THERMAL AND PHOTOINDUCED CHEMISTRY OF MO(CO)(6) ON CLEAN AND CHEMICALLY-MODIFIED RU(001)

The thermal and photoinduced desorption and decomposition of Mo(CO)(6) were studied on the clean and chemically modified Ru(001) surfaces. M o(GO)(6) adsorbs dissociatively on the clean Ru(001) forming CO and Mo (CO)(x) fragments. The first and second monolayers of molecularly adso rbed Mo(CO)(6) desorb at 215 and 210 K, respectively. Chemical modific ations of the surface with O- and S-adatoms strongly influence the ads orption of Mo(CO)(6) by both stabilizing the first molecular layer of Mo(CO)(6) and by suppressing the decomposition. Photochemical studies were conducted for one monolayer of molecular Mo(CO), adsorbed on the clean as well as the O- and CO-saturated Ru(001) surfaces by UV irradi ation at various wavelengths (290-390 nm). Both photodesorption and ph otodecomposition through the direct UV absorption by the adsorbed Mo(C O)(6) molecule were observed. However, the extent of photodecompositio n was considerably enhanced on the CO-presaturated surface in comparis on to the clean Ru(001). This is probably due to the decrease in the q uenching of electronically excited Mo(CO)(6) by the presence of a laye r of adsorbed CO on the surface.