Spatial distributions of desorbing products in steady-state NO and N2O reductions on Pd(110).
The angular and velocity distributions of desorbing product N(2) were examined over the crystal azimuth in steady-state NO+CO and N(2)O+CO reactions on Pd(110) by cross-correlation time-of-flight techniques. At surface temperatures below 600 K, N(2) desorption in both reactions splits into two directional lobes collimated along 41 degrees -45 degrees from the surface normal toward the [001] and [001] directions. Above 600 K, the normally directed N(2) desorption is enhanced in the NO reduction. Each product desorption component, as well as CO(2), shows a fairly asymmetric distribution about its collimation axis. Two factors, i.e., the anisotropic site structures and the reactant orientation and movements, are operative to induce such asymmetry, depending on the product emission mechanism.
Effect of co-adsorbed CO and reaction temperature on the dynamics of N2 desorption under steady-state N2O-CO reaction on Rh(110).
We have investigated the effect of co-absorbed CO and reaction temperature on the angular distribution of N(2) desorption by N(2)O decomposition under the steady state of N(2)O-CO reaction on Rh(110). Spatial distributions of desorbing product N(2) emission have been measured at various surface temperatures and CO coverages. The decomposed N(2) collimates at 48°-61° off normal in the parallel plane to [001] and [110] directions, indicating that adsorbed N(2)O just before the decomposition is oriented along the [001] direction. Although the inclined and collimated N(2) desorption is always observed at any steady-state CO coverage and reaction temperature, the shape of the collimated N(2) distribution varied dependent on the co-adsorbed CO coverage. The distribution becomes sharp and shifts toward the surface normal direction with increasing CO coverage. These effects of adsorbed CO on the angular distribution of N(2) are interpreted by the collision of desorbed N(2) with co-adsorbed CO.
Some recent investigations of adsorbate/metal interactions by electron energy loss spectroscopy
Abstract In this paper, an attempt is made to examine the role of electron energy loss spectroscopy (EELS) in the range of techniques available in surface chemistry. The strength of the method lies in the relatively straightforward way in which adsorbeb species can be identified. The different scattering mechanisms, each with their associated selection rules, can be exploited to give structural information about the adsorbate/substrate system. These points are discussed and illustrated with examples from recent work at Liverpool. To exemplify the broad range of EELS reference is made to the following systems H/W{100}, HCO − 2 /Pt{110} and C 5 H 5 N/Pt{110}.