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 sup ersonic molecular beams. The probability of chemisorption scales appro ximately with the component of translational energy normal to the surf ace (E(i) cos(2) theta(i)) for deuterated ethane and methane, with sli ght 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 s caling is obeyed at a constant vibrational energy.