Translational energy and state resolved observations of D and D2 thermally desorbing from D clusters chemisorbed on graphite.

Direct D atom desorption, as well as associative desorption of D(2) molecules are observed in thermal desorption from D atoms chemisorbed on a C(0001) surface by combining laser induced T-jumps with resonance enhanced multiphoton ionization detection. Bleaching curves suggest that different classes of chemisorbed D atom clusters are present on the initial surface. The energy resolved atomic desorption flux, obtained via time of flight techniques, compares favorably (via detailed balance) with theoretical calculations of atomic sticking. Density functional theory calculations of chemical processes (atomic desorption, atomic diffusion/cluster annealing, and associative desorption) on an extensive set of four atom H(D) clusters chemisorbed on C(0001) provide a good interpretation of the experiments. State and energy resolved D(2) desorption fluxes are compared with previous state averaged results. In combination with density functional theory calculations these measurements reveal a substantial energy loss (>1 eV) to the surface in the associative desorption.