TRANSFORMATION OF IRIDIUM(110) (1X1) INTO (1X2) AND SPATIAL-DISTRIBUTION OF REACTIVE CARBON-DIOXIDE DESORPTION

The spatial distribution of the desorption flux of CO2 produced on Ir(110) (1 x 1) and (1 x 2) surfaces was studied by means of angle-resolved thermal desorption and low-energy electron diffraction. The distribution is collimated along the bulk surface normal on (1 x 1). It is sharp in the [001] direction and sharper in the [11BAR0] direction. This distribution is consistent with the model that the reactive desorption occurs on a short bridge site. On (1 x 2) surfaces, two-directional desorption was observed, which was collimated along the axis at the polar angle of 26 deg in both [001] and [001BAR] directions. The distribution in the [11BAR0] direction is collimated along the bulk surface normal. The reactive desorption was suggested to take place on a threefold hollow site on the declining terrace. The spatial distribution changed from the (1 x 1) type of the (1 x 2) type during the transformation of the surface structure. This structure change was confirmed by low-energy electron diffraction.