TY - BOOK A1 - Föhlisch, Alexander T1 - Phasenübergänge und Ultrakurzzeitdynamik : Antrittsvorlesung 2010-05-12 N2 - Föhlisch wird in seinem Vortrag die großen Zukunftsthemen der Mensch streifen: Energie, Umwelt und Struktur der Materie. Die Komplexität ihrer elementaren Prozesse erfordert die komplementäre Betrachtung der damit verbundene Dimensionen von Energie, Zeit und Raum. Dies lässt sich inzwischen mit Synchrotronstrahlungsquellen in größter Präision darstellen. Y1 - 2010 UR - http://info.ub.uni-potsdam.de/multimedia/show_projekt.php?projekt_id=63 PB - Univ.-Bibl. CY - Potsdam ER - TY - JOUR A1 - Hennies, Franz A1 - Pietzsch, Annette A1 - Berglund, Martin A1 - Föhlisch, Alexander A1 - Schmitt, Thorsten A1 - Strocov, Vladimir A1 - Karlsson, Hans O. A1 - Andersson, Joakim A1 - Rubensson, Jan-Erik T1 - Resonant inelastic scattering spectra of free molecules with vibrational resolution N2 - Inelastic x-ray scattering spectra excited at the 1s(-1) pi* resonance of gas phase O-2 have been recorded with an overall energy resolution that allows for well-resolved vibrational progressions. The nuclear wave packet dynamics in the intermediate state is reflected in vibrational excitations of the electronic ground state, and by fine-tuning the excitation energy the dissociation dynamics in the predissociative B' (3) Pi(g) final state is controlled. Y1 - 2010 UR - http://prl.aps.org/ U6 - https://doi.org/10.1103/Physrevlett.104.193002 SN - 0031-9007 ER - TY - JOUR A1 - Beye, Martin A1 - Föhlisch, Alexander T1 - A soft X-ray approach to electron-phonon interactions beyond the Born-Oppenheimer approximation JF - Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy N2 - With modern soft X-ray methods, the whole field of electron-phonon interactions becomes accessible directly in the ultrafast time domain with ultrashort pulsed X-ray sources, as well as in the energy domain through modern highly resolving spectrometers. The well-known core-hole clock approach plays an intermediate role, resolving energetic and temporal features at the same time. In this perspective paper, we review several experiments to illustrate the modern advances in the selective study of electron-phonon interactions as fundamentally determining ingredients for materials properties. We present the different complementary approaches that can be taken with soft X-ray methods to conquer this field beyond the Born-Oppenheimer approximation. KW - Electron-phonon coupling KW - Resonant inelastic X-ray scattering KW - X-ray emission spectroscopy KW - Near edge X-ray absorption fine structure Y1 - 2011 U6 - https://doi.org/10.1016/j.elspec.2010.12.032 SN - 0368-2048 VL - 184 IS - 3-6 SP - 313 EP - 317 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Sun, Y. -P. A1 - Hennies, Franz A1 - Pietzsch, Annette A1 - Kennedy, B. A1 - Schmitt, Thorsten A1 - Strocov, Vladimir N. A1 - Andersson, Joakim A1 - Berglund, Martin A1 - Rubensson, Jan-Erik A1 - Aidas, K. A1 - Gel'mukhanov, F. A1 - Odelius, Michael A1 - Föhlisch, Alexander T1 - Intramolecular soft modes and intermolecular interactions in liquid acetone JF - Physical review : B, Condensed matter and materials physics N2 - Resonant inelastic x-ray scattering spectra excited at the O1s(-1)pi* resonance of liquid acetone are presented. Scattering to the electronic ground state shows a resolved vibrational progression where the dominant contribution is due to the C-O stretching mode, thus demonstrating a unique sensitivity of the method to the local potential energy surface in complex molecular systems. For scattering to electronically excited states, soft vibrational modes and, to a smaller extent, intermolecular interactions give a broadening, which blurs the vibrational fine structure. It is predicted that environmental broadening is dominant in aqueous acetone. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevB.84.132202 SN - 1098-0121 VL - 84 IS - 13 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Pietzsch, Annette A1 - Sun, Y. -P. A1 - Hennies, Franz A1 - Rinkevicius, Z. A1 - Karlsson, Hans O. A1 - Schmitt, Thorsten A1 - Strocov, Vladimir N. A1 - Andersson, Joakim A1 - Kennedy, B. A1 - Schlappa, J. A1 - Föhlisch, Alexander A1 - Rubensson, Jan-Erik A1 - Gel'mukhanov, F. T1 - Spatial quantum beats in vibrational resonant inelastic soft X-ray scattering at dissociating states in oxygen JF - Physical review letters N2 - Resonant inelastic soft x-ray scattering (RIXS) spectra excited at the 1 sigma(g) -> 3 sigma(u) resonance in gas-phase O-2 show excitations due to the nuclear degrees of freedom with up to 35 well-resolved discrete vibronic states and a continuum due to the kinetic energy distribution of the separated atoms. The RIXS profile demonstrates spatial quantum beats caused by two interfering wave packets with different momenta as the atoms separate. Thomson scattering strongly affects both the spectral profile and the scattering anisotropy. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevLett.106.153004 SN - 0031-9007 VL - 106 IS - 15 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Arhammar, C. A1 - Pietzsch, Annette A1 - Bock, Nicolas A1 - Holmstroem, Erik A1 - Araujo, C. Moyses A1 - Grasjo, Johan A1 - Zhao, Shuxi A1 - Green, Sara A1 - Peery, T. A1 - Hennies, Franz A1 - Amerioun, Shahrad A1 - Föhlisch, Alexander A1 - Schlappa, Justine A1 - Schmitt, Thorsten A1 - Strocov, Vladimir N. A1 - Niklasson, Gunnar A. A1 - Wallace, Duane C. A1 - Rubensson, Jan-Erik A1 - Johansson, Borje A1 - Ahuja, Rajeev C. T1 - Unveiling the complex electronic structure of amorphous metal oxides JF - Proceedings of the National Academy of Sciences of the United States of America N2 - Amorphous materials represent a large and important emerging area of material's science. Amorphous oxides are key technological oxides in applications such as a gate dielectric in Complementary metal-oxide semiconductor devices and in Silicon-Oxide-Nitride-Oxide-Silicon and TANOS (TaN-Al2O3-Si3N4-SiO2-Silicon) flash memories. These technologies are required for the high packing density of today's integrated circuits. Therefore the investigation of defect states in these structures is crucial. In this work we present X-ray synchrotron measurements, with an energy resolution which is about 5-10 times higher than is attainable with standard spectrometers, of amorphous alumina. We demonstrate that our experimental results are in agreement with calculated spectra of amorphous alumina which we have generated by stochastic quenching. This first principles method, which we have recently developed, is found to be superior to molecular dynamics in simulating the rapid gas to solid transition that takes place as this material is deposited for thin film applications. We detect and analyze in detail states in the band gap that originate from oxygen pairs. Similar states were previously found in amorphous alumina by other spectroscopic methods and were assigned to oxygen vacancies claimed to act mutually as electron and hole traps. The oxygen pairs which we probe in this work act as hole traps only and will influence the information retention in electronic devices. In amorphous silica oxygen pairs have already been found, thus they may be a feature which is characteristic also of other amorphous metal oxides. KW - stochastic quench KW - X-ray absorption spectroscopy KW - ab initio KW - coating Y1 - 2011 U6 - https://doi.org/10.1073/pnas.1019698108 SN - 0027-8424 VL - 108 IS - 16 SP - 6355 EP - 6360 PB - National Acad. of Sciences CY - Washington ER - TY - JOUR A1 - Sun, Y-P A1 - Pietzsch, Annette A1 - Hennies, Franz A1 - Rinkevicius, Z. A1 - Karlsson, Hans O. A1 - Schmitt, Thorsten A1 - Strocov, Vladimir N. A1 - Andersson, Joakim A1 - Kennedy, B. A1 - Schlappa, J. A1 - Föhlisch, Alexander A1 - Gel'mukhanov, F. A1 - Rubensson, Jan-Erik T1 - Internal symmetry and selection rules in resonant inelastic soft x-ray scattering JF - Journal of physics : B, Atomic, molecular and optical physics N2 - Resonant inelastic soft x-ray scattering spectra excited at the dissociative 1 sigma(g) -> 3 sigma(u) resonance in gas-phase O(2) are presented and discussed in terms of state-of-the-art molecular theory. A new selection rule due to internal spin coupling is established, facilitating a deep analysis of the valence excited final states. Furthermore, it is found that a commonly accepted symmetry selection rule due to orbital parity breaks down, as the core hole and excited electron swap parity, thereby opening the symmetry forbidden 3 sigma(g) decay channel. Y1 - 2011 U6 - https://doi.org/10.1088/0953-4075/44/16/161002 SN - 0953-4075 VL - 44 IS - 16 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Pontius, N. A1 - Kachel, T. A1 - Schüssler-Langeheine, C. A1 - Schlotter, W. F. A1 - Beye, Martin A1 - Sorgenfrei, Nomi A1 - Chang, C. F. A1 - Föhlisch, Alexander A1 - Wurth, W. A1 - Metcalf, P. A1 - Leonov, I. A1 - Yaresko, A. A1 - Stojanovic, N. A1 - Berglund, Martin A1 - Guerassimova, N. A1 - Duesterer, S. A1 - Redlin, H. A1 - Duerr, H. A. T1 - Time-resolved resonant soft x-ray diffraction with free-electron lasers femtosecond dynamics across the Verwey transition in magnetite JF - Applied physics letters N2 - Resonant soft x-ray diffraction (RSXD) with femtosecond (fs) time resolution is a powerful tool for disentangling the interplay between different degrees of freedom in strongly correlated electron materials. It allows addressing the coupling of particular degrees of freedom upon an external selective perturbation, e. g., by an optical or infrared laser pulse. Here, we report a time-resolved RSXD experiment from the prototypical correlated electron material magnetite using soft x-ray pulses from the free-electron laser FLASH in Hamburg. We observe ultrafast melting of the charge-orbital order leading to the formation of a transient phase, which has not been observed in equilibrium. Y1 - 2011 U6 - https://doi.org/10.1063/1.3584855 SN - 0003-6951 VL - 98 IS - 18 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Thielemann-Kühn, Nele A1 - Hoffmann, P. A1 - Föhlisch, Alexander T1 - A versatile detector for total fluorescence and electron yield experiments JF - Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques N2 - The combination of a non-coated silicon photodiode with electron repelling meshes makes a versatile detector for total fluorescence yield and electron yield techniques highly suitable for x-ray absorption spectroscopy. In particular, a copper mesh with a bias voltage allows to suppress or transmit the electron yield signal. The performance of this detection scheme has been characterized by near edge x-ray absorption fine structure studies of thermal oxidized silicon and sapphire. The results show that the new detector probes both electron yield and for a bias voltage exceeding the maximum photon energy the total fluorescence yield. Y1 - 2012 U6 - https://doi.org/10.1063/1.4754126 SN - 0034-6748 VL - 83 IS - 9 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Kunnus, Kristjan A1 - Rajkovic, Ivan A1 - Schreck, Simon A1 - Quevedo, Wilson A1 - Eckert, Sebastian A1 - Beye, Martin A1 - Suljoti, Edlira A1 - Weniger, Christian A1 - Kalus, Christian A1 - Gruebel, 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 - Föhlisch, Alexander T1 - A setup for resonant inelastic soft x-ray scattering on liquids at free electron laser light sources JF - Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques N2 - 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. Y1 - 2012 U6 - https://doi.org/10.1063/1.4772685 SN - 0034-6748 VL - 83 IS - 12 PB - American Institute of Physics CY - Melville ER -