OXIDATION OF H ON RH(111) - H2O PRODUCT VELOCITY AND ANGULAR-DISTRIBUTIONS

The translational energy distribution for the H2O product from the rea ction of H-2 and O-2 on Rh(111) was measured as a function of surface temperature at two different oxygen coverages. The results are well re presented by Maxwell-Boltzmann velocity distributions significantly co oler than the surface temperature. For [O]=0.2 monolayers (ML), the pr oduct H2O is slightly faster than for [O] = 0.1 ML. The energy distrib utions are very close to those observed for the trapped and desorbed m olecules when scattering low energy H2O molecular beams from the Rh(11 1). We also measured the angular dependence of the energy and intensit y of the product H2O at T-s=650 K. The velocity distribution of the H2 O product is independent of final angle, and the relative intensities are cosine distributed. (C) 1995 American Institute of Physics.