ABSTRACT
The therlnal C02 desorption curves of the same kind as those in Figs. 6.7 and 6.9 exhibited the existence of three different reaction states on the surface precovered with oxygen on which, in addition, different amounts of CO ,vere adsorbed at 80 K:
1. Desorption peak at 420 K was observed for 80 < 0.05 and 8CO < 0.4 when no LEED detectable phase of COads or 0ads was present and CO could react with isolated 0ads atolns or small clusters of a atolns in next-nearest-neighbor positions. At higher oxygen coverages, but ahvays below 80 = 0.25, this peak appeared also in the situation when both p (2 x 2) islands of oxygen and (/3 x /3) R 30° islands of carbon monoxide "vere present (8 0 ~ 8 CO ~ 0.15) and the reaction could occur at the peritneter of oxygen islands.
