TY  - JOUR
A1  - Jay, Raphael M.
A1  - Norell, Jesper
A1  - Eckert, Sebastian
A1  - Hantschmann, Markus
A1  - Beye, Martin
A1  - Kennedy, Brian
A1  - Quevedo, Wilson
A1  - Schlotter, William F.
A1  - Dakovski, Georgi L.
A1  - Minitti, Michael P.
A1  - Hoffmann, Matthias C.
A1  - Mitra, Ankush
A1  - Moeller, Stefan P.
A1  - Nordlund, Dennis
A1  - Zhang, Wenkai
A1  - Liang, Huiyang W.
A1  - Kunnus, Kristian
A1  - Kubicek, Katharina
A1  - Techert, Simone A.
A1  - Lundberg, Marcus
A1  - Wernet, Philippe
A1  - Gaffney, Kelly
A1  - Odelius, Michael
A1  - Föhlisch, Alexander
T1  - Disentangling Transient Charge Density and Metal-Ligand Covalency in Photoexcited Ferricyanide with Femtosecond Resonant Inelastic Soft X-ray Scattering
JF  - The journal of physical chemistry letters
N2  - 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.
Y1  - 2018
U6  - https://doi.org/10.1021/acs.jpclett.8b01429
SN  - 1948-7185
VL  - 9
IS  - 12
SP  - 3538
EP  - 3543
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Kubin, Markus
A1  - Kern, Jan
A1  - Gul, Sheraz
A1  - Kroll, Thomas
A1  - Chatterjee, Ruchira
A1  - Loechel, Heike
A1  - Fuller, Franklin D.
A1  - Sierra, Raymond G.
A1  - Quevedo, Wilson
A1  - Weniger, Christian
A1  - Rehanek, Jens
A1  - Firsov, Anatoly
A1  - Laksmono, Hartawan
A1  - Weninger, Clemens
A1  - Alonso-Mori, Roberto
A1  - Nordlund, Dennis L.
A1  - Lassalle-Kaiser, Benedikt
A1  - Glownia, James M.
A1  - Krzywinski, Jacek
A1  - Moeller, Stefan
A1  - Turner, Joshua J.
A1  - Minitti, Michael P.
A1  - Dakovski, Georgi L.
A1  - Koroidov, Sergey
A1  - Kawde, Anurag
A1  - Kanady, Jacob S.
A1  - Tsui, Emily Y.
A1  - Suseno, Sandy
A1  - Han, Zhiji
A1  - Hill, Ethan
A1  - Taguchi, Taketo
A1  - Borovik, Andrew S.
A1  - Agapie, Theodor
A1  - Messinger, Johannes
A1  - Erko, Alexei
A1  - Föhlisch, Alexander
A1  - Bergmann, Uwe
A1  - Mitzner, Rolf
A1  - Yachandra, Vittal K.
A1  - Yano, Junko
A1  - Wernet, Philippe
T1  - Soft x-ray absorption spectroscopy of metalloproteins and high-valent metal-complexes at room temperature using free-electron lasers
JF  - Structural dynamics
N2  - X-ray absorption spectroscopy at the L-edge of 3d transition metals provides unique information on the local metal charge and spin states by directly probing 3d-derived molecular orbitals through 2p-3d transitions. However, this soft x-ray technique has been rarely used at synchrotron facilities for mechanistic studies of metalloenzymes due to the difficulties of x-ray-induced sample damage and strong background signals from light elements that can dominate the low metal signal. Here, we combine femtosecond soft x-ray pulses from a free-electron laser with a novel x-ray fluorescence-yield spectrometer to overcome these difficulties. We present L-edge absorption spectra of inorganic high-valent Mn complexes (Mn similar to 6-15 mmol/l) with no visible effects of radiation damage. We also present the first L-edge absorption spectra of the oxygen evolving complex (Mn4CaO5) in Photosystem II (Mn < 1 mmol/l) at room temperature, measured under similar conditions. Our approach opens new ways to study metalloenzymes under functional conditions. (C) 2017 Author(s).
Y1  - 2017
U6  - https://doi.org/10.1063/1.4986627
SN  - 2329-7778
VL  - 4
PB  - American Institute of Physics
CY  - Melville
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  - 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  - Sellberg, Jonas A.
A1  - McQueen, Trevor A.
A1  - Laksmono, Hartawan
A1  - Schreck, Simon
A1  - Beye, Martin
A1  - DePonte, Daniel P.
A1  - Kennedy, Brian
A1  - Nordlund, Dennis
A1  - Sierra, Raymond G.
A1  - Schlesinger, Daniel
A1  - Tokushima, Takashi
A1  - Zhovtobriukh, Iurii
A1  - Eckert, Sebastian
A1  - Segtnan, Vegard H.
A1  - Ogasawara, Hirohito
A1  - Kubicek, Katharina
A1  - Techert, Simone
A1  - Bergmann, Uwe
A1  - Dakovski, Georgi L.
A1  - Schlotter, William F.
A1  - Harada, Yoshihisa
A1  - Bogan, Michael J.
A1  - Wernet, Philippe
A1  - Föhlisch, Alexander
A1  - Pettersson, Lars G. M.
A1  - Nilsson, Anders
T1  - X-ray emission spectroscopy of bulk liquid water in "no-man's land"
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - The structure of bulk liquid water was recently probed by x-ray scattering below the temperature limit of homogeneous nucleation (T-H) of similar to 232 K [J. A. Sellberg et al., Nature 510, 381-384 (2014)]. Here, we utilize a similar approach to study the structure of bulk liquid water below T-H using oxygen K-edge x-ray emission spectroscopy (XES). Based on previous XES experiments [T. Tokushima et al., Chem. Phys. Lett. 460, 387-400 (2008)] at higher temperatures, we expected the ratio of the 1b(1)' and 1b(1)" peaks associated with the lone-pair orbital in water to change strongly upon deep supercooling as the coordination of the hydrogen (H-) bonds becomes tetrahedral. In contrast, we observed only minor changes in the lone-pair spectral region, challenging an interpretation in terms of two interconverting species. A number of alternative hypotheses to explain the results are put forward and discussed. Although the spectra can be explained by various contributions from these hypotheses, we here emphasize the interpretation that the line shape of each component changes dramatically when approaching lower temperatures, where, in particular, the peak assigned to the proposed disordered component would become more symmetrical as vibrational interference becomes more important. (C) 2015 AIP Publishing LLC.
Y1  - 2015
U6  - https://doi.org/10.1063/1.4905603
SN  - 0021-9606
SN  - 1089-7690
VL  - 142
IS  - 4
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Eckert, Sebastian
A1  - Beye, Martin
A1  - Pietzsch, Annette
A1  - Quevedo, Wilson
A1  - Hantschmann, Markus
A1  - Ochmann, Miguel
A1  - Ross, Matthew
A1  - Minitti, Michael P.
A1  - Turner, Joshua J.
A1  - Moeller, Stefan P.
A1  - Schlotter, William F.
A1  - Dakovski, Georgi L.
A1  - Khalil, Munira
A1  - Huse, Nils
A1  - Föhlisch, Alexander
T1  - Principles of femtosecond X-ray/optical cross-correlation with X-ray induced transient optical reflectivity in solids
JF  - Applied physics letters
N2  - The discovery of ultrafast X-ray induced optical reflectivity changes enabled the development of X-ray/optical cross correlation techniques at X-ray free electron lasers worldwide. We have now linked through experiment and theory the fundamental excitation and relaxation steps with the transient optical properties in finite solid samples. Therefore, we gain a thorough interpretation and an optimized detection scheme of X-ray induced changes to the refractive index and the X-ray/optical cross correlation response. (C) 2015 AIP Publishing LLC.
Y1  - 2015
U6  - https://doi.org/10.1063/1.4907949
SN  - 0003-6951
SN  - 1077-3118
VL  - 106
IS  - 6
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Xin, Hong
A1  - LaRue, Jerry
A1  - Oberg, Henrik
A1  - Beye, Martin
A1  - Turner, J. J.
A1  - Gladh, Jörgen
A1  - Ng, May L.
A1  - Sellberg, Jonas A.
A1  - Kaya, Sarp
A1  - Mercurio, G.
A1  - Hieke, F.
A1  - Nordlund, Dennis
A1  - Schlotter, William F.
A1  - Dakovski, Georgi L.
A1  - Minitti, Michael P.
A1  - Föhlisch, Alexander
A1  - Wolf, Martin
A1  - Wurth, Wilfried
A1  - Ogasawara, Hirohito
A1  - Norskov, Jens K.
A1  - Ostrom, Henrik
A1  - Pettersson, Lars G. M.
A1  - Nilsson, Anders
A1  - Abild-Pedersen, Frank
T1  - Strong Influence of Coadsorbate Interaction on CO Desorption Dynamics on Ru(0001) Probed by Ultrafast X-Ray Spectroscopy and Ab Initio Simulations
JF  - Physical review letters
N2  - We show that coadsorbed oxygen atoms have a dramatic influence on the CO desorption dynamics from Ru(0001). In contrast to the precursor-mediated desorption mechanism on Ru(0001), the presence of surface oxygen modifies the electronic structure of Ru atoms such that CO desorption occurs predominantly via the direct pathway. This phenomenon is directly observed in an ultrafast pump-probe experiment using a soft x-ray free-electron laser to monitor the dynamic evolution of the valence electronic structure of the surface species. This is supported with the potential of mean force along the CO desorption path obtained from density-functional theory calculations. Charge density distribution and frozen-orbital analysis suggest that the oxygen-induced reduction of the Pauli repulsion, and consequent increase of the dative interaction between the CO 5 sigma and the charged Ru atom, is the electronic origin of the distinct desorption dynamics. Ab initio molecular dynamics simulations of CO desorption from Ru(0001) and oxygen-coadsorbed Ru(0001) provide further insights into the surface bond-breaking process.
Y1  - 2015
U6  - https://doi.org/10.1103/PhysRevLett.114.156101
SN  - 0031-9007
SN  - 1079-7114
VL  - 114
IS  - 15
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Schreck, Simon
A1  - Beye, Martin
A1  - Sellberg, Jonas A.
A1  - McQueen, Trevor
A1  - Laksmono, Hartawan
A1  - Kennedy, Brian
A1  - Eckert, Sebastian
A1  - Schlesinger, Daniel
A1  - Nordlund, Dennis
A1  - Ogasawara, Hirohito
A1  - Sierra, Raymond G.
A1  - Segtnan, Vegard H.
A1  - Kubicek, Katharina
A1  - Schlotter, William F.
A1  - Dakovski, Georgi L.
A1  - Moeller, Stefan P.
A1  - Bergmann, Uwe
A1  - Techert, Simone
A1  - Pettersson, Lars G. M.
A1  - Wernet, Philippe
A1  - Bogan, Michael J.
A1  - Harada, Yoshihisa
A1  - Nilsson, Anders
A1  - Föhlisch, Alexander
T1  - Reabsorption of soft x-ray emission at high x-ray free-electron laserfluences
JF  - Physical review letters
N2  - We report on oxygen K-edge soft x-ray emission spectroscopy from a liquid water jet at the Linac Coherent Light Source. We observe significant changes in the spectral content when tuning over a wide range of incident x-ray fluences. In addition the total emission yield decreases at high fluences. These modifications result from reabsorption of x-ray emission by valence-excited molecules generated by the Auger cascade. Our observations have major implications for future x-ray emission studies at intense x-ray sources. We highlight the importance of the x-ray pulse length with respect to the core-hole lifetime.
Y1  - 2014
U6  - https://doi.org/10.1103/PhysRevLett.113.153002
SN  - 0031-9007
SN  - 1079-7114
VL  - 113
IS  - 15
PB  - American Physical Society
CY  - College Park
ER  -