AN ESD AND ESDIAD INVESTIGATION OF TIO2(110)-SO2

The energy and angular distribution of the electron-stimulated O+ ion yield have been measured from clean and SO2-dosed rutile TiO2(110). ES D spectra from the clean surface indicate ion emission at three energi es: 2.5, 4.0 and 6.5 eV. By comparison with previous calculations, the 4.0 and 6.5 eV features can be assigned to emission of in-plane and b ridging O atoms, respectively. The elongation of the ESDIAD image in t he [110BAR] azimuth is consistent with that predicted for the in-plane O atoms. While the O+ energy distribution changes significantly follo wing SO2 adsorption at 130 K and again following sequential annealing, there is little change to the ESDIAD pattern. The latter result is co nsistent with emission from surface sulphate species, although it coul d also be due to a residual substrate effect.