TY - JOUR A1 - Kroll, Thomas A1 - Kern, Jan A1 - Kubin, Markus A1 - Ratner, Daniel A1 - Gul, Sheraz A1 - Fuller, Franklin D. A1 - Löchel, Heike A1 - Krzywinski, Jacek A1 - Lutman, Alberto A1 - Ding, Yuantao A1 - Dakovski, Georgi L. A1 - Moeller, Stefan A1 - Turner, Joshua J. A1 - Alonso-Mori, Roberto A1 - Nordlund, Dennis L. A1 - Rehanek, Jens A1 - Weniger, Christian A1 - Firsov, Alexander A1 - Brzhezinskaya, Maria A1 - Chatterjee, Ruchira A1 - Lassalle-Kaiser, Benedikt A1 - Sierra, Raymond G. A1 - Laksmono, Hartawan A1 - Hill, Ethan A1 - Borovik, Andrew S. A1 - Erko, Alexei A1 - Föhlisch, Alexander A1 - Mitzner, Rolf A1 - Yachandra, Vittal K. A1 - Yano, Junko A1 - Wernet, Philippe A1 - Bergmann, Uwe T1 - X-ray absorption spectroscopy using a self-seeded soft X-ray free-electron laser JF - Optics express : the international electronic journal of optics N2 - X-ray free electron lasers (XFELs) enable unprecedented new ways to study the electronic structure and dynamics of transition metal systems. L-edge absorption spectroscopy is a powerful technique for such studies and the feasibility of this method at XFELs for solutions and solids has been demonstrated. However, the required x-ray bandwidth is an order of magnitude narrower than that of self-amplified spontaneous emission (SASE), and additional monochromatization is needed. Here we compare L-edge x-ray absorption spectroscopy (XAS) of a prototypical transition metal system based on monochromatizing the SASE radiation of the linac coherent light source (LCLS) with a new technique based on self-seeding of LCLS. We demonstrate how L-edge XAS can be performed using the self-seeding scheme without the need of an additional beam line monochromator. We show how the spectral shape and pulse energy depend on the undulator setup and how this affects the x-ray spectroscopy measurements. (C) 2016 Optical Society of America Y1 - 2016 U6 - https://doi.org/10.1364/OE.24.022469 SN - 1094-4087 VL - 24 SP - 22469 EP - 22480 PB - Optical Society of America CY - Washington ER - TY - JOUR A1 - Mitzner, Rolf A1 - Rehanek, Jens A1 - Kern, Jan A1 - Gul, Sheraz A1 - Hattne, Johan A1 - Taguchi, Taketo A1 - Alonso-Mori, Roberto A1 - Tran, Rosalie A1 - Weniger, Christian A1 - Schröder, Henning A1 - Quevedo, Wilson A1 - Laksmono, Hartawan A1 - Sierra, Raymond G. A1 - Han, Guangye A1 - Lassalle-Kaiser, Benedikt A1 - Koroidov, Sergey A1 - Kubicek, Katharina A1 - Schreck, Simon A1 - Kunnus, Kristjan A1 - Brzhezinskaya, Maria A1 - Firsov, Alexander A1 - Minitti, Michael P. A1 - Turner, Joshua J. A1 - Möller, Stefan A1 - Sauter, Nicholas K. A1 - Bogan, Michael J. A1 - Nordlund, Dennis A1 - Schlotter, William F. A1 - Messinger, Johannes A1 - Borovik, Andrew S. A1 - Techert, Simone A1 - de Groot, Frank M. F. A1 - Föhlisch, Alexander A1 - Erko, Alexei A1 - Bergmann, Uwe A1 - Yachandra, Vittal K. A1 - Wernet, Philippe A1 - Yano, Junko T1 - L-edge x-ray absorption spectroscopy of dilute systems relevant to metalloproteins using an X-ray free-electron laser JF - The journal of physical chemistry letters N2 - L-edge spectroscopy of 3d transition metals provides important electronic structure information and has been used in many fields. However, the use of this method for studying dilute aqueous systems, such as metalloenzymes, has not been prevalent because of severe radiation damage and the lack of suitable detection systems. Here we present spectra from a dilute Mn aqueous solution using a high-transmission zone-plate spectrometer at the Linac Coherent Light Source (LCLS). The spectrometer has been optimized for discriminating the Mn L-edge signal from the overwhelming 0 K-edge background that arises from water and protein itself, and the ultrashort LCLS X-ray pulses can outrun X-ray induced damage. We show that the deviations of the partial-fluorescence yield-detected spectra from the true absorption can be well modeled using the state-dependence of the fluorescence yield, and discuss implications for the application of our concept to biological samples. Y1 - 2013 U6 - https://doi.org/10.1021/jz401837f SN - 1948-7185 VL - 4 IS - 21 SP - 3641 EP - 3647 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Kunnus, Kristjan A1 - Josefsson, I. A1 - Schreck, Simon Frederik A1 - Quevedo, W. A1 - Miedema, P. S. A1 - Techert, S. A1 - de Groot, F. M. F. A1 - Föhlisch, Alexander A1 - Odelius, M. A1 - Wernet, Ph. T1 - Quantifying covalent interactions with resonant inelastic soft X-ray scattering BT - case study of Ni2+ aqua complex JF - Chemical physics letters N2 - 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. KW - Transition-metal ion KW - Aqueous solution KW - Covalent interaction KW - Resonant inelastic X-ray scattering KW - Ligand-field state KW - Charge-transfer state Y1 - 2016 U6 - https://doi.org/10.1016/j.cplett.2016.12.046 SN - 0009-2614 SN - 1873-4448 VL - 669 SP - 196 EP - 201 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Leitner, T. A1 - Josefsson, Ida A1 - Mazza, T. A1 - Miedema, Piter S. A1 - Schröder, H. A1 - Beye, Martin A1 - Kunnus, Kristjan A1 - Schreck, S. A1 - Düsterer, Stefan A1 - Föhlisch, Alexander A1 - Meyer, M. A1 - Odelius, Michael A1 - Wernet, Philippe T1 - Time-resolved electron spectroscopy for chemical analysis of photodissociation BT - Photoelectron spectra of Fe(CO)(5), Fe(CO)(4), and Fe(CO)(3) JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - The prototypical photoinduced dissociation of Fe(CO)(5) in the gas phase is used to test time-resolved x-ray photoelectron spectroscopy for studying photochemical reactions. Upon one-photon excitation at 266 nm, Fe(CO)(5) successively dissociates to Fe(CO)(4) and Fe(CO)(3) along a pathway where both fragments retain the singlet multiplicity of Fe(CO)(5). The x-ray free-electron laser FLASH is used to probe the reaction intermediates Fe(CO)(4) and Fe(CO)(3) with time-resolved valence and core-level photoelectron spectroscopy, and experimental results are interpreted with ab initio quantum chemical calculations. Changes in the valence photoelectron spectra are shown to reflect changes in the valenceorbital interactions upon Fe-CO dissociation, thereby validating fundamental theoretical concepts in Fe-CO bonding. Chemical shifts of CO 3 sigma inner-valence and Fe 3 sigma core-level binding energies are shown to correlate with changes in the coordination number of the Fe center. We interpret this with coordination-dependent charge localization and core-hole screening based on calculated changes in electron densities upon core-hole creation in the final ionic states. This extends the established capabilities of steady-state electron spectroscopy for chemical analysis to time-resolved investigations. It could also serve as a benchmark for howcharge and spin density changes in molecular dissociation and excited-state dynamics are expressed in valence and core-level photoelectron spectroscopy. Published by AIP Publishing. Y1 - 2018 U6 - https://doi.org/10.1063/1.5035149 SN - 0021-9606 SN - 1089-7690 VL - 149 IS - 4 PB - American Institute of Physics CY - Melville ER - TY - GEN A1 - Jay, Raphael J. A1 - Norell, Jesper A1 - Kunnus, Kristjan A1 - Lundberg, Marcus A1 - Gaffney, Kelly A1 - Wernet, Philippe A1 - Odelius, Michael A1 - Föhlisch, Alexander T1 - Dynamcis of local charge densities and metal-ligand covalency in iron complexes from femtosecond resonant inelastic soft X-ray scattering T2 - Abstracts of Papers of the American Chemical Society Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:se:uu:diva-370051 SN - 0065-7727 VL - 256 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Beye, Martin A1 - Öberg, Henrik A1 - Xin, Hongliang A1 - Dakovski, Georgi L. A1 - Föhlisch, Alexander A1 - Gladh, Jorgen A1 - Hantschmann, Markus A1 - Hieke, Florian A1 - Kaya, Sarp A1 - Kühn, Danilo A1 - LaRue, Jerry A1 - Mercurio, Giuseppe A1 - Minitti, Michael P. A1 - Mitra, Ankush A1 - Moeller, Stefan P. A1 - Ng, May Ling A1 - Nilsson, Anders A1 - Nordlund, Dennis A1 - Norskov, Jens A1 - Öström, Henrik A1 - Ogasawara, Hirohito A1 - Persson, Mats A1 - Schlotter, William F. A1 - Sellberg, Jonas A. A1 - Wolf, Martin A1 - Abild-Pedersen, Frank A1 - Pettersson, Lars G. M. A1 - Wurth, Wilfried T1 - Chemical Bond Activation Observed with an X-ray Laser JF - The journal of physical chemistry letters N2 - The concept of bonding and antibonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Here we apply time-resolved soft X-ray spectroscopy at a free electron laser to directly observe the decreased bonding antibonding splitting following bond-activation using an ultrashort optical laser pulse. Y1 - 2016 U6 - https://doi.org/10.1021/acs.jpclett.6b01543 SN - 1948-7185 VL - 7 SP - 3647 EP - 3651 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Ostrom, H. A1 - Oberg, H. A1 - Xin, H. A1 - Larue, J. A1 - Beye, Martin A1 - Gladh, J. A1 - Ng, M. L. A1 - Sellberg, J. A. A1 - Kaya, S. A1 - Mercurio, G. A1 - Nordlund, D. A1 - Hantschmann, Markus A1 - Hieke, F. A1 - Kuehn, D. A1 - Schlotter, W. F. A1 - Dakovski, G. L. A1 - Turner, J. J. A1 - Minitti, M. P. A1 - Mitra, A. A1 - Moeller, S. P. A1 - Föhlisch, Alexander A1 - Wolf, M. A1 - Wurth, W. A1 - Persson, Mats A1 - Norskov, J. K. A1 - Abild-Pedersen, Frank A1 - Ogasawara, Hirohito A1 - Pettersson, Lars G. M. A1 - Nilsson, A. T1 - Probing the transition state region in catalytic CO oxidation on Ru JF - Science N2 - Femtosecond x-ray laser pulses are used to probe the carbon monoxide (CO) oxidation reaction on ruthenium (Ru) initiated by an optical laser pulse. On a time scale of a few hundred femtoseconds, the optical laser pulse excites motions of CO and oxygen (O) on the surface, allowing the reactants to collide, and, with a transient close to a picosecond (ps), new electronic states appear in the OK-edge x-ray absorption spectrum. Density functional theory calculations indicate that these result from changes in the adsorption site and bond formation between CO and O with a distribution of OC-O bond lengths close to the transition state (TS). After 1 ps, 10% of the CO populate the TS region, which is consistent with predictions based on a quantum oscillator model. Y1 - 2015 U6 - https://doi.org/10.1126/science.1261747 SN - 0036-8075 SN - 1095-9203 VL - 347 IS - 6225 SP - 978 EP - 982 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Ovsyannikov, Ruslan A1 - Karlsson, P. A1 - Lundqvist, M. A1 - Lupulescu, C. A1 - Eberhardt, W. A1 - Föhlisch, Alexander A1 - Svensson, S. A1 - Martensson, N. T1 - Principles and operation of a new type of electron spectrometer - ArTOF JF - Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy N2 - A new energy and angular electron analyzer ArTOF (Angular Resolved Time of Flight) is described. The analyzer is based on simultaneous measurement of flight times and angles in an advanced electron lens system. In angular modes the new analyzer combines an increase in transmission by almost three orders of magnitude with improved resolution, in comparison to standard state-of-the-art electron spectrometers. In this report we describe some design principles and we give a review of calibration and alignment procedures necessary for the use of the ArTOF on a synchrotron radiation facility. Our program scripts to handle the large datasets are also discussed. Furthermore we give a broad description of the new research fields that benefit from the use of the ArTOF and give a short summary of the first results of angle resolved photoemission measurement with ArTOF using the single-bunch X-ray pulses from the BESSY II storage ring facility. (C) 2013 Published by Elsevier B.V. KW - ARPES KW - Time of flight KW - Synchrotron KW - Electron spectroscopy Y1 - 2013 U6 - https://doi.org/10.1016/j.elspec.2013.08.005 SN - 0368-2048 SN - 1873-2526 VL - 191 IS - 12 SP - 92 EP - 103 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kunnus, Kristjan A1 - Josefsson, Ida A1 - Schreck, Simon A1 - Quevedo, Wilson A1 - Miedema, Piter S. A1 - Techert, Simone A1 - de Groot, Frank M. F. A1 - Odelius, Michael A1 - Wernet, Philippe A1 - Föhlisch, Alexander T1 - From Ligand Fields to Molecular Orbitals: Probing the Local Valence Electronic Structure of Ni2+ in Aqueous Solution with Resonant Inelastic X-ray Scattering JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - 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. Y1 - 2013 U6 - https://doi.org/10.1021/jp4100813 SN - 1520-6106 VL - 117 IS - 51 SP - 16512 EP - 16521 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Beye, Martin A1 - Föhlisch, Alexander T1 - Soft X-ray probes of ultrafast dynamics for heterogeneous catalysis JF - Chemical physics : a journal devoted to experimental and theoretical research involving problems of both a chemical and physical nature N2 - Soft X-ray spectroscopy is one of the best tools to directly address the electronic structure, the driving force of chemical reactions. It enables selective studies on sample surfaces to single out reaction centers in heterogeneous catalytic reactions. With core-hole clock methods, specific dynamics are related to the femtosecond life time of a core-hole. Typically, this method is used with photoemission spectroscopy, but advancements in soft X-ray emission techniques render more specific studies possible. With the advent of bright femtosecond pulsed soft X-ray sources, highly selective pump-probe X-ray emission studies are enabled with temporal resolutions down to tens of femtoseconds. This finally allows to study dynamics in the electronic structure of adsorbed reaction centers on the whole range of relevant time scales - closing the gap between kinetic soft X-ray studies and the atto- to femtosecond core-hole clock techniques. KW - Core-hole clock KW - Resonant inelastic X-ray scattering KW - Ultrafast surface science KW - Photoelectron spectroscopy Y1 - 2013 U6 - https://doi.org/10.1016/j.chemphys.2012.03.023 SN - 0301-0104 SN - 1873-4421 VL - 414 IS - 5 SP - 130 EP - 138 PB - Elsevier CY - Amsterdam ER -