The decomposition of nitrogen oxides on Pd(110); An angular and velocity distribution study of desorbing product

摘要

Angular and velocity distributions of desorbing N_2,N_2O, and NO molecules were studied in the decomposition ofNO and N_2O on a palladium (110) surface at both thermaldesorption and steady state conditions by means of a cross-correlation time-of-flight techniques. In TD measurements, theresults of N_2 desorption were very similar in bothdecompositions of NO and N_2O although the desorption peakedround 500 K in the NO decomposition, and below 180 K in theother. Desorbing N_2 molecules are characterized by a sharp off-normal emission in a plane along the (001) direction and thehyperthermal velocity with the mean translational energy of 0.47-0.22 eV. The desorption of N_2O showed a cosine angulardistribution and a Maxwellian velocity distribution at the surfacetemperature, indicating a complete accommodation with thesurface. Similar dosorption dynamics was confirmed in SSmeasurement. It is concluded that N_2O produced on the surfaceis the intermediate for the decomposition of NO on Pd (110).