N2 desorption in the decomposition of adsorbed N2O on Rh(110)

The decomposition of N 2 O(a) was studied on Rh( 110) at 95-200 K through the analysis of the angular distributions of desorbing N 2 by means of angle-resolved thermal desorption. N 2 O(a) was highly decomposed during the heating procedures, emitting N 2 (g) and releasing O(a). N 2 desorption showed four peaks, at 105-110 K (β 4 -N 2 ), 120-130 K (β 3 -N 2 ), 140-150 K (β 2 -N 2 ), and 160-165 K (β 1 -N 2 ). The appearance of each peak was sensitive to annealing after oxygen adsorption and also to the amount of N 2 O exposure. The β 1 -N 2 peak was major at low N 2 O exposures and showed a cosine distribution. On the other hand, β 2 -N 2 and β 3 -N 2 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 4 -N 2 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 N 2 O was proposed as the precursor for inclined N 2 desorption.