The adsorption and reactions of NO on Ag(111) at 80 K

Abstract

The adsorption of NO on Ag(111) at 80 K has been studied by high resolution electron energy loss spectroscopy (HREELS) and thermal desorption spectroscopy (TDS). At low exposures (≤0.05 L) NO is adsorbed in part dissociatively and in part molecularly in two different threefold bridge states (in upright and bent or tilted orientation with respect to the surface normal). The NO molecules in the threefold bridge position are desorbed at 100 K. With increasing exposure the desorption temperature shifts gradually to 110 K. At medium exposures (∼0.13 L) additional NO is adsorbed molecularly in an atop position with an upright orientation in admixture with atomic N and O and molecular NO adsorbed in threefold bridge states. The NO molecules adsorbed in atop position are weakly bonded on the surface and are desorbed at about 90 K. Simultaneously, N2O is formed and adsorbed on the surface. At saturation a new bent or tilted NO species in atop position appears on the surface and the amount of N2O significantly increases. The N2O molecules are desorbed at 90, 110, and 190 K. At saturation all the NO and NO-derived species (the threefold bridge and atop states, N2O and atomic oxygen and nitrogen) coexist on Ag(111).