Spatial distribution of N-2 and NO desorbing from a Rh(533) surface

The spatial distribution of N-2 and NO desorbing from Rh(533), Rh(S)-[4(111)x(100)], was measured along the [<6(5)over bar>(5) over bar] direction (along the steps) after adsorption of NO at 320 K. The N-2 desorption at 450 K and 600 K showed a specific spatial distribution, that is, there was no peak either normal to the (111) terraces (theta=+14.4 degrees) or normal to the (100) steps (theta=-40.3 degrees), but a desorption maximum around theta=-15 degrees. Integrated TPD spectra of N-2 from the NO preadsorbed Rh(533) surface were very similar to those on Rh(111), but the spatial distribution of N-2 from Rh(533) indicates desorption of N-2 from the boundary between the (111) terraces and the vacant (100) steps. The spatial distribution of NO desorbing from the Rh(533) surface at 420 K obeyed (1.5)theta, indicative of desorption normal to the crystal surface. Contrary to this, the spatial cos distribution of the desorption of NO molecules produced by the recombination reaction of adsorbed N and O desorbed at 550 K exhibits a peak intensity at theta=+15 degrees (normal to the (111) terraces). (C) 1997 American Institute of Physics.