectroscopy2016Inngår i: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 59, nr 5-7, s. 583-590Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dye-sensitized interfaces in photocatalytic and solar cells systems are significantly affected by the choice of electrolyte solvent. In the present work, the interface between the hydrophobic Ru-complex Z907, a commonly used dye in molecular solar cells, and TiO2 was investigated with ambient pressure photoelectron spectroscopy (AP-PES) to study the effect of water atmosphere on the chemical and electronic structure of the dye/TiO2 interface. Both laboratory-based Al K alpha as well as synchrotron-based ambient pressure measurements using hard X-ray (AP-HAXPES) were used. AP-HAXPES data were collected at pressures of up to 25 mbar (i.e., the vapor pressure of water at room temperature) showing the presence of an adsorbed water overlayer on the sample surface. Adopting a quantitative AP-HAXPES analysis methodology indicates a stable stoichiometry in the presence of the water atmosphere. However, solvation effects due to the presence of water were observed both in the valence band region and for the S 1s core level and the results were compared with DFT calculations of the dye-water complex.

  • 13. Eriksson, Susanna K.
    et al.
    Josefsson, Ida
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Ellis, Hanna
    Amat, Anna
    Pastore, Mariachiara
    Oscarsson, Johan
    Lindblad, Rebecka
    Eriksson, Anna I. K.
    Johansson, Erik M. J.
    Boschloo, Gerrit
    Hagfeldt, Anders
    Fantacci, Simona
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Rensmo, Håkan
    Geometrical and energetical structural changes in organic dyes for dye-sensitized solar cells probed using photoelectron spectroscopy and DFT2016Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, nr 1, s. 252-260Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of alkoxy chain length in triarylamine based donor acceptor organic dyes are investigated with respect to the electronic and molecular surface structures on the performance of solar cells and the electron lifetime. The dyes were investigated when adsorbed on TiO2 in a configuration that can be used for dye sensitized solar cells (DSCs). Specifically, the two dyes D35 and D45 were compared using photoelectron spectroscopy (PES) and density functional theory (DFT) calculations. The differences in solar cell characteristics when longer alkoxy chains are introduced in the dye donor unit are attributed to geometrical changes in dye packing while only minor differences were observed in the electronic structure. A higher dye load was observed for D45 on TiO2. However, D35 based solar cells result in higher photocurrent although the dye load is lower. This is explained by different geometrical structures of the dyes on the surface.

  • 14. Eriksson, Susanna K.
    et al.
    Josefsson, Ida
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Ottosson, Niklas
    Öhrwall, Gunnar
    Björneholm, Olle
    Siegbahn, Hans
    Hagfeldt, Anders
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Rensmo, Hakan
    Solvent Dependence of the Electronic Structure of I- and I-3(-)2014Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 118, nr 11, s. 3164-3174Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present synchrotron-based I4d photoelectron spectroscopy experiments of solutions from LiI and LiI3 in water, ethanol, and acetonitrile. The experimentally determined solvent-induced binding energy shifts (SIBES) for the monatomic I- anion are compared to predictions from simple Born theory, PCM calculations, as well as multiconfigurational quantum chemical spectral calculations from geometries obtained through molecular dynamics of solvated clusters. We show that the SIBES for I- explicitly depend on the details of the hydrogen bonding configurations of the solvent to the I- and that static continuum models such as the Born model cannot capture the trends in the SIBES observed both in experiments and in higher-level calculations. To extend the discussion to more complex polyatomic anions, we also performed experiments on I-3(-) and I-/I-3(-) mixtures in different solvents and the results are analyzed in the perspective of SIBES. The experimental SIBES values indicate that the solvation effects even for such similar anions as I- and I-3(-) can be rather different in nature.

  • 15.
    Ertan, Emelie
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Kimberg, Victor
    Gel'mukhanov, Faris
    Hennies, Franz
    Rubensson, Jan-Erik
    Schmitt, Thorsten
    Strocov, Vladimir N.
    Zhou, Kejin
    Iannuzzi, Marcella
    Foehlisch, Alexander
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Pietzsch, Annette
    Theoretical simulations of oxygen K-edge resonant inelastic x-ray scattering of kaolinite2017Inngår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, nr 14, artikkel-id 144301Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Near-edge x-ray absorption fine structure (NEXAFS) and resonant inelastic x-ray scattering (RIXS) measurements at the oxygen K edge were combined with theoretical spectrum simulations, based on periodic density functional theory and nuclear quantum dynamics, to investigate the electronic structure and chemical bonding in kaolinite Al2Si2O5(OH)(4). We simulated NEXAFS spectra of all crystallographically inequivalent oxygen atoms in the crystal and RIXS spectra of the hydroxyl groups. Detailed insight into the ground-state potential energy surface of the electronic states involved in the RIXS process were accessed by analyzing the vibrational excitations, induced by the core excitation, in quasielastic scattering back to the electronic ground state. In particular, we find that the NEXAFS pre-edge is dominated by features related to OH groups within the silica and alumina sheets, and that the vibrational progression in RIXS can be used to selectively probe vibrational modes of this subclass of OH groups. The signal is dominated by the OH stretching mode, but also other lower vibrational degrees of freedom, mainly hindered rotational modes, contribute to the RIXS signal.

  • 16.
    Ertan, Emelie
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Lundberg, Marcus
    Kragh Sørensen, Lasse
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Setting the stage for theoretical X-ray spectra of the H2S molecule with RASPT2 calculations of the energy landscapeManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Electronic valence- and core-excitations into the anti-bonding orbitals of the H2S molecule have been calculated within a multi-configurational wave-function framework (RASPT2). Potential energy surfaces and transition dipole moments have been derived in two dimensions for the S-H stretching coordinates. The |S1s-1, 6a11> and |S1s-1, 3b21> core-excited states in H2S are nearly degenerate along the symmetric stretching coordinate, for which we have identified two conical intersections. The small energy splitting of the S1s-1 core-excited states at equilibrium geometry arise from an avoided crossing at broken symmetry. Compared to the water molecule, which exhibit state-selective gating to different vibrational modes [Nat. Commun. 8 14165 (2017)] in its well-separated O1s-1 core-excited states, we expect a strong coupling between the close-lying |S1s-1, 6a11> and |S1s-1, 3b21> states. This could lead to dissociative dynamics observable in K-edge RIXS. The S2p-1 core-excited states form two dense manifolds of spin-orbit coupled states, which can be schematically characterised as bound |S2p-1,3b21> and dissociative |S2p-1,6a11> states. We identify three conical intersections in the singlet and triplet states along the symmetric stretching coordinate. Mapping the molecular singlet and triplet states to the atomic dissociation limit reveals a symmetry selection rule, leading to an off-set of the 1|3a1-1,6a11> state relative to the other S2p-1 core-excited states. The dense manifolds of S2p-1 core-excited states will complicate the analysis of Kα-edge RIXS, but dynamical effects could be evaluated through detuning and in comparison to L-edge XAS. In L-edge RIXS, the dynamical effects well be more pronounced due to a longer life-time of the S2p-1 core-excited states compared to the S1s-1 core-excited states.

  • 17.
    Ertan, Emelie
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Savchenko, Viktoriia
    Ignatova, Nina
    da Cruz, Vinicius Vaz
    Couto, Rafael C.
    Eckert, Sebastian
    Fondell, Mattis
    Dantz, Marcus
    Kennedy, Brian
    Schmitt, Thorsten
    Pietzsch, Annette
    Foelisch, Alexander
    Gel'mukhanov, Faris
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Kimberg, Victor
    Ultrafast dissociation features in RIXS spectra of the water molecule2018Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, nr 21, s. 14384-14397Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this combined theoretical and experimental study we report on an analysis of the resonant inelastic X-ray scattering (RIXS) spectra of gas phase water via the lowest dissociative core-excited state |1s-1O4a11. We focus on the spectral feature near the dissociation limit of the electronic ground state. We show that the narrow atomic-like peak consists of the overlapping contribution from the RIXS channels back to the ground state and to the first valence excited state |1b-114a11 of the molecule. The spectral feature has signatures of ultrafast dissociation (UFD) in the core-excited state, as we show by means of ab initio calculations and time-dependent nuclear wave packet simulations. We show that the electronically elastic RIXS channel gives substantial contribution to the atomic-like resonance due to the strong bond length dependence of the magnitude and orientation of the transition dipole moment. By studying the RIXS for an excitation energy scan over the core-excited state resonance, we can understand and single out the molecular and atomic-like contributions in the decay to the lowest valence-excited state. Our study is complemented by a theoretical discussion of RIXS in the case of isotopically substituted water (HDO and D2O) where the nuclear dynamics is significantly affected by the heavier fragments' mass.

  • 18.
    Ertan, Emelie
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Savchenko, Viktoriia
    Ignatova, Nina
    Vaz da Cruz, Vinicius
    Couto, Rafael
    Eckert, Sebastian
    Fondell, Mattis
    Dantz, Marcus
    Kennedy, Brian
    Schmitt, Thorsten
    Pietzsch, Annette
    Föhlisch, Alexander
    Gel'mukhanov, Faris
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Kimberg, Victor
    Ultrafast dissociation features in RIXS spectra of the water moleculeManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    In this combined theoretical and experimental study we report on an analysis of the resonant inelastic X-ray scattering spectra (RIXS) of gas phase water via the lowest dissociative core-excited state |1sO-14a11>. We focus on the spectral feature near the dissociation limit of the electronic ground state. We show that the narrow atomic-like peak consists of the overlapping contribution from the RIXS channels  back to the ground state and to the first valence excited state |1b1-14a11> of the molecule. The spectral feature has signatures of ultrafast dissociation (UFD) in the core-excited state, as we show by means of ab initio calculations and time-dependent nuclear wave packet simulations. We show that the electronically elastic RIXS channel gives substantial contribution to the atomic-like resonance due to the strong bond length dependence of the magnitude and orientation of the transition dipole moment. By studying the RIXS for an excitation energy scan over the core-excited state resonance, we can understand and single out the molecular and atomic-like contributions in the decay to the lowest valence-excited state. Our study is complemented by a theoretical discussion of RIXS in the case of the isotope substituted water (HDO and D2O) where the nuclear dynamics is significantly affected by the heavier fragments' mass.

  • 19. Gadegaard, Ane Riis
    et al.
    Thogersen, Jan
    Jensen, Svend Knak
    Nielsen, Jakob Brun
    Jena, Naresh K.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Jensen, Frank
    Keiding, Søren Rud
    Spectroscopy and picosecond dynamics of aqueous NO22014Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 141, nr 6, s. 064310-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate the formation of aqueous nitrogen dioxide, NO2 formed through femtosecond photolysis of nitrate, NO3- ( aq) and nitromethane CH3NO2(aq). Common to the experiments is the observation of a strong induced absorption at 1610 +/- 10 cm(-1), assigned to the asymmetric stretch vibration in the ground state of NO2. This assignment is substantiated through isotope experiments substituting N-14 by N-15, experiments at different pH values, and by theoretical calculations and simulations of NO2-D2O clusters.

  • 20. Gaffney, K. J.
    et al.
    Ji, M.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Park, S.
    Sun, Z.
    H-bond switching and ligand exchange dynamics in aqueous ionic solution2011Inngår i: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 504, nr 1-3, s. 1-6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aqueous ionic solutions lubricate the chemical machinery of the environment and life. Understanding the impact of ions on the properties of aqueous solutions and how these modified properties influence chemical and conformational dynamics remains an important and elusive objective of physical chemistry research. Here we discuss recent advances in our understanding that have been derived from ultrafast vibrational spectroscopy and molecular dynamics simulations.

  • 21. Grönbeck, Henrik
    et al.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Photoemission core-level shifts reveal the thiolate-Au(111) interface2010Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, s. 085416-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The nature of the thiolate/Au(111) interface is a long-standing puzzle. It has been suggested that thiolates drive surface reconstruction, however, a consensus regarding the adsorption configuration is missing. Herein, the density-functional theory is used to evaluate surface core-level shifts (SCLSs) for methyl thiolates on Au(111) assuming a representative set of different surface reconstructions. The SCLSs are found to provide sensitive fingerprints of the anchoring configuration, and it is only thiolate adsorption in the form of MeS-Au-SMe complexes that can be reconciled with experimental data.

  • 22.
    Hahlin, Maria
    et al.
    Uppsala universitet.
    Johansson, Erik M J
    Uppsala universitet.
    Plogmaker, Stefan
    Uppsala universitet.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hagberg, Daniel P
    Sun, Licheng
    KTH, Organisk kemi.
    Siegbahn, Hans
    Uppsala universitet.
    Rensmo, Håkan
    Uppsala universitet.
    Electronic and molecular structures of organic dye/TiO(2) interfaces for solar cell applications: a core level photoelectron spectroscopy study.2010Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 12, nr 7, s. 1507-17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electronic and molecular properties of three organic dye molecules with the general structure donor-linker-anchor have been investigated using core level photoelectron spectroscopy (PES). The molecules contain a diphenylaniline donor unit, a thiophene linker unit, and cyanoacrylic acid or rhodanine-3-acetic acid anchor units. They have been investigated both in the form of a multilayer and adsorbed onto nanoporous TiO(2) and the experimental results were also compared with DFT calculations. The changes at the dye-sensitized TiO(2) surface due to the modification of either the donor unit or the anchor unit was investigated and the results showed important differences in coverage as well as in electronic and molecular surface properties. By measuring the core level binding energies, the sub-molecular properties were characterized and the result showed that the adsorption to the TiO(2) influences the energy levels of the sub-molecular units differently.

  • 23. Hahlin, Maria
    et al.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Magnuson, Martin
    Johansson, Erik M. J.
    Plogmaker, Stefan
    Hagberg, Daniel P.
    Sun, Licheng
    Siegbahn, Hans
    Rensmo, Håkan
    Mapping the frontier electronic structures of triphenylamine based organic dyes at TiO2 Interafaces2011Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, s. 3534--3546Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The frontier electronic structures of a series of organic dye molecules containing a triphenylamine moiety, a thiophene moiety and a cyanoacrylic acid moiety have been investigated by photoelectron spectroscopy (PES), X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and resonant photoelectron spectroscopy (RPES). The experimental results were compared to electronic structure calculations on the molecules, which are used to confirm and enrich the assignment of the spectra. The approach allows us to experimentally measure and interpret the basic valence energy level structure in the dye, including the highest occupied energy level and how it depends on the interaction between the different units. Based on N 1s X-ray absorption and emission spectra we also obtain insight into the structure of the excited states, the molecular orbital composition and dynamics. Together the results provide an experimentally determined energy level map useful in the design of these types of materials. Included are also results indicating femtosecond charge redistribution at the dye/TiO2 interface.

  • 24. Ignatova, Nina
    et al.
    Cruz, Vinicius V.
    Couto, Rafael C.
    Ertan, Emelie
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Zimin, Andrey
    Guimaraes, Freddy F.
    Polyutov, Sergey
    Ågren, Hans
    Kimberg, Victor
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Gel'mukhanov, Faris
    Gradual collapse of nuclear wave functions regulated by frequency tuned X-ray scattering2017Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, artikkel-id 43891Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As is well established, the symmetry breaking by isotope substitution in the water molecule results in localisation of the vibrations along one of the two bonds in the ground state. In this study we find that this localisation may be broken in excited electronic states. Contrary to the ground state, the stretching vibrations of HDO are delocalised in the bound vertical bar 1a(1)(-1) 2b(2)(>)(1) core-excited state in spite of the mass difference between hydrogen and deuterium. The reason for this effect can be traced to the narrow canyon-like shape of the potential of the vertical bar 1a(1)(-1) 2b(2)(1 >) state along the symmetric stretching mode, which dominates over the localisation mass-difference effect. In contrast, the localisation of nuclear motion to one of the HDO bonds is preserved in the dissociative core-excited state vertical bar 1a(1)(-1) 4a(1)(1 >) . The dynamics of the delocalisation of nuclear motion in these core- excited states is studied using resonant inelastic X-ray scattering of the vibrationally excited HDO molecule. The results shed light on the process of a wave function collapse. After core-excitation into the vertical bar 1a(1)(-1) 2b(2)(1 >) state of HDO the initial wave packet collapses gradually, rather than instantaneously, to a single vibrational eigenstate.

  • 25. Ignatova, Nina
    et al.
    da Cruz, Vinicius V.
    Couto, Rafael C.
    Ertan, Emilie
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Ågren, Hans
    Guimaraes, Freddy F.
    Zimin, Andrei
    Polyutov, Sergey P.
    Gel'mukhanov, Faris
    Kimberg, Victor
    Infrared-pump-x-ray-probe spectroscopy of vibrationally excited molecules2017Inngår i: Physical Review A, ISSN 2469-9926, Vol. 95, nr 4, artikkel-id 042502Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We develop a theory of infrared (IR)-pump-x-ray-probe spectroscopy for molecular studies. We illustrate advantages of the proposed scheme by means of numerical simulations employing a vibrational wave packet technique applied to x-ray absorption and resonant inelastic x-ray scattering (RIXS) spectra of the water molecule vibrationally excited by a preceding IR field. The promotion of the vibrationally excited molecule to the dissociative 1a(1)(-1)4a(1) and bound 1a(1)(-1)2b(2) core-excited states with qualitatively different shapes of the potential energy surfaces creates nuclear wave packets localized along and between the OH bonds, respectively. The projection of these wave packets on the final vibrational states, governed by selection and propensity rules, results in spatial selectivity of RIXS sensitive to the initial vibrationally excited state, which makes it possible to probe selectively the ground state properties along different modes. In addition, we propose to use RIXS as a tool to study x-ray absorption from a selected vibrational level of the ground state when the spectral resolution is sufficiently high to resolve vibrational overtones. The proposed technique has potential applications for advanced mapping of multidimensional potential energy surfaces of ground and core-excited molecular states, for symmetry-resolved spectroscopy, and for steering chemical reactions.

  • 26. Jain, Kalpna
    et al.
    Kaniyankandy, Sreejith
    Kishor, Shyam
    Josefsson, Ida
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Ghosh, Hirendra N.
    Singh, Khundrakpam S.
    Mookerjee, Sumit
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Ramaniah, Lavanya M.
    Density functional investigation and some optical experiments on dye-sensitized quantum dots2015Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, nr 43, s. 28683-28696Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dye-sensitized quantum dots (QDs) are promising candidates for dye-sensitized solar cells (DSSCs). Here, we report steady state (absorption and photoluminescence) optical measurements on several sizes of CdS QDs ligated with Coumarin 343 dye (C-343) and two different solvents, viz., chloroform and toluene. We further report detailed first principles density functional theory and time-dependent density functional theory studies of the geometric, electronic and optical (absorption and emission) properties of three different sized capped QDs, ligated with C-343 dye. The absorption spectrum shows a QD-size-independent peak, and another peak which shifts to blue with decrease in QD size. The first peak is found to arise from the dye molecule and the second one from the QD. Charge transfer using natural transition orbitals (NTOs) is found to occur from dye-to-QDs and is solvent-dependent. In the emission spectra, the luminescence intensity of the dye is quenched by the addition of the QD indicating a strong interaction between the QD and the dye.

  • 27. Jain, Kalpna
    et al.
    Kishor, Shyam
    Singh, Khundrakpam S.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Ramaniah, Lavanya M.
    Quantum dots as an electron or hole acceptor: on some factors affecting charge transfer in dye-quantum dot composites2018Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, nr 42, s. 27036-27048Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report a density functional theory (DFT)/time dependent DFT (TDDFT) computational investigation on some factors affecting the nature of charge transfer in CdS quantum dots (QDs) of two different sizes attached to one or two units of dyes among three species viz., coumarine (C343), fluorescein (FLU) and NKX-2388 (NKX). The direction and nature of charge transfers have been ascertained from natural transition orbital analysis. Factors affecting the charge transfer mechanism include the interaction of dyes with QDs, the interaction of a dye with another dye and the effect of solvation. The strength of interaction of the dye and QD depends on the orientation of the dye unit(s) and the type of anchoring group of the dyes and even the direction of charge transfer reverses for different orientation of the dye with respect to the QD in some systems. In addition, hybridized energy levels of the dye-QD composites are formed which leads to direct charge transfer. We observe both direct and indirect charge transfers for different excited states, which is indeed an interesting feature. Interestingly, when two dye molecules are attached to a QD, the direct charge transfer exists between dyes of the same species only. The energy levels, as well as corresponding absorption peaks, exhibit pronounced energy shifts in implicit solvation models.

  • 28. Jay, Raphael M.
    et al.
    Norell, Jesper
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Eckert, Sebastian
    Hantschmann, Markus
    Beye, Martin
    Kennedy, Brian
    Quevedo, Wilson
    Schlotter, William F.
    Dakovski, Georgi L.
    Minitti, Michael P.
    Hoffmann, Matthias C.
    Mitra, Ankush
    Moeller, Stefan P.
    Nordlund, Dennis
    Zhang, Wenkai
    Liang, Huiyang W.
    Kunnus, Kristian
    Kubicek, Katharina
    Techert, Simone A.
    Lundberg, Marcus
    Wernet, Philippe
    Gaffney, Kelly
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Föhlisch, Alexander
    Disentangling Transient Charge Density and Metal-Ligand Covalency in Photoexcited Ferricyanide with Femtosecond Resonant Inelastic Soft X-ray Scattering2018Inngår i: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 9, nr 12, s. 3538-3543Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Soft X-ray spectroscopies are ideal probes of the local valence electronic structure of photocatalytically active metal sites. Here, we apply the selectivity of time resolved resonant inelastic X-ray scattering at the iron L-edge to the transient charge distribution of an optically excited charge-transfer state in aqueous ferricyanide. Through comparison to steady-state spectra and quantum chemical calculations, the coupled effects of valence-shell closing and ligand-hole creation are experimentally and theoretically disentangled and described in terms of orbital occupancy, metal-ligand covalency, and ligand field splitting, thereby extending established steady-state concepts to the excited-state domain. pi-Back-donation is found to be mainly determined by the metal site occupation, whereas the ligand hole instead influences sigma-donation. Our results demonstrate how ultrafast resonant inelastic X-ray scattering can help characterize local charge distributions around catalytic metal centers in short-lived charge-transfer excited states, as a step toward future rationalization and tailoring of photocatalytic capabilities of transition-metal complexes.

  • 29.
    Jena, Naresh Kumar
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Josefsson, Ida
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Eriksson, Susanna K.
    Hagfeldt, Anders
    Siegbahn, Hans
    Bjorneholm, Olle
    Rensmo, Håkan
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Solvent-Dependent Structure of the I-3(-) Ion Derived from Photoelectron Spectroscopy and Ab Initio Molecular Dynamics Simulations2015Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, nr 10, s. 4049-4055Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ab initio molecular dynamics (MD) simulations of the solvation of LiI3 in four different solvents (water, methanol, ethanol, and acetonitrile) are employed to investigate the molecular and electronic structure of the I-3(-) ion in relation to X-ray photoelectron spectroscopy (XPS). Simulations show that hydrogen-bond rearrangement in the solvation shell is coupled to intramolecular bond-length asymmetry in the I-3(-) ion. By a combination of charge analysis and I 4d core-level XPS measurements, the mechanism of the solvent-induced distortions has been studied, and it has been concluded that charge localization mediates intermolecular interactions and intramolecular distortion. The approach involving a synergistic combination of theory and experiment probes the solvent-dependent structure of the I-3(-) ion, and the geometric structure has been correlated with the electronic structure.

  • 30. Ji, Minbiao
    et al.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Gaffney, K J
    Large angular jump mechanism observed for hydrogen bond exchange in aqueous perchlorate solution.2010Inngår i: Science (New York, N.Y.), ISSN 1095-9203, Vol. 328, nr 5981, s. 1003-5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The mechanism for hydrogen bond (H-bond) switching in solution has remained subject to debate despite extensive experimental and theoretical studies. We have applied polarization-selective multidimensional vibrational spectroscopy to investigate the H-bond exchange mechanism in aqueous NaClO4 solution. The results show that a water molecule shifts its donated H-bonds between water and perchlorate acceptors by means of large, prompt angular rotation. Using a jump-exchange kinetic model, we extracted an average jump angle of 49 +/- 4 degrees, in qualitative agreement with the jump angle observed in molecular dynamics simulations of the same aqueous NaClO4 solution.

  • 31. Johansson, Erik M. J.
    et al.
    Edvinsson, Tomas
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hagberg, Daniel P.
    Sun, Licheng
    Hagfeldt, Anders
    Siegbahn, Hans
    Rensmo, Hakan
    Electronic and molecular surface structure of a polyene-diphenylaniline dye adsorbed from solution onto nanoporous TiO22007Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, nr 24, s. 8580-8586Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The surface electronic and molecular structure of a new organic chromophore useful for dye-sensitized nanostructured solar cells has been investigated by means of electron spectroscopy. Initially the use of a simple molecular system containing the polyene-diphenylaniline chromophore in a solar cell device was verified. The electronic and molecular surface structure of the functional dye-sensitized interface was then investigated in detail by a combination of core level spectroscopy, valence level spectroscopy, X-ray absorption spectroscopy, and resonant photoemission spectroscopy. The results indicate a dominating orientation of the molecule at the surface, having the diphenylaniline moiety pointing out from the surface. Valence level spectroscopy, X-ray absorption spectroscopy, and resonant photoemission spectroscopy were used to experimentally delineate the frontier electronic structure of the molecule, and the experimental spectra were analyzed against theoretical spectra, based on density functional theory. Together the investigation gives insight into energy matching of the molecular electronic states with respect to the TiO2 substrate as well as the localization of the frontier electronic states and the direction of the charge-transfer absorption process with regards to the TiO2 surface.

  • 32. Johansson, Erik M J
    et al.
    Hedlund, Maria
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Siegbahn, Hans
    Rensmo, Håkan
    Frontier electronic structures of Ru(tcterpy)(NCS)3 and Ru(dcbpy)2(NCS)2: a photoelectron spectroscopy study.2007Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 126, nr 24, s. 244303-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The frontier electronic structures of Ru(tcterpy)(NCS)3 [black dye (BD)] and Ru(dcbpy)2(NCS)2 (N719) have been investigated by photoelectron spectroscopy (PES), X-ray absorption spectroscopy (XAS) and resonant photoelectron spectroscopy (RPES). N1s XAS has been used to probe the nitrogen contribution in the unoccupied density of states, and PES, together with RPES over the N1s edge, has been used to delineate the character of the occupied density of states. The experimental findings of the frontier electron structure are compared to calculations of the partial density of states for the nitrogens in the different ligands (NCS and terpyridine/bipyridine) and for Ru4d. The result indicates large similarities between the two complexes. Specifically, the valence level spectra show two well separated structures at low binding energy. The experimental results indicate that the outermost structure in the valence region largely has a Ru4d character but with a substantial character also from the NCS ligand. Interestingly, the second lowest structure also has a significant Ru4d character mixed into the structure otherwise dominated by NCS. Comparing the two complexes the BD valence structures lowest in binding energy contains a large contribution from the NCS ligands but almost no contribution from the terpyridine ligands, while for N719 also some contribution from the bipyridine ligands is mixed into the energy levels

  • 33.
    Johansson, Erik M. J.
    et al.
    Uppsala universitet.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Plogmaker, Stefan
    Uppsala universitet.
    Gorgoi, Mihaela
    Helmholtz Zentrum Berlin, BESSY II.
    Svensson, Svante
    Uppsala universitet.
    Siegbahn, Hans
    Uppsala universitet.
    Rensmo, Håkan
    Uppsala universitet.
    Spin-Orbit Coupling and Metal-Ligand Interactions in Fe(II), Ru(II), and Os(II) Complexes2010Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, nr 22, s. 10314-10322Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The purpose of the present paper is to experimentally map the energy levels governing the trends observed in oxidation potentials and absorption spectra of M(bpy)32+ complexes (bpy = 2,2′-bipyridine, M = Fe(II), Ru(II), and Os(II)). Molecular films of the transition metal complexes were investigated with element specific methods using photoelectron spectroscopy (PES) at high kinetic energy using hard X-rays and by X-ray absorption spectroscopy (XAS). The results were compared to electronic structure calculations on the complexes and the ligand. The approach allows us to experimentally measure and interpret the energy levels in terms of spin−orbit coupling and metal−ligand interactions. Specifically, it was verified that the anomaly in the trend in oxidation potentials could be explained by a large spin−orbit coupling for the Os(bpy)32+. The influence of the different metal ions on the state formed upon light absorption was also investigated by N 1s X-ray absorption, and from the spectra we could determine the relative position of the levels originating from d−σ and π contributions. The results for the occupied and unoccupied electronic levels explain the lower energy of the MLCT transition of the Os(bpy)32+ in comparison to the Ru(bpy)32+.

  • 34.
    Josefsson, Ida
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Eriksson, Susanna K.
    Ottosson, Niklas
    Ohrwall, Gunnar
    Siegbahn, Hans
    Hagfeldt, Anders
    Rensmo, Håkan
    Björneholm, Olle
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Collective hydrogen-bond dynamics dictates the electronic structure of aqueous I-3(-)2013Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, nr 46, s. 20189-20196Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The molecular and electronic structures of aqueous I-3 and I ions have been investigated through ab initio molecular dynamics (MD) simulations and photoelectron (PE) spectroscopy of the iodine 4d core levels. Against the background of the theoretical simulations, data from our I4d PE measurements are shown to contain evidence of coupled solute-solvent dynamics. The MD simulations reveal large amplitude fluctuations in the I-I distances, which couple to the collective rearrangement of the hydrogen bonding network around the I-3(-) ion. Due to the high polarizability of the I-3(-) ion, the asymmetric I-I vibration reaches partially dissociated configurations, for which the electronic structure resembles that of I-2 + I-. The charge localization in the I-3(-) ion is found to be moderated by hydrogen-bonding. As seen in the PE spectrum, these soft molecular vibrations are important for the electronic properties of the I-3(-) ion in solution and may play an important role in its electrochemical function.

  • 35.
    Josefsson, Ida
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Eriksson, Susanna K.
    Rensmo, Håkan
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Solvation structure around ruthenium(II) tris(bipyridine) in lithium halide solutions2016Inngår i: Structural Dynamics, ISSN 2329-7778, Vol. 3, nr 2, artikkel-id 023607Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The solvation of the ruthenium(II) tris(bipyridine) ion ([Ru(bpy)(3)](2+)) is investigated with molecular dynamics simulations of lithium halide solutions in polar solvents. The anion distribution around the [Ru(bpy)(3)](2+) complex exhibits a strong solvent dependence. In aqueous solution, the iodide ion forms a solvent shared complex with [Ru(bpy)(3)](2+), but not in the other solvents. Between Cl- and [Ru(bpy)(3)](2+), the strong hydration of the chloride ion results in a solvent separated complex where more than one solvent molecule separates the anion from the metal center. Hence, tailored solvation properties in electrolytes is a route to influence ion-ion interactions and related electron transfer processes.

  • 36.
    Josefsson, Ida
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Eriksson, Susanna K.
    Rensmo, Håkan
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Solvation Structure Around Ruthenium(II) Tris(bipyridine) in Lithium Halide SolutionsManuskript (preprint) (Annet vitenskapelig)
  • 37.
    Josefsson, Ida
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Kunnus, Kristjan
    Schreck, Simon
    Föhlisch, Alexander
    de Groot, Frank
    Wernet, Philippe
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Ab Initio Calculations of X-ray Spectra: Atomic Multiplet and Molecular Orbital Effects in a Multiconfigurational SCF Approach to the L-Edge Spectra of Transition Metal Complexes2012Inngår i: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 3, nr 23, s. 3565-3570Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new ab initio approach to the calculation of X-ray spectra is demonstrated. It combines a high-level quantum chemical description of the chemical interactions and local atomic multiplet effects. We show here calculated L-edge X-ray absorption (XA) and resonant inelastic X-ray scattering spectra for aqueous Ni2+ and XA spectra for a polypyridyl iron complex. Our quantum chemical calculations on a high level of accuracy in a post-Hartree–Fock framework give excellent agreement with experiment. This opens the door to reliable and detailed information on chemical interactions and the valence electronic structure in 3d transition-metal complexes also in transient excited electronic states. As we combine a molecular-orbital description with a proper treatment of local atomic electron correlation effects, our calculations uniquely allow, in particular, identifying the influence of interatomic chemical interactions versus intra-atomic correlations in the L-edge X-ray spectra.

  • 38.
    Khan, Shehryar
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Kowalewski, Jozef
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    A complete normal mode analysis of the Zero-Field Splitting in paramagnetic hexaaqua Mn(II) and Ni(II) complexesManuskript (preprint) (Annet vitenskapelig)
  • 39.
    Khan, Shehryar
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Kubica-Misztal, Aleksandra
    Kruk, Danuta
    Kowalewski, Jozef
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Systematic theoretical investigation of the zero-field splitting in Gd(III) complexes: Wave function and density functional approaches2015Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 142, nr 3, artikkel-id 034304Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The zero-field splitting (ZFS) of the electronic ground state in paramagnetic ions is a sensitive probe of the variations in the electronic and molecular structure with an impact on fields ranging from fundamental physical chemistry to medical applications. A detailed analysis of the ZFS in a series of symmetric Gd(III) complexes is presented in order to establish the applicability and accuracy of computational methods using multiconfigurational complete-active-space self-consistent field wave functions and of density functional theory calculations. The various computational schemes are then applied to larger complexes Gd(III)DOTA(H2O)(-), Gd(III)DTPA(H2O)(2-), and Gd(III)(H2O)(8)(3+) in order to analyze how the theoretical results compare to experimentally derived parameters. In contrast to approximations based on density functional theory, the multiconfigurational methods produce results for the ZFS of Gd(III) complexes on the correct order of magnitude.

  • 40.
    Khan, Shehryar
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Peters, V.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Kowalewski, Jozef
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Zero-field splitting in the isoelectronic aqueous Gd(III) and Eu(II) complexes from a first principles analysis2018Inngår i: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 503, s. 56-64Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The zero-field splitting (ZFS) of the ground state octet in aqueous Eu(II) and Gd(III) solutions was investigated through multi-configurational quantum chemical calculations and ab initio molecular dynamics (AIMD) simulations. Investigation of the ZFS of the lanthanide ions is essential to understand the electron spin dynamics and nuclear spin relaxation around paramagnetic ions and consequently the mechanisms underlying applications like magnetic resonance imaging. We found by comparing clusters at identical geometries but different metallic centres that there is not a simple relationship for their ZFS, in spite of the complexes being isoelectronic-each containing 7 unpaired f electrons. Through sampling it was established that inclusion of the first hydration shell has a dominant (over 90 %) influence on the ZFS. Extended sampling of aqueous Gd(III) showed that the 2nd order spin Hamiltonian formalism is valid and that the rhombic ZFS component is decisive.

  • 41.
    Khan, Shehryar
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Pollet, Rodolphe
    Vuilleumier, Rodolphe
    Kowalewski, Jozef
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    An ab initio CASSCF study of zero field splitting fluctuations in the octet ground state of aqueous [Gd(iii)(HPDO3A)(H2O)]2017Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 147, nr 24, artikkel-id 244306Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, we present ab initio calculations of the zero-field splitting (ZFS) of a gadolinium complex [Gd(m)(HPDO3A)(H2O)] sampled from an ab initio molecular dynamics (AIMD) simulation. We perform both post-Hartree-Fock (complete active space self-consistent field-CASSCF) and density functional theory (DFT) calculations of the ZFS and compare and contrast the methods with experimental data. Two different density functional approximations (TPSS and LC-BLYP) were investigated. The magnitude of the ZFS from the CASSCF calculations is in good agreement with experiment, whereas the DFT results in varying degrees overestimate the magnitude of the ZFS for both functionals and exhibit a strong functional dependence. It was found in the sampling over the AIMD trajectory that the fluctuations in the transient ZFS tensor derived from DFT are not correlated with those of CASSCF nor does the magnitude of the ZFS from CASSCF and DFT correlate. From the fluctuations in the ZFS tensor, we extract a correlation time of the transient ZFS which is on the sub-picosecond time scale, showing a faster decay than experimental estimates.

  • 42. Kubica, A.
    et al.
    Kowalewski, Jozef
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Kruk, D.
    Odelius, Michel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Zero-field splitting in nickel(II) complexes: A comparison of DFT and multi-configurational wavefunction calculations2013Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 138, nr 6, s. 064304-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The zero-field splitting (ZFS) is an important quantity in the electron spin Hamiltonian for S = 1 or higher. We report calculations of the ZFS in some six- and five-coordinated nickel(II) complexes (S = 1), using different levels of theory within the framework of the ORCA program package [F. Neese, Wiley Interdiscip. Rev.: Comput. Mol. Sci. 2, 73 (2012)]10.1002/wcms.81. We compare the high-end ab initio calculations (complete active space self-consistent field and n-electron valence state perturbation theory), making use of both the second-order perturbation theory and the quasi-degenerate perturbation approach, with density functional theory (DFT) methods using different functionals. The pattern of results obtained at the ab initio levels is quite consistent and in reasonable agreement with experimental data. The DFT methods used to calculate the ZFS give very strongly functional-dependent results and do not seem to function well for our systems.

  • 43. Kunnus, K.
    et al.
    Josefsson, Ida
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Rajkovic, I.
    Schreck, S.
    Quevedo, W.
    Beye, M.
    Weniger, C.
    Grübel, S.
    Scholz, M.
    Nordlund, D.
    Zhang, W.
    Hartsock, R. W.
    Gaffney, K. J.
    Schlotter, W. F.
    Turner, J. J.
    Kennedy, B.
    Hennies, F.
    de Groot, F. M. F.
    Techert, S.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wernet, Ph.
    Föhlisch, A.
    Identification of the dominant photochemical pathways and mechanistic insights to the ultrafast ligand exchange of Fe(CO)(5) to Fe(CO)(4)EtOH2016Inngår i: Structural Dynamics, ISSN 2329-7778, Vol. 3, nr 4, artikkel-id 043204Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We utilized femtosecond time-resolved resonant inelastic X-ray scattering and ab initio theory to study the transient electronic structure and the photoinduced molecular dynamics of a model metal carbonyl photocatalyst Fe(CO)(5) in ethanol solution. We propose mechanistic explanation for the parallel ultrafast intra-molecular spin crossover and ligation of the Fe(CO)(4) which are observed following a charge transfer photoexcitation of Fe(CO)(5) as reported in our previous study [ Wernet et al., Nature 520, 78 (2015)]. We find that branching of the reaction pathway likely happens in the (1)A(1) state of Fe(CO)(4). A sub-picosecond time constant of the spin crossover from B-1(2) to B-3(2) is rationalized by the proposed B-1(2) -> (1)A(1) -> B-3(2) mechanism. Ultrafast ligation of the B-1(2) Fe(CO)(4) state is significantly faster than the spin-forbidden and diffusion limited ligation process occurring from the B-3(2) Fe(CO)(4) ground state that has been observed in the previous studies. We propose that the ultrafast ligation occurs via B-1(2) -> (1)A(1) -> (1)A'Fe(CO)(4)EtOH pathway and the time scale of the (1)A(1) Fe(CO)(4) state ligation is governed by the solute-solvent collision frequency. Our study emphasizes the importance of understanding the interaction of molecular excited states with the surrounding environment to explain the relaxation pathways of photoexcited metal carbonyls in solution.

  • 44. Kunnus, K.
    et al.
    Josefsson, Ida
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Schreck, S.
    Quevedo, W.
    Miedema, P. S.
    Techert, S.
    de Groot, F. M. F.
    Föhlisch, A.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wernet, Ph.
    Quantifying covalent interactions with resonant inelastic soft X-ray scattering: Case study of Ni2+ aqua complex2017Inngår i: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 669, s. 196-201Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We analyze the effects of covalent interactions in Ni 2p3d resonant inelastic X-ray scattering (RIXS) spectra from aqueous Ni2+ ions and find that the relative RIXS intensities of ligand-to-metal charge-transfer final states with respect to the ligand-field final states reflect the covalent mixing between Ni 3d and water orbitals. Specifically, the experimental intensity ratio at the Ni L-3-edge allows to determine that the Ni 3d orbitals have on average 5.5% of water character. We propose that 2p3d RIXS at the Ni L-3-edge can be utilized to quantify covalency in Ni complexes without the use of external references or simulations.

  • 45. Kunnus, Kristjan
    et al.
    Josefsson, Ida
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Ivan, Rajkovic
    Schreck, Simon
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Quevedo, Wilson
    Beye, Martin
    Weniger, Christian
    Grübel, Sebastian
    Scholz, Mirko
    Nordlund, Dennis
    Zhang, Wenkai
    Hartsock, Robert W.
    Gaffney, Kelly J.
    Schlotter, William F.
    Turner, Joshua J.
    Kennedy, Brian
    Hennies, Frank
    de Groot, Frank M. F.
    Techert, Simone
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wernet, Philippe
    Föhlisch, Alexander
    Mechanistic insight into the ultrafast ligand addition and spin crossover reactions following Fe(CO)5 photodissociation in ethanolArtikkel i tidsskrift (Fagfellevurdert)
  • 46. Kunnus, Kristjan
    et al.
    Josefsson, Ida
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Rajkovic, Ivan
    Schreck, Simon
    Stockholm Univ, Dept Phys, AlbaNova Univ Ctr, SE-10691 Stockholm, Sweden.
    Quevedo, Wilson
    Beye, Martin
    Grübel, Sebastian
    Scholz, Mirko
    Nordlund, Dennis
    Zhang, Wenkai
    Hartsock, Robert W.
    Gaffney, Kelly J.
    Schlotter, William F.
    Turner, Joshua J.
    Kennedy, Brian
    Hennies, Franz
    Techert, Simone
    Wernet, Philippe
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Föhlisch, Alexander
    Anti-Stokes resonant x-ray Raman scattering for atom specific and excited state selective dynamics2016Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 18, artikkel-id 103011Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ultrafast electronic and structural dynamics of matter govern rate and selectivity of chemical reactions, as well as phase transitions and efficient switching in functional materials. Since x-rays determine electronic and structural properties with elemental, chemical, orbital and magnetic selectivity, short pulse x-ray sources have become central enablers of ultrafast science. Despite of these strengths, ultrafast x-rays have been poor at picking up excited state moieties from the unexcited ones. With time-resolved anti-Stokes resonant x-ray Raman scattering (AS-RXRS) performed at the LCLS, and ab initio theory we establish background free excited state selectivity in addition to the elemental, chemical, orbital and magnetic selectivity of x-rays. This unparalleled selectivity extracts low concentration excited state species along the pathway of photo induced ligand exchange of Fe(CO)(5) in ethanol. Conceptually a full theoretical treatment of all accessible insights to excited state dynamics with AS-RXRS with transform-limited x-ray pulses is given-which will be covered experimentally by upcoming transform-limited x-ray sources.

  • 47. Kunnus, Kristjan
    et al.
    Josefsson, Ida
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Schreck, Simon
    Quevedo, Wilson
    Miedemaa, Piter S.
    Techert, Simone
    de Groot, Frank M. F.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wernet, Philippe
    Föhlisch, Alexander
    From Ligand Fields to Molecular Orbitals: Probing the Local Valence Electronic Structure of Ni2+ in Aqueous Solutions with Resonant Inelastic X-ray Scattering2013Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 117, s. 16512-16521Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bonding of the Ni2+(aq) complex is investigated with an unprecedented combination of resonant inelastic X-ray scattering (RIXS) measurements and ab initio calculations at the Ni L absorption edge. The spectra directly reflect the relative energies of the ligand-field and charge-transfer valence-excited states. They give element-specific access with atomic resolution to the ground-state electronic structure of the complex and allow quantification of ligand-field strength and 3d–3d electron correlation interactions in the Ni2+(aq) complex. The experimentally determined ligand-field strength is 10Dq = 1.1 eV. This and the Racah parameters characterizing 3d–3d Coulomb interactions B = 0.13 eV and C = 0.42 eV as readily derived from the measured energies match very well with the results from UV–vis spectroscopy. Our results demonstrate how L-edge RIXS can be used to complement existing spectroscopic tools for the investigation of bonding in 3d transition-metal coordination compounds in solution. The ab initio RASPT2 calculation is successfully used to simulate the L-edge RIXS spectra.

  • 48. Kunnus, Kristjan
    et al.
    Zhang, Wenkai
    Delcey, Mickael G.
    Pinjari, Rahul V.
    Miedema, Piter S.
    Schreck, Simon
    Quevedo, Wilson
    Schroeder, Henning
    Foehlisch, Alexander
    Gaffney, Kelly J.
    Lundberg, Marcus
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wernet, Philippe
    Viewing the Valence Electronic Structure of Ferric and Ferrous Hexacyanide in Solution from the Fe and Cyanide Perspectives2016Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 120, nr 29, s. 7182-7194Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The valence-excited states of ferric and ferrous hexacyanide ions in aqueous solution were mapped by resonant inelastic X-ray scattering (RIXS) at the Fe L-2,L-3 and N K edges. Probing of both the central Fe and the ligand N atoms enabled identification of the metal-and ligand-centered excited states, as well as ligand-to-metal and metal-to-ligand charge-transfer excited states. Ab initio calculations utilizing the RASPT2 method were used to simulate the Fe L-2,L-3-edge RIXS spectra and enabled quantification of the covalencies of both occupied and empty orbitals of pi and sigma symmetry. We found that pi back-donation in the ferric complex is smaller than that in the ferrous complex. This is evidenced by the relative amounts of Fe 3d character in the nominally 2 pi CN- molecular orbital of 7% and 9% in ferric and ferrous hexacyanide, respectively. Utilizing the direct sensitivity of Fe L-3-edge RIXS to the Fe 3d character in the occupied molecular orbitals, we also found that the donation interactions are dominated by sigma bonding. The latter was found to be stronger in the ferric complex, with an Fe 3d contribution to the nominally 5 sigma CN- molecular orbitals of 29% compared to 20% in the ferrous complex. These results are consistent with the notion that a higher charge at the central metal atom increases donation and decreases back-donation.

  • 49.
    Leetmaa, Mikael
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Ljungberg, Mathias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Ogasawara, H.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Näslund, L.Å.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Nilsson, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Are Recent Water Models Obtained by Fitting Diffraction Data Consistent with IR/Raman and X-ray Absorption Spectra?2006Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 125, s. 244510-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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. ©2006 American Institute of Physics

  • 50.
    Leetmaa, Mikael
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Wikfeldt, Kjartan Thor
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Ljungberg, Mathias P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Swenson, Jan
    Nilsson, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Pettersson, Lars G. M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Diffraction and IR/Raman Data do not Prove Tetrahedral Water2008Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 129, nr 8, artikkel-id 084502Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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 D2O; 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.

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