Desorption of products in 193 nm photo-induced reactions in (O2 + CO) adlayers on Pt(112)

Abstract

The spatial distributions of desorbing products were examined in 193 nm photo-induced reactions in O₂ + CO adlayers on stepped Pt(112) = [(s)3(111) × (001)]. At high coverage of O₂(a) and CO(a), both O₂ and CO₂ desorption collimated closely along the (111) terrace normal. The results were compared with those in thermal CO oxidation, and the origin of the collimation angle shift in the latter is discussed. On the other hand, at low CO(a) coverage, O₂ and CO₂ desorption collimated in inclined ways in the plane along the surface trough. At these collimation positions, the kinetic energy of desorbing O₂ and CO₂ was maximal, confirming the hot-atom collision mechanism.