XUV laser stimulated desorption at FLASH

The XUV laser desorption experiments aim to an understanding of the dynamics of electron transfer processes at surfaces initiated by high photon energies. The chemistry of hydrogen on graphitic and silicate surfaces is of central importance for the generation of molecular hydrogen and hydrogen containing molecules in interstellar molecular clouds [1]. With the short wavelengths and thus high photon energies of the FEL electronically excited states can be populated and involved in these processes which are not accessible with radiation of less energy. This leads to a better understanding especially of the ultrafast high-energy component of the electron interaction. The tunability of the FEL radiation is an essential feature in gaining insight in the topology of the involved electronic states and potentials of substrates and adsorbates and their dispersion, quantities largely unknown for many systems. These fundamental questions shall be studied on model systems. In November/December 2005 and September 2006 we used the beamtime at beamline 1 (BL1) for investigations of laser induced desorption of NO, atomic hydrogen, and atomic deuterium from a highly oriented pyrolytic graphite (HOPG) surface. Here we present part of these results.