Angular and velocity distributions of desorbing product carbon dioxide from two reaction sites on platinum(110)(1×2)

Abstract

The angular and velocity distributions of desorbing product CO2 were studied on a platinum(110)(1×2) surface over a wide range of CO coverages by means of angle-resolved thermal desorption combined with a cross-correlation time-of-flight (TOF) technique. Heating the coadsorption layer of CO and oxygen yields four CO2 formation peaks P1–CO2 (∼400 K), P2–CO2 (300 K), P3–CO2 (250 K), and P4–CO2 (170 K)]. The angular distribution of each CO2 produced at high CO coverages consists of three desorption components. Two of them show desorption collimated along the inclined terrace normal; the other shows it along the bulk surface normal. The former is assigned to reaction on the inclined terrace, and the latter mostly to reaction on the bottom of the trough. The translational temperature of each desorption component is derived by deconvoluting the TOF spectrum. This temperature reaches 1000–1500 K. The maximum translational temperature is always observed in the normal direction of each reaction site. For P2–and P3–CO2, the maximum translational temperature of the normal-directional component is lower than that of the inclined components. For P4–CO2, on the other hand, the maximum translational temperature of the normal-directional component is close to that of the inclined components. A transfer mechanism of reaction sites is proposed.