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Start date: 2010 × search.filters.applied.f.series: EPJ Web of Conferences 41 (2013) × WGL Institute: MBI ×

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Now showing 1 - 10 of 15
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    Ultrafast inter-ionic charge transfer of transition-metal complexes mapped by femtosecond x-ray powder diffraction
    (Les Ulis : EDP Sciences, 2013) Zamponi, F.; Freyer, B.; Juvé, V.; Stingl, J.; Woerner, M.; Chergui, M.; Elsaesser, T.
    Transient electron density maps are derived from x-ray diffraction patterns of photoexcited [Fe(bpy)3]2+(PF6 -)2 powder. Upon photoexcitation, the 5T 2 quintet state reveals a charge transfer from the PF 6- ions and from the Fe atoms to neighboring bpy units. The charge transfer from the Fe points to a partial and weak charge-transfer character of this state.
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    Ultrafast two-dimensional THz spectroscopy of graphene
    (Les Ulis : EDP Sciences, 2013) Bowlan, P.; Martinez Moreno, E.; Reimann, K.; Woerner, M.; Elsaesser, T.
    With two-dimensional THz spectroscopy the dynamics of low-energy carriers in graphene is determined. Both intra- and interband absorption contribute to the observed ultrafast pump-probe signals.
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    Ultrafast IR pump-probe and 2D-IR photon echo spectroscopy of adenosine-thymidine base pairs
    (Les Ulis : EDP Sciences, 2013) Greve, C.; Preketes, N.K.; Costard, R.; Koeppe, B.; Fidder, H.; Nibbering, E.T.J.; Temps, F.; Mukamel, S.; Elsaesser, T.
    We characterize diagonal and off-diagonal anharmonicities of N-H stretching vibrations in adenosine and thymidine monomers and in A•T-base pairs in chloroform solution, showing the important role of coupling between vibrationally excited N-H stretching states.
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    Probing nucleobase photoprotection with soft x-rays
    (Les Ulis : EDP Sciences, 2013) McFarland, B.K.; Farrell, J.P.; Berrah, N.; Bostedt, C.; Bozek, J.; Bucksbaum, P.H.; Coffee, R.; Cryan, J.; Fang, L.; Feifel, R.; Gaffney, K.; Glownia, J.; Martinez, T.; Mucke, M.; Murphy, B.; Miyabe, S.; Natan, A.; Osipov, T.; Petrovic, V.; Schorb, S.; Schultz, T.; Spector, L.; Tarantelli, F.; Tenney, I.; Wang, S.; White, W.; White, J.; Gühr, M.
    Nucleobases absorb strongly in the ultraviolet region, leading to molecular excitation into reactive states. The molecules avoid the photoreactions by funnelling the electronic energy into less reactive states on an ultrafast timescale via non-Born-Oppenheimer dynamics. Current theory on the nucleobase thymine discusses two conflicting pathways for the photoprotective dynamics. We present our first results of our free electron laser based UV-pump soft x-ray-probe study of the photoprotection mechanism of thymine. We use the high spatial sensitivity of the Auger electrons emitted after the soft x-ray pulse induced core ionization. Our transient spetra show two timescales on the order of 200 fs and 5 ps, in agreement with previous (all UV) ultrafast experiments. The timescales appear at different Auger kinetic energies which will help us to decipher the molecular dynamics.
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    Ultrafast charge relocation in an ionic crystal probed by femtosecond x-ray powder diffraction
    (Les Ulis : EDP Sciences, 2013) Woerner, M.; Zamponi, F.; Rothhardt, P.; Stingl, J.; Elsaesser, T.
    Transient electron density maps of potassium dihydrogen phosphate(KH 2PO4, KDP) are derived from femtosecond x-ray powder diffraction patterns. Upon photoexcitation, the low-frequency TO soft mode is elongated impulsively and modulates the electronic charge distribution on the length scale of interatomic distances, much larger than the vibrational amplitude of the nuclear motion. The results demonstrate a charge transfer from the volumes around the P-atoms to those containing the O - H·· ·O units and a quadrupolar distortion of the K+ charge distribution. This behavior reflects the interplay of nuclear motions and electric polarizations in the ionic crystal lattice.
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    Ultrafast proton coupled electron transfer (PCET) dynamics in 9-anthranol-aliphatic amine system
    (Les Ulis : EDP Sciences, 2013) Ghosh, H.N.; Adamczyk, K.; Verma, S.; Dreyer, J.; Nibbering, E.T.J.
    Femtosecond infrared absorption studies strongly suggest that photoexcited 9-anthranol takes part in an ultrafast electron transfer (ET) reaction in electron-donating triethylamine solvent, but that ultrafast proton coupled electron transfer (PCET) occurs in diethylamine solvent.
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    Femtosecond x-ray diffraction using the rotating crystal method
    (Les Ulis : EDP Sciences, 2013) Freyer, B.; Stingl, J.; Zamponi, F.; Woerner, M.; Elsaesser, T.
    We demonstrate the rotating-crystal method in femtosecond x-ray diffraction. Structural dynamics of a photoexcited bismuth crystal is mapped in a pump-probe scheme by measuring intensity changes of many Bragg reflections simultaneously.
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    Chirped auger electron emission due to field-assisted post-collision interaction
    (Les Ulis : EDP Sciences, 2013) Schütte, B.; Bauch, S.; Frühling, U.; Wieland, M.; Gensch, M.; Plönjes, E.; Gaumnitz, T.; Azima, A.; Bonitz, M.; Drescher, M.
    We have investigated the Auger decay in the temporal domain by applying a terahertz streaking light field. Xenon and krypton atoms were studied by implementing the free-electron laser in Hamburg (FLASH) as well as a source of high-order harmonic radiation combined with terahertz pulses from an optical rectification source. The observed linewidth asymmetries in the streaked spectra suggest a chirped Auger electron emission which is understood in terms of field-assisted post-collision interaction. The experimentally obtained results agree well with model calculations.
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    Ultrafast OH-stretching frequency shifts of hydrogen-bonded 2-naphthol photoacid-base complexes in solution
    (Les Ulis : EDP Sciences, 2013) Prémont-Schwarz, M.; Xiao, D.; Sekharan, S.; Batista, V.S.; Nibbering, E.T.J.
    We characterize the transient solvent-dependent OH-stretching frequency shifts of photoacid 2-naphthol hydrogen-bonded with CH3CN in the S0- and S1-states using a combined experimental and theoretical approach, and disentangle specific hydrogen-bonding contributions from nonspecific dielectric response.
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    Excited state dynamics of liquid water near the surface
    (Les Ulis : EDP Sciences, 2013) Buchner, F.; Ritze, H.-H.; Beutler, M.; Schultz, T.; Hertel, I.-V.; Lübcke, A.
    Time resolved photoelectron spectroscopy explores the excited state dynamics of liquid water in presence of cations close to the surface. A transient hydrated electroncation complex is observed.