ALKANE ACTIVATION VIA PRECURSOR-MEDIATED DISSOCIATION ON IR(110)

Precursor-mediated dissociative adsorption dominates over direct dissociation on Ir(110)-(1 X 2) at low incident kinetic energies for surface temperatures at least up to 1000 K. Direct-unactivated dissociative adsorption is at most a minor contributor to dissociation, even though the top of the barrier for dissociative adsorption lies below the energy zero for the gaseous species. These results suggest that a one-dimensional potential energy surface that combines precursor-mediated adsorption and dissociative adsorption does not even qualitatively represent the reaction pathway, since on this basis direct access to the dissociated state is expected. From the kinetic parameters that represent this range of temperature and kinetic energies and a knowledge of the trapping dynamics, the initial dissociation probability can be predicted from 150 K to 1000 K from simple precursor kinetics.