Atomic and molecular states of oxygen chemisorbed on tungsten(112)

High-resolution electron energy-loss spectroscopy, x-ray photoemission spectroscopy, and low-energy electron diffraction have been used to characterize the adsorption of oxygen on tungsten(112) as a function of temperature and coverage. Two atomic adsorption sites are observed at 300 K, while at 100 K a molecular state is also observed. Coverage-dependent shifts in the vibrational spectra suggest that atoms in the first adsorption site both strongly influence and are strongly influenced by a lateral shift surface reconstruction while atoms adsorbed in the second site have only a limited relation to the reconstruction. Molecular adsorption is blocked by the atoms in the second site, but occurs only after population of the first site