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

Abstract

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-N2), 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 N2O 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.