@book{Foehlisch2010, author = {F{\"o}hlisch, Alexander}, title = {Phasen{\"u}berg{\"a}nge und Ultrakurzzeitdynamik : Antrittsvorlesung 2010-05-12}, publisher = {Univ.-Bibl.}, address = {Potsdam}, year = {2010}, abstract = {F{\"o}hlisch wird in seinem Vortrag die großen Zukunftsthemen der Mensch streifen: Energie, Umwelt und Struktur der Materie. Die Komplexit{\"a}t ihrer elementaren Prozesse erfordert die komplement{\"a}re Betrachtung der damit verbundene Dimensionen von Energie, Zeit und Raum. Dies l{\"a}sst sich inzwischen mit Synchrotronstrahlungsquellen in gr{\"o}ßter Pr{\"a}ision darstellen.}, language = {de} } @article{HenniesPietzschBerglundetal.2010, author = {Hennies, Franz and Pietzsch, Annette and Berglund, Martin and F{\"o}hlisch, Alexander and Schmitt, Thorsten and Strocov, Vladimir and Karlsson, Hans O. and Andersson, Joakim and Rubensson, Jan-Erik}, title = {Resonant inelastic scattering spectra of free molecules with vibrational resolution}, issn = {0031-9007}, doi = {10.1103/Physrevlett.104.193002}, year = {2010}, abstract = {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.}, language = {en} } @article{PontiusKachelSchuesslerLangeheineetal.2011, author = {Pontius, N. and Kachel, T. and Sch{\"u}ssler-Langeheine, C. and Schlotter, W. F. and Beye, Martin and Sorgenfrei, Florian and Chang, C. F. and F{\"o}hlisch, Alexander and Wurth, W. and Metcalf, P. and Leonov, I. and Yaresko, A. and Stojanovic, N. and Berglund, Martin and Guerassimova, N. and Duesterer, S. and Redlin, H. and Duerr, H. A.}, title = {Time-resolved resonant soft x-ray diffraction with free-electron lasers femtosecond dynamics across the Verwey transition in magnetite}, series = {Applied physics letters}, volume = {98}, journal = {Applied physics letters}, number = {18}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0003-6951}, doi = {10.1063/1.3584855}, pages = {3}, year = {2011}, abstract = {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.}, language = {en} } @article{BeyeFoehlisch2011, author = {Beye, Martin and F{\"o}hlisch, Alexander}, title = {A soft X-ray approach to electron-phonon interactions beyond the Born-Oppenheimer approximation}, series = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, volume = {184}, journal = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy}, number = {3-6}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0368-2048}, doi = {10.1016/j.elspec.2010.12.032}, pages = {313 -- 317}, year = {2011}, abstract = {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.}, language = {en} } @article{SunHenniesPietzschetal.2011, author = {Sun, Y. -P. and Hennies, Franz and Pietzsch, Annette and Kennedy, B. and Schmitt, Thorsten and Strocov, Vladimir N. and Andersson, Joakim and Berglund, Martin and Rubensson, Jan-Erik and Aidas, K. and Gel'mukhanov, F. and Odelius, Michael and F{\"o}hlisch, Alexander}, title = {Intramolecular soft modes and intermolecular interactions in liquid acetone}, series = {Physical review : B, Condensed matter and materials physics}, volume = {84}, journal = {Physical review : B, Condensed matter and materials physics}, number = {13}, publisher = {American Physical Society}, address = {College Park}, issn = {1098-0121}, doi = {10.1103/PhysRevB.84.132202}, pages = {4}, year = {2011}, abstract = {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.}, language = {en} } @article{PietzschSunHenniesetal.2011, author = {Pietzsch, Annette and Sun, Y. -P. and Hennies, Franz and Rinkevicius, Z. and Karlsson, Hans O. and Schmitt, Thorsten and Strocov, Vladimir N. and Andersson, Joakim and Kennedy, B. and Schlappa, J. and F{\"o}hlisch, Alexander and Rubensson, Jan-Erik and Gel'mukhanov, F.}, title = {Spatial quantum beats in vibrational resonant inelastic soft X-ray scattering at dissociating states in oxygen}, series = {Physical review letters}, volume = {106}, journal = {Physical review letters}, number = {15}, publisher = {American Physical Society}, address = {College Park}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.106.153004}, pages = {4}, year = {2011}, abstract = {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.}, language = {en} } @article{ArhammarPietzschBocketal.2011, author = {Arhammar, C. and Pietzsch, Annette and Bock, Nicolas and Holmstroem, Erik and Araujo, C. Moyses and Grasjo, Johan and Zhao, Shuxi and Green, Sara and Peery, T. and Hennies, Franz and Amerioun, Shahrad and F{\"o}hlisch, Alexander and Schlappa, Justine and Schmitt, Thorsten and Strocov, Vladimir N. and Niklasson, Gunnar A. and Wallace, Duane C. and Rubensson, Jan-Erik and Johansson, Borje and Ahuja, Rajeev C.}, title = {Unveiling the complex electronic structure of amorphous metal oxides}, series = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {108}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, number = {16}, publisher = {National Acad. of Sciences}, address = {Washington}, issn = {0027-8424}, doi = {10.1073/pnas.1019698108}, pages = {6355 -- 6360}, year = {2011}, abstract = {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.}, language = {en} } @article{SunPietzschHenniesetal.2011, author = {Sun, Y-P and Pietzsch, Annette and Hennies, Franz and Rinkevicius, Z. and Karlsson, Hans O. and Schmitt, Thorsten and Strocov, Vladimir N. and Andersson, Joakim and Kennedy, B. and Schlappa, J. and F{\"o}hlisch, Alexander and Gel'mukhanov, F. and Rubensson, Jan-Erik}, title = {Internal symmetry and selection rules in resonant inelastic soft x-ray scattering}, series = {Journal of physics : B, Atomic, molecular and optical physics}, volume = {44}, journal = {Journal of physics : B, Atomic, molecular and optical physics}, number = {16}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0953-4075}, doi = {10.1088/0953-4075/44/16/161002}, pages = {5}, year = {2011}, abstract = {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.}, language = {en} } @article{ThielemannKuehnHoffmannFoehlisch2012, author = {Thielemann-K{\"u}hn, Nele and Hoffmann, P. and F{\"o}hlisch, Alexander}, title = {A versatile detector for total fluorescence and electron yield experiments}, 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 = {9}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0034-6748}, doi = {10.1063/1.4754126}, pages = {3}, year = {2012}, abstract = {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.}, 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} }