REACTION OF COADSORBED NITRIC-OXIDE AND NITROGEN-ATOMS ON RH(111)

We have studied the reaction of nitrogen atoms (N) with nitric oxide m olecules (NO) coadsorbed on a Rh(lll) catalyst in order to isolate the reaction of these two species as an elementary step (e.g., in the NO + CO reaction mechanism) and determine the products of that reaction, Electron beam dissociation of adsorbed NO was used to cleanly prepare N atom coverages between 0.05 and 0.5 monolayers. By using isotopicall y labeled NO and N reactants, we determined that NO and N react, under our conditions, to form only N2O. In contrast to previous reports, we see no evidence that suggests that NO and N can react to form N-2 as a product. In complementary experiments, we have completed computer mo deling of an NO temperature-programmed desorption experiment. These si mulations show that NO dissociation rates in the high NO coverage limi t are as much as 500 times slower than previously reported dissociatio n in the low coverage limit. (C) 1995 Academic Press, Inc.