@article{YinInhesterVeeduetal.2017, author = {Yin, Zhong and Inhester, Ludger and Veedu, Sreevidya Thekku and Quevedo, Wilson and Pietzsch, Annette and Wernet, Philippe and Groenhof, Gerrit and F{\"o}hlisch, Alexander and Grubmueller, Helmut and Techert, Simone}, title = {Cationic and Anionic Impact on the Electronic Structure of Liquid Water}, series = {The journal of physical chemistry letters}, volume = {8}, journal = {The journal of physical chemistry letters}, publisher = {American Chemical Society}, address = {Washington}, issn = {1948-7185}, doi = {10.1021/acs.jpclett.7b01392}, pages = {3759 -- 3764}, year = {2017}, abstract = {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.}, 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{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{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{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} } @unpublished{FoehlischdeGrootOdeliusetal.2014, author = {F{\"o}hlisch, Alexander and de Groot, F. M. F. and Odelius, Michael and Techert, Simone and Wernet, P.}, title = {Comment on "state-dependent electron delocalization dynamics at the solute-solvent interface: soft-x-ray absorption spectroscopy and lambda b initio calculations"}, series = {Physical review letters}, volume = {112}, journal = {Physical review letters}, number = {12}, publisher = {American Physical Society}, address = {College Park}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.112.129302}, pages = {2}, year = {2014}, language = {en} } @article{YinRajkovicKubiceketal.2014, author = {Yin, Zhong and Rajkovic, Ivan and Kubicek, Katharina and Quevedo, Wilson and Pietzsch, Annette and Wernet, Philippe and F{\"o}hlisch, Alexander and Techert, Simone}, title = {Probing the Hofmeister effect with ultrafast core-hole spectroscopy}, series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, volume = {118}, journal = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, number = {31}, publisher = {American Chemical Society}, address = {Washington}, issn = {1520-6106}, doi = {10.1021/jp504577a}, pages = {9398 -- 9403}, year = {2014}, abstract = {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.}, 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} } @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} }