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  - Wernet, Philippe
A1  - Kunnus, Kristjan
A1  - Josefsson, Ida
A1  - Rajkovic, Ivan
A1  - Quevedo, Wilson
A1  - Beye, Martin
A1  - Schreck, Simon
A1  - Gruebel, S.
A1  - Scholz, Mirko
A1  - Nordlund, Dennis
A1  - Zhang, Wenkai
A1  - Hartsock, Robert W.
A1  - Schlotter, William F.
A1  - Turner, Joshua J.
A1  - Kennedy, Brian
A1  - Hennies, Franz
A1  - de Groot, Frank M. F.
A1  - Gaffney, Kelly J.
A1  - Techert, Simone
A1  - Odelius, Michael
A1  - Föhlisch, Alexander
T1  - Orbital-specific mapping of the ligand exchange dynamics of Fe(CO)(5) in solution
JF  - Nature : the international weekly journal of science
N2  - Transition-metal complexes have long attracted interest for fundamental chemical reactivity studies and possible use in solar energy conversion(1,2). Electronic excitation, ligand loss from the metal centre, or a combination of both, creates changes in charge and spin density at the metal site(3-11) that need to be controlled to optimize complexes for photocatalytic hydrogen production(8) and selective carbon-hydrogen bond activation(9-11). An understanding at the molecular level of how transition-metal complexes catalyse reactions, and in particular of the role of the short-lived and reactive intermediate states involved, will be critical for such optimization. However, suitable methods for detailed characterization of electronic excited states have been lacking. Here we show, with the use of X-ray laser-based femtosecond-resolution spectroscopy and advanced quantum chemical theory to probe the reaction dynamics of the benchmark transition-metal complex Fe(CO)(5) in solution, that the photo-induced removal of CO generates the 16-electron Fe(CO)(4) species, a homogeneous catalyst(12,13) with an electron deficiency at the Fe centre(14,15), in a hitherto unreported excited singlet state that either converts to the triplet ground state or combines with a CO or solvent molecule to regenerate a penta-coordinated Fe species on a sub-picosecond timescale. This finding, which resolves the debate about the relative importance of different spin channels in the photochemistry of Fe(CO)(5) (refs 4, 16-20), was made possible by the ability of femtosecond X-ray spectroscopy to probe frontier-orbital interactions with atom specificity. We expect the method to be broadly applicable in the chemical sciences, and to complement approaches that probe structural dynamics in ultrafast processes.
Y1  - 2015
U6  - https://doi.org/10.1038/nature14296
SN  - 0028-0836
SN  - 1476-4687
VL  - 520
IS  - 7545
SP  - 78
EP  - 81
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - INPR
A1  - Föhlisch, Alexander
A1  - de Groot, F. M. F.
A1  - Odelius, Michael
A1  - Techert, Simone
A1  - Wernet, P.
T1  - Comment on "state-dependent electron delocalization dynamics at the solute-solvent interface: soft-x-ray absorption spectroscopy and lambda b initio calculations"
T2  - Physical review letters
Y1  - 2014
U6  - https://doi.org/10.1103/PhysRevLett.112.129302
SN  - 0031-9007
SN  - 1079-7114
VL  - 112
IS  - 12
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Wernet, Philippe
A1  - Kunnus, Kristjan
A1  - Schreck, Simon
A1  - Quevedo, Wilson
A1  - Kurian, Reshmi
A1  - Techert, Simone
A1  - de Groot, Frank M. F.
A1  - Odelius, Michael
A1  - Föhlisch, Alexander
T1  - Dissecting local atomic and intermolecular interactions of transition-metal ions in solution with selective X-ray spectroscopy
JF  - The journal of physical chemistry letters
N2  - Determining covalent and charge-transfer contributions to bonding in solution has remained an experimental challenge. Here, the quenching of fluorescence decay channels as expressed in dips in the L-edge X-ray spectra of solvated 3d transition-metal ions and complexes was reported as a probe. With a full set of experimental and theoretical ab initio L-edge X-ray spectra of aqueous Cr3+, including resonant inelastic X-ray scattering, we address covalency and charge transfer for this prototypical transition-metal ion in solution. We dissect local atomic effects from intermolecular interactions and quantify X-ray optical effects. We find no evidence for the asserted ultrafast charge transfer to the solvent and show that the dips are readily explained by X-ray optical effects and local atomic state dependence of the fluorescence yield. Instead, we find, besides ionic interactions, a covalent contribution to the bonding in the aqueous complex of ligand-to-metal charge-transfer character.
Y1  - 2012
U6  - https://doi.org/10.1021/jz301486u
SN  - 1948-7185
VL  - 3
IS  - 23
SP  - 3448
EP  - 3453
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Kunnus, Kristjan
A1  - Josefsson, Ida
A1  - Rajkovic, Ivan
A1  - Schreck, Simon
A1  - Quevedo, Wilson
A1  - Beye, Martin
A1  - Grübel, Sebastian
A1  - Scholz, Mirko
A1  - Nordlund, Dennis
A1  - Zhang, Wenkai
A1  - Hartsock, Robert W.
A1  - Gaffney, Kelly J.
A1  - Schlotter, William F.
A1  - Turner, Joshua J.
A1  - Kennedy, Brian
A1  - Hennies, Franz
A1  - Techert, Simone
A1  - Wernet, Philippe
A1  - Odelius, Michael
A1  - Föhlisch, Alexander
T1  - Anti-Stokes resonant x-ray Raman scattering for atom specific and excited state selective dynamics
JF  - NEW JOURNAL OF PHYSICS
N2  - 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.
KW  - ultrafast photochemistry
KW  - excited state selectivity
KW  - anti-Stokes resonant x-ray raman scattering
KW  - free electron lasers
KW  - resonant inelastic x-ray scattering
Y1  - 2016
U6  - https://doi.org/10.1088/1367-2630/18/10/103011
SN  - 1367-2630
VL  - 18
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Yin, Zhong
A1  - Rajkovic, Ivan
A1  - Veedu, Sreevidya Thekku
A1  - Deinert, Sascha
A1  - Raiser, Dirk
A1  - Jain, Rohit
A1  - Fukuzawa, Hironobu
A1  - Wada, Shin-ichi
A1  - Quevedo, Wilson
A1  - Kennedy, Brian
A1  - Schreck, Simon
A1  - Pietzsch, Annette
A1  - Wernet, Philippe
A1  - Ueda, Kyoshi
A1  - Föhlisch, Alexander
A1  - Techert, Simone
T1  - Ionic solutions probed by resonant inelastic X-ray scattering
JF  - Zeitschrift für physikalische Chemie : international journal of research in physical chemistry and chemical physics
N2  - X-ray spectroscopy is a powerful tool to study the local charge distribution of chemical systems. Together with the liquid jet it becomes possible to probe chemical systems in their natural environment, the liquid phase. In this work, we present X-ray absorption (XA), X-ray emission (XE) and resonant inelastic X-ray scattering (RIXS) data of pure water and various salt solutions and show the possibilities these methods offer to elucidate the nature of ion-water interaction.
KW  - X-ray Spectroscopy
KW  - XAS
KW  - XES
KW  - RIXS
KW  - Anions
KW  - Cations
KW  - Liquid Jet
KW  - Synchrotron Radiation
Y1  - 2015
U6  - https://doi.org/10.1515/zpch-2015-0610
SN  - 0942-9352
VL  - 229
IS  - 10-12
SP  - 1855
EP  - 1867
PB  - De Gruyter
CY  - Berlin
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  - Yin, Zhong
A1  - Rajkovic, Ivan
A1  - Kubicek, Katharina
A1  - Quevedo, Wilson
A1  - Pietzsch, Annette
A1  - Wernet, Philippe
A1  - Föhlisch, Alexander
A1  - Techert, Simone
T1  - Probing the Hofmeister effect with ultrafast core-hole spectroscopy
JF  - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
N2  - In the current work, X-ray emission spectra of aqueous solutions of different inorganic salts within the Hofmeister series are presented. The results reflect the direct interaction of the ions with the water molecules and therefore, reveal general properties of the salt-water interactions. Within the experimental precision a significant effect of the ions on the water structure has been observed but no ordering according to the structure maker/structure breaker concept could be mirrored in the results indicating that the Hofmeister effect if existent may be caused by more complex interactions.
Y1  - 2014
U6  - https://doi.org/10.1021/jp504577a
SN  - 1520-6106
VL  - 118
IS  - 31
SP  - 9398
EP  - 9403
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Yin, Zhong
A1  - Inhester, Ludger
A1  - Veedu, Sreevidya Thekku
A1  - Quevedo, Wilson
A1  - Pietzsch, Annette
A1  - Wernet, Philippe
A1  - Groenhof, Gerrit
A1  - Föhlisch, Alexander
A1  - Grubmueller, Helmut
A1  - Techert, Simone
T1  - Cationic and Anionic Impact on the Electronic Structure of Liquid Water
JF  - The journal of physical chemistry letters
N2  - Hydration shells around ions are crucial for many fundamental biological and chemical processes. Their local physicochemical properties are quite different from those of bulk water and hard to probe experimentally. We address this problem by combining soft X-ray spectroscopy using a liquid jet and molecular dynamics (MD) simulations together with ab initio electronic structure calculations to elucidate the water ion interaction in a MgCl2 solution at the molecular level. Our results reveal that salt ions mainly affect the electronic properties of water molecules in close vicinity and that the oxygen K-edge X-ray emission spectrum of water molecules in the first solvation shell differs significantly from that of bulk water. Ion-specific effects are identified by fingerprint features in the water X-ray emission spectra. While Mg2+ ions cause a bathochromic shift of the water lone pair orbital, the 3p orbital of the Cl- ions causes an additional peak in the water emission spectrum at around 528 eV.
Y1  - 2017
U6  - https://doi.org/10.1021/acs.jpclett.7b01392
SN  - 1948-7185
VL  - 8
SP  - 3759
EP  - 3764
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schreck, Simon
A1  - Pietzsch, Annette
A1  - Kennedy, Brian
A1  - Sathe, Conny
A1  - Miedema, Piter S.
A1  - Techert, Simone
A1  - Strocov, Vladimir N.
A1  - Schmitt, Thorsten
A1  - Hennies, Franz
A1  - Rubensson, Jan-Erik
A1  - Föhlisch, Alexander
T1  - Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering
JF  - Scientific reports
N2  - Thermally driven chemistry as well as materials’ functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future.
Y1  - 2016
U6  - https://doi.org/10.1038/srep20054
SN  - 2045-2322
VL  - 6
PB  - Nature Publ. Group
CY  - London
ER  -