Search Results

Now showing 1 - 4 of 4
  • Item
    Experimental strategies for optical pump - Soft x-ray probe experiments at the LCLS
    (Bristol : Institute of Physics Publishing, 2014) McFarland, B.K.; Berrah, N.; Bostedt, C.; Bozek, J.; Bucksbaum, P.H.; Castagna, J.C.; Coffee, R.N.; Cryan, J.P.; Fang, L.; Farrell, J.P.; Feifel, R.; Gaffney, K.J.; Glownia, J.M.; Martinez, T.J.; Miyabe, S.; Mucke, M.; Murphy, B.; Natan, A.; Osipov, T.; Petrovic, V.S.; Schorb, S.; Schultz, T.; Spector, L.S.; Swiggers, M.; Tarantelli, F.; Tenney, I.; Wang, S.; White, J.L.; White, W.; Gühr, M.
    Free electron laser (FEL) based x-ray sources show great promise for use in ultrafast molecular studies due to the short pulse durations and site/element sensitivity in this spectral range. However, the self amplified spontaneous emission (SASE) process mostly used in FELs is intrinsically noisy resulting in highly fluctuating beam parameters. Additionally timing synchronization of optical and FEL sources adds delay jitter in pump-probe experiments. We show how we mitigate the effects of source noise for the case of ultrafast molecular spectroscopy of the nucleobase thymine. Using binning and resorting techniques allows us to increase time and spectral resolution. In addition, choosing observables independent of noisy beam parameters enhances the signal fidelity.
  • Item
    Correlated rotational alignment spectroscopy of isolated molecules and molecular mixtures
    (Les Ulis : EDP Sciences, 2013) Schröter, C.; Kosma, K.; Schultz, T.
    We present a novel multi-pulse spectroscopic method for the correlated analysis of molecular mass, rotational structure and electronic structure. First experiments investigate carbon disulfide and butadiene.
  • Item
    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.
  • Item
    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.