Collision-induced desorption in 193-nm photoinduced reactions in (O2+CO) adlayers on Pt(112).

The spatial distribution of desorbing O(2) and CO(2) was examined in 193-nm photoinduced reactions in O(2)+CO adlayers on stepped Pt (112)=[(s)3(111)x(001)]. The O(2) desorption collimated in inclined ways in the plane along the surface trough, confirming the hot-atom collision mechanism. In the presence of CO(a), the product CO(2) desorption also collimated in an inclined way, whereas the inclined O(2) desorption was suppressed. The inclined O(2) and CO(2) desorption is explained by a common collision-induced desorption model. At high O(2) coverage, the CO(2) desorption collimated closely along the (111) terrace normal.