@article{ObergGladhAnniyevetal.2015,
  author    = {Oberg, H. and Gladh, J{\"o}rgen and Anniyev, Toyli and Beye, Martin and Coffee, Ryan and F{\"o}hlisch, Alexander and Katayama, T. and Kaya, Sarp and LaRue, Jerry and Mogelhoj, Andreas and Nordlund, Dennis and Ogasawara, Hirohito and Schlotter, William F. and Sellberg, Jonas A. and Sorgenfrei, Nomi and Turner, Joshua J. and Wolf, Martin and Wurth, W. and Ostrom, Henrik and Nilsson, Anders and Norskov, Jens K. and Pettersson, Lars G. M.},
  title     = {Optical laser-induced CO desorption from Ru(0001) monitored with a free-electron X-ray laser: DFT prediction and X-ray confirmation of a precursor state},
  series = {Surface science},
  volume    = {640},
  journal   = {Surface science},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0039-6028},
  doi       = {10.1016/j.susc.2015.03.011},
  pages     = {80 -- 88},
  year      = {2015},
  abstract  = {We present density functional theory modeling of time-resolved optical pump/X-ray spectroscopic probe data of CO desorption from Ru(0001). The BEEF van der Waals functional predicts a weakly bound state as a precursor to desorption. The optical pump leads to a near-instantaneous (<100 fs) increase of the electronic temperature to nearly 7000 K. The temperature evolution and energy transfer between electrons, substrate phonons and adsorbate is described by the two-temperature model and found to equilibrate on a timescale of a few picoseconds to an elevated local temperature of similar to 2000K. Estimating the free energy based on the computed potential of mean force along the desorption path, we find an entropic barrier to desorption (and by time-reversal also to adsorption). This entropic barrier separates the chemisorbed and precursor states, and becomes significant at the elevated temperature of the experiment (similar to 1.4 eV at 2000 K). Experimental pump-probe X-ray absorption/X-ray emission spectroscopy indicates population of a precursor state to desorption upon laser-excitation of the system (Dell'Angela et al., 2013). Computing spectra along the desorption path confirms the picture of a weakly bound transient state arising from ultrafast heating of the metal substrate. (C) 2015 Elsevier B.V. All rights reserved.},
  language  = {en}
}
@article{KatayamaAnniyevBeyeetal.2013,
  author    = {Katayama, T. and Anniyev, Toyli and Beye, Martin and Coffee, Ryan and Dell'Angela, M. and F{\"o}hlisch, Alexander and Gladh, J. and Kaya, S. and Krupin, O. and Nilsson, A. and Nordlund, D. and Schlotter, W. F. and Sellberg, J. A. and Sorgenfrei, Nomi and Turner, J. J. and Wurth, W. and {\"O}str{\"o}m, H. and Ogasawara, H.},
  title     = {Ultrafast soft X-ray emission spectroscopy of surface adsorbates using an X-ray free electron laser},
  series = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy},
  volume    = {187},
  journal   = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy},
  number    = {1},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0368-2048},
  doi       = {10.1016/j.elspec.2013.03.006},
  pages     = {9 -- 14},
  year      = {2013},
  abstract  = {We report on an experimental system designed to probe chemical reactions on solid surfaces on a sub-picosecond timescale using soft X-ray emission spectroscopy at the Linac Coherent Light Source (LCLS) free electron laser (FEL) at the SLAC National Accelerator Laboratory. We analyzed the O 1s X-ray emission spectra recorded from atomic oxygen adsorbed on a Ru(0001) surface at a synchrotron beamline (SSRL, BL13-2) and an FEL beamline (LCLS, SXR). We have demonstrated conditions that provide negligible amount of FEL induced damage of the sample. In addition we show that the setup is capable of tracking the temporal evolution of electronic structure during a surface reaction of submonolayer quantities of CO molecules desorbing from the surface.},
  language  = {en}
}
@article{Dell'AngelaAnniyevBeyeetal.2013,
  author    = {Dell'Angela, M. and Anniyev, Toyli and Beye, Martin and Coffee, Ryan and F{\"o}hlisch, Alexander and Gladh, J. and Katayama, T. and Kaya, S. and Krupin, O. and LaRue, J. and Mogelhoj, A. and Nordlund, D. and Norskov, J. K. and Oberg, H. and Ogasawara, H. and Ostrom, H. and Pettersson, Lars G. M. and Schlotter, W. F. and Sellberg, J. A. and Sorgenfrei, Nomi and Turner, J. J. and Wolf, M. and Wurth, W. and Nilsson, A.},
  title     = {Real-time observation of surface bond breaking with an X-ray Laser},
  series = {Science},
  volume    = {339},
  journal   = {Science},
  number    = {6125},
  publisher = {American Assoc. for the Advancement of Science},
  address   = {Washington},
  issn      = {0036-8075},
  doi       = {10.1126/science.1231711},
  pages     = {1302 -- 1305},
  year      = {2013},
  abstract  = {We used the Linac Coherent Light Source free-electron x-ray laser to probe the electronic structure of CO molecules as their chemisorption state on Ru(0001) changes upon exciting the substrate by using a femtosecond optical laser pulse. We observed electronic structure changes that are consistent with a weakening of the CO interaction with the substrate but without notable desorption. A large fraction of the molecules (30\%) was trapped in a transient precursor state that would precede desorption. We calculated the free energy of the molecule as a function of the desorption reaction coordinate using density functional theory, including van der Waals interactions. Two distinct adsorption wells-chemisorbed and precursor state separated by an entropy barrier-explain the anomalously high prefactors often observed in desorption of molecules from metals.},
  language  = {en}
}