@article{WernetKunnusJosefssonetal.2015, author = {Wernet, Philippe and Kunnus, Kristjan and Josefsson, Ida and Rajkovic, Ivan and Quevedo, Wilson and Beye, Martin and Schreck, Simon and Gruebel, S. and Scholz, Mirko and Nordlund, Dennis and Zhang, Wenkai and Hartsock, Robert W. and Schlotter, William F. and Turner, Joshua J. and Kennedy, Brian and Hennies, Franz and de Groot, Frank M. F. and Gaffney, Kelly J. and Techert, Simone and Odelius, Michael and F{\"o}hlisch, Alexander}, title = {Orbital-specific mapping of the ligand exchange dynamics of Fe(CO)(5) in solution}, series = {Nature : the international weekly journal of science}, volume = {520}, journal = {Nature : the international weekly journal of science}, number = {7545}, publisher = {Nature Publ. Group}, address = {London}, issn = {0028-0836}, doi = {10.1038/nature14296}, pages = {78 -- 81}, year = {2015}, abstract = {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.}, language = {en} } @article{KunnusJosefssonRajkovicetal.2016, author = {Kunnus, Kristjan and Josefsson, Ida and Rajkovic, Ivan and Schreck, Simon and Quevedo, Wilson and Beye, Martin and Gr{\"u}bel, Sebastian and Scholz, Mirko and Nordlund, Dennis and Zhang, Wenkai and Hartsock, Robert W. and Gaffney, Kelly J. and Schlotter, William F. and Turner, Joshua J. and Kennedy, Brian and Hennies, Franz and Techert, Simone and Wernet, Philippe and Odelius, Michael and F{\"o}hlisch, Alexander}, title = {Anti-Stokes resonant x-ray Raman scattering for atom specific and excited state selective dynamics}, series = {NEW JOURNAL OF PHYSICS}, volume = {18}, journal = {NEW JOURNAL OF PHYSICS}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1367-2630}, doi = {10.1088/1367-2630/18/10/103011}, pages = {9}, year = {2016}, abstract = {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.}, language = {en} } @article{YinRajkovicVeeduetal.2015, author = {Yin, Zhong and Rajkovic, Ivan and Veedu, Sreevidya Thekku and Deinert, Sascha and Raiser, Dirk and Jain, Rohit and Fukuzawa, Hironobu and Wada, Shin-ichi and Quevedo, Wilson and Kennedy, Brian and Schreck, Simon and Pietzsch, Annette and Wernet, Philippe and Ueda, Kyoshi and F{\"o}hlisch, Alexander and Techert, Simone}, title = {Ionic solutions probed by resonant inelastic X-ray scattering}, series = {Zeitschrift f{\"u}r physikalische Chemie : international journal of research in physical chemistry and chemical physics}, volume = {229}, journal = {Zeitschrift f{\"u}r physikalische Chemie : international journal of research in physical chemistry and chemical physics}, number = {10-12}, publisher = {De Gruyter}, address = {Berlin}, issn = {0942-9352}, doi = {10.1515/zpch-2015-0610}, pages = {1855 -- 1867}, year = {2015}, abstract = {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.}, language = {en} } @article{PietzschHenniesMiedemaetal.2015, author = {Pietzsch, Annette and Hennies, Franz and Miedema, Piter S. and Kennedy, Brian and Schlappa, Justine and Schmitt, Thorsten and Strocov, Vladimir N. and F{\"o}hlisch, Alexander}, title = {Snapshots of the Fluctuating Hydrogen Bond Network in Liquid Water on the Sub-Femtosecond Timescale with Vibrational Resonant Inelastic x-ray Scattering}, series = {Physical review letters}, volume = {114}, journal = {Physical review letters}, number = {8}, publisher = {American Physical Society}, address = {College Park}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.114.088302}, pages = {5}, year = {2015}, abstract = {Liquid water molecules interact strongly with each other, forming a fluctuating hydrogen bond network and thereby giving rise to the anomalous phase diagram of liquid water. Consequently, symmetric and asymmetric water molecules have been found in the picosecond time average with IR and optical Raman spectroscopy. With subnatural linewidth resonant inelastic x-ray scattering (RIXS) at vibrational resolution, we take sub-femtosecond snapshots of the electronic and structural properties of water molecules in the hydrogen bond network. We derive a strong dominance of nonsymmetric molecules in liquid water in contrast to the gas phase on the sub-femtosecond timescale of RIXS and determine the fraction of highly asymmetrically distorted molecules.}, language = {en} } @article{SchreckPietzschKunnusetal.2014, author = {Schreck, Simon and Pietzsch, Annette and Kunnus, Kristjan and Kennedy, Brian and Quevedo, Wilson and Miedema, Piter S. and Wernet, Philippe and F{\"o}hlisch, Alexander}, title = {Dynamics of the OH group and the electronic structure of liquid alcohols}, series = {Structural dynamics}, volume = {1}, journal = {Structural dynamics}, number = {5}, publisher = {American Institute of Physics}, address = {Melville}, issn = {2329-7778}, doi = {10.1063/1.4897981}, pages = {14}, year = {2014}, abstract = {In resonant inelastic soft x-ray scattering (RIXS) from molecular and liquid systems, the interplay of ground state structural and core-excited state dynamical contributions leads to complex spectral shapes that partially allow for ambiguous interpretations. In this work, we dissect these contributions in oxygen K-edge RIXS from liquid alcohols. We use the scattering into the electronic ground state as an accurate measure of nuclear dynamics in the intermediate core-excited state of the RIXS process. We determine the characteristic time in the core-excited state until nuclear dynamics give a measurable contribution to the RIXS spectral profiles to tau(dyn) = 1.2 +/- 0.8 fs. By detuning the excitation energy below the absorption resonance we reduce the effective scattering time below sdyn, and hence suppress these dynamical contributions to a minimum. From the corresponding RIXS spectra of liquid methanol, we retrieve the "dynamic-free" density of states and find that it is described solely by the electronic states of the free methanol molecule. From this and from the comparison of normal and deuterated methanol, we conclude that the split peak structure found in the lone-pair emission region at non-resonant excitation originates from dynamics in the O-H bond in the core-excited state. We find no evidence that this split peak feature is a signature of distinct ground state structural complexes in liquid methanol. However, we demonstrate how changes in the hydrogen bond coordination within the series of linear alcohols from methanol to hexanol affect the split peak structure in the liquid alcohols. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.}, language = {en} } @article{RubenssonSoderstromBinggelietal.2015, author = {Rubensson, Jan-Erik and Soderstrom, Johan and Binggeli, Christian and Grasjo, Joakim and Andersson, Johan and Sathe, Conny and Hennies, Franz and Bisogni, Valentina and Huang, Yaobo and Olalde, Paul and Schmitt, Thorsten and Strocov, Vladimir N. and F{\"o}hlisch, Alexander and Kennedy, Brian and Pietzsch, Annette}, title = {Rydberg-Resolved Resonant Inelastic Soft X-Ray Scattering: Dynamics at Core Ionization Thresholds}, series = {Physical review letters}, volume = {114}, journal = {Physical review letters}, number = {13}, publisher = {American Physical Society}, address = {College Park}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.114.133001}, pages = {5}, year = {2015}, abstract = {Resonant inelastic x-ray scattering spectra excited in the immediate vicinity of the core-level ionization thresholds of N-2 have been recorded. Final states of well-resolved symmetry-selected Rydberg series converging to valence-level ionization thresholds with vibrational excitations are observed. The results are well described by a quasi-two-step model which assumes that the excited electron is unaffected by the radiative decay. This threshold dynamics simplifies the interpretation of resonant inelastic x-ray scattering spectra considerably and facilitates characterization of low-energy excited final states in molecular systems.}, language = {en} } @article{SchreckPietzschKennedyetal.2016, author = {Schreck, Simon and Pietzsch, Annette and Kennedy, Brian and Sathe, Conny and Miedema, Piter S. and Techert, Simone and Strocov, Vladimir N. and Schmitt, Thorsten and Hennies, Franz and Rubensson, Jan-Erik and F{\"o}hlisch, Alexander}, title = {Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering}, series = {Scientific reports}, volume = {6}, journal = {Scientific reports}, publisher = {Nature Publ. Group}, address = {London}, issn = {2045-2322}, doi = {10.1038/srep20054}, pages = {7}, year = {2016}, abstract = {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.}, language = {en} } @article{SellbergMcQueenLaksmonoetal.2015, author = {Sellberg, Jonas A. and McQueen, Trevor A. and Laksmono, Hartawan and Schreck, Simon and Beye, Martin and DePonte, Daniel P. and Kennedy, Brian and Nordlund, Dennis and Sierra, Raymond G. and Schlesinger, Daniel and Tokushima, Takashi and Zhovtobriukh, Iurii and Eckert, Sebastian and Segtnan, Vegard H. and Ogasawara, Hirohito and Kubicek, Katharina and Techert, Simone and Bergmann, Uwe and Dakovski, Georgi L. and Schlotter, William F. and Harada, Yoshihisa and Bogan, Michael J. and Wernet, Philippe and F{\"o}hlisch, Alexander and Pettersson, Lars G. M. and Nilsson, Anders}, title = {X-ray emission spectroscopy of bulk liquid water in "no-man's land"}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {142}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {4}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.4905603}, pages = {9}, year = {2015}, abstract = {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.}, language = {en} } @article{KunnusRajkovicSchrecketal.2012, author = {Kunnus, Kristjan and Rajkovic, Ivan and Schreck, Simon and Quevedo, Wilson and Eckert, Sebastian and Beye, Martin and Suljoti, Edlira and Weniger, Christian and Kalus, Christian and Gruebel, Sebastian and Scholz, Mirko and Nordlund, Dennis and Zhang, Wenkai and Hartsock, Robert W. and Gaffney, Kelly J. and Schlotter, William F. and Turner, Joshua J. and Kennedy, Brian and Hennies, Franz and Techert, Simone and Wernet, Philippe and F{\"o}hlisch, Alexander}, title = {A setup for resonant inelastic soft x-ray scattering on liquids at free electron laser light sources}, series = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques}, volume = {83}, journal = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques}, number = {12}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0034-6748}, doi = {10.1063/1.4772685}, pages = {8}, year = {2012}, abstract = {We present a flexible and compact experimental setup that combines an in vacuum liquid jet with an x-ray emission spectrometer to enable static and femtosecond time-resolved resonant inelastic soft x-ray scattering (RIXS) measurements from liquids at free electron laser (FEL) light sources. We demonstrate the feasibility of this type of experiments with the measurements performed at the Linac Coherent Light Source FEL facility. At the FEL we observed changes in the RIXS spectra at high peak fluences which currently sets a limit to maximum attainable count rate at FELs. The setup presented here opens up new possibilities to study the structure and dynamics in liquids.}, language = {en} } @article{EckertNorellMiedemaetal.2017, author = {Eckert, Sebastian and Norell, Jesper and Miedema, Piter S. and Beye, Martin and Fondell, Mattis and Quevedo, Wilson and Kennedy, Brian and Hantschmann, Markus and Pietzsch, Annette and van Kuiken, Benjamin and Ross, Matthew and Minitti, Michael P. and Moeller, Stefan P. and Schlotter, William F. and Khalil, Munira and Odelius, Michael and F{\"o}hlisch, Alexander}, title = {Untersuchung unabh{\"a}ngiger N-H- und N-C-Bindungsverformungen auf ultrakurzen Zeitskalen mit resonanter inelastischer R{\"o}ntgenstreuung}, series = {Angewandte Chemie}, volume = {129}, journal = {Angewandte Chemie}, number = {22}, issn = {1521-3757}, doi = {10.1002/ange.201700239}, pages = {6184 -- 6188}, year = {2017}, abstract = {Die Femtosekundendynamik nach resonanten Photoanregungen mit optischen und R{\"o}ntgenpulsen erm{\"o}glicht eine selektive Verformung von chemischen N-H- und N-C-Bindungen in 2-Thiopyridon in w{\"a}ssriger L{\"o}sung. Die Untersuchung der orbitalspezifischen elektronischen Struktur und ihrer Dynamik auf ultrakurzen Zeitskalen mit resonanter inelastischer R{\"o}ntgenstreuung an der N1s-Resonanz am Synchrotron und dem Freie-Elektronen-Laser LCLS in Kombination mit quantenchemischen Multikonfigurationsberechnungen erbringen den direkten Nachweis dieser kontrollierten photoinduzierten Molek{\"u}lverformungen und ihrer ultrakurzen Zeitskala.}, language = {de} } @article{EckertNorellMiedemaetal.2017, author = {Eckert, Sebastian and Norell, Jesper and Miedema, Piter S. and Beye, Martin and Fondell, Mattis and Quevedo, Wilson and Kennedy, Brian and Hantschmann, Markus and Pietzsch, Annette and Van Kuiken, Benjamin E. and Ross, Matthew and Minitti, Michael P. and Moeller, Stefan P. and Schlotter, William F. and Khalil, Munira and Odelius, Michael and F{\"o}hlisch, Alexander}, title = {Ultrafast Independent N-H and N-C Bond Deformation Investigated with Resonant Inelastic X-Ray Scattering}, series = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, volume = {56}, journal = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1433-7851}, doi = {10.1002/anie.201700239}, pages = {6088 -- 6092}, year = {2017}, abstract = {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.}, language = {en} } @article{VazdaCruzErtanCoutoetal.2017, author = {Vaz da Cruz, Vinicius and Ertan, Emelie and Couto, Rafael C. and Eckert, Sebastian and Fondell, Mattis and Dantz, Marcus and Kennedy, Brian and Schmitt, Thorsten and Pietzsch, Annette and Guimaraes, Freddy F. and {\AA}gren, Hans and Odelius, Michael and F{\"o}hlisch, Alexander and Kimberg, Victor}, title = {A study of the water molecule using frequency control over nuclear dynamics in resonant X-ray scattering}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {19}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c7cp01215b}, pages = {19573 -- 19589}, year = {2017}, abstract = {In this combined theoretical and experimental study we report a full analysis of the resonant inelastic X-ray scattering (RIXS) spectra of H2O, D2O and HDO. We demonstrate that electronically-elastic RIXS has an inherent capability to map the potential energy surface and to perform vibrational analysis of the electronic ground state in multimode systems. We show that the control and selection of vibrational excitation can be performed by tuning the X-ray frequency across core-excited molecular bands and that this is clearly reflected in the RIXS spectra. Using high level ab initio electronic structure and quantum nuclear wave packet calculations together with high resolution RIXS measurements, we discuss in detail the mode coupling, mode localization and anharmonicity in the studied systems.}, language = {en} } @article{EckertNiskanenJayetal.2017, author = {Eckert, Sebastian and Niskanen, Johannes and Jay, Raphael Martin and Miedema, Piter S. and Fondell, Mattis and Kennedy, Brian and Quevedo, Wilson and Iannuzzi, Marcella and F{\"o}hlisch, Alexander}, title = {Valence orbitals and local bond dynamics around N atoms of histidine under X-ray irradiation}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {19}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c7cp05713j}, pages = {32091 -- 32098}, year = {2017}, abstract = {The valence orbitals of aqueous histidine under basic, neutral and acidic conditions and their X-ray induced transformations have been monitored through N 1s resonant inelastic X-ray scattering. Using density functional ab initio molecular dynamics simulations in the core-hole state within the Z + 1 approximation, core-excitation-induced molecular transformations are quantified. Spectroscopic evidence for a highly directional X-ray-induced local N-H dissociation within the scattering duration is presented for acidic histidine. Our report demonstrates a protonation-state and chemical-environment dependent propensity for a molecular dissociation, which is induced by the absorption of high energy photons. This case study indicates that structural deformations in biomolecules under exposure to ionizing radiation, yielding possible alteration or loss of function, is highly dependent on the physiological state of the molecule upon irradiation.}, language = {en} } @article{JayNorellEckertetal.2018, author = {Jay, Raphael M. and Norell, Jesper and Eckert, Sebastian and Hantschmann, Markus and Beye, Martin and Kennedy, Brian and Quevedo, Wilson and Schlotter, William F. and Dakovski, Georgi L. and Minitti, Michael P. and Hoffmann, Matthias C. and Mitra, Ankush and Moeller, Stefan P. and Nordlund, Dennis and Zhang, Wenkai and Liang, Huiyang W. and Kunnus, Kristian and Kubicek, Katharina and Techert, Simone A. and Lundberg, Marcus and Wernet, Philippe and Gaffney, Kelly and Odelius, Michael and F{\"o}hlisch, Alexander}, title = {Disentangling Transient Charge Density and Metal-Ligand Covalency in Photoexcited Ferricyanide with Femtosecond Resonant Inelastic Soft X-ray Scattering}, series = {The journal of physical chemistry letters}, volume = {9}, journal = {The journal of physical chemistry letters}, number = {12}, publisher = {American Chemical Society}, address = {Washington}, issn = {1948-7185}, doi = {10.1021/acs.jpclett.8b01429}, pages = {3538 -- 3543}, year = {2018}, abstract = {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.}, language = {en} } @article{EckertVazdaCruzErtanetal.2018, author = {Eckert, Sebastian and Vaz da Cruz, Vinicius and Ertan, Emelie and Ignatova, Nina and Polyutov, Sergey and Couto, Rafael C. and Fondell, Mattis and Dantz, Marcus and Kennedy, Brian and Schmitt, Thorsten and Pietzsch, Annette and Odelius, Michael and F{\"o}hlisch, Alexander}, title = {One-dimensional cuts through multidimensional potential-energy surfaces by tunable x rays}, series = {Physical review : A, Atomic, molecular, and optical physics}, volume = {97}, journal = {Physical review : A, Atomic, molecular, and optical physics}, number = {5}, publisher = {American Physical Society}, address = {College Park}, issn = {2469-9926}, doi = {10.1103/PhysRevA.97.053410}, pages = {7}, year = {2018}, abstract = {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.}, language = {en} } @article{ErtanSavchenkoIgnatovaetal.2018, author = {Ertan, Emelie and Savchenko, Viktoriia and Ignatova, Nina and Vaz da Cruz, Vinicius and Couto, Rafael C. and Eckert, Sebastian and Fondell, Mattis and Dantz, Marcus and Kennedy, Brian and Schmitt, Thorsten and Pietzsch, Annette and F{\"o}hlisch, Alexander and Odelius, Michael and Kimberg, Victor}, title = {Ultrafast dissociation features in RIXS spectra of the water molecule}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {20}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {21}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c8cp01807c}, pages = {14384 -- 14397}, year = {2018}, abstract = {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.}, language = {en} } @article{CoutoCruzErtanetal.2017, author = {Couto, Rafael C. and Cruz, Vinicius V. and Ertan, Emelie and Eckert, Sebastian and Fondell, Mattis and Dantz, Marcus and Kennedy, Brian and Schmitt, Thorsten and Pietzsch, Annette and Guimaraes, Freddy F. and Agren, Hans and Odelius, Michael and Kimberg, Victor and F{\"o}hlisch, Alexander}, title = {Selective gating to vibrational modes through resonant X-ray scattering}, series = {Nature Communications}, volume = {8}, journal = {Nature Communications}, publisher = {Nature Publ. Group}, address = {London}, issn = {2041-1723}, doi = {10.1038/ncomms14165}, pages = {7}, year = {2017}, abstract = {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.}, language = {en} } @article{SchreckBeyeSellbergetal.2014, author = {Schreck, Simon and Beye, Martin and Sellberg, Jonas A. and McQueen, Trevor and Laksmono, Hartawan and Kennedy, Brian and Eckert, Sebastian and Schlesinger, Daniel and Nordlund, Dennis and Ogasawara, Hirohito and Sierra, Raymond G. and Segtnan, Vegard H. and Kubicek, Katharina and Schlotter, William F. and Dakovski, Georgi L. and Moeller, Stefan P. and Bergmann, Uwe and Techert, Simone and Pettersson, Lars G. M. and Wernet, Philippe and Bogan, Michael J. and Harada, Yoshihisa and Nilsson, Anders and F{\"o}hlisch, Alexander}, title = {Reabsorption of soft x-ray emission at high x-ray free-electron laserfluences}, series = {Physical review letters}, volume = {113}, journal = {Physical review letters}, number = {15}, publisher = {American Physical Society}, address = {College Park}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.113.153002}, pages = {6}, year = {2014}, abstract = {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.}, language = {en} } @misc{FondellEckertJayetal.2017, author = {Fondell, Mattis and Eckert, Sebastian and Jay, Raphael Martin and Weniger, Christian and Quevedo, Wilson and Niskanen, Johannes and Kennedy, Brian and Sorgenfrei, Florian and Schick, Daniel and Giangrisostomi, Erika and Ovsyannikov, Ruslan and Adamczyk, Katrin and Huse, Nils and Wernet, Philippe and Mitzner, Rolf and F{\"o}hlisch, Alexander}, title = {Time-resolved soft X-ray absorption spectroscopy in transmission mode on liquids at MHz repetition rates}, series = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, number = {780}, issn = {1866-8372}, doi = {10.25932/publishup-43752}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-437529}, pages = {12}, year = {2017}, abstract = {We present a setup combining a liquid flatjet sample delivery and a MHz laser system for time-resolved soft X-ray absorption measurements of liquid samples at the high brilliance undulator beamline UE52-SGM at Bessy II yielding unprecedented statistics in this spectral range. We demonstrate that the efficient detection of transient absorption changes in transmission mode enables the identification of photoexcited species in dilute samples. With iron(II)-trisbipyridine in aqueous solution as a benchmark system, we present absorption measurements at various edges in the soft X-ray regime. In combination with the wavelength tunability of the laser system, the set-up opens up opportunities to study the photochemistry of many systems at low concentrations, relevant to materials sciences, chemistry, and biology.}, language = {en} } @article{FondellEckertJayetal.2017, author = {Fondell, Mattis and Eckert, Sebastian and Jay, Raphael Martin and Weniger, Christian and Quevedo, Wilson and Niskanen, Johannes and Kennedy, Brian and Sorgenfrei, Florian and Schick, Daniel and Giangrisostomi, Erika and Ovsyannikov, Ruslan and Adamczyk, Katrin and Huse, Nils and Wernet, Philippe and Mitzner, Rolf and F{\"o}hlisch, Alexander}, title = {Time-resolved soft X-ray absorption spectroscopy in transmission mode on liquids at MHz repetition rates}, series = {Structural dynamics}, volume = {4}, journal = {Structural dynamics}, publisher = {American Institute of Physics}, address = {Melville}, issn = {2329-7778}, doi = {10.1063/1.4993755}, pages = {11}, year = {2017}, abstract = {We present a setup combining a liquid flatjet sample delivery and a MHz laser system for time-resolved soft X-ray absorption measurements of liquid samples at the high brilliance undulator beamline UE52-SGM at Bessy II yielding unprecedented statistics in this spectral range. We demonstrate that the efficient detection of transient absorption changes in transmission mode enables the identification of photoexcited species in dilute samples. With iron(II)-trisbipyridine in aqueous solution as a benchmark system, we present absorption measurements at various edges in the soft X-ray regime. In combination with the wavelength tunability of the laser system, the set-up opens up opportunities to study the photochemistry of many systems at low concentrations, relevant to materials sciences, chemistry, and biology. (C) 2017 Author(s).}, language = {en} } @misc{EckertNorellMiedemaetal.2017, author = {Eckert, Sebastian and Norell, Jesper and Miedema, Piter S. and Beye, Martin and Fondell, Mattis and Quevedo, Wilson and Kennedy, Brian and Hantschmann, Markus and Pietzsch, Annette and van Kuiken, Benjamin E. and Ross, Matthew and Minitti, Michael P. and Moeller, Stefan P. and Schlotter, William F. and Khalil, Munira and Odelius, Michael and F{\"o}hlisch, Alexander}, title = {Untersuchung unabh{\"a}ngiger N-H- und N-C-Bindungsverformungen auf ultrakurzen Zeitskalen mit resonanter inelastischer R{\"o}ntgenstreuung}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1121}, issn = {1866-8372}, doi = {10.25932/publishup-43668}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-436688}, pages = {7}, year = {2017}, abstract = {Die Femtosekundendynamik nach resonanten Photoanregungen mit optischen und R{\"o}ntgenpulsen erm{\"o}glicht eine selektive Verformung von chemischen N-H- und N-C-Bindungen in 2-Thiopyridon in w{\"a}ssriger L{\"o}sung. Die Untersuchung der orbitalspezifischen elektronischen Struktur und ihrer Dynamik auf ultrakurzen Zeitskalen mit resonanter inelastischer R{\"o}ntgenstreuung an der N1s-Resonanz am Synchrotron und dem Freie-Elektronen-Laser LCLS in Kombination mit quantenchemischen Multikonfigurationsberechnungen erbringen den direkten Nachweis dieser kontrollierten photoinduzierten Molek{\"u}lverformungen und ihrer ultrakurzen Zeitskala.}, language = {de} } @misc{CoutoCruzErtanetal.2017, author = {Couto, Rafael C. and Cruz, Vinicius V. and Ertan, Emelie and Eckert, Sebastian and Fondell, Mattis and Dantz, Marcus and Kennedy, Brian and Schmitt, Thorsten and Pietzsch, Annette and Guimar{\~a}es, Freddy F. and {\AA}gren, Hans and Gel'mukhanov, Faris and Odelius, Michael and Kimberg, Victor and F{\"o}hlisch, Alexander}, title = {Selective gating to vibrational modes through resonant X-ray scattering}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1124}, issn = {1866-8372}, doi = {10.25932/publishup-43692}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-436926}, pages = {9}, year = {2017}, abstract = {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.}, language = {en} } @misc{EckertNorellMiedemaetal.2017, author = {Eckert, Sebastian and Norell, Jesper and Miedema, Piter S. and Beye, Martin and Fondell, Mattis and Quevedo, Wilson and Kennedy, Brian and Hantschmann, Markus and Pietzsch, Annette and van Kuiken, Benjamin E. and Ross, Matthew and Minitti, Michael P. and Moeller, Stefan P. and Schlotter, William F. and Khalil, Munira and Odelius, Michael and F{\"o}hlisch, Alexander}, title = {Ultrafast Independent N-H and N-C Bond Deformation Investigated with Resonant Inelastic X-Ray Scattering}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1115}, issn = {1866-8372}, doi = {10.25932/publishup-43687}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-436873}, pages = {7}, year = {2017}, abstract = {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.}, language = {en} } @misc{VazdaCruzErtanCoutoetal.2017, author = {Vaz da Cruz, Vinicius and Ertan, Emelie and Couto, Rafael C. and Eckert, Sebastian and Fondell, Mattis and Dantz, Marcus and Kennedy, Brian and Schmitt, Thorsten and Pietzsch, Annette and Guimar{\~a}es, Freddy F. and {\AA}gren, Hans and Gel'mukhanov, Faris and Odelius, Michael and F{\"o}hlisch, Alexander and Kimberg, Victor}, title = {A study of the water molecule using frequency control over nuclear dynamics in resonant X-ray scattering}, series = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, number = {781}, issn = {1866-8372}, doi = {10.25932/publishup-43690}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-436901}, pages = {19573 -- 19589}, year = {2017}, abstract = {In this combined theoretical and experimental study we report a full analysis of the resonant inelastic X-ray scattering (RIXS) spectra of H2O, D2O and HDO. We demonstrate that electronically-elastic RIXS has an inherent capability to map the potential energy surface and to perform vibrational analysis of the electronic ground state in multimode systems. We show that the control and selection of vibrational excitation can be performed by tuning the X-ray frequency across core-excited molecular bands and that this is clearly reflected in the RIXS spectra. Using high level ab initio electronic structure and quantum nuclear wave packet calculations together with high resolution RIXS measurements, we discuss in detail the mode coupling, mode localization and anharmonicity in the studied systems.}, language = {en} }