@article{BeyeAnniyevCoffeeetal.2013,
  author    = {Beye, Martin and Anniyev, Toyli and Coffee, Ryan and Dell'Angela, Martina and F{\"o}hlisch, Alexander and Gladh, J. and Katayama, T. and Kaya, S. and Krupin, O. and Mogelhoj, A. and Nilsson, A. and Nordlund, D. and Norskov, J. K. and Oberg, H. and Ogasawara, H. and Pettersson, Lars G. M. and Schlotter, W. F. and Sellberg, J. A. and Sorgenfrei, Florian and Turner, J. J. and Wolf, M. and Wurth, Wilfried and Ostrom, H.},
  title     = {Selective ultrafast probing of transient hot chemisorbed and precursor States of CO on Ru(0001)},
  series = {Physical review letters},
  volume    = {110},
  journal   = {Physical review letters},
  number    = {18},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {0031-9007},
  doi       = {10.1103/PhysRevLett.110.186101},
  pages     = {6},
  year      = {2013},
  abstract  = {We have studied the femtosecond dynamics following optical laser excitation of CO adsorbed on a Ru surface by monitoring changes in the occupied and unoccupied electronic structure using ultrafast soft x-ray absorption and emission. We recently reported [M. Dell'Angela et al. Science 339, 1302 (2013)] a phonon-mediated transition into a weakly adsorbed precursor state occurring on a time scale of >2 ps prior to desorption. Here we focus on processes within the first picosecond after laser excitation and show that the metal-adsorbate coordination is initially increased due to hot-electron-driven vibrational excitations. This process is faster than, but occurs in parallel with, the transition into the precursor state. With resonant x-ray emission spectroscopy, we probe each of these states selectively and determine the respective transient populations depending on optical laser fluence. Ab initio molecular dynamics simulations of CO adsorbed on Ru(0001) were performed at 1500 and 3000 K providing insight into the desorption process.},
  language  = {en}
}
@article{Dell'AngelaAnniyevBeyeetal.2015,
  author    = {Dell'Angela, Martina and Anniyev, Toyli and Beye, Martin and Coffee, Ryan and F{\"o}hlisch, Alexander and Gladh, J{\"o}rgen and Kaya, Sarp and Katayama, Tetsuo and Krupin, Oleg and Nilsson, Anders and Nordlund, Dennis and Schlotter, William F. and Sellberg, Jonas A. and Sorgenfrei, Florian and Turner, Joshua J. and {\"O}str{\"O}m, Henrik and Ogasawara, Hirohito and Wolf, Martin and Wurth, Wilfried},
  title     = {Vacuum space charge effects in sub-picosecond soft X-ray photoemission on a molecular adsorbate layer},
  series = {Structural dynamics},
  volume    = {2},
  journal   = {Structural dynamics},
  number    = {2},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {2329-7778},
  doi       = {10.1063/1.4914892},
  pages     = {10},
  year      = {2015},
  abstract  = {Vacuum space charge induced kinetic energy shifts of O 1s and Ru 3d core levels in femtosecond soft X-ray photoemission spectra (PES) have been studied at a free electron laser (FEL) for an oxygen layer on Ru(0001). We fully reproduced the measurements by simulating the in-vacuum expansion of the photoelectrons and demonstrate the space charge contribution of the high-order harmonics in the FEL beam. Employing the same analysis for 400 nm pump-X-ray probe PES, we can disentangle the delay dependent Ru 3d energy shifts into effects induced by space charge and by lattice heating from the femtosecond pump pulse. (C) 2015 Author(s).},
  language  = {en}
}