Dynamics of charge transfer states on metal surfaces: The competition between reactivity and quenching

The dynamics of excited states of adsorbates on surfaces caused by charge t ransfer is studied. Both negative and positive charge transfer processes ar e possible. In particular we are interested in positive charge transfer fro m a metal surface to molecular or atomic oxygen adsorbed on the surface. On ce the negatively charged oxygen on the surface loses an electron it become s chemically activated. The ability of this species to react depends on the quenching time or back transfer. The analysis of these processes is based on a set of diabatic potential energy surfaces each representing a differen t charged oxygen species. The dynamics is followed by solving the multichan nel time-dependent Schrodinger equation or Liouville von Neumann equation. Due to the nonadiabatic character of these reactions large isotope effects are predicted.