Picosecond snapshots of the nanometer world: Filming the movement of atoms and molecules with a very special camera: time-resolved Low Energy Electron Diffraction

In order to observe phenomena on the molecular level, it is necessary to develop a technique that is sensitive to all the microscopic spatial degrees of freedom on the time scale of the molecular processes. For the case of surface physics, the standard tool for structure determination is Low-Energy-Electron-Diffraction (LEED). This technique, endowed in a so-called 'pump-probe experiment' framework has the potential to follow in real time the excitation and the relaxation dynamics at surfaces on the picosecond time scale (1 ps=10^(-15) s). This book describes the realization of the first proof-of-principle experiment for time-resolved LEED (t-LEED). The design, realization and characterization of a home-built electron gun is presented: with such a tool, a temporal resolution of few picosecond was achieved. First experiments were performed to track in real time phase transitions occuring on surfaces and dynamics of the so-called space-charge effect: the emission of electrons on a metal surface by an intense pump pulse via multi-photon absorption processes.