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  - Schreck, S.
A1  - Sorgenfrei, Florian
A1  - Trabant, C.
A1  - Pontius, N.
A1  - Schüßler-Langeheine, C.
A1  - Wurth, W.
A1  - Föhlisch, Alexander
T1  - Stimulated X-ray emission for materials science
JF  - Nature : the international weekly journal of science
N2  - Resonant inelastic X-ray scattering and X-ray emission spectroscopy can be used to probe the energy and dispersion of the elementary low-energy excitations that govern functionality in matter: vibronic, charge, spin and orbital excitations(1-7). A key drawback of resonant inelastic X-ray scattering has been the need for high photon densities to compensate for fluorescence yields of less than a per cent for soft X-rays(8). Sample damage from the dominant non-radiative decays thus limits the materials to which such techniques can be applied and the spectral resolution that can be obtained. A means of improving the yield is therefore highly desirable. Here we demonstrate stimulated X-ray emission for crystalline silicon at photon densities that are easily achievable with free-electron lasers(9). The stimulated radiative decay of core excited species at the expense of non-radiative processes reduces sample damage and permits narrow-bandwidth detection in the directed beam of stimulated radiation. We deduce how stimulated X-ray emission can be enhanced by several orders of magnitude to provide, with high yield and reduced sample damage, a superior probe for low-energy excitations and their dispersion in matter. This is the first step to bringing nonlinear X-ray physics in the condensed phase from theory(10-16) to application.
Y1  - 2013
U6  - https://doi.org/10.1038/nature12449
SN  - 0028-0836
VL  - 501
IS  - 7466
SP  - 191
EP  - +
PB  - Nature Publ. Group
CY  - London
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  -