DISSOCIATIVE CHEMISORPTION OF OXYGEN ON IR(110) AS A FUNCTION OF ANGLE OF INCIDENCE - THE EFFECTS OF KINETIC-ENERGY AND SURFACE-TEMPERATURE

Using supersonic molecular beams we have measured the initial probability of dissociative chemisorption of molecular oxygen on the Ir(110) surface as a function of the polar angle of incidence and the incident kinetic energy at surface temperatures of 88, 400, and 1000 K. For incident energies between 4 and 27 kcal/mol (the highest energy investigated) the data can be collapsed onto a single curve by plotting them as a function of the variable E(i) cos(n) theta(i). This exponent n decreases with increasing surface temperature from 2 (88 K) to 1.56 (1000 K). These results indicate that even for a microscopically rough surface such as Ir(110), the importance of parallel momentum dissipation is dictated by surface temperature and not just by surface geometry.