N₂ Desorption in the Decomposition of Adsorbed N₂O on Rh(110)

The decomposition of N₂O(a) was studied on Rh(110) at 95-200 K through the analysis of the angular distributions of desorbing N₂ by means of angle-resolved thermal desorption. N₂O(a) was highly decomposed during the heating procedures, emitting N₂(g) and releasing O(a). N₂ desorption showed four peaks, at 105-110 K (β₄-N₂), 120-130 K (β₃-N ₂), 140-150 K (β₂-N₂), and 160-165 K (β₁-N₂). The appearance of each peak was sensitive to annealing after oxygen adsorption and also to the amount of N₂O exposure. The β₁-N₂ peak was major at low N ₂O exposures and showed a cosine distribution. On the other hand, β₂-N₂ and β₃-N₂ 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 β₄-N₂ 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 N₂O was proposed as the precursor for inclined N₂ desorption.