DISSOCIATIVE STICKING OF O-2 ON AL(111)

The dissociative sticking probability, S-0, of O-2 on Al(111) has been measured as a function of incident translational and vibrational ener gy. S-0 rises from approximate to 10(-2) for energies approximate to 3 0 meV to near unity in the range 0.6-2.0 eV, demonstrating an activate d dissociation event. Vibrational excitation enhances the sticking. Su rface temperature has no effect on S-0. A peculiar dependence on polar angle is observed. The results are used to discuss possible mechanism s for the recent observation [H. Brune et al. Phys. Rev. Lett. 68, 624 (1992)] of widely separated O atoms after O-2 dissociation on Al(111) .