TY  - JOUR
A1  - Beye, Martin
A1  - Anniyev, Toyli
A1  - Coffee, Ryan
A1  - Dell'Angela, Martina
A1  - Föhlisch, Alexander
A1  - Gladh, J.
A1  - Katayama, T.
A1  - Kaya, S.
A1  - Krupin, O.
A1  - Mogelhoj, A.
A1  - Nilsson, A.
A1  - Nordlund, D.
A1  - Norskov, J. K.
A1  - Oberg, H.
A1  - Ogasawara, H.
A1  - Pettersson, Lars G. M.
A1  - Schlotter, W. F.
A1  - Sellberg, J. A.
A1  - Sorgenfrei, Florian
A1  - Turner, J. J.
A1  - Wolf, M.
A1  - Wurth, Wilfried
A1  - Ostrom, H.
T1  - Selective ultrafast probing of transient hot chemisorbed and precursor States of CO on Ru(0001)
JF  - Physical review letters
N2  - 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.
Y1  - 2013
U6  - https://doi.org/10.1103/PhysRevLett.110.186101
SN  - 0031-9007
VL  - 110
IS  - 18
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Beye, Martin
A1  - Öberg, Henrik
A1  - Xin, Hongliang
A1  - Dakovski, Georgi L.
A1  - Föhlisch, Alexander
A1  - Gladh, Jorgen
A1  - Hantschmann, Markus
A1  - Hieke, Florian
A1  - Kaya, Sarp
A1  - Kühn, Danilo
A1  - LaRue, Jerry
A1  - Mercurio, Giuseppe
A1  - Minitti, Michael P.
A1  - Mitra, Ankush
A1  - Moeller, Stefan P.
A1  - Ng, May Ling
A1  - Nilsson, Anders
A1  - Nordlund, Dennis
A1  - Norskov, Jens
A1  - Öström, Henrik
A1  - Ogasawara, Hirohito
A1  - Persson, Mats
A1  - Schlotter, William F.
A1  - Sellberg, Jonas A.
A1  - Wolf, Martin
A1  - Abild-Pedersen, Frank
A1  - Pettersson, Lars G. M.
A1  - Wurth, Wilfried
T1  - Chemical Bond Activation Observed with an X-ray Laser
JF  - The journal of physical chemistry letters
N2  - The concept of bonding and antibonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Here we apply time-resolved soft X-ray spectroscopy at a free electron laser to directly observe the decreased bonding antibonding splitting following bond-activation using an ultrashort optical laser pulse.
Y1  - 2016
U6  - https://doi.org/10.1021/acs.jpclett.6b01543
SN  - 1948-7185
VL  - 7
SP  - 3647
EP  - 3651
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Dell'Angela, Martina
A1  - Anniyev, Toyli
A1  - Beye, Martin
A1  - Coffee, Ryan
A1  - Föhlisch, Alexander
A1  - Gladh, Jörgen
A1  - Kaya, Sarp
A1  - Katayama, Tetsuo
A1  - Krupin, Oleg
A1  - Nilsson, Anders
A1  - Nordlund, Dennis
A1  - Schlotter, William F.
A1  - Sellberg, Jonas A.
A1  - Sorgenfrei, Florian
A1  - Turner, Joshua J.
A1  - ÖstrÖm, Henrik
A1  - Ogasawara, Hirohito
A1  - Wolf, Martin
A1  - Wurth, Wilfried
T1  - Vacuum space charge effects in sub-picosecond soft X-ray photoemission on a molecular adsorbate layer
JF  - Structural dynamics
N2  - 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).
Y1  - 2015
U6  - https://doi.org/10.1063/1.4914892
SN  - 2329-7778
VL  - 2
IS  - 2
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Xin, Hong
A1  - LaRue, Jerry
A1  - Oberg, Henrik
A1  - Beye, Martin
A1  - Turner, J. J.
A1  - Gladh, Jörgen
A1  - Ng, May L.
A1  - Sellberg, Jonas A.
A1  - Kaya, Sarp
A1  - Mercurio, G.
A1  - Hieke, F.
A1  - Nordlund, Dennis
A1  - Schlotter, William F.
A1  - Dakovski, Georgi L.
A1  - Minitti, Michael P.
A1  - Föhlisch, Alexander
A1  - Wolf, Martin
A1  - Wurth, Wilfried
A1  - Ogasawara, Hirohito
A1  - Norskov, Jens K.
A1  - Ostrom, Henrik
A1  - Pettersson, Lars G. M.
A1  - Nilsson, Anders
A1  - Abild-Pedersen, Frank
T1  - Strong Influence of Coadsorbate Interaction on CO Desorption Dynamics on Ru(0001) Probed by Ultrafast X-Ray Spectroscopy and Ab Initio Simulations
JF  - Physical review letters
N2  - We show that coadsorbed oxygen atoms have a dramatic influence on the CO desorption dynamics from Ru(0001). In contrast to the precursor-mediated desorption mechanism on Ru(0001), the presence of surface oxygen modifies the electronic structure of Ru atoms such that CO desorption occurs predominantly via the direct pathway. This phenomenon is directly observed in an ultrafast pump-probe experiment using a soft x-ray free-electron laser to monitor the dynamic evolution of the valence electronic structure of the surface species. This is supported with the potential of mean force along the CO desorption path obtained from density-functional theory calculations. Charge density distribution and frozen-orbital analysis suggest that the oxygen-induced reduction of the Pauli repulsion, and consequent increase of the dative interaction between the CO 5 sigma and the charged Ru atom, is the electronic origin of the distinct desorption dynamics. Ab initio molecular dynamics simulations of CO desorption from Ru(0001) and oxygen-coadsorbed Ru(0001) provide further insights into the surface bond-breaking process.
Y1  - 2015
U6  - https://doi.org/10.1103/PhysRevLett.114.156101
SN  - 0031-9007
SN  - 1079-7114
VL  - 114
IS  - 15
PB  - American Physical Society
CY  - College Park
ER  -