ANGULAR AND VIBRATIONAL EFFECTS IN THE DIRECT DISSOCIATIVE CHEMISORPTION OF DEUTERATED METHANE AND ETHANE ON IR(110)

We have measured the initial probability of dissociative chemisorption of deuterated methane and ethane on the reconstructed Ir(110) surface as a function of polar angle of incidence using vibrationally hot supersonic molecular beams. The probability of chemisorption scales approximately with the component of translational energy normal to the surface (E(i) cos(2) theta(i)) for deuterated ethane and methane, with slight systematic deviations. These deviations are explained in terms of the translational energy distribution of the incident molecular beam. We conclude that in the limit of a monoenergetic beam, normal-energy scaling is obeyed at a constant vibrational energy.