TY  - JOUR
A1  - Kunnus, Kristjan
A1  - Josefsson, I.
A1  - Rajkovic, Ivan
A1  - Schreck, Simon
A1  - Quevedo, Wilson
A1  - Beye, Martin
A1  - Weniger, C.
A1  - Gruebel, S.
A1  - Scholz, M.
A1  - Nordlund, D.
A1  - Zhang, W.
A1  - Hartsock, R. W.
A1  - Gaffney, K. J.
A1  - Schlotter, W. F.
A1  - Turner, J. J.
A1  - Kennedy, B.
A1  - Hennies, F.
A1  - de Groot, F. M. F.
A1  - Techert, S.
A1  - Odelius, Michael
A1  - Wernet, Ph.
A1  - Föhlisch, Alexander
T1  - Identification of the dominant photochemical pathways and mechanistic insights to the ultrafast ligand exchange of Fe(CO)(5) to Fe(CO)(4)EtOH
JF  - Structural dynamics
N2  - We utilized femtosecond time-resolved resonant inelastic X-ray scattering and ab initio theory to study the transient electronic structure and the photoinduced molecular dynamics of a model metal carbonyl photocatalyst Fe(CO)(5) in ethanol solution. We propose mechanistic explanation for the parallel ultrafast intra-molecular spin crossover and ligation of the Fe(CO)(4) which are observed following a charge transfer photoexcitation of Fe(CO)(5) as reported in our previous study [ Wernet et al., Nature 520, 78 (2015)]. We find that branching of the reaction pathway likely happens in the (1)A(1) state of Fe(CO)(4). A sub-picosecond time constant of the spin crossover from B-1(2) to B-3(2) is rationalized by the proposed B-1(2) -> (1)A(1) -> B-3(2) mechanism. Ultrafast ligation of the B-1(2) Fe(CO)(4) state is significantly faster than the spin-forbidden and diffusion limited ligation process occurring from the B-3(2) Fe(CO)(4) ground state that has been observed in the previous studies. We propose that the ultrafast ligation occurs via B-1(2) -> (1)A(1) -> (1)A'Fe(CO)(4)EtOH pathway and the time scale of the (1)A(1) Fe(CO)(4) state ligation is governed by the solute-solvent collision frequency. Our study emphasizes the importance of understanding the interaction of molecular excited states with the surrounding environment to explain the relaxation pathways of photoexcited metal carbonyls in solution. (C) 2016 Author(s).
Y1  - 2016
U6  - https://doi.org/10.1063/1.4941602
SN  - 2329-7778
VL  - 3
PB  - American Institute of Physics
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ostrom, H.
A1  - Oberg, H.
A1  - Xin, H.
A1  - Larue, J.
A1  - Beye, Martin
A1  - Gladh, J.
A1  - Ng, M. L.
A1  - Sellberg, J. A.
A1  - Kaya, S.
A1  - Mercurio, G.
A1  - Nordlund, D.
A1  - Hantschmann, Markus
A1  - Hieke, F.
A1  - Kuehn, D.
A1  - Schlotter, W. F.
A1  - Dakovski, G. L.
A1  - Turner, J. J.
A1  - Minitti, M. P.
A1  - Mitra, A.
A1  - Moeller, S. P.
A1  - Föhlisch, Alexander
A1  - Wolf, M.
A1  - Wurth, W.
A1  - Persson, Mats
A1  - Norskov, J. K.
A1  - Abild-Pedersen, Frank
A1  - Ogasawara, Hirohito
A1  - Pettersson, Lars G. M.
A1  - Nilsson, A.
T1  - Probing the transition state region in catalytic CO oxidation on Ru
JF  - Science
N2  - Femtosecond x-ray laser pulses are used to probe the carbon monoxide (CO) oxidation reaction on ruthenium (Ru) initiated by an optical laser pulse. On a time scale of a few hundred femtoseconds, the optical laser pulse excites motions of CO and oxygen (O) on the surface, allowing the reactants to collide, and, with a transient close to a picosecond (ps), new electronic states appear in the OK-edge x-ray absorption spectrum. Density functional theory calculations indicate that these result from changes in the adsorption site and bond formation between CO and O with a distribution of OC-O bond lengths close to the transition state (TS). After 1 ps, 10% of the CO populate the TS region, which is consistent with predictions based on a quantum oscillator model.
Y1  - 2015
U6  - https://doi.org/10.1126/science.1261747
SN  - 0036-8075
SN  - 1095-9203
VL  - 347
IS  - 6225
SP  - 978
EP  - 982
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - JOUR
A1  - Pontius, N.
A1  - Kachel, T.
A1  - Schüssler-Langeheine, C.
A1  - Schlotter, W. F.
A1  - Beye, Martin
A1  - Sorgenfrei, Florian
A1  - Chang, C. F.
A1  - Föhlisch, Alexander
A1  - Wurth, W.
A1  - Metcalf, P.
A1  - Leonov, I.
A1  - Yaresko, A.
A1  - Stojanovic, N.
A1  - Berglund, Martin
A1  - Guerassimova, N.
A1  - Duesterer, S.
A1  - Redlin, H.
A1  - Duerr, H. A.
T1  - Time-resolved resonant soft x-ray diffraction with free-electron lasers  femtosecond dynamics across the Verwey transition in magnetite
JF  - Applied physics letters
N2  - Resonant soft x-ray diffraction (RSXD) with femtosecond (fs) time resolution is a powerful tool for disentangling the interplay between different degrees of freedom in strongly correlated electron materials. It allows addressing the coupling of particular degrees of freedom upon an external selective perturbation, e. g., by an optical or infrared laser pulse. Here, we report a time-resolved RSXD experiment from the prototypical correlated electron material magnetite using soft x-ray pulses from the free-electron laser FLASH in Hamburg. We observe ultrafast melting of the charge-orbital order leading to the formation of a transient phase, which has not been observed in equilibrium.
Y1  - 2011
U6  - https://doi.org/10.1063/1.3584855
SN  - 0003-6951
VL  - 98
IS  - 18
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Dell'Angela, M.
A1  - Anniyev, Toyli
A1  - Beye, Martin
A1  - Coffee, Ryan
A1  - Föhlisch, Alexander
A1  - Gladh, J.
A1  - Katayama, T.
A1  - Kaya, S.
A1  - Krupin, O.
A1  - LaRue, J.
A1  - Mogelhoj, A.
A1  - Nordlund, D.
A1  - Norskov, J. K.
A1  - Oberg, H.
A1  - Ogasawara, H.
A1  - Ostrom, 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, W.
A1  - Nilsson, A.
T1  - Real-time observation of surface bond breaking with an X-ray Laser
JF  - Science
N2  - 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.
Y1  - 2013
U6  - https://doi.org/10.1126/science.1231711
SN  - 0036-8075
VL  - 339
IS  - 6125
SP  - 1302
EP  - 1305
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - JOUR
A1  - Katayama, T.
A1  - Anniyev, Toyli
A1  - Beye, Martin
A1  - Coffee, Ryan
A1  - Dell'Angela, M.
A1  - Föhlisch, Alexander
A1  - Gladh, J.
A1  - Kaya, S.
A1  - Krupin, O.
A1  - Nilsson, A.
A1  - Nordlund, D.
A1  - Schlotter, W. F.
A1  - Sellberg, J. A.
A1  - Sorgenfrei, Florian
A1  - Turner, J. J.
A1  - Wurth, W.
A1  - Öström, H.
A1  - Ogasawara, H.
T1  - Ultrafast soft X-ray emission spectroscopy of surface adsorbates using an X-ray free electron laser
JF  - Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy
N2  - 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.
KW  - X-ray emission spectroscopy
KW  - Surface science
KW  - Free electron laser
KW  - Ultrafast
Y1  - 2013
U6  - https://doi.org/10.1016/j.elspec.2013.03.006
SN  - 0368-2048
VL  - 187
IS  - 1
SP  - 9
EP  - 14
PB  - Elsevier
CY  - Amsterdam
ER  - 
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  - de Jong, S.
A1  - Kukreja, R.
A1  - Trabant, C.
A1  - Pontius, N.
A1  - Chang, C. F.
A1  - Kachel, T.
A1  - Beye, Martin
A1  - Sorgenfrei, Florian
A1  - Back, C. H.
A1  - Braeuer, B.
A1  - Schlotter, W. F.
A1  - Turner, J. J.
A1  - Krupin, O.
A1  - Doehler, M.
A1  - Zhu, D.
A1  - Hossain, M. A.
A1  - Scherz, A. O.
A1  - Fausti, D.
A1  - Novelli, F.
A1  - Esposito, M.
A1  - Lee, W. S.
A1  - Chuang, Y. D.
A1  - Lu, D. H.
A1  - Moore, R. G.
A1  - Yi, M.
A1  - Trigo, M.
A1  - Kirchmann, P.
A1  - Pathey, L.
A1  - Golden, M. S.
A1  - Buchholz, Marcel
A1  - Metcalf, P.
A1  - Parmigiani, F.
A1  - Wurth, W.
A1  - Föhlisch, Alexander
A1  - Schuessler-Langeheine, Christian
A1  - Duerr, H. A.
T1  - Speed limit of the insulator-metal transition in magnetite
JF  - Nature materials
N2  - As the oldest known magnetic material, magnetite (Fe3O4) has fascinated mankind for millennia. As the first oxide in which a relationship between electrical conductivity and fluctuating/localized electronic order was shown(1), magnetite represents a model system for understanding correlated oxides in general. Nevertheless, the exact mechanism of the insulator-metal, or Verwey, transition has long remained inaccessible(2-8). Recently, three- Fe- site lattice distortions called trimeronswere identified as the characteristic building blocks of the low-temperature insulating electronically ordered phase(9). Here we investigate the Verwey transition with pump- probe X- ray diffraction and optical reflectivity techniques, and show how trimerons become mobile across the insulator-metal transition. We find this to be a two- step process. After an initial 300 fs destruction of individual trimerons, phase separation occurs on a 1.5 +/- 0.2 ps timescale to yield residual insulating and metallic regions. This work establishes the speed limit for switching in future oxide electronics(10).
Y1  - 2013
U6  - https://doi.org/10.1038/NMAT3718
SN  - 1476-1122
SN  - 1476-4660
VL  - 12
IS  - 10
SP  - 882
EP  - 886
PB  - Nature Publ. Group
CY  - London
ER  -