@article{OvsyannikovKarlssonLundqvistetal.2013, author = {Ovsyannikov, Ruslan and Karlsson, P. and Lundqvist, M. and Lupulescu, C. and Eberhardt, W. and F{\"o}hlisch, Alexander and Svensson, S. and Martensson, N.}, title = {Principles and operation of a new type of electron spectrometer - ArTOF}, series = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, volume = {191}, journal = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, number = {12}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0368-2048}, doi = {10.1016/j.elspec.2013.08.005}, pages = {92 -- 103}, year = {2013}, abstract = {A new energy and angular electron analyzer ArTOF (Angular Resolved Time of Flight) is described. The analyzer is based on simultaneous measurement of flight times and angles in an advanced electron lens system. In angular modes the new analyzer combines an increase in transmission by almost three orders of magnitude with improved resolution, in comparison to standard state-of-the-art electron spectrometers. In this report we describe some design principles and we give a review of calibration and alignment procedures necessary for the use of the ArTOF on a synchrotron radiation facility. Our program scripts to handle the large datasets are also discussed. Furthermore we give a broad description of the new research fields that benefit from the use of the ArTOF and give a short summary of the first results of angle resolved photoemission measurement with ArTOF using the single-bunch X-ray pulses from the BESSY II storage ring facility. (C) 2013 Published by Elsevier B.V.}, language = {en} } @article{KunnusJosefssonSchrecketal.2013, author = {Kunnus, Kristjan and Josefsson, Ida and Schreck, Simon and Quevedo, Wilson and Miedema, Piter S. and Techert, Simone and de Groot, Frank M. F. and Odelius, Michael and Wernet, Philippe and F{\"o}hlisch, Alexander}, title = {From Ligand Fields to Molecular Orbitals: Probing the Local Valence Electronic Structure of Ni2+ in Aqueous Solution with Resonant Inelastic X-ray Scattering}, series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, volume = {117}, journal = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, number = {51}, publisher = {American Chemical Society}, address = {Washington}, issn = {1520-6106}, doi = {10.1021/jp4100813}, pages = {16512 -- 16521}, year = {2013}, abstract = {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.}, language = {en} } @article{BeyeFoehlisch2013, author = {Beye, Martin and F{\"o}hlisch, Alexander}, title = {Soft X-ray probes of ultrafast dynamics for heterogeneous catalysis}, series = {Chemical physics : a journal devoted to experimental and theoretical research involving problems of both a chemical and physical nature}, volume = {414}, journal = {Chemical physics : a journal devoted to experimental and theoretical research involving problems of both a chemical and physical nature}, number = {5}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0301-0104}, doi = {10.1016/j.chemphys.2012.03.023}, pages = {130 -- 138}, year = {2013}, abstract = {Soft X-ray spectroscopy is one of the best tools to directly address the electronic structure, the driving force of chemical reactions. It enables selective studies on sample surfaces to single out reaction centers in heterogeneous catalytic reactions. With core-hole clock methods, specific dynamics are related to the femtosecond life time of a core-hole. Typically, this method is used with photoemission spectroscopy, but advancements in soft X-ray emission techniques render more specific studies possible. With the advent of bright femtosecond pulsed soft X-ray sources, highly selective pump-probe X-ray emission studies are enabled with temporal resolutions down to tens of femtoseconds. This finally allows to study dynamics in the electronic structure of adsorbed reaction centers on the whole range of relevant time scales - closing the gap between kinetic soft X-ray studies and the atto- to femtosecond core-hole clock techniques.}, language = {en} } @article{KoenneckeFollathPontiusetal.2013, author = {K{\"o}nnecke, Rene and Follath, R. and Pontius, N. and Schlappa, J. and Eggenstein, F. and Zeschke, T. and Bischoff, P. and Schmidt, J. -S. and Noll, T. and Trabant, C. and Schreck, S. and Wernet, Ph. and Eisebitt, S. and Senf, F. and Schuessler-Langeheine, Christian and Erko, A. and F{\"o}hlisch, Alexander}, title = {The confocal plane grating spectrometer at BESSY II}, series = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, volume = {188}, journal = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0368-2048}, doi = {10.1016/j.elspec.2012.11.003}, pages = {133 -- 139}, year = {2013}, abstract = {At BESSY II a confocal plane grating spectrometer for resonant inelastic X-ray scattering (RIXS) is currently under commissioning. The new endstation operates with a source size of 4 x 1 mu m(2) provided by its dedicated beamline. The RIXS-spectrometer covers an energy range from 50 eV to 1000 eV, providing a resolving power E/Delta E of 5000-15,000. The beamline allows full polarization control and gives a photon flux of up to 7 x 10(14) photons/s/0.1 A/0.1\%bandwidth by offering a resolving power E/Delta E of 4000-12,000.}, language = {en} } @article{BeyeWernetSchuesslerLangeheineetal.2013, author = {Beye, Martin and Wernet, Ph. and Sch{\"u}ßler-Langeheine, Christian and F{\"o}hlisch, Alexander}, title = {Time resolved resonant inelastic X-ray scattering: a supreme tool to understand dynamics in solids and molecules}, series = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, volume = {188}, journal = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, number = {3}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0368-2048}, doi = {10.1016/j.elspec.2013.04.013}, pages = {172 -- 182}, year = {2013}, abstract = {Dynamics in materials typically involve different degrees of freedom, like charge, lattice, orbital and spin in a complex interplay. Time-resolved resonant inelastic X-ray scattering (RIXS) as a highly selective tool can provide unique insight and follow the details of dynamical processes while resolving symmetries, chemical and charge states, momenta, spin configurations, etc. In this paper, we review examples where the intrinsic scattering duration time is used to study femtosecond phenomena. Free-electron lasers access timescales starting in the sub-ps range through pump-probe methods and synchrotrons study the time scales longer than tens of ps. In these examples, time-resolved resonant inelastic X-ray scattering is applied to solids as well as molecular systems.}, language = {en} } @article{MitznerRehanekKernetal.2013, author = {Mitzner, Rolf and Rehanek, Jens and Kern, Jan and Gul, Sheraz and Hattne, Johan and Taguchi, Taketo and Alonso-Mori, Roberto and Tran, Rosalie and Weniger, Christian and Schr{\"o}der, Henning and Quevedo, Wilson and Laksmono, Hartawan and Sierra, Raymond G. and Han, Guangye and Lassalle-Kaiser, Benedikt and Koroidov, Sergey and Kubicek, Katharina and Schreck, Simon and Kunnus, Kristjan and Brzhezinskaya, Maria and Firsov, Alexander and Minitti, Michael P. and Turner, Joshua J. and M{\"o}ller, Stefan and Sauter, Nicholas K. and Bogan, Michael J. and Nordlund, Dennis and Schlotter, William F. and Messinger, Johannes and Borovik, Andrew S. and Techert, Simone and de Groot, Frank M. F. and F{\"o}hlisch, Alexander and Erko, Alexei and Bergmann, Uwe and Yachandra, Vittal K. and Wernet, Philippe and Yano, Junko}, title = {L-edge x-ray absorption spectroscopy of dilute systems relevant to metalloproteins using an X-ray free-electron laser}, series = {The journal of physical chemistry letters}, volume = {4}, journal = {The journal of physical chemistry letters}, number = {21}, publisher = {American Chemical Society}, address = {Washington}, issn = {1948-7185}, doi = {10.1021/jz401837f}, pages = {3641 -- 3647}, year = {2013}, abstract = {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.}, language = {en} } @article{SunMiaoPietzschetal.2013, author = {Sun, Y. -P. and Miao, Q. and Pietzsch, Annette and Hennies, F. and Schmitt, T. and Strocov, V. N. and Andersson, Joakim and Kennedy, B. and Schlappa, J. and F{\"o}hlisch, Alexander and Gel\&rsquo, and mukhanov, F. and Rubensson, J. -E.}, title = {Interference between Resonant and Nonresonant Inelastic X-Ray Scattering}, series = {PHYSICAL REVIEW LETTERS}, volume = {110}, journal = {PHYSICAL REVIEW LETTERS}, number = {22}, publisher = {AMER PHYSICAL SOC}, address = {COLLEGE PK}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.110.223001}, pages = {4}, year = {2013}, abstract = {A detailed study of inelastic x-ray scattering from the ground state to the (3)Sigma(g)(3 sigma(-1)(g)3s(g)(1)) state of the O-2 molecule is presented. The observed angular anisotropy shows that the vibrational excitations within this final state are strongly dependent on the polarization of the incident radiation. The analysis demonstrates that this is a manifestation of interference between resonant and direct nonresonant inelastic x-ray scattering. This interference provides a new tool to monitor nuclear dynamics by relative rotation of the polarization vectors of the incident and scattered photons.}, language = {en} } @article{EschenlohrBattiatoMaldonadoetal.2013, author = {Eschenlohr, Andrea and Battiato, Marco and Maldonado, R. and Pontius, N. and Kachel, T. and Holldack, K. and Mitzner, Rolf and F{\"o}hlisch, Alexander and Oppeneer, P. M. and Stamm, C.}, title = {Ultrafast spin transport as key to femtosecond demagnetization}, series = {Nature materials}, volume = {12}, journal = {Nature materials}, number = {4}, publisher = {Nature Publ. Group}, address = {London}, issn = {1476-1122}, doi = {10.1038/NMAT3546}, pages = {332 -- 336}, year = {2013}, abstract = {Irradiating a ferromagnet with a femtosecond laser pulse is known to induce an ultrafast demagnetization within a few hundred femtoseconds. Here we demonstrate that direct laser irradiation is in fact not essential for ultrafast demagnetization, and that electron cascades caused by hot electron currents accomplish it very efficiently. We optically excite a Au/Ni layered structure in which the 30 nm Au capping layer absorbs the incident laser pump pulse and subsequently use the X-ray magnetic circular dichroism technique to probe the femtosecond demagnetization of the adjacent 15 nm Ni layer. A demagnetization effect corresponding to the scenario in which the laser directly excites the Ni film is observed, but with a slight temporal delay. We explain this unexpected observation by means of the demagnetizing effect of a superdiffusive current of non-equilibrium, non-spin-polarized electrons generated in the Au layer.}, language = {en} } @article{deJongKukrejaTrabantetal.2013, author = {de Jong, S. and Kukreja, R. and Trabant, C. and Pontius, N. and Chang, C. F. and Kachel, T. and Beye, Martin and Sorgenfrei, Nomi and Back, C. H. and Braeuer, B. and Schlotter, W. F. and Turner, J. J. and Krupin, O. and Doehler, M. and Zhu, D. and Hossain, M. A. and Scherz, A. O. and Fausti, D. and Novelli, F. and Esposito, M. and Lee, W. S. and Chuang, Y. D. and Lu, D. H. and Moore, R. G. and Yi, M. and Trigo, M. and Kirchmann, P. and Pathey, L. and Golden, M. S. and Buchholz, Marcel and Metcalf, P. and Parmigiani, F. and Wurth, W. and F{\"o}hlisch, Alexander and Schuessler-Langeheine, Christian and Duerr, H. A.}, title = {Speed limit of the insulator-metal transition in magnetite}, series = {Nature materials}, volume = {12}, journal = {Nature materials}, number = {10}, publisher = {Nature Publ. Group}, address = {London}, issn = {1476-1122}, doi = {10.1038/NMAT3718}, pages = {882 -- 886}, year = {2013}, abstract = {As the oldest known magnetic material, magnetite (Fe3O4) has fascinated mankind for millennia. As the first oxide in which a relationship between electrical conductivity and fluctuating/localized electronic order was shown(1), magnetite represents a model system for understanding correlated oxides in general. Nevertheless, the exact mechanism of the insulator-metal, or Verwey, transition has long remained inaccessible(2-8). Recently, three- Fe- site lattice distortions called trimeronswere identified as the characteristic building blocks of the low-temperature insulating electronically ordered phase(9). Here we investigate the Verwey transition with pump- probe X- ray diffraction and optical reflectivity techniques, and show how trimerons become mobile across the insulator-metal transition. We find this to be a two- step process. After an initial 300 fs destruction of individual trimerons, phase separation occurs on a 1.5 +/- 0.2 ps timescale to yield residual insulating and metallic regions. This work establishes the speed limit for switching in future oxide electronics(10).}, language = {en} } @article{KatayamaAnniyevBeyeetal.2013, author = {Katayama, T. and Anniyev, Toyli and Beye, Martin and Coffee, Ryan and Dell'Angela, M. and F{\"o}hlisch, Alexander and Gladh, J. and Kaya, S. and Krupin, O. and Nilsson, A. and Nordlund, D. and Schlotter, W. F. and Sellberg, J. A. and Sorgenfrei, Nomi and Turner, J. J. and Wurth, W. and {\"O}str{\"o}m, H. and Ogasawara, H.}, title = {Ultrafast soft X-ray emission spectroscopy of surface adsorbates using an X-ray free electron laser}, series = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, volume = {187}, journal = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, number = {1}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0368-2048}, doi = {10.1016/j.elspec.2013.03.006}, pages = {9 -- 14}, year = {2013}, abstract = {We report on an experimental system designed to probe chemical reactions on solid surfaces on a sub-picosecond timescale using soft X-ray emission spectroscopy at the Linac Coherent Light Source (LCLS) free electron laser (FEL) at the SLAC National Accelerator Laboratory. We analyzed the O 1s X-ray emission spectra recorded from atomic oxygen adsorbed on a Ru(0001) surface at a synchrotron beamline (SSRL, BL13-2) and an FEL beamline (LCLS, SXR). We have demonstrated conditions that provide negligible amount of FEL induced damage of the sample. In addition we show that the setup is capable of tracking the temporal evolution of electronic structure during a surface reaction of submonolayer quantities of CO molecules desorbing from the surface.}, language = {en} }