Regensburg 2019 – wissenschaftliches Programm
PLV XI: Plenarvortrag
Donnerstag, 4. April 2019, 08:30–09:15, H1
Beyond the molecular movie: The ultrafast electronic structure view of surface dynamics — •Martin Wolf — Fritz Haber Institute of the Max Planck Society, 14195 Berlin, Germany
In a Born-Oppenheimer description, atomic motions evolve across a potential energy surface determined by the occupation of electronic states as a function of nuclear coordinates. A key goal of structural dynamics is therefore to record a "molecular movie" of the atom positions. Ultrafast photo-induced phase transitions provide a test case for how the forces and resulting nuclear motion along the reaction co-ordinate originate from a non-equilibrium population of excited electronic states. Moreover, small changes of nuclear positions in solids can correlate with dramatic electronic structure changes (e.g. conductivity). In this talk I discuss recent advances in time-resolved spectroscopy allowing for direct probing of the underlying fundamental steps of ultrafast non-equilibrium dynamics of solids and surfaces like ultrafast phase transitions, coherent lattice excitations or chemical reactions at surfaces. Utilizing photoemission with femtosecond XUV laser pulses (trARPES), we obtain direct access to the transient electronic structure during the ultrafast phase transition in indium nanowires on Si(111) and lay out a detailed reaction pathway. Experiments at the X-ray free electron laser LCLS performed with time-resolved resonant inelastic x-ray scattering (trRIXS) provide direct insight into chemical bond formation in ultrafast surface reactions. Finally I will discuss recent attempts to access the space-time limit in surface dynamics using time-resolved scanning probe techniques.