N Desorption in the Decomposition of Adsorbed NO on Rh(110)

The decomposition of NO(a) was studied on Rh(110) at 95-200 K through the analysis of the angular distributions of desorbing N by means of angle-resolved thermal desorption. NO(a) was highly decomposed during the heating procedures, emitting N(g) and releasing O(a). N desorption showed four peaks, at 105-110 K (β-N), 120-130 K (β-N ), 140-150 K (β-N), and 160-165 K (β-N). The appearance of each peak was sensitive to annealing after oxygen adsorption and also to the amount of NO exposure. The β-N peak was major at low N O exposures and showed a cosine distribution. On the other hand, β-N and β-N on an oxygen-modified surface revealed inclined and sharp collimation at around 30° off the surface normal in the plane along the [001] direction, whereas β-N on a clean surface collimated at around 70° off the surface normal, close to the [001] direction. An inclined or surface-parallel form of adsorbed NO was proposed as the precursor for inclined N desorption.