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] dir ection (along the steps) after adsorption of NO at 320 K. The N-2 deso rption 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 d esorption 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) indicate s desorption of N-2 from the boundary between the (111) terraces and t he vacant (100) steps. The spatial distribution of NO desorbing from t he Rh(533) surface at 420 K obeyed (1.5)theta, indicative of desorptio n normal to the crystal surface. Contrary to this, the spatial cos dis tribution of the desorption of NO molecules produced by the recombinat ion reaction of adsorbed N and O desorbed at 550 K exhibits a peak int ensity at theta=+15 degrees (normal to the (111) terraces). (C) 1997 A merican Institute of Physics.