Electron and light induced manipulation of single molecules

The electrons of the tip of a low temperature scanning tunneling microscope are used to alter individual molecules. Apart from more simple surface processes as diffusion, rotation, and dissociation of molecule, we have concentrated on more complex processes as hydrogen bond rearrangement and isomerization reactions. The principle feasibility of the processes was demonstrated. Moreover, the energetic reaction thresholds were determined. This allowed to determine the underlying excitation mechanisms.Furthermore, we developed a unique combination of a low temperature scanning tunneling microscope with a femto-second laser. The coupling of the laser beam into the tunneling gap is achieved. The laser induces in the surface energetic electrons that may lead to similar processes to the adsorbed molecules as the electrons from a scanning tunneling microscope tip. So far, hydrogen bond rearrangement, CO Diffusion and CO2 production were demonstrated and partly modeled quantitatively. In future, a two-pulse correlation experiment will lead to sub-ps time resolution of the surface processes. This combination will give unprecedented insight into the local dependence of non-adiabatic reactions on surfaces.