INTERACTION OF CO WITH O, N, AND NO ON RU(001) - EVIDENCE FOR BRIDGE-ADSORBED CO, SITE CHANGES, AND FORMATION OF ISOCYANATE SPECIES

In a search for the formation of interesting new molecular species, the interaction of CO with oxygen and dissociated NO on Ru(001) has been studied by using TPD, HREELS, and LEED. At 120 K, CO is adsorbed onto disordered or ordered (2 x 2) oxygen layers in a bridge form with the nu(CO) vibration at 1850 cm-1 not observed before, in addition to a linear form [nu(CO) approximately 2050 cm-1]. These two forms are observed also when CO is adsorbed onto partially or fully dissociated NO layers; some interesting interaction properties of molecular NO and CO, such as reciprocal site changes, emerge. After these N-containing coadsorbate layers are heated, a new loss peak at 2170 cm-1 appears in the temperature region 200-350 K. This peak is interpreted as due to the formation of an isocyanate (NCO) surface species. The mechanism of its formation process is discussed; it appears to consist in a reaction between N adatoms and adsorbed CO, where the latter is most likely to be the bridge species.