Structural dynamics of surfaces by ultrafast electron crystallography: Experimental and multiple scattering theory
Recent studies in ultrafast electron crystallography (UEC) using a reflection diffraction geometry have enabled the investigation of a wide range of phenomena on the femtosecond and picosecond time scales. In all these studies, the analysis of the diffraction patterns and their temporal change after excitation was performed within the kinematical scattering theory. In this contribution, we address the question, to what extent dynamical scattering effects have to be included in order to obtain quantitative information about structural dynamics. We discuss different scattering regimes and provide diffraction maps that describe all essential features of scatterings and observables. The effects are quantified by dynamical scattering simulations and examined by direct comparison to the results of ultrafast electron diffraction experiments on an in situ prepared Ni(100) surface, for which structural dynamics can be well described by a two-temperature model. We also report calculations for graphite surfaces. The theoretical framework provided here allows for further UEC studies of surfaces especially at larger penetration depths and for those of heavy-atom materials.
Additional Information© 2011 American Institute of Physics. Received 1 September 2011; accepted 2 November 2011; published online 2 December 2011. This work was supported by the National Science Foundation (NSF) and the Air Force Office of Scientific Research (USAFOSR) in the Center for Physical Biology at Caltech supported by the Gordon and Betty Moore Foundation. One of the authors (S.S.) gratefully acknowledges a scholarship from the Alexander von Humboldt-Foundation.
Published - Schaefer2011p16837J_Chem_Phys.pdf